Applied Mechanics and Materials Vol. 493

Abstract: The present study was aimed at fabricating porous ceramic scaffolds via polymeric sponge method for biomedical applications using as synthesized Zinc doped Hydroxyapatite (ZnHA) powders. Zn doped HA powders were prepared via sol-gel method using diammonia hydrogen phosphate [(NH4)2HPO4] and calcium nitrate tetrahydrate [Ca (NO3)2.4H2 as starting materials. The obtained powders were then used for the preparation of porous ZnHA scaffolds via polymeric sponge method. The green porous bodies so developed by impregnating cellulosic sponges with HA slurries, were subjected to sintering process at a temperature of 1300 Field-emission scanning electron microscopy (FESEM) was used to observe the surface morphology of the powder and sintered porous sample. The structure and crystallinity of (Zn)HA powder and the sintered porous samples was analyzed using X-ray diffractometer whereas Fourier transform infrared spectroscopy (FTIR) was used to determine the presence of various phases in the powder. FESEM results showed the formation of agglomerates at an increased Zn concentration. The morphology of the porous samples showed high degree of fusion and densification with an increase in Zn concentration. Preliminary mechanical testing results show that maximum compression strength of HA porous bodies was 0.12 MPa.

Abstract: Zinc oxide (ZnO) is a unique material which has been used in many researches. However synthesizing nanosize ZnO remains a challenge. This deal with the preparation of ZnO nanoparticles was synthesized by a self-combustion technique. In the self-combustion technique, nanoparticles was obtained by heating the materials until the mixture combusts at 110°C. ZnO nanoparticles were synthesized from Zn (NO₃)₂.6H₂O precursor observed in two different solvent. The first set of experiment involved dissolving Zn (NO₃)₂.6H₂O in nitric acid (HNO₃) and adding ZnO, whereas for the second Ethylene Glycol (C₂H₆O₂) was used as the solvent. The material was stirred at 250 r.p.m continuously for 1 month and 3 days. The mixture was then heated up until it combusted at 110°C. Samples were then annealed at 400°C for 1 hour . The ZnO samples were characterized using X-Ray Diffraction (XRD), Raman Spectroscopy, and Field Emission Scanning Electron Microscope (FESEM). The XRD analysis showed major peak at 20-30 of 2 theta scale with [10, [00, and [10 plane of the wurtzite hexagonal structure for both sets of ZnO samples. Samples were observed at raman shift for 138 and 439 cm^-1 and 141 and 443 cm^-1 before and after annealing. Synthesized ZnO 1 resulted the morphology of single crystal nanorods with average dimensions of 18 nm wide and 154 nm long. ZnO 2 has obtained the morphology of single crystal nanosphere with average diameter of 30 nm.Keywords: Zinc Oxide, Ethylene Glycol, Self-Combustion Technique

Abstract: In the present work, a friction composite material which will be used for material of train brake shoe was investigated to study the effect of ingredients on flexural strength. The Taguchi method is used to measure relative effect of ingredients on flexural strength of composite. Taguchi L₈ orthogonal array which consists of 7 factors with 2 levels each is applied to perform experiment. Ingredients of friction composite were considered as factors or parameters and % volume for each factor was varied at 2 levels. Phenolic resin and barite (BaSO₄) were not included as factor. Phenolic resin was always kept constant at 30 % volume and % volume of barite (BaSO₄) was varied to compensate the changing of other ingredients amount. The results show that glass fiber and cast iron chip have significant effect on increasing of flexural strength of brake shoe composite. Conversely, NBR has significant effect on decreasing of flexural strength of brake shoe material. Cashew dust, Cu short wire, fly ash and graphite have insignificant effect on flexural strength. Cu short wire cant play a role as reinforcement fiber in brake shoe composite because there is weak bonding between Cu short wire and matrix.

Abstract: A dielectric property study was performed across a wide range of frequencies and temperatures onring opening polymerisation of ε-caprolactone system in order to relate quantitatively their dielectric properties to microwave heating mechanisms. An analysis of the results concluded that heating mechanism of the polymerisation mixtures in a microwave field was controlled by the dielectric properties of monomer, where the monomer was the major component (>90 % volume/volume) as well as the component with highest dielectric loss and dissipation factor. The penetration depth of mixtures at 2.45 GHz was noted to increase from ~0.58 cm (at 20 C) to ~3.3 cm (at 150 °C). This small penetration depth limits the potential to achieve the successful scale up of a microwave-assisted polymerisation of ε-caprolactone in batch mode at 2.45 GHz. As a result, this will lead to inhomogeneous bulk temperature distribution within the polymerisation mixture and irreproducible chemistry. However, a fast heating rate based on a high value of dissipation factor and dielectric loss of the polymerisation mixtures shows potential to enable the reaction to be completed in a few seconds that may allow the polymerisation to be transferred to a continuous flow process. In so doing, small diameter tubular reactors can be employed hence removing this penetration depth issue. Thus, the polymerisation mixtures dielectric properties are worth to be considered to ensure the reliability and reproducibility of the microwave assisted synthesis of poly-ε-caprolactone at large scale production.

Abstract: In this work, finite element (FE) model of spherical indentation has been developed and validated. The relationships between constitutive materials parameters (σ_y and n) of elastic-plastic materials, indentation P-h curves and hardness on spherical indenters has been systematically investigated by combining representative stress analysis and FE modelling using steel as a typical model material group. Parametric FE models of spherical indentation have been developed. Two new approaches to characterise the P-h curves of spherical indentation have been developed and evaluated. Both approaches were proven to be adequate and effective in predicting indentation P-h curves. The concept and methodology developed is to be used to predict Rockwell hardness value of materials through direct analysis and validated with experimental data on selected sample of steels. The Hardness predicted are compared with the experimental data and showed a good agreement. The approaches established was successfully used to produce hardness values of a wide range of material properties, which is then used to establish the relationship between the hardness values with representative stress.

Abstract: Barium titanate BaTiO₃ (BTO) - barium hexaferrite BaFe₁₂O₁₉ (BHF) nanocomposite could be as a raw material of multiferroic. Multiferroic is a class of materials with coupled electric, magnetic and structural order parameters that yield simultaneous effects of ferroelectric, ferromagnetism and ferroelasticity in the same material. This material has potential applications in such as spintronic devices and sensors. This work was an earlier research towards formation of multiferroic material. Knowing magnetic properties that will lead to a better understanding of magnetoelectric coupling in multiferroic material is the objective of this research.The samples were BTO and BHF prepared by sol-gel and then were mixed to synthesize composite in bulk system by a conventional techniques in various of weight fraction between BTO : BHF = 1:1 ; 1:2 and 1:3, then samples were sintered at 925°C for 5, 10 and 15 hours for each fraction respectively. Composite phase study was carried out using X-Ray Diffraction (XRD). MPS Magnet Physik EP3 Permagraph L was used to characterize magnetic properties. No residual phases were identified in the XRD analysis for all parameters. The peaks can be only indexed to BaTiO₃ and BaFe₁₂O₁₉ phases for all parameters respectively confirming the formation of a BaTiO₃-BaFe₁₂O₁₉ composite system. Barium titanate retains its tetragonal structure while barium hexaferrite exhibits hexagonal structure. For weight fraction of BaFe₁₂O₁₉ until 2 parts there is an increase of intrinsic coersive and saturation magnetization value. The maximum values of intrinsic coersive for samples with 5, 10 and 15 hours sintering are of 361.3 kA/m, 359.0 kA/m and 391.6 kA/m respectively and the maximum values of saturation are of 0.1515 T, 0.1516 T and 0.1414 T respectively leading to good characteristics of multiferroic materials.

Abstract: Polysulfone (PSf) membrane is catogorized as hydrophobic membrane that easily fouled during membrane operation process. The presence of second hydrophilic polymer which added into membrane casting solutions plays a crucial role in adjusting the membrane properties. This hydrophilic polymer was employed in hydrophobic polymer membranes in order to improve hydrophilicity and performance as well as formed antifouling ultrafiltration (UF) membranes. In this study, a hydrophilic polymer, cellulose acetate phthalate (CAP) was added into polysulfone (PSf) membrane casting solutions by blending technique to produce PSf/CAP blend membranes. Flat sheet asymmetric PSf/CAP blend membranes were prepared by wet phase inversion method. The results revealed that an increase in CAP increased the hydrophilicity properties of PSf/CAP blend membranes compared to pure PSf membrane. The significant changes in size and numbers of microvoids and macrovoids in the morphological structures of PSf/CAP blend membranes were due to CAP promote the instantaneous liquid-liquid demixing during phase inversion process.

Abstract: Natural gas in the form of compressed natural gas (CNG) has a pressure of 20 MPa. Glass fiber/vinyl ester composite has potential to be formed into a CNG tube. This study uses a numerical analysis method and tubular approching to assess composite ability to accept internal pressure loading, refered to failure criteria Tsai-Hill. The number of layers and fiber direction are chosen as independent variable. Configuration angle (+70, +25) provided a more optimal result than using a single angle. Composites are in a safe condition on 180^th layer. Thus, the glass fiber composite material / vinyl ester is not recommended to apply in the CNG tube manufacture.

Abstract: Solid oxide fuel cells (SOFC) are the current research having several potential to obtain high efficiency, high energy–density power generation which operated at relatively higher temperature. Yttrium oxide (Y₂O₃) contributions at high temperature are accelerating to the development oxide layer of FeCr alloy. The aim of this research is to investigate the microstructure of Fe/Cr added with Y₂O₃ acting as a reactive element. The purpose is to improve macrostructure of Fe/Cr powders which can be applied at steel industry. In this study the mixing process of Fe/Cr and Y₂O₃ powder was conducted via ultrasonic treatment at a frequency of 22 kHz, and at two different holding time of 2.5 h and 3.5 h. The particle size of chromium (Cr) can be reduced by ultrasonic treatment at from 60µm to 30µm through threshing the cluster of Cr particle. It shows that the ultrasonic vibration effectively removes oxides and other contaminates on a surface coating. Therefore, homogeneity of the parent material, segregation, and uniform distribution of second phase were increased.

Abstract: Barium hexaferrite (BaFe₁₂O₁₉) with hexagonal structure has been known as the high performance magnetic for Radar Absorber Material (RAM). Barium hexaferrite (BaM) was synthesized by sol gel auto combustion to get an homogeneous nanoparticle of BaM. Barium hexaferrites obtained from solution mixture between barium nitrate and ferri nitrate nonahidrat with precipitation of ion barium (Ba^{2 +}) and ferri (Fe^{3 +}) by solution of sodium hydroxide. Sample prepared with mol ratio of Fe / Ba 11 then added ammoniac in order that pH varies become 7,5; 9; and 11. Citric acid added in order that happen process of combustion. The stirring time was varieties by 1, 2, 3 hours. The effect of pH, stirring time, microstructure, phase,and magnetic properties were investigated using X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and a vibrating sample magnetometer (VSM). The results showed that the highest coercivity was 0.6 Tesla and the smallest crystal size 414.409 nm was obtained for pH 7.5 and stirring time 2 hours. The largest magnetic saturation 55.54 emu /g was reached for pH 7.5 with stirring time 1 hour