Advanced Materials Research Vol. 1088

Abstract: A new fluorinated acrylate terpolymer hydrophobic polymer was prepared by emulsifier-free inverse microemulsion polymerization using methyl methacrylate (MMA) and hexafluorobutyl acrylate (HFBA) as monomers, and methyl polyethylene glycol methacrylate (MPEGMA) as polymerizable emulsifier. Membrane properties were characterized by means of FT-IR, SEM and Contact Angle Meter. The effect of fluorinated monomer content, water content in the inverse precursor microemulsion on the surface morphologies and hydrophobicity of the polymer film was mainly discussed. Morphological studies of the fluorinated polyacrylate polymers by SEM showed that discrete granular microstructures were obtained from precursor microemulsion with higher water content. On the other hand, smooth and continuous surface morphologies were found with lower water content. Contact angle revealed that the fluorine preferentially enriched at the film-air interface and more hydrophobic that the film-glass interface. The amount of HFBA had significantly effects on the film properties. The water contact angle of the film-air interface increased as the amount of HFBA increased from 0 ml to 4 ml and then remained almost unchangeable. The film formed from the fluorinated polyacrylate polymer with higher water content in the precursor microemulsion exhibited better hydrophobicity in comparison with the film formed from the fluorinated polyacrylate polymer with the lower water content, and it confirmed that rough surface have high water contact angles.

Abstract: A plasma enhanced atomic layer deposition process has been demonstrated for Lanthanum oxide films using La (thd)₃ precursor and oxygen plasma. The chemical and electrical properties of La₂O₃ ultra-thin films on Si (100) substrates before and after post-annealing in N₂ ambient have been investigated. X-ray photoelectron spectroscopic revealed that interface reactions take place after annealing process which lead to oxygen insufficiency, as well as the balance band offset decreases with the increase of annealing temperature. The capacitance-voltage and current-voltage characteristics show La₂O₃ capacitors annealed at 900 °C have negligible hysteresis, smaller interface trap density in comparison with as-deposited samples, but larger flat band voltage and higher gate-leakage current density due to the appearance of oxygen vacancy in the La₂O₃ films.

Abstract: WC-FeAl composites were fabricated by vacuum sintering technique from mixture of WC and FeAl powders containing various oxygen content. Mechanical properties such as hardness, fracture toughness and transverse rupture strength were influenced by the oxygen content in the powders. Control of the oxygen content was succeeded by changing the powder preparation process. Contrary to expectations, the reduction of oxygen content led to degrade the fracture toughness and transverse rupture strength of the composites. This result was attributed to the microstructural change in the sintered composite. The sintered composite of lower oxygen content exhibited WC grain growth or inhomogeneous microstructure, which can be the cause of degradation of those mechanical properties. It was concluded that the oxygen content was one of the key factors to influence the microstructure or mechanical properties of WC-FeAl composites.

Abstract: Chlorine additives are often used to improve the combustion performance of pulverized coal injection (PCI) in blast furnace. The influence of chlorine additives on pulverized coal combustion rate was analyzed and the micrograph of unburned pulverized coal (UPC) was observed by SEM in order to analyze the influence mechanism of chlorine additives. The results show that proper addition amount of CaCl₂, NaCl, MgCl₂ and FeCl₃ respectively promotes pulverized coal combustion in different degrees. The average size of UPC is smaller and the micrograph becomes irregular when the chlorine additives are increased. While beyond the appropriate addition amount, the combustion rate of PCI reduces. During the combustion process of pulverized coal with chlorine additives, HCl is produced which prevents the combustion process.

Abstract: With the aim of developing a durable tool for friction stir processing (FSP) of cast iron, the durability of a Ti (C,N)-Ni cermet tool has been investigated and compared with that of a WC-Co cemented carbide tool. Results of exposure tests in air revealed that the WC-Co cemented carbide sample oxidized rapidly above 973 K, whereas the cermet material showed little oxidization even after holding at a temperature of 1103 K. When these tools were used for the FSP of cast iron surfaces, it was found that an oxide layer of over 100 μm was generated on the lateral faces of the WC-Co cemented carbide tool after it was used to work a length of 400 mm. In contrast, a thin oxide layer of only 5 μm was generated after the cermet tool worked a length of 2400 mm. Cross sections of the iron casts (FC250) subject to FSP using these tools showed that in a bowl-shaped region approximately 1.5 mm deep the initial pearlite structures changed to martensite structures. The martensite structures in this region had a Vickers hardness of 600 to 800 HV, while that of the initial pearlite structure was about 280 HV.

Abstract: The high vacuum electron beam welding-brazing was used to joining vanadium alloy (V-5Cr-5Ti) with stainless–steel (HR-2). The temperature fields and stress distributions in the V-5Cr-5Ti/HR-2 joint during the welding process were numerically simulated and the effect of the electron beam off-set distance was studied. The results show that the accurate heat input and proper molten pool position can help to control the fusion ratio of the V/Fe. The electron beam should off set on the stainless steel side rather than vanadium alloy side, and the best range of the distances off-set is 0-0.5mm. The residual stress appears to be bimodal and asymmetric. The maximum lateral residual tensile stress reached 388MPa at the V-5Cr-5Ti side. The joints with the characters of welding and brazing and the metallurgically bonded joint was achieved with 0.3mm beam off-set. With the liquid-to-solid interalloying of dissimilar materials controlled well, a reaction zone is gained on the interface. The maximum tensile strength of vanadium alloy/stainless-steel dissimilar alloy jointswas up to 200MPa with no defect.

Abstract: TiC based cermet is a candidate material for alternatives of WC-Co used in tools/dies. Ordinary, Ni and Co, etc. are used as a metal binder of TiC based cermet. They are kinds of rare metals, therefore it is desired that metal binders are also replaced with the ubiquitous materials. FeAl intermetallic alloys are one of candidate materials of alternative rare metal binder made from ubiquitous materials. FeAl is well-known as an extremely resistance material to corrosion under oxidizing atmospheres, sulfidizing atmospheres, and in molten salts. Combination of intermetallic and carbide, the hardness is very high, but it would be brittle. In this work, TiC-FeAl alloys are made by wet milling and pulsed electric current sintering to improve transverse rupture strength while the hardness is kept. We achieved that TiC-40 vol. % (Fe-40 at. % Al) alloy with hardness of 17.7 GPa and T.R.S. of 1.9 GPa.

Abstract: The heat treatment process parameters are designed by orthogonal test method. Choosing the most important three parameters of the deformation aging parameters, deformation at room temperature, aging temperature and aging time as 3 factors and each factor uses 4 levels. 16 sets of experiments are organized in accordance with orthogonal table to get each factor in order of priority in effecting on the experimental results and the optimal process combination. Through experiments, the optimal process combination agrees with the actual.

Abstract: Adopting experimental method to examine clinching is able to apply to the joining of similar and dissimilar titanium alloy in this study. Also, to use tensile-shear test to figure out mechanical properties of clinched joints to TA1-TA1 clinched joints and Al5052-TA1 clinched joints. The results show that average load of TA1-Al5052 clinched joints is largely lower than the average load of TA1-TA1 clinched joints. Average load of TA1-TA1 is around 4427.58, equal to 3.85 times to Al5052-TA1.The two types of fractured joints are all neck shear fracture of the upper sheets. Therefore, the strength of joints is dependant to the material of the upper sheet. The formability of TA1-TA1 clinched joints are superior to Al5052-TA1, and average displacement of TA1-TA1 clinched joints is about 1.23 times to Al5052-TA1 clinched joints.

Abstract: The effect of enhanced solution treatment on microstructures, tensile properties, intergranular corrosion and exfoliation corrosion of a 6013 type aluminum alloy proceeded via various solution treatment were investigated by optical microscopy (OM), scanning electron microscopy (SEM), tension testing and corrosion resistance testing. The results show that compared with the conventional solution treatment (560°C×2 h), the enhanced solution treatment (560°C×2 h+570°C×2 h) can improve ultimate tensile strength and elongation, the corrosion resistance become worse after 151°C×8 h+191°C×8 h artificial aging. The tensile strength increase is believed to resulting from the coarse second phases dissolve. The corrosion resistance decrease is due to grain growth.