Papers by Keyword: Surface Structure

Abstract: In this project, the surface structure of III-V semiconductor, GaAs, was altered to enhance the optical and electronic properties of the semiconductor. This project involved the designing and fabrication of non-porous and porous GaAs structures using SILVACO TCAD tools. The porous GaAs with different pore depth were designed and simulated to investigate the effect of pore depth on the optical and electrical properties of GaAs semiconductor. The pore depth of porous GaAs structure was varied with 2, 4, 6 and 8 μm. The porous GaAs structures were then tested for the metal-semiconductor-metal (MSM) photodetector device application. The non-porous and porous GaAs MSM photodetectors were compared systematically through current-voltage (I-V) characteristics, current gain, and spectral response. The result showed that the porous GaAs MSM photodetector has better performance in terms of electrical and optical properties than the non-porous photodetector. Amongst the MSM GaAs photodetectors, the porous GaAs photodetector with pore depth of 6 μm obtained the highest current gain value of 3.22. While for optical properties, the spectral response showed the current intensity of 11.370 µA which was recorded at the peak wavelength of 880 nm. Therefore, porous GaAs showed good potential and can be used for optoelectronic device applications such as MSM photodetector.

Abstract: Bamboo is well known as the oldest structural material that possess unique anatomical structure and superior mechanical properties. It has become a subject of interest worldwide and research is being conducted for its structural applications including safety, durability and also mechanical properties. Many studies carried out previously indeed have shown superior strength of bamboo. Most of the research circulate on the mechanical properties improvement using chemical, plasma, enzyme, fungi and nanocellulose coating treatment. However, despite the conventional treatments’ advantages, but they are impractical, costly and it able to change the structure of the treated materials. This study aims to evaluate the morphological properties of untreated and treated of Semantan bamboo culm (Gigantochloa scortechinii) after subjected to a simple and cost-effective epoxy treatment. By using Alicona Infinite Focus 3D profilometer machine, the comparison between the untreated and treated surfaces of bamboo can be obtained under profile surface roughness test. Meanwhile, the depth formation of the treated surfaces also can be obtained by using the same machine under profile form management test. Next, optical microscope was used later to examine the epoxy matrix treatment formation of the untreated and treated bamboo surfaces. The result revealed that the application of epoxy treatment gave a better surface roughness and structure as it treat the bamboo strips and concurrently gave a thin layer of coating to the bamboo strips. The findings of this study suggest that epoxy treatment can be an effective and economical approach to treat natural fiber as it resulting in good surface structure which simultaneously increase the chemical and mechanical interlocking; thus, the bond between matrix and natural fiber become stronger.

Abstract: The surface structure of Hydroxyapatite (HAp) particles during hydrothermal synthesis and their protein adsorption behavior was investigated. The HAp particles were prepared by mixing calcium acetate solution and diammonium hydrogen phosphate solution by hydrothermal synthesis. When the temperature of mixture were heated up to 120°C, 150°C and 180°C, the HAp particles were collected during hydrothermal synthesis. The adsorption properties of proteins onto HAp were studied using three types of proteins: bovine serum albumin (BSA), myoglobin (MGB) and lysozyme (LSZ). Surface analysis by BET revealed that their pore volumes were decreased by increasing synthesis temperature. The adsorbed amount of BSA and LSZ per unit milligrams showed no obvious difference in all of the HAp particles prepared with synthesis temperature. In contrast, the amount of MGB adsorbed onto HAp particles synthesized at 120°C, 150°, and 180°C shows the decreasing with an increasing synthesis temperature. This result suggests that the adsorbed amount of MGB was decreased by decreasing pore volume of HAp particles.

Abstract: New data on the structure of silicon-containing oxide layers SiO₂+TiO₂ on titanium formed by the method of plasma electrolytic oxidation (PEO) as well as on the structure and catalytic activity in CO oxidation of MnO_x+SiO₂+TiO₂/Ti composites formed on their basis using impregnation and annealing methods have been obtained. It has been demonstrated that silicon and titanium are rather homogeneously distributed over the SiO₂+TiO₂ coating bulk. The coating outer part is silicon-enriched titanium-depleted. The MnO_x+SiO₂+TiO₂/Ti composites catalyze the CO conversion at temperatures above 100°C. Nanowhiskers consisting predominantly of manganese oxides have been found on the surface of the MnO_x+SiO₂+TiO₂/Ti composites.

Abstract: This study investigates how roughness and coatability of sheet moulding compound (SMC) components can be improved by modifying the surface morphology of the compression tool. A modular tool was developed that allowed to mould SMC work pieces simultaneously with different tool surfaces. In this study, mainly the tool roughness was modified using various surface treatments. Three different SMC formulations were applied to mould 2D components using the modular system. It was found that the demoulding was affected by both the tool morphology and the SMC formulations. Contamination of the tool by SMC material could be reduced by chrome-plating. The morphology of the tool was transferred to the SMC work piece if the structures were larger than 5 µm. The adhesion strength of a coating system differed for the three SMC formulations. While two of them showed generally good coatability, the coating adhesion on the third formulation decreased with increasing roughness of the tool used for moulding.

Abstract: In this study, aluminum nitride films were formed on aluminum substrates by gas nitriding in order to improve their low emissivities. To accomplish this, aluminum alloys were subjected to nitriding conditions at 773 and 823 K for 0–5 h, using alumina and magnesium powders. The resulting aluminum nitride films were several micrometers thick and the films were dark brown or black. The surface structures of the aluminum nitride films were investigated using a scanning electron microscope, which showed fine acicular aluminum nitride nodules with diameters on the order of several micrometers. Emissivities were evaluated at 298 K using Fourier transform infrared spectroscopy, in a wavelength range of 2–14 μm. Total emissivities at temperatures between 323 and 383 K were estimated from emissivity results obtained at 298 K. It was subsequently found that emissivity decreases with increasing wavelength and an emissivity of 0.80 was observed at a wavelength of 2 μm. Total emissivity was 0.49 % at 298 K and was in excess of 0.50 between 323 and 383 K.

Abstract: The structure of the coating layer has a strong influence on the optical and physical properties of paper as well as on the print quality. Ink is transferred and sets onto the paper surface in the printing process, which affect printing quality and usage of ink. The objective of this experiment was to investigate the influence of calender on coating surface structure and Printability. The surface structure was explored in the method of numerical and visual analysis using mercury porosimetry measurement and scanning electron microscopy (SEM). The findings indicated that the calender treatment affected the pore size, depth and distribution of the coated paper surface. It could be concluded that Calender could increase the smoothness, gloss and paper surface efficiency of coated paper, which resulted in lower amount of ink usage, lower amount of ink absorption and higher print density.

Abstract: Silicon-containing oxide layers deposited on titanium using the plasma electrolytic oxidation (PEO) method were modified with manganese and cobalt compound through impregnation followed by annealing. The obtained manganese composites are catalytically active in the process of oxidation of CO at 100 оС, while cobalt-containing structures demonstrate this type of activity at temperatures above 200оС. The composition and surface structure of the obtained systems were investigated by means of X-ray phase and energy dispersive analyses and by high resolution scanning electron microscopy (SEM). Granule-like particles with diameters of a few dozens of nanometers were observed on the surface of oxide-cobalt layers on titanium, whereas the surface of oxide-manganese layers was coated by nano-whiskers of diameters <50 nm and length <1 μm. The presence of manganese-containing nano-whiskers substantially increases the catalyst specific surface, thus facilitating the attainment of higher degree of transformation of initial gaseous substances.

Abstract: The aim of this study was to investigate the surface composition and morphology of fast-growing Alkaline peroxide mechanical pulping (APMP). Surface ultrastructure of APMP were modified by cellulase. The fiber ultrastructure and cellulose crystallinity before and after treatment with cellulose enzyme were analyzed by Atomic force microscopy (AFM). The results showed that surface particle size can be reduced to 300nm and bump of fiber surface became obvious. According to the phase contrast image and topography, cell wall region separate clearly. The specific surface area of single fiber became bigger.

Abstract: Study on the impact of activation agent for Activated semi-coke structure Activated semi-coke were prepared choosing KOH and ZnCl₂ as activating agent by orthogonal experiments, and the effect on properties of activated were also be researched. The influence of different activating agents for activated semi-coke the structure of activated semi-coke were analyzed by using SEM and FTIR. Performance and structure of ZnCl₂ activated semi-coke were compared with KOH activated .The result showed that ZnCl₂ activated semi-coke and KOH activated were obviously different. The former have developed in macroporous structure. The latter have developed in mesoporous and micropore and had Uniform pore distribution. The infrared spectra of two activated semi-coke is similar.