Papers by Keyword: Purity

Abstract: Paper investigates the possibility of producing silicon from silica contained in Shoda-Kedela (Oni-Gebi district, Georgia) quartz deposition. Characterization of silica from Shoda-Kedela quartz rock is carried by its crushing, grinding, thermal analysis, studying composition and density. Metallurgical grade silicon (MG-Si) is obtained by reducing Shoda-Kedela quartz in its reaction with coke in an electric arc furnace at temperature of ~1800°C. The obtained in this way material reveals that Shoda-Kedela silica containing of 99.58% SiO₂ would be useful for developing the silicon high-technology production.

Abstract: The interaction among cutting parameters during the turning process is complex and non-linear, hence making linear predicting methods unsuitable for use. This study is a presentation of hierarchical clustering of surface roughness using acoustic emission signals during single point diamond turning of RSA-443. The intention of the study is to establish if clusters generated by portioning algorithms can be reliably used to understand the internal structure of data. Acquisition of acoustic emission signals has been achieved by a Kistler Piezotron sensor. AE root mean square, prominent frequency and peak rate are extracted from the processed captured AE signals while surface roughness is physically measured using a Kistler Taylor Hobson Profilometer. Validation of the generated clusters has been achieved by using the Purity measure. The computed purity is 1, which is an exhibition of the high quality of the hierarchical clustering result. Hence, clustering can be reliably utilized to understand the internal structure of surface roughness data during single point diamond turning.

Abstract: The samples of Eu_2-xCe_xCuO₄ (ECCO) with x = 0.10, 0.13, 0.17 and 0.20 have been synthesized by the solid reaction method without annealing process [1,2]. Each sample is covered by CuO powder to prevent excess oxygen entering the sample during heating process. The purpose of this research is to study the crystal structure and the level of phase purity in ECCO samples in the wide ranges of doping concentration of ECCO. The results of X-ray diffraction (XRD) characterization showed that the main peaks of T' tetragonal structure were observed in all samples. From the XRD analysis, it was found that the level of phase purity of ECCO was 100 % for x = 0.10, 100 % for x = 0.13, 79.5.% for x = 0.17, and 79.1 % for x = 0.20, respectively. For the lattice constant, it is found that both a and c-axis did not change significantly as the concentration increased. These results show that the synthesis method with CuO covering has succeeded in synthesizing materials with high phase purity although the constants do not change significantly when the concentration increased. However, there are some impurity phases found in high concentration of x that is probably due to the existence of excess oxygen, which was not fully absorbed by CuO Covering.

Abstract: Silica in nanoscale has various superior properties which leads to a wide range of applications. Most researches used and metal alkoxides as the sources but very few researches attempted at preparing nanosilica powder from the agricultural waste which environmental friendly and inexpensive. This research is presented as the studies of optimization of parameters involved during preparation, aimed to improve the purity of silica produced. In this work, rice husk ash (RHA) precursor was subjected to precipitation method in order to produce nanosilica powder. Acid leaching and thermal treatment were done as a pre-synthesis process. The process parameters that have been studied were the refluxed NaOH concentration, heating time, and temperature, in which the properties were then evaluated during characterization process. The results from X-Ray Flourescence (XRF) confirmed that it is possible to extract 100% purity of silica from RHA treated by the combination of thermal treatment, acid leaching, refluxed with 2.5 M of NaOH and heated at 50°C for 48 hours. X-Ray Diffraction (XRD) illustrated that the produced silica is in amorphous state. Meanwhile, the mean particle size of the spherical shape of silica obtained ranging from 44.7 nm to 1.23 μm. Therefore, the best mean particle size obtained was by using the sample refluxed with 2.5 M NaOH and heated at 50°C for 48 hours, which were confirmed by Scanning Electron Microscope (SEM) and Field Emission Scanning Electron Microscope (FESEM). These findings on the optimum parameters indicate the successful production of highest purity of nanosilica powder with nanoscaled particle size.

Abstract: The samples of Eu_2-xCe_xCuO₄ (ECCO) with x = 0.09 (Eu_1.91Ce_0.09CuO₄) and x = 0.16 (Eu_1.84Ce_0.16CuO₄) have been synthesized by the solid reaction method without annealing. Each sample is covered with CuO to prevent excess oxygen entering the sample. The purity and electrical resistivity were investigated by x-ray Diffraction (XRD) and resistivity measurements. From the XRD analysis, it was found that the purity of ECCO phase was 93.5% with tetragonal structure of T’ for x = 0.09 while 96.1% for x = 0.16. These results show that the synthesis method with CuO covering has succeeded in synthesizing materials with high purity. From the electrical measurements, the trace of superconductors was not observed in all samples. It is probably the existence of excess oxygen, which was not fully absorbed by CuO Covering.

Abstract: Tantalum carbide (TaC) coating, produced in an ultrahigh temperature chemical vapor deposition (CVD) process, exhibited high thermal and chemical stabilities, low emissivity, and high purity. The present research investigated through modeling the TaC emissivity and reactivity impacts on the temperature, C/Si ratio and growth rate in SiC physical vapor transport (PVT) process. The TaC coating effect was further validated by SiC crystal shape and quality through a series of growth experiments. As our study revealed, TaC coating can act as a protection and isolation layer to extend graphite component life, improve radial temperature uniformity, maintain SiC sublimation stoichiometry, suppress impurity migration, and reduce energy consumption. Ultimately a TaC-coated graphite crucible set is expected to improve SiC PVT process control and product quality.

Abstract: The 3003 aluminum alloy melt was treated with three types of melt purification, and the effect of melt purification on the microstructure and mechanical properties of the alloy was investigated. The results show that the impurity content of 3003 aluminum alloy with untreated (UT) reached 0.6801 %. After the process of conventional purification treatment (CPT) and efficient purification treatment (EPT), the impurity content of the alloy decreased significantly, and the fluidity of aluminum melt was improved. Finely dispersed inclusions particles can promote nucleation, refine the size of the cast crystal. Alloy strength and plasticity have increased using the process of CPT and EPT, in particular, EPT is the most obvious. It shows that the purity of aluminum melt plays a key role in the mechanical properties of the alloy.

Abstract: In order to improve the purity of bearing steel, the VIM+ESR+VAR triple smelting process was used to smelt 9Cr18Mo stainless bearing steel. The content of harmful elements, non-metallic inclusions and microstructure of the steel were studied. The results show that, the content of harmful elements of the steel is very low. A fairly small number of non-metallic inclusions are uniformly distributed and fine. The purity of the steel reaches a higher level. After thermal processing and heat treatment, the microstructure of the steel is the same as 9Cr18Mo bearing steel smelted by normal process, but the primary carbides in the steel is more uniform distribution and finer.

Abstract: Large temperature gradient was introduced to improve the removal rate of metal impurity in silicon ingot during direction solidification. The concentration of metal impurities in the silicon ingot with a large temperature gradient is 0.96 ppmw. The solidification time is reduced by 20% due to the fast speed of crystal growth improved; meanwhile the purity is increased by 64%.

Abstract: Using high quality carbon raw material,high quality silica raw material , the β-SiC powder are prepared by high-temperature vacuum smelting method. The effects of different materials and electrical power to the product of β-SiC quality has been studied. The microstructure and phase analysis of β-SiC powder samples were observed by Scanning Electron Microscopy and X-ray diffraction. The result shows that the raw materials are better, the product quality are better. In addition, the result also indicates that the β-SiC powder have better quality when the power are 3000W.