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Publisher Summary This chapter describes finishing and application of aluminum coating. Vitreous enameling of metals, particularly iron and copper, is an ancient art. It is a coating based on mixed salts in the form of powdered glass, known as frit, that is applied to the metal that is then fused under high temperature to form a glass-like coating, hard, and durable, but not very flexible. Normal enamels applied to most other metals are unsuitable for aluminum as the fusion temperature of the frit is near or above its melting point. Special frits were developed for aluminum that had a lower fusion temperature at around 550°C, but even at these temperatures the aluminum becomes annealed and loses much of its potential strength. The frit is manufactured by fusing a mixture of quartz with soda, potash, and boric acid to which titanium dioxide is added as an opacifier. After fusion and mixing, it is quenched in water and finely ground with inorganic pigments, and titanium or lithium oxide to form the frit.

The investigation deals with the development of some white enamels for copper watch dials, thermometer scale plates, and signs. The effect of varying Na2O, PbO, cryolite, SiO2 and B2O3 on the properties of the enamels was studied in twenty enamel compositions. The following conclusions were reached: (1) Correct melting is extremely important in the preparation of copper enamels; (a) Slow air cooling of the frit is preferable to quenching in water. (b) Repeated melting tends to promote opacity and to eliminate dissolved gases. (2) A somewhat reducing atmosphere during firing avoids oxidation of the copper. (3) Slight changes in enamel composition have a decided effect on the resultant properties. (4) Sodium oxide promotes gloss but reduces opacity very decidedly. (5) Lead oxide promotes fusibility without materially reducing opacity, except by dilution. (6) Cryolite is not a desirable flux or opacifier as it tends to develop a matt finish. (7) It is desirable to keep the boric oxide content low and good enamels may be produced without it. (8) By using “white arsenic” as an opacifier tin oxide is unnecessary. (9) The following were the best enamels obtained and these appear to be equal to a number of watch dial enamels examined: C-19 and C-20. 20. (10) A second group of compositions which appear to promote results equal to those in use for thermometer scales, advertising letters, etc., are C-10. 10. C-21, C-22, and C-24. In selecting these compositions, all factors such as opacity, gloss, texture, fit and resistance to attack of copper have been considered.

The purpose of this paper is to discuss the results of some recent experiments using evacuated powders as insulation for very low temperatures. Particular emphasis is given to the mechanics of radiant heat transfer through evacuated powders to which metal particles of various sizes were added as opacifier s. A powder with an apparent mean thermal conductivity of l,7μw/cm-°K between 300 and 20°K is reported.

Made available in DSpace on 2018-12-11T16:59:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-04-01 Statement of problem Silicone elastomers undergo physical and chemical degradation with disinfecting solutions. Phytotherapy may be a suitable solution for disinfection. However, its effect on the properties of the silicone material is unknown. Purpose The purpose of this in vitro study was to evaluate the effect of disinfection with conventional and plant-extract solutions and of artificial aging on the hardness and color stability of a facial silicone associated with pigments and an opacifier. Material and methods Four hundred specimens of silicone (MDX4-4210) were fabricated (5×6 mm). Two pigment shades and 1 dry opacifier were combined in the tested material, and 4 groups (n=10) were obtained: colorless (GI), colorless with opacifier (GII), medium pigment with opacifier (GIII), and black pigment with opacifier (GIV). Specimens were subjected to disinfection (30 days) using saline solution, water, and neutral soap (digital friction, 30 seconds), chlorhexidine 4%, Hydrastis canadensis, and Cymbopogon nardus extracts (immersion, 10 minutes). Shore A hardness (ASTM D2240) and color analyses were performed before and after disinfection. Specimens were then exposed to 1008 hours of artificial aging (ASTM 53) and subjected to final hardness and color readings. The results were analyzed with ANOVA and the Tukey significant difference test (α=.05). Results The opacifier increased the hardness (GII). For GII, the H. canadensis solution and the friction with water and soap promoted significantly reduced hardness; the friction also promoted a reduction in this property for GIV. The GIII was not affected after disinfection. A significant difference was found between the ΔE values of the specimens disinfected with H. canadensis, C. nardus, and chlorhexidine, and specimens subjected to saline solution and neutral soap. Conclusion The hardness of MDX4-4210 after the experimental procedure was considered clinically acceptable for facial prostheses. All groups showed clinically unacceptable color alterations regardless of the disinfecting solution. Department of Dental Materials and Prosthodontics Araçatuba Dental School São Paulo State University (UNESP), José Bonifácio Oral Patology and Surgery Department School of Dentistry Federal University of Minas Gerais Department of Dermatologic Infectious and Parasitic Diseases Medical School FAMERP Department of Dental Materials and Prosthodontics Araçatuba Dental School São Paulo State University (UNESP), José Bonifácio

Films of halide complexes of silver can be electrodeposited onto, or removed from, transparent indium tin oxide contacts in less than 10 msec using a clear liquid mixture of dimethyl sulfoxide (DMSO), silver halide, alkali metal halide, and bromine or iodine. The solutions do not attack the contacts, even at high voltages, as long as adequate silver remains in solution. Variations include a mulled mixture of an opacifier and superionic conductor particles in a variety of organic solvents. The electro‐optic properties of experimental display structures are discussed.

Color modifiers and opacifiers for composite resins have been in use for several years. A custom color modifier/ opacifier system can be made by the dentist with the unfilled resin (bonding agent and glaze) and powder from a porcelain staining kit (Fig. 1). By mixing a bonding agent with a powder from the porcelain staining kit, color modifiers of various hues (color) and chromas (intensity) can be made. Hue is determined by the choice of the specific stain, while Chroma is controlled by the amount of powder incorporated into the liquid bonding agent. The Chroma will increase as more powder is incorporated into the bonding agent. Conversely, Chroma decreases as the powder is diluted by the bonding agent. A light-cured resin (visable or ultraviolet) is a better choice to control Chroma because it is not diluted by the catalyst component that is needed in a chemically cured system. The Value (brightness) of the color modifier is controlled by adding white powder to the modifier to increase

The causes of opacification and the function of opacifiers in white ware glazes are discussed briefly. The relative covering power of tin oxide is shown to be greater than that of zircon oxide under the same conditions. The fluidity of the glaze is affected by the amount of opacifier used and can be controlled in commercial practice by the use of a simple inclined testing block.