Advanced Materials Research Vol. 800

Abstract: Connecting rod fracture splitting is a novel connecting rod big end separation precision machining technology. It has become one of the critical technologies in engine production in developed countries. By studying and analyzing the splitting process theory, affecting factors on splitting quality and the expansion force ratio, finite element analysis was conducted by using modern engineering software. Upon design and fabrication a testing device, lots of experiments were carried out. Experiment results show, the study method is effective, the splitting quality can be obtained by homemade equipment. The same equipment can be used for varying temperature and different material splitting analysis in the future.

Abstract: Shape-stabilized phase change materials can store thermal energy and save energy when it is added into the wall. The phase change temperature, latent heat and the stability of shape-stabilized phase change materials with different component were studied experimentally. The critical mass fraction of paraffin required in the materials is given. It is proved that the shape-stabilized phase change material is ideal material used in the phase change wall because it has good stability and uniformity, higher latent heat and suitable phase change temperature.

Abstract: A sol-gel method combined with spin-coating process has been developed for deposition of nanostructured thin films of La_0.85Sr_0.15MnO₃ (LSM) on La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ(LSCF) pellets. The quality of the LSM films depends sensitively on the solution chemistry and other processing parameters. It was found that the optimal molar ratio of citric acid to ethylene glycol and to metal ions is 4:16:1 for the LSM sol. An amount of ethylene glycol was added into initial LSM sol to adjust the viscosity and the best value tested was 1.62×10^-2 Pas. A more uniform LSM film can be obtained with a suitable heating rate during firing. Modification of LSCF with a thin film coating of LSM has potential to enhance both stability and electrocatalytic activity for oxygen reduction.

Abstract: The Ag coating was deposited on the surface of Al-Ag alloy powder by electroless plating process. 10 wt% of AgNO3 was put in the powder for precursor replacement reaction, and then added the powder into electroless plating bath which contained glucose solution, solution of silver ammonia, thiourea solution, tartaric acid solution and absolute ethanol. The effects of formula components were analyzed. The surface morphology of the prepared composite particles was studied with SEM and their chemical compositions were confirmed by XRD. With the chemical etching method, silver content of the powder was determined. The studies have shown that an uniform, complete and dense silver coating for the Al-Ag composite powders was generated by this method, with the silver content being 20wt%, and the conductivity was favorable.

Abstract: Novel Ce³⁺ and Tb³⁺ co-doped LiLa2BO5 phosphor, synthesized by a solid state reaction in reductive atmosphere, exhibits enriched emission spectrum in the green region .The XRD patterns, photoluminescence spectra and SEM were recorded and the effects of Tb³⁺ and Ce³⁺ concentration, sintering condition on the luminescent properties of as-synthesized phosphors were investigated. The emission spectra under ultraviolet (200--350 nm) radiation showed a dominant peak at 544 nm attributed to the ⁵D₄⁷F_J(J=0,1,2...6) transition of Tb³⁺, which was greatly enhanced by the co-doping of Ce³⁺, indicating that there occurred an efficient nonradioactive energy transfer from Ce³⁺ to Tb³⁺. The experimental result shows that the optimum Ce³⁺ and Tb³⁺ doping concentrations are 15 at% and 10 at% respectively.Keywords: Green phosphor; High luminescence efficiency; LiLa2BO5:Ce³⁺,Tb³⁺ ; Rare earths

Abstract: The melting temperature, microstructures, and mechanical properties of the Sn-Zn-0.5Ag-0.5Ga, Sn-Zn-0.5Ag-0.45Al and Sn-Zn-0.5Ga-0.45Al lead-free solders were investigated. The results indicate that the addition of 0.5 wt% Ag to the Sn-Zn based alloys destroy the eutectic structure and results in the formation of Ag-Zn compound and hypoeutectic structure. The variation in the microstructure lowers the UTS. By the addition of Al the UTS and elongation of the 0.5Ag-0.45Al alloy can be decreased due to the Al diffused to the interface of the Ag-Zn compound/Sn-Zn eutectic structure to form Al-Zn compound. The 0.5Ga-0.45Al alloy shows a typical eutectic structure with the light contract β-Sn and the darker needle-like phase, as well as a small amount of Al-Zn phase with a near diamond shape. Gallium uniformly distributes in the Sn matrix and Zn rich phases. The 0.5Ga-0.45Al solder had the highest UTS and elongation, while 0.5Ag-0.45Al had the lowest UTS and elongation. The results indicate that Ga and Al exhibits prominent influence on the microstructure as well as the mechanical properties of the solders.

Abstract: The hot deformation behavior of Mg-3.5Zn-0.6Y-0.5Zr alloy was investigated by compressive tests of strain rate ranges of 0.002~1 s^-1 and deformation temperature ranges of 300~450 °C using a Gleeble 1500D thermal simulator. The flow stresses in different deformation conditions are measured. The results show that flow stress is significantly affected by both deformation temperature and strain rate, the flow stress increases with increase in strain rate and decreases in deformation temperature during the hot compression process. The constitutive equation established on the basis of data of activation energy and stress exponent is a hyperbolic sine function.

Abstract: ZnO nanorods were obtained by hydrothermal method using Zn (NO₃)₂ and N₄(CH₂)₆ as raw materials, crystalline nanoplate ZnO grew on the columnar facets of the primary ZnO rods when citrate was introduced in the reaction system. The crystalling phase of ZnO particle was characterized by X-ray diffraction, the morphology was observed by SEM, the structure was indicated by FTIR. The result showed that the average nanoparticle diameter of ZnO was around 60 nm. Through the photocatalytic degradation of dibutyl phthalate (DBP) in aqueous solution under the illumination of UV light, nanoplate ZnO displayed high photocatalytic activity, the degradation efficiency was rising to 87.8% at 60 min illumination time.

Abstract: Taking the high-strength steel 22MnB5 as the research object, starting from the phase transformation and the performance of the sheet at high temperature, the impact of various process parameters on the part was studied, pressing the stringers with hot forming technology simultaneously. Using metallurgical microscope, hardness tester and universal tensile testing machine, the microstructure and mechanical properties of the parts were analysed. The result show that, under the selected process parameters, the microstructure of the workpiece is desired lath martensite, the hardness is above 450HV, the tensile strength is above 1450MPa, which meet the production requirements.

Abstract: The toughness of cement-based materials, related to the performance such as durability and strength, attracts much more attention nowadays. In this paper, the curve of bending load-deflection was adopted to research the influencesof polymers (dispersibility emulsion powder, PVA and styrene butadiene latex) and fibers (PVAF, steel fiber,basalt fiber) on basic mechanical properties and toughness. The results show that the PVAF pre-incorporate in cement motor could improve the toughness of cement motor. In addition, an environmental scanning electron microscopic analysis (ESEM) and hardness were adopted to analyze the microscope morphology of polymer films inside of hardened cementitious composites.