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By D. C. McLean, S. A. McKay

The purpose of this paper is threefold: 1) to describe actual ground control installations made at the various mines of the International Nickel Co. (Canada) Ltd mines in Sudbury, Ont. during a planned test program. 2) to suggest new ground control techniques which are now possible by the use of fully grouted bolts 3) to indicate the possible economic advantages to be gained by the use of resins and resin grouted bolts to control difficult ground conditions. Were a theme selected for this paper it would be: "Preserve the original roof in best condition possible by the use of smooth blasting techniques and fully grouted roof bolts — since the original rock is the best and cheapest material available for ground support." TYPES OF BONDED BOLTS As has been shown previously, there are several ways in which a bolt may be bonded. These are illustrated in Fig. 1 and 2. There are three general types of grouted bolts: 1) pretensioned, 2) post-tensioned, and 3) untensioned. The type which will be of most benefit to the user will depend upon the particular ground support problem involved. Despite the many arguments propounded for the necessity for using a tensioned bolt, ample evidence exists from actual experience that untensioned bolts can be effective in many instances. The outstanding characteristic of a grouted bolt is that it provides the user with a variety of rock consolidation techniques heretofore unavailable with conventional rock bolts. Many of the unusual characteristics of grouted reinforcing bar have been evaluated by researchers in the concrete structure field.' Underground application has largely been pioneered in the construction field, with especially good work being reported from the Snowy Mountains Hydroelectric Authority in Australia. Techniques developed there using cement grouted bolts are now being adapted in many large government construction projects in this country with excellent results. The ap- plications described in this paper are those in which Cyanamid's Roc Loc Mining Kits were used exclusively. SLUSHER DRIFTS AND FINGER RAISES (BOX HOLE BROWS, DASHES) A common mining problem especially where block caving methods are applied is that of maintaining the roof in slusher trenches particularly at the intersections of the trench with the feed raises (box holes) through which the large fragments of broken ore tumble. Typical sections are shown in Fig. 3 and 4. In Fig. 3, the drift is normally driven 7 ft wide by 8 ft high initially. The rock involved is a hard norite (diabase) which is usually competent but has "block cleavage". This roof has a tendency to fall out in large blocks when subjected to operating stresses. Depending upon the initial condition of the roof, the drift is either lined with 2 to 3 ft of concrete immedi-

Jan 1, 1964

By Robert E. Thurmond

DISCOVERY of a commercial ore deposit has resulted from a program emphasizing geophysical techniques and concentrating upon exploration of alluvial-covered areas. United Geophysical Co. selected these areas as offering the best possibility of success, for here the surface evidence of ore deposits has been hidden from the eyes of prospector and geologist alike. Pima mining district, Pima County, Arizona, was selected for initial exploration. The project was successful in that a commercial ore deposit was discovered and proved through drilling and extensive underground development. A limited region of activity was chosen and library research was begun on available economic and regional geological publications relating to the mining districts. Field reconnaissance of those districts which seemed to hold exploration possibilities provided a general picture and ascertained the existence of alluvial-covered areas of interest. At the conclusion of the reconnaissance trips all data obtained were compiled, and the district which seemed to present the best exploration possibilities was selected by statistical methods. The statistical summary was based on the following considerations: Geological Factors: 1—type of intrusive, P—presence of favorable host rocks, 3—apparent intensity of mineralization, and 4—presence of favorable structure in covered or unexplored areas. Economic Factors: 1—past production from district or mine; 2—size, shape, grade, and type of ore deposit in the district; 3—ease of acquiring mineral rights; and 4—general development facility. Exploration Favorability Factors: 1—results to be anticipated from geological methods alone; 2—application of geophysical methods, namely, topographic conditions, surface interference, depth-size relation, physical property contrasts as related to ores or controlling structural features; and 3—drilling factors. Admittedly, many of these, factors do not lend themselves to absolute evaluation, but relative evaluation, subject to inaccuracies of personal judgment, is always possible. A relative scale from 1 to 10 was established for every factor, representing varying degrees of favorability. For each district a numerical evaluation of each factor was established and a numerical total determined. The obvious advantage of this scheme is that a more concise summation can be presented by numerical means than can be achieved by descriptive means. After a district had been selected as favorable, the first step was to carry out more detailed geological and economic studies to narrow down the areas of interest. The second step was to compile all available geological data from publications and add to these data by mapping where necessary. Geological interpretation and projection of structural or other control into covered or unexplored areas was made whenever logical. To determine the possibilities of geophysical application and to select a geophysical method, physical property contrasts were related to mineral assemblages and/or structural control. If geophysics seemed applicable, trial profiles were run crossing the area normal to the strike and spaced

Jan 1, 1955

By Ehsan Alavi, Brian Hagan, Colin LaVassar, Glen Frank, Derek Dugan, Rick Capka, Lisa Mori

"Tunnel face instability is one of the most common issues in EPB tunneling. The evaluation of an ideal face support pressure is a critical element in the design and construction phases of EPB tunneling. In this study, measured tunnel face pressures in three EPB tunneling projects (University Link U230 and U220 projects and the Northgate Link Extension N125 Project) for Sound Transit in Seattle, WA are compared with the calculated analytical methods. This comparison shows that the analytical methods generally overestimate the required tunnel face support. The best practice for managing the face pressure in EPB tunneling operation is discussed based on the experience gained through these projects. Furthermore, the algorithm that is developed for identifying ground loss in these projects is addressed. INTRODUCTION Earth pressure balanced tunneling relies on using muck within the chamber to support the face. Muck is pressurized by controlling the advance rate of the tunnel boring machine and the speed of the screw conveyor. Target face pressure is typically calculated by using the geotechnical assumptions in the geotechnical baseline report. The concept behind EPB tunneling is that the application of sufficient face support pressure will prevent tunnel face instability and the resultant over excavation. Tunnel face instabilities caused by a lack of sufficient face support can lead to ground loss and surface settlement (Anagnostou & Kovári 1996, Kirsch 2010). A certain support pressure must be achieved to counteract water and earth pressure with an adequate factor of safety. While the water pressure can be predicted accurately, the determination of the resultant earth pressure on the face is less precise. This becomes manifested in the relatively high partial safety factors on the earth pressure."

Jan 1, 2016

By Mwaba CC

Ok Tedi Mining Ltd has been using flotation for the production of copper/gold concentrates from a complex copper sulphide ore for several years. During this period, much effort has been devoted to metall- urgical treatment of the ore. This paper examines some of the mineralogical aspects of the sulphide minerals in the ore using the electron microprobe analyser. Results have revealed the complexity of the copper sulphide minerals and in particular, chalcocite. Analysis of both plant and laboratory flotation products has provided further insight into the effects of mineralogy on the flotation of copper and iron sulphides. A significant observation is that some of the pyrite minerals apparently exhibit natural floatability. The implications of the mineralogical characteristics of the sulphide minerals on the flotation of the ore are also discussed.

Jan 1, 1991

The rocks of Waihi and the surrounding district are almost entirely rhyolitic and ande5itic in character. Sedimentary rocks, with the exception of some surface deposits of clay loosely compacted conglomerate, etc., and one or two thin and broken beds of a very poor lignite, occasionally changed by igneous agencies into a bituminous coal, are almost absent. In the shafts sunk by the Waihi and Grand Junction companies outside the outcropping andesitic area of the Martha Hill, more than one old surface or lake bottom has been passed through. At these points layers of sand, consolidated volcanic mud and tuff, accompanied by numerous broken fragments of imperfectly silicified wood have been enccuntered, but these occurrences may, for the purpose of this paper, be neglected.The youngest rock of the district are rhyolites, probably of Pliocene age. At least three distinct classes of rhyolitic lava, each possessing features of unusual interest, may be made out. None of these, however, is gold-bearing. The youngest flow, a light-coloured, fine-grained rock, is remarkable owing to its enclosing at times fragments of carbonised wood, varying in size from mere specks up to quite large pieces of almost pure charcoal. Rhyolitic tuff is also met with. The rhyolites cover a large extent of nearly flat country east, south, and west of Waibi, here and there rising into barren, stony hills.Below the rhyolites, geologically speaking, but for the most part. forming hills which bound the rhyolitic plain, or rise out of it as isolated patches, come ahdesites of older...

Jan 1, 1902

By Gerhard Bayer

X-ray and thermoanalytical studies were carried out on the formation and stability of Ca-, Mg-and Mn-tungstate, and of the corresponding minerals scheelite and wolframite. The tungstates were synthesized by different methods: precipitation from solution, solid state reactions, displacement reactions with solutions and in the solid state. The reactivity of natural scheelite and wolframite with different salt solutions and in mixtures with other minerals was investigated.

Jan 1, 1989

This paper presents a brief discussion of three case histories to illustrate several aspects of the question of blasting in or immediately adjacent to concrete. The results demonstrate a need to make dramatic upward revisions in previous criteria, whether it be the standard particle velocity criteria or damage response spectra bounds, - especially those which include conservative upper limits of constant acceleration for the high-frequency portion of the spectrum. It is demonstrated, also, that conventional off-the-shelf blast-monitoring instruments are not capable of monitoring small blasts at close range. Both the frequencies and the levels of effect are beyond the range of such instruments. These case histories suggest further that there is a need to review the applicability of certain wellknown equations of elasticity.

Jan 1, 1980

By R. A. Turpin

Bethlehem Steel's Research Department is developing a set of computer programs as mine-planning tools for Bethlehem's coal mines. Several of these computer programs have been completed and have been in routine use by Bethlehem Mines personnel since early 1975. The production scheduling and ventilation planning programs have been installed on an interactive time-sharing computer. The use of time sharing allows mines in remote locations to access these planning tools through standard phone lines and low-cost computer terminals. The capabilities of the interactive production scheduling and ventilation planning programs are briefly described. The advantages of implementing them using time sharing are discussed. A case study illustrates some of the benefits that planning based on the use of these programs has already provided.

Jan 1, 1977

By R. G. Robins

The processing of gold bearing sulphide minerals which contain arsenopyrite and various complex arsenic sulphides results in arsenic containing emissions and effluents which are suspect in relation to clean air and clean water standards. Removal of arsenic from gaseous emissions is briefly reviewed. The use of lime to stabilise aqueous residues as either calcium arsenate or calcium arsenite is shown to be inadequate for long term disposal since both compounds are converted into calcium carbonate due to the influence of carbon dioxide in the atmosphere. Mixed calcium arsenate-phosphate residues are similarly unstable, but present better stability than the straight calcium compounds. Alternative disposal methods are reviewed whereby the arsenic is converted to more stable compounds, such as barium arsenate, titanium (IV) arsenate, and arsenic sulphide.

Jan 1, 1984

By Milton C. Neul

As recently as the mid-1930's, steam and rail haulage were still the primary means of moving large quantities of rock. However, 2- to 5-ton standard on-highway trucks were beginning to be used in the mining industry's efforts to lower haulage costs. It was quickly obvious that rubber-tired equipment was more flexible, faster and more maneuverable. The trend towards haulage trucks had begun. Now while savings were being realized, the severe operating conditions encountered in open pit operations proved too much for the lightly constructed frames, gasoline engines and highly inflated tires. As a result, a few years later, the first 10 to 15-ton, two-axle heavy duty trucks were designed specifically to operate under off-highway conditions.

Jan 3, 1966

By Rixford A. Beals

Dry grinding without balls is feature of this mill now in use in three countries on two continents. Materials being ground commercially include iron ore, gold ore, asbestos rock, and slag. New large beneficiation plants have been using an almost standardized crushing and grinding flowsheet. Typically a primary gyratory is followed by several stages of fine crushing and grinding is often carried out in a rod mill operating ahead of one or more ball mills. The clearly labeled trend is to an increasing number of stages with a decreased reduction ratio per machine. Current Aerofall mill installations represent a complete reversal of this trend-one mill replaces the several stages of crushing and grinding a more conventional flowsheet would call for.

Sep 1, 1955

By Junli Xu, Xianwei Hu, Kaiyu Xie, Liangxing Li, Zhongning Shi, Zhaowen Wang, Bingliang Gao, Aimin Liu

Al-Ti master alloys were prepared by aluminothermic reduction between the dissolved titanium dioxide and aluminum in cryolite melts at 960oC. The kinetic analysis by differential scanning calorimetry indicated that the apparent activation energy of the reaction of reducing titanium dioxide by aluminium is 22.3 kJ/mol, and the reaction order is 0.5. The products were analyzed by means of X-ray diffraction, X-ray fluorescence, scanning electron microscopy and energy dispersive spectrometer. Results from X-ray diffraction showed that the phase compositions of produced alloys are Al and Al3Ti. In addition, Al-Ti master alloys containing 2-6 mass% Ti were formed at different reduction time of 2-5h in aluminothermic reduction experiment.

Jan 1, 2015

By R. A. Wagstaff

The method of charging a reverberatory furnace has changed many times since smelting was introduced in this country from the old smelters of Swansea, England. The cause of the latest change at the Garfield plant has been the excessive fineness of the charge due to fine grinding in the concentration of the crude copper ores. The many desirable features of deep-bath smelting as now used at Garfield have been proved. The old method of dropping the charge through holes in the arch (known as center-feed method) causes excessive dusting which makes heavy slag and flue-dust losses, also rapid deterioration of the silica brickwork of the furnace through fusion with the iron oxides from the dust. The purpose of this paper is to describe a gun feeder that was designed to overcome the disadvantages of the older methods of center feeding and still maintain the good features of deep-bath smelting with the hot finer charge. A gun feeder was designed to introduce the finely divided hot calcines under the moving gas stream of the combustion zone and still have them spread in a uniform blanket over the highly heated matte bath. The temperature of the furnace was so great that it was impossible to maintain a stationary feeder, so a movable feeder was designed that could be introduced into the highly heated zone and be withdrawn after the charge had been dropped. It was necessary to protect the nozzle of the gun with a water-cooled coil. Many different types of protected nozzles were tried, such as air jackets, water jackets and heat-resisting steel alloys, but none proved satisfactory. The angle of inclination of the feeder was found to be an important factor in spreading the charge evenly over the surface of the bath. An angle of 34" to 37" was found to be the most advantageous. To allow a continuous flow of ore from the charge car to the point of discharge inside the furnace, the feeder was made with telescopic connections. The pipe leading from the car is stationary and forms the inside part of the telescope. The outside section of the telescope is movable, and is

Jan 1, 1934

Discussion of the paper of W. R. SHIMER, presented at the New York meeting, February, 1915, and printed in Bulletin No. 99, March, 1915, pp. 557 to. 585. WILLIAM R. WEBSTER, Philadelphia, Pa.-I would like to ask Mr. Shimer how the finishing temperature of the H-beams and other beams rolled on the Gray mill at Bethlehem compare with the rolling temperatures of the rails referred to in this paper. Also, how the reductions in the rolling of the beams compare with the reductions in the rolling of the rails. I would also like to know if any drop tests were' made on the rails referred to as having been allowed to cool and then annealed; in other words, what results, if any, were obtained from tests on rails after the internal strains of rolling had been removed; and in the matter of the rail blooms, I would like to ask if they are not often heated to a higher temperature than is desirable on account of the thin flanges in order to carry the heat through to the finishing pass. The tensile strength of the steel in these rails is given as 125,000 lb. per square inch, which is almost as high as tire steel. If some of these blooms were rolled into rounds of about the same section as the head of the rail, would you not get better results from tension tests than those from the head of the rail? In other words, in rolling rounds, whether you would not be able to control the rolling and finishing temperatures better than is possible in the rail, owing to thin section of the rail flanges. Some years ago I had experience with the rolling temperatures of tire steel, running from about 127,000 to 133,000 tensile strength. These tires had the tensile strength and the deflection specified. One of the manufacturers had no trouble whatever, after a little experimenting, in meeting the conditions of the specification. Another manufacturer who made some of these tires came to the office and stated that he had tried tires from three heats of steel and could not meet the specifications and

Jan 5, 1915

By John B. Myers

VERMICULITE is a name used to describe micaceous material that exfoliates when heated. It is hydrated magnesium-aluminum-iron silicate. The chemical composition, color, physical appearance, and degree of exfoliation vary. COMPOSITION, PROPERTIES, AND ORIGIN Vermiculite has the characteristic micaceous structure of basal cleavage and readily splits into thin laminae, which are soft, pliable, and inelastic. The monoclinic crystal faces are often marked by triangular lines at 60° and 120°. Hardness is 1.5; specific gravity, 2.2-2.7; luster pearly to greasy; colors, amber, bronze, reddish brown, dark green, and black. Feel is soapy, particularly when wet. When heated it exfoliates by expanding at right angles to the cleavage into long wormlike pieces (the name vermiculite is from the Latin veamiculari, to breed worms). This important characteristic of expansion is believed to be a mechanical separation of the layers when the contained water is converted into steam. Warping of the unit layers may also contribute to the expansion. The increase in bulk volume of commercially prepared material is 8 to 12 times but individual flakes may increase in size more than this. Pure vermiculite is a distinct mineral and has the structural formula (OH), (Mg,Fe)3 (Si,Al,Fe)4 010.4H20. It rarely occurs in this pure form, but generally as a mixed mineral of varying structure. One explanation is that the mixed material is composed of unit layers of inter-stratified pure vermiculite and biotite. The essential difference between the two is that unit cell structure of vermiculite contains a layer of water molecules whereas the biotite cell contains potassium instead of the water. The water content of the mixed vermiculite is less than that of pure vermiculite but more than that of biotite. Pure biotite does not expand when heated. If the proportion of biotite layers in a vermiculite is too high it will adversely affect the degree of exfoliation. Within a given deposit, the great mass of material may approach a definite com-position with local areas of greater biotite content. It is not uncommon to find also small pockets of pure biotite but these are generally segre-

Jan 1, 1949

By G. Koves

The behavior of case-hardened AISI C-1213 free -machining steel under complex impact-fatigue -wear load conditions was investigated. The inherently poor dynamic properties of the steel are mainly affected by the stress distribution in the case, component shape, and tempering. Cold-riveted components showed unexpectedly high dynamic strength compared to basic parts. A compromise beatment—which provides good dynamic properties, reasonable wear resistance, and fair riveting characteristics—zuas developed. A number of mechanical components in data-processing machines are made of free-machining carbon steel. Although, selected primarily due to manufacturing requirements, components made of these grades frequently undergo complex heat treatment and must sustain impact-fatigue loads. A typical free-machining steel is the AISI C-1213 grade, which is a resulfurized and rephosphorized open-hearth steel. While the undesirable effects of sulfur and phosphorus on the mechanical properties are well-known, data on dynamic properties are scarce.1"3 Rapid rotating or oscillating motion while carry- ing a high cyclic load requires a combination of wear resistance with high endurance limit and impact toughness. The inherently poor dynamic properties of the free-machining steel are further degraded by the machining, which introduces local stress-concentration areas. While the heat treatment (usually case hardening) improves some mechanical properties, it necessarily impairs others. Another problem arises when components, such as studs, must be fastened by riveting. The high crack-sensitivity of the free-machining steel, especially in the presence of a hardened case, makes this operation difficult. In view of the preceding considerations, it is of interest to investigate the behavior of a typical component under complex impact-fatigue-wear loading conditions in order to explore the effects of material, machining, and heat treatment, to obtain specific data on the dynamic characteristics of free-machining steel, and to arrive at a process which would adequately utilize the inherent qualities of this material. EXPERIMENTAL PROCEDURE To simulate actual service conditions, a typical component was selected, based on frequency of application, complexity of load, and processing difficulties. The dimensions and shape of the component—a stud used in many electromechanical document-handling machines—are shown in Fig. 1.

Jan 1, 1964

THE slag performs two useful functions. in open-hearth steel-making. First, it is the means of disposal of all the impurities, save carbon, which are removed from the charge materials in refining the steel, so it must be suited to receiving and retaining as much as possible of undesirable elements with minimum loss of iron and useful alloying elements. Second, the slag serves as a buffer between the flame and the bath and transfers oxygen to the metal at a measured pace contrasted with the violent and difficultly controlled oxidation of the bessemer process. At the same time, the slag is a thermal insulator that limits the rate at which heat can be delivered to the metal from the flame, and a heavy slag blanket thereby serves as a brake on production rates. It has been said with justification that the secret of good steel- making is to make a good slag and the steel will take care of itself. In a broad sense, the subject of slag control includes not only the adjustment of the composition of the slag but also of its relative weight in terms of percentage of the metal-bath weight. The slag is made up essentially of: (1) oxides formed by oxidation of silicon, manganese, phosphorus, and iron in the charge, (2) SO2, MnO, MgO, and other oxides charged as such or introduced incidentally with ores or fluxes or by refractory erosion, and (3) lime charged or fed to the heat to neutralize the "acidic" oxides present (SiO2 and P2O5). Obviously, if practically perfect control were possible over the composition of the charge as well as over the oxidation process during the melting period, both slag weight and composition would be very nearly predetermined, and the control problem would be solved. Unfortunately, only a somewhat imperfect control over these factors is possible, so the operator must begin during the lime boil and continue through the refining period to discover and correct departures from the normal pattern of slag development. To do this as the heat progresses, the first helper must be able to make quick estimates of the composition and physical state of develop-

Jan 1, 1951

By Elmars Ence, Harold Margolin

The titanium-aluminum system has been investigated in the composition region 0 to 34 pct Al in the temperature range 800" to 1450°C. The phases encountered in this region were: a,ß, TiAl3, The reactions observed are as follows: 13 ; L - 6T. A1, 0 (15 pct Al) + 6 (18 pct Al) - yTi Al (16.5 pct Al) at -1170°C andP (7 pctpct Al) + y (9.2 pet Al) - ah(9 pct Al) at - 1060°C. A eutectoid reaction: y — a +d belm 700°C is postulated. THE Ti-A1 system has been the sub.ect of a number of investigations. Several of these1-3 have indicated extensive solubility of A1 in both a and ß titanium. Ence and Margolin, as a result of work on the Ti-A1-0 system:'5 have shown that the a solubility ofalumi-num is considerably restricted, and found that a compound, Ti2A1 existed in the region formerly designated as Q a This structure was identified as hexagonal with c/a = 0.803. Pietrokowsky confirmed the existence of this phase7 and pointed out that the structure was isomorphous with Ti3Sn.8 Although the existence of Ti,A1 has been confirmed by others,9-12 there has been considerable disagreement regarding the composition and mode of formation. A detailed reinvestigation of the Ti-A1 system has been published by Sagel et al.13 The tentative diagram indicated two phases, a, and e, occurring in the former all a region. The a, phase has the same structure as Ti2A1 and was indicated as having a broad region of solubility. Epsilon, a tetragonal phase, was shown to form within the a, solubility region. AS a result of unpublished work,14 Ence and Mugy3 olin disagreed with the interpretation of Sage1 et al., although some common features existed. The present study was conducted in an attempt to clarify prevailing uncertainties. EXPERIMENTAL PROCEDURE Alloy Preparation—Alloys were prepared from iodide titanium (99.9 pct Ti with less than 0.01 pct Zr) or Bureau of Mines electrolytic titanium (BHN-73) and high purity aluminum (99.99 pct). Alloys were arc-melted in argon or helium atmosphere as 15-g buttons in the composition range up to 34 pct Al. Depending on need, alloys were made in increments varying from 0.25 to 2 pct Al. Up to five 15-g buttons of some compositions were made. Weight losses during melting did not exceed about 1 pct of the charge and chemical analysis revealed that both titanium and aluminum were evaporated. In general, nominal and analyzed compositions agreed within 0.5 pct and therefore nominal compositions were used in plotting the data. Unavoidably, some overlap of composition occurred, particularly where small increments of A1 were used. The small increments were primarily used to obtain alloys which would fall into the narrow a -, r region and this purpose was achieved. In general, the data obtained from Bureau of Mines base titanium and iodide titanium alloys were in agreement. Forging—Both as-cast and forged samples were employed. Samples were heated for hand forging by an oxygen-hydrogen torch to the region 1200" to 1300°C. A titanium anvil and cover plate were used to prevent any iron pick-up and consequent formation of a low melting point compound. Frequent reheating kept the temperature in the desired range. Under these conditions, alloys containing up to 15.5 pct could be successfully forged. To check on the depth of contamination, forged alloys were heated slightlybelow the ß transformation temperature. Metal was removed to a depth below the contaminated surface so revealed, and the subsequent results obtained from these samples agreed closely with those secured from as-cast material. Heat Treatment—Prior to heat treatment, all alloys were vacuum annealed to remove hydrogen. Samples

Jan 1, 1962

By Robson Jacinto Coelho

A equipe da Coqueria identificou a possibilidade de reduzir o Burn Loss, que é a perda de material por queima durante o processo de coqueificação. Após uma série de estudos, utilizando a metodologia Seis Sigma, identificou-se oportunidades de melhorias operacionais que trariam mais eficiência, estabilidade operacional e consequente aumento na produção de coque e vapor, tais como: maior controle na admissão de ar, controle das perdas de coque e carvão, vedação dos fornos de coque e execução de paradas programadas específicas para Preservação Refratária, com foco na redução do back log e consequente prolongamento da vida útil das baterias de fornos de coque. A redução Burn Loss aumenta o rendimento coque/ carvão, com consequente redução do consumo específico de carvão e aumento na produção de coque e vapor. A implantação desse projeto permitiu a redução de 2,5 dólares por tonelada de aço produzida no Fiscal Year 16/17.

Oct 30, 2017

By Mari Yamamoto

Controlled thermolysis of gold(I) complex, [Au(C13H27COO)(PPh3)], at 180 °C for 5 h under an N2 atmosphere affords the new type of monodispersed spherical gold nanoparticles capped by myristate and a small amount of PPh3 ligands (average diameter 23±1.5 nm), in spite of no use of solvent, reducing agent and stabilizer. Much attention has been paid to the preparation and structure determination of transition metal nanoparticles, because of their widespread use in technological applications.1 In general, the chemical reduction of metal salts and organometallic complexes2 by the use of reducing agent is carried out to prepare gold nanoparticles. In some cases, a large amount of solvent and stabilizers such as surfactants,3 polymers4 and ligands5 are used to prevent agglomeration of particles and control the particle size. For instance, Brust et al. reported a two-phase reduction of AuCl4 - by NaBH4 in the presence of dodecanethiol as stabilizer to prepare gold nanoparticles.6 On the other hand, O?Brien et al. recently reported an one-phase preparation of gold nanoparticles by the reduction of AuCl4 - by NaBH4 in the mixture of tri-n-octylphosphine oxide and octadecylamine which act as both solvent and stabilizer, but this procedure also needs reducing agent.7

Oct 1, 2003