Good potential of biocompatibility and excellent mechanical properties, porous Ti-6Al-4V has become a great interest for biomedical applications. In this study, porous Ti-6Al-4V was fabricated by Metal Injection Molding (MIM) using Palm Stearin (PS) and Polyethylene (PE) binder together with sodium chloride (NaCl) as a space holder. Rheological characterization was performed to evaluate the flowability of the feedstocks for injection molding and the feedstocks exhibited a pseudoplastic behavior which is suitable for injection. The as-sintered parts were fabricated as the mixing, injection molding, debinding and sintering were conducted successfully. The mechanical properties of the as-sintered parts were investigated via tensile test and the results obtained were closed with the established range. Shrinkage, density and X-Ray Diffractometry (XRD) of the as-sintered parts were compared with the theoretical values which were found closed to the acceptable ranges. The microstructure of the surface and cross-section were observed under Scanning Electron Micrograph (SEM) and optical microscope to analyze the specimens before and after sintering. Generally, palm stearin binder system added with space holder to fabricate porous Ti-6Al-4V by MIM is feasible and has shown a good potential for biomedical applications.
The dental restorations by the usage of implants have been one of the most favourable treatment. However, the existing dense dental implant causes overloading towards the human bone that triggers ‘stress shielding effect’ and also implant loosening. This paper focused on the development of highly porous Ti-6Al-4V dental implant by metal injection molding with palm stearin binder system with an addition of sodium chloride as space holder which has been established in the fabrication of porous Ti-6Al-4V. The evaluated compositions consist of the powder volume fraction of 63vol% and 65vol%. SEM analysis shows that highly porous Ti-6Al-4V dental implant were obtained. The average density is 3.325g/cm3 for 63vol% sample and 3.915g/cm3 for 65vol% sample. While for the Vickers hardness are 113.68HV and 162.8HV for 63vol% and 65vol% respectively.
In the modern world with an extensive improvement of science and technologies, alumina (Al2O3) ceramics have been identified as one of the usable materials in production of electronic components. This project attempts to investigate the magnesite (MgCO3) effect to Al2O3 sintering for heat sink application. The effect of MgO percentage varying from 0% to 50% has been in investigated, emphasizing on the flexural strength test, thermal conductivity test, elastic modulus test, shrinkage percentage and density measurement. The result revealed that the MgO give an effect to the final thermal conductivity and mechanical properties of Al2O3 material at high sintering temperature (i.e. at temperature of 1600°C). Throughout an X-ray diffraction (XRD) analysis of Al2O3 and MgO compositions, it was revealed that spinel, periclase and corundum phases exist for all sintered temperature which contributes to strengthen grain boundaries and improved mechanical properties.
Debinding process of injection moulded Ti-6Al-4V feedstock was divided into two parts: solvent debinding process to eliminate palm stearin (PS) and thermal pyrolysis to eliminate polyethylene (PE). Solvent debinding process used heptane at optimum temperature, 60°C to remove PS binder completely as temperature is the only parameter that can be optimized. Thermal pyrolysis parameters for removal of PE binder from the injected 65vol% Ti-6Al-4V feedstock have been optimized by using Taguchi method. Heating rate, temperature and time were the selected factors during experiment to be applied in the L9(34) Taguchi orthogonal array (OA) to find the best set of parameters to produce highest density of brown part. Thermal pyrolysis process was done at optimum parameters: heating rate: 5°C/min; temperature: 510°C; and time: 90 minutes. Analysis of Variance (ANOVA) was employed to find the best signal to noise ratio (S/N) to express the contribution of the factors towards quality characteristic. Based on the results, heating rate has the greatest contribution (54.63%), followed by duration time of thermal pyrolysis (24.40%) and temperature (19.25%).
Current trend for manufacturers associated to MIM industry try to enhance the feedstock in term of its characteristics, since it is the most crucial part of the MIM process. This paper covered the characterization and rheological studies on a ready-made feedstock of stainless steel 316L which is vital to determine the availability and suit the needs of many advanced applications. There are three different experiments involved which are Scanning Electron Microscope (SEM), Differential Scanning Calorimeter (DSC), Thermogravimetric (TGA) and Capillary Rheometer. Observation through SEM gives an insight of the bonding microstructure matrices of the feedstock and also determines the homogeneity of the feedstock. DSC testing defines the melting temperature of the 3 binders used which are 62.07°C for surfactant, 178.72°C for filler and 236.61°C for backbone binder. From TGA result, it showed that the total weight loss of feedstock was 39%. Throughout the capillary rheometer testing, the feedstocks viscosity was decreasing as the shear rate increasing. The feedstock exhibits pseudoplastic behaviour since its flow behaviour index was less than 1. It is founded that at the temperature of 190°C, the feedstock exhibits the best characteristics for injection.
Construction on problematic soil that has low bearing capacity, low shear strength, high compressibility, and high water-content will interfere with the smooth construction process and will affect time and cost due to repetitive maintenance. Pavement built on problematic soil as its subgrade is exposed to pavement failures, such as fatigue cracking, longitudinal cracking, and pumping, owing to swelling or shrinkage due to moisture variation and differential settlement. Therefore, improvement of the ground needs to commence so as to improve its load bearing capacity, in order to sustain the load on top of it. Consequently, the main aim of this study is to determine the effectiveness of crumb tyre rubber mixed with soil samples as one of the soil stabilisation techniques and to establish the optimum usage percentage of crumb tyre rubber as a stabiliser. Clayey sand soil was mixed with 5%, 10% and 15% of crumb tyre rubber by weight of the soil sample and was tested for physical properties, such as particle size distribution and plasticity index. In obtaining the changes in strength, mixed clayey sand-crumb tyre rubber samples were subjected to compaction and California Bearing Ratio (CBR) tests. The results showed that the increment of crumb tyre rubber percentage as an additive, increased the CBR value and therefore enhanced the strength of the modified soil. However, the crumb tyre rubber stabiliser affected the optimum moisture content and maximum dry density of the modified samples by decreasing their values. The optimum percentage of crumb tyre rubber mixture was found to be 10% by weight at the end of this study. These findings indicate that the measured crumb tyre rubber is suitable for supporting the clayey sand soil for the subgrade of pavement construction. ABSTRAK: Pembinaan di atas tanah bermasalah yang mengandungi kapasiti galas rendah, kekuatan ricih rendah, kebolehmampatan tinggi dan kandungan air tinggi akan mengganggu kelancaran proses pembinaan dan akan menjejaskan kekangan masa dan wang akibat penyelenggaraan berulang. Jalan raya yang dibina di atas tanah yang bermasalah akan mengalami kegagalan turapan seperti keretakan, rekahan membujur dan pengepaman, disebabkan oleh subgrednya terdedah kepada pembengkakan atau pengecutan akibat perubahan kelembapan dan pemendapan berbeza. Oleh itu, penambah baikan tanah perlu dilakukan bagi mencapai kapasiti galas beban lebih baik untuk menampung beban di atasnya. Oleh itu, tujuan utama kajian ini adalah bagi menentukan keberkesanan serpihan tayar getah yang dicampur dengan sampel tanah sebagai salah satu teknik penstabilan tanah dan menentukan peratusan optimum penggunaan tayar getah sebagai penstabil. Tanah pasir liat sebagai bahan utama dalam kajian ini dicampur dengan 5%, 10% dan 15% serbuk tayar getah mengikut berat sampel tanah dan telah diuji sifat fizikalnya, seperti taburan saiz zarah dan indeks keplastikan. Perubahan dalam kekuatan ditentukan dengan cara menggaul sebatian sampel tayar getah bersama pasir tanah liat dan diuji dengan eksperimen pemadatan dan ujian Nisbah Bearing California (CBR). Dapatan kajian menunjukkan bahawa penambahan peratusan serbuk tayar getah sebagai bahan penstabil telah meningkatkan nilai CBR dan sekaligus meningkatkan kekuatan tanah yang diubah suai. Walau bagaimanapun, penstabil tayar getah mempengaruhi kandungan lembapan optimum dan ketumpatan kering maksimum sampel yang diubah suai dengan nilai berkurang. Pada akhir kajian ini, peratusan optimum bancuhan serbuk tayar getah yang diperolehi adalah sebanyak 10% berat sampel. Dapatan ini menunjukkan bahawa tayar getah remah adalah sesuai dalam menyokong tanah pasir liat bagi subgred pembinaan turapan.
Most Ti-6Al-4V implant used today are often much stiffer than human bone. However, the young modulus of those Ti-6Al-4V implants can be reduced through the formation of porous structure. Palm stearin binder system with an addition of sodium chloride as space holder has been established in the fabrication of porous Ti-6Al-4V. Thus, this paper focuses on the compressive mechanical properties of porous Ti-6Al-4V with utilization of palm stearin binder system along with sodium chloride (NaCl) as the space holder. The evaluated compositions consist of the powder volume fraction of 63vol% and 65vol%. The samples were compacted by thermal compacting machine at temperature of 160oC. Two different debinding processes involved, which are heptane solvent and water leaching. Then the samples were sintered up to three different temperatures, which are 1200oC, 1250oC and 1300oC. Mechanical properties of the porous Ti-6Al-4V were characterized by axial compression testing. The maximum compressive stress and Young’s modulus of the samples were determined to be 403.87MPa and 9.92GPa.
Aluminium alloys is widely applied in heat sink but its application of heat absorption is still unsatisfied. While, Aluminum Nitride (AIN) was discovered as another option for heat sink application because of its great thermal conductivity and it also has high electrical conductivity at high temperature. Thus, the mechanical and chemical properties of a sintered mixed powder of Alumina and AIN are investigated experimentally. There are five different compositions of mixed powder of Alumina-AIN and sintered at three different sintering temperatures which are 1400°C, 1500°C and 1600°C. As applying a high sintering temperature on samples inducted great flexural strength and increase it modulus of rupture. High sintering temperature (1600°C) also affected the materials microstructure as the particle was arranged closely between each other and reduces the amount of porosity. The application of high temperature in the mixture of AIN with Alumina reduces the occurrence of flaws like cracking and accordingly improves the strength. These combination of Alumina-AIN brought acceptable result in thermal conductivity value analysis and as well enhancing the thermal conductivity.
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