Metallic ceramics

Sealed metal-ceramic X-ray tubes are in use since the sixties. Whereas glass tubes still are the most common known form of X-ray tubes in the public, and are certainly the most used technology firom point of view of sold tubes per year, metal-ceramic X-ray tubes in lots of applications are state-of-the-art. 

Since metal-ceramic technology due to some reasons is the more expensive technology, its use presently is restricted to high-power or special applications. 

In both glass and metal-ceramic tubes, the insulating material serves not only as an insulator, but for other purposes as well ... 

The metal envelope of a metal-ceramic tube can be adapted to tbe shape desired. Production is standard technology. 

X-ray tubes are used in a broad variety of technical applications the classical application certainly is the radiographic inspection. For the penetration of high-Z materials, relatively high power is required. This lead to the development of X-ray tubes for laboratory and field use of voltages up to 450 kV and cp power up to 4,5 kW. Because of design, performance and reliability reasons, most of these maximum power stationary anode tubes are today made in metal-ceramic technology. 

There is a trend in the last years to extend the application range of metal-ceramic tubes also to medium power portable equipment 160kV to 300kV portable systems are well known in the market. 

An advantage of the use of ceramics over the use of glass as an insulator in X-ray tubes is the larger freedom in design due to better stability and more reliable quality of the ceramics. Therefore, typical markets for metal-ceramic tubes are applications where only a relatively low amount of tubes, but in special designs, are used. 

Our company is dedicated solely to metal-ceramic X-ray tubes since 25 years over this time, we have made lots of different tube models especially for tyre inspection systems. The major reasons for the use of metal-ceramic tubes in this inspection technology are robustness, their small and individual shapes, and the frequent need for modifications of their design due to custom designed systems. 

All these specific needs in this market lead to the metal-ceramic technology as the most economic solution for X-ray tubes. 

At present time, metal-ceramic technology is quite expensive and its superior performance pays only in specific applications. 

Metal-ceramic technology would be -if price problems were neglected- the better choice for a variety of small-power X-ray applications. The problem is that an universal X-ray tube is not (and probably will never be) available. 

Flence, the aims of the new series of metal-ceramic X-ray tubes for lower applications were ... 

Most of the advantages of MCB technology can be used to make small anode-grounded metal-ceramic X-ray tubes as well. These could be water- or air-cooled and reach power ranges up to 1 kW at voltages up to lOOkV. 

The metal-ceramic X-ray tubes described here provide new possibilities to the developer of X-ray equipment ... 

Reliability performance of new equipment profit from the innovative metal-ceramic concept. 

The well-known properties of metal-ceramic X-ray tubes are now available for applications in the low budget range. 

Wu R and Freeman A J 1994 Magnetism at metal-ceramic interfaces effects of a Au overlayer on the magnetic properties of Fe/MgO(001) J. Magn. Magn. Mater. 137 127-33... 

Because of the high functional values that polyimides can provide, a small-scale custom synthesis by users or toU producers is often economically viable despite high cost, especially for aerospace and microelectronic appHcations. For the majority of iudustrial appHcations, the yellow color generally associated with polyimides is quite acceptable. However, transparency or low absorbance is an essential requirement iu some appHcations such as multilayer thermal iusulation blankets for satellites and protective coatings for solar cells and other space components (93). For iutedayer dielectric appHcations iu semiconductor devices, polyimides having low and controlled thermal expansion coefficients are required to match those of substrate materials such as metals, ceramics, and semiconductors usediu those devices (94). 

Tabular alumiaa is the ideal base material for high alumiaa brick and monolith liners ia the metal, ceramic, and petrochemical iadustries. 

Polymers, metals, ceramics, and glasses may be utilized as biomaterials. Polymers (see Ppolymerprocessing), an important class of biomaterials, vary gready in stmcture and properties. The fundamental stmcture may be one of a carbon chain, eg, in polyethylene or Tedon, or one having ester, ether, sulfide, or amide bond linkages. PolysiHcones, having a —Si—O—Si— backbone, may contain no carbon. 

Plasma processing technologies ate used for surface treatments and coatings for plastics, elastomers, glasses, metals, ceramics, etc. Such treatments provide better wear characteristics, thermal stability, color, controlled electrical properties, lubricity, abrasion resistance, barrier properties, adhesion promotion, wettability, blood compatibility, and controlled light transmissivity. 

The high elastic modulus, compressive strength, and wear resistance of cemented carbides make them ideal candidates for use in boring bars, long shafts, and plungers, where reduction in deflection, chatter, and vibration are concerns. Metal, ceramic, and carbide powder-compacting dies and punches are generahy made of 6 wt % and 11 wt % Co ahoys, respectively. Another apphcation area for carbides is the synthetic diamond industry where carbides are used for dies and pistons (see Carbon). 

Because of their unique combination of physical and chemical properties, manufactured carbons and graphites are widely used in several forms in high temperature processing of metals, ceramics, glass, and fused quartz. A variety of commercial grades is available with properties tailored to best meet the needs of particular appHcations (45). Industrial carbons and graphites are available in a broad range of shapes and sizes. 

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

Special low fusing porcelain veneers are appHed to pure (unalloyed) titanium dental castings. It is important that firing be done either in a vacuum or inert atmosphere to protect the metal surface from excessive oxidation. The strength of the metal-ceramic bond is apparently adequate although the bonding is thought to involve primarily a mechanical rather than a chemical component. 

Membrane Tyjie.s A detailed taxonornv oF membranes is bevond the scope oF this handbook. Membranes rnav be made From physical solids (metal, ceramic, etc.), homogeneous Films (polvmer, metal, etc.), heterogeneous solids (polvmer mixes, mixed glasses, etc.), solutions (iisiiallv polvmer), a.svmrnetric structures, and liquids. 

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