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L. Stachowicz

Bio: L. Stachowicz is an academic researcher from University of Minnesota. The author has contributed to research in topics: Ceramic & Wafer. The author has an hindex of 3, co-authored 3 publications receiving 52 citations.
Topics: Ceramic, Wafer, Plasma torch, Diamond, Sintering

Papers
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Journal ArticleDOI
TL;DR: In this paper, a triple torch plasma reactor was used to generate a convergent plasma volume to entrain the participating gases, and three coalescing plasma jets produced by this reactor direct the dissociated and ionized gaseous species onto (100) silicon wafer substrates where the diamond grows.
Abstract: Diamond crystals and films have been success full y synthesized by DC thermal plasma jet CVD at a pressure of I atrn. A novel triple torch plasma reactor has been used to generate a convergent plasma volume to entrain the participating gases. Three coalescing plasma jets produces! by this reactor direct the dissociated and ionized gaseous species onto ( 100) silicon wafer substrates where the diamond grows. In a typical 10-min run, depending on the method of .substrate preparation, either microcrystals with sizes up to 8 μm or continuous films with thicknesses of 1–2 μm have been obtained. X-ray diffraction, scanning electron microscopy, and Raman spectroscopy have been used for the characterization of the crystals and of the films.

28 citations

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TL;DR: In this article, a new method to overcome the problems of reactive/corrosive gases in the preparation of ultrafine SiC powders was described, where rice hull was used as the solid precursor.
Abstract: Recently the synthesis of ultrafine powders has drawn considerable attention because these powders can have physical and chemical properties superior to those of bulk specimens. In particular, emphasis is on the preparation of ultrafine ceramic powders for their applications in the development of sintered products having higher density and lower sintering temperature. One such industrially important ceramic material is SiC. In many cases ultrafine SiC has been prepared by thermal plasma processes [1]. However, these processes require one or more reactive/corrosive gases. This letter describes a new method to overcome such problems. For this purpose thermally pretreated rice hull was used as the solid precursor. Rice hull, an agricultural waste product, was first used by Cutler [2] as a starting material for the production of silicon carbide. Since the rice hull route promises to be most economical, much attention has recently been paid to it [3-6]. Rice hull consists of silica in hydrated amorphous form, and cellulose which yields carbon when thermally decomposed. The relative abundance of silica with very high surface area in close proximity to active carbon in rice hull makes it amenable for SiC formation during the pyrolysis process. The possible reaction was given by Lee and Cutler [7] as

18 citations

Journal ArticleDOI
TL;DR: In this article, heat-treated rice hulls have been used as precursor material for synthesis of ultrafne SiC in a RF plasma reactor Rice hulls containing finely distributed silica and active carbon act as a source for SiC formation.
Abstract: Heat-treated rice hulls have been used as precursor material for synthesis of ultrafne SiC in a RF plasma reactor Rice hulls containing finely distributed silica and active carbon act as a source for SiC formation The plasma-synthesized powder contained ultrafnc β-SiC with excess carbon and some unreacted silica Post-treatment processes such as oxidation and acid (HF) treatment appear to be effective in removing the excess carbon and silica

10 citations


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Journal ArticleDOI
TL;DR: In this paper, the physics and chemistry of the plasma jet and other atmospheric pressure sources are reviewed, including transferred arcs, plasma torches, corona discharges, and dielectric barrier discharges.
Abstract: Atmospheric-pressure plasmas are used in a variety of materials processes. Traditional sources include transferred arcs, plasma torches, corona discharges, and dielectric barrier discharges. In arcs and torches, the electron and neutral temperatures exceed 3000/spl deg/C and the densities of charge species range from 10/sup 16/-10/sup 19/ cm/sup -3/. Due to the high gas temperature, these plasmas are used primarily in metallurgy. Corona and dielectric barrier discharges produce nonequilibrium plasmas with gas temperatures between 50-400/spl deg/C and densities of charged species typical of weakly ionized gases. However, since these discharges are nonuniform, their use in materials processing is limited. Recently, an atmospheric-pressure plasma jet has been developed, which exhibits many characteristics of a conventional, low-pressure glow discharge. In the jet, the gas temperature ranges from 25-200/spl deg/C, charged-particle densities are 10/sup 11/-10/sup 12/ cm/sup -3/, and reactive species are present in high concentrations, i.e., 10-100 ppm. Since this source may be scaled to treat large areas, it could be used in applications which have been restricted to vacuum. In this paper, the physics and chemistry of the plasma jet and other atmospheric-pressure sources are reviewed.

1,288 citations

Journal ArticleDOI
TL;DR: A critical review on the processing and application of rice husks (RHs) for the production of various silicon-based materials and of active carbon is presented in this paper, which addresses the different processing methods, the effects of various process parameters on the pyrolysis stage, the influence of physical, chemical and thermal treatments, activating conditions and activated carbon consolidation mechanisms.

433 citations

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TL;DR: In this article, the methods of synthesizing silicon-based materials from rice husks and their applications are reviewed in a very comprehensive manner, including silicon carbide, silica, silicon nitride, silicon tetrachloride, and pure silicon.
Abstract: Rice husk (RH) has now become a source for a number of silicon compounds, including silicon carbide, silica, silicon nitride, silicon tetrachloride, zeolite, and pure silicon. The applications of such materials derived from rice husks are very comprehensive. The methods of synthesizing these silicon-based materials from RHs and their applications are reviewed in this paper.

368 citations

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TL;DR: Atmospheric pressure plasma jets have a long history of more than 50 years as discussed by the authors and during this time their design and plasma generation mechanism has been developed and adapted to various fields of applications.
Abstract: Atmospheric pressure plasma jets have a long history of more than 50 years. During this time their design and plasma generation mechanism has been developed and adapted to various fields of applications. This review aims at giving an overview of jet devices by starting with a brief history of their development. This is followed by an overview of commonly used terms and definitions as well as a survey of different classification schemes (e.g. geometry, excition frequency or specific energy input) described in literature. A selective update of new designs and novel research achievments on atmospheric pressure plasma jets published in 2012 or later shows the impressive variety and rapid development of the field. Finally, a brief outlook on the future trends and directions is given.

347 citations

Journal ArticleDOI
TL;DR: In this article, fundamental aspects of anatomy of wood and molecular structure of wood cell wall affecting the bio-organic-inorganic conversion process are reviewed, and basic approaches to convert the native biopolymeric materials into non-oxide as well as oxide ceramic products include pyrolytic decomposition resulting in a porous carbon replica (template) which may subsequently be reacted to form carbide phases or may be infiltrated with non-reacting sols or salts which can further be processed to yield oxide reaction products.
Abstract: Lignocellulosics represent the organic matter produced by trees. Biopolymers such as cellulose, hemicellulose and lignin are the major macromolecular constituents of ligneous cell walls which are distinguished by a hierarchical fibrilar composite micro structure. Fundamental aspects of anatomy of wood and molecular structure of wood cell wall affecting the bioorganic–inorganic conversion process are reviewed. Basic approaches to convert the native biopolymeric materials into non-oxide as well as oxide ceramic products include: (i) pyrolytic decomposition resulting in a porous carbon replica (template) which may subsequently be reacted to form carbide phases or may be infiltrated with non-reacting sols or salts which can further be processed to yield oxide reaction products; (ii) infiltration of chemically preprocessed native lignocellulosic products with gaseous or liquid organometallic and metalorganic precursors and subsequent oxidation to remove the free carbon phase. Conversion of native (wood tissue) lignocellulosics into ceramics with a microstructure pseudomorphous to the bioorganic template anatomy offers a great potential for designing novel ceramics with anisotropic cellular morphologies. These might be of interest for applications as high temperature resistant exhaust gas filters and catalyst carriers in energy, environmental and automotive industries, bioinert and corrosion resistant immobilization supports for living cells, microbes, or enzymes in biotechnology and medicine.

290 citations