Applied Mechanics and Materials Vol. 248

Abstract: Reed and sivergrass are natural biological materials, the process parameters of being used as raw materials of biocomposite were determined. Microscopic structure of reed and silvergrass was characterized by environment scanning electron microscopy. Best reed-silvergrass particleboard process parameters were drawn from orthogonal test, that adhesive addition is 14%, press temperature is 1800C, and press time is 7min. The effects of reed/silvergrass particles mixing ratio on mechanical properties of reed-sivergrass particleboard were also discussed, mechanical properties of reed-silvergrass particleboard reached the maximum value at reed/silvergrass particles mixing ratio 3/2.

Abstract: Reed is a natural biological material and has great potential as reinforced material in bio-composites.The morphology and element contents of reed stem were investigated using scanning electronic microscopy equipped with energy dispersive spectrometer (SEM/EDS). And the effects of the mass mixing ratio of reed and poplar particles, dosage of water repellent on the physical and mechanical properties of reed/poplar composites were determined. Results indicated that the outside surface of reed stem has high silica content.The mass mixing ratio of 6:4 or 5:5 resulted in an optimum reed/poplar products. As the mass mixing ratio ranged from 4:6 to 10:0, the composites could be produced without adding additional water repellent. Therefore, it is possible to manufacture qualified reed/poplar composites by using urea-formaldehyde resin.

Abstract: In this work, different types of amine-attached MCM-41 are prepared with different preparation methods. The poly (ethyleneimine) (PEI) and γ-(aminopropyl) triethoxysilane (APTS) are attached to the pore surface of MCM-41 silica. The comparison between impregnation of PEI and covalence attachment of APTS to the MCM-41 support are investigated. X-ray diffraction, Roman spectra, and Thermal analysis are used to characterize the obtained samples. The characterization results confirm that the amino groups are attached to the pore structure of MCM-41. The CO₂ adsorption capacities of different amine attached MCM-41 silicas are investigated employing CO₂ adsorption isotherm. MCM-41-APTS show a considerable CO₂ uptake, suggesting their potential usage for the CO2 adsorbent.

Abstract: The performances of material fatigue can be illustrated by the S-N curve, the p-S-N curve and the fatigue limit, which are very important to engineering and the mechanical design. Recently, the author proposed a new method to determine a conditional probability density distribution surface(CPDDS) of the material, and the surface can reflects most properties of the material’s fatigue. Methods to obtain the theoretical fatigue limit and the p-S-N curve are introduced in this paper on the basis of previous study. The methods are applied on the fatigue test data of C45 steel, and the p-S-N curves that obtained by various methods are compared in this paper.

Abstract: The electrochemical properties of traditional carbon materials and applications of these materials based electrodes as well as physical and chemically modified carbon materials electrodes would be reviewed. Hence, the scope of the current review is limited to analytical electrochemistry using carbon materials electrode, and 48 references are cited.

Abstract: Explosive field-emission graphite has the advantages of low cost, long lifetime, low outgassing rate and can operate stably at a large number of pulses, thus it has become an important candidate for repetition frequency, long-pulse high-power microwave (HPM) devices. In this paper, two types of graphite cathodes with different microstructures are investigated on their explosive field-emission properties. These cathodes are operated in a vacuum diode system at a voltage of 230 kV and a pulse duration of ~110 ns. The study reveals that the graphite cathode with smaller, cross-linked grains generates higher current at shorter current risetime compared to the cathode with larger grains. Furthermore, the microstructure defect regions of the graphite cathodes are more susceptible to destruction than the perfect microcrystalline regions during explosive emission process due to the combination effects of explosion of surface microprotrusions and Joule heating.

Abstract: Magnesium hydride is considered as one of the most interesting alternatives for the reversible storage of hydrogen. In this study,The feasibility and reaction process of different materials（Mg and pretreated Al powders(mainly composed of Al and Ni)）were discussed and investigated by thermodynamic calculation. The effects of material proportioning, mill time, mill energy density were also investigated by XRD analysis and TG-DSC technique, and analyzed the essence mechanism. The results show that nano-sized MgH2 and Mg(AlH4)2 could be directly synthesized by pure Mg and pretreated Al powder, The product composite hydrides release 2.7wt% H2 through multi-step decompositions, of which the starting endothermic peaks are as low as 265°C.

Abstract: The objective is to observe the advantage of the poly(vinylidene difluoride)-modified (PVDF-modified) bioartificial liver (BAL) reactors in the drug screening of Chinese herbs quercetin and resveratrol. The active ingredients of quercetin (0.1 mmol/L) was used to acted on rat hepatic cells for 12 hours both in the PVDF-modified and in the unmodified bioartificial liver reactors, then cisplatin (0.2 mmol/L) was added for 24 hours. Another Chinese herb resveratrol (0.1 mmol/L) was used with the same treatment. Finally, the synthesis of urea and albumin, the activities of lactate dehydrogenase (LDH) and aminotransferase (AST) were detected in these two cultured hepatocytes. Significant difference of the synthesis of urea and albumin was obtained between the PVDF-modified and the unmodified BAL reactors, and a less significant difference was for the activities of LDH and AST. The results showed that the PVDF-modified BAL reactor was more sensitive than the unmodified in liver toxicity and in activity of the liver-protective medicine. Hence, the PVDF-modified BAL reactor is more suitable for clinical drug screening.

Abstract: La_1-xSr_xMnO₃ (LSMO) has recently shown promising features as a metal-insulator material over a limited range of Sr doping (x=0.175 to 0.25). Its thermal property has been commonly measured through the very expensive calorimetric method. In this paper, a considerably more convenient thermal investigation approach to this issue through the thermal irradiation theory is proposed. LSMO compounds were synthesized with a wide range of x (0.15 to 0.5) using the precisely controlled Pechini sol-gel method. XRD phase structure analysis and XPS composition and chemical state study were adopted for quality assurance of the compounds. Resistance and infrared reflectance of the samples were measured respectively with the help of the four probe technique in temperature range of 150K to 380K and an infrared spectrometer over a temperature range of 153 K to 544 K. Investigations showed a good correlation between these two measures approving the metal-insulator characteristic of all the samples. Calculation of the total normal emittance (ε_N(T)) of the compounds was innovatively simplified using the measured reflectivity data through the thermal irradiation theory for graybody. Moreover, the results showed that every x ratio fabricated through the precisely controlled Pechini method presented a unique ε_N(T) characteristic with a different metal-insulator transition temperature.

Abstract: Volcanic ash becomes environmental important issues as waste material if it is not effectively reduced or reused. In engineering practice, utilization of volcanic ash as substitution material is limited. Indonesia has a large road on soft soil and volcanic ash. The objectives of this paper are focused to study the characterization, classification and utilization of volcanic ash as soil stabilization material which give benefit in engineering practice and also be environmental friendly material. Engineering properties, mineral composition and soil mixture characteristics involve physical and mechanical properties are discussed. Result shows that the effect of addition of volcanic ash after curing time 14 days can improve the engineering properties of soft soil, decrease liquid limit, change curve of grain size distribution, increase bearing capacity, and decrease swelling potential. The soil-volcanic ash mixture with 35% of volcanic ash and 5% of lime is obtained as optimum mixture design. This result is still early stage and need further study.