Search Results (215)

Wittichenite Cu₃BiS₃ is a promising thermoelectric material with intrinsically low thermal conductivity owing to its complex crystal structure and strong lattice anharmonicity; however, its thermoelectric performance is limited by low carrier concentration and insufficient electrical conductivity. In this study, Cu₃Bi_1−xSn_xS₃ (x = 0.02–0.06) compositions were designed by substituting Sn⁴⁺ for Bi³⁺ sites, and dense single-phase bulk specimens were prepared using mechanical alloying followed by hot pressing. The effects of Sn doping on charge transport and thermoelectric properties were then systematically examined. Structural analysis confirmed that Sn was successfully incorporated into the Cu₃BiS₃ lattice without secondary phase formation, accompanied by anisotropic lattice contraction associated with the difference in ionic radii between Sn⁴⁺ and Bi³⁺. With increasing Sn content, the carrier concentration increased from approximately 10¹⁶ cm⁻³ to the 10¹⁷ cm⁻³ level, whereas the Hall mobility remained nearly unchanged, resulting in a substantial enhancement in electrical conductivity. Although the Seebeck coefficient decreased with increasing carrier concentration, the reduction was moderate, leading to an improved power factor of 0.10 mW·m⁻¹·K⁻² at 673 K. The thermal conductivity remained low, approximately 0.30–0.40 W·m⁻¹·K⁻¹, across the entire composition range, and the electronic contribution was less than 1%, indicating that heat transport was predominantly governed by the lattice contribution. These results demonstrate that Sn doping effectively improves the electrical transport properties while preserving the intrinsically low lattice thermal conductivity of Cu₃BiS₃. Consequently, a maximum ZT of 0.18 was achieved at 673 K, corresponding to a 64% improvement compared with the undoped specimen. Therefore, this study suggests that carrier concentration control via aliovalent doping is an effective strategy for enhancing the thermoelectric performance of wittichenite. Full article

In this study, polyamide 6/poly(butylene-adipate-terephthalate) (PA6/PBAT) blends, potentially applied as novel self-healing matrices for structural composites, were developed and characterized. The blends were melt-compounded at different PBAT amounts (from 20 up to 50%vol) and hot pressed. Rheological analysis showed a decreased in the storage and loss moduli of PA6 with PBAT, maintaining viscosity levels suitable for conventional melt-processing operations. FT-IR and FESEM observations demonstrated the formation of blends with immiscible morphology and uniformly dispersed PBAT domains. Quasi-static tensile tests showed a progressive decrease in tensile modulus and strength with PBAT, but a strong improvement in the elongation at break. The blend containing 30%vol PBAT showed satisfactory stiffness (2.2 GPa), strength (42 MPa) and elongation at break (10.5%) compared to PA6 (3.4 GPa, 62 MPa and 5.2%), thus this formulation was selected for self-healing assessment. Its repair efficiency was quantified as recovery of the fracture toughness (K_IC) after a thermal treatment at 150 °C for 30–120 min under pressure from 1–3 MPa. The highest healing efficiency (28%) was obtained after 120 min under 1 MPa, conditions at which the PBAT reduced its viscosity and flowed across the crack interface. Therefore, the blend with 30%vol PBAT will be considered in future for the preparation of multifunctional composites with thermal self-healing capability. Full article

Continuous medium-density fiberboard (MDF) production presents a persistent quality-assurance problem: destructive laboratory tests return results too late to prevent off-specification material from accumulating before a corrective response is possible. This study develops an inspection-oriented predictive quality framework using industrial Distributed Control System (DCS) data and automated machine learning, treating the production line as an integrated nine-stage system in which upstream process disturbances propagate through coupled thermomechanical and chemical operations before becoming visible in final panel properties. Two quality targets were modeled across Ultralight (UL) and Standard Thin (STD) panels using 3365 production batches and 327 DCS process variables. The pipeline combined Random Forest imputation, Pearson collinearity filtering ($\left|r\right|\ge 0.8$), target-specific feature selection, and stacked ensemble regression via H2O AutoML. The Vertical Density Profile Index (VSC), a plant-reported scalar derived from X-ray density profiling, was predicted accurately in both product families (test RMSE: 1.39 and 1.78, index units for UL and STD respectively), reflecting its close coupling to drying stability, resin dosing, and thermal conditions. Internal Bond strength (IB) was harder to predict, especially for thin STD panels (test RMSE: 78.93 kPa vs. 27.41 kPa for UL), as core-layer bonding mechanisms are only indirectly observable through standard DCS instrumentation. Model-agnostic feature importance rankings were physically coherent across both product families, with dominant predictors concentrated in drying, resin application, forming, and hot pressing, consistent with the coupled-subsystem nature of MDF quality formation. The historical dataset was dominated by acceptable and over-quality IB production, which precluded conformity classification and sampling-reduction analysis; a prospective dataset with near-threshold observations is required for those evaluations. Within that scope, the framework provides continuous quality estimates, identifies deviations from the desired operating range, and supports inspection planning as a complement to formal laboratory testing. Full article

Cu-deficient bornite Cu_5−xFeS₄ (x = 0–0.20) samples were synthesized by mechanical alloying (MA) followed by hot pressing (HP) to investigate the effects of Cu-site non-stoichiometry on structural evolution, charge transport, and thermoelectric performance. X-ray diffraction confirmed single-phase bornite formation after MA, whereas a minor chalcopyrite CuFeS₂ secondary phase appeared in highly Cu-deficient samples after HP, indicating reduced phase stability during thermal consolidation. Rietveld refinement revealed anisotropic lattice distortion and a gradual decrease in unit-cell volume with increasing Cu deficiency. Hall-effect measurements showed that Cu vacancies act as acceptor defects, increasing the hole concentration to the order of 10¹⁸–10¹⁹ cm⁻³ while reducing carrier mobility through enhanced defect scattering. Consequently, the electrical conductivity increased, whereas the Seebeck coefficient decreased with increasing Cu deficiency. The power factor was enhanced, reaching 0.46 mW m⁻¹ K⁻² at 723 K for Cu_4.80FeS₄. The thermal conductivity remained low at 0.48–0.77 W m⁻¹ K⁻¹ owing to dominant lattice contributions and intensified phonon scattering. As a result, Cu_4.80FeS₄ exhibited a 52% higher ZT at 523 K than stoichiometric Cu₅FeS₄, demonstrating that Cu deficiency is an effective strategy for tuning carrier concentration and defect structure in bornite. Full article

Direct hot press forming (DHPF) of Zn-coated press-hardening steel (PHS) has not been widely adopted by industry due to liquid metal embrittlement (LME), which occurs when coated steel is hot stamped above the Fe-Zn peritectic temperature (~782 °C). In the present study, low-temperature hot stamping was performed on a 2.0 wt% Mn PHS to avoid LME by preventing liquid zinc formation during plastic deformation while achieving target mechanical properties (yield strength (YS) ≥ 1100 MPa and ultimate tensile strength (UTS) ≥ 1500 MPa) and preserving corrosion performance. The enhanced hardenability, indicated by a critical cooling rate (CCR) of 10 °C/s, enabled a predominantly martensitic microstructure following DHPF at 550–700 °C. Tensile testing of samples extracted from U-shaped panels yielded similar results for uncoated and Zn-coated samples, with a YS of ~1170 MPa, a UTS of ~1600 MPa, a uniform elongation (UE) of 0.05, and a total elongation (TE) of 0.09, demonstrating the preservation of baseline mechanical properties in the coated samples. Microstructural analysis confirmed the absence of LME-induced substrate cracking. Additionally, XRD, SEM-BSE, and EDS analyses confirmed Γ-Fe₃Zn₁₀ formation in DHPF galvanized coatings, with volume fractions averaging ~0.6, well above the critical value of 0.15, irrespective of the DHPF temperature, demonstrating the formation of a cathodically protective coating microstructure. Full article

The reliable joining of graphite and Cu holds significant promise for applications in electronic heat dissipation and sliding electrical contacts. However, the substantial differences in their physicochemical properties, poor wettability, and mismatch in coefficients of thermal expansion often result in low joint strength. In this study, a two-step joining strategy combines surface modification with low-temperature sintering, and this is proposed for fabrication of Cu/graphite joints. First, the graphite surface is modified using an AgCuTi active filler alloy under vacuum conditions. Ti preferentially segregates at and reacts with the graphite interface, leading to the formation of an Ag-Cu eutectic modified layer on the graphite surface. Subsequently, low-temperature joining of the modified graphite to a Cu substrate is achieved via a hot-pressing sintering process using a Ag paste. In the sintered joint, the Ag sintered layer forms sound metallurgical bonds with both the Cu substrate and the graphite-modified layer. When the sintering temperature is 250 °C, the joint exhibits a shear strength of 30 MPa, which is significantly higher than that of a directly brazed joint. This strategy effectively reduces thermal residual stress in the joint during cooling and shifts the failure location from the brittle graphite substrate to the ductile Ag sintered layer, thereby substantially enhancing the mechanical performance. Full article

Adhesive-free bonding technology for alkali-treated wood eliminates the need for aldehyde-based adhesives. In this study, poplar wood was treated separately with sodium hydroxide (NaOH) and citric acid. The treated poplar panels were sealed and stored for a predetermined period, followed by pretreatment processes including rinsing and air-drying. Subsequently, deionized water was applied to the surface of the citric acid-treated poplar, which was then laminated with the NaOH-treated poplar to complete the panel assembly. Finally, adhesive-free bonded poplar glulam was fabricated through a hot-pressing process. The bonding strength was evaluated, and the optimal process parameters were determined as follows: NaOH solution mass fraction of 5%, citric acid solution mass fraction of 8%, hot-pressing time of 90 min, hot-pressing temperature of 130 °C, and hot-pressing pressure of 2 MPa. Under these optimal conditions, the bonding strength reached 5.82 MPa. Fourier transform infrared spectroscopy and scanning electron microscopy analyses of the bondline were conducted. The results showed significant degradation of hemicellulose within the bondline, accompanied by slight degradation of lignin and cellulose, which promoted the formation of a molten fiber-encapsulating structure during the hot-pressing process. Full article

Sustaining rice productivity under the dual constraints of freshwater scarcity and low-temperature stress represents a pressing challenge for high-latitude japonica rice systems worldwide. There is an urgent need to develop coupled irrigation–agronomic management strategies that jointly safeguard yield stability and water use efficiency (WUE) in cold-region rice production. In this study, a two-year field experiment was conducted in 2024–2025 on albic soil (Albic Luvisols, WRB; θfc 38.2% v/v, pH 5.80, clayey texture with poor permeability and a propensity for subsurface waterlogging) in the Sanjiang Plain, Heilongjiang Province, China (47°15′ N, 133°28′ E), with nine coupled “irrigation regime × auxiliary practice” treatments, comprising conventional continuous flooding, four-level controlled irrigation (CI) at lower thresholds of 60%, 70%, 75%, and 80% θfc, and their combinations with film mulching (FM) or a humic-acid-based soil amendment (SA). An interpretable machine-learning diagnostic framework was developed, with elastic net (EN) as the primary analytical model and random forest (RF) as a nonlinear control, to simultaneously identify core yield predictors and outlier treatments. The principal findings were: (i) The soil-amendment-coupled 75% θfc CI treatment (SACI) increased grain yield by 12.3% and reduced water input by 17.0% relative to conventional continuous flooding, with WUE reaching 1.801 kg m⁻³, a 35.3% gain over the control (p < 0.05); these improvements were consistent across both individual years (year × treatment interaction: p = 0.601; inter-year rank correlation ρ = 0.967). Lowering the CI threshold below 75% θfc significantly reduced grain yield through diminished effective-panicle retention. (ii) Multi-method consensus analysis (Kendall’s W = 0.871, p < 0.01) identified root volume at the milk stage as the most strongly and consistently associated statistical predictor of yield formation, with convergent mechanistic support from independent rhizosphere evidence (Eh, TTC reductive activity). Definitive causal validation awaits isotope-tracing experiments. (iii) The film-mulching × continuous-flooding treatment (FMCG) was diagnosed as a yield-response outlier (permutation test p = 0.003), three in situ rhizosphere measurements (redox potential, root TTC-reducing activity, and rhizosphere temperature) supported the proposed mechanism of hot–anoxic rhizospheric inhibition. Methodologically, this study develops a four-level evidence convergence framework that integrates intra-model self-consistency, cross-model (EN vs. RF) consensus, independent rhizosphere evidence, and distribution-free permutation testing, with Jackknife+ conformal prediction and companion Monte Carlo simulations (1000 replicates) used to quantify the reliability boundaries under small-sample conditions (n = 27). These findings provide an evidence-based irrigation–soil co-management strategy for cold-region rice production in Northeast China, and the proposed diagnostic paradigm offers a generalizable, reliability-quantified methodological template for interpretable small-sample modeling in multifactorial coupled field experiments. Full article

The abnormal effect of hot isostatic pressing (HIP) on the fatigue properties of DD6 single crystal superalloy was investigated. The results showed that HIP combined with standard heat treatment (SHT) reduced the fatigue life under 880 °C and 800 MPa. HIP treatment eliminated inner shrinkage porosity effectively; however, the amount of micropores increased in the subsequent SHT. Moreover, HIP treatment enlarged the size of γ′ precipitates gradually and altered the morphology of carbides greatly. Small MC carbides decomposed into M₂₃C₆ carbides, and a serrated structure formed on the surface of large-size MC carbides, which led to the positive and negative effects on fatigue properties, respectively, depending on the morphology and size of carbides. Recrystallized microstructures were observed after HIP treatment, accompanied by fine, continuous precipitates along recrystallized grain boundaries. This led to a sharp decline in the elevated-temperature fatigue properties of DD6 superalloy fabricated at a drawing velocity of 150 μm/s. The abnormal decrease in fatigue life of DD6 single crystal superalloy was attributed to micropore formation, coarsening of γ′ precipitates and recrystallization. Thus, it is essential to optimize the HIP treatments in the future development of single crystal superalloy blades. Full article

Wittichenite (Cu₃BiS₃) was synthesized by mechanical alloying (MA) followed by hot pressing (HP), and its phase evolution, thermal stability, charge transport behavior, and thermoelectric performance were systematically examined. X-ray diffraction analysis of the MA powders revealed broadened diffraction peaks, indicating reduced crystallinity and refined crystallite size. After HP consolidation, a well-defined single-phase orthorhombic wittichenite structure was obtained. These results demonstrate that the mechanically induced solid-state synthesis was effectively initiated during MA and subsequently completed through crystallization, defect relaxation, and densification during HP. The MA–HP processed specimens exhibited high relative densities of 94–98% of the theoretical value and a homogeneous microstructure without detectable compositional segregation or grain-boundary enrichment, confirming the formation of a structurally and chemically stable single-phase bulk material. Thermal analysis identified a reversible polymorphic phase transition from P2₁2₁2₁ to Pnma at low temperature, followed by structural relaxation and the onset of partial decomposition at higher temperatures, indicating that Cu₃BiS₃ retains structural integrity below 700 K, which defines the relevant operating window for thermoelectric evaluation. The samples exhibited p-type semiconducting behavior, with electrical conductivity increasing with temperature due to thermally activated hole transport and showing an additional enhancement across the structural transition region. The Seebeck coefficient remained positive over the entire temperature range and decreased gradually with increasing temperature, consistent with semiconductor transport characteristics. The thermal conductivity remained low at 0.30–0.38 W·m⁻¹·K⁻¹, with a negligible electronic contribution, confirming that heat transport is dominated by lattice phonon scattering. As a result of the combined increase in electrical conductivity and intrinsically low thermal conductivity, the dimensionless figure of merit (ZT) increased continuously with temperature and reached 0.17 at 673 K. These results demonstrate that the MA–HP route provides an effective and scalable strategy for producing phase-pure Cu₃BiS₃ with controlled microstructure and reproducible thermoelectric performance. Full article

A thermoreversible dynamic covalent network was constructed in recycled polyethylene terephthalate (RPET) via Diels–Alder (DA) chemistry to enhance mechanical performance, reprocessability, and self-healing. Furan-functionalized RPET (RPET-3F) was first prepared from maleated RPET (RPET-MA), followed by crosslinking with bismaleimide (BMI) at different feed ratios. FTIR spectra confirmed the successful grafting of furan groups and the formation of DA adducts. With increasing BMI content, the gel fraction and crosslink density increased substantially, whereas the swelling ratio decreased, indicating the progressive development of a three-dimensional network. RPET-3F-2B showed the highest network integrity among all samples. DSC analysis revealed a distinct retro-DA dissociation peak at 143 °C and a recrosslinking peak near 124 °C, confirming the thermal reversibility of the DA network. Owing to the optimized network structure, RPET-3F-2B exhibited the best mechanical properties and excellent reprocessability, retaining stable performance after three hot-pressing cycles. After repeated reprocessing, its tensile strength remained 74% higher than that of RPET-MA, while the elongation at break was still improved by about 10%. Moreover, the sample showed efficient thermally induced self-healing at 150 °C, with surface cracks nearly disappearing after 4 h. These results demonstrate that DA chemistry offers a promising route to the high-value reutilization of RPET into recyclable, multifunctional polymer materials. Full article

Twelve white-rot fungal isolates were evaluated for their potential to produce mycelium leather from rice straw, based on growth characteristics, biomass production, and mechanical properties. Among these, Trametes sp. SW25-2 exhibited rapid growth on culture medium and dense mycelial formation on rice straw substrate. The effects of nutrient supplementation, substrate-to-medium ratio, and processing conditions on mycelium-leather formation were systematically examined. No significant differences were observed among different carbon (glucose, maltose, and sucrose) and nitrogen sources (yeast extract, peptone, and ammonium sulphate), indicating that the fungus effectively utilised rice straw as the primary substrate. An optimal ratio of 1 g rice straw to 10 mL culture medium (90.9% moisture content) enabled complete colonisation and the formation of a compact mycelial structure, achieving a maximum tensile strength of 2.78 MPa under optimised hot-pressing conditions (120 °C, 60 s, 1 MPa). Hot-pressing conditions significantly influenced material properties. A higher temperature (120 °C) increased tensile strength but reduced elongation at break, while a lower temperature (60 °C) produced more flexible materials. Scanning electron microscopy revealed that post-treatment and hot pressing transformed the mycelial network into a dense and cohesive structure. The resulting mycelium leather demonstrated suitable physical properties and was successfully fabricated into prototype products, highlighting its potential as a sustainable bio-based material derived from agricultural waste. Full article

Hot-press forming (HPF) steel is a promising lightweight material for automotive applications but suffers from oxidation and reduced corrosion due to high-temperature processing. Aluminized coatings, particularly Al-10Si, are widely used to mitigate this issue. However, HPF heat treatment can create brittle alloy layers with cracks, compromising retention and increasing corrosion risk. This study investigated the effects of Sr addition on the microstructure and corrosion resistance of Al-Si-coated HPF steel. Al-Si and Al-Si-Sr coatings were applied to steel substrates and subjected to heat treatment to produce heat-treated (HT) Al-Si and HT Al-Si-Sr samples. Sr addition refined and spheroidized eutectic Si particles, improved coating homogeneity, and mitigated vertical crack formation in the Al-Fe-Si intermetallic layer. The resulting dense, crack-free alloy layer effectively shielded the Fe substrate from corrosion. After heat treatment, Sr facilitated the formation of a fine lamellar microstructure and a dense, continuous oxide film, enhancing coating retention and sustaining barrier protection. These improvements significantly delayed corrosion propagation into the Fe substrate. Corrosion resistance was evaluated using salt-spray tests (ASTM B117), potentiodynamic polarization, and electrochemical impedance spectroscopy in 3.5 wt.% NaCl solutions. Microstructural analyses revealed that even minimal Sr content (0.05%) considerably enhanced the performance of Al-Si coatings, demonstrating industrial applicability. This study highlights the potential of Sr-added Al-Si coatings in addressing the demand for lightweight and corrosion-resistant materials in the automotive industry, offering a viable solution for high-performance and environmentally sustainable applications. Full article

Single-phase Cu₄Bi₄Se₉ was successfully synthesized through a simple and rapid process combining mechanical alloying (MA) and hot pressing (HP). The phase formation behavior, microstructural evolution, charge transport characteristics, and thermoelectric properties were systematically investigated. X-ray diffraction analysis as a function of MA time confirmed that all powders crystallized into a single orthorhombic phase with space group Pnma. No decompositions or secondary phases were observed after HP sintering, indicating high phase stability. Thermogravimetric and differential scanning calorimetric analyses revealed distinct endothermic peaks at 714–717 K for all samples, corresponding to the onset of the decomposition of Cu₄Bi₄Se₉. Microstructural observations showed that the relative density decreased with increasing HP temperature (>573 K), accompanied by grain growth and pore formation, reflecting the competition between Cu–Se interdiffusion and pore coarsening during high-temperature sintering. Hall effect measurements indicated p-type conduction for all samples, with carrier concentrations on the order of 10¹⁷ cm⁻³ and carrier mobilities of approximately 10² cm² V⁻¹ s⁻¹. With increasing temperature, the electrical conductivity increased monotonically, while the Seebeck coefficient gradually decreased, resulting in a maximum power factor of 0.12 mW m⁻¹ K⁻² at 573 K. The total thermal conductivity remained extremely low, ranging from 0.33 to 0.48 W m⁻¹ K⁻¹, with the electronic contribution accounting for less than 10%, indicating that lattice thermal transport is dominant. The suppressed lattice thermal conductivity is attributed to the combined effects of Cu atomic rattling, asymmetric bonding induced by Bi 6s² lone-pair electrons, and strong anharmonic phonon scattering arising from the complex crystal structure. Consequently, Cu₄Bi₄Se₉ achieved a peak dimensionless figure of merit ZT of 0.19 in the temperature range of 573–623 K, demonstrating that the MA–HP process enables stable phase formation and competitive thermoelectric performance without post-annealing. Full article

Magnesium (Mg) reinforced polylactic acid (PLA) composites have attracted increasing interest for orthopedic implants to solve the insufficient strength of PLA and to utilize the bioactive advantages of Mg ions in promoting bone formation. However, the weak interfacial adhesion between the Mg and PLA limits the applications of the composite. In this study, a dual interfacial enhancement approach was designed to combine surface fluorination with perforation. During hot pressing, molten PLA infiltrates the pores to form a ‘rivet-like’ mechanical interlocking. This structure significantly alters the load transfer and degradation behaviors of the composite. Compared to pure PLA, the dual treatment significantly elevated the bending strength by 49%, alongside an increase in the bending strain from 15% to 25%. Moreover, in vitro degradation tests revealed that this strategy suppresses H₂-induced delamination, and stabilizes both pH and Mg²⁺ release. Consequently, the bending strength remained at 86% after six weeks of in vitro degradation. In addition, the composite exhibits excellent biocompatibility, with MC3T3-E1 cell viability exceeding 90% in 100% extract. These results demonstrate that the reinforced Mg/PLA composite exhibits excellent mechanical properties, degradation stability, and biocompatibility, showing high potential for load-bearing orthopedic fixation applications. Full article