Effects of Ta2O5 on the microstructure and electrical properties of ZnO linear resistance ceramics

ZnO-Al2O3-MgO-TiO2-SiO2-Ta2O5 (ZnO-based) linear resistance ceramics with doping different molar percentages of Ta2O5 were prepared by a conventional ceramics method. Effects of Ta2O5 additives on the phase composition, microstructures, and electrical properties of ZnO-based linear resistive ceramics were investigated. The results show that doping Ta2O5 can refine the grains of the main crystalline phase ZnO and the secondary crystalline phase ZnAl2O4 in terms of microstructure, and also can reduce the grain boundary barrier and optimize the I-V characteristics in terms of electrical properties. In addition, the doping of Ta2O5 can improve the stability of the resistivity , and the impedance frequency indicates that the doping of Ta2O5 makes the sample suitable for high-frequency electric fields. The resistivity of the sample doped with 0.2 mol% Ta2O5 is 56.2 Ω·cm, and this sample has the best grain boundary barrier height, nonlinear coefficient and temperature coefficient of resistance of 0.054 eV, 1.04 and -3.48×10-3 / ℃，respectively.

Fast and Efficient Removal of Uranium onto a Magnetic Hydroxyapatite Composite: Mechanism and Process Evaluation

The exploration and rational design of easily separable and highly efficient sorbents with satisfactory capability of extracting radioactive uranium (U)-containing compound(s) are of paramount significance. In this study, a novel magnetic hydroxyapatite (HAP) composite (HAP@ CoFe2O4), which was coupled with cobalt ferrite (CoFe2O4), was rationally designed for uranium(VI) removal through a facile hydrothermal process. The U(VI) ions were rapidly removed using HAP@ CoFe2O4 within a short time (i.e., 10 min), and a maximum U(VI) removal efficiency of 93.7% was achieved. The maximum adsorption capacity (Qmax) of the HAP@CoFe2O4 was 338 mg/g, which demonstrated the potential of as-prepared HAP@CoFe2O4 in the purification of U(VI) ions from nuclear effluents. Autunite [Ca(UO2)2(PO4)2(H2O)6] was the main crystalline phase to retain uranium, wherein U(VI) was effectively extracted and immobilized in terms of a relatively stable mineral. Furthermore, the reacted HAP@CoFe2O4 can be magnetically recycled. The results of this study reveal that the suggested process using HAP@CoFe2O4 is a promising approach for the removal and immobilization of U(VI) released from nuclear effluents.

The Effect of Sodium Hydroxide Concentration on the Structure of Iron Oxides@Bacterial Cellulose and their Catalytic Activity for Methylene Blue Degradation in Solution

Heterogeneous fenton , although offering promises for large scale wastewater treatment, is still hindered in its practicality due to its modest catalytic activity. The usage of catalyst supportas been demonstrated previously toecrease the overall particle size to improve its catalytic performance. In this demonstration, fenton catalysts were prepared using the sol-gel method and bacterial cellulose (BC) as catalyst support, with varying sodium hydroxide (NaOH) concentrations (0.01; 0.1 and 1 M). NaCl impurities' presence was successfully eliminated by reducing NaOH concentration relative to the previous 4 M concentration. Lower NaOH concentration leads to a more favorable condition for the formation of smaller non-agglomerated particles and magnetite (Fe3O4) as its main crystalline phase. It was found that the best performing catalyst was produced using 1 M NaOH and was able to degrade Methylene blue solution up to 53.8% remaining dye concentration within two hours.

Facile decoration of CdS nanoparticles on TiO2: robust photocatalytic activity under LED illumination

A facile approach is presented to obtain visible-light-active TiO2/CdS nanocomposites with visible-light photocatalytic activity. Ordered nanospheres of TiO2 (with anatase as the main crystalline phase) were synthesized using evaporation-induced self-assembly (EIS) with P123 block polymer without any hazardous additives. Then, a rapid microwave (MW) protocol was used to obtain visible-light-absorbing nanocomposites between TiO2 and CdS in just 10 s. Based on Rietveld refinements of X-ray diffractrograms and elemental analysis it was found that nanoparticles of CdS are mainly decorated between the nanospheres of TiO2, which can simultaneously improve light absorption and suppress the unwanted photo-corrosion effects. The prepared nanocomposites were put to test for the removal of malachite green as a model pollutant from aqueous media under irradiation. The results revealed, that excessive loading results in unwanted surface covering and less than ideal activity, but for the sample with optimized loading, about 86 and 77% of the pollutant was degraded after 100 min of illumination at room temperature under the xenon short-arc and LED illumination, respectively.

EFFECT OF MODIFYING ZIRCONIUM OXIDE ADDITIVE ON THE PROPERTIES OF CERAMIC MATERIALS OF THE Y2O3–Al2O3–SiO2 SYSTEM OBTAINED BY THE SOL-GEL METHOD

The effect of the modifying additive ZrO2 on the rheological properties, the processes of structure and phase formation of the compositions of the Y2O3–Al2O3–SiO2 system obtained by the sol-gel method has been investigated. It was found that the temperature range of crystallization of the compositions of the Y2O3–Al2O3–SiO2 system with the addition of ZrO2 is 1020–1270 °C and with an increase in the concentration of zirconium oxide, the amount of the main crystalline phase of yttrium pyrosilicate (β-Y2Si2O7) decreases and the concentration of the zirconium-containing phase – the tetragonal modification of zirconium oxide and zirconium silicate ZrSiO4 -increases.

Optimization of heat treatment of glass-ceramics made from blast furnace slag

CaO–MgO–Al2O3–SiO2 glass-ceramics with diopside as the main crystalline phase were prepared by melting blast furnace slag obtained from Baotou Iron and Steel Company. The effect of heat treatment on the crystallization behavior of glass-ceramics, containing a large proportion of melted blast furnace slag, was studied by means of differential thermal analysis and scanning electron microscopy. The optimum heat-treatment regime was obtained by orthogonal experimental results for glass-ceramics in which blast furnace slag comprised 70% of the composition and 1% Cr2O3 and 4% TiO2 were used as nucleating agents. The nucleation temperature was 750°C for 2.5 h and the crystallization temperature was 930°C for 1 h. Under this regime, the performance of the glass-ceramic was better than that of other groups in the orthogonal experiment.

The Crystallization Behaviors of SiO2-Al2O3-CaO-MgO-TiO2 Glass-Ceramic Systems

To evaluate the crystallization behavior of Ti-bearing blast furnace slag-based glass ceramics, SiO2-Al2O3-CaO-MgO-TiO2 systems with various TiO2 were investigated. The crystallization process and mechanical properties were analyzed. The results show that with TiO2 increasing, exothermic peak temperature (Tp) decreases, and the crystallization is promoted by the introduction of TiO2. A small amount of TiO2 (≤4%) addition can significantly promote crystallization, and when TiO2 continues to increase, the crystallization is decreased slightly. The Avrami parameter (n) of all samples is less than 4, indicating that in prepared glass-ceramics, it is hard to achieve three-dimensional crystal growth. The main crystalline phase is akermanite–gehlenite. The addition of TiO2 has no obvious effect on the type of main crystalline phase. The prepared glass-ceramic with 4% TiO2 show good mechanical properties with the hardness values of 542.67 MPa. The recommended content of TiO2 is 4% for preparing glass-ceramics.

Lattice Vibrational Characteristics and Structures-Properties Relationships of Non-Stoichiometric Nd[Mg0.5Sn0.5(1+x)]O3 Ceramics

Non-stoichiometric Nd[Mg0.5Sn0.5(1+x)]O3 (-0.04 ≤ x ≤ +0.04) - type samples were prepared using a traditional two-step solid-state sintering process. Their crystal structures, phase compositions, dielectric properties and lattice vibrational characteristics were identified in detail. Double perovskite Nd(Mg0.5Sn0.5)O3 with a monoclinic structure was distinguished as the main crystalline phase, pure phase was obtained when x < 0, and the sample [Nd(Mg0.5Sn0.49)O3] at x = -0.02 shows the excellent dielectric properties: εr = 18.74, Q × f = 47,979 GHz. Lattice vibrational characteristics were clarified with Raman and infrared active modes assigned and illuminated, accurately. The intrinsic properties were fitted by four-parameter semi-quantum model, which show that the low-frequency infrared modes yield a more significant contribution to permittivity and dielectric loss. Raman shifts of modes F2g(A) and F2g(B) correlate with dielectric constants negatively, which implies that the bond length has a positive correlation with permittivity. Full widths at half maximum of vibritional modes A1g(O) correlate with dielectric loss values positively and correlate with the degree of order (S) negatively.

Curcumin Incorporation into Zn3Al Layered Double Hydroxides—Preparation, Characterization and Curcumin Release

Curcumin (CR) is a natural antioxidant compound extracted from Curcuma longa (turmeric). Until now, researches related to the incorporation of CR into layered double hydroxides (LDHs) were focused only on hybrid structures based on a MgxAl-LDH matrix. Our studies were extended towards the incorporation of CR in another type of LDH-matrix (Zn3Al-LDH) which could have an even more prolific effect on the antioxidant activity due to the presence of Zn. Four CR-modified Zn3Al-LDH solids were synthesized, e.g., PZn3Al-CR(Aq), PZn3Al-CR(Et), RZn3Al-CR(Aq) and RZn3Al-CR(Et) (molar ratio CR/Al = 1/10, where P and R stand for the preparation method (P = precipitation, R = reconstruction), while (Aq) and (Et) indicate the type of CR solution, aqueous or ethanolic, respectively). The samples were characterized by XRD, Attenuated Total Reflectance Fourier Transformed IR (ATR-FTIR) and diffuse reflectance (DR)-UV–Vis techniques and the CR-release was investigated in buffer solutions at different pH values (1, 2, 5, 7 and 8). XRD results indicated a layered structure for PZn3Al-CR(Aq), PZn3Al-CR(Et), RZn3Al-CR(Aq) impurified with ZnO, while RZn3Al-CR(Et) contained ZnO nano-particles as the main crystalline phase. For all samples, CR-release revealed a decreasing tendency towards the pH increase, and higher values were obtained for RZn3Al-CR(Et) and PZn3Al-CR(Et) (e.g., 45% and 25%, respectively at pH 1).

Synthesis and Characterization of SmBa2Cu3Oy Powder Prepared by Solid-State Reaction

In this work, the SmBa2Cu3Oy (Sm-123) powder was successfully prepared by solid-state reaction method under a normal air atmosphere using a stoichiometric ratio (i.e., Sm:Ba:Cu = 1:2:3) of high-purity Sm2O3, BaCO3 and CuO starting powders. Thermal properties of the as-calcined powder were studied by DSC/TGA technique and the results showed a formation of Sm-123 phase at 900 °C. The as-calcined powder was prepared by heating the starting precursors at 900 °C for 6–30 h. Phase identification was determined using an X-ray diffractometer (XRD). The quantitative phase analysis was analyzed by fitting the XRD pattern using the GSAS-II program. The result of XRD showed that the SmBa2 Cu3Oy (Sm-123) was identified as the main crystalline phase. The morphology was observed by scanning electron microscopy (SEM) with chemical composition identification from EDS mode. The surface of Sm-123 powder exhibited large agglomerates with a size range of ∼4.44–6.75 m. The Raman spectra showed a vibrational Raman-active phonon mode lying at around ∼502–508 cm–1. The peaks originated from the apical oxygen O(4) (i.e., O(4)-Ag mode) along the c-axis could be correlated with the oxygen deficiency in the CuO2 planes of orthorhombic SmBa2Cu3Oy. The calculated oxygen content from these peaks tended to decrease with increasing calcination time. All of these frequencies confirmed the presence of phonon and bonding typical for the 123-type structure.