Materials Letters: X最新文献

Herein, characteristics of the nanostructured silica powders (NsSP) synthesized from Philippine rice hull ash-based sodium silicate solution by precipitation (pH 2, pH 6) and calcination (600 °C, 900 °C) were presented. Characterizations confirmed that the synthesized NsSP contains high amount of SiO₂. NsSP obtained at pH 2 revealed higher mass losses by ∼ 12 % until 900 °C and higher intensities of –OH and Si–OH bonds than obtained at pH 6. Calcination of NsSP at 900 °C removes the Si–OH bond leading to a relative growth in the SiO₂ primary particles but SiO₂ structure remained amorphous. Morphology of NsSP obtained at pH 2 were cloud-like while NsSP obtained at pH 6 were bead-like and more distinct.

Composite polyurethane (PU) foams were effectively synthesized by the mass polymerization method with concentrations of natural basalt powder from 0 to 100 wt%. By increasing basalt's content, the foams had more considerable growth, suggesting a catalyst effect of its inherent metallic compounds during the reaction. Adding basalt powder decreased the traction and compression resistances and increased the foam's density and thermal stability. Still, the increase in basalt content reduced the burning time of the foams, indicating enhanced properties as a flame retardant and self-extinguishing capacity compared to traditional foams.

Rational method for micro alloying auto sheet rolled steel of low-pearlite, 10 HFTBch steel, which contributed to more uniform indicators of the mechanical properties of welded joints obtaining in the heat-affected zone and weld was chosen. It brought them closer to the properties of the base metal.

In the present work, we report the fabrication and characterization of undoped ZnO and Cadmium Sulfide (CdS) and Zinc Oxide (ZnO) thick films. The structural properties of ZnO films are characterized by X-ray Diffraction (XRD). It is evident from XRD that, the crystallite size of fabricated ZnO and CdS-ZnO films are 45 nm and 38 nm respectively. Optical properties have been investigated by U-V absorption. It is observed from U-V Spectroscopy that the band gap decreases with CdS doping. We found that all deposited ZnO thin films are to be polycrystalline structures of wurtzite, and the crystallite size of ZnO is in the nanometric range which further decreases with CdS doping.

Laser powder bed fusion (LPBF) has revolutionized many industries. In this paper, we report a new approach of LPBF for oxide ceramics with selective oxidation that reduces cracks and manufacturing defects. In this method, laser energy density was used to control the oxidation within the material article. Cuprous oxide was additively manufactured into CuO with remarkable crack reduction and improvement in microstructure. The effect of process parameters on the microstructure of Cu₂O and its oxidation behavior toward energy beam of different laser powers were analyzed. The experimental results clarified that the oxidation was increased by increasing the laser power in the presence of oxygen.

The use of engineering ceramics with intricate geometries is limited by manufacturing processes and lack ease of machinability of ceramics. Additive manufacturing of pre-ceramic polymers which are pyrolyzed into ceramics after 3D printing has recently been used to circumvent traditional manufacturing processes creating ceramics with complex geometries, however, mechanical characterization is limited. Polymer-derived ceramics and their green-body precursors are printed using digital light projection 3D printing in two orientations (0°- and 90°- to the build plate) and mechanically characterized. The results show that mechanical anisotropy exists both in the green-body polymer samples where the 0°-samples are stronger and stiffer than their 90°-counterparts and the final ceramics, where the stronger samples are fabricated at 90° despite isotropic hardness measurements. Through the manufacturing process, it was noted that samples undergoing pyrolysis built in the 90°-orientation have a pyrolysis survival rate of 94% whereas the 0°-samples showed a survival rate of 54%. The results suggest that the build-direction of 3D printed green-bodies plays a role in both material manufacturing and mechanical integrity of the final ceramic materials.

The solidification rate of materials affects the properties of the cast product and the pouring temperature also influences the freezing conditions of cast-metal alloys. The propose of this study is to evaluate the tensile strength of cast samples by using five variations of pouring temperatures through permanent molds by a gravity casting process. The results showed that the tensile strength maximum was 443 MPa at 1210 °C, the freezing range affected the tensile properties of cast samples.

Lumefantrine, exhibits poor bioavailability due to its very low solubility. A liquisolid compact of lumefantrine was prepared with mesoporous silica as a novel coating material. Lactose anhydrous and syloid 244FP were selected as carrier and coating materials respectively. Varying the carrier to coating ratio from 10 to 35, six formulations were prepared and evaluated for tests for tablets. thermal, surface characteristics, surface morphology, and surface area analysis. The tabletability of the formulation lactose to syloid 244FP ratio at 20:1 was found to be the best among all in terms of compression characteristics, faster disintegration, and enhanced dissolution. Hence it can be concluded that the use of a suitable amount of mesoporous silica in the formulation of liquisolid compact could significantly enhance the dissolution of the drug.

An effect of variation of slit widths of excitation and emission monochromators on emission intensity, peak position and asymmetric ratio of Eu³⁺ has been observed in YPO₄:Eu³⁺. Stark splitting is observed. Eu³⁺ ion occupies D_2d site symmetry in crystal lattice. However, asymmetric ratio is observed to be lesser in value ∼≤1.5. The possible explanation for low value of asymmetric ratio is explained.