نشریه مطالعات در دنیای رنگ
سال یازدهم شماره 3 (پیاپی 42، پاییز 1400)

Food consumers around the world are looking for pleasant and attractive food in terms of taste and appearance. At the same time, they seek its safety and healing. Food color is a major factor and one of the most important properties to its acceptance and selection. Dyes can enhance or mask the natural color of food, identify or decorate food. During the processing of foods, a significant amount of their original color is lost. This defect can be eliminated by using synthetic or natural food dyes. Due to the side effects of synthetic dyes such as multiple poisonings in the short and long term, allergenic reactions, behavioral and neurological effects, and consumer awareness, many synthetic food dyes have been replaced with natural ones today. In addition, natural dyes have antimicrobial, antioxidant, and therapeutic properties against diseases and health disorders. Anthocyanins, carotenoids, phenolic compounds, red beet derivatives, anato, chlorophylls, and some curcuminoids are some of the most widely used natural dyes that are legally available. This report aims to provide a scientific approach in the field of synthetic/natural food dyes. It also describes the industrial and biological technologies used to optimize food attractions, expiration dates, sustainability, public preferences, and prospects for the industry.

According to the origin and the solubility in the coating, Colored materials are divided into inorganic pigments and organic dyes. Since the late 18th century, Barium sulfate has been used as a white pigment in different supports, either unaccompanied or combined with other pigments. The present paper aims to review the Characteristics and application of barite. In addition to representing a brief history of this pigment, white pigments' most important physical and chemical properties have been studied. Also, all of the structural, physical, chemical, and visual properties of barium sulfate pigment, which is the main issue of this article, with the preparation, identification, and diagnosis methods, have been studied. Although this pigment was used later than the other white pigments, its production and convenience of application have expanded usage in art and industry due to its attractive properties.

Diamond has unique properties compared to other materials. Despite these features, its application in the industry is minimal due to its scarcity and high price. Due to recent technological advances, it has become possible to deposit thin synthetic diamond coatings on the surface of various substrates such as metal and ceramics. For example, tungsten carbide–cobalt composites (WC-Co) are common materials in tribological applications and cutting tools that synthetic diamond coatings can be deposited on them. Reports in this field show that the deposition of synthetic diamond coatings by chemical vapor deposition (CVD) on the surface of carbide tools significantly improves their mechanical and tribological properties and leads to improved performance. The industrial use of synthetic diamond coatings has increased due to high wear resistance, excellent hardness, and low friction coefficient. For this reason, extensive research has been done to eliminate defects, improve the properties, and expand this category of coatings. However, one of the significant problems of synthetic diamond coatings is their low adhesion strength on the tool surfaces; Therefore, many researchers have focused on increasing the adhesion of these coatings. To achieve proper adhesion in these coatings, many characteristics of the coating-substrate system, such as the optimal thickness of the coating and minimizing the residual thermal stress, must be considered. Therefore, to attain synthetic diamond coatings with unique properties, it is necessary to design the microstructure and architecture of the coatings carefully. This article aims to review the researches conducted to improve the performance of diamond protective coatings.

Nowadays, fossil fuels, which are limited sources, are used to produce energy. According to energy consumption and its growing trend, it is necessary to introduce new sources of energy production. As a renewable, eco-friendly and abundant energy source, the sun has attracted the attention of the world. Solar energy is directly converted into electric energy with the help of photovoltaic devices. Dye-sensitized solar cells deliver a cheaper and dependable alternative for numerous photovoltaic devices such as mineral, thin-film, and hybrid solar cells. The performance of dye-sensitized solar cells depended on photosensitizer (Dye), electrolyte, and the semiconductor. Organometallic complex dyes are an important group of photosensitizer compounds that are suitable for use in the solar cell structure. These compounds illustrate an excellent performance in DSSCs, and an efficiency of about 17% was reported. The most important metal used in the synthesis of these compounds is ruthenium, which has shown the best efficiency. This article provides an overview of the types of organic-mineral complexes as sensitizers (dyes) in dye-sensitized solar cells.

Vegetable-tanned leathers, especially tanned with condensed tannins, are susceptible to acidic conditions due to their degradable nature, leather-making process, and air pollutants. These factors lead to severe degradation of the leather called acid degradation or red rot. Leathers from historical times are subject to acidic degradation, and if left untreated, a large amount of them will be lost. Therefore, leather conservation has long been studied to control acidic degradation. However, due to the poor performance of many treatments, preventing this degradation remains a severe challenge of the conservation of historical leather artifacts. The materials used in the treatment of acid-degraded leathers can be classified into consolidants, coatings, stabilizers, and also, in some cases, dressings and lubricants. However, many of these materials are now obsolete due to their poor performance. Accordingly, the present study has reviewed the literature on the treatments of acid degradation in historical leathers. This paper aims to describe the studies done to date and contribute to future studies.

Magnesium and its alloys have unique properties, including low density, high specific strength, excellent damping capacity, and excellent workability. These qualities have made them extremely attractive for aerospace and automotive telecommunications equipment applications. Magnesium is highly reactive due to its high intrinsic chemical activity. However, the oxide it forms has little substrate protection, unlike aluminum titanium oxides, thus limiting its widespread use. One way to improve the surface properties of this metal and its alloys is coating. Plasma electrolytic oxidation (PEO) as a new coating process is a good option for applying a corrosion abrasion-resistant ceramic layer to metals like magnesium that strongly form a passive film. This coating has crack, porosity, and defects that allow corrosive agents to penetrate the metal layer easily. The use of nanoparticles in the electrolyte reduces existing porosity by creating composite coatings. In this case, more compact coating and diffusion of corrosive ions between the coating layers are harder, thus improving alloys' corrosion resistance and abrasion resistance. This study investigates the effect of zinc oxide pigment nanoparticles on improving PEO coatings and their mixing mechanisms in the electrolyte.