Indo Korea Science and Technology

Cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) are known for their transparency and high 10B density, which provides a large thermal-neutron cross-section, yet their potential for space neutron shielding has not been explored. The fabrication of transparent c-BN films remains challenging, and the chemical vapor deposition growth of h-BN beyond 70nm, or with precise thickness control and high uniformity, has not been reported except by our group. Here, we present a space window design integrating an h-BN-based neutron shielding layer with advanced ceramic bulletproof layers and a γ-ray shielding layer. By incorporating C and O into h-BN, sp2-sp3 hybridized BN (HBN) reduces the refractive index mismatch with the SiO2 substrate, achieving 90.9% transmission at 550nm at 11.9µm thickness and enabling stable, transparent growth up to 79.2µm with minimized thermal expansion mismatch. The optically optimized HBN (B0.39N0.39C0.06O0.16) shows reduced boron content, but the enriched formation of 63.4% c-BN, with its higher boron density, compensates for this loss. The resultant density is 3.01g cm-3, evaluated from neutron-shielding probability, and HBN achieves the same neutron-shielding efficiency as h-BN at 3% reduced thickness.

ABSTRACT This study examines the cooling performance of lithium‐ion (Li‐ion) batteries in electric vehicles, emphasizing the importance of maintaining temperatures below 35°C to ensure efficiency and safety. A simulation‐based approach is used to study battery pack cooling using a liquid coolant (deionized water) within a cold plate system, focusing on a 16‐cell battery pack connected in series‐parallel. A novel stereoscopic‐serpentine cold plate design is implemented. The thermal response of the battery pack is evaluated under constant and worldwide harmonized light vehicles test cycle (WLTC Class 3 drive) discharge rates. The inlet temperature and inlet flow velocities of the liquid coolant are varied. The simulation results for the stereoscopic‐serpentine cold plate design are compared with those for the traditional serpentine bottom cold plate design. The new design improved coolant flow and effectively reduced temperature differences in the battery pack. The findings highlight that lowering the coolant temperature is significantly more effective for reducing the battery temperature than increasing the coolant flow speed, with a 1% decrease in coolant temperature leading to a 7.1% reduction in the maximum battery temperature, compared with a mere 0.21% reduction from a 1% increase in coolant flow speed.

This study explores the magnetic and electronic properties of 3dtransition metal doped phosphorene monolayers using first principles calculations, with a focus on their potential two dimensional (2D) spintronics applications. We identify Ti, V, Cr, Mn and Fe doping induces magnetism in otherwise nonmagnetic phosphorene with respective magnetic moment of 1μB, 2μB, 3μB, 4μBand 3μBper dopant. The induced magnetic moment is attributed to the intra-atomic charge transfer (from 4sto 3d) and subsequent spin-dependent electronic redistribution at the dopant site. Among the doped systems, Cr and Mn doped phosphorene exhibit ferromagnetic (FM) ground states with critical temperatures of 217.8 K and 733.5 K, respectively. On the other hand, Ti, V and Fe doping favor antiferromagnetic ordering with relatively lower critical temperatures, 147.1 K, 58.7 K and 52.2 K, respectively. While Ti and V doping retains semiconducting character with a band gap of 0.31 eV and 0.17 eV, respectively, the Cr, Mn and Fe doped systems are found to be metallic in nature. Notably, the Fe and V doped phosphorene monolayers exhibit unconventional compensated magnetism that combines the privilege of both ferromagnetism (spin-split band structure) and antiferromagnetism (zero net magnetization). While the former doped system is identified as a quasi-altermagnetic material, the latter one is predicted to be a Luttinger compensated magnetic semiconductor. Since they can facilitate an effective spin transport without any unwanted FM coupling, therefore, the Fe and V doped phosphorene monolayers are the preferred superior materials for applications in next-generation 2D spintronics.

In this work, wereport the results of density functional theory(DFT) calculations on a van der Waals (VdW) heterostructure formedby vertically stacking single-layers of tungsten disulfide and graphene(WS2/graphene) for use as an anode material in lithium-ion batteries(LIBs). The electronic properties of the heterostructure reveal thatthe graphene layer improves the electronic conductivity of this hybridsystem. Phonon calculations demonstrate that the WS2/graphene heterostructureis dynamically stable. Charge transfer from Li to the WS2/grapheneheterostructure further enhances its metallic character. Moreover,the Li binding energy in this heterostructure is higher than thatof the Li metal’s cohesive energy, significantly reducing thepossibility of Li-dendrite formation in this WS2/graphene electrode. Ab initio molecular dynamics (AIMD) simulations of the lithiatedWS2/graphene heterostructure show the system’s thermal stability.Additionally, we explore the effect of heteroatom doping (boron (B)and nitrogen (N)) on the graphene layer of the heterostructure andits impact on Li-adsorption ability. The results suggest that B-dopingstrengthens the Li-adsorption energy. Notably, the calculated open-circuitvoltage (OCV) and Li-diffusion energy barrier further support thepotential of this heterostructure as a promising anode material forLIBs.

MAX phase is a family of ceramic compounds, typically known for their metallic properties. However, we show here that some of them may be narrow bandgap semiconductors. Using a series of first-principles calculations, we have investigated the electronic structures of 861 dynamically stable MAX phases. Notably, Sc2SC, Y2SC, Y2SeC, Sc3AuC2, and Y3AuC2 have been identified as semiconductors with band gaps ranging from 0.2 to 0.5 eV. Furthermore, we have assessed the thermodynamic stability of these systems by generating ternary phase diagrams utilizing evolutionary algorithm techniques. Their dynamic stabilities are confirmed by phonon calculations. Additionally, we have explored the potential thermoelectric efficiencies of these materials by combining Boltzmann transport theory with first-principles calculations. The relaxation times are estimated using scattering theory. The zT coefficients for the aforementioned systems fall within the range of 0.5 to 2.5 at temperatures spanning from 300 to 700 K, indicating their suitability for high-temperature thermoelectric applications.

A necessity to distinguish between the influence of powder shape and size (particle size distribution) is especially demanding for highly filled metal powder feedstocks employed in additive manufacturing and powder injection molding. As their processability is evaluated through rheological behavior, the study focuses on the effect of powder size/shape on a wall slip, which is a typical phenomenon determining flow performance of these materials. Water and gas atomized 17-4PH stainless steel powders with D50 of about 3 and 20 μm are admixed into a binder containing low-density polyethylene, ethylene vinyl acetate, and paraffin wax. Mooney analysis to intercept the slip velocity of 55 vol. % filled compounds reveals that wall slip effect appears to vary significantly with size and shape of metal powders—round shaped and large particles are the most prone to the wall slip. However, the evaluation is affected by the type of the flow streams resulting from the geometry of the dies—conical dies reduce the slip up to 60% in case of fine and round particles.