A Relative Method Model For Physical Properties Evaluation Of Ceramic Coating And Its Verification

The development of evaluating and test technology of material properties is of vital importance for structure design and materials security service. However, in the field of modern engineering material and structure performance testing, there still have some kinds of blind zones restricted the materials application and development. That is it is hardly to obtain some material properties directly by using conventional test method. Such as with the rapid development and application of ceramic coatings in aerospace and other fields in recent years, evaluating method and technology of coatings performance is delayed seriously compare with its fast research and development. There is no practical and feasible evaluating method to measure the material properties including thermal expansion coefficient and density of ceramic coating, elastic modulus and fracture strength of coating in high temperature. And as the current hot topic in the field of new energy, the performance of double-glass photovoltaic module in building integrated photovoltaic(BIPV) include nominal module operating temperature(NMOT) has no testing method so far. Therefore, in order to solve these problems, it is necessary to develop feasible indirect approaches to estimate the material performance for material researcher and engineer.Aiming at this significant technical requirements and problems, an indirect evaluating method, the relative method, was proposed to evaluate the material properties via a theoretical relationship between the unknown and measurable properties.Because of the physical properties of the ceramic coating can’t be obtained through directly testing like block material, theoretical relationship of elastic modulus among coating, coated sample and substrate sample was established based on the equivalent stiffness model. While the elastic moduls of coated sample and substrate could be evaluated by bending method and impulse excitation technology. The elastic modulus of ceramic coating at high temperature was evaluated by impulse excitation test combined with relative method. Three types of coating structure were analyzed: single-face coating; two-face coating and four-face coating. The testing method of evaluating elastic modulus of each layer in multilayer coatings was proposed. That is the part over the layer should be ground first and the part below this layer could be regarded as equivalent substrate. Thus a new coating-substrate system was formed. This method was demonstrated to be valid and convenient by experiments on CVD Si C coating,glaze coating and thermal barrier coatings.In a similar way, in order to solve the problem about thermal expansion coefficient of ceramic coating cannot test directly, using the relative method combined with uniform interface stress model to establish the thermal expansion coefficient theoretical relationship among coating, coated sample and substrate sample. While the latter two parameters could be measured conveniently through thermal expansion instrument, therefore the thermal expansion coefficient of ceramic coating can be obtained. The feasibility of this test method was confirmed by experimental results of CVD Si C coating. Furthermore, using relative method combined with Archimedes method, the density theoretical relationship among coating, coated sample and substrate sample can be deserved. The density of coated sample and substrate can be measured conveniently by Archimedes method, thus the density of coating can be obtained. No matter what kind of performance parameters evaluation, the basic processes are summarized by three steps, that also can be called three steps: i) measure the properties of a coated specimen; ii) measure the properties of the substrate specimen; iii) calculate the properties of the coating via the measured values in above two steps based on the relationship among the three parameters. By using this simple method to obtain the three physical properties of coatings which can’t be test at domestic and overseas in the past years.There is no national standard about nominal module operating temperature(NMOT) test method for Building Integrated Photovoltaic(BIPV) modules. An in-lab testing method based on relative method for determining NMOT of BIPV modules is proposed. In order to simulate the real operation condition of modules, the influence of ambient temperature, wind speed and optimal load resistor to NMOT were analyzed. The surface temperature, interior temperature and back temperature of BIPV module were measured and the NMOT was determined. This method was demonstrated to be valid compared with long-term experiments in out-door testing environment.The main achievement of this study is establishing three kinds of constitutive relation of coating performance evaluation with relative method. Thereby to make the coating performance can be tested and verified by experiments. The relative method also used for nominal module operating temperature testing of photovoltaic double glass components at the same time.