Applied Mechanics and Materials Vols. 152-154

Abstract: This paper describes the brazing technique of SiCp/2014Al aluminum matrix composite. The surface reinforcements were partly exposed and the surface was deposited by vapor deposition process. Observing the microstructure of the brazing joint, Cu and M6 aluminum filler metal are more adaptable for the brazing process than Ti and 4047 aluminum filler metal. The tensile strength of the as-welded joint can reach 181MPa. The fractography of the brazing joint indicates that the fill metal can not wet the parent composite, which is the main reason for the loss of strength. Furthermore, the porosity caused by high brazing temperature and the aggregated reinforcement on the parent composite are two other important reasons for the brazing joint strength lost.

Abstract: The minimum switching field threshold and switching speed are key parameters for the magnetic recording in writing. This paper presents the dynamic precession of the moments of the grains based on LL equation.Under microwave-assisted reversal conditions, the influence of the differences between the angle of Anisotropy field on the magnetic moment reversal and loading speed of reversal magnetic field in two interacting particles is investigated.

Abstract: This study presents a design process of ZrO2/Ti functionally graded thermal barrier coatings (FG TBCs) based on a mean-field nonlinear micromechanical approach developed by Tsukamoto [1], which takes into account the time-independent and dependent inelastic deformation, such as plasticity of metals, creep of metals and ceramics, and diffusional mass flow at the ceramic/metal interface. The effect of compositional gradations on micro-stress states in the FG TBCs has been examined. The suitable compositional gradations have been proposed for typical thermo-mechanical boundary conditions in terms of thermal-stress relaxations, thermal-shielding and light-weight characteristics.

Abstract: An intelligent algorithm of energy analysis was put forward based on statistical data of Sinosteel Jilin ferroalloy Co., Ltd. Momentum BP algorithm of variable learning rate which used widely was adopt so as to complete energy consumption scientific analysis and overcome efficacious the weakness that standard BP calculation model convergence slowly and easy to make network into a local minimum. The energy analysis model of ferroalloy enterprise was present and the Pareto order was proposed though quantitative analysis of main factors that influence energy consumption. It was helpful to make energy policy and to promote energy saving as theoretical basis.

Abstract: Several processing methods have been used to obtain silica from rice husk with a persistent problem of lack of scalability from laboratory scale to levels of production necessary for commercial or industrial applications, at low cost. To address this draw-back, a novel method- hydro thermo-baric process, was developed and used to process high purity silica from rice husk. Since the suitability of rice husk silica in a given application is dependent on the nature of its structure and morphology and the two parameters are affected by the processing methods used in obtaining the silica, this paper reports the preliminary studies done on the silica obtained from this novel method using XRF, XRD, FESEM and EDX. XRD results show that the silica produced, which by XRF analysis had purity approaching 98%, is amorphous in nature. FESEM images showed that the particles have nanometric size. However, EDX results show an increase in residual carbon in the silica, with increase in the processing temperature. BET analysis showed an increased surface area from 21.42m2/g to 133.94m2/g for the untreated and treated samples, respectively.

Abstract: According to MD simulation results, pressing depth between two bonding materials will affect bonding strength. Alloy material (Al0.9Cu0.1) had void defect phenomenon in low bonding speed condition because the increasing chance of atom migration which will result in low bonding strength. High tensile speed causes material fracture phenomena happen earlier than low speed. Material stress in low speed is smaller than in high speed. Fracture morphology of material is different in different tensile speed. In low speed condition, material can be stretched thinner than in high speed condition. Material in high temperature has greater kinetic energy than low temperature; therefore, material in high temperature has better formability and behaves larger tensile strain than low temperature. For pure aluminum, when temperature raises to 900K which is close to melting point (933K), its crystal structure is no longer belongs to F.C.C. structure, so bonding strength is weaker than low temperature. Large size material has larger contact area than small size material; therefore, the tensile force and tensile strength of the former are larger than the latter. The order of bonding strength for these three materials is: binary alloy > pure copper > pure aluminum.

Abstract: This paper adopted freeze casting method to prepare porous Al₂O₃ ceramic bodies with different volume percentage and interconnected pore channels as the preform. The porous Al₂O₃ ceramic bodies were pressureless infiltrated with Nb-35Ti-20Al-10Cr alloy (atom percentage, at%) by using electromagnetic induction furnace. The results indicated that there is a well wettability between Nb-35Ti-20Al-10Cr melt and porous Al₂O₃ ceramic body. And it would be possible to infiltrate Nb-35Ti-20Al-10Cr melt into porous Al₂O₃ ceramic body through pressureless infiltration. The microstructure observation for the Nb-35Ti-20Al-10Cr/Al₂O₃ composites demonstrated that it was still retained the layer structure characteristics of the preform. The Nb-35Ti-20Al-10Cr melt was filled into the interconnected pore channels existed in the porous Al₂O₃ ceramic bodies and the Nb, Ti, Al, Cr alloy elements diffused into the reinforced Al₂O₃ particles during pressureless infiltration.

Abstract: Activated cement with the characters of low water demand and high activity was made with Portland cement clinker and dehydrate-gypsum and liquid superplasticizer which were used as grinding additive in the grinding process. Three states of grinding effect exist with correspondence of different dosages of super-plasticizer: the optimal grinding aid dosage, the critical dosage, and the supercritical dosage. First, under the condition of the optimal grinding effect, the activated cement had the maximum strength with little dosage of super-plasticizer and small effect on the performance of activated cement; second, within the critical dosage, the strength of activated cement was similar to the common cement, more super-plasticizer were held and the performance of cement was obviously improved; third, within the supercritical dosage, the strength of activated cement was reduced, but it can accommodate much super-plasticizer, and had a remarkable influence on the performance of cement. The experiment also shows that different properties of low water demand activated cement can be made with admixture of different concentrations of super-plasticizer. Within the allowed limit, use more admixtures was in compile with green environmental protection concept, improve the durability of concrete, and resolve the problem of compatibility between common cement and super-plasticizer, and offered technical support in the produce of commercial concrete by directly use of Portland cement clinker.

Abstract: (Eu, Dy) doped Sr3Al2O6 phosphors with high brightness and long afterglow were achieved by a high-temperature solid state reaction. Luminescence measurements indicate that the phosphor Sr3Al2O6:Eu prepared in normal atmosphere exhibits a sharp orange emission peaking at 591 nm excited by 221nm light, which is intrinsic f-f transition generated from Eu3+. Whereas, the phosphors Sr3Al2O6:Eu and Sr3Al2O6:Eu,Dy prepared in a weak reducing atmosphere show both a sharp orange emission peaking at 591nm excited by 221-nm light and a broad green emission peaking at 510nm excited by 328nm light, which resulted from Eu2+ transition between 4f65d1 and 4f7 electron configurations. The investigation results suggest that Eu3+ and Eu2+ co-exist in Sr3Al2O6 matrix synthesized in weak reducing atmosphere. In all samples, only Sr3Al2O6: Eu, Dy prepared in a weak reducing atmosphere has high intensity afterglow after excited by the UV source. The decay curve of Sr3Al2O6: Eu, Dy phosphor contains the rapid-decaying process and the slow-decaying process and can be fitted by a bi-exponential decay function. The measurement of thermal simulated luminescence demonstrates that only appropriate deep trap energy level and high trap concentration can generate optimum long-afterglow performance.

Abstract: Turbocharged solid propellant ramjet (TSPR) is the combination of solid propellant gas generator air turbo ramjet (ATR)with solid ramjet, is cycle of augmented ATR, the parametric performance calculation were carried out for TSPR, The effects of independent design parameters including parameters of compressor and turbine and propellants were studied and the preferred compressor, turbine and propellants were obtained for TSPR; The operation envelop of TSPR and ATR were obtain under the preferred component limitation, the results shows that TSPR offers wide speed-altitude operation envelope, high specific thrust, high specific impulse, it is combining the advantages of the ATR and solid ramjet, and suitable for tactical missiles application meets potential requirements for boosting and cruising.