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1
Razzell, Anthony Gordon. "Silicon carbide fibre silicon nitride matrix composites." Thesis, University of Warwick, 1992. http://wrap.warwick.ac.uk/110559/.
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Silicon carbide fibre/silicon nitride matrix composites have been fabricated using the reaction bonded silicon nitride (RBSN) and sintered reaction bonded silicon nitride (SRBSN) processing routes. A filament winding and tape casting system was developed to produce sheets of parallel aligned fibres within a layer of green matrix ('prepreg') which were cut, stacked and hot pressed to form a plate. This was nitrided and (in the case of SRBSN matrix composites) hot pressed at 1700°C to density the matrix. The magnesia (MgO) and the yttria/alumina (Y2O3/AI2O3) additive SRBSN systems were investigated as matrices for ease of processing and compatibility with the matrix. The MgO additive Si3N4 matrix reacted with the outer carbon rich layer on the surface of the fibres, framing a reaction layer approx. 2pm in thickness. A reaction layer was also observed with the Y2O3/AI2O3 additive matrix, but was thinner (< 0.5um), and was identified as silicon carbide from the electron diffraction pattern. X-ray mapping in the SEM was used to investigate the spatial distribution of elements within the interface region to a resolution < lum, including light elements such as carbon. The 6wt%Y203/ 2wt%Al203 additive SRBSN system was chosen for more detailed investigation, and the majority of characterisation was performed using this composition. Oxidation of composite samples was carried out at temperatures between 1000°C and 1400°C for up to 1000 hours. Little damage was visible after 100 hours for all temperatures, corresponding to a relatively small drop in post oxidation bend strength. After 1000 hours at 1000°C both carbon rich outer layers and the central carbon core of the fibre were removed. Samples were severely oxidised after 1000 hours at 1400°C, having a glass layer on the outer surface and replacement of near surface fibre/matrix interfaces with glass. The post oxidation bend strengths for both conditions were approx.2/3 of the as fabricated strength. Less damage was observed after 1000 hours at 1200°C, and the post oxidation bend strength was higher than the 1000°C and 1400°C samples. Mechanical properties of the SRBSN matrix composite were investigated at room temperature and elevated temperatures (up to 1400°C). The average room temperature values for matrix cracking stress and ultimate strength (in bend) were 651.1 and 713.2 MPa respectively, with corresponding Weibull moduli of 5.7 and 8.7. The stresses are comparable to similar monolithic silicon nitrides. Room temperature tensile matrix cracking and ultimate strength were 232MPa and 413MPa, lower than the bend test results, which were attributed to bending stresses in the sample, lowering the apparent failure stresses. The samples failed in a composite like manner (i.e. controlled rather than catastrophic failure), with a substantially higher woric of fracture than monolithic materials. The average matrix cracking and ultimate bend strength at 1200°C were 516MPa and 554MPa, dropping to 178MPa and 486MPa at 1400°C (the matrix cracking stress was indistinct at 1400°C due to plasticity). The creep and stress rupture properties at 1300°C were investigated in four point bend, using dead-weight loading. The creep rate was KH/s at a stress of 200MPa, lower than a hot pressed silicon nitride with MgO additive, and higher than a hot isostatically pressed Y2O2/SÍO2 additive silicon nitride. A cavitation creep mechanism was deduced from the stress exponent, which was >1. Failure by stress rupture did not have a lower limit, which is also associated with cavitation of the amorphous grain boundary phase.
2
Durham, Simon J. P. "Carbothermal reduction of silica to silicon nitride powder." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74221.
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The processing conditions for carbothermal reduction of silica to silicon nitride was found to be sensitive to several key processing parameters: namely the intimacy of mixing of carbon and silica, the temperature, the specific high surface area of carbon, the nitrogen gas purity and the action of the nitrogen gas passing through the reactants.Sol-gel processing was found to provide superior mixing conditions over dry mixing, which allowed for complete conversion to silicon nitride at optimum carbon:silica ratios of 7:1. The ideal reaction temperature was found to be in the range of 1500$ sp circ$C to 1550$ sp circ$C. Suppression of silicon oxynitride and silicon carbide was achieved by ensuring that: (a) the nitrogen gas was gettered of oxygen, and (b) that the gas passed through the reactants. Thermodynamic modelling of the Si-O-N-C system showed that ordinarily the equilibrium conditions for the formation of silicon nitride are very delicate. Slight deviations away from equilibrium leads to the formation of non-equilibrium species such as silicon carbide caused by the build-up of carbon monoxide. Reaction conditions such as allowing nitrogen gas to pass through the reactants beneficially moves the reaction equilibrium well away from the silicon carbide and silicon oxynitride stability regions.
The particle size of silicon nitride produced from carbon and silica precursors was of the order of 2-3 $ mu$m and could only be reduced to sub-micron range by seeding with ultra-fine silicon nitride. It was shown that the mechanism of nucleation and growth of unseeded reactants was first nucleation on the carbon by the reaction between carbon, SiO gas and nitrogen (gas-solid reaction), and then growth of the particles by the gas phase reaction (CO, SiO, N$ sb2$).
3
Hadian, Ali Mohammad. "Joining of silicon nitride-to-silicon nitride and to molybdenum for high-temperature applications." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41370.
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The evolution of advanced ceramic materials over the past two decades has not been matched by improvements in ceramic joining science and technology, particularly for high temperature applications. Of the techniques being evaluated for joining ceramics, brazing has been found to be the simplest and most promising method of fabricating both ceramic/ceramic and ceramic/metal joints. A key factor in ceramic brazing is wetting of the ceramic by the filler metal.This study deals with the application of brazing for the fabrication of $ rm Si sb3N sb4/Si sb3N sb4$ and $ rm Si sb3N sb4/Mo$ joints using Ni-Cr-Si brazing alloys based on AWS BNi-5 (Ni-18Cr-19Si atom%). Thermodynamic calculations were performed to predict wetting at $ rm Si sb3N sb4$/Ni-Cr-Si alloys interfaces. By using some simplifying assumptions and suitable scaling of the reaction, the model predicted that Ni-Cr-Si alloys with Ni/Cr = 3.5 and X$ sb{ rm Si}$ $<$ 0.25 would react chemically with and wet $ rm Si sb3N sb4$. Good agreement was found between the theoretical calculations and experimental results.
Brazing experiments were carried out to study the joinability of $ rm Si sb3N sb4$ with various Ni-Cr-Si filler metals which had already shown good wetting characteristics on $ rm Si sb3N sb4$. The $ rm Si sb3N sb4/Si sb3N sb4$ joints formed with a 10 atom% Si brazing alloy exhibited the highest strength ($ approx$120 MPa) which was mainly due to the presence of a CrN reaction layer at the ceramic/filler metal interface. The high temperature four-point bend strengths of $ rm Si sb3N sb4/Si sb3N sb4$ joints were markedly higher than the room temperature values. A high strength of about 220 MPa was achieved when the joints were tested at 900$ sp circ$C.
From the results of the $ rm Si sb3N sb4/Mo$ joining experiments it was found that the joint quality and microstructure were strongly influenced by the composition of the filler metal and such brazing variables as time and temperature. Of all the $ rm Si sb3N sb4$/Mo joints, those made with the S10 brazing alloy at 1300$ sp circ$C for 1 min. exhibited the highest strength of 55 MPa.
Finally, in all the cases, the shear strength of all the joints was found to be lower than their four-point bend values.
4
Yi, Jae Hyung. "Silicon rich nitride for silicon based laser devices." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44315.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Page 214 blank.
Includes bibliographical references.
Silicon based light sources, especially laser devices, are the key components required to achieve a complete integrated silicon photonics system. However, the fundamental physical limitation of the silicon material as light emitter and the limited understanding of tli~ excitation mechanism of Er in dielectric media by optical and electrical pumping methods impedes the progress of the research activities in this area. Silicon rich nitride (SRN) has been investigated as a strong candidate for silicon based laser devices. SRN has many advantages over other Si-based materials systems. These advantages include a high electrical injection level at low voltages, a low annealing temperature for Si nanocluster (Si-nc) formation and a large refractive index for strong optical confinement. Strong light emission from localized states in Si-nc embedded in SRN was demonstrated with a PLQE (Photoluminescence Quantum Efficiency) of 7%. This effect was confirmed through several experiments and first principle calculations. Thue Morse aperiodic structures were fabricated with light emitting SRN and SiO2 materials, for the first time. Through the resonance phenomena achieved using this approach an emission enhancement of a factor of 6 was demonstrated experimentally. A sequential annealing technique was investigated to enhance the light emission from the Si-nc based light emitter. Electrical injection was greatly improved with annealing treatments of SRN based devices. In particular, bipolar electrical injection into SRN led to electroluminescence which was comparable to photoluminescence in peak shape and spectral position. Er doped SRN (Er:SRN) was fabricated through a co-sputter technique to achieve light emission at the wavelength of 1.54 [mu]m.
(cont.) Energy transfer from SRN td Er was confirmed and shown to have a strong dependence on Si content. Si racetrack resonator structures with a low loss value of 2.5 dB/cm were fabricated through a Local Oxide (LOCOS) process and coupled with an Er:SRN layer to investigate gain behavior. Electrical injection properties into the Er:SRN layer were investigated and the electroluminescent device was fabricated. A detailed discussion on optical and electrical excitation of Er is provided to clarify the difference of the Er excitation mechanisms. A comparison of key simulation parameters used within the two level equations for optical and electrical excitation of Er atoms is provided to explain how the parameters contribute to each excitation mechanism. The most significant differences between the parameters and excitation mechanisms are also explained. Finally a summary of important factors to achieve a silicon based laser is provided and discussed for future investigation based on the experimental data and the investigation presented in this work.
by Jae Hyung Yi.
Ph.D.
5
Li, Wenyu. "The fabrication of silicon nitride-titanium nitride composite materials." Thesis, University of Leeds, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305875.
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Saxena, Pawan. "Slip casting of silicon nitride." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56974.
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Slip casting is a well established technique for the manufacture of traditional ceramic bodies, such as clays and whitewares. It combines complex shaping with high green densities, resulting in low shrinkage and good densification behaviour.This method, however, has received little attention in the field of engineering ceramics especially with regard to silicon nitride. Commercial fabrication of silicon nitride, a major contender for high temperature applications due to its excellent thermomechanical properties, has been confined to hot pressing. This is an expensive process and has geometrical limitations.
Slip casting, followed by sintering, has been identified as a potentially economical alternative fabrication method, however a number of parameters have to be optimized before a good slip cast silicon nitride body can be made. The aim of the present work is to control parameters such as pH, viscosity and deflocculation in order to form dense, homogeneous, slip cast silicon nitride bodies.
A detailed investigation of the rheological properties of Si$ sb3$N$ sb4$ and careful control of processing parameters, made it possible to produce slip cast Si$ sb3$N$ sb4$ bodies having up to 97% TD on sintering. Mechanical strength values obtained by slip casting were compared with those obtained by die-pressing. Strength values of the slip cast material was limited by iron inclusions entrained in processing.
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Ovri, J. E. O. "Diametral-compression of silicon nitride." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378585.
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Knight, Patrick J. "Nitride formation at silicon surfaces." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238903.
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Rockett, Chris H. "Flexural Testing of Molybdenum-Silicon-Boron Alloys Reacted from Molybdenum, Silicon Nitride, and Boron Nitride." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16293.
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MoSiB alloys show promise as the next-generation turbine blade material due to their high-temperature strength and oxidation resistance afforded by a protective borosilicate surface layer. Powder processing and reactive synthesis of these alloys has proven to be a viable method and offers several advantages over conventional melt processing routes. Microstructures obtained have well-dispersed intermetallics in a continuous matrix of molybdenum solid-solution (Mo-ss). However, bend testing of pure Mo and Mo-ss samples has shown that, while the powder processing route can produce ductile Mo metal, the hardening effect of Si and B in solid-solution renders the matrix brittle. Testing at elevated temperatures (200°C) was performed in order to determine the ductile-to-brittle transition temperature of the metal as an indication of ductility. Methods of ductilizing the Mo-ss matrix such as annealing and alloying additions have been investigated.
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Martinelli, Antonio Eduardo. "Diffusion bonding of silicon carbide and silicone nitride to molybdenum." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40191.
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This study focuses on various aspects of solid-state diffusion bonding of two ceramic-metal combinations, namely: silicon carbide-molybdenum (SiC-Mo), and silicon nitride-molybdenum (Si$ rm sb3N sb4$-Mo). Single SiC-Mo and $ rm Si sb3N sb4$-Mo joints were produced using hot-uniaxial pressing. The microstructure of the resulting interfaces were characterized by image analysis, scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and X-ray diffraction (XRD). The mechanical properties of the joints were investigated using shear strength testing, depth sensing nanoindentation, and neutron diffraction for residual stress measurement.SiC was solid-state bonded to Mo at temperatures ranging from 1000$ sp circ$C to 1700$ sp circ$C. Diffusion of Si and C into Mo resulted in a reaction layer containing two main phases: $ rm Mo sb5Si sb3$ and Mo$ sb2$C. At temperatures higher than 1400$ sp circ$C diffusion of C into $ rm Mo sb5Si sb3$ stabilized a ternary phase of composition $ rm Mo sb5Si sb3$C. At 1700$ sp circ$C, the formation of MoC$ rm sb{1-x}$ was observed as a consequence of bulk diffusion of C into Mo$ sb2$C. A maximum average shear strength of 50 MPa was obtained for samples hot-pressed at 1400$ sp circ$C for 1 hour. Higher temperatures and longer times contributed to a reduction in the shear strength of the joints, due to the excessive growth of the interfacial reaction layer. $ rm Si sb3N sb4$ was joined to Mo in vacuum and nitrogen, at temperatures between 1000$ sp circ$C and 1800$ sp circ$C, for times varying from 15 minutes to 4 hours. Dissociation of $ rm Si sb3N sb4$ and diffusion of Si into Mo resulted in the formation of a reaction layer consisting, initially, of $ rm Mo sb3$Si. At 1600$ sp circ$C (in vacuum) Mo$ sb3$Si was partially transformed into $ rm Mo sb5Si sb3$ by diffusion of Si into the original silicide, and at higher temperatures, this transformation progressed extensively within the reaction zone. Residual N$ sb2$ gas, which originated from the decomposition of $ rm Si sb3N sb4,$ dissolved in the Mo, however, most of the gas escaped during bonding or remained trapped at the original $ rm Si sb3N sb4$-Mo interface, resulting in the formation of a porous layer. Joining in N$ sb2$ increased the stability of $ rm Si sb3N sb4,$ affecting the kinetics of the diffusion bonding process. The bonding environment did not affect the composition and morphology of the interfaces for the partial pressures of N$ sb2$ used. A maximum average shear strength of 57 MPa was obtained for samples hot-pressed in vacuum at 1400$ sp circ$C for 1 hour.
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Chen, Wan Lam Florence Photovoltaics & Renewable Energy Engineering Faculty of Engineering UNSW. "PECVD silicon nitride for n-type silicon solar cells." Publisher:University of New South Wales. Photovoltaics & Renewable Energy Engineering, 2008. http://handle.unsw.edu.au/1959.4/41277.
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The cost of crystalline silicon solar cells must be reduced in order for photovoltaics to be widely accepted as an economically viable means of electricity generation and be used on a larger scale across the world. There are several ways to achieve cost reduction, such as using thinner silicon substrates, lowering the thermal budget of the processes, and improving the efficiency of solar cells. This thesis examines the use of plasma enhanced chemical vapour deposited silicon nitride to address the criteria of cost reduction for n-type crystalline silicon solar cells. It focuses on the surface passivation quality of silicon nitride on n-type silicon, and injection-level dependent lifetime data is used extensively in this thesis to evaluate the surface passivation quality of the silicon nitride films. The thesis covers several aspects, spanning from characterisation and modelling, to process development, to device integration. The thesis begins with a review on the advantages of using n-type silicon for solar cells applications, with some recent efficiency results on n-type silicon solar cells and a review on various interdigitated backside contact structures, and key results of surface passivation for n-type silicon solar cells. It then presents an analysis of the influence of various parasitic effects on lifetime data, highlighting how these parasitic effects could affect the results of experiments that use lifetime data extensively. A plasma enhanced chemical vapour deposition process for depositing silicon nitride films is developed to passivate both diffused and non-diffused surfaces for n-type silicon solar cells application. Photoluminescence imaging, lifetime measurements, and optical microscopy are used to assess the quality of the silicon nitride films. An open circuit voltage of 719 mV is measured on an n-type, 1 Ω.cm, FZ, voltage test structure that has direct passivation by silicon nitride. Dark saturation current densities of 5 to 15 fA/cm2 are achieved on SiN-passivated boron emitters that have sheet resistances ranging from 60 to 240 Ω/□ after thermal annealing. Using the process developed, a more profound study on surface passivation by silicon nitride is conducted, where the relationship between the surface passivation quality and the film composition is investigated. It is demonstrated that the silicon-nitrogen bond density is an important parameter to achieve good surface pas-sivation and thermal stability. With the developed process and deeper understanding on the surface passivation of silicon nitride, attempts of integrating the process into the fab-rication of all-SiN passivated n-type IBC solar cells and laser doped n-type IBC solar cells are presented. Some of the limitations, inter-relationships, requirements, and challenges of novel integration of SiN into these solar cell devices are identified. Finally, a novel metallisation scheme that takes advantages of the different etching and electroless plating properties of different PECVD SiN films is described, and a preliminary evalua-tion is presented. This metallisation scheme increases the metal finger width without increasing the metal contact area with the underlying silicon, and also enables optimal distance between point contacts for point contact solar cells. It is concluded in this thesis that plasma enhanced chemical vapour deposited silicon nitride is well-suited for n-type silicon solar cells.
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Tatli, Zafer. "Silicon nitride and silicon carbide fabrication using coated powders." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394640.
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Turan, Servet. "Microstructural characterisation of silicon nitride-silicon carbide particulate composites." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627653.
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Quinn, R. W. "Machining damage in silicon nitride ceramics." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/843210/.
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This Thesis is primarily concerned with the effects of abrasive machining (diamond grinding) and diamond indentation on the fracture properties of a range of silicon nitride materials. Test specimens machined to surface finishes representative of those found on Aero Gas Turbine components were produced for Modulus of Rupture (MOR) testing, and variations in the fracture strengths were assessed. Optical and Scanning Electron Microscopy (SEM) were performed as a means of identifying the nature of the defects found within these materials. Having determined the dependence of strength and reliability on the machined surface finish, attempts were made to palliate the machining damage by thermal annealing and Nitrogen Ion Implantation. X-ray diffraction residual stress measurements were performed in order to quantify the magnitude of the near surface stresses in both the "as machined" and annealed conditions.* Diamond indentation techniques (Vickers and Knoop) were employed in order to determine the hardness of the materials studied and to quantify the extent of the Indentation Size Effect (ISE). These studies were then extended to the point of indentation fracture as a means of assessing the materials fracture toughness (KIC) and the nature of the crack systems beneath the indentation. *Residual stress measurements were carried out on a sub contract basis at the CEGB Central Laboratories by P E J Flewitt and D Lonsdale, their help throughout this work is gratefully acknowledged.
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Turner-Adomatis, Bonnie L. "Shock-enhanced sintering of silicon nitride." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/18905.
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Muscat, Daniel. "Silicon nitridesilicon nitride whisker-reinforced composites." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60102.
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One of the major setbacks of ceramic materials is their inherent brittle nature which often leads to catastrophic failure, especially under impact and tensile stress conditions. Whisker-reinforcement of ceramic matrices has been shown to be an effective way of increasing toughness. However, the hot-pressing techniques being used at present are expensive. Si$ sb3$N$ sb4$ is a major contender for high temperature application, mainly due to its excellent mechanical, chemical and thermal properties.In this work Si$ sb3$N$ sb4$ whiskers have been incorporated into a Si$ sb3$N$ sb4$ matrix and densified using pressureless sintering. An isotropic distribution of whiskers in the starting powder was seen to inhibit shrinkage of the bulk material as a result of whisker bridging.
An extrusion process was developed to align the whiskers such that they do not impinge on one another. This was done using a water soluble, cellulose based plasticizer. The process was sensitive to water content and mixing. Entrapped air caused problems in the extrudate, resulting in misaligned areas in the microstructure. Relative densities of 94.5% were obtained for composites having 15% whiskers. The toughness of this material was measured to be 13.5MPa.m$ sp{1/2}$ in the direction perpendicular to the direction of extrusion.
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Wang, W. "Rolling contact fatigue of silicon nitride." Thesis, Bournemouth University, 2010. http://eprints.bournemouth.ac.uk/17764/.
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Silicon Nitride has traditionally been used as rolling contact bearing material owing to its superior performance compared to bearing steels. Its successful application as a bearing element has led to the development of Silicon Nitride in other rolling contact applications in the automotive industry and the power industry. However, a major limitation of its wider application is its high material and machining cost, especially the cost associated with the finishing process. In the present study, a low cost sintered and reaction-bonded Silicon Nitride is used to study the surface machining effects on its rolling contact fatigue performance. Studies have been carried out to link the surface strengths of Silicon Nitride derived from half-rod and C-Sphere flexure strength specimens to the rolling contact lives of Silicon Nitride rod and ball specimens. The rolling contact fatigue tests were carried out on ball-on-rod and modified four-ball machines. Three types of surface with coarse, fine and RCF-conventional finishing conditions were examined. Flexure strength tests on half-rod and C-Sphere showed an increasing surface strength from specimens with coarse, fine to RCF-conventionally machined conditions. During rolling contact fatigue tests of as-machined specimens, no failures were observed on either ball-on-rod or four-ball tests after 100 million stress cycles. However, a trend of decreasing wear volumes was measured on the contact path of rods and balls with coarse, fine and RCF-conventional conditions. In four-ball tests, spall failures were observed on pre-cracked specimens. There was a trend of increasing rolling contact fatigue lifetime from pre-cracked specimens with coarse, fine to RCF-conventional machining conditions. The study of Silicon Nitride machining was also carried out using an eccentric lapping machine to investigate the effect of eccentricity on the finishing rate of hot isostatically-pressed and sintered and reaction-bonded Silicon Nitride. The eccentricity had no significant impact on finishing rate as concluded in this study. The effect of lubricant viscosity and chemistry on the rolling contact fatigue performance of Silicon Nitride was also studied. The result is inconclusive.
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Pettersson, Maria. "Silicon nitride for total hip replacements." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-247800.
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For more than 50 years total hip replacements have been a common and successful procedure to increase patient mobility and quality of life. The 10-year implant survival rate is 97.8%. However, for longer implantation times there are limitations linked to the negative biological response to wear and corrosion products from the currently used biomaterials. In this thesis silicon nitride (SiNx) coatings were evaluated for use in total hip replacements, on the articulating bearing surface and modular taper connections. Homogeneous, dense SiNx coatings were deposited using reactive high power impulse magnetron sputtering (HiPIMS) up to a thickness of 8 µm. The N/Si atomic ratios ranged from 0.3 to 1.1 and the coatings showed a low surface roughness. The wear rate of a SiNx coated cobalt chromium molybdenum alloy (CoCrMo) was similar to that of bulk Si3N4, and less than one 46th of uncoated CoCrMo, an alloy that is commonly used in joint replacements. Wear debris generated from SiNx coatings was round in shape, with a mean size of 40 nm, and ranged between 10 and 500 nm. Model particles, similar in size and shape as the wear debris, were soluble in simulated body fluid. The dissolution rate was higher than the expected rate of debris generation. Along with the size of the debris, which is not in the critical range for macrophage activation, this dissolution may limit negative biological reactions. The SiNx coatings also dissolved in simulated body fluid. The coating with the highest N/Si ratio exhibited the lowest dissolution rate, of 0.2 to 0.4 nm/day, while CoCrMo under the same condition dissolved at a rate of 0.7 to 1.2 nm/day. SiNx-coated CoCrMo exhibited a reduced release of Co, Cr and Mo ions into the solution by two orders of magnitude, compared to uncoated CoCrMo. Si3N4 evaluated under micro-displacement in a corrosive environment, replicating the modular taper, showed a lower corrosion current compared to common biomedical alloys. SiNx coatings may also act beneficially to reduce issues associated with this type of contact. SiNx coatings have shown several properties in a laboratory environment that are hypothesised to increase the longevity of joint replacements. The promising results encourage further evaluation closer to the clinical application of total hip replacements, in particular in the articulating bearing surface and in modular tapers.
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Karecki, Simon Martin. "Alternative chemistries for etching of silicon dioxide and silicon nitride." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/43304.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 123-126).
by Simon Martin Karecki.
M.S.
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Pooley, David Martin. "Vertical silicon single-electron devices with silicon nitride tunnel barriers." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621302.
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Kim, Hyoun-Ee. "Gaseous corrosion of silicon carbide and silicon nitride in hydrogen /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487327695622538.
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Kurra, Sri Harsha. "Nondestructive testing for finding out the displacement of crack in silicon nitride." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Wiseman, Charles R. "Production of silicon and silicon nitride powders by a flow reactor." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182874102.
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Grove, Richard Sebastian. "Processing and properties of silicon and silicon nitride injection moulding formulations." Thesis, Brunel University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311263.
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Hepburn, A. R. "Charge trapping instabilities in amorphous silicon/silicon nitride thin film transistors." Thesis, Open University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381605.
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Bae, Dohyun. "Sputtering fabrication of silicon nitride and silicon oxide based dichroic mirrors." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98645.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 37).
Thin films in optical materials utilize the properties of multiple materials to obtain specific and fine-tuned transmission, absorption and reflectance at wavelengths. Dichroic mirrors exhibit very different reflectance and transmission rates at certain cut-off wavelengths, which can be adjusted using changes in layer materials and thickness. This is due to constructive optical interference between alternating layers of two thin films of different refractive indices. This study explored the sputtering methods of thin-film multilayers to form dichroic mirrors in the visible spectrum for future solar-cell applications. Silicon oxide and silicon nitride targets were selected as materials used in the sputtering process. The sputtered multilayers and films were then characterized and analyzed using spectrophotometry. The transmission spectrum of the initial multilayer depicted failure in transmission at wavelengths under 500nm. The components of the multilayer were then sputtered and analyzed to troubleshoot the problematic nitride films. Transmission spectra were utilized to select each following process, and both reactive sputtering and cosputtering were explored as means of creating nitride films with functional properties. Transmission spectra were analyzed using the Swanepoel method to quantify optical characteristics to assure reactive sputtering of the targets in a nitrogen environment as a viable direction of mirror construction. Possible further work include the use of other targets such as titanium oxide, and different chamber gas mixtures for finer control in the composition of the film layers.
by Dohyun Bae.
S.B.
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Morgan, B. A. "Current transport in hydrogenated amorphous silicon nitride." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/842874/.
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A defect band is formed in hydrogenated amorphous silicon nitride (a-SiNx:H) due to current stressing of the material. This gives rise to an increase in conductivity, referred to as current induced conductivity. This thesis investigates the current transport mechanisms that occur in the induced defect band, by comparing the temperature dependence of the conductivity of several sets of a-SiNx:H thin film diodes. These sets were systematically current stressed to different levels with one set remaining unstressed. Samples with energy gaps of 2.06 eV and 2.28 eV were considered. We show that around room temperature a modified Poole-Frenkel description of conduction (i.e. field enhanced hopping of carriers via charged defect states) provides a good fit to the data. Using this model the activation energy of current transport was calculated and shown to depend on the material band gap. Data fitting to the Poole-Frenkel model provided further support for the field-assisted hopping mechanism. Previous investigations had suggested that the defect band resides in the lower half of the band gap, so that current transport through the defect band was then expected to be due to the movement of holes, in a manner consistent with Poole-Frenkel conduction. By considering samples grown on p-type and n-type substrates, we demonstrated that transport was indeed the result of the movement of holes through the defect states within the induced defect band. At lower temperatures the experimental data is poorly described by a modified Poole-Frenkel type process, so further mechanisms were considered, including variable-range hopping and nearest-neighbour hopping. Due to the similar nature and slight temperature dependence of each process, differentiating between the two mechanisms proved difficult. However, other factors such as the temperature range and defect density favoured variable-range hopping transport. By assuming this form of low temperature hopping transport, conduction through the defect-band of the a-SiNx:H, could then be convincingly explained over the entire temperature range from 320 K to 20 K in terms of two dominant transport mechanisms, Poole-Frenkel conduction and variable-range hopping.
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Trivedi, Dhruti Mayur. "Fabrication and characterization of silicon nitride nanopores." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7288.
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The fabrication of synthetic nanopores with dimensional and electrical properties similar to organic alpha-hemolysin (α-HL) nanopores is required for the development of a novel genotyping device. This thesis details the development of synthetic nanopores with diameters below 5 nm fabricated by sputtering a free standing silicon nitride membrane using a tightly focused electron beam. Nanometer control is achieved with sputtering rates of 0.5 – 0.75 nm/s. This technique is further extended to fabricate a proof-of-concept array of 44 sub-5 nm nanopores in a single membrane to enable the detection of unamplified genomic DNA with acceptable signal-to-noise.
As-drilled inorganic nanopores have inferior electrical characteristics compared to α-HL. Careful study, however, revealed electrical noise sources that could be effectively reduced by chemical pretreatment of the pores and surface coating with poly-di-methyl-siloxane (PDMS). The chemical pretreatment targeted 1/f noise, while the PDMS reduced dielectric noise with an overall reduction in RMS current noise by a factor of 10. This resulted in processed nanopores with extremely favorable noise characteristics. These low noise silicon nitride nanopores were used to demonstrate single-molecule DNA translocation and probe capture with exceptional signal-to-noise ratios ranging from 40 – 150.
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Zarnon, Linda Christina. "Grain boundary control of silicon nitride ceramics." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55655.
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Lemus-Ruiz, Jose. "Diffusion bonding of silicon nitride to titanium." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37760.
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The use of ceramic has gradually increased over the past few years. Si3N4 is one of the most important ceramics used as structural material for high temperature applications. The practical use of advanced ceramics depends on the reliability of ceramic/metal joining techniques and the properties of the resulting interfaces. This work focuses on various aspects of diffusion bonding of Si3N4 to Ti as well as on the use of Ti-foil interlayer during the self-joining of Si3N4. Si3N4/Ti and Si3N 4/Ti-foil/Si3N4 combinations were diffusion joined by hot-uniaxial pressing and the microstructural characterization of the resulting interfaces was carried out by SEM, EPMA, and X-ray diffraction.Diffusion bonding was carried out at temperatures ranging from 1200 to 1500ºC using different holding times, pressures, and surface roughness of the joining materials. The results showed that Si3N4 could not be bonded to Ti at temperatures lower than 1400ºC, however successful joining at higher temperatures. Joining occurred by the formation of a reactive interface on the Ti side of the joint. At temperatures greater than 1330ºC, liquid formation occurred by the interaction of Ti with Si promoting bonding, as well as the high affinity of Ti for Si resulted in rapid interface formation of silicides, initially Ti5Si3. EPMA and X-ray diffraction confirmed the presence of Ti5Si3, TiSi, and TiN at the interface. The surface roughness of the joining materials plays an important role since thicker interfaces were obtained for polished samples compared to as-ground samples. The interfaces grew in a parabolic fashion with the formation of various Ti-silicides (Ti5Si3 and TiSi) as well as Ti-nitride (TiN) at the interface.
Evaluation of joint strengths as a function of the experimental parameters such as, joining temperature and time was obtained by four-point bending test performed on Si3N4/Ti/Si3N4 joints. Strong joints were produced at joining temperatures greater than 1450ºC with average bend strength of more than 100 MPa. The maximum joint strength was obtained in samples hot-pressed at 1500ºC and 120 minutes reaching a value of 147 MPa.
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Matsushita, Yoshiaki. "Diffusion bonding of silicon nitride to metals." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333487.
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Briggs, D. J. E. "The creep behaviour of silicon nitride ceramics." Thesis, Swansea University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636155.
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The creep properties of silicon nitride ceramics have usually been discussed by reference to the dependence of the secondary creep rate (εs) on stress (σ) and temperature (T) using a power law relationship of the form:-hskip 0.5cm εs = Aσn(-Q_c/RT) where 'A' and 'n' are constants and 'Q_c' is the activation energy for creep. Studies show, however, that the creep properties of ceramics can not be adequately characterised by measurement of only the secondary creep rate. The evidence indicates that traditional approaches to creep should be abandoned in favour of a new method of analysing creep data termed the <θ> projection concept. This provides equations which describe the creep curve shape and its dependence on test conditions. In this investigation the creep data for five silicon nitride ceramics [obtained in other studies] has been extended by carrying out creep tests on two of the materials at a range of conditions of stress and temperature. The creep data for all five materials has been analysed using both traditional approaches and the θ projection concept. Microstructural studies of the materials have also been carried out. The creep properties of the materials have been related to their microstructural features. It is shown that creep properties are strongly dependent on the character of the intergranular amorphous phase. The investigation shows that the limitations of traditional approaches to creep of silicon nitride ceramics can be overcome by using the θ projection concept to analyse creep behaviour. The θ analysis has been used to identify the dominant influences on creep behaviour patterns. The evidence indicates that the creep behaviour patterns of these materials can be strongly affected by oxidation influenced changes in the character of the intergranular phase. The time and temperature dependence of these changes can influence the stress and temperature dependence of creep curve shape.
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Murakami, T. "Predicting creep behaviour of silicon nitride ceramics." Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638280.
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Rahman, I. Ab. "Production of silicon nitride from rice husks." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382871.
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Alhabill, Fuad N. F. "Dielectric behaviour of silicon nitride epoxy nanocomposites." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/419656/.
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Nanodielectric materials have potential to meet the requirements of next generation insulation technology by offering attractive electrical, mechanical and/or thermal properties. A precise understanding of the factors and mechanisms that control the properties of nanocomposites could enable the tailoring and engineering of these composites to meet the requirements of a particular application. The surface chemistry of nanoparticles and their interactions with the base material are very important factors, among others, such as moisture adsorption and particle dispersion, which affect the electrical performance of nanodielectrics. This study examines factors that affect the electrical behaviour of silicon nitride/epoxy nanocomposites. First, a critical review of the models that have been proposed in the literature to describe the electrical behaviour of nanocomposites was conducted. Based on this review, a new model, namely the particle interphase model, was devised. The main proposition of this model is that nanoparticles contain a high concentration of defects close to their surfaces, which could be due to foreign atoms, surface geometrical irregularities or coordinative unsaturation, and these defects can perturb the electronic states in the outer layer of the particles which, consequently, may have a critical impact on the electrical behaviour of the bulk material. Therefore, unlike the existing models, which broadly are based on the proposition of a polymeric interphase layer around the nanoparticles, this model proposed the presence of a thin interphase layer inside the boundaries of the particles themselves that, from an electrical perspective, might have a more profound impact on the performance of nanodielectrics. The experimental investigation started by characterising the surface chemistry of the nanofiller, where it was identified that the silicon nitride nanoparticles are covered with amine groups on their surface. Since these surface amine groups are the same as the amine groups in the hardener, this led to that these surface groups can react with the resin’s epoxy groups and, thus, affect the resin/hardener stoichiometry. Consequently, the influence of the nanofiller on the epoxy matrix might be related to a commensurate change in the matrix stoichiometry, rather than being directly associated with the presence of the nanofiller. To investigate this hypothesis, the effect of changing the resin/hardener stoichiometry was studied. By changing the ratio of resin to hardener, a better understanding of the electrical behaviour and its relationship with the structure, dynamics and chemistry of the considered epoxy networks was achieved. Detailed electrical characterization showed that, in the glassy state, electrical properties of the studied epoxy networks are sensitive to the network’s chemical content, rather than to variations in the network’s structure or dynamics. Using formulations that contain an excess of hardener has a detrimental impact on DC conductivity, DC breakdown strength and water uptake of the resulting networks, whereas, decreasing the hardener content leads to enhancements in these properties. Conversely, AC breakdown results indicated that this parameter does not vary on changing the stoichiometry, which suggests that the AC and DC breakdown strengths are controlled by different mechanisms. A tentative explanation for the AC breakdown behaviour is suggested. For silicon nitride filled systems, based on differential scanning calorimetry results, it was estimated that the inclusion of 2 wt% and 5 wt% of the silicon nitride nanofiller displaces the resin/hardener stoichiometry by ~6.5 % and ~18 %, respectively. This finding was further corroborated by dielectric spectroscopy and water absorption results. Therefore, this study renders conclusive evidence that nanofillers can directly and significantly affect the curing process of an epoxy network and, thus, this parameter should always be considered when introducing nanofillers into thermosetting matrices. Such a finding implies the presence of covalent bonding between the nanoparticles and the surrounding polymer and, therefore, offered an opportunity to question what is usually conjectured in literature that strong filler/polymer interactions can affect or confine the molecular dynamics of the polymer layer around the particles and also lead to better particle dispersion. The results indicate that while this chemical bonding leads to good nanoparticle dispersion, it does not have an appreciable influence on the segmental dynamics of the polymer. According to the uncertainties of the experimental technique used here, any affected polymeric layer around the particles should not have a thickness greater than 0.8 nm. While the nanofiller stoichiometric effect explains many aspects of the electrical behaviour of the considered nanocomposites, it cannot account alone for the whole picture. The obtained data indicate the presence of additional effect that superimposes on the filler stoichiometric effect in influencing the electrical behaviour. Modifying the particle surface chemistry, via heat treatment at 1050 °C, showed that this additional effect is related to the particle interphase characteristics. The results demonstrate the crucial impact of the particle interphase and thus provide experimental credence to the proposed model.
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Hassan, Shereen Hassan Mohamed Gaber. "Sol-gel preparation of silicon nitride materials." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72951/.
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Sol-gel techniques are mainly used for oxides but are of growing interest for non-oxide materials. They allow formation of solid materials through gelation of precursor solutions and can be used to control composition and to produce a large number of useful morphologies such as films, monoliths, aerogels, foams and materials with ordered pores on various length scales. Often the synthesis of non-oxide materials using sol-gel methods has focused on producing powders for applications such as catalysis, where controlled porosity and basic catalytic sites are the point of interest. In this thesis, formation of silicon nitride based materials as thin films, aerogels, inverse opal films and phosphor powders have been synthesised using non-oxide sol-gel methods. For thin films formation of amorphous silicon nitride, [Si(NHMe)4] solution in tetrahydrofuran (THF) with ammonia in the presence of a triflic acid catalyst was used. The sols formed from this mixture were used to make films using a simple dip coating technique. A number of coating and pyrolysis regimes have been compared. Aerogels were prepared through a small change in the sol preparation conditions leading to bulk gelation, supercritical drying was then applied to these gels. For templated films, the precursor was dissolved in hexane and polystyrene array tiles were coated with that solution using dip, drop or capillary techniques. The effects of several coating techniques and different pyrolysis temperatures on film morphologies have been studied. In addition, the sol-gel process offers an effective and controllable means of adding elements into Si-N matrix with the aim of combining the low reactivity of silicon nitride materials with other functional properties. Co-ammonolysis of a rare-earth amide with a silicon amide is shown to be an effective route to phosphor materials. Amorphous Tb:SiNx composition show strong photoluminescence and the variation in PL intensity with composition has been probed.
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Nel, Jacqueline Margot. "Processing and properties of silicon nitride ceramics." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/21682.
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Bibliography: pages 129-139.Silicon nitride, Si₃N₄, ceramics were produced using either silicon or silicon nitride powder. The silicon was reaction bonded in nitrogen atmosphere to form reaction bonded Si₃N₄,which was then sintered between 1700°C and 1800°C to form a dense Si₃N₄ ceramic. The silicon nitride powder compacts were also sintered between 1700°C and 1800°C. In order to achieve densification Y₂O₃-A1₂O₃ additive combination was used in both processing routes. The physical and mechanical properties of the Si₃N₄ materials was found to be dependent on the processing conditions. The post sintered reaction bonded Si₃N₄ materials had the highest densities and hardness values, while the sintered Si3N4 materials had the highest strength and toughness values. The microstructure was also influenced to a great extent by the processing conditions, and this in tum influenced the mechanical properties of the ceramics.
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Matović, Branko. "Low temperature sintering additives for silicon nitride." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10806387.
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Luginbühl, Reto. "Photobonding of biomacromolecules to Silicon Nitride surfaces /." [S.l.] : [s.n.], 1997. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Fallqvist, Amie. "Aberration-Corrected Analytical Electron Microscopy of Transition Metal Nitride and Silicon Nitride Multilayers." Licentiate thesis, Linköpings universitet, Tunnfilmsfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-102176.
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Two multilayer thin films have been studied: TiN/SiNx and ZrN/SiNx. A double-corrected transmission electron microscope (TEM) was utilized for imaging and spectroscopy. Imaging was carried out in scanning mode (STEM) for all samples. Energy dispersive X-ray (EDX) spectrometry was used for chemical mapping of the ZrN/SiNx samples and electron energy loss spectrometry (EELS) for atomic coordination of the nitrogen in the TiN/SiNx samples. In the TiN/SiNx multilayer the structure of the epitaxially stabilized cubic SiNx was investigated. The high-resolution STEM images were compared with image simulations of SiNx in B1 (sodium chloride) and B3 (zinc blende) configurations and were found to be most similar to the B1 configuration. Core-loss EEL spectra were compared with calculated spectra and corroborated a resemblance with the B1 configuration. The ZrN/SiNx multilayers were initially believed to show a similarity to TiN/SiNx but further investigations with STEM showed that the SiNx is amorphous. For samples deposited at 800 °C a SiNx layer thickness ≤6 Å the SiNx forms precipitates at grain boundaries and surface defects of the ZrN resulting in a columnar distribution of the SiNx, which was further revealed by EDX. For such samples the ZrN grows by epitaxial lateral overgrowth. For samples deposited at 800 °C but with a SiNx layer thickness of 6 Å the SiNx starts to form more laterally extending layers and for thicknesses ≥8 Å the SiNx grows into continuous, amorphous layers causing the following ZrN layers to assume a polycrystalline microstructure. The transition from epitaxial ZrN with columnar, amorphous SiNx, to multilayers of polycrystalline ZrN and amorphous SiNx layers appears at an even smaller thickness of SiNx if the deposition temperature is lowered, which is explained by the lowered adatom mobility.
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McCann, Michelle Jane, and michelle mccann@uni-konstanz de. "Aspects of Silicon Solar Cells: Thin-Film Cells and LPCVD Silicon Nitride." The Australian National University. Faculty of Engineering and Information Technology, 2002. http://thesis.anu.edu.au./public/adt-ANU20040903.100315.
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This thesis discusses the growth of thin-film silicon layers suitable for solar cells using
liquid phase epitaxy and the behaviour of oxide LPCVD silicon nitride stacks on silicon
in a high temperature ambient.¶
The work on thin film cells is focussed on the characteristics of layers grown using liquid
phase epitaxy. The morphology resulting from different seeding patterns, the transfer of
dislocations to the epitaxial layer and the lifetime of layers grown using oxide compared
with carbonised photoresist barrier layers are discussed. The second half of this work
discusses boron doping of epitaxial layers. Simultaneous layer growth and boron doping
is demonstrated, and shown to produce a 35um thick layer with a back surface field
approximately 3.5um thick.¶
If an oxide/nitride stack is formed in the early stages of cell processing, then characteristics of the nitride may enable increased processing flexibility and hence the realisation
of novel cell structures. An oxide/nitride stack on silicon also behaves as a good anti-
reflection coating. The effects of a nitride deposited using low pressure chemical vapour
deposition on the underlying wafer are discussed. With a thin oxide layer between the
silicon and the silicon nitride, deposition is shown not to significantly alter effective life-times.¶
Heating an oxide/nitride stack on silicon is shown to result in a large drop in effective
Lifetimes. As long as at least a thin oxide is present, it is shown that a high temperature
nitrogen anneal results in a reduction in surface passivation, but does not significantly
affect bulk lifetime. The reduction in surface passivation is shown to be due to a loss of
hydrogen from the silicon/silicon oxide interface and is characterised by an increase in
Joe. Higher temperatures, thinner oxides, thinner nitrides and longer anneal times are all
shown to result in high Joe values. A hydrogen loss model is introduced to explain the
observations.¶
Various methods of hydrogen re-introduction and hence Joe recovery are then discussed
with an emphasis on high temperature forming gas anneals. The time necessary
for successful Joe recovery is shown to be primarily dependent on the nitride thickness
and on the temperature of the nitrogen anneal. With a high temperature forming gas
anneal, Joe recovery after nitrogen anneals at both 900 and 1000oC and with an optimised
anti-reflection coating is demonstrated for chemically polished wafers.¶
Finally the effects of oxide/nitride stacks and high temperature anneals in both nitrogen
and forming gas are discussed for a variety of wafers. The optimal emitter sheet
resistance is shown to be independent of nitrogen anneal temperature. With textured
wafers, recovery of Joe values after a high temperature nitrogen anneal is demonstrated
for wafers with a thick oxide, but not for wafers with a thin oxide. This is shown to be
due to a lack of surface passivation at the silicon/oxide interface.
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Sheldon, Brian William 1959. "The formation of reaction bonded silicon nitride from silane derived silicon powders." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14453.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1989.Includes bibliographical references (leaves 222-227).
by Brian William Sheldon.
Sc.D.
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Zhang, Xuefei. "Synthesis and Characterization of Zr1-xSixN Thin Film Materials." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/ZhangX2007.pdf.
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Henry, Frédéric. "Caractérisation de décharges magnétron Ar/NH3 et Ar/H2/N2 pour la synthèse de films minces de nitrure de silicium." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209837.
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Lors de ce travail nous avons étudié la synthèse de nitrure de silicium en utilisant des décharges magnétron Ar/NH3 et Ar/H2/N2. Nous nous sommes intéressés particulièrement à la caractérisation de la décharge. Le paramètre de diagnostic le plus utilisé pour caractériser une décharge magnétron est la mesure de la tension de décharge, mais ces mesures ne donnent qu’une vue partielle du processus de pulvérisation même si le régime de pulvérisation peut être défini :métallique ou réactif. En effet, aucune information chimique ne peut être extraite des courbes de tension: d’autres techniques d’analyse sont donc indispensables. Nous avons utilisé la spectroscopie des photoélectrons X (XPS) pour analyser la chimie de la surface de la cible et la spectroscopie d’émission optique (OES) pour analyser la phase gazeuse.La combinaison des mesures de tension et XPS a permis de mettre en évidence l’empoisonnement de la surface de la cible, consécutif à la formation d’une couche de nitrure de silicium lors de la pulvérisation dans un mélange Ar/NH3. Dans le cas du mélange Ar/H2/N2, les mesures de tension ne permettent pas avec certitude de confirmer un empoisonnement de la cible, néanmoins les mesures XPS mettent en évidence, comme pour le mélange Ar/NH3, la présence d’une couche de nitrure de silicium. Les mesures OES ont permis de détecter les mêmes espèces dans les deux types de mélange gazeux, seule l’espèce NH n’a pas été détectée dans le mélange Ar/H2/N2. Parmi les espèces détectées, certaines sont directement pulvérisées de la cible; il a été possible de relier l’intensité de celles-ci avec l’état de surface de la cible dans le cas du plasma Ar/NH3.
Nous avons également étudié l’instabilité du processus de pulvérisation en combinant des mesures de tension, OES et XPS. Avec une vitesse de pompage de 230 l/s, nous avons observé une très faible hystérèse de la tension pour les deux types de mélange gazeux. Dans le cas du plasma Ar/NH3, nous avons pu mettre en évidence que la bande de l’espèce NH peut être utilisée comme paramètre de contrôle de la décharge. Finalement, nous avons caractérisé les films obtenus par XPS et spectroscopie infrarouge. La stoechiométrie des films déposés va dépendre de la quantité d’ammoniac ou d’azote injecté dans la décharge, les films déposés avec NH3 sont contaminés par quelques pourcents d’oxygène alors que ceux déposés avec le mélange Ar/H2/N2 en sont dépourvus.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Jackson, Helen C. "Effect of variation of silicon nitride passivation layer on electron irradiated aluminum gallium nitride/gallium nitride HEMT structures." Thesis, Air Force Institute of Technology, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3629786.
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Silicon nitride passivation on AlGaN\GaN heterojunction devices can improve performance by reducing electron traps at the surface. This research studies the effect of displacement damage caused by 1 MeV electron irradiation as a function of the variation of passivation layer thickness and heterostructure layer variation on AlGaN/GaN HEMTs. The effects of passivation layer thickness are investigated at thicknesses of 0, 20, 50 and 120 nanometers on AlGaN\GaN test structures with either an AlN nucleation layer or a GaN cap structures which are then measured before and immediately after 1.0 MeV electron irradiation at fluences of 1016 cm-2. Hall system measurements are used to observe changes in mobility, carrier concentration and conductivity as a function of Si3N4 thickness. Models are developed that relate the device structure and passivation layer under 1 MeV radiation to the observed changes to the measured photoluminescence and deep level transient spectroscopy. A software model is developed to determine the production rate of defects from primary 1 MeV electrons that can be used for other energies and materials. The presence of either a 50 or 120 nm Si 3N4 passivation layer preserves the channel current for both and appears to be optimal for radiation hardness.
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Plucknett, Kevin. "Hot isostatic pressing of silicon nitride based ceramics." Thesis, University of Warwick, 1990. http://wrap.warwick.ac.uk/37879/.
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Several techniques have been developed for the encapsulation, and subsequent hotisostatic pressing (HIPing), of silicon nitride (Si3N4) based ceramics. Green-state and densified billets of silicon nitride were vacuum encapsulated in either glass tube or powder. Glass powder encapsulation allows complex shaped ceramic pieces to be HIPed. A selection of silicon nitride compositions were HIPed to near-theoretical density (>97% T. D. ) after encapsulation in either Pyrex glass tube or powder. The silicon nitride compositions studied included single yttria (Y203) additive materials that cannot be densified by conventional pressureless sintering, hence the requirement for pressurised sintering. Similar ceramic compositions were also densified using the commercial ASEA HIP process for comparison. The bulk ceramic microstructure was generally similar to pressureless sintered type materials, with a complete a- to ß- Si3N4 transformation, although a finer microstructure and lower matrix phase volume were apparent. The ceramic/encapsulant interaction during HIP was generally assessed using a boron nitride (BN) interlayer. When a thick layer (> 50 μm thickness) was retained after HIP negligible interaction was apparent. A thin silicon oxynitride (Si2N2O) surface layer was observed to form with thinner interlayers. Penetration of the molten encapsulant glass through the porous BN layer occurs during HIP, leading to an increase in the Si4+ and 02- concentration at the ceramic surface and the subsequent re-precipitation of Si2N2O in preference to ß- Si3N4. Direct penetration of the encapsulant glass into the porous ceramic occurs in the absence of a BN barrier layer and a similar encapsulant dependent compositional modification was observed. Sub-surface ceramic contamination by boron was apparent in isolated samples HIPed in a Pyrex-type glass at ASEA. Interaction between the encapsulant and ceramic did not significantly affect the post-HIP surface oxidation rate, when compared with the bulk material.
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Liu, Junling. "Plasma spray deposition of silicon nitride composite coatings." Thesis, London South Bank University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288111.
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Pugh, M. D. "Processing reaction bonded silicon nitride towards full density." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372578.
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Huang, Tzung-Shi. "Integration of III-nitride semiconductors with silicon technology." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400229.
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Scott, J. A. "Plane form grinding of silicon nitride ceramic materials." Thesis, University of Bristol, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317964.
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