Papers by Keyword: Crystal Morphology

Abstract: This study deals with the synthesis of cubic shape platinum nanoparticles (Pt NPs) by adjusting the oleylamine (OAm):polyvinylpyrrolidone (PVP) ratio in the solution media. The mass ratios between the OAm:PVP were respectively set to the 1:2, 1:1, 2:1 values. Platinum acetylacetonate (Pt(acac)₂) was used as Pt precursor and the reduction of this salt to the metallic Pt was provided by microwave irradiation technique. It is seen that increasing amount of OAm triggers the formation of cubic shape Pt NPs. The average sizes of the Pt NPs fall in the range of 6-8 nm. The unsupported Pt NPs were directly used as a catalyst for the oxygen reduction reaction (ORR). According to the hydrodynamic ORR voltammograms of the catalysts, the Pt NPs prepared with 1:2 (OAm:PVP) exhibit the highest current density at all stirring rates of rotating disc electrode (RDE). Besides, Pt NPs prepared with 2:1 (OAm:PVP) have the minimum charge transfer resistance based on electrochemical impedance spectroscopy (EIS) analysis conducted at 0.9 V. After all these analyses, Pt NPs were synthesized using extra five different ratios (1.5:1, 1:1.5, 2.5:1, 3:1, 1:3) of (OAm:PVP) for thoroughly examining the optimum value for the ORR catalytic activity. As a result, the Pt NPs prepared with a 2.5:1 (OAm:PVP) ratio provided the best performance among all the catalysts.

Abstract: In this study, the effect of a high-temperature annealing process on AlN is investigated. The high-temperature annealing process reduces the screw dislocation density of the AlN film to 2.1x10⁷ cm^-2. The AlN surface is highly flat. Through HRXRD and Raman spectroscopy, the stress mode changes in the sputtered AlN film before and after high-temperature annealing were studied in depth. Based on the HTA-AlN template, a high-quality, high-Al composition AlGaN epitaxial wafer, with a (0002) plane rocking curve FWHM of 246 arcsec , was prepared at 1080°C The growth mode of AlGaN grown directly on the AlN template at low temperature is summarized.

Abstract: Crystal quartz mineral belongs to the mineralogy of quartz family. Colorless crystals formed when pure, can form different types of color centers when containing trace elements such as Fe, the article mainly studies the crystal morphology of the different characteristics and to further explore the mechanism from the chemical synthesis of crystal morphology formed mechanism.

Abstract: The crystallization of calcium carbonate was conducted by the reaction of calcium acetate with urea in the presence of polyvinylpyrrolidone (PVP). The morphology and polymorphism of these products were characterized with field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results showed that hierarchical CaCO₃ spheres were prepared in the presence of PVP. Varying the amount of PVP can prominently regulate the aggregation and self-assembly process of calcium carbonate precursor formed in mixed solvent.

Abstract: In this paper, the ZnO crystal was synthesized using hydrothermal method through 24 hours reaction with 35 % filling factor at 430°C. When the mineralizer concentration is rather low (eg. lmol/L NaOH), only ZnO microcrystal is produced. The mineralizer concentration increases, the larger crystal was present. When 5 mol/L NaOH served as mineralizer, the extent of the synthesized crystal was nearly 500m. The ZnO cryslals with length of 1500m were present when 3ml/L KOH served as mineralizer. Respectively when 3mol/L NaOH and lmol/L KBr were used as mineralizer, the extent of the synthesized crystal was nearly 700m , the diameter was 200m and the exposed faces m { 100}, p { 101 } was complete , so we obtained the higher quality crystals. Besides the larger crystal, a great deal of microcrystal and nanocrystallites cluster was also present in the product.

Abstract: In this paper, the ZnO crystal was synthesized using hydrothermal method through 24 hours reaction with 35 % filling factor at 430°C. When the mineralizer concentration is rather low (eg. lmol/L NaOH), only ZnO microcrystal is produced. The mineralizer concentration increases, the larger crystal was present. When 5 mol/L NaOH served as mineralizer, the extent of the synthesized crystal was nearly 500m. The ZnO cryslals with length of 1500m were present when 3ml/L KOH served as mineralizer. Respectively when 3mol/L NaOH and lmol/L KBr were used as mineralizer, the extent of the synthesized crystal was nearly 700m , the diameter was 200m and the exposed faces m { 100}, p { 101 } was complete , so we obtained the higher quality crystals. Besides the larger crystal, a great deal of microcrystal and nanocrystallites cluster was also present in the product.

Abstract: Nowadays the treatment way of circulating cooling water is mainly confined in the scale removal direction and effect is limited, but in scale inhibition direction few reports. To solve this problem, the study proposed a new technology of high-frequency electric field-colloid-electric adsorption. Simulation circulating water was treated by the self-made electrolytic system in high frequency DC electric field, obtained the optimum conditions by adjusting different electrochemical parameters, and analysed the mechanism of the process. The result suggests that this process has excellent scale inhibition, it reflected the good descaling effect by soften and peel the aging scale, it also can effectively change the crystal morphology, it is convenient, efficient and environment friendly.

Abstract: One of the key issues is in crystal growth technologies is control of crystal morphology. This paper attends to understand film growth in its full generality is to propose a growth law, and it is capable of describing all types of growth mechanisms and determining the growth morphology at different stages of growth. We refer to an axiomatic approach to identify the important scaling in growth processes. One way to determine which processes dominate the competition is to form dimensionless parameters which embody the competitions between pairs of kinetic processes.

Abstract: In this paper , the ZnO crystal was synthesized using hydrothermal method through 24 hours^' reaction with 35 % filling factor at 430°C. When the mineralizer concentration is rather low (eg. lmol/L NaOH), only ZnO microcrystal is produced. The mineralizer concentration increases, the larger crystal was present. When 5 mol·L^-1 NaOH served as mineralizer, the extent of the synthesized crystal was nearly 500μm. The ZnO cryslals with length of 1500μm were present when 3ml·L^-1 KOH served as mineralizer. Respectively when 3mol·L^-1 NaOH and lmol·L^-1 KBr were used as mineralizer, the extent of the synthesized crystal was nearly 700μm , the diameter was 200μm and the exposed faces m { 100} , p { 101 } was complete , so we obtained the higher quality crystals. Besides the larger crystal, a great deal of microcrystal and nanocrystallites cluster was also present in the product.

Abstract: TiO2 films consisting of rod-like to sphere-like TiO2 particles on glass slides were synthesized by assembly technique. The results showed that the shape and size of TiO2 particles could be manipulated using different concentrations of polyethylene glycol 20000. By increasing of PEG, the shapes of the TiO2 particles transformed from rod-like to sphere-like, the size of TiO2 particles became gradually smaller. The size became bigger when an excess amount of PEG was added. With the adding of PEG，the amount of the TiO2 , the hydroxyl content, and the rutile phase content on the surface of TiO2 films increased, respectively. The photocatalytic activity of TiO2 films added PEG was higher than that of unadded samples.