Type High Pressure Apparatus Research Articles

Disproportionation of pyrophyllite into new phases at high pressure and temperature

The phase relations of pyrophyllite were investigated in the pressure range of 10–20 GPa and at temperatures between 600–1400°C, using a split-sphere type high pressure apparatus. Pyrophyllite has been found to disproportionate into a mixture of stishovite and a X phase (unknown phase) at pressures higher than 10 GPa, and to disproportionate into a mixture of stishovite and a monoclinic phase at pressures higher than 14.5 GPa, when at a temperature of 1000°C. From the X-ray powder data, the unit cell dimensions of the monoclinic phase were determined to be a = 9.800(6) A ̊ , b = 18.232(13) A ̊ , c = 5.356(4) A ̊ , β = 103.78(5)°. The stability fields of the X phase and the monoclinic phase were also investigated in detail. As pyrophyllite is often used as a pressure medium or as components of the pressure cells in high-pressure and high-temperature apparatuses, the efficiency of pyrophyllite as a pressure medium under the conditions of pressures higher than 10.0 GPa and under the conditions of elevated temperatures is briefly discussed.

Construction of liter-class large volume high pressure apparatus for materials synthesis

A belt type high pressure apparatus was constructed with a chamber volume of about 1000 cc and an hydraulic press to operate the apparatus. The maximum pressure generated in the chamber is 6 GPa for a first step and 10 GPa for the final goal. The 6 GPa apparatus (FB120) was designed by the use of high speed steel anvils and a cylinder core. To prevent plastic deformation of the inner wall of the core special cell and inner sleeve materials of smaller thermal conductivity were adopted. A 30 000 ton wire winding frame type press was constructed for this purpose. The design and analysis of the press frame deformation during wire winding is presented.

Measurement of Ultrasonic Wave Velocities in Solid under High Pressure

A new method for the measurement of ultrasonic wave velocities in solid under very high pressures up to 14 GPa has been developed. In a pressure range below 4 GPa a piston-cylinder type apparatus was employed. In an extended pressure range up to 14 GPa a double stage split-sphere type high pressure apparatus was used. A pulse-echo-overlap method was adopted for the wave velocity measurement with a piston-cylinder apparatus. Meanwhile, a simple pulse transmission method is the only applicable method in the higher pressure range. Examples of data for NaCl and baked pyrophillite are presented.

Crystal-chemical characterization of NaAlSiO4 with the CaFe2O4 structure

AbstractA high-pressure modification of NaAlSiO4, with the calcium ferrite structure was synthesized at pressures higher than 24 GPa using a double-stage split-sphere type high-pressure apparatus. The unit cell dimensions are: a=10.1546(8), b=8.6642(8), c= 2.7385(4) Å, and V = 240.93(3) Å3 with the space group Pbnm. Calculated density is 3.916(1) g/cm3. The crystal structure was determined by the ordinary powder X-ray method. Both M1O6 and M2O6 octahedra run parallel to the c-axis, forming edge-shared double chains. The shared edges exhibit remarkable shortening (2.25–2.39 Å). Sodium atoms are located in the ‘tunnel’ formed by the linked double chains, being in eightfold co-ordination. The structure is very similar to that predicted by Dempsey and Strens (1976) with the aid of the DLS method. The possible instability of the calcium ferrite type of Mg2SiO4 is discussed.

Compression of the Sputtered NaCl-type InSb

The effect of the hydrostatic pressure on the sputtered NaCl-type InSb was studied up to 80 kbar. The cubic anvil type high pressure apparatus with the energy dispersive X-ray diffraction apparatus was used. The NaCl-type InSb was found to be stable up to 80 kbar. The pressure-density relation was discussed in connection with the several high pressure crystal forms and evaporated amorphous InSb.

The Effect of Pressure Medium with Pre Formed Gaskets on Cubic Type High Pressure Apparatus

The Effect of Pressure Medium with Pre Formed Gaskets on Cubic Type High Pressure Apparatus

The Effect of Intensification plate on Tetrahedral Type High Pressure Apparatus

The Effect of Intensification plate on Tetrahedral Type High Pressure Apparatus

Order-Disorder Transition in CuAu Alloy at High Pressure

Order-disorder transitions in a thin film of CuAu alloy were studied at pressures ranging up to 100 kb by measuring the electrical resistance and by using a Bridgman-anvil type high pressure apparatus. At high temperatures, pressures were determined with reference to the melting points of zinc. The rate of change of the transition temperature with respect to the pressure is 2.0 deg/kb in the studied range. From the pressure and temperature dependences of the relaxation time, the activation energy and the activation volume were estimated to be 0.7 eV and 3.8 Å3, respectively. The change of the electrical resistance associated with the transition from CuAu I phase to CuAu II was not observed in the present study.

Synthesis of Coesite from Ultra Fine Particles

Coesite, a high pressure phase of SiO2, was synthesized without H2O or any other catalizing component at temperatures as low as 250°C from ultra fine particles (80 Å in diameter) of silica produced by the gas evaporation technique. The ultra fine particles were worked by a tetrahedral anvil type high pressure apparatus up to a pressure of 50 kbar at 450°C for 30 minutes and almost 100% of the particles were crystallized into coesite. Mechanically ground quartz and silica-gel of a few µm in size were also worked under the same condition. The reaction speed of recrystallization of the ultra fine particles was roughly estimated to be ten times or more that of particles of micron size.

Stability of richterite 50-tremolite 50 solid solution at high pressures and possible presence of sodium calcic amphibole under upper mantle conditions

High pressure experiments have been made on the stability of richterite 50-tremolite 50 solid solution by the piston-cylinder type high pressure apparatus in the pressure range from 15 to 40 kb, at temperatures from 700 to 1150°C. This amphibole is stable up to 40 kb at 700°C, and the breakdown pressure gradually decreases with increasing temperatures. It is suggested that this amphibole, on the basis of high pressure experiments, may occur in the upper mantle.

Dense Forms of Rare Earth-Iron Garnets, YIG, GdIG and TbIG

The stability of some rare earth-iron garnets is investigated under high temperature-pressure conditions by means of a girdle type and a piston-cylinder type high pressure apparatus. High pressure transformation of R3Fe5O12 (R=Y3+, Gd3+ and Tb3+) from the garnet structure to the distorted perovskite structure is found to occur. These results make it possible to draw the boundaries of these transformations in equilibrium as P(Kb)=0.038T(^°C)-26.1(±2.8) for Y3Fe5O12, P(Kb)=0.035T(^°C)-.194(±3.0) for Gd3Fe5O12 and P(Kb)=0.048T(^°C)-37.2(±4.1) for Tb3Fe5O12. Ferrimagnetism is observed in these high pressure phases and this property can be explained by the number of superexchange coupling between iron atoms on the octahedral and dodecahedral sites.

Specimen Cell and Gasket Assembly in Girdle Type High Pressure Apparatust

Pressure calibration and pressure distribution measurement in the sample holder were carried out on the girdle type high pressure apparatus with cone angle of 90' of both piston and cylinder, and the relation between arrangement of specimen cell and gasket assembly was discussed.In the apparatus where the diameter of the piston tip was equal to the inner diameter of the cylinder (Fig.1), the composite gasket as shown in Fig.2-(b) was found favorable. In this case, the hydrostatic condition in the sample was almost satisfied (Fig.5). However, the considerable amounts of stresses loaded on the walls of the cylinder and the apparatus could not last so long. The fracture of the piston and cylinder was experienced (Fig.6). In the improved apparatus where the diameter of the piston was smaller than the inner diameter of the cylinder (Fig.7), the gasket shown in Fig.8-(c) was found to be the best among ones examined. Higher pressure could be attained due to intensification effect and the load on the walls of the piston and cylinder was less, although hydrostatic condition was not attained (Fig.10). This improved girdle type apparatus was able to operate sufficiently long at, pressure in the range of 15-60 kb.

COMPRESSIONAL WAVE VELOCITY IN OLIVINE NODULES AT HIGH PRESSURE AND TEMPERATURE

Compressional wave velocities in an olivine nodule from Takashima Islet, Karatsu, were measured up to 900°C and 18kb. Piston-cylinder type high pressure apparatus was used. The sample showed strong elastic anisotropy, so that the velocities passing through the specimens in the three mutually perpendicular directions were observed, and the temperature derivatives of the wave velocity at constant pressure, (∂Vp/∂T)P, were determined. The average of (∂Vp/∂T)P of the three directions is about -0.73m/sec/deg. This value may give good approximation for the isotropic case. The pressure derivative of the wave velocity at constant temperature, (∂Vp/∂P)T, is 11.0m/sec/kb for the present sample. Combining both derivatives, the critical thermal gradient for the compressional wave velocity, (∂T/∂P)Vp, is 15.1deg/kb.

鉄-炭素系合金および実用鋼の等温変態におよぼす圧力の影響

The effects of high pressure on the isothermal transformation are studied for three high purity Fe-C alloys and commercial steels. The specimens (3mm∅×3mm) are inserted into a “girdle” type high pressure apparatus and the isothermal transformation are carried out at 29 or 38.5kbar.The results obtained were as follows:(1) The rates of isothermal transformation both in Fe-C alloys and commercial steels are retarded by pressure, and the retardation is much stronger in the latter.(2) By increasing the pressure from 29 to 38.5kbar in all alloys and steels, the incubation time increases by approximately five times.(3) The structures obtained in isothermal transformation at high temperature can be explained from the phase equilibrium diagram under high pressure which is different from that at atmospheric pressure.(4) As singular structures appeared in the transformation at low temperature and high pressure, ‘aggregate’ or “columnar bainite” structures are observed in place of the acicular bainite at atmospheric pressure. The ranges in which those structures appear are determined.(5) The shape of carbide in a commercial steel containing 1.1%C changes from spherical shape to acicular one with the increase of pressure from 29 to 38.5kbar.

Preparations of BaSnS 3, SrSnS 3 and PbSnS 3 at high pressure

New complex tin sulfides, BaSnS 3, SrSnS 3 and PbSnS 3 with orthorhombic NH 4CdCl 3 structure were prepared in a piston cylinder type high pressure apparatus at 500 to 800°C and 20 kb. Their unit cell parameters at room temperature were determined as follows: a = 8.527 A, b = 14.515 A, c = 3.933 A and V = 486.8 A 3 for BaSnS 3; a = 8.264 A, b = 14.116 A, c = 3.867 A and V = 451.1 A 3 for SrSnS 3; and a = 8.740 A, b = 14.079 A, c = 3.796 A and V = 467.1 A 3 for PbSnS 3. None of them transformed to the perovskite structure below 60 kb and 900°C.

Synthesis of Cubic Boron Nitride

This research was carried out on a part of study of synthesis of cubic boron nitride. I part alloy catalyst of Fe3Al, Ag18Cd82 or Ag58Cd42 and 4 parts hexagonal boron nitride were filled up in a platinum tube approximately 4mm in diameter and 8mm long. Three filled methods were used, that is, sandwich type, mixture type of alloy catalyst and hexagonal boron nitride, and bar type of catalyst. The assembly was placed for 30 minutes at maximum about 80kbars and about 2200°C, using a modified girdle type high pressure apparatus. The cubic boron nitride thus formed was isolated from the mixture and was identified by Debye-Scherrer pattern, hardness test and etc.In the case of Fe3Al alloy catalyst, cubic boron nitride with tetrahedron, octahedra and etc., having a zinc-blende struture, could be synthesized over about 1550°C and 45kbar. Its crystal size was about 80μ. The hexagonal boron nitride powder showed an increase in crystal size with increasing temperatures and pressures. The equilibrium line between the hexagonal and cubic forms was located at the extensions of Wentorf's experimental line and the line calculating from thermodynamic data.In the case of Ag18Cd82 and Ag58Cd42 alloys, cubic boron nitride could be obtained over about 1000°C and 32kbar and high yields of it did with increasing temperatures and pressures. The cubic-hexagonal boron nitride equilibrium line was in the same manner as Fe3Al alloy catalyst. Crystal size was about 80 and 150μ, using Ag58Cd42 and Ag18Cd82 alloys, respectively.Alloy of Ag-Cd system was diffused into hexagonal boron nitride at the rate of about 0.10mm/min.

Stability Region of Chrysotile [Mg<sub>6</sub>Si<sub>4</sub>O<sub>10</sub>(OH)<sub>8</sub>] under High Pressure and High Temperature

The stability region of chrysotile in the system MgO-SiO2-H2O has previously been investigated by Bowen and Tuttle, showing that chrysotile can be prepared at temperatures below 500°C, and at water vapor pressures from 2, 000 to 40, 000lb/in2 and break down into forsterite, talc and water vapor under hydrothermal conditions above 500°C. But the treated pressures were much lower, as described above.This research was carried out as a part of the study on the synthesis of fluor-chrysotile [Mg6Si4O10(F)8]. Mixtures of SiO2 (amorphous) and Mg(OH)2 (brucite) specimens corresponding to chrysotile composition, and natural chrysotile were treated at temperatures ranging from 300° to 600°C and pressures from 2 to 40 kb using a simple squeezer type high pressure apparatus. The present experimental results have indicated that chrysotile can not be formed at 10kb and temperatures above 510°C, at 20kb above 530°C.The pressure-temperature curve of the equilibrium, chrysotile _??_ talc+forsterite+water vapor, was appeared to be lying on the extrapolated line of Bowen and Tuttle's pressure-temperature curve. The value of (∂P/∂T) was about 8.0×102(bar/deg.) and was in good agreement with that calculated by thermodynamic data. The synthesized chrysotile crystal was always appeared as minute tubular, not platy and fibrous by photographs in the electron microscope and had the low refractive indices of chrysotile.

High pressure synthesis of a new perovskite PbSnO 3

PbSnO 3 with a distorted perovskite structure was prepared in a tetrahedral anvil type high-pressure apparatus by the reaction of orthorhombic PbO and SnO 2 at 500°C and 60 to 70 kb. The crystal is assigned by indices of a monoclinic lattice at room temperature: a = c = 4.076 A ̇ , b = 4.043 A ̇ , β = 89°45′. It undergoes a phase transition to a cubic perovskite above around 400°K.

Effect of Pressure on Graphitization of Carbon. I. Heat Treatment of Soft Carbon under 1,3 and 5 kbar

Abstract Polyvinylchloride coke was heat-treated under the quasi-hydrostatic pressure of 1,3, and 5 kbar by using a simple piston cylinder type high pressure apparatus. The process of graphitization under pressure was studied kinetically by analyzing the profile of the (002) diffraction line. It was found that the accelerating effect of pressure on the graphitization of carbon became more pronounced at higher pressure. The process of graphitization under 3, and 5 kbar seemed to take place in at least two stages. In the first stage, the profile of the (002) line shifted simply from the position of the original line to 26.0° in 2θ, which corresponded to a c0-spacing of 6.85 Å. In the next stage, a new component, having a c0-spacing of about 6.72 Å, appeared in addition to the first component, having a c0-spacing of 6.85 Å. Therefore, the profiles of the (002) line became composite. Under 1 kbar, however, no composite profiles were observed and the c0 Spacing decreased gradually with heat treatment. Approximate values for the activation energy and activation volume for graphitization under 3–5 kbar were estimated to be 80–120 kcal/mol, and −7–−9 cc/mol, respectively.

Stability Region of Topaz [Al<sub>2</sub>SiO<sub>4</sub>F<sub><i>x</i></sub>(OH)<sub>2-<i>x</i></sub>

This research was carried on as a part of the study on the synthesis of topaz [Al2SiO4Fx(OH)2-x]. Mixtures of SiO2 and Al2O3 gels and AlF3 specimens corresponding to compositions Al2SiO4Fx(OH)2-x, where x=0.0, 1.0, 1.5 and 2.0 were treated at temperature ranging from 300° to 2200°C at pressures ranging from the atmospheric pressure to 70kb using squeezer and girdle type high pressure apparatus. The heat treatment temperature was measured by a platinum-rhodium thermocouple inserted in the specimen chamber or was estimated from the relations between the temperature and heating power imput at several pressures. Minerals in the treated specimens were identified by the X-ray diffraction method, the infrared spectroscopy and the microscopic observations.No topaz was found in the heat-pressure treated products of the mixture of x=0.0. Under 700°C, pyrophyllite, corundum, and α-quartz etc. were formed as the crystalline phases at arbitary pressure. Kyanite was stable at pressure over about 30kb at 1000°C and above 35kb at 1500°C. Under these conditions, sillimanite, mullite and silica were obtained. Above 1900°C at 40kb, liquid and vapor phases were found.In the specimen of x=1.0, topaz was stable at pressures above 10kb at 1000°C and above 30kb at 1600°C. Under these pressures at the respective temperatures, mixture of mullite and silica was obtained as the stable crystalline phases. It seems that topaz melts incongruently to corundum, liquid and vapor at temperatures from 1700°C to 1900°C at 40kb. Liquid and vapor phases were found above 1900°C at same pressure.In the specimen of x=2.0, it was obtained nearly similar result in comparison with a case of x=1.0, but a stability region of topaz was expanded wider.Maximum size observed of synthesized topaz was about 0.2mm long. The color of topaz was slightly transparent.