Advanced Materials Research Vols. 299-300

Abstract: The cross-linking degree of polyethylene glycol acrylate (PEGA) gel by free-radical solution polymerization was investigated in which PEGA was prepared by chemical modification. The structural morphology, crystal property, thermal property and thermostability were investigated using scanning electron microscope (SEM), polarization microscope (POM), differential scanning calorimeter (DSC), and thermogravimetric analysis (TG), respectively. The results showed that the chain segment of PEG had good activity in lightly cross-linked PEGA gel, the crystallization enthalpy of PEGA gel achieved to 122 J/g, and the duration of its soaking time was about 490 s. Furthermore, chain segment of PEG were bound in PEGA gel, but the crystallization enthalpy of PEGA gel achieved to 64.60 J/g, its soaking time was continued for about 430 s. PEGA gel had a better thermal stability below 300 °C.

Abstract: Semi-IPN phase change material (PCM) which is suitable for the temperature adjustment textile field is prepared by solution copolymerization. The structure of framework material is a three-dimensional network prepared by N-hydroxymethyl acrylamide, and the phase change material is prepared by polyethylene glycol with molecular weigh 2000. The orthogonal experimental method is used for determining the optimum formula and investigating the various factors on the phase change material properties. Structure and properties of the composite properties are synthesized by SEM, DSC, TGA. The result shows: the advanced process of making composite phase change material is that PEG owns 70% of the overall mass fractions, initiator owns 2.5% of monomer mass fractions, the molar ratio of cross-linker monomer is 1:8, the reaction time is 3 hours, and mass ratio of monomer to water is 1:6. The prepared composite material is distributed uniformly of framework holes, and it has a well fixed effect to the phase change material, which the phase transition temperature is 32.92 °C, the enthalpy is up to 108.41 J / g. It also has a good thermal stability, and applies to the spinning environment which the temperature is not higher than 300 °C.

Abstract: UV (ultraviolet) sensor is widely used in many fields such as missile early warning, spacecraft autonomous navigation, global positioning and so on. Comparing with other semiconductor based UV sensor, ZnO nanowire (NW) UV sensor have many unique advantages including visual light blind, biocompatible, low cost and so on. But, two main shortages, low photo response () and long recover time, embarrass the application of single wire ZnO UV sensor. In this paper, we introduce the working principle of ZnO NW UV sensor and expound some methods for increasing photo response, enhancing sensitivity and shortening response and reset time of ZnO NW UV sensor. Besides this, we introduce a kind of UV sensor fabricated by integrated ZnO NWs recently. The photo response of this UV sensors reaches the order of mA, when exposed to UV light at 4.5 mW/cm². It also has perfect stability and reliability. Because of these properties, this new kind of UV sensors has a great potential for application.

Abstract: Magnesium alloys are being used as structural components in industry because of their high strength to weight ratio. But their high electrochemical activity and poor corrosion resistance limited their applications. Therefore, surface modifications are needed for protection purpose. This paper studied the anodic micro-arc oxidation and electroless Ni-P plating surface modifications on AZ80 magnesium alloy. The SEM, XRD and EDS were used to characterize the surface coating. It shows that a micro-porous MgO layer with the pores size 5 – 20 μm was fabricated on the bare magnesium alloy. The nodule Ni-P deposition could be prepared on the out layer of MgO with Ni/P atomic ratio being 1.4. The pores in MgO layer could be sealed by the following Ni-P deposition. Therefore the corrosion resistance of the magnesium alloy could be further improved.

Abstract: Raw slurry blending process is the key process in the sintering alumina production. In this blending process, raw materials are alkali powder, red mud, blending ore and limestone, and the product is the raw slurry. The optimal operation control objective of this blending process is to make the quality indices of the raw slurry into their targeted ranges. The key step to realize this control objective is to decide the appropriate set-points of the control loop. An automatic setting control method is proposed in this paper. During the setting process, case-based reasoning is adopted to obtain the appropriate set-points of the control loops according to the process data and state. By using this setting control method, appropriate set-points can be obtained and the operation control objectives can be realized.

Abstract: Gradient porous NiTi alloys were fabricated by powder metallurgy method using NH₄HCO₃ as space-holder. The effect of content and distribution of NH₄HCO₃ on pore characteristic, phase composition and compressive properties was studied. The results showed the content of TiNi phase increased with the decrease of the content of NH₄HCO₃. When the distribution of NH₄HCO₃ varying form 12wt%-12wt%-12wt% to 12wt%-6wt%-12wt% and 12wt%-0wt%-12wt%, the stress and elastic modulus of porous NiTi alloys increased from 228MPa to 321MP and 446MPa, from 4.8GPa to 5.6GPa and 6.8GPa, respectively. Compared with uniform porous materials, gradient porous NiTi alloy exhibited better superelasticity.

Abstract: Transparent ZnO:Al films deposited by RF/DC magnetron sputtering in room temperature are annealed under gaseous ammonia ambient and air ambient, respectively. The characteristics of ZnO films are examined by XRD, SEM, Hall measurement and optical transmission spectra. The XRD and SEM analysis shows that both films are crystallized in the wurzite phase with a preferential orientation along the c-axis and have a smooth dense surface. Hall measurement results indicate ZnO:Al films annealed under ammonia ambient convert to p-type conduction with the high carrier concentration of 8.3×10¹⁸ cm^-3. Optical transmission spectra show a high transmittance (~85%) in the visible region.

Abstract: The effect of micro-beam plasma arc (MPA) surface remelting Ti alloy (Ti-6Al-4V) sheets was investigated. The results show that more satisfactory hardened layer could be acquired after MPA scanning process on TC4 titanium alloy. The composition, crystalline structure and micro-hardness in the remelted layer of TC4 were examined by OM, SEM, XRD and Vickers' micro-hardness tests, respectively. There were no micro-cracks or impurity in the treated sample after scanning by MPA. The micro-hardness of the treated samples was significantly improved as compared with the untreated substrates. X-ray diffraction results indicated that the surface remelting layer composed of phases, which was similar to the substrate. The micro-hardness of the surface was improved to 420 HV_0.3 as compared to 190 HV_0.3 of substrate. The increased hardness was obtained due to the micro-structural changes caused by rapid solidification owing to the self-quenching effect of the substrate after MPA remelting.

Abstract: This paper adopted freeze casting method to prepare porous Al₂O₃ ceramic bodies with interconnected pore channels as a preform. The preform was pressureless infiltrated with Nb-Al binary alloy by using electromagnetic induction furnace. The results indicated that the Nb-Al melt solidified as a sphere-like body under the surface tension driving. It was difficult to obtain Nb-Al binary alloy matrix Al₂O₃ ceramic composites. However, the wettability between Nb-Al melt and porous Al₂O₃ ceramic bodies was improved obviously while the Ti and Cr alloying elements were added into Nb-Al binary alloy. Also, the resultant Nb-35Ti-20Al-10Cr melt was filled into the interconnected pore channels existed in the Al₂O₃ preform by pressureless infiltration.

Abstract: The 6061Al matrix composites reinforced with SnO₂-coated aluminum borate whisker were fabricated using squeeze casting method. The composites with different SnO₂ coating contents were extruded successfully at 350°C with the extrusion rate of 18mm/s. The results show that the Sn particles at the interface as liquid state at extrusion temperature result in the reduction of the extrusion load and the decrease of the probability of whisker fracture during hot deformation process. Moreover, unlike many surface cracks can be seen in the extruded composite without whisker coating, the surface crack-free extruded rods can be obtained for composites with whisker coating. The ABOW/SnO/6061Al composites tensile properties increased obviously after extrusion.