Materials Letters最新文献

In this study, a comprehensive investigation was carried out to analyse the effects of direct fluorination on the structural, morphological, wettability, thermal and optical properties of polyethylene terephthalate (PET) films. The results show significant changes in surface composition and structure, as well as changes in surface morphology induced by fluorination. In addition, an increase in surface hydrophilicity and surface free energy were observed after fluorination. Although there appeared to be a slight decrease in thermal stability of the fluorinated PET films, they exhibited increased optical transmittance in the UV–visible spectrum compared to the original PET films. These findings demonstrate how fluorinated PET films have better surface qualities, which makes them appropriate for a range of uses including printing, coating, and optoelectronics.

Nanofibrous membranes with super-wetting feature exhibit promising application for oil/water emulsion separation, but achieving high separation efficiency in harsh environments remains challenging. Herein, superhydrophobic/superoleophilic nanofibrous membrane based on polyacrylonitrile (PAN) and hydrophobically modified graphene oxide (GO) was prepared by electrospinning technique. The multidimensional roughness that was produced by the overlapping of modified GO and nanofibers was crucial in producing superhydrophobic and superoleophilic wettability. For a variety of water-in-oil emulsions, the obtained nanofibrous membranes demonstrated outstanding oil/water separation performance. The maximum permeate flux reached 5135.8 L·m⁻²·h⁻¹ with separation efficiency higher than 99.1 %. More importantly, the obtained nanofibrous membranes showed stable separation performance in strongly corrosive solutions or at high temperatures. This work presents a versatile way to fabricate functional membranes for the separation of water-in-oil emulsions.

Cemented carbides are widely used for cutting and drilling tools. They usually combine a WC hard carbide phase and a Co-based ductile binder. NbC-Ni materials are considered as a possible alternative, especially for wear applications. The advantageous economic situation for raw materials sourcing, their interesting mechanical properties and low density have raised a new interest for these materials. However, mechanical properties can be limited by the rapid grain growth during liquid phase sintering, as compared to WC-Co. Grain growth can be controlled by the addition of secondary carbides. In this paper, a quantitative EBSD analysis of grain growth is performed for NbC-12 vol%Ni materials sintered at 1450 °C with controlled addition of Mo₂C and WC. The average grain size decreases continuously with Mo₂C addition. The results are discussed based on a more detailed interface characterization and on a previous model for the cooperative migration of phase boundaries and grain boundaries.

Compared with the additive manufacturing of single sand material, it is more difficult to form multi-material composite sand mold. The paper focuses on the influence of sand laying process for the multi-material composite sand mold, explores the change rules in the quality of different curing agent content of composite sand mold, realizes the high quality and high precision sand laying of multi-material sand, and expands the application of composite sand mold in complex structure and high performance products.

Hybrid particulate metal matrix composites with specific strength can be used in various applications. The mechanical properties of these composites can be improved by correctly choosing the type, volume fraction, size, and distribution of reinforcements and metal matrix. In this research, to make Al/Al₂O₃-SiC hybrid composites, aluminum chips were prepared by machining, and then the chips were coated with Al₂O₃ and SiC reinforcements by suspension method. For composite making, first, aluminum-coated chips were molded inside a steel mold and after heat treatment at 645 °C for 2 h the chips were hot pressed. The microstructure of the fabricated composites was examined by optical and SEM microscope, and then compression and tensile strength behavior were studied. The microstructural results showed a sound composite without any porosities and cracks. The hybrid composite with 12 wt% reinforcements showed high compressive strength (370 MPa).

Hydroxyapatite nanoparticles (HAP-NPs) were synthesized using a microemulsion (cetyltrimethylammonium bromide (CTAB) and dimethyl sulfoxide (DMSO) as surfactants) method. The influence of the optimum ratios of CTAB concentrations as surfactants in the microemulsion on HAP morphology was investigated. After dispersing the HAP powders, a high-speed spin coating process at 2500 RPM was employed to produce HAP coatings on the Ti-6Al-4V alloy. The HAP-NP properties were characterized using techniques such as XRD, FTIR, FESEM, and AFM. Studies utilizing electrochemical impedance spectroscopy (EIS) in a simulated body fluid (SBF) solution. The corrosion resistance of coated samples compared to bare substrate increased from 67 to 853.34 kΩ cm².

For the first time, translucent, dense (>97 %), pure cubic 20 mol.% CaO-doped ZrO₂ ceramics (20CaSZ) with suitable mechanical properties were achieved through hot-pressing. The ceramic depicted a maximum transmittance value of ∼73 % for a 1.5 mm thick pellet at 600 nm. The 20CaSZ ceramic was hot-pressed at 1500 °C for 15 min and displayed a phase-pure cubic symmetry. The average grain size of ∼2 μm, hardness of ∼14.5 GPa, and indentation toughness of ∼1.9 MPa.m^1/2 were assessed. Combining low birefringence and low optical scattering by grain boundaries helped to achieve translucency for hot-pressed 20CaSZ ceramic.

Cordierite-mullite ceramics are well-suited for use as kiln furniture due to their superior mechanical strength and thermal shock resistance. This study explores the development of cordierite-mullite refractory castables bonded with magnesium oxychloride (MOC) cement. These castables were created using calcined kaolin aggregates and a matrix comprised light-burned magnesia, calcined alumina, milled sand, and magnesium chloride hexahydrate. Interaction between light-burned magnesia and magnesium chloride hexahydrate produced a needle-like MOC cement phase, significantly enhancing the green strength of the castables. After firing at 1350 °C for 4 h, the MOC crystals decomposed, forming robust cordierite and mullite phases. The resulting sintered castables demonstrated a modulus of rupture of 14.55 MPa, a bulk density of 1.95 g/cm³, a porosity of 24.84 %, and a thermal expansion coefficient of 2.89x10⁻⁶°C⁻¹. These findings indicate the effectiveness of MOC cement bonding for manufacturing high-strength cordierite-mullite refractory castables, making them ideal for kiln furniture applications.

The hardness variation and the behavior of elemental diffusion in pulse current-assisted laser melting of multi-pass monolayer coatings and HAZ were investigated. The results showed that the coating microstructure grains were refined when the pulse current intensity increased from 5A to 10A. The electromagnetic effect generated by the pulse current drove the Fe element in the matrix to diffuse into the coating. When the pulse current was increased to 20 A, the electromagnetic impact effect overcame the bonding strength between the molten pool metals, which caused the coating to transcrystalline repture in the direction of the current movement. Meanwhile, when the pulse current increased within limits, the reduction of grain size and Fe diffusion resulted in more than two-fold hardness enhancement of the coating and HAZ.

For preventing environmental pollution and realizing resource utilization of agricultural and forestry wastes, biochar was formed after high temperature pyrolysis of citrus peels under anoxic conditions, and employed as catalyst to activate peroxymonosulfate (PMS) for degrading tetracycline hydrochloride (TC) in wastewater. Furthermore, α-FeOOH modified biochar was fabricated through an alcohol-assisted hydrothemal method for proving the catalytic activity of biochar. The prepared catalysts were characterized by several characterization techniques. Results showed that the catalytic activity of α-FeOOH modified biochar was much better than that of biochar or α-FeOOH, which is attributed to the synergistic effects of biochar and α-FeOOH on the PMS activation. Meanwhile, the effects of PMS concentration, co-existing ions (Cl^-, NO₃⁻), and humic acids (HA) on the degradation of TC were investigated through static experiments. More importantly, radical trapping experiment tests suggested that hydroxyl radical (•OH), sulfate radical (SO₄^•-), and singlet oxygen (¹O₂) were generated during the process of catalyst activation of PMS, and ¹O₂ played the main role for TC degradation.