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Fabrication of Transparent Yttria Ceramics by Spark Plasma Sintering

100%
Korkmaz E., Sahin F.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 3
460-462
EN
Rapid densification of yttria (Y₂O₃) ceramics without sintering aids via spark plasma sintering at relatively low temperature of 1300°C for 40 minutes at two-step pressure profile, followed by post-annealing at 1050°C for 6 hours in air was attempted. Effect of preload pressure on microstructure, Vickers hardness, fracture toughness and optical in-line transmittance was investigated. Densification during spark plasma sintering did not involve any phase transformation and all phases have shown cubic structure according to X-ray analysis. The highest hardness and fracture toughness value was recorded to be 7.60±0.18 GPa and 1.16±0.07 MPa m^{1/2} with 10 MPa preload and 100 MPa final load. In addition to this, the highest transmittance with a value of 76.7% at a wavelength of 2000 nm was obtained when studied with 10 MPa preload and 100 MPa final load.
2
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Spark Plasma Sintering of Boron Carbide Ceramics Using Metallic Silicon in Square Cross Section

100%
Cengiz M., Sahin F.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1370-1372
EN
B₄C ceramics were fabricated by spark plasma sintering (SPS) technique with 5 vol.% silicon as sintering additive. Optimization of SPS method production parameters for B₄C ceramics having geometries 50×50×5 mm, square cross section will be performed. The sintering process was carried out at different temperatures by applying 40 MPa of pressure under vacuum atmosphere. The effect of silicon additive, sintering temperature and different soaking times on density, vickers hardness, fracture toughness and microstructure were examined. The mechanical properties of the B₄C ceramics having silicon as additive were compared with the results of monolithic B₄C. The hardness and fracture toughness of the samples were evaluated by the vickers indentation technique. Microstructures of spark plasma sintered B₄C samples with different parameters in square cross section were characterized by using SEM technique.
3
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B₄C-CNT Produced by Spark Plasma Sintering

100%
Apak B., Sahin F.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1029-1031
EN
H.C. Starck HS Grade boron carbide (B₄C) powders with multi-walled carbon nanotube (CNT) were sintered by Spark Plasma Sintering (SPS) method in a vacuum atmosphere to obtain highly dense and fine grained final ceramic products. Powder mixtures were densified by SPS at 1650 and 1725°C using 40 MPa pressure for 5 min. The effects of heating rate, spark plasma sintering temperature and CNT additive on density, hardness, fracture toughness and microstructures of B₄C-CNT samples are investigated. Density measurements were carried out using Archimedes method. Hardness and fracture toughness were examined by Vickers indentation technique. Scanning Electron Microscope (SEM) was used to observe microstructural investigation.
4
Content available remote

The Spark Plasma Sintering of Silicon Carbide Ceramics Using Alumina

81%
Unlu M., Goller G., Yucel O., Sahin F.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
257-259
EN
SiC ceramics were fabricated by spark plasma sintering technique with the use of Al_2O_3 additive. The sintering process was carried out at three different temperatures in the range of 1700-1800C applying two different pressures 40 and 80 MPa under vacuum atmosphere. The effect of additive, different temperatures and pressures on densification behaviour, density, Vickers hardness, fracture toughness, and microstructure were examined. The hardness and fracture toughness of the samples were evaluated by the Vickers indentation technique. Microstructure of spark plasma sintered SiC samples were characterized by using scanning electron microscopy technique. The highest value of fracture toughness 5.9 ± 0.2 MPa m^{1/2} was achieved with the addition of 5 vol.% Al_2O_3.
5
Content available remote

Spark Plasma Sintering of Boron Carbide Ceramics Using Different Sample Geometries and Dimensions

61%
Cengiz M., Yavas B., Celik Y., Goller G., Yucel O., Sahin F.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
260-262
EN
B_4C ceramics were fabricated by spark plasma sintering technique at 1700°C-1800C for 5 min under applied pressure of 50 MPa under vacuum atmosphere. Two different grades of B_4C powder from H.C. Starck Company namely HP grade and HS grade were used in all related experiments. Effect of sample geometry and dimensions as well as sample thickness on sintering parameters were analyzed. Samples having 5 mm thickness and 50 mm diameter, 8 mm thickness in circular geometries and 50 × 50 square cross-section, 8 mm thickness were fabricated. Using the powder, which provided the densest sample, yttrium oxide (Y_2O_3) was added, mixed and sintered. Optimization of SPS method production parameters for pure B_4C samples and B_4C samples with 5 wt% yttrium oxide additive were accomplished. The effect of geometry on density, Vickers hardness, fracture toughness, and microstructure were examined. The hardness and fracture toughness values of the samples were evaluated by the Vickers indentation technique.
6
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Processing, Mechanical and Nuclear Characterization of Boron Carbide Ceramics Consolidated by Spark Plasma Sintering

61%
Cengiz M., Ozer S., Buyuk B., Tugrul A., Yucel O., Goller G., Sahin F.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 2B
B-187-B-189
EN
Boron carbide (B₄C) ceramics were produced by spark plasma sintering technique with 5, 10, 15, and 20 vol.% aluminum (Al) in order to improve sintering behaviours of B₄C ceramics. B₄C ceramics were produced, having square cross-section and 50 × 50 × 5 mm³ dimensions. The sintering process was carried out at different temperatures by applying 40 MPa of pressure with 100°C/min under vacuum. The effects of various amounts of Al additive and sintering temperature on density, vickers hardness, fracture toughness and microstructure were examined. The hardness and fracture toughness of the samples were evaluated by the Vickers indentation technique. Microstructures of the samples were characterized by scanning electron microscopy technique. Fast neutron attenuation properties of the ceramics having highest density were also investigated.
7
Content available remote

Radiation Shielding Properties of Spark Plasma Sintered Boron Carbide-Aluminium Composites

61%
Buyuk B., Tugrul A., Cengiz M., Yucel O., Goller G., Sahin F.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 2B
B-132-B-134
EN
In this study gamma and neutron attenuation properties of boron carbide-aluminium (B₄C-Al) composites were investigated. B₄C-Al composites were produced by spark plasma sintering method. Aluminum percentages in the B₄C-Al composites were 0%, 10%, 15%, and 20% by volume. The composite materials were performed against gamma and neutron sources. Cs-137 and Co-60 gamma radioisotopes were used as gamma sources and Pu-Be neutron howitzer was used for neutron source. Theoretical mass attenuation coefficients were determined by using XCOM computer code and compared with the experimental results. It has been seen that the experimental results were close to the theoretical results. Total macroscopic cross-sections of the samples were determined for Pu-Be neutrons. It is concluded that increasing aluminum ratio in the B₄C-Al composites causes higher gamma attenuation behavior for Cs-137 and Co-60 gamma sources and the total macroscopic cross-sections of the B₄C-Al composites decrease by increasing Al concentration.
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