Structure and mechanical properties of ceramic coatings fabricated by plasma electrolytic oxidation on aluminized steel

Ceramic coatings were formed by plasma electrolytic oxidation (PEO) on aluminized steel. Characteristics of the average anodic voltages versus treatment time were observed during the PEO process. The micrographs, compositions and mechanical properties of ceramic coatings were investigated. The results show that the anodic voltage profile for processing of aluminized steel is similar to that for processing bulk Al alloy during early PEO stages and that the thickness of ceramic coating increases approximately linearly with the Al layer consumption. Once the Al layer is completely transformed, the FeAl intermetallic layer begins to participate in the PEO process. At this point, the anodic voltage of aluminized steel descends, and the thickness of ceramic coating grows more slowly. At the same time, some micro-cracks are observed at the Al2O3/FeAl interface. The final ceramic coating mainly consists of gamma-Al2O3, mullite, and alpha-Al2O3 phases. PEO ceramic coatings have excellent elastic recovery and high load supporting performance. Nanohardness of ceramic coating reaches about 19.6 GPa. (c) 2007 Elsevier B. V. All rights reserved.

Determination of interface properties between micron-thick metal film and ceramic substrate using peel test

Peel test measurements have been performed to estimate both the interface toughness and the separation strength between copper thin film and Al2O3 substrate with film thicknesses ranging between 1 and 15 mu m. An inverse analysis based on the artificial neural network method is adopted to determine the interface parameters. The interface parameters are characterized by the cohesive zone (CZ) model. The results of finite element simulations based on the strain gradient plasticity theory are used to train the artificial neural network. Using both the trained neural network and the experimental measurements for one test result, both the interface toughness and the separation strength are determined. Finally, the finite element predictions adopting the determined interface parameters are performed for the other film thickness cases, and are in agreement with the experimental results.

Investigations of cohesive zone properties of the interface between metal film and ceramic substrate at nano- and micro-scales

Cohesive zone characterizations of the interface between metal film and ceramic substrate at micro- and nano-scales are performed in the present research. At the nano-scale, a special potential for special material interface (Ag/MgO) is adopted to investigate the interface separation mechanism by using MD simulation, and stress-separation relationship will be obtained. At the micro-scale, peeling experiment is performed for the Al film/Al2O3 substrate system with an adhesive layer at the interface. Adhesive is a mixture of epoxy and polyimide with mass ratio 1:1, by which a brittle cohesive property is obtained. The relationships between energy release rate, the film thickness and the adhesive layer thickness are measured during the steady-state peeling. The experimental result has a similar trend as modeling result for a weak adhesion interface case.

Tracing the Basque presence in eastern Canada during the 16th and 17th centuries, through ceramic remains: the example of the glazed pottery produced in Bilbao

Poster presentado en Society for Post-Medieval Archaeology Conference, in St John's, Newfoundland,(Canadá)(June 2010)

Determination Of Interfacial Properties Between Metal Film And Ceramic Substrate With An Adhesive Layer

Peel test measurements and inverse analysis to determine the interfacial mechanical parameters for the metal film/ceramic system are performed, considering that there exist an epoxy interface layer between film and ceramic. In the present investigation, Al films with a series of thicknesses between 20 and 250 mu m and three peel angles of 90, 135 and 180 degrees are considered. A finite element model with the cohesive zone elements is used to simulate the peel test process. The finite element results are taken as the training data of a neural network in the inverse analysis. The interfacial cohesive energy and the separation strength can be determined based on the inverse analysis and peel experimental result. (C) 2008 Elsevier Ltd. All rights reserved.

Mechanisms of thermal shock failure for ultra-high temperature ceramic

The materials considered in our analysis were ZrB2 ceramic matrix composites. Effect of two different additives (graphite and AlN) on thermal shock stability for the materials was measured by water quench test. It showed that it may provide more stable thermal shock properties with additives of graphite. It was explained by different thermal properties and crack resistance of the two materials in detail. Surface oxidation was one of main reasons for strength degradation of ceramic with additives of graphite after quenched in water, and surface crack was one of main reasons for strength degradation of ceramic with additives of AlN after quenched in water. It was presented that it was a potential method for improving thermal shock stability of ZrB2 ceramic matrix composites by introducing proper quantities of graphite.

Experimental Study Of Multi-Hole Cooling For Integrally-Woven, Ceramic Matrix Composite Walls For Gas Turbine Applications

In this paper, multi-hole cooling is studied for an oxide/oxide ceramic specimen with normal injection holes and for a SiC/SiC ceramic specimen with oblique injection holes. A special purpose heat transfer tunnel was designed and built, which can provide a wide range of Reynolds numbers (10(5)similar to 10(7)) and a large temperature ratio of the primary flow to the coolant (up to 2.5). Cooling effectiveness determined by the measured surface temperature for the two types of ceramic specimens is investigated. It is found that the multi-hole cooling system for both specimens has a high cooling efficiency and it is higher for the SiC/SiC specimen than for the oxide/oxide specimen. Effects on the cooling effectiveness of parameters including blowing ratio, Reynolds number and temperature ratio, are studied. In addition, profiles of the mean velocity and temperature above the cooling surface are measured to provide further understanding of the cooling process. Duplication of the key parameters for multi-hole cooling, for a representative combustor flow condition (without radiation effects), is achieved with parameter scaling and the results show the high efficiency of multi-hole cooling for the oblique hole, SiC/SiC specimen. (C) 2008 Elsevier Ltd. All rights reserved.

Experimental investigation of optical beam deflection based on PLZT electro-optic ceramic

Based on the optical characteristics of PLZT electro-optic ceramic, two kinds of electro-optic deflectors, triangular electrode structure and optical phased array technology, are studied in detail by using transverse electro-optic effect. Theoretically, the electro-optic deflection characteristics and mechanisms of the deflectors are analyzed. Experimentally, the optical characteristics of ceramic wafer, such as the phase modulation, the hysteresis and the electro-induced loss characteristics, are measured firstly, and then the beam deflection experiments are designed to verify the theoretical results. Moreover, the effect of temperature on the performance of triangular electrode deflector is investigated. The characteristics of both deflectors are also compared and illuminated. (c) 2007 Optical Society of America.