Preparation and Characterization of Pure SiC Ceramics by HTPVT Induced by Seeding with SiC Nanoarrays

Dense SiC ceramics were fabricated by high-temperature physical vapor transport (HTPVT) growth process using SiC nanoarrays as the crystal seeds, which was obtained by vacuum heat treatment of amorphous SiC films prepared by plasma-enhanced chemical vapor deposition (PECVD) with a porous anodic aluminum oxide (AAO) template. In the HTPVT process, two-step holding was adopted, and the temperature at the first step was controlled at 2100 and 2150 °C to avoid SiC nanoarrays evaporation, and the grain size of SiC crystal increased with the increase in temperature and decrease in the pressure of Ar. The temperature of the second step was 2300 °C, and rapid SiC grain growth and gradual densification were achieved. The prepared SiC ceramics exhibited a relative density of more than 99%, an average grain size of about 100 μm, a preferred orientation along the (0 0 0 6) plane, a Vickers hardness of about 29 GPa, a flexural strength of about 360 MPa, and thermal conductivity at room temperature of more than 200 W·m−1·K−1.

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Characterization of HCl-Doped Polyaniline-Ag Nanocomposite Prepared by Chemical and Physical Combinative Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.677.55 ◽

2013 ◽

Vol 677 ◽

pp. 55-60 ◽

Cited By ~ 1

Author(s):

Bing Hu ◽

Yang Cao ◽

Rong Ying Huang ◽

Jian Bo Fu ◽

Hong Qiu

Keyword(s):

Grain Size ◽

Ag Nanoparticles ◽

Room Temperature ◽

Rf Sputtering ◽

Chemical Polymerization ◽

Average Grain Size ◽

Doped Polyaniline ◽

Agcl Nanoparticles

HCl-doped polyaniline (HCl-PANI) powder is synthesized by using a chemical polymerization procedure. Then Ag nanoparticles are deposited on the HCl-PANI at room temperature by RF sputtering. After this process, the nanocomposite is obtained by the chemical and physical combinative method. The nominal Ag content in the nanocomposite ranges from 1.0 wt% to 3.3 wt%. For all the nanocomposites, the Ag nanoparticles convert to AgCl nanoparticles. Namely, the HCl-PANI-AgCl nanocomposites are obtained. A content of the AgCl in the nanocomposite increases with increasing Ag content. The AgCl nanoparticle consists of many grains. An average grain size of AgCl is about 40 nm and is independent of the Ag content. A conductivity of the nanocomposite decreases with increasing Ag content.

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Deposition of Photoluminescent Nanocrystalline Silicon Films by SiF4-SiH4-H2 Plasmas

MRS Proceedings ◽

10.1557/proc-452-809 ◽

1996 ◽

Vol 452 ◽

Cited By ~ 6

Author(s):

G. Cicala ◽

G. Bruno ◽

P. Capezzuto ◽

L. Schiavulli ◽

V. Capozzi ◽

...

Keyword(s):

Grain Size ◽

Porous Silicon ◽

Vapor Deposition ◽

Room Temperature ◽

Energy Gap ◽

Chemical Vapor ◽

Nanocrystalline Silicon ◽

X Ray Diffraction ◽

X Ray ◽

Average Grain Size

AbstractVisible photoluminescence at 1.62 eV has been observed at room temperature from fluorinated and hydrogenated nanocrystalline silicon (nc-Si:H,F) produced in a typical plasma enhanced chemical vapor deposition system. The use of SiF4-SiH4-H2 mixture, because of the H2 dilution and the presence of SiF4, favours the amorphous - crystalline transition through the etching process of the amorphous phase. The x - ray diffraction measurements give an average grain size of about 100 Å. The presence of these nanocrystals shifts the absorption edge of the films towards higher energy. An energy gap of 2.12 eV is estimated, although the hydrogen content in the material is only 4.5 at. %. The temperature dependence of the photoluminescence behaves similarly to that of porous silicon.

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Plasma Enhanced Chemical Vapor Deposition and Characterization of Hydrogenated Amorphous SiC Films on Si

Materials Science Forum ◽

10.4028/www.scientific.net/msf.338-342.325 ◽

2000 ◽

Vol 338-342 ◽

pp. 325-328 ◽

Cited By ~ 1

Author(s):

Yi Hua Wang ◽

Jian Yi Lin ◽

Zhe Chuan Feng ◽

Soo Jin Chua ◽

Cheng Hon Huan Alfred

Keyword(s):

Chemical Vapor Deposition ◽

Vapor Deposition ◽

Chemical Vapor ◽

Amorphous Sic ◽

Hydrogenated Amorphous ◽

Sic Films

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Effect of Initial Alpha-SiC Content on Thermal Conductivity of Silicon Carbide Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.616.23 ◽

2014 ◽

Vol 616 ◽

pp. 23-26 ◽

Cited By ~ 2

Author(s):

Kwang Young Lim ◽

Tae Young Cho ◽

Young Wook Kim ◽

Seung Jae Lee

Keyword(s):

Thermal Conductivity ◽

Grain Size ◽

Room Temperature ◽

Phase Content ◽

Sic Ceramics ◽

Α Phase ◽

Average Grain Size ◽

Carbide Ceramics ◽

Equiaxed Grains ◽

Silicon Carbide Ceramics

By using α-and/or β-SiC powders, the effects of initial α-phase content on the microstructure and thermal properties of the SiC ceramics sintered with Y2O3 and Sc2O3 were investigated. When α-SiC powder was used, the microstructure consisted of large equiaxed grains and small equiaxed grains. The average grain size decreased with increasing α-SiC content in the starting composition. The thermal conductivity decreased with increasing α-SiC content in the starting composition. Such results suggest that the grain growth of SiC ceramics is beneficial in increasing the thermal conductivity of liquid-phase sintered SiC ceramics. The thermal conductivity of SiC ceramics processed from a 90% β-SiC-10% α-SiC powder mixture was 159 W/m∙K at room temperature.

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Preparation and Characterization of Ca0.8Sr0.2ZrO3 Powders Prepared by Soft Chemical Route

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.336-338.968 ◽

2007 ◽

Vol 336-338 ◽

pp. 968-970

Author(s):

Ji Xia Lei ◽

Xiao Lin Liu ◽

Tao Yan ◽

Jian Feng Chen

Keyword(s):

Grain Size ◽

Room Temperature ◽

Heating Temperature ◽

Strontium Zirconate ◽

Chemical Route ◽

Average Grain Size ◽

Conventional Sintering ◽

Oxalate Coprecipitation ◽

Soft Chemical Route

Precursors of calcium strontium zirconate (Ca0.8Sr0.2ZrO3) were synthesized by oxalate coprecipitation method. TG-DTA was used to characterize the thermal decomposition behaviors of the precursors. The XRD results revealed that the powders crystallized as cubic Ca0.8Sr0.2ZrO3 with increasing heating temperature up to 1000°C. Calcium strontium zirconate ceramics were obtained under conventional sintering conditions by using the as-prepared Ca0.8Sr0.2ZrO3 powders. The SEM micrographs of the ceramics sintered at 1450oC exhibited narrow grain-size distribution with the average grain size around 0.7 4m. The dielectric properties showed that, dielectric constant of the Ca0.8Sr0.2ZrO3 was about 24.0 and dielectric loss was 0.002 at the frequency of 1GHz and the room temperature.

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High thermal conductivity of pure dense SiC ceramics prepared via HTPVT

Functional Materials Letters ◽

10.1142/s1793604719500322 ◽

2019 ◽

Vol 12 (03) ◽

pp. 1950032 ◽

Cited By ~ 2

Author(s):

Yuchen Deng ◽

Yaming Zhang ◽

Nanlong Zhang ◽

Qiang Zhi ◽

Bo Wang ◽

...

Keyword(s):

Thermal Conductivity ◽

Silicon Carbide ◽

Grain Size ◽

Phase Composition ◽

Room Temperature ◽

Vapor Transport ◽

Physical Vapor Transport ◽

Growth Substrate ◽

Sic Ceramics ◽

Evolution Of Microstructure

Pure dense silicon carbide (SiC) ceramics were obtained via the high-temperature physical vapor transport (HTPVT) method using graphite paper as the growth substrate. The phase composition, the evolution of microstructure, the thermal diffusivity and thermal conductivity at RT to 200∘C were investigated. The obtained samples had a relative density of higher than 98.7% and a large grain size of 1[Formula: see text]mm, the samples also had a room-temperature thermal conductivity of [Formula: see text] and with the temperature increased to 200∘C, the thermal conductivity still maintained at [Formula: see text].

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Experimental and Numerical Investigation of the ECAP Processed Copper: Microstructural Evolution, Crystallographic Texture and Hardness Homogeneity

Metals ◽

10.3390/met11040607 ◽

2021 ◽

Vol 11 (4) ◽

pp. 607

Author(s):

A. I. Alateyah ◽

Mohamed M. Z. Ahmed ◽

Yasser Zedan ◽

H. Abd El-Hafez ◽

Majed O. Alawad ◽

...

Keyword(s):

Grain Size ◽

Equal Channel Angular Pressing ◽

Cross Section ◽

Room Temperature ◽

Pure Copper ◽

High Density ◽

Ecap Processing ◽

Heterogeneous Distribution ◽

Angular Pressing ◽

Average Grain Size

The current study presents a detailed investigation for the equal channel angular pressing of pure copper through two regimes. The first was equal channel angular pressing (ECAP) processing at room temperature and the second was ECAP processing at 200 °C for up to 4-passes of route Bc. The grain structure and texture was investigated using electron back scattering diffraction (EBSD) across the whole sample cross-section and also the hardness and the tensile properties. The microstructure obtained after 1-pass at room temperature revealed finer equiaxed grains of about 3.89 µm down to submicrons with a high density of twin compared to the starting material. Additionally, a notable increase in the low angle grain boundaries (LAGBs) density was observed. This microstructure was found to be homogenous through the sample cross section. Further straining up to 2-passes showed a significant reduction of the average grain size to 2.97 µm with observable heterogeneous distribution of grains size. On the other hand, increasing the strain up to 4-passes enhanced the homogeneity of grain size distribution. The texture after 4-passes resembled the simple shear texture with about 7 times random. Conducting the ECAP processing at 200 °C resulted in a severely deformed microstructure with the highest fraction of submicron grains and high density of substructures was also observed. ECAP processing through 4-passes at room temperature experienced a significant increase in both hardness and tensile strength up to 180% and 124%, respectively.

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ATOMIC FORCE MICROSCOPY AND XRD ANALYSIS OF SILVER FILMS DEPOSITED BY THERMAL EVAPORATION

International Journal of Modern Physics B ◽

10.1142/s021797920603319x ◽

2006 ◽

Vol 20 (02) ◽

pp. 217-231 ◽

Cited By ~ 4

Author(s):

MUHAMMAD MAQBOOL ◽

TAHIRZEB KHAN

Keyword(s):

Atomic Force Microscopy ◽

Grain Size ◽

Surface Characterization ◽

Room Temperature ◽

Thermal Evaporation ◽

Xrd Analysis ◽

Force Microscopy ◽

Atomic Force ◽

Average Grain Size ◽

20 Nm

Thin films of pure silver were deposited on glass substrate by thermal evaporation process at room temperature. Surface characterization of the films was performed using X-ray diffraction (XRD) and atomic force microscopy (AFM). Thickness of the films varied between 20 nm and 72.8 nm. XRD analysis provided a sharp peak at 38.75° from silver. These results indicated that the films deposited on glass substrates at room temperature are crystalline. Three-dimension and top view pictures of the films were obtained by AFM to study the grain size and its dependency on various factors. Average grain size increased with the thickness of the deposited films. A minimum grain size of 8 nm was obtained for 20 nm thick films, reaching 41.9 nm when the film size reaches 60 nm. Grain size was calculated from the information provided by the XRD spectrum and averaging method. We could not find any sequential variation in the grain size with the growth rate.

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Properties and Application of Undoped Hydrogenated Microcrystalline Silicon Thin Films

MRS Proceedings ◽

10.1557/proc-149-173 ◽

1989 ◽

Vol 149 ◽

Cited By ~ 5

Author(s):

J. Kanicki ◽

E. Hasan ◽

D. F. Kotecki ◽

T. Takamori ◽

J. H. Griffith

Keyword(s):

Grain Size ◽

Deposition Temperature ◽

Etch Rate ◽

Chemical Vapor ◽

Microcrystalline Silicon ◽

Silicon Thin Films ◽

Hydrogen Dilution ◽

Average Grain Size ◽

Structural And Electrical Properties ◽

Deposition Conditions

ABSTRACTDevice quality undoped hydrogenated microcrystalline silicon has been prepared by plasma enhanced chemical vapor deposition under different conditions. The dependence of physical, chemical, structural, and electrical properties on the deposition conditions has been investigated. Conductive (conductivity above 10−3Ω−1 cm−1) and resistive (conductivity around 10−9Ω−1cm−1) layers having approximately the same grain size, at a given substrate temperature, have been deposited between 200 and 500°C at two different hydrogen dilutions. Independently of the hydrogen dilution, the average grain sized is dependent on the deposition temperature and the film thickness; and a maximum average grain size of about 40 nm has been achieved for a thick film deposited at 500°C. The density of paramagnetic defects also increases with increasing deposition temperature, which indicates that more dangling bond defects are introduced as the total area of the grain boundaries increases. The etch rate decreases with increasing deposition temperature, and for the films deposited at 250 and 500°C the etch rate has been measured to be 6.6 and 2.7 nm/min, respectively. Thin film transistors incorporating a microcrystalline channel have been fabricated and evaluated. The best device had the following properties: field effect mobility, threshold voltage, and on/off current ratio of about 0.8 cm2/V sec, below 5 V, and around 106, respectively.

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