To address the issues of weak interfacial bonding and limited wear life in brazed diamond tools, this study investigates the synergistic effect of salt-bath-deposited carbide coatings and Cu-Sn-Ti filler on the interfacial microstructure, crack evolution, and tribological performance of brazed diamond joints. Raw diamond and Cr/ Mo/W/Ti-coated diamond particles prepared via a ternary LiCl-KCl-NaCl salt bath were brazed using Cu-Sn-Ti filler at 960 degrees C for 10 min. Compared to uncoated diamond, the salt-bath coating reduced diamond graphitization by 41.0%-79.5%, with Mo@diamond and W@diamond showing the greatest thermal protection. Crosssectional TEM (HRTEM/SAED) of the Mo@diamond joint directly reveals a dual-layer carbide structure: an inner Mo2C layer (similar to 75 nm) formed during salt bath plating, and an outer TiC layer (similar to 68 nm) formed during brazing via reaction between active Ti from the filler and outward-diffusing carbon. SEM-EDS confirms analogous dual-layer morphologies in Cr, W, and Ti@diamond joints. Crucially, the pre-existing carbide layer displaces the brittle Sn3Ti5 phase > 20 mu m away from the diamond-filler interface, converting it from a proximal crack trigger into a remote harmless constituent. This Sn3Ti5 displacement, combined with the crack-deflection and stress-dissipation functions of the dual-layer carbide rivets, significantly suppresses crack propagation during wear. Quantitatively, W@diamond exhibits the lowest post-wear crack rate (0.293) and the highest proportion of stable flattening wear (57.2%) with zero diamond pull-out, whereas Cr@diamond shows the highest crack rate (0.552) and 50% massive fracture with 7.1% pull-out. Consequently, Mo@diamond and W@diamond joints achieve superior wear resistance, with grinding volumes of 49.5 mg and 51.3 mg and mass losses of 110.2 mg and 107.8 mg, respectively-substantially lower than Cr@diamond, Ti@diamond, and uncoated diamond joints. This work establishes a fundamental structure-property relationship for coated diamond brazed joints, providing a scientific basis for designing high-performance diamond tools with prolonged service life.
The effects of reaction temperature and calcium oxide addition on the content and forms of nitrogen and phosphorus in the thermal solvent extraction products of municipal sludge were systematically investigated. In addition, the LCA method was introduced for the first time into this process. Three quantitative indicators including nitrogen extraction efficiency (NEE), phosphorus enrichment factor (PEF), and phosphorus bioavailability conversion ratio (AP/TP) were constructed. By combining experimental data with the Ecoinvent database, the carbon emissions, net energy consumption, and substitution emission reduction benefits of nitrogen and phosphorus recovery under different operating conditions were quantified. The optimal conditions were identified as 300 degrees C with a CaO dosage of 4 g/100 g sludge, under which both NEE and PEF reached their maximum values. Below this temperature, the thermal solvent extraction reaction was dominated by pyrolysis, whereas at higher temperatures, decomposition and condensation were prone to occur, leading to the formation of polycyclic aromatic hydrocarbons or graphitized structures. With increasing temperature and CaO dosage, the conversion of protein nitrogen to pyridinic nitrogen, pyrrolic nitrogen, and quaternary ammonium compounds was promoted, and these nitrogen species possess enhanced thermal stability. The proportion of apatite phosphorus in the residue increased from 44.6% to 72.6%. A net carbon emission of 389.5 kg CO2-eq/t dry sludge was obtained, which is considerably lower than that of direct sludge incineration.
Phase-change thermal management at nanoscale interfaces is strongly influenced by interfacial energy transport, bubble nucleation, and fluid-surface interactions. The combined use of nanofluids, nanostructured surfaces, and external electric fields provides a promising strategy for boiling heat transfer enhancement, but the underlying atomic-scale coupling mechanism remains insufficiently understood. In this study, molecular dynamics simulations were performed to investigate electric-field-regulated boiling of copper nanofluids on a nanostructured Cu-graphene hybrid surface. Two nanoparticle radii, 1.985 and 2.708 nm, were considered under a fixed particle-number configuration, corresponding to different nanoparticle volume fractions. The results show that the smaller-particle system exhibits earlier nucleation and a stronger later-stage thermal response than the larger-particle system, which may be associated with enhanced particle mobility, more uniform energy redistribution, and easier activation of preferential nucleation regions at the heterogeneous interface. The electricfield effect is strongly dependent on the nanoparticle configuration. For the larger-particle system, the sinusoidal field provides the most evident enhancement, whereas the DC fields show limited or slightly adverse effects. For the smaller-particle system, electric fields do not necessarily advance nucleation onset, but they improve later-stage energy uptake, fluid temperature, and evaporation intensity. Increasing the frequency of the sinusoidal field from 0.05 to 0.3 THz progressively advances nucleation and promotes bubble growth within the investigated range. Local energy mapping and nanoparticle trajectory analysis suggest that the observed enhancement arises from electric-field-induced modulation of interfacial water structure, energy redistribution, and particle-fluid interactions near the heterogeneous Cu-graphene interface. These findings provide atomistic insights into the coupled regulation of nanofluid boiling heat transfer by surface nanostructures and external electric fields.
Refractory high-entropy alloys (RHEAs) have excellent mechanical properties at high temperatures and show significant application potential in extreme environments such as aerospace and nuclear reactors. The inherent high-entropy effect, sluggish diffusion effect, lattice distortion effect, and “cocktail” effect of RHEAs endow them with high strength, excellent oxidation resistance, corrosion resistance, and wear resistance, demonstrating stronger competitive advantages compared to traditional alloys. However, the alloy composition and preparation methods significantly affect the high-temperature mechanical properties and oxidation resistance of refractory high-entropy alloys. This work systematically reviews the effects of different elements and preparation processes on the mechanical properties and oxidation resistance, investigating the mechanisms of mechanical property enhancement, oxidation behavior, and failure mechanisms of RHEAs. Furthermore, this study compares the microstructure and mechanical properties of the same RHEAs prepared using different techniques, analyzing the influence of the processing method on their structure and performance.
In recent years,a new type of fast emerging heterostructure materials(HSMs)has emerged in the field of metal materials.This material is composed of soft and hard regions with significant strength differences due to the heterogeneity of microstructure,crystal structure and composition.It can effectively break the inverted relationship between strength and ductility of traditional homogeneous materials,which mainly depends on the synergistic strengthening effect:hetero-deformation induced(HDI)strengthen-ing and hardening.This paper adequately reviewed the heterogeneous deformation fundamentals,the microstructure characteristics and mechanical properties of various HSMs prepared by different process-ing methods.Meanwhile,we assess the mechanical behavior and influencing factors of the synergistic strengthening effect from the perspective of microscopic strain/stress,damage mechanism and key het-erostructured parameters.In addition,the numerical simulations of HSMs are systematically revealed,which offers theoretical guidance for their quantitative design with the best mechanical properties.This paper aims to construct the relationships among the heterostructures,microscopic deformation mecha-nisms and macroscopic mechanical properties,provide a valuable reference for the optimal heterostruc-tures,and explore crucial scientific issues that warrant further investigation.
