Effects Of ZnO Content Research Articles

Preparation, properties and formation mechanism of transparent anorthite-based glass-ceramic glaze with high hardness

The transparent anorthite-based glass-ceramic glaze was prepared at 1200 °C by mineral raw materials. The effect of ZnO content on the structures and properties of the anorthite glass-ceramic glaze was studied by XRD, SEM-EDS, HR-TEM, high temperature microscope, micro-Vickers hardness tester and comprehensive thermal analyzer. Furthermore, the formation mechanism of anorthite was investigated systematically. The results reveal that the introduction of ZnO results in the decrease of melting temperature, elimination of the diopside, reduction of the thermal expansion coefficient, and improvement of the mechanical properties of the glazes markedly. The major crystalline phases of glazes change from the coexistence of anorthite and diopside to single anorthite with the increase of ZnO content from 0 wt% to 6.45 wt%, and the relative anorthite content increases from 26.87 wt% to 49.83 wt%. Both the size and number of anorthite grains with a distribution of the card structure gradually increases as increasing the ZnO content. The increase of anorthite improves the scattering ability of visible light and then reduces the transparency of the glaze. The Vickers hardness and flexural strength of glazes improve from 5.26 GPa and 45.95 MPa to 7.20 GPa and 72.79 MPa, respectively. The thermal expansion coefficient decreases from 6.328 × 10−6/°C to 5.781 × 10−6/°C (600 °C). Anorthite crystal generates from the reaction of genhlenite, SiO2 and Al2O3 at 1100 °C, and the gehlenite forms through the reaction of metakaolin and CaO. The study shows that the plate-like anorthite crystallizes when the content of ZnO is 3.33 wt%, the Vickers hardness of glass-ceramic glaze is 6.56 GPa with a great transparency.

Efficient removal of Cr(VI) from wastewater by ZnO-polyacrylic acid/cellulose fiber/polyethylene glycol hydrogel: Synergistic effect of adsorption and photocatalytic reduction

A novel polyacrylic acid/carboxylated nanocellulose fiber/polyethylene glycol hydrogel loaded with nano-ZnO (ZnO-PAA/CNF/PEG: GH-2 (wt(ZnO)% = 12% and wt(PEG)% = 16%)) was synthesized to remove Cr(VI) from wastewater by adsorption synergistic photocatalytic reduction. The effects of ZnO content, PEG content and pH on the removal efficiency of Cr(VI) were investigated. The removal performance and mechanism of Cr(VI) by hydrogels were systematically studied by various techniques. The results showed that when the initial pH = 2, the initial concentration of Cr(VI) = 20 mg/L, the hydrogel dose = 0.5 g/L, and Irradiation power of mercury lamp was 500 W, the removal efficiency of Cr(VI) was 97.22% (dark adsorption for 60 min and photocatalysis for 50 min). The addition of PEG greatly reduced the agglomeration of nano-ZnO in GH-2 and facilitated the separation of photogenerated electron-hole pairs. The adsorption process of Cr(VI) by GH-2 accords with pseudo-second-order kinetics. The photocatalytic process conforms to the pseudo-first-order reaction kinetics. Under the optimal experimental conditions, the removal efficiency of Cr(VI) by GH-2 was still as high as 87.99% after 5 cycles. The removal mechanism of Cr(VI) was mainly through electrostatic attraction, chemical adsorption and photocatalytic reduction. This study provides a feasible method for the synthesis of hydrogel materials with excellent adsorption synergistic photocatalytic performance for the treatment of Cr(VI)-containing wastewater.

Effect of ZnO Content on the Optical H2 Sensing Properties of Porous Pt/(WO3)1−x(ZnO)x Films

Effect of ZnO Content on the Optical H2 Sensing Properties of Porous Pt/(WO3)1−x(ZnO)x Films

Effect of ZnO on the crystallization behavior and properties of SiO2–CaO–Al2O3–Fe2O3 glass-ceramics prepared from simulated secondary slag after reduction of copper slag

The feasibility of preparing low-cost glass-ceramics from Zn-containing dust and secondary molten slag generated during the carbothermal reduction of copper slag was investigated. Analytical-grade agents, such as ZnO, Fe2O3, SiO2, CaO, and Al2O3, were used to simulate the dust and secondary slag. The effect of ZnO content on the crystallization behavior, structure, and mechanical properties of the glass-ceramics was investigated through X-ray diffraction analysis, scanning electron microscopy-energy dispersive spectrometry, differential scanning calorimetry, Fourier transform infrared spectroscopy, and Raman spectroscopy. The results showed that with increased ZnO content from 0 to 6 wt%, the crystallization activation energy of base glass increased from 386.05 to 425.89 kJ/mol. Meanwhile, the average value of the crystal growth index increased from 1.91 to 4.10, and the highest crystallization rate of the glass-ceramics increased from about 1.44 to 23.11 mm3/min. The increased ZnO in glass-ceramics promoted the precipitation of gehlenite, but inhibit the crystallization of anorthite. When the ZnO content was 6 wt%, the comprehensive properties of the glass-ceramics were better; the flexural strength, microhardness, volume density, water absorption rate, and open porosity were 58.67 MPa, 738.35 HV, 2.92 g/cm3, 0.44% and 1.27%, respectively.

Bioadaptable bone regeneration of Zn-containing silicocarnotite bioceramics with moderate biodegradation and antibacterial activity

Preparing novel bioceramics with bioadaptability of high osteogenesis and moderate degradation is particularly challenging. In this work, zinc containing silicocarnotite (Ca5(PO4)2SiO4, CPS) scaffolds (Zn-CPS) were applied as a potential novel therapy for bone defect since the good antibacterial capacity and biocompatibility of Zn. The effects of ZnO content on antibacterial capacity, protein adsorption, osteogenesis and degradation behavior of Zn-CPS bioceramics were investigated and the related mechanism was also discussed. The obtained Zn-CPS bioceramics showed enhanced antibacterial capacity, osteogenesis and degradation. In general, the antibacterial capacity and osteogenesis of Zn-CPS improved with the increase of ZnO content, while the degradation behavior of Zn-CPS exhibited different laws in vitro and in vivo. Specifically, after implantation for 12 weeks, the bone formation percent and degradation percent of 5Zn-CPS could up to 43.0% and 50.9%, indicating an excellent bioadaptability. Moreover, proteomics analysis of adsorbed proteins on Zn-CPS indicated that the addition of ZnO into CPS may activate PI3K-Akt signaling pathway to promote osteogenesis, and degradation contrast in vitro and in vivo also demonstrated that in vivo related factors, such as proteins, cells and enzymes played the crucial role in degradation. These findings imply that Zn-CPS bioceramics are promising materials for bone defect repair with infections.

Effect of ZnO on Properties of Gels for Heritage Objects Conservation.

One of the current research objectives is the development of new films for the conservation of glass heritage objects. The value of historical glass objects is given by the technology and raw materials used in production as well as their transparency and color. Their colors are correlated with oxide composition rich in transitional metals, which decrease resistance of corrosive agents from the atmosphere. In this paper, SiO2-ZnO gels have been designed to protect historical glass objects. The sol–gel method used to obtain gels is a powerful tool for functionalizing different materials. An important functionalization is the antibacterial activity. By applying a gel, the coated material is able to decrease the growth of bacteria. After deposition, some gels must be strengthened by heat treatment. The effect of ZnO content (10 mol% and 20 mol%) on the properties of the studied gels was investigated by Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and antibacterial tests. Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, and the halotolerant bacterium, Virgibacillus halodenitrificans, isolated from a salt crystal from Unirea mine, Slănic Prahova, Romania, were used. The gel Gel 2 (SiO2-ZnO (20 mol%)) showed the best properties.

Hydrothermal Synthesis of ZnO–doped Ceria Nanorods: Effect of ZnO Content on the Redox Properties and the CO Oxidation Performance

The rational design of highly efficient, noble metal-free metal oxides is one of the main research priorities in the area of catalysis. To this end, the fine tuning of ceria-based mixed oxides by means of aliovalent metal doping has currently received particular attention due to the peculiar metal-ceria synergistic interactions. Herein, we report on the synthesis, characterization and catalytic evaluation of ZnO–doped ceria nanorods (NR). In particular, a series of bare CeO2 and ZnO oxides along with CeO2/ZnO mixed oxides of different Zn/Ce atomic ratios (0.2, 0.4, 0.6) were prepared by the hydrothermal method. All prepared samples were characterized by X-ray diffraction (XRD), N2 physisorption, temperature-programmed reduction (TPR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The CO oxidation reaction was employed as a probe reaction to gain insight into structure-property relationships. The results clearly showed the superiority of mixed oxides as compared to bare ones, which could be ascribed to a synergistic ZnO–CeO2 interaction towards an improved reducibility and oxygen mobility. A close correlation between the catalytic activity and oxygen storage capacity (OSC) was disclosed. Comparison with relevant literature studies verifies the role of OSC as a key activity descriptor for reactions following a redox-type mechanism.

One-step hydrothermal preparation and characterization of ZnO–TiO2 nanocomposites for photocatalytic activity

ZnO–TiO2 nanowire composites with different Zn/Ti molar ratios were prepared by one-step hydrothermal process. The crystal structure, surface morphology and chemical state of the samples were characterized by XRD, SEM, TEM and XPS. The effect of ZnO content on the photocatalytic performance was investigated by degradation of Rhodamine B dye under xenon lamp illumination. The XRD result indicated that Zn/Ti molar ratio significantly affected the crystallinity and phase composition of ZnO–TiO2 composites. SEM images showed that ZnO nanoparticles of smaller size were dispersed on the surface of TiO2 nanowires and aggregated in the TiO2 framework. The optimal Zn/Ti molar ratio of 5% was obtained with highest photocatalytic activity, which could be attributed to the superior charge separation ability.

Methanol steam reforming for hydrogen production over ternary composite ZnyCe1Zr9Ox catalysts

Developing the catalysts for methanol steam reforming (MSR) via interfacial construction still remains many challenges. In this study, the effects of ZnO content on the performance of ZnyCe1Zr9Ox were studied for MSR. The best-performing Zn1Ce1Zr9Ox catalyst exhibited full methanol conversion and higher H2 production rate of 0.31 mol·h−1·gcat−1 at 400 °C. Characterization results revealed the synergistic effect among ZnO, CeO2 and ZrO2 after forming a solid solution and the incorporation of Zn2+ into Ce1Zr9Ox matrix not only modulate the ratio of surface OLatt/OAds, but also generate new Zn–O–Zr interfacial structure corresponding to the lattice/bridge oxygen to increase the selectivity of CO2. The excess oxygen vacancies on the samples surface favor the decomposition of methanol to generate the undesired CO. This study proposes a new design strategy for developing highly efficient composite MSR catalysts by control of the lattice/bridge oxygen and surface oxygen vacancy.

Effects of ZnO addition on the sintering behavior and mechanical properties of magnesium aluminate spinel ceramics

AbstractThis article discusses the successful preparation of high‐strength solid solution spinel ceramics via a solid‐state reaction sintering process employing MgAl2O4. The effects of ZnO content on the sintering behavior, bulk density, apparent porosity, phase composition, microstructure, cold modulus of rupture, and modulus of elasticity of the MgAl2O4‐based ceramics are investigated. The results show that the formed MgAl2O4‐based ceramics represent an MgAl2O4–ZnO solid solution, which markedly improves the sinterability, densification, and mechanical properties of the pure MgAl2O4 ceramic and decreases the sintering activation energy.

Sponge‐like chitosan‐based nanostructured antibacterial material as a topical hemostat

ABSTRACTIn this study, chitosan/alginic acid/zinc oxide (CHI/AA/ZnO) nanostructured hydrogel sponges were fabricated by incorporating ZnO nanoparticles (<100 nm) into polymer matrix to develop a new potential biomaterial for hemorrhage control. For this purpose, the crosslinked CHI/AA/ZnO nanostructured sponges were synthesized by freeze‐drying technique. Genipin was used as a crosslinker. The prepared chitosan‐based sponges were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy—energy‐dispersive spectroscopy analysis. The effects of ZnO content on the physicochemical characteristics of sponge‐like nanostructured hydrogels were evaluated by swelling ratio in two different pH values. Physical immobilization of dexamethasone as a model drug in hydrogel matrix resulted sustained release of drug more than 3 days. Antibacterial activity of hydrogel sponges was assessed against Staphylococcus aureus. The cytotoxicity and hemostatic efficacy of crosslinked CHI/AA/ZnO sponge like‐nanostructured hydrogels was evaluated in vitro and in vivo, respectively. The results of this study demonstrated that the prepared CHI/AA/ZnO nanostructured sponge had the potential to be an antibacterial topical hemostat. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47522.

Enhanced mechanical property of Ca5(PO4)2SiO4 bioceramic by a biocompatible sintering aid of zinc oxide

In the present work, a biocompatible additive ZnO was used to enhance the sintering of calcium phosphate silicate (CPS)11CPS: Ca5(PO4)2SiO4. bioceramic and improve its mechanical property. Sol-gel prepared CPS powders were mechanically mixed with various amount of ZnO and then sintered at high temperatures to prepare Zn-CPS bioceramics. The effects of ZnO content and sintering temperature on microstructure and bending strength of Zn-CPS bioceramics were investigated and the related mechanism was also discussed. The results showed that ZnO could significantly enhance the sintering of CPS and improve its bending strength accordingly. The Zn-CPS bioceramic with 1 wt% ZnO sintered at 1300 °C exhibited a highest bending strength of 80.8 MPa. The enhanced densification of Zn-CPS bioceramics might be attributed to the liquid phase appeared during the sintering process and the formation of Ca2ZnSi2O722HT: Ca2ZnSi2O7. (HT) nano-grains at grain boundaries. It is expected that Zn-CPS bioceramics could have both good mechanical property and excellent bioactivity.

Enhanced dielectric and energy-storage properties in ZnO-doped 0.9(0.94Na0.5Bi0.5TiO3−0.06BaTiO3)−0.1NaNbO3 ceramics

[0.9(0.94Na0.5Bi0.5TiO3−0.06BaTiO3)−0.1NaNbO3]-xZnO (NBT-BT-NN-xZnO, x=0, 0.5wt%, 1.0wt%, 1.5wt%, and 2.0wt%) ferroelectric ceramics were fabricated using a conventional solid-state reaction method. The effects of ZnO content on dielectric, energy-storage and discharge properties were systematically investigated. Dielectric constant and difference between maximum and remanent polarization were significantly improved by ZnO doping. Dielectric constant of NBT-BT-NN-1.0-wt% ZnO was 3218 at 1kHz and room temperature, i.e. one time bigger than that of pure NBT-BT-NN ceramic. As a consequence, a maximum energy-storage density of 1.27J/cm3 with a corresponding efficiency of 67% was obtained in NBT-BT-NN-1.0-wt% ZnO ceramic. Moreover, its pulsed discharge energy density was 1.17J/cm3, and 90% of which could be released in less than 300ns. Therefore, ZnO doped NBT-BT-NN ceramic with a large energy-storage density and short release time could be a potential candidate for applications in high energy-storage capacitors.

Effects of ZnO content on microstructure and properties of maleated EPDM/zinc oxide composites

Properties of maleic anhydride-grafted ethylene–propylene–diene terpolymer/zinc oxide (MAH-g-EPDM/ZnO) composites with varying ZnO contents were characterized by the crosslink density, average grain size of zinc oxide, and ionomeric bond formation. The crosslink densities were measured by swelling method, the average grain sizes of ZnO were determined by X-ray diffraction (XRD), and the ionomeric bond formation was observed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). By increasing the ZnO content, the crosslink density increased, the average ZnO grain size increased, and level of the ionomeric bond formation tended to increase. The modulus increased and then reached to a plateau, whereas the elongation at break decreased and then reached to a plateau with increase in the ZnO content. From the experimental results, the proper ZnO content was found to be about 5 phr. Various crosslink types formed in the MAH-g-EPDM/ZnO composite were discussed.

Microstructure and properties of ZnO doped CaO–Al2O3–SiO2 ceramic for LTCC applications

The effects of ZnO content and sintering temperature on the microstructure, bending strength, coefficient of thermal expansion and dielectric properties of Li2O–Al2O3–SiO2 glass–ceramic are presented. The prepared Li2O–Al2O3–SiO2 glass–ceramic could be used for the application of LTCC substrate. Glass powders were produced by conventional melt-quenching technique. The sintering and crystallization behavior of glass powders was explored using scanning electron microscopy, differential thermal and X-ray diffraction analyses. The crystalline phase formation in the calcination of Li2O–Al2O3–SiO2 samples has shown a major phase of Li2OAl2O37.5SiO2 and two minor phases ZrO2 and CaMgSi2O6. Increasing ZnO content at the expense of SiO2 was shown to not only promote the densification and lower the linear shrinkage, but also enhance the bending strength and the coefficient of thermal expansion of the glass–ceramic. The linear shrinkage and density of samples will decrease with the increasing sintering temperature.

ZnO-doped BaTiO3-Na0.5Bi0.5TiO3-Nb2O5-based ceramics with temperature-stable high permittivity from –55 °C to 375 °C

A lead-free, high-permittivity and high-temperature X–R type dielectric material was successfully prepared in ZnO-doped BaTiO3-Na0.5Bi0.5TiO3-Nb2O5(BNN)- based system. The effects of ZnO content on the phase structure, electric and dielectric properties of the ceramics were investigated. Results indicate that ZnO addition plays a critical role in increasing permittivity and improving the temperature stability. The 5wt% ZnO-doped sample shows the optimal dielectric performance (εr=2404; tanδ=1.76%; ΔC/C20°C<±13%) that satisfies EIA X-R specification. In particular, the ceiling working temperature is significantly enhanced from 200°C to 375°C and the permittivity is increased to 2404 by doping ZnO. These results suggest that these materials are promising candidates for preparing miniaturized ultra-broad temperature multilayer ceramic capacitors.

Effects of ZnO content on the performance of Pd/Zr0.5Al0.5O1.75 catalysts used in lean-burn natural gas vehicles

Mixed oxides obtained by adding varying amounts of ZnO into Zr0.5Al0.5O1.75 were used as supports to prepare 1.5% Pd catalysts. The catalyst activity and H2O tolerances of the catalysts were evaluated in a gas mixture simulating the exhaust of lean-burn natural gas-fueled vehicles. The catalysts were further characterized by N2 adsorption-desorption, X-ray diffraction, H2 temperature programmed reduction and X-ray photoelectron spectroscopy. The catalytic activity was greatly influenced by ZnO contents in Zr0.5Al0.5O1.75 support. The catalyst containing 15% ZnO exhibited a light-off temperature and complete conversion temperature for CH4 in the absence of H2O of 278 and 314 °C, respectively; while these same values in the presence of H2O were 342 and 371 °C, respectively. These results indicate that this combination of materials offers excellent catalytic activity at low temperature and also exhibits significant H2O tolerance.

Synthesis at the nanoscale of ZnO into poly(methyl methacrylate) and its characterization

In this paper, PMMA/ZnO nanocomposites have been prepared by a very simple, facile and versatile chemical approach. The prepared PMMA/ZnO nanocomposites possess no color, high transparency, good thermal stability, UV-shielding capability, luminescence and homogeneity. The chemical process involved solution mixing of ZnO nanoparticles dispersed in DMAc with the Polymethylmethacrylate (PMMA) matrix dissolved in the same solvent. The effect of ZnO content on the physical properties of the PMMA matrix is investigated by X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, UV–Vis absorption and photoluminescence spectroscopy. It was found that pure hexagonal ZnO nanoparticles with an average particle size of 4–8 nm were homogeneously dispersed in the PMMA matrix. A significant improvement in thermal properties was observed with the incorporation of 1.0 wt% ZnO nanoparticles. The prepared nanocomposite films are highly transparent and a clear excitonic peak is observed in their absorption spectra. Measurement of room temperature photoluminescence spectra shows intensive near-band edge emission peak at 3.28 eV without any structural defects for a nanocomposite film with a filler content of 1.0 wt%.

Phase structure and electrical properties of (K0.5Na0.5)NbO3–(Bi0.5Na0.5)ZrO3 lead-free ceramics with a sintering aid of ZnO

0.95(K0.5Na0.5)NbO3–0.05(Bi0.5Na0.5)ZrO3–xZnO (KNN–BNZ–xZnO) lead-free piezoceramics were prepared by the conventional solid-state method, and effects of ZnO content on their phase structure, microstructure, and electrical properties were studied. The ceramics with x=0.01 possess the mixture of both rhombohedral–orthorhombic and orthorhombic–tetragonal phase boundaries. Their grain size becomes more homogenous and much smaller with the addition of ZnO. Enhanced dielectric and piezoelectric properties (e.g., d33=320pC/N, kp=0.484, TC=320°C) were observed in the ceramic with x=0.01. These results show that such a material system belongs to be a promising lead-free piezoelectric material.

Microstructure and Electrical Properties of K0.5Na0.5NbO3-LiSbO3-BiFeO3-x %molZnO Lead-Free Piezoelectric Ceramics

Lead-free piezoelectric ceramics {0.996[(0.95(K0.5Na0.5)NbO3-0.05LiSbO3]-0.004BiFeO3}-xmol%ZnO were prepared through a conventional ceramics sintering technique. The effect of ZnO content on structure, microstructure, and piezoelectric properties of KNN-LS-BF ceramics was investigated. The results reveal that ZnO as a sintering aid is very effective in promoting sinterability and electrical properties of the ceramics sintered at a low temperature of 1,020 °C. The ceramics show a single-perovskite structure with predominant tetragonal phase, and coexistence of orthorhombic and tetragonal phases is observed for x = 2.5–3.0. The addition of ZnO causes abnormal grain growth. A dense microstructure is also obtained at x = 2.0 because the relative density reaches up to 94.6 %. The morphotropic phase boundary and dense microstructure lead to significant enhancement of the piezoelectric properties. The ceramic with x = 1.5 exhibits optimum electrical properties as follows: d33 = 280 pC/N, kp = 46 %, Qm = 40.8, Pr = 25 μC/cm2, Ec = 1.2 kV/mm, and Tc = 340 °C.