CERAMIC SCIENCE & ENGINEERING
Year:2017 | Volume:6 | Issue:2 |Papers Count:7

Nanocomposite ceramic-based coatings, due to its high hardness and wear resistance, are improved wear behavior of aluminum and its alloys. In this study, zirconia nanocomposite coating applied on Al 2024 by using sol-gel method and dip coating process with the use of zirconium propoxide and aluminum tri-sec butylate. Then phase, structural and morphology properties of coatings evaluated by using GIXRD, FTIR, FESEM, AFM, as well as nano-mechanical properties of coatings were investigated by using nano-scratch and nano-indentation at two different loads, such as 50 and 60 mN. Results indicated that the formation of a homogeneous, smooth and low cracked ziconia-alumina nanocomposite coating with a thickness of approximately 800 nm. The presence of alumina cause to enhance the mechanical properties such as hardness and elastic modulus to 1.15 and 15 GPa, respectively, resulting in improve the wear behavior of coating with the friction coefficient of 0.51 and dominate the abrasive with shear mechanism.

In this paper, the effect of sodium silicate concentration on microstructure and corrosion behavior of ceramic coating on 5052 Al alloy formed by plasma electrolytic oxidation (PEO) was studied. For this purpose, the electrolytes with 6, 12 and 18 g/l sodium silicate were used. The scanning electron microscope (SEM) was used for investigation of surface and cross section of coating. The phase analyzing of substrate and coated sample were conducted by X-ray diffraction pattern (XRD). Corrosion behavior of coated sample and substrate were investigated with electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test in 3.5 %wt. sodium chloride corrosive solution. With survey of SEM images was confirmed that, the coated sample with 12 g/l sodium silicate has most uniform and compact structure with finest pores size. Study of XRD pattern illustrated that there are α- Al2O3, g- Al2O3 , mullite (3Al2O3 .2SiO2) and Mg2 SiO4 phases in coating. Also, result of corrosion tests proved that the coated sample in 12 g/l sodium silicate has highest corrosion resistance. The corrosion resistance of this coated sample was 1588 KΩ.cm2 that was 188 times more than corrosion resistance of 5052 Al alloy substrate.

Black pigment with micron size has been used for ages in ceramic industry. Recently, black submicron pigments have attracted great interest in ceramic industry due to their particle size. This pigment has been distinguished for preparing of ceramic ink suitable for ink-jet technology. In this research, black sub - micron pigments were synthesized by the combustion method based on cobalt chromite (Mnx CoCr2-xO4) with different amount of manganese. The all samples were calcinated at 1000oC. Samples were characterized by X-ray diffraction, colorimetry, scanning electron microscopy. The results showed that the optimum amount of manganese was 0.9%mol. In the presence of Manganese as dopant the color of pigment will change from to black. The morphology of the particles indicating that particles were synthesized in sun-micron range mainly 200-400 nm by combustion method.

In this research, the aim is the synthesis and characterization of a free-CaF2 mold powder via Ceramics Compounds such as TiO2, B2O3, ZnO and Na2O. For this purpose, in this research, 12 powder samples were prepared using compounds such as TiO2, B2O3, SiO2, Na2O, ZnO, Li2O, CaO, MgO, MnO, K2O, CaF2 and Portland Cement Clinker. To characterize laboratory samples, groove viscometer test, XRD, SEM and STA analyses were used. Results showed that with the formation of phases such as gehlenite, akermanite, nepheline, provskite, Na2ZnSiO4 and B2SiO5 , the formation of crystalline particles in glass matrix, conformity crystallization and melting temperatures of the free-CaF2 sample with crystallization, and melting temperatures of original mold powder, a free-CaF2 mold powder was synthesized and characterized via TiO2, B2O3, ZnO and Na2O. This powder was developed in laboratory scale, and the viscosity and the crystallization of the powder was the same as those of the original powder. This sample of mold powder can be a suitable replacement for the original powder.

The aim of this research is to study the influence of starch content and sintering temperature on microstructure, physical and mechanical properties of porous alumina bodies prepared by gel casting. Samples with 60.5, 63 and 65.5 wt% alumina and 7.5, 5 and 2.5 wt% corn starch, respectively, were ball milled 3 hours, casted into the molds and heated into drier (86 oC, 2 h) to gelatinization process. The dried samples were sintered 1h at 1400, 1450 and 1500 oC. After sintering, the samples properties were reported: bulk density 1.41-1.68 g.cm-3, open porosity 53.92-62.01% and Cold Crushing Strength (CCS) 0.98-3.82 MPa. Phase Analysis of the samples in 1500oC showed the peaks of α-alumina phase Also, Microstructural evaluation showed large pores remaining connected by small necks after starch burning out which caused interconnecting porosities and permeability increase.

ZrB2 is a ultra-high temperature ceramic (UHTC' s) with a high melting point of over 3040 ° C with unique properties. Of the major problems with ZrB2 is its weakness of sinterability, that in this study adding SiC in micron and nano as a secondary phase and B4C as an additive tried to overcome this problem. Systematic studies were performed on the pressureless sintering of ZrB2 –SiC nanocomposites. At first changes in particle size were investigated as a result of different milling times and optimization of this time. Then the effect of different weights of SiC micron and nano with addition of B4 C was investigated. Samples were pressurelessly sintered at 2050oC, 2100oC, 2150oC and 2200oC for one hour. ZrB2 –SiC nanocomposites with 10%wt nano SiC and 3%wt B4 C have an average hardness of 14.85±0.5 GPa and toughness around 3.8 MPam1/2 . At the final stage, the samples were oxidized at 1500 ºC in the air atmosphere and appearance and weight variations were investigated. The results showed that the addition of B4C is not only useful for sintering but also useful for oxidation resistance.

In this investigation Y2O3: Eu3+ nano powders were synthesized via combustion method with the approximate size of 50 nm. Then in order to remove the remained organic materials and also improve the crystal structure, the products were heat treated at 400, 800 and 1000 °C. The size and morphology of synthesized nano structures were studied by scanning and transmission electron microscopes. Also, to study the optical properties, a photoluminescence analyzer (PL) machine was employed. In this research, it was found that the type of solvent and the temperature of post heat treatment have significant effects on the morphology and luminescence properties of phosphors. Also, the stoichiometric values of the considered combustion reactions were calculated in the terms of valences of oxidizers and reducers.