Key Engineering Materials Vol. 573

Abstract: A series of ratcheting experiments and finite element analysis simulation under bending loading for Z2CND18.12N stainless steel elbows were carried out. Chaboche and modified Ohno-Wang model are applied to evaluate structural ratcheting response simulations. It is found that ratcheting strain initiates firstly in the hoop direction and increases in the axial direction with the increasing of loading. The Ratcheting strain rate grows with the increase of the reversed in-plane bending load or internal pressure for both specimens with different loadings. Comparison of simulation and experiment showed that modified Ohno-Wang model presented simulation more reasonably.

Abstract: This article mainly studied the influence rule of heat treatment temperature on the performances of Inconel690 heat transfer tube. The microstructure, mechanical performances and corrosion properties were studied under different heat treated conditions. The optimized heat treatment process was obtained. The conclusions was as follows: with the increase of solution temperature from 1050°C to 1150°C, the mean grain size varied from 12μm to 58μm, the room temperature tensile strength and yield strength reduced gradually, while the elongation elevated gradually. The alloy had a good resistance to pitting corrosion after solutionization during 1090~1100°C.The massive carbides (M₂₃C₆) were precipitated along grain boundaries after sensitization processing. And with the increase of sensitization temperature, its morphology transform from tiny semicontinuous to coarsening continuously, multi-layered distribution emerged during higher sensitization temperature range. Along with the sensitization temperature rising, alloy 690 has better resistance to intergranular corrosion. As the sensitization temperature was higher than 750°C with isothermal holding for 2 hours, the desensitization phenomenon occurred, and the ability of anti-intergranular corrosion for alloy 690 could be enhanced distinctly.

Abstract: Polypyrrole coating doped with dodecylsulfate anions was electrodeposited by cyclic voltammetry and constant current technique on type 304 stainless steel used for bipolar plates of a proton-exchange membrane fuel cell from a basic solution of 0.2M pyrrole monomer solution containing dodecylsulfate sodium as supporting electrolyte. The morphology and corrosion performance of Ppy coated samples were investigated. Microscopic observations showed that the polypyrrole synthesized by constant current technique present a more dense constitution. Electrochemical measurements in 0.1M HCl solution showed that the polypyrrole synthesized by constant current technique provided better protection for the stainless steel.

Abstract: The microstructure evolution and control for Alloy 690 during cold rolling and annealing treatment was investigated. Cold rolling specimens were deformed in the strain range from 15% to 70% with strain rates from 0.01 to 10s^-1. Subsequent annealing treatment was carried out in the range of 1060~1100°C for dwell time 3~15mins. Rolling reduction, annealing temperature and annealing time except strain rate had obviously influence on grain size and hardness. Little coarsening of grains were observed below 1060°C during annealing treatment, whereas grains coarsened obviously over 1080°C. Besides, the behavior of grain growth for alloy 690 was investigated systematically.

Abstract: In this research, the compression deformation were investigated under different elevated temperatures and strain rates, in order to obtain the creep constitutive equation. The effects of aperture load and pore shape on the compression properties of porous Cu alloys were studied by simulating the creep compression deformation at elevated temperature in ANSYS software. Pore size, pore shape and load are the main factors on the high temperature compression creep properties in porous Cu alloys. Samples with larger pore size, higher load and temperature showed inferior compression creep resistance such as bigger creep deformation, faster creep rates, and more unstable creep deformation. Stress concentrations generating around the edge in the wall of the pore were observed. Otherwise, the shape of pore has a severe influence on the structure properties of the material, i.e. every increase of pore edge corresponds to a decrease of stability in structure.

Abstract: With more and more universities expanding and redesigning their landscape spaces, therefore their outdoor furnitures shape, dimension, quality and usage are also changing and redesigning. One of the significant changes in the design process is the taking of users needs/concerns into account. This change is influenced by a community-based design concept found in public spaces design. In this paper, we propose a Design for Assembly Study (DFA) which is focus on examining the past practice of outdoor wooden Materual furniture design in campus spaces by using Quality Function Deployment (QFD) to fill in this missing link. The employment of different matrices to capture the relationship between the voice of customer (VOC) and subsequent design and quality characteristics compose an evaluation framework suitable to fill the gap in the assembly procedure of outdoor wooden frame furniture. The study also produces several insights applies on outdoor wooden furniture design in campus space. Keywords: Wooden Material, Outdoor furniture, Outdoor space, Design Evaluation Procedure

Abstract: Pd-Ag alloy powders were prepared on the stainless steel by pulse electrodeposition. Cyclic voltammetry found the reduction potential of Pd, Ag and Pd-Ag. The composition and morphology of Pd-Ag were investigated by means of SEM, EDS.

Abstract: N-type ZnO nanorod arrays and p-type NiO thin films have been prepared on the ITO substrates by chemical bath deposition (CBD) and sol-gel spin coating method, respectively, then followed by thermal treatment at 400 °C for 1 h. The ZnO nanorod arrays have length of around 1.5 μm and diameter of around 55 nm; the thickness of the NiO film is around 340 nm with average grain size of 22 nm. The sensing properties of the n-type ZnO and the p-type NiO for the detection of aqueous ethanol solutions at room temperature are investigated using electrical impedance spectroscopy (EIS). The EIS results reveal that the series resistance (R_s) is as low as 27 Ω; the charge-transfer resistance (R_ct) remarkably contributes to the sensing properties of the ethanol sensor, and decreases with a decreasing concentration (99.5%-1%) from 17.0 kΩ to 2.6 kΩ. An equivalent circuit with capacitors and resistors was developed to investigate the conduction process according to complex impedance (Nyquist) diagrams. In low concentration range, the electron conduction process is dominated by the R_ct and a constant phase element (CPE); however, in high concentration ethanol solution, the conduction process is dominated by polarization and decomposition of the absorbed water with larger R_ct observed. Moreover, I-V measurements were carried out to evaluate the sensitivity of n-ZnO and p-NiO nanostructures at room temperature.

Abstract: The glass sealant with pre-forming frame structure, used for joining dissimilar materials of planar type SOFC devices, was fabricated by molding process. The flow phenomena during glass molding were investigated by computational modeling. The physical properties of glass sealant fluid were constructed in numerical models. The process parameters, such as mold pressing velocity, initial glass fluid temperature (or viscosity of glass sealant), and initial mold temperature, were examined. As results, the sealants formability could be characterized by molten glass temperature, near the gap between upper and lower molds. If the temperature is greater than its glass transformation temperature Tg, the formability become better, and vice versa. Keywords: solid oxide fuel cells (SOFCs), computational modeling, glass sealant.

Abstract: Lead-free thick film resistors (TFRs) were prepared by mixing of ruthenium oxide (RuO₂) and CaO-B₂O₃-SiO₂ based-glass. The resistors were post-fired on alumina and co-fired in LTCC substrates. Different metal oxides were added into the glass phase, such as Nb₂O₅, MnO₂, MoO₃, Fe₂O₃, TiO₂. They were used as temperature coefficient of resistor (TCR) adjustment agents of the resistors. The microstructures variations and interactions at the interface between resistors and substrates were investigated. The additives made glass structure loose and conductivity of resistor decrease, the TCR values of the resistors moved toward negative direction. When 4wt% MnO₂ was added into the glass, the thick-film resistors embedded in LTCC had conductivity of 2.46 (Ω-cm)^-1, the temperature coefficient of resistor decreased to 12 ppm/°C. The conductivities of the resistors films were depended on the volume fractions of conductor-agglomeration (RuO₂), microstructures, and TCR additives of the resistor layers