Boron Nitride/Carbon Fiber High-Oriented Thermal Conductivity Material with Leaves-Branches Structure.

In the realm of thermal interface materials (TIMs), high thermal conductivity and low density are key for effective thermal management and are particularly vital due to the growing compactness and lightweight nature of electronic devices. Efficient directional arrangement is a key control strategy to significantly improve thermal conductivity and comprehensive properties of thermal interface materials. In the present work, drawing inspiration from natural leaf and branch structures, a simple-to-implement approach for fabricating oriented thermal conductivity composites is introduced. Utilizing carbon fibers (CFs), known for their ultra-high thermal conductivity, as branches, this design ensures robust thermal conduction channels. Concurrently, boron nitride (BN) platelets, characterized by their substantial in-plane thermal conductivity, act as leaves. These components not only support the branches but also serve as junctions in the thermal conduction network. Remarkably, the composite achieves a thermal conductivity of 11.08 W/(m·K) with just an 11.1 wt% CF content and a 1.86 g/cm3 density. This study expands the methodologies for achieving highly oriented configurations of fibrous and flake materials, which provides a new design idea for preparing high-thermal conductivity and low-density thermal interface materials.

Robust Superamphiphobic Coating Applied to Grease-Proof Mining Transformer Components.

The iron core and heat sink in a mining transformer are susceptible to damage from oil spills or the harsh mine environment; the deterioration of oil products in the underground environment and transformers produce massive amounts of harmful liquid substances, which may lead to unnecessary economic losses in drilling engineering. To overcome this issue, a convenient and economical way to protect transformer components was developed. Herein, we proposed an air spray technology at room temperature for the preparation of antigreasy superamphiphobic coatings, which are suitable for bulk metallic glass transformer cores and ST13 heat sinks. The addition of polypyrrole powder effectively improves the thermal conductivity and specific heat of the coating in the range of 50-70 °C. More importantly, the fabricated coating has excellent repellency to liquids, such as water, ethylene glycerol, hexadecane, and rapeseed oil. Meanwhile, the coating has excellent physical and chemical resistance and outstanding antifouling features, which provide a feasible solution for combating grease pollution and corrosion in the mine environment. Taking multifaceted stability into consideration, this work contributes to enhancing the application of superamphiphobic coatings in the fields of protecting transformer components in the harsh environment or during transformer operation faults.

Asymmetric Robust Superhydrophobic/Superhydrophilic Janus Membranes for the Moisture Proofing of Oil and Purification of Water.

The performance degradation of oil caused by moisture and water pollution induced by the infiltration of oil can result in huge losses for society. This is especially true of stable emulsified mixtures of oil and water, which are difficult to separate and urgently require a processing method. In this work, a robust Janus membrane prepared by combining simple electrodeposition and spraying processes was used to separate water-in-transformer oil/lubricating oil emulsions and various oil-in-water emulsions. The membrane with outstanding separation efficiency was also endowed high flux to emulsions, even after 10 separation cycles and 100 sand impact tests, indicating that separation ability was retained. Furthermore, the excellent resistance to acidic and alkaline liquids of the superhydrophobic side groups of the membrane increased the possibility of its service in harsh environments. This study's findings reveal great potential regarding the expansion and application of oil-water separation materials.

Effect of Laser Remelting Strategy on the Forming Ability of Cemented Carbide Fabricated by Laser Powder Bed Fusion (L-PBF).

Due to the high degree of design freedom and rapid prototyping, laser powder bed fusion (L-PBF) presents a great advantage in the super-hard cemented carbide compared with conventional methods. However, optimizing processing parameters to improve the relative density and surface roughness is still a challenge for cemented carbide fabricated by L-PBF. For this, the effect of the remelting strategy on the forming quality of the L-PBF processed cemented carbide was studied in this article, aiming to explore a suitable process window. The surface quality, relative density, microstructure, and microhardness of the cemented carbide parts fabricated under a single melting and remelting strategy were compared. The results showed that the remelting strategy could efficiently improve the specimens' surface quality and relative density. Besides, the cracks were not obviously aggravated, and the WC grains could distribute more homogeneously on the binder matrix under the remelting strategy. Therefore, the microhardness showed an improvement compared to the single melting strategy.

Effects of Different Substrates on the Formability and Densification Behaviors of Cemented Carbide Processed by Laser Powder Bed Fusion.

Cemented carbide materials are widely applied in cutting tools, drill tools, and mold fabrication due to their superior hardness and wear resistance. Producing cemented carbide parts via the laser powder bed fusion (L-PBF) method has the advantage of fabricating complex structures with a rapid manufacturing speed; however, they were underdeveloped due to their low density and crack formation on the blocks. This work studied the effect of different substrates including 316L substrates, Ni200 substrates, and YG15 substrates on the forming quality of WC-17Co parts fabricated by L-PBF, with the aim of finding the optimal substrate for fabrication. The results revealed that the Ni200 substrates had a better wettability for the single tracks formation than other substrates, and bonding between the built block and the Ni200 substrate was firm without separation during processing with a large range of laser energy inputs. This guaranteed the fabrication of a relatively dense block with fewer cracks. Although the high laser energy input that led to fine crack formation on the blocks formed on the Ni200 substrate, it was found to be better suited to restricting cracks than other substrates.

Effects of Titanium-Implanted Dose on the Tribological Properties of 316L Stainless Steel.

The effects of titanium (Ti) ion-implanted doses on the chemical composition, surface roughness, mechanical properties, as well as tribological properties of 316L austenitic stainless steel are investigated in this paper. The Ti ion implantations were carried out at an energy of 40 kV and at 2 mA for different doses of 3.0 × 1016, 1.0 × 1017, 1.0 × 1018, and 1.7 × 1018 ions/cm2. The results showed that a new phase (Cr2Ti) was detected, and the concentrations of Ti and C increased obviously when the dose exceeded 1.0 × 1017 ions/cm2. The surface roughness can be significantly reduced after Ti ion implantation. The nano-hardness increased from 3.44 to 5.21 GPa at a Ti ion-implanted dose increase up to 1.0 × 1018 ions/cm2. The friction coefficient decreased from 0.78 for un-implanted samples to 0.68 for a sample at the dose of 1.7 × 1018 ions/cm2. The wear rate was slightly improved when the sample implanted Ti ion at a dose of 1.0 × 1018 ions/cm2. Adhesive wear and oxidation wear are the main wear mechanisms, and a slightly abrasive wear is observed during sliding. Oxidation wear was improved significantly as the implantation dose increased.

Abrasive Wear Resistance of Plasma-Nitrided Ti Enhanced by Ultrasonic Surface Rolling Processing Pre-Treatment.

The objective of the given work was to investigate abrasive wear behaviours of titanium (Ti) treated by ultrasonic surface rolling processing (USRP) pre-treatment and plasma nitriding (PN). Simulated lunar regolith particles (SLRPs) were employed as abrasive materials during characterization of tribological performances. The experimental results showed that SLRPs cause severe abrasive wear on Ti plasma-nitrided at 750 °C via the mechanism of micro-cutting. Due to the formation of a harder and thicker nitriding layer, the abrasive wear resistance of the Ti plasma-nitrided at 850 °C was enhanced, and its wear mechanism was mainly fatigue. USRP pre-treatment was effective at enhancing the abrasive wear resistance of plasma-nitrided Ti, due to the enhancement of the hardness and thickness of the nitride layer. Nevertheless, SLRPs significantly decreased the friction coefficient of Ti treated by USRP pre-treatment and PN, because the rolling of small granular abrasives impeded the adhesion of the worn surface. Furthermore, USRP pre-treatment also caused the formation of a dimpled surface with a large number of micropores which can hold wear debris during tribo-tests, and finally, polishing and rolling the wear debris resulted in a low friction coefficient (about 0.5).

Fast pyrolysis characteristics of two typical coastal zone biomass fuels by thermal gravimetric analyzer and down tube reactor.

This study aimed at investigating fast pyrolysis behavior and products distribution of two typical coastal zone biomass fuels (Jerusalem artichoke stalk (JAS) and reeds (Re) by TGA and a homemade down tube reactor. The kinetic analysis with different ramping rates was conducted by FWO and DAEM models. The liquid, gaseous and solid products are characterized to study the influence of temperature. Results indicate that high heating rates may be overcome some resistances to mass or heat transfer inside the particles of biomass, and lead to a higher conversion rates and Re species is preferable to JAs in terms of thermochemical conversion because of the lower apparent activation energy for total conversion. Moreover, the pyrolysis conditions - temperature under fast pyrolysis in a down tube pyrolysis unit will make the covalent bonds in the biomass degradation more rapidly, gave significant influence on the yields and properties of liquid, gaseous and solid products.

Tribological Behavior of Titanium Alloy Treated by Nitriding and Surface Texturing Composite Technology.

This study experimentally investigated the effect of surface textures on the tribological mechanism of nitrided titanium alloy (Ti⁻6Al⁻4V). The titanium alloy samples were nitrided at various temperatures ranging from 750 to 950 °C for 10 h in a plasma nitriding furnace. Then, surface textures were fabricated on the polished titanium alloy and plasma nitrided samples by laser process system. The surface roughness, microhardness, and constitution of samples treated by single nitriding and samples treated by composite technology were characterized. The tribological properties of the samples were investigated on a CSM ball-on-disc tribometer. The results show that plasma nitriding effectively enhances the wear resistance of the substrate. The wear rate decreases first and then increases with the increase of nitriding temperature, and the wear rate reaches the minimum at 900 °C. However, the increase in roughness caused by nitriding treatment leads to an increase in the friction coefficient. It is found that surface textures can obviously reduce the friction coefficient of the nitrided titanium alloy. In addition, it can also reduce the wear rate of titanium alloys after nitriding at 900 and 950 °C. It can be concluded that the nitriding and surface texturing combined treatment can obviously reduce the friction coefficient and wear rate at the nitriding temperatures of 900 and 950 °C. This is attributed to the combined effect of high hardness of nitride layers and the function of micro-trap for wear debris of surface textures.

C Fibers@WSe2 Nanoplates Core-Shell Composite: Highly Efficient Solar-Driven Photocatalyst.

Recently, WSe2 as a typical transition metal dichalcogenide compound has attracted extensive attention due to its potential applications in electronic and optoelectronic devices. However, WSe2 alone cannot be directly used as a photocatalyst due to its inferior performance possibly caused by the strong recombination of photogenerated electron-hole pairs. Here a novel C fibers@WSe2 nanoplates core-shell composite (NPCSC) was successfully synthesized via facile, one-step thermal evaporation, in which numerous WSe2 thin nanoplates were in situ, densely and even vertically grown on the surface of the C fibers. Such composite presents highly solar-driven photocatalytic activity and stability for the degradation of various organic aqueous dyes including methylene blue and rhodamine B, and highly harmful gases like toluene, showing the great potential for environmental remediation by degrading toxic industrial chemicals using sunlight. Under simulated sunlight irradiation, comparing with commercially available WSe2 powder, the as-synthesized C fibers@WSe2 NPCSC presents significantly enhanced reaction rate constants by a factor of approximately 15, 9, and 3 for the degradation of aqueous methylene blue, aqueous rhodamine B, and gaseous toluene, respectively, due to the effective separation of photogenerated electron-hole pairs promoted by the rapid transfer of photogenerated electrons through C fibers. Moreover, this one-step thermal evaporation is an easy-handling, environmentally friendly, and low-cost synthesis method, which is suitable for large-scale production.

High-performance varistors simply by hot-dipping zinc oxide thin films in Pr6O11: Influence of temperature.

High-performance ZnO-Pr6O11 thin-film varistors were fabricated simply by hot-dipping oxygen-deficient zinc oxide thin films in Pr6O11 powder. The films had a composition of ZnO0.81 and a thickness of about 200 nm, which were deposited by radio frequency magnetron sputtering a sintered zinc oxide ceramic target. Special attention was paid on the temperature dependence of the varistors. In 50 min with hot-dipping temperature increased from 300-700 °C, the nonlinear coefficient (α) of the varistors increased, but with higher temperature it decreased again. Correspondingly, the leakage current (IL) decreased first and then increased, owing mainly to the formation and destroying of complete zinc oxide/Pr6O11 grain boundaries. The breakdown field (E1mA) decreased monotonously from 0.02217 to 0.01623 V/nm with increasing temperature (300-800 °C), due to the decreased number of effective grain boundaries in the varistors. The varistors prepared at 700 °C exhibited the optimum nonlinear properties with the highest α = 39.29, lowest IL = 0.02736 mA/cm2, and E1mA = 0.01757 V/nm. And after charge-discharge at room temperature for 1000 times, heating at 100 or 250 °C for up to 100 h, or applying at up to 250 °C, the varistors still performed well. Such nanoscaled thin-film varistors will be very promising in electrical/electronic devices working at low voltage.

Effect of SiC nanowhisker on the microstructure and mechanical properties of WC-Ni cemented carbide prepared by spark plasma sintering.

Ultrafine tungsten carbide-nickel (WC-Ni) cemented carbides with varied fractions of silicon carbide (SiC) nanowhisker (0-3.75 wt.%) were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC) and tantalum carbide (TaC) as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS) Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker.

Mechanical and biomedical properties of copper-containing diamond-like carbon films on magnesium alloys.

The high susceptibility to corrosion of magnesium alloys may lead to their rapid degradation in the human body and thus greatly jeopardizes their applications as potential biodegradable bone implant materials. To improve their mechanical properties and biocompatibility, Cu-DLC films were coated on Mg alloys in a mid-frequency dual-magnetron system. The anti-corrosion properties, frictional properties, and degradation behaviours of these coated films were then investigated as a means of evaluating their protective effects on the Mg alloys. The results exhibited a rather low coefficient of friction (COF) µ in simulated body fluid conditions for the film doped with a:C-Cu8.7% when compared with the Cu-DLC films doped with other contents. This is mainly because the a:C-Cu8.7% film gives higher hardness, lower intrinsic stress, and more superior adherence. Tests also suggested that the hemocompatibility and protective-ability of the Mg alloys deposited with the a:C-Cu8.7% film were greatly improved when compared with their uncoated counterparts. Analysis of the mechanism involved with the biocompatibility of Cu-DLC films revealed that adequate diffusion of nanosized Cu crystallites into the DLC films on the Mg alloys can result in a high ID/IG ratio, a relatively smooth surface, and a low coefficient of friction. Such diffusion effectively suppresses the release of Mg ions from the Mg alloys, and subsequently improves the film hemocompatibility and protective-ability.

Influence of Cr contents and nanograin sizes on microstructure, mechanical and sliding tribological behaviors of hard Cr-diamond-like carbon films.

The influence of Cr content and nanograin size on the microstructure, the mechanical and sliding tribological behaviors of Cr-containing diamond-like carbon (Cr-DLC) films, deposited on (100) Si substrate by a mid-frequency dual-magnetron system, was explored. The Cr-containing nanoparticles (combining Cr with C) were dispersed in the amorphous DLC matrix while some nanoparticles were transformed into compounds of C/Cr. The incorporation of Cr into Cr-DLC films improved the crystallinity of the Cr-rich nanoparticles and partially converted the nanoparticles to Cr/C phase. The films with Cr content ranging between 5-10 at% and with Cr-containing nanograin sizes in range of 15-27 nm were found to possess higher hardness, lower intrinsic stress, lower coefficient of friction (COF) and wear rate than those of 16-28 at% Cr content and 46-74 nm nanograin sizes. The superhard Cr-DLC film with 8.3 at% Cr and 18.4 nm Cr-containing grain gave the favorable micro-tribological characteristics with COF at micro approximately 0.1 and wear rate at 3.6 x 10(-8) mm3/Nm.

Aligned Si(3)N(4)@SiO(2) coaxial nanocables derived from a polymeric precursor.

Well-aligned coaxial nanocables, composed of a crystalline alpha-Si(3)N(4) inner core and amorphous SiO(2) outer shell, were prepared on silicon substrates by pyrolysis of a preceramic polymer (perhydropolysilazane) with iron as catalyst. The nanocables have high density, and the longest nanocable can be up to millimeters. Photoluminescence measurement reveals a strong ultraviolet emission band centered at 360 nm and a weaker visible-light emission at 625 nm. The growth mechanism of the nanocables is discussed in detail.

Influence of ag content and nanograin size on microstructure, mechanical and sliding tribological behaviors of Ag-DLC films.

Diamonds like carbon (Ag-DLC) films of nine Ag contents were deposited on (100) Si substrate in a mid-frequency dual-magnetron system. The influence of Ag content and nanograin size on the microstructure, mechanical properties and sliding tribological behaviors of the films has been investigated. It is found that (i) the Ag nanocrystallites were dispersed in the amorphous DLC matrix, and increasing Ag content resulted in an upward tendency of the Ag nanocrystallite size; (ii) the films with Ag content ranging between 3.3-11.4 at% and with Ag nanograin sizes in range of 5.4-16.8 nm exhibited higher hardness, lower intrinsic stress, better adhesion, and lower friction coefficient and wear rate as compared with those of 14.7-23.6 at% Ag content and 19.7-34.7 nm nanograin sizes; and (iii) the best combined properties were achieved for the film deposited with 8.7 at% Ag and with grain size 12.9 nm.