Low Temperature Oxidation Behaviors of CNTs/MoSi2 Composites

2014 ◽  
Vol 983 ◽  
pp. 116-120
Author(s):  
Houan Zhang ◽  
He Jian Wu ◽  
Jia Lin ◽  
Si Yong Gu ◽  
Lei Yu
Keyword(s):  
Electron Microscopy ◽  
Molybdenum Disilicide ◽  
Phase Identification ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Low Temperature Oxidation ◽  
Temperature Oxidation ◽  
X Ray ◽  
Scanning Electron ◽  
Oxidation Behaviors

Molybdenum disilicide (MoSi2) matrix composites with various contents of carbon nanotubes (CNTs) were fabricated by sintering in vacuum at 1550 °C for 1 h. The oxidation behaviors of CNTs/MoSi2composites at 400 °C and 500 °C for 200 h in air were studied. Results showed that the weight loss of CNTs/MoSi2composites increased with the increase of CNTs content. “Pest” phenomenon happened at 400 °C but not at 500 °C. Phase identification and microstructure of the samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that many MoO3whiskers and microcracks only occurred on the surface of CNTs/MoSi2composites when oxidized at 400 °C in air, which leaded to the catastrophic disintegration of CNTs/MoSi2composites.

scholarly journals Chemical Stability of Ti3C2 MXene with Al in the Temperature Range 500–700 °C

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1979 ◽  
Author(s):  
Jing Zhang ◽  
Shibo Li ◽  
Shujun Hu ◽  
Yang Zhou
Keyword(s):  
Electron Microscopy ◽  
Chemical Stability ◽  
Metal Matrix ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Transmission Electron ◽  
Work First ◽  
Scanning Electron

Ti3C2Tx MXene, a new 2D nanosheet material, is expected to be an attractive reinforcement of metal matrix composites because its surfaces are terminated with Ti and/or functional groups of –OH, –O, and –F which improve its wettability with metals. Thus, new Ti3C2Tx/Al composites with strong interfaces and novel properties are desired. To prepare such composites, the chemical stability of Ti3C2Tx with Al at high temperatures should be investigated. This work first reports on the chemical stability of Ti3C2Tx MXene with Al in the temperature range 500–700 °C. Ti3C2Tx is thermally stable with Al at temperatures below 700 °C, but it reacts with Al to form Al3Ti and TiC at temperatures above 700 °C. The chemical stability and microstructure of the Ti3C2Tx/Al samples were investigated by differential scanning calorimeter, X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy.

scholarly journals Development of TiB and nanocrystalline Ti-reinforced novel hybrid Ti nanocomposite produced by powder metallurgy

2022 ◽  
Author(s):  
D. A. Angel ◽  
T. Mikó ◽  
F. Kristály ◽  
M. Benke ◽  
Z. Gácsi
Keyword(s):  
Electron Microscopy ◽  
Powder Metallurgy ◽  
Hybrid Composites ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Transformation Mechanism ◽  
Vacuum Sintering ◽  
X Ray ◽  
Titanium Monoboride ◽  
Scanning Electron

AbstractTitanium monoboride (TiB) whisker-reinforced titanium (Ti) matrix composites were produced by powder metallurgy, through vacuum sintering. TiB is formed by thermal decomposition of TiB2 precursor. In addition, a new hybrid composite was developed by admixing nanograined and nanocrystalline (more important) Ti to enhance the transformation mechanism of TiB2 to TiB phase. The morphology and particle size of the initial powders, mixtures and the microstructure of the composites have been studied by scanning electron microscopy (SEM). The phase analysis and transformation monitoring were performed by X-ray diffraction (XRD). The sintered composites were also subjected to compressive strength and hardness measurements. According to XRD results, through the addition of nanocrystalline Ti, a probable enhancement of the TiB2 → TiB transformation occurred producing more TiB whiskers in the hybrid composites. All samples of the hybrid composites exhibited improved yield strength (1365 MPa) and hardness (358 HV) compared to the non-hybrid ones 927 MPa and 254 HV, respectively. Graphical abstract

Nucleation and growth of iron oxides in olivines, (Mg,Fe)2SiO4

1970 ◽  
Vol 37 (291) ◽  
pp. 790-800 ◽  
Author(s):  
P. E. Champness
Keyword(s):  
Electron Microscopy ◽  
Iron Oxide ◽  
Amorphous Silica ◽  
Nucleation And Growth ◽  
X Ray Diffraction ◽  
Low Temperature Oxidation ◽  
Temperature Oxidation ◽  
X Ray ◽  
The Matrix ◽  
Equiaxed Grains

SummaryIron-rich olivines have been oxidized in air in the laboratory and the mechanism of their breakdown has been elucidated using X-ray diffraction and electron microscopy. Low-temperature oxidation (500–800 °C) produces well-oriented hematite- and magnetite-like precipitates together with amorphous silica. The reaction is a cellular one in which thin needles of oxide about 50–100 Å apart grow into the matrix separated by regions of amorphous silica. Nucleation of spherical colonies of the iron oxide and silica occurs on dislocations.Although the hematite or magnetite always shows the same topotactic relationship with the matrix, the direction in which the needle-like precipitates grow is determined by the orientation of the nucleating dislocation. The small size and highly distorted nature of these precipitates accounts for the diffuseness of their X-ray reflections.Oxidation at 1000 °C produces undistorted equiaxed grains of the oxides about 0·2 μm in size. They are surrounded by silica, which produces a disordered electron diffraction pattern. As the temperature is raised, the silica achieves more structural order and the oxide grains increase in size.

Microstructure Evolution of In Situ Synthesized VC Reinforced Iron Matrix Composites

2012 ◽  
Vol 217-219 ◽  
pp. 71-74
Author(s):  
Jing Wang ◽  
Si Jing Fu ◽  
Shu Yong Jiang ◽  
Hong Cheng
Keyword(s):  
Electron Microscopy ◽  
In Situ Synthesis ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Iron Matrix ◽  
X Ray ◽  
Matrix Microstructure ◽  
The Matrix ◽  
Scanning Electron

Iron matrix composite reinforced with VC reinforcements was produced by in situ synthesis technique. The microstructure of the composites was characterized by X-ray diffraction and scanning electron microscopy. The micrographs revealed the morphology and distribution of the reinforcements. The results show that the composite consists of VC carbide as the reinforcing phase and α-Fe as the matrix. The distribution of spherical VC particulates in iron matrix is uniform, and the matrix microstructure of Fe-VC composite is pearlite.

Thin-film reactions of Al with Co, Cr, Mo, Ta, Ti, and W

1989 ◽  
Vol 4 (4) ◽  
pp. 815-820 ◽  
Author(s):  
E. G. Colgan ◽  
J. W. Mayer
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phase Diagrams ◽  
Refractory Metals ◽  
Rutherford Backscattering ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

The thin-film interactions of Al with refractory metals (Co, Cr, Mo, Ta, Ti, and W) have been investigated. The composition and thickness of the reacted aluminide layers were determined by Rutherford backscattering and phase identification was made by x-ray diffraction. Scanning electron microscopy was used to examine the lateral uniformity. The initial aluminide phases to grow are the Al-rich phases: Co2Al9, Cr2Al13, MoAl12, TaAl3, TiAl3, and WAI12. These are the most Al-rich phases on the phase diagrams. The reaction temperatures varied between 350 and 525 °C.

Effects of Cr and Al on High Temperature Oxidation Resistance of Nb-Si System Intermetallics

2007 ◽  
Vol 546-549 ◽  
pp. 1485-1488 ◽  
Author(s):  
Shi Yu Qu ◽  
Ya Fang Han ◽  
Jin Xia Song ◽  
Yong Wang Kang
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Products ◽  
X Ray Diffraction ◽  
Temperature Oxidation ◽  
X Ray ◽  
Scanning Electron

The effects of Cr and Al on high temperature oxidation resistance of Nb-Si system intermetallics have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and weight gain method. The results showed that the high temperature oxidation resistance can be substantially improved by proper Cr or Al addition. The further analysis revealed that Cr promotes the formation of CrNbO4 in scale and improve the adherence between the oxide scale and the substrate. It also found that Al improves the surface morphology of oxide scale and changes oxidation products by promoting the AlNbO4 formation.

Alloying of Molybdenum Disilicide with Aluminum by SHS

2014 ◽  
Vol 1025-1026 ◽  
pp. 585-590
Author(s):  
Ying Zhou ◽  
Jin Xiao ◽  
Guo Tian Ye ◽  
Chen Yong Liu
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Molybdenum Disilicide ◽  
Hexagonal Structure ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
X Ray ◽  
High Temperature Synthesis ◽  
Aluminum Substitution ◽  
Scanning Electron

In this work, a series of samples of Mo (Si1-xAlx)2 (X =0, 0.10,0.20,0.30,0.40) were prepared by self-propagating high-temperature synthesis (SHS). The influence of the addition of Al on the structures and the micrographs of the final compounds were investigated. X-ray diffraction pattern characterization (XRD) and scanning electron microscopy (SEM) were used to characterize the obtained products. It was found that, the reactions between Mo and Si could be promoted with introducing Al during the SHS process. The high temperature β-MoSi2 phase with hexagonal structure (C40) was obtained and the peaks of the C40 phase shifted towards a higher d value with increasing aluminum substitution. The substitution of Al could reach to 40%. The morphology of the final products was similar with that of the raw Mo powders, which was independent of Al contents.

Preparation and Study on the Properties of Gypsum Whiskers Reinforced Resin Matrix Composites

2013 ◽  
Vol 327 ◽  
pp. 189-192
Author(s):  
Chuan Wei Du ◽  
Guo Zhong Li
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Strengthening Mechanism ◽  
Resin Matrix ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resin Matrix Composite ◽  
The Stability ◽  
Scanning Electron

In this paper, gypsum whiskers reinforced resin matrix composites were prepared with the desulfurization gypsum by the technology of atmospheric acidification. The influences of stabilization reagent on the stability of the gypsum whiskers were studied. Meanwhile, the enhanced effects of surface treatment and different contents of gypsum whiskers on the resin matrix composite were analyzed. Scanning electron microscopy, metallographic microscopy, X-ray diffraction test were taken to conduct analysis of the morphology and the aspect ratio of gypsum whiskers. Besides, the mechanical properties of gypsum whiskers reinforced resin matrix composites were tested, and cross-section scanning was used to analyze the strengthening mechanism.

Identification of calcium oxalate crystals in dried or fixed tobacco leaf

1984 ◽  
Vol 42 ◽  
pp. 288-289
Author(s):  
Vicki L. Baliga ◽  
Mary Ellen Counts
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Calcium Oxalate ◽  
Growth And Development ◽  
Polarized Light ◽  
Calcium Oxalate Crystals ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Calcium is an important element in the growth and development of plants and one form of calcium is calcium oxalate. Calcium oxalate has been found in leaf seed, stem material plant tissue culture, fungi and lichen using one or more of the following methods—polarized light microscopy (PLM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction.Two methods are presented here for qualitatively estimating calcium oxalate in dried or fixed tobacco (Nicotiana) leaf from different stalk positions using PLM. SEM, coupled with energy dispersive x-ray spectrometry (EDS), and powder x-ray diffraction were used to verify that the crystals observed in the dried leaf with PLM were calcium oxalate.

Environmental scanning electron microscopy of fresh human gallstones reveals new morphologies of precipitated calcium salts

1992 ◽  
Vol 50 (2) ◽  
pp. 1322-1323
Author(s):  
Howard S. Kaufman ◽  
Keith D. Lillemoe ◽  
John T. Mastovich ◽  
Henry A. Pitt
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Environmental Scanning Electron Microscopy ◽  
Environmental Scanning ◽  
X Ray Diffraction ◽  
Calcium Salts ◽  
Cholesterol Gallstones ◽  
X Ray ◽  
Ca Carbonate ◽  
Scanning Electron

Gallstones contain precipitated cholesterol, calcium salts, and proteins. Calcium (Ca) bilirubinate, palmitate, phosphate, and carbonate occurring in gallstones have variable morphologies but characteristic windowless energy dispersive x-ray (EDX) spectra. Previous studies of gallstone microstructure and composition using scanning electron microscopy (SEM) with EDX have been limited to dehydrated samples. In this state, Ca bilirubinates appear as either glassy masses, which predominate in black pigment stones, or as clusters, which are found mostly in cholesterol gallstones. The three polymorphs of Ca carbonate, calcite, vaterite, and aragonite, have been identified in gallstones by x-ray diffraction, however; the morphologies of these crystals vary in the literature. The purpose of this experiment was to study fresh gallstones by environmental SEM (ESEM) to determine if dehydration affects gallstone Ca salt morphology.Gallstones and bile were obtained fresh at cholecystectomy from 6 patients. To prevent dehydration, stones were stored in bile at 37°C. All samples were studied within 4 days of procurement.

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