Search Results (118)

Recently, we have described SrMo_1-xMg_xO_3-δ perovskites (x = 0.1, 0.2) as excellent anode materials for solid oxide fuel cells (SOFCs), with mixed ionic and electronic conduction (MIEC) properties. After depositing on the solid electrolyte, they were annealed for sintering at high temperatures (typically 1000 °C), giving rise to oxidized scheelite-type phases, with SrMo_1-xMg_xO_4-δ (x = 0.1, 0.2) stoichiometry. To obtain the active perovskite phases, they were reduced again in the working anode conditions, under H₂ atmosphere. Therefore, there must be an excellent reversibility between the oxidized Sr(Mo, Mg)O_4-δ scheelite and the reduced Sr(Mo, Mg)O_3-δ perovskite phases. This work describes the topotactical oxidation, by annealing at 400 °C in air, of the SrMo_0.9Mg_0.1O_3-δ perovskite oxide. The characterization by X-ray diffraction (XRD) and neutron powder diffraction (NPD) was carried out in order to determine the crystal structure features. The scheelite oxides are tetragonal, space group I4₁/a (No. 88), whereas the perovskites are cubic, s.g. Pm-3m (No. 221). The Rietveld refinement of the scheelite phase from NPD data after annealing the perovskite at 400 °C and cooling it down slowly to RT evidences the absence of intermediate phases between perovskite and scheelite oxides, as well as the presence of oxygen vacancies in both oxidized and reduced phases, essential for their performance as MIEC oxides. The topotactical relationship between both crystal structures is discussed. Full article

The development of thermoelectric modules based on skutterudite materials requires stable, low-resistance interfaces between segments operating at different temperature ranges. This study investigates the microstructure, thermoelectric performance, and thermal stability of the following two joints: In_0.4Co₄Sb₁₂/Co₄Sb_10.8Te_0.6Se_0.6 (n-type) and CeFe₃Co_0.5Ni_0.5Sb₁₂/In_0.25Co₃FeSb₁₂ (p-type), fabricated by pulse plasma sintering (PPS). Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses confirmed the formation of well-bonded interfaces without pores or cracks. Aging at 773 K for 168 h did not result in morphological or chemical degradation, and phase composition remained unchanged according to X-ray diffraction (XRD). Surface Seebeck coefficient mapping and contact resistance measurements showed negligible changes after annealing, confirming electrical stability. To provide context for potential applications, theoretical energy conversion efficiencies were estimated based on measured thermoelectric properties, yielding 13.2% and 10.1% for the n- and p-type segmented legs, respectively. Additionally, measured coefficients of thermal expansion (CTE) indicated low mismatch between jointed materials, supporting good mechanical compatibility. The results demonstrate that the selected material combinations are thermally, chemically, and electrically stable and can be effectively used in segmented thermoelectric legs for intermediate-temperature applications. Full article

This study presents a probabilistic analysis of how thermal conductivity and hardness affect surface integrity in CNC turning, focusing on five engineering materials: Aluminum Alloy 6061, Brass C26000, Bronze C51000, Carbon Steel 1020 Annealed, and Stainless Steel 304 Annealed. Surface roughness and waviness parameters were measured across five zones per material under controlled conditions. Results revealed a strong inverse correlation between thermal conductivity and surface irregularities. Aluminum Alloy 6061 (167 W/m·K, 95 HBW) exhibited the best surface finish (R_a_avg ≈ 1.7664 µm; W_a_avg ≈ 0.8242 µm), while Carbon Steel 1020 Annealed (51 W/m·K, 170 HBW) demonstrated the poorest finish (R_a_avg ≈ 4.0780 µm; W_a_avg ≈ 3.8384 µm). Intermediate materials followed consistent trends: Brass C26000 (R_a_avg ≈ 2.5398 µm; W_a_avg ≈ 1.5364 µm), Bronze C51000 (R_a_avg ≈ 1.8862 µm; W_a_avg ≈ 0.9299 µm), and Stainless Steel 304 Annealed (R_a_avg ≈ 0.9031 µm; W_a_avg ≈ 0.5914 µm). High thermal conductivity materials exhibited narrower parameter distributions (σ_R_a ≤ 0.40 µm), while harder materials showed increased variability (σ_R_a ≥ 0.60 µm). Probabilistic models, validated with high confidence (R² > 0.95), offer predictive insights for optimizing machining strategies. These findings support material-specific process adjustments to enhance surface quality, tool life, and functional reliability in aerospace, automotive, and biomedical applications. Full article

To address the issue of cracking in cold-rolled medium manganese steel caused by the formation of a large amount of martensite after hot rolling, intermediate annealing was conducted prior to cold rolling. The research results indicate that after 1 h of intermediate annealing at a temperature of 700 °C, some martensite is replaced by ferrite and residual austenite, leading to a reduction in rolling stress. The dissolution of cementite leads to an increase in the solubility of the alloying elements in austenite. This increases the volume fraction and carbon content of austenite. Following cold rolling and final heat treatment, the Mn content is higher in both martensite and residual austenite, while it is relatively lower in ferrite. Elevated C and Mn content enhances the stability of the austenite. The elongation of the sample with intermediate annealing increased from 17% to 27%, and the yield strength slightly decreased. During the tensile process, ferrite provides plasticity during the early stage of deformation. As strain increases, martensite begins to deform, making a significant contribution to the material’s strength. The TRIP effect of austenite contributes most of the plasticity, especially the stable thin-film residual austenite. When the residual austenite is exhausted, the incompatibility between ferrite and martensite leads to crack propagation and eventual fracture. Full article

The ultra-thin Invar alloy strips are widely used in the manufacture of the fine masks; cold rolling of such thin strips (<100 μm) poses significant difficulties, primarily due to the limited number of grains within the thickness range. Consequently, it is important to understand the grain structure and property evolutions of the ultra-thin Invar alloy strips during cold rolling. In this study, an annealed Invar36 alloy strip, 100 µm thick, was cold rolled to different thicknesses, and the surface deformation morphologies, cross-sectional grain structure, intracrystalline microstructure and tensile properties of these thin strips were characterized and analyzed. The results show that plastic deformation of the initial annealed equiaxed grains is not uniform, depending on the grain orientation, resulting in different slip bands morphologies, unevenness and increase in roughness. Meanwhile, the grain rotation and rolling texture develop with increasing cold rolling reduction. The dislocation density in the 60% cold-rolled strip is about decuple that of the original annealed strip, and high-density tangled dislocations are formed, making the tensile strength increase from 430 MPa to 738 MPa. Grain refining and proper intermediate annealing are proposed to optimize the thickness uniformity, evenness and surface roughness. Full article

We report the photocatalytic (PC) response of titanium oxide (TiO_x) films grown by reactive DC magnetron sputtering under oblique-angle-deposition (OAD) and subjected to post-deposition flash-lamp-annealing (FLA). Under ballistic growth conditions, OAD yields TiO_x films with either compact or inclined columnar structure as the deposition incidence angle (α) with respect to the substrate normal varies from zero to grazing. On the one hand, films produced for α ≤ 45° display a compact and opaque structure comprising the formation of nanocrystalline cubic titanium monoxide (c-TiO) phase. On the other hand, films grown at larger α (≥60°) display tilted columns with amorphous structure, yielding highly porous films and an increased transparency for α > 75°. For TiO_x films grown at large α, FLA induces phase transformation to nanocrystalline anatase from the amorphous state. In contrast to as-grown samples, FLA samples display PC activity as assessed by bleaching of methyl orange dye. The best PC performance is attained for an intermediate situation (α = 60–75°) between compact and columnar structures. The obtained photoactivity is discussed in terms of the different microstructures obtained by OAD and posterior phase formation upon FLA. Full article

The automotive and aerospace industries increasingly rely on lightweight, high-strength materials to improve fuel efficiency, making the joining of dissimilar metals such as aluminum and steel both beneficial and essential. However, a major challenge in these joints is the formation of brittle intermetallic compounds (IMCs) at the interface, even when using low heat-input solid-state welding methods like friction stir welding (FSW). Furthermore, IMC growth at elevated temperatures significantly limits the service life of these joints. In this study, an intermediate layer of stainless steel was deposited on the steel surface prior to FSW with aluminum. The resulting Al–Steel joints were subjected to heat treatment at 400 °C and 550 °C to investigate IMC growth and its impact on mechanical strength, with results compared to conventional joints without the intermediate layer. The intermediate layer significantly suppressed IMC formation, leading to a smaller reduction in mechanical strength after heat treatment. Joints with the intermediate layer achieved their highest strength (350 MPa) after heat treatment at 400 °C, while conventional joints exhibited their highest strength (225 MPa) in the as-welded condition. At 550 °C, both joint types experienced a decline in strength; however, the joint with the intermediate layer retained a strength of 100 MPa, whereas the conventional joint lost its strength entirely. This study provides an in-depth analysis of the role of IMC growth in joint strength and demonstrates how the intermediate layer enhances the thermal durability and mechanical performance of Al–Steel joints, offering valuable insights for their application in high-temperature environments. Full article

To achieve the optimal planning of grid resource storage for a large-scale distribution network (DN), a cluster partition-based zonal planning method for the DN, considering reliability, is proposed. Firstly, a comprehensive clustering partition index is proposed, which includes the modularity index, power balance index, and node affiliation index. A hybrid genetic–simulated annealing algorithm is employed to perform the cluster partition. Secondly, a three-layer joint expansion planning model based on cluster partitioning is proposed. At the upper level, a route planning model is established to optimize the routing of the cluster. At the intermediate level, a location and capacity planning model for distributed photovoltaics and energy storage is formulated, taking uncertainties into account. By introducing uncertainty parameters, the range of uncertainty for sources and loads is characterized. At the lower level, reliability indices within the clusters are calculated to ensure operational reliability while reducing the conservatism of the optimization outcomes. Finally, the proposed method is applied to a real distribution network in China, demonstrating its effectiveness in improving the economic efficiency of DN planning. Full article

A novel double-impurity doping process for silicon (Si) surfaces was developed, utilizing nanosecond-laser melting of an 11 nm thick gold (Au) top film and a Si wafer substrate in a laser plasma-activated liquid nitrogen (LN) environment. Scanning electron microscopy revealed a fluence- and exposure-independent surface micro-spike topography, while energy-dispersive X-ray spectroscopy identified minor Au (~0.05 at. %) and major N (~1–2 at. %) dopants localized within a 0.5 μm thick surface layer and the slight surface post-oxidation of the micro-relief (oxygen (O), ~1.5–2.5 at. %). X-ray photoelectron spectroscopy was used to identify the bound surface (SiN_x) and bulk doping chemical states of the introduced nitrogen (~10 at. %) and the metallic (<0.01 at. %) and cluster (<0.1 at. %) forms of the gold dopant, and it was used to evaluate their depth distributions, which were strongly affected by the competition between gold dopants due to their marginal local concentrations and the other more abundant dopants (N, O). In this study, 532 nm Raman microspectroscopy indicated a slight reduction in the crystalline order revealed in the second-order Si phonon band; the tensile stresses or nanoscale dimensions of the resolidified Si nano-crystallites envisioned by the main Si optical–phonon peak; a negligible a-Si abundance; and a low-wavenumber peak of the Si₃N₄ structure. In contrast, Fourier transform infrared (FT-IR) reflectance and transmittance studies exhibited only broad structureless absorption bands in the range of 600–5500 cm⁻¹ related to dopant absorption and light trapping in the surface micro-relief. The room-temperature electrical characteristics of the laser double-doped Si layer—a high carrier mobility of 1050 cm²/Vs and background carrier sheet concentration of ~2 × 10¹⁰ cm⁻² (bulk concentration ~10¹⁴–10¹⁵ cm⁻³)—are superior to previously reported parameters of similar nitrogen-implanted/annealed Si samples. This novel facile double-element laser-doping procedure paves the way to local maskless on-demand introductions of multiple intra-gap intermediate donor and acceptor bands in Si, providing related multi-wavelength IR photoconductivity for optoelectronic applications. Full article

The current intensive development of steelmaking is being impeded by a scarcity of pure scrap. The potential to replace pure scrap with metallized raw materials that are naturally alloyed with vanadium and titanium, such as annealed unfluxed titanomagnetite pellets, could facilitate the achievement of key objectives in metallurgical development, particularly in the smelting of electric steel. The objective of this research was to produce annealed and metallized pellets from titanomagnetite concentrate under laboratory conditions, with the intention of further processing them as a commercial product in a blast furnace or as an intermediate product for the production of hot briquetted iron (HBI). The results demonstrate that pellets derived from titanomagnetite concentrate exhibit sufficient compressive strength (up to 300 kg/pellet) and a degree of metallization exceeding 90%, which aligns with the requirements for electric steelmaking. The suitability of pellets derived from titanomagnetite concentrate for use in both blast furnaces and metallization processes has been corroborated. Full article

In this work, rice-husk-derived biochar (RBC) was synthesized by using simple one-step pyrolysis strategies and served as catalysts to activate peroxymonosulfate (PMS) for degrading sulfamethoxazole (SMX). When the annealing temperature (T) = 800 °C, RBC₈₀₀ exhibits the typical hardwood structure with several micropores and mesoporous. Furthermore, RBC₈₀₀ obtains more defect sites than RBC₆₀₀, RBC₇₀₀, and RBC₉₀₀. In the RBC₈₀₀/PMS system, the removal rate of the SMX reached 92.0% under optimal conditions. The kinetic reaction rate constant (k_obs) of the RBC₈₀₀/PMS system was 0.009 min⁻¹, which was about 1.50, 1.28, and 4.50 times that of the RBC₆₀₀/PMS (k_obs = 0.006 min⁻¹), RBC₇₀₀/PMS (k_obs = 0.007 min⁻¹), and RBC₉₀₀/PMS (k_obs = 0.002 min⁻¹) systems, respectively. In the RBC₈₀₀/PMS system, sulfate radical (SO₄^•−) is the main active species. Compared with other active sites, the hydroxyl group (C-OH) on the surface of RBC₈₀₀ interacts more strongly with PMS, which is more likely to promote the stretching of the O-O bond of the PMS, thus breaking into the activated state and significantly reducing the activation energy required for reaction. The degradation intermediates of SMX were speculated, and the toxicity analysis was conducted. Generally, this work reveals in depth the interaction between reactive sites of biochar-based catalysts and PMS at the molecular level. Full article

This paper studies the structural parameters and electrophysical properties (dielectric and piezo electric, as well as currents of thermostimulated depolarization) of samples of composition 0.20BiScO₃·0.45PbTiO₃·0.35PbMg_1/3Nb_2/3O₃ (or in short 0.20BS·0.45PT·0.35PMN) obtained by ceramic and melt-hardening methods of synthesis. In the ceramic method, the samples were obtained from the starting oxides by two-stage firing. In the melt method, amorphous precursors were first obtained from heat-treated and non-heat-treated starting oxide mixtures by melting and subsequent quenching under sharply gradient temperature conditions. Samples were obtained after grinding, pressing, and thermal annealing of the synthesized precursors, and four types of samples differing in size and shape of the intermediate precursor particles (crystallites) were obtained. The X-ray phase analysis showed that the predominant phase in the studied samples is the perovskite phase; in both types of samples, up to 5 wt.% of impurity phase with pyrochlore structure was also present. The samples of 0.20BS·0.45PT·0.35PMN exhibit dielectric properties characteristic of relaxor ferroelectrics, and the polarized samples exhibit a pronounced piezo effect with a piezo modulus value of d₃₃~200 pC/N. A comparative analysis of the properties of the samples obtained by different methods has been carried out. The essential advantage of the melt method is that its use allows obtaining varieties of four kinds of ferroelectric relaxors and reduces the time of synthesis of samples by 2–3 times. Full article

Ethyl maltol was investigated using matrix isolation infrared spectroscopy and DFT calculations. In an argon matrix (14.5 K), the compound was found to exist in a single conformer (form I), characterized by an intramolecular hydrogen bond with an estimated energy of ~17 kJ mol⁻¹. The IR spectrum of this conformer was assigned, and the molecule’s potential energy landscape was explored to understand the relative stability and isomerization dynamics of the conformers. Upon annealing the matrix to 41.5 K, ethyl maltol was found to predominantly aggregate into a centrosymmetric dimer (2× conformer I) bearing two intermolecular hydrogen bonds with an estimated energy of ca. 28 kJ mol⁻¹ (per bond). The UV-induced (λ > 235 nm) photochemistry of the matrix-isolated ethyl maltol was also investigated. After 1 min of irradiation, band markers of two rearrangement photoproducts formed through the photoinduced detachment-attachment (PIDA) mechanism, in which the ethyl maltol radical acts as an intermediate, were observed: 1-ethyl-3-hydroxy-6-oxibicyclo [3.1.0] hex-3-en-2-one and 2-ethyl-2H-pyran-3,4-dione. The first undergoes subsequent reactions, rearranging to 4-hydroxy-4-propanoylcyclobut-2-en-1-one and photofragmenting to cyclopropenone and 2-hydroxybut-1-en-1-one. Other final products were also observed, specifically acetylene and CO (the expected fragmentation products of cyclopropenone), and CO₂. Overall, the study demonstrated ethyl maltol’s high reactivity under UV irradiation, with significant photochemical conversion occurring within minutes. The rapid photochemical conversion, with complete consumption of the compound in 20 min, should be taken into account in designing practical applications of ethyl maltol. Full article

The impact of wet treatment using an (NH₄)₂S-alcohol solution on the interface state of the p-GaN/Ni/Au/Pt contact system and laser diode processing was investigated. Sulfur wet cleaning resulted in reduced surface roughness and contact resistivity. The lowest specific contact resistance (ρ_c < 1 × 10⁻⁴ Ω·cm²) was achieved with samples treated with an (NH₄)₂S-isopropanol solution, whereas the highest resistivity (ρ_c = 3.3 × 10⁻⁴ Ω·cm²) and surface roughness (R_a = 16 nm) were observed in samples prepared by standard methods. Annealing the contact system in an N₂ + O₂ + H₂O atmosphere caused degradation through species inter-diffusion and metal-metal solid solution formation, irrespective of the preparation method. Standard prepared substrates developed a thin GaN-Au intermediate layer at the interface after heat treatment. Enhanced adhesion and the absence of GaN decomposition were observed in samples additionally cleaned with the (NH₄)₂S-solvent solution. Complete oxidation of nickel to NiO was observed in samples that underwent additional sulfur solution treatment. The intensity of metal species mixing and nickel oxidation was influenced by the metal diffusion rate and was affected by the initial state of the GaN substrate obtained through different wet treatment methods. Full article

Standard AA5083 (ZSE000), AA5083 modified with 0.3 wt.% Zr and 0.3wt.% Sc (ZSE330) and AA5083 modified with 0.3 wt.% Zr, 0.2wt.% Sc and 0.1wt.%Er(ZSE321) sheets were fabricated through a short process (including a simulated twin-belt continuous casting, subsequent direct rolling, intermediate annealing, cold rolling and stress-relief annealing) to systematically investigate the influence of partially substituting Er for Sc on the microstructure, mechanical properties and corrosion resistance of short-processed Al-4.7Mg-0.6Mn-0.3Zr-0.3Sc sheets. The results show that ZSE321 presents the optimal tensile properties (UTS: 541 MPa; 0.2%PS: 469 MPa and EF:7.7%) among the three experimental sheets. This is attributed to significant grain refinement, the inhibition of the recrystallization and promotion on the precipitation of Al₃(Sc, Zr, Er) nanoparticles. Furthermore, the corrosion properties of the experimental sheets were also explored in this study, and the short-processed ZSE321 sheet presents the optimum corrosion resistance. Full article