Advanced Materials Research Vol. 789

Abstract: As versatile biomass-based diol precursors, N,N'-1,2-ethanediylbis-(4-hydroxy-pentanamide) (1) and 4-hydroxy-N-(2-hydroxyethyl)-pentanamide (2) are potential monomers to synthesize novel polyurethanes through adding di-isocyanates. This study reported the structural analysis and molecular behavior of polyurethanes obtained from polymerization of the diol precursors with aliphatic and aromatic di-isocyanates (hexamethylene diisocyanate, HDI (3), and phenyl-diisocyanate, PDI (4)) in (N,N-dimethylacetamide (DMA) solvents with triethylamine (TEA) catalysts. ¹H-NMR, ¹³C-NMR and Elemental Analysis confirmed structure of the polyurethanes built from both diols and di-isocyanates and FTIR indicated interaction among polyurethane molecules showed at lower wave numbers such as 2855-2976 cm^-1 for hydrogen-bonded NH groups and 1621-1643 cm^-1 for hydrogen-bonded C=O groups. Furthermore a study on influence of the inter-and intra-molecular hydrogen bonding on the thermal and mechanical properties of the polyurethanes would be an interesting investigation for the next study.

Abstract: The millimeter wave (MMW) sintering of alumina ceramic had been performed. The results revealed that MMW sintered alumina has higher density than that of conventional method on all sintering temperature. However microstructure evaluation demonstrates that grain growth of MM wave annealed alumina is faster than in conventional annealing. It indicates that MM wave enhanced mass transport and solid state reaction rates during sintering. The empirical observations of microwave enhancements have been broadly known as microwave effect. Even though no satisfactory theory existed to explain the effect but the presence the electromagnetic waves (EMW) during microwave heating is clearly the key. In this paper, microwave effect on grain growth of alumina ceramic is presented. Some effective and unique characteristics of the EMW sintering were also discussed as well.

Abstract: Smart concrete is an innovative material because it can serve as a sensor without any additional sensors in it. It is reinforced with carbon fiber that has gone through the pyrolysis process at high temperature to produce carbon content above 90%. The carbon fiber used in this study was Polyacrylonitrile. The working principle of carbon fiber sensor works piezoresistivity that respond to changes in mechanical (stress and strain) to electrical impulses. The resistivity changes that will be converted into units of load on the display circuit system. Key to success of this research was the concrete formulations and systems were sensitive and accurate readings so that any small change in resistivity could be directly detected. Variations in carbon fiber were added to the 0-1% by weight of cement with interval 0.5. Fly ash was added as a filler to reduce the use of cement. Results obtained from dynamic cyclic testing showed that the compressive strength was the best in the concrete without carbon fiber, then decline in line with the increased number of carbon fiber. But inversely proportional to the resistivity of the concrete produced. Smart concrete must have a high sensitivity to changes in stress / strain, it should also meet the required concrete strength both press and flexible to avoid initial crack.

Abstract: Several biodegradable polymers have been explored to develop biodegradable edible films in order to reduce the use of conventional plastics. In this study, edible biocomposite film is made from gelatin filled with Bacterial Cellulose Microcrystal (BCMC). BCMC is produced from nata de coco paste, which is hydrolyzed with cellulase enzyme. In making biocomposite, gelatin matrix is first dissolved in distilled water and then mixed with BCMC filler solution in ultrasonic bath. The solution resulted is then casted and dried in room temperature. The addition of BCMC is proven to improve physical properties, mechanical, and thermal properties of the resulting material. BCMC distribution of SEM showed increasing the tensile strength test results, DSC, and WVTR. When the BCMC concentration was varied from 1-4 wt% of the gelatin mass, tensile strength and glass transition temperature (Tg) increased from 37.07 MPa to 74.04 MPa and 27.520°C to 39.60°C, respectively. Water Vapour Transmission Rate (WVTR) decreased from 37.77 gr.m^-2.h^-1 to 19.73 gr.m^-2.h^-1. Tensile test and DSC results also increased when varying the sonication time from 3-6 minutes, from 48.57 MPa to 57.23 MPa and 25.890°C to 37.290°C. WVTR decreased from 36.09 gr.m^-2.h^-1 to 20.54 gr.m^-2.h^-1.

Abstract: Polymer poly (1-vinyl-1,2,4-triazole) have been synthesized via free radical polymerization using the monomer 1-vinyl-1,2,4-triazole and the initiator azobisisobutyronitrile (AIBN) in toluene as solvent. Proton conducting membranes were prepared by adding nitrilotri (methyl triphosphonic acid) as a dopant into a solution of poly (1-vinyl-1,2,4-triazole) at various molar ratios. The mixture was cast in polished poly (tetrafluoroethylene), PTFE plates and the solvent was evaporated carefully at temperatures of 50 °C for 12 hours. Interaction between the polymer and the dopants have been studied through; FTIR spectrum, thermogravimetric analysis (TG), glass transition temperature using DSC and proton conductivity of membranes made using dielectric-impedance analyzer Novocontrol. Proton conductive membranes with molar ratio of 0.25 was obtained proton conductivity of 8.52 x 10^-4 S/cm at 150 ^°C.

Abstract: Plastics are synthetic polymers, made from petroleum and its derivatives which are non biodegradable. Today, more people used plastic bags to support their activities ,which caused the supply of plastic shopping bags to increase in large number. Plastic bags, eventually, are usually used as garbage which would cause negative impact on the environment. Environmental friendly plastic bags are made from renewable raw materials, such as starch from cassava, corn or others. There are the ones entirely starch based such as Enviplast (biodegradable); the ones with partial mixture of starch with plastic ores such as Ecoplas (biodegradable), the ones plastic ores are formulated with additives Oxium (oxodegradble), and conventional made from plastic ores only. Distinguishing characteristics of samples plastic shopping bags which were taken from domestic and abroad supermarkets can be seen from the result of FTIR, SEM, and AAS analysis along with burial in soil. Density of domestic plastic bag (1.119 g/cm³ ) are 49.55% smaller than samples abroad 2.258 g/cm^{3 .}This means that in the country, a space to hold trash bags in the same weight needed almost 2x larger. Another discovery are some plastic shopping bags are labeled eco-friendly ,but had conventional plastic characteristisc .

Abstract: The emergence of white layer in each process of Electric Discharge Machining (EDM) becomes the focus of attention of the experts. It is harder than the base metal would be advantageous to withstand friction engine components, such as the plastic molding industry. From various studies it has been reported that the increase in the value of hardness of white layer either due to migration of the electrode material and dielectric fluid to the white layer. This paper discusses the influence of electrodes Cu, CuCr and graphite as well as jatrophacurcas dielectric fluid to the surface of the material SKD 61, microhardness of the white layer, Tool Wear Rate (TWR) of Material Removal Rate (MRR), Surface roughness (Ra) and the microstructure. Initial studies conducted are the transesterification and characterization of jatrophacurcas to determine the dielectric strength and the content of metal elements. Furthermore, the EDM testing is done to dies steel of SKD 61 using the electrodes of Cu, CuCr and Graphite. The use of jatrophacurcas yield the best MRR when using Graphite electrodes followed Cu last CuCr. While the smallest TWR produced by Cu electrode, CuCr and then the highest is Graphite. The relative wear which is the ratio TWR with MRR, for the three types of electrodes is always great at a small current then decreases and then tends to be stable with the increase of electric current. Jatrophacurcas for the three types of electrodes provide higher TWR than kerosene. This means that migration of materials is beneficial because larger material, but in terms of the geometric accuracy of the product can lead to decreasing of dimensional tolerances. Vickers hardness values of white layer is achieved by CuCr electrodes, Graphite lowest. Microstructural observation results of EDM white layer using graphite electrodes produce a more uniform thickness than the white layer using Cu and CuCr electrodes. The conclusion of this study that jatrophacurcas can be used as a dielectric fluid in EDM process, because electrode wear during EDM process is relatively high compared with kerosene that is mean more profitable in the surface treatment process of dies steel of SKD 61.

Abstract: In metal forming process by die casting method, nitriding plays an important role in increasing the surface hardness. The influence of shot peening and shot blasting to the modified. H13 tool steel before nitriding process has been studied. Nitriding has been done in a gas vacuum furnace, at temperature of 510°C for 5 hours. Shot peening was conducted by using steel balls with a pressure of 461 kPa. Shot blasting has been done after shot peening using SiC particles. Characterization of the sample surface before and after the variation process is focused on changing the microstructure, micro hardness distribution, depth and composition nitriding layer. It has been found that shot peening prior to nitriding increase the maximum surface hardness to 1196 HV and effective depth of diffusion layer to 72 μm. Meanwhile, the nitriding without any prior surface treatment produces a maximum hardness of HV 1101.4 with effective depth of diffusion layer of 54 μm. Shot peening prior to nitriding produces white layer thickness of 4.1 μm thicker compared to white layer developed in nitriding without shot peening which produces 3.7 μm. While on nitrided material without any preceded surface treatment did not reveal any white surface layer.

Abstract: In this study, the optimization of material removal rate (MRR) and surface roughness (SR) simultaneously in a WEDM process by using Taguchi method with fuzzy logic has been applied. The Wire EDM process parameters (flushing pressure, on time, open voltage, off time and servo voltage) were optimized with considerations of multiple performance characteristics, i.e., MRR and SR. Based on the Taguchi method, an L₁₈ mixed-orthogonal array table was chosen for the experiments. Fuzzy reasoning of the multiple performance characteristics has been developed based on fuzzy logic, which then converted into a fuzzy reasoning grade or FRG. As a result, the optimization of complicated multiple performance characteristics was transformed into the optimization of single response performance index. Experimental results have shown that machining performance characteristics of Wire EDM process can be improved effectively through the combination of Taguchi method and fuzzy logic.

Abstract: Application of a light-weight material, such as an aluminum alloy, on a turbine impeller can enhance the efficiency of an Organic Rankine Cycle power plant that operates at temperatures below 150 °C. The density of an aluminum alloy only one-third that of steel. However, increased strength of aluminum alloys is needed for turbine impeller qualification. Investment casting was chosen to produce radial inflow turbine impeller due to their complex geometry and precision. It can replace machining process, which is time-consuming and less efficient because of material removal. This study describes the investment casting process used to produce a radial inflow impeller turbine. The study also identifies defects, microstructures and properties of radial inflow turbine impeller. The turbine impeller were produced from Al-7Si-4Mg alloy with 0.38, 3.82, and 6.0 wt. % Cu. Visual examination showed that the turbine impeller was free of macro defects and misruns. Microstructures were characterized by Optical Microscopy and SEM. The structures consisted of α-Al, Si eutectic, AlMgSi, AlMgFeSi (Chinese script) and CuAl₂. The higher hardness value of 54HRB was affected by Cu content due to the good mechanical properties of fasa CuAl₂^.