Belt apparatus

A belt apparatus is capable of hoi ding pressures of 7 GPa (70 kbar) and temperatures of up to 3300 K for periods of hours. The maximum steady-state temperatures are limited by melting of the refractory near the reaction 2one (13). 

In the belt apparatus, the sample is contained in a noble metal capsule (a BN or MgO container is used for chalcogenides) and surrounded by pyrophyllite and a graphite sleeve, the latter serving as an internal heater. In a typical high-pressure run, the sample is loaded, the pressure raised to the desired value and then the temperature increased. After holding the pressure for about 30 minutes, the sample is quenched (400 K s ) while still under pressure. The pressure is then released after the sample has cooled to room temperature. 

The e - y transition boundary was determined by measuring the resistance changes during the transition in a high-compression belt apparatus (Bundy, 1965) and in an internally heated diamond-anvil cell (Boehler, 1986 Mao et al, 1987). The boundary was also determined by in situ X-ray diffraction measurements in an internally heated diamond-anvil cell (Boehler, 1986 Dubrovinsky et al, 1998), in a laser-heated diamond-anvil cell (Shen et al, 1998), and in a multi-anvil apparatus (Funamori et al, 1996 Lfchida et al, 2001). The boundaries determined by Mao et al. (1987), Shen et al (1998), and Lfchida et al (2001) are in good agreement, but are all at —75 K higher temperature (or —2 GPa lower pressure) than the boundary determined by Funamori et al. (1996), Boehler (1986), and Bundy (1965). 

Fig. 1.15 (a) A girdle device with conicai pistons and (b) a belt apparatus (S) sample space. The shaded areas are gaskets. (From reference 1.)... 

Remove the belt-apparatus from the hydraulic press and open it by taking off the upper part. Recover the sample in its protective capsule, and characterize it by classical methods, after having removed the potassium chloride (resulting from the decomposition of KCIO3) by rapid dissolution in water. (A new high-pressure cell must be used for each experiment.)... 

The design and the structure of the equipment are directly related to which of these types of radiation are used. For example, using a belt apparatus with the specific high-pressure cell shown in Fig. 7.18, electrical measurements have been made at various temperatures and pressures. 

A brief diversion is necessary at this point to make a few comments concerning the apparatus. The Belt apparatus makes use of two opposing, conical pistons thrust into opposite ends of a symmetrical, tapered chamber (Figs. 6, 7). Relative motion of the pistons with respect to the chamber is afforded by a compressible gasket. The solid pressure transmitting material... 

Squeezing in the diamond anvil cell at 400 kbar is more efficient than in the belt apparatus at 40 kbar. The metastable quenched high-pressure phases MSi2 (M = Ca, Sr, Ba) obtained in the belt apparatus showed only a volume decrease of approximately 10%. 

The essential difference between the belt and girdle devices is the shape of the die bore/taper and the matching anvils. For the belt apparatus, the die bore is curved continuously from center to outer surface whereas, for the girdle, the die bore is straight and proceeds out on both sides in a linear progression. 

The belt apparatus (Fig. 7.3) provides an ideal high pressure-high temperature combination for solid-state synthesis. This apparatus was used for the synthesis of diamonds some years ago. It actually involves a combination of the piston-cylinder and the opposed anvil designs. The apparatus consists of two conical pistons made of tungsten carbide, which ram through a specially shaped chamber from opposite directions. The chamber and pistons are laterally supported by several steel rings,... 

Synthetic diamond (H. Tracy Hall) Hall synthesizes diamonds using a high-pressure, high-temperature belt apparatus that can generate 120,000 atmospheres of pressure and sustain a temperature of 1,800 degrees Celsius in a working volume of about 0.1 cubic centimeter. 

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