Advanced Materials Research Vol. 893

Abstract: In the current study, wear and frictional performances of different metals are investigated under different operating parameters against stainless steel counterface under dry contact conditions. The experiments performed using block on ring machine. Microscopy was used to examine the damage features on the worn surface and categorize the wear mechanism. Thermal imager was used to understand the thermal loading in the interface during the rubbing process. The results revealed that the operating parameters influence the wear and frictional behaviour of all the metals. Brass metal exhibited better wear and frictional behaviour compared to others. Three different wear mechanisms were observed, i.e. two body abrasion (Brass), three body abrasion (Aluminium) and adhesive (Mild Steel).

Abstract: Fire resistance performance in steel building is very important for sustaining structural stability during a fire. However, the fire performance has been evaluated by fire test with only one length of the H-section made of an ordinary strength structural steel, such as SS 400 or SM 400. These have the same yield strength, but SM 400 has a better weldability. Therefore, the determination of fire protective materials can be difficult when the H-section made of SS 400 and SM 400 is applied into columns having different lengths are changed. In this paper, an evaluation was conducted to suggest a new guideline for the fire resistance of H-section built with an ordinary strength steels such as SS 400 and SM 400 and having variance of lengths. The results revealed the H-section made of SM 400 showed a little better fire resistance performance. Also, the longer the length of column, the less the fire resistance. Therefore, a new guideline is required to compensate the fire resistance of longer column than that from fire tested.

Abstract: The influence of ions chloride concentration and pH value on the corrosion resistance of high-alloyed material UNS N08028 in the sodium chloride solution is investigated. Results show that the corrosion potential is active cathodically with the increase of chloride concentration. The current density and corrosion rate both increase with increasing chloride concentration and decreasing pH value.

Abstract: This study was focused on the effect of VC addition on the microstructure and mechanical properties of the prepared ultrafine grained cemented carbides. VC was added to the rawoxide materials which were synthesized to the WC-Co composite powder by the in-situ reduction and carbonization process. The ultrafine grained WC-Co alloys were fabricated by the spark plasma sintering technique using the prepared WC-Co composite powder. The phase constitution, microstructure characteristics and mechanical properties of the sintered ultrafine grained cemented carbides were analyzed quantitatively. The study proposed that VC plays a significant role in decreaseing the grain size of the prepared WC-Co alloy. The ultrafine grained WC-Co alloy with high comprehensive properties can be obtained as an appropriate addition of VC in the developed process.

Abstract: Linear and nonlinear viscoelastic behaviors of a Zr₅₅Al₁₀Ni₅Cu₃₀ bulk metallic glass are investigated through experiments and described by the fictive stress model. Systematic deviations between the predicted stress-strain curves by fictive stress model and by the experimental results were found. In order to describe the flow stress curves of the Zr₅₅Al₁₀Ni₅Cu₃₀ BMG at different temperatures and strain rates in the supercooled liquid region more precisely, the fictive stress model was modified. The parameters of the model were optimized by the genetic algorithm, and a time relaxation factor Z' was introduced. The comparisons of the predicted compressive stress-strain curves and extrusion load-punch stroke curve by the modified fictive stress model with the experimental data show good agreements.

Abstract: Separation of trace heavy metal ions with BaS from solutions of five kinds of systems was studied. One was prepared with the solution (called as original solution here) leached from pyrolusite with pyrite and H₂SO₄, and the other four kinds of systems were prepared in the laboratory according to the composition of the original solution. They are respectively: a ternary system of NiSO₄CoSO₄ZnSO₄; two quaternary systems of (NH₄)₂SO₄NiSO₄CoSO₄ZnSO₄ and MnSO₄NiSO₄CoSO₄ZnSO₄; a quintuple system of MnSO₄(NH₄)₂SO₄NiSO₄CoSO₄ZnSO₄. The experiments have researched the effect of reaction time and dosage of BaS on the separation of heavy metal ions. According to the results, it took the five systems 10minutes to reach the equilibrium state and re-dissolution was found in the results. As the increasing of BaS dosage, the residual heavy metal ions would reduce, but the results of five systems were different when the same BaS was used.

Abstract: In this work, a Full Factorial Experimentation technique, Design of Experiment (DOE) was developed and used to control the parameter of RIE (Reactive Ion Etching) process on a silicon wafer with aluminium layer. The objective of this work is to examine the Reactive Ion Etching (RIE) process on aluminium with different parameter, which are temperature, vacuum, RF (Radio Frequency) power and gas flow. Then, AFM (Atomic Force Microscope) and Lambda 950 spectrometer are used to analyse the grain size and light reflectance on the test specimen after RIE process. From the result, all four parameters of RIE were give an effect on grain size and surface reflectance on the test specimen. The parameter of gas flow is the most influence factor for grain size and surface reflectance in RIE process for aluminium layer compared to other parameters in this work.

Abstract: Objective: The aim of this study was to evaluate the adhesion of Streptococcus mutans (S. mutans) on different types of orthodontic brackets commonly used in Thailand. Materials and Methods: The adhesion of S. mutans on 7 types of orthodontic brackets (Clarity, Spirit MB, Inspire Ice, 3M, Tomy, Ormco and W&H) was investigated in vitro. The saliva-coated brackets were immersed in a flat-bottomed 96-well plate containing S. mutans suspension (10⁸ CFU/ml) and incubated at 37 ̇C in 10% CO₂ and 100 rpm for 2 hours. The adhered bacterial cells were fixed by 99% methanol and stained with 0.5% crystal violet. The quantity of adhesion was determined by measuring optical density (OD) at 590 nm. The data were analyzed with Kolmogorov-Smirnov test, Levene test, one way ANOVA and Games-Howell post hoc test. Results: Significantly higher bacteria adhesion was found on Clarity, Spirit MB, Tomy, Ormco and W&H compared to Inspire Ice and 3M Gemini. However, there were no significant differences among the different types of bracket materials (ceramic, plastics and metal). Conclusion: The amount of bacteria adhesion was independent of the type of bracket materials. The size and shape of brackets also played an important role in the amount of adhesion of microorganism.

Abstract: Fluorocarbons were added into the mixture of modified starch and sodium alginate to get uniform coating solution, and the solution was then coated on the surface of transparent paper. The color as well as grease barrier property of paper at different coating weight were studied. The results showed that color under different coating weights were not significantly different from base paper. The scanning electron microscopy (SEM) diagram showed the surface of paper became smoother and more homogeneous as the coating weight increased. The grease barrier property of coated papers were significantly improved compared with base paper according to Tappi-559 kit test. A highest grease rating number of 12 was obtained when the coating weight became 3.3 g/m². The dynamic changes in contact angle studies revealed that the contact angle of the base paper was continuously decreased from 29.41 °minutes to 23.46 °within 20, the contact angles of coated papers were significantly increased, and reaching a steady state within 2min with the maximum rate of contact angle change was of merely 0.06 ° / min.

Abstract: The microstructures of carbonized rice husk (CRH) and apricot stone (CAS) were studied to understand its adsorption of crude petroleum from water. Carbonize temperature affects the pore development of CRH, resulting in elongated large pores, as evident from the SEM data. The sorption capacities of CRH and CAS were compared in relation to different petroleum products. It was evaluated their possible practical use for water clean up from petroleum spills.