Search Documents

By G. E. Keller, G. D. Coe

Several methods have been devised for rapid determination of sulfur in coal using a high-temperature combustion furnace. The fundamental principles of the various methods are similar but the techniques vary widely. The method described herein is no different in principle from some of its predecessors but varies considerably in technique. Originally devised to overcome the low-accuracy criticism leveled against the others, the tube-furnace method has proved successful for limited applications. Work is being done to widen the applicability of the technique. Subsequent to the work of A. Vita1 in 1920, a number of investigators have published data dealing with the rapid determination of sulfur in coal using a high-temperature combustion furnace.2-5 These, together with several unpublished methods, involve wide differences in technique although they are all similar in principle. Investigation of typical details of procedure showed that poor precision or accuracy could be attributed to one or more of the following: 1) inadequate quantity of sample to be representative, 2) a delivery tube temperature too low to confine condensation to a washable area of the tube, 3) no provision for back washing the delivery tube, 4) incomplete absorption of the sulfur compounds due to inadequate bubbler, and 5) the false assumption that all of the sulfur is evolved as sulfur dixoide. The method herein discussed is no different in principle from some of its predecessors; the differences are in technique. Although the method is rapid—a determination can be completed in 5 min— accuracy has riot been sacrificed in order to achieve speed. MATERIALS AND EXPERIMENTAL WORK Fig. 1 shows the arrangement of the equipment. A metered volume of oxygen is passed through calcium chloride for removal of moisture, then through Ascarite for removal of carbon dioxide, and thence through a glass tee to the feed end of the combustion tube. Connected to the side arm of the glass tee is a rubber tube that is closed with a pinch clamp during combustion of a sample. The products of combustion are expelled through a Vycor bubbler, the end of which is submerged 3 cm below the surface of a 1 pct hydrogen peroxide solution contained in a 300 ml high-form beaker. At the completion of the 4-min combustion period the contents of the beaker are titrated to a yellow end point, using a methyl red indicator, with 0.05 N sodium hydroxide (or sodium tetraborate). The pinch clamp on the tube leading from the tee in the oxygen line is then opened and mouth suction applied to draw the hydrogen peroxide up into the bubbler past the ell, almost to the rubber tube connecting the bubbler to the combustion tube. This washing of the bubbler is repeated until no further acid reaction with the indicator is obtained. The hydrogen peroxide-sul-furic acid solution is then titrated to the final yellow end point. Test work conducted at the Robena Laboratory disclosed the following critical conditions that had important bearing on the precision of the method: Weight of Sample: Several series of tests wherein the sample weight ranged from 0.1 to 0.5 g of -60 mesh coal showed that the lowest variance (standard deviation squared) resulted from the use of 0.5-g samples; the variance was slightly greater when 0.3-g samples were used, and with less than a 0.3-g sample weight the variance increased rapidly with decrease in weight. Although the use of a 0.5-g sample invariably resulted in a very slight explosion as soon as the sample entered the hot zone of the combustion tube, this did not detract from the precision of the method. Temperatures: Mott and Wilkinson5 found that a combination of low temperature (1250°C) and low oxygen flow rate (less than 700 ml per min) tended to give high results due to formation of oxides of nitrogen. Although the method herein employs a much higher oxygen rate than 700 ml per min, as an additional precaution to assure accurate results, 1315°C (2400° F) is recommended as the most desirable furnace temperature. The temperature of the elbow of the bubbler should be at least 75°C to minimize condensation

Jan 1, 1961

By W. M. Dressel

The Federal Bureau of Mines has obtained data by differential thermal analysis of the various minerals that represent the nation's resources in manganese. These data are supported by X-ray diffraction analysis, chemical analysis, mineralography, and optical mineralogy, and provide fundamental information on the response of each mineral to thermal treatment in oxidizing, reducing, and neutral atmospheres. The information can be applied advantage¬ously in the identification of manganese minerals. Its greatest potential value, however, lies in the application of the quantitative data on the reaction temperatures, rates, and products to the more efficient extraction of manganese from U.S. ores. Thermal analysis curves are presented for certain manganese minerals, namely hausmannite, bixbyite, braunite, pyrolusite, lithiophorite, cryptomelane, hollandite, manganite, rhodochrosite, and rhodonite. The original minerals and the products of their thermal decomposition were identified by X-ray diffraction analysis, supplemented by chemical analysis and mineralogical identification.

Jan 1, 1961

By T. E. Gray

This report describes the preparation characteristics of the signifi¬cant coalbeds in Preston County, W. Va. It is one in a series of reports planned to determine coals suitable for the production of metallurgical coke, either as mined or after beneficiation. Over 2 million tons of coal was produced in Preston County, W. Va. in 190, none of which was cleaned mechanically. Estimates as of January 1, 1959, indicate that more than 3 billion tons of coal remained in the county in beds 12 inches or more thick. The Bakerstown, Mahoning, Upper Freeport, and Upper Kittanning beds were selected by the Bureau of Mines for study based on current production and estimated minable reserves. Sample locations were selected after study of the literature, conferences with mining engineers and mining company offi¬cials in the field, and examination of available sites. Four samples were collected from the Bakerstown and Upper Freeport beds and one each from the Mahoning and Upper Kittanning beds.

Jan 1, 1961

By M. G. Zabetakis

This publication contains highlights of a 4-hour lecture and demonstration by the Bureau of Mines on the fire and explosion hazards of flammable liquids and solids, oxidizing materials, corrosive liquids, and compressed gases. The authors first presented this material as part of a 2-week course given to officers and enlisted men at the U.S. Coast Guard's Dangerous-Cargo Handling School, established at Fort Eustis, Va., in 1959. The Bureau was asked to present the lecture and demonstration because of the extensive experience of its researchers in handling certain harardous commodities.

Jan 1, 1961

By C. G. Dunn, J. L. Walter

The c/laracterzstics of cube-oriented nuclei ard other matrix grains that are associated with secondary, recrystallization to the cube texture in high-purity silicon iron were investigated by me-tallographic and X-ray methods. The results show that the structure consists of relatively perfect grains of average diameter between one and two times the sheet thickness ad that the texture has a moderately strong (110) [001] component and a weak (100) [001] component. The results also indicate that matrix stability results from the two-dimensional nuture of the graitzs and that cube-orzented nuclei are neither more Perfect nor larger grains than other matrix grains but have a preferred [001] direction in the rolling direction and have a more effective driving force for growth than other grains because of a low (100) surface energy. THE structures and textures of fine-grained rnatrices determine to a large extent the kinds of secondary recrystallization textures that form on annealing. The understanding of secondary recrystallization processes therefore depends on adequate information about the initial matrices. Matrices usually have three characteristics: 1) they consist of fine-grained primary recrystallization structures, 2) the fine-grained structures are stable toward normal grain growth, and 3) they contain secondary recrystallization nuclei. Stability toward normal grain growth may be due to either a strong single orientation texture (texture inhibition)' or a dispersed second phase (dispersed phase inhibition).2"4 If normal grain growth is not inhibited by either of these two factors, it nevertheless stops when the average grain size is between one and two times the sheet thick- ness.5 This thickness effect satisfies one of the characteristics of a matrix for secondary recrystallization. Its importance in the development of the cube texture in high-purity silicon iron by secondary recrystallization was pointed out by the authors in a recent paper on tertiary recrystallization7 and will be discussed further in the present paper. Assmus, Detert, and he8 have provided some information on a matrix for secondary recrystallization to the cube texture in silicon iron. They found a (110)[001] or Goss texture with enough spread about the rolling direction to include a small amount of the (100)[00l] orientation. The distribution of the [00l] directions was strongest parallel to the rolling direction for both (100) primaries and cube secondaries. These authors found no correlation between size of a matrix grain and orientation and concluded that some property other than size must be the distinguishing characteristic of the cube-oriented nucleus. No consideration was given, it

Jan 1, 1961

By J. B. Coher, M. B. Bever

COLD work destroys long-range order, as was first observed by Dehlinger and Graf.1 Dahl2 showed that the mechanical disordering caused by cold work produces changes in those properties that are affected by long-range order. The existence of order has a marked effect on tile manner in which an alloy deforms and therefore on its mechanical properties.L' The relation between order and deformation behavior however, is only beginning to be understood. Seemann and G1ander4 suggested that cold work reduces an ordered alloy to a kind of gruel of antiphase domains. According to Cottrell,5 superdis-locations and pairs of dislocations in a slip plane connected by a strip of anti-phase domain boundary provide deformation mechanisms which do not change the state of order. In general, however, slip may be expected to produce new domain boundaries and destroy order if dislocations move on intersecting planes or cut through existing domain boundaries. The yield strength of an ordered alloy may pass through a maximum with decreasing domain size.5"7 The reduction of domain size resulting from cold work may, therefore, lead to a maximum in strength properties. Flinn8 suggests that dislocations can climb by short-range diffusion during deformation and thus can generate domain boundaries not only on slip planes, but also on other planes which will be those with the lowest domain-boundary energy. It has long been known that the rate of strain hardening of an alloy in the ordered state is larger than in the disordered state.3'9 Also the slip bands in ordered CU3, AU10 and Ni3Mn" are finer than in the disordered alloys. The stress which causes initial yielding in Cu,Au passes through a maximum with decreasing domain size.6'12 A maximum has also been observed in the hardness of ordered Ni3Mn as a function of strain.' These observations suggest, but do not prove, that domain size reduction occurs during deformation. According to Fisher13 slip destroys short-range order and thus the strength of an alloy is related to the degree of short-range order present. Rudman and Averbach14 and Averbach et a1.,15 demonstrated that cold work reduces short-range order in copper-gold and gold-silver alloys. Destruction of long-range and short-range order by cold work implies slip on an appreciable fraction of planes. Yielding of an alloy in which short-range order exists or antiphase domain boundaries are present should be discontinuous because the first dislocations moving across the slip plane meet with the largest resistance.5 Such discontinuous yielding has been observed in CU3AU6,16 and Cuzn.l7 This phenomenon, however, can also be explained by mechanisms not involving order.b The published investigations of the effects of cold work on alloys with long-range or short-range order have not been covered thoroughly in reviews of order-disorder phenomena. These investigations, therefore, will be listed here. They have been concerned with strength properties> 2,3,6,8,9,12,16-21 electrical resistivity,2,4,18,19,21-26: thermoelectric power, magnetic properties,2,18,21,26 and X-ray strain'1,2,14,15,27,28 The slip systems and the appearance of the microstructure after deformation in ordered and disordered alloys have also been investigated. 6.10.ll,l7,23,29,30 The alloys used in these investigations were copper-gold. 1-4,6,9,10,14,16,18 23-26,28,29 copper-zinc. L7. 19. 20,30 nickel-manganese,2 11,21 iron-aluminum. iron-nickel,' copper palladium,4,18,22 gold-silver.4,18,22 and palladium-silver-copper.4 In the work reported here. the changes in properties of polycrystalline Cu3Au were investigated as functions of strain in wire drawing and rolling. Specimens were heat treated before deformation

Jan 1, 1961

By Ivan F. Avery

The design productive capacity of natural-gasoline and cycling plants in the United States on January 1, 1960, was 54.6 million gallons per day, according to the Bureau of Mines biennial survey. This represents an increase of 5.8 million gallons per day during the 2-year period since the last survey. The major increases occurred in Louisiana, Oklahoma, New Mexico and Texas. In Utah, natural gasoline capacity was reported for the first tine at 320 thousand gallons per day as of January 1, 1960. The total number of plants increased from 584 on January 1, 1958, to 596 on January 1, 1960. However, the operating plants decreased from 558 to 555 in the same period.

Jan 1, 1961

By E. G. King

Many of the rare-earth oxides are now commercially available in pure form and they have a variety of potential technical uses. Thermodynamic data for these oxides, however, are rather sparse. It is one of the functions of the Bureau of Mines to fill the need for this type of information. This report gives the results of low-temperature heat-capacity and high-temperature heat-content measurements by the Bureau of Mines of lanthanum sesquioxide. The entropy at 298.15° K. was evaluated and heat-content and entropy increments above 298.15° K. were obtained to 1,800° K. The results were combined with the known heat of formation at 298.15° K. to derive heats and free energies of formation at higher temperatures. Sufficient information is now available to permit reliable thermodynamic calculations involving lanthanum sesquioxide within the temperature range 298° to 2,000° K.

Jan 1, 1961

By Joseph Grumer

An instrumented spherical vessel has been used for many years to study laminar combustion waves. Concurrent measurements of flame speed and pressure-rise rates have led to evaluations of burning velocities, the pressure dependence of the burning velocity, and the expansion ratios of the gases passing through the combustion wave. For the most part, these studies have involved flames initially at atmospheric or subatmospheric pressure. The old spherical vessel used by the Bureau of Mines was not designed for use at elevated pressures. Moreover, being made of wrought iron, it was susceptible enough to corrosion to prohibit its use with many combustible mixtures that figure in industrial research. In mid-1956, under sponsorship of the Office of Naval Research, the Bureau undertook the development of a stainless steel spherical vessel capable of withstanding explosions of gaseous mixtures at initial pressures as high as 20 atm. and initial temperatures as high as 250° C. The design called for a double array (cross) of closely spaced small windows for observation of the flame as it traversed the vessel and a piezoelectric transducer to measure concurrently pressure-rise rates. Because no commercial contractor was willing to bid on the construction of such a vessel, it was built at the Bureau's Bruceton machine shop.7

Jan 1, 1961

By Hubert E. Risser

At the outset of a discussion on the adaptability of Illinois coals for use in iron and steel production, it is perhaps well to define terms. ?Adaptability? as used in this context, means that a coal can be, adapted to use within a given technological and economic framework. For a coal to be adaptable, to use in the manufacture of metallurgical coke within the present technological and economic framework, it must possess, among other things, at least the following characteristics: 1. The coal must be capable of producing, alone or in combination with other coals, a coke that can meet at least a minimum standard of required performance in the present-day blast furnace. The coke must have sufficient strength, stability, hardness, and freedom from impurities to make it suitable. 2. If the coal in its raw form does not meet these requirements, it must be amenable to beneficiation or upgrading so that the requirements can be met. 3. It must be available in uniform quality and in sufficient quantities to meet the need. 4. Use of the coal must be economically attractive. If its quality is equivalent; to that of the coals with which it must compete, it must be no more expensive than they. If It is better, a premium price may perhaps be demanded. If, in any respect, it is the least bit less suitable, the cost must be lower to offset its disadvantages.

Jan 1, 1961

By W. A. Cole

This report covers the preliminary phase of an investigation of clays, shales, and certain rocks in Wisconsin to determine the feasibility of processing lightweight aggregate in the State. The study was extended to include rotary-kiln testing of a limited number of shale samples, and to an appraisal of the Maquoketa shale resources in eastern Wisconsin. A total of 45 samples of clays, shales, and other argillaceous rocks of Wisconsin were tested. The lower Maquoketa shale is the only material found to date that offers possibilities as a source of material that can be processed in a rotary kiln for lightweight aggregate. Bedrock occurrences of the Maquoketa shale are found in the eastern and southwestern parts of the State. The populous southeastern region of Wisconsin presents a large potential marketing area for lightweight aggregate. For this reason special study was directed to the Maquoketa shale in the eastern district.

Jan 1, 1961

By J. Nagy, D. W. Mitchell, E. M. Murphy

In 1957 research was initiated in the U.S. Bureau of Mines experimental coal mine near Pittsburgh, Pa., to study factors affecting foam generation and transport, to evaluate the effectiveness of high-expansion foam for controlling mine fires, and to develop techniques for applying the method under U.S. mining conditions. These investigations showed that high-expansion foam containing at least 0.2 oz of water per cu ft of foam is effective in controlling experimental underground fires burning coal, wood, and oil. Sometimes the fire was completely extinguished, but more often, it was brought under sufficient control to permit either a direct attack on the fire with a stream of water or loading of the hot material into cars. A progress report' prepared in July 1958 summarized the initial achievements of the USBM experiments. Since then other phases of the foam-plug method for attacking fires have been studied in the laboratory and in the mine. Previous studies by British engineers' of the foam-plug method for fighting mine fires indicated that high-expansion foam was effective in controlling experimental timber fires in an underground passageway. Their subsequent workx-1 pertained to the practical aspects of fighting large fires within a mining area with a foam-plug. CONTROLLING EXPERIMENTAL FIRES In the USBM tests foam was formed by spraying a dilute solution of a foaming agent on a metal or cotton net of 1/8 to 1/4-in. mesh. Air passing through the continuously wetted net forms bubbles of 1/2 to 11/2-in. diam and produces a honeycomb of foam that fills the passageway. Under the ventilating-air pressure, this light-weight plug moves forward through the passageways, around sharp corners, and over obstacles. as illustrated in Fig. 1. High-expansion foam was transported to a wood fire, an oil fire, and 13 coal fires. Figs. 3 and 4 show a typical coal fire before and after attack with foam. In 12 of the 15 experiments the fire was brought under control when the water content of foam was 0.2 oz or more per cu ft. A fire was considered controlled when the flames were quenched and observers could cross the area without wearing breathing apparatus or protective clothing. In the other three experiments, conducted when the water content was less than 0.2 oz per cu ft of foam, the flames were retarded but the fire was not controlled. Coal fires have been attacked successfully by foam introduced at points varying from 155 to 1010 ft from the fire. The time of burning in coal beds 10 in. thick ranged from 11/2 to 5 hrs or more. Most of the experimental fire beds were 15 ft in length. However, in one experiment a floor fire 25 ft long and 5 ft wide was constructed $5 upwind from another fire 15 ft in length; in another instance, the fire was 100 ft long and 5 ft wide. Foam was applied to the fires for periods ranging from 7 to 36 min. The time required for foam application depends on the extent of the fire, time of burning, water content of foam, foam velocity, and degree of fire control desired. In addition to the coal fires, foam was transported to a fire covering 45 sq ft, produced by 15 gal of oil burning in metal trays on the floor. The foam extinguished the oil fire in about 1 min. In one other test, the burning of 1100 lb of dry sawmill slabs stacked in open cribs 4 ft high and 16 ft long was brought under control by foam in 2 min. Composition of Gases in Return Air: In several of the experiments samples of the return air from fire zones were collected; composition of the atmosphere before, during, and after foam application was then determined. Because of condensation in the relatively cool sampling tube, the amount of water vapor was not determined. Analyses showed that concentration of carbon dioxide and combustible gases increased as the foam began passing over the fire. This resulted from the decrease in the volume of air when foam generation started and from the formation of gases when water reached the fire.* The quantity of gases generated would not be greater than that from an equivalent amount of water applied directly to the fire. The highest total concentration of combustibles (CO, CH1, and H2 mixture) obtained during the experiment was about 2 pct; this occurred 6 min after foam reached the fire. This atmosphere was nonex-plosive, but calculations show that if the air flow were reduced to about 5 fpm and if the rate of gas liberation from the fire remained constant, the mixture would be explosive. The use of foam on a fire in all probability would affect the normal ventilation of a mine. If the mine is gassy, this factor must be carefully considered before the foam is applied. APPLICATION OF THE FOAM-PLUG TECHNIQUE IN MINES Equipment and procedures for applying the foam-plug methods must be adapted to the prevailing conditions at a particular mine. Some factors to be considered in developing equipment are: size or extent of the mine, dimensions and number of entries, ventilation system, mining methods, haulage facilities, availability of water, amount of methane liberated, and existing fire-control apparatus. • In most experiments the initial air velocity of 200 fpm decreased to 50 to 100 fpm as the foam plug increased In length.

Jan 1, 1961

By M. O. Holowaty, C. M. Squarcy

Bituminous coal furnaces give way to coke, and by 1880, the American iron and steel industry was growing at a tremendous rate. In the twentieth century, the number of operating blast furnaces was cut in half while pig iron capacity more than doubled. Bituminous coal furnaces Attempts to relieve the shortage of charcoal by the use of bituminous coal in American furnaces began quite early. Use of bituminous coal in the blast furnace was restricted to areas lacking anthracite deposits but rich in deposits of bituminous coaL The largest concentration of bituminous coal furnaces was in Western Pennsylvania, West Virginia and Western New York state. Other areas included Kentucky and southern portions of the states of Indiana and Illinois. The first trials were made in Pennsylvania around 1780. Gradually several more furnaces began charging coal with their burdens as a partial substitution for charcoal. These so called cheaters were numerous, especially in Western Pennsylvania, which around 1810 began to expand its ironmaking capacity to catch up with the Lehigh Valley and the Schuylkill According to the existing references, complete bituminous coal burdens began to be used in this area only around 1840 when the ironmakers hastily adopted the hot blast apparatus introduced from England. The majority of these furnaces were built, however, after 1844 when an extensive experimental program, carried out at the Shenango Steam and Water Hot Blast Charcoal, Coke and Raw-Coal Furnace produced favorable results, with coal containing up to 35 pct volatile matter. The furnace was located near the Shenango River on the Lackawannok Run, five miles northwest of Mercer, Pennsylvania. It was built, owned, and operated by David Hogeland of Mercer. The first furnace was built in 1836 or 1837 as a charcoal furnace. Soon, however,

Jan 1, 1961

By Leonard Obert

Subsidence to surface occurs in a large proportion of underground mines. Preliminary to any indication of subsidence on the surface, there is usually a breaking up and sloughing of the cover into the mine opening which, in a period of time ranging from minutes to many years, progresses to the surface, This process is referred to as subsurface subsidence. In many mining operations, information regarding the process of subsurface subsidence is important, For example, if there are buildings or other improvements on the surface, or if the direction of the subsurface subsidence might threaten other underground workings--such as shafts--or if the subsidence might be progressing in a direction which would fall outside the anticipated subsidence limits, the problem could assume special significance.

Jan 1, 1961

A recently developed technique for use in collieries is described in which samples of gas of relatively high vitiation value are obtained from points deep within a developing goaf by means of pipes. This technique prevents dilution of small quantities of carbon monoxide by large quantities of fresh ventilation air and eliminates interference from shotfiring gases. By using the technique it should be possible to assign a characteristic ratio of carbon monoxide to oxygen consumed to any district and to predict the onset of heatings.INTRODUCTIONGas analysis has played a vital role in detecting heatings in collieries all over the world. By analysing return air from a district and by calculating the percentage ratio of volume of carbon monoxide found to oxygen consumed (known simply as the "carbon monoxide ratio") it has been found possible, in many cases, to assign a characteristic ratio to a district under consideration. This characteristic ratio serves as an index of the spontan~ous combustion tendency of a goaf area. Any definite and consistent increase in the ratioabove the normal figure· indicates that a heating is developing and hence adequate preparations may be made to deal with the trouble.This ratio technique was developed by Graham (1920-21) who found (Table 1) that the temperature of oxidizing coal was directly related to the ratio obtained from analyses of the effluent gas.Until recently, most attempts to employ a similar technique in collieries working the Greta Seam (N.S.W.) were not successful. From experience gained over the past few...

Jan 1, 1961

By K. E. Tame

The Bureau of Mines is studying possible modifications in conventional uranium ore-processing steps to confine and permit controlled disposal of radioactive wastes. Surveys of Ra226 contamination of liquid wastes from uranium mills indicated that the Vanadium Corporation of America plant at Durango, Colo., had one of the more urgent problems. A possible procedure for minimizing the waste disposal problem was to reuse the waste solution in the mill--in effect, erasing the need for disposal of liquid waste. In examining this possibility, interlocked bench-scale leaching and solvent extraction tests simulating the Durango flowsheet were made. The simulated reuse of barren raffinate for leaching and washing was carried through three separate campaigns of 9, 12, and 35 cycles each.

Jan 1, 1961

By John E. Shelton

The growing interest in beryllium as a structural material, and its in-creased use in recent years for atomic energy application, have led both government and industry to express concern over the inadequacy of the beryllium resources in the United States and the free world. Contemplated and proposed uses for this unique material will surpass the capacity of the domestic beryllium mining industry to supply raw material, which is presently extracted from relatively small deposits by hand sorting. The need for a simple beneficiation process for beryl ores has long been recognized by the Bureau of Mines, but to date no single process has proved satisfactory for treating deposits containing a sufficient tonnage of beryl ore to warrant commercial exploitation. As a part of the Bureau's continuing effort to develop an economical recovery process, this report describes flotation research on samples of beryl-bearing pegmatites from the George Roebling mine in Connecticut, and the Colony mine in New Hampshire. The study resulted in two methods of treatment to which the ores responded reasonably well.

Jan 1, 1961

By Alan Bauer, Melvin A. Cook

Measured detonation pressures of "prills and oil" (94/6 ammonium nitrate/fuel oil) and three of the new "slurry" blasting agents are presented and compared with computed, ideal detonation pressures and with detonation pressures expected from the measured detonation velocities. Results seem to show that the peak pressure in the detonation wave in these cases is the Chapman-Jouguet pressure and that no "spike" exists in these detonation waves. The absence of the Zeldovich-von Neumann "spike" is noteworthy in view of the very long reaction zone lengths of these mixtures. The measured detonation pressure of one of the slurry blasting agents (DBA-3") under steel confinement ( 172 kilobars) is shown to be considerably greater than the ideal detonation pressure of 75 per cent gelatin dynamite (p. = 135 kilobars) despite the fact that the detonation was still somewhat non-ideal in "DBA-3," its computed ideal detonation pressure being 180 kb. The popular 94/b AN /FO blasting agent exhibited a detonation pressure of only 13.5 kb in 5" paper tubes, but 37.5 kb in 5"• steel pipe compared with a computed ideal pressure of 40 kb.

Jan 1, 1961

By W. W. Smeltzer

The linear formation rates of wustite films have been determined over the temperature range 590° to 1030°C using a vacuum microbalance technique. These rates are dependent directly on the partial pressure of carbon dioxide, Activation energies for film and scale formation in carbon dioxide and oxygen atmospheres are equivalent to either the dissociation energies of carbon dioxide and oxygen, or the activation energy for the diffusion of cation vacancies in wustite. Of the metals, iron is the most widely used basic constituent of durable alloys despite its intrinsic property of converting at a relatively rapid rate to the oxides from which it is derived. This property has accounted partially for many investigations on the oxidation of iron at low and high temperatures. Interpretation of the results have been complicated by formation of multilayers containing the various oxide phases. To aid in elucidation of the oxidation kinetics, measurements have been carried out in this investigation on the growth of the wustite surface layer. There are several studies directly related to the objective of this investigation. The growth of multilayer scales has been demonstrated to be diffusion controlled in oxygen at atmospheric pressure over the temperature range 450" to 1200°C by Davies, Simnad, and Birchenall.' To gain an insight into the diffusion mechanism, Himmel, Mehl, and ~irchenall' determined the self-diffusion coefficients of iron in wustite, magnetite, and hematite. These results were used to evaluate the oxidation rates of iron and its oxides, taking as a basis the theoretical parabolic rate equation developed by Wagner., The evaluations were compared to experimental data and were shown to provide essential confirmation of this theory. Fischbeck, Neundeubel, and salzer4 have demonstrated that the oxidation of iron in carbon dioxide and other atmospheres at high temperature obeys a linear relationship. Because the Arrhenius temperature coefficients of the reaction rate constants changed at the A, point they concluded that the passage of iron into the oxide controlled the reaction. This viewpoint has been accepted by Benard and ~albot' to explain the occurrence of linear rates in oxygen before the onset of diffusion-controlled parabolic oxidation. This basic premise of a rate-controlling reaction at the iron/oxide interface has been questioned recently by Hauffe and Pfeiffer.' Since the formation of wustite may follow a linear or parabolic relationship depending on the pressure of the gaseous re-actant, they propose that linear oxidation is determined by a chemisorption reaction while parabolic oxidation is controlled by diffusion. As confirmation of this viewpoint, Hauffe and pfeiffer6 and Pfeiffer and ~aubmeyer' have established that the linear scaling constants of wustite formation at 1000°C in carbon-dioxide or low-pressure oxygen atmospheres

Jan 1, 1961

By T. J. Whalen, M. Humenik

The liquid surface tension of copper-nickel ad copper-nickel-titanium-carbon alloys and the wettability of titanium caybyde by these alloys have been measuhed. It was found that the surface tensions of the binary copper-nickel alloys Lie on a smooth curve between the end members, copper and nickel. The addition of small amounts of titanium and carbon has nO effect on the surface tensions of copper-nickel alloys. Small additions of nickel to copper significantly reduce the contact angle of Ike alloy with titanium carbide. From a Gibbs treatment, nickel is shown to be adsorbed at the titanium carbide-alloy interface. X HE microstructure of two-phase materials has been shown to be influenced largely by the interfacial energies between the phases present.' , In systems prepared by powder metallurgy techniques and densi-fied in the presence of liquid phase, a precise analysis of microstructure and interfacial energy relationships requires a knowledge of the solid-solid interface energies and liquid-solid interface energies. However, marly metal-nonmetal systems are characterized by the "sweating" of the liquid during sintering, and in these systems wettability is a principal consideration. The wetting in turn is dictated by the various interface energies of the system, as shown in Fig. 1 for a liquid drop formed on a solid substrate. The equation which expresses the vectorial balance of surface forces in the horizontal plane, at the point of contact, A, is given by: where ssv = solid-vapor interface energy sSL = solid-liquid interface energy sLV= liquid-vapor interface energy 6 = contact angle measured through the liquid phase. The angle and the surface tension, slv, can be measured accurately by the sessile drop method.3, The absolute value of the surface energy of the solid cannot be determined by this method, but with reasonable changes in the composition of the liquid only, the value of ssv can be considered constant. The changes in contact angle, then, can be attributed to changes in sSL and sLV and since sLV can be measured, the changes in sSL can be determined. Several studies have indicated that the surface and bulk properties of solid alloys can be correlated with electronic structure. The catalytic activity of copper-nickel alloys was reported to follow the dband vacancies in these alloys.5 Nickel has been considered to have 0.6 holes per atom in the d-band. The addition of copper to nickel is thought to bring about a filling of the d-band of nickel, since each copper atom contributes one electron. Thus, at an atomic concentration of 60 Cu-40 Ni (62 wt pct Cu-38 wt pct Ni) the d-band is believed to be full, and magnetic measurements support this view.6 If the electronic structure is influencing a property of the alloy, this property should show some sort of discontinuity as the composition changes from one side of the 60 Cu-40 Ni composition to the other. Since the catalytic activity can be considered as a surface property of the alloy, it is logical to assume that other surface properties, such as surface tension, may also be influenced by electronic structure. The suggestion has been made that there is a correlation between the solid titanium carbide-liquid Cu-Ni alloy interfacial energy and d-band filling.7 One purpose of this investigation was to determine if the changes taking place in the electronic structure with compositional changes in the solid copper-nickel alloys were reflected in the surface tension values of the liquid alloys. Such a change, if present, would lend support to the suggestion that one can refer to discrete energy bands in the liquid state. Other purposes of the present study were to investigate in detail the wettability in the system copper-nickel-titanium carbide, and to discuss the possible processes which take place during wetting in this system.

Jan 1, 1961