In this study, we have prepared aluminum oxide (Al 2 O 3 nanoparticles) NPs with size ranging from 50 to 90 nm by laser ablation of aluminum target in ethanol. The effect of laser fluence on the structural, morphological and optical properties of Al 2 O 3 was demonstrated and discussed. X-ray diffraction XRD results confirm that the synthesized Al 2 O 3 NPs are crystalline in nature. The sample prepared at 3.5 J/cm 2 /pulse exhibits single phase of c-Al 2 O 3 , while the XRD patterns of the nanoparticles synthesized at 5.3 and 7.5 J/cm 2 /pulse show the co-existence of the a-Al 2 O 3 and c-Al 2 O 3 phases. Nanostructured Al 2 O 3 films have been used as anti-reflecting coating and surface passivation layer to improve the photoresponse characteristics of silicon photodiode. The experimental data showed that the optical energy gap decreases from 5.3 to 5 eV as the laser fluence increases from 3.5 to 7.3 J/cm 2 . The lowest optical reflectivity was found for silicon photodiode deposited with a single layer of Al 2 O 3 prepared at 3.5 J/cm 2 /pulse. The effect of laser fluence on the refractive index and extinction coefficient of the nanostructured Al 2 O 3 film was studied. The photosensitivity of the silicon photodiode increased from 0.4 to 1.4 AW -1 at 800 nm after depositing Al 2 O 3 prepared at 3.5 J/cm 2 /pulse, followed by rapid thermal annealing at 400°C for 60 s.
The interrelationships between mechanical and electrical properties are important to characterize one signifies the other, especially for brittle materials such as glass. The relationship between Weibull modulus from electrical breakdown and Weibull modulus from three-point bending test and other mechanical properties has been studied for soda lime glass slides. The results show that the electrical breakdown and Weibull modulus increased with the rate of rising voltage increases from 20.1-24.7 kV/mm and 10.9-13.78, respectively. The value of Weibull modulus was calculated by using mechanical strength is (12), this result identified the conditions necessary to achieve the same results in electrical breakdown strength test. Therefore, the best rate of rising voltage in the electric breakdown test is 2 kV/s which gives the same results as the mechanical tests. This means that it is possible in the future to evaluate the dielectric products electrically in terms of matching mechanical strength specifications using electrical tests.
Porcelain is one of the most important ceramic materials with a wide range of traditional and technical applications. Since most mixtures of porcelain have a high sintering temperature, bentonite has been added in this research to improve the characteristics of sintering and burning. The porcelain mixture consisted of the following Iraqi raw materials: 30% wt kaolin, 30 wt% non-plastic clay (grog), 10% wt sodium feldspar, 10 wt% potassium feldspar and 20 wt% flint. After the mechanical mixing process and transfer the powder mixture to the slurry by adding distilled water, then different weight percentage of the sodium bentonite(0, 2.5, 5, 7.5 and 10) wt% was added. The specimens were prepared by using the solid casting method, and after the drying process, the specimens were burned at1100 oC. The results of x-ray diffraction showed that bentonite reduced the crystallization of the main ceramic phases (mullite, quartz), which stimulates the appearance of amorphous glass phases. Also, the loss of mass on ignition increased when the addition of bentonite from 5.66% to 8.2%. There was also a great convergence between the granules of porcelain when adding bentonite and thus increase the shrinkage of the dimensions from 9.33% to 12.37 %. This led to increasing the bulk density from 1.97 g/cm3 to 2.67 g/cm3 at firing temperature 1100oC, and the porosity was decreased from 17.1% to 1.44%. Diametrical strength and flexural strength (bending) increased with bentonite (14.88 to 34.46MPa), (6.2 to 8.65 MPa), respectively.
Partial Stabilized Zirconia (PSZ) was prepared from adding 3 wt % of MgO or adding 8 wt% of Y 2 O 3 to 90 wt % ZrO 2 Powder and mixed by wet method, then dried and firing mixture to 1500C to obtain PSZ ceramic powder. Glass-Ceramic (Li 2 SiO 3 ) and (LiAlO 2 ) prepared by dissolve lithium carbonate and lithium hydroxide with Nano-Silica (SiO 2 ) and Nano-Alumina (Al 2 O 3 ) respectively. Those glass-ceramic mixed with PSZ in different percentage (2.5,5,7.5,10) and sprayed on furnaces bricks for petroleum refineries. An increase in the chemical resistance of the acid on the surface of the Refractory bricks was observed when coating with the glass-ceramic mixture, as well as increasing the hardness and thermal shock resistance. Lithium silicate coated specimens are more spared and homogeneous on the surface compared to lithium laminate coated.
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