Advanced Materials Research Vols. 1025-1026

Abstract: The effect of the holding time on the surface hardening of commercially pure titanium (CP-Ti) by thermo-chemical treatment (TCT) process was studied in the present paper. Surface treatments with three different times were carried out and investigated. The TCT process using nitrogen gas was carried out under vacuum atmosphere in treatment time (0.5, 1, 2 h) at 800 °C (thermo-chemical nitriding temperatures). The hardened surface was analyzed by scanning electron microscope (SEM) to observe the microstructure of cross-sections of TCT-treated specimens. In observations of the gradient-hardened inner-layer, as the holding time was increased the layer thicker and the depth of the Ti2N + TiNx layer was higher. And the specimen thickness of Ti2N and TiNx layers, measured from cross-section specimen was about 9 μm, 10 μm and 13 μm, respectively.

Abstract: Titanium has high specific strength, low elastic modulus, and good corrosion resistance. Especially, beta titanium alloys are used for jet engine, turbine blade in automobile and aerospace industries because of its good formability. Among the beta titanium alloys, LCB (Low-Cost Beta) titanium alloys were developed to make economical and mechanical advantages by not using high-cost beta stabilizer like Nb, Zr, Ta but using low-cost beta stabilizer like Mo, Fe, Cr, etc. In LCB titanium alloys, adding a small amount of boron makes grain refinement in cast ingot. This study has analyzed the changes of microstructure which can change mechanical properties after heat treatment and the plastic deformation in case of adding a small amount of boron.

Abstract: The effect of styrene-ethylene/buthylene-styrene triblock copolymer (SEBS) on the thermal and rheological properties of thermoplastic polyurethane/polypropylene (TPU/PP) blends was investigated. For the selection of polymer materials and polymer blends for various fields of applications the stability of materials under constant deformation are very important. The blends were therefore characterized by measuring secondary viscoelastic functions creep, recovery and creep modulus using dynamic mechanical analysis (DMA) in the creep fatigue regime. The master curves at the reference temperature of 25°C were created by time-temperature correspondence (TTC) principle. The correlation of the creep modulus with time, temperature and addition of compatibilizer was discussed. The differential scanning calorimetry (DSC) results indicated that the addition of SEBS as a compatibilizer in TPU/PP blends increases glass transition temperature (T_g) and decreases crystallinity (χ_c). SEBS block copolymer acts as an efficient compatibilizer for TPU/PP blends.

Abstract: In this study there was found that ionizing beta radiation increased the strength of bonded joints and improved the adhesion properties of linear low – density polyethylene (LLDPE). Generally, for the formation of quality bonded joint it is important to wet the adhesive bonding surface well. Wettability is characterized by the contact angle of wetting. The liquid has to have a lower surface tension than the solid in order to be able to wet the solid substance. The measurement results indicated that ionizing beta radiation was a very effective tool for the improvement of adhesive properties and increased the strength of bonded joints of linear low – density polyethylene. Bonded surfaces with ionizing beta radiation doses of 0, 66, 132 and 198 kGy were irradiated. The best results were achieved by irradiation at dose of 132 kGy by which the highest surface energy and the highest strength of bonded joints of LLDPE were achieved. The strength of bonded joints after irradiation was increased up to 60 % compared to untreated material. A similar trend was observed even for contact angle of wetting and surface energy.

Abstract: Three-dimensional (3-D) periodic hematite scaffold was successfully fabricated by direct writing method as a catalyst for degradation of organic contaminants. Photo-catalytically active α-Fe₂O₃ nanoparticles have been synthesized by sol-gel technique. Aqueous slurries of iron oxides were freeform fabricated to produce hematite scaffolds with a 3-D periodic architecture and multiscale porosity. The catalytic activity of the hematite scaffolds was evaluated in the degradation of Methylene Blue (MB). It was found that the degradation rate of MB dye was over 83%. The result strongly indicates that the hematite scaffolds exhibits a high catalytic activity. Moreover, this work provides an important step forward in the creation of suitable structures for photocatalyst.

Abstract: Electrical discharge grinding (EDG) is an advanced machining process and can be utilised to fabricate complex geometry of PCD tools. However, the PCD removal mechanism in this process is complicated. This study was carried out to understand the difference in PCD surface structure with difference EDG polarities. The study revealed that the finishing process with negative polarity is the reason for the porous structure on the surface. Further analysis on the chemical element and carbon structure were implemented as the morphological examination of the surface.

Abstract: The paper describes the series of tests of fiber – cement plates. The first part is focused on determining the values of tensile bending strength for plates subjected to freeze – thaw cycle. The second part is focused of the influence of putting the plates into hot water on bending strength. The third part is described the procedure of monitoring the saturation – desiccation on bending strength.

Abstract: Influence of mould release agent for surface properties of concrete with special matrix are presented in this paper. Porosity, roughness and sorption capacity was tested depending on the selected separators. These properties are very important for architectural concrete or further non-treated concrete mainly due to efflorescence. From the results obtained follows that the different kind of separators as well as type of cements have impact on the concrete surface properties.

Abstract: Complex of measurements methods for indicate white efflorescence are presented in this paper. This article is focus on primary efflorescence, specifically lime based, which cannot be completely avoided. Tests involve not only qualitative and quantitative methods but also recommended additional measurement. Because there are not any standard for determination this kind of efflorescence, this set of tests should help for design concrete elements and limited risks of its creation.

Abstract: In this work, the Fe_xO_y catalysts were prepared by the co-precipitation method. The catalysts were characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and Brunauer-Emmett-Teller (BET) surface analysis. From XRD results, the Fe_xO_y with the wastewater to coagulant ratio of 1:2 catalyst (Fe_xO_y-1:2) calcined at 600 °C for 6 h showed the presence of the wustite (FeO) form. XANES analysis showed the phase of FeO in Fe_xO_y-1:2 calcined at 600 °C for 6 h which corresponded to the result from XRD. The Fe_xO_y 1:1 catalyst had higher specific surface area and larger total pore volume compared to the Fe_xO_y 1:2 catalyst.