A linear polycarbosilane containing m-carborane units: Synthesis and characterization as precursor for SiC/B4C ceramics

2017 ◽  
Vol 30 (10) ◽  
pp. 1267-1275 ◽  
Author(s):  
Quan Zhou ◽  
Zhengqiang Peng ◽  
Mingze Yang ◽  
Hao Hu ◽  
Ning Song ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Gel Permeation Chromatography ◽  
Inert Atmosphere ◽  
Composite Ceramics ◽  
X Ray Diffraction ◽  
Metathesis Reaction ◽  
X Ray ◽  
Air Atmosphere ◽  
Transmission Electron

The precursor of poly(carborane)(silicon-acetylene) (PCBS) for silicon carbide (SiC)/B4C composite ceramics was synthesized by a salt metathesis reaction. The molecular weight of PCBS was measured by gel permeation chromatography and the corresponding structures were identified by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). After thermal curing, the PCBS was converted to a dark red brittle nonporous monolith and the thermal stability was significantly improved, especially in an air atmosphere. Thermogravimetric analysis indicated that the 5% weight loss temperatures were 595°C and 633°C under nitrogen and air atmospheres, respectively, and the corresponding residues at 1000°C were 86.42% and 90.42%. After a heat treatment at 1600°C under inert atmosphere, the well-dispersed SiC/B4C ceramic was obtained and characterized by FTIR, X-ray diffraction analysis, Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained SiC/B4C ceramic has a good high-temperature and oxidation resistance which can be applied to aviation, aerospace, and other ultra-high temperature conditions.

scholarly journals A novel and facile method for silica nanoparticles synthesis from high temperature vulcanization (HTV) silicon

10.30544/134 ◽  
2016 ◽  
Vol 22 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Mohammad Senemar ◽  
Ali Maleki ◽  
Behzad Niroumand ◽  
Alireza Allafchian
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silica Nanoparticles ◽  
Amorphous Silica ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Nanoparticles Synthesis ◽  
Novel Method ◽  
Scanning Electron

This study is introducing a facile and novel method for synthesis of amorphous silica nanoparticles. Silica nanoparticles were synthesized by pyrolysis and combustion of high temperature vulcanization (HTV) silicone at 700 oC for 1 h. The products were investigated employing transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Brunauer Emmett and Teller (BET) test and Fourier Transform Infrared (FTIR) Spectroscopy. The results indicated that the method is capable of synthesis of amorphous silica nanoparticles with sizes of mostly between 10 and 50 nm.

Microstructure and Anti-Friction Effect of Ball-Milled Expanded Graphite

2013 ◽  
Vol 704 ◽  
pp. 110-113
Author(s):  
Hong Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ball Milling ◽  
Expanded Graphite ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Friction Effect ◽  
Air Atmosphere ◽  
Transmission Electron

Expanded graphite (EG) was ball-milled in a high-energy mill (planetary-type) under an air atmosphere. The products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The anti-friction effect of milled EG used as lubricating additive was investigated. After ball-milling, the relatively ordered graphene planes of original EG become deformed, and the d002 spacing becomes broadened. The milled EG used as lubricating additive have an anti-friction effect, and the effect is more marked than that of original EG.

Effect of NaCl on Synthesis of Si-SiC Nanocomposites by Self Propagating High Temperature Synthesis

2013 ◽  
Vol 664 ◽  
pp. 449-453 ◽  
Author(s):  
Sutham Niyomwas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
Nano Composite ◽  
Argon Gas ◽  
X Ray ◽  
High Temperature Synthesis ◽  
Transmission Electron ◽  
Scanning Electron

The Si-SiC nanocomposites have been synthesized by self-propagating high temperature synthesis (SHS) from natural precursors. The effects of difference amount of added NaCl from 0 to 0.75 moles to the reactants on the Si-SiC conversion and particle size were investigated. The reaction were carried out in a SHS reactor under static argon gas at the pressure of 0.5 MPa. The nanocomposite results have been characterized by scanning electron microscope, Transmission Electron Microscopy and X-ray diffraction. The results showed that the production of nano-composite materials using SHS process is feasible and agree well with the thermodynamics calculations.

In situ high temperature X-ray diffraction, transmission electron microscopy and theoretical modeling for the formation of WO3 crystallites

CrystEngComm ◽  
2015 ◽  
Vol 17 (36) ◽  
pp. 6985-6998 ◽  
Author(s):  
Suman Pokhrel ◽  
Johannes Birkenstock ◽  
Arezoo Dianat ◽  
Janina Zimmermann ◽  
Marco Schowalter ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
High Temperatures ◽  
Structural Transformation ◽  
Theoretical Modeling ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

The structural transformation of WO3 at high temperatures.

Behavior of carbon nanotubes under high pressure and high temperature

2000 ◽  
Vol 15 (2) ◽  
pp. 560-563 ◽  
Author(s):  
D. S. Tang ◽  
L. C. Chen ◽  
L. J. Wang ◽  
L. F. Sun ◽  
Z. Q. Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
High Pressure ◽  
High Temperature ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Diamond Crystallization ◽  
Graphite Sheets

The structural changes of carbon nanotubes induced by high pressure and high temperature were investigated by means of x-ray diffraction, Raman scattering, scanning electron microscopy, and transmission electron microscopy. It is shown that, with increasing pressure and temperature, the lattice constant d002 of tubes shortens, and then tubes collapse into tapelike ones; at the same time the C–C bonds at high curvature break, which lead the tapelike tubes to break into graphite sheets as diamond crystallization centers. Compared with graphite, the diamond particles from carbon nanotubes have many defects as the trace of tubes.

Process-Induced Deformations and Stacking Faults in 4H-SiC

2006 ◽  
Vol 911 ◽  
Author(s):  
Robert S Okojie ◽  
Xianrong Huang ◽  
Michael Dudley ◽  
Ming Zhang ◽  
Pirouz Pirouz
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
High Resolution ◽  
Stress Measurement ◽  
Stacking Faults ◽  
Film Stress ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

AbstractWe used Film Stress Measurement (FSM), Transmission Electron Microscopy (TEM), and High-Resolution X-ray Diffraction (HRXRD) techniques to obtain further knowledge with respect to the deformation, warpage, and stacking faults (SF's) that are induced in n-type 4H-SiC wafers and epilayers when subjected to mechanical polishing and high temperature (1150 oC) processing.

Synthesis of Carbon Nanospheres with Small Diameterby Microwave Pyrolysis of Methane Directly

2013 ◽  
Vol 745-746 ◽  
pp. 371-375
Author(s):  
Dong Ju Fu ◽  
Xie Rong Zeng ◽  
Wei Li Zhang ◽  
Jian Jun Chen ◽  
Dong Shuang Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cross Sections ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
Carbon Nanospheres ◽  
Microwave Pyrolysis ◽  
X Ray ◽  
Air Atmosphere ◽  
Transmission Electron ◽  
Uniform Diameter

Carbon nanospheres of uniform diameter around 40 nm have been achieved in the absence of catalyst by microwave pyrolysis chemical vapor deposition. The products have been characterized by field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The results show that the nanospheres with high purity, which are solid by their cross-sections, consisting of concentric incompletely closed graphitic layers. Their thermal stability in dynamic air atmosphere is also discussed.

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