Isostatic compression

In the case of isostatic compression the same pressure is exerted on the ceramic mass on all sides. The mass is contained in a rubber mould and this is immersed in a liquid inside a pressure vessel. By pressurizing the liquid you can apply the same pressure on the mould from all directions (figure 9.15). This method is especially used for fanciful and asymmetrical objects. 

Additional source of information for UHMWPE acetabular cups arises from the quantitative analysis of polarized Raman spectra. Figure 17.6 shows photographs and the outcome of such analysis for two acetabular cups, which were retrieved after substantially different in vivo lifetimes. The retrieved acetabular cups were both belonging to male patients and sterilized by y-rays, but produced by different processes. One acetabular component (manufactured in 2002 by Biomet Inc.) was prepared by isostatic compression molding and sterilized before implantation by a dose of 33 kGy of y-rays. It was retrieved due to infection after 2 years 5 months. This cup will be referred to as the short-term retrieval. The other retrieval (manufactured in 1995 by Zimmer Inc.) was prepared by Ram-extruded molding and sterilized in air by a dose of 25-37 kGy of y-rays. For this latter cup, the follow-up pe-... 

To be referred to next is the most modem diamond anvU type, generating pressures of order of 10 -100 GPa. The cell illustrated in Figure 6(e) consists of two gem diamonds with optically flat surfaces, between which a sample confined in a drilled hole of a thin metal gasket is sandwiched. To attain isostatic compression an inert gas or an organic liquid, like a 4 1 volume mixture of methanol and ethanol, is contained with the sample. The generated pressure is measured directly from the pressure shift of the fluorescence line of mby powder mixed with the sample. Temperatures to 5000 K can be obtained by laser heating. The quantity of sample confined in a typically 0.1-mm-wide hole is extremely small, just a few microcrystals. At present, research has focused on in situ observations using X-ray and other optical methods, rather... 

Bika et al. (2001) explained how fracture planes can be formed under compressive forces and showed how different stress-strain curves can be for uniaxial tension, uniaxial compression, and isostatic compression... 

The bars are carved in a tin dioxide block. To obtain this block, an isostatic compression at 4.10 Pa is apphed to a tin dioxide powder, it is then sintered at 800°C. The golden metallic films associated with these samples, are elaborated irsing cathodic prrlverization, and have a thickness of 450 nm. 

Hafidi Alaoui A, Woignier T, Phalippou J, Scherer GW (1998) Room Temperature Densification of Aerogel by Isostatic Compression. J Sol Gel Sci Technol 13 365-369... 

Perin L, Faivre A, Calas-Etienne S, Woignier T, (2004) Nanostructural damage associated with isostatic compression of silica aerogels, J Non-Cryst Solids 333 68... 

Alaoui A.H., Woignier T., Phalippou J., Scherer G.W. Room temperature densification of aerogels by isostatic compression. J. Sol-Gel Sci. Technol. 1998 13 365 Alie C., Pirard R., Lecloux AJ., Pirard J.-P. Preparation of low density xerogels through additives to TEOS-based alcogels. J. Non-Cryst. Solids 1999 246 216 Alie C., Pirard R, Pirard J.-P. Study of the morphology of porous silica materials. Stud. Surf. Sci. Catal. 2000 128 177... 

Figure 9.6. The soft-walled permeameter cell would revolutionize the use of permeametry measurements for monitoring the fineness of powders, a) The soft-walled permeameter cell allow for isostatic compression of a powder sample to a known porosity. (7hen the pressure is released, and the bottom cap removed, the powder plug will drop out. b) A simple permeameter circuit which could be used on-line to provide feedback to a powder production line.

Once the powder is obtained, the consolidation of ODS materials can be achieved either by hot extmsion, or by hot isostatic compression (HIC). It could be possible to replace those processes by consolidation by spark plasma sintering (SPS). CEA ODS materials were mainly obtained from prealloyed powder atomized by Aubert et Duval... 

Starting stock material GUR 1050 isostatically compression molded... 

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