Search Results (659)

The development of sustainable encapsulation materials with tunable thermomechanical properties remains a critical challenge for photovoltaic reliability. Currently, the mainstream encapsulant for polycrystalline silicon solar cells is crosslinked EVA (Ethylene-Vinyl Acetate), which complicates the end-of-life recycling and reuse of modules. There is an urgent need to develop a novel encapsulant that combines excellent barrier properties with thermoplastic recyclability. Herein, we report a novel series of thermally decomposable CO₂-based thermoplastic polyurethane (PPC-TE) films engineered through the rational design of soft and hard segments. Utilizing polycarbonate diol (PPCDL) and polyether glycol (PEG) as soft segments, we systematically tailor material properties by modulating PEG-to-PPCDL ratios (5–20 wt%) and PEG molecular weights (1000–4000 g/mol). The optimized PPC-TE films exhibit excellent transmittance (>90%), adjustable glass transition temperature (T_g: 35.1 °C~11.6 °C), and remarkable mechanical adaptability (51~92 HA). The PPC-TE films exhibit water vapor permeability (WVP) as low as 14.8 g·mm·m⁻²·day⁻¹ and oxygen permeability (OP) of 4.13 cc·mm·m⁻² day⁻¹ at 15 wt% PEG content, surpassing commercial ethylene–vinyl acetate (EVA) encapsulants. Notably, these films demonstrate fully thermal decomposition above 350 °C, facilitating eco-friendly photovoltaic device recycling. Superior adhesion to glass substrates is evidenced by peel strengths up to 37 N/cm (PPC-TE2000-20) and the shrinkage rate is as low as 3%. This work contributes to improving the long-term stability of solar cells and has the potential for large-scale production. Full article

High-performance cutting materials are central to modern production engineering. Cemented carbides dominate industrial tooling, while polycrystalline boron nitride (PcBN) is established for hard turning and finishing nickel-based alloys. The associated tool manufacturing chains are energy- and effort-intensive, motivating approaches that reduce material losses and primary energy demand. This study quantifies energy consumption across the production of solid carbide cutting tools with a focus on near-net-shape green machining, its impact on subsequent grinding and material recirculation. It also quantifies energy consumption for regrinding PcBN cutting tools. Power measurements were recorded during green machining and tool grinding of cylindrical versus pre-contoured (green-machined) blanks, including coolant units for the carbide tools during operation. Tool performance of the carbide tools was assessed via milling tests in 42CrMo4; PcBN reground tools were evaluated in Inconel 718. In the process chain of carbide tool production, specific energy decreased from 6.98 to 6.36 kWh/kg (−8.88%) despite +0.461 kWh/kg for green machining; direct recirculation of green-machined material saved an additional 5.861 kWh/kg. Reground PcBN inserts achieved comparable tool life to new tools while reducing energy by ≈85% per insert. The dominant levers for energy reduction are shorter grinding times in the presence of high machine and coolant base loads and systematic regrinding of high-embodied-energy tools. Full article

The magnetic properties of materials similar to Nd-Fe-B permanent magnets are highly sensitive to microstructure. Using Hybrid Monte Carlo micromagnetics simulations, we systematically investigate how grain boundary (GB) and grain crystallographic orientation affect coercivity (H_c) and remanence (M_r). A polycrystalline model with independently adjustable microstructural parameters is constructed via Voronoi tessellation. Our results show that increasing GB width from 2 nm to 10 nm reduces Hc by 32% and M_r by 16%. Grain boundary acts as both a nucleation site and pinning center: a wider GB facilitates reverse domain nucleation, especially at the triple junctions. However, domain wall propagation is underpinned by GB during the propagation process. For a thick GB, H_c decreases with increasing GB saturation magnetization (M_s′), because the thick weakly magnetic layer weakens exchange coupling between adjacent grains, shifting the reversal behavior from collective switching to more localized nucleation. Increasing the average easy-axis tilt angle reduces H_c, as the misalignment lowers the effective anisotropy component along the applied field direction, facilitating magnetization reversal. These findings confirm the importance of GB and texture control in optimizing the magnetic performance of Nd-Fe-B permanent magnets, offering references for experimental investigations. Full article

HfO₂ films have become a critical component for advanced electronics and a wide range of applications. However, their implementation requires control of their microstructure and defects, which often act as charge carrier traps, leading to leakage current in devices and hindering their dielectric properties. Here, we deposit HfO₂ thin films by atomic layer deposition (ALD) on sapphire, Ga₂O₃, and InGaO₃ substrates at low temperature and investigate the dependence of their crystal structure on substrate type, annealing, and thickness. X-ray diffraction measurements showed that alloying Ga₂O₃ with a modest amount of Indium transferred HfO₂ films from amorphous to polycrystalline, an important finding that may be applicable to the deposition of other material systems. The study also presents an interesting approach to measuring shallow and deep traps formed in the films and shows how to control their levels and distributions in the band gap. The measurements reveal that the difference in band gap between the substrate and film, as well as the presence of impurities, strongly influences trap densities and depths. Electron paramagnetic resonance (EPR) measurements were performed to probe the electronic structure of specific point defects detectable by EPR and to correlate these results with trap measurements. Full article

This study presents experimental evidence of random magnetic behavior in modified barium hexaferrites. We demonstrate a significant shift in the magnetic properties of these materials upon the incorporation of divalent cations (Ni²⁺, Cu²⁺, Mn²⁺), which produces the formation of ceramic nanocomposites. X-ray diffraction, scanning electron microscopy, and laser diffraction reveal that these systems comprise micron-sized clusters formed by sintering polycrystalline nanoparticles. The cation incorporation occurs randomly across each sample, creating conditions conducive to random anisotropy magnetism. We confirm this behavior in our samples by fitting the magnetization data near saturation to a corresponding theoretical model. Additionally, we investigate the microwave absorption capabilities of these systems in the GHz range by calculating the reflection loss coefficient of mm-thick samples using transmission-line theory. The results predict broad (up to 2 GHz) and high (around 60 dB on average) absorption signals. In the case of the thinnest samples (1–2 mm), the Cu-substituted system presents broader absorption bandwidths than the pure hexaferrite and, therefore, proves to be more efficient for stealth applications in lightweight sectors. These findings suggest ceramic nanocomposites are promising candidates for random anisotropy magnets, highlighting their potential as efficient microwave absorbers, consistent with recent theoretical predictions. Full article

Brittle materials such as single crystals, polycrystalline ceramics, and amorphous glass are indispensable in modern industry. Driven by improvements in equipment performance, the required fabrication precision for optical elements and devices has reached nanoscale and is steadily advancing toward atomic level. Despite their outstanding physical and chemical properties, fabricating a defect-free surface with nanometer-level roughness on brittle materials is challenging due to microcracking, brittle fracture and severe tool wear. In recent years, field-assisted cutting has emerged to overcome the bottleneck in ultra-precision cutting of brittle materials. This review summarizes investigations of material removal mechanisms of brittle materials in ultra-precision cutting and surveys representative field-assisted cutting technologies—including laser, vibration, magnetic field, and ion implantation assisted cutting—highlighting how these fields broaden ductile-regime machining and suppress the machining-induced defects. This review further discusses the emerging multi-field coupling strategies and outlines future research directions in machining mechanisms to enable high-efficiency, low-damage, and high-consistency manufacturing of brittle materials. Full article

Superhydrophobic materials have clear potential for mitigating rain/humidity-induced damage to cultural heritage. In the present study, the wetting properties of Paraloid B72 were tailored to achieve superhydrophobicity by incorporating modified calcium carbonate (CaCO₃) nanoparticles (NPs). B72 is a well-established conservation product while CaCO₃ is chemically compatible with calcareous materials commonly found in cultural heritage buildings and objects. Initially, the wettabilities of CaCO₃ NPs, functionalised with caproic (C6), caprylic (C8), lauric (C12), myristic (C14), palmitic (C16), and stearic (C18) acid, were evaluated by measuring water contact angles (CAs) on NP pellets. For NPs with short hydrocarbon chains, CA increased with chain length, from 66.3° for CaCO₃-C6 to 118.0° for CaCO₃-C12 NPs. For NPs with longer chains, CA remained stable and around 118°. Based on these results, CaCO₃-C12 NPs were selected for further investigation and subjected to transmission electron microscopy analysis, which revealed chain-like agglomerates of aggregated nanocrystallites (5–10 nm) forming 40–150 nm polycrystalline NPs. Scanning transmission electron microscopy combined with elemental mapping revealed a homogeneous distribution of Ca, C, and O within the NPs. Next, CaCO₃-C12 NPs were dispersed in B72 solutions and sprayed onto limestone, which was employed as a model calcite-rich substrate. At optimal NP concentration, the resulting composite coating exhibited superhydrophobicity (CA > 150°), while it induced minimal colour alteration to limestone and effective resistance to capillary water absorption. The fluorine-free coating also demonstrated good durability against UV exposure, drop impact, salt attack, freeze–thaw cycles, tape peeling, drop pH variations, and thermal treatment. Full article

Nanoparticles of ferrimagnetic magnetite (Fe₃O₄) are cornerstones of modern nanoscience and technology, primarily due to their superparamagnetic behavior. Beyond traditional applications in magnetorheology and magnetic hyperthermia, these materials are increasingly vital in fields like active matter, where precise surface fine-tuning is crucial. While coating isotropic, quasi-spherical magnetite nanoparticles with silica is a well-established and versatile route towards functionalization, transferring this achievement to nanorod systems remains a significant challenge. Successful coating of these high-aspect-ratio geometries would allow to exploit the direction-dependent properties and increased magnetic anisotropies. However, current literature largely focuses on polycrystalline rods composed of small, clustered subunits, which limits their magnetic potential. This work describes a breakthrough in the homogeneous silica coating and stabilization of monocrystalline magnetite nanorods. We demonstrate that the superior magnetic properties of these “naked” monocrystalline rods induce strong dipole-dipole interactions, which trigger aggregation and typically prevent the isolation of individual and homogeneously coated core-shell nanoparticles. By investigating the specific mechanisms of this aggregation, we established a robust coating procedure that yields the desired isolated particles. Critically, we show that the magnetite nanorods retain their monocrystalline integrity within the silica shell, thereby preserving the enhanced magnetic properties of the original nanocrystals. Full article

Elastic wave scattering in polycrystalline materials has been a long-lasting topic in seismology and physical acoustics. Numerous analytical scattering models have been reported for polycrystals with random grain orientations. However, the elastic wave scattering in polycrystals with a preferred grain orientation (crystallographic texture) has not been well studied. This study develops a general ultrasonic scattering model that correlates the scattering coefficients and attenuation coefficients with orientation distribution coefficients (ODCs) for polycrystalline materials with a crystallographic texture. These models are valid for aggregates of triclinic grains with arbitrary texture symmetry. Since different terminologies for orientation distribution functions (ODFs) are adopted in quantitative texture analysis, the relations between different terminologies are also summarized in this study. Furthermore, for two special cases—hexagonal polycrystalline materials with a fiber texture and cubic polycrystalline materials with orthotropic texture symmetry—explicit expressions for the ultrasonic backscattering coefficient through ODCs are derived. The explicit relationship between ultrasonic backscattering and ODCs not only manifests how the individual texture coefficients impact ultrasonic scattering but also makes it possible to determine ODCs up to the eighth order experimentally from ultrasonic scattering measurements. This type of forward model also can be applied to the microstructure characterization of textured polycrystals. Full article

The operational ability of a unit or mechanism depends mainly on the quality of the mechanically produced working surfaces. Many materials can be assigned to a group of hard-to-cut materials that includes titanium- and aluminum-based alloys, a new class of heat-resistant alloys, SiCp/Al composites, hard alloys, and other alloys. The difficulties in their machining are related not only to the high temperatures achieved on the contact pads under mechanical load and the extreme cutting conditions but also to the properties of those materials, which affect the adhesion of the chip to the tool faces, hindering chip flow. One of the possible solutions to reduce those effects and improve the operational life of the tool, and as a consequence, the final quality of the working surface of the unit, is texturing the rake face of the tool with microgrooves or nanogrooves, microholes or nanoholes (pits, dimples), micronodes, cross-chevron textures, and other microtextures, the depth of which is in the range of 3.0–200.0 µm. This review is addressed at systematizing the data obtained on micro- and nanotexturing of PCD tools for cutting hard-to-cut materials by different techniques (fiber laser graving, femto- and nanosecond laser, electrical discharge machining, fused ion beam), additionally subjected to fluorination and dip- and drop-based coatings, and the effect created by the use of the textured PCD tool on the machined surface. Full article

Tin selenide (SnSe) is a sustainable, lead-free IV–VI semiconductor whose layered orthorhombic crystal structure induces pronounced electronic and phononic anisotropy, enabling diverse energy-related functionalities. This review systematically summarizes recent progress in understanding the structure–property–processing relationships that govern SnSe performance in thermoelectric and optoelectronic applications. Key crystallographic characteristics are first discussed, including the temperature-driven Pnma–Cmcm phase transition, anisotropic band and valley structures, and phonon transport mechanisms that lead to intrinsically low lattice thermal conductivity below 0.5 W m⁻¹ K⁻¹ and tunable carrier transport. Subsequently, major synthesis strategies are critically compared, spanning Bridgman and vertical-gradient single-crystal growth, spark plasma sintering and hot pressing of polycrystals, as well as vapor- and solution-based thin-film fabrication, with emphasis on process windows, stoichiometry control, defect chemistry, and microstructure engineering. For thermoelectric applications, directional and temperature-dependent transport behaviors are analyzed, highlighting record thermoelectric performance in single-crystal SnSe at hi. We analyze directional and temperature-dependent transport, highlighting record thermoelectric figure of merit values exceeding 2.6 along the b-axis in single-crystal SnSe at ~900 K, as well as recent progress in polycrystalline and thin-film systems through alkali/coinage-metal doping (Ag, Na, Cu), isovalent and heterovalent substitution (Zn, S), and hierarchical microstructural design. For optoelectronic applications, optical properties, carrier dynamics, and photoresponse characteristics are summarized, underscoring high absorption coefficients exceeding 10⁴ cm⁻¹ and bandgap tunability across the visible to near-infrared range, together with interface engineering strategies for thin-film photovoltaics and broadband photodetectors. Emerging applications beyond energy conversion, including phase-change memory and electrochemical energy storage, are also reviewed. Finally, key challenges related to selenium volatility, performance reproducibility, long-term stability, and scalable manufacturing are identified. Overall, this review provides a process-oriented and application-driven framework to guide the rational design, synthesis optimization, and device integration of SnSe-based materials. Full article

In this study, we investigated the electrochemical reduction of carbon dioxide (CO₂) using a phosphorus-doped polycrystalline diamond (PDD) electrode and compared it with a conventional boron-doped diamond (BDD) electrode. In the reduction reaction of CO₂ in a 0.5 M KCl aqueous solution, the PDD electrode showed high selectivity for formic acid production over a wide potential range. This tendency was particularly evident at potentials below −1.8 V (vs. RHE). Moreover, at more negative potentials of −2.4 V and −2.6 V, formic acid remained the dominant product, while hydrogen evolution was the main reaction on the BDD electrode at the negative potentials. Similarly, in electrochemical reduction using an 0.1 M KClO₄ aqueous solution, carbon monoxide was confirmed to be a major product, and hydrogen generation was effectively suppressed in a more negative potential range. In other words, PDD is a promising electrode material that can efficiently convert CO₂ into valuable chemicals while suppressing hydrogen evolution, even in negative potential regions. Full article

A $5\mathrm{n}\mathrm{m}$ thick polycrystalline $N{i}_{81}F{e}_{19}$ film was sputter-deposited onto a circular 3-inch diameter, $390\mathsf{\mu }\mathrm{m}$ thick single-crystal wafer with $Si{O}_2$ surface layers. The magnetoresistance (MR) of the sample was analyzed as a function of applied DC magnetic field and temperature using the Van der Pauw technique. Magnetic measurements were carried out over a temperature range of 25 °C to 350 °C using a Lake Shore Hall Effect Measurement System (HEMS). An external magnetic field ranging from $+14\mathrm{k}\mathrm{G}$ to $-14\mathrm{k}\mathrm{G}$ was applied at each temperature value to observe changes in resistance. Hall coefficients and resistance were obtained by applying current in both directions with different contact configurations. Machine learning techniques, including Random Forest Regression, were employed to predict magnetoresistivity beyond 350 °C; the best-performing model achieved $R^2$ values up to $0.9449$ with MSE as low as $0.0071$, and enabled Curie temperature estimation with $T_C\approx 590.97°\mathrm{C}$. This study highlights the potential of machine learning in accurately forecasting material properties beyond experimental limits, providing enhanced predictive models for the magnetoresistive behavior and critical temperature transitions of $N{i}_{81}F{e}_{19}$ . Full article

The solid-state synthesis of alkali–tantalum(V) oxyfluorides KTa₂O₅F and CsTa₂O₅F was revisited with the aim of streamlining their preparation as single-phase polycrystalline solids. Alkali fluorides (KF, CsF) and trifluoroacetates (KH(CF₃COO)₂, CsH(CF₃COO)₂) and tantalum oxide (Ta₂O₅) were used as precursors. Reaction temperatures were optimized by means of thermal analysis coupled with powder X-ray diffraction. Phase-pure KTa₂O₅F was obtained by heating stoichiometric mixtures of KF + Ta₂O₅ and KH(CF₃COO)₂ + Ta₂O₅ at 900–1000 °C in alumina crucibles under ambient atmosphere. Similar conditions were employed to synthesize phase-pure CsTa₂O₅F from a stoichiometric mixture of CsF + Ta₂O₅ heated to 800 °C. On the other hand, the preparation of CsTa₂O₅F from a mixture of CsH(CF₃COO)₂ + Ta₂O₅ required an excess of the trifluoroacetate precursor to obtain the targeted oxyfluoride as the sole crystalline phase. Results presented herein demonstrate that mixed-metal oxyfluorides previously thought to be synthetically challenging may be synthesized via facile solid-state reactions without the need for specialized containers and stringent conditions. In addition to streamlined synthetic routes to alkali– tantalum(V) oxyfluorides, a neutron powder diffraction study of the crystal structure of KTa₂O₅F is presented to fill a gap in crystallographic databases commonly accessed by materials and solid-state chemists. Full article

With the discovery of amorphous oxide semiconductors, a new era of electronics opened. Indium gallium zinc oxide (IGZO) overcame the problems of amorphous and poly-silicon by reaching mobilities of ~10 cm²/Vs and demonstrating thin-film transistors (TFTs) are easy to manufacture on transparent and flexible substrates. However, mobilities over 30 cm²/Vs have been difficult to reach and other materials have been introduced. Recently, polycrystalline In₂O₃ has demonstrated breakthroughs in the field. In₂O₃ TFTs have attracted attention because of their high mobility of over 100 cm²/Vs, which has been achieved multiple times, and because of their use in scaled devices with channel lengths down to 10 nm for high integration in back-end-of-the-line (BEOL) applications and others. The present review focuses first on the material properties with the understanding of the bandgap value, the importance of the position of the charge neutrality level (CNL), the doping effect of various atoms (Zr, Ge, Mo, Ti, Sn, or H) on the carrier concentration, the optical properties, the effective mass, and the mobility. We introduce the effects of the non-parabolicity of the conduction band and how to assess them. We also introduce ways to evaluate the CNL position (usually at ~E_C + 0.4 eV). Then, we describe TFTs’ general properties and parameters, like the field effect mobility, the subthreshold swing, the measurements necessary to assess the TFT stability through positive and negative bias temperature stress, and the negative bias illumination stress (NBIS), to finally introduce In₂O₃ TFTs. Then, we will introduce vacuum and non-vacuum processes like spin-coating and liquid metal printing. We will introduce the various dopants and their applications, from mobility and crystal size improvements with H to NBIS improvements with lanthanides. We will also discuss the importance of device engineering, introducing how to choose the passivation layer, the source and drain, the gate insulator, the substrate, but also the possibility of advanced engineering by introducing the use of dual gate and 2 DEG devices on the mobility improvement. Finally, we will introduce the recent breakthroughs where In₂O₃ TFTs are integrated in neuromorphic applications and 3D integration. Full article