Advanced Materials Research Vols. 538-541

Abstract: The purpose of the experiment is to get more ideal color and raise the value of Locust wood after heat treatment. We chose ethanol as the solvent and heated locust wood in vapor environment at 120°C for 24 hours. Compare the infrared absorption spectrum of heat treated powder and heat treated powder after extracted. It turned out that: (1) extraction could wipe out the great mass of substance with ethenyl(C=C), ether bond(C-O-C), hydroxy (-OH) and aromatic ring; (2) The synthetic reaction and decomposition reaction of ethenyl(C=C), ether bond(C-O-C), hydroxy (-OH) and aromatic ring would lead to decrease of b* and rise of a*, but have no impact on L*;(3) Heat treatment would reduce the number of aromatic nucleus. Hydroxyl would be oxidized to carbonyl group. Instauration organic esters produced. Heat treated wood after extracted wouldn’t occur these reaction. Powder’s infrared absorption spectrum also shows that functional group in aromatic ring has decreased after extraction and heat treated.

Abstract: Prepared PP/ nano-TiO2 composites by MeltExtrusion,according to compare the changing of their elongation at break、yield strength and tensile strength before and after microwave irradiation, using SEM、TEM and FIR to observe the change，then could obtain that on one side microwave irradiation could vibration the group of molecular chain, friction produce energy makes composites degradation, on the other side, it improves the distribution of inorganic particle in matrix, two phase compatibility and interface combination, from that ,we get the plastic mechanism of microwave irradiation.

Abstract: B2O3 is used as fluxing agent of converter slag to substitute for CaF2 so as to reduce fluorine pollution and decrease the melting temperature. Hemisphere method is used to measure the melting temperature of samples. Effect of ω(CaO)/ω(SiO2), content of Fe2O3 and content of B2O3(CaF2) on the melting temperature of CaO-SiO2-F2O3-B2O3(CaF2) system have been studied. Results indicate that the melting temperature of samples are decreased when B2O3 substitute for CaF2 equally with equal ω(CaO)/ω(SiO2) and content of Fe2O3 [ω(CaO)/ω(SiO2)=1.5~5.0, Fe2O3=0~30%], the melting temperature of samples are decreased remarkably with the increase of content of B2O3 [ω(CaO)/ω(SiO2)= 2.5].

Abstract: In the process of characterizing AlGaN/GaN HEMTs on Si (111), Sapphire, 4H-SiC substrates, various Rapid Thermal Annealing (RTA) conditions for the Ti/Al/Ta/Au ohmic contact process and the resulting surface analysis have been investigated. In order to achieve a low ohmic contact resistance (RC) and a high quality surface morphology, we tested seven steps (800 °C to 920 °C) annealing temperatures and two steps (15, 30 sec) annealing times. According to these annealing temperatures and times, the optimal ohmic resistance of 3.62 × 10^-6 Ohm • cm² on Si(111) substrate, 9.44 × 10^-6 Ohm • cm² on Sapphire substrate and 1.24 × 10^-6 Ohm • cm² on 4H-SiC substrate are obtained at an annealing temperature of 850 °C and an annealing time of 30 sec, 800 °C and an annealing time of 30 sec and 900 °C and an annealing time of 30 sec, respectively. The surface morphologies of the ohmic contact metallization at different annealing temperatures are measured using an Atomic Force Microscope (AFM). AFM morphology Root Mean Square (RMS) level determines the relationship of the annealing temperature and the annealing time for all of the samples. According to these annealing temperatures and times, the optimal ohmic surface RMS roughness of 13.4 nm on Si(111) substrate, 3.8 nm on Sapphire substrate and 2.9 nm on 4H-SiC substrate are obtained at an annealing temperature of 850 °C and an annealing time of 30 sec, 800 °C and an annealing time of 30 sec and 900 °C and an annealing time of 30 sec, respectively.

Abstract: Surface acoustic wave(SAW) propagation properties including propagation phase velocity, power flow angle(PFA), anisotropic factor, electromechanical coupling factor(k2) and temperature coefficient of frequency(TCF) are calculated in an optimal region defined by Euler angle (90o,0o~20o,0o~180o) for LGS crystal. It is concluded that the Euler angle (90o, 20o, 122.23o) and (90o, 17.5o, 121.9o) possess superior SAW performance, which have zero PFA, low TCF and moderate k2 simultaneously. We can give priority to these cut-types in the SAW applications at high temperature.

Abstract: To promote the deoxygenization efficiency of modified sponge iron deaerator, the deoxygenization mechanism was studied with the aid of kinetics and characterized analysis. The application of modified sponge iron deaerator for high pressure boiler feed water was investigated as well. The results showed that the process of deoxygenization was a first order reaction regarding for active sites decay. The modified sponge iron was able to reduce dissolved oxygen (DO) level from ppm levels down to a few ppb levels and the dissolved iron in outlet can be removed completely by ion exchange resin. Therefore, the application of modified sponge iron deaerator for high pressure boiler feed water was feasible.

Abstract: The porous nanocrystalline Fe0.2(Co20Ni80)0.8 alloy microfibers with diameters of 2-4 μm have been prepared by the citrate-gel and phase transformation process. The sound absorption coefficient for microfibers samples is measured by the standing wave tube method and it is is over 0.8 for the 15 mm thick sample at the frequency range of 2300-6000 Hz, which is extended to 600-6300 Hz for the 40 mm thick sample. The band width with the sound absorption coefficient above 0.6 is wider than 4300 Hz for the 15 mm thick sample and 5800 Hz for the 40 mm thick sample. For the 40 mm thick sample, the maximum absorption coefficient, noise absorption coefficient, noise reduction coefficient and half-width of the absorption peak are 0.99, 0.59, 0.64 and 5828 Hz, respectively. These microfibers are promising advanced acoustic absorbers.

Abstract: Studies have proved that enhancing epoxy matrices by adding carbon nanotubes to form structural reinforcements has significantly improved mechanical properties at very low carbon nanotube loading. That mechanical properties of aligned composites are better than those of random ones has been demonstrated in past studies; however, alignment is not easy to achieve in carbon nanotube epoxy-matrix bulk composite by conventional techniques. In this study, epoxy-matrix bulk composites reinforced by aligned multi-walled carbon nanotubes (MWCNTs) are prepared using an RF electric field to elicit dipolar interactions among the nanotubes in a viscous matrix following immobilization by curing under continuous application of an anisotropic electric field and the fracture toughness is experimentally characterized later. The processes of actively aligned MWCNTs epoxy-matrix bulk composite were controlled as a function of CNT weight fraction, the frequency of dielectrophoretic field and processing time. Carbon nanotubes are not only aligned along the field but also migrate laterally to enhance thickness. Eventually, addition of nanotubes improved the mechanical properties of the MWCNT/epoxy bulk composites, and the increase in the flexural modulus and fracture toughness with the aligned nanotube composite is two times greater than the improvement for the randomly oriented composite.

Abstract: In order to improve physicochemical properties of Tilapia skin collagen (TSC), 1-ethyl-3-(3-dimethyl amino-propyl)-carbodiimide (EDC) was used as a cross-linking agent for TSC matrices. The difference in physicochemical properties between cross-linked and uncross-linked TSC was characterized by measuring shrinkage temperature, water uptake and anti-enzyme effect. The results indicated that, after the cross-linking, the thermal stability was increased; the anti-enzyme effect was improved obviously. It is thus concluded that the EDC cross-linking greatly improve the physicochemical properties of TSC.

Abstract: The present paper focuses on the experimental investigation of the aluminothermic reduction of magnesia under vacuum condition with the fixed magnesia to aluminum molar ratio of 11:6. The influences of reaction temperature and time on the reduction ratio of magnesia were studied. The chemical composition, phase constitution and morphology of the condensed magnesium and the briquettes after thermal reduction were investigated by X-ray diffraction, scanning electron microscopy equipped with energy dispersive spectrometry. The reduction ratio of magnesia increases with the increase in the reaction temperature and time. The briquettes after thermal reduction at 1050°C-1150°C are mainly composed of the spinel, unreacted magnesia and aluminum. The briquette after 1 hrs thermal reduction at 1200°C contains corundum, magnesium aluminium oxide, trace amount of spinel, unreacted MgO and aluminium.