MoS2 is one of the most widely researched materials for electronic applications. While MoS2 can be exfoliated by inserting Li ions, this method is limited by the high reactivity of Li, requiring vacuum or inert gas conditions. To overcome this challenge, this study investigated organic-molecule-based exfoliation methods. The intercalation energies and exfoliation energies associated with inserting exfoliation agents (NH4, NH3(CH3), NH2(CH3)2, NH(CH3)3, and N(CH3)4) into MoS2 were examined. NH(CH3)3 was found to be more energetically stable than the other agents when they were inserted between the MoS2 layers. Also, intercalation of NH(CH3)3 and N(CH3)4 leads to a larger expansion of the MoS2 interlayer spacing, which effectively weakens interlayer interactions and lowers the exfoliation energy of MoS2. Therefore, NH(CH3)3 is expected to enable the commercialization of MoS2 nanosheets, as it allows for the large-scale exfoliation of MoS2 under atmospheric conditions.
In this study, to develop a refractory ceramic raw material with excellent lithium corrosion resistance, a gamma-LiAlO2 raw material was manufactured from Li2CO3-Al2O3 via a solid-state reaction method, and its corrosion resistance against Li(Ni0.8Co0.1Mn0.1) was estimated by mixing it with corundum (Al2O3). To evaluate the basic properties of the manufactured gamma-LiAlO2, its crystalline phase(XRD), crystalline phase fraction(Rietveld), and thermal expansion coefficient(TMA) were examined, while its microstructure(SEM) and crystalline phase were analyzed to determine the lithium corrosion behavior. The results of the basic property analysis of gamma-LiAlO2 revealed that its single crystalline phase consisted of Li2CO3 and Al2O3 with a mixing ratio (wt.%) of 5.5:4.5, and the highest crystalline phase fraction (96.81%) was achieved. The results of the lithium corrosion behavior analysis demonstrated that as the added amount of gamma-LiAlO2 increased, the corrosion depth of the cut surface decreased from 1800 to 600 & micro;m, thereby improving the lithium corrosion resistance by up to 66%.
The effect of BaTiO3 (BT) ceramics texturing along < 111 > on piezoelectric and dielectric properties was investigated. Strongly < 111 > textured BT ceramics were fabricated using template grain growth technique with plate-like < 111 > templates. The influence of template content and sintering conditions on texture development was systematically examined. An optimized composition with 5 mol% template, sintered at 1300 degrees C for 5 h, achieved a high Lotgering factor (LF) of 95% and a relative density >= 95%. The dielectric constant (epsilon(r)) increased with the degree of texturing, reaching 3260 at an LF of 95%. Similarly, the piezoelectric charge coefficient (d(33)) increased with LF, reaching 227 pC/N after poling at 3 kV/mm for 10 minutes. This enhancement with increasing LF is attributed to crystallographic domain engineering induced by < 111 > texturing, which enables spontaneous polarization switching along three equivalent < 001 > directions under an applied electric field, thereby enhancing the piezoelectric and dielectric properties.
Silica microparticles are widely used in various fields, including chromatography, catalysis, and drug delivery systems, owing to their excellent intrinsic properties and micrometer-scale. To improve product quality and reproducibility, it is necessary to develop a preparation method for monodisperse silica microparticles with tunable size. Although monodisperse silica microparticles can be prepared using microfluidic devices, silica gel tends to form in premixed reaction precursor solutions over time, leading to clogging of the flow channels. This paper reports a preparation method for monodisperse silica microparticles across a wide size range while mitigating channel clogging. Specifically, monodisperse droplets of an aqueous sodium silicate solution were generated using a microfluidic device and subsequently reacted with an aqueous sodium bicarbonate solution outside the device. By adjusting the flow channel dimensions, gas pressure for the aqueous phase flow, and oil phase flow rate, monodisperse silica microparticles were successfully prepared over a size range spanning two-orders-of-magnitude.
Metal oxides play a crucial role in engineering nanocomposites, offering enhanced surface performance for metals in demanding industrial applications. In this work, Ni - Cr oxide nanocomposites were synthesized via co-precipitation and deposited onto carbon steel (St12) substrates using electrophoretic deposition (EPD) under varying coating times (1-3 min) and voltages (100-120 V), followed by sintering at 750 degrees C. Structural, morphological, and chemical characteristics were analyzed using XRD, FTIR, TEM, FESEM, and optical microscopy (OM). The as-synthesized nanocomposite comprised NiO and NiCr2O4 phases with an average crystallite size of 28.8 nm. After sintering, the coatings contained Ni, Al, NiAl2O4, and NiCr2O4 phases. Mechanical and electrochemical performances were assessed through microhardness, ball-on-disk wear, electrochemical impedance spectroscopy (EIS), and polarization tests. Coatings substantially improved hardness, wear resistance, and corrosion resistance compared to bare St12. The 100 V-3 min coating exhibited the highest wear resistance (mass loss = 1.2 mg), whereas the 120 V-3 min coating showed the lowest (2.0 mg). The coating with a current density of 8.7 & micro;A & centerdot;cm(- 2) demonstrated the lowest corrosion rate, while EIS analysis revealed that the 110 V-3 min sample achieved the highest total resistance (R-t=7934.6 Omega), far surpassing the uncoated substrate (R-t=134.49 Omega). Equivalent electrical circuit modeling provided insight into the corrosion mechanisms of all tested samples.
This study evaluates how adding 0.2 wt% EMSIL-DRY (TM), a commercial low-melting burn-out polymeric multifilament fiber used to enhance permeability during dry-out, affects the pore-network evolution, thermal-gradient development, and ultrasonic integrity of ultra-low cement castables (ULCCs). Cubic specimens (6 '' and 11 '') were heat-treated at 350 degrees C, 560 degrees C, and 730 degrees C to assess porosity evolution, thermal gradients, and integrity. Mercury intrusion porosimetry showed increased total porosity, especially intraparticle, with fiber addition. Interparticle porosity rose at intermediate temperatures due to fiber burnout but decreased at 730 degrees C. A secondary pore network (0.1-2 mu m) improved vapor release and reduced internal thermal gradients by up to 23.75% at 560 degrees C. Despite a decrease in P-wave velocity (4120 m/s to 3880 m/s), structural integrity was preserved. Larger specimens exhibited more pronounced effects, highlighting scale-dependent behavior. Overall, fiber addition improved thermal dissipation by enhancing pore connectivity and permeability while preserving ultrasonic integrity, offering practical insights for optimizing refractory castables in high-temperature industrial environments.
In this work, the densification kinetics of the unbonded TiC materials were studied based on the high-temperature creep theory to clarify the sintering evolution mechanism and microstructure evolution process. The ZrO2 nanoparticles were introduced to optimize and modify the microstructure and achieve low-temperature densification and refinement of the TiC materials. In addition, the mechanical properties of the unbonded TiC materials were systematically studied under different sintering temperatures. During the oscillatory pressure sintering, the mechanical properties of the TiC materials reached the optimal levels at the holding time of 1650 degrees C and time of 30 min with the bending strength and fracture toughness of 902 MPa and 8.6 MPa & centerdot;m(1/2), respectively. Introducing ZrO2 nanoparticles into the TiC matrix did not reduce the densification temperature but significantly inhibited the growth of TiC grains. Introducing ZrO2 nanoparticles altered the fracture mode of the TiC materials from the mixture of intergranular and transgranular fractures to only transgranular fractures. The cracks propagated smoothly with minimal resistance, and t-ZrO2 was stabilized. Thus, the fracture toughness of the TiC materials decreased by 18%.
The attritor grinding of a binary glass and alumina system was studied to clarify how the packing volume controls the comminution kinetics and morphology of the ground glass. Glass and alumina particles of 1 mm were mixed at a 1 to 1 weight ratio and milled dry at 800 rpm with packing volumes of 40 mL and 80 mL. Size distributions were measured by sieving, component separation in each size fraction was quantified by X-ray fluorescence, and glass morphology was evaluated by scanning electron microscopy. Population balance modeling yielded the grinding rate constant and size distribution index for glass. The 80 mL condition promoted faster early size reduction in 10 min, whereas the 40 mL condition achieved stronger long-term comminution in 40 min, leading to a reversal in the grinding performance in the glass size distribution with time. The aspect ratio increased under both conditions, whereas circularity decreased more significantly at 40 mL, indicating more angular fragmentation. Discrete element method simulations showed that 80 mL increased the collision frequency but was dominated by low-energy impacts in an upper slow-moving layer. In contrast, 40 mL enhanced the high-energy impacts, particularly particle-wall collisions near the agitator, thereby accelerating fragmentation.
Interest in new-generation materials is increasing daily. New studies and research on MAX phases in many different structures and the superior mechanical and physical properties of MXenes make MXenes the focus of research. In this study, the synthesis, characterization, and gamma-ray shielding properties of niobium-based MAX phases (Nb2AlC) and MXenes obtained from this powder (Nb2CTx) were investigated. Nb2AlC and Nb2CTx stand out from other MAX phase materials with superior properties in materials with mechanical, thermal, electrical, and chemical resistance properties. Selective etching of Al layers was performed using hydrofluoric acid (HF) to produce Nb2AlC MAX phase powders and Nb2CTx MXenes. The etching parameters (HF concentration: 38-40%, time: 30-360 h) were optimized to obtain exfoliated accordion-like MXene nanostructures. The best MXene transformation occurred after 168 h of etching. Gamma-ray attenuation measurements highlight their potential in nuclear applications by utilizing their oxidation resistance, thermal stability, and mechanical strength. In addition, the-radiation shielding properties of MAX phase materials were investigated, and the best result was obtained for Nb2AlC.
This study systematically investigates the tribological behaviors and mechanisms of SiCp/Al composite under high-temperature conditions. Reciprocating ball-on-flat friction and wear tests were conducted at room temperature, 200 degrees C, and 400 degrees C. The frictional coefficient and wear volume were measured, and the worn surfaces were characterized using morphological analysis, chemical composition analysis, and hardness testing to elucidate the influence of temperature on the wear performance. The results indicate that both the frictional coefficient and wear volume of the composite increase monotonically with rising temperature. The underlying mechanism involves intensified aluminum alloy matrix softening and oxidation at high temperatures, which aggravates abrasive wear. At room temperature, the dominant wear mechanism is abrasive wear. As the temperature increases to 200 degrees C and 400 degrees C, matrix softening and oxidation promote the formation of additional hard abrasive particles, consequently intensifying the wear degree. This research clarifies the dominant role of matrix softening and oxidation in the high-temperature wear resistance of SiCp/Al composite, providing a theoretical basis for their application in high-temperature tribological components.
Ion doping and microstructure optimization are effective methods for enhancing the piezoelectric properties of Ba0.88Ca0.12Ti0.88Zr0.12O3 (BCZT) ceramics. To investigate the combined effects of Fe3+ doping and grain size on the piezoelectric properties , we doped 0.1 mol% Fe into BCZT and sintered at various temperatures using two-step sintering method. Our results indicate that Fe3+ doping caused the lattice of BCZT to shrink while increasing sintering temperatures, the sintering process was accelerated, resulting in larger grain sizes. It is believed that relatively large grains usually induce larger domains, facilitating the motion of domain walls, and increasing remnant polarization. However, excessively high sintering temperatures and large grain sizes may cause unfavorable compositional changes and harm densification, leading to a reduction in piezoelectric properties, such as d(33) and T-c. In this study, the BCZT ceramic samples that were calcined at 1200 degrees C and sintered at T-1 of 1550 degrees C and T-2 of 1300 degrees C exhibited the optimal performance, with the highest remnant polarization (P-r) similar to 14.8 mu C/cm(2), the largest piezoelectric constant (d(33)) similar to 420 pC/N at room temperature, and the highest Curie temperature (T-c) similar to 115 degrees C. These findings suggest that Fe3+ doping and sintering optimization are effective methods for discovering high-performance BCZT ceramics through microstructure optimization.
Silicon nitride (Si3N4) ceramics, combining excellent resistivity and high-temperature stability, are widely used in SF6-insulated high-voltage DC electrical equipment. This study attempted to fabricate Si3N4 insulating ceramics with superior dielectric and good mechanical properties using the stepwise pressureless sintering method, Y2O3-Al2O3 as a sintering additive, and four types of raw Si3N4 powders. The latter's characteristics were found to strongly influence both the mechanical and electrical properties of the ceramics. Specifically, powders with higher alpha-phase content, lower oxygen content, and a uniform particle size distribution contribute to obtaining dense ceramics with excellent mechanical properties. Furthermore, powders with a higher alpha-phase content and uniform particle size distribution enhance the volume resistivity of the Si3N4 ceramics, while smaller average particle sizes and lower oxygen content further improve the temperature stability of the ceramic resistivity.
Chloride-based Li2FeCl4 has emerged as a promising candidate high-voltage, highly deformable cathode material for all-solid-state lithium-ion batteries. However, further enhancement of Li-ion conductivity is required for practical application. In this study, we synthesized Br-substituted Li2FeCl3.8Br0.2 and examined how partial anion substitution influences both the crystal structure and Li-ion conductivity. X-ray diffraction confirmed that a single-phase cubic framework was retained and that the lattice constant remained unchanged despite Br incorporation. As a result of AC impedance measurements, the ionic conductivity was confirmed to increase approximately twofold, from 2.0 & times; 10(-5) S/cm for the pristine material to 4.0 & times; 10(-5) S/cm for the Br-substituted sample. In an effort to uncover the underlying mechanism of this enhancement, first-principles calculations (Density Functional Theory) combined with genetic algorithm - driven structural optimization were performed. The calculations indicated that Br substitution promoted a more disordered occupancy of Li ions across the sites along the conduction pathways. These results demonstrate that targeted anion substitution effectively tunes the Li-site energy landscape and controls Li-ion conductivity in chloride cathode materials.
