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By Richard W. Hanford

The geotechnical construction industry generally considers soil mixing to be defined as an in situ ground improvement or treatment method by which a dry or wet reagent is introduced into the ground and is blended with the soil by mechanical or rotary mixing tools. This results in relatively homogenous mixtures whose engineering properties are improved and are greater than the soil properties before mixing. Reagents usually include cement, but may also include processed clay such as bentonite, when a reduction in hydraulic conductivity is desired, or other proprietary chemicals when chemical stabilization is the objective. Mixing may be either shallow or deep. Shallow Mixing is the term arbitrarily used for treatment of soils within the upper 30 feet; Deep Mixing denotes treatment below 30 feet to the depth limits of the equipment. Mixing equipment may consist of single or multiple-shaft tools having cutting and mixing blades of many different configurations. To avoid using proprietary nomenclature, reference to Shallow Mixing Methods (SMM) and Deep Mixing Methods (DMM) are the preferred terms. Although originally developed and patented in the United States in 1956, in situ construction using various soil mixing methods is more prevalent in Japan and the Scandinavian countries. Reintroduced into the United States from Japan in 1986 for ground improvement and liquefaction mitigation at Jackson Lake Dam, Wyoming, acceptance of soil mixing methods has been gradual but slow. Applications typically include:

Jan 1, 2001

By Lynn M. Gould

Syncrude Canada operates the largest oil sands crude oil production facility in the world and produces over 13 percent of Canada?s total oil requirements. To do this, Syncrude mines the oil sand in open pits, extracts the raw oil known as bitumen from the sand using water-based processes and upgrades it into sweet light crude oil by fluid coking, hydroprocessing, hydrotreating and reblending. The final product, Syncrude Sweet Blend (SSB) is sent by pipeline to three Edmonton area refineries and then to pipeline terminals which ship the SSB to refineries in Canada and the United States. As parts of the Mildred Lake Base Mine reached their economic life, they were replaced with new facilities at the Aurora satellite mine. Aurora is situated on Oilsand Leases 10, 12, and 34, 35 kilometres northeast of the Mildred Lake facility. (Figure 1) In 2000 the first hydrotransport low energy extraction production train started up at Aurora. A second production train is scheduled for start up in 2003. Open pit mining at Aurora occurs using two hydraulic shovels, two cable shovels, and trucks ranging from 320 ton to 380 ton payload capacities.

May 1, 2002

By Antonio Adel dos Santos

Visando elucidar o comportamento da carepa terciária durante a laminação de tiras a quente, em um aço produzido como laminado a quente e com rigorosa exigência de qualidade superficial, foi realizada uma parada forçada do laminador, impondo-se, imediatamente, um resfriamento rápido da superfície da tira. Amostras coletadas na região do arco de contato mostraram que a carepa possui espessura na faixa de 10 ?m a 14 ?m na entrada das cadeiras, sendo reduzida para 7 ?m com a deformação, sem ocorrência de ruptura. Tais características indicam que, do ponto de vista do comportamento no trem acabador, a carepa apresenta espessura e plasticidade adequadas para evitar defeitos nos produtos laminados. A carepa foi constituída predominantemente por Fe3O4, óxido plástico na temperatura de laminação. Foi desenvolvido e aplicado um modelo de crescimento da carepa, que forneceu valores de espessura muito próximos dos medidos, se tornando uma ferramenta útil para análise da influência de condições de processo na carepa.

Oct 30, 2017

By K. Oraee

Rate of penetration of Tunnel Boring Machines (TBM) has a significant role in the planning, measurement of productivity and performance of any tunneling project. In this paper, the application of Adaptive Neuro Fuzzy Inference System (ANFIS) in prediction of TBM penetration rate is evaluated. For this purpose, a database including Rock Quality Designation (RQD), Uni-axial Compressive Strength (UCS) of the rock, the Distance between Planes of Weakness (DPW) in the rock mass, and empirical data regarding rate of penetration of TBM from several tunneling projects are collected. The Rate of Penetration is then estimated by using ANFIS. These results are then compared with measured TBM penetration rates (actual data). It is concluded that ANFIS can be applied successfully for such purpose and result in high accuracy for prediction for the rate of penetration of TBM. The method provided in this paper can assist the mining engineer to estimate the performance of tunneling accurately.

Jan 1, 2012

By Henry John Luna Córdova

El presente trabajo describe el proceso de gestión de calidad en la administración de los derechos mineros a través de la automatización de procesos desarrollados por el Instituto Nacional de Concesiones y Catastro Minero (INACC) organismo público descentralizado del Sector Energía y Minas que administra el Procedimiento Ordinario Minero para el otorgamiento de Concesiones Mineras, el Catastro Minero Nacional y la distribución del Derecho de Vigencia a escala nacional. Entre otras funciones de dicha institución está la creación de una serie de base de datos numérica, que le han permitido optimizar dichos procesos en calidad. Así como en el aspecto de la administración del Derecho de Vigencia y Penalidad, se creó el software para automatizar sus procesos y efectuar el cobro respectivo en las entidades del sistema financiero nacionall. Finalmente en el aspecto catastral, se generalizó el uso de coordenadas UTM (PSAD56) para identificar los derechos mineros, asimismo, se crearon los parámetros de transformación de coordenadas WGS84 a UTM.

Jul 31, 2003

By Roger M. Buckeridge, Charles D. Reese, Silvio M. Martino, William T. Carey, Ansel H. Graham

FUNCTIONS OF RAIL HAULAGE SYSTEMS The principal application of rail haulage in under¬ground mining is in the movement of ore or coal pro¬duction from near the mining areas out to a processing plant. In some cases, such production haulage may end at a shaft pocket or slope belt conveyor transfer station, depending on the type of mine and the geo¬logical placement of the mineral being mined. Main-Line Haulage The basic reasons for choosing main-line rail haul¬age are high-tonnage production per shift and long haulage distances. The choice between rail and other systems, such as belt conveyors, is not easy and requires an integrated study of many factors: tonnage, distance, grade, product size, number of producing areas, ore reserve, safety, capital cost, operational and maintenance cost, and the mining system. Projecting a main-line rail haulage system for com¬parison with other systems requires a choice of many variables which are interrelated. The project must start with consideration of the mining system, tonnages per day, distances and grades, and loading and dumping conditions. Rail mine cars of different sizes and types are studied. High tonnage demands consideration of wider track gages. A suggested minimum for metal mines is 914.4 mm (36 in.); for coal mines, 1066.8 mm (42 in.). The choice of the train size should be governed by tonnage per shift, physical factors of loading and dumping, cycle time, and the number of trains that can be operated and safely controlled. After the size of the train is determined, the type, size, and specifi¬cations of the locomotive can be selected. The loco¬motive may be trolley, battery, or diesel; selection guides are discussed elsewhere in this chapter. The advantages of rail main-line haulage are high tonnage capacity, flexibility, reliability, safety, low operational and maintenance cost, and dual usage of the system (supply haulage, for example). The dis¬advantages are high capital investment, high installation cost, the requirement for more maintenance facilities, and restriction to certain ore reserves and mine pro¬jections. Supply Haulage Supply haulage is a basic requirement of any mine, but the type and volume of supplies vary with the type of mineral being mined, the mining methods, and the size of the mine. A mine developed for rail main¬line haulage gains supply haulage through the addition of a secondary track system to extend the main line closer to the producing areas. Additional haulage equipment, generally smaller, is also added. It is neces¬sary to design into the rail system more switch bypass points and train control systems. The track system standards demanded by rail main-line haulage con¬tribute to the reliability and efficiency of the supply haulage function, whereas a supply track system to supplement other haulage systems often suffers from poorer track and installation standards. When belt conveyors are chosen for production haulage, a rail supply haulage system is often installed rather than using rubber-tired vehicles for supply haul¬age. The conditions of the seam or ore body create these items for consideration: haulage grade of more than 6% favors rubber-tired vehicles; longer haulage distances favor rail; difficulty in maintaining a smooth roadway favors rail; and movement beyond the end of a rail system generally requires rubber-tired vehicles, making a single system rather than a dual system attractive. Although operation of a supply haulage system may be concentrated on a single shift of a multiple-shift mining operation, proper planning and supervision are required if the haulage is to be efficient. Often the newer personnel at a mine are assigned to supply haul¬age which may add to the difficulty of obtaining maxi¬mum efficiency. Supply haulage by rail offers the advantages of high reliability, lower maintenance, and high efficiency over long distances. The disadvantages are less flexibility, high installation costs, and rubber-tired vehicles for use beyond the inby end of track often required. Personnel Movement The efficient and comfortable movement of the miner to and from his work area has a significant effect on his daily output. Minimizing man-trip time also becomes more and more important as hourly wages increase. Personnel are generally moved over a rail system by one of three methods: a specialized personnel carrier to which a certain number of men who work in a certain area are assigned; a combination vehicle, used to carry personnel but also capable of being used as a light supply/utility locomotive during a working shift; and man-trip cars towed by a supply locomotive. The first and second methods are used in coal mines where long distances make speed and comfort important. The third method is more common in metal mines. Equipment Movement As mining equipment technology has advanced, many mining machines and their subcomponents have grown in size. This trend requires careful planning for adding specialized carriers to handle the movement of larger equipment. Continuous miners, longwall equipment, raise borers, and ventilation equipment are examples of machines which may be difficult to move and which require special handling. The selection of the weight, speed, and operating characteristics of supply locomotives used to move equipment is important. Larger mines may often justify a special group of loco¬motives for this application.

Jan 1, 1982

By K W. Bian, Y M. Liu

Tongkuangyu Copper Mine is currently the only mine in China employing block caving. It comprises two large orebodies known as the No 4 orebody and the No 5 orebody. They are approximately 50° in dip angle, 80 to 240 m in width and 800–1000 m in strike length. The two orebodies are separated by a distance of 110–130 m. Production with block caving originally, ie Phase 1 project started at Tongkuangyu from the first undercut at a depth of 200–300 m below the ground surface and designated as Lift 810 m in late 1989 and has continued to the present. During the last 25 years Tongkuangyu has mined three lifts: Lifts 810 m, 690 m and 530 m. The previous two lifts utilised a slusher process with an annual designed production rate of 4 Mt. In this context the lift name represents the elevation of track haul level.The Tongkuangyu Phase 2 project serves for two lifts (ie Lift 530 m and 410 m) under the elevation of 690 m and the annual designed production rate is 6 Mt. Since the orebody is approximately 50° in dip angle, it is originally designed that production at Lift 530 m is comprised of one main extraction level and two auxiliary extraction levels in the footwall and undercutting is started from one end of the extraction footprint forward to another end, which is from north-east to south-west.Production at Lift 530 m started from March 2011 and reached to 6.39 Mt in 2013 and 6.9 Mt in 2014. Additionally, Tongkuangyu improved block caving processes and used modern mining equipment, which differ from the previous two lifts. Blastholes for undercutting and drawbell-preparation are now drilled using jumbos. The blasted ore is transferred to the underground crushing station via 10 t electric load-haul-dumps (LHDs) and then delivered to surface via a belt conveyor 3200 m long.Due to increasing ground pressure, a consequence of mining depth increase, stress abutment and inadequate support, significant damage occurred at the Tongkuangyu Copper Mine with production at Lift 530 m. This resulted in significant production delays and rehabilitation costs. A series of improvements have since been implemented including an advanced undercut sequence and increased ground support. All of these improvements have allowed Tongkuangyu to alleviate ground control issues, reduce operating costs and ensure safe production.CITATION:Liu, Y M and Bian, K W, 2016. Production at Lift 530 m of Tongkuangyu Copper Mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 385–392 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Donald J. Ninteman

This Bureau of Mines publication is a literature study of the problem of spontaneous oxidation and combustion of sulfides in underground mines. It summarizes the present-day hazards, process mechanisms, and prevention and control techniques of this growing problem in underground mines. The iron sulfides generally have the greatest tendency to oxidize, particularly pyrrhotite. The presence of moisture and oxygen is essential for the oxidation reaction. Highly fractured sulfides, when found with timber or combustible refuse in slowly circulating air, pose the most serious fire hazard. Quenching with water is effective in quickly dealing with local hot spots, but ventilation at high flaw rates is the most effective and economical means for long-term prevention and control.

Jan 1, 1978

By H. F. Yancey

Traditionally the Pacific Northwest has relied on hydroelectric power, which has been both abundant and cheap. However, comparatively few hydroelectric sites capable of providing low-cost power remain, therefore the need for supplemental thermal generation, perhaps within the next decade, is generally recognized. Based on the present cost and availability of competing fuels, coal seems to be the logical choice for projected thermal power plants. Power companies and public utilities have become interested in establishing reserves of coal for future use. One deposit explored in 1958-59 lies in southern Thurston and northern Lewis Counties, Wash., near Centralia. Drilling, totaling 22,700 feet, proved the existence of 70 million tons of strippable coal--an ample reserve for the projected power plant. The coal, like most others and particularly those of Washington and Oregon, when mined in full seam section by mechanical methods, would require cleaning to make it suitable for use. The amount and nature of the impurities in this coal dictated a thorough investigation of its cleaning characteristics to establish economic factors and to insure proper preparation-plant design. Therefore, arrangements were made through a cooperative agreement to conduct such work at the Seattle Coal Research Laboratory of the Bureau of Mines. This report describes that investigation. The results are of interest primarily in connection with the utilization of this particular deposit, but some of the information developed is applicable to other deposits of low-rank coals in the West, because the impurities in these coals differ greatly in behavior from those generally associated with the higher rank coals of the Appalachian field.

Jan 1, 1961

By Alice H. Zhu

Belt conveyors are widely used in materials handling industries. The bulk materials which can be transported include ores, coal, earth, grain, limestone, wood chips, fertilizer components such as potash and many others. Along with the new technology development and enhanced industrial automation requirements, belt conveyor instrumentation has also been modernized to improve conveyor availability and performance. Traditionally, belt conveyors are equipped with emergency pull cord switches to shut the conveyor down, misalignment switches to signal the belt offline condition, speed sensors to detect the belt slippage, and level switches to prevent material plugging in the discharge chute. Belt rip detectors are also normally provided for long belt conveyors. As a rule, equipment condition monitoring is not automated at most operating facilities, but is performed manually by maintenance staff via time-based surveillance. The new generation of condition monitoring instrumentation and control equipment can be successfully utilized to design a reliable, cost-effective, and centralized monitoring system, capable of monitoring a wide variety of mechanical equipment. The implementation of the condition monitoring automated system can provide continual monitoring of the plant equipment to ensure safe operation of the equipment to its required capacity. Any abnormal behavior of the motors, gear reducers and pulleys can be analyzed, alarmed, and recorded immediately, so problems can be detected and resolved before critical components failure. Therefore, the current trend is to provide the belt conveyors with condition monitoring system in addition to the traditional instrumentation, where temperature probes and vibration sensors can be installed on motors, gear reducers and all pulleys. Another innovative development is a three-in-one type belt rip detector which combines laser, tray and cord type detection together to ensure a prompt belt tear indication. The purpose of this paper is to present the latest development of belt conveyor instrumentation and introduce the application of newly developed instruments.

Nov 1, 2011

By Richard E. Danell

"There are a variety of approaches for wall control blasting in open pit mining operations. Safety forworking in the pit is the principal benefit. There are also a number of economic and productivitybenefits when appropriate techniques are used. The purpose and requirements of wall control blasting can vary quite significantly for different operations. When considering blast design, geology, geotechnical factors, drilling, explosives, economics and blasting history are all part of the engineering design process. In many operations, there is a high reliance on blasting history and economics for determining wall control blasting measures. This presentation outlines approaches that broaden the design process and discusses their advantages."

Jan 1, 1997

By K Niiranen

Luossavaara-Kiirunavaara AB (LKAB) operates one iron ore mine, three concentration plants and three pelletising plants in Kiruna, Sweden. The current methods of separation at the beneficiation plants are low intensity magnetic separation (LIMS) and reverse apatite flotation, where the wet LIMS stage is regarded as the crucial part of silica separation from the ore. Because future silica levels are expected to increase in the incoming material to the beneficiation plants, geometallurgy has become an important area of development and research.A laboratory-scale methodology was developed for the systematic characterisation of the ore for mineral processing, with the focus on the high silica ore type B2 and newly discovered subtypes. This methodology combines mineralogical, geochemical and process mineralogical characteristics. Automated mineralogy (QEMSCAN®) is used to study the modal mineralogy, the distribution of silicate minerals in different particle size classes after comminution, the deportment of silicon (Si) between various silicates and the degree of liberation and intergrowth of magnetite and silicates. An essential stage in the systematic characterisation of the ore deposit for mineral processing is the estimation and simulation of different parameters from the laboratory scale to the full scale at the concentration plants. This is achieved by using empirical models based on the data collected at the mineral processing plants. As the first step to implement the geometallurgical information, the current geological model is reconstructed with the mineralogy and the two, newly defined subtypes of high silica ore type B2 are separated into different domains.To study the reduction of the SiO2 content in the magnetite concentrate, a large-scale reverse cationic silicate flotation laboratory test program was initiated in early spring 2016. This program investigated potential silicate flotation in the beneficiation plants at the Kiirunavaara site. The second target is to implant mineral processing parameters into the block model based on the new geological model. This information provides a good basis for making a prognosis for mine planning and a quality prognosis regarding the crude ore for mineral processing.CITATION:Niiranen, K, 2017. A geometallurgical perspective on a high-grade iron ore deposit at Kiirunavaara, northern Sweden, in Proceedings Iron Ore 2017, pp 309–318 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Gary Choate

The work presented in this report represents the background activity which led to the fabrication and testing of a greenhorn and crowd limit switch system for electric shovels. The program began With a literature search and manufacturers product review to gather material as a basis for concept generation. Visits to three open pit mines provided information from operation and maintenance managers which was useful in preparing design concepts. These concepts were evaluated through laboratory tests and engineering analysis to select a final design concept. The resultant greenhorn is four separate shock absorbing pads each enclosed in a housing which bolts to the end of a dipper handle adaptor. The plungers impact against stops mounted to the saddle block. The crowd limit control is a nonmechanical device which senses the location of the dipper and makes appropriate commands to the crowd motor to insure against impacting the greenhorns. The electronic crowd limit control is redundant and indicates malfunction modes. The greenhorn prevents shovel damage in the unlikely event of impact.

Jan 1, 1983

By Michael S. Miller

In 1987 and 1988, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied the 3,100-acre Borah Peak Wilderness Study Area (10-047-004) and a 708-acre parcel adjacent to the north in order to evaluate their identified mineral resources. The study area is located in Custer County, ID, about 18 mi northwest from MacKay. The study area lies along the western foothills of the Lost River Range and is underlain by quartzite, sandstone, shale, argillite, dolostone, and limestone. The Lost River fault, a major active fault, lies along the length of the study area. Large alluvial fans spread out from valleys originating east of the study area.

Jan 1, 1989

By Christoph Müller

Information exchange for mine process optimization is essential. Today, modern mining equipment uses the IREDES standard to exchange production plans and reports for easy management and storage. To gain further benefits from process optimization, a mine wide access to real-time information is needed as e.g.: The current status of a machine, operational details etc. Presently, real-time data exchange systems are developed by machine producers. Each machine producer uses its own way of gathering, managing, and storing production data. These proprietary mining processes increase the complexity of cross platform data exchange and management for mines which involves machines produced by different vendors. Casting and unifying the data requires much effort. For this purpose, ?IREDES On-line? currently is being introduced. The standard defines an open, web based method for the exchange of volatile real time machine information. Two different principles are used: Web Services for cross platform information exchange within the IT world and the optional OPC UA for use with automation and process control systems. With such a standard information from machines of different vendors may be managed by using one common platform without spending the effort for dedicated interface development. Additionally, information management and storage will become straight forward since all the data are of the same format. The IREDES On-line standard utilizes the latest IT technologies as well as the knowledge and experiences gained from the previous IREDES standard. The paper explains the benefits, the use, as well as the technical design of the standard and gives application examples from the practice.

Oct 1, 2009

This paper presents an initial investigation into the viability of co-kriging the grades of multiple mining cuts in a two dimensional, thin reef scenario. Deposits with gradational mineralized zones, in the perpendicular sense, are not as well served by the use of reef accumulation and thickness as deposits characterized by a sharp distinction between ore and waste rock. South African Bushveld Complex platinum deposits and Witwatersrand gold deposits are examples of this distinction. The calculation of an optimal mining cut is of paramount importance in the mining of Bushveld platinum. Two-dimensional kriging of a constant stoping width mining cut is an effective method for resource calculations once a cut is decided, but this begs the question of how to decide on the cut. Comparison of multiple cuts is used as a way of achieving this decision on many of Anglo Platinum’s operations. Although the kriging of each cut is valid in isolation, occasional negative values occur when incremental grades between overlapping cuts are calculated. Negative incremental grades cannot reflect reality. They are thought to be related to the inability of the method to include the strong continuity in the perpendicular direction demonstrated by the relevant variograms. Co-kriging of related variables has been investigated as a potential means tore impose this inherent order relationship. Various co-kriging options have been investigated. The method has been tested on a real data set from an established platinum operation. One of three types of anomaly has been investigated so far. The results show that co-kriging the mining cut grade as the primary variable, with just one secondary variable, the reef thickness, eliminates most occurrences. Severe anomalies remaining are arguably indicative of population mixing and might be more effectively treated by rezoning the data. Aim—To investigate the viability of co-kriging the grades of multiple mining cuts as a method for resolving anomalies in the estimation of such cuts on Bushveld platinum deposits, with applicability to other thin reef type deposits with a gradational not sharp cut-off between ore and waste in the direction perpendicular to the reef. Keywords: co-kriging, cross variograms, ordinary kriging, platinum, two-dimensional, grade profile

Jan 1, 2003

By M Ridd

The Pasminco Century Mine (PCML) is located 250 kilometres north-north-west of Mt Isa in Queensland. As one of the worldÆs largest zinc mines, PCML comprises mining and milling operations at Lawn Hill, concentrate filtering and shipping facilities at Karumba in the Gulf of Carpentaria, and a 304 km slurry pipeline connecting the two operations.Mineralisation at Century occurs in the upper part of the Lawn Hill formation and is comprised of siltstones, shale and sandstone. Pyrite occurs immediately above the mineralised sequence, and throughout the footwall carbonaceous shale forming the lower proportion of the deposit. Zinc predominantly occurs as sphalerite (ZnS) and lead as galena (PbS). These sulfides are very fine-grained and may oxidise rapidly upon exposure. The pyrite, sphalerite and galena are the main potential sources of acid rock drainage (ARD) or heavy metal leachate at the mine site.To minimise the generation of ARD in the waste rock dumps, they are constructed in a specific manner and waste rock is classified into the following three classes based on competence and acid forming/consuming capabilities:Class 1: Competent rock, non-acid forming or acid-consuming material. Class 2: Non-competent, non-acid forming or acid-consuming material. Class 3: Acid-forming material. The generalised Waste Rock Dump Design for current operations comprises an outer zone of Class 1 material and inner zone with Class 2 and 3 material. Limestone is the Class 1 material used for both its structural support and acid neutralising capacity. Reserves of limestone at the mine site are limited. Net acid generation (NAG) tests confirm that a mix of limestone and shales can be net acid consuming.Field based and laboratory based trials have been established at PCML to quantify blending levels of limestone and shale that will produce leachates both neutral in pH and low in metal/salt concentrations. This paper will discuss the first six months results (of a two-year sampling program) from the trials.

Jan 1, 2004

By C. M. Smith

HOWARD N. EAVENSON, acting for the last time as president of the Institute, presided at the annual business meeting on Tuesday afternoon at 4 o'clock. He spoke briefly of his visits with Local Sections last fall, and read a scholarly address on "Mineral Fuels and Civilization," scheduled for early publication in these columns. Karl Eilers presented the Treasurer's report, showing last year's income to be $134,967.44, compared with expenses of $133.266.51. Comparable figures for 1933 were $121,689.90 and $115,462.60. The Institute's peak income was in 1923 about $208,000. Newell G. Alford read the report of the Membership Committee showing 750 new members elected and placed on the rolls in 1934, compared with 328 in 1933. Losses by resignation last year were 81, compared with 262 in 1933; and 691 were suspended for non-payment of dues, compared with 747 the year before. Total membership, including 579 Student Associates, was 7742 at the end of 1934. Applications for membership have been coming in freely the last few months.

Jan 1, 1935

By Belmira Benedita de Lima

Estudos no sistema Nb-B mostram a fase Nb5B6 com formação peritética a partir do líquido, porém sua estabilidade abaixo de 2.000°C não é comprovada experimentalmente. Há também dúvidas sobre a ocorrência da fase Nb2B3 neste binário. Este trabalho tem como objetivo o estudo da estabilidade das fases Nb5B6 e Nb2B3 nas temperaturas de 1.400°C e 1.800°C. Amostras com composições nas estequiometrias Nb5B6 e Nb2B3 foram produzidas através de fusão a arco assim como confeccionadas a partir de misturas de pós de B e NbB. Pastilhas com composição Nb5B6 foram produzidas com e sem adição de semente da fase Nb5B6. Os tratamentos térmicos em 1.400°C foram realizados por até 10h enquanto aqueles em 1800°C por até 1h, todos em atmosfera estática de argônio. As microestruturas das amostras, tanto no estado bruto de fusão como após tratamento térmico, foram caracterizadas por difração de raios X (XRD). Os resultados confirmam a formação fase Nb5B6 a partir do líquido e nas amostras produzidas via metalurgia do pó. A fase Nb2B3 não é observada nas amostras no estado bruto de fusão e nas amostras produzidas via metalurgia do pó tratadas termicamente a 1.800°C, porém, esta fase se estabiliza nas amostras produzidas via metalurgia do pó tratadas a 1.400°C, indicando sua estabilidade com formação peritetóide a partir das fases Nb3B4 e NbB2, abaixo de 1.800°C.

Aug 8, 2018

By J. Katzur

Recently in Germany, novel artificial humus in combination with water-storing hydrogels has successfully been tested as soil improving material in pot experiments. The novel artificial humus (NOVIHUM®) is derived from lignite through oxidative ammonolysis. The product contains c. 5.5% nitrogen. Using NOVIHUM® as fertiliser, variable amounts of the contained nitrogen are gradually available to the plant, depending on the hydrolysis rates of the different N-compounds. NOVIHUM® is a unique combination of long-term fertiliser and stable humus. The tested hydrogel is a polyacrylate/poly-amide copolymer, which is able to improve the water holding capacity of the soil and to retard significantly desiccation. In May 2000, in Germany (Aue region), an experimental site was set up under extremely difficult growing conditions for trees (Quercus petraea) on a uranium spoil pile of the mining company WISMUT Ltd. The oak plots treated with NOVIHUM® and hydrogel showed increased total increment-values, which mainly are the result of the second growth phase. Obviously, these plants profit from the favourable physical parameters of the substrate and the use of the novel artificial humus as nitrogen source. The oak trees can better use the plant-available NH4-nitrogen released from the artificial humus during the planting year. In Greece, an experiment was set up in December 2000 aiming to the afforestation (Pinus nigra, Abies cephalonica) of a bauxite spoil pile of SILVER & BARYTE ORES MINING Co. S.A., on the Parnassus Mountain. The scope was to demonstrate, that the above soil improving materials are also appropriate for the recultivation of sites under extreme climatic and orographic conditions. The first results revealed, that where NOVIHUM® and hydrogel were combined, plant growth was greater than the average. The one-year results of the experiments fulfil our expectations concerning the application of NOVIHUM® in combination with hydrogel for the afforestation of problematic sites, such as the south-exposed steep slopes of the spoil piles of uranium mining. They may represent the most detrimental sites for afforestation in Europe.

Jan 1, 2002