Coating Thickness Difference Research Articles

Microwave cavity resonator sensor with an octagonal cross section for thickness measurement of coatings on carbon fibre composites

Manual painting is commonly conducted on an aircraft's exterior, and the coating thickness should be within the allowable range. For quality control, the thickness requires accurate assessment. However, the current non-destructive testing techniques for metallic substrates cannot be well suited to the widely used carbon fibre-reinforced polymer composites, which are less conductive. Here we present a new microwave cavity resonator sensor, in which an octagonal cross section (an intermediate shape between a cylinder and a sphere) is adopted to easily eliminate mode degeneracy. A design strategy incorporating electromagnetic simulation is presented, and an accurate model is developed for the extraction of the resonance frequency and quality factor from the asymmetrical responses. In the tests, the open cavity is placed on a composite sample, and coating thickness change causes cavity wall impedance perturbation, leading to resonance frequency shift. From the experiments, a linear relationship is seen between the coating thickness difference and resonance frequency shift, thereby facilitating the estimation process. As the resonant electromagnetic fields are similar to those of the cylindrical TE011 mode, insensitivity to the conductivity and anisotropy of the composite is also demonstrated, enabling convenient implementation. Reasonable accuracy is obtained for thicknesses up to 2 mm. In the prediction of two- and multi-layered coating cases, errors within ±5% are obtained. The sensor developed offers efficient on-site measurement of paint coatings on carbon fibre composite structures.

Вплив екструзійних модифікаторів обмазувальних мас на різнотовщинність електродного покриття

Вплив екструзійних модифікаторів обмазувальних мас на різнотовщинність електродного покриття

Effect of extrusion modifiers of coating mixture on electrode coating thickness difference

Effect of extrusion modifiers of coating mixture on electrode coating thickness difference

Modeling Temperature Distributions in Thermal Barrier Coatings with Various Thicknesses

The geometric model of thermal barrier coatings (TBCs) was established. Two cases based on the standard thickness of the ceramic layer existed. These were the steps of TBCs thickness were being higher than the standard layer and those of lower than standard layer. The heat transfer processes of these two cases were simulated with the ANSYS software. The change process of thermal effusivity was analyzed in the two cases and the coating thickness differences effect on the surface temperature distributions of TBCs was analyzed through the time course curves of temperature difference. Moreover, the difficulty of detection for these two cases with infrared nondestructive testing was discussed according to maximum temperature difference and the maximum temperature contrast ratio. The result demonstrated that all curves of thermal effusivity with various thickness differences coincided with each other at the initial and longer times, where the ceramic layer thickness was lower than the standard layer. This was more easily detectable compared to the higher thickness and the maximum temperature contrast ratio or the maximum temperature difference increased as the coating thickness difference increased.

Effects of film coating thickness and drug layer uniformity on in vitro drug release from sustained-release coated pellets: A case study using terahertz pulsed imaging

Film coating thickness and terahertz electric field peak strength (TEFPS) were determined using terahertz pulsed imaging (TPI) and employed for the analysis of sustained-release coated pellets (theophylline layered sugar cores coated with Kollicoat ® SR:Kollicoat ® IR polymer blends). The effects of coating thickness, drug layer uniformity and optional curing were investigated using eight batches of pellets. Ten pellets from each batch were imaged with TPI to analyse the coating morphology (depicted in TEFPS) and thickness prior to release measurements. The results showed TEFPS values of 15.8% and 14.5% for pellets with a smooth drug layer coated at 8.2 and 12.5% (w/w) polymer weight-gain, respectively. Whereas 6.7% was derived for pellets with a coarse drug layer coated at both weight-gains. Although there were major differences in TEFPS, the resulting drug release kinetics were very similar. It was also shown that a 36 μm coating thickness difference was not drug release rate determining. These results suggested that drug release for the pellets studied was not predominately governed by drug diffusion through the polymeric film coating but probably to a large extent limited by drug solubility. TPI proved to be highly suitable to detect non-homogeneities in the drug layer and polymeric film coating.

Residual stress measurement in carbon coatings of optical fibers from the fiber bending curvature and coating thickness difference

The residual stress measurement in carbon coatings of optical fibers is theoretically and experimentally investigated. A simple formula used to measure the residual stresses in the thin film deposited on a cylindrical substrate with the bending curvature is proposed. During a temperature drop, the carbon-coated optical fiber is bent due to the nonuniform deposition of coating materials. The axial residual stresses in carbon coatings of optical fibers can be measured from the fiber bending curvature and coating thickness difference. Furthermore, if Young’s modulus of carbon coatings is known, the thermal expansion coefficient of carbon coatings can be determined.

Electroplating preparation of Ni–Al 2O 3 graded composite coatings using a rotating cathode

In order to develop a new technique for fabricating Ni–Al 2O 3 graded coatings, a polyhedron cathode was used, which is composed of eight pieces of copper foil fixed on the side faces of a regular octagonal nylon prism. The stirring rate was 350 rpm. For pure nickel deposition, the coating thickness difference between different side faces is increased when the electrolyte is stirred. The particle concentration has no evident effect on the coating thickness, but affects the particle content in different coatings. The largest difference of particle contents appears while the Al 2O 3 particle concentration of the electrolyte is 80 g/L. Based on these results, the graded composite coating was fabricated through rotating the cathode.

Proximate composition and antinutritive substances in chickpea (cicer arietinum L) as affected by the biotype factor

A study was made of both Desi (16 cultivars) and Kabuli (21 cultivars) chickpea biotypes grown under the same environmental conditions in order to evaluate the influence of the biotype factor as source of variance of the proximate composition and antinutritive substances content. Differences were found between the two biotypes for fat, total dietary fibre (TDF), insoluble dietary fibre (IDF), phytic acid and tannin content. Desi biotypes revealed lower fat and phytic acid contents, whereas Kabuli biotypes showed lower TDF, IDF and tannin content. Differences in coat thickness, as reported in the literature, are confirmed as a source of differences between the two biotypes in the fat, TDF, IDF, phytic acid and tannin content. © 1998 Society of Chemical Industry.

Variações estacionais no pelame de vacas da raça Jersey e sua correlação com a produção leiteira

Coat thickness of 45 Jersey cows was measured in two seasons of year (winter and summer) in order to calculate the correlations between hair coat thickness and milk production. All measurements were taken in four selected regions of animal body: shoulders, loin, rump and ribs. Differences in coat thickness were observed amongst animals and amongst regions of animal body either in summer or winter seasons. Correlations between coat thickness and milk production seem to indicate that higher milk production cows have thinnest hair coat, being the most significant those coefficients related to the regions of shoulders and ribs in summer time.