Effect of annealing temperature on the tribological behavior of ZnO films prepared by sol-gel method

The tribological behavior of zinc oxide (ZnO) films grown on glass and silicon (100) substrates by sol-gel method was investigated. Particularly, the as-coated films were post-annealed at different temperatures in air to investigate the effect of annealing temperature. Crystal structural and surface morphology of the films were measured by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). XRD patterns and AFM images indicated that the crystallinity and grain size of the films were enhanced and increased, respectively, with temperature. The tribological behavior of films was evaluated by sliding the ZnO films against a Si₃N₄ ball under 0.5 gf normal load using a reciprocating pin-on-plate tribo-tester. The wear tracks of the films were measured by AFM to quantify the wear resistance of the films. The results showed that the wear resistance of the films could be improved by the annealing process. The wear resistance of the films generally increased with annealing temperature. Specifically, the wear resistance of the films was significantly improved when the annealing temperature was higher than 550° C. The increase in the wear resistance is attributed to the increase in hardness and modulus of the film with annealing temperature.     

Low temperature dielectric studies of zinc oxide (ZnO) nanoparticles prepared by precipitation method

Using zinc nitrate as a precursor and NaOH starch as a stabilizing agent, hexagonal zinc oxide (ZnO) nanoparticles has been synthesized by precipitation method. The transmission electron microscopy (TEM) images show particles of nearly uniform spherical size of around 40 nm. The infrared spectroscopy (FT-IR) measurement reveals the peak at 500 cm^?1, corresponding to the Zn–O bond. Dielectric studies of ZnO nanoparticles show frequency dependence dielectric anomaly at low temperature (85–300 K). Results reveal that the capacitance and loss tangent decrease with the frequency while these parameters improve with the increasing of temperature. The increase of a.c. conductivity with the temperature indicates that the mobility of charge carriers is responsible for hopping and electronic polarization in ZnO nanoparticles.     

Effect of Cr-doping on the structural and optical properties of CdS nanoparticles prepared by chemical precipitation method

Undoped and Cr doped CdS nanoparticles have been prepared by chemical precipitation method. X-ray diffraction analysis reveals that the undoped and Cr doped CdS nanoparticles exhibit hexagonal structure and the average particle size of the nanoparticles is in the range of 2.2–3.8 nm. The HRTEM studies show that the average particle size of undoped and Cr doped CdS nanoparticles is in the range of 2–3.7 nm. The compositional analysis results indicates that Cd, S and Cr are present in the samples. From the optical studies it is observed that the absorption edge of the prepared CdS and Cr doped CdS nanoparticles are shifted towards the shorter wavelength region (blue shift) when compared to that of bulk CdS and this shift is due to the quantum confinement effect present in the samples.     

Effect of annealing temperature and pH on morphology and optical property of highly dispersible ZnO nanoparticles

Highly dispersible zinc oxide nanoparticles were produced in large quantity via a simple solution method. The effect of temperature and pH impact on as-prepared ZnO nanoparticles with respect to the morphological and optical characteristics has been investigated. The average particle size of ZnO nanoparticles increased with increasing annealing temperature. A sharp UV band-edge emission was observed in as-prepared ZnO nanoparticles with negligibly less intense deep level emission. However, upon annealing at high temperature in air, UV band-edge emission disappears with an evolution of a broad deep level emission in photoluminescence spectra. Similarly, by adjusting the pH of reaction medium from 4 to pH = 8 using ammonium hydroxide solution, particle size gets bigger and bigger leads to red-shift in UV band-edge emission and an appearance of deep level emission peak. At pH = 8, well resolved sharp X-ray diffraction peaks were observed with lower FWHM values due to higher crystallite sizes.     

Photocatalytic and antibacterial activities of ZnO nanoparticles synthesized by chemical method

Journal of Materials Science: Materials in Electronics - In this study, ZnO NPs were synthesized and reporting first time using capping agent SDS with Zn (NO3)2 and KOH as precipitating agent. The...     

Synthesis and photoluminescence of Eu-doped ZnO microrods prepared by hydrothermal method

Eu-doped ZnO microrods, with wurtzite structure and [0 0 0 1] growth direction have been successfully synthesized on Si (1 0 0) substrates by a simple hydrothermal method. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), lifetime decay curves, photoluminescence (PL) and photoluminescence excitation (PLE) spectra, respectively. These results indicate that Eu³⁺ ions are located in the distorted lattice sites near the surface of the ZnO microrods. Additionally, it is also suggested that the surface defects may act as a step in the process of energy transfer from ZnO to Eu³⁺ ions.     

Effect of annealing temperature on ZnO:Al/p-Si heterojunctions

Al-doped, zinc oxide (ZnO:Al) films with a 1.2 at.% Al concentration were deposited on p-type silicon wafers using a sol-gel dip coating technique to produce a ZnO:Al/p-Si heterojunction. Following deposition and subsequent drying processes, the films were annealed in vacuum at five different temperatures between 550 and 900 °C for 1 h. The resistivity of the films decreased with increasing annealing temperature, and an annealing temperature of 700 °C provided controlled current flow through the ZnO:Al/p-Si heterojunction up to 20 V. The ZnO:Al film deposited on a p-type silicon wafer with 1.2 at.% Al concentration was concluded to have the potential for use in electronic devices as a diode after annealing at 700 °C.     

Effect of temperature on the characteristics of ZnO nanoparticles produced by laser ablation in water

Effect of the water temperature on the characteristics of zinc oxide nanoparticles (NPs) produced by laser ablation process is investigated experimentally. The fundamental wavelength of a Q-switched Nd:YAG laser was employed to irradiate a high-purity zinc plate in distilled water at different temperatures of 0, 20, 40 and 60^°C. The produced NPs were diagnosed by UV–vis–NIR spectroscopy, X-ray diffraction method, transmission electron microscopy and scanning electron microscopy. Results show that with increase in the water temperature from 20 to 60^°C, size of NPs decreases while their bandgap energy increases. Maximum ablation rate occurs at the highest temperature. Crystalinity also increases with increase in the water temperature. The abnormal behaviour of water at 0–4^°C affects the NPs characteristics.     

ZnO nanoparticles embedded in sapphire fabricated by ion implantation and annealing

ZnO nanoparticles were fabricated in sapphire (α-Al(2)O(3) single crystal) by Zn ion implantation (48?keV) at an ion fluence of 1 × 10(17)?cm(-2) and subsequent thermal annealing in a flowing oxygen atmosphere. Transmission electron microscopy (TEM) analysis revealed that metallic Zn nanoparticles of 3-10?nm in dimensions formed in the as-implanted sample and that ZnO nanoparticles of 10-12?nm in dimensions formed after annealing at 600?°C. A broad absorption band, peaked at 280?nm, appeared in the as-implanted crystal, due to surface plasma resonance (SPR) absorption of metallic Zn nanoparticles. After annealing at 600?°C, ZnO nanoparticles resulted in an exciton absorption peak at 360?nm. The photoluminescence (PL) of the as-implanted sample was very weak when using a He-Cd 325?nm line as the excitation source. However, two emission peaks appeared in the PL spectrum of ZnO nanopraticles, i.e., one ultraviolet (UV) peak at 370?nm and the other a green peak at 500?nm. The emission at 500?nm is stronger and has potential applications in green/blue light-emitting devices.     

Effect of annealing temperature on the structural and magnetic properties of Co-doped TiO2 nanoparticles via complex-polymer sol-gel method

Co-doped TiO2 nanoparticles were synthesized via non hydrous complex-polymer sol-gel method. A series of Co(x):Ti1-x O2 samples with x = 0.01, 0.03, 0.05, 0.08 and 0.10, were prepared and subsequently annealed at 400 degrees, 600 degrees and 800 degrees C. Structural and magnetic properties of Co(x):Ti1-x O2 have been studied by means of X-ray diffraction and DC magnetometry. All samples annealed at 400 degrees C show a paramagnetic behavior with an average grain size of 11 nm. With increasing annealing temperatures a complete crystallization is seen with growth of the cluster size up to 31 nm with clear evidence of a presence of CoTiO3. For all concentrations and annealing conditions no sign of a metallic phase, even at x = 0.10, is seen.     

Controlled fluorescence resonance energy transfer between ZnO nanoparticles and fluorophores in layer-by-layer assemblies

We controlled the fluorescence resonance energy transfer (FRET) between ZnO nanoparticles and rhodamine B (RB) within multilayered thin films prepared by the layer-by-layer (LbL) assembling method. Positively charged ZnO nanoparticles and RB-labeled poly(allyamine hydrochloride) (RB-PAH) were accurately incorporated into LbL assemblies of polyelectrolytes. The distance between ZnO nanoparticles and RB-PAH was adjusted by varying the number of layers of pure polyelectrolytes, leading to the controlled FRET from ZnO nanoparticles to RB-PAH.     

Effect of the annealing temperature on transparency and conductivity of ZnO:Al thin films

Highly aluminum-doped zinc oxide (ZnO:Al) films were grown by rf-magnetron sputtering at low temperature from aerogel nanoparticles and characterized by structural, electrical and optical techniques. Nanoparticles with a size of about 30 nm were synthesized by sol–gel method using supercritical drying in ethyl alcohol and annealed at different temperatures with different gas atmospheres. The ZnO films were polycrystalline textured, preferentially oriented along the (002) crystallographic direction normal to the film surface. The films show within the visible wavelength region an optical transmittance of more than 90% and low electrical resistivity of 10^− 3 Ω cm at room temperature.     

Effect of sintering temperature on the properties of Cu-Co ferrites prepared by oxalate precipitation method

Polycrystalline Cu-Co ferrite powder was synthesized following oxalate precipitation method. The samples of the compound Cu_0.5Co_0.5Fe₂O₄ were heated at different temperatures in the range of 773-1173 K and were characterized by X-ray diffraction and SEM techniques. The results of XRD show the formation of single-phase cubic spinel structure. The lattice parameter showed a minimum value for the sample heated at 1073 K. It has been observed that grain size increases with the increase in temperature and is maximum (3.2 μm) for the powder sintered at 1173 K.     

Fabrication of pure ZnO nanoparticles by polymerization method

ZnO nanoparticles have received enormous attention due to their wide range of application such as diodes, ultraviolet-protection films, catalysts, sensors, ceramics and solar energy transformation parts. In the current research, ZnO nanoparticles were prepared by polymer decomposition. Synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transition electron microscopy (TEM) and size distribution of these particles was investigated. Narrow size distribution of particles with a diameter of 20–30 nm and the regular distribution of ZnO nanoparticles were attributed to the application of poly amidoxime polymer. The results show that the polymer thermal decomposition technique is a feasible method for production of ZnO nanoparticles.     

Luminescence enhancement due to energy transfer in ZnO nanoparticles and Eu ions co-doped silica

SiO₂ thin films co-doped with ZnO nanoparticles and Eu^3 + ions were prepared by sol-gel method. The formation of nano-sized ZnO particles was confirmed by X-ray diffraction patterns and transmission electron microscopy. The characteristic emission bands from Eu^3 + ions can be observed at room temperature and the luminescence intensity is increased obviously by introducing ZnO nanoparticles into Eu^3 +-doped silica films. The integrated luminescence intensity is influenced by the concentration and size of ZnO particles, suggesting effective energy transfer from nano-sized ZnO to Eu^3 + ions. It is argued that the efficient luminescence enhancement occurs under the suitable Zn^2 + amount and annealing temperature.     

Effect of the mixing rate on the morphology and photocatalytic activity of ZnO powders prepared by a precipitation method

The urchin-like shape of ZnO powders was prepared by mixing of Zn²⁺ and NaOH solutions at various mixing rates. In this work, ε-Zn(OH)₂ was the first precipitant that was subsequently transformed to ZnO in the alkaline medium during heating. The size of the urchin-like shape of the ZnO powder decreased with a decrease of the mixing rate. The large urchin-like shape also had a large diameter of its hexagonal facet (0 0 0 1) and showed the highest photocatalytic degradative activity on methylene blue.     

均匀沉淀法制备碳纳米管/氧化锌复合材料的研究

采用均匀沉淀法制备了碳纳米管(CNTs)负栽氧化锌(ZnO)粒子复合材料,并利用扫描电子显微镜(SEM)、X光衍射分析(XRD)以及热失重分析(TGA)手段对复合粒子进行了表征.研究结果表明:锌离子浓度取0.4mol/L至1.0mol/L时,所得复合材料中的氧化锌粒子大小均匀细小,分散性较好,形貌以粒状为主,大小在40nm左右;纳米氧化锌粒子与碳纳米管结合力较强,CNTs/ZnO复合材料在超声作用下能够稳定存在;反应时间越长,氧化锌粒子含量越高,晶粒越大;热解温度越高,热解时间越长,氧化锌晶粒尺寸越大.