Barium fluoride, properties

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). 

Plasma-sprayed, flame-plated, or electrolytically deposited coatings of powders of Al O Ci O TiN, WC, and Ti02 can be applied as wear-resistant ceramics on metal substrates with or without Co, Ni, or Cr incorporated to improve mechanical properties. Silver, barium fluoride—calcium fluoride, and other modifying materials have also been found useful in ceramic coatings for improved friction and wear properties (35). Diamond coatings are also being developed (36). 

Unlike the behavior observed on YSZ substrates, the orientation of the film Is not dependent on the presence of unreacted barium fluoride. In fact, films on SrTiOj substrates display better superconducting properties when all the fluorides are reacted. Figure 8 shows the resistance vs temperature of a film grown on (100)... 

It has been clearly shown that radiopaque materials are needed (16,17) for visualization of aspirated or swallowed dentin-e fragments. This is accomplished with additives such as barium sulfate, barium fluoride, bariiun or bismuth glasses, and halogenated organic compounds. The physical properties of the materials are significantly affected by large quantities of these additives. ANSI/ADA specifications or requirements for radiopaque materials for dentin-e-based polymers have been described (18). 

Nowadays a large number of functional crystals belongs to the TTB family and presents electro-optic, ferro- piezo- pyroelectric properties (e g. the well-known barium sodium niobate Ba2NaNb50i5 (BNN)). In this work iron and manganese based Kx(lvr%(]Vr )i-xF3 fluorides (0.4solid state reaction and characterised by different diffraction techniques in order to investigate their crystalline stmcture. 

Because barium titanate has interesting properties, many methods have been used to grow single crystals of this compound. One of the most popular techniques, using a potassium fluoride flux, was first employed by Remeika.1... 

Barium is a member of the alkaline-earth group of elements in Group 2 (IIA) of the period table. Calcium [7440-70-2], Ca, strontium [7440-24-6], Sr, and barium form a closely allied series in which the chemical and physical properties of the elements and their compounds vary systematically with increasing size, the ionic and electropositive nature being greatest for barium (see Calcium and calcium alloys Calcium compounds Strontium and STRONTIUM COMPOUNDS). As size increases, hydration tendencies of the crystalline salts increase solubilities of sulfates, nitrates, chlorides, etc, decrease (except fluorides) solubilities of halides in ethanol decrease thermal stabilities of carbonates, nitrates, and peroxides increase and the rates of reaction of the metals with hydrogen increase. 

The preparation and properties of barium monofluorotrioxiodate, BalOsF, have been described. This sparingly soluble salt was prepared by the reaction of the hydrated hydroxide Ba(0H)2,2H20 with the compound IVIO2F2 in alcohol, and was characterized by X-ray diffraction and i.r. and Raman spectroscopy. The lOsF " ion has three oxygen atoms equidistant from iodine, and, for this reason, easily breaks down in aqueous solution to iodate and fluoride. ... 

Piezoelectricity links the fields of electricity and acoustics. Piezoelectric materials are key components in acoustic transducers such as microphones, loudspeakers, transmitters, burglar alarms and submarine detectors. The Curie brothers [7] in 1880 first observed the phenomenon in quartz crystals. Langevin [8] in 1916 first reported the application of piezoelectrics to acoustics. He used piezoelectric quartz crystals in an ultrasonic sending and detection system - a forerunner to present day sonar systems. Subsequently, other materials with piezoelectric properties were discovered. These included the crystal Rochelle salt [9], the ceramics lead barium titanate/zirconate (pzt) and barium titanate [10] and the polymer poly(vinylidene fluoride) [11]. Other polymers such as nylon 11 [12], poly(vinyl chloride) [13] and poly (vinyl fluoride) [14] exhibit piezoelectric behavior, but to a much smaller extent. Strain constants characterize the piezoelectric response. These relate a vector quantity, the electrical field, to a tensor quantity, the mechanical stress (or strain). In this convention, the film orientation direction is denoted by 1, the width by 2 and the thickness by 3. Thus, the piezoelectric strain constant dl3 refers to a polymer film held in the orientation direction with the electrical field applied parallel to the thickness or 3 direction. The requirements for observing piezoelectricity in materials are a non-symmetric unit cell and a net dipole movement in the structure. There are 32-point groups, but only 30 of these have non-symmetric unit cells and are therefore capable of exhibiting piezoelectricity. Further, only 10 out of these twenty point groups exhibit both piezoelectricity and pyroelectricity. The piezoelectric strain constant, d, is related to the piezoelectric stress coefficient, g, by... 

The pyroelectric detectors now being manufactured in quantity use either LiTaOj or a ceramic based on PZT modified to enhance its pyroelectric properties [8.43]. Strontium Barium Niobate (SBN) [8.44] and polyvinylidene fluoride films [8.36a, d] are also used. The use of polymer films could expand as the understanding of these films increases. 

Piezoelectricity, from Greek Klet elv meaning to press, to squeeze [41], is the interplay between mechanical and electrical features of a material or a device. Changing one will impact the other. There are different types of materials that show these properties. Quartz, topaz, and tourmaline minerals human and animal bone tissue different proteins Rochelle salts (sodium, potassium tartrate tetrahydrate) barium titanate, lead zirconate titanate, PZT and the polymer poly (vinyUdene fluoride) (PVDF), are some examples. Piezoelectricity, compared to many other areas of science, was relatively recently discovered, by Jacques and Pierre Curie [42] working with quartz among other minerals. 

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