The development of new practices in nuclear research reactor safety aspects and optimization of recent nuclear reactors needs knowledge on forced convective heat transfer within sub-channels formed between several nuclear fuel rods or heat exchanger tubes, not only in the fully developed regime but also in the developing regime or laminar flow regime. The main objective of this research was to find a new correlation equation for calculating the convective heat transfer coefficient in the vertical square sub-channels. Recently, a simulation study was conducted to find a new heat transfer correlation equation for calculating the convective heat transfer coefficient within a vertical square sub-channel in the developing regime or laminar flow regime for Reynolds number range 400 ≤ Re ≤ 1700. Simulations were carried out using a computational fluid dynamics (CFD) code and modeling already defined in the software. The novelty of the research lies in the analysis of the entrance effect for the sub-channel by proposing a new empirical correlation that can then be inserted into the STAT computer code. The surface temperature distribution around the tangential direction of the active cylinders shows that the implementation of active and dummy cylinders in the current study can simulate sub-channels that exist in a real nuclear reactor core. The current study shows that the flow simulated in this study is in its developing condition (entrance region). A new forced convective heat transfer correlation for the developing region in the form of Nu = 2.094(Gz)^0.329 for the Graetz number range 161 ≤ Gz ≤ 2429 was obtained from the current study.

HAp and Zr-doped HAp nanoparticles were synthesized from bovine bone and local zircon material by using the hydrothermal method. XRD analysis showed that the HAp and Zr-doped HAp nanoparticles had hexagonal structure with a crystallite size of 20-36 nm and the lattice constants a = 9.8-9.9? and c = 6.5-6.8 ?. XRD data also showed that up to 20 at.% of Zr can be accommodated in HAp crystal structure. The lattice constant and cell volume decreased with increasing Zr concentration. FTIR data confirmed that the majority of functional groups that exist on the surface of the HAp and Zr-doped HAp nanoparticles were the hydroxyl and phosphate groups. Suspensions with the HAp and Zr-doped HAp nanoparticles prepared using citric acid as dispersant were stable with zeta potential between ?31 and ?35mV at pH = 7. Reactive oxygen species are generated on the produced HAp and Zr-doped Hap nanoparticles and confirm their potential for application in photodynamic therapy.

The development of high-entropy alloys (HEAs) for high-temperature applications has been driven by the limitation of nickel-based superalloys in achieving optimal efficiency at higher temperatures for higher efficiency in power generation engines. The alloys must have high oxidation resistance and microstructural stability at high temperatures. Relatively equimolar multi elements involved in HEAs produce microstructure containing a single solid solution or multiphase that improves the mechanical properties and oxidation resistance resulting from sluggish diffusion and core effects. In this study, the oxidation behavior and microstructural changes of Al_0.75CoCrFeNi HEA at 900, 1000, and 1100 °C in air atmosphere were investigated. Based on the XRD and SEM-EDS analysis, the mechanism of oxide scale formation and microstructural changes of the substrate are proposed. The results show that the oxidation behavior of the alloy follows a logarithmic rate law. Different oxide compounds of CoO, NiO, Cr₂O₃, and CrO₃, θ-Al₂O₃, α-Al₂O₃, and Ni(Cr,Al)₂O₄ with semicontinuous oxides of Al₂O₃ with Cr₂O₃ subscale and an oxide mixture consisting of spinel of Ni(Cr,Al)₂O₄ and Co(Cr,Al)₂O₄ were found. During oxidation, Widmanstätten of FCC-A1 and BCC-B2/A2 phases in the substrate have changed. Spheroidization of B2 and a reduction in volume fraction decrease the hardness of the substrates.

To develop new biomaterials for implant applications, the novel biomaterial multi component Zr-Mo-Ti-xY (x = 1, 2, 3) alloys were developed as a solution to increase mechanical properties and a corrosion resistance and to reduce the toxicity of biomaterials for implant. This research is aimed to investigate the effects of yttrium (Y) element addition to the microstructural transformation, mechanical properties and corrosion behavior of the alloy. The Zr-6Mo-4Ti-xY (x = 1, 2, 3) alloys are made by melting the metals using a vacuum single arc melting furnace with high purity argon gas flow at atmospheric pressure and tungsten electrodes with a six-times remelted process. The hardness test was conducted using the Vickers hardness tester, the microstructure analysis was done using the optical microscopes, and the alloy compound and phases using the XRD and corrosion resistance test were carried out using the polarization method in simulated body fluid Ringer's lactate solution. The values of the hardness test of Zr-6Mo-4Ti-xY (x = 1, 2, 3) alloys are 461.8,301.5 and 335.1 HV, respectively. The basketweave-shaped microstructure with the addition of yttrium moderately creates little grain measure. The corrosion rate of Zr-6Mo-4Ti-xY (x = 1, 2, 3) alloys which are 0.3159, 0.2705 and 0.3759 mpy respectively, are categorized as outstanding (the corrosion resistance of < 1 mpy) so that it can be considered as a potential biomaterial for implant applications.