Abstract: A new preparation of alumina from high iron bauxite, which has not been being made reasonably use of yet, has been studied. Iron in high iron bauxite was removed by carbothermal reduction and aluminum-rich slag could be obtained. Then aluminum was extracted from aluminum-rich slag by ammonium sulfate roasting. After leaching, Al2(SO4)3 was obtained, which can be used for preparation of alumina. The effects of roasting temperature, roasting time, ammonium sulfate/aluminum-rich slag mass ratio were investigated. Optimum roasting conditions from aluminum-rich slag by ammonium sulfate were found as roasting temperature:400°C;roasting time:120min;ammonium sulfate/aluminum-rich slag mass ratio:6. Approximately 98% of aluminum was effectively extracted.
Abstract: 1-3 piezoelectric-damping composites were fabricated using piezoelectric ceramic as functional filler and epoxy resin as matrix by cut-filling method. The fabrication procedure of the composites was introduced. The effect of ceramic volume fraction on the damping behavior and the piezoelectric strain factor d33 were studied. The results show that the damping property was firstly improved, and then decreased with the increase of the ceramic volume fraction. An optimal ceramic volume fraction of 15% was shown. TA increased from 29.78 to 32.34. The piezoelectric strain factor d33 reached 323pC·N-1.
Abstract: In order to enhance the lateral compression energy absorption capability of round steel tube without obviously increasing the mass of round steel tube, this paper has developed the polyurethane foam filled round steel tube and through experimental comparison, studied such parameters as the laterally-compressed platform loading, total absorbed energy and energy absorbed per unit mass for the filled tubes and empty tubes of three kinds of pipe diameter. The results show that the round steel tube filled with polyurethane foam can change the deformation mode of round steel tube and increase the energy absorption capability of steel tube substantially with very little increase of mass; the energy absorption efficiency is obviously higher than the one of empty steel tube.
Abstract: This paper investigated the anti-penetration performance of different sandwich structures plate using numerical simulation method. Finite elements models of the bullet and sandwich plate were established. The penetration performance of sandwich plate by bullet was simulated by software of LS-DYNA and dynamic response of the bullet during the penetration process was got. The results show that the anti-penetration performance is different because of the different cores in the plate. Besides, the density of the aluminum foam core has a direct effect on the performance. This paper could provide some reference for the designing of sandwich structures.
Abstract: In this research the Thermogravimetric analysis (TGA) under nitrogen was used to investigate the thermal decomposition processes and sound absorption coefficients was measured using Impedance tube according to ASTM standard E1050 - 10 two microphone method for 2 types of polymer matrix composites. Sample 1 was made of rice straw (RS) reinforced with polypropylene matrix and Sample 2 was made of kenaf fiber reinforced with polypropylene matrix, both composites were fabricated using hot compression moulding technique. The thermal behaviour is of practical interest for conditions associated with temperatures above the atmospheric, as in fire damage, curing or process involving heating procedures. The sound absorption coefficient for a material is the fraction or percentage of incident sound energy that is absorbed by the material. The function of absorptive materials is to transform impinging acoustic energy into heat. The thermal stability of the composites was found to be higher than that of rice straw, kenaf fibers and the polypropylene matrix. The sound absorption coefficients of composites increased as the frequency increased. However, they decreased at the frequency of 1000 Hz and increased again. This decrease and increase was due to the specific characteristic of Lignocellulosic fibers reflecting sound at 1300 Hz but absorbing sound in the middle and high frequency ranges.
Abstract: ZnO microspheres with complete and perforated morphologies were synthesized by a simple solvothermal method via regulating solvent composition. Material characterization has included XRD, SEM, XPS, Raman spectrum and Brunauer–Emmet–Teller (BET) methods. The introduction of ethanol into the solvent resulted in the morphology change from complete to perforated spheres, meanwhile generated more surface adsorption sites and larger specific surface area as demonstrated by XPS and BET analysis. A possible formation mechanism of ZnO microspheres is proposed to explain the perforation development process. The gas sensing performances of the sensors prepared using the complete and perforated spheres were compared to reveal the positive impact of morphology change.
Abstract: Now a day’s sustainable development becomes an increasingly significant goal in the evaluation and promotion of Industries. There is currently considerable interest in developing sustainable acoustic absorbers. This research aims to develop and characterize composite materials made of Epoxy resin reinforced with luffa fibres as sustainable acoustic absorbers. The fibres where chemically modified by alkaline treatment and its effects on the fibre-matrix interaction were also evaluated. The effect of chemical modification on fibre morphology was studied by Scanning electron microscope (SEM). Likewise, the sound absorption coefficient of composites were studied using 2 types of Impedance tube methods namely Two microphone transfer function and standing wave method. The thermal analyses of composites were made using Thermogravimetric analysis. The sound absorption coefficient of untreated and treated composites across a range of frequencies was very similar. To be more specific, untreated composites appeared to perform better than those of treated ones. After chemical modifications, the SEM characterization showed that the alkaline treatment changed the morphology of fibers, resulting in decrease in sound absorption coefficients of composites. This is probably due to the new morphological aspect. The thermal characterization of composites shows that dehydration and degradation of lignin occurred around 40 - 260°C and maximum percentage cellulose was found to decompose at 380°C.
Abstract: The lecture discusses various machining methods of advanced ceramics, their performances and limitations. These methods include both conventional turning, grinding and milling operations and some selected from the category of non-traditional machining processes like electrical discharge machining, laser assisted milling, abrasive water jet and other are presented as well. Special consideration is given to machinable glass ceramic and aluminum nitride ceramic representing structural ceramics due to their wide range of applications and attractive properties
Abstract: The structure and properties of cast metals and alloys are in a high degree influenced by crystallization conditions. By the technological interventions into the crystallization process the mechanical properties and structural parameters of castings can be enhanced. The present contribution deals with the regularities of crystallization of alloys Al-Si produced by die casting process.