Powder characteristics and sintering behavior of Ag-doped YBa2Cu3O7−x produced by aerosol decomposition

1992 ◽  
Vol 7 (4) ◽  
pp. 827-836 ◽  
Author(s):  
Timothy L. Ward ◽  
Toivo T. Kodas ◽  
Altaf H. Carim ◽  
Donald M. Kroeger ◽  
Huey Hsu
Keyword(s):  
Submicron Particles ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Powder Synthesis ◽  
X Ray ◽  
Grain Sizes ◽  
Powder Characteristics ◽  
Scanning Electron ◽  
Nitrate Solutions ◽  
Reaction Routes

YBa2Cu3O7−x (1-2-3) powders and 1-2-3 powders doped with 14 wt. % Ag (AgYBa2Cu3O7−x) were produced using aerosol decomposition of nitrate solutions. Powder produced at T > 900 °C consisted of submicron particles and had Tc ≍ 92 K in magnetic susceptibility measurements. As-produced Ag-doped powder was a composite of nearly phase-pure 1-2-3 and crystalline Ag (by x-ray diffraction) for reactor temperatures between 900 °C and 950 °C, whereas powder produced at T≥ 970 °C contained significant amounts of Y2BaCuO5 which were not found in 1-2-3 synthesis in the absence of Ag. This implied that the melting of Ag (∼960 °C) or the Ag-O eutectic (∼940 °C) promoted decomposition of 1-2-3 during powder synthesis. Dilatometry showed that 1-2-3 and Ag/1-2-3 powders densified rapidly between 800 °C and 875 °C, achieving nearly 90% of theoretical density after heating to 875 °C at 5 °C/min in air. Pellets of the Ag-doped powder were also sintered for 2-60 h at 895 °C in air. Scanning electron and optical microscopy revealed that Ag grains remained fine and uniformly distributed, varying in size from ∼1 μm after 2 h to 3–7 μm after 60 h, while 1-2-3 grains became plate-shaped with thicknesses of 1–5 μm and lengths of 10–30 μm after 60 h. Thus, the use of aerosol Ag /1-2-3 powders allows the use of lower processing temperatures and shorter times to produce dense ceramics with smaller Ag and 1-2-3 grain sizes than can be obtained using solid-state reaction routes.

Carbothermal Reduction Synthesis of Zirconium Diboride Powders Assisted by Microwave

2010 ◽  
Vol 105-106 ◽  
pp. 203-206
Author(s):  
Hai Long Wang ◽  
Shi Xun Zhang ◽  
De Liang Chen ◽  
Qian Fei Han ◽  
Hong Xia Lu ◽  
...  
Keyword(s):  
Surface Area ◽  
Carbothermal Reduction ◽  
Nitrogen Absorption ◽  
X Ray Diffraction ◽  
Powder Synthesis ◽  
X Ray ◽  
Bet Model ◽  
Powder Characteristics ◽  
Higher Temperature ◽  
Scanning Electron

ZrB2 powder has been prepared through carbothermal reduction boronization of zirconia/boron carbide/carbon mixtures heating assisted by microwave. The powder characteristics were investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), nitrogen absorption (BET model) and scanning electron microscope (SEM). The experiments indicated that excessive B4C is necessary and the carbothermic reaction reacts severely at a higher temperature and complete at 1600oC. The crystallite size has ranged from 50-100 nm, according to the calculated surface area. Highest purity of ZrB2 powder, which was synthesized at 1600oC, is 99.67 wt%. The surface area of ZrB2 powder synthesis at 1600oC is 18.33 m2/g. Vibration of temperature should affect the purity of ZrB2, as the sub reaction acted.

Effects of CaB2O4 Content on the Sintering Behavior of Hexagonal Boron Nitride

2011 ◽  
Vol 675-677 ◽  
pp. 131-134
Author(s):  
Yu Xia Cao ◽  
Ling Zhong Du ◽  
Wei Gang Zhang
Keyword(s):  
Boron Nitride ◽  
Diffraction Analysis ◽  
Apparent Density ◽  
Cross Sections ◽  
Hexagonal Boron Nitride ◽  
Sintering Behavior ◽  
Rockwell Hardness ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes

CaB2O4 was added into hexagonal boron nitride (hBN) to improve the sintering behaviors of hBN. CaB2O4 and hBN were mixed and then pressed into plates. The plates were sintered at 2000°C for 5h under a N2 ambience. The phase compositions with different CaB2O4 contents were examined with X-ray diffraction analysis. The fracture cross-sections of the hBN plates were investigated by SEM. The apparent density and Rockwell hardness were also measured. The results show that the hBN particles had a plate-like shape and the grain sizes of hBN increased with increasing CaB2O4 contents. The apparent density and Rockwell hardness decreased with increasing CaB2O4 contents. When the CaB2O4 content was 15(wt) %, the hBN has the average grain sizes of 3μm in diameter and 200nm in thickness, the apparent density of 1.06 g/cm3 and the Rockwell hardness of 3, respectively.

The Effects of Ternary Elemental Additions on the Structure and Magnetic Properties of Nanocrystalline Feco Powders

2002 ◽  
Vol 753 ◽  
Author(s):  
I. Baker ◽  
R. G. Quiller ◽  
M. Robson ◽  
D. Wu
Keyword(s):  
Magnetic Properties ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
Before And After ◽  
Diffraction Peaks ◽  
Computer Controlled ◽  
Steel Balls ◽  
Scanning Electron

ABSTRACTPowders of near-equiatomic Fe and Co were mechanically milled with additions of Zr, C, Ni, Cu and/or B for 60 hr using stainless steel balls in a Svegari attritor operated at 1300 r.p.m. under argon. The milled powders were examined before and after annealing at 600 °C. The morphologies and sizes of the powders were examined using a scanning electron microscope. The grain sizes were characterized from the widths of X-ray diffraction peaks obtained using a computer-controlled x-ray diffractometer and the lattice parameters were determined. The resulting magnetic properties were measured using a vibrating sample magnetometer.

Fabrication of Lead Barium Titanate Ceramics via Conventional Solid-State Mixed Oxide Technique

2008 ◽  
Vol 55-57 ◽  
pp. 209-212 ◽  
Author(s):  
Theerachai Bongkarn ◽  
P. Panya
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Mixed Oxide ◽  
Perovskite Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Calcination Temperatures ◽  
Grain Sizes ◽  
Titanate Ceramics ◽  
Scanning Electron

(Pb0.925Ba0.075)TiO3 (PBT) ceramics have been prepared using a mixed oxide technique. The phase formation and morphology were studied in detail via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The pure tetragonal perovskite structure was discovered with calcination temperatures above 800 oC. The percentage of perovskite phase and particle size tends to increase with the increasing of calcination temperatures. The PBT ceramics sintered at various temperatures belonged to a pure tetragonal perovskite phase. The average grain sizes increased from 0.90 to 6.44 µm with the increase of sintering temperatures from 1100 to 1200 oC. The highest density was obtained from the sample that sintered at 1150 and 1200 oC

Effect of h-BN on Sintering Behavior, Microstructures and Mechanical Properties of YAG Bulk Composites

2016 ◽  
Vol 697 ◽  
pp. 395-398 ◽  
Author(s):  
Shi Bin Li ◽  
Jie Guang Song ◽  
Hong Ying Ru ◽  
Xiao Bo Bai
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Precipitation Process ◽  
Sintering Behavior ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Composite Powders ◽  
X Ray ◽  
Co Precipitation ◽  
Scanning Electron

The shell structure YAG composite powders with different volume fraction (15, 20 and 25vol%) micro h-BN have been prepared by co-precipitation process. The bulk composites were performed by pressure sintering at 1600°C under a pressure of 30MPa in vacuum. The mechanical properties (elastic modulus, hardness, and fracture toughness) and relative density of the composites were investigated detailedly. Furthermore, phase composition and microstructure of the composites were analyzed thoroughly by X-ray diffraction, scanning electron microscopy. Meanwhile, good machinability is maintained due to the low hardness of the second phase.

High Strength Mg-Zn-Y-Ce-Zr Alloy Bars Prepared by RS and Extrusion Technology

2005 ◽  
Vol 488-489 ◽  
pp. 495-498 ◽  
Author(s):  
Xuefeng Guo ◽  
Jacob Kinstler ◽  
Lilia Glazman ◽  
Dan Shechtman
Keyword(s):  
Grain Boundaries ◽  
High Strength ◽  
Submicron Particles ◽  
Commercial Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Matrix ◽  
Extrusion Technology ◽  
Scanning Electron ◽  
Zr Alloy

Based on the commercial alloy ZK60 which contains 6%Zn, high strength Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr magnesium alloy bars of 10 to 50 mm in diameters were prepared by rapid solidification (RS) and extrusion processes （RSE）. For those RSE solid bars, the ultimate tensile strengths steadily maintain on a level of 490 to 520 MPa, the elongations are between 6 to 10%. The HV50 hardness is between 85 and 90. In order to reveal materials microstructures both RS ribbons and RSE solid bars, the Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr alloy was analyzed with an optical microscopy (OM), a scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) and an X-ray diffraction apparatus. It was found that the microstructure of the RS ribbon consists of super saturated (Mg) solid solution; thermally stable Mg3Y2Zn3 (W) and Mg7Ce2 intermetallic compound particles which uniformly dispersed interior grains and W and Mg7Ce2 compound networks at grain boundaries. After extrusion, the microstructure of RSE Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr solid bar consists of the same phases as the RS ribbons. The networks existing at RS ribbon’s grain boundaries were break up into submicron particles and dispersed uniformly on the matrix formed after extrusion.

Preparation of Alumina Powders through Pyrocatechol, Resorcinol Mediated Sol-Gel Method

2016 ◽  
Vol 850 ◽  
pp. 742-747
Author(s):  
Xiang Zhang ◽  
Ping Yun Li ◽  
Xiao De Guo ◽  
Ting Yan
Keyword(s):  
Electron Microscopy ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
Xrd Study ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Scanning Electron ◽  
Organic Monomer

Ultrafine alumina powders were synthesized through pyrocatechol and resorcinol mediated sol-gel process. Aluminum nitrate was applied as the Al source and PVP was the dispersant. X-ray diffraction (XRD) study displayed that γ-Al2O3 powders formed in the range of 800-900 °C, and then γ-Al2O3 transformed to α-Al2O3 at higher temperatures, pure α-Al2O3 powders could be obtained at 1000 °C by using resorcinol as organic monomer. The results of transmission electron microscopy (TEM) revealed that Al2O3 nanoparticles with γ crystalline phase had grain sizes in the range of 5-40 nm. Scanning electron microscopy (SEM) observation displayed that the morphology of the prepared α-Al2O3 powders had aggregated bodies formed by Al2O3 grains in the range of 0.2-0.5μm. These results provide a new way of preparation of alumina powders.

scholarly journals Karakteristik Struktur Mikro dan Gugus Fungsi Komposit Silika Sekam Padi dan Aspal

2020 ◽  
Vol 8 (1) ◽  
pp. 93-100
Author(s):  
Ediman Ginting Suka ◽  
◽  
Ira Sudarsono Putri ◽  
Reka Puspitasari ◽  
Reza Arsela ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Compressive Strength ◽  
Functional Groups ◽  
Amorphous Silica ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
Sample Composition ◽  
Scanning Electron

Composite of rice husk and asphalt silica was carried out at a ratio of 1: 0.7; 1: 0.8 and 1: 0.9 and heated at 150oC for 3 hours. The characteristics of the phase structure, microstructure, and functional groups were analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) and Fourier Transform Infrared (FTIR), physical properties analysis (density, porosity) and mechanics (compressive strength). The XRD results showed that the phase in asphalt silica composites detected amorphous carbon at 2θ = 18º and amorphous silica with the amorphous silica peak shifted from 2θ = 22º to 2θ = 20º. Microstructure analysis shows that cracks and clusters are bigger with grain sizes of 7,742 µm, 8,495 µm and 10,921 µm respectively, and the sample composition shows percentage of silicon (Si), Oxygen (O) and sodium (Na), respectively. decreases and the percentage of carbon (C), sulfur (S) increases. The results of FTIR show that the functional groups of Si-OH, Si-O-Si and Si-O bonds are decreasing and the functional groups of C-H bonds are increasing. The addition of asphalt causes the value of density increases, the value of porosity and compressive strength decreases.

Photocatalytic Properties of WO3 Particles with Different Grain Sizes

2016 ◽  
Vol 697 ◽  
pp. 284-287
Author(s):  
Zhen Guang Shen ◽  
Zhi Jian Peng ◽  
Jing Wen Qian ◽  
Xiu Li Fu
Keyword(s):  
Electron Microscopy ◽  
Methylene Blue ◽  
Thermal Evaporation ◽  
Photocatalytic Properties ◽  
X Ray Diffraction ◽  
Thermal Evaporation Method ◽  
X Ray ◽  
Grain Sizes ◽  
Degradation Effect ◽  
Scanning Electron

WO3 particles with different grain sizes were prepared by a thermal evaporation method. The composition, morphology, and optical properties of the samples were analyzed by powder X-ray diffraction, scanning electron microscopy, and UV–vis absorption and photoluminescence spectroscopy. Their photocatalytic properties were evaluated by decomposing methylene blue in aqueous phase. It was found that the smaller the grain size of the prepared WO3 particles, the better the degradation effect on methylene blue.

3YTZP-Al2O3 Powders Synthesized by the Coprecipitation Route

2006 ◽  
Vol 530-531 ◽  
pp. 677-682 ◽  
Author(s):  
R.H.L. Garcia ◽  
Valter Ussui ◽  
Nelson Batista de Lima ◽  
Dolores Ribeiro Ricci Lazar
Keyword(s):  
Laser Diffraction ◽  
Aqueous Environment ◽  
Processing Conditions ◽  
X Ray Diffraction ◽  
Scanning Electronic Microscopy ◽  
Electronic Microscopy ◽  
Powder Synthesis ◽  
X Ray ◽  
Powder Characteristics ◽  
Coprecipitation Route

The addition of alumina in a zirconia stabilized in a tetragonal phase matrix enhances ceramic hardness and inhibits the tetragonal → monoclinic phase transformation of zirconia when exposed to an aqueous environment. These characteristics are important for applications such as bioceramics and structural materials. For these purposes, the strict control of powder synthesis and the processing conditions are vital to tailor the ceramic characteristics. This work evaluates the influence of 20 wt% alumina in a Y-TZP matrix on powder characteristics, obtained by coprecipitation route, and calcined from 600 to 1200°C for 1 and 3 hours. The powders obtained were characterized by X-ray diffraction, scanning electronic microscopy, laser diffraction and gaseous adsorption (BET). The results reveal that presence of Al3+ inhibits the crystallization of composite at lower temperatures.

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