Advanced Materials Research Vols. 105-106

Abstract: Hydrogen from biomass gasification is reviewed as one of the promising clean energies approaches in the future for fuel cell. However, the syngas from biomass gasification usually contains a certain amount of tar, which could not only decrease the efficiency of gasification process and hydrogen production, but also condense as a dense mixture and impose a series of serious problems. So “Excess Enthalpy Gasification (EEG)” is put forward and applied into biomass gasification and a novel biomass gasifier is presented for the purpose of tar-free and hydrogen-rich syngas in this work. The structure characteristic of the gasifier and tar conversion characteristic are analyzed detailedly to prove the feasibility and excellence performance for producing tar-free and hydrogen-rich syngas from biomass gasification.

Abstract: Substrates have critical effect on efficiency and cost of hydrogen production technology. Tradition evaluation index system which based on hydrogen production rate and conversion rate has limitation in comparing the economic value of different substrates utilized in hydrogen production system. This paper studies emergy of a fermentative biohydrogen production technology, comparing different biomass: wastewater and sewage sludge, the municipal solid waste and lignocellulosic biomass when they are used as substrates. Net emergy yield ratio, environmental loading ration and emergy-based sustainability index are measured. According to these indices, it shows an important role in reducing hydrogen production cost by developing cheap substrates. The results shows, the values of three indices were best when municipal wastewater was used as a substrate, it can reduce hydrogen production cost dramatically, obtain hydrogen and purify water simultaneously, benefit the environment protection.

Abstract: Aluminum nitride (AlN) is a stoichiometric compound with the hexagonal wurtzite structure. AlN has excellent thermal conductivity and good properties as electronic insulator. It displays good mechanical resistance up to elevated temperatures and is resistant against corrosion by molten metals. Bulk AlN may therefore be used as a refractory structural material as well as a substrate for high power microelectronic devices. However, it is very difficult for sintering high-density AlN at lower temperature than 1800°C. Nano-sized AlN powders were sintered by hot press sintering at low temperature of 1500~1700°C and mechanical properties were investigated. β-AlN and β-Al2O3 were detected when the sintering temperature is 1600°C. The phase transition β-AlN to α-AlN was discovered at a 1700°C sintering temperature. Relative density and average grain size were increasing with the increasing of sintering temperature, and fracture form is intercrystalline crack in 1500°C and transcrystalline crack in 1700°C. 97.3% relative density and 850nm average grain size were deserved at 1700°C.

Abstract: Basing on the experimental data collected, the mechanical model of reinforced concrete beams’ gradual failure has been set up, to test differ reinforced components with loads and study the process of split. At last the influence of reinforcement’s number on components’ intensity and failure process are analyzed by using MFPA2D (Material Failure Process Analysis) software, started with the analysis of formula cracks after experiments. The results showed that the number of reinforcement is not the more the better. When ultra-reinforced beam appears, its mechanical capacity enhances but the bars won’t do their best, furthermore, it is uneconomical. Accordingly, less-reinforced beam should also be avoided for safe. Everything possible should be made to avoid ultra-reinforced beam and less-reinforced beam in engineering. By all means, this conclusion has practical significance during our practice.

Abstract: In this research, raw kaolin is processed by oxidation-reduction fining method and then baked to produce mullite precursor, which can prepared multi-phase mullite nanocrystals at low temperature hydrothermal conditions under normal pressure. According to the analysis of the controlling factors of NaOH mole ratio in the hydrothermal system, reaction temperature, holding time and the precursor concentration, etc., we studied the effect of above-mentioned factors on the grain size of product. The results show that when NaOH concentration 3mol/L, hydrothermal reaction temperature 80°C, holding time 3 h, precursor concentration 0.15g/ml, the morphology of the prepared nanocomposite with grains size of 60 ~ 90nm appears spherical-like, also the uniform dispersion can be acquired.

Abstract: The ternary layered machinable Ti3SiC2 ceramics were synthesized at 1300°C by high-energy milling and hot pressing sintering using Ti,Si and C powder as starting material. The reaction mechanism was examined by XRD, SEM and thermodynamic analysis. The results show that Ti-Si-C powders were transformed to Ti, Si and little TiSi, SiC,Ti5Si3 intermetallics by milled for 18 hours. In this process, the little Ti and C transformed to TiSi phase in early stage, and then the most of residual elements reacted to form SiC and Ti5Si3 intermetallics. Finally, Ti, Si, SiC, Ti5Si3 intermetallics and TiSi reacted to yield Ti3SiC2 by hot pressing sintering. And the sintering temperatures had a significant impact on the yielded content of Ti3SiC2 phase. Besides. The Ti3SiC2 would decompose if the temperature was high enough.

Abstract: A new technology for producing high purity 4A-molecular sieve was developed with high modulus sodium silicate liquor and sodium aluminate liquor extracted from coal fly ash as starting materials. The sodium silicate liquor extract was purified by precipitating ferrous, titanium, and other impurities by carbon dioxide injection. Concentration of carbon dioxide in the extract was maintained at 48%, and the pH value of the extract controlled in the range of 11 and 11.2. After that, the purified sodium silicate liquor was mixed with sodium aluminate liquor in the ratios of SiO2/Al2O3=2.0, Na2O/SiO2=1.6 and H2O/Na2O=60. The mixture was then heated to 90°C and kept for 2 h. A high purity 4A-molecular sieve product was obtained after washing and drying the crystals obtained from the reaction mixture. The molecular sieve product has a purity of 99% and aperture of 0.4nm. Its calcium absorption capacity is about 290mg/g. The product was also characterized by SEM, BET, XRD and IR analysis.

Abstract: The titaniferous blast furnace slag was selected as a kind of main raw material in the glass preparation. The glass system was separated phase into boron-rich phase and silicon-rich phase in Na2O-CaO-Al2O3-B2O3-SiO2-TiO2 system, and the changes of the two-phase composition after heat treated at different temperatures were studied. Results indicated that the network adjustment oxide existing in boron-rich phase was only CaO when phase separation temperature was below 750°C, and Na2O concentrated in silicon-rich phase. With the phase separation temperature rising, the distribution of Al2O3 and CaO was almost unchanged, whereas Na2O transferred from the silicon-rich phase to boron-rich phase gradually. In the phase separation process, TiO2 concentrated and crystallized on the phase separation interface.

Abstract: Glass-ceramics with desired microstructures and properties are controlled by nucleation and crystallization. The nucleation and crystallization of glass, which include the nucleation, crystal growth rates and the activation energy, are important in understanding the stability of glass in practical applications. The activation energy of crystallization (E) plays an important role in determining the utility of glass ceramic. The amorphous to crystalline transformation in glass can be investigated by isothermal and non-isothermal method which is differential scanning calorimetric (DSC). In the isothermal method, the sample is measured as a function of time, while in the non-isothermal method the sample is recorded as a function of temperature. An advantage of the non-isothermal method is the possibility of reaching a test temperature instantaneously and during the time, which system needs to stabilize. However, the isothermal method does not have this advantage. In the present work, this technique was used to calculate the activation energy of CaO-Al2O3-SiO2-CeO2 glass-ceramics. DSC technique can be used as to determine the optimum heat treatment temperature. The advantage of the DSC technique in study of glass-ceramics is that it requires much less time.