US2995776A - High pressure, high temperature apparatus and method - Google Patents

Description

Aug. 15, 1961 A. A. GiARDlNl ET AL 7 2,995,776

HIGH PRESSURE, HIGH TEMPERATURE APPARATUS AND METHOD Filed March 31, 1960 FIG. 2

i N29: w a; E f ll INVENTORS ARMANDO A GIARD/NI JOHN E. rro/A/as.

WH W ATTORNEY United States Patent O 2,995,776 HIGH PRESSURE, HIGH TEMPERATURE APPARATUS AND METHOD Armando A. Giardini and John E. Tydings, Long Branch,

NJ.. assignors to the United States of America as represented by the Secretary of the Army Filed Mar. 31,1960, Ser. No. 19,125

3 Claims. (Cl. 1816.5) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

The present invention relates to. a high pressure apparatus and the method for obtaining of very high pressures, such as those in the order of about 1,600,000 pounds per square inch and including means to enable such apparatus to be operated at high temperatures, such as in the neighborhood of 4000 C.

In recent years, work and study in the development of equipments in the high pressure, high temperature field has assumed considerable importance in two principle catztgories. The first and most important is the extention of knowledge and understanding of the properties of matter. In this regard, research'has been reported on the effects of high pressures and temperatures on the dielectric properties of various materials, index of refraction,

optical absorption. magnetic permeability, crystal strucv ture transitions. electronic transitions, electrical and thermal conductivity, melting phenomena, thermoelectric power and-electromotive force, viscosity, surface compressibility, general strength of materials, wave transmission, reaction rates. radioactive disintegration and condensed crystal structures. The second category is of more practical nature with a potential to practical electronic application. Essentially it deals with the synthesis of stable or metastable forms of new materials or phases of existing materials.

Heretofore for extra high pressure work, various forms of pressure vessels or bombs have been designed, and in current use, which encompass three basic patterns of pistons, namely, (1) the simple or right circular cylindrical piston; (2) the tapered or anvil type of piston; and

(3) the stepped, or compounded piston. In all such cases pressure is applied externally to the opposing pairs of pistons by means of a hydraulic press or other suitable means to create the desired pressure within the sample space, that is, the space or area in which the material or sample to be worked upon is confined between the adjacent ends of the two pistons. In this regard, current processcs requiring pressure in the range of from 3x10 3 10 atmospheres are carried out using fluid pressure transmitting media. However, it has been found that in utilizing pressure bombs or apparatus at pressures beyond approximately 3 x10 atmospheres all known fluid media solidify. Upon solidification these materials become brittle and possess relatively high shear strength. In most cases therefore it has been found that such fluid media are no longer capable of transmitting pressure with a sufficient degree of homogeneity. I

The present invention is concerned with a high pressure vessel that utilizes an improved stepped or compounded piston that seeks to avert and overcome some of the deficiencies and potential weaknesses of that type in prior use. Thus, for example, it has been known that when pressure vessels utilizing a stepped piston are utilized at relativclyhigh pressure ranges, that is in the neighborhood of the limiting strength of the materials used, lateral failures occur at the step plane due to the sharp stress gradient at this position. It has also been found that con siderable difficulties have been encountered in attempting to provide means to generate high temperatures in the ICC 2 sample space in such pressure vessels due to the inherent design limitation of this type of pressure apparatus.

In view of the foregoing, a' primary object of the pres ent invention is to provide a high pressure apparatus that can be consistently operated at high pressures, that is, in the area of 1,600,000 pounds per square inch at the same time that the sample is heated to temperatures in the neighborhood of 4000 C. We have discovered that if in the utilization of the stepped type piston-cylinder pressure vessel, a solid, that is weak, orlow in shear strength under pressure is placed within the so called support area." hereinafter describedin detail, as a pressure transmining medium, results in the regions indicated above can be consistently obtained; ,Morespecifically, the high pressure apparatus of our invention includes a pair of opposed multiple steppedv pistons that are engageable in respective stepped cylinder bores. I The sample or working space. that is the area 'in'whichfthe material to be subjected lays, is located between the opposing faces of the smaller diameter pistons. The compressible solid piston and cylinder support material is placed .withinthe annular spaces formed betweenn the respective large pis ton. tapers and the steps of the smaller cylinder bore; {The compressible material allows movement to the pistons andsimultaneously provides sup'port'to the' normally exposed back portion of the over-stressed small piston ,and also' the exposed end faces of the cylinderin which the said piston rides.

A complete immersion ofeachismall piston is accomplished by useof athjn' shim'fofso ft rnetalfoilat the end face in contact with'the a'nviI-jpis'tonl I Other objectivesi'a'nd features of the in've apparent from the' disclosures'finthe specification and the accompanyingdrawinginwhiehzQ FIG. 1 is a vertical cross-sectional view, with parts shown in elevation ofa detailed view. of-thepiston-eylinder arrangement of a preferred embodiment of the invention; I i v FIG. 2 is a cross-sectional view, with parts shown in elevation of the assembly of the apparatus incorporating the piston-cyl-inder'array shown in FIG. 1; and

FIG. 3 is an exploded perspective view of those components of -the apparatus indicated between the lines A-A of FIG. 1. v.

' One embodiment of the high pressure, high temperature apparatus is shown in FIG. 2 and includes, as a framework, a pair of high strength spaced plates 11, 13 suitably bolted as shown at 15. The plates 11, 13 are provided with centrally disposed openings, as shown, in which a pair of identical opposing carbide pistons 17, 19, respectively, are slideably cngageable. As shown, the respective confined ends of the pistons 17, 19, that is the ends between the plates 11, ,13, terminate-in tapered portions. The respective other 'ends arelinked respectively to the compression pistons 20, 22of a.hydraulic press not shown in further detail, and which'are used to apply the hydraulic forces to the pistons 17, 19. The pistons 17, 19 ride in carbide cylinders 21, 23 which have their respective upperand lower (as viewed in FIG.

1) or outer faces in abutment with the plates 11, 13, re-

spectively. Inoperable engagement with the pistons 17, 19 are a pair'of opposing spaced pistons 25, 27 each of a diameter smaller than that of the pistons 17, 19. The pistons 25, 27 ride in acarbide cylinder 29 which is located intermediate, and in abutment with the lower and upper faces of the cylinders 21, 23, respectively. As can be seen from the drawing, this arrangement of pistons and cylinders defines two areas 31, hereinafter called the support areas, the bounds of each area being the tapered ends of the pistons 17, 19; the inner peripheral walls of the cylinders 21, 23 and portions of the top and bottom surfaces of the cylinder 29. It is noted that the outer peripheral surfaces of the cylinders 21, 23, and 29 form "tion will be I a continuous surface and are confined and supported by a series of bands 33, 35, 37, 39, of high strength steel or other suitable material which are confined between the plates 11. 13. The very high pressure area of the apparatus is shown at 41 and is that area defined by the inner peripheral wall of cylinder 29 and the exposed faces of the pistons 25, 27. In order to introduce the high temperatures required in the operation of the apparatus. a heating element of suitable design, such as resistance wires linked to the material or sample worked upon, is provided within the high pressure area 41. Current for heating the element may be introduced through the electrically conductive pistons 20, 17, 25, and their oppositely aligned like pistons. Electrical isolation between the electrically conductive pistons and the cylinder is provided by very thin sheathings of a very thin suitable insulator or dielectric such as of paper or nylon and shown at 45. If it is desired to make temperature measurements under specific operating conditions, a thermocouple can be placed into the high pressure area 41 through a small axial here through the pistons 17, 25. In order not to encumber the drawings, no details of either the electrical arrangement to the heating element, or the thermocouple have been shown.

An important feature of the present invention resides in a technique, including means, for generating pressures within the apparatus generally far in excess of the strengths of such materials that are conventionally used in systems to generate such high pressurees. We have discovered that if a compressible pressure transmitting solid material is placed with in the support areas 31, externally generated support pressures to the normally overstressed components are set up to accomplish the objectives of the present invention. One ideally suited compressible pressure transmitting solid is pyrophyllite for use in the system. However. it has been found that compounds such as silver chloride (AgCl); silver bromide (AgBr); silver cyanide (AgCN); silver sulphate (Ag SO calcium carbonate (CaCO cobalt chloride (CoCl euprous chloride (CuCl); cupric chloride (CuCl2); lead carbonate (PbCo lead monoxide (PbO); lead sulphate (PbSO4); mercurous chloride (I-IgCl); mercuric sulphate (Hg SO sodium chloride (NaCl): and ammonium chlorate (NH CIO can be used. For the same use, aggregates such as soapstone, lithographic limestone, hot pressed boron nitride and the pyrophyllite heretofore mentioned, may be used.

In the operation and utilization of the high pressure apparatus herein described, the sample of material to be worked is placed in the high pressure area 41 and a suitable compressible pressure transmitting solid, e.g.,

pyrophyllite, is placed in each area 31. To prevent the loss of any of the compressible material through the clearance between cylinder 21 and piston 17, there are provided a pair of steel rings 47, each substantially V shaped in cross section and which fit against the tapered periph eral edge of the pistons 17, 19 as shown. Between the rings 47 and the tapered portion of the cylinder are placed rings 48 of insulating material. The hydraulic forces required are applied to the back faces of the pistons 17, 19 through pistons 20, 22. As the forces are applied, the various piston assemblies converge along their axes. A portion of the force applied to the larger pistons 17, 19 is transmitted directly to the pistons 25, 27 which in turn generate the very high pressure in the high pressure area 41. The remaining effective force applied to the pistons 17, 19 is expended upon the solid compressible support material in the support area 31. As this material is compressed, it transmits pressure both on the exposed peripheral surfaces of the pistons 25, 27 and on both the top and bottom exposed faces of cylinders 29.

In FIG. 3 there are shown details of the high pressure piston-cylinder assembly and its added and related components which may not be apparent from an inspection of FIGS. 1 and 2. Referring specifically to the lower half of FIG. 3, the lowermost item is the insulating ring 48. Above the insulating ring are shown the steel sealing ring 47; a representative machined solid compressible support element 49, such as pyrophyllite heretofore mentioned, and that is confined in the support area 31. There is next shown the high pressure piston 27, preferably made of tungsten carbide (6% cobalt) and a metal electrical contact 51 which serves to provide broadest coverage of the electrically conducting 6% cobalt content of the high pressure piston. Intermediate the opposing like components is shown, in cutaway perspective view, the thin electrical insulating diaphragm 45. Shown within the diaphragm 45 is a tubular shaped mass 55 made of a thermal and insulating material, the hollow core of which serves as a receptacle for the sample or material to be worked upon in the high pressure apparatus herein described. The mass 55 may be made of any one of the compounds or aggregates heretofore mentioned utilized as a pressure transmitting material in the support areas 31, and serves in the same manner to transmit pressure to the sample worked upon. Completing the assembly are ceramic plugs 57 which serve to confine the sample material worked upon within the high pressure area.

While there has been herein described one specific form of high pressure apparatus and method of operating the same, it is within the spirit of the invention to make changes therein without departing from its scope. Thus, for example, while the mechanical arrangement of the present device includes a two stepped piston-cylinder array, it is within the scope of this invention to use any number, within practical limits, of successive reduced size pistons to accomplish the objective of the invention. It is also known that under certain operating conditions, the mass 55 of compressible matter can be omitted from within the high pressure area. While throughout the specification the materials making up the specific components, and the support material have been specifically identified, it is obvious that other materials or aggregate of substantially similar properties can be utilized.

It is also within the scope of the invention to utilize one-half of the apparatus. that is a multi-stepped piston such as shown at 17 and 25, and wherein the bottom of the cylinder 29 would be closed or plugged and the sample to be worked upon would be contained within the bore of cylinder 29.

What is claimed as new is:

1. An apparatus for generating high pre swrcs including a pair of mutual opposing identical multi-stepped pistons wherein each of said pairs includes first and second abutting pistons and wherein said first piston is of a diameter larger than that of said second smaller piston and wherein the end surface of said first piston that is in abutment with said second piston is tapered, and wherein the first and second pistons are respectively engageable in discrete first and second respective abutting cylinders whereby there is formed a first pressure area, the bounds of which are defined by the inner peripheral wall of said first cylinder and a portion of the top surface of said second cylinder, a solid' compressible pressure transmitting material in said pressure area, and further including a confined second very high pressure working area defined by the inner peripheral walls of said second cylinder and the exposed-face of said smaller piston, means for preventing the escape of said pressure transmitting material from said first pressure area, and a framework for confining said pistons and cylinders.

2. An apparatus of the kind set forth in claim Wherein said pistons are electrically conductive and including means for electrically isolating said pistons from the remainder of the apparatus.

3. An apparatus for generating high pressures including a pair of mutual opposing identical multi-steppcd pistons wherein the pistons of each discrete pair include a first larger and a second smaller abutting pistons and respectiveiy engageable in discrete first larger and second smaller area, and a framework including a series of binding rings abutting cylinders whereby there is formed at least one for confining said pairs of pistons and cylinders. pressure area, the bounds of which are defined by the inner peripheral surface of said larger cylinder and a por- References Cited in the file of this Patent tion of the top surface of the next immediate partially 5 UNITED STATES PATENTS abutting smaller cylinder, and further including a confined very high pressure working area defined by the g 5' inner peripheral walls of said second smaller cylinder and 2941245 23? :2: 1960 the exposed face of said smaller piston, a solid compres- 2:941:248 Han June 21, 1960 sible pressure transmitting material within said pressure 10

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