Calcium borosilicate

Calcium bentonites, 6 664—666, 696 Calcium borosilicate, allowed pigment in... 

The Engelhard product based on calcium borosilicate glass flakes is said to give a star-like glitter to coatings. 

Danburite is calcium borosilicate with an orthorhombic structure (2/m2/ mljm) and space group Pnam. The natural danburite in our study consisted of five samples from a variety of geologic environments. Concentrations of potential luminescence impurities in one sample are presented in Table 4.8. 

A trade name for calcium borosilicate is Halox CW 291, -2230 (Halox Pigments, USA). 

Calcium metaborate is claimed to be advantageously incorporated into frits as fire retardants in fire doors particularly for those based on sodium silicate. It is believed that calcium borosilicate will be formed upon heating in these compositions.40... 

More generally, acidic depolymerization products can be leached out of many films of paint, unless suitable pigments are incorporated. Zinc dust plus zinc oxide was the original acid scavenger. Zinc phosphate, zinc ferrite, and calcium borosilicate will each exert an anodic inhibitive function at pH values exceeding 7 while zinc chromate, zinc tetroxychromate, and strontium chromate act independently of pH value (Van Eijnsbergen, 1988). In general, the pH of aqueous paint film extracts should be between 7.5 and 8.5 and certainly not below 6 or above 10. 

C-glass Calcium borosilicate glasses used in corrosive acid environments ... 

Datolite is calcium borosilicate with a monoclinic structure (2/m) and space group P2i/c. It consists of superimposed complex sheets of linked oxygen and O, OH tetrahedra around silicon and boron atoms respectively the Si04 and B(0,0H)4 tetrahedra alternate, forming rings of four and eight tetrahedra. The natural datolite... 

Calcium borosilicates, which are available in several grades, with varying B2O3 content (not suitable for immersion or semi-immersion service or water-based resins [23])... 

Calcium borosilicate is a compiex composite of calcium siiicate avaiiabie commercially in grades differing in borate content and oii absorption value. Its anticorrosive properties are derived from the aikaiinity of the pigment as weii as anodic and cathodic passivation. 

Glass in the form of fibres is relatively inexpensive and is the principal form of reinforcement used in plastics. The fibres are produced by drawing off continuous strands of glass from an orifice in the base of an electrically heated platinum crucible which contains the molten glass. The earliest successful glass reinforcement had a calcium-alumina borosilicate composition developed... 

Acid resistance This property is best appreciated when the glass structure is understood. Most enamel frits are complex alkali metal borosilicates and can be visualised as a network of Si04 tetrahedra and BO, triangular configurations containing alkali metals such as lithium, sodium and potassium or alkaline earth metals, especially calcium and barium, in the network interstices. 

Figure 3. Effect of scatter from calcium emission on the observed background signal in the region of the zinc, I = 213.9-nm line. Note that the borosilicate glass filter prevents any visible radiation from entering the spectrometer CSSj.

Borosilicate pigments [59794-15-19] usually contain calcium or zinc ions in a matrix of silicon dioxide and boron trioxide, x (Ca,Zn)-y Si04 zB03. Aqueous slurries of this white pigment are alkaline (pH > 9). Borosilicate pigments are... 

Preparation and Uses. Boric acid can be prepared in the laboratory by acid hydrolysis of a variety of boron compounds, including halides, esters, salts, and hydrides. It is prodnced commercially by reactions of snlfinic acid with sodium borates in the United States, and with sodium and calcium borates in Turkey. In Sonth America, boric acid is prodnced by reaction of sulfuric acid with ulexite, a mixed sodium-calcium borate. Boric acid is also produced in Rnssia from the borosilicate mineral datolite. 

Table 6 shows the major metal oxides and the iron oxide impurity levels of typical borosilicate Type I glass. Up to 0.05% by weight (500 ppm) iron oxide as Fe O may exist in the borosilicate Type I glass. Thus, the increase in iron levels with time likely reflects a slow leaching of iron from the glass vial. Consistent with this explanation is that similar increases in silicon, aluminum, calcium, and barium levels are also observed in older product lots as shown in Table 6. Note that these nontransition metal ions are not known to participate in the type of reactions depicted in Figure 6. Furthermore, it is not clear if the expected increase in iron leaching from amber vials (Table 6) will be readily compensated for by the reduced light transmission at the causative wavelengths offered by utilizing the amber vial as the primary package.

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