Search Results (431)

Directional control of heat flow is essential for advanced energy and electronic systems, yet strategies for tuning anisotropic phonon transport in low-dimensional materials remain limited. Hollow tellurium (Te) nanowires were synthesized via a solvothermal method and modified through Pd electroless plating to achieve tunable anisotropic thermal transport. Structural analyses confirmed Pd incorporation as nanoscale surface deposits without crystalline Pd phases, while SEM observations revealed cavity enlargement due to galvanic displacement at higher PdCl₂ concentrations. Bulk films prepared by cold pressing exhibited direction-dependent behavior. Thermal conductivities remained nearly unchanged below 2.2 mM PdCl₂, but at 5.5 mM, the in-plane value increased to 2.14 W/(m·K) and the cross-plane value decreased to 0.39 W/(m·K), enhancing the anisotropy ratio from 2.71 to 5.49. This divergence arises from direction-selective phonon scattering, where Pd-rich regions promote in-plane heat flow while junction irregularity suppresses cross-plane transport. These results demonstrate a controllable approach for engineering anisotropic thermal properties in functional energy materials. Full article

The generation of high-purity hydrogen via chemical reaction from hydrogen-rich materials is one of the ways in the alternative energy industry. In this approach, the utilization of catalytic materials that possess the capacity to initiate the decomposition of the starting material and the subsequent release of hydrogen is of paramount importance. In this study, nickel/cobalt-plated copper catalysts (NiCo/Cu) are presented, comprising from 4 to 90 wt.% of cobalt as catalytic materials for hydrogen generation via sodium borohydride (NaBH₄) hydrolysis reaction. The NiCo/Cu catalysts were synthesized via electroless deposition from glycine-based baths, utilizing Ni²⁺ and Co²⁺ ions as metal sources and morpholine borane (MB) as the reducing compound. The catalytic performance in alkaline NaBH₄ hydrolysis was found to correlate with the cobalt loading in the coating. The maximum rate of hydrogen production, which was determined to be 14.22 L min⁻¹ gcat⁻¹, was achieved at 343 K for a catalyst composed of 90 wt.% Co. The reaction proceeded with the activation energy of 52.5 kJ mol⁻¹, while the catalyst exhibited high durability, preserving nearly 88% of its initial activity after five successive reaction cycles. The combination of nickel and cobalt, along with their synergistic effect and high efficiency in the borohydride hydrolysis reaction, makes them promising catalysts. Full article

Although powder metallurgy (PM) is known as a near-net-shape fabrication process, a large number of PM parts need to be machined for dimensional conformance or to produce complex geometrical features that cannot be achieved through compaction. However, due mainly to the presence of porosity, the machinability of PM steels is difficult compared to that of wrought steels and can add 20% or more to the overall fabrication cost of PM parts. Among the various measures known to improve the machinability of PM steels, the addition of machining aids, either as admixed or pre-alloyed constituents, is the most popular. Manganese sulfide (MnS) is by far the most common machinability-enhancing additive used in the PM steel industry. Although it is extremely efficient in improving the machining response of PM steels, MnS is known to have detrimental effects on mechanical properties and corrosion resistance. Thus, the use of MnS involves a compromise between obtaining good machinability at the expense of lower mechanical properties and corrosion resistance. In this study, free graphite particles are introduced as a new additive that not only noticeably improves the machinability of PM steel components but also does not affect their mechanical properties or corrosion resistance. It was found that it is possible to obtain free graphite particles in press-and-sintered PM steel components by coating graphite particles with a metallic layer. This coating prevents graphite from diffusing into the iron matrix while creating metallurgical bonds with the surrounding steel matrix during sintering. In this research, graphite particles were coated with nickel and copper through a cementation process. A heat treatment was then performed on this newly developed material to obtain a more uniform single-layer coating and achieve dimensional changes during sintering that are similar to those measured when MnS is used as a machinability enhancer. The results showed that the tensile properties as well as the fatigue resistance of components made of FC-0208-type PM steel containing admixed copper/nickel-coated graphite particles are not affected by the presence of the latter. Moreover, the corrosion resistance of the samples containing copper/nickel-coated graphite was found to be the same as that of samples without the additive, which is a significant improvement on the case where MnS is used. The performance of the newly developed additive in terms of machinability was also characterized in drilling. It was found that this new additive has an identical machinability-enhancing performance to admixed MnS. Full article

Mg-Zn-Ca bulk metallic glasses (BMGs) have attracted significant attention in the field of biodegradable metallic biomaterials due to their desirable in vivo degradability and high strength. However, their relatively high brittleness limits further practical applications. In this work, porous Fe skeleton-reinforced Mg-Zn-Ca bulk metallic glass composites (BMGCs) were fabricated by pressure infiltration using porous Fe skeleton as the toughening phase and Mg₆₆Zn₃₀Ca₃Sr₁ alloy as the matrix. It was found that electroless copper plating improved the interfacial wettability between molten Mg and Fe, as well as the infiltration-forming capability of the BMGCs. Quasi-static compression tests showed that the BMGC exhibited a compressive strength of 500 MPa, a plastic strain of 0.2%, and a yield strength of 420 MPa, representing a significant improvement over the matrix BMG alloy. The fracture surface displayed a vein-like pattern, indicating a noticeable transition from brittle to ductile fracture behavior. Thus, the porous Fe skeleton-reinforced Mg-Zn-Ca BMGC shows promise as a potential biodegradable biomedical material. Moreover, the preparation route presented here offers a new perspective for developing degradable Mg-Zn-Ca-based BMGCs. Full article

Electroless Ni–P coatings are widely used for corrosion and wear protection, yet their ability to deliver water-based superlubricity and the role of phosphorus content remain insufficiently understood. Here, electroless Ni–P coatings with four P contents (3.4, 6.4, 9.0, and 12.4 wt%) were deposited on GCr15 steel with nearly constant thickness and comparable initial roughness, and were tested against Si₃N₄ balls in neutral 0.5 M NaH₂PO₂ solution. Friction measurements, together with surface topography characterization and tribofilm analysis, were used to link P content with tribofilm chemistry and superlubricity. All coatings achieved macroscale superlubricity, exhibiting steady-state friction coefficients below 0.01, while the running-in time decreased markedly as P content increased. During sliding, the wear tracks underwent mechano-chemical polishing to Sa ≈ 11–12 nm and formed phosphate–silicate tribofilms enriched in P–O and Si–O species on both the coating and the counterface. These findings establish a composition–tribofilm–superlubricity relationship in the Ni–P/NaH₂PO₂ system and demonstrate that P-content optimization is an effective internal design lever to accelerate running-in, mitigate wear, and achieve robust superlubricity under neutral aqueous lubrication. Full article

This study conducts a systematic comparison of binary Ni-P, ternary Ni-W-P, and ternary Ni-Ce-P electroless coatings on 6061-T6 aluminum alloy, focusing on the effects of post-plating heat treatment at 300, 350, and 400 °C. The originality of this work lies in its direct comparison of W and Ce doping under identical conditions and its identification of a critical brittle transition that decouples hardness from wear resistance. All coatings achieved peak hardness at 350 °C, with Ni-W-P reaching approximately 1691 ± 45 HV_0.1 due to Ni₃P precipitation and solid-solution strengthening. However, a key finding is the severe embrittlement of the Ni-P coating at 300 °C, where its wear rate increased by over 50 times despite a hardness increase. Treatment at 400 °C degraded wear performance across all systems, likely due to precipitate coarsening and substrate over-aging. The best overall performance within the tested window was achieved with the Ni-Ce-P coating heat-treated at 350 °C for 1 h, which exhibited a fine nodular structure and reduced the wear rate by 98.9% compared to the bare substrate. These results highlight the importance of balancing hardness and toughness, identifying an optimized processing window for enhancing the tribological performance of lightweight aluminum components. Full article

Silver-coated copper powder, possessing both excellent electrical conductivity and cost advantages, holds broad application prospects in electronic packaging and conductive materials. This study investigates the surface characteristics of copper powders produced by different methods and the effect of surface modification on electroless silver plating. It also analyses the regulatory role of silver content on coating structure and corrosion resistance. Results indicate varying responses to modifiers among different copper powders: contact angle decreased from 52.9° to 50.3° for physically modified copper powder and from 61.9° to 40.9° for chemically modified copper powder, demonstrating significantly improved surface wettability and enhanced silver layer coverage integrity. As silver content increased from 8 wt% to 15 wt%, the silver layer’s compactness increased, enhancing corrosion resistance. The self-corrosion current densities for physically and chemically modified copper powders decreased from 1.285 × 10⁻⁵ and 1.120 × 10⁻⁵ A·cm⁻² to 4.671 × 10⁻⁶ and 5.075 × 10⁻⁶ A·cm⁻², respectively. At 15 wt% silver content, the emergence of free silver particles on the powder surface led to reduced stability. This study elucidates the synergistic regulation mechanism between the properties of the copper powder matrix and the silver coating content on the silver-coated copper powder structure and its corrosion resistance. It provides experimental evidence for the design and application of high-performance silver-coated copper powders. Full article

When fabricating high-entropy alloy particle-reinforced metal matrix composites via friction stir processing, the relatively low heat input led to insufficient interfacial diffusion between the particles and matrix, thereby compromising the composite properties. To address this issue, this study introduced an electroless copper plating step followed by heat treatment to produce Cu-coated HEA particles with an interfacial diffusion layer. These modified particles were then incorporated into a copper matrix via friction stir processing to form composites with an intentionally designed interfacial diffusion layer. The results indicate that the diffusion layer structure contributed to excellent interfacial bonding. The resulting composite exhibited a simultaneous enhancement in both strength and ductility. The tensile strength and elongation reached 372.5 MPa and 34.2%, respectively, representing increases of 20.4% and 54% compared to pure copper. The wear rate of the composite reduced by 33.7% relative to pure copper. Quantitative analysis indicated that the contribution of fine-grain strengthening, Orowan strengthening, dislocation strengthening, and load transfer strengthening to the overall strength was 41.2 MPa, 0.3 MPa, 12.7 MPa, and 15.7 MPa, respectively. Full article

This work presents the fabrication and a systematic evaluation of an ionic polymer-metal composite (IPMC) sensor, focusing on its potential for human motion monitoring and human–computer interaction. The sensor was fabricated via a solution casting and electroless plating process, and its morphology characterized using scanning electron microscopy. The sensing performance was comprehensively assessed, revealing high sensitivity (1.059 mV/N) in the low-pressure region, a fast response time (~50 ms), and reliable stability over prolonged cyclic testing. Furthermore, the sensor can respond to both the magnitude and rate of applied mechanical stimuli. To explore its application potential, the IPMC was tested in scenarios ranging from input pattern recognition—including distinguishing mouse-click patterns, handwritten letters, and binary-encoded presses—to human motion monitoring, where it effectively captured and differentiated signals from facial expressions, swallowing, breathing, and joint movements. The results suggest that the developed IPMC sensor is a promising candidate for applications in wearable health monitoring and flexible interactive systems. Full article

The recycling of a planar composite Pd membrane over a porous stainless-steel support modified with a CeO₂ interlayer (Pd/CeO₂/PSS) was investigated using a leaching-based recycling strategy to recover palladium while maintaining the support’s structural integrity. The membrane was prepared by a continuous flowing electroless pore-plating method (cf-ELP-PP) previously developed by our group. A series of experiments was conducted to evaluate the effect of leaching conditions—temperature, acid concentration, and duration—on Pd extraction and support preservation. Nitric acid (HNO₃) was used as the leaching agent, and the condition of 30 vol.% HNO₃ at 35 °C for 24 h was found to enable complete Pd recovery with limited dissolution of metals from the support. The regenerated supports exhibited an Fe-Cr oxide layer and part of the CeO₂ interface, allowing the elimination of cleaning and calcination steps in the membrane reprocessing workflow. A new Pd-CeO₂ interfacial layer was applied, followed by Pd redeposition via cf-ELP-PP. The resulting recycled membrane exhibited a homogeneous and defect-free Pd layer, with hydrogen permeation performance comparable to that of membranes fabricated on fresh supports. These results demonstrate that Pd membranes can be successfully fabricated on recycled 316L stainless-steel substrates, supporting the viability of this approach for material reuse in membrane technology. Full article

Phosphorus recovery from wastewater as struvite via electrochemical magnesium dosing is a promising approach to address the growing demand for fertilizers. However, its large-scale implementation is often constrained by energy requirements. To overcome this limitation, this study investigates electroless struvite precipitation from cheese whey wastewater using sacrificial magnesium anodes. Under optimal conditions, up to 90% of the phosphorus was recovered within 4–6 h. In this process, spontaneous magnesium dissolution acts as the driving force for phosphorus precipitation and is strongly influenced by the wastewater’s ionic composition. To identify conditions that favor efficient recovery, the effects of ammonium, chloride, and sulfate ions were evaluated by monitoring phosphorus removal and magnesium corrosion behavior. Sulfate ions enhanced magnesium corrosion more strongly than chloride during the initial stages, likely due to stronger coulombic interactions with Mg²⁺ at the electrode–electrolyte interface, whereas chloride ions were more effective at disrupting the passivation layer that develops over time. Based on these observations, a mechanistic interpretation of ion-specific effects on anodic corrosion is proposed. Solid-phase analyses using multiple characterization techniques confirmed struvite formation, with ammonium sulfate and ammonium chloride systems yielding the highest product purity. Overall, these findings improve the understanding of electroless struvite precipitation and highlight its potential as an energy-efficient approach for nutrient recovery. Full article

Hydroxamic acid extractants, such as LIX984, demonstrate high efficiency in extracting nickel from electron-free nickel waste solutions; however, they suffer from a slow extraction rate. This study investigated the effect of adding 2–5 vol.% of three organophosphate extractants (P507, P204, and Cyanex272) to LIX984. The results show that incorporating 2–5 vol.% of P507 or Cyanex272 significantly improves both extraction efficiency and kinetics. The addition of organophosphate extractants increased the extraction rate by 1.5–10 times, indicating a direct correlation between the extractant content and the acceleration of the extraction process, with higher concentrations yielding faster extraction. Compared to the use of LIX984 alone, where nickel extraction efficiency was only 46%, the addition of 5 vol.% P507 increased efficiency to over 99%, with a substantial improvement in extraction rate. Similarly, 2 vol.% P204 achieved a nickel removal efficiency of 99.8%. In non-electroplating waste solutions (pH 4–6), selective removal of iron and zinc impurities was achieved by first adding 2–5 vol.% P204 or P507, followed by adjusting the pH to 6–7 and using a mixture of organophosphate extractants. The spent electroless nickel plating baths were then treated with LIX984 combined with organophosphoric acid extractants, yielding nickel salt solutions of higher purity. Thus, P507, P204, and Cyanex272 serve as effective promoters for the hydroxamic acid extractant LIX984, resulting in both enhanced nickel extraction efficiency and faster extraction kinetics. Full article

Additive manufacturing (AM) offers significant potential for producing complex, cost-effective, and high-performance components in the radio frequency and microwave industry. To significantly benefit from the manufacturing and design freedoms AM offers, AM-based microwave research must shift toward creating designs inherently optimized for AM. This study investigates various AM methods and materials for fabricating a polarizer operating in the K-band, a device widely used in microwave systems and well-suited for AM due to its intricate geometry. Four manufacturing approaches—machining and electroforming, stereolithography and electroless plating, bound metal deposition, and selective laser melting—were evaluated for accuracy, surface quality, and electrical performance. The polarizers were characterized through both single and back-to-back measurements and compared against CST Studio Suite simulations. To better understand discrepancies in performance, further analysis of material properties was conducted using conductivity measurements, skin depth calculations, optical microscopy, and scanning electron microscopy imaging. The results demonstrate that AM techniques can achieve good agreement with simulations and reveal the strengths and limitations of each method, guiding the selection of suitable AM processes for reliable and precise microwave component fabrication in the K-band. Full article

This review article summarizes the most widely used and effective technologies for producing protective and functional bilayer coatings. Particular attention is given to methods such as electroplating and electroless metallization, chemical vapor deposition, thermal spray and vacuum arc deposition, conversion treatments, laser modification, and organic layer deposition. Bilayer architectures are highlighted for their ability to overcome the limitations of single-layer coatings by combining complementary functionalities, resulting in enhanced adhesion, improved corrosion resistance through pore sealing or superhydrophobic surface states, and increased wear and crack resistance. This article is intended for researchers, materials scientists, and engineers engaged in surface engineering, corrosion protection, and advanced manufacturing, providing them with a clear understanding of the mechanisms, advantages, and practical applications of bilayer coatings. By synthesizing recent developments, comparative analyses, and performance data, the review enables readers to make informed decisions about the selection, design, and implementation of bilayer coatings for diverse industrial applications, ranging from aerospace and automotive components to medical devices and energy systems. Full article

Nickel-based superalloys require protective low-activity aluminide coatings to withstand high-temperature oxidation and corrosion in turbine applications. As opposed to conventional gas processes, this study investigates the mechanisms of formation of alternative low-activity nickel aluminide coatings on the René N5 superalloy through electroless nickel pre-deposition followed by slurry aluminizing. Different thicknesses of electroless nickel layers (5, 10, 25 μm) were deposited and subsequently aluminized with varying slurry amounts (5–16 mg/cm²) under controlled heat treatments at 700–1080 °C with heating rates of 5 and 20 °C/min. Without electroless pre-deposition, high-activity coatings with refractory element precipitates formed. With electroless nickel, a precipitate-free low-activity coating developed, with thickness increasing linearly from 15 to 40 μm proportional to the initial electroless layer. An increasing slurry amount raised the overall coating thickness from 27 to 67 μm. Kirkendall porosity formed exclusively during the δ-Ni₂Al₃ to β-NiAl phase transformation at elevated temperature. Reducing the heating rate from 20 to 5 °C/min significantly decreased void formation by promoting more balanced Ni-Al interdiffusion. This work demonstrates that combining electroless nickel with slurry aluminizing provides an efficient route for producing low-activity coatings with controlled microstructure and minimal porosity. Full article