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1
Dawson, Ty Grant. "Machining hardened steel with polycrystalline cubic boron nitride cutting tools." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17787.
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Abrão, Alexandre Mendes. "The machining of annealed and hardened steels using advanced ceramic cutting tools." Thesis, University of Birmingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249408.
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Cook, Grant O. III. "Joining Polycrystalline Cubic Boron Nitride and Tungsten Carbide by Partial Transient Liquid Phase Bonding." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2366.
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Friction stir welding (FSW) of steel is often performed with an insert made of polycrystalline cubic boron nitride (PCBN). Specifically, MS80 is a grade of PCBN made by Smith MegaDiamond that has been optimized for the FSW process. The PCBN insert is attached to a tungsten carbide (WC) shank by a compression fitting. However, FSW tools manufactured by this method inevitably fail by fracture in the PCBN. Permanently bonding PCBN to WC would likely solve the fracturing problem and increase the life of PCBN FSW tools to be economically viable. Partial transient liquid phase (PTLP) bonding, a process used to join ceramics with thin metallic interlayers, was proposed as a method to permanently bond PCBN to WC. PTLP bonding is often performed using three layers of pure elements. On heating, the two thin outer interlayers melt and bond to the ceramics. Concurrently, these liquid layers diffuse into the thicker refractory core until solidification has occurred isothermally. A procedure was developed to reduce the number of possible three-layer PTLP bonding setups to a small set of ideal setups using logical filters. Steps in this filtering method include a database of all existing binary systems, sessile drop testing of 20 elements, and a routine that calculates maximum interlayer thicknesses. Results of sessile drop testing showed that the PCBN grade required for this research could only be bonded with an alloy of Ti, Cu, Mg, and Sb. Two PTLP bond setups were tested using this special coating on the PCBN, but a successful bond could not be achieved. However, a PTLP bond of WC to WC was successful and proved the usefulness of the filtering procedure for determining PTLP bond setups. This filtering procedure is then set forth in generalized terms that can be used to PTLP bond any material. Also, recommendations for future research to bond this grade of PCBN, or some other grade, to WC are presented.
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Ng, Eu-Gene. "Modelling of the cutting process when machining hardened steel with polycrystalline cubic boron nitride(PCBN)tooling." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511485.
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Al-Watban, Ali. "The application of the soft impression technique to evaluate flow stress, creep and frictional deformation of polycrystalline diamond and cubic boron nitride." Thesis, University of Hull, 1996. http://hydra.hull.ac.uk/resources/hull:8054.
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Metal shaping processes are clear examples of engineering applications where a hard material is worn by a softer one - i.e. the tool and workpiece respectively. The soft impressor technique, introduced by Brookes and Green (1973), has proved valuable in measuring the relevant mechanical properties of tool materials - e.g. the measurement of the flow stress of diamond single crystals at temperatures up to 1500°C (Brookes, 1992). In this work, the technique has been extended further in order to form a basis for the comparison and evaluation of ultra-hard materials. Three main aspects of the performance of these tool materials have been covered: the effect of temperature on flow stress; cumulative deformation under point loading conditions; wear due to repeated traversals (fatigue). In the first part, the technique has been extended to determine the flow stress of polycrystalline diamond and cubic boron nitride as a function of temperature and a mathematical model has been proposed to estimate the flow stress in isotropic polycrystalline materials. This model was first analysed by Love (1928) and was used as the basis on which to identify the threshold pressure above which dislocation movement is initiated in diamond single crystals (Brookes et al (1990)). The applicability of this model for polycrystals was verified by correlating the yield strength of polycrystalline copper, measured in tension, with the determination of minimum contact mean pressure to plastically deform the same material. According to the model, the first evidence of plastic deformation should be observed at the contact periphery and this has been verified in this work. Consequently, using this approach, the effect of temperature on the flow stress of polycrystalline diamond (Syndax) and polycrystalline cubic boron nitride (Amborite) has been established and it is shown that there are three distinct regimes. In regime I, the deformation is brittle and fracture occurs above a given mean pressure; in regime II dislocations are mobile and the flow stress decreases sharply as the temperature rises; and in regime III the flow stress is independent of the temperature. In the earlier work, the brittle-ductile transition temperature (BOT) has been identified as that temperature where regime I ends and II begins. Above the BDT, time dependent plastic flow has been observed, in all of these materials, leading to a measurable increase in the size of the impression. However, this particular type of cumulative deformation, described as impression creep, is shown to be different to conventional creep as measured under uniaxial stress conditions. Finally, the room temperature friction and deformation of various polycrystalline diamond based specimens, Le. aggregates with a binder phase of cobalt (Syndite) or silicon carbide (Syndax), a polycrystalline coating produced by a chemical vapour deposition processes (CVDite) and cubic boron nitride (Amborite) were studied when softer metallic and ceramic sliders were used. As a result of increasing the number of traversals, significant wear of the CVDite diamond coating by softer metallic sliders (aluminium and mild steel) was observed. This could be attributed to the high level of residual stresses in the diamond layer which is thought to be due to the difference in the thermal expansion coefficients of the coatings and their substrates. Burton et al (1995) reported a strain of 0.3% on the surface of the diamond coating and hence the tensile stress on the upper side of the coating will be equivalent to about 3.0 GPa. This value is comparable to the theoretical cleavage strength of diamond. It is suggested an additional tensile stress, due to the sliding friction, could have caused cleavage of individual diamond crystals. The resultant wear debris then becoming embedded in the metallic slider. These embedded diamond particles in the tip of the slider could be responsible for the increased friction and wear.
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JAYASEELAN, VIDHYA SAGAR. "STUDY OF POLYCRYSTALLINE DIAMOND THIN FILMS GROWN IN A CUSTOM BUILT ECR PE-CVD SYSTEM." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin975513169.
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Stradějová, Alena. "Supertvrdé řezné materiály a jejich efektivní využití." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228617.
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The master’s thesis is aimed at superhard cutting materials (polycrystalline diamond and polycrystalline cubic boron nitride) and their effective utilization. It describes the characteristics and production of these materials and evaluates product ranges of the most significant producers of tools and tool materials in given area. It further compares working conditions of selected world's producers which are related to the growing utilization of these materials in machining process. The thesis also deals with the cutting power of tools and provides a technical-economic assessment of the discussed issue.
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Vampola, Lukáš. "Supertvrdé materiály a jejich efektivní využití." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229434.
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Diploma thesis is focused on cutting superhard materials (polycrystalline diamond and polycrystalline cubic boron nitride). It deals with physical, mechanical and cutting properties, production and effective use. Evaluative product range of superhard cutting materials of the prominent world producers in terms of cutting conditions and type of materials machined in turning.
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Bourne, Robert W. "An optical study of cubic boron nitride." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328531.
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Deyneka, Nataliya [Verfasser]. "Properties of nanocrystalline cubic boron nitride films / Nataliya Deyneka." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2003. http://d-nb.info/1015354882/34.
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Chan, Chit-yiu. "Nucleation and growth of cubic boron nitride thin films /." access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ap-b19887693a.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2005."Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references (leaves 147-154)
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Law, Ka Cheong. "Temperature parameter at synthesis of cubic boron nitride films." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174477a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.
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Ozkol, Engin. "Production Of Boron Nitride." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609646/index.pdf.
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Boron nitride is found mainly in two crystal structuresin hexagonal structure (h-BN) which is very much like graphite and in cubic structure (c-BN) with properties very close to those of diamond. h-BN is a natural lubricant due to its layered structure. It is generally used in sliding parts of the moving elements such as rotating element beds in turbine shafts. Since c-BN is the hardest known material after diamond it is used in making hard metal covers. In addition to its possible microelectronics applications (can be used to make p-n junction), its resistance to high temperatures and its high forbidden energy gap are its superiorities over diamond. Recent studies have shown that c-BN can be produced by Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD) in plasma. But these studies have failed to determine how all of the production parameters (boron and nitrogen sources, composition of the gas used, substrate, RF power, bias voltage, substrate temperature) affect the c-BN content, mechanical stress and the deposition rate of the product with a systematic approach. The systematic study was realized in the range of available experimental ability of the present PVD and CVD equipment and accessories. The BN films were produced in the plasma equipment for CVD using RF and MW and magnetron sputtering and were studied with the measurement and testing facilities. It is believed that with this approach it will be possible to collect enough experimental data to optimize production conditions of BN with desired mechanical and optoelectronic properties. h-BN films were successfully deposited in both systems. It was possible to deposit c-BN films with the MW power, however they were weak in cubic content. Deposition at low pressures eliminated the hydrogen contamination of the films. High substrate temperatures led to more chemically and mechanically stable films.
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Fong, Tsz Wang. "Surface roughness parameter at synthesis of cubic boron nitride films." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174143a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
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Cesur, Halil. "Development Of Cubic Boron Nitride (cbn) Coating Process For Cutting Tools." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610640/index.pdf.
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In today’
s market conditions, higher tool life and durable cutting tools which can stand high cutting speeds are required in chip removal process. In order to improve the performance of cutting tools, coatings are employed extensively. Cubic boron nitride (cBN) is a new kind of coating material for cutting tools due to its outstanding properties and testing of cBN as a hard coating for machining have been increasing in recent years. However, there are some challenges such as compressive residual stress, poor adhesion and limiting coating thickness during the deposition of cBN on substrates. In this study, cubic boron nitride (cBN) coatings are formed on cutting tools from hexagonal boron nitride (hBN) target plates. For this purpose, a physical vapor deposition (PVD) system is utilized. PVD system works on magnetron sputtering technique in which material transfer takes place from target plate to substrate surface. Firstly, cBN coatings are deposited on steel and silicon wafer substrates for measurements and analyses. Compositional, structural and mechanical measurements and analysis are performed for the characterization of coatings. Next, several types of cutting tools are coated by cBN and the effects of cBN coatings on cutting performance are investigated. Finally, it can be said that cubic boron nitride coatings are successfully formed on substrates and the improvement of wear resistance and machining performance of cBN coated cutting tools are observed.
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Lung, Kai Chun. "Cubic boron nitride/nanodiamond composite films for the application in SAW devices." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21175020a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.
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Chan, Victory Tak Wah. "Temperature parameter at synthesis of cubic boron nitride films by chemical vapor desposition." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21173989a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
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Maranon, Walter. "Characterization of Boron Nitride Thin Films on Silicon (100) Wafer." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3942/.
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Cubic boron nitride (cBN) thin films offer attractive mechanical and electrical properties. The synthesis of cBN films have been deposited using both physical and chemical vapor deposition methods, which generate internal residual, stresses that result in delamination of the film from substrates. Boron nitride films were deposited using electron beam evaporation without bias voltage and nitrogen bombardment (to reduce stresses) were characterize using FTIR, XRD, SEM, EDS, TEM, and AFM techniques. In addition, a pin-on-disk tribological test was used to measure coefficient of friction. Results indicated that samples deposited at 400°C contained higher cubic phase of BN compared to those films deposited at room temperature. A BN film containing cubic phase deposited at 400°C for 2 hours showed 0.1 friction coefficient.
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Abendroth, B. "Ion-induced stress relaxation during the growth of cubic boron nitride thin films." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28863.
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Abendroth, Barbara. "Ion induced stress relaxation during the growth of cubic boron nitride thin films." Doctoral thesis, [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972228373.
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Abendroth, B. "Ion-induced stress relaxation during the growth of cubic boron nitride thin films." Forschungszentrum Rossendorf, 2004. https://hzdr.qucosa.de/id/qucosa%3A21713.
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Chong, Yat Ming. "The study of cubic boron nitride/diamond composite films for sensing and mechanical applications /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ap-b23749003f.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2009."Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 127-136)
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Vemuri, Prasanna. "Synthesis of cubic boron nitride thin films on silicon substrate using electron beam evaporation." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc5542/.
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Cubic boron nitride (cBN) synthesis has gained lot of interest during the past decade as it offers outstanding physical and chemical properties like high hardness, high wear resistance, and chemical inertness. Despite of their excellent properties, every application of cBN is hindered by high compressive stresses and poor adhesion. The cost of equipment is also high in almost all the techniques used so far. This thesis deals with the synthesis of cubic phase of boron nitride on Si (100) wafers using electron beam evaporator, a low cost equipment that is capable of depositing films with reduced stresses. Using this process, need of ion beam employed in ion beam assisted processes can be eliminated thus reducing the surface damage and enhancing the film adhesion. Four sets of samples have been deposited by varying substrate temperature and the deposition time. scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) techniques have been used to determine the structure and composition of the films deposited. X-ray diffraction (XRD) was performed on one of the samples to determine the thickness of the film deposited for the given deposition rate. Several samples showed dendrites being formed as a stage of film formation. It was found that deposition at substrate temperature of 400oC and for a period of one hour yielded high quality cubic boron nitride films.
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Figueira, Luís António Cortês. "Maquinagem do aço D2 (AISI) endurecido com recurso a ferramentas cerâmicas e CBN (Cubic Boron Nitride)." Master's thesis, Universidade de Aveiro, 2004. http://hdl.handle.net/10773/17942.
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Mestrado em Engenharia MecânicaO aumento dos custos de produção, o aumento da competitividade e a crescente dificuldade na maquinagem de novos materiais endurecidos tem obrigado a um investimento no desenvolvimento de novas ferramentas cerâmicas e ultra-duros “CBN – Cubic Boron Nitride”. As cerâmicas e os ultra-duros são classes de materiais para ferramentas com potencial na aplicação em operações de acabamento com elevadas velocidades de corte e altas taxas de remoção aplicadas à maquinagem de aços endurecidos com durezas superiores a 45 HRC. Nesta dissertação pretende-se avaliar o efeito da nova geometria “wiper – raio de ponta múltiplo” e do material constituinte das ferramentas cerâmicas à base de alumina (Al2O3), no torneamento em operações de acabamento do aço D2 (AISI), endurecido (temperado e revenido) com uma dureza aproximada de 60 HRC. Pretende efectuar-se uma avaliação comparativa do desempenho das ferramentas cerâmicas e das ferramentas de CBN. O estudo da maquinabilidade analisou o processo de torneamento (força e potência de corte), o acabamento de superfície na peça e o comportamento da ferramenta (desgaste e vida). Foram realizados testes da caracterização do desgaste das ferramentas por intermédio de microscopia electrónica de varrimento (MEV) e microanálise por dispersão de energia (EDS). Os resultados experimentais permitiram efectuar uma análise estatística sobre a influência dos parâmetros processuais (velocidade de corte e avanço) e do tempo de corte na maquinabilidade analisada através da força e potência de corte, a rugosidade na peça e o desgaste na ponta da ferramenta. Foi também estudada a influência do penetramento (profundidade de corte) na maquinabilidade do material. Finalmente foi efectuado um estudo comparativo do desempenho da ferramenta cerâmica e CBN.
The advances in ceramic and polycrystalline cubic boron nitride (CBN) materials and processing technology are directly involved with the need to use materials that are increasingly more difficult to machining, increasing competition and rapidly rising manufacturing costs. Ceramics and ultra hard materials are the newest upcoming classes of tool materials with potential for a wide range of high speed finishing operations as well as for high removal rate machining materials with more difficult to machining with hardness over 45 HRC. This thesis intend to do an evaluation of the cutting edge geometry effects, like “multiple tool nose radius – wiper” and the effect of different ceramic (Al2O3) tool materials on steel D2 (AISI) hardened and tempered to 60 HRC. The machinability study process evaluation consider (cutting force, cutting power), work material observed on surface finishing and tool behaviour determined by tool wear. Were performed tool wear characterization tests by means the use of scanning electron microscopy (SEM) and also energy dispersion spectroscopy (EDS). The experimental results were submitted to graphic and statistical tools, to discriminate the cutting parameters influences on the cutting process, surface finishing and tool wear. The experimental results were submitted to a statistical analysis of cutting parameters contribution (cutting speed, feed rate) and cutting time, on the cutting forces, surface finishing and tool wear. It was also analysed the effect of cutting dept on the machinability behaviour. Finally were compared the best performed ceramic and CBN tool results to evaluate the different behaviours.
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Karlsson, Johan. "Theoretical Routes for c-BN Thin Film Growth." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-191181.
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c-BN has been in focus for several years due to its interesting properties. The possibility for large area CVD is a requirement for the realization of these different properties in various applications. Unfortunately, there are at present severe problems in the CVD growth of c-BN. The purpose with this research project has been to theoretically investigate, using DFT calculations, the possibility for a layer-by-layer CVD growth of c-BN. It could be established that, PEALD, using a BF3-H2-NH3-F2 pulse cycle and a diamond substrate, is a promising method for deposition of c-BN films. The gaseous species will decompose in the plasma and form BFx, H, NHx, and F species (x = 0, 1, 2, 3). The H and F radicals will uphold the cubic structure by completely hydrogenate, or fluorinate, the growing surface. However, surface radical sites will appear during the growth process as a result of atomic H, or F, abstraction reactions. The addition of NHx growth species (x = 0, 1, 2) to B radical sites, and BFx growth species (x = 0, 1, 2) to N radical sites, will then result in a continuous growth of c-BN.
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Kobayashi, Toshiro. "A fundamental study of the formation of cubic-nitride films using ion-assisted deposition and graded Ti-B-N interlayers." Thesis, University of Salford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244847.
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Teplý, Radek. "Supertvrdé materiály a jejich efektivní využití." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230154.
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Diploma thesis is focused on the superhard cutting materials (polycrystalline diamond, polycrystalline boron nitride) and presents their physico-mechanical properties, production, efficient use, new trends. It assesses the range of cutting tool materials and individual front world producers in terms of optimum cutting conditions for turning operations and type of material to be machined. Further, these cutting materials are compared between different manufacturers to bring out thein differences in cutting conditions.
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Marcos, Gustavo Pollettini. "Desenvolvimento de um sistema de texturização para rebolos de CBN vitrificado baseado em análise modal." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18156/tde-06122018-113507/.
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Superfícies funcionais dependem do controle das características das superfícies de um material para obter-se um desempenho funcional desejado. Essas superfícies têm importância em diversas áreas na engenharia, como: eletrônica, ótica, energia e tribologia. No campo da tribologia, uma aplicação é em virabrequins. A funcionalização da superfície adiciona micro cavidades que diminuem o atrito e aumentam as forças de sustentação do virabrequim. Para isso, essas cavidades possuem uma geometria específica, uma microrampa. Devido a essa forma especial, a fabricação dessas microrampas é complexa, já tendo sido alcançada empregando a metodologia de texturização com rebolos padronizados. Essa metodologia consiste na inscrição de padrões geométricos no rebolo durante a dressagem, posteriormente transferidos para a peça. Como a indústria moderna utiliza rebolos de CBN de ligante vitrificado para a retificação de virabrequins, a metodologia de texturização supracitada deve ser aplicável a esse ferramental. Esse trabalho descreve o desenvolvimento de uma unidade de dressagem capaz de inscrever padrões geométricos em rebolos de CBN vitrificados, sendo seu projeto baseado em análise modal. O trabalho apresenta as restrições de projeto, conceitos de solução, simulações dinâmicas e modelagem do processo de texturização. Para maximizar a resposta dinâmica, a unidade foi projetada para operar próxima de sua frequência natural. A unidade projetada é capaz de inscrever padrões geométricos no rebolo utilizando um disco dressador rotativo, e as texturas das peças produzidas com esse rebolo padronizado apresentam boa precisão geométrica para a aplicação em virabrequins.Engineered surfaces rely on the control of the surface characteristics of a material to achieve a desired functional performance. These functional surfaces are important in several areas of engineering, such as: electronics, optics, energy and tribology. On tribology field, an application is in crankshafts. The surface functionalization is achieved by adding micro-cavities that reduce friction and increase crankshaft lift forces. These cavities have a specific geometry, called microramp. Due to this special geometry, manufacturing microramps is a complex process, having been achieved using the methodology of texturizing via grinding. This methodology consists in the inscription of geometric patterns in the grinding wheel during the dressing operation, later transferred to the piece. As the modern industry uses vitrified CBN grinding wheels for crankshaft grinding, the texturing methodology should be applicable to this tool. This work describes the development of a dressing unit capable of inscribing geometric patterns in vitrified CBN grinding wheels, having its design based on modal analysis. The work presents the design constraints, solution concepts, dynamic simulations and modeling of the texturing process. To maximize dynamic response, the unit is designed to operate near its natural frequency. The designed unit can inscribe geometric patterns on the grinding wheel using a rotating dressing disc, and the textures of the parts produced have good geometric precision for crankshaft applications.
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MORAES, Elizane Efigenia. "Propriedades eletrônicas e de transporte de amostras nanoestruturadas de Nitreto de Boro Cúbio Hidrogenado." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17344.
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Nesta dissertação estudamos as propriedades de transporte do nitreto de boro cúbico (cBN, para a sigla em inglês) com as superfícies de uma amostra de quatro camadas passivadas com hidrogênio: em uma superfície o H se liga ao B e na outra ao N. As características do transporte são investigadas com a introdução de dois eletrodos de ouro (Au), em equilíbrio eletrostático com a amostra e submetidos a uma diferença de potencial V em intervalos de interesse: 0:2 V 0:2, 1 V 1 e 3 V 3. O teste de tunelamento com voltagem nula também foi realizado. As principais propriedades observadas são brevemente relatadas em seguida: (i) Os eletrodos são idênticos (no cálculo inicial do programa Siesta adicionamos uma camada "tampão"de átomos, a qual é desconsiderada no programa Transiesta-propriedades de transporte. A simetria dos eletrodos (esquerda e direita) se manifesta com PDOS idênticos para voltagem nula nos intervalos de energia investigados; (ii) A característica I-V (corrente versus voltagem) da amostra apresenta um pico acentuado para V 0:25. A origem deste pico é atribuída à ocorrência do nível quase localizado do H, situado abaixo do nível de Fermi e hibridizado com estados sp3 do B, como evidenciado no cálculo de DFT (Siesta) da estrutura eletrônica e densidade de estados do sistema de quatro camadas. De fato, uma análise dos PDOS dos eletrodos e da amostra sugere que esta interpretação é compatível com o cálculo numérico do Transiesta para o tunelamento através da amostra e o cálculo das características IV através da Fórmula de Landauer-Büttiker: na configuração de equilíbrio mencionada, as correntes máximas obtidas foram Imax(V = 0:25 Volts ) = 163 pico Ampéres (pA) e Imax(V = 2:5 ) = 380 pA. (iii) Enfatizamos que, no intervalo 0:2 V 0:2 a característica IV é muito semelhante àquela observada em diodos de junção p-n. Por outro lado, no intervalo 3 V 3 a retificação é bem menos efetiva para jV > 0:2j ; (iV) outra observação de destaque é o aumento da corrente, isto é, jImax(V = 0:8 )j = 9:85 nano Ampéres (nA) quando a distância dos eletrodos e a amostra é diminuída. Os resultados sugerem o prosseguimento e o aprofundamento das investigações, tendo em vista o uso potencial do cBN passivado com hidrogênio em dispositivos eletrônicos.
In this thesis we study the transport properties of cubic boron nitride (cBN) with the surfaces of a sample of four layers hydrogen terminated hydrogen: on a surface, H binds to B and on the other, to N. The characteristics of the transport are investigated after the introduction of two gold electrodes in an electrostatic equilibrium with the sample and subjected to a potential difference V in intervals of interest:0:2 V 0:2, 1 V 1 e 3 V 3. Tunneling test with zero voltage was also made. The main observed properties are reported briefly: (i) the electrodes are identical (within a layer buffer atoms only considered in the initial calculation Siesta program, to simulate a bulk behavior, therefore it is not considered in Transiesta program, that is, for the calculation of transport properties). The symmetry of electrodes (left and right) manifests with identical PDOS to zero voltage in between the energy intervals investigated; (ii) The IV characteristic (current versus voltage) of the sample shows a sharp peak for V 0:25. The origin of this peak is attributed to the occurrence of nearly located H level, situated below the Fermi level and hybridized with sp3 states of B, and evidenced in the DFT calculation (Siesta) of the electronic structure and density of states of the four layer system. The PDOS electrode and the sample analyses suggest that this interpretation is compatible with Transiesta numerical calculation of the tunneling through the sample and to calculate the current versus voltage I (V) by the Landauer-Büttiker formula: the aforementioned balance setting, the maximum currents obtained were Imax(V = 0:25 Volts ) = 163 peak amps (pA) and Imax(V = 2:5 ) = 380 pA; (iii) - Another important observation was the increase in current, i.e. jImax(V = 0:8 )j = 9:85 nano amps (nA) when the distance of the electrodes and the sample is reduced. The results suggest the continuation and deepening of the study, considering the potential use of CBN passivated with hydrogen in electronic devices.
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Veselý, Ondřej. "Obrábění kalených ocelí." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443236.
Full textAbstract:
Diploma thesis on Machining hardened steels is focused on the analysis of longitudinal turning of hardened steel 14 109 by using a tool from PKNB in terms of measuring the force load using a dynamometer and then evaluating the surface quality. The theoretical part deals with the issue of turning technology, cutting materials and heat treatment of steel. In the practical part, the influence of cutting conditions on the resulting values was assessed during the experiment. Twelve samples with different combinations of cutting conditions were tested, then was selected a sample that met the criterion of combining minimum cutting forces values and surface quality. The experiment shows that force load values can be achieved twice less by combining cutting conditions with an appropriate combination.
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Koutský, Jiří. "Deformační, napjatostní a pevnostní analýza vysokotlaké složené nádoby využitím metody konečných prvků." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-227874.
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Strength and strain analysis of high pressure compound vessel, which is used to produce superhard materials (for example synthetic diamond). This work was elaborated to compare the stresses and strains calculated by Prof. Jan Vrbka making use of the FEM program ‘Prokop’17 years ago with those gained with the contemporary FEM Ansys program. The vessel is loaded by internal pressure of size 6 GPa. The elastic-plastic material be-haviour is taken into account. Real value of friction between rings and non-uniform temperature field is included into the calculation. The process of assembling the compound vessel is simulated step by step.
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Martincová, Zdeňka. "Supertvrdé řezné materiály a jejich efektivní využití." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228006.
Full textAbstract:
Diploma thesis is intended on a polycrystalic diamond and a pocrystalic cubic boron nitride from the standpoint of their description, physical, mechanical and cutting properties, use and contemporary trends of development at renowned producers of tools and tool materials. The aim of the work was a complex working of conditions (type of cutting material, cutting conditions), which are recommended by choice producers for the effective turning applications their kind of superhard tool materials.
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Grausgruber, Jiří. "Supertvrdé materiály a jejich efektivní využití." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228927.
Full textAbstract:
n the first part of this diploma thesis there are described basic findings about superhard cutting materials (sorts, notation, structure, physical-mechanical properties, usage, production) and evaluates this tool of material from the aspect of cutting ability. The second part focused on complex data processing about assortment of superhard cutting materials of significant tools materials producers and comparison of work conditions (kind of machined ma-terials, cutting conditions), which are recommend for effective turning applica-tions by producers.
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Fonblanc, Diane. "Nouvelles céramiques de confinement de plasmas à base de BN issues de précurseurs organométalliques : application aux moteurs à effet Hall." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0076.
Full textAbstract:
L’objectif de cette thèse est de développer une nouvelle génération de matériaux céramiques de confinement plasma pour les moteurs à effet Hall en mettant en oeuvre la voie PDCs pour polymer-derived ceramics ou voie des polymères précéramiques.Un état de l’art des différents matériaux de confinement et un bilan des travaux précédemment menés sur ce sujet ont permis de déterminer les paramètres essentiels de tels matériaux et de s’orienter vers l’utilisation des polymères précéramiques commeprécurseurs des matériaux envisagés. Après avoir détaillé les différents protocoles permettant de modifier chimiquement un polymère commercial avec le bore, de mettre en forme les composés obtenus puis de réaliser la pyrolyse pour générer la céramique, des pièces denses céramiques Si-B-(C)-N ont été réalisées avec une teneur variable en bore. Une étude complète allant de la structure chimique des polymères jusqu’aux propriétés des céramiques résultantes a permis de sélectionner la formulation optimale du polymère comme précurseur de céramique. Des composites c-BN/Si-B-(C)-N ont ensuite été préparés parajout de charges, puis mis en forme et caractérisés avant de procéder à un changement d’échelle visant à préparer des bagues céramiques de taille moteur. La dernière partie consiste en une ouverture sur l’utilisation des polymères précéramiques pour la réalisation de pièces denses Si-Al-(C)-N de composition contrôlée avec en particulier une étude sur l’impact de l’aluminium sur les propriétés des polymères et des céramiquesThe main objective is here to develop a new generation of ceramic materials used for plasma confinement in Hall-effect thrusters using the PDCs (polymer-derived ceramics) route. A state of the art of the different confinement materials and a review of the previous work done on this topic allowed to determine the key parameters of such materials and to move towards the use of preceramic polymers as precursors of the materials envisaged. After having detailed the various protocols used to chemically modify a commercial polymer with boron, to shape the compounds obtained and then to convert the polymers into ceramics bypyrolysis, Si-B-(C)-N dense ceramic pieces have been produced with various boron content. A complete study from the chemical structure of the polymers to the properties of the resulting ceramics allowed selecting the optimal formulation of the polymer as a ceramic precursor. c-BN/Si-B-(C)-N composites were then prepared by filler addition, then shaped and characterized before a scale-up to prepare engine-size ceramic rings. The last part consists of an opening on the use of the PDCs route for the realization of dense Si-Al-(C)-N pieces of controlled composition, with a study of the impact of aluminum on the polymers andceramics properties
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Shonhiwa, Aron Tamisa. "Alumina - cubic boron nitride composite materials." Thesis, 2008. http://hdl.handle.net/10539/5028.
Full textAbstract:
Alumina – cubic boron nitride composites (30% cBN by volume) with a hardness of 24.6 GPa, fracture toughness of 3.9 MPa m1/2 and a density of 96.5% were successfully synthesized via the reaction bonded aluminum oxide process. This involved initially heat treating mixtures of aluminum with alumina and cubic boron nitride in an oxidizing atmosphere so as to oxidize the aluminum into new alumina crystallites. This initial heat treatment was done at temperatures not exceeding 1000 oC so as to avoid oxidation of cubic boron nitride. X- ray diffraction and gravimetry were used to assess the degree of oxidation of aluminum into alumina during the oxidation stage. It was not possible to fully oxidize all the aluminum and at higher temperatures (1000 oC) some of the cubic boron nitride started to form B2O3. The optimum oxidizing temperature was found to be 800 oC.
The second heat treatment , meant for densification was done in an inert atmosphere (argon and vacuum) in a graphite heated hot press furnace at 1300 oC under a pressure of 80 MPa for 2 hours.
Phase analysis , microstructural analysis and density measurements were done using X-ray diffraction, Scanning electron microscopy and the Archimedes method respectively. Hardness and fracture toughness were determined using the indentation method.
After hot pressing there was no evidence of hexagonalisation . All the cubic boron nitride was present in the cubic form and was evenly distributed within the alumina matrix . The degree of densification decreased with increase in cubic boron nitride loading. Hardness and fracture toughness on the other hand increased with increasing cubic boron nitride loading.
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Shi, Zhongde. "Grinding with electroplated cubic boron nitride (CBN) wheels." 2004. https://scholarworks.umass.edu/dissertations/AAI3118332.
Full textAbstract:
Electroplated cubic boron nitride (CBN) wheels are manufactured with a single layer of CBN superabrasive grains held on the wheel hub by an electroplated nickel bond. Unlike other conventional and superabrasive wheels, these wheels are not periodically trued or dressed. Consequently, their performance during grinding varies significantly as the wheel wears down and its topography changes. An investigation was undertaken of the grinding process with electroplated CBN wheels. The topography of unused wheels of various different grain sizes was characterized in terms of areal grain density and protrusion height distribution of the grain tips. Internal cylindrical and straight surface grinding tests were then conducted to investigate the wheel wear and its effect on the wheel topography and grinding performance. Grinding tests were performed mostly on hardened AISI 52100 steel over a wide range of operating conditions. Measurements were made of the forces, grinding power, surface roughness, radial wheel wear, and wheel topography. The overall radial wheel wear in each case was found to consist of an initial transient followed by a steady state regime. With continued grinding, a progressive increase in power and a decrease in surface roughness were observed. Wheel failure tended to occur by stripping of the abrasive layer when the radial wear reached about 70–80% of the grain dimension. Wheel wear was found to occur by attrition, grain fracture, and grain pullout. Attritious wear increases the active grain density and causes wheel dulling which lead to a smoother workpiece and higher forces. The effects of attritious wear are offset to a greater or lesser degree by grain fracture and grain pullout. Grain fracture which dominates in the steady state is shown to be related to the uncut chip thickness taken by an individual cutting point. The initial transient wear at the start of grinding is mainly due to pullout of loosely held grains, although grain fracture also contributes to the transient. The results of this work provide the technological basis for predicting grinding behavior, design of grinding cycles, and optimal utilization of the process with electroplated CBN wheels.
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Garrett, Jethro Christopher. "SPS consolidation of cubic boron nitride reinforced alpha-SiAlON ceramics." Thesis, 2013. http://hdl.handle.net/10539/12536.
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Peng, Chao-Hua, and 彭昭華. "Characteristics of vitrified binders for Cubic Boron Nitride grinding wheels." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/99810847807113883252.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
103
In this study, the glass-ceramic binding agent of cubic boron nitride (CBN) grinding wheel were developed and investigated. The Diopside (CaMgSi2O6) was selected to be used in glass-ceramic systems. This type of ceramic binders have high dressibility, high rigidity, high wear resistance, high heat resistance and other characteristics. Glass ceramics have high density and can be sintered at low-temperature. Furthermore, the glass-ceramic phase structure and crystallization degree can be controlled by post-treatment. Because of these reasons, this study uses different heat treatment methods to control the phase composition ratio, to improve the physical properties in order to increase the internal structure of the glass network, as a result TiO2 was added to obtain high strength glass ceramic binder. This experiment was designed to use glass compositions with Ca-Mg-Si-B (CMSB) as the main components, and TiO2 as the modifier, in order to form ceramic binding agent. When more than 30% of B2O3 was added, we can effectively increase the CBN abrasive wetting property. Mg, Ca, Ba and other alkaline earth (AE) elements, possess larger ionic radius, higher electronic valence, higher bonding energy, and therefore oxide bonding is more stable than those in the alkali metal group. The covalent/ionic bonding of AE elements can increase structural strength, enhance physical properties of the glass and therefore decrease thermal expansion coefficient of glass. Therefore in this experimental we use Ca: Mg: Si = 1: 1: 2 ratio of ingredients to formulate the binder, and add 2 ~ 8 mol% of TiO2 into the final glass melt in order to produce Ti4+ bonds inside the glass to increase network density and to increase physical strength of the glass. FT-IR were also employed to investigate the glass, and TiO2 addition was found to generate [TiO4] and [TiO6] bonding in the glass, which increases network density, and physical strength of the glass phase. TiO2 can also work as a nucleation agent in the experiment and therefore we perform heat treatments to make diopside crystal phase precipitate with different heat treatment parameters to control the ratio of glass-ceramic phases in CMSB glass. Heat treatment at 760oC for 5 hours and at 800oC for 2 hours of the CMSB4T specimens produce surface hardness of up to 572 HV and 592 HV, and bending strength of 97.4 Mpa and 98.5 Mpa. Analyzing the crystal phase using Rieveld method indicates 18% and 44% of formation of the diopside phase. Although longer holding time and higher annealing temperature generate more diopside crystal phase, no significant increase in hardness and bending strength, indicating an appropriate arrangement of the glass network and the amount of crystal phase provides optimum hardness and bending strength of the binding agent. As to toughness of the CMSB4T glass ceramics, the material treated at 760oC, 2hrs with fewer diopside phase (6%) exhibit fracture toughness of about 0.073 MPa√m; on the other hand, the specimen treated at 760oC, 10 hrs with a crystallinity of 82.7% show a the fracture toughness of 0.177 MPa√m, implying that fracture toughness of the glass-ceramics increases with the amount of the diopside phase. The current results show that a designed glass-ceramic system based upon alkaline-earth element provides better toughness, strength and thermal expansion than those with alkaline elements, which may work as a better CBN binding agent in grinding wheel applications.
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Chu, Hung-Yu, and 朱宏宥. "The Sintering of Polycrystalline Cubic Boron Nitride:The Function of Al-Si Alloy." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/36239883790142053489.
Full textAbstract:
碩士國立臺灣大學
地質科學研究所
97
Cubic boron nitride (cBN) is a high pressure synthetic material, having extreme hardness just next to diamond. Among superhard materials, cBN is the most stable when it applies at high temperature (>1000℃). Prior studies show that Silicon (Si) reacts hardly with cBN at temperatures as high as 1500℃, which imposes difficulty for the formation of superhard material, C-Si3N4. In this research, we use Aluminum (Al) as a major reagent to react with cBN and Silicon (Si) as an inhibitor for AlN formation to modulate free Nitrogen (N). The newly generated free N, which can not react timely with Al to form AlN, may react with Si to form Si3N4. There are two major parts in this research. Part I includes the sintering experiments at high temperature (1350℃) in vacuum, and part II is sintering under ultra-high pressure and high temperature (HTHP) (1350℃, 5.5 GPa). The results from low pressure experiments show that Si reacts successfully with BN to form Si3N4, although the density and mechanical property of the sintering body have not reach the requirement. This result infers that we can also successfully sinter Si3N4 –bearing body with better mechanical property at HTHP. In part II with HTHP experiment, we successfully synthesized superhard PcBN (Hv 5400) from Si-Al and cBN. We also repeated this experiment with nano cBN particle. The result indicates that mechanical property of PcBN sintering body using nano particles is no better than micro particles. Experiments by adding two materials B4C and AlN in Si-Al and cBN show the increase of amorphous materials in the sintering body which resulted in the observed deterioration of entire mechanical property of PcBN .
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Erasmus, Rudolph Marthinus. "Optical properties and mechanical stress in cubic boron nitride and diamond." Thesis, 2013. http://hdl.handle.net/10539/12572.
Full textAbstract:
A thesis submitted to the Faculty of Science, University of the Witwatersrand,
Johannesburg, in fulfilment of the requirements for the degree of Doctor of
PhilosophyRaman and photoluminescence (PL) spectroscopy techniques were used to investigate the mechanical properties of diamond and cubic boron nitride (cBN) by optical means. Both these materials have extreme mechanical properties that make them the material of choice for many industrial applications, ranging from cutting and grinding to wire-drawing dies. The results obtained on single crystal diamond, polycrystalline diamond (PCD) and cBN are summarised below. Micro-Raman and photoluminescence (PL) spectroscopy were used to map the threedimensional (3D) stress and deformation distributions surrounding a plastic impression made in a synthetic, type Ib single crystal diamond. Using data from the Raman peak position, a 3D map of the stress contours surrounding the impression was generated, while the Raman width data yielded a map of the plastic deformation volume. The stress contours compare favorably with the resolved shear stress contours calculated for diamond. PL intensity maps of the zero phonon line (ZPL) associated with the [N-V]– defect centre at 1.945eV provide images of the extent of vacancy formation and movement during the impression process. Data concerning the position and width of the ZPL correspond well with the Raman results. Polycrystalline diamond (PCD) tools commonly consist of a PCD layer sintered onto a cobalt-tungsten carbide (Co-WC) substrate. These tools are used in diverse applications and both the magnitude and distribution of the stresses in the PCD layer affect tool behavior. These stresses in sample drillbits were investigated by means of micro-Raman spectroscopy. Cyclic annealing of a sample drillbit to 600 oC shows that the tool properties are retained after 5 cycles, while similar cycling to 800 oC resulted in a permanent decrease of the average surface compressive stress. This implies a reduction in the drillbit’s ability to resist crack formation and propagation and is thus a degradation of the tool properties. The method of Raman mapping of stress and deformation in diamond was also applied to single crystals of cBN. Indentations on cubic boron nitride (cBN) crystals and polycrystalline cubic boron nitride (PcBN) composites were mapped and the shifts of the cBN Raman lines from their unstressed positions used to quantify the residual stresses in the boron nitride due to the deformation brought about by the indentation. These were found to be of the order of 1 GPa. vi These measurements illustrated for the first time the use of Raman spectroscopy to study residual stresses in boron nitride. Defects in cBN were studied using photoluminescence spectroscopy at low temperature (< 10 K) of two types of cBN irradiated at ambient temperature with 1.9 MeV electrons. All the samples were small (<1 mm diameter) single crystals of cBN. Three defect centres (with narrow lines at 2.28 eV, 2.15 eV and 1.98 eV) were introduced in both the amber-coloured and blackbrown coloured samples by the irradiation. The amber coloured sample also showed a defect centre (at 1.65 eV) that is present before and after irradiation. Line shape analysis of the zero phonon lines of all three irradiation-induced centres showed that the lines are predominantly Gaussian in character, suggesting that linetype defects such as dislocations are a prevalent characteristic of these crystals. Raman spectroscopy of cBN single crystals as a function of temperature was performed over a wide temperature range from 4 K to 1373 K. The low temperature measurements extended the data previously reported in literature, as this data ranged from room temperature upwards. It was concluded from the shift of Raman peak position with temperature that both linear expansion and anharmonic effects were required to adequately account for the observed data. This is in agreement with previously published findings. Both 3- and 4-phonon processes were required to account for the observed linewidths as a function of temperature, again in agreement with literature. The results presented here and in the associated journal publications illustrate clearly how optical spectroscopy techniques can serve as non-destructive characterisation tools for the mechanical properties of ultra-hard materials.
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"Characterization of Cubic Boron Nitride Interfaces with in situ Photoelectron Spectroscopy." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.38531.
Full textAbstract:
abstract: Cubic boron nitride (c-BN) has potential for electronic applications as an electron emitter and serving as a base material for diodes, transistors, etc. However, there has been limited research on c-BN reported, and many of the electronic properties of c-BN and c-BN interfaces have yet to be reported. This dissertation focused on probing thin film c-BN deposited via plasma enhanced chemical vapor deposition (PECVD) with in situ photoelectron spectroscopy (PES). PES measurements were used to characterize the electronic properties of c-BN films and interfaces with vacuum and diamond. First, the interface between c-BN and vacuum were characterized with ultraviolet PES (UPS). UPS measurements indicated that as-deposited c-BN, H2 plasma treated c-BN, and annealed c-BN post H2 plasma treatment exhibited negative electron affinity surfaces. A dipole model suggested dipoles from H-terminated N surface sites were found to be responsible for the NEA surface. Then, Si was introduced into c-BN films to realize n-type doped c-BN. The valence structure and work function of c-BN:Si films were characterized with XPS and UPS measurements. Measurements were unable to confirm n-type character, and it is concluded that silicon nitride formation was the primary effect for the observations. Finally, XPS measurements were employed to measure the band offsets at the c-BN/diamond interface. Measurements indicated the valence band maximum (VBM) of c-BN was positioned ~0.8 eV above the VBM of diamond.Dissertation/Thesis
Doctoral Dissertation Physics 2016
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Machaka, Ronald. "Ion Beam Modifications of Boron Nitride By Ion Implantation." Thesis, 2008. http://hdl.handle.net/10539/5581.
Full textAbstract:
The search for alternative methods of synthesizing cubic boron nitride (cBN), one of
the hardest known materials, at low thermo-baric conditions has stimulated considerable
research interest due to its great potential for numerous practical industrial applications.
The practical applications are motivated by the material’s amazing combination of extraordinarily superior properties.
The cBN phase is presently being synthesized from
graphite-like boron nitride modifications at high thermo-baric conditions in the presence
of catalytic solvents or by ion–beam assisted (chemical and physical) deposition methods.
However, the potential and performance of cBN have not been fully realized largely due
to central problems arising from the aforementioned synthesis methods.
The work reported in this dissertation is inspired by the extensive theoretical investigation of the influence of defects in a ecting the transformation of the hexagonal boron nitride (hBN) phase to the cBN phase that was carried out by Mosuang and Lowther (Phys
Rev B 66, 014112 (2002)). From their investigation, using an ab-initio local density approach, for the B, C, N, and O simple defects in hBN, they concluded that the defects
introduced into hBN could facilitate a low activation–energy hexagonal-to-cubic boron
nitride phase transformation, under less extreme conditions.
We use ion implantation as a technique of choice for introducing ‘controlled’ defects
into the hot–pressed polycrystalline 99.9% hBN powder samples. The reasons are that the
technique is non–equilibrium (not influenced by dilusion laws) and controllable, that is
the species of ions, their energy and number introduced per unit area can be changed and
monitored easily. We investigate the structural modifications of hBN by ion implantation.
Emphasis is given to the possibilities of influencing a low activation–energy hBN-to-cBN
phase transformation. The characterization of the structural modifications induced to the
hBN samples by implanting with He+ ions of energies ranging between 200 keV and 1.2
MeV, at fluences of up to 1.0 1017 ionscm2, was accomplished by correlating results
from X-Ray Di raction (XRD), micro-Raman (-Raman) spectroscopy measurements,
and two-dimensional X-Y Raman (2D-Raman) mapping measurements. The surface to
pography of the samples was investigated using Scanning Electron Microscopy (SEM).
E orts to use Surface Brillouin Scattering (SBS) were hampered by the transparency of
the samples to the laser light as well as the large degree of surface roughness. All the
implantations were carried out at room temperature under high vacuum.
2D-Raman mapping and -Raman spectroscopy measurements done before and after
He+ ion irradiation show that an induced hBN-to-cBN phase transformation is possible:
nanocrystals of cBN have been observed to have nucleated as a consequence of ion implantation,the extent of which is dictated by the fluences of implantation.
The deviationof the measured spectra from the Raman spectra of single crystal cBN is expected, has been observed before and been attributed to phonon confinement e ects. Also observed are phase transformations from the pre-existing hBN modification to: (a) the amorphous boron nitride (aBN), (b) the rhombohedral boron nitride (rBN) modifications, (c) crystalline and amorphous boron clusters, which are a result of the agglomeration of elementary boron during and immediately after ion implantation.
These transformations were observed at high energies. Unfortunately, the XRD measurements carried out could not complement the Raman spectroscopy outcomes probably because the respective amounts of the transformed materials were well below the detection limit of the instrument used in the former case.
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Jhang-HueiYin and 殷彰輝. "Growths of Cubic Boron Nitride Films by Plasma-Assisted Hot-Filament Chemical Vapor Deposition." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/61298907492727411873.
Full textAbstract:
碩士國立成功大學
化學工程學系碩博士班
98
As the gradually growing technology, the applications of ceramic materials become more importance. There are many hard thin films have been researched, such as diamond films and cubic-boron nitride films. The extreme hardness, lower friction coefficient, higher wear resistance and chemical inertness of diamond make it useful for diverse mechanical and electronic applications . c-BN, isostructural to diamond, possesses many similar extreme properties to diamond. The special properties are inertness against iron and oxygen even at high temperature, as well as the possibility of use as n- and p-type doped semiconductors. In this study, cubic-boron nitride thin films were deposited on silicon (111) wafer by Inductively-Coupled-Plasma Chemical Vapor Deposition using BCl3, N2, H2, Ar as reactant gases. Films were deposited at various plasma density and negative bias to the substrate. Our result demonstrate that the deposition process was highly sensitive to plasma density and substrate bias voltage. By using the appropriate parameters for c-BN deposition mode, consisting of more than 45% cubic phase were successfully deposited.
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Abendroth, Barbara [Verfasser]. "Ion induced stress relaxation during the growth of cubic boron nitride thin films / vorgelegt von Barbara Abendroth." 2004. http://d-nb.info/972228373/34.
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Hsiao, Jui-Sheng, and 蕭瑞聖. "Brazing of Orthogonal Grit-Array Cubic Boron Nitride to A Steel Substrate Using a Ccpper-Tin-Titanium Alloy." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/11365744524922209249.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
88
By using discrete alignment perforated sheet and uniform gelatine tape, the aim of this study is to apply a ternary alloy brazing to the fabrication of monolayer orthogonal array CBN grit and matrices with same protrusion improving grinding performance. The firing was carried out in a vacuum furnace in order to prevent oxidation of metallic constituents which would inhibit wetting and flow of the braze alloy. After the active metal brazing process, the performance assessment was conducted with the Cemeron Plint TE-77 wear tester and modified Jones & Shipman surface grinding machine. Microstructure and interfacial reaction layer was investigated by OM, SEM, EDS, XRD and EPMA, the characteristics of the brazed substrate in this study has monolayer -controlled grit pitch setting Rcontrolled grit protrusion ¯chemical bonding °grit saving. Due to excellent wetting and bonding of the grit and the interfacial layer, there is no grit pull-out during the reciprocating abrasive wear test and simulated grinding service.
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Eyhusen, Sören. "Phase formation processes in the synthesis of boron nitride thin films." Doctoral thesis, 2005. http://hdl.handle.net/11858/00-1735-0000-0006-B57A-C.
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Irshad, H. M., B. A. Ahmed, M. A. Ehsan, Tahir I. Khan, T. Laoui, M. R. Yousaf, A. Ibrahim, and A. S. Hakeem. "Investigation of the structural and mechanical properties of micro-/nano-sized Al2O3 and cBN composites prepared by spark plasma sintering." 2017. http://hdl.handle.net/10454/17078.
Full textAbstract:
YesAlumina-cubic boron nitride (cBN) composites were prepared using the spark plasma sintering (SPS) technique. Alpha-alumina powders with particle sizes of ∼15 µm and ∼150 nm were used as the matrix while cBN particles with and without nickel coating were used as reinforcement agents. The amount of both coated and uncoated cBN reinforcements for each type of matrix was varied between 10 to 30 wt%. The powder materials were sintered at a temperature of 1400 °C under a constant uniaxial pressure of 50 MPa. We studied the effect of the size of the starting alumina powder particles, as well as the effect of the nickel coating, on the phase transformation from cBN to hBN (hexagonal boron nitride) and on the thermo-mechanical properties of the composites. In contrast to micro-sized alumina, utilization of nano-sized alumina as the starting powder was observed to have played a pivotal role in preventing the cBN-to-hBN transformation. The composites prepared using nano-sized alumina reinforced with nickel-coated 30 wt% cBN showed the highest relative density of 99% along with the highest Vickers hardness (Hv2) value of 29 GPa. Because the compositions made with micro-sized alumina underwent the phase transformation from cBN to hBN, their relative densification as well as hardness values were relatively low (20.9–22.8 GPa). However, the nickel coating on the cBN reinforcement particles hindered the cBN-to-hBN transformation in the micro-sized alumina matrix, resulting in improved hardness values of up to 24.64 GPa.
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"Studies of low energy ion bombardment of cubic boron nitride (111) surfaces by reflection electron energy loss spectroscopy: 低能離子轟擊立方氮化硼(111)表面之反射電子能量損失譜硏究." 2002. http://library.cuhk.edu.hk/record=b6073492.
Full textAbstract:
Yuen Yung Hui.Thesis (Ph.D.)--Chinese University of Hong Kong, 2002.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.
Yuen Yung Hui.
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Vetter, Ulrich. "Lanthanide Doped Wide Band Gap Semiconductors: Intra-4f Luminescence and Lattice Location Studies." Doctoral thesis, 2003. http://hdl.handle.net/11858/00-1735-0000-0006-B555-B.
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