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A bearing material in an artificial knee joint has to have good thermal and mechanical properties to prevent wear in order to be used as a tibial tray. Despite its well-known good properties, ultrahigh molecular weight polyethylene (UHMWPE) still needs to be modified to enhance its physical strength in its use in artificial joints. In this research, composites made from UHMWPE and hydroxyapatite (HA) were prepared by mechanical alloying and hot press method and their thermal and mechanical properties were modified using gamma rays. The composites were prepared using various HA loading ratios and irradiated using gamma rays at doses of 0, 25, 50, and 75 kGy. The effects of HA loading and gamma irradiation on thermal and mechanical properties were studied by various methods. The results showed that the addition of HA enhanced the hardness of UHMWPE by 8–15% and the maximum stress up to 38%. Gamma irradiation enhanced the crystallinity by 113–172%, the melting point by 0.6–0.7%, and decreased the break elongation of composites by 23–48%. Addition of polyvinyl alcohol (5% w/w) in composites reduced their rigidity by 16–47% and hardness by 3–9%.

Preliminary studies have been conducted to determine the benefits of using palm fiber and shells as thermal neutron radiation shielding materials. The method in this research using Neutron Activation Analysis (NAA). However, based on the results of SEM-EDX data analysis, it was found that palm fiber and shells containing carbon were 70.92% and 73.25%, respectively. Furthermore, the carbon element is expected to absorb thermal neutron radiation and its ability was analyzed by using the material activation method due to neutron exposure. For the purpose of this study, the BATAN PSTBM Neutron Radiography facility was used for the activation. Thermal neutron flux on gold pieces that passed the natural neutron radiation shield made from palm fiber and palm shells was analyzed before and after passing through the shield in the NAA PSTBM BATAN laboratory. This analysis showed that the attenuation coefficient of palm fiber is 0.9538 cm−1 and palm shells are 1.0837 cm−1. Therefore, it can be concluded that both materials can be used as thermal neutron radiation shielding materials. Keywords: Palm shells, Palm fiber, Radiation shield

Bone implants is a way to cure broken bones which is being developed. The implants can be made of metals, ceramics and polymers. Metallic materials commonly used are titanium (Ti), stainless steel, and metal alloys. This study used Co-based alloys, i.e. CoCrMo coated with titanium nitride (TiN) which was then coated on hidroxyapatite (HAp). The HAp coating on the surface of CoCrMo alloy was done by biomimetic methods, first by soaking the metal alloys in simulated body fluid (SBF) solution for 18, 24, and 36 hours. The immersion in the SBF solution produced white coat on the surface of the metal alloy. The layers formed were analyzed by scanning electron microscope (SEM) and characterized by x-ray diffractometer (XRD). Based on the SEM results of 36 hours treatment, the morphology of apatite crystal formed fine grains. According to XRD result, there were HAp peaks at angles 2θ 31.86, 32.25, dan 39.48. However, there were also CaCO3 peaks at angles 2θ 29.46, 36.04, and 46.79. It indicated the pure HAp is not yet formed.