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By A. Lawson

"Continued and expanded use of underground diesel-powered equipment is considered desirable in order to achieve necessary production capability, particularly when coal becomes increasingly in demand as an energy source. Although diesel engines are derated for underground use, concern has been expressed in many quarters regarding the health effects of worker exposure to diesel-generated particulate and NOx emissions. This concern will increase as Canadian diesel fuel quality becomes heavier and with higher sulphur content. This could result in a requirement to increase ventilation rates by 50%.This paper describes the results of studies of various approaches designed to reduce diesel emissions. Two major approaches have been followed: fuel modification, and emission control hardware development. The results of progress in the development of these approaches will be described.Fuel modification includes the application of water/diesel and methanol/diesel fuel emulsions to the engine. Details of the techniques employed in this approach will be described, together with the effects on diesel emissions. (The paper is concerned with the emission aspects only, not the possible major engine modifications and/ or substitute materials of construction for 100070 methanol.) Use of methanol has the added advantage of acting as a diesel fuel substitute and extender, and there are expectations that underground diesel engines could eventually operate on close to 100% methanol fuel, thereby eliminating particulate emissions. The results of emission control hardware development will also be presented and will include the effects of catalysts, water scrubbers, exhaust filters and exhaust gas recirculation techniques on emissions. A combined systems approach employing a number of these components appears to be the most viable method of controlling the complete array of diesel emissions.This work should culminate in a better understanding of the costs involved in employing fuel modification or emission control hardware relative to the costs of increased ventilation which mpy be necessary to maintain a safe working environment for the underground worker."

Jan 1, 1981

The Marvel Loch Operations (MLO) plant was treating ores from up to six MLO sources and in addition needed to blend externally sourced ores with its own ores. This presented a metallurgical accounting dilemma, which was subsequently addressed by the design, implementation and testing of an automatic sampling system. The MLO automatic sampler was well designed and has been the subject of previous internal and external reviews. The sampling action is fully automated and the unit is essentially self cleaning particularly when sampling primary ores. The purpose of this paper is to document the rationale behind the design, the specific details of the sampling station, its use for ore purchase purposes and an assessment of the sampling system to meet the needs of the operator.

Mar 1, 2010

By SUHAINA ISMAIL, NORLIA BAHARUN, SHAIK ABDUL RAHMAN, WAN NUR SYAFIQAH ANUAR, MOHAMMAD REZAEI ARDANI

Refractory gold ore contains sulfide minerals like pyrite, chalcopyrite and sphalerite that are difficult to be directly leached by cyanidation or by lixiviants such as thiourea and halides. In such cases, it is necessary to perform oxidative pretreatment of the ore to oxidize the sulfide matrix, and gold particles can be exposed to the solution during the leaching process [1]. In recent years, hypochlorite and chloride solutions have been introduced as alternative materials for hydrometallurgical methods of gold extraction instead of cyanide solution [2]. A previous study by Hasab et al. [3] reported that the gold dissolution rate in hypochlorite solution was higher than in the cyanidation process, due to the presence of hypochlorous acid (HOCl) as a strong oxidizing agent. In a hypochlorite leaching system, the change in pH can influence the presence of oxidant species in the solution: the hypochlorite ion (OCl−) is stable in pH greater than 7.5, HOCl can be found in pH between 4.0 and 7.5, and aqueous chlorine (Cl2 (aq)) is the predominant oxidant when pH is below 4.0. As HOCl is the most effective oxidizing agent for gold extraction, pH should be maintained in the range of HOCl stability [4].

By Gustavo De la Torre

Más allá de contar con las certificaciones ISO 9001, ISO 14001, Y OHSAS 18001, la planta concentradora de Cerro Lindo busca ser catalogada como un desempeño de categoría mundial, lo que implica usar la capacidad total del área (procesos, tecnología y talento humano) basado en un equipo de alta performance-EAR, y gestionar de forma sistemática seguridad, salud ocupacional, medio ambiente, costos, productividad, calidad y confiabilidad, además del proceso productivo. En el presente artículo se analiza información recopilada durante la fase de crecimiento, se presentan diferentes etapas en desarrollo y se describen los estudios realizados en la planta de beneficio, a nivel técnico y de gestión, con óptimos resultados de producción, eficiencia e indicadores metalúrgicos.

Apr 30, 2018

By X Feng, X Zhang, W Sun, Y Zhe, K Hou, B Zhao, H Liu

Pulang Copper Mine, being China's largest newly built mine using block caving, boasts an annual production capacity of 12.5 million tons. Production level and roadway stability hold the key to the successful application of block caving. However, with Tong Kuangyu being the only mine in China which has applied such a method, we currently lack relevant experience in the successful application of the method. This paper has studied the influence of different rock mass zonings, fault thickness, fault dip angles, on-site construction quality on the production level, roadway stability of block caving through numerical simulation and analysed the roadway stability in different kinds of support solutions so as to ensure the successful application of block caving in Pulang Copper Mine. The results have shown that the existing support method in Pulang Copper Mine can meet the requirement of roadway support in zone II and III, but could not satisfy the demand in terms of support strength in the relatively fragmented zone I area. When roadway passes through the fault, the deformation of surrounding rock and plastic zone of roadway will gradually decrease with the increase of fault dip angle; the deformation of surrounding rock and plastic zone of roadway will gradually increase with the increase of fault thickness. An ideal support effect can be achieved through the joint support of grouting and bolting when roadway passes through the fault. In the measured model of on-site construction, there is stress concentration in the intersection between the access and transverse drift of ore removal. Therefore, the stability of the roadway can be improved by improving the construction quality. CITATION:Sun, W, Hou, K, Zhang, X, Feng, X, Liu, H, Zhe, Y and Zhao, B, 2018. Research on supporting technology for production level roadways of block caving in Pulang Copper Mine, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 95–106 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By Doyle A. Ellerbruch

An FM-CW microwave system was investigated for measuring coal layer thickness. Measurements were made in three different mines near Pittsburgh, Pennsylvania, near Fairview, West Virginia, and near Coffeen, Illinois. Microwave frequencies in the range 1-2 GHz were used to measure samples up to 55 cm thick. All samples were backed with a naturally occurring shale. Measurements were also made on coal and shale samples compounded in the laboratory at the Bureau of Mines Pittsburgh Mining and Safety Research Center near Bruceton, Pennsylvania. The results indicate that layer thickness can be determined in most cases, although large anomalies may, in some cases, produce misleading results. Many anomalies that were detected with the FM-CW system were verified visually by drilling into the coal layer. The dielectric constant of coal apparently varies significantly within a coal seam. The form of the output signals from the FM-CW system seem to simplify the data interpretation and analysis process as compared to the manually swept microwave system used previously. It appears that this technique has the potential of measuring changes in the dielectric constant of a coal seam and providing an output that can be used for real-time corrections in layer thickness; measurement.

Jan 1, 1976

By Christoph Sedivy

Industrie 4.0 is slowly but surely arriving in the melt shops. Furnaces are being equipped with more and more sensors, digital models are increasing the degree of automation, and information is being shared between different aggregates within the plant. Because the electrode control system plays a key role in electric steelmaking, it naturally assumes an important position in the melt shop’s Industrie 4.0 strategy. In addition to reliable, state-of-the-art core regulation functionality, monitoring and reporting tools and the ability to communicate with other equipment are also required. Therefore, the latest generation of our electrode control system, the Melt Expert, was developed based on Industrie 4.0 design principles. Intelligent plant condition diagnostics, performance monitoring, and user-defined reporting are essential modules in this new system. With these functionalities, electrode control systems are developing into the information and control center of the furnace. A newly developed software app brings most relevant process information to mobile devices. This feature allows steelmakers to keep an eye on the performance of their equipment anytime and anywhere. This paper describes the new features of the electrode control system and shares our customers’ operational experience. Our focus is on the practical aspects of plant status monitoring, KPI reporting, and diagnostic functionality as well as the improvements achieved.

Oct 30, 2017

By D. R. Boyle

"The Murray Brook precious metal (Au, Ag) gossan deposit is one of nine supergene mineral deposits that have developed over polymetallic massive sulfide deposits in the Bathurst Camp of New Brunswick. Reserves consist of 1.9 Mt of gossan containing 1.53 g/t Au and 65.9 g/t Ag. The supergene zone at Murray Brook consists of six distinct units: a) altered massive sulfide, b) pyrite-quartz sand, c) massive sulfide gossan, d) disseminated sulfide gossan, e) ferruginized wallrock, and f) leached bedrock. The massive sulfide gossan constitutes the main body of economic mineralization and consists of goethite, primary quartz, secondary amorphous silica, K-Fe-Pb-As- Sb-Ag hydrated sulfate and oxide minerals (beudantite, plumbojarosite, jarosite, bindheimite, scorodite), trace cinnabar, and cassiterite of primary origin. The order of stability of sulfide minerals during oxidation was pyrite _ arsenopyrite _ galena _ Bi-Sb sulfosalts _ chalcopyrite _ tetrahedrite group _ sphalerite.Two mass balance techniques (isovolumetric and conservative element) indicate elemental depletion in gossan relative to primary ore in the order: S>Cd=Zn>Cu=Mn>Na=Ca>Fe=Al=V> Mg= K=Se=Hg>Pb>Ti>Ag>Mo=P>Ba; and enrichment in the order Au>As>Sb>Si>Bi. Tin, as cassiterite, is conservative.Mineralogic and paleomagnetic data suggest that the gossan deposit formed under a warm temperate climate throughout the Pliocene. The rate of oxidation and the compositional nature of the ore was significantly influenced by: a) the position of the primary sulfide zone in a downward moving hydrological system, b) primary sulfide composition and zonation that promoted the development of a strong electrochemical oxidation system, and c) pronounced intercalation of carbonate and sphalerite mineralization in sulfide zones, which promoted rapid development of secondary porosity, permeability and downward flow of oxygenated groundwater.During progressive oxidation and physico-chemical erosion of the gossan zone, Au was transported downward in groundwaters, probably as a Auo colloid complex, to be concentrated in the lower horizons of the gossan profile. The precipitation of Au was greatly increased in the pyrite/arsenopyrite zones. Gold concentration was multi-cyclic with continual dissolution and nucleation of the metal until final concentration in the void structures of the gossan. Leaching experiments and microprobe analyses indicate that Au is present in the gossan as submicron composite sols of Au-Ag-silica."

Jan 1, 1995

By D. R. Boyle

"Abstract - The Murray Brook precious metal (Au, Ag) gossan deposit is one of nine supergene mineral deposits that have developed over polymetallic massive sulfide deposits in the Bathurst Camp of New Brunswick. Reserves consist of 1.9 Mt of gossan containing 1.53 g/t Au and 65.9 g/t Ag. The supergene zone at Murray Brook consists of six distinct units: a) altered massive sulfide, b) pyrite-quartz sand, c) massive sulfide gossan, d) disseminated sulfide gossan, e) ferruginized wallrock, and f) leached bedrock. The massive sulfide gossan constitutes the main body of economic mineralization and consists of goethite, primary quartz, secondary amorphous silica, K-Fe-Pb-As- Sb-Ag hydrated sulfate and oxide minerals (beudantite, plumbojarosite, jarosite, bindheimite, scorodite), trace cinnabar, and cassiterite of primary origin. The order of stability of sulfide minerals during oxidation was pyrite > arsenopyrite > galena > Bi-Sb sulfosalts > chalcopyrite > tetrahedrite group > sphalerite.Two mass balance techniques (isovolumetric and conservative element) indicate elemental depletion in gossan relative to primary ore in the order: S>Cd=Zn>Cu=Mn>Na=Ca>Fe=Al=V> Mg= K=Se=Hg>Pb>Ti>Ag>Mo=P>Ba; and enrichment in the order Au>As>Sb>Si>Bi. Tin, as cassiterite, is conservative.Mineralogic and paleomagnetic data suggest that the gossan deposit formed under a warm temperate climate throughout the Pliocene. The rate of oxidation and the compositional nature of the ore was significantly influenced by: a) the position of the primary sulfide zone in a downward moving hydrological system, b) primary sulfide composition and zonation that promoted the development of a strong electrochemical oxidation system, and c) pronounced intercalation of carbonate and sphalerite mineralization in sulfide zones, which promoted rapid development of secondary porosity, permeability and downward flow of oxygenated groundwater.During progressive oxidation and physico-chemical erosion of the gossan zone, Au was trans- ported downward in groundwaters, probably as a Auo colloid complex, to be concentrated in the lower horizons of the gossan profile. The precipitation of Au was greatly increased in the pyrite/arsenopyrite zones. Gold concentration was multi-cyclic with continual dissolution and nucleation of the metal until final concentration in the void structures of the gossan. Leaching experiments and microprobe analyses indicate that Au is present in the gossan as submicron composite sols of Au-Ag-silica."

Jan 1, 1995

By Annika Gram, Teddy Johansson, Lutfi Ay

Micropiles transfer tension or compression forces as well as cyclic loads into the ground via skin friction. The Self Drilling Micropiles (SDM) can be utilized for permanent applications. The hollow bar simultaneously acts, as drilling rod, injection tube and reinforcement for the micropile. The SDM system can be used in any type of soil, including unstable soils, without the need for temporary casing. Injecting a cement grout through the hollow steel tendon ensures that the borehole is filled from the bottom to the top. The system is fast, simple, and flexible. The installation minimises noise, vibration, and spoil. There are many potential applications, including foundations, underpinning, resisting uplift, dynamic/cyclic load applications and geothermal installations. The SDM technology were introduced to India first time in the Indian history and utilised in the 4G and 5G network projects. The SDM challenge the traditional cast-in-situ piles in the 4G project and raft foundations in the 5G project. Utilisations of the tensile and the compressive strength capacity of SDM with smart solutions results in noticeably big costs, 17-38 % depending on the soil conditions and time savings. The cost of the SDM solutions was about 40% less than the cast-in-situ piles and raft foundations in an ongoing 5G project. The SDM were used successfully in the liquefiable soil types as well.

Nov 1, 2022

By B. Pesic

This is an extension of the work on recovery of silver and manganese from Ag-Mn ores, and recovery of silver and gallium from flue dust from phosphate industry. Carbon adsorption was considered as the most adequate method for recovery of silver from thiourea leach solutions. For this reason it was decided to examine the characteristics of adsorption of silver on activated carbon. Coconut hard shell activated carbon was used for this study. Ag(TU)2C1 complex was dissolved into thiourea solution to give 2 gpl stock solution. Thy studied parameters were: loading isotherms at 25°C, 35°C, and 45°C, initial kinetics as a function of thiourea concentration, temperature, pH, N2, and O2. It was found that the loading capacity of carbon for silver and thiourea was 137-150 mg/g and 514 mg/g, respectively, at 25 °C.

Jan 1, 1986

NEW YORK SECTION ALLEN H. ROGERS, Chairman, H. C. PARMELEE, vice-chairman, FOREST RUTHERFORD, Vice-chairman, W. S. DICKSON, Secretary, 71 BROADWAY, NEW YORK, N. Y. J. E. JOHNSON, JR. F. T. RUBIDGE, Treasurer, P. G. SPILSBURY A meeting of the New York Section was held at The Machinery Club on Friday evening, Oct. 4, 1918, The Chairman, Allen H. Rogers, presiding. The CHAIRMAN.-MOST of us, I suppose, have been affected more or less by The request of The Fuel Administration that we leave our automobiles standing in The garages on Sundays. We shall all be interested in hearing about The situation that has called forth This, request, and The Oil Administrator, Mr. Requa, has kindly come from Washington to Tell us about it. MARK L. REQUA.-I am very glad To Tell you about the oil problem during This war period. The United States is supplying by far The greater part of all The petroleum products consumed in Great Britain, France and Italy. In addition To This, we have had To supply a marked increase in our domestic consumption, not only of The refined products, but of fuel oil as well. The combination has put a strain on The oil industry, which it is very difficult To meet. The oil companies, being under contract, had no option as To who should get Their oil first, and They were delivering pro rata To everybody; manufacturers of furniture were getting oil with The same regularity as Those who were making aeroplanes or munitions, and The oil companies felt that something should be done. The first order with which I had. anything To do was The priority list for The delivery of fuel oil. That list contained 12 classifications, beginning with bunker fuel and railroads, and you will realize The complexity of The situation when you hear that munitions plants are in class 11. The priority list held during The winter, but transportation became so bad, because of The number of ships that were Taken for trans-Atlantic use, that some of The oil companies were not able To deliver more Than about 60 per cent. into class 5, and nothing beyond that point. To add To the Troubles, the Tank-car mileage fell off. The average for 1917 was about 36 miles per car per day. in January, 1918, it dropped To about 8 miles, and it must have been nearly zero in The early part. of February. Because of The extremely severe winter, furthermore, pipe lines were not delivering anywhere near Their normal capacity. A new priority list has recently been promulgated, introducing a few slight changes. Natural gas has been brought under its provisions, and it has been extended To include The Pacific Coast, which was not considered necessary last winter. The situation in The gas industry is not satisfactory; it is estimated that There will be a decrease of 10 To 20 per cent. in The quantity of natural gas available This winter, as compared with last winter.

Jan 11, 1918

By Felipe Sombra dos Santos

Este trabalho tem por objetivo principal sintetizar e caracterizar nanopartículas de ferro de valência zero (nFVZ) para degradação de substâncias recalcitrantes, através de Processos Oxidativos Avançados. A primeira etapa consiste na sintetização nFVZ, através da reação utilizando reagentes ferrosos, com o agente redutor borohidreto de sódio, em condições controladas (pH, temperatura e velocidade de agitação do sistema). Agentes complexantes e dispersantes, como o ácido cítrico e o etilenoglicol, respectivamente, foram utilizados durante a sinterização para avaliar a variação da formação do tamanho das partículas obtidas. A caracterização foi realizada através dos ensaios de distribuição de tamanho de partículas, microscopia óptica interfacial e microscopia eletrônica de transmissão (MET). Foi observado que a concentração de ácido cítrico de 0,009 mols e o volume de 100 mL de etilenoglicol, mostraram-se como os melhores valores obtidos. Todavia o ácido se tornou um interferente na reação ao ser utilizado com o SDS. Os resultados da microscopia eletrônica de transmissão comprovam que as partículas obtidas estão na escala nanométrica.

Aug 16, 2017

By A. L. Coello Velázquez

The subject of this paper is particle population balance models (PBM) that describe mineral impact crushing behavior; it is mainly concerned with the selection and fragmentation distribution function due to their importance in this context. The data obtained by Datta (1999) by applying impact pendulum testing to single limestone particles, used by Austin (2002, 2004a and 2004b) to obtain the principal parity of fragmentation functions, were processed in order to compare them with the results of other authors, such as Nikolov (2002 and 2004) and Vogel and Peukert (2003 and 2005) so as to increase knowledge of impact crushing. From this data it has been possible to obtain the performance models of the principal parameters of fragmentation function, thereby reducing the number of experiments necessary to model the impact crushing process. The authors also propose a simplification of the selection function model posited by Austin (2002).

Jan 1, 2011

By Gary Peach, Peter Mason

Planning and estimating progress rates and costs for tunnelling is always best done based on experience and historic precedent. Much precedent is available but the use of data monitoring, data mining and other retrieval techniques on modern TBM machines can enable this to be further expanded and refined. Advance rates can be related much more closely to rock types as can associated rock bolt and mesh/ shotcrete requirements. This in turn can lead to a further refinement in best likely combinations of equipment, such as shotcrete jumbos, better selected for the anticipated conditions, rather than the potential advance rates of the machine. Efficient and timely construction of the tunnel will also be linked to times needed for finishing work, such as contact and void grouting and to how this can be initiated while the TBM is still in operation, in order to save overall construction time. Indeed, this in turn may affect the most preferable layout and construction details of the permanent tunnel. Considerable experience has been gained in the use of two large diameter TBM tunnel drives through the Himalayas at the Neelum-Jhelum hydropower project in Pakistan. All the above aspects will be discussed in the paper based on the considerable experience and data which came from that operation, including appropriate measures in highly stressed areas potentially subject to rock burst.

Jun 13, 2021

By Soumitry J. Ray

Poor visibility of powered industrial vehicles, such as forklifts, used in industry is often the cause of accidents that include pedestrians. Current standards allow up to 20 % non-visible regions for forklifts where measurement of these regions is performed by using lamps. A collaboration of research organizations, including National Institute of Standards and Technology, Georgia Institute of Technology (NIST), and Direct Dimensions, has been evaluating advanced methods for measuring a forklift operator?s visibility. These methods can potentially improve visibility standards. They can also help forklift and sensor manufacturers to determine (1) how visibility-assist sensors and algorithms can be designed and (2) where sensors can be mounted on forklifts. This paper includes explanation of visibility measurement experiments performed and results, associated language suggested to standards organizations, and a prototype design for measuring the visibility of forklifts automatically.

Aug 1, 2013

By Carl-Oscar Nilsson, Åke B. Nilsson

"The embankment dam at Storfinnforsen is 23 m high and was completed in 1954. The dam has an impervious zone with timber sheet piles and a support fill of glacial till. The pore water pressure in the downstream shoulder has during recent years increased due to deterioration in the sealing function of the timber sheet piling. There is a concern that the high pore water pressure in the glacial till will cause internal erosion initiating at a thin coarse transition layer between the glacial till and the rock fill along the downstream toe. As a remedial action in order to improvement of the leakage resistance a supporting berm of coarse rockfill against the downstream slope of the dam was constructed in year 2013. In addition a new impervious seal in the centre of the dam e.g. a diaphragm wall was considered. However, after further studies and a trial stretch of 40 drains each 20 m long and diameter 0.3 m an alternative with vertical drilled drains in the downstream support was selected. A contract has now started up to drill in a similar way to treat the full length of the dam with drains. The work is in the planning to be completed in 2016.Dam ConstructionStorfinnforsen Embankment Dam was put into operation in 1954. The dam is 330 m long and maximum height is approximately 23 m. The dam is constructed with a central core zone and supporting zones of earth and rockfill on the upstream and downstream sides giving an almost symmetrical cross-section about the dam axis, see Fig. 1. The upstream slope is 2H:1V down to el. 270 and 2.5H:1V below. On the downstream side the slope is 1.75H:1V down to +269 and 2H:1V below. The core zone consists of a timber sheet pile wall with a Zone 5 of glacial till, approximately 2 m wide, adjacent to the wall on the upstream side."

Jan 1, 2016

By João Veludo, Eduardo Júlio, Helen D. Robinson, Jesús E. Gómez

"Utilization of micropiles for structural retrofit requires connection of the micropiles to the footings of the existing structure. Almost ten years ago, an experimental research effort was carried out in the US to investigate the magnitude and mechanism of development of the bond strength between micropiles and existing concrete. The study resulted in important conclusions on the mechanism of connection capacity development and provided specific recommendations for practical design of micropile-to-footing connections. In the last five years, the original study was complemented by an intensive experimental effort in Portugal aimed at answering many of the questions still remaining on this topic. This paper is a summary of the knowledge that is presently available on the capacity of micropile-to-existing footing connections. It presents the results and observations of model tests performed in the US and Portugal, as well as some tests from actual construction sites. The paper presents clear evidence that friction may be the most important component of connection capacity. It also presents a clear correlation between confinement and connection capacity.IntroductionUtilization of micropiles for structural retrofit requires connection of the micropiles to the footings of the existing structure. This is often accomplished by drilling through the footing and developing the connection by direct bond between the micropile grout and the existing concrete. Almost ten years ago, an experimental research effort was carried out in the US to investigate the magnitude and mechanism of development of the bond strength between micropiles and existing concrete. Smooth and textured micropile inserts of varying lengths were tested to failure inside pre-drilled holes of varying diameters. That investigation led to several publications (Gomez et al. 2005, Wilder et al. 2005, Cadden 2009) on the mechanism of development of bond strength between micropiles and concrete, which included a chart for preliminary bond value selection depending on the diameter of the hole and texture of the micropile.An intensive testing program was carried out in Portugal in the last five years. The program focused on answering questions posed by the original investigation and on finding the relationship between connection capacity and level of confinement. Both investigations, and especially the testing performed in Portugal, provided an invaluable amount of information on the mechanisms of failure of micropile-to-footing connections. This information should be the basis for development of design procedures that, until now, were not available."

Jan 1, 2015

By Markssuel Teixeira Marvila

Este trabalho tem por objetivo avaliar a possibilidade de obtenção de revestimento cerâmico prensado semiporoso utilizando misturas, por via seca, de argila caolinítica com fonolíto. Foram utilizados traços contendo 20% e 40% de incorporação de fonolíto em peso em relação a massa cerâmica em duas granulometrias distintas (fonolíto passado na peneira #50 e #200). Para efeito comparativo, avaliou-se uma massa cerâmica industrial proveniente do polo cerâmico de Campos dos Goytacazes e uma massa cerâmica sem incorporação de fonolíto. Foram preparados corpos de prova por prensagem uniaxial calcinados em temperaturas variando entre 1050 a 1200º C. Nas amostras queimadas, foram realizados ensaios tecnológicos para determinação da retração linear, resistência mecânica (compressão diametral) e absorção de água. Os resultados mostraram que a adição de fonolíto reduziu a absorção de água da argila. Além disso, o incremento do teor de fonolíto e a redução de sua granulometria somente foram eficientes em temperaturas elevadas. Com isso, a incorporação de fonolíto a uma argila caolinítica pode possibilitar a obtenção de revestimentos semiporosos com parâmetros melhorados. Entretanto uma ressalva dever ser feita: há necessidade de incremento da temperatura final de queima em comparação com patamares utilizados por indústrias do polo cerâmico de Campos dos Goytacazes.

Oct 30, 2017

By Raimison Bezerra de Assis

Ferritas são compostos cerâmicos que apresentam propriedades magnéticas, sendo estas dependentes da sua estrutura cristalina. Dentre as ferritas, a do tipo Ni-Zn é uma das mais promissoras, em virtude da microestrutura e das propriedades magnéticas deste material. Este trabalho teve como objetivo analisar a microestrutura e propriedades magnéticas da ferrita Ni-Zn dopada com íons (TR) Sm3+. A ferrita Ni-Zn-Sm foi obtida pelo método dos precursores poliméricos, a partir da dissolução do ácido cítrico, nitrato de ferro, nitrato de níquel, nitrato de zinco, nitrato de samário e etilenoglicol. A resina obtida foi pirolisada a 350°C/2h com taxa de aquecimento de 10°C/min. e calcinada a 650°C/3h com taxa de aquecimento de 10°C/min. O material resultante foi caracterizado por difração de raios-X (DRX), microscopia eletrônica de varredura (MEV) e magnetometria de amostra vibrante (VSM). Os resultados mostraram a formação de fase única da ferrita Ni-Zn-Sm, com partículas aglomeradas e características magnéticas de material macio "soft", com baixa coercividade (0,189 kOe) e magnetização de saturação (47,699 emu/g).

Aug 8, 2018