Increasing ZnO Content Research Articles

DC surface flashover characteristics of ZnO/Epoxy composites at room temperature and 77 K

Epoxy (EP) resin based nano-composites are widely used in high voltage direct current (HVDC) high temperature superconducting (HTS) power cable. In this paper, the DC surface flashover characteristics of ZnO/EP composites were studied at both room temperature and 77 K. The samples were made by dispersing ZnO nano-particles into EP resin with various weight percentages of 0%, 1%, 3%, 6% and 10%, respectively. The experiments were carried out with a cryogenic system in which DC high voltages ranging from 0 kV to 100 kV were supplied. The results showed that the surface flashover voltages increased with the increase of ZnO content at both room temperature and 77 K, and the surface flashover voltages at 77 K were higher than that at room temperature for composites with the same ZnO content.

In situ synthesis of fluorapatite‐ZnO nanocomposite powder via mechanical alloying for biomedical applications

AbstractThis research aimed to synthesize of fluorapatite(FA)–ZnO (FAZ) nanocomposite powder using a one‐step mechanical alloying process without any post‐calcification process. Furthermore, the role of various concentrations of ZnO (0, 4, 8, 11, and 15 wt.%) on the chemical and biological characteristics of FA was examined. Our research confirmed the successful synthesize of FAZ nanopowders with irregular‐shaped particles and particle size of 38‐52 nm. The crystallinity, crystallite size, and c‐axes parameter of FA decreased with increasing ZnO content. Moreover, while all FAZ powders revealed superior bioactivity than FA, FA‐8 wt.% ZnO nanopowder significantly enhanced MG63 cell proliferation. Besides, between various samples, FA‐11 wt.% ZnO nanopowder revealed drastically greater antibacterial activity. It could be concluded that the in‐situ synthesis of FAZ powder meaningfully improved the biological activity of FA making it a promising coating for orthopedic and dental implants.

Structural, optical and impedance spectroscopy study of thin film of polyaniline (PANI/ZnO) nanocomposite

Modern organic electronic and power electronic devices gained attention due their superior performance and efficiency with reduced cost. While nanocomposites of these organic semiconductors have high potential to further enhance these properties. In this work, thin films of zinc oxide-polyaniline (ZnO-PANI) nanocomposite with different compositions of ZnO (50, 60 and 70 wt%) are deposited by spin coater onto the surface of p-Si. The phase identification of the samples is identified through x-ray diffraction analysis. Pure ZnO showed wurtzite crystalline while PANI and nanocomposites of ZnO-PANI showed amorphous structure. The optical absorption band gap was evaluated from Ultraviolet–visible spectroscopy absorption studies and band gaps were calculated from Tauc’s plots. The Ultraviolet–visible spectroscopy showed that by increasing ZnO content in the nanocomposite, the band gap increases from 3.25 eV to 3.3 eV and 3.4 eV for 50–50, 60–40 and 70–30 wt% respectively. The AC electrical properties of the nanocomposites were studied by using impedance spectroscopy. The parameters extracted from the impedance plots and conductivity values showed that 50–50 wt% is more conductive while that of 70%–30% wt is more resistive.

Dielectric and piezoelectric properties of (K0.475Na0.495Li0.03) NbO3-0.003ZrO2/PVDF 0–3 composite reinforced with two types of nano-ZnO particles

(K0.475Na0.495Li0.03) NbO3–0.003ZrO2 (KNNL-Z) ceramic was synthesized by the conventional solid-state reaction method. The purchased ZnO nanorods (denoted as ZnO1) and synthesized ZnO nanocakes (denoted as ZnO2) were used in the preparation of two types of composites fabricated by hot-pressing process using KNNL-Z ceramic powder, two kinds of ZnO nanoparticles, and PVDF polymer. The effects of the ZnO nanoparticles on the crystalline structures, morphology, thermal, dielectric, and piezoelectric properties of the composites were studied systemically. The KNNL-Z ceramic possesses a perovskite-type orthorhombic phase and the PVDF polymer mainly possesses α, β, and γ phases. Two kinds of ZnO all possess hexagonal wurtzite structures without any impurity phase. Interestingly, the incorporation of the ZnO nanoparticles has great impact on lattice constants and strain. In addition, the β phase content increases when the ZnO nanoparticles are added. From differential scanning calorimetry (DSC) measurements, it is found that the ZnO nanoparticles can enhance the thermal stability of composites. Moreover, the dielectric and piezoelectric properties are also found to be improved with the increase of ZnO content. Especially when 10 wt% ZnO2 is added, the dielectric constant reaches the value of 469.4 (100 Hz) at room temperature and the piezoelectric coefficient is 55 pC/N. After 30 days of aging test, it is obvious that all the composites present a good stability of piezoelectric property.

Effect of ZnO incorporation on the structural, thermal and optical properties of phosphate based silicate glasses

Zinc based phosphate-silicate glasses with a molar composition of (0.9-x)NaPO3-0.1SiO2-xZnO (0 ≤ x ≤ 0.3 mol%) were successfully synthesized by melt quenching technique. The amorphous state of the glass series was checked using X ray diffraction (XRD).The variation of density, molar volume and refractive index were correlated to increase in the compactness of the vitreous network when ZnO oxide is progressively introduced.The Fourier transformed infrared and Raman spectroscopy investigations revealed that the glass network depolymerized with the increase of ZnO content. This result induces the disruption of metaphosphate chains (Q2) suggesting the formation of phosphate dimers (Q1).The DSC analysis shows the increase of Tg and Tc with the incorporation of ZnO oxide is due to the development of a more compact network structure.Optical properties were investigated by means of UV–visible spectroscopy. The variation of the band gap energy (Eopt) of the glass series were attributed to the increase of the non bridging oxygen (NBO) resulting from the disruption of the metaphosphate chains.

Thermal annealing and channel composition influences on the electrical properties of transparent-TFTs based on Zn-In-SnO ternary compound: Experiment and modeling

In this study, we present a quantitative analysis of the electrical properties of a series of bottom- gate top-contact n-channel transparent thin film transistors (TFTs) based on zinc indium tin oxide (Zn-In-SnO) ternary compound with various ZnO content. In addition, the effect of annealing on the TFTs electrical properties was examined theoretically and experimentally. The obtained results revealed that the thermal annealing of fabricated devices in air atmosphere at 300 °C has enhanced their performances; this behavior is well observed for all devices fabricated with different composition of Zn-In-SnO. TFTs having the lowest Zn content of 17.1% and annealed 300°C showed the high electrical performances in term of drain current, saturation mobility, threshold voltage. For the total resistance modeling of the fabricated devices with various content of ZnO and that annealed 300 °C, grain boundary model based on Meyer–Neldel rule was applied. The obtained results revealed that the total resistance was increased with increasing ZnO content. Furthermore, an analytical model has been refined in order to reproduce the current-voltage relationships of the fabricated TFTs using the overall resistance obtained from the NMR–GBT model. The calculated results are in good agreement with the experimental measurements of all fabricated devices. The obtained performance of TFTs based on zinc indium tin oxide with low content of ZnO and annealed will be promising for application in the future backplane of flat panel displays.

Dielectric and piezoelectric properties of 0.970(0.95(K0.485Na0.515)NbO3–0.05LiSbO3)–0.015CuO–0.015Al2O3/PVDF 0–3 composite reinforced with two kinds of ZnO powder

0.970(0.95(K0.485Na0.515)NbO3–0.05LiSbO3)–0.015CuO–0.015Al2O3 (KNNLS–CA) ceramic powder obtained through the conventional solid state reaction. The ZnO nanoparticles (denoted as ZnO1) and poly (vinylidene fluoride) (PVDF) were supplied from commercial companies. The self-synthesized ZnO powder (denoted as ZnO2) were prepared by hydrothermal method using Zn (CH3COO)2·2H2O and NaOH. Subsequently, the two kinds of composites were fabricated by hot-pressing process using KNNLS–CA ceramic powder, two kinds of ZnO powder and PVDF polymer. The effects of the ZnO on the crystalline structures, morphology, thermal stability, densities and electric properties of composites were studied systemically. The KNNLS–CA ceramic possesses a perovskite phase with orthorhombic symmetry and peaks from the second phase of K3Li2Nb5O15 (PDF#52-0157) are detected by X-ray diffraction. PVDF polymer mainly possesses α, β and γ phases. Two kinds of ZnO all possess hexagonal wurtzite structures without any impurity phase. It is worth noting that the ZnO particles have great impacts on lattice constants, strain and crystallinity. In addition, the ZnO particles can enhance the relative fraction of β phase in PVDF and improve the thermal stability of the composite. Interestingly, the dielectric and piezoelectric properties are also found to be improved with the increase of ZnO content. Especially, when 10 wt.% ZnO2 is doped, the dielectric permittivity reaches the value of 586.4 (100 Hz) at room temperature and the piezoelectric constant is 64 pC/N. After 30 days of aging test, it is obvious that all the composites present a good stability of piezoelectric property.

Preparation and characterization of invert ZnO–B2O3 glasses and its shielding behavior towards gamma irradiation

Binary zinc borate glasses with invert compositions (50–75 mol % ZnO) were prepared by melting and annealing technique. The glasses were collectively characterized by measuring and identifying their structural building groups through FTIR spectroscopy and their optical transparency beside also their thermal expansion parameters. FTIR spectra reveal compact vibrational bands within the mid region 400-1700 cm−1 reflecting both triangular and tetrahedral borate groups beside the sharing of ZnO as either modifier oxide or as B–O–Zn linkages and possibly ZnO4 groups. The optical absorption measurements reveal that the studied undoped ZnO–B2O3 glasses show distinct UV absorption extending from 200 to 370 nm with three peaks and these UV absorption peaks are related to unavoidable trace iron (Fe3+) impurities contaminated within the chemicals used for the preparation of the zinc borate glasses. The optical absorption spectra after gamma irradiation with a dose of 5 Mrad reveal the maintenance of the UV spectra identified before irradiation with the appearance of a minor curvature at 510 nm in the spectra of two samples and disappeared at high ZnO contents. Such optical spectral result after irradiated refers to suggested shielding effect towards gamma irradiation with high ZnO content in the studied invert compositions. Both the dilatometric softening temperatures and density data show obvious increase with the first increase of ZnO content up to 70% and then reveal constancy. This behavior is correlated with the mode of housing Zn2+ ions in the network structure which is assumed to form some ZnO4 groups at high percent of ZnO giving compactness to the network of such glasses.

Influence of ZnO-doping on the properties of high-ferrite cement clinker

Responding to the strategy of sustainable development, Cement manufacturing industry become an effective method to dispose municipal solid waste (MSW). Zinc is a heavy metal element that might be introduced by industrial wastes to the cement kilns, resulting in a performance degradation. High-Ferrite Cement (HFC), as a kind of sulphate-resistant Portland cement has attracted extensive interesting. Different from the mineral composition of Portland cement, HFC have a low C3S and high C4AF, which may be have a better solidification capacity due to the content increase of solid solution C4AF. This study attempt to explore the influence of doping ZnO on the performance of HFC. The results indicated that the compressive strength of 28 days increased from 57.1 to 70.3 MPa when the content of doping ZnO reached 1.5 wt% and hydration reactivity increased with the increase of ZnO content. The reason could be ascribed to the decrease of retardation effect on C3S and increase of promotion effect on C4AF with the change of miner composition of cement clinker. Beyond that, promotion plays a pivotal role between the two factors. The mechanism analysis indicated that ZnO doping promoted the transformation of Fe in the C4AF from [FeO4] to [FeO6] and increased the effective charge, resulting in a higher hydration reactivity. The result obtained varied from that reported in previous researches, and proved out that HFC can be a good material to Zn solidification/stabilization.

Facile Synthesis of Nano-Diced SnO2–ZnO Composite by Chemical Route for Gas Sensor Application

The simple chemical bath deposition (CBD) method is used to synthesize SnO2–ZnO nanocomposite at room temperature. Formation of SnO2–ZnO nancomposite is confirmed by the x-ray diffraction (XRD) pattern of annealed films. Scanning electron microscopy (SEM) micrographs of nanocomposite SnO2–ZnO depict that morphological change from nanocubes to manifold hexagonal nanorods with an increase in ZnO content in a composite sample. Also, pure SnO2 sample exhibits interconnected nanospheres. Electron dispersive spectroscopy (EDS) is employed to confirm elemental compositions in composite films. SnO2–ZnO samples were applied as a sensor for different test gases, namely liquified petroleum gas (LPG), ethanol, ammonia (NH3), and hydrogen sulfide (H2S). The maximum response of 59.67% is observed for ethanol at an operating temperature of 275°C and 24 ppm gas concentration. Also, a composite sensor shows a quick response in comparison with a bare sensor. This superior performance of composite over pure sensor may be attributed to a n–n heterojunction at intergrain boundaries. The SnO2–ZnO sensor is found to be selective towards ethanol even at lower gas concentrations.

The temperature-dependent electric properties of ZnO-doped Bi0.5Na0.5TiO3–BiCoO3 lead-free piezoceramics

In order to resolve the depolarization of Bi0.5Na0.5TiO3-based ceramics, the ZnO particles was introduced into the relaxor ferroelectric Bi0.5Na0.5TiO3–0.025BiCoO3 ceramics. The depolarization temperature increases with increasing ZnO content, the Td increase from around 150 °C to around 180 °C at 0.3 mol% ZnO. The BNT-0.025BC ceramics doped with 0.1 mol% ZnO possessed high ferroelectric properties (Ps = 37.0811 μC/cm2, Pr = 33.7322 μC/cm2 and Ec = 6.49315 kV/mm). These results not only can be used for making high temperature electromechanical devices, but also have great effect on the understanding of the mechanism of the depolarization.

Effect of ZnO and MoO3 Addition on Thermal and Mechanical Properties of Tellurite Glasses

In the present study, zinc‐molybdenum‐tellurite glasses are prepared and their thermal, thermo‐mechanical, viscous, and mechanical properties for mid‐IR molded glass lens applications are studied. From the thermal analysis, it is found that the glass transition temperature, onset crystallization temperature, and stability parameters slightly increase with an increase in ZnO content in both series of glasses. Thermal expansion coefficient decreases from 16.56 to 14.67 × 10−6 K−1 as the ZnO content increased from 10 to 30 mol%. For fixed 10 mol% of MoO3 content, Knoop hardness slightly decreases from 3009 to 2842 MPa as ZnO content increases from 10 to 30 mol% whereas it increases for 20 mol% of MoO3. The results indicate that the addition of ZnO and MoO3 contents into the tellurite glass system increases bridging oxygen contribution and in turn network compactness of tellurite matrix.

FTIR and Raman spectroscopy studies of ZnO-doped BaO⋅2B2O3 glass matrix

The glasses of the xZnO-(1-x)[0.33BaO-0.67B2O3] system (0 ≤ x ≤ 0.35) were prepared by the melt quenching technique. The FTIR and Raman spectroscopy were employed to study the influence of zinc oxide on the boron-oxygen network structure of the binary BaO-B2O3 glass matrix. Increasing ZnO content was found to induce progressive conversion of four-fold coordinated boron species to the trigonal borate units. The increase in the fraction of three-fold coordinated borate units is primarily related to the transformation of [BØ4]− tetrahedral units into BØ2O− metaborate units at x ≤ 0.15. The high-charged pyro- and orthoborate units are formed in the glass structure at further increase in x. These effects are discussed concerning the nature of the borate network at various ZnO contents. The density of the studied glasses was found to be gradually increased with increasing ZnO content, while the molar volume exhibits an opposite trend.

The structure of model glasses of the amorphous phase of glass-ceramic glazes from the SiO2[sbnd]Al2O3[sbnd]CaO[sbnd]MgO[sbnd]Na2O[sbnd]K2O[sbnd]ZnO system

In this work, particular attention was paid to the structural characteristics of the amorphous phase in glass-ceramic glazes from the SiO2Al2O3CaOMgONa2OK2OZnO system. The study was carried out on model glasses whose chemical composition corresponds to the chemical composition of the vitreous phase of the glazes determined on the basis of electron probe micro-analyzer (EMPA). Structural investigations of the obtained model glasses were carried out using the mid-infrared (MIR) and solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The solid-state MAS-NMR study carried out on 27Al and 29Si nuclei showed that all aluminum and silicon ions have tetrahedral coordination and thus form the glass network. The results of the 29Si solid-state MAS-NMR measurements also showed that with the increase of ZnO content in the glass chemical composition, the number of Q3 and Q2 silicon-oxygen units increases at the expense of Q4 (where n is the number of bridging oxygens), thus indicating an increase in the degree of depolymerization of the alumino-silico-oxygen network of studied of glasses. Analysis of the MIR spectra of the obtained glasses confirmed the conclusions from the solid-state MAS-NMR research, i.e. that Zn2+ ions cause depolymerization of the glass network of glazes. The weakening of the network of glasses resulted in lowering of the transformation and dilatometric softenings temperature. The tests carried out on model glasses allow drawing conclusions about the structure and properties of the vitreous phase of real glazes.

CuZn Catalysts Superior to Adkins Catalysts for Dimethyl Adipate Hydrogenolysis

AbstractIndustrial hydrogenolysis of esters to alcohols relies on the use of Adkins catalysts whose production and disposal is an environmental burden. This work is focused on CuZn catalysts that represent an ecological alternative to Adkins catalysts. Four CuZn catalysts with Cu/Zn atomic ratio ranging from 0.5 to 2.0 and single phase CuO and ZnO catalysts were prepared by co‐precipitation and their hydrogenolysis activity was compared with a commercial Adkins catalyst. Dimethyl adipate was used to test the catalyst performance in a flow reactor at temperatures ranging from 175 to 205 °C and hydrogen pressure of 16 MPa. The increase in ZnO content was directly responsible for the reduction in copper crystallite size and increase in the catalyst specific surface area. The CuZn catalysts exhibited higher conversion than the Adkins catalyst despite their specific surface area declined during the experiments more significantly than that of the Adkins catalyst. Nonetheless, the TOF of CuZn catalysts exceeded that of the commercial Adkins catalyst.

Thermal and optical properties of lithium-zinc-tellurite glasses

(100-X-Y)TeO2-XLi2O-YZnO, X = 10, 15 and 20, Y = 0, 5, 10, 15, 20, 25 and 30 mol%, glasses have been prepared by the melt quenching technique. Density and molar volume have been identified for every glass sample. Differential Scanning Calorimetry (DSC), optical absorption in the ultraviolet–visible region, Raman spectroscopy and linear refractive index have been achieved. DSC results show a considerable increase in glass stability with the replacement of TeO2 by ZnO. The Band Gap energy, determined from UV-VIS results, gradually increases in all set of samples. The Raman spectroscopy results confirm a structural change: with the increase of ZnO content (until TeO2 = 65 mol%), a decrease of non-bridging oxygens is verified, which decreases the polarizability of the system and increasing the Band Gap energy.

Modifier role of ZnO on the structural and transport properties of lithium boro tellurite glasses

To study the modifier role of ZnO on the structural and transport properties, the quaternary glass system xZnO-(30-x) Li2O-10TeO2–60B2O3 (x = 0, 5, 10, 15 and 20 mol%) was prepared by the conventional melt quenching technique. Amorphous nature of the prepared glasses was confirmed by X-ray diffraction studies. Density (ρ) of the glass samples was measured by Archimedes' principle and it was found to vary non-linearly between 3.06 and 3.44 g/cm3 with the addition of heavy metal oxide (ZnO) mole concentration. Oxygen packing density (OPD) values also varied non-linearly between 66.78 and 74.69 g atm/1. Glass transition temperature (Tg) of the glass system was measured using temperature modulated differential scanning calorimeter and Tg was found to increase from 429 °C-449 °C with the increase of ZnO content. Based on the density and molecular weight of the glass composition, mechanical properties like Young's modulus (E), Shear modulus (S), Bulk modulus (K) etc., have been calculated with the help of Makishima-Mackenzie model in terms of the packing ratio (Vρ) and dissociation energy (Gt). FTIR and Raman spectroscopy studies reveal that the glass network consists of various types of BO3, BO4 units along with TeO3, TeO4 and ZnO4 structural units. To study transport properties, AC conductivity measurements were carried out on the glass system in the frequency range 5 Hz-35 MHz and it was observed that the ionic conductivity plays significant role. At low temperatures (30 °C and 50 °C) the results of conductivity did not give good results. AC conductivity of the studied glass system is increased with increase in frequency and temperature. The highest value of AC conductivity of the glass network is of the order 10−2 Ω−1 cm−1. Impedance plots (Cole-Cole) exhibited semicircle behaviour.

Effect of ZnO content on microstructure, crystallization behavior, and thermal properties of xZnO-30B2O3-(65-x)Bi2O3-5BaO glass

xZnO-30B2O3-(65-x)Bi2O3-BaO (x = 40–60 mol%) glasses were prepared by the melt quenching method. The microstructure, crystallization behavior, and thermal properties of the glasses were investigated. The results show that the samples with 40–55 mol% ZnO possess an amorphous structure after melting at 950 °C. When the ZnO content increases to 60 mol%, the sample possesses strip-shaped Zn3B2O6 crystals after melting at 950 °C, and becomes homogenous glass at 1050 °C. The thermal expansion coefficient (TEC) decreases from 10.294 to 7.43 × 10−6/°C when the ZnO content increases from 40 to 60 mol%. Both the glass transition temperature and glass softening temperature increase with increasing ZnO content. In addition, needle-shaped Bi2ZnB2O7 crystals are observed on the glass surface after annealing at crystallization temperatures for 1 h, and the amount of crystals decreases with increasing ZnO content. Furthermore, the weight loss ratio of the glasses increases gradually as the content of ZnO increases. After 48 h, the magnitude of weight loss value in 6 wt% of HNO3 or NaOH solution at 90 °C is 10−3 g/cm3∙min while it is 10−7 g/cm3∙min in deionized water.

Investigation of structural properties of hydroxyapatite/ zinc oxide nanocomposites; an alternative candidate for replacement in recovery of bones in load-tolerating areas

Abstract Sol-gel method was used to synthetize hydroxyapatite and zinc oxide nanoparticles whose formation and nano structural properties were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FT-IR) techniques. Results confirmed that they possess hexagonal structure containing spherical nanoparticles. Then, HAP/ZnO nanocomposites containing different amounts of ZnO were prepared using cold pressing method at a pressure of 370 MPa, followed by sintering at a the temperature of 1000 °C for 3 h in atmospheric air. Their structural properties were investigated using similar techniques. These grain-structured nanocomposites also have hexagonal lattice structure whose crystallinity is reduced through increase in ZnO content. This is while heat-treated pure samples possess the highest crystallinity. Increasing ZnO content in composite samples results in better conglomeration, decrement of the mean size of conglomerated grains and uniform conglomeration size distribution. Pore space study indicates the ability of the composite samples to provide a suitable environment for bone tissue to grow and exchange body fluids. Also, compressive resistance measurement indicates that these samples have compressive strength between 11.48 MPa & 17.43 MPa. Finally, it can be deduced that the sample with 30 wt% ZnO has appropriate properties to replace real bone.

Effects of ZnO addition on thermal properties, degradation and biocompatibility of P45Mg24Ca16Na(15−x)Znx glasses

Abstract Four phosphate-based glass formulations in the system P45Mg24Ca16Na(15−x)Znx, referred to as P45Znx (x = 0, 5, 10 and 15 mol%), were prepared using a melt quenching process. The effect of ZnO addition on density, molar volume, thermal properties and degradation rates were studied. An increase in the glass transition, crystallisation, melting and liquidus temperatures were seen when replacing Na2O with ZnO. The molar volume of the bulk glasses was seen to decrease with increasing ZnO content. The dissolution rate of the zinc-free glass was 2.48 × 10−8 kg m−2 s−1 and addition of 5 mol% ZnO resulted in a reduction of the dissolution rate to 1.68 × 10−8 kg m−2 s−1. However, further addition of ZnO from 5 mol% to 15 mol% increased the dissolution rate of the glass system. The glasses were deliberately crystallised and XRD studies identified the Z n2P2O7 phase for glass code P45Zn5, and Zn(PO3)2 phase for P45Zn10 and P45Zn15 glasses. Cyto-compatibility studies were conducted using MG63 cells for 14 days. An overall increase in the metabolic activity and DNA concentration of cells was seen from day 1 to day 14 for all glass formulations investigated. However, increasing ZnO content from 0 to 15 mol% seemed to have a negative effect on the cellular activity. Interestingly, a remarkably higher ALP activity was seen at day 14 for glass codes P45Zn5 and P45Zn10 in comparison with the TCP control and the P45Zn0 glass.