Advanced Materials Research Vol. 979

Abstract: The YBa₂Cu₃O_7-δ(Y123) compounds were synthesized by solid state reaction method. The home-made four-probes apparatus was used for the resistivity measurement. The highest T_c is 91.95 K in sample C and sample A has lowest T_c onset at 89.85 K. The crystal structure properties and oxygen content were characterized by powder X-ray diffraction using CuK_α radiation (λ=1.5406 Å). The Pmmm and Pnma space group corresponding on the superconducting phase and the non-superconducting phase. The atomic position of samples were consisted of various element atom. The longer time of oxygen-doping, the increase the critical temperature , superconducting phase and c lattice parameters.

Abstract: In this study, the properties of re-melted soda-lime silicate glass cullet doped with TiO₂ were investigated in order to study the potentials to use as parent glass for glass-ceramics. TiO₂ of 0.5, 1 and 3 mol% was doped into the 71SiO₂-10Na₂O-6K₂O-5CaO-4MgO-2SrO-TiO₂-Al₂O₃ glass cullet and melted at 1500°C for 3 hours, and then annealed at 550 °C. The optical and physical properties were examined. It was found that the refractive index and density of glasses were raised with increasing of TiO₂ concentration. The optical properties measured by UV-Vis spectrophotometer showed that the UV edge in the absorption spectra was shifted to a higher wavelength, and the transmission at 583 nm was decreased. The CIE L*a*b* color measurement showed that the glasses were slightly colorless but the appearance of yellow increased with higher TiO₂ concentration. Lower thermal expansion coefficient and higher glass transition temperature as well as the dilatometric softening point were observed as the concentration of TiO₂ was increasing. Finally, the calculated activation energy was 476, 493, 506 and 637 kJ/mol with 0, 0.5, 1 and 3 mol% doped TiO₂, respectively. At doped TiO₂ of 3 mol%, the properties of glass were changed rapidly due to the substitution of [Ti⁴⁺] in local [Si⁴⁺] resulting in increasing the bond strength in glass structure.

Abstract: The pairing mechanism of research used the bisoliton model. The exact formular of T_c equation of cuprate superconductors which taken into account the exponential repulsion between bisoliton is derived. We find that the value of critical temperature depended on bisoliton density which confirm the experimental data that the critical temperature depended on the doping level.

Abstract: In this work, the physical and optical properties of soda-lime-borate glasses doped with V₂O₅ concentration of 0.0 to 2.5 in mol% have been investigated. The glass samples were prepared by the normal melt-quench technique. The results show that the density and refractive index decreased with additional 0.5 mol% content of V₂O₅. Then both results increased with increasing V₂O₅ content from 1.0-2.5 mol%. The optical absorption spectra of glass samples were measured by UV-visible spectrophotometer in the wavelength range 300-1100 nm and color coordinate in CIEL*a*b* system. The absorption peaks locate around 605 and 960 nm for all V₂O₅ concentration that are associated to V⁴⁺ ions and produce the brown color.

Abstract: The improvement in impact properties of wood plastic composite from acrylate-styrene-acrylonitrile (ASA) and bagasse was reported in this work. The effect of type and content of impact modifier by using styrene-butadiene-rubber (SBR) and ethylene-acrylic acid (EAA) as impact modifier on morphology and mechanical properties of wood plastic composite were investigated. Wood plastic composites, prepared from ASA and 50 phr of bagasse by varying amount of impact modifier (both SBR and EAA) from 0-40 wt% of ASA were prepared by melt-blending technique. All materials were mixed by using a two-roll-mill, shaped into sheets by a compression molding machine and specimens were cut with a cutting machine. Then, the obtained materials were characterized, including morphology, impact strength and flexural properties. From SEM micrographs showed that wood plastic composites with using SBR as impact modifier showed more compatible with ASA matrix than EAA. This is a consistency results with mechanical properties such as impact properties, which indicated that the impact strength was improved with increasing the amount of SBR from 0-40 wt% of ASA. However, wood plastic composite with EAA showed the reduction of impact strength. So, it could be demonstrated from this study that the most appropriate impact modifier for wood plastic composite from ASA and bagasse was styrene-butadiene-rubber.

Abstract: Studies on the effect of percentages of epoxide group in thermoplastic elastomer as a compatibilizer on properties of polyamide6 (PA6) and low-density polyethylene (LDPE) blends was successfully carried out in this study. Thermoplastic epoxidized natural rubber (TPENR), made from epoxidized natural rubber (ENR) and LDPE, prepared from 3 types of ENR, i.e., ENR-20, ENR-50 and ENR-70, with the ratio of 90/10 of LDPE/ENR by weight. TPENR was applied as a compatibilizer into the blend of PA6/LDPE/TPENR at the ratio by weight of 80/20/1 by using a twin screw extruder at 235°C. All test specimens were characterized for phase morphology, impact strength and rheological behaviour. Results exhibited that phase morphology of PA6/LDPE blend was incompatible. The addition of TPENR improved the compatibility of PA6/LDPE blends. With inclusion of TPENR-20 as a compatibilizer, the uniformity and the maximum reduction of dispersed phase sized were observed. Moreover, it was revealed that the rheological properties such as shear viscosity increased when compared with PA6/LDPE incompatible blend. In addition, it was found that the highest shear viscosity and also the highest impact strength were obtained for the blend of PA6/LDPE compatibilized by TPENR-20. This result was further supported by SEM images, which showed that the smallest dispersed phase size occurred when a TPENR-20 was used as a compatibilizer. So, it was clearly demonstrated in this study that the suitable type of TPENR, i.e., TPENR-20, has an effect on improving phase morphology and properties of PA6/LDPE blends.

Abstract: The photoluminescence and physical properties of lithium yttrium borate glasses doped with Eu₂O₃ were studied in this work. The glasses were prepared by the melt-quenching technique and varied the Eu₂O₃ doped concentration between 0.00-1.50 mol%. We found that, the molar volume and density of these glasses showed linear increasing tendency with Eu₂O₃ concentration. The absorption bands were observed in UV and NIR region. For the Eu³⁺ doped glasses, the excitation bands centered at 363, 383, 394, 414, 465, 526 and 533 nm were observed with 613 nm emission wavelength. While in the emission spectra, the bands centered at 590, 613, 652 and 701 nm were observed with excitation of 394 nm. The intensity of excitation and emission bands increased with increasing of Eu₂O₃ concentration.

Abstract: The nanocrystalline ZnO powders were synthesized by a direct thermal decomposition using zinc acetate dihydrate as starting materials. The precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at 300 °C. The precursors were calcined at different temperatures of 400, 500, and 600 °C for 4 h. The structure of the prepared samples was studied by XRD, confirming the formation of wurtzite structure. The synthesized powders exhibited the UV absorption below 400 nm (3.10 eV) with a well defined absorption peak at around 285 nm (4.35 eV). The estimated direct bandgaps were obtained to be 3.19, 3.16, and 3.14 eV for the ZnO samples thermally decomposed at 400, 500, and 600°C, respectively.

Abstract: This work studied possibilities of using waste silicon carbide (SiC) particles from abrasive industry as alternative filler in natural rubber (NR) compounds. The rubber was prepared by using natural rubber grade STR 5L and waste silicon carbide loading of 0, 10, 20, 30 and 40 phr. Firstly, the rubber were compounded by using two roll mill and then using Oscillating Disc Rheometer for studying cure time at one hundred and fifty degree Celsius. Then, shear viscosity and extrudate swell of the compounded natural rubber were characterized by using capillary rheometer at 100°C. The result showed that the apparent shear viscosity increased slightly with increasing waste silicon carbide loading and the percentage of extrudate swell was found to be a decreasing function of the filler loading. Then, test tensile by using the prepared samples for studying tensile modulus, tensile strength and elongation at break. The result showed that tensile modulus and tensile strength increased with increasing waste silicon carbide. On the other hand, the elongation at break of the filled natural rubber decreased with increasing waste silicon carbide. Finally, bring the sample to test hardness by using shore A. Results indicated that waste silicon carbide direct variation with the indicator of hardness.

Abstract: This research was to elucidate the antagonism of natural anti-and pro-oxidants in synthetic polyisoprene rubber (IR) grade 2200 as a model system. Alanine and linoleic acid was chosen as natural anti-and pro-oxidants, respectively. These two amino acids were directly added into the rubber by mixing in two-roll mill. Peroxide vulcanization and three types of the sulfur curing system, i.e., conventional vulcanization (C.V.), efficient vulcanization (E.V.) and semi-E.V. have been studied. Cure properties of the rubber compounds were characterized with moving die rheometer (MDR) at 150 and 170°C for sulfur and peroxide vulcanizing systems, respectively. The compounded rubbers were divided into two parts. The former was pressed on a hydraulic hot press machine and cut to a dumbbell specimen according to ASTM D412 type C. Then, the rubber specimens were subjecting to accelerate the thermal oxidative degradation at 100°C under air-circulating oven with various times. The deterioration of the aged rubber specimens was determined by tensile test. The latter was shaped and characterized by ozone resistance in accordance with ISO 1431/1. For tensile test, the results showed that only the C.V. system of the sulfur cure, the tensile stress at 200% strain of IR comprised alanine and linoleic acid with the ratio of 1:1 was higher predominantly than that of the cured IR control. In addition, the peroxide cured IR mixed with alanine and linoleic acid cannot be passed the heat aging for 96 h. For the ozone resistance, the results exhibited that all specimens appeared uncountable number of crack but only the IR cured by peroxide presented the length of crack less than 1 mm (C-3). It might be concluded from the experiment that anti-oxidative activity of the alanine plays a vital role in the rubber vulcanizate only for C.V. system. However, the existing of both alanine and linoleic acid in the sulfur cured IR was not outstandingly changed for the ozone resistance but not that for the peroxide cured IR.