Abstract: Zinc oxide (ZnO) is a wide band gap (~3.37 eV) semiconductor. Thin film ZnO has many attractive applications in optoelectronics and sensors. Recently, nanostructured ZnO (e.g. ZnO quantum dot) has been demonstrated as a hyperbolic material; its dielectric function has opposite signs along different crystal axes within the mid-infrared, making it an interesting material for metamaterials and nanophotonics. Conventional sputtering deposition usually leads to the formation of polycrystalline ZnO films with randomly oriented grains and rough surface. This work demonstrated a solution-based process to grow ZnO thin films with highly oriented nanocrystals. Low-temperature plasmas were employed to modulate the microstructure and optical properties of the films. Such highly anisotropic nanostructured transparent semiconductor films may lead to interesting material properties in developing new optoelectronic devices.

Keywords: Zinc oxide, sol-gel, oxygen plasma, crystal size.

Abstract: Carbon nanotubes (CNTs) coated on the WC/Co micropunch with diameter in 150 μm for prolonging the life of micropunch was investigated. Carbon nanotubes were synthesized by homemade method. With scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the morphology and structure of CNTs had been expressed. After the punching test with Ti as substrate, the effect of CNTs for prolonging the life of micropunch on the wear loss and the surface morphology of micropunch had been studied by confocal laser, SEM, digital balance etc. Results show the wear of CNTs coated micropunch decreases obviously. Even in the severe wear period the wear loss is less than that of non-CNTs coated micropunch. Compared with the micropunch without CNTs coating, the promising results are due to the formation of a transfer film at the contact region by rubbing of the CNT forest, CNTs produced adheres to the micropunch surface avoiding direct contact during the punching period and providing lubricant properties to the interface by virtue of their graphitic nature. Also, the relevant mechanism was illustrated primarily.

Keywords: Carbon nanotubes, micropunch, wear characteristic, WC/Co.

Abstract: The paper presents some new technological sequences of electron beam evaporation and deposition of high-temperature metal-ceramic coatings.

The main attention is given to two-layer Me-Cr-Al-Y/ZrO₂-Y₂O₃ coatings with transition layers of the total thickness of up to 0.2 mm.

Chemical composition and structures of the main layers (metal, ceramics) and substrate/metal and metal/ceramics transition layers, as well as the respective physico-mechanical properties are considered.

A method of deposition of these coatings in one technological cycle of evaporation and condensation with application of evaporation composite ingot is proposed.

Examples of coating “design” and respective equipment for practical application in gas turbine construction are given.

Keywords: Electron-beam evaporation and deposition (EB-PVD), high-temperature coating, multilayered thermal-barrier coating, crucible-evaporator, gas turbine blades.

Abstract: Commercially available Co-base powder was modified with the addition of 10 wt. percentage WC which was further modified with 5 and 10 wt. percentage CrC addition in order to obtain three coatings namely Co+10 wt. percentage WC, Co+10 wt. percentage WC+5 wt. percentage CrC and Co+10 wt. percentage WC+10 wt. percentage CrC. The coatings were deposited by flame spraying process. The microstructure of these coatings mainly showed eutectic containing Co with almost same amount in three coatings. Other phases such as W dominated and Cr dominated carbides were also observed. The 10 wt. percentage CrC coating showed the highest Vickers hardness and lowest wear rate. The coefficient of friction was also observed low in the 10 wt. percentage CrC coating as compared with other coatings.

Keywords: Atomic force microscopy, time of flight secondary ion mass spectrometry, Auger electron spectroscopy, coil coating, Cr-free pretreatment, topography.