Mixture Of ZnO Research Articles

Formation mechanism and properties of nanorod-structured ZnO films prepared by pyrolysis of Zn acetate films

Nanorod-structured ZnO (NR-ZnO) films were formed on glass substrates by thermal treatment of Zn acetate films in a closed-type tube furnace. The formation mechanism of the NR-ZnO films is proposed as follows: the volatile Zn acetate was vaporized from the top region of the Zn acetate films; the mixture of ZnO and Zn acetate groups in the intermediate region acted as a seed layer; and ZnO NRs were grown in the intermediate region via the vapor-solid process of the volatile groups. The as-formed NR-ZnO films exhibited a wurtzite crystal structure with strong c-axis orientation. The optical bandgap of the film was ∼3.27 eV, and photoluminescence emissions centered at 3.10, 2.98, and 2.81 eV were observed. The diffuse and specular transmittance values of the film were ∼95% and 59% at 550 nm, respectively. This difference originated from the structure of the NRs, which increased the light path length in the films.

Evolution of morphology and defect states in mechanically processed ZnO+xMWCNTs nanosystems

We used scanning electron microscopy (SEM), X-ray diffraction (XRD), laser particle size (LPS) measurements, electron paramagnetic resonance (EPR) and Raman spectroscopy to monitor the evolution of morphology and defect states in mechanically processed mixtures of ZnO and multi-walled carbon nanotubes (MWCNTs) with different content of the latter (0.1%, 0.8% and 2.5% by weight). The morphology and defect structure of initial ZnO powders have significant effect on the properties of nanoparticles formed due to MP. Initial agglomerated ZnO particles of 100–800 nm size are destroyed by MP, producing after 390 min the particle size of ∼40–50 nm. The resulting particles form aggregates with a size of the order of 10 μm. EPR measurements showed the presence of magnetic nanoinclusions Fe3О4 in ZnO component, which cause this aggregation. Increasing MP time, initiates the weak asymmetric signal at g ∼2.001. This signal was attributed to C–C bonds broken due to MP of MWCNTs, which interact with conduction electrons generated by the same process. Raman spectra exhibited characteristic features due to both ZnO and MWCNTs. After MP for 90 min, for all ZnO+xMWCNTs samples almost complete suppression of Raman peaks due to ZnO phase was evident. Nevertheless, after the longest MP for 390 min their partial regeneration was observed. The bands attributable to the carbon component were D, G, G′ and D+G modes. The changes in ID/IG and IG'/IG intensity ratios observed are indicative of a decrease in the degree of MWCNT graphitization with increasing MP duration.

Synthesis of g‐C3N4/ZnO composites with enhanced photocatalytic activity under visible light

AbstractThe g‐C3N4/ZnO composites were synthesized by heating a mixture of urea and ZnO at 500°C and denoted as g‐C3N4/ZnO‐w, where w is the weight ratio of urea/ZnO and equals to 3, 4 and 5. The obtained materials were characterized by X‐ray diffraction, infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, ultraviolet‐visible diffuse reflectance spectroscopy. The results showed that all g‐C3N4/ZnO‐w samples are composites of orthorhombic ZnO and g‐C3N4. The photocatalytic activity of g‐C3N4/ZnO‐w samples was evaluated by degradation of methylene blue in water under visible light. Among them, g‐C3N4/ZnO‐4 sample exhibits the highest photocatalytic efficiency. The enhancement of photocatalytic activity of the g‐C3N4/ZnO composites compared to single components, g‐C3N4 and ZnO was observed, which can be attributed to the reduction of combination rate of photogenerated electron – hole pairs in the composites.

Emission and Structure-Varying ZnO and Carbon Nanocrystal Composite in Mechanical Processing

Morphology, photoluminescence (PL), and Raman scattering spectra have been investigated for mixtures of ZnO+0.1%C nanocrystals (NCs) at different stages of mechanical processing (MP). The transformation of graphite into graphene monolayers covering the ZnO NC surface is revealed for the first MP stage. The interaction with oxygen has been detected in the second MP stage which leads to the dissolution of oxygen interstitials in the ZnO NCs and to the formation of graphene (graphite) oxides. Increasing the concentration of the oxygen interstitials in ZnO NCs also enhances the intensity stimulation of the orange PL band (2.18eV). Simultaneously, the PL band peaking at 2.82–2.90 eV is detected in the PL spectra of the ZnO+0.1%C NC mixture after MP for 9–90 min. Then, the variation of the ZnO NC shape, agglomeration of ZnO NCs, modification of ZnO defects and decreasing PL intensity have been detected after prolonged MP for 390 min. It is expected that short stages of MP can be useful for ZnO NC surface covering by graphene layers or graphene (graphite) oxides.

Preparation and characterization of spinel type Zn2TiO4 nanocomposite

Zinc orthotitanate Zn2TiO4 spinel structures have been prepared by solid state reaction in two stages. First, a mixture of ZnO and TiO2 (67% anatase+33%rutile) in a molar ratio of 2:1 was mechanically milled for 6 and 18 h, at room temperature, in a high energy planetary ball mill under argon atmosphere. Next, the ball milled powders were calcined at 900 °C for 2 h, pressed into pellets and then sintered for 4 h at 1100 °C in air. Phase formation, microstructure, surface morphology and optical properties were characterized by X-ray diffraction, Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, atomic force microscopy and UV–visible spectrophotometery. The mechanical milling process for 6 h gives rise to the formation of nanocrystalline orthotitanate Zn2TiO4 (15.5%, <L> = 13.2 nm) in addition to unreacted rutile TiO2, anatase TiO2 and ZnO structures. As the milling process progresses up to 18 h, the volume fraction of Zn2TiO4 increases to about 44.5%. The sintered pellets exhibit a composite structure where about a small amount of rutile nanograins are dispersed into the Zn2TiO4 matrix. FT-IR and Raman results confirm the biphasic character of the sintered pellets. The band gap energy is milling time dependent. It varies from 3.22 for pellet 6 h to 3.45 for pellet 18 h.

Competitive crystallization of β-Zn2SiO4 and ZnO in an aluminosilicate glass

Transparent glass-ceramics containing a mixture of ZnO and β-Zn2SiO4 or solely ZnO are fabricated through a competitive crystallization behavior of ZnO and β-Zn2SiO4 in a potassium zinc aluminosilicate glass. Both ZnO and β-Zn2SiO4 are precipitated simultaneously at the initial stage of thermal treatment, whereas sole crystallization of ZnO occurs when thermal treatments are performed at a high temperature (> 640 °C for 20 h) or for a long period of time (> 10 h at 650 °C). A detailed Raman scattering study and microscopic observation suggest that this competitive crystallization is due to the decomposition of β-Zn2SiO4 into ZnO and SiO2 during thermal treatment. This work would be of interest to the fabrication of active ions doped luminescent glass-ceramics by selective crystallization of ZnO and β-Zn2SiO4.

DC Magnetron Sputtered IZTO Thin Films for Organic Photovoltaic Application.

IZTO20 (In0.6Zn0.2Sn0.2O1.5) ceramic target was prepared from oxide mixture of In2O3, ZnO, and SnO2 powders. IZTO20 thin films were then deposited onto glass substrate at 400 °C by DC magnetron sputtering. The average optical transmittance determined by ultraviolet-visible spectroscopy was higher than 85% for all films. The minimum resistivity of the annealed IZTO20 thin film was approximately 6.1×10-4 Ω·cm, which tended to increase with decreasing indium content. Substrate heating and annealing were found to be important parameters affecting the electrical and optical properties. An organic photovoltaic (OPV) cell was fabricated using the IZTO20 film deposited under the optimized condition as an anode electrode and the efficiency of up to 80% compared to that of a similar OPV cell using ITO film was observed. Reduction of surface roughness and electrical resistivity through annealing treatment was found to contribute to the improved efficiency of the OPV cell.

Microstructure, optical, dielectric and electrical characterizations of Mn doped ZnO nanocrystals synthesized by mechanical alloying

Mn doped ZnO nanocrystals are successfully synthesized, for the first time, by mechanical alloying the stoichiometric mixture of pure ZnO and Mn powders. The structural and compositional analyses are carried out using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Rietveld's analysis of the XRD patterns confirms the formation of single phase wurtzite Zn0.90Mn0.10O nanostructures. Different structural and microstructural parameters such as lattice parameters, crystallite size, r.m.s. strain, stacking faults etc. have been ascertained from the Rietveld analysis. UV–vis spectra are analyzed for band gap measurement and photoluminescence (PL) emission spectra have also been analyzed for estimating different structural defects and optical features of the samples. Temperature dependent dc electrical behavior is studied and the conduction mechanism has been explained by the Godet variable range hopping theory (3D G-VRH). Complex impedance analysis is used to distinguish the grain and grain boundary contribution to the system and it suggests the dominance of grain resistance in the synthesized samples. The dielectric behavior, electric modulus and ac conductivity are studied as a function of temperature (573–773 K) and frequency (100 Hz to 3 MHz). The optical and electrical characterizations predict that the synthesized materials have potential for use in optoelectronics applications.

Tribological behavior of ZnO-Si3N4 nanoparticles-based lubricating grease

Currently, nanoparticles have been widely used as lubricant additives, few researches have investigated their applications as additives for lubricating grease. In this paper, mixtures of ZnO and Si3N4 nanoparticles were added into grease as additives. XRD and TEM were utilized to the investigate phase composition, microstructure and morphology of the nanomaterials. The composite grease was prepared by introducing ZnO and Si3N4 nanoparticles into the grease matrix through ultrasonic dispersion. Then, tribological properties of the composite grease were measured through a MMW-1A universal friction tester. Results showed that the best lubrication performance was achieved when the composite grease contains 1 wt% ZnO and 0.5 wt%Si3N4. Under this condition, the friction coefficient and wear scar diameter decreased to 0.0701 and 0.727, which is 34.3% and 8.3% lower than that of the base greases, respectively. The morphology of composite nanoparticles is beneficial to the enhancement of antifriction property, which can be seen from SEM images. In addition, EDS analysis illuminated the accumulation of Zn and Si on the friction surface. Further researches proved its great potentials in alleviation of vibration, noise and temperature rise for high speed bearings, since the ZnO-Si3N4 nanoparticles-based composite grease showed excellent lubrication and antifriction properties.

Effect of surfactant materials to nanoparticles formation under pulsed plasma conditions and their antibacterial properties

Pulsed plasma between two Zn rods submerged into aqueous solution of cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) surfactants resulted in formation of pure ZnO nanorods, while the pulsed plasma between two Zn rods in water without surfactant yielded a mixture of ZnO and Zn nanoparticles. Carbon coated ZnO nanorods with about 20 nm thickness and 150 nm length were synthesized by this method using different surfactant materials such as CTAB and SDS. Cu nanoparticles of about 10 nm in size were also synthesized by the pulsed plasma in aqueous solution of 0.2% gelatine as surfactant material. Surfactant materials served as protective and stabilizing agent and induced formation of smaller sized particles with larger surface area, which in turn inhibited excellent antibacterial activity for Escherichia coli (E.coli). Silver nanoparticles stabilized by SDS exhibited much higher antibacterial activity against E.coli than that of without surfactant.

Structural and electronic properties of Al-doped ZnO semiconductor nanopowders: Interplay between XRD and PALS experiments and first-principles/DFT modeling

A combined experimental and novel theoretical ab initio structural and electronic study was performed in order to characterize ZnO semiconductor nanopowders doped with Al atoms. For this, powder mixtures of ZnO and metallic Al in adequate proportions yielding different contents of Al (5, 10, and 30 at. %) were prepared by mechanical milling. The systems were characterized by X-ray diffraction and positron annihilation lifetime spectroscopy measurements. Additionally, combining two first-principles methods based on the Density Functional Theory (DFT) we calculated the final equilibrium structures for different concentrations of Al dopants and Zn vacancies in ZnO, predicting afterwards the characteristic positron annihilation lifetimes at these equilibrium structures. In addition to the structural relaxations, the ab initio predictions of the electronic properties in the studied systems help us to understand deeper the origin and characteristics of different positrons traps.This experimental and ab initio/DFT combined study allows to verify the dopant incorporation into the ZnO wurtzite structure and to extract the maximum information from the experimental data, giving an insight into the different defect complexes and their influence in the structural and electrical properties.

Optical fiber based humidity sensor using Ag decorated ZnO nanorods

This paper describes the fabrication of fiber optic humidity sensor based on silver decorated ZnO nanostructures. The synthesized powders were characterised by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The composite mixture of ZnO and Ag-ZnO were coated on plastic optical fiber by brush coating method. Povinyl alchol (PVA) was used as a temporary binder for the coating. The humidity sensing behavior of the fabricated sensors were studied by exposing it to different humidity levels ranging from 20 to 95%RH at room temperature. The optimised nano composite shows better responsivity and recovery time.

PHOTOLUMINESCENCE OF ZnO NANOSTRUCTURE PREPARED BY CATALYST - ASSISTED VAPOR - LIQUID - SOLID TECHNIQUE

ZnO semiconductor nanostructures have been synthesized by thermal evaporation of mixture of ZnO and graphite powders. The thin layer of gold coated on Si substrates was used as a catalyst. The structure analysis shows high crystallinity of ZnO, their preferred orientation along the (0 02) plane of the wurtzite phase and their chemical purity. The scanning electron microscopy (SEM) images of products indicate that ZnO nanowires have a diameter of about 40 - 150 nm and a length of up to tens of micrometers. The morphology and structure of ZnO nanowires and nanorods depend on the thicknesses of the Au layers. The fact that Au nanoparticles are located at the tips of the nanowires represents a strong evidence for a growth process dominated by the vapor - liquid - solid mechanism. The low temperature photoluminescence spectra of the ZnO nanowires indicate a group of the ultraviolet narrow peaks and a blue - green very broad peak at 500 nm.

Enhanced ethanol gas sensing performance of the networked Pd, In2O3-codecorated ZnO nanorod sensor

ZnO nanorods codecorated with Pd and In2O3 nanoparticles were synthesized by thermal evaporation of a mixture of ZnO and graphite powders in an oxidizing atmosphere and followed by solvothermal deposition of Pd and In2O3 and their ethanol gas sensing properties were examined. Pristine ZnO nanorods, Pd-decorated ZnO nanorods and In2O3-decorated ZnO nanorods were also prepared in a similar manner. The codecorated ZnO nanorod sensor showed significantly stronger response to ethanol than the other three sensors, suggesting a synergistic effect of Pd and In2O3 codecoration. The former also showed faster response and recovery than the latter. The pristine and codecorated ZnO nanorod sensors exhibited selectivity toward ethanol over other gases such as acetone, CO, benzene, and toluene. The underlying mechanism for the enhanced sensing performance of the Pd, In2O3-codecorated ZnO nanorod sensor toward ethanol is discussed.

PENGARUH SUBSTITUSI ION Ti-Zn TERHADAP SIFAT KEMAGNETAN dan SIFAT PENYERAPAN GELOMBANG ELEKTROMAGNETIK MATERIAL SISTEM BaFe12-xTix/2Znx/2O19

Substitution of Ti+4 and Zn+2 ions on magnetic material BaFe12-xTix/2Znx/2O19 (x = 0 and 2) using the wet milling method has been performed. This research was conducted to get information the influence of Ti-Zn substitution on magnetic properties and its absorption. The magnetic material BaFe12-xTix/2Znx/2O19 is synthesized from a mixture of oxide materials, BaCO3, Fe2O3, TiO2 and ZnO. The mixture was milled for 5 hours, dried at 1000C then sintered at 10000C for 5 hours. The refinement result of the X-ray diffraction pattern shows that the sample has single phase BaFe12O19 with doping concentration of x = 0 and 2. The hysteresis curve shows that coercivity field value decreased in the sample with doping concentration of x = 2. The result of electromagnetic wave absorption shows that the substituted sample with Ti+4 and Zn+2 ions (doping concentration x = 2) has the highest absorption peak at a frequency of 11,2 GHz with reflection loss value (RL) of -24,3 dB. Electromagnetic wave absorption reaches 94% with sample thickness is about 1,0 mm. Therefore, the magnetic material BaFe12-xTix/2Znx/2O19 (x = 2) can be used for application of the electromagnetic wave absorber.&#x0D; Keywords: Substitution, BaFe12-xTix/2Znx/2O19, wet milling, reflection loss, electromagnetic wave absorber.

Solar and visible active amino porphyrin/SiO2[sbnd]ZnO for the degradation of naphthol blue black

Although SiO2 falls in the category of insulator, we used 70% SiO2 and 30% of ZnO mixture for photocatalytic application. SiO2ZnO was prepared by a simple solid dispersion method, before making a mixture of oxides; SiO2 and ZnO were prepared by a sol-gel and physical grinding methods, respectively. The prepared SiO2ZnO was chemically modified with 5,10,15,20-meso-tetra-(para-amino)-phenyl-porphyrin (TPAPP) and used for the degradation of an azo dye naphthol blue black (NBB) under direct sunlight as well as visible light. Before making a TPAPP/SiO2ZnO composite, the surface modification of SiO2ZnO was carried out with glycidoxypropyltrimethoxy silane (GPTMS) which acts as a coupling agent. The TPAPP modified SiO2ZnO was characterized by FT-IR, XRD, SEM, FE-SEM with elemental mapping, EDS and DRS measurements. A mechanism was proposed for NBB degradation by TPAPP/SiO2ZnO under sun light. The catalyst was found to be reusable.

Control of Elemental Distribution in the Nanoscale Solid-State Reaction That Produces (Ga1-xZnx)(N1-xOx) Nanocrystals.

Solid-state chemical transformations at the nanoscale can be a powerful tool for achieving compositional complexity in nanomaterials. It is desirable to understand the mechanisms of such reactions and characterize the local-level composition of the resulting materials. Here, we examine how reaction temperature controls the elemental distribution in (Ga1-xZnx)(N1-xOx) nanocrystals (NCs) synthesized via the solid-state nitridation of a mixture of nanoscale ZnO and ZnGa2O4 NCs. (Ga1-xZnx)(N1-xOx) is a visible-light absorbing semiconductor that is of interest for applications in solar photochemistry. We couple elemental mapping using energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope (STEM-EDS) with colocation analysis to study the elemental distribution and the degree of homogeneity in the (Ga1-xZnx)(N1-xOx) samples synthesized at temperatures ranging from 650 to 900 °C with varying ensemble compositions (i.e., x values). Over this range of temperatures, the elemental distribution ranges from highly heterogeneous at 650 °C, consisting of a mixture of larger particles with Ga and N enrichment near the surface and very small NCs, to uniform particles with evenly distributed constituent elements for most compositions at 800 °C and above. We propose a mechanism for the formation of the (Ga1-xZnx)(N1-xOx) NCs in the solid state that involves phase transformation of cubic spinel ZnGa2O4 to wurtzite (Ga1-xZnx)(N1-xOx) and diffusion of the elements along with nitrogen incorporation. The temperature-dependence of nitrogen incorporation, bulk diffusion, and vacancy-assisted diffusion processes determines the elemental distribution at each synthesis temperature. Finally, we discuss how the visible band gap of (Ga1-xZnx)(N1-xOx) NCs varies with composition and elemental distribution.

Effect of thermo-mechanical treatments on corrosion behavior of Cu-15Ni-8Sn alloy in 3.5 wt% NaCl solution

The microstructure and corrosion behavior of the Cu-15Ni-8Sn-1.0Zn- 0.8Al-02Si alloy treated with different thermo-mechanical processes in 3.5 wt% NaCl solution was investigated by electrochemical test, electron microscopy and XPS analysis. Compared with single-stage thermo-mechanical treatment (cold rolling by 60% reduction and then aging at 450 °C for 0.5 h), the alloy with two-stage treatment (pre-aging at 400 °C for 0.5 h, cold rolling by 60% reduction and then aging at 450 °C for 0.5 h) had finer ordered precipitates and less coarse, discontinuous precipitates, resulting in better corrosion resistance performance. The corrosion product layer was mainly a mixture of Cu2O, CuO, NiO, Ni(OH)2, SnO, SnO2, ZnO and Al2O3, with a transition from Cu2O to CuO and Cu(OH)2 occurring during the corrosion process.

Local structural changes of nano-crystalline ZnFe2O4 during lithiation and de-lithiation studied by X-ray absorption spectroscopy

X-ray absorption spectroscopy was carried out to investigate local structural changes around Fe and Zn atoms of the nano-crystalline spinel ferrite ZnFe2O4 anode material at various states-of-charge during the 1st and 2nd lithiation/de-lithiation. From the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), we propose a possible structure evolution process of the ZnFe2O4 electrode during the 1st discharge and charge cycle. A mixture of metallic iron, ZnO, metallic zinc, LiZn and Li2O phases seem to be formed as the cell is firstly discharged to 0.02V. Instead of the original ZnFe2O4 spinel phase, the metallic iron and zinc particles are re-oxidized to Fe2O3 and ZnO phases during the subsequent de-lithiation. A reversible redox reaction between Fe2O3, ZnO and lithium ions is found in the 2nd cycle. The formation of SEI layer in the initial cycles plays a major role in the irreversible capacity of the electrode. The inactive disordered ZnO formed due to the conversion reaction of ZnFe2O4 during the 1st lithiation is probably the main reason for the poor electrochemical behavior of the nano-crystalline ZnFe2O4 electrode.

Effect of a ZnO buffer layer on structural and electrical properties of ZnO:Al,P thin films grown by RF magnetron sputtering

Abstract Structural and electrical properties of ZnO:Al 0.01 P 0.04 thin films were investigated with respect to the growth temperature of the ZnO buffer layers deposited by RF magnetron sputtering. The ZnO buffer layers on c -plane sapphires showed three different types of in-plane orientation relationships between ZnO and Al 2 O 3 at different growth temperatures: ZnO[10 1 0] // Al 2 O 3 [10 1 0] at 200 °C, a mixture of ZnO[10 1 0] // Al 2 O 3 [10 1 0] and ZnO[10 1 0] // Al 2 O 3 [11 2 0] at 300 °C, and ZnO[10 1 0] // Al 2 O 3 [11 2 0] at 600 °C. The in-plane orientation of the ZnO:Al 0.01 P 0.04 thin film followed the orientation of the ZnO buffer layer regardless of its growth temperature. The ZnO:Al 0.01 P 0.04 film grown on a ZnO buffer layer deposited at 600 °C had a carrier concentration of 1.18 × 10 16 cm −3 , mobility of 7.16 × 10° cm 2 /(V s), and resistivity of 7.36 × 10 1 Ω cm, indicating p -type characteristics.