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Processing reaction bonded silicon nitride towards full densityPugh, M. D. January 1986 (has links)
No description available.
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Microstructural development and control of ceramics in the Ca-Si-Al-O-N systemWood, Christopher Andrew, 1973- January 2001 (has links)
Abstract not available
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Correlating structural and optical properties of silicon nanocrystals embedded in silicon nitride: An experimental study of quantum confinement for photovoltaic applicationsScardera, Giuseppe, ARC Centre of Excellence in Advanced Silicon Photovoltaics & Photonics, Faculty of Engineering, UNSW January 2008 (has links)
Silicon nanocrystals embedded in silicon nitride have received attention as promising materials for optoelectronic applications. More specifically, band gap engineering of novel materials based on silicon nanocrystals has been proposed for possible application in an all-silicon tandem solar cell within the field of `third generation' photovoltaics. Such an application would require nanocrystals to exhibit quantum confinement whereby the optical and electrical properties of a film could be tuned by controlling the size of these `quantum dots'. This thesis investigates the correlation between the structural and optical properties of silicon nanocrystals grown in silicon nitride multilayer structures via solid phase crystallisation, as part of an experimental investigation into quantum confinement. A study of the relevant processing parameters for the solid phase crystallization of silicon nanocrystals in amorphous silicon nitride is presented and the effectiveness of the multilayer approach for controlling nanocrystal size is demonstrated. Structural characterisation using transmission electron microscopy and glancing incidence x-ray diffraction is complemented with a new application of Fourier transform infrared spectroscopy for the detection of silicon nanocrystals. A case study on the effects of annealing temperature on the photoluminescence from silicon nitride multilayers is presented. While a clear correlation between the structural, molecular and optical properties is demonstrated, evidence of quantum confinement remains ambiguous. The investigation into the limits of parameter space for the formation of silicon nanocrystals in silicon nitride multilayers also leads to the formation of a novel Si-Si3N4 nanocomposite material. A comprehensive study of the photoluminescence from silicon nanocrystals embedded in nitride is presented in the context of homogeneous and multilayer nitride films. Size dependent PL and absorption is demonstrated for silicon nitride multilayers with silicon-rich silicon nitride layer thicknesses varying from 1 to 4.5 nm, indicating the formation of quantum wells. These same structures are annealed to form arrays of silicon nanocrystals. Although the PL and absorption spectra suggest quantum effects, inherent ambiguities remain. The findings in this thesis provide greater insight into the nature of confinement and indicate the need for further research if the successful implementation of these structures into an all silicon tandem cell is to be achieved.
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Kinetics of nano-sized Si₃N₄ powder synthesis via ammonolysis of SiO vaporVongpayabal, Panut 27 May 2003 (has links)
An 89 mm-diameter vertical tubular-flow reactor was used to study the kinetics
of nano-sized silicon nitride powder synthesis via the animonolysis of SiO vapor at
temperatures ranging from 1300°C to 1400°C. The SiO generation rate was controlled
by adjusting the mass of SiO particles initially charged in the SiO generator, when the
flow rate of carrier gas argon was maintained unchanged. The molar feed ratio of
NH₃/SiO at the feeder outlets was maintained in large excess of the stoichiometric ratio
ranging from about 100 to 1200 mol NH₃/mol SiO.
The SiO-NH₃ reaction yielded two different morphologies of silicon nitride
products at different locations in the reactor: nano-sized powder with an averaged
particle size of about 17 nm and whiskers with a variety of shapes and diameters of a
few micrometers. Nano-sized powder was the dominant product in the system and its
mass fraction over the total product varied from 83% to 100%, depending on operating
conditions.
The contact pattern between SiO vapor and NH₃ inside the reacting zone was
one of the most important parameters that affected Si₃N₄ formation kinetics. When a
small single tube was employed for feeding NH₃ (flow condition J), a highest
efficiency of SiO vapor utilization was achieved at a high level of SiO conversion. The
SiO conversion increased from 72% to 91% with an increase in the residence time
from 0.17 s to 0.69 s, indicating that the SiO-NH₃ reaction was not instantaneous but
was relatively fast.
When the molar feed rate of NH₃ was 2-3 orders of magnitude greater than that
of SiO vapor, the rate of nano-sized powder synthesis was independent of NH₃
concentration and of first order with respect to the SiO concentration. A pseudo-first
order rate expression was proposed, and the apparent activation energy was determined
to be 180 kJ/mol.
The gas flow in the reactor simulated with a computational fluid dynamic
program revealed that whisker formed where the stagnation of gas flow formed. A
power law rate expression for whisker formation was proposed based on measured
rates of whisker formation and simulation-predicted reactant-gas concentrations. / Graduation date: 2004
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Kinetic study on the synthesis of Si���N��� via the ammonization of SiO vaporLin, Dah-cheng 08 November 1995 (has links)
Graduation date: 1996
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Shock-enhanced sintering of silicon nitrideTurner-Adomatis, Bonnie L. 08 1900 (has links)
No description available.
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Correlating structural and optical properties of silicon nanocrystals embedded in silicon nitride: An experimental study of quantum confinement for photovoltaic applicationsScardera, Giuseppe, ARC Centre of Excellence in Advanced Silicon Photovoltaics & Photonics, Faculty of Engineering, UNSW January 2008 (has links)
Silicon nanocrystals embedded in silicon nitride have received attention as promising materials for optoelectronic applications. More specifically, band gap engineering of novel materials based on silicon nanocrystals has been proposed for possible application in an all-silicon tandem solar cell within the field of `third generation' photovoltaics. Such an application would require nanocrystals to exhibit quantum confinement whereby the optical and electrical properties of a film could be tuned by controlling the size of these `quantum dots'. This thesis investigates the correlation between the structural and optical properties of silicon nanocrystals grown in silicon nitride multilayer structures via solid phase crystallisation, as part of an experimental investigation into quantum confinement. A study of the relevant processing parameters for the solid phase crystallization of silicon nanocrystals in amorphous silicon nitride is presented and the effectiveness of the multilayer approach for controlling nanocrystal size is demonstrated. Structural characterisation using transmission electron microscopy and glancing incidence x-ray diffraction is complemented with a new application of Fourier transform infrared spectroscopy for the detection of silicon nanocrystals. A case study on the effects of annealing temperature on the photoluminescence from silicon nitride multilayers is presented. While a clear correlation between the structural, molecular and optical properties is demonstrated, evidence of quantum confinement remains ambiguous. The investigation into the limits of parameter space for the formation of silicon nanocrystals in silicon nitride multilayers also leads to the formation of a novel Si-Si3N4 nanocomposite material. A comprehensive study of the photoluminescence from silicon nanocrystals embedded in nitride is presented in the context of homogeneous and multilayer nitride films. Size dependent PL and absorption is demonstrated for silicon nitride multilayers with silicon-rich silicon nitride layer thicknesses varying from 1 to 4.5 nm, indicating the formation of quantum wells. These same structures are annealed to form arrays of silicon nanocrystals. Although the PL and absorption spectra suggest quantum effects, inherent ambiguities remain. The findings in this thesis provide greater insight into the nature of confinement and indicate the need for further research if the successful implementation of these structures into an all silicon tandem cell is to be achieved.
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Discrete element modelling of silicon nitride ceramics crack formation and propagation in indentation test and four point bending test /Senapati, Rajeev. January 2009 (has links)
Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.
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A study of the optical and electronic properties of amorphous silicon nitridePiggins, Nicholas January 1988 (has links)
Amorphous a-SiNx (:H) films have been prepared by radio-frequency sputtering in an argon-nitrogen-hydrogen atmosphere. Both hydrogenated and non-hydrogenated films were studied along with films prepared by the glow-discharge decomposition of a gaseous mixture of silane and ammonia. Photoemission experiments were performed on the sputtered samples. The position and strength of the core levels were determined, along with the plasma energies as a function of x. A comprehensive study of the number and types of defects present within a-SiN(:H) was undertaken. Films sputtered at room temperature and at 200°C, both with and without hydrogen, were studied along with films prepared by the glow-discharge technique. The results obtained are discussed in the light of existing models. Certain characteristic energies obtainable from optical data have been found for hydrogenated and non-hydrogenated films. These results are then related to other experimental results, in particular those from photoemission measurements. Reflection measurements have been made in the range 0.5eV to 12eV on the sputtered and glow-discharge films. From the reflection measurements e2 spectra were determined by Kramers-Kronig analysis. The dependence of the optical joint density of states with alloying was found from the data. It was found from these measurements that the top of the valence band gradually changes from Si3p states to N 2p states.
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CMZP and Mg-doped Al2TiO5 Thin film Coatings for High Temperature Corrosion Protection of Si3N4 Heat ExchangersNguyen, Thierry Huu Chi 28 April 1998 (has links)
Silicon nitride (Si3N4) is a potentially good ceramic material for industrial heat exchangers. However, at elevated temperatures and in coal combustion atmospheres its lifetime is severely reduced by oxidation. To increase its corrosion resistance, the formation of a protective oxidation barrier layer was promoted by the deposition of oxide thin films. Homogeneous and crack-free oxide coatings of calcium magnesium zirconium phosphate (CMZP) and magnesium doped aluminum titanate (Mg-doped Al2TiO5) were successfully deposited on Si3N4 using the sol-gel and dip-coating technique. Coated and uncoated samples were then exposed to a sodium containing atmosphere at 1000*C for 360 hours to simulate typical industrial environment conditions. Structural post-exposure analyses based on weight loss measurements and mechanical tests indicated better corrosion resistance and strength retention for CMZP coated Si3N4 compared to as received and Mg-doped Al2TiO5 coated Si3N4. This difference was attributed to the protective nature of the corrosion layer, which in the case of CMZP, significantly impeded the inward diffusion of oxygen to the Si3N4 surface. / Master of Science
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