Impact of Sintered Temperature on the Heat and Cation Transport in NaK-BASE Tube

Alkali metal thermoelectric converter (AMTEC) is a clean energy converter that can be coupled with biomass for power generation. In present research, the transport of heat and cation was investigated in NaK-BASE tubes prepared at different sintered temperatures. The heat conduction and the fractal model were employed to investigate the temperature distributions based on the microstructures of the NaK-BASE tubes sintered at different temperatures, and the transport of Na+ and K+ in NaK-BASE tube was simulated by Poisson-Nernst-Planck multi-ions transport model, and the cation concentrations and surface charge densities were obtained in the NaK-BASE tubes with different temperatures. The results showed that microstructure of the NaK-BASE was related to the sintered temperature, and the microstructure of the NaK-BASE impacted the temperature distribution, the cation concentration and the surface charge density of Na+ and K+ in the NaK-BASE tubes. At the same heat source temperature, the average temperature in the NaK-BASE prepared at high sintered temperature was higher than that prepared at low sintered temperature. In addition, the increase of the average temperature resulted in the increase of the cation concentration and the surface charge density of Na+ and K+ in the NaK-BASE, therefore, the performance of the NaK-AMTEC could be enhanced by increasing the sintered temperature and the average temperature of the NaK-BASE.

Study on the Sintering and Mg Composition Effect on MgB2 Superconducting Bulks and Wires Synthesized by Powder-in-Sealed-Tube Method

Numerous research efforts aimed at the MgB2 (Magnesium diboride) as a superconducting material due to its higher critical temperature than Nb-based superconductors such as NbTi, Nb3Sn. Nowadays MgB2 is becoming more popular as the candidate to be applied on medical devices and large-scale applications because of its full coherence lengths, improved critical current density and fields, and simple crystal structure. In this study, we fabricated the 4 mm MgB2 superconducting wires by mixing stoichiometric mole ratio of Mg: B with 1.0:2.0 and 1.1:2.0 through the Powder-In-Sealed-Tube (PIST) method to optimize high critical temperature (TC) than the conventional MgB2 bulk and wire. Furthermore, we decreased the diameter of 4 mm to 1.8 mm wire and analyze the effect of critical temperature. The specimens were sintered at a different temperature to investigate the sintering effect of MgB2 superconducting wire. The resistivity versus temperature relationship, surface morphology, and crystal phase was characterized using Cryogenic system, SEM (Scanning Electron Microscopy), and XRD (X-ray Diffractometer), respectively. We optimized the high Tc,onset for the bulk and 4 mm wire compared to other studies that are 42.1K and 40.3K respectively at 800°C sintered temperature. Finally, the results suggest that the stoichiometric ratio of MgB2 exhibited excellent feasibility to prepare conventional MgB2 superconducting wire.

Effects of Sintering Temperature on Densification, Microstructure and Mechanical Properties of Al-Based Alloy by High-Velocity Compaction

This present work investigates the effects of sintering temperature on densification, mechanical properties and microstructure of Al-based alloy pressed by high-velocity compaction. The green samples were heated under the flow of high pure (99.99 wt%) N2. The heating rate was 4 °C/min before 315 °C. For reducing the residual stress, the samples were isothermally held for one h. Then, the specimens were respectively heated at the rate of 10 °C/min to the temperature between 540 °C and 700 °C, held for one h, and then furnace-cooled to the room temperature. Results indicate that when the sintered temperature was 640 °C, both the sintered density and mechanical properties was optimum. Differential Scanning Calorimetry, X-ray diffraction of sintered samples, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, and Transmission Electron Microscope were used to analyse the microstructure and phases.

EFFECT OF BINDER COMPOSITION AND SINTERING TEMPERATURE ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF WC-7(Ni,Fe) HARD ALLOYS PREPARED BY FREE CAPSULE HIP TECHNIQUE

<p class="AMSmaintext">In this research, WC-7(Ni,Fe) hard alloys were prepared by ball milling, cold compaction and finally consolidated by hot isostatic pressing. The effect of binder composition and sintering temperature were investigated in term of the microstructure, density and mechanical properties of sintered samples. Density of hard alloys was measured by the Archimedes' principle while the microstructure was observed using a scanning electron microscope. The Vickers hardness was investigated at load of 30KG and the fracture toughness was calculated based on the Palmqvist crack method. The results revealed that the density of sintered samples was obtained in the range of 14.65 to 14.8 g/cm³ meanwhile the measured Vicker hardness and fracture toughness were respectively achieved from 1260 to 1520 HV30 and 11,7 to 17,5 MPa.m^1/2 depending on the binder composition and sintered temperature.</p>