Compact ceramic

Chemical engineers could also work to devise processes to improve the flow characteristics of powders after they are formed. Such research would help control agglomeration of particles in subsequent processing steps as well as facilitate the production of compacted ceramic preforms. For example, gas-solid chemical reactions might be used to tailor the chemical composition of powders. As another example, better methods of componnding powders with binders might be achieved by processes that mix powders with suitable binders in a liquid and then spray dry the resulting suspension. 

ISO standards, reliability and, 26 993 Isostatic compaction, ceramics processing, 5 649... 

Ferrato M, Thonon B. A compact ceramic plate-fin heat exchanger for gas turbine heat recovery. In Shah RK, ed. Compact Heat Exchangers for the Process Industry. Begell House, 1997. 

Bishop. B.. R. Higgins. R. Abrams and R. Goldsmith. 1994. Compact ceramic membrane filters for advanced air pollution control, presented at 3rd Int. Conf. Inorg. Membr.. Worcester. MA. USA. 

Abrams R.F. and Goldsmith R.L., Compact ceramic membrane gas filter, in Gas Cleaning at High Temperatures, Clift R. and Seville J.P.K., eds.. Chapman Hall, London, (1993), p. 346. 

A comparison of laser ionization mass spectrometry (LI-MS) and LA-ICP-MS for the characterization of compact ceramics [123,124] provided limits of detection that were much lower (in the nanogram-per-gram range) with the former technique than with the latter. However, Ll-MS is a time-consuming analytical technique with photoplate detection of mass-separated ions compared to LA-ICP-MS, which uses fast electrical ion registration. 

Pressure sintering is especially significant for covalent substances exhibiting a low sintering activity under normal pressure (e.g, SiC, Si3N4), With some substances of this kind, hot pressing is the only way of manufacturing a dense compact ceramic product. 

Krell, A., Klimke, J., Hutzler, T. 2009. Transparent compact ceramics Inherent physical issues. Optical... 

In comparison with die compaction, isostatic pressing can provide compacts with much less defects or flaws. However, delamination and fracture caused by springback could be present if the pressure is released too fast. In addition, isostatic pressing has been rarely used to directly compact ceramic powders, due to its difficulty in handling powder samples. In most cases, it is used to further increase the density of green bodies either before or after the calcination step. Usually, the increase in density after isostatic compaction is less than 10 %, but that is sufficient to promote the densification of green bodies of most transparent ceramics. 

Figure 5.10. Densification during sintering of two titania compacts. Ceramic A is sol-gel made and ceramic B is made of commercially available milled powder. The former sinters at lower temperature and to a higher final density. With permission from Engineered Materials Handbook, Vol. 4, Ceramics and Glasses (1991). ASM International, Materials Park, OH.

Solids can be prepared as single crystals, glasses, thin films, powders, or sintered powder compacts (ceramics). Powders may be noncrystalline or polycrystalline, exhibit-... 

With advanced Nd YAG lasers at atmospheric pressure, as utilized when coupling with ICP-OES or MS, selective volatilization is moderate. However, in the case of brass, it is as high as in spark ablation and causes problems in calibration [257]. In recent work, favorable working conditions in laser ablation studies were also shown to apply at reduced pressures of around 10-100 mbar [255, 258, 259]. In a number of cases, analytes in very different matrices were found to give signals which fitted astonishly well with the same calibration curves from OES, and a nearly matrix-independent calibration could be applied. This would be very welcome in the analysis of compact ceramics, for which no other direct analysis methods exist. By careful optimization of the laser working conditions, it is now possible to obtain very reproducible sample material from plastics, as shown by Hemmerlin and Mermet [260]. 

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