Materials Science
Safa Luay Jasim; Shihab A. Zaidan; Enas Muhi Hadi
Abstract
Refractory ceramics were produced using silicon carbide (SiC) as the main component in combination with different weight percentages of Iraqi white kaolin (20%, 40%, 60% and 80%). Two different weight percentages of alumina (5% and 10%) were then added to each SiC-kaolin mixture. The samples were effectively ...
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Refractory ceramics were produced using silicon carbide (SiC) as the main component in combination with different weight percentages of Iraqi white kaolin (20%, 40%, 60% and 80%). Two different weight percentages of alumina (5% and 10%) were then added to each SiC-kaolin mixture. The samples were effectively mixed, molded, dried and fired at 1300 °C. The structural and physical properties were measured, including X-ray diffraction, apparent porosity, water absorption and thermal conductivity. X-ray diffraction showed that the addition of Al2O3 to the SiC-kaolin composite increased the mullite phase by interacting with the excess silica formed during the firing of kaolin or with the silica formed during the oxidation of SiC. The increase in kaolin content in the composite without alumina was accompanied by a decrease in physical properties, as the apparent porosity decreased from 30.17% to 17.95% and the water absorption from 16.31% to 7.07%. The addition of 80 wt.% kaolin led to a decrease in thermal conductivity from 35 to 15 W/m.K. The addition of 10 wt% Al2O3 also reduced the apparent porosity and water absorption to 13.85% and 5.33% respectively for the (SiC-20 wt% kaolin) sample. The apparent porosity and water absorption of the sample (SiC-80 wt% kaolin) with 10 wt% Al2O3 reached the lowest values of 9.44% and 3.55%, respectively. The thermal conductivity decreased from 15 to 12 W/m.K. This study found that adding alumina improves refractory efficiency due to its high melting point, making it ideal for high-temperature applications.
Nanotechnology
Amani Z. Al Ani; Shihab A. Zaidan
Abstract
The mechanical and electrical properties relation is very important, especially for brittle material. Nano Alumina-unsaturated polyester (PS/Al2O3) composites were prepared by casting PS with different percentages (1, 2, 3, and 4 wt%) of Nano alumina. Electrical breakdowns caused cracks to form around ...
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The mechanical and electrical properties relation is very important, especially for brittle material. Nano Alumina-unsaturated polyester (PS/Al2O3) composites were prepared by casting PS with different percentages (1, 2, 3, and 4 wt%) of Nano alumina. Electrical breakdowns caused cracks to form around the breakdown point, and the length and quantity of cracks increased with dispersed powder added increases. The research involved determining Weibull modulus from an electrical strength test, and mechanical strength by piston-on-three-ball test. The results showed that Weibull modulus and dielectric breakdown increase during the rate of rising voltage (RRV) increases, especially 5 kV/s. the maximum Weibull modulus measured by the electrical breakdown was at a high RRV is 34.58 (PS/Al2O3). High RRV leads to electromechanical breakdown and electrothermal strength at low RRV. While the Weibull modulus by the piston-on-three-balls test is lower than the Weibull modulus calculated by electrical strength. Therefore, this mechanical test is more accurate in identifying defects that fail due to an increase in the affected area of the applied stress. Scanning electron microscope (SEM) images showing the homogeneous distribution of the powders within the polymeric matrix. Some pores were present in the structure of the composite despite the measures taken to increase the dispersion using ultrasound waves. Those pores caused fluctuating results in all electrical and mechanical tests.
Materials Science
Duraid Mahdi; Shihab Zaidan; Muthafar Al-Hilli
Abstract
The work idea is finding out how the homogeneity of dielectric strength property in lithium metasilicate glass-ceramic with addition weight percentage increasing of CuO. It prepared four specimens, one without CuO addition lithium metasilicate glass-ceramic LSGC and consists of Li2O-SiO2 binary system ...
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The work idea is finding out how the homogeneity of dielectric strength property in lithium metasilicate glass-ceramic with addition weight percentage increasing of CuO. It prepared four specimens, one without CuO addition lithium metasilicate glass-ceramic LSGC and consists of Li2O-SiO2 binary system glass batch with weight percentages 45 wt% Li2O and 55 wt% SiO2. It added to the binary system CuO with different weight percentages to prepare the rest three specimens in front of the Li2O weight percentage decreasing as 1 wt% LC1S, 2 wt% LC2S, and 3 wt% LC3S. The glass batches for four specimens were mixed and used melting-quenching method at temperature of 1195OC for soaking time 2 hrs. It used platinum crucible (90 Pt-10 Rh) and immediately cooled in the cold water of temperature at 3OC. This process was repeated twice for all specimens and the produced frit was milled by agate mortar. Addition of P2O5 and TiO2 as nucleating agents with weight percentage 3 wt% P2O5 and 1 wt% TiO2 and prepared compact discs with dimensions 18 diameter × 2.58 thickness mm by the used biaxial hydraulic press with 5 ton for 30 s under pressure. The heat treatment was done for all glass batch compact discs of temperature at 950OC for 6 hrs as soaking time and breakdown voltage test was done executed 10 different spots in each specimen and Weibull modulus was used to know the homogeneity of dielectric strength property and coincided with Field Emission Scanning Electron Microscopes (FE-SEM) images. It got a good match between Weibull modulus results and FESEM images which indicating that Weibull modulus is the active tool that can be used for knowing the homogeneity of any property. The high average dielectric strength is 9.116 kV/mm for LC1S while the lower average dielectric strength is 7.101 kV/mm for LSGC and this back to more homogeneity and fewer defects in LC1S than LSGC.
