Advanced Materials Research Vols. 415-417

Abstract: A modified Tessier sequential extraction procedure was employed to investigate the speciation of Cr in cement products. The amount of Cr in extracting solution was determined by atomic absorption spectrophotometer and extraction residue was analyzed based on the results of XRD, SEM and EDS. The distribution of Cr in cement was discussed also. Cr existing as species exchangeable or bound to carbonates increases with curing age gradually.

Abstract: Hot dip galvanizing treatments of Galvalume were studied by using methods of Gleeble thermal simulation experiment and optical microscopy(OM), scanning electronic microscopy (SEM), X-ray energy dispersive analysis(EDAX), X-ray diffraction(XRD) and so on. Meanwhile, surface morphology, microstructure, phases and the respective compositions of Al-Zn alloy coating plate were investigated, the formation of hot dipped 55％Al-Zn alloy coating were analyzed. The results show that to get better coated surface, in-zinc pot temperature should be controlled in the range of 590~610°C, and height of air-knife nozzle should be kept in the range of 150~200mm. Surface layer of 55％Al-Zn alloy coating is covered by Al-Zn alloy, the intermediate alloy layer is consisted of binary and ternary compounds, such as θ phase (FeAl₃), Al_0.3Fe₃Si_0.7 and Al_3.21Si_0.47.

Abstract: The resilience of mattress foam has influenced on body pressure distribution characteristic of mattress and human comfort. This paper dealt with resilience of foam and body pressure distribution through resilience test instrument for mattress foam and body pressure distribution system. The results showed that the resilience of latex foam was better and the body pressure distribution of mattress with latex foam layer was better. This study results have important reference value to the flexibility of mattress and comfort design.

Abstract: This paper deals with the interaction mechanism between in situ Nb₂C-V₂C nanoparticles and solid/liquid interface during the rapid solidification of Fe-Nb-V alloy ribbons. In situ Nb₂C-V₂C nanoparticles reinforced Fe alloy matrix composite were carried out by in situ reaction and melt spun with a high-speed centrifugal spray. According to the setting of a force balance for the in situ nanoparticles in front of the S/L interface during the high-speed centrifugal spray of Fe-Nb-V alloy melt as following: F = F_{buoyant force} + F_repulsive + F_{viscous force} + F_{centrifugal force}, authors get the critical velocity that S/L interface engulfs particles is proportional to the radius of particles. TEM observation indicates that the less the size of particle is, the more easily S/L interface engulfs particles.

Abstract: Cu-10Ni-5Mo alloys have been prepared by arc-melting and induction melting injection moulding. The effects of melting processes on the microstructure and thermal conductivity of Cu-10Ni-5Mo alloys were studied. The results show that the grain of Cu-10Ni-5Mo alloy prepared by arc-melting is coarse and the structure includes α solid solution and Mo-Ni phase. The grain of Cu-10Ni-5Mo alloy prepared by induction melting injection moulding is superfine and the structure is α solid solution. Under this experiment condition, the coefficient of thermal conductivity of Cu-10Ni-5Mo alloy prepared by arc-melting is 56.9 W/(m•K)，while that of Cu-10Ni-5Mo alloy prepared by induction melting injection moulding is 35.7 W/(m•K). The melting points of Cu-10Ni-5Mo alloy prepared by two methods all increase and are little different.

Abstract: Polyoxymethylene (POM) composites filled with low-density polyethylene (LDPE) and wood fibers were prepared by injection-molding. Friction and wear tests were carried out in a reciprocating sliding tribotester. Results showed that 5wt.%LDPE acted effectively as the internal lubricant for POM. Further addition of the wood fiber increased the wear rate of the POM/LDPE composites but had little effect on the coefficient of coefficient in the presence of LDPE. SEM observations showed that the main wear mechanism for unfilled POM was adhesive wear, while in the case of POM composites abrasion and fatigue seemed to govern the wear process. It was suggested that, the POM/LDPE/Wood fiber composite, which is low-cost and environmentally friendly, has the potential for tribological applications.

Abstract: The functionalized TiO₂ with poly(methyl methacrylate) (TiO₂-PMMA) was prepared by atom transfer radical polymerization (ATRP), and its reinforcement for epoxy composites was studied. The functionalized TiO₂ was characterized by Fourier transform infrared (FT-IR), Thermal gravimetric analysis (TGA) and 1H nuclear magnetic resonance (NMR). The properties of nanocomposites were measured by impact testing, bending experiment and Scanning electron microscopy (SEM). Because of the grafting of PMMA and the higher interaction between TiO₂-PMMA and epoxy matrix, the composites exhibited the enhancement of mechanical properties at lower content. As the functionalized TiO₂ content is 0.5 wt%, the impact strength and bending strength of composite increased nearly 142% and 37%, respectively, compared to the neat epoxy resin.

Abstract: The novel transmission line based on metamaterials substrate was studied theoretically. The characteristic impedance and transmission wavelength of such transmission line are analytically calculated in framework of classical transmission-line theory. Moreover, the characteristic of similar micro-strip line were also studied with FEM simulation. Results showed that using metamaterials as a substrate, the characteristic impedance would be greatly increased, providing a new method to reduce the loss in the RF circuit. The transmission wavelength would be effectively extended at the same frequency. That was the electromagnetic radiation would greatly reduce in such RF circuit. Once the transmission wavelength was much larger than the size of the circuit board, the circuit theory could be adopted in RF design. Which would greatly reduce the difficulty of RF design.

Abstract: AlN-ZrO₂(Ca) composites were prepared with two kinds of Ca-stabilized zirconia (ZrO₂(Ca), i.e Ca-PSZ, particle size d₅₀=65μm and d₅₀=7.5μm) and three kinds of AlN power (d₅₀=15μm, d₅₀=0.5μm and d₅₀=40nm) as raw material in N2 atmosphere by pressureless sintering at 1850 oC. The phase compositions and microstructures of composites were investigated by XRD, SEM and EDS.The sintering performance of the composites was measured by the checking of the bending strength, and the apparent porosity of samples. The results showed that phase compositions of the composites consisted of major phases C-ZrO₂ and AlN and minor phase CaAl₁₂O₁₉. It was harder that AlN-ZrO₂(Ca) composites were sintered than ZrO₂(Ca) material. It was major cause that phase CaAl₁₂O₁₉ formed and its abnormal growed in the boundary layer between AlN particle and ZrO₂(Ca) matrix. With 2mm AlN particles as raw material, AlN-ZrO₂(Ca) composites had better sintering performance when concent of AlN equaled to 8%.

Abstract: As part of the continuing studies to develop high performance composite based on new kind of phenylethynyl end-capped imide oligomers for aerospace applications, PETI-type polyimide composites were prepared from carbon fibre (CF) and polyimide matrix resin derived from dianhydride (s-BPDA), 2,5-bis(4-aminophenoxy)-biphenyl(p-TPEQ) and 4-phenylethynylphthalic anhydride (PEPA). The mechanical properties were tested at both room temperature and 177 °C. The flexural properties were determined by 3-point-bending at room temperature. Thermal aging test was carried out by exposing samples at 177°C over 1000 hours, and the mechanical properties were also evaluated before and after isothermal aging. It was demonstrated that the composite had good thermal and mechanical properties.