A Mathematical Model for Determining Carbon Coating Thickness and Its Application in Electron Probe Microanalysis

In electron probe microanalysis where materials are coated with a thin conductive carbon coat before analysis, the X-ray intensity detected from a specimen may be affected to various degrees by the thickness of the carbon coating. Differences in the carbon film thickness between specimens and standards may lead to errors in analytical results, particular for lower energy X-rays. In this study, we demonstrate that the location and the distance of the specimen relative to the carbon tip in the coating chamber can affect the thickness of the carbon film produced on the specimen surface during carbon coating. The closer the specimen is to the carbon tip contacting point, the thicker is the carbon film deposited. A mathematical model to calculate the carbon film thickness at different locations on the coater plate is established, based on the assumption that carbon atoms evaporate from the carbon tip equally in all directions during the coating process. In order to reduce the differences in the carbon coating thickness, we suggest moving the carbon rod to a higher position, moving the thinner samples to the center and thicker samples to the edge of the coater plate, and using a rotating circular coater plate during coating.

Effect of Oxygen Incorporation on the Properties of AlF3 Films

In order to reveal the influence of oxidization on the properties of AlF3 films, single layers of AlF3 were deposited at different substrate temperature by thermo evaporation technique with or without oxygen injected into the coating chamber. The chemical composition, total stress, optical properties and laser damage resistance of samples were characterized. Comparative study indicates the AlF3 films prepared under higher oxygen pressure have more oxides which result from hydration process in atmosphere. The presence of oxides also reduces total stress and optical absorption of the fluoride coatings.

New Powder Coating Equipment to Produce Continuous Fibre Thermoplastic Matrix Towpregs

Thermoplastics are replacing traditional thermosetting resins as matrices in composite materials in many applications due to their enhanced properties. Thermoplastics exhibit better toughness, durability and damping properties and provide the options of continuous processing, reshaping, and reparability, as well as more favourable recycling and processing routes that do not involve chemical reactions [1]. However, their high melt viscosity makes it difficult to impregnate continuous fibres, which restricts commercial applications. Recently developed dry coating techniques allow the production of long fibre thermoplastic matrix towpregs without most of the previous impregnation problems [2, 3]. In this work, a new coating line was developed to produce long fibre dry coated thermoplastic matrix towpregs at rates compatible with industrial production. The polymer deposition rate was considerably increased to allow processing towpregs at greater speeds (approx. 10 m/min) than current equipment. A new coating chamber was used to allow improved control of the fibre and polymer contents and the towpreg impregnation quality. Other general improvements were also made in the equipment to allow better monitoring of the towpreg processing. Glass or carbon fibres with polypropylene towpregs (GF/PP and CF/PP, respectively) were produced on the new coating line which were then submitted to extensive tests to verify their polymer content and impregnation quality. This paper presents the results of the tests and discusses the optimization of the new dry coating line. The results show that the new deposition chamber allows production of economical thermoplastic matrix towpregs with improved efficiency that may be used in the industrial production of composites for commercial markets.