Dissertations / Theses: 'Till characterization'

1

Prvanovic, Aleksandar. "Influence of Soil Joints on Permeability of Glacial Till." Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1428615878.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Larsson, Anna. "Karaktärisering av morän i Aitikgruvan för användning vid efterbehandling av gråberg." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-153685.

Full text

Abstract:

The Aitik Mine is the largest copper mine in Europe and every year, 15 – 20 Mt waste rock is deposited in dumps located close to the mine. This waste rock can contain sulfides, which if exposed to oxygen can cause leeching and formation of acid rock drainage. To prevent this from happening, Boliden has designed a dry cover system to prevent leaching from occurring. The purpose of this study was to characterize existing stockpiles of till at Boliden’s Aitik Mine site in the context of requirements for the closure cover system. The till was evaluated primarily of its suitability for use in a highly compacted layer (HCL), since Boliden has a cover system design that has to provide the necessary control on oxygen diffusion rates to underlying waste rock material over the long term. The sampling took place on three of the stockpiles and a total of 31 test pits were excavated. A total of 27 samples of soil were collected and analyzed for particle size distribution (PSD) testing. Following review of PSD results, select samples were tested for hydraulic conductivity and compaction testing. The PSD results showed that all materials were fine-grained sand with some gravel, cobbles and silt. Results also show the amount of clay particles (0,004 mm) were relatively low across the three stockpiles. The result for the hydraulic conductivity were higher than Boliden’s prescriptive criteria. The results indicate that the sampled till would require addition of sodium bentonite to be able to construct a HCL with a hydraulic conductivity not exceeding Boliden’s criteria.

APA, Harvard, Vancouver, ISO, and other styles

3

Collins, Alyssa A. "Characterization of disease reduction by cover crops in a no-till pumpkin production system." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.46 Mb., p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3220741.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Steward, Genevieve Christine. "Diffuse reflectance spectroscopy for the characterization of calcareous glacial till soils from North Central Montana." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/steward/StewardG1206.pdf.

Full text

Abstract:

Diffuse reflective spectroscopy (DRS) is a method of soil carbon (C) quantification. In this study, the Vis-NIR (350-2500 nm) and MIR (2500-25000 nm) regions were evaluated to determine respective predictive accuracies of soil organic and inorganic carbon (SOC and SIC, respectively). The dataset included 315 soil samples of glacial till origin, obtained from six independent farm sites within the Golden Triangle region of Montana, with depths ranging from 0-100 cm. For Vis-NIR analysis, Local vs. Regional vs. Global calibration sets were compared by six-fold cross validation by site of C predictions developed by Partial Least Squares (PLS) regression and Boosted Regression Trees (BRT). First derivative spectral data was used along with four preparation methods: (i) field moist and (ii) dry cores, (iii) 2-mm sieved ("Sieved") and (iv) milled samples (<200-Âµm, "Milled") were used to evaluate the potential application to in-situ analysis. The most accurate SOC predictions were from Milled samples using a Local calibration set. SOC predictions were a result of SOM electronic absorptions within the visible region. The most accurate SIC predictions were from Sieved samples with a Local calibration set. Within the MIR analysis, spectral transformations, KBr dilution and Regional vs. Local calibrations were evaluated using the same independent validation procedure of PLS calibrations. Spectral transformations included: absorbance (AB), first derivative (D) and Kubelka-Munk (KM) from samples prepared both with and without KBr dilution. The most accurate SOC predictions were obtained from models developed with the D transformation of Local spectral data. SOC predictions were a result of SOM, clay and carbonate absorptions. The most accurate SIC prediction was from the KM transformation of Local spectral data. KBr diluted samples gave comparable regional predictive accuracy to neat samples. Specular reflection was found in neat sample spectral signatures; with Local core addition, neat samples built more accurate prediction models despite these distortions. In the end, it was determined that the MIR region provides more accurate predictions of soil C for calcareous glacial till soils of north central Montana. But, the Vis-NIR region presents an accurate method while existing as the less expensive and more efficient route.

APA, Harvard, Vancouver, ISO, and other styles

5

Malmström, Martin. "Tillbaka till texten : derivativt skrivande i en svensk gymnasieklass." Licentiate thesis, Malmö högskola, Institutionen för kultur, språk och medier (KSM), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-7622.

Full text

Abstract:

This licentiate thesis investigates fiction writing and reading in up- per secondary school in Sweden. Inspired by fanfiction I created a teaching project of derivative writing in which the students in a se- cond-year social science class wrote short stories derived from 20th century novels. They also gave peer response, both orally and in writing. Finally they wrote a reflective text about the project. The main purpose of the study is to describe and analyse the teaching project. The primary material is the students’ short sto- ries. Drawing from theories of intertextuality, most notably Genette’s transtextuality theory and fanfiction theories, I analyse how the students make use of the source text. Theories of narratology have been used to analyse techniques of storytelling, mainly characterization and focalization. In the analysis of the stu- dents’ written comments on each other’s texts I draw from re- sponse theories. The results show that the students tend to stay close to the source texts. The most common subgenre is refocalization, that is to change the perspective to one of the secondary characters’ view. Refocalization seems to be an efficient way of deepening the under- standing of the main character of the source text; in many of the students’ stories the protagonist functions as the focalized object. Which novel the students read plays an important part in how fo- calization is expressed, however. Short stories based on novels with complex focalization tend to be focalized in a variety of ways whereas stories based on novels with fixed focalization mostly fol- low the pattern of the source text. Reading the short stories and, not least, the reflective texts it becomes evident that the characters are extremely important in this kind of literature, more so than semiotic theories of characters have acknowledged; the characters are more than merely functions. In the chapter about peer response I argue that many students write analyses of the text they are about to respond to rather than give advice about how to proceed. It is difficult to see if the response is of any help to the writer. Thus, I question whether peer response has any other effect than strength- ening the social bonds between the group members. The study shows that creative writing could very well be an in- tegral part of the education in Swedish in upper secondary school. Derivative writing may function as an alternative to traditional lit- erary analyses. Refocalizing is a way of seeing the story from a dif- ferent viewpoint, which could enhance the students’ sense of empa- thy. Questions of focalization might also lead to discussions of power. Furthermore, creative writing may make the students more attentive as writers. In the new syllabus Gy 11, however, the op- portunities for working with creative writing are, unfortunately, limited.

APA, Harvard, Vancouver, ISO, and other styles

6

Wallrabenstein, Till [Verfasser]. "Clinical characterization and prognostic impact of SF3B1 and TP53 gene mutations in myelodysplastic syndromes / Till Wallrabenstein." Ulm : Universität Ulm, 2018. http://d-nb.info/1172351635/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Lesker, Till Robin [Verfasser]. "Molecular characterization of clover and dill infecting cryptic viruses : detection, protein interactions and evolutionary relationships / Till Robin Lesker." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://d-nb.info/1063981751/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Lesker, Till [Verfasser]. "Molecular characterization of clover and dill infecting cryptic viruses : detection, protein interactions and evolutionary relationships / Till Robin Lesker." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://nbn-resolving.de/urn:nbn:de:gbv:089-7884270243.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Bruhn, Cecilia. "Production and Characterization of Scintillating CaWO$_4$ Single Crystals for Rare Event Searches CaWO$_4$ är latex kodning för att få till den kemiska formeln." Thesis, KTH, Fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168012.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Dai, Shao-Bo [Verfasser], Kai [Akademischer Betreuer] Tittmann, Ralf [Gutachter] Ficner, and Till [Gutachter] Ischebeck. "Mechanistic and Structural Characterization of Thiamine Diphosphate Dependent Enzyme Transketolases from Human and E.coli / Shao-Bo Dai ; Gutachter: Ralf Ficner, Till Ischebeck ; Betreuer: Kai Tittmann." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://d-nb.info/1160753520/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Ekholm, Marika. "Från barnbok till värdegrund -En motivstudie om huruvida en populär skönlitterär barnbok, Handbok för superhjältar- del 6:Utan hopp, kan bidra med grund för värdegrundsarbete i årskurs F-3." Thesis, Örebro universitet, Institutionen för humaniora, utbildnings- och samhällsvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-92504.

Full text

Abstract:

The purpose of this study is to analyze a children’s book to examine if it is a useful tool for teachers to use while working with the set values that the Swedish curriculum deems central to education. In order to create such a tool, a survey was made to ascertain what books are currently popular among Swedish children in the age range of 6-9, and the using indirect characterization and the literary concepts of theme and motif as a method, the goal has been to determine whether this book is suitable for working with questions that are related to the aforementioned values.The result showed that the chosen book, Guide for superheroes- part 6: Without hope, (2021) by Elias and Agnes Våhlund contained all of the five values that the Swedish curriculum deems central to education. The results, then, indicate that this book is a suitable tool to use while working with values in the classroom. However, this survey only analyzes the book as a tool and not how to use it in the education. The effectiveness of any tool is also dependent on how the teacher are using it, which I do not include in this study.

APA, Harvard, Vancouver, ISO, and other styles

12

Müller, Daniel [Verfasser], Till [Akademischer Betreuer] Marquardt, Thomas [Akademischer Betreuer] Pieler, and Andreas [Akademischer Betreuer] Wodarz. "Identification and characterization of molecular mechanisms driving the functional specification of motor neurons : the Delta like homolog 1 protein / Daniel Müller. Gutachter: Thomas Pieler ; Andreas Wodarz. Betreuer: Till Marquardt." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://d-nb.info/1042305420/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Revelo, Nuncira Natalia Hasel Verfasser], Silvio [Akademischer Betreuer] Rizzoli, Mikael [Akademischer Betreuer] Simons, Tobias [Akademischer Betreuer] [Moser, Till [Akademischer Betreuer] Marquardt, André [Akademischer Betreuer] Fiala, and Michael [Akademischer Betreuer] Hörner. "A novel membrane-binding probe for the morphological and molecular characterization of synaptic vesicle recycling pathways / Natalia Hasel Revelo Nuncira. Gutachter: Mikael Simons ; Tobias Moser ; Till Marquardt ; André Fiala ; Michael Hörner. Betreuer: Silvio Rizzoli." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1070996084/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Goldberg, Eli Aaron. "Archaeometric Characterization of Roman Tile Fabrics from the Sangro Valley, Italy." Oberlin College Honors Theses / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1337712720.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Lai, Justin Yi-Shen. "Design and characterization of a planar mechanism for passive tilt-compensation." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/62993.

Full text

Abstract:

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 81-83).
This work investigated the design and testing of a planar mechanism for passively compensating tilt between two flat surfaces brought into close proximity. The proposed design uses flexural components which eliminate friction and ensure smooth motion. To achieve this alignment in one of the two surfaces, two heights were fixed. The first height was fixed by a preload from a micrometer head. The second height was fixed by the clamping of a post. This was achieved by using a variation of an existing in-plane clamp design. After the post was clamped, the alignment from the conformal contact of the two surfaces was fixed. An error analysis is presented to estimate the uncertainty in the alignment. For experimentally characterizing the tilt error, capacitance probes were used to measure the alignment errors. It was found that the maximum uncertainty in the alignment was on the order of 50 [mu]rad, making this design suitable for micro-scale planar alignment applications.
by Justin Yi-Shen Lai.
S.B.

APA, Harvard, Vancouver, ISO, and other styles

16

Gu, Xun. "Measuring Ultracomplex Supercontinuum Pulses and Spatio-Temporal Distortions." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5082.

Full text

Abstract:

This thesis contains two components of research: studies of supercontinuum pulses generated in the novel microstructure fiber, and research on spatio-temporal coupling in ultrafast laser beams. One of the most exciting developments in optics in recent years has been the invention of the microstructure optical fiber. By controlling the structural parameters of these novel fibers in design and manufacturing, their dispersion profile can be freely tailored, opening up a huge application base. One particularly interesting effect in the microstructure fiber is the generation of ultrabroadband supercontinuum with only nJ-level Ti:sapphire oscillator pulse pump. This supercontinuum is arguably the most complicated ultrafast pulse ever generated, with its huge time-bandwidth product (> 1000 from a 16-cm-long fiber). Although many applications have been demonstrated or envisioned with this continuum, its generation is a very complicated process that is poorly understood, and the characteristics of the continuum pulses are not clearly known. In this work, we make a full-intensity-and-phase measurement of the continuum pulses using cross-correlation frequency-resolved optical gating (XFROG). The results reveal surprising unstable fine spectral structure in the continuum pulses, which is confirmed by single-shot measurements. Our study on the coherence of the continuum, on the other hand, shows that the spectral phase of the supercontinuum is fairly stable. Numerical simulations are carried out whose results are in good agreement with experiments. The second component of this thesis is the study of spatio-temporal coupling in ultrafast beams. We propose two definitions of spatial chirp, point out their respective physical meanings, and derive their relationship. On the common perception of the equivalence between pulse-front tilt and angular dispersion, we show that the equivalence only holds for plane waves. We establish a generalized theory of ultrafast laser beams with first-order spatio-temporal couplings, and discover a new pulse-front tilt effect associated with the combination of spatial chirp and temporal chirp. For the measurement of spatio-temporal distortions, the effects of such distortions in the input beam to a GRENOUILLE trace are carefully studied. An algorithm is proposed and tested to retrieve information about the distortions from the GRENOUILLE trace.

APA, Harvard, Vancouver, ISO, and other styles

17

FREITAS, Yuri Menezes. "Azulejos portugueses dos séculos XVII e XVIII em Pernambuco: patologias e caracterização tecnológica." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17279.

Full text

Abstract:

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-07T13:55:08Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Azulejos Portugueses dos Séculos XVII e XVIII em Pernambuco - Patologias e Caracterização Tecnológica. BDTD.pdf: 10379660 bytes, checksum: 1f03ff2520483b344dcdce49c9ef1fc2 (MD5)
Made available in DSpace on 2016-07-07T13:55:08Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Azulejos Portugueses dos Séculos XVII e XVIII em Pernambuco - Patologias e Caracterização Tecnológica. BDTD.pdf: 10379660 bytes, checksum: 1f03ff2520483b344dcdce49c9ef1fc2 (MD5) Previous issue date: 2015-08-27
CNPq
Em Pernambuco, azulejos portugueses dos séculos XVII e XVIII estão presentes em vinte edificações religiosas. Neste período, em Portugal, houve modificações na organização produtiva dos azulejos, objetivando adaptar-se às demandas de épocas distintas. Esta pesquisa busca compreender se tais modificações promoveram variações na caracterização tecnológica destes azulejos históricos. Foi realizado o levantamento de danos dos azulejos deste período, constatando-se uma baixa qualidade das peças pertencentes à primeira metade do século XVIII, em consequência da alta demanda existente. Os azulejos desta fase são os mais abundantes e apresentam os mais elevados índices de patologias, quando comparados às duas outras fases azulejares. Além da caracterização tecnológica através do levantamento de danos, amostras de azulejos setecentistas foram submetidos às análises química e mineralógica. Os ensaios de caracterização física são destrutíveis, e como as peças históricas não podem ser mutiladas, realizou-se a reprodução tecnológica do corpo cerâmico destas peças, com base na composição identificada através das análises e utilizando-se de técnicas da manufatura tradicional. A caracterização da tecnologia dos azulejos históricos realizada neste trabalho reforça os estudos no âmbito do conhecimento técnico do azulejo, fornecendo subsídios para profissionais da área de conservação do patrimônio material possam intervir com materiais e métodos adequados, preservando assim este bem cultural.
In Pernambuco, there are Portuguese tiles from the seventeenth and eighteenth centuries in twenty religious buildings. During this period, in Portugal, to meet the demands of different times, there were changes in the production process of these tiles. This research seeks the understanding of whether such changes cause variations in technological characterization of these historical tiles. A field research was conducted to analyze the damage in these Portuguese tiles, and there was noted that there is a low quality of parts belonging to the first half of the eighteenth century, because of the high demand existent in that period. The tiles of this period are the majority, and have the highest rates of damage compared to tiles from other two periods. Besides the technological characterization obtained through the field research, samples of these eighteenth-century tiles were submitted to chemical and mineralogical analyzes. Physical characterization tests are destructible and, as historical items cannot be damaged, a reproduction of the ceramic body of these parts had been performed, based on the identification of its composition and manufacturing techniques. The characterization of the technology of the historical tiles performed in this work reinforces the studies regarding the specialized knowledge of historical tiles, providing support to professionals of specialized areas to intervene with appropriate materials and methods, thus preserving this cultural asset.

APA, Harvard, Vancouver, ISO, and other styles

18

Edwards, Clinton Lee. "On the pointing and jitter characterization of MEMS two-axis (tip-tilt) mirrors." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7616.

Full text

Abstract:

Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

APA, Harvard, Vancouver, ISO, and other styles

19

Ozer, Muhammed Said. "Production And Characterization Of Magnesium Oxychloride Cement Based Polishing Bricks For Polishing Of Ceramic Tiles." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610266/index.pdf.

Full text

Abstract:

Magnesium oxychloride cement (MOC) based grinding and polishing bricks developed for polishing of granite based ceramic tiles were produced and characterized. For surface grinding 46 and 180 grit size SiO2 powder embedded MOC based abrasive bricks
for polishing 600 and 1200 grit size SiC powder embedded MOC based abrasive bricks followed by neat (unreinforced) MOC pastes were applied on ceramic tiles. Three different neat MOC pastes depending on MgO/MgCl2 molar ratio in the paste e.g. 6/1, 7/1, and 8/1, were formed and evaluated. Grinding bricks were formed by adding 30 weight percentage, wt%, of both SiO2 powders. Polishing bricks were formed by adding 20, 25, and 30 wt% of both SiC powders. X-Ray diffraction analyses revealed that MOC F5 was the main crystalline phase in the neat MOC pastes. Additions of both SiO2 and SiC powders enhanced mechanical properties namely
compressive strength and abrasion resistance, chemical durability in water and polishing ability of MOC paste. More than 25 wt% addition of SiC powders had a tendency to decrease the compressive strength and water resistance of MOC paste. Polishing performance of abrasive bricks was evaluated in terms of mean surface roughness of ceramic tiles and abrasive brick consumption upon polishing. Scanning Electron Microscope examinations revealed the evidences of the reasons that 25 wt% SiC powder embedded abrasive bricks has the best qualifications in terms of abrasion resistance and polishing performance.

APA, Harvard, Vancouver, ISO, and other styles

20

Morrow, Benjamin M. "Characterization and Modeling of Creep Mechanisms in Zircaloy-4." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1307372079.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Fleckenstein, Tilly Thea [Verfasser], Johannes [Akademischer Betreuer] Buchner, and Michael [Akademischer Betreuer] Groll. "Sip1, a Unique Small Heat Shock Protein of the Nematode Caenorhabditis elegans : a Structural and Functional Characterization / Tilly Thea Fleckenstein. Betreuer: Johannes Buchner. Gutachter: Michael Groll ; Johannes Buchner." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1079001840/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

"Thermal Interface Material Characterization Under Thermo-mechanical Stress of Induced Angle of Tilt." Master's thesis, 2011. http://hdl.handle.net/2286/R.I.14293.

Full text

Abstract:

abstract: Thermal interface materials (TIMs) are extensively used in thermal management applications especially in the microelectronics industry. With the advancement in microprocessors design and speed, the thermal management is becoming more complex. With these advancements in microelectronics, there have been parallel advancements in thermal interface materials. Given the vast number of available TIM types, selection of the material for each specific application is crucial. Most of the metrologies currently available on the market are designed to qualify TIMs between two perfectly flat surfaces, mimicking an ideal scenario. However, in realistic applications parallel surfaces may not be the case. In this study, a unique characterization method is proposed to address the need for TIMs characterization between non-parallel surfaces. Two different metrologies are custom-designed and built to measure the impact of tilt angle on the performance of TIMs. The first metrology, Angular TIM Tester, is based on the ASTM D5470 standard with flexibility to perform characterization of the sample under induced tilt angle of the rods. The second metrology, Bare Die Tilting Metrology, is designed to validate the performance of TIM under induced tilt angle between the bare die and the cooling solution in an "in-situ" package testing format. Several types of off-the-shelf thermal interface materials were tested and the results are outlined in the study. Data were collected using both metrologies for all selected materials. It was found that small tilt angles, up to 0.6°, have an impact on thermal resistance of all materials especially for in-situ testing. In addition, resistance change between 0° and the selected tilt angle was found to be in close agreement between the two metrologies for paste-based materials and phase-change material. However, a clear difference in the thermal performance of the tested materials was observed between the two metrologies for the gap filler materials.
Dissertation/Thesis
M.S. Mechanical Engineering 2011

APA, Harvard, Vancouver, ISO, and other styles

23

周鵬程. "Characterization and design guidelines of submicron LATID (LArge Tilt-angle Implanted Drain) MOS devices." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/15526742661171195197.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Chiang, Che-Hung, and 江哲宏. "A Characterization of TiAl Intermetallic Compound and its Brazing with Magnesium Using Non-silver Filler Metal." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/39113852623292251031.

Full text

Abstract:

碩士
國立高雄應用科技大學
模具工程系
98
Ti-Al intermetallic compounds are getting popular due to their high temperature strength, low specific weight and anti-oxidation. The Brazing of Ti-Al intermetallic compounds and light metals such as magnesium and titanium is applied for sport goods on other assembles. This study is to manufacture the Ti-Al intermetallic compounds by vacuum induction melting under controlling the addition of niobium element, and then braze the magnesium metals using the filler metals of non-silver Mg-37.6Sn alloys. The hardness testing and shear testing are used to evaluate the hardness of Ti-Al intermetallic compounds and the shear strength after brazing Ti-Al intermetallic compound and magnesium metals, respectively. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to analyze the microstructures. The results show that the more niobium elements can make the dendrite structure and γ (TiAl) phase to have finer grains in as-casted Ti-Al intermetallic compounds and induce more eutectic structures of α2+γ after homogenizing of Ti-Al intermetallic compounds. In addition, the hardness of Ti-Al intermetallic compounds increase with niobium contents. The magnesium and tin elements diffuse more easily to magnesium metals than Ti-Al intermetallic compounds due to the lower activation energy of diffusion constant. The shear testing also indicate that the 2%Nb containing Ti-Al intermetallic compounds are brazed with magnesium metals have more shear strength, which show the elongated grains after shear in fractographs, while the 3%Nb containing Ti-Al intermetallic compounds brazed with magnesium see to have lowest shear strength because of the non-deformable fracture modes.

APA, Harvard, Vancouver, ISO, and other styles

25

Lin, Yu-Chiao, and 林雨樵. "Characterization of GaN grown on tilt-cut γ-LiAlO 2 by molecular beam epitaxy for different growth temperatures." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/3b88hc.

Full text

Abstract:

碩士
國立中山大學
物理學系研究所
99
We study the properties of m-plane GaN structure on LiAlO 2 substrate grown by plasma-assisted molecular-beam epitaxy (PAMBE). Lattice parameters of LiAlO 2 are close to GaN, the interface between LiAlO 2 and GaN showed a good lattice matching. Low lattice mismatch can reduce the defect generation, improve crystal quality. However, lattice mismatch still exist, more or less density of defect still can be observed. The density of defect was reduced in the sample at high temperature. In this study, we investigate GaN on LiAlO 2 by scanning electron microscope (SEM), atomic force microscope (AFM), photoluminescence (PL) and X-ray diffraction (XRD) for different growth temperatures.

APA, Harvard, Vancouver, ISO, and other styles

26

Llanos, Princess Stephanie. "Characterization of industrial made TiAlN, TiAlCN and TiAlN/TiAlCN coatings used for machining of Ti6Al4V aerospace alloy." Master's thesis, 2021. http://hdl.handle.net/10316/95529.

Full text

Abstract:

Dissertação de Mestrado Conjunto Europeu em Tribologia de Superficies e Interfaces apresentada à Faculdade de Ciências e Tecnologia
A investigação e desenvolvimento de ligas de titânio tem vindo a ser alvo de estudo durante as últimas décadas devido às suas superiors propriedades físicas, químicas e mecânicas quando comparado com outros ligas. No entanto, o fabrico de components em ligas de titânio é mais caro e requer mais tempo de processamento em comparação com outros metais devido à sua grande dificuldade de maquinar. Uma das principais soluções atualmente usadas para melhorar a maquinação das ligas de titânio é a aplicação de revestimentos na superficie das ferramentas de corte, que por um lado permitem aumentar a vida de ferramenta de corte e por outro melhorar a qualidade da superfície maquinada. Nesta tese, revestimentos industriais depositados em monocamada (TiAlN, TiAlCN) e em multicamada (TiAlN/TiAlCN) foram caracterizados relativamente a diferentes propriedades para determiner quais dos revestimentoa apresentam o melhor compromisso entre propriedades. Os revestimentos depositados foram caracterizados quanto à sua composição química, estrutura, morfologia, resistência à oxidação, estabilidade térmica, propriedades mecânicas e comportamento tribológico à temperatura ambiente. Como esperado os revestimentos apresentam diferentes composições químicas de Ti, Al, N e C devido à diferente composição dos alvos usados e potência aplicadas aos alvos durante a deposição. Todos os revestimentos apresentam uma estrutura fcc. A morfologia dos revestimentos em secção transversal exibem um crescimento columnar, onde o revestimento TiAlN apresenta uma morfologia mas densa do ques os outros revestimentos. O ponto de início de oxidação dos revestimentos é dependente da composição química dos revestimentos: ~900°C, ~850°C e ~800°C para os revestimentos TiAlN, TiAlCN e TiAlN/TiAlCN, respectivamente. Os testes isotérmicos realizados às amostras a 900°C durante 2 h aos revestimentos, promoveram a total oxidação dis revestimentos TiAlCN e TiAlN/TiAlCN, enquanto que o revestimento TiAlN foi apenas parcialmente oxidado. A notável resistência à oxidação do revestimento TiAlN deve-se à formação de uma camada continua e protetora de Al2O3 no topo da camada de óxido. A formação dessa fase foi identificada por difração de raios-x analyses SEM. O revestimento TiAlN/TiAlCN apresentou os maiores valores de dureza – 38 GPa e modulo de elastecidade – 363 GPa, entre os diferentes revestimentos. Após o recozimento, o revestimento TiAlN exibiu um grande aumento de dureza devido ao aumento da sua cristalinidade. Nos testes tribológicos, o coeficiente de atrito, a profundidade de desgaste e a taxa especifica de desgaste corroboram os resultados de dureza e tenacidade. As pistas de desgaste exibem um mecanismo de abrasão, caracterizadas pela presença de ranhuras e detritos. O revestiemnto TiAlN/TiAlCN apresentou o melhor desempenho tribológico devido à combinação de alta dureza e alta tenacidade à fratura em comparação coms outros revestimentos.
The research and development on titanium alloys have been nourishing for quite some time due to their superior physical, chemical and mechanical properties. However, manufacturing titanium is more expensive and requires longer time compared with other metals due to its poor machinability. One of the leading solutions to address the difficulty in machining titanium is to deposit coating on the cutting tools in order lengthen the service lifetime and ensure good quality of machined surface. In this study, industrial made monolithic TiAlN, monolithic TiAlCN and multilayered TiAlN/TiAlCN coatings were thoroughly characterized to determine which coating displayed the best combination of properties. The deposited coatings were fully characterized for their chemical composition, structure and morphology, oxidation resistance, thermal stability, mechanical properties and tribological performance at room temperature. The coatings reported different chemical composition of Ti, Al, N and C due to the different targets, chemical composition and power applied to the target during deposition. All films displayed a fcc NaCl type structure. The SEM micrographs of the cross-section and surface morphology of the as-deposited coatings exhibited a columnar growth with TiAlN showing the densest structure. The onset point of oxidation was measured to be ~900°C, ~850°C and ~800°C for TiAlN, TiAlCN and TiAlN/TiAlCN, respectively. After the isothermal test at 900°C for 2 h, TiAlCN and TiAlN/TiAlCN were fully oxidized while a huge portion of the TiAlN coating still exists. The remarkable oxidation resistance of the latter coating was driven by the formation of a continuous and protective oxide scale Al2O3 on top of the oxide layer. The presence of this oxide scale was confirmed by XRD, SEM micrograph and elemental map distribution. The as-deposited TiAlN/TiAlCN reported the highest H and E values at 38 GPa and 363 GPa, respectively. Upon annealing, TiAlN exhibited a huge increase in hardness due to increase in crystallinity. In the tribological tests, the coefficient of friction, wear depth and wear rate corroborate the hardness and toughness results of the coatings. The wear track exhibit abrasion mechanism which is characterized by grooves and scratches and the presence of wear debris in fish-like form. The multilayered TiAlN/TiAlCN showed the best tribological performance due to the combination of high hardness and high fracture toughness compared to the monolithic TiAlN and TiAlCN coatings.
Outro - Project MCTool21 - POCI-01-0247-FEDER-045940

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Till characterization'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles