Дисертації з теми "Heat resistant materials"
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1
Nilsson, Erik. "Oxidation of heat resistant stainless steels in a pelletizing process." Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26622.
Анотація:
Godkänd; 2014; 20140331 (niriel); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Erik Nilsson Ämne: Konstruktionsmaterial/Engineering Materials Uppsats: Oxidation of Heat Resistant Stainless Steels in a Pelletizing Process Examinator: Biträdande professor Marta-Lena Antti, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Ph.D., Research Leader Rikard Norling, Swerea KIMAB AB, Kista Tid: Tisdag den 27 maj 2014 kl 10.00 Plats: E632, Luleå tekniska universitet
2
Davis, Robert Bruce. "Design and development of advanced castable refractory materials /." Full text open access at:, 2001. http://content.ohsu.edu/u?/etd,187.
3
Nam, Jae-Do. "Polymer matrix degradation : characterization and manufacturing process for high temperature composites /." Thesis, Connect to this title online; UW restricted, 1991. http://hdl.handle.net/1773/9867.
4
Peng, Wu Tseng. "Evaluation of ceramic candle filters degradation and damage location using four-point bending tests." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1105.
Анотація:
Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains x, 85 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 81-82).
5
Chhasatia, Viralsinh. "Characterization of thermal interface materials using flash diffusivity and infrared microscopy methods." Diss., Online access via UMI:, 2009.
Анотація:
Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009.Includes bibliographical references.
6
Fox, Bronwyn Louise. "The manufacture, characterization and aging of novel high temperature carbon fibre composites." View thesis entry in Australian Digital Theses Program, 2001. http://thesis.anu.edu.au/public/adt-ANU20011207.114246/index.html.
7
Khattab, Ahmed. "Exploratory development of VARIM process for manufacturing high temperature polymer matrix composites." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4186.
Анотація:
Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (month day, year) Vita. Includes bibliographical references.
8
Marenkov, V. I. "Fermi level of carriers in the volume filling defects structure based on heat-resistant metals." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20600.
Анотація:
The volume filling defects structure based on metals are widely used in modern nan-
otechnology, especially when creating high temperature sensors and structural elements
based on metal foams [1]. The development of contactless and nondestructive methods for
diagnosis and test control parameters of multiply connected matrix base material is a very
important and interesting aspect of the application [2]. In a heat-resistant metal with the
volume filling defects (VFD) (micro- and nanopores with complex topologies and sizes,
see. Figure 1) it is primarily its strength and electrical and physical characteristics. Almost
all rapid methods of such measurements are based on both electrical measurements data
and on fundamental functional relationships establishing of the microstructure parameters
and the dispersion medium carriers [3]. The influence of a disordered set of volume filling
defects (VFD) (micro- and nano-pores of complex topology and various sizes, Figure 1.) is
the unsolved problem on the electronic properties of the micro heterogeneous materials
theory.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20600
9
Yan, Jin. "Aspects of instrumented indentation with applications to thermal barrier coatings." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 177 p, 2007. http://proquest.umi.com/pqdweb?did=1397913961&sid=17&Fmt=2&clientId=8331&RQT=309&VName=PQD.
10
Renier, Mark C. "Equipment and process development for fabrication of rhenium-based composites by chemical vapor infiltration." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/18915.
11
de, Bussac Arnaud. "A study of deformation and fatigue in model Ni-base superalloys." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/20174.
12
Lundberg, Daniel, Filip Wilson, Hjalmar Gunnarsson, Leo Sjörén, Robin Xu, and Erik Djurberg. "Long term aging and creep exposure for advanced heat resistant alloys : A phase analysis." Thesis, Uppsala universitet, Institutionen för materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-446407.
Анотація:
This project was ordered by Sandvik Materials Technology and was performed by a group of students at Uppsala university. The purpose of the project was to study precipitation behavior and structure stability in six advanced heat resistant alloys. Each sample were subjected to a creep rupture test in 600 or 700°C depending on the alloy type. Two parts of each alloy where examined; one part which had been affected by creep and another part which was unaffected by creep. A literature study was performed first to gain knowledge of the scientific theory utilized in this project, namely creep, precipitation hardening, and about the different materials which were analyzed. Preliminary results for the phase composition of the materials were obtained from a Thermo-Calc (TC) simulation. The SEM-images showed nothing noteworthy for any sample due to the roughness of the sample surfaces. The EDS-analysis showed chromium depletion in the centers of the aged samples of HT9 and Sanicro® 75X. Other minority phases such as Cr23C6 in Sanicro®70, P-phase and a titanium nitride phase in sanicro® 60X, VB in Esshete 1250 and Sigma-phase in 4C54 were identified using EDSmapping. It was found that when using XRD to analyze the phase compositions of small samples it is impractical to have the samples cast in bakelite beforehand. The XRD-results obtained in this project showed that more than 90% of the XRD diffractogram for every sample was graphite, which made the identification of minority phases impossible. The quality of the LOM-images varied greatly between samples, for 4C54 grain sizes were measured in all images, for Esshete 1250 grain sizes were measured for the crept sample, and for Sanicro® 60X measurements could only be taken from one image. Most of the sample preparation was insufficient to achieve the test results necessary for complete microstructural analysis and phase analysis of the samples. The mistakes in the practical steps of the project were noted and improvements for these mistakes are presented in the conclusion.
13
Liu, Yi Johnson R. Wayne. "Packaging of silicon carbide high temperature, high power devices processes and materials /." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/doctoral/LIU_YI_31.pdf.
14
Yu, Xinghua. "Characterization and Modeling of Heat Affected Zone Microstucture in a Blast Resistant Steel." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1262201157.
15
Lopes, Shailesh M. "Synthesis, characterization and applications of fats and oil derived phase change materials." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5938.
Анотація:
Thesis (Ph. D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 20, 2009) Vita. Includes bibliographical references.
16
Fernandez-Zelaia, Patxi. "Thermomechanical fatigue crack formation in nickel-base superalloys at notches." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/48991.
Анотація:
Hot sections of gas engine turbines require specialized materials to withstand extreme conditions present during engine operation. Nickel-base superalloys are typically used as blades and disks in the high pressure turbine section because they possess excellent fatigue strength, creep strength and corrosion resistance at elevated temperatures. Components undergo thermomechanical fatigue conditions as a result of transient engine operation. Sharp geometric features, such as cooling holes in blades or fir-tree connections in disks, act as local stress raisers. The material surrounding these features are potential sites of localized inelastic deformation and crack formation. To reduce customer costs associated with unnecessary overhauls or engine down-time, gas turbine manufacturers require accurate prediction methods to determine component endurances. The influence of stress concentration severity on thermomechanical fatigue crack formation is of particular importance as cracks often initiate in these hot spots. Circumferentially notched specimens were utilized to perform thermomechanical fatigue experiments on blade material CM247LC DS and disk material PM IN100. A parametric study on CM247LC DS was performed utilizing four notched specimens. Experimental results were coupled with finite element simulations utilizing continuum based constitutive models. The effects of applied boundary conditions on crack initiation life was studied in both alloys by performing experiments under remotely applied force and displacement boundary conditions. Finite element results were utilized to develop a life prediction method for notched components under thermomechanical fatigue conditions.
17
Nilsson, Erik A. A. "Degradation Mechanisms of Heat Resistant Steel at Elevated Temperatures : In an Iron Ore Pelletizing Industry." Doctoral thesis, Luleå tekniska universitet, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62162.
Анотація:
This thesis focuses on the different degradation mechanisms of the stainless steel in a travelling grate in a Grate-Kiln iron ore pellet indurator. The travelling grate is a conveyor belt that transports green-body pellets to a rotary kiln while the pellets are being dried and pre-heated to a temperature of 900-1100 °C by recycled hot air. After unloading of the pellets to the rotary-kiln for further sintering, the travelling grate is cooled in room temperature while returning to the loading zone of the wet pellets. The steel was tested during thermal cycling in a test-rig, in order to simulate the influence of thermo mechanical fatigue and oxide spallation. The influence of erosion-deposition was investigated in a modified horizontal industrial combustion kiln at 800 °C, with slag and coal from production used as erosive media and combustion fuel, respectively. The influence of minor alloying additions of Mn, Si and Ti on the microstructure was explored by eight different casted alloy compositions. Isothermal heat treatments were performed at 800 °C during 200 hours on steel immersed in deposits recovered from a travelling grate in production. The three main degradation mechanisms found in this work are thermal spallation, erosion-deposition and deposit induced accelerated corrosion (DIAC). Thermal spallation of the oxide layer is caused by the thermal expansion difference between the oxide and the metal during heating and cooling. It has been found that Ti improves the spallation resistance while Si reduces it. Spallation of deposits is another cause believed to increase the degradation. Erosion-deposition appears due to simultaneous erosion and deposition of particles on the travelling grate that causes erosion or deposition depending on the amount of alkali metals in the environment. The velocity of the particles also influences erosion and deposition in the way that higher velocities increase erosion. DIAC is proposed to form on the travelling grate due to the concentration of chloride- and sulphate containing alkali metals in the deposits. Other than these major degrading mechanisms, minor degradation mechanisms such as internal oxidation, sigma formation, carburization and sensitization towards inter-granular attack have been found inside the steel during heating. Thermo mechanical fatigue (TMF) causes intergranular cracks in the material of the travelling grate. Casting issues such as micro-segregation have also been addressed in this thesis. A few different ways to improve degradation resistance have been proposed, such as homogenization heat treatments, optimization of process parameters and inhibitor solutions.
18
Ibanez, Alejandro R. "Modeling creep behavior in a directionally solidified nickel base superalloy." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5353.
19
Teague, Michael Phillip. "Modeling and measurement of thermal residual stresses and isotope effects on thermo physical properties of ZrB₂-SiC ceramics." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/MichaelTeague_09007dcc8056387c.pdf.
Анотація:
Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 27, 2008) Includes bibliographical references.
20
Namjoshi, Shanatanu Ashok. "Reaction synthesis of dynamically-densified Ti-based intermetallic and ceramic forming powders." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19572.
21
Boldt, Paul Henry. "Room temperature indentation of molybdenum disilicide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/NQ42836.pdf.
22
Ventura, Julieta Angelica. "High temperature oxidation behavior of Nb-20Mo-15Si-5B-20Cr alloy." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
23
Rockett, Chris H. "Flexural Testing of Molybdenum-Silicon-Boron Alloys Reacted from Molybdenum, Silicon Nitride, and Boron Nitride." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16293.
Анотація:
MoSiB alloys show promise as the next-generation turbine blade material due to their high-temperature strength and oxidation resistance afforded by a protective borosilicate surface layer. Powder processing and reactive synthesis of these alloys has proven to be a viable method and offers several advantages over conventional melt processing routes. Microstructures obtained have well-dispersed intermetallics in a continuous matrix of molybdenum solid-solution (Mo-ss). However, bend testing of pure Mo and Mo-ss samples has shown that, while the powder processing route can produce ductile Mo metal, the hardening effect of Si and B in solid-solution renders the matrix brittle. Testing at elevated temperatures (200°C) was performed in order to determine the ductile-to-brittle transition temperature of the metal as an indication of ductility. Methods of ductilizing the Mo-ss matrix such as annealing and alloying additions have been investigated.
24
Middlemas, Michael Robert. "A Nitride-Based Reaction for the Formation of a Three-Phase Molybdenum-Silicon-Boron Intermetallic Alloy." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7190.
Анотація:
The alloy Mo-3Si-1B (wt%) may have the fracture toughness and oxidation resistance required for use as jet turbine engine blades. Mo-3Si-1B (wt%) forms a three-phase mixture of and #945;-Moss, A15 (Mo3Si) and T2 (Mo5SiB2). It has been observed that at high-temperatures, the A15 and T2 intermetallics form a oxidation resistant borosilicate glass coating. To achieve the proper combination of mechanical and thermal properties, the material must have a molybdenum matrix with a fine dispersion of intermetallics to produce a continuous protective layer. In this project, reactive sintering of molybdenum, Si3N4 and BN powders was used to create a semi-continuous molybdenum matrix with a fine dispersion of the A15 and T2 intermetallics. Sintering of the materials was further enhanced by the use of submicron-sized reactants. X-ray diffraction analysis was used verify the desired phases were formed. It was determined that formation of the A15 intermetallic phases begins as low as 1200?nd formation of T2 begins at 1300? The reactions are complete by 1400? Samples with bulk densities as high as 95% of theoretical were produced. Scanning electron microscopy images reveal a microstructure with dispersed intermetallics in a semi-continuous molybdenum matrix with grain sizes on the order of 1-4 and #956;m. It was found that by varying parameters such as mixing method and heating rates, it is possible to engineer the final microstructure, changing the level of dispersion of the intermetallics and continuity of the matrix.
25
Lipke, David William. "Novel reaction processing techniques for the fabrication of ultra-high temperature metal/ceramic composites with tailorable microstructures." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/43750.
Анотація:
Ultra-high temperature (i.e., greater than 2500°C) engineering applications present continued materials challenges. Refractory metal/ceramic composites have great potential to satisfy the demands of extreme environments (e.g., the environments found in solid rocket motors upon ignition), though general scalable processing techniques to fabricate complex shaped parts are lacking. The work embodied in this dissertation advances scientific knowledge in the development of processing techniques to form complex, near net-shape, near net-dimension, near fully-dense refractory metal/ceramic composites with controlled phase contents and microstructure.
Three research thrusts are detailed in this document. First, the utilization of rapid prototyping techniques, such as computer numerical controlled machining and three dimensional printing, for the fabrication of porous tungsten carbide preforms and their application with the Displacive Compensation of Porosity process is demonstrated. Second, carbon substrates and preforms have been reactively converted to porous tungsten/tungsten carbide replicas via a novel gas-solid displacement reaction. Lastly, non-oxide ceramic solid solutions have been internally reduced to create intragranular metal/ceramic micro/nanocomposites. All three techniques combined have the potential to produce nanostructured refractory metal/ceramic composite materials with tailorable microstructure for ultra-high temperature applications.
26
Pang, Lisa Yee San. "Thin film diamond : electronic devices for high temperature, high power and high radiation applications." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313317.
27
Sharpe, Heather Joan. "Effect of Microstructure on High-Temperature Mechanical Behavior of Nickel-Base Superalloys for Turbine Disc Applications." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16255.
Анотація:
Engineers constantly seek advancements in the performance of aircraft and power generation engines, including, lower costs and emissions, and improved fuel efficiency. Nickel-base superalloys are the material of choice for turbine discs, which experience some of the highest temperatures and stresses in the engine. Engine performance is proportional to operating temperatures. Consequently, the high-temperature capabilities of disc materials limit the performance of gas-turbine engines. Therefore, any improvements to engine performance necessitate improved alloy performance.
In order to take advantage of improvements in high-temperature capabilities through tailoring of alloy microstructure, the overall objectives of this work were to establish relationships between alloy processing and microstructure, and between microstructure and mechanical properties. In addition, the project aimed to demonstrate the applicability of neural network modeling to the field of Ni-base disc alloy development and behavior.
A full program of heat-treatment, microstructural quantification, mechanical testing, and neural network modeling was successfully applied to next generation Ni-base disc alloys. Mechanical testing included hot tensile, hot hardness, creep deformation, creep crack growth, and fatigue crack growth. From this work the mechanisms of processing-structure and structure-property relationships were studied. Further, testing results were used to demonstrate the applicability of machine-learning techniques to the development and optimization of this family of superalloys.
28
LEITE, ANTONIO M. dos S. "Investigação da resistência à corrosão por pites do aço inoxidável duplex tipo 2404 (UNS S82441) submetido à soldagem por atrito com pino não-consumível (FSW)." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28016.
Анотація:
Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-17T16:32:32Z
No. of bitstreams: 0Made available in DSpace on 2017-11-17T16:32:32Z (GMT). No. of bitstreams: 0
Os aços inoxidáveis duplex são largamente utilizados na fabricação de equipamentos para a indústria de óleo e gás, utilizados tanto no ambiente onshore quanto offshore. Sua grande limitação é que, com o aumento de temperatura, ocorre precipitação de fases indesejáveis, que reduzem drasticamente a resistência à corrosão e as propriedades mecânicas desses materiais. Considerando o efeito deletério da soldagem a fusão nos aços inoxidáveis duplex, a soldagem por atrito com pino não-consumível (FSW) é amplamente considerada como alternativa aos processos convencionais. Como no FSW a união dos materiais ocorre no estado sólido, muitos dos problemas de soldabilidade associados às técnicas tradicionais de soldagem por fusão são evitados. Neste trabalho, amostras retiradas da zona misturada (ZM), das zonas afetadas pelo calor (ZTA e ZTMA) e do metal de base (MB) de chapas de aço inoxidável lean duplex LDX 2404® (UNS S82441) soldadas por atrito com pino não-consumível foram caracterizadas microestruturalmente e tiveram sua resistência à corrosão avaliada por meio de ensaios eletroquímicos. Os resultados obtidos nos ensaios eletroquímicos indicaram que as zonas afetadas pelo calor e a ZM se mantiveram tão resistentes à corrosão localizada quanto o MB. Permitiram concluir também que a excelente resistência à corrosão da liga está associada ao teor elevado de N.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
29
Gockel, Brian Timothy. "Developing the capability to examine environmental effects on small fatigue crack growth." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271184488.
Анотація:
Thesis (M.S. in Mechanical Engineering) -- University of Dayton.Title from PDF t.p. (viewed 06/22/10). Advisor: Robert Brockman. Includes bibliographical references (p. 42-44). Available online via the OhioLINK ETD Center.
30
Nguyen, QuynhGiao N. "High Temperature Volatility and Oxidation Measurements of Titanium and Silicon Containing Ceramic Materials." Abstract only. Full text release has been delayed at the author's request until December 31, 2010, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1239291812.
Анотація:
Thesis (Ph.D.)--Cleveland State University, 2008Abstract. Includes bibliographical references (p. 110-111). Electronic full text release has been delayed at the author's request until December 31, 2010.
31
Saillard, Audric. "Modeling and simulation of stress-induced non-uniform oxide scale growth during high-temperature oxidation of metallic alloys." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33898.
Анотація:
The metallic alloys employed in oxidizing environment at high temperature rely on the development of a protective oxide scale to sustain the long-term aggressive exposition. However, the oxide scale growth is most of the time coupled with stress and morphological developments limiting its lifetime and then jeopardizing the metallic component reliability. In this study, a mechanism of local stress effect on the oxidation kinetics at the metal/oxide interface is investigated. The objective is to improve the understanding on the possible interactions between stress generation and non-uniform oxide scale growth, which might result in a precipitated mechanical failure of the system. Two different oxides are studied, alumina and chromia, in two different industrial systems, thermal barrier coatings and solid oxide fuel cell interconnects. A specific thermodynamic treatment of local oxide phase growth coupled with stress generation is developed. The formulation is completed with a phenomenological macroscopic framework and a numerical simulation tool is developed allowing for realistic analyses. Two practical situations are simulated and analyzed, concerning an SOFC interconnect and a thermal barrier coating system, for which oxide scale growth and associated stress and morphological developments are critical. The consequence of the non-uniform oxide growth on the system resistance to mechanical failure is investigated. Finally, the influences of material-related properties are studied, providing optimization directions for the design of metallic alloys which would improve the mechanical lifetime of the considered systems.
32
Morata, Royes Joan. "Wear resistance of heat-treated Advanced High Strength Steels and casting." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80526.
Анотація:
The necessity to improve the durability of the machinery used in the milling industry has lead to several types of research. One study is focused on the plates that are located in the stationary and moving jaws of crushers to diminish particles sizes of Gneiss and Diabase rocks. Thus, one type of approach to increase its durability is by reducing the material loss of the plates. Amongst all the parameters to reduce the wear ratio that includes inputs from geometry to load, just the hardness input of the material can be in constant development. Consequently, there are two well-known types of heat treatment that can produce this change in hardness and are named Carbide Free Bainite (CFB) and Quenching and Partitioning (QP). In this master thesis the topic is to perform the QP heat treatments for two compositions A and B to obtain the microstructure of the steels that consist in a mix of austenite, bainite and martensite which considerably increase the hardness while the toughness is not drastically reduced due to the austenite soft phase. Five samples have been studied at four different partitioning temperatures: QP250 A, QP180 B, QP210 B, QP240 B and Mn Steel as it is the composition most used nowadays in the industry. In order to characterise both mechanical properties and microstructural features, different analysis had been performed with Micro-indentations, Charpy-V, Gouging Abrasion Tests, Optical Microscopy, Scanning Electron Microscopy and X-Ray Diffraction. These analysis had been done in the samples before and after wear as a result in change of the microstructure. As the abrasive-impact of the rocks collide with the sample, austenite transforms to martensite by induced plasticity called TRIP effect. Thus, the surface of the alloy is harder than the bulk material as no austenite is found and the wear ratio is seen to be improved. The results have shown several behaviours. Austenite transforms in its majority to fresh martensite which is an unstable martensitic phase but harder than tempered martensite that is the stable martensitic phase. Moreover, the difference in hardness between the bulk and the surface produce an affected depth layer as a consequence of the abrasive-impact penetration of rocks in which the microstructure has fully transformed to martensite on the surface and the austenite phase increases as it goes further inside the steel. The thinner this layer is, the better wear ratio presents the alloy. From all the samples, the best combination of hardness and toughness is for QP210 B.
33
Bloss, Matthew C. "Ultrasonic metal welding the weldability of stainless steel, titanium, and nickel-based superalloys /." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1198168491.
34
Adair, Benjamin Scott. "Thermo-mechanical fatigue crack growth of a polycrystalline superalloy." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/46027.
Анотація:
A study was done to determine the temperature and load interaction effects on the fatigue crack growth rate of polycrystalline superalloy IN100. Temperature interaction testing was performed by cycling between 316°C and 649°C in blocks of 1, 10 and 100 cycles. Load interaction testing in the form of single overloads was performed at 316°C and 649°C. After compiling a database of constant temperature, constant amplitude FCGR data for IN100, fatigue crack growth predictions assuming no load or temperature interactions were made. Experimental fatigue crack propagation data was then compared and contrasted with these predictions. Through the aid of scanning electron microscopy the fracture mechanisms observed during interaction testing were compared with the mechanisms present during constant temperature, constant amplitude testing. One block alternating temperature interaction testing grew significantly faster than the non-interaction prediction, while ten block alternating temperature interaction testing also grew faster but not to the same extent. One hundred block alternating testing grew slower than non-interaction predictions. It was found that as the number of alternating temperature cycles increased, changes in the gamma prime morphology (and hence deformation mode) caused changes in the environmental interactions thus demonstrating the sensitivity of the environmental interaction on the details of the deformation mode. SEM fractography was used to show that at low alternating cycles, 316°C crack growth was accelerated due to crack tip embrittlement caused by 649°C cycling. At higher alternating cycles the 316°C cycling quickly grew through the embrittled crack tip but then grew slower than expected due to the possible formation of Kear-Wilsdorf locks at 649°C. Overload interaction testing led to full crack retardation at 2.0x overloads for both 316°C and 649°C testing. 1.6x overloading at both temperatures led to retarded crack growth whereas 1.3x overloads at 649°C created accelerated crack growth and at 316°C the crack growth was retarded.
35
Пітак, Ярослав Миколайович. "Вогнетривкі та жаростійкі неформовані матеріали на основі композицій системи RO – R₂O₃ – RO₂ – P₂O₅". Thesis, Національний технічний університет "Харківський політехнічний інститут", 2005. http://repository.kpi.kharkov.ua/handle/KhPI-Press/40380.
Анотація:
Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.17.11 – технологія тугоплавких неметалічних матеріалів. – Національний технічний університет “Харківський політехнічний інститут”, Харків, 2005. Дисертація присвячена розробці наукової концепції створення вогнетривких та жаростійких неформованих матеріалів на основі композицій системи RO – R₂O₃ – RO₂ – P₂O₅. Досліджено субсолідусну будову чотирикомпонентних систем: M–A–S–P, C–А–S–P, Zn–Z–S–B, Zn–A–Z–S, C–M–S–P, A–Z–S–P, M–Z–S–P, C–A–S–B, C–A–Z–S, C–M–A–S, C–Sr–A–Z. Визначено співіснуючі фази в системах, виконано триангуляцію потрійних підсистем та тетраедрацію чотирикомпонентних систем, визначено їх об’єми та ступінь асиметрії, побудовано топологіч-ний граф взаємозв’язку елементарних тетраедрів, надано геометро-топологічну характеристику фаз систем, проведено оцінку евтектичних температур в перерізах систем та побудовано поверхні ліквідусу перетинів. На підставі фізико-хімічних досліджень систем розроблено принципи одержання нових вогнетривких та жаростійких неформованих матеріалів. Розроблені нові склади вогнетривких теплоізоляційних матеріалів, жаростійких та вогнетривких цементів та бетонів на їх основі, набивних мас з високими фізико-механічними та технічними властивостями. Встановлено закономірності фазоутворення, та розроблено принципи одержання цих матеріалів.Thesis for Doctor of Technical Sciences degree on the speciality 05.17.11 – technology of refractory not metal materials. – National Technical University “Kharkiv Polytechnic Institute”, Kharkiv, 2005. The thesis is devoted to develop scientific conception of creation of fire-resistant and heat resisting materials on the basis of the system RO – R₂O₃ – RO₂ – P₂O₅ compositions. The sub-solidus structure of the four component systems has been investigated: M–A–S–P, C–А–S–P, Zn–Z–S–B, Zn–A–Z–S, C–M–S–P, A–Z–S–P, M–Z–S–P, C–A–S–B, C–A–Z–S, C–M–A–S, C–Sr–A–Z. The co-existed phases in the systems have been determined, the tetrahedra for quaternary systems have been carried out, the volumes elementary tetrahedrons have been determined, the topological characteristic of phases of systems have been given. On the basis of physic-chemical researches of the systems the principles of reception new fire-resistant and heat resisting unforming materials have been developed. New compositions of materials on the base of refractories and cements with high physical, mechanical and technical properties have been developed. The principles of phase-formation have been set up and the principles of obtaining these materials have been worked out.
36
Pathak, Sayali V. "Enhanced Heat Transfer in Composite Materials." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1368105955.
37
Cross, Robert. "Processing of vertically aligned carbon nanotubes for heat transfer applications." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31828.
Анотація:
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Graham, Samuel; Committee Member: Das, Suman; Committee Member: Joshi, Yogendra. Part of the SMARTech Electronic Thesis and Dissertation Collection.
38
Hong, Charles S. M. Eng Massachusetts Institute of Technology. "Improving the heat, fire, and melt resistance of elastomeric seals on military gas masks." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54549.
Анотація:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 62-63).
Improvised Explosive Devices (IED's) have wreaked havoc amongst American and Coalition troops. They have been the number one killer of Coalition forces. Many times the impact knock out fuel tanks which then catch on fire, causing life threatening burn injuries. As a counter, the military unveiled new fire/melt resistant clothing. In the case of a chemically contaminated environment, the soldier will have to rely on a gas mask with an elastomeric seal that is not resistant to fire or melting. If a soldier is traveling in a vehicle with his or her gas mask on and gets hit by an IED, facial and eye bum injuries are very possible. New material must be found that can help prevent these injuries, particularly concerning the seal. The goal is to find the best combination of a suitable elastomer, curing agent, and filler that can give the soldier precious time to escape a burning vehicle. Various types of materials are discussed concerning thermal, other physical properties, cost, and relevant patents.
by Charles S. Hong.
M.Eng.
39
Joubert, K. J. "The influence of tempering on the corrosion resistance of newly developed steels." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/21797.
Анотація:
Bibliography: pages 105-113.This thesis deals with the effect of heat treatment on the localized corrosion resistance of the low carbon, chromium containing steels, designated 825, 102A and 122 which recently have been developed. The potentiodynamic polarization technique has been employed to determine the corrosion characteristics of the three steels. The results do not accurately reflect the effect heat treatment has on corrosion rates but scanning electron microscopy of corroded surfaces does allow a characterization. Both tempering temperature and time at temperature have a significant influence on the corrosion behaviour of chromium steels because the type, size and morphology of carbide precipitates are determined by the temperature and time of temperi ng. Localized pitting corrosion predominates for specimens tempered at temperatures below 450°C. Intergranular corrosion together with general corrosion occur after tempering at temperatures. in excess of 450°C. The resul ts of hardness tests show that secondary hardeni ng occurs after tempering between 450°C and 600°C. Secondary hardening suggests the presence of chromium carbides which deplete the surrounding matrix of chromium leaving it susceptible to active general corrosion (within the grains) and intergranular corrosion (at grain boundaries). A model showing the effect that 12% chromium, in comparison to 8% chromium, has on the corrosion resistance, is proposed. The significance of these results with regard to the application of the steels is discussed.
40
Seidl, Jakub. "Návrh podnikového finančního plánu." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2020. http://www.nusl.cz/ntk/nusl-417364.
Анотація:
This master’s thesis is focused on a Draft of a Corporate Financial Plan for industrial company P-D Refractories CZ a.s. for years 2019 to 2022. First chapter of this master’s thesis is oriented in goals, methods and approaches of this thesis. Next part is aiming at theoretical solution for financial planning. Third chapter contains information about analyzed company, application of selected methods of strategic analysis and financial analysis including evaluation of the state of company and detection of potential deficiencies. Last chapter of this thesis is focused on suggestion, formation and evaluation of the financial plan for P-D Refractories CZ a.s. for next four years.
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Monobe, Luis Shiguenobu. "Caracterização do envelhecimento da liga 20Cr32Ni+Nb fundida por centrifugação e de seu efeito sobre o comportamento mecânico a frio." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-08012008-155251/.
Анотація:
Fornos petroquímicos constituem a parte mais importante da indústria de derivados de petróleo. São nesses fornos que se processam as reações químicas imprescindíveis ao processamento dos produtos que constituem nosso cotidiano, como os fertilizantes, polímeros, produtos farmacêuticos e alimentícios. Devido ao caráter fortemente endotérmico dos processos, associado a reações catalíticas provocada numa mistura reacional de vapor de água com hidrocarbonetos (caso da reforma para obtenção de hidrogênio) ou craqueamento por pirólise (processo de pirólise), estes fornos são continuamente aquecidos. Com o objetivo de aumento de produção e produtividade, os fornos têm sido submetidos a condições de temperatura e pressão cada vez mais extremas. Nos fornos de pirólise, adicionalmente tem-se aumentado consideravelmente a velocidade do fluido e para tanto têm tido as seções transversais dos condutos diminuídas levando a um aumento das tensões de trabalho. Além disso, paradas e partidas desses fornos têm se mostrado um elemento crucial na operação. É comum que durante a parada desses fornos se detecte fragilização desse material após certo tempo de serviço à temperatura de trabalho. Quedas significativas nos valores de alongamento têm sido reportadas sendo que em algumas situações, componentes apresentam valores nulos de alongamento à temperatura ambiente quando ensaios mecânicos são efetuados em corpos de prova retirados dos mesmos. Devido a essa fragilização, com conseqüente diminuição nos valores de alongamento, operações de reparo por soldagem têm se mostrado freqüentemente impraticáveis resultando no sucateamento do componente. Nesse trabalho caracterizou-se a fragilização ocorrida no material 20Cr32Ni+Nb que é usado nos coletores de saída de fornos que embora operem em temperaturas mais baixas, estão sujeitos também aos mesmos requisitos de pressão do forno. Para melhor caracterizar o material em estudo, um tubo centrifugado foi analisado tomando-se o cuidado de extrair corpos de prova em regiões que propiciassem microestrutura reprodutível. Para garantir que os corpos de prova fossem submetidos a temperaturas e tempos similares com boa precisão, estes foram envelhecidos em equipamento de ensaios de fluência, porém sem aplicação de tensão. Os corpos de prova envelhecidos foram então ensaiados com tração à temperatura ambiente e o alongamento da fratura foi registrado, evidenciando a fragilização. A região da cabeça do corpo de prova foi examinada por metalografia óptica e por microscópio eletrônico de varredura (MEV). As fraturas foram igualmente examinadas no microscópio eletrônico de varredura. Os resultados obtidos na microscopia ótica, com e sem ataque, bem como no MEV não evidenciaram quaisquer alterações microestruturais significativas que justificassem a alteração do comportamento mecânico com o envelhecimento. Análises fratográficas também não evidenciaram alteração significativa no mecanismo de fratura que ocorre pela nucleação de micro-cavidades (dimples). Adicionalmente procurou-se comprovar ou rejeitar a hipótese de que a fragilização seria causada ela precipitação de um intermetálico frágil em contorno de grão: a chamada fase G (um silicieto misto de nióbio e níquel com estequiometria Ni16Nb6Si7, estrutura cúbica de faces centradas e parâmetro de rede a0 = 1,13nm). A análise dos resultados não evidencia fase nova, nem uma mudança de modo de fratura de trans para intergranular, que poderiam comprovar uma influência da fase G no processo de fragilização (ao menos até o limite de resolução das técnicas experimentais aqui empregadas).Petrochemical furnaces play an important role in the oil industry. In these furnaces, the essential chemical reactions take place in order to get everyday products like fertilizers, polymers, products for pharmaceutic and food industry. Due to the highly endothermic characteristics of these processes, these furnaces are heated up. It is common during shutdowns and startups of these furnaces, to have fragilization of this material after an aging time at working temperatures. This fragilization impairs repair when needed. In order to have an increase in production and productivity, the furnaces are continuously submitted to higher temperature and pressure working conditions. Pyrolisis furnaces have been also subjected to an increase in fluid speed and in order to reach this, the transverse area of tubes has been significantly decreased resulting in an increase in working stresses. Besides, shutdowns and startups have been a crucial part of operation. Fragilization in this material in service at high temperatures is frequently detected during shutdowns. Significant losses in elongation have been reported and sometimes components show no elongation at room temperature when samples are subjected to tensile testing. Due to this fragilization and low elongation values, repair by welding is sometimes useless resulting in scrapping the component. In this work the characterization of the fragilization that occurs in a 20Cr32Ni+Nb centrifugally cast tube, whose application is the outlet collectors that, though operate in lower temperature, are subjected to the pressure requirements of the furnace. In order to better characterize the material, one centrifugally cast tube was analysed taking care of having the test samples from regions that could provide similar microstructures. In order to assure that the samples were submitted to temperature and time with good accuracy, they were aged in a creep testing machine, but without application of load. The aged samples were then tensile tested at room temperature and the fracture elongation was calculated, evidencing the fragilization. The head of the test sample was examined by optical metalography and Scanning Electron Microscopy (SEM). The fractured areas were also examined by SEM. The results from optical microscopy, with or without etching, as well as SEM did not show any microstructural changes that could explain the changes in mechanical behavior with during aging. Additionally one aims to confirm or reject the hypothesis of the fragilization being caused by the precipitation of an fragile intermetallics in the grain boundary: the socalled G-phase (a silicide of Niobium and Nickel with stoichiometry Ni16Nb6Si7 , face centered cubic and lattice parameter of a0 = 1,13nm). The results did not either evidence this new phase nor a change in the fracture mode from trans to intergranular which could confirm the influence of this phase in the fragilization process (at least in the resolution limits of the experimental procedures here employed).
42
Houl, Yassine. "Increasing Effective Thermal Resistance of Building Envelope's Insulation Using Polyurethane Foam Incorporated with Phase Change Material." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1505159/.
Анотація:
Incorporating insulation material with phase change materials (PCMs) could help enhance the insulation capability for further building energy savings by reducing the HVAC loadings. During the phase change process between the solid and liquid states, heat is being absorbed or released by PCMs depending on the surrounding temperature. This research explores the benefits of a polyurethane (PU)-PCM composite insulation material through infiltrating paraffin wax as PCM into PU open cell foam. The new PU-PCM composite provides extra shielding from the exterior hot temperatures for buildings. Through this study, it was demonstrated that PU-PCM composite insulation could potentially help building energy savings through reducing the loads on the HVAC systems based on the building energy modeling using EnergyPlus. The Zero Energy Lab (ZØE) at the University of North Texas was modeled and studied in the EnergyPlus. It is a detached building with all wall facades exposed to the ambient. It was determined that the new PU-PCM insulation material could provide 14% total energy saving per year and reduce the electricity use due to cooling only by around 30%.
43
Kasali, Suraju Olawale. "Thermal diodes based on phase-change materials." Thesis, Poitiers, 2021. http://www.theses.fr/2021POIT2254.
Анотація:
Nous étudions dans cette thèse la rectification thermique de diodes thermiques radiatives ou conductive constituées de matériaux à changement de phase.Cette thèse est divisée en trois parties. Dans les premières parties, nous modélisons comparativement les performances d’une diode thermique conductive sphérique et cylindrique constitués de VO2 présentant un transition de phase et des matériaux n’en présentant pas. Des expressions analytiques aux bornes des diodes sont dérivées. Des flux thermiques, des facteurs de rectifications ainsi que les profils de température à l’intérieur de la diode sont obtenus. Nos résul-tats montrent que les différentes géométries de diodes ont un impact significatif sur les profils de température et les flux thermiques, mais moins un sur les facteurs de rectification. Dans ce travail, nous avons obtenu des facteurs de rectification maximaux allant jusqu’à 20.8% et 20.7%, qui sont supérieurs à celui prédit pour une diode plane constituée de VO2. Nous montrons également que des facteurs de rectification similaires à ceux obtenus avec le VO2 dans les géométries sphériques et cylindriques peuvent être atteints avec des matériaux à changement de phase dont le contraste de conductivité est plus important que dans le cas du VO2. Dans la deuxième partie, nous étudions la rectification de diodes thermiques constituées de deux matériaux à changement de phase. Avec, l’idée de générer un facteur de redressement plus élevé que dans le cas d’une diode thermique conductive ne comprenant qu’un matériau à changement de phase unique. Là encore, le travail a conduit à l’établissement d’expressions explicites pour les profils de température, les flux thermiques et le facteur de rectification. Nous avons obtenu un facteur de rectification optimal de 60% avec une variation de température de 250 K couvrant les transitions métal-isolant des deux matériaux. Dans la troisième partie de notre travail, nous avons modélisé et optimisé la rectification thermique de diodes thermiques planes, cylindriques et sphériques radiatives à base de deux matériaux à changement de phase. Nous savons calculer et analyser les facteurs de rectification de ces trois diodes et obtenu les facteurs de rectification optimaux respectifs pour les trois géométries 82%, 86% et 90.5%. Nos résultats montrent que la géométrie sphérique est la meilleure pour optimiser la rectification des courants thermiques radiatifs. De plus, des facteurs de rectification potentiellement supérieurs à ceux prédits ici peuvent être réalisés en utilisant deux matériaux à changement de phase avec des contrastes d’émissivités plus élevés que ceux proposés ici. Ces résultats analytiques et graphiques fournissent un guide utile pour optimiser les facteurs de rectification des diodes thermiques conductives et radiatifs basées sur des matériaux à changement de phase de géométries différentesThe thermal rectification of conductive and radiative thermal diodes based on phase-change materials, whose thermal conductivities and effective emissivities significant change within a narrow range of temperatures, is theoretically studied and optimized in different geometries. This thesis is divided into three parts. In the first part, we comparatively model the performance of a spherical and cylindrical conductive thermal diodes operating with vanadium dioxide (VO2) and non-phase-change materials, and derive analytical expressions for the heat flows, temperature profiles and optimal rectification factors for both diodes. Our results show that different diode geometries have a significant impact on the temperature profiles and heat flows, but less one on the rectification factors. We obtain maximum rectification factors of up to 20.8% and 20.7%, which are higher than the one predicted for a plane diode based on VO2. In addition, it is shown that higher rectification factors could be generated by using materials whose thermal conductivity contrast is higher than that of VO2. In the second part, on the other hand, we theoretically study the thermal rectification of a conductive thermal diode based on the combined effect of two phase-change materials. Herein, the idea is to generate rectification factors higher than that of a conductive thermal diode operating with a single phase-change material. This is achieved by deriving explicit expressions for the temperature profiles, heat fluxes and rectification factor. We obtain an optimal rectification factor of 60% with a temperature variation of 250 K spanning the metal-insulator transitions of VO2 and polyethylene. This enhancement of the rectification factor leads us to the third part of our work, where we model and optimize the thermal rectification of a plane, cylindrical and spherical radiative thermal diodes based on the utilization of two phase-change materials. We analyze the rectification factors of these three diodes and obtain the following optimal rectification factors of 82%, 86% and 90.5%, respectively. The spherical geometry is thus the best shape to optimize the rectification of radiative heat currents. In addition, potential rectification factors greater than the one predicted here can be realized by utilizing two phase-change materials with higher emissivities contrasts than the one proposed here. Our analytical and graphical results provide a useful guide for optimizing the rectification factors of conductive and radiative thermal diodes based on phase-change materials with different geometries
44
Müller, Jiří. "Kotevní silikátový expanzní materiál se zvýšenou teplotní odolností." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392344.
Анотація:
This master thesis deals with the development of an expansive anchor material. This material is intended especially for the engineering and power industry where the operating conditions cause thermal stresses of the anchor. In order to meet the requirements for a firm and secure connection of the anchored part, it is necessary to achieve excellent physical-mechanical properties of the developed material such as high compressive strength, high tensile strength based on the base, and resistance to thermal stresses till 200 ° C. All of these processes must be achieved after the ageing of the cement material. Due to the current trend of modern materials that are environmentally friendly, the use of partial replacements for Portland cement is used as a substitute for a primary binder.
45
Friček, Jakub. "Sledování vlivu keramické vazby na vlastnosti izolačních žáromateriálů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225890.
Анотація:
Thermal insulating refractories are an integral part of each thermal unit since they reduce its energy consumption. The current phenomenon of saving in both environmental and financial aspects reflects in searching for such possibilities to produce at lower manufacturing and material costs. One of the possible ways is to valorise waste materials. The theoretical part then deals with the division of refractory materials, classification of thermal insulation refractory materials and manufacturing technologies. The experiment is focused on the production of insulating refractory materials made from plastic dough with a possibility of using sawdust and materials made by pressing mixture moist, with a focus on coal bottom ash. Both of these technologies will be tested for the possibility of modification by using mixed clays and of increasing the strength by using clays with lower sintering temperature.
46
TRIBUIANI, CHIARA. "Analisi sperimentale di componenti edilizi per la riqualificazione energetica degli edifici." Doctoral thesis, Università Politecnica delle Marche, 2021. http://hdl.handle.net/11566/291054.
Анотація:
Oggetto principale del progetto di ricerca è stata la valutazione del comportamento energetico di componenti edilizi attraverso l’analisi sperimentale in situ con la realizzazione di mock up configurati per lo scopo.
In prima battuta, lo studio si è concentrato sulle problematiche inerenti ai consumi energetici estivi, il comfort interno e la salubrità degli ambienti prefiggendosi l’obiettivo di analizzare nuove strategie per l’ottimizzazione dell’involucro edilizio. La tematica dell’isolamento termico è stata, quindi, declinata sotto diversi aspetti: tipologia dei materiali isolanti e le loro caratteristiche chimico-fisiche, tipologia delle strutture edilizie che necessitano di isolamento, principali parametri termici da considerare e infine la traduzione, in termini di sperimentazione in sito, di un modello comparativo tra involucri termici su una struttura esistente fortemente inerziale ma priva di isolamento termico: mock up realizzato a Fabriano.
La necessità di raggiungere standard energetici sempre più stringenti si è generalmente tradotta con la scelta e l’utilizzo di materiali isolanti con alte prestazioni per coibentare le pareti dei nostri edifici. Una corretta valutazione dei vantaggi e degli svantaggi legati a questa tecnica costruttiva è della massima importanza al fine di comprendere al meglio il comportamento termico delle strutture opache. Pertanto, la ricerca portata avanti, riporta i dati sperimentali e analitici ottenuti dallo studio di una parete ad elevata inerzia termica coibentata con due diversi strati isolanti esterni (metodologia in gergo definita come isolamento “a cappotto”) per soddisfare i requisiti nZEB italiani sulla resistenza termica e focalizzandosi sulle problematiche nell’ambito del clima mediterraneo.
Infatti, il surriscaldamento degli ambienti interni e, quindi, l'uso eccessivo dei sistemi di raffrescamento rappresenta uno dei principali problemi sia per la salute degli occupanti che per i consumi energetici, in particolar modo durante il periodo estivo. Ne consegue che, al fine di limitare questo problema, è necessaria una progettazione appropriata e/o un adeguamento energetico dell'involucro edilizio che utilizzi un approccio globale e sinergico.
Altro argomento di ricerca, seguito parallelamente al primo, è stato lo studio dei cool materials da applicare in sistemi di raffrescamento passivo degli edifici declinando la tecnica del cool roof alle facciate degli edifici. L’obiettivo dello studio è stato quello di valutare gli effettivi benefici che i cool materials possono avere una volta applicati su pareti verticali, al posto delle tradizionali vernici per esterni, e valutarne la convenienza in termini di costi-benefici-durabilità. Questi materiali possono contribuisce alla riduzione della temperatura superficiale dell’agglomerato abitativo grazie ad un migliore bilancio energetico relativo alle superfici in gioco favorendo la mitigazione dell’effetto di isola di calore urbana. Inoltre, l’utilizzo di pareti con corrette stratigrafie e il giusto posizionamento dell’isolamento con materiali che rispondano a condizioni al contorno dinamiche, soprattutto nei climi Mediterranei come il nostro, possono rappresentare una risposta alle problematiche riguardanti il miglioramento dell’efficienza energetica del nostro patrimonio edilizio. Il progetto di ricerca sui cool materials ha previsto una fase preliminare di studio dei materiali, formulazione delle pitture sperimentali e, infine, la preparazione del mock up sul quale installare i pannelli da monitorare durante il periodo estivo.
Riassumendo, la problematica della riqualificazione degli edifici rispetto all’isolamento estivo ha affrontato, principalmente, i seguenti argomenti:
• l’inerzia termica e la sua relazione con l’isolamento termico dell’involucro nel periodo estivo;
• lo studio dei materiali e la loro sperimentazione in condizioni reali, ovvero in regime dinamico;
• l’applicazione sperimentale dei cool materials sulle pareti verticali esterne per valutarne l’efficacia in termini di contenimento delle temperature superficiali.The main object of the research project was the evaluation of the energy behavior of construction components through in situ measurement and experimental analysis with dedicated mock-up. At first, the study has focused on issues related to energy consumption over the summertime, indoor comfort’s situations and environment’s salubrity with the aim of analysing new strategies towards building envelope’s upgrade. Therefore, the topic of thermal insulation has been listed into different aspects: the type of insulating materials and their chemical-physical characteristics, the type of building structures that require insulation, the main thermal parameters to be considered within the research and, at last, the translation, in terms of on-site test, of a comparative model between several thermal envelopes applied on a highly inertial structure lacking of thermal isolation: mock up made in Fabriano. The use of high-performance insulating materials to insulate the building walls is the necessary consequence to achieve the higher strict energy standards. The urgent need of reaching higher energetic standards has brought to choosing high-performance isolating materials to insulate buildings. A correct evaluation of pros and cons of this specific construction technique is extremely fundamental in order to achieve a better understanding of opaque structures thermal behaviour’s. Perhaps, the current research reports experimental and analytical data obtained from the study of a high thermal inertia surface insulated with two different external isolating layers, to meet the Italian nZEB requirements on thermal resistance and focusing on set of problems caused by the Mediterranean climate conditions. In fact, the indoor environment overheating and, consequently, the excessive use of cooling systems represents one of the main problems both for the occupants’ health and for energy consumption, especially during the summertime. It follows that, in order to decrease the problem, a global and synergistic approach is necessary to design energy efficient building envelopes. Another topic of the research, in line with the first one covered, has been conducted on studying cool materials to be applied to passive cooling techniques with the application of cool roof technique to the building facades. The aim of the study was to assess the benefits of those materials when applied to vertical envelopes instead of traditional outdoor coatings and evaluate their convenience in terms of costs-benefits-durability. These materials can contribute to exterior’s temperature reduction of the housing agglomeration thanks to a better energy balance of the surfaces, facilitating the mitigation of the urban heat island effect. Furthermore, resolutions to the problems concerning the energy improvement of our building heritage can be represented by the use of correct stratigraphy walls and the right placement of the insulating materials that respond to dynamic boundary conditions, especially in Mediterranean climate. The research project on cool materials involved a preliminary phase of the materials study, the formulation of the experimental paints and, at last, the mock up preparation on which to install the panels to be monitored over the summertime period. In summary, the problem of building energy upgrading in regard to summer insulation is focused on the main following topics: • thermal inertia and its relationship with the thermal insulation of the envelope over summertime period; • the study of materials and their experimentation in real conditions, or rather in a dynamic regime; • the experimental application of cool materials on external vertical walls in order to evaluate their beneficial impact on surface’s temperature.
47
Pourrahimi, Amir Masoud. "The synthesis, surface modification and use of metal-oxide nanoparticles in polyethylene for ultra-low transmission-loss HVDC cable insulation materials." Doctoral thesis, KTH, Polymera material, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190808.
Анотація:
Polyethylene composites which contain low concentrations of metal-oxide nanoparticles e.g. ZnO and MgO are emerging materials for the use in insulations of extruded high-voltage direct-current (HVDC) cables. The challenge in the development of the composites with ultra-low electrical conductivity is to synthesize uniform and high-purity metal-oxide nanoparticles, which are functionalized with hydrophobic groups in order to make them compatible with polyethylene. The thesis reports different approaches to prepare this new generation of insulation materials. Different reaction parameters/conditions – zinc salt precursor, precursor concentrations and reaction temperature – were varied in order to tailor the size and morphology of the ZnO nanoparticles. It was shown that different particle sizes and particle morphologies could be obtained by using different zinc salt precursors (acetate, nitrate, chloride or sulphate). It was shown that 60 °C was a suitable reaction temperature in order to yield particles with different morphologies ranging from nano-prisms to flower-shaped superstructures. For removal of reaction residuals from the particles surfaces, a novel cleaning method based on ultrasonication was developed, which was more efficient than traditional water-replacement cleaning. After cleaning, the presence of one atomic layer of zinc-hydroxy-salt complex (ZHS) on the nanoparticle surfaces was suggested by thermogravimetry and infrared spectroscopy. A method involving three steps – silane coating, heat treatment and silica layer etching – was used to remove the last trace of the ZHS species from the nanoparticle surface while preserving its clean and active hydroxylated surface. The surface chemistry of these nanoparticles was further tailored from hydroxyl groups to hydrophobic alkyl groups with different lengths by reactions involving methyltrimethoxysilane (C1), octyltriethoxysilane (C8) and octadecyltrimethoxysilane (C18). MgO nanoparticles were prepared by aqueous precipitation of Mg(OH)2 followed by a partial transformation to MgO nanoparticles via heat treatment at 400 °C. The surface regions of the MgO nanoparticles convert into a hydroxide phase in humid media. A novel method to obtain large surface area MgO nanoparticles with a remarkable inertness to humidity was also presented. The method involved three steps: (a) thermal decomposition of Mg(OH)2 at 400 °C; (b) silicone oxide coating of the nanoparticles to prevent inter-particle sintering and (c) a high temperature heat treatment at 1000 °C. These MgO nanoparticles showed essentially no sign of formed hydroxide phase even after extended exposure to humid air. The functionalized metal-oxide nanoparticles showed only a minor adsorption of phenolic antioxidant, which is important in order to obtain nanocomposites with an adequate long-term stability. Tensile testing and scanning electron microscopy revealed that the surface-modified metal-oxide nanoparticles showed improved dispersion and interfacial adhesion in the polyethylene matrix with reference to that of unmodified metal-oxide nanoparticles. The highly “efficient” interfacial surface area induced by these modified nanoparticles created the traps for charge carriers at the polymer/particle interface thus reducing the DC conductivity by more than 1 order of magnitude than that of the pristine polyethylene.Polyetenkompositer med mycket låga halter av ZnO och MgO metalloxid nanopartiklar är en växande kategori material för användning som isolering av extruderade kablar avsedda för likriktad högspänning. En utmaning i utvecklingen av dessa material kan relateras till den praktiska kompositframställningen, vilken innefattar framställning av högrena metalloxid nanopartiklar som ytmodifieras med hydrofoba molekylstrukturer för att möjliggöra blandning med den hydrofoba polyetenplasten. Denna avhandling behandlar olika metoder för att framställa denna generation av isoleringsmaterial. Vid syntesen av de rena nanopartiklarna krävdes optimering av ett antal olika reaktionsparametrar för att uppnå tillfredställande slutresultat i form av partikelstorlekar och partikelmorfologier. Dessa inkluderade val av zinksalt, zinksaltkoncentration vid utfällning, samt reaktionstemperatur vid framställningen. Experimenten avslöjade att olika partikelstorlekar och partikelmorfologier kunde framställas som endast korrelerat mot källan av zinkjonerna, och berodde av vilka motjoner som zinkatomerna haft i zinksaltet (acetat, nitrat, klorid eller sulfat). Optimering av reaktionstemperaturen visade att ca 60 °C utgjorde en lämplig start för utvärdering av synteserna, som resulterade i olika partikelmorfologier i form av pyramidformade nanopartiklar till blomformationer. Utöver de specifika reaktionsparametrarna utvecklades även en ny ultrasonikeringsmetod för att rena ytorna hos partiklarna från motjoner relaterade till de valda specifika salterna. Metodiken som visade sig avsevärt mer effektiv än sedvanlig rening att utfällda nanopartiklar via repetitivt vattenutbyte, och skapade förutsättningar etablering av kolloidal stabilitet och fragmentering av aggregat i vattensuspensionerna. Efter ultrasonikeringsreningen beräknades de kvarvarande zinkhydroxidsalterna (ZHS) utgöra endast ett atomlager ZHS utifrån termogravimetriska data kompletterade med infraröd spektroskopi. En metod att eliminera de kvarvarande ZHS-komplexen från ytan av partiklarna tillämpades/utvecklades, inkluderade ytbeläggning av partiklarna med silan, följt av värmebehandling samt etsning av den resulterande kiseloxidytan, för att uppnå en ren hydroxylyta på partiklarna. Ytkemin hos dessa partiklar modifierades från att bestå av hydroxylgrupper till att utgöras av hydrofoba alkylgrupper med olika längder relaterade metyltrimetoxysilan (C1), oktyltrietoxysilan (C8), eller oktadekyltrimetoxysilan (C18). Även MgO nanopartiklar framställdes via vattenutfällning av Mg(OH)2 partiklar, vilka omvandlades till MgO nanopartiklar via en lågtemperatur värmebehandling vid 400°C. Ytan av dessa partiklar omvandlades dock till hydroxid i fuktig miljö. En ny metod att bibehålla den stora ytarean av MgO nanopartiklarna med anmärkningsvärd motståndskraft mot att omvandlas till hydroxid utvecklades således. Metoden består av (a) en låg temperatur omvandling av Mg(OH)2, (b) en kiseloxidytbehandling av nanopartiklarna för att undvika partikelsintring vid högre temperaturer och (c) en hög temperaturbehandling vid 1000 °C. De framställda partiklarna uppvisade ingen anmärkningsvärd känslighet mot luftfuktighet och bibehöll MgO sammansättningen efter exponering mot fukt. De modifierade metalloxid nanopartiklarna visade mycket liten adsorption av fenoliska antioxidanter, vilket medförde en långtidsstabilitet hos polyeten nanokompositerna. De ytmodifierade metalloxidpartiklarna visade även förbättrade möjligheter för dispergering och yt-kompatibilitet med/i polyetenmatrisen i jämförelse med omodifierade metalloxidpartiklar, utifrån mätningar baserade på dragprovning och svepelektronmikroskopi. Slutligen, de utvecklade ytorna på de modifierade nanopartiklarna skapade ett polymer/nanopartikel gränssnitt som kunder fungera som laddningsansamlingsområden i nanokompositerna, vilket resulterade i en storleksordning minskad ledningsförmåga hos kompositerna jämfört med den rena polyetenen.
QC 20160829
48
Guéroult, Bertrand. "Influence de la microstructure sur la resistance a l'usure des ceramiques : etude de traitements post-frittage et developpement d'un essai de rayage." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0094.
Анотація:
On a cherche a mettre en evidence les differents effets de la microstructure et des proprietes intrinseques des materiaux etudies (al::(2)o::(3), sic, sialon) sur les mecanismes d'enlevement de matiere lors de l'usure par frottement a sec. Des modifications microstructurales ou morphologiques ont ete tentees par divers traitements de frittage ou de post-frittage. En particulier, on a etudie les effets du pressage isostatique chaud et de l'implantation ionique sur les proprietes mecaniques et tribologiques du sialon fritte. On a developpe un essai de rayage pour remplacer les essais d'indentation mal adaptes du fait du role joue par les debris d'usure consideres comme un troisieme corps. On a etudie les mecanismes creant ces debris ou les faisant evoluer. Il apparait que le rayage et l'usure des ceramiques, deux phenomenes lies a la creation de debris (avec ou sans circulation), doivent etre consideres comme faisant appel principalement au caractere plastique de debris agglomeres
49
Bravenec, David. "Diagnostika a návrh eliminace tepelných mostů budov." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265536.
Анотація:
This thesis presents a comparison of building materials for vertical bearing structures of buildings, thermal insulation materials and mutual combination of structural materials and insulators. Furthermore, there are possibilities for solving the most common insulation thermal bridges construction. The paper evaluated the pros and cons of different combinations of building materials. Teplo and Area programs were used for the calculations.
50
Kinkelin, Christophe. "Etude expérimentale d’un amortisseur thermique composite MCP-NTC." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI100/document.
Анотація:
L’amortisseur thermique étudié dans le cadre de cette thèse a pour objectif de limiter les pics de température des composants électroniques fonctionnant en régime transitoire au moyen d’une structure composite consistant en un réseau de nanotubes de carbone (NTC) rempli de matériau à changement de phase (MCP) solide-liquide, le tout étant contenu dans un boîtier en silicium (Si). Ce système passif vise à augmenter l’inertie thermique volumique du composant grâce à la chaleur latente du MCP tout en maintenant une bonne conductance thermique grâce aux NTC. Un dispositif expérimental polyvalent a été développé spécifiquement pour caractériser les différentes générations d’échantillons fabriqués par les partenaires du projet THERMA3D. L’excitation thermique de l’échantillon est réalisée au moyen d’un laser en face amont et la réponse thermique est mesurée par caméra infrarouge simultanément sur les faces amont et aval. L’application d’une peinture sélectionnée sur l’échantillon permet d’accéder à sa température après un étalonnage dédié. Des méthodes d’estimation de paramètres ont été développées pour quantifier les deux caractéristiques essentielles de l’amortisseur thermique que sont sa capacité de stockage thermique et sa résistance thermique. Les sensibilités de la résistance thermique aux caractéristiques de la connexion Si/NTC et à la longueur des NTC ont été étudiées et les résistances thermiques d’interface Si/NTC ont été identifiées comme dominantes au sein du système. Des essais de cyclage thermique ont permis d’évaluer la fiabilité de l’ensemble de manière accélérée. Le comportement du MCP et la qualité du matériau de scellement ont été analysés par voie optique. Par ailleurs, la plus élevée des deux résistances thermiques d’interface Si/NTC a été localisée grâce à la visualisation infrarouge du réseau de NTC à travers le silicium semi-transparent. Enfin, une méthode de contrôle non destructif de la qualité de l’interface Si/NTC a été développée pour les amortisseurs thermiques de dernière générationThe purpose of the studied thermal damper is to smooth the temperature peaks of transient electronic components via a composite structure consisting of an array of carbon nanotubes (CNT) filled with solid-liquid phase change material (PCM), the whole being embedded in a silicon (Si) casing. This passive system is intended to increase the thermal inertia per unit of volume of the electronic component thanks to the latent heat of the PCM while maintaining a high thermal conductance thanks to the CNT. A versatile test bench was specifically developed in order to characterize the different generations of samples fabricated by the partners of the THERMA3D project. The thermal excitation of the front side of the sample is generated by a laser and the thermal response is measured simultaneously on the front and back sides by an infrared camera. A selected paint can be deposited on the sample in order to access its temperature by means of a dedicated calibration. Parameter estimation methods were developed in order to quantify both main characteristics of the thermal damper: its heat storage capacity and its thermal resistance. The sensitivities of the thermal resistance to the features of the Si/CNT connection and to the length of the CNT were studied and it was found out that the interfacial thermal resistances Si/CNT are dominant in the system. Thermal cycling tests enabled to assess the reliability of the thermal damper in an accelerated manner. The behavior of the PCM and the quality of the sealing material were optically analyzed. Besides, the infrared visualization of the CNT array through the semi-transparent silicon enabled to identify the highest of both Si/CNT interfacial thermal resistances. Finally, a non-destructive testing method for the evaluation of the quality of Si/CNT interfaces was developed for the latest generation of thermal dampers