Preparation of high‐density YBa2Cu3Oxceramics with improved superconducting properties by hot pressing under controlled atmosphere

1990 ◽  
Vol 68 (11) ◽  
pp. 5908-5910 ◽  
Author(s):  
M. Kuwabara ◽  
H. Shimooka
Keyword(s):  
Hot Pressing ◽  
High Density ◽  
Controlled Atmosphere ◽  
Superconducting Properties

Oxygenation characteristics in high-density YBa2Cu3Ox ceramics

1991 ◽  
Vol 6 (7) ◽  
pp. 1398-1403 ◽  
Author(s):  
M. Kuwabara ◽  
H. Shimooka ◽  
I. Katayama ◽  
T. Inada
Keyword(s):  
Oxygen Content ◽  
Hot Pressing ◽  
Sintered Density ◽  
High Density ◽  
Superconducting Properties ◽  
Oxygen Annealing ◽  
A Value

Oxygenation characteristics in high-density YBa2Cu3Ox ceramics with a relative sintered density ≥97%, which were produced by hot-pressing to have various oxygen contents as-hot-pressed, have been investigated. The results indicate that the oxygenation characteristic in the materials was strongly affected by their oxygen content before oxygenation; that is, the attainable oxygen content (directly connected with the superconducting temperature Tc) of the materials after oxygenation increases with a decrease in their oxygen content before oxygenation. Oxygen annealing at 500 °C for 24 h dramatically increased the oxygen content of an YBa2Cu3Ox with x = 6.08 before the oxygen annealing up to 6.90, while the oxygen content of an YBa2Cu3Ox ceramic with x = 6.32 before oxygenation rose only to a value of 6.61 after the same oxygen annealing. This newly observed phenomenon on the oxygenation characteristic in the present materials may provide an idea for improving the superconducting properties in high-density YBa2Cu3Ox ceramics.

A Transparent and Tough β-Si3N4 Ceramic with a Whiskery Microstructure

2015 ◽  
Vol 655 ◽  
pp. 1-5
Author(s):  
Peng Xi Li ◽  
Hong Qiang Wang ◽  
Liu Cheng Gui ◽  
Jun Li ◽  
Hai Long Zhang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Amorphous Phase ◽  
Hot Pressing ◽  
High Density ◽  
Indentation Fracture ◽  
Indentation Fracture Toughness ◽  
Resultant Material

The transparent β-Si3N4ceramic with a whisker-like microstructure was prepared by hot-pressing at 2000 °C for 26 h, with MgSiN2as an additive. The resultant material achieves the maximum transmittance of 70 % at the wavelength of about 2.5 μm and the transmittance value keeps higher than 60 % in the range of 700-4500 nm wavelength, which is attributed to the very small amount of the intergranular amorphous phase along with high density. The present transparent β-Si3N4ceramic exhibits an indentation fracture toughness of 7.2±0.3 MPa m1/2.

ChemInform Abstract: Microstructure and Superconducting Properties of High-Density Consolidated YBa2Cu3Ox.

ChemInform ◽  
1989 ◽  
Vol 20 (9) ◽  
Author(s):  
R. N. SHELTON ◽  
D. ANDREASEN ◽  
P. KLAVINS ◽  
H. W. CHAN ◽  
B. L. OSLIN ◽  
...  
Keyword(s):  
High Density ◽  
Superconducting Properties

scholarly journals Environmentally-Friendly High-Density Polyethylene-Bonded Plywood Panels

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1166 ◽  
Author(s):  
Pavlo Bekhta ◽  
Ján Sedliačik
Keyword(s):  
Mechanical Properties ◽  
Hot Pressing ◽  
High Density Polyethylene ◽  
Phenol Formaldehyde ◽  
Urea Formaldehyde ◽  
Physical And Mechanical Properties ◽  
Core Layer ◽  
High Density ◽  
Pressing Pressure ◽  
Pressing Time

Thermoplastic films exhibit good potential to be used as adhesives for the production of veneer-based composites. This work presents the first effort to develop and evaluate composites based on alder veneers and high-density polyethylene (HDPE) film. The effects of hot-pressing temperature (140, 160, and 180 °C), hot-pressing pressure (0.8, 1.2, and 1.6 MPa), hot-pressing time (1, 2, 3, and 5 min), and type of adhesives on the physical and mechanical properties of alder plywood panels were investigated. The effects of these variables on the core-layer temperature during the hot pressing of multiplywood panels using various adhesives were also studied. Three types of adhesives were used: urea–formaldehyde (UF), phenol–formaldehyde (PF), and HDPE film. UF and PF adhesives were used for the comparison. The findings of this work indicate that formaldehyde-free HDPE film adhesive gave values of mechanical properties of alder plywood panels that are comparable to those obtained with traditional UF and PF adhesives, even though the adhesive dosage and pressing pressure were lower than when UF and PF adhesives were used. The obtained bonding strength values of HDPE-bonded alder plywood panels ranged from 0.74 to 2.38 MPa and met the European Standard EN 314-2 for Class 1 plywood. The optimum conditions for the bonding of HDPE plywood were 160 °C, 0.8 MPa, and 3 min.

A Hydroxycarbonate Route to Superconductor Precursor Powders

1987 ◽  
Vol 99 ◽  
Author(s):  
J. A. Voigt ◽  
B. C. Bunker ◽  
D. H. Doughty ◽  
D. L. Lamppa ◽  
K. M. Kimball
Keyword(s):  
Critical Temperature ◽  
Structural Integrity ◽  
Nitrate Solution ◽  
High Density ◽  
Tetramethylammonium Hydroxide ◽  
Precipitation Process ◽  
High Critical Temperature ◽  
Superconducting Properties ◽  
Superconducting Ceramics ◽  
Precursor Powders

ABSTRACTA precipitation process is described for the preparation of powders that can be thermally decomposed to form high critical temperature superconductors such as YBa2Cu3O7. In the process, a cationic solution (a concentrated chloride or nitrate solution) is instantaneously mixed with an anionie solution (a mixture of tetramethylammonium hydroxide and carbonate) to produce a metal-hydroxycarbonate precipitate having the metal stoichiometry of the desired superconducting oxide. The calcining and sintering of the precipitates is critical in controlling the structural integrity and morphology of the superconducting ceramics made from the chem-prep powders, as well as controlling superconducting properties. Under appropriate conditions, high density (>95%) materials that exhibit good superconducting characteristics can be prepared with the chem-prep powders.

Effect of Ag-particulate addition on processing, microstructure, and properties of MgO-whisker-reinforced bulk BPSCCO high-Tc superconductor composites

1996 ◽  
Vol 11 (6) ◽  
pp. 1373-1382 ◽  
Author(s):  
Y. S. Yuan ◽  
M. S. Wong ◽  
S. S. Wang
Keyword(s):  
Mechanical Properties ◽  
Solid State ◽  
Hot Pressing ◽  
Ceramic Materials ◽  
Superconducting Properties ◽  
High Tc ◽  
High Tc Superconductor ◽  
Processing Variables ◽  
Mechanical Strengths ◽  
State Processing

In associated papers [Y. S. Yuan, M. S. Wong, and S. S. Wang, J. Mater. Res. 11, 8–17 (1996); J. Mater. Res. (1996, in press)] it has been shown that weak thermo-mechanical properties of a bulk monolithic high-Tc superconductor (HTS) can be improved by introducing strong ceramic whiskers into the HTS ceramic materials. In this paper, we report a further study of incorporating Ag particulates, (Ag)p, in a bulk monolithic BPSCCO and in the MgO-whisker reinforced BPSCCO composite. Effects of the (Ag)p addition on processing, microstructure, and superconducting and mechanical properties of the bulk monolithic BPSCCO and the (MgO)w/BPSCCO composite are investigated. The results indicate that the highly ductile Ag particulates promote densification of the BPSCCO matrix phase in the composite during hot pressing. The microstructure of the HTS composite with the (Ag)p addition is similar to that in the HTS material without the (Ag)p. The (MgO)w/BPSCCO composite with 10% (by weight) Ag particulates has been shown to possess excellent superconducting properties. The (Ag)p addition to both the monolithic BPSCCO and the (MgO)w/BPSCCO is found to increase appreciably their fracture toughnesses, but has little effects on mechanical strengths of the materials. Quantitative relationships have been established among solid-state processing variables, HTS phase developments, microstructures, and superconducting and mechanical properties of the (Ag)p/BPSCCO and the (MgO)w/(Ag)p/BPSCCO HTS composites.

Biocompatibility of CaSiO3 /High-Density Polyethylene Composites Prepared by Hot-Pressing

2006 ◽  
Vol 309-311 ◽  
pp. 1161-1164 ◽  
Author(s):  
Miho Tanuma ◽  
Yoshikazu Kameshima ◽  
Akira Nakajima ◽  
Kiyoshi Okada ◽  
Shigeo Asai ◽  
...  
Keyword(s):  
Hot Pressing ◽  
High Density Polyethylene ◽  
Ceramic Powder ◽  
High Density ◽  
Apatite Formation ◽  
Composite Surface ◽  
Ceramic Particles ◽  
Fast Bone ◽  
The Matrix

We have reported that CaSiO3 ceramics show very fast bone-like apatite formation in simulated body fluid (SBF). However, CaSiO3 ceramics have disadvantages in their mechanical properties and shapability. It is therefore more effective to develop composites of CaSiO3 particles dispersed in a matrix of polymer or metal. Such composites are usually prepared by homogeneously blending the ceramic powder with the matrix component. This method is, however, ineffective for the preparation of biocompatible polymers or metals because only the surfaces containing accidentally-exposed ceramic particles play a role in generating apatite in SBF. It is therefore necessary to add a large volume of ceramic powder and also to abrade the surface to expose more of the ceramic particles. In this study, CaSiO3/high-density polyethylene (HDPE) composites were prepared by hot-pressing to introduce surface CaSiO3 particles and their biocompatibilities were evaluated under in vitro conditions using SBF. CaSiO3 powders were spread on a HDPE plate and hot-pressed at 140oC and 4.9-14.7 MPa for 2 min. The composite sample (about 10×10×1 mm3 in size) was immersed in 30ml SBF (sample/solution ratio of 2.5 g/l) at 36.5oC. After 14 days soaking, the apatite product particles covered most of the composite surface and formed apatite layers. Bone-like apatite particles were formed only on the surface regions containing exposed CaSiO3 particles but no apatite was formed on the CaSiO3 particles buried in the HDPE matrix. The results show that this surface deposition method is very effective in developing biocompatibility in the composites using very small amounts of CaSiO3 powder (about <1 %v) compared with results reported for hydroxyapatite and AW glass-ceramic powders (requiring about 40 %v). It is also found that the inhomogeneous state of the CaSiO3 particles in the surface of the present composites strongly influences their biocompatibility. It will be necessary to improve the homogeneity of CaSiO3 dispersion in the surface of the composites to achieve a more uniform surface apatite layer.

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