Search Results (1,919)

Monocrystalline silicon is an excellent semiconductor material for integrated circuits. Its surface quality has an enormous effect on its service life. The surfaces are formed by ultra-precision machining using nano-grinding, one of the technologies that can achieve surface roughness at the nano- or sub-nano-scale. Therefore, subsurface damage of monocrystalline silicon in nano-grinding was studied by establishing a molecular dynamics simulation model, and the impact of machining parameters on the force–thermal behavior was analyzed. The results reveal that the mechanism of subsurface damage is mainly structural phase transformation and amorphization. In nano-grinding of monocrystalline silicon, the tangential grinding force has a relatively major role in material removal. With increasing grinding depth and grinding speed, the grinding heat rises, and a certain degree of high temperature strengthens the toughness of the material, improving the subsurface quality of monocrystalline silicon. Therefore, subsurface damage in monocrystalline silicon can be controlled by reducing the grinding depth and increasing the grinding speed. Full article

Andrographolide (ADG) is a typical poorly water-soluble drug, and a co-amorphous strategy was used here to improve its aqueous solubility. Co-amorphous systems of ADG and amino acids with a 1:1 molar ratio were screened via the neat ball milling method. L-lysine (Lys) and L-tryptophan (Trp) can be used as co-formers with ADG, forming a co-amorphous phase, which was confirmed by powder X-ray diffraction, IR and Raman spectroscopy. ADG-Trp showed poor solubility at 37 °C, which was close to that of raw ADG (0.08 mg·mL⁻¹). ADG-Lys showed unexpectedly enhanced solubility, at 0.5 mg·mL⁻¹ in the media of water and PBS (pH 7.4) and 0.3 mg·mL⁻¹ in the medium of HCl buffer (pH 1.2) at 37 °C. ADG-Lys showed good storage stability for 5 months, but its thermal stability was poor and it could recrystallize at 100 °C. Compared with ADG-Trp, ADG-Lys has weaker hydrogen bonding interactions and stronger hydrophobic interactions related to ADG molecules, which might cause the unusual enhancement in solubility. To our knowledge, ADG-Lys prepared in this work shows the maximum ADG content (70 wt.%) and the highest ADG solubility among the reported ADG amorphous solid dispersions and co-amorphous systems. Full article

Protective coatings are essential for extending the service life of components exposed to harsh conditions, such as pipes used in industrial systems, where wear and corrosion remain constant challenges. This study explores the development of a nano-sized TiO₂-reinforced electroless nickel-based ternary (Ni-W-P) alloy and composite coating on API X60 steel, a high-strength carbon steel pipe grade widely used in oil and gas pipelines, using an alkaline hypophosphite-reduced bath. The surface morphology, microstructure, elemental composition, structure, phase evolution, adhesion, and roughness of the coatings were analyzed using optical microscopy, FESEM, EDS, XRD, AFM, cross-cut tape test, and 3D profilometry. The tribological performance was evaluated via Vickers microhardness measurements and reciprocating wear tests conducted under dry conditions at a 5 N load. The TiO₂ nanoparticle-reinforced composite coating achieved a consistent thickness of approximately 24 µm and exhibited enhanced microhardness and reduced coefficient of friction (COF), although the addition of nanoparticles increased surface roughness (S_a). Annealing the electroless composites at 400 °C led to a significant improvement in their tribological properties, primarily owing to the grain growth, phase transformation, and Ni₃P crystallization. XRD analysis revealed phase evolution from an amorphous state to crystalline Ni₃P upon annealing. Both the alloy and composite coatings exhibited excellent adhesion performances. The combined effect of TiO₂ nanoparticles, tungsten, and Ni₃P crystallization greatly improved the wear resistance, with abrasive and adhesive wear identified as the dominant mechanisms, making these coatings well suited for high-wear applications. Full article

The toxicity of lead in conventional perovskites and their inherent chemical instability impede the commercialization of perovskite-based optoelectronics. Therefore, it is vital to develop chemically stable and environmentally friendly Pb-free alternatives. Recently, zero-dimensional (0D) all-inorganic Cs₂ZnCl₄ doped with Sn(II) has emerged as a promising candidate, exhibiting superior chemical robustness, minimal biotoxicity, and exceptional optoelectronic properties. In this work, pressure effects on structure and optical properties in Sn(II)-doped all-inorganic zero-dimensional halide perovskite are investigated both experimentally and theoretically. The structure–property relationship of Sn(II)-doped Cs₂ZnCl₄ is studied using high-pressure techniques. Piezochromism, accompanied by a remarkable change in emission color from orange/red and green to orange/yellow, was obtained from 1 atm to 22.5 GPa. Angle dispersive synchrotron X-ray diffraction (ADXRD) patterns and Raman spectra manifest that the material underwent an isostructural phase transition followed by amorphization with increasing pressure. The piezochromism and band gap engineering originate from the pressure-induced lattice compression and isostructural phase transition. This work advances STE emission studies and provides a robust strategy to boost emission efficiency and to construct multifunctional materials with piezochromism in environmentally friendly perovskites, thus facilitating diverse future applications. Full article

Polyethylene glycol (PEG) is among the most intensively researched and applied polymers, exhibiting a very wide range of industrial, pharmaceutical, and biomedical applications. The strongest and most highly diagnostic absorbance in the FTIR spectrum of PEG and of PEG-containing polyurethanes, is the ether C-O-C stretching absorbance, which consistently appears as a triple-peak absorbance in a semicrystalline state. Surprisingly, this phenomenon has very seldom been mentioned or elaborated, and no direct structural diagnostic FTIR assignment has been determined for each component of the triple-peak. The present research conclusively demonstrates that the left-side and right-side components of the triple-peak are assigned to the chain-fold regions and the extended-chain regions of the crystallized chains, respectively, while the strong-wide central component is assigned to the randomly oriented chains in the amorphous phase of the semicrystalline PEG. The present demonstration was facilitated via the synthesis of a highly oriented fibrillar polyurethane block-copolymer, exclusively containing extended-chain-crystallized PEG soft-segments, obtained through dense hard-segment crosslinking under vigorous unidirectional shear-stress continuously applied during the synthesis. The present research results enable us to directly relate the FTIR spectra of PEG and block copolymers synthesized thereof, to their crystallization mechanisms and chain conformations, thus facilitating the development of improved industrial processing methods. Full article

In this paper, the molecular dynamics simulation method was adopted to systematically study the microstructure evolution behavior of TiAl alloys under impact compression under three typical crystal orientations ([001], [110], [111]). By analyzing the characteristics of structural phase transition, defect type evolution, dislocation expansion, and radial distribution function, the anisotropic response mechanism under the joint regulation of crystal orientation and impact velocity was revealed. The results show that the [111] crystal orientation is most prone to local amorphous transformation at high strain rates, and its structural collapse is due to the rapid accumulation and limited reconstruction of dislocations/faults. The [001] crystal orientation is prone to forming staggered stacking of layers and local HCP phase transformation, presenting as a medium-strength structural disorder. Under the strain regulation mechanism dominated by twinning, the [110] orientation exhibits superior structural stability and anti-disorder ability. With increases in the impact velocity, the defect type gradually changes from isolated dislocations to large-scale HCP regions and amorphous bands, and there are significant differences in the critical velocities of amorphous transformation corresponding to different crystal orientations. Further analysis indicates that the HCP structure and the formation of layering faults are important precursor states of amorphous transformation. The evolution of the g(r) function verifies the stepwise disintegration process of medium and long-range ordered structures under shock induction. It provides a new theoretical basis and microscopic perspective for the microstructure regulation, damage tolerance improvement, and impact resistance design of TiAl alloys under extreme stress conditions. Full article

Objectives: Transforming poorly soluble crystalline drugs into their amorphous form is a well-established strategy in pharmaceutical science to enhance their solubility and improve their clinical efficacy. However, developing amorphous forms of organic drugs for pharmaceutical applications presents significant technical hurdles due to the lack of suitable analytical tools for the amorphization process. Carbamazepine is a crystalline BCS class II drug commonly used for epilepsy and trigeminal neuralgia, whose clinical efficacy is compromised by its low solubility and slow dissolution. Therefore, this study focuses on investigating the amorphization of carbamazepine to enhance its solubility by using a micro-droplet precipitation system. Methods: These micro-droplets serve as individual reactors, enabling homogeneous nucleation for precipitation of carbamazepine. During crystallization, carbamazepine undergoes an intermediate liquid–liquid phase transition characteristic of two-step nucleation. By varying the solvent’s composition (methanol/water), we characterized the kinetics and stability of the intermediate liquid phase under various conditions. Results: Our results indicate that carbamazepine can undergo either a one-step liquid-to-amorphous-solid phase transition or a two-step liquid-to-crystalline-solid phase transition. Notably, both transitions pass through a liquid-to-dense-liquid phase separation process starting from the supersaturated solution, where the generated intermediate phases exhibit different sizes and numbers that are influenced by the solvent and its concentration. Conclusions: Our findings not only elucidate the mechanism underlying the carbamazepine phase transition but also propose a novel method for studying the amorphous process, which could be broadly applicable to other poorly soluble pharmaceutical compounds and may be helpful to amorphous formulations production, potentially offering significant improvements in drug efficacy and patient compliance. Full article

In this paper, various Ga₂O₃ films, including amorphous Ga₂O₃ films, β-Ga₂O₃, and α-Ga₂O₃ epitaxial films, have been nitridated and converted to single-crystalline GaN layers on the surface. Although the original Ga₂O₃ films are different, all the converted GaN layers exhibit the (002) preferred orientation and the porous morphologies. The ~200 µm GaN thick films have been grown on the nitridated Ga₂O₃ films using the halide vapor phase epitaxy (HVPE) method. Raman analysis indicates that all the HVPE-GaN films grown on nitridated Ga₂O₃ films are almost stress-free. An obvious GaN porous layer/Ga₂O₃ structure has been observed in the interface between GaN thick films and sapphire substrates. The porous GaN layers can be used as promising templates for the preparation of free-standing GaN substrates. Full article

The precursor-derived ceramic route is recognized as an advanced and efficient technique for fabricating ceramic matrix composites, particularly suitable for the development and microstructural tailoring of continuous fiber-reinforced ceramic matrix composites. In this work, octamethylcyclotetrasiloxane and tetravinylcyclotetrasiloxane were employed as monomers to synthesize a branched siloxane via ring-opening polymerization. A subsequent hydrosilylation reaction led to the formation of polyvinylsiloxane with a three-dimensional crosslinked structure. The precursor exhibited excellent fluidity, adjustable viscosity, and superior thermosetting characteristics, enabling efficient impregnation and densification of reinforcements through the polymer infiltration and pyrolysis process. Upon pyrolysis, the polyvinylsiloxane gradually converted from an organic polymer to an amorphous inorganic ceramic phase, yielding silicon oxycarbide ceramics with a high ceramic yield of 81.3%. Elemental analysis indicated that the resulting ceramic mainly comprised silicon and oxygen, with a low carbon content. Furthermore, the material demonstrated a stable dielectric constant (~2.5) and low dielectric loss (<0.01), which are beneficial for enhanced thermal stability and dielectric performance. These findings offer a promising precursor system and process reference for the low-cost production of high-performance, multifunctional ceramic matrix composites with strong potential for engineering applications. Full article

To address the critical challenge of synergistically enhancing both high-temperature mechanical properties and thermal conductivity in neutron-absorbing materials for dry storage of spent nuclear fuel, this study proposes an innovative strategy. This approach involves the controlled distribution, size, and crystalline states of nano-Al₂O₃ within an aluminum matrix. By combining plastic deformation and heat treatment, we aim to achieve a structurally integrated functional design. A systematic investigation was conducted on the microstructural evolution of Al₂O₃/10 wt.% B₄C/Al composites in their forged, extruded, and heat-treated states. We also examined how these states affect high-temperature mechanical properties and thermal conductivity. The results indicate that applying hot extrusion deformation along with optimized heat treatment parameters (500 °C for 24 h) allows for a lamellar dispersion of nano-Al₂O₃ and a crystallographic transition from amorphous to γ-phase. As a result, the composite demonstrates a tensile strength of 144 MPa and an enhanced thermal conductivity of 181 W/(m·K) at 350 °C. These findings provide theoretical insights and technical support for ensuring the high density and long-term safety of spent fuel storage materials. Full article

Quarry dust (QD) landfill causes environmental issues that cannot be ignored. In this study, we systematically explore its potential application as a supplementary cementitious material (SCM) in cemented paste backfill (CPB), revealing the activated mechanism of modified QD (MQD) and exploring the hydration process and workability of CPB containing QD/MQD. The experimental results show that quartz, clinochlore and amphibole components react with CaO to form reactive dicalcium silicate (C₂S) and amorphous glass phases, promoting pozzolanic reactivity in MQD. QD promotes early aluminocarbonate (M_c) formation through CaCO₃-derived CO₃²⁻ release but shifts to hemicarboaluminate (H_c) dominance at 28 d. MQD releases active Al³⁺/Si⁴⁺ due to calcination and deconstruction, significantly increasing the amount of ettringite (AFt) in the later stage. With the synergistic effect of coarse–fine particle gradation, MQD-type fresh backfill can achieve a 161 mm flow spread at 20% replacement. Even if this replacement rate reaches 50%, a strength of 19.87 MPa can still be maintained for 28 days. The good workability and low carbon footprint of MQD-type backfill provide theoretical support for—and technical paths toward—QD recycling and the development of low-carbon building materials. Full article

This article deals with the effect of Kr¹⁵⁺ ion irradiation on the structure and properties of partially stabilized zirconium dioxide (ZrO₂ + 3 mol. % Y₂O₃) ceramics. Ion irradiation is used to simulate radiation damage typical of operating conditions in nuclear reactors and space technology. It is shown that with an increase in the irradiation fluence, point defects are formed, dislocations accumulate, and the crystal lattice parameters change. At high fluences (>10¹³ ions/cm²), a phase transition of the monoclinic (m-ZrO₂) phase to the tetragonal (t-ZrO₂) and cubic (c-ZrO₂) modifications is observed, which is accompanied by a decrease in the crystallite size and an increase in internal stresses. Changes in the mechanical properties of the material were also observed: at moderate irradiation fluences, strengthening is observed due to the formation of dislocation structures, whereas at high fluences (>10¹⁴ ions/cm²), a decrease in strength and a potential amorphization of the structure begins. The change in the phase composition was confirmed by X-ray phase analysis and Raman spectroscopy. The results obtained allow a deeper understanding of the mechanisms of radiation-induced phase transformations in stabilized ZrO₂ and can be used in the development of ceramic materials with increased radiation resistance. Full article

In our study, supercapacitor electrodes were prepared by depositing electroless Ni-B coating on copper plates, followed by nitric acid etching. The composition and the micro- and phase structure of the coatings were investigated by ICP-OES, PFIB-SEM, and XRD techniques. The original pebble-like structure of the coating consists of 0.8–10 µm particles, with an X-ray amorphous phase structure. The surface morphology and porosity of the coating can be tuned simply by changing the etching time. The supercapacitive performance of the electrodes was evaluated by means of cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy measurements. The capacitance of the coating was found to vary on the etching time according to a maximum function, allowing for the determination of an optimal duration to obtain a specific capacitance of 157 mF/cm² (at 0.5 A/g). An excellent charge storage retention of 178% was found after 5000 CV cycles at a scan rate of 50 mV/s owing to the evolved electrochemically active network on the surface of the electrode, indicating a long-term stable and reliable electrode. Full article

This study presents a cost-effective, carbon-negative construction material for affordable housing, developed entirely from locally available agricultural wastes: rice husk ash, wood ash, and rice straw—materials often problematic to dispose of in many African regions. Rice husk ash provides high amorphous silica, acting as a strong pozzolanic agent. Wood ash contributes calcium oxide and alkalis to serve as a reactive binder, while rice straw functions as a lightweight organic filler, enhancing thermal insulation and indoor climate comfort. These materials undergo natural pozzolanic reactions with water, eliminating the need for Portland cement—a major global source of anthropogenic CO₂ emissions (~900 kg CO₂/ton cement). This process is inherently carbon-negative, not only avoiding emissions from cement production but also capturing atmospheric CO₂ during lime carbonation in the hardening phase. Field trials in Kenya confirmed the composite’s sufficient structural strength for low-cost housing, with added benefits including termite resistance and suitability for unskilled laborers. In a collaboration between the University of Tartu and Kenyatta University, a semi-automatic mixing and casting system was developed, enabling fast, low-labor construction of full-scale houses. This innovation aligns with Kenya’s Big Four development agenda and supports sustainable rural development, post-disaster reconstruction, and climate mitigation through scalable, eco-friendly building solutions. Full article

The single-crystal diamond (SCD), owing to its extreme physical and chemical properties, serves as an ideal substrate for quantum sensing and high-frequency devices. However, crystal anisotropy imposes significant challenges on fabricating high-quality micro-nano structures, directly impacting device performance. This work investigates the effects of femtosecond laser processing on the SCD under two distinct crystallographic orientations via single-pulse ablation. The results reveal that ablation craters along the <100> orientation exhibit an elliptical shape with the major axis parallel to the laser polarization, whereas those along the <110> orientation form near-circular craters with the major axis at a 45° angle to the polarization. The single-pulse ablation threshold of the SCD along <110> is 9.56 J/cm², representing a 7.8% decrease compared to 10.32 J/cm² for <100>. The graphitization threshold shows a more pronounced reduction, dropping from 4.79 J/cm² to 3.31 J/cm² (31% decrease), accompanied by enhanced sp² carbon order evidenced by the significantly intensified G-band in the Raman spectra. In addition, a phase transition layer of amorphous carbon at the nanoscale in the surface layer (thickness of ~40 nm) and a narrow lattice spacing of 0.36 nm are observed under TEM, corresponding to the interlayer (002) plane of graphite. These observations are attributed to the orientation-dependent energy deposition efficiency. Based on these findings, an optimized crystallographic orientation selection strategy for femtosecond laser processing is proposed to improve the quality of functional micro-nano structures in the SCD. Full article