Bulletin of Materials Science最新文献

Utilization of waste pollution to solve electromagnetic waves pollution is a good strategy towards a green future. In this study, we have used two different biowastes, wheat stubble and peanut hulls, as biocarbon sources to obtain two diverse inherited morphologies, i.e., sheet-like morphology from wheat stubble and distorted/ripped biocarbon morphology from peanut hulls. Detailed microwave absorption characterization analysis shows that the distorted/ripped morphology has better reflection loss and effective absorption bandwidth (EAB) as compared to the sheet-like morphology. Furthermore, ({{text{MnFe}}}_{2}{{text{O}}}_{4}) particles are also used to get composites with both types of biocarbon. The minimum reflection loss (RL_mini) value achieved by the ripped biocarbon/({{text{MnFe}}}_{2}{{text{O}}}_{4}) is − 40.6 dB, with EAB being 5.6 GHz (13.2–7.6 GHz). Our findings show that better microwave absorption performance is attributed to the distorted/ripped morphology and by biocarbon–({{text{MnFe}}}_{2}{{text{O}}}_{4}) synergetic influence. These findings open a route for biowaste and magnetic waste to be used in controllable microwave absorption applications.

Noble metal like Pt or Au deposited on reducible oxides like TiO₂ is one of the promising catalysts for CO oxidation, which has many applications including developing long-life sealed-off CO₂ lasers, pollution control, etc. Catalytic oxidation of CO is pre-requisite for sealed-off CO₂ lasers, because dissociation of lasing CO₂ molecules in gas discharge decreases the laser power and may kill laser action in few minutes. Hence, this study was aimed to investigate the CO oxidation efficiency of in-house prepared Pt–TiO₂ and Au–TiO₂ catalysts, both at room temperature and under discharge conditions. The results of XPS and CO₂ conversion measurements revealed that the post-reduction of catalyst plays a very important role for increasing the Pt⁰ and efficiency of CO oxidation to about 80%. Importantly, in the presence of gas discharge, considerably higher catalytic performance was observed for Pt–TiO₂ catalyst with respect to their performance at room temperature and commercial gold (Au)-coated catalyst present in CO₂ laser tubes.

In this work, a series of materials composed of Ba_1−xY_xTi_1−x/4O₃ noted as BYT with x = 0, 0.025, 0.05, 0.075, 0.1 and 0.15 were prepared by hydrothermal route at 200°C for 24 h. Pressure, temperature and pH of the environment are essential factors for obtaining a pure phase. The effect of yttrium (Y³⁺) on the structural and dielectric properties of barium titanate was studied. Pure phases of the perovskite structure without secondary phases were confirmed by X-ray diffraction analysis. Raman spectroscopy analysis of the obtained samples confirms the presence of different vibration modes characteristic of the pure quadratic phase. Using a scanning electron microscope, the texture, morphology and microstructure of Ba_1−xY_xTi_1−x/4O₃ ceramics were observed. The study of dielectric properties was examined by impedance spectroscopy of dielectric measurements in the frequency range from 1 kHz to 2 MHz as a function of temperature, confirming the incorporation of yttrium and highlighting its influence on Curie temperature (T_c) and permittivity value (ε_r).

The novel plasma ageing technique has been used to investigate the effects of different treatment times of a co-polymer reinforced with montmorillonite nanoclay, where the effects of plasma ageing of the reinforced acrylic co-polymer (BA, STY and MAA) were obtained with nanoclay (sodium MMT) at different concentrations. The molecular weights of the samples were obtained by observing the change in the viscosity of the nonreinforced polymers, as well as an analysis of the thermal properties using the thermogravimetric analysis technique to determine their thermal stability, which showed an early decomposition of the exposed nanoreinforced materials to plasma concerning the reference sample 0 min. The differential scanning calorimetry analysis showed an increase in the glass transition temperature when adding the nanoreinforcement, but a decrease with saturation, likewise, it was observed that when adding this nanoreinforcement (MMT) to the polymeric matrix this protects the matrix when exposed to plasma. This acquires an increase in elastic modulus, which indicates a fragility in the nanomaterial. The structure of the nanocomposite was studied by means of the X-ray diffraction technique of the samples exposed to plasma treatment, obtaining patterns where intercalated nanocomposites are present.

In order to improve the properties of melamine foam (MF), a new polyimide–melamine composite foam (PI–MF) was prepared by microwave irradiation foaming with polyimide microspheres (PI) as a modifier and melamine resin as matrix. The micromorphology, temperature resistance, flame retardant and smoke suppression properties and mechanical properties of the foam were characterized and tested. It was observed by SEM that PI microspheres were closely connected to the skeleton of the MF, FT-IR characterization proved the existence of polyimide in the PI–MF. When the amount of PI microspheres is 30%, the overall performance of PI–MF is better. The temperature of 5% weight loss (T_5%) is 326.02°C, the limit oxygen index is 35.48%, the maximum smoke density is 9.21%, the smoke density rank is 5.43, the formaldehyde content is 46.65 mg kg⁻¹, and the elongation at break of the foam is 35.89%. The introduction of PI microspheres has a good effect on the modification of the thermal stability, flame retardant and smoke suppression properties, and mechanical properties of the MF, and has broadened the application range of polyimide. It also provides a new method for the modification of MF.

The conductivity and electric modulus formalism in tellurite-modified lithium borate glasses with composition (100–x) − (33.35Li₂O–66.65B₂O₃) − (x)TeO₂, (x = 0, 5, 10, 15, 20 and 25 mol%) have been prepared. Electric modulus, relaxation mechanism and conductivity parameters were investigated to understand the dielectric properties of the glass matrix in the temperature range between 403 and 583 K, and the frequency range between 100 Hz and 5 MHz. The experimental data of ac conductivity was fitted to Jonscher’s power law. The parameters like dc conductivity (σ_dc), frequency exponent (S) and crossover frequency (W_H) were extracted. The conductivity of the glass matrix was found to exhibit anomalous increasing behaviour with TeO₂ content. The decreasing trend in the values of the frequency exponent with the temperature rise demonstrates the correlated barrier hopping mechanism in the conduction process. The electric modulus data fitted to Davidson–Cole model and Kohlrausch–Williams–Watts model have revealed nearly the same values of β (Kohlrausch exponent), which depict the conductivity relaxation process. Other electrical parameters such as bulk resistance (R_b), capacitance (A_o) and stretching exponent (n) were also extracted by fitting the impedance data to the R-CPE model using Zview software. The dc conductivity of lithium boro tellurite glasses was found to follow Arrhenius behaviour and the corresponding activation energy was determined (0.5847–1.0004 eV).

Nanocrystalline yttria-stabilized zirconia (YSZ) was synthesized by a modified co-precipitation method. The process involves the use of molecular water associated with metal precursors to facilitate the hydroxylation. In this method, triethylamine was used to generate hydroxide ions from the molecular water of precursors, which helps to produce the metal hydroxides. Since no external water is utilized during the precipitation process, it is expected that the as-prepared and calcined materials should have minimum aggregation caused by the hydrogen bonding. The as-prepared and calcined YSZ powders are characterized by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDX), Brunauer Emmett-Teller (BET), transmission and scanning electron microscopy (TEM and SEM) and electrochemical impedance spectroscopy (EIS). Cubic phase YSZ, having yttria content of 8 mol%, has been formed at a calcination temperature of 650°C. The YSZ powder has a surface area of 88 m² g^–1 and the particle diameters measured from TEM are in the range of 8–15 nm, which is in good agreement with the average particle diameter, which is ~12 nm, obtained from surface area. The materials produced have grain boundary oxygen ion conductivity of 0.073 S cm^–1 at 800°C, which is one of the main parameters for SOFC to get higher power density.

A convenient approach from a practical point of view is proposed for assessing rheology of aqueous acetic acid rat tail collagen solutions by determining the kinematic viscosity (v), which depends only on the solution outflow time and is directly measured on cheap and affordable capillary viscometers. In this case, it is irrelevant to take into account the solvent outflow time and temperature correction, unlike relative, specific, reduced and intrinsic viscosities. Influence of the temperature as well as duration and periodicity of ultrasonic treatment on v of 0.3 wt.% solution of rat tail collagen in 0.02 M aqueous CH₃COOH was studied for the first time. Additionally, the influence of a temperature on v of mixtures of this collagen solutions with CaCl₂, poly(NIPAM), poly(N-vinylpyrrolidone), pluronic F-127 as well as with CaCl₂+poly(NIPAM), CaCl₂+poly(N-vinylpyrrolidone) and with CaCl₂+pluronic F-127 in a similar acetic acid aqueous solutions was studied. Linear regression dependences of the influence of a temperature on v of collagen solutions and its above-mentioned mixtures (R² is closest to 1) up to 40°C have been found, which make it possible to predict the viscosity characteristics of these solutions at the temperature of interest. It was found that shorter initial sonication periods at 20°C followed by relaxation stages minimize the decrease in v of pure collagen solutions. Results of the research can be useful for scientists, doctors and tissue engineers who carry out research in the field of regenerative medicine in predicting and selecting a temperature as well as ultrasonic parameters for bioprinting with collagen bioinks.

A difficult issue in petroleum reservoirs is the preservation of hydrocarbons after exploitation, because hydrocarbon components volatilize rapidly when they are exposed in the air. In this article, we have proposed ethylene oxide to encapsulate shale oils. The polymer has exhibited excellent mechanical and spectroscopic properties with a tensile strength of 19.160 MPa, which can hold the strong pressure of fresh shale sample. The polymer also has exhibited a transparent window in the visible range over 99.5%mm⁻¹ from 400 to 800 nm, indicating that no chromophores were generated during the polymerization process. Subsequently, the shale oil from the Biyang depression was encapsulated by the ethylene oxide for over 2000 hours at room temperature. Combined with confocal laser scanning microscopy, it was found that ethylene oxide has a superior ability in the preservation of shale oil while oils were rapidly volatilized in the exposed area. Contrasted to the exposed area, the encapsulated area exhibited a strong fluorescence intensity due to the accumulation of oil. This designed polymer can be applied in solving the problem of preservation of shale oils.

Spinel nanoferrites have gained tremendous research interest in the field of biomedical applications and memory devices. We present detailed studies on the microstructure and nanoscale properties of high purity cobalt ferrite nanomaterials, which were prepared by the citrate precursor method at varying annealing temperatures. XRD measurements showed an increase in the crystallite size from 29 to 40 nm with the increase in annealing temperature from 500 to 700°C. Field emission scanning electron microscopy (FESEM) and transmission eletron microscopy (TEM) analysis revealed the average grain size between 0.092 and 0.129 µm and particle size of 102 nm of the synthesized cobalt nanoferrite. Energy dispersive X-ray (EDX) analysis confirmed the presence of Co, Fe and O with appropriate stoichiometric ratio in synthesized nanoferrite. Fourier-transform infrared spectroscopy identified the metal oxide bonds between 465 and 579 cm⁻¹ in these nanoferrites. The energy band gaps decrease from 3.77 to 3.26 eV with the increase in annealing temperature as measured using UV–Visible spectroscopy. Photoluminescence study indicates the radiative defects and oxygen voids in CoFe₂O₄ nanocrystals present in the synthesized samples. With the increase in temperature, the magnetic parameters like saturation magnetization, coercivity, etc. shows significant changes. The increase in annealing temperature resulted in the reduction of capacitance, dielectric constant and loss tangent values in the frequency range of 100 Hz–5 MHz which is measured using impedance analyser on the palette samples. The observed magnetic parameters, oxygen vacancies and low dielectric loss may facilitate these materials for their possible use in bio-inspired nanorobotic, hydroelectric cells and high frequency applications.