نشریه مطالعات در دنیای رنگ
سال پنجم شماره 3 (پیاپی 18، پاییز 1394)

In two decades، the third generation solar cells in other words، dye-sensitized solar cells or Geratzel cells to silicon cells due to lower production costs and relatively high efficiency of conversion of light to electricity is highly regarded. One of the most important sections of dye-sensitized solar cells is titanium dioxide layer coated on FTO، which the role this layer is the recipient of excited electron dye and transfer to FTO substrate. So the preparation and application of this layer have an important role in the performance of dye-sensitized solar cells. Develop and apply methods this layer is divided into two general classes as physical and chemical methods. The physical methods include laser pulses and spattering and the chemical methods include chemical vapor، sol-gel، dip-coating، spin coating، spray pyrolysis coating and electro-coating. The chemical methods are noteworthy for facility of doing، no need for wrapped laboratory equipment and conditions laboratory compared to the physical methods. Among chemical methods، sol-gel method is important over other chemical methods due to possibility of control of thickness and properties of prepared layer with facility and high accuracy. The aim of the present paper is presentation methods the preparation of titanium dioxide thin films for dye-sensitized solar cells.

Galvanized steel needs surface preparation before application of paint coatings to enhance adhesion and corrosion resistance. Surface preparation usually includes physical and/or chemical cleaning and conversion coating process. Conversion coating provide higher corrosion resistance and better adhesion to the polymeric top coat leading to longer lifetime. Chromate based conversion coatings were widely used in industrial applications for their considerable corrosion resistance. However; it showed carcinogenic and toxic effect for human and environment, which led to the replacement of these coatings. One of the replacements is silane compounds which are considered as green compounds due to the restricted side effects on human and environment. It is shown that these compounds have considerable corrosion resistance and in particular cases higher than that of chromate compounds. This paper reviews the parameters affecting the deposition of the organosilanes on galvanized steel, dopants effects and the methods used for characterization and evaluation of the deposited film properties.

Chemical treatment of the metal substrates prior coating application is an effective way of improving the adhesion and corrosion protection properties of the organic coatings. Conversion coatings i.e. chromate and phosphate have been widely used for this purpose and improved the organic coating adhesion and corrosion protection properties significantly. However, the use of such coatings has been strictly restricted in recent years because of its high toxicity and environmental problems. Recently, sol-gel based coatings have been introduced as more environmental friendly alternative, less costly, high accessibility for equipment and easy to application on the metal substrates. In this study, the preparation procedures and application methods of the sol-gel based coatings as well as the main factors affecting theirs properties will be discussed. Also, the constraints and prospects of this area of research will be discussed.

Color preference mostly indicates individual personality and taste expression. The topic of color preference is very attractive these days since it affects the demand and sales of merchandize. The reasons behind individual color preferences has been studied and published numerous times. The researchers are trying to find the answer to the differentiator factors of each individual color of choice. Preliminary factors are color saturation, brightness, hue, context in addition to the personality and taste of the observer which is affected through culture, sex, age and life experiences. There are colors that are more preferable by most viewers regardless of their individual differentiating factors, such as Blue. On the other hands, there are colors that are less favorable by most viewers like Brown and Yellow. Therefore we can conclude that there is some similarity in some differentiating factors among different people with different ages and cultures that make viewers favor one color and dislike another most of the time. In this article some of these factors influencing the color preference are presented briefly.

Attention to biopolymers has been increased due to increase of the environmental awareness, crude oil price and challenges of earth warming. Because of the polymers derived from renewable sources, using these compounds have the lowest negative effects on the final products as comparing to oil-based polymers. One of the most important biocompatible and biodegradable polymer is polylactic acid PLA, which has been used in the textiles with different applications. In the present study, dyeing process and fastness properties of the PLA fibers were reviewed. Effects of dyeing condition such as, temperature, time, dye bath pH, dyes structure and dyeing at ultrasonic wave medium were considered. Also exhaustion values of the PLA and PET fibers were compared and dyeing fastnesses of PLA fibers were presented.

Photocatalytic oxidation is one of the air purification methods for organic pollutant deterioration such as formaldehyde, Volatile organic compounds, bacteria and other chemicals under UV lights. One of the major applications of photocatalyst is in building coatings. Radicals are formed when a photocatalyst is subjected to radiation. The end products of these chain reactions are water and carbon dioxide, if the reactions are fully completed mineralization. If mineralization does not take place, then a great number of side products can be formed, whose properties are not well understood. In this paper performance of photocatalysts, usual and typical photocatalyst, the ways for improvement of photocatalysts performance, deactivation, performance evaluation of PCO air purification, intermediates production and problems were investigated.

This paper aims to review the recent achievements in field of self-healing coatings, as an important class of smart coatings. In this paper, basic definitions and terminology related to the self-healing coatings are presented. Then, various strategies and mechanisms which have been recently implemented in developing of self-healing coatings are introduced. Extrinsic and intrinsic strategies and different mechanisms including microcapsules, hollow fibers, and reversible covalent and non-covalent linkages are the most important approaches which are reviewed. It was demonstrated that the intrinsic strategies are simpler and more efficient in comparison with extrinsic ones. Finally, potential applications and commercialized technologies in field of self-healing coatings are summarized.

The presence of soluble salts at the substrate/coating interface can lead to the premature deterioration of organic coatings. Industry and marine atmospheres, pretreatment with contaminated abrasives and de-icing salts are main sources to contaminate substrates. In this paper, the effects of soluble salts on coating performance are studied. The analyzing methods of type and quantity of salts and also the methods for removing soluble salts are described. In addition, permissible level of soluble salts for different coatings is explained.