Dynamic Consolidation of Ceramic Powders: Practicalities, Problems, and Prospects

1983 ◽  
Vol 24 ◽  
Author(s):  
William H. Gourdin
Keyword(s):  
Cohesive Crack ◽  
Particle Sizes ◽  
Ceramic Powders ◽  
Complex Interplay ◽  
Surface Areas ◽  
Technological Potential ◽  
All Ceramic ◽  
Dynamic Consolidation ◽  
Powder Characteristics ◽  
Powder Compacts

ABSTRACTI present an assessment of the technological potential ofshock wave consolidationof ceramic powders as a technique for producing well-bonded, uniform, crack-free monoliths. Current compaction methods are briefly reviewed and the characteristics of the consolidated material are presented. The shock and release histories experienced by powder compacts in simple compaction assemblies are complex and I conclude that such simple assemblies are unlikely to yield structurally sound bodies. Control of the stress history over the entire loading cycle is necessary if the tensile stresses which develop during release are to be reduced to acceptable levels. Such exacting control is difficult to achieve, and becomes increasingly difficult as the peak stresses are increased. The powder must therefore be sufficiently plastic at moderate stresses to permit densification and bonding of the compact without destruction of the compact during release. Not all ceramic powders will satisfy this criterion. Local microstructural modification, including interfacial melting, is limited by the fine particle sizes and large surface areas of many ceramic powders. Production of cohesive, crack-free bodies thus depends upon a complex interplay between shock history, material properties, and powder characteristics which is poorly understood. I conclude that the technology of dynamic consolidation of ceramic powders will be difficult to develop and will have limited applications.

Influence of Powder Characteristics on Sintering of AlN Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 1409-1412 ◽  
Author(s):  
Jin Yu Qiu ◽  
Koji Watari ◽  
Yuji Hotta ◽  
Kenshi Mitsuishi
Keyword(s):  
Final Stage ◽  
Sintering Temperature ◽  
Sintering Behavior ◽  
Particle Sizes ◽  
Sintering Aid ◽  
Surface Areas ◽  
Initial Stage ◽  
Primary Particles ◽  
Powder Characteristics ◽  
Specific Surface Areas

The sintering behavior of AlN powders with different particle sizes and specific surface areas was investigated in the present work. 4.5-8.0mass% of the as-synthesized sintering aid from the Li2O-Y2O3-CaO system was added to these AlN powders, and they were then fired at 1400-1650oC for 6h. At the initial stage of sintering the fine AlN powder, it was recognized that sintering of primary particles occurred in agglomerations. With an increase of firing temperature, particles were rearranged and grains grew rapidly at the final stage. On contrary, in sintering of samples using the coarse AlN powder, the densification increased with raising sintering temperatures slowly, and the sintering temperature higher than 1650oC was required to obtain densified specimens.

PLZT:Nd3+ Ceramics for Photonic Applications

2012 ◽  
Vol 82 ◽  
pp. 32-37 ◽  
Author(s):  
Malgorzata Plonska ◽  
Wojciech A. Pisarski ◽  
Beata Wodecka-Dus ◽  
Lukasz Cienki
Keyword(s):  
Optical Properties ◽  
High Purity ◽  
Raw Materials ◽  
Ceramic Materials ◽  
Ceramic Powders ◽  
Pressing Method ◽  
All Ceramic ◽  
Neodymium Concentration ◽  
Sintering Conditions ◽  
Dielectric And Optical Properties

In the present work the influence of neodymium concentration (0-1at-%) and sintering conditions on 8/65/35 PLZT:Nd3+ ceramics were studied. All ceramic powders were synthesized by MOM technique from high purity raw materials (>99,9%), and subsequently sintered by free sintering and hot uniaxial pressing method. To analyze the powders and ceramics more the XRD, EDS SEM, and ferroelectric measurements were performed. Optical spectra were examined for all prepared samples, and their optical properties were analyzed using reflectance, excitation and luminescence measurements. The study gives a detailed account of the relationships between doping and preparing conditions on the basic physical and dielectric and optical properties of obtained ceramic materials.

Influence of powder characteristics on the properties of green compacts of Bi-2212 powders

1997 ◽  
Vol 12 (1) ◽  
pp. 21-27 ◽  
Author(s):  
D.-W. Yuan ◽  
M. D. Aesoph ◽  
J. Kajuch
Keyword(s):  
High Temperature ◽  
Confining Pressure ◽  
Plastic Behavior ◽  
Particle Sizes ◽  
Green Density ◽  
High Temperature Superconducting ◽  
Powder Characteristics ◽  
The Relationship ◽  
Powder In Tube ◽  
Superconducting Applications

With the growing potential for use of Bi-2212 powders in high temperature superconducting applications, it is important to understand the processing characteristics of the material. To meet this need, the present work established the relationship between confining pressure and green density for powders of different particle sizes and morphologies. Mechanical properties, including elastic and plastic behavior, of the resulting green compacts were also measured as a function of relative density. Particle size and size distribution are shown to have a significant impact on the properties of interest. The implications of such findings are discussed with respect to the powder-in-tube process for making high temperature superconducting wire and tape.

scholarly journals Effect of porosity and particle size on microwave heating of copper

2010 ◽  
Vol 42 (2) ◽  
pp. 169-182 ◽  
Author(s):  
A. Mondal ◽  
A. Shukla ◽  
A. Upadhyaya ◽  
D. Agrawal
Keyword(s):  
Particle Size ◽  
Particle Sizes ◽  
Metallic Materials ◽  
Bulk Materials ◽  
Microwave Furnace ◽  
Particulate Form ◽  
Heating Profiles ◽  
Powder Compacts ◽  
Heating Behavior ◽  
Difference Time

The present study investigates the effect of varying particle size and porosity on the heating behavior of a metallic particulate compact in a 2.45GHz multimode microwave furnace. Experiments on copper suggest that unlike monolithic (bulk) materials, metallic materials do couple with microwaves when they are in particulate form. The powder compacts having higher porosity and smaller particle sizes interact more effectively with microwaves and are heated more rapidly. A dynamic electromagnetic-thermal model was developed to simulate the temporal temperature distribution using a 2-D finite difference time domain (FDTD) approach. The model predicts the variation in temperature with time during heating of copper powder compacts. The simulated heating profiles correlate well with those observed from experiments.

Influence of Powder Particle Size of Slurries on Mechanical Properties of Porous Hydroxyapatite Ceramics

2005 ◽  
Vol 284-286 ◽  
pp. 365-368 ◽  
Author(s):  
Yin Zhang ◽  
Yoshiyuki Yokogawa ◽  
Tetsuya Kameyama
Keyword(s):  
Particle Size ◽  
Flexural Strength ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Particle Sizes ◽  
Wet Milling ◽  
Median Particle Size ◽  
Powder Characteristics ◽  
Median Particle

The effect of different particle sizes on the flexural strength and microstructure of three different types of hydroxyapatite (HAp) powders was studied. The powder characteristics of laboratory synthesized HAp powder (Lab1 and Lab2) were obtained through a wet milling method, and the median particle size and the specific surface area of powders are different with the dryness period. The median particle sizes of Lab1 and Lab2 are 0.34 µm and 0.74 µm, and the specific surface areas of Lab1 and Lab2 are 38.01 m2/g and 19.77 m2/g. The commercial HAp had median particle size of 1.13 µm and specific surface area of 11.62m2/g. The different powder characteristics affected the slip characteristics, and the flexural strength and microstructure of the sintered porous HAp bodies are also different. The optimum value for the minimum viscosity in these present HAp slip with respect to its solid loading and the optimum amount of the deflocculant were investigated. The flexural strengths of the porous HAp ceramics prepared by heating at 1200°C for 3 hrs in air were 17.59 MPa for Lab1 with a porosity of 60.48％, 10.51 MPa for Lab2 with a porosity of 57.75％, and 3.92 MPa for commercial HAp with a porosity of 79.37％.

A New Insight into the Mechanistic Study on Synthesis of Silica Nanospheres

2007 ◽  
Vol 124-126 ◽  
pp. 1249-1252
Author(s):  
Dong Shin Yun ◽  
Hyun Jung Kim ◽  
Hyun Chang Shin ◽  
Venkatathri Narayanan ◽  
Jung Whan Yoo ◽  
...  
Keyword(s):  
Physicochemical Characteristics ◽  
Mechanistic Study ◽  
Partial Hydrolysis ◽  
Particle Sizes ◽  
Species Concentration ◽  
Surface Areas ◽  
Ft Ir ◽  
Alkoxy Groups ◽  
Hydrolysis Of ◽  
Insight Into

The physicochemical characteristics (SEM, N2 adsorption, FT-IR, MASNMR) of samples from kinetics (10 min, 20 min, 30 min, 1 h and 3h) of hydrolysis of tetraethyl orthosilicate (TEOS) gives new insight into the synthesis of nanosphere. The particle sizes are increased with time, however, the surface areas decreased. FT-IR investigation reveals the presence of high intensed silanol groups of 960 cm-1 at 10 min, which reduced on progress of the reaction time. This suggests the partial hydrolysis and condensation of alkoxy groups in TEOS. 29Si MASNMR analysis shows the presence three different silica species(Q4, Q3 and Q2) in 10 and 20 min samples. The intensity of Q2 species decreases with time and other species concentration were increased.

Thermal stability of nanometer-sized NiO and Sm-doped ceria powders

2002 ◽  
Vol 17 (9) ◽  
pp. 2266-2274 ◽  
Author(s):  
Yoshihiro Okawa ◽  
Toshitatsu Matsumoto ◽  
Toshiya Doi ◽  
Yoshihiro Hirata
Keyword(s):  
Primary Particle ◽  
Solid Oxide ◽  
Cubic Phase ◽  
Particle Sizes ◽  
Doped Ceria ◽  
Secondary Particles ◽  
Surface Areas ◽  
Cerium Oxalate ◽  
Oxalate Solution ◽  
Thermal Stability Of

A fine NiO powder and a Sm-doped ceria powder with a composition of Ce0.8Sm0.2O1.9 were synthesized by heating the oxalate precursors at 300–1200 °C in air to produce a cermet (anode material) for solid oxide fuel cell. A 0.2 M Ni(NO3)2 solution and a 0.2 M Ce(NO3)3–Sm(NO3)3 solution were mixed with 0.4 M oxalate solution, respectively, to produce the oxalate precursors. Only the cubic phase of Ce0.8Sm0.2O1.9 was formed in the calcined powders from the Sm-doped cerium oxalate. However, the mixed phases of NiO and Ni were produced in the NiO precursor after the calcination at 300–600 °C. At higher temperatures, only NiO was detected. The primary particle sizes, which were determined from the Brunauer-Emmett-Teller analysis surface areas, were 60 nm for NiO and 10 nm for Ru/Sm-doped ceria (SDC) after the heat treatment at 400 °C. The oxalate precursors of SDC and NiO provided 433 and 259 kJ/mol of the activation energy, respectively, for sintering/grain growth in the temperature range from 600 to 1200 °C. As-produced SDC precursor formed platelike secondary particles of 0.5–2-μm length by the heating at 800 °C. Heating of Ni oxalate at 800 °C produced isotropic fine NiO secondary particles of 0.5–2-μm sizes.

Preparation And Characterization Of Ultra-Small Sized Metal And Semiconductor Particles In Sol-Gel Materials

1994 ◽  
Vol 346 ◽  
Author(s):  
Kyung Moon Choi ◽  
Kenneth J. Shea
Keyword(s):  
Pore Size ◽  
Surface Area ◽  
Sol Gel ◽  
High Vacuum ◽  
Particle Sizes ◽  
Transition Metal Clusters ◽  
Surface Areas ◽  
Sol Gel Process ◽  
Bridged Silsesquioxanes

ABSTRACTPoly(l,4-phenylene)-bridged and poly(1,6-hexylene)-bridged silsesquioxanes (PPS and HPS) were prepared by the sol-gel process. The surface areas and pore diameters of these porous xerogels were obtained by BET and BJH methods, respectively. These porous materials were used as a confinement matrix for the growth of small-sized semiconductor and transition metal clusters. Quantum-sized CdS particles in PPS (approximately 58+12 Â) and HPS (91+16 Â) matrices were prepared by first soaking the xerogel in a CdCl2 solution. Following a washing with water, a Na2S solution was then added. EDAX and electron diffraction techniques were used to identify the CdS particles. The particle sizes of CdS in PPS and HPS were determined by both UV measurements and from TEM images. Small-sized Cr clusters were prepared in dried xerogels by an internal doping method. Mixed Cr/CdS phases were also prepared by internal loading of a chromium metal precursor. Following deposition of CdS the xerogel was heated at 120 °C under high vacuum, resulting in formation of intimately mixed phases of Cr metal and CdS. Changes in morphology, in particular the surface area and pore size distribution were noted. A decrease in surface area and an increase in pore size were observed as a result of Cr metal deposition.

INFLUENCE OF TIN POWDER CHARACTERISTICS ON THE SINTERING OF IRON-TIN-COPPER POWDER COMPACTS

1972 ◽  
Vol 15 (30) ◽  
pp. 153-165 ◽  
Author(s):  
S. K. Chatterjee ◽  
J. V. Castell-Evans ◽  
P. A. Ainsworth
Keyword(s):  
Copper Powder ◽  
Powder Characteristics ◽  
Powder Compacts

scholarly journals Molten salt synthesis of TiB2 nanopowder by reduction of TiO2 with MgB2

2021 ◽  
Vol 15 (1) ◽  
pp. 40-46
Author(s):  
Liaqat Shah
Keyword(s):  
Molten Salt ◽  
Research Work ◽  
Molten Salt Synthesis ◽  
Average Particle ◽  
Particle Sizes ◽  
High Concentration ◽  
Active Materials ◽  
Surface Areas ◽  
Salt Mass ◽  
Mass Ratios

This research work presents the preparation of TiB2 nanopowders by molten-salt synthesis (MSS) technique from TiO2 and MgB2 as starting active materials and MgCl2 as a molten salt. The pure TiB2 nanopowders were finally prepared using 2M HCl aqueous solution to leach the synthesized samples. The effects of the firing temperature, firing time and reactants to salt ratio on the TiB2 nanopowders formation were examined. The results demonstrated that the TiB2 formation was completed even with reactants to salt mass ratio of 1:2 at 1000 ?C for 4 h. The TiB2 nanopowders synthesized with 1:2, 1:5 and 1:10 reactants to salt mass ratios have different particle sizes. Thus, the average particle sizes estimated from BET surface areas were 59, 55 and 46 nm for the samples synthesized with 1:2, 1:5 and 1:10 reactants to salts mass ratios, respectively. These results illustrated that the high concentration of MgCl2 plays a key role in the particles? size reduction. The above results assured that this research study presents a new low-temperature synthesis route for nano-sized metal diboride powders.

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