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Jan 1, 1925

By Alexander Coucoulas

FABRICATION of thin-film circuits deposited on glass substrates requires the formation of permanent electrical contacts. Since thin films are in the order of a few thousand angstroms thick and are deposited on nonconductive surfaces such as glass, new methods of lead attachment are being pursued in the microelectronics industry. Ultrasonic welding is being considered in thin-film technology since joining can be accomplished between a wide variety of dissimilar materials.l,' Ultrasonic welding is accomplished by a transducer-coupling-tip system which converts high-frequency electrical energy into mechanical vibrations and delivers it into the weld region. During the process the tip oscillates in a direction parallel to the surface of the weldments, inducing shear stresses in the work pieces which are clamped between the tip and anvil. Though the basic bonding mechanism is not clearly understood, it has been described as closely akin to friction welding. In the course of an investigation concerned with ultrasonic we!ding of aluminum wires to tantalum thin films (1400A) deposited on glass, low weld strengths were related to glass failure. Upon investigating this condition, an improved method of bonding was developed where the aluminum was held at a temperature where a minimum amount of strain hardening occurred during the introduction of ultrasonic energy. Experimental Procedure. Aluminum wires (0.015 in,) were bonded to tantalum thin films with an optimized set of welding parameters (power, time, clamping force) employing a commercial 100-w 60-kc ultrasonic welder. Forty-five degree shear-peel tests, where the lead is pulled at a 45-deg angle with respect to the substrate at 0.2 in. per min, produced a large variation from zero to the strength of the wire, Table I. Inspection of the weld region generally revealed: glass cracking before and after testing; the removal of glass nuggets from the substrate by the lead during testing, Table I; thin-film penetration. In an effort to improve the shear-peel strength, the aluminum between the tip and substrate was heated above ambient temperature through an argon gas media prior to and during welding with the same parameters employed above. With the addition of heat: wire deformation was increased; shear-peel tests all failed at the weld-wire junction, leaving the bonded portion undisturbed; no evidence of glass cracking or film penetration prior to or after testing was observed. In order to prevent failure at the weld-wire junction due to excessive wire deformation, 0.035-in. aluminum wires were welded to tantalum thin films with an optimized set of welding and heating parameters. As

Jan 1, 1967

By H. L. Talbot, R. S. Young, A. Golledge

THE differentiation of, oxidized forms of lead from lead sulphide in complex products by chemical analysis is of considerable importance to certain mining and metallurgical companies. A method for the separation of "oxide" lead, (non-sulphide), from sulphide lead, based on the solubility of the former and virtual insolubility of the latter in concentrated ammonium acetate solution, has been employed for many years in the industry.1,2 Unfortunately this solvent, while satisfactory for lead sulphate and carbonate, is without action on lead phosphates or vanadates, with the result that at Rhodesia Broken Hill Development Co. where these latter minerals are present, they have counted as sulphides when using this procedure. For the control of operations in the new concentrator it became necessary to have a closer check on sulphide lead than could be obtained by the only current method of differentiating this constituent from oxidized lead. For some time this problem has engaged our attention, and after a large number of solvents had been tried, the following procedure was evolved. Like all methods depending on selective solution in a complex material, it will not give 100 pct separation into oxide and sulphide portions. Because of the ease of oxidation of galena this is almost an impossibility. Our procedure will, however, give a recovery of 99-100 pct of the oxidized lead, contaminated with very small quantities of lead sulphide, and a corresponding recovery of 97-98 pct of the sulphide lead. The procedure is simple and reproducible, and gives results quite satisfactory for routine control purposes. EXPERIMENTAL For this work standard samples of the following pure lead minerals were obtained from Broken Hill, Northern Rhodesia. These were hand-picked specimens, and were carefully ground to - 200 mesh. Since it was realized that a fair-sized sample would be necessary for this work to thoroughly test the large number of procedures we had in mind, a compromise had to be effected between a few grams of very pure minerals and a large sample of lower grade material. For this work the presence of gangue was not deleterious, so long as the oxide lead minerals did not contain lead sulphide, and vice versa. Table I shows the lead minerals used, and their total lead content, both theoretical and actual. Apart from the pyromorphite the minerals are seen by analysis to be quite pure. Many solutions were tried in an effort to dissolve the oxidized lead minerals and

Jan 1, 1947

By Zay, Jeffries

THE effect of thoria (ThO2) on grain growth in tungsten was discussed in some detail in a paper presented before this Institute by one, of the authors in 1918.1 In that paper it " was assumed that the, thoria was present in the tungsten entirely as a mechanical mixture. There was no indication in the experiments described that even a trace of the thoria was in solid solution in the tungsten. Langmuir,2 however, observed that thoriated-tungsten filaments under certain conditions showed electron emissions many thousand times greater than unthoriated tungsten at the same temperature. He concluded from his studies that a slight amount of the thoria had dissociated on heating the filament to a temperature near 220°. C. At this temperature and higher, part of the thorium diffuses to the surface of the filament where it evaporates at. a much faster rate relatively, than the tungsten, and also at a rate, nearly as fast as it is brought to the surface by diffusion: If the temperature is lowered to say 1800°,. C., diffusion of the thorium atoms to the surface is more rapid than evaporation, sown adsorbed film of thorium atoms is produced on the surface of the tungsten filament. The electron emission is governed by the outside layer of atoms so the emission from such a filament might be expected to approxi¬mate that of a thorium filament at the same temperature. PRESENCE OF METALLIC THORIUM IN THORIATED TUNGSTEN If the filament containing the adsorbed film of thorium. is heated to a sufficiently high temperature, the thorium atoms evaporate: rapidly and the electron emission becomes more nearly that of tungsten. On cooling again to 1800° C., or thereabouts, the emission 'builds up gradually to a maximum. The filament containing the adsorbed layer of thorium atoms is said to be "activated." By studying the rates of activation under different conditions of prior thermal treatment and at different temperatures, Langmuir was able to arrive at an estimate of the

Jan 1, 1927

Jan 1, 1914

By G. St. J. Perrott

During the past year, the Bureau of Mines has carried on an investigation of liquid-oxygen explosives (L.O.X.) to supplement the work described in previous publications.' The present paper gives results of the first part of this work, which was a laboratory investigation of the properties of typical combustibles used in L.O.X., and the relation of these properties to the absorption and retention of oxygen by the explosives and their explosive characteristics. No attempt will be made to describe the development of liquid-oxygen explosives, because this phase of the subject has been well covered.2 The L.O.X. cartridge consists of a paper wrapper filled with an absorbent combustible material that is saturated with liquid oxygen by soaking it therein. After saturation, the cartridge is removed from the liquid and fired with fuse and cap, or electric detonator, in a manner similar to other explosives. Certain types of cartridge may be detonated with fuse alone, requiring no cap to initiate the detonation. ' By suitable variation of the nature and density of the combustible, cartridges having a wide variety of explosive characteristics may be made.

Jan 1, 1925

By James E. Harding

The usual method of sampling mineral deposits is to drill holes and assay the sludge or core. Though the results thus obtained may not represent the true average value of the deposit, it is on these results that estimates of practically all large orebodies are made. In a large number of cases, the results of exploitation fall far short of the estimated value of the orebody. The standard method of making these estimates is to find the cubic contents of triangular prisms, in the apexes of which the drill holes are placed, by. multiplying the surface area by the average depth of the ore in the three drill holes and then multiplying the cubic contents by the specific gravity of the ore or rock to find the tonnage. The assay value is found by dividing the sum of the products of the depth of ore in each hole and the corresponding assay value by the sum of the depths of the ore in the three holes. As the latter part of this method is subject to many mathematical errors, it should not be depended on. Some engineers, therefore, use a discount factor, but as this factor is either arbitrarily selected or is obtained by obscure methods, the results are no better than guesswork. The standard method is correct when the drill holes are so laid out that the triangular prisms are equilateral in cross-section. But as ore deposits cannot always be drilled into at regular intervals and because of the human factor, if many holes are drilled, triangular prisms of all degrees of angularity are produced. In such cases it is necessary to assume that the influence of the different holes is not the same in all directions, which assumption of course is absurd. The area of the triangular prism is usually found by scaling; an ore-body of sufficient size to justify churn drilling is too large to be handled conveniently on maps having a scale larger than from 1000 to 1 to 1,500 to 1 and maps of such scales cannot be accurately measured. A variable is thus introduced in the first operation. In addition, the scaling is frequently done from blueprints, which sometimes shrink as much as 4 per cent. between printing, washing, and drying. The error due to scaling may be eliminated by surveying the location of each hole and

Jan 1, 1922

By W. M. Lehrer

RECENT development of high-temperature brazing alloys has required information regarding the eutec-tic temperature and composition of the Pd-rich section of the Pd-B system.. Literature on this subject was found to be scanty with no complete system yet determined. Buddery and welch1 report an inter-metallic compound occurring in the Pd-B system at 6.33 wt pct B (PdsBz). Another source, Sieverts and Bruning,2 indicates that after annealing at 700°C, a 1.6 and a 2.0 wt pct B alloy were two phase whereas a 0.75 pct B alloy was single phase. Recent work3 using a hot-stage microscope has proposed a eutectic temperature of 743OC. This method utilized the observation of the onset of incipient melting at grain boundaries. The eutectic composition, however, was not determined. METHODS AND PR0CEDURES Five alloys were prepared by triple inert arc-melting high-purity palladium (95.98 pct) with additions of 2 to 6 pct purified amorphous boron. The alloys were crushed within a hardened steel mortar with a steel pestle. The 2 pct alloy, however, was too tough to be crushed in the above manner so was crushed by successive reductions through a rolling mill. Approximately 17 to 18 g of the crushed alloy was used in the thermal analysis. The alloys were melted in pure quartz crucibles. The thermocouple protection tubes were also of quartz and fused along the inside wall of crucibles to prevent floating of the thermocouple. This was an expediency as centering of the thermocouple in the melt would have been preferable. Melting was done in a tube furnace with a slow flow of tank helium maintained as a protective atmosphere. Heating and cooling rates were maintained at 3.5OC per min through the critical temperature ranges by means of a synchronous motor hook-up to a furnace controller. All specimens were heated to 100°C over the indicated liquidus on heating prior to reversing to the cooling cycle. Specimens emerged from the furnace with mirrorlike brightness attesting to the protective quality of the helium atmosphere. Thermal arrests were detected by the differential thermocouple technique using chrome l-alumel couples and nickel as the reference specimen. Arrests were recorded on a Leeds-Northrup automatic X-Y recorder. The specimen temperature and temperature difference were read to + 7.5OC and ± 1.5OC, respectively. These readings were well within the sensitivity of the instrument amplifier. Chromel-alumel couples were used in lieu of Pt-Rh as very few arrests were contemplated in excess of 1200" to 1300°C, the approach of instability. No standardization was performed on these thermocouples subsequent to their use. RESULTS The thermal arrest temperatures obtained are plotted in Fig. 1 as a function of wt pct B. The composition function was obtained by chemical analysis of portions of the specimens after the thermal analysis was completed. The 2 to 6 pct nominal alloys were found to have 1.80, 2.35, 3.65, 4.18 and 5.90

Jan 1, 1960

On Jan. 1, Harvard opened its reorganized School of Engineering and will continue the work during the summer to enable the entrants to complete a full year's work by the opening of the next academic year in September. Some time ago Harvard University and the Massachusetts Institute of Technology agreed to combine effort in engineering instruction, making use of funds provided under the will of the late Gordon McKay. The agreement was objected to and the Massachusetts Supreme Court held that the arrangement was not in accord with the provisions of the will. The new arrangement has been approved both by the trustees of the McKay estate and by the governing boards of the university. Instruction will be offered in the following subjects; mechanical engineering, civil engineering, sanitary engineering, electrical engineering, mining and metallurgy, and industrial chemistry. Henry Lloyd Smyth has been appointed professor of mining and metallurgy, Albert Sauveur, professor of metallurgy and metallography, and Louis C. Graton, professor of economic geology.

Jan 2, 1919

By Bailey, Lewis Newton

Bailey, Lewis Newton, Master Engineer, Senior Oracle, 4th Regiment, U. S. Engineers, Headquarters Company, died of pneumonia, at Camp Merritt, N. J., on April 30, 1918. Baird, Louis, Lieut., Royal Field Artillery, British Army, died on the battlefield in 1915. Ballamy, John H., Capt., 103d Engineers, killed in action near Fismes, Aug. 9, 1918. Burt, Andrew, died in active service, 1916. Cobeldick, William Morley, Royal Engineers, died from gas poisoning on October 7, 1915. Dougall, Ralph, 4th University Co., Princess Patricia Regiment, killed in action early in the war. Evans, Alfred Winter, Lieut.-Col., New Zealand Rifle Brigade, D. S. 0., D. C. M. killed in action on October 12, 1917. Gorman, Thomas C., Lieut., Canadian Engineers, killed in France, Mar. 18, 1918. Hague, William, 1st Lieut., Engineer Officers' Reserve Corps, died in active service, Jan. 1,, 1918. Hall, William T., Capt., Royal Flying Corps, killed in action, May 19, 1917.

Jan 11, 1918

W. H. PORTH, New York, N.Y.-I would like to ask what effect segregation of lead would have upon the corrosion of sheet zinc; also what effect would abnormal percentages of iron have upon the ductility of Sheet zinc? One of our difficulties seemed to be that the cells, when standing on the shelf, corroded. We have attributed this to local action in the zinc sheet. We would like to know whether the segregation of, these impurities in this sheet zinc will have any effect on the local action occur-ring in sheet zinc. Lately we have had difficulty in punching some sheet zinc, in that the sheets split in the die. The section that split seemed to have an abnormallly high percentage of cadmium and iron; would that cause it to become brittle? C. H. MATHEWSON.-Iron is one of the most unwelcome impurities when high ductility is the principal requirement in rolled zinc. High

Jan 12, 1919

By David B. Reger

The value of carbon ratios in determining the boundaries of possible oil deposits appears to have passed the hypothetical stage. The theory that the ratio of fixed carbon in pure coals is an invariable index of incipient metamorphism in both surface and underground rocks and that it may be applied in defining the limits of petroleum, advanced by David White,' has been received with keen interest by many petroleum geologists. Detailed isocarb maps have been prepared of the Pennsylvanian area of North Texas and Eastern Oklahoma by M. L. Fuller.² A similar map of the coal-bearing area of West Virginia is given here. An isocarb3 is a line showing an equal fixed-carbon percentage, pure coal basis; the term has been proposed by David White to supersede a less expressive nomenclature. The term carbon ratio is applied to the pereentage of carbon in pure coal after water and ash have been eliminated. As a comparatively small number of analyses have been made on this basis, it is usually necessary to compute the ratio by dividing the fixed carbon of the proximate analysis by the sum of the fixed carbon and volatile matter of the same analysis. Many thousands of proximate analyses have been made by the West Virginia Geological Survey, covering nearly every county in which coal is found. Numerous others have been made by the U. S. Geological Survey and the U. S. Bureau of Mines, but as uniformity of results is best secured by adhering to one set of analyses, the tests of the West Virginia Survey have been cxclusively used.

Jan 1, 1921

A. 11. P. WYNNE, San Jose de Gracia, Sinaloa, Mex. (communication to the Secretary): In the comparative tests reported by Mr. Tays, the stamp-batteries were provided with various styles and mesh-sizes of screens, while the Bryan mill was run throughout with a slot-punched Russia iron, equivalent to a 30mesh wire screen. This is a somewhat onc-sided method of comparison. Should not the Bryan mill also have had the chance to show what it could do with other screens? I cannot wholly approve Mr. Tays's proposed improvements upon the Bryan mill. In my judgment, the inventor has given us a machine well-adapted to the work for which it was designed, namely, the crushing and amalgamation of soft ores. In my judgment, the principal cause of failure to amalgamate satisfactorily in the Bryan mill is not, as Mr. Tays thinks, the shallowness of the basin, or the lack of copper plate about the inside periphery of the mill, but rather the want of experience and practical knowledge on the part of most amalgamators. Having had experience, not with one Bryan mill only, but with several, and taking into consideration the experience of other capable mill-men, I am positive that the proper way to save gold ill this mill is: first, to use enough quicksilver to keep the amalgam liquid, thus allowing it to accumulate in the annular space between the dies and the rims of the basin; secondly, to replace the old dies, when a little more than half worn-out, with new ones; and, thirdly, to clean up the mill at least every two weeks—or oftener, if rich ore is being treated. It is evident that Mr. Tap endeavored to amalgamate quite " hard," as is done in a stamp-battery, in which case the swash of the pulp would scour off portions of the hard amalgam adhering to the inside plates and dash it through the screens— after which a considerable amount would be lost through floating on, or in, the pulp in its journey over the outside plates, and

Jan 1, 1900

By L. W. Kempf

A BALANCED system of internal stress is set up in any metallic structure by plastic deformation below the annealing temperature. The internal stress induced by cold rolling or other fabricating processes is generally recognized and its magnitude is known to be, within certain limits, a function of the degree of cold deformation. The plastic deformation that may accompany rapid cooling from elevated temperatures may not materially change the form of the product. The internal stresses so induced are not, therefore, so evident and nonrecognition of their presence has at times led to engineering failures. The heat treatment of aluminum alloys is a relatively new art and little information is available regarding the magnitude of stresses induced luring the commercial heat treatment of aluminum alloy products is the industrial use of aluminum increases, it is inevitable that products of increasingly large volume be required. It has become necessary in the present commercial utilization of aluminum to heat-treat castings and forgings weighing hundreds of pounds. One of the factors governing the magnitude of internal stresses arising from rapid cooling at elevated temperatures is that of the, size of the structure being treated. Some of the other factors are: cooling rate, elastic properties of the alloy, thermal expansivity, thermal conductivity, and the presence or absence of phase changes. Practically all aluminum alloys have a high coefficient of thermal expansion and some are capable of developing relatively high

Jan 1, 1934

By B. M. Larsen

NEVER having actually tried to engage in the systematic education of anyone, and having little direct knowledge of the practical problems and limitations in the field of education, I can pose only as a "nonexpert" in this field, one whose ideas are to be regarded as personal opinions. The necessity for compromise between educational ideals and the practical limitations of time, money, and mental capacities of both student and teacher is evident in the preparation of an end product that we may regard with a reasonable degree of conviction as a professional engineer. We need to do so many things. The engineering student must have a clear understanding of the basic sciences; he should develop manual skills and co-ordination; he should speak and write the language with simple clarity and directness; he should gather knowledge of a special field; and, he should be educated for living in a broad ..

Jan 1, 1948

By Maynard H. Jameson

Earlier investigations of the potential-drop-ratio method of electrical prospecting have indicated that under suitable conditions this method is well adapted to the location of formation boundaries in stratified ground. A description of this development was given several years ago by H. Lundberg and Th. Zuschlag.l The curves published by these authors for the potential-drop-ratio variation above a horizontal contact indicated a definite relation of the position of the curve peak to the depth of the interface. The theory underlying this relation was subsequently studied by Z. Mitera in greater detail,' and the theoretical deductions were compared with the results of tank experiments. The investigations available at this writing were confined to studies of horizontal formation boundaries. It is the purpose of this paper to extend the scope of the previous work to the problem of dipping layers. Theory Consider the case of three media of different resistivities, whose interfaces are not parallel. If a point-source is located in one of these interfaces, its images do not lie in a straight line, but on the circumference of a circle whose center is at the hypothetical junction of the interfaces. R. F. Aldredgea determined the relation that exists between the degrees of dip of the two interfaces and the distances between the various images and the point for which the potential is to be found. As seen in Fig. I, three media of resistivities PO, p1, and p2 are involved, and the source I is located at the interface of the media Coo) and (p1). The perpendicular depth of the lower interface is h, 0 is the dip, R is the distance between source I and potential point P, and r is the distance between the images and that point. To distinguish between images lying above the ground interface and those below, the notation "odd" and "even" images will be employed; images below the ground interface will be termed "odd" and those above "even." The following relations govern the distances between either kind of images and the potential point: EvEn Odd Ta — R r1 - [rl] - [RS + 4h(h + R sin 01½ r, = [r] =. [R1 + 4h cos 0)2(h + -R sin 0)1½ ri - [r3] ={r3} [R* + 4h(4 cos2 0 - i)1 (h + R sin 0)l½ r4 = [r4] = [R2 + 4h(4 cos $ cos 30)1 (h + R sin 0)]½ r, — [r4] - [R2 + 4h(4 cos9 R cos 20 + cos 48)2 (h + R sin 01½ I RI + 4h[2 cos 30(4 cos2 0 - I)12 (h + R sin 8)1 ½ rn - [r4] - [R2 + 4hlf(cOs 0)18(h + R sin R)l½ As previously pointed out, the images of the source are on the circumference of a circle. If the angle of dip is 0, the angle measured from the horizontal to the first image is 28; to the second image it is 48, and so on. Since the limit of the reflecting interface is at its outcrop, the last possible

Jan 1, 1946

By Maynard H. Jameson

Earlier investigations of the potential-drop-ratio method of electrical prospecting have indicated that under suitable conditions this method is well adapted to the location of formation boundaries in stratified ground. A description of this development was given several years ago by H. Lundberg and Th. Zuschlag.l The curves published by these authors for the potential-drop-ratio variation above a horizontal contact indicated a definite relation of the position of the curve peak to the depth of the interface. The theory underlying this relation was subsequently studied by Z. Mitera in greater detail,' and the theoretical deductions were compared with the results of tank experiments. The investigations available at this writing were confined to studies of horizontal formation boundaries. It is the purpose of this paper to extend the scope of the previous work to the problem of dipping layers. Theory Consider the case of three media of different resistivities, whose interfaces are not parallel. If a point-source is located in one of these interfaces, its images do not lie in a straight line, but on the circumference of a circle whose center is at the hypothetical junction of the interfaces. R. F. Aldredgea determined the relation that exists between the degrees of dip of the two interfaces and the distances between the various images and the point for which the potential is to be found. As seen in Fig. I, three media of resistivities PO, p1, and p2 are involved, and the source I is located at the interface of the media Coo) and (p1). The perpendicular depth of the lower interface is h, 0 is the dip, R is the distance between source I and potential point P, and r is the distance between the images and that point. To distinguish between images lying above the ground interface and those below, the notation "odd" and "even" images will be employed; images below the ground interface will be termed "odd" and those above "even." The following relations govern the distances between either kind of images and the potential point: EvEn Odd Ta — R r1 - [rl] - [RS + 4h(h + R sin 01½ r, = [r] =. [R1 + 4h cos 0)2(h + -R sin 0)1½ ri - [r3] ={r3} [R* + 4h(4 cos2 0 - i)1 (h + R sin 0)l½ r4 = [r4] = [R2 + 4h(4 cos $ cos 30)1 (h + R sin 0)]½ r, — [r4] - [R2 + 4h(4 cos9 R cos 20 + cos 48)2 (h + R sin 01½ I RI + 4h[2 cos 30(4 cos2 0 - I)12 (h + R sin 8)1 ½ rn - [r4] - [R2 + 4hlf(cOs 0)18(h + R sin R)l½ As previously pointed out, the images of the source are on the circumference of a circle. If the angle of dip is 0, the angle measured from the horizontal to the first image is 28; to the second image it is 48, and so on. Since the limit of the reflecting interface is at its outcrop, the last possible

Jan 1, 1946

By Robert H. Carpenter

Major trends in exploration geochemistry during the past year included an increased level of geochemical exploration by both government and private industry: greater sophistication in sampling, analytical and interpretive techniques: and increased activity on the part of universities and state geological surveys. The evolution of applied geochemistry in North America from a useful prospecting tool to an invaluable exploration method is largely due to efforts of the mining industry, the USGS and the Geological Survey of Canada. In the U.S., there has been a distinct reluctance on the part of universities to conduct research or to offer courses dealing principally with applied geochemistry. Most university geochemists have not been responsive to industry needs because government sponsorship of geochemical research in universities has been overwhelmingly in favor of theoretical, rather than applied research: and, because of the mistaken notion that exploration geochemistry is not sufficiently academic. A critical shortage of specialists in this field has resulted. Specialists in Exploration Geochemistry Needed Based on the response to a brief questionnaire sent to universities in the U.S. and Canada, there is some evidence suggesting a reversal in this trend. Graduate courses devoted to exploration geochemistry are currently being offered in geology departments at the following universities: University of British Columbia, Colorado School of Mines, University of Idaho, McGill University, University of New Mexico, Pennsylvania State University and the University of Utah. Other departments report that applied geochemistry is included in general geochemistry courses. A survey of recent publications suggests increased research interest in exploration geochemistry by university geologists.

Jan 1, 1970

By C. S. Smith, K. K. Ikeuye

In an earlier paper1 one of the authors called attention to the significance of the relative free energies of grain boundaries and interphase boundaries in alloys in determining the shape and distribution of micro-constituents. The ratio of the interphase and inter-crystalline boundary energies (that is, —?12, where ?12 is the energy of the interface between a crystal of phase 1 and a crystal of phase 2, and ?11 is the energy of the boundary between two crystals of phase 1) will be denoted by F. It is this ratio that determines, by the simple triangle of forces relation, the dihedral angle, ?, of phase 2 where it adjoins a boundary between two grains of phase 1. On a metallographic sample various angles are actually obtained because of the random orientation of the plane of observation, but the statistically most frequent angle is the true one. These basic principles were discussed in detail in the earlier paper. The experiments described below show the effect of both composition and temperature on ? and T for some alloys containing a liquid phase, and provide data on the rate of approach to the equilibrium angles in both solid and liquid phases. All the alloys were melted in a graphite crucible and cast into ingots 3/4 by 11/8 in. cross-section. Some of the aluminum alloys consisted of two immiscible liquids from which uniform castings could not be obtained. The amount of liquid phase varied locally to a considerable extent and the analyses were meaningless. Nevertheless, the composition of the liquid would not differ from that in an alloy of the intended gross composition, and the synthetic composition of the alloys was therefore used in considering the surface energy results. The ingots were given initial deformation by cold-rolling to 50 pct reduction, annealed, and given a second 50 pct reduction prior to cutting into small samples for heat treatment at the times and temperatures subsequently reported. The resulting micro-samples were carefully prepared metallographically and examined at magnifications of 650, 1280, or 2500. The objectives used were 21X, 0.40 NA (dry); 41X, 0.65 NA (dry); and 80X, 1.40 NA (oil emulsion). The appropriate angles were measured by rotation of the stage of a Bausch and Lomb metallograph to align the appropriate boundaries successively with a cross-hair in a micrometer eyepiece. About 250 angles were measured on each phase. Though the angles were read to 1°, the accuracy is probably not above 3°, because of uncertainty in setting the cross-hair tangent to the sometimes curved boundary. The corners of very small particles, particularly in early stages of adjustment after cold-rolling, were difficult to measure and the results were slightly dependent on the magnification used (compare Fig 1-C and 1-D). With particles of larger size and more nearly equilibrium shape, magnification made no difference (vide Fig 1-F and 1-G). The measured angles were grouped in 10° intervals (5° if ? was less than 20°) and plotted in bar

Jan 1, 1950

By C. D. Hall, F. E. Dollarhide

Fluid Ioss agent.s for crude oil and for water have been studied in dynamic tests. A treatment using a spearhead with a fluid loss agent followed by plain fluid appears feas ible in crude oil, but not in water. An equation for spearhead depletion shows that spurt loss relative to fracture width must be low, if the portion of spearhead fluid in the treatment is to be small. The presence of colloidal matter in crude oils aids the fluid Ioss agent. Unlike in kerosene, where flow limited the agent deposition, in crude oils the filter cake continually formed and leak-off declined. The volume-time relation varied somewhat for different crudes, but was best described by a square root of time function. Spurt loss was inversely proportional to agent concentration. After the fluid loss agent initiated the filter cake, the crude oil colloids built on it effectively. A 2-minute or a 5-minute spearhead with double the normal agent concentration gave the same fluid Ioss curve as the same concentration did for a 30-minute test. The agents tested in water gave fluid Ioss plots on which, for the first few minutes, volume was proportional to the square root of time, but later became proportional to time. For fracture area calculation the customary square root of time function is a satisfactory approximation. Leak-off rates and spurt losses were higher in water systems than in oils. The spurt Ioss tended to be inversely proportional to concentration. In spearhead tests, the filter cakes were not eroded by water flow. However, the rather high spurt loss values make spearhead treatments impractical for water-based fluids. Introduction The effects of dynamic testing conditions on the performance of fluid loss agents in kerosene have been studied previously.' We have extended the work to include crude-oil- and water-based fracturing fluids. An understanding has been gained of the mechanisms of formation and functioning of the filter cakes of fluid loss agents. The practical aspects of evaluating performance of agents in relation to fracture area calculations also are considered. The feasibility of using the fluid loss agent in a spearhead stage of the treatment is examined further for both types of fluids. Experimental Procedure The dynamic fluid loss tests were performed in an apparatus similar to the high-pressure apparatus described in a previous publication.' A fracturing fluid was circulated over a rock surface located in a closed pressurized loop. The fluid flowed axially over the cylindrical surface of a core 2 in. in diameter X 3.5 in. long, mounted (with the flat ends sealed off) in a pipe, with 0.117 in. annular clearance. The filtrate was collected in a central hole in the core and led through valves to graduated cylinders. Provision was made for changing quickly the circulating fluid during the test (spearhead runs) without interrupting the filtration pressure. The only modifications were to add heating tapes and water jackets for the tests with crude oils, all conducted at ISOF, and to change all parts exposed to the test fluid to stainless steel for the tests with water-based fluids. The latter tests were made at room temperature, 80F. Three crude oils were tested. A mixed crude, obtained from a local refinery, contained a considerable amount of light ends. For safety reasons, it was stripped to 250F vapor temperature before use in the fluid loss tests. The other two oils were used as obtained from lease tanks. One was a greenish-brown, 37" API paraffinic crude, and the other was a black, 32" API asphaltic crude. The fluid loss agent for oil, here designated for brevity as Agent A, was Adomite@ Mark II*, a granular solid commercial agent, the same as previously tested in kerosene.' Three different compositions of fluid loss agents were tested in Tulsa tap water. Agent B was adomit& Aqua*, a solid commercial fluid loss agent, comprising clays and hydrophilic gums principally derived from starch. Agent C was a mixture of three parts of Agent B with two parts of silica flour. Agent D was Dowel1 J137, a mixture of guar gum and silica flour. The test cores were cut from contiguous blocks of Berea or Bandera sandstones. For the oil tests, the cores were oven dried, evacuated, saturated with kerosene, and the kerosene permeability was measured. The cores used with the water-based fluids were pretreated by saturating with 3 percent calcium &loride solution to minimize pemeability damage by the fresh water due to clay migration. The

Jan 1, 1969