Synthesis of Ultrafine Cr3C2 Powders by Carbothermal Reduction of Precursors

2012 ◽  
Vol 549 ◽  
pp. 310-313
Author(s):  
Yong Zhong Jin ◽  
Fa Ming Ye ◽  
Chun Hai Liu ◽  
Rui Song Yang
Keyword(s):  
Electron Microscopy ◽  
Carbothermal Reduction ◽  
Complex Oxide ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Precursor Method ◽  
Air Drying ◽  
X Ray ◽  
Homogeneous Chemical ◽  
Scanning Electron

Ultrafine Cr3C2 powders with globular-like particle of ~0.3-0.8 μm were synthesized by a new precursor method, namely carbothermal reduction of complex chromium oxide-carbon mixture, which was made initially from salt solution containing chromium and carbon elements by air drying and subsequent calcining at 400 °C for 1 h. Phase composition of reaction products was discussed by X-ray diffraction (XRD), and microstructure of the calcined powders and final products was studied by scanning electron microscopy (SEM). The results show that the synthesizing temperature of Cr3C2 powders was reduced greatly by the new precursor method. Thus, the preparation of ultrafine Cr3C2 powders is at only 1000 °C for 2 h. The lowering of synthesizing temperature is mainly due to the homogeneous chemical composition of the complex oxide-carbon mixture. There is a coarsening tendency of Cr3C2 powders with the increase of reaction temperature and time.

Biomorphic SiC Prepared from Carbonized Millet by Sol-Gel and Carbothermal Reduction Processing

2010 ◽  
Vol 152-153 ◽  
pp. 1683-1686
Author(s):  
Qing Wang ◽  
Ya Hui Zhang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Silicon Carbide ◽  
Phase Composition ◽  
Carbothermal Reduction ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbon Template ◽  
Scanning Electron

Biomorphic silicon carbide (bioSiC) was prepared by high temperature pyrolysis and sol-gel and carbothermal reduction processing at 1600 oC. The morphology and microstructure of carbon-silica composites and purified bioSiC samples were characterized by scanning electron microscopy. The phase composition of the resulting sample was analyzed by X-ray diffraction. The results suggest that the bioSiC mainly consists of cubic ß-SiC, and principally replicates the shape and microstructure of the carbon template.

Carbothermal Synthesis of Cr3C2-WC-Ni Nanocomposite Powders

2013 ◽  
Vol 661 ◽  
pp. 3-6 ◽  
Author(s):  
Yong Zhong Jin ◽  
Fa Ming Ye ◽  
Xian Guang Zeng ◽  
Rui Song Yang
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Scanning Electron Microscopy ◽  
Carbothermal Reduction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbothermal Synthesis ◽  
Unit Cells ◽  
Nanocomposite Powders ◽  
Scanning Electron

Cr3C2-WC-Ni nanocomposite powders with ~50-100 nm were synthesized from precursors by vacuum-aided carbothermal reduction at only 750 °C for 2 h. The phase composition and microstructure of the synthesized products were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The present study shows that Cr3C2-WC-Ni nanocomposite powders contain two kinds of solid-solution phases, namely Ni and (Cr, W)3C2solid solution, respectively. WC and W2C phases do not appear inreaction products due to the dissolution of tungsten atoms into Ni and Cr3C2unit cells. Especially, there is a change of the crystalline structure for (Cr, W)3C2phase from 750 °C to 800 °C.

The Research on the (1-x) PZT-x PMN Piezoelectric Materials

2014 ◽  
Vol 700 ◽  
pp. 148-151
Author(s):  
Gui Gui Peng ◽  
Shun Min Hu ◽  
De Yi Zheng
Keyword(s):  
Electron Microscopy ◽  
Electromechanical Coupling ◽  
Piezoelectric Properties ◽  
Piezoelectric Materials ◽  
Electromechanical Coupling Coefficient ◽  
X Ray Diffraction ◽  
Precursor Method ◽  
Pure Perovskite Structure ◽  
X Ray ◽  
Scanning Electron

It is well known that piezoelectric ceramics are wildly used in many fields such as electrical sensors, actuators, alarm equipments etc. In this paper，the microstructure and the piezoelectric properties of Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 (PMNZT) were studied. A novel B-site precursor method was adopted for preparing of Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 samples. For investigating the crystallographic phase and microstructure of the samples, X-ray diffraction(XRD) and scanning electron microscopy(SEM) methods have been adopted respectively. The results show that a pure perovskite structure can be obtained after sintering at 1220°C for 2h. Through this experiment, it has been found that when sintering at 1220°C for 2h and the amounts of the Pbx（Nb2/3Mg1/3）xO3 (PMN) is 0.14, the Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 samples are with the best electrical properties as follows: dielectric constant (ε) is 1858, dielectric loss(tanδ) is 0.017, electromechanical coupling coefficient (Kp) is 0.515, piezoelectric constant(d33) is 362PC/N

Use of Fly Ash and Cu-Slag from Mexico to Make Alkali Cements and Hybrid Cements

2016 ◽  
Vol 1813 ◽  
Author(s):  
M. Rendón Belmonte ◽  
A. Palomo Sánchez ◽  
A. Fernández Jiménez ◽  
A. Torres Acosta ◽  
M. Martínez Madrid ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Fly Ash ◽  
Chemical Characterization ◽  
Copper Slag ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naoh Solution ◽  
Scanning Electron

ABSTRACTThis paper focus on evaluating the ability to use Mexican fly ash (FA) and copper slag (CS) to produce alkali cements (0% OPC) or hybrid cements (20% OPC + 80% fly ash). The alkali activators used were two: 8 M NaOH solution for alkali cements and NaCl with sodium silicate for hybrid cement (HYC). Results of mechanical testing and characterization of the reaction products formed after 2 and 28 days are presented and discussed. Mechanical strength in some cases exceeded 20 MPa, at 2 days curing. The chemical characterization techniques used were X-Ray Diffraction (XRD) and scanning electron microscopy (SEM).

scholarly journals Preparation of biomorphic SiC ceramics

2008 ◽  
Vol 40 (2) ◽  
pp. 141-145 ◽  
Author(s):  
A. Egelja ◽  
J. Gulicovski ◽  
A. Devecerski ◽  
M. Ninic ◽  
A. Radosavljevic-Mihajlovic ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Carbothermal Reduction ◽  
Oxide Ceramic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbon Preform ◽  
Sic Ceramics ◽  
Porous Sic ◽  
Scanning Electron

This paper deals with a new method for producing non-oxide ceramic using wood as a template. SiC with a woodlike microstructure has been prepared by carbothermal reduction reactions of Tilia wood/TEOS composite at 1873K. The porous carbon preform was infiltrated with TEOS (Si(OC2H5)4), as a source of silica, without pressure at 298K. The morphology of resulting porous SiC ceramics, as well as the conversion mechanism of wood to SiC ceramics, have been investigated by scanning electron microscopy (SEM/EDS) and X-ray diffraction analysis (XRD). Obtained SiC ceramics consists of ?-SiC with traces of ?-SiC.

Influence of CeO2 Additive on the Phase Transformations of Zirconia from Zircon Ore by Carbothermal Reduction Process

2014 ◽  
Vol 602-603 ◽  
pp. 238-241 ◽  
Author(s):  
Teng Yu Wang ◽  
You Guo Xu ◽  
Zhao Hui Huang ◽  
Ming Hao Fang ◽  
Yan Gai Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Phase Transformations ◽  
Carbothermal Reduction ◽  
Heating Temperature ◽  
Reduction Process ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Additive Increase ◽  
Scanning Electron

This paper mainly discusses the influences of heating temperatures and CeO2 additive contents on the phase transformations of zirconia from zircon ore by carbothermal reduction. The phase transformations of zirconia from zircon ore by carbothermal reduction were monitored by X-ray diffraction. The microstructure of the product was characterized by scanning electron microscopy. The results show that without adding CeO2, the optimized heating temperature of zircon carbothermal reduction was 1600 °C and the main phases of the product were m-ZrO2, ZrC and β-SiC, t-ZrO2; After adding CeO2, the main phase of the products consists of t-ZrO2, m-ZrO2, ZrC and β-SiC when the heating temperature is 1600 °C. CeO2 additive can be introduced into zirconia lattice and can cause it to form cerium stabilized zirconia. Zirconia in the product would be turned into partially stabilized zirconia with cerium addition from 5 wt% to 20 wt%. However, the form of zirconia in the product is not changed greatly with the amount of CeO2 additive increase.

scholarly journals Mineralogical transformation and microstructure of the alluvials clays

2019 ◽  
Vol 51 (1) ◽  
pp. 57-70 ◽  
Author(s):  
Isaac Bomeni ◽  
Armand Wouatong ◽  
Francois Ngapgue ◽  
Kamgang Kabeyene ◽  
Nathalie Fagel
Keyword(s):  
Electron Microscopy ◽  
Raw Materials ◽  
Reaction Products ◽  
Clay Brick ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mineral Phases ◽  
Fired Bricks ◽  
Alluvial Clay ◽  
Scanning Electron

Mineralogical transformations and microstructures during the firing alluvial clays from Monoun plain were studied. The firing of clays was carried out in the temperature range from 800 to 1150?C. Minerals transformation was investigated by X-ray diffraction, polarize stereomicroscopy and scanning electron microscopy (SEM). In the raw materials, typical assemblages with quartz, kaolinite, goethite, anatase, hematite, gibbsite and feldspar were observed. Many neoformed mineral phases were identified with the reaction products including mullite, cristobalite, spinel, amorphous phase which occurred in the high temperature (1050-1150?C) in the fired bricks. The quartz phenocrist with some microlites oxides embedded in few mesostasis glass have been illustrated at 950?C by stereomicroscopy analysis. At 1150?C, the vitreous matrix has embedded phenocrist of quartz and other relic minerals. The best temperature for fired alluvial clay brick was discovered between 1050-1150?C.

Carbothermal reduction of low-grade pyrolusite by microwave heating

RSC Advances ◽  
2014 ◽  
Vol 4 (102) ◽  
pp. 58164-58170 ◽  
Author(s):  
Qianxu Ye ◽  
Hongbo Zhu ◽  
Libo Zhang ◽  
Peng Liu ◽  
Guo Chen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Crystal Structures ◽  
Microwave Heating ◽  
Energy Dispersive Spectroscopy ◽  
Carbothermal Reduction ◽  
Low Grade ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

Pyrolusite was carbothermally reduced using coal by microwave heating, and the crystal structures and microstructures of the samples were characterized after microwave heating using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS).

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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