Search Results (125)

Accelerated industrialization and surging energy demands have led to continuously rising atmospheric CO₂ concentrations. Developing sustainable methods to reduce atmospheric CO₂ levels is crucial for achieving carbon neutrality. Concurrently, the rapid development of new energy vehicles has driven a significant increase in demand for lithium-ion batteries (LIBs), which are now approaching an end-of-life peak. Efficient recycling of valuable metals from spent LIBs represents a critical challenge. This study employs conventional hydrometallurgical processing to recover valuable metals from spent LIBs. Subsequently, Ni-doped Co₃O₄ (Ni:Co₃O₄) supported on the natural mineral attapulgite (ATP) was synthesized via a sol–gel method. The incorporation of a small amount of Ni into the Co₃O₄ lattice generates oxygen vacancies, inducing a localized surface plasmon resonance (LSPR) effect, which significantly enhances charge carrier transport and separation efficiency. During the photocatalytic reduction of CO₂, the primary product CO generated by the Ni:Co₃O₄/ATP composite achieved a high production rate of 30.1 μmol·g⁻¹·h⁻¹. Furthermore, the composite maintains robust catalytic activity even after five consecutive reaction cycles. Full article

Novel high-entropy perovskite oxide powders were synthesized using a sol-gel process. The B-site contained five cations: chromium, cobalt, iron, manganese, and nickel. The B-site cations were present on an equiatomic basis. The A-site cation was lanthanum, with calcium doping. The amount of A-site doping varied from 0 to 30 at%, yielding a composition of La_1−xCa_x(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O_3−δ. The resulting perovskite powders were pressurelessly sintered in air at 1400 °C for 2 h. Sintered densities were measured, and the grain structure was imaged via scanning electron microscopy to investigate the effect of doping. Samples were cut and polished, and their resistance was measured at varying temperatures in air to obtain the electrical conductivity and the mechanism that governs it. Plots of electrical conductivity as a function of composition and temperature indicate that the increased configurational entropy of the perovskite materials has a demonstrable effect. Full article

The design of friction materials with integrated friction reduction and wear resistance functions has been a research challenge for many researchers and scholars, based on this problem, this paper proposes a nickel-based hard-soft composite coating structure. With 20CrMo steel as the matrix material, Ni20 powder doped with reinforced phase WC as hard coating material, using laser melting technology to prepare nickel-based hard coating on the surface of 20CrMo. PTFE emulsion and MoS₂ as a soft coating are prepared on the hard coating, and the nickel-based hard-soft composite coating is formed. At 6N-0.3 m/s, the new interface structure obtains the optimum tribological performance, and compared to 20CrMo, the friction coefficient and wear amount are reduced by 83% and 93% respectively. The new friction interface can obtain stable and prominent tribological properties at wide load and low to high speed, which can provide the guidance on the structural design of friction reduction and wear resistance materials. Full article

A novel catalyst with a metal sulfide/hydroxide heterostructure was prepared by introducing sulfur ions into NiMnFe layered hydroxide by a simple hydrothermal method, using a series of characterization methods and electrochemical tests to explore the optimal sulfur ion doping amount. The XPS results show that the introduction of sulfur ions leads to a change in metal electron delocalization, which is conducive to the OER procedure. The newly formed metal sulfide can not only improve the conductivity of NiMnFe LDH/NF electrode materials but also enhance the intrinsic catalytic activity of the materials. The electrochemical performance indicated that the S₂-NiMnFe LDH/NF catalyst required only 205 mV overpotential to provide a current density of 10 mA⁻², and the Tafel slope was only 45.79 mV dec⁻¹. In addition, the large turnover frequency value (1.2614 S⁻¹) reflects the excellent intrinsic activity of the novel catalytic material. Full article

The synthesis method of the Pr-doped CeO₂ catalyst support in Ni/Pr-CeO₂ CO₂ methanation catalysts is varied by changing the type/basicity of the precipitating solution and the hydrothermal treatment temperature. The use of highly basic NaOH as the precipitating agent and elevated hydrothermal treatment temperature (100 or 180 °C) leads to the formation of structured Pr-doped CeO₂ nanorods and nanocubes, respectively, whereas the use of a mildly basic NH₃-based buffer in the absence of hydrothermal treatment (i.e., co-precipitation) leads to an unstructured mesoporous morphology with medium-sized supported Ni nanoparticles. The latter catalyst (Ni/CP_NH3) displays a high surface area, high population of moderately strong basic sites, high oxygen vacancy population, and favorable Ni dispersion. These properties lead to a higher catalytic activity for CO₂ methanation (75% CO₂ conversion and 99% CH₄ selectivity at 350 °C) compared to the catalysts with structured nanorod and nanocube support morphologies, which are found to contain a significant amount of leftover Na from the synthesis procedure that can act as a catalyst inhibitor. In addition, the best-performing Ni/CP_NH3 catalyst is shown to be highly stable, with minimal deactivation during time-on-stream operation. Full article

Lithium-rich layered oxide (LLO) has received extensive attention from researchers due to its high initial discharge capacity (≥250 mAh g⁻¹). However, defects such as its high initial irreversible capacity, voltage decay, and poor rate performance have severely limited its commercialization. These issues arise because the Li₂MnO₃ component in LLO is activated during the initial cycle, leading to the participation of lattice oxygen anions (O²⁻) in redox reactions. This results in irreversible oxygen loss (O₂) and subsequent structural phase transitions. To address these challenges, this study focuses on Li₁.₂Ni₀.₁₃Co₀.₁₃Mn₀.₅₄O₂ as the host material, utilizing abundant exposed (010) plane secondary particles and employing a vanadium (V) doping strategy to enhance electrochemical performance. The V forms strong V-O bonds with the lattice oxygen, effectively suppressing irreversible oxygen loss and improving structural stability. The results demonstrate that the LLO achieves the best electrochemical performance as the doping amount is 1 mol%, and the capacity retention improves from 74.5% (undoped) to 86% (V-doped) after 140 cycles at 0.5 C. Full article

La_1−xCa_x(Co_0.25Cr_0.25Fe_0.25Ni_0.25)O_3−δ perovskite powders were prepared via a sol-gel process. The A-site was doped with calcium, while four elements—cobalt, chromium, iron, and nickel—in equiatomic amounts made up the B-site. The configurational entropy was calculated to increase with the addition of calcium from medium to high entropy. The synthesized powders were heated to 1400 °C in air for 2 h to sinter them. The effect of doping on the resulting sintered materials was observed via density measurements and electron microscopy. The electrical conductivity was measured in air as a function of temperature to 900 °C. Conductivity versus composition indicates that an increase in entropy has a marked effect on electrical conductivity, leading to two distinct relationships with temperature. Full article

This study investigates the interfacial reactions of FeCoNiCr and FeCoNiMn medium-entropy alloys (MEAs) with Sn and Sn-3Ag-0.5Cu (SAC305) solders at 250 °C. The evolution of interfacial microstructures is analyzed over various aging periods. For comparison, the FeCoNiCrMn high-entropy alloy (HEA) is also examined. In the Sn/FeCoNiCr system, a faceted (Fe,Cr,Co)Sn₂ layer initially forms at the interface. Upon aging, the significant spalling of large (Fe,Cr,Co)Sn₂ particulates into the solder matrix occurs. Additionally, an extremely large, plate-like (Co,Ni)Sn₄ phase forms at a later stage. In contrast, the Sn/FeCoNiMn reaction produces a finer-grained (Fe,Co,Mn)Sn₂ phase dispersed in the solder, accompanied by the formation of the large (Co,Ni)Sn₄ phase. This observation suggests that Mn promotes the formation of finer intermetallic compounds (IMCs), while Cr facilitates the spalling of larger IMC particulates. The Sn/FeCoNiCrMn system exhibits stable interfacial behavior, with the (Fe,Cr,Co)Sn₂ layer showing no significant changes over time. The interfacial behavior and microstructure are primarily governed by the dissolution of the constituent elements and composition ratio of the HEAs, as well as their interactions with Sn. Similar trends are observed in the SAC305 solder reactions, where a larger amount of fine (Fe,Co,Cu)Sn₂ particles spall from the interface. This behavior is likely attributed to Cu doping, which enhances nucleation and stabilizes the IMC phases, promoting the formation of finer particles. The wettability of SAC305 solder on MEA/HEA substrates was further evaluated by contact angle measurements. These findings suggest that the presence of Mn in the substrate enhances the wettability of the solder. Full article

In order to meet the demand for high-frequency current sensors in 5G communication and new energy fields, there is an urgent need to develop high-performance nickel-zinc ferrite-based co-fired ceramic magnetic cores. In this study, a nickel-zinc ferrite core based on low temperature co-fired ceramic (LTCC) technology was developed. The regulation mechanism of BaCo_0.06Bi_0.94O₃ doping on the low-temperature sintering characteristics of NiZn ferrites was systematically investigated. The results show that the introduction of BaCo_0.06Bi_0.94O₃ reduces the sintering temperature to 900 °C and significantly improves the density and grain uniformity of ceramics. When the doping amount is 0.75 wt%, the sample exhibits the lowest coercivity of 35.61 Oe and the following optimal soft magnetic properties: initial permeability of 73.74 (at a frequency of 1 MHz) and quality factor of 19.64 (at a frequency of 1 MHz). The highest saturation magnetization reaches 66.07 emu/g at 1 wt% doping. The results show that BaCo_0.06Bi_0.94O₃ doping can regulate the grain boundary liquid phase distribution and modulate the magnetocrystalline anisotropy, which provides an experimental basis and optimization strategy for the application of LTCC technology in high-frequency current sensors. Full article

Solid oxide fuel cells (SOFCs) have become promising devices for converting chemical energy into electrical energy. Altering the microstructure of cathode materials to enhance the activity and stability of the oxygen reduction reaction is particularly important. Herein, Pr_0.5Ba_0.5Co_1−XNi_XO_3+δ with a tetragonal perovskite structure was synthesized through the sol–gel method. The polarization resistance of the symmetrical half-cell with Pr_0.5Ba_0.5Co_0.9Ni_0.1O_3+δ as the cathode was 0.041 Ω·cm² at 800 °C and 0.118 Ω·cm² lower than that of the symmetrical cell with Pr_0.5Ba_0.5CoO_3+δ as the cathode, indicating that the Pr_0.5Ba_0.5Co_1−XNi_XO_3+δ cathode material had high catalytic activity during the electrochemical reaction. The results of electron paramagnetic resonance revealed that the concentration of oxygen vacancies increased as the Ni doping amount increased to 0.15. As a result of the increase in the Ni doping amount, the thermal expansion coefficient of the Pr_0.5Ba_0.5CoO_3+δ cathode material was effectively reduced, resulting in improved matching between the cathode and electrolyte material. The power density of the single cell increased by 69 mW·cm⁻². Therefore, Pr_0.5Ba_0.5Co_1−XNi_XO_3+δ is a promising candidate cathode material for high-performance SOFCs. Full article

Molybdenum disulfide (MoS₂) is a promising catalyst for hydrogen evolution through water electrolysis with low cost and high efficiency, but its hydrogen evolution performance can be further improved. Using sodium molybdate (Na₂MoO₄·2H₂O) and thiourea (NH₂CSNH₂) as raw materials, MoS₂ was prepared by the hydrothermal method. Ni-doped MoS₂(Ni-MoS₂) was prepared by using nickel dichloride dihydrate (NiCl₂·2H₂O) as a Ni source and doping Ni into MoS₂ by the hydrothermal method. Under the conditions of different temperatures (190 °C, 200 °C, and 210 °C) and different Ni doping molar ratios (2%, 3%, and 4%), the optimum temperature and doping ratio of the prepared materials were explored by conducting a hydrogen evolution reaction (HER) by the electrolysis of water. The results showed that the optimum preparation temperature was 200 °C and the optimum molar ratio of Ni doping was 3%. Graphene oxide (GO) was obtained by oxidation of graphite (G), and then Ni-MoS₂/GO was prepared by the hydrothermal method with Ni-MoS₂ and GO. The performance of HER was tested. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectroscopy (XPS). The results show that the composite Ni-MoS₂/GO has good HER performance, which is better than that of MoS₂ or Ni-MoS₂. In 0.5 M H₂SO₄ solution, the η₁₀ is as low as 196 mV, the Tafel slope is 122 mV/dec, the C_dl is 13.98 mF/cm², and it has good stability. The enhancement of electrocatalytic activity is mainly due to the doping of a small amount of Ni, which increases the defects of the catalyst and forms more active sites. GO improves the conductivity of the material. Ni doping and GO compounding promote the HER performance of MoS₂. Full article

Laser cladding technology is an effective method for producing wear-resistant coatings on damaged substrates, improving both wear and corrosion resistance, which extends the service life of components. However, the fabrication of hard and brittle materials is highly susceptible to the problem of cracking. Using gradient transition layers is an effective strategy to mitigate the challenge of achieving crack-free laser-melted wear-resistant coatings. This study presents the cracking issue of laser cladding Ni60B (NiCrBSi) coatings on 38CrMoAl (18CrNiMo7-6) steel by designing a gradient transition layer infused with varying amounts of Ni powder. We examine how different levels of Ni doping in the transition layer influence the fabrication of the Ni60B coating. The results indicate that the cracking mechanism of Ni60B is primarily due to the brittleness and hardness of the fusion cladding layer, which can result in cold cracks under residual tensile stress. Increasing the nickel content in the transition layer reduces the difference in thermal expansion coefficients between the cladding layer and the substrate. Additionally, the nickel in the transition layer permeates the cladding layer due to the laser remelting effect. The physical phase within the cladding layer transitions from the initial CrB, M₇C₃, and γ-Ni solid solution to γ-Ni solid solution and Ni-B-Si eutectic, with a small amount of boride and carbide hard phases. As the nickel doping in the transition layer increases, the proportion of the toughness phase dominated by Ni elements significantly rises, leading to a decrease in the hardness of the fused cladding layer. However, the average hardness of the fusion cladding layer in crack-free samples was measured at 397.5 ± 5.7 HV_0.2, which is 91% higher than that of the substrate. Full article

Water electrolysis is a promising path to the industrialization development of hydrogen energy. The exploitation of high-efficiency and inexpensive catalysts become important to the mass use of water decomposition. Ni-based nanomaterials have exhibited great potential for the catalysis of water splitting, which have attracted the attention of researchers around the world. Here, we prepared a novel Mo-doped NiFe-based layered double hydroxide (LDH) with a nanoarray microstructure on Ni foam. The doping amount of Mo can significantly change the microstructure of the electrocatalysis, which will further affect the oxygen evolution reaction (OER) performance of water splitting. This novel nanomaterial required only an overpotential of 227 mV for 10 mA cm⁻² and a Tafel slope of 54.8 mV/dec in 1 M KOH. Meanwhile, there was no Mo, and the NiFe-LDH needed 233 mV to attain to 10 mA cm⁻². Compared to the NiFe-LDH without Mo, the NiFeMo-LDH nanosheet arrays exhibited enhanced activities with 17.1 mV/dec less Tafel in OER. The good performance of the electrocatalyst is ascribed to the special nanosheet arrays and the heterostructure of the Ni-Fe-Mo system. These features help to increase the active surface, enhancing the efficient charge transfer and the reactive activity in OER. Full article

The titanium dioxide (TiO₂) photocatalyst is an important semiconducting material that exhibits environmental purification functions when exposed to light. Elemental doping of TiO₂ is considered an important strategy to improve its photocatalytic activity. Herein, we have achieved the low-temperature, atmospheric-pressure synthesis of anatase TiO₂ particles with doping of 3d metals (Fe, Co, Ni and Cu) based on the liquid phase deposition technique. All products prepared by adding 3d metals were found to consist of TiO₂ crystals in the anatase phase with a fine protruding structure of about 40 nm on the surface, as was the case without the addition of metal ions. Iron and copper were observed to be incorporated at higher concentrations than cobalt and nickel, with an elemental addition of up to 4 at% and 1 at%, respectively, when 10 mM iron and copper nitrate were applied. Such doping efficiency could be explained by the difference in ionic radius and chemical stability. A narrowing of the optical band gap with doping elements was also observed, and it was found that optical sensitivity could be imparted down to the visible-light region of 2.4 eV (Fe: 4 at% addition). Furthermore, the 3d metal-doped TiO₂ demonstrated in this study was shown to exhibit photocatalytic methane degradation activity. The amount of methane degradation per unit area of the microparticles was twice as great when iron and copper were added, compared to the undoped counterpart. It has been demonstrated that the strategy of doping TiO₂ with 3d metal ions by low-temperature synthesis methods is effective in enhancing carrier dynamics and introducing surface active sites, thus increasing methane degradation activity. Full article

In this study, CoCrFeNiY_x (x = 0, 0.1, 0.2, 0.3) high entropy alloy (HEA) coatings were produced on Ti6Al4V by laser cladding. The influence of Y on the microstructure and mechanical properties of CoCrFeNi HEA coatings was systematically examined. The analysis uncovered that the coatings primarily consist of three principal phases: α(Ti), Ti₂Ni, and TiC. The incorporation of Y led to enhanced lattice distortion, which positively influenced solid solution strengthening. Moreover, grain refinement resulted in a denser microstructure, significantly reducing internal defects and thereby enhancing the coating’s performance. The average microhardness of the CoCrFeNiY_0.2 coating was 702.46 HV_0.2. The wear rates were 1.16 × 10⁻³ mm³·N⁻¹·m⁻¹ in air and 3.14 × 10⁻³ mm³·N⁻¹·m⁻¹ in a neutral solution, which were 27.0% and 30.8% lower than those of the CoCrFeNi coatings, respectively, indicating superior wear resistance. The Y content in the CoCrFeNiY_0.3 coating was excessively high, resulting in the formation of Y-rich clusters. The accumulation of these impurities at the grain boundaries led to crack and pore formation, thereby reducing the wear resistance of the coating. Our study demonstrated that laser cladding an optimal amount of Y-doped CoCrFeNi HEA coatings on the Ti6Al4V substrate significantly enhanced the microstructure and mechanical properties of the substrate, particularly its wear resistance in both air and neutral environments, thereby improving the durability and reliability of titanium alloys in practical applications. Full article