Advanced Materials Research Vols. 1025-1026

Abstract: In this paper, the technique of irradiation of thin films by Ga+ ions inside of scanning electron microscope, by a focused ion beam is developed. The influence of irradiation on magnetic properties of thin epitaxial films of Co, grown by molecular beam epitaxy in ultrahigh vacuum on a silicon surface with a intermediate layer of copper atoms. It has been shown that low radiation doses lead to an increase of magnetic hardness of the samples. At higher doses, there is a decrease of coercive force, which is apparently due to a change of crystalline structure of the material. An interesting fact is that in the dose range of 10¹²-10¹⁵ the relative remanences is practically unchanged and only at higher doses the magnetic properties of the film worsen.

Abstract: A series of research had been conducted to alter the performance of carbon membranes by manipulating the parameters during the fabrication process. In this study, the effects of carbonization temperature on the performance of carbon membrane were investigated. Matrimid-based carbon membrane supported on ceramic tube was fabricated through the dip-coating technique. The prepared membranes were characterized by using the scanning electron microscopy (SEM) and pure gas permeation test for the study on morphological structure and gas separation performance, respectively. The carbonization process was performed at different carbonization temperatures (600, 700, and 800 ^oC) for the same heating rate of 1 ^oC/min under Ar flow. The increment of carbonization temperature produced carbon membrane with small size of pores. The carbon membrane prepared at 800 ^oC showed the highest CO₂/CH₄ and CO₂/N₂ selectivity of 79.65 and 74.76, respectively.

Abstract: Nonlinear refractive indexes and two-photon absorption coefficients of new biosilicate nanocomposite materials based on precursor tetrakis (2-hydroxyethyl) orthosilicate (Si-precursor THEOS) were determined by created portative automation measuring complex based on Z-scan technique. Influence of different additives on nonlinear optical properties such media is considered. Energy thresholds of forming filaments and the efficiency of conversion initial radiation in supercontinuum in the range 400-700 nm are considered.

Abstract: Ni₂P/TiO₂-Al₂O₃ catalysts were prepared by impregnation of nickel phosphate precursors followed by reduction in hydrogen. The catalysts were characterized by X-ray diffraction (XRD), N₂-adsorption specific surface area measurements (BET), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetry differential thermal analysis (TG-DTA). The effects of reduction temperature on catalyst structure and HDS activity were studied using a lab-scale continuous flow fixed-bed reactor.. The results indicated that the catalyst prepared with reduction temperature of 973 K exhibited the best performance. At a reaction temperature of 606 K, a pressure of 3.0 MPa, a hydrogen/oil ratio of 500 (V/V), and a weight hourly space velocity (WHSV) of 2.0 h^-1, the conversion of DBT HDS was 96.0%.

Abstract: Objective: The study aimed to investigate the amount of fluoride release from 3 brands of elastomeric ligatures in vitro, after exposure to daily fluoride mouthrinse. Materials and Methods: The study used 3 brands of elastomeric ligatures (Morelli, Brazil; Unitek, USA; Thai, Thailand). Two elastomeric ligatures from each brand were moistened by de-ionized water and then divided into control and test groups (n=5 per group). In both groups, elastomeric ligatures were placed in individual plastic bottle with 3 ml of de-ionized water. However, In the test group, They were exposed to fluoride mouthrinse (250 ppm fluoride/0.05%NaF) for 1 minute daily. All samples were stored at 37°C for 1, 3, 5, 7 days. After the end of each observation period, the amount of fluoride release in de-ionized water was measured by fluoride ion electrode. The data were analyzed by Kraskal-Wallis and Mann-Whitney U tests (p<0.05). Results: Amount of fluoride release in test group was greater than in the control group in all 3 brands. Within 7 days of daily fluoride exposure, the fluoride released from elastomeric ligatures was continuously increased. Fluoride release from Morelli (0.067±0.013 ppm) and Unitek (0.067±0.012 ppm) were significantly higher than Thai (0.040±0.03 ppm). The fluoride level measured from Morelli and Unitek were not significantly different. Conclusion: The orthodontic elastomeric ligatures can absorb fluoride from mouthwash and release the detectable amount of fluoride within seven days. This fluoride might help prevention of enamel decalcification adjacent to the bracket during orthodontic treatment.

Abstract: The aim was to investigate particles of poly (methylmethacrylate)(PMMA) prepared by suspension polymerization using different concentration of a stabilizer and by varying of the agitation speed at 300, 400, and 500 rpm. Particle size distribution (PSD), and morphology of the PMMA powders were observed and compared with commercial orthodontic PMMA powder. The experimental results indicated that the increasing the agitation speed tends to decrease the particles size at 0.08 wt % stabilizer.

Abstract: Objective: To evaluate the effects of interchanging the liquid components of two commercially available orthodontic auto-polymerizing acrylic resin in their flexural properties, clarity and setting time

Abstract: This paper presents the comparison of water droplets on insulating surface under alternating current (AC) and direct current (DC) electric field. Besides that, it is demonstrated about the insulator deterioration under both electric field stressed due to an ageing and partial discharge (PD) phenomenon. The vital parameters factors are water droplets conductivity, droplet volume, surface roughness and droplet positioning that they cause to occur the electric field intensification. The field is intensified at the interface between the droplet, air and insulating material. Thus, the PD occurred due to electric field intensification increases with the deformed droplet. The deformation of water droplet under AC electric field stress is more intense than DC field. The electrostatic forces change the droplet shapes and spread them along the electric field direction. The local electric field intensification provokes the PD giving way to reduction of hydrophobicity of insulator surfaces. In addition, the PD activity could appear as a trigger for a surface breakdown. And the localized arcs cause damage to insulating material then finally leads to deterioration of insulation materials and the pollutant contamination.

Abstract: This paper focuses on possibilities in increasing the user comfort of seating furniture in public waiting interiors. There are several aspects helping to achieve the best comfort of sitting, such as appropriate ergonomic design, shape, or material composition. While every of the said aspects have a significant impact on the final comfort, it would be better, or even essential, to adopt a complex view of this issue. One of the complex ways to increase the user comfort is to observe the interaction of the human (the “user”) with the material. The paper describes tactile properties in the interaction with basic types of materials the public gets in direct contact with when sitting in public waiting interiors. The conducted research focuses on tactile properties leading to contact comfort of the most used materials, and analyses the properties in relation to temperature, roughness, hardness and comfort. The four mentioned tactile properties are essential for our goal – an increase in user comfort. The preferred materials were defined according to a preceding terrain survey which explored what materials are most commonly used for present seating furniture. The paper then presents the methodology and results of the research focusing on interaction between the human user and the material. The results of the said research might prove useful for future designing and development of seating furniture which focuses on the user’s sensational balance and calmness, i.e. the optimal comfort.

Abstract: In this paper, thermodynamic analysis on reduction of lateritic nickel ore by CO₂/H₂ mixed gas was performed based on activity theory. Effects of CO₂/H₂ ratio and temperature on selective reduction of laterite ore were investigated. The calculation result shows that the metallization of Fe and Ni could be promoted by each other because of the variation of the Fe and Ni activity, which accounts for the inescapability of Fe metallization. When laterite nickel ore was reduced by mixed gas with a CO₂/H₂ ratio of 9/1 and a gas flow of 100mL/min at 800°C for 1h, a product with a Ni metallization rate over 95% and a Ni/Fe ratio as much as 2.6 was prepared.