Anvil Type High Pressure Apparatus Research Articles

Melting of polyolefins in different organic matrices after plastic deformation at high pressure

Mixtures of ultra-high-molecular-weight high-density polyethylene (UHMWPE), low-density polyethylene (LDPE), and polypropylene (PP) with various low-molecular-weight compounds were subjected to plastic deformation under a pressure of 1 GPa on an anvil-type high-pressure apparatus. The analysis of the mixtures was carried out by the DSC method and it was found that the thermograms of the deformed mixtures in the temperature range of 30- 100°C contain endothermic peaks of melting of small polymer crystals and exothermic peaks of cold crystallization. The enthalpies of melting of polymers in mixtures could be either higher or lower than the enthalpies of melting of the initial polymers. Exothermic peaks were present on the thermograms of mixtures with fluorescein at temperatures above the T m of polymers. Exo- and endothermic peaks below the T m of polymers, as well as exothermic peaks above the T m of polymers, were associated with the epitaxial growth of polymer crystals. The characteristics of thermal processes in deformed mixtures correlated with the amount of CH 3 groups in macromolecules.

Thermogravimetric and DSC Studies of Mixtures of Aluminum Powder with Low-Molecular Organic Compounds after Plastic Deformation under High Pressure

Powdered mixtures of aluminum with 20 wt % of organic components were subjected to plastic deformation under a pressure of 0.5–4.0 GPa on an anvil-type high-pressure apparatus and then investigated by thermogravimetry and DSC. In deformed mixtures in the T-range of 30–500°C, there was a decrease in mass associated with the decomposition of organic components, while there was an increase in mass associated with the oxidation of aluminum in the T-range of 500–800°C. The mass changes were accompanied by exothermic effects. The enthalpies of exoeffects in the high-temperature range were always higher than in the low-temperature range. The magnitudes of exothermic effects depended on the content of carbon and oxygen in organic molecules; in a series of organic acids, they depended on the pH of acids.

Development of cubic anvil type high pressure apparatus for neutron diffraction

High-pressure neutron diffraction (HPND) experiments in extended pressure and temperature ranges can provide invaluable information for understanding many pressure-induced emergent phenomena, such as unusual phase transitions and quantum critical behavior involving spin, orbital, charge and structural degrees of freedom, in strongly correlated materials. Many apparatuses for different purposes of HPND experiments have been developed in several laboratories. Recently, a clamp-type cubic anvil high pressure cell that can generate pressure over 7 GPa at 3 K was developed for low-temperature HPND measurements. In this paper, characteristics of the clamp-type cubic anvil high pressure cell are presented and its performances are demonstrated by measuring magnetic neutron scattering under pressure on MnP single crystal samples.

Spontaneous growth of diamond from MnNi solvent-catalyst using opposed anvil-type high-pressure apparatus

In this paper an overview of the application of opposed anvil-type high-pressure and high-temperature apparatus for spontaneous growth of diamond crystals by solvent-catalyst technique is presented. The process makes use of a molten Mn47Ni53 catalyst to initiate the graphite–diamond transformation reaction. The pressure and temperature requirements to obtain reproducible spontaneous diamond crystallization were around 52.5–54kbar and 1270–1320°C. The crystals had well-shaped cubo-structured morphology with the {100} and {111} faces and grain sizes of 0.2–0.5mm. This work can stimulate future experimental exploration of spontaneous diamond crystallization by using other solvent-catalyst metals.

Development of cubic anvil type high pressure apparatus for neutron scattering at low temperature

Development of cubic anvil type high pressure apparatus for neutron scattering at low temperature

Effect of pressure on the magnetization measurements of Fe 2P

The ferromagnetic compound Fe 2P shows a first-order paramagnetic to ferromagnetic transition at T C=209 K. To investigate the magnetic properties of this compound under high pressures above 3 GPa, it has been tried to measure the magnetization using a diamond anvil type high-pressure apparatus by MPMS (quantum design). As the results of trial and error, we have succeeded to obtain the data with sufficient precision to understand the substantial behavior of the compound even under considerable high pressures above 5.0 GPa.

Effect of Hydrostatic Pressure on Molecular Conductors, Pd(dmit) 2 Salts

A series of molecular conductors β′-( cation)[Pd(dmit) 2] 2 ( cation = Et 2Me 2 P and Me 4P) exhibit various complicated pressure-induced phenomena. Resistivity measurements under high pressure up to 8 GPa have been carried out using a clamp-type piston-cylinder cell and cubic anvil type high pressure apparatus. The Et 2Me 2P salt shows non-metallic phases at low and high pressure regions, between which a metallic phase appears. The application of pressure suppresses the low-temperature resistivity of this salt. However, the non-metallic behavior still remains at low temperature under 8 GPa. For the Me 4P salt, the metal-to-non-metal transition temperature reaches a minimum at 0.83 GPa and turns to increase with increasing pressure up to 8 GPa, showing no metallic state stable at low temperature

High-pressure transformations in NaAlSiO 4 and thermodynamic properties of jadeite, nepheline, and calcium ferrite-type phase

Phase transitions in NaAlSiO 4 were examined at 3.5–27 GPa and 950–1600 °C using a multianvil-type and a Bridgman anvil-type high-pressure apparatus. The results show that NaAlSiO 4 nepheline first dissociates into an assemblage of NaAlSi 2O 6 jadeite and β-NaAlO 2 with distorted zincite structure at about 4 GPa. At about 7 GPa, this assemblage changes to jadeite plus α-NaAlO 2 with distorted rocksalt structure. Jadeite and α-NaAlO 2 react to form an NaAlSiO 4 phase with calcium ferrite structure at 18–20 GPa, and this boundary has a negative slope. Enthalpies of nepheline and calcium ferrite-type NaAlSiO 4, jadeite, and α- and β-NaAlO 2 were measured by high temperature oxide melt solution calorimetry. The enthalpy for transition of NaAlSiO 4 nepheline to jadeite plus β-NaAlO 2 was 6.2±4.4 kJ/mol and that for the β-α-transition in NaAlO 2 was 23.6±2.4 kJ/mol at 298 K. The enthalpy of formation of NaAlSiO 4 calcium ferrite from jadeite plus α-NaAlO 2 was 79.6±6.9 kJ/mol at 298 K. The calculated boundaries of these transitions from the measured enthalpy data are generally consistent with those by experimental determination, considering the errors of the measured enthalpies and thermophysical properties of the relevant phases and the uncertainty of pressure in the high-pressure experiments. The calculated boundary for dissociation of jadeite to calcium ferrite plus stishovite has a positive slope. The present calculation of the transition boundaries involving NaAlSiO 4 calcium ferrite may suggest that configurational entropy of calcium ferrite possibly due to Al–Si disorder could contribute to the slopes of the boundaries.

The Evaluation of Pressure Under Heating in a High Pressure Apparatus

The possibility of high pressure evaluation at high temperature in the anvil type high pressure apparatus (HPA), is analyzed by a simple model. It is shown that at a certain moment after HPA loading the deformation of the compressible gasket may be described by equations for the elastic strains of matter, particularly by the Murnaghan equation. The latter can be used for high pressure evaluation by the measurement of gasket thickness. Some experimental data in the range of P-T parameters 3.5–4.5 GPa and 1300–1500 K are cited as examples of utilizing this high pressure evaluation method.

High pressure/high temperature treatment of melt textured YBCO high temperature superconductors

Bulk cylindrical blocks of YBCO, 30 mm in diameter and 17 mm in thickness, are prepared by a modified Melt Textured Growth batch process. Blocks are consisting of weak textured 1–2 cm3 grains. Samples with dimensions of about (8×8×5) mm3 are cutted from the blocks, encapsulated in ZrO2 and inserted in a recessed anvil-type high pressure apparatus assembly for high pressure (1–5 GPa)/high temperature (700–950 °C) treatment (HP-HT) under quasi isostatic conditions.

Isothermal compression curve of MgSiO3 tetragonal garnet

The bulk modulus of MgSiO3 tetragonal garnet was measured using a diamond anvil-type high-pressure apparatus combined with synchrotron radiation. An imaging plate X-ray detector was used to get high resolution diffraction data and the whole-powder-pattern decomposition method was employed to analyze the tetragonal unit cell which was only slightly distorted from cubic symmetry. The isothermal bulk modulus (K0) of the garnet-structured MgSiO3 was determined to be 161 GPa when (dKdP)0 was assumed to be 4.Combining this result with previous results, the compositional dependence of the bulk modulus of majorite in a pyrope-enstatite join is expressed as K0(GPa)=(171.8±3.5)−(0.11±0.5)XEn where XEn is the mole fraction of the enstatite composition in majorite.

Numeric modeling of the strength and longevity of structures with allowance for scale effect. Report 2. Investigation of the strength and longevity of hard-alloy dies for high-pressure apparatus

The results of evaluation of the structural strength and longevity of a hard-alloy die of anvil-type high-pressure apparatus (HPA) with recesses intended for the synthesis of superhard materials are presented. Calculations are performed by the finite-element method (FEM) with allowance for the characteristic features of content interaction and the thermoelastoplastic stress-strain state of the basis HPA components, as well as the structural inhomogeneity of the material, which is sensitive to scale effect. Isolines of equivalent stresses in the die in accordance with the Pisarenko-Lebedev strength criterion after assembly of the HPA and in its loading regime with the effective pressure and temperature are obtained. The number of load cycles required to fail the die is established using the developed longevity criterion. The dependence of the strength and operational stability of geometrically similar dies on their effective volume, which agrees satisfactorily with experimental data, is investigated.

Ｂｉ‐Ｐｂ‐Ｓｒ‐Ｃａ‐Ｃｕ‐Ｏ系酸化物超伝導体の摩砕と一軸加圧成形の効果

The formation behavior of an amorphous phase in grinding and its recrystallization behavior by heat-treatment of seed-added powder were observed using a starting powder of the high Tc phase (2223 phase) superconductor having the composition Bi1.5Pb0.4Sr2.0Ca2.0Cu3.2Oy. The effects of uniaxial press-forming in the opposed anvil type high pressure apparatus were investigated in relation to the properties of sintered compacts (bulk density, phase microstructure, critical temperature, etc.).Grinding the starting powder in agate mortar for 10-20 min initiated the formation of an amorphous phase and nearly completely amorphous phase was obtained by grinding for 100min. The heat treatment (at 850°C for 2h) of the amorphous powder which was added by 50 wt % starting powder as seeds, result-ed in the recrystallization to high Tc phase (2223 phase) in the presence of a trace of low Tc phase (2212 phase)Starting powder packed in a copper ring gasket was press-formed under high pressure (0.5-1.5 G P a) . A small amount of low Tc phase coexisted with high Tc phase in the specimen formed at 1.0 G Pa. The bulk density of the sintered compact prepared by the subsequent sintering at 850°C for 40h under one atmospheric pressure was 5.4g/em, and the critical onset and offset temperatures were 115K and 103K, respectively.

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.

Elastic properties of single-crystal NaCl under high pressures to 80 kbar.

Adiabatic elastic moduli for a NaCl single-crystal under high pressures up to 80kbar at room temperature were determined through ultrasonic sound velocity measurements in a cubic anvil-type high pressure apparatus with a solid pressure transmitter. Ultrasonic measurements far both the longitudinal and transverse waves were carried out simultaneously by a pulse-echo-overlap technique. Pressures were determined by X-ray measureinents of NaCl based upon Decker's equation of state. The adiabatic bulk modulus Ks calculated from the Decker's formulae as well as various pressures was combined with the ultrasonic sound velocity to provide pressure dependence of elastic moduli Cij for NaCl. Results of measurements yield zero-pressure values of C11=5.16×1011, C12=1.22×1011 and C44=1.36×1011dynes/cm2. The plots of Cij versus pressure are fit by a least square method with straight lines for pressure range zero to 80kbar, to give the following slopes: ∂C11/∂p=8.72, ∂C12/∂p= 1.22 and ∂C44/δp=0.31. In the overlapping pressure range, ∂Cij/∂p values obtained by this work ae slightly smaller than those obtained by others.

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.

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.

Olivine-spinel solid solution equilibria in the system Mg2SiO4-Fe2SiO4

Olivine-spinel solid solution equilibria in the system Mg2SiO4-Fe2SiO4 have been studied over the pressure range 43 to 96 kb at 800°, 1000°, and 1200°C with the aid of tetrahedral anvil-type high-pressure apparatus. From the compositions of coexisting olivine and spinel solid solutions, the transition pressure of Mg2SiO4 from olivine to spinel structure was calculated to be 127 kb at 800°C, 140 kb at 1000°C, and 151 kb at 1200°C. The olivine-spinel transition in the mantle was concluded to begin at 370 km at a temperature of about 1150°C, when composition of the mantle olivine is assumed at (Mg0.9 Fe0.1)2SiO4. Spinel and olivine solvus curves suggest that the two-phase region ranges from 18 to 28 kb (50- to 80-km width) in the mantle.

Heat treatment of carbon under high pressure

Polyvinylchloride coke, petroleum coke based carbon and glassy carbon were heat treated at various temperatures under high pressure using a modified anvil type high pressure apparatus. The lattice spacing c 0 of Polyvinylchloride coke prepared at 680°C, petroleum coke based carbon calcined at 1100°C and glassy carbon prepared at 700°C was found to change very rapidly around 1400–1500°C with heat treatment under pressure of 10 kbar. The profile of (002) diffraction was found to be complex for the Polyvinylchloride coke heat treated at temperatures in the range of the rapid change of c 0. In the cases of Polyvinylchloride coke calcined at 1500° and at 2000°C, no rapid change of c 0 was observed with heat treatment under 10 kbar. The acceleration effect of pressure on graphitization was observable only at temperatures above the temperature of calcination for each coke. In the case of glassy carbon, which is a typical non-graphitizing carbon, a graphitic material with c 0 6.72 Å was obtained after heat treatment at 2500°C under 10 kbar, while this value of c 0 is never obtained by heat treatment of the glassy carbon even above 3000°C under atmospheric pressure. The c 0 lattice spacing of graphite obtained by freezing the liquid carbon under 10 kbar was found to be 6.709 ± 0.002 A ̊ .

Demonstration of the electrical conductivity jump produced by the olivine-spinel transition

The electrical conductivity of both the olivine and spinel polymorphs of Fe2SiO4 has been determined at 300 to 1200°K and at 31 to 62 kb by means of a tetrahedral anvil-type high-pressure apparatus. It is established that the olivine-spinel transition is responsible for the discontinuous change in the electrical conductivity of Fe2SiO4, the conductivity jump at the time of the formation of spinel from olivine amounting to about two orders of magnitude at 900°K. It is suggested that this discontinuous increase in the electrical conductivity of Fe2SiO4 arises chiefly from a decrease in the activation energy which may be directly related to the smaller molar volume of the spinel polymorph. The electrical conductivity distribution within the earth's upper mantle as related to the experimental results is discussed.