Ceramic formulations

Other multiphase ceramics. Numerous multiphase ceramic formulations for conditioning of various wastes have been designed (Harker 1988). These so-called tailored ceramics were developed for immobilization of complex defence wastes at the Savannah River Plant and Rockwell Hanford Operation (Harker 1988). Tailored ceramics include ACT and REE hosts (fluorite-structure solid solutions, zirconolite. 

Lithium carbonate. [CAS 554-l3-2j. LLCOi. mp 72.6CC, slightly soluble in H 0. Lised in glass, enamel, and ceramic formulations, in the cleclrovvinning of aluminum, and in the manufacture of other lithium compounds. The compound also has been used in the treatment of manic-depressive psychoses. 

Undoubtedly, changes in porosity (such as bulk and surface porosity and diameter of individual pores) of nanophase ceramic formulated by Webster et al. (1999) provide an explanation for the observed differences in mechanical properties of respective nanophase and conventional ceramic formulations for example, individual surface pores four times smaller were achieved in nanophase (67-nm grain size) compared to conventional (179-nm grain size) HA formulations (Webster et al., 2000a). Compared to conventional formulations, therefore, the bending modulus of nanophase ceramics... 

Nanostructured ceramics provide alternatives not yet fully explored for orthopedic and dental implant applications the improved mechanical properties of these novel ceramic formulations, in addition to their established exceptional biocompatibility, constitute characteristics that promise improved orthopedic and dental efficacy. Requirements applicable for the design of nanophase ceramics for orthopedic and dental applications include the following ... 

Surface properties (such as topography and wettability) of bioceramics similar to human bone can be obtained by decreasing the grain size of ceramic formulations into the nanometer regime. Such surface properties must be incorporated into proactive bioceramics for orthopedic and dental applications surface properties similar to those of physiological bone are needed in order to promote select cell interactions that lead to sufficient osseointegration between an orthopedic or... 

This chapter is devoted to the behavior of the powders of the candidate acid phosphates and oxides in solution. Taking into account the intermediate products formed by the dissolution of individual components, a model for kinetics of ceramic formulation is presented. Once the solubility characteristics of the binder components is estabhshed, the solubility will be related to the thermodynamic properties of these components and the amount of heating and cooling will be estimated from the thermodynamic properties. That will be done in Chapter 6. 

However, 1000 °C leads to a very rapid reaction if anode reform is attempted and in many cases the result is excessive thermal stress of the ceramic electrolyte, so that conventional reformers must be used. As a consequence there has come about a class of intermediate-temperature SOFCs based on alternative ceramic formulations, 500 °C operation having been achieved by a metal/ceramic fuel cell by the company Ceres (see Chapter 4) set up by Imperial College London. 

Barium Minerals Barite (BaS04) and witherite (BaCOs) are commonly used to supply barium in ceramic formulations. Purified barium carbonate, made by dissolution and repredpitation, is used most frequently in ceramic processes and as fluxing compounds in the grazes, ass, and enamels of electronic ceramics and in heavy day products to prevent scumming. The use of these minerals have the drawback that upon heating they give off gas, which can cause cracks. 

Chromia Chromite Cr2Fe04 is the most commonly used chromium-containing mineral for ceramic formulations. This mineral has a spinel crystal structure, where the iron may be replaced by magnesium and aluminum. Chromite is used in ceramics largely as a refractory in the form of burned and chemically bonded bricks. For this purpose, a low-silica material is desired. When low silica is desired, chromic oxide is extracted from chromite by dissolution in add, removal of the iron impiu-ity by liquid—liquid extraction, and precipitation of the hydroxide, which is subsequently calcined to the oxide. Chromic oxide is used as a color additive to azes and enamels and in ferrite production to give magnetic materials. 

Other Metal Carbides A host of other metal carbides are used in ceramic formulations. These include TaC, TiC, Cr3C2, VC, M02C, B4C, WC, and ZrC. These metal carbide powders are produced by car-bothermal reduction of the relevant metal oxide or reaction of the relevant metal with carbon in CO or an inert atmosphere. These metal carbides are used as abrasives and in hig -temperature wear applications. 

The subsolidus composition-temperature phase diagram for the unmodified Pb(Zr, Ti)03 system is shown in Figure IT Most useful ceramic formulations are located close to... 

Neokunibond Optigel CL Osmos N. Major constituent of Bentonite and Fuller s earth. Used as a binder and plasticizer for ceramic formulations ion exchange builder in detergents thixotropic agent for liq. soaps flocculant for water treatment. Industrial chromatographic techniques White powder bulk d = 300-370 g/l. Kaopolite. 

P. Aungkavattana, K. Hemra, D.Atong, S. Wongkasenjit, N. Kuanchertchoo, S. Kulprathipanja Alumina ceramic formulation for extmsion process Thai Patent no. 0601005855 (2006). 

Bioceramics are used in the human body. The response of these materials varies from nearly inert to bioactive to resorbable. Nearly inert bioceramics include alumina (AI2O3) and zirconia (Zr02). Bioactive ceramics include hydroxyapatite and some special glass and glass-ceramic formulations. Tricalcium phosphate is an example of a resorbable bioceramic it dissolves in the body. Three issues will determine future progress ... 

Barium Osumilite. A glass-ceramic formulation BaMg2Al3(Si9Al303o) patented by J. J. Brennan et al (U.S. Pat 4589900,1986, used as the foundation material for composites. 

This group includes naturally occurring materials, used mostly in construction, such as limestone (marble), sandstone (SiOj), and granite (aluminum silicates). These materials are cut or ground to a desired configuration after being mined liom the ground. We also have included data for a small number of minerals that are used in many fine ceramic formulations. Table 1.5 provides chemical formulas, hardness, and density for many such materials. 

The final applications discussed here are electrodes and metallizations for fine ceramics. This includes ohmic contact pastes for varistors and thermistors as well as materials for complex multilayer components. Figure 8.105 illustrates a cross-sectional view of a ceramic chip capacitor. The internal electrode can be Pt, Pd, or Ag-Pd depending on the type of ceramic formulation and its respective firing temperature. The end termination may be Ag or Ag-Pd and is typically required to be platable. The technical requirements of these materials are extremely challenging. 

Smectite - The smectites are water swellable cl s having a sheet or platelet structure. Smectite is the mineralogical term for this class of clays, which includes montmorillonite, hectorite, and saponite. Montmorillonite clays derive their name from the Montmorillon section of France where this material was first observed and later classified. Most smectites are more commonly known under the geological term bentonite. By convention, a bentonite is understood to be an ore or product with a substantial smectite content. The name bentonite derives from Fort Benton, Wyoming, the site of an important deposit. Lattice substitutions within the smectite clays creates a charge imbalance which is compensated by exchangeable alkali and alkaline earth cations. This contributes to the ability of these clay to swell and impart considerable plasticity in ceramic formulations. When the exchangeable cations are predominately sodium, the individual platelets can separate to produce a colloidal structure in water. 

Uses Internal lubricant, wetting control agent used in plaster, plaster Joint compds., and ceramic formulations... 

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