Bismuth, properties

Bismuth properties. The physical properties of bismuth are listed in Table 23-1. 

There is often a wide range of crystalline soHd solubiUty between end-member compositions. Additionally the ferroelectric and antiferroelectric Curie temperatures and consequent properties appear to mutate continuously with fractional cation substitution. Thus the perovskite system has a variety of extremely usehil properties. Other oxygen octahedra stmcture ferroelectrics such as lithium niobate [12031 -63-9] LiNbO, lithium tantalate [12031 -66-2] LiTaO, the tungsten bron2e stmctures, bismuth oxide layer stmctures, pyrochlore stmctures, and order—disorder-type ferroelectrics are well discussed elsewhere (4,12,22,23). 

Solders are alloys that have melting temperatures below 300°C, formed from elements such as tin, lead, antimony, bismuth, and cadmium. Tin—lead solders are commonly used for electronic appHcations, showing traces of other elements that can tailor the solder properties for specific appHcations. 

Bismuth V n d te. The use of lead chromate pigments has been slowly phased out of many appHcations. Thus a search for more environmentally acceptable relatively inexpensive yeHow pigments having exceHent coloristic properties has been ongoing. 

In the calciaation process, a mixture of corresponding oxides and an optional modifier, eg, molybdic acid, are milled together to achieve a homogenous mixture. The mixture is calciaed at 750—950°C and milled to a desired particle size. Wet milling ia an alkaline medium is recommended to remove any unreacted vanadium salts that ate beheved to degrade the pigmentary properties of bismuth vanadate (39). 

Selenium has also been shown to act synergistically with bismuth to improve the machinabifity of brasses (113). The machining properties are similar to those of the leaded brasses used in plumbing appfications. Environmental concerns arising from the leaching of lead brasses necessitates a replacement of the lead. 

Solders. In spite of the wide use and development of solders for millennia, as of the mid-1990s most principal solders are lead- or tin-based alloys to which a small amount of silver, zinc, antimony, bismuth, and indium or a combination thereof are added. The principal criterion for choosing a certain solder is its melting characteristics, ie, soHdus and Hquidus temperatures and the temperature spread or pasty range between them. Other criteria are mechanical properties such as strength and creep resistance, physical properties such as electrical and thermal conductivity, and corrosion resistance. 

Other. Insoluble alkaline-earth metal and heavy metal stannates are prepared by the metathetic reaction of a soluble salt of the metal with a soluble alkah—metal stannate. They are used as additives to ceramic dielectric bodies (32). The use of bismuth stannate [12777-45-6] Bi2(Sn02)3 5H20, with barium titanate produces a ceramic capacitor body of uniform dielectric constant over a substantial temperature range (33). Ceramic and dielectric properties of individual stannates are given in Reference 34. Other typical commercially available stannates are barium stannate [12009-18-6] BaSnO calcium stannate [12013 6-6] CaSnO magnesium stannate [12032-29-0], MgSnO and strontium stannate [12143-34-9], SrSnO. ... 

Antimony is also used as a dopant in n-ty e semiconductors. It is a common additive in dopants for siHcon crystals with impurities, to alter the electrical conductivity. Interesting semiconductor properties have been reported for cadmium antimonide [12050-27-0] CdSb, and zinc antimonide [12039-35-9] ZnSb. The latter has good thermoelectric properties. Antimony with a purity as low as 99.9+% is an important alloying ingredient in the bismuth teUuride [1304-82-17, Bi Te, class of alloys which are used for thermoelectric cooling. 

The physical properties of bismuth, summarized ia Table 1, are characterized by a low melting poiat, a high density, and expansion on solidification. Thermochemical and thermodynamic data are summarized ia Table 2. The soHd metal floats on the Hquid metal as ice floating on water. GaUium and antimony are the only other metals that expand on solidification. Bismuth is the most diamagnetic of the metals, and it is a poor electrical conductor. The thermal conductivity of bismuth is lower than that of any other metal except mercury. 

Bismuth trioxide is practically insoluble in water it is definitely a basic oxide and hence dissolves in acids to form salts. Acidic properties are just barely detectable, eg, its solubiUty slightly increases with increasing base concentration, presumably because of the formation of bismuthate(III) ions, such as Bi(OH) g and related species. 

Bismuth trisulfide has been used as a high temperature lubricant and has been of interest for its photo- and thermoelectric properties. 

Metals such as copper, iron, or a combination of the two, usually modified with tin, bismuth, and/or lead ate used as binders of sintered friction materials where deformation under the high forming pressure is requited to lock together the property modifiers within a matrix. Metals such as copper, iron, zinc, aluminum, and occasionally lead are also used as friction modifiers. 

Cobalt is the thirtieth most abundant element on earth and comprises approximately 0.0025% of the earth s cmst (3). It occurs in mineral form as arsenides, sulfides, and oxides trace amounts are also found in other minerals of nickel and iron as substitute ions (4). Cobalt minerals are commonly associated with ores of nickel, iron, silver, bismuth, copper, manganese, antimony, and 2iac. Table 1 Hsts the principal cobalt minerals and some corresponding properties. A complete listing of cobalt minerals is given ia Reference 4. 

Radiopaque materials are used to determine the location of aspirated dentures and fragments (205,206). Opacifying additives include barium sulfate, barium fluoride, barium or bismuth glasses, and brominated organic monomers and polymers. The incorporation of these additives into the resin base or tooth can adversely affect physical properties. Radiopaque materials meeting the requirement for ANSI/ADA specifications for denture-base polymer have been described (207). 

Arsenic, Antimony and Bismuth Table 13.4 Some physical properties of Group 15 elements... 

T ble 13.6 Some physical properties of the trihalides of arsenic, antimony and bismuth... 

Bismuth Niobium is resistant to bismuth at temperatures up to 560°C but is attacked at higher temperatures and is therefore not considered a suitable container for handling liquid bismuth even under oxygen-free conditions Furthermore, the stress-rupture properties of niobium are significantly lowered when the metal is tested in molten bismuth at 815°C . 

Bismuth Liquid bismuth has little action on tantalum at temperatures below 1000°C " , the rate of attack at 870°C being less than 0.13 mm/y, and exerts not detrimental effects on the stress rupture properties of tantalum at 815°C, but is causes some intergranular attack at 1000°C . 

Perhaps the most obvious metallic property is reflectivity or luster. With few exceptions (gold, copper, bismuth, manganese) all metals have a silvery white color which results from reflecting all frequencies of light. We have said previously that the electron configuration of a substance determines the way in which it interacts with light. Apparently the characteristic reflectivity of metals indicates that all metals have a special type of electron configuration in common. 

Bromopyrogallol red. This metal ion indicator is dibromopyrogallol sulphon-phthalein and is resistant to oxidation it also possesses acid-base indicator properties. The indicator is coloured orange-yellow in strongly acidic solution, claret red in nearly neutral solution, and violet to blue in basic solution. The dyestuff forms coloured complexes with many cations. It is valuable for the determination, for example, of bismuth (pH = 2-3. nitric acid solution endpoint blue to claret red). 

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