bluuebunny/crossref_metadata_2025 huggingface dataset:
Method of Surface Treatment of Carbon Fiber and its Evaluation
Authors: Wang Xiao Chu , Zhou Le , Wang Jun Wei
Published: October 2013

In order to improve the tensile strength and crack resistance of carbon fiber reinforced concrete, enhance the bond strength of carbon fiber and concrete, and improve the durability of concrete component, this article describes the basic methods and study progress of carbon fiber surface treatment. At the same time, the advantages and disadvantages of various methods are analyzed. The effect of oxidation is more obvious than its of non-oxidation, but the method of the oxidation require more complex conditions, and it is suitable for industrial production of sound equipment, and it need for strict control conditions; the method non-oxidation is used after the oxidation of carbon fiber, then the effect will be more better than the effect of without oxidation. Increasing the surface roughness of carbon fiber and improving the toughness of concrete lay a theoretical foundation for practical application of carbon fiber.
Effect of Exogenous Galactose on EPS Production during Bioleaching of Pyrite by Acidithiobacillus ferrooxidans
Authors: Pavez Beatriz , Saavedra Albert , Diaz Mauricio , Gentina Juan Carlos
Published: October 2013

Extracellular polymeric substances (EPS) play an important role in the attachment of bacteria to sulphide minerals, biofilm formation and efficiency of the bioleaching process. Previous studies have suggested a potential connection between galactose and EPS formation. In this context, the influence of exogenous galactose on EPS formation during the bioleaching of pyrite was studied. In order to fully adapt the microorganism to bioleaching conditions it was performed a total of five consecutive sub cultures, one every fifteen days, taking for each one inocula from previous culture in shake flasks with 200 ml of fermentation medium at 30°C, 200 rpm, 40 gL-1 mineral and an initial pH of 1,8. Assays were performed in a medium supplemented with exogenous galactose (0.25% w/v) and without exogenous galactose (control), both with an initial concentration of ferric sulphate in the first three sub cultures of 5 gL-1, decreasing in the last two sub cultures to 2.5 gL-1. Samples of three cultures in both conditions were analyzed using confocal laser scanning microscopy (CLSM) labelling the cells with propidium iodide and EPS carbohydrates with Wheat Germ Agglutinin (WGA). Samples obtained on the last day of the fifth culture showed that the EPS layer on the particle surface was 5.00 μm3/μm2 in the case of the control condition and 6.10 μm3/μm2 when bioleaching was carried out in the presence of exogenous galactose. Also it was observed that in the fifth sub culture the volumetric productivity of total iron in the control experiment was 0.0065 gL-1.h-1 compared with 0.0076 gL-1.h-1 obtained in presence of galactose. The results reveal that the presence of galactose in the bioleaching solution stimulates EPS's formation and apparently also favour the pyrite bioleaching process.
Physiological, Genomic, and Proteomic Characterization of New “Ferrovum” Strains Obtained from a Pilot Plant for Mine-Water Treatment
Authors: Schlömann Michael , Kipry Judith , Mosler Sophie , Poehlein Anja , Keller Andreas , Janneck Eberhard , Erler Beate , Tominski Claudia , Jwair Rawaa Jaffer , Gelhaar Nadja , Seifert Jana , Daniel Rolf , Mühling Martin
Published: October 2013

Ferrovum is a recently found new genus of acidophilic iron-oxidizing bacteria.Ferrovumspp. dominate the microbial community of a pilot plant for biological mine-water treatment and together with someGallionellarelatives appear to be key players of the process. Isolation ofFerrovumstrains should greatly be facilitated by a new APPW medium. Sequencing of the genome ofFerrovumsp. JA12 so far did not point to any alternative electron donors and also did not reveal genes for nitrogen fixation.
How the RegBA Redox Responding System Controls Iron and Sulfur Oxidation in Acidithiobacillus ferrooxidans
Authors: Moinier Danielle , Byrne Deborah , Amouric Agnès , Bonnefoy Violaine
Published: October 2013

Valuable metals as well as ferrous iron and sulfur compounds are released from ore by ferric iron and sulfuric acid chemical attack. Biomining microorganisms allow the recycling of these products by oxidizing ferrous iron and/or sulfur compounds. The energy released from the oxidation of these substrates is used for the growth of the acidophilic chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans. The respiratory pathways involved in these respiratory processes have been deciphered and the expression of the genes encoding these redox proteins is dependent on the electron donor present in the medium. Furthermore, in the presence of both ferrous iron and sulfur, the genes involved in iron oxidation are expressed before those involved in sulfur oxidation. We propose that the global redox responding two component system RegBA is responsible for this regulation since (i) the redox potential increases during iron oxidation but remains stable during sulfur oxidation and (ii) the transcriptional regulator RegA binds the regulatory region of a number of genes/operons involved in iron and sulfur oxidation.
To understand the mechanism of the At. ferrooxidans RegBA system, the regA gene and the DNA corresponding to the DNA binding domain of RegA were cloned in an expression plasmid in Escherichia coli. The recombinant proteins, RegA and RegA-HTH respectively, were purified. The binding of RegA-HTH, phosphorylated and unphosphorylated RegA on the regulatory region of some target operons have been compared by gel shift mobility assay.
Two-Stage Airlift Bioreactor System for Efficient Iron Oxidation and Jarosite Precipitation
Authors: Kaksonen Anna H. , Morris Christina , Hilario Felipe , Rea Suzy , Li Jian , Usher Kayley , Wylie Jason , Ginige Maneesha P. , Cheng Ka Yu , du Plessis Chris
Published: October 2013

Continuous high-rate iron oxidation and removal of jarosite precipitates from solution at low pH and ambient temperature and pressure was successfully demonstrated. The bio-catalysed iron oxidation and jarosite precipitation is promising as a unit process for a variety of hydrometallurgical process flow sheets, where it allows for iron removal from ferrous solutions without the requirement for chemical addition and with negligible base metal co-precipitation losses. The process demonstrated performance that could be used in a large scale industry unit. A two-stage airlift bioreactor (ALBR) system comprised of two ALBRs, each with its own settler, was operated for iron oxidation and precipitation at room temperature with a mixed culture of mesophilic iron oxidisers. The two-stage reactor design allowed for optimization of overall reactor kinetics by facilitating the growth of low (430 mV vs Ag/AgCl) and high (517 mV) redox potential iron oxidizers in the respective reactors. The influent (pH 1.5) contained (g L-1) 15 Fe2+, 1.5 Cu, 1.5 Ni, nutrients and trace elements. The hydraulic retention time (HRT) was decreased stepwise to evaluate process performance. With the lowest HRTs (8 h in ALBR1 and 10 h in ALBR2), the overall iron oxidation and precipitation rates of the two-stage system were 0.75 ± 0.02 g L-1 h-1 and 0.15 ± 0.01 g L-1 h-1, respectively and overall iron oxidation and precipitation efficiencies of 94 ± 3% and 18 ± 1 %, respectively. The percent of influent Fe, S, Cu and Ni removed as precipitates from settlers were 30.9%, 16.7%, 1.1% and 0.2%, respectively. The precipitates were predominately comprised of (>95%) jarosite with potassium jarosite being the dominant form, followed by hydronium, ammonium and sodium jarosites. In conclusion, the two-stage ALBR system allowed efficient iron oxidation and precipitation of the oxidised iron as well settling jarosite with only minor loss of Cu and Ni via co-precipitation.
Bioleaching of Covellite from Low Grade Copper Sulphide Ore and Tails
Authors: Zepeda Victor J. , Cautivo Dina , Galleguillos Pedro A. , Soto José , Contador Yasna , Demergasso Cecilia
Published: October 2013

The economic importance of copper production in Chile has prompted the study of new strategies for the optimal management of mineral resources, including processing of low grade ore and even processing tails (processed ore). Currently, heap bioleaching is the most convenient technology to treat low grade copper sulphide ores bearing chalcopyrite, chalcocite and covellite. Covellite is a secondary copper sulphide occurring in copper sulphide deposits and it is also formed by acidic dissolution of chalcocite. In leaching processes, the main factors influencing the dissolution of covellite are the electrochemical potential (Eh) and temperature.This work aimed at assessing the effect of different concentrations of total iron (3.0 and 6.0 g/L) and temperatures (30 and 50°C) in the bioleaching of covellite contained in a low grade copper ore and the same ore after a previous process of bioleaching at ambient temperature. Initial composition of low-grade ore was chalcocite (0.58%), chalcopyrite (0.56%), covellite (0.30%) and pyrite (2.73%), while the processed ore contained chalcopyrite (0.47%), covellite (0.28%), chalcocite (0.10%) and pyrite (3.32%). Covellite was mostly dissolved (>90%) in both unprocessed and processed ore, independently of the temperature and total iron concentrations. However a higher total copper recovery was achieved in tests performed at 50°C due to higher dissolution of primary ores, especially in unprocessed ore. The microbial activity was confirmed by Most Probable Number (MPN) analyses of iron and sulfur oxidizing microorganisms. The microbial population was dominated by Acidithiobacillus spp. in tests operated at 30°C, while in tests operated at 50° Sulfobacillus spp. were the most abundant organisms.
Bioleaching of Spent Hydrotreating Catalyst by Thermophilic and Mesophilic Acidophiles: Effect of Decoking
Authors: Bharadwaj Abhilasha , Ting Yen Peng
Published: October 2013

Spent hydrotreating catalyst is a major solid waste from the petroleum industry. Although bioleaching of these wastes has been reported, research to date has focused on mesophiles. Bioleaching of industrial wastes by thermophiles has not been investigated. The bioleaching ability of thermophilic archaea Acidianus brierleyi was examined and compared with the commonly used mesophile Acidithiobacillus thiooxidans to establish the potential for high temperature leaching of spent catalyst. Spent Ni-Mo catalyst embedded in an alumina matrix containing substantial amounts of coke (i.e. carbonaceous deposits and volatile foulants) was used in this study. Decoking (i.e. removal of these deposits) as a pre-treatment and its effect on the leaching characteristics were examined. Spent catalyst is considered a hazardous waste since the toxic metal concentration exceeded the regulatory limit for land disposal and failed the toxicity characteristic leaching procedure (TCLP) test. Bioleaching with A. brierleyi and At. thiooxidans reduced the heavy metal leachate concentration to below regulated levels for safe waste disposal. Leaching efficiencies of 31% Al, 65% Ni and 44% Mo were achieved for coked catalyst using spent medium from At. thiooxidans. With decoked catalyst and spent medium from A. brierleyi, higher leaching efficiencies of 76% Al, 98% Ni and 93% Mo were attained. These results demonstrate the feasibility and the higher efficacy of spent medium leaching of decoked catalyst by acidophilic thermophiles.
Bioleaching of Sulphide Minerals with Sulfobacillus acidophilus at 45°C
Authors: Escobar Blanca , Bravo Daniela , Jaque Indira , Collari Aldo , Vargas T.
Published: October 2013

Copper sulphide ore bioleaching processes are currently under full development in Chile and worldwide, for treatment of: secondary sulphide in heaps [1], low-grade ores in dumps, and concentrates in reactors at high temperatures [2]. Abundant knowledge is available in the literature and great experience has been gathered about the behavior of mesophilic microorganisms and their application in bioleaching of sulfides in heaps and dumps [, as well as, about the behavior of extreme thermophilic microorganisms in reactors [. However, there is little information about the behavior of some moderately thermophilic microorganisms in the dissolution of chalcopyrite and pyrite at 45oC [. This is the case ofS. acidophilus, a gram-positive rod shaped that often forms endospores and grow at temperature optima, generally between 45 and 55°C. It has been characterized as a chemolithoheterotrophic bacteria that obtains energy from the oxidation of ferrous iron or from reduced sulfur compounds and that utilizes yeast extracts as a carbon source [.S. acidophiluswas isolated by Golovacheva and Karavaiko [ and described by Norris et al. [. Limited literature exists about its participation in bioleaching processes. In this work, we present experimental results obtained from the bioleaching of chalcopyrite and pyrite withS. acidophilusat 45°C, and compare them with those obtained withAt. ferrooxidansat 30°C.
Biomass Production and Inoculation of Industrial Bioleaching Processes
Authors: Parada Pilar , Morales Pedro , Collao Roberto , Bobadilla-Fazzini Roberto A. , Badilla Ricardo
Published: October 2013

Microbial activity inleaching processes accounts for 4% of today’s copper produced in the world. Factorsrelated with lesser overall metal recoveries, no recovery of precious metalsand molybdenum in comparison with conventional concentration/smelting &refining technologies and the high prices of metals inhibit the use of bioleachingat a larger scale. In order to increase bioleaching rates and overall metal recoveries,continuous inoculation of the ore with a leaching solution containing specific adaptedconsortium of microorganisms, allows an early expression of microbial activity,reducing 2-3 fold the time required by ore native bearing microflora to grow.This leaching solution concentrated in microorganisms can be produced by meansof bioreactors operated in continuous regime. Unfortunately biomining microorganisms have a very low duplication timewhen comparing to common microbes like E.colior B. subtilis, that forces the useof huge volume bioreactors in the case of conventional bioreactors, to ensurethe growth of microorganisms have sufficient residence time. To overcome thisproblem, we have designed a very efficient air-lift bioreactor (Patent Registration No. CL 48319), that can be used at industrial operations for the production ofsolutions with a high concentration of biomining microorganisms, for theinoculation of bioleaching heaps, with lesser residence time in comparison toconventional bioreactors. Ourbioreactor has an internal recirculation for producing sulfide-ore bioleachingsolutions, with a phase-separating and solids-recirculation system, without theneed to impel the suspension containing the solids towards the bioreactor withpumps, using diatomaceous earth, ferric precipitates and/or elemental sulfur asa solid support to immobilize iron and/or sulfur-oxidizing microorganisms. Dependingon the source of energy supplied for the growth of the microorganisms, thebioreactor can produce either a solution concentrated in ferric ions andiron-oxidizing bacteria or sulfur oxidizing bacteria. In order to validate ourbioreactor design at industrial scale, a trial was carried out in an air-liftbioreactor of 35 m3 nominal capacity, which is part of a biomassplant located in Radomiro Tomic Division of CODELCO. In this article, theresults of the test proving the advantages and satisfactory design of ourbioreactor for producing continuously iron-oxidizing bacteria and sulfuroxidizing bacteria for inoculation and irrigation of heaps and dumps are shown.
How Flexible are the Prokaryote Consortia in the Extreme Habitat of the Copahue Geothermal System?
Authors: Zurakoski Natasha , Giaveno Alejandra , Ulloa Ricardo , Lavalle Teresa Laura , Urbieta María Sofía , Donati Edgardo R.
Published: October 2013

Microbial consortia taken from an extreme environment were grown at different temperature and enrichment media. The consortia response to environmental changes was evaluated in order to investigate their metabolic flexibility. The molecular technique, DGGE (denaturing gel gradient electrophoresis) was carried out to evaluate the biodiversity. The results show that each consortium was able to grow according to the available resources, demonstrating their flexibility. A selective development was detected when growing conditions were similar to those found in the natural environment even though some species were able to grown even in conditions far away from those present in the sampling sites.
Immobilization of New Isolated Iron Oxidizing Bacteria on Natural Carriers
Authors: Vardanyan Arevik K. , Markosyan L.S. , Vardanyan Narine S.
Published: October 2013

The bioleaching of sulfide minerals by iron oxidizing bacteria are implemented by direct and indirect mechanisms. The direct dissolution of minerals is caused by the attack of sulfide ions by enzymatic system of bacteria. In the indirect mechanism the ferric ion from oxidation of ferrous iron serves as a leaching agent that reacts chemically with the minerals. The increase of ferrous ion oxidation contributes to the intensification of bioleaching process. On this purpose the immobilization of iron oxidizing bacteria on different organic and inorganic carriers (calcium alginate, carragiran, ceramic support, activated carbon, porous glass, etc.) has been implemented which allows to increase cell concentration. In the present work for the first time the native shungit, zeolit and their chemically modified forms have been used for immobilization of new isolated iron oxidizing bacteria of the genera Leptospirillum and Sulfobacillus. Efficient physico-chemical conditions for immobilization on the mentioned carriers have been developed. The ferrous ion oxidation by immobilized cells has been studied both in shake-flasks experiments and in the glass column using air-lift process. It has been shown that in both cases the rate of iron oxidation considerably enhances in comparison with free cells.
Underground Degradation of Lignite Coal Spoil Material by a Mixed Microbial Community under Acid Mine Drainage Conditions
Authors: Willscher Sabine , Knippert Doreen , Ihling Heiko , Kühn Denise , Starke Sophie
Published: October 2013

In a field study, biogeochemical processes in a large lignite coal spoil area with moderate AMD generation were investigated. Underneath this area, large amounts of groundwater are impacted by degradation and transformation processes of coal remainders in the former open pit mining area. An investigation was performed to find out the sources for the ground and surface water contaminations of larger areas.
Samples were taken from different places and different depths of the coal spoil area and were investigated for different metabolic groups of microorganisms. As a result, fungi are able to degrade humic matter in coal spoil heaps in a first step to oligomers. Other microorganisms do a further degradation of first intermediates in a commensalic community. Streptomycetes do a cleavage of lignocelluloses, strepto- and other actinomycetes also degrade cellobiose and xylose related parts of the humic coal spoil matter. The different members of the microbial community exist in different “floors” of the spoil area: fungi and most Actinomycetes prefer the oxic zone, whereas degraders of aromatic and heterocyclic compounds can also exist in the capillary and ground water zones; here more frequently Arthrobacter, Pseudomonas, Rhodococcus and Mycobacterium strains were detected. Ferric iron formed in biooxidation of pyrite seems to play an important role as a catalyst for oxic as well as anaerobic degradation of complex organic matter in the underground. A complex linkage between microbial Fe-, S-, C- and N-cycles was figured out on this site that induces a high and long-term impact on ground water contamination in this area.
Sulfate Removal from Extremely Acidic Wastewaters Using Consortia of Acidophilic Sulfate-Reducing Bacteria
Authors: Nancucheo Ivan , Johnson D. Barrie
Published: October 2013

A low pH sulfidogenic bioreactor, maintained between pH 2.8 and 4.0, was used to lower sulfate concentrations in two extremely acidic (pH 1.3 to 3.0) synthetic mine waters that contained ferrous iron but no other chalcophilic metals. Tests with water carried out with synthetic mine water from a German site showed that 98% of the sulfate present could be removed by manipulating the water pH and concentration of electron donor (glycerol) for the sulfate-reducing bacteria. While more sulfate was removed with synthetic Chilean mine water (up to 35 mmoles L-1), this only accounted for between 50-60% of the total present. There was close agreement between the stoichiometry of glycerol used and the amount of sulfate removed, particularly with the German mine water.
Insights into Bacterial Community Structure of a Commercial Copper Bioheapleaching Plant: Growth of Heterotrophic Bacteria in the System
Authors: Liu Xing Yu , Chen Bo Wei , Wen Jian Kang
Published: October 2013

The distribution and diversity of bacterial community in Zijinshan commercial non-aeration copper bioheapleaching system operated at pH 0.8 for three years were investigated. The 24 meters high heap was cut off by mechanical digger. On the trapezoidal cross-section of the heap, 9 ore samples were taken from different vertical and horizontal locations and investigated by 16S rRNA gene clone library. Another 3 liquid samples from raffinate solution pond, spray solution pond and pregnant solution pond were also applied to 16S rRNA gene clone library analysis. The retrieved 1166 clone sequences from 12 samples were mainly related to genus Acidithiobacillus (42.36%), genus Leptospirillum (37.73%) and genus Sulfobacillus (6.52%). Relative high amount of heterotrophic bacteria were distributed at the ore surface in the internal part of the heap and in the liquid samples respectively. The retrieved heterotrophic bacterial sequences were mainly related to genus Acidiphilium (accounting 11.11% to 32.00% percent in the liquid samples), genus Acidovorax (accounting 12.37% in A1 sample), genus Pelomonas (accounting 4.17% to 10.31% in several ore samples) and genus Aquabacterium (accounting 10.31% in C2 sample). Bacterial diversity in the heap was increased from the surfcae layer to the interior of the heap. The proportion of genus Leptospirillum horizontally increased from the inner to the outer part while vertically decreased from lower depth (2-3 years leaching time) to higher depth(3-6 month leaching time), and reverse correlation of genus Acidithiobacillus was found in the heap. Our finding indicated that heterotrophic bacteria may play very important roles in the commercial bioheapleaching system, and revealed high distribution of genus Leptospirillum in the outer part of this non-aerated heap.
Influences of pH Buffers on the Growth of Acidithiobacillus thiooxidans and Biodesulfurization Efficiency
Authors: Liu Xiao Rong , Su Chang , Jiang Sheng Cai , Liu Yan Jun , Li Hui
Published: October 2013

More than 90% of metal sulfides in vanadium-bearing titanomagnetite concentrates in Panzhihua (China) are pyrrhotite. It is difficult to remove pyrrhotite from iron ores through conventional mineral processing technologies as magnetic separation and flotation. Desulfurization with the help of microorganisms is a promising alternative way relating to the implementation in dissolution. The effects of pH buffers on growth of Acidithiobacillusthiooxidans and biodesulfurization efficiency of vanadium-bearing titanomagnetite concentrates were investigated. 61.86% of sulfur can be removed from the concentrates after bioleaching for 15 days for a 10% pulp density. While 10% of citric-disodium hydrogen phosphate buffer was added into the solution, Acidithiobacillusthiooxidans grew significantly faster and the biodesulfurization rate was increased by 12.34%, accompanying with pH stabilised at ~ 3.0. Boruitan-Luobisen buffer was helpful to keep pH in a good situation, whereas it inhibited the growth of Acidithiobacillusthiooxidans seriously and brought down the biodesulfurization efficiency.
Comparison of Indigenous and Exogenous Mesophilic Bacteria for the Bioleaching of Low Grade Copper Ores
Authors: Sun Jia Lin , Ngom Ba Ba , Liu Yi , Yin Hua Qun , Liang Yi Li , Liu Xue Duan , Zhu Jing He
Published: October 2013

Using indigenous microorganisms in biomining processes assures few ecological distortions and less time consumption for adaptation. However, there is a debate as to whether an indigenous microbial community is more efficient than one composed of microbial strains selected for specific physiological traits. In order to provide thoughtful opinions in such a debate, a cross-comparison of six strains isolated from two different regions: Chambishi Copper Mine (Zambia) and Dexing Copper Mine (China), was conducted. Physiological properties and leaching performancesof Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferriphilum in pure and mixed culture were studied. The results showed that strains within species presented similar traits while copper resistance was not species-specific. In terms of leaching efficiency, native strains always achieved higher cell density and greater iron and copper extraction rates than the exogenous. In addition, microbial community analysis revealed the different mixed culture shared almost the same profile, and At. ferrooxidans strains always outcompeted the other strains.
Finishing Methods of Tools Functional Surfaces
Authors: Lukovics Imrich , Čop Jiří
Published: October 2013

Article shows the calculation of the stress in a rotating disc and the possibility of using proprietary forms of instruments for speed grinding. It presents the results of speed and efficient cutting tools in machining these materials alloyed with chromium. In addition, it notes the results of the influence of technological conditions on the quality of surfaces, the residual stress in the workpiece, resulting from the machining speed and the influence of technological conditions on the wear of grinding wheels. Finally, some options for the use of finishing techniques in practice are mentioned.
Detection of Surface Damage after Grinding of Large Case–Hardened Bearing Rings
Authors: Čilliková Maria , Neslušan Miroslav , Kolařík Kamil , Mičúch Marián
Published: October 2013

This paper deals with detection of surface damage after grinding of bearing rings made of case hardened steel. Micromagnetic technique based on Barkhausen noise is adopted for monitoring of surface integrity during grinding rings of large diameter (1500 mm). Except micromagnetic testing, investigation of surface integrity is also expressed in such parameters as structure alterations, residual stresses measured via X - ray technique and microhardness measurement. It was found that Barkhausen noise technique enables reliable detection of surface integrity and damage induced by dry grinding and insufficient coolant supply can be easily distinguished.
Simulation of Grinding Process of Polycrystalline Superhard Materials
Authors: Grabchenko Anatoly I. , Fedorovich Vladimir A. , Pyzhov Ivan , Fadeev Valery , Babenko Eugene , Klimenko Vitaly
Published: October 2013

The results of investigation in order to increase the efficiency of using diamond-abrasive and edge tool made of superhard materials (SHM) on the basis of 3D methodology of complex research of the interrelated processes of their manufacturing and operation are presented. Creation of 3D simulation methodology of processes of sintering of abrasive-diamond tools and processes of grinding of edge SHM tools with their application allows us to increase considerably the reliability of obtained results, to reduce the extent of experimental studies for determination of optimum conditions for grinding and to develop new technologies, tools and equipment. The scientific hypothesis about the expediency of using diamond powders with thick metal coatings in diamond-abrasive tools on metal bonds are proposed and proved on the basis of theoretical research. The research results are implemented as a number of grinding techniques with controllable cutting relief of the wheels and devices which realize them. Using the results of the research makes it possible to increase the reliability of the edged tool made of SHM as far back as at the stage of its sharpening.
Shape Investigation of Worn Cutting Inserts with Utilization of Active Triangulation
Authors: Morovič Ladislav , Vagovský Juraj , Buranský Ivan
Published: October 2013

The paper deals with utilization of active triangulation method for shape investigation of cutting inserts after wear. For measuring of cutting insert shape a method using the structured light (fringe projection) was used. As a measuring device the optical 3D scanner GOM ATOS II TripleScan SO was used. Cutting inserts with different shapes was measured. With the measurement method mentioned in the paper the accurate shape of the cutting insert can be captured. From the 3D model moreover it is possible to measure the geometrical properties as well as tool wear, plastical deformation, build-up-edge, corner damage and chipping of cutting insert.
New Ways at the Fine Grinding
Authors: Novák Martin
Published: October 2013

The traditional approach to grinding is to operate within the limits of surface quality. The requirements for surface quality in grinding are higher than those in other common machining operations such as turning and milling. The surface quality of machined parts is very important for precise production and assembly. When we focus on roughness parameters after grinding, we can establish the limits of these parameters for typical grain materials: Al2O3, SiC, CBN, SG and others. Increasing demands on accuracy and quality of production leads to research concerned with the properties of these materials and the surface quality after grinding. This paper shows new possibilities for the ground surface with focus on surface roughness obtained under varying combinations of cutting conditions. The influence of the grinding wheel, cutting parameters and coolant on higher surface quality is assessed by roughness parameters Ra, Rz, Rt and the Material portion of a surface profile. These high-precision ground surfaces are shown to have a Nanometres (10-9) unit topography demonstrating that the process is able to replace other finishing technologies such as superfinishing or honing.
Molecular Dynamics Modelling of Nanometric Cutting
Authors: Markopoulos Angelos P. , Kalteremidou Kalliopi Artemi L.
Published: October 2013

In this paper the modelling and simulation of nanometric cutting of copper with diamond cutting tools, with the Molecular Dynamics method is considered. A 2D model of orthogonal cutting, with nanoscale features, is constructed. In this model two different potential functions to simulate the interaction of the atoms within the workpiece and between the workpiece and the tool are used; LennardJones potential for the former and the Morse potential for the latter case. From the simulation the chip formation can be observed and analysed. The model is used for the simulation of nanocutting with three different nanometric depths of cut from which the cutting forces are calculated and compared. With increasing depth of cut, cutting forces also tend to increase. The proposed model can be successfully used for the modelling of cutting operations that continuum mechanics cannot be applied or experimental and measurement techniques are subjected to limitations or it is difficult to be carried out, such as ultra-precision machining, micro-cutting, miniaturization and nanoscale cutting.
Surface Roughness after Machining and Influence of Feed Rate on Process
Authors: Čep Róbert , Janásek Adam , Petrů Jana , Sadilek Marek , Mohyla Petr , Valíček Jan , Harničárová Marta , Czán Andrej
Published: October 2013

The aim of the work is find out influence of feed rate on the quality for the machined surface, especially surface roughness. The experiment was carried out by cutting tool HURCO VMXt30 with respect to the following cutting parameter: cutting speed 250; 350; 450; 550 and 850 m.min-1, feed 0,1; 0,5 and 1,0 mm/tooth. For testing was used two most common materials in the steel grade 1.1191 (12 050) and 1.2343 (19 552), and we chose two ordinary parameters of surface roughness; Ra - arithmetical mean roughness deviation and Rz - the largest inequalities height profile in the transverse direction and the longitudinal direction of machining. The structural equations will be the result which can describe the character depending on the cut surface parameters.
Introducing a Risk-Management Concept for Holonic Manufacturing Supply Chains
Authors: Skapinyecz Róbert , Illés Béla
Published: October 2013

In the paper, an emerging approach for risk-management in holonic manufacturing networks is going to be introduced, one that is based partly on the already-proven methods of process capability and six-sigma, but combines these with a novel cost-model and a general form of the extended enterprise architecture. The aim of the research is to develop this approach into an easily adaptable, network-based evaluation tool that would be especially suitable for holonic manufacturing systems, but might also be applied in other fields of the industry as well.
Overview and Latest Developments in Photoconductance Lifetime Measurements in Silicon
Authors: Sinton Ronald A. , Blum Adrienne L. , Swirhun James S.
Published: October 2013

Photoconductance measurements have been one of the most common ways to measure the lifetime in silicon for over 60 years. Since 1985, the most common method for doing calibrated lifetime measurements is using an eddy-current sensor to monitor photoconductance as a function of time and illumination, providing data that can be interpreted in terms of carrier density and hence lifetime. Here we present recent extensions to this measurement technique that have generalized the method. Bulk lifetime measurements on industrial samples are presented. The information available from the effects of grain boundaries on eddy-current measurements are summarized. Recent applications for the use of these instruments for measurement of mobility in compensated materials are also described.
Properties of Point Defects in Silicon: New Results after a Long-Time Debate
Authors: Bracht Hartmut , Kube René , Hüger Erwin , Schmidt Harald
Published: October 2013

The contributions of vacancies and self-interstitials to silicon (Si) self-diffusion are a matter of debate since many years. These native defects are involved in dopant diffusion and the formation of defect clusters and thus influence many processes that take place during Si single crystal growth and the fabrication of silicon based electronic devices. Considering their relevance it is remarkable that present data about the properties of native point defects in Si are still limited and controversy. This work reports recent results on the properties of native point defects in silicon deduced from self-diffusion experiments below 850°C. The temperature dependence of silicon self-diffusion is accurately described by contributions due to vacancies and self-interstitials assuming temperature dependent vacancy properties. The concept of vacancies whose thermodynamic properties change with temperature solves the inconsistency between self-and dopant diffusion in Si but further experiments are required to verify this concept and to prove its relevance for other material systems.
Theoretical Study of the Impact of Stress on the Behavior of Intrinsic Point Defects in Large-Diameter Defect-Free Si Crystals
Authors: Sueoka Koji , Kamiyama Eiji , Vanhellemont Jan
Published: October 2013

For the development of the crystal pulling process for 450 mm-diameter defect-free Si crystals, the impact of thermal stress on intrinsic point defect behavior during crystal growth is studied using extensive density functional theory calculations. The impact of thermal stress on the so-called Voronkov criterion and on void formation is clarified and compared with published experimental results.
First Principle Study of the Diffusion of Oxygen and Oxygen Complexes in Si, SiGe Solid Solutions and Si Nanocrystals
Authors: Gusakov Vasilii
Published: October 2013

In the framework of a unified approach the diffusion coefficient (the prefactor and activation barrier) of an interstitial oxygen Oi, the hydrogen molecule H2, vacancy, oxygen dimer in silicon crystals and Oi in Si1-xGex solid solutions, silicon nanotubes and nanowires has been calculated. For all the above cases, the calculated values of the diffusion coefficient are in good agreement with the experimental data. The calculated equilibrium structures, electrical activity, the vibrational spectrum, the mechanism of diffusion of oxygen dimer fully describe the experimental results. Our study has revealed that the diffusivity of impurities (defects) in alloys can decrease considerably and this variation results from the fact that the prefactor depends on the concentration of component elements of the alloy.
The Trivacancy and Trivacancy-Oxygen Family of Defects in Silicon
Authors: Markevich Vladimir P. , Peaker Anthony R. , Hamilton Bruce , Lastovskii S.B. , Murin Leonid I. , Coutinho Jose , Rayson Mark J. , Briddon Patrick R. , Svensson Bengt Gunnar
Published: October 2013

The data obtained recently from combined deep-level-transient spectroscopy (DLTS), local vibrational mode (LVM) spectroscopy and ab-initio modeling studies on structure, electronic properties, local vibrational modes, reconfiguration and diffusion paths and barriers for trivacancy (V3) and trivacancy-oxygen (V3O) defects in silicon are summarized. New experimental results on the introduction rates of the divacancy (V2) and trivacancy upon 4 MeV electron irradiation and on the transformation of V3 from the fourfold coordinated configuration to the (110) planar one upon minority carrier injection are reported. Possible mechanisms of the transformation are considered and discussed.
Monoisotopic 28Si in Spin Resonance Spectroscopy of Electrons Localized on Shallow Donors
Authors: Ezhevskii Alexander A. , Popkov Sergey A. , Soukhorukov Andrey V. , Guseinov Davud V. , Konakov Anton A. , Abrosimov Nikolay V. , Riemann Helge
Published: October 2013

The inverted structure of the 1s ground state of lithium in silicon provides a unique opportunity to study inter-valley spin-orbit interactions of donor electrons. A study of lithium doped silicon enriched in the 28Si isotope with a low oxygen content (N 21014 cm3) has demonstrated at low temperatures (T = 3.8 K) a family of electron spin resonance (ESR) spectra with anisotropic g factors associated with Li donor centres. The spectra were investigated without and with application of external stress to the sample and their g factors were found to be less then 2.000. The analysis of experimental data and numerical simulation of the spectra and their angular dependencies in the second order perturbation theory assuming the splitting of states due to internal strains in the crystal is larger than the Zeeman and spin-orbit splitting have shown that the spectrum, having g tensor components corresponding to the tetragonal symmetry, consists of two lines belonging to the triplet state T2, and the other two lines in the spectrum have an angular dependence behaviour of the doublet states E. The ratio of the inter-valley spin-orbit coupling λ and λ' to the Δ parameters, characterizing the splitting of the states under internal strains have been defined. From the dependencies of the triplet ESR lines intensity on the compressive stress of the crystal along the [11 it was obtained the value of the internal strains, which allowed to determine the parameters of the spin-orbit coupling λ and λ'. Their values were found to be three orders of magnitude smaller than were obtained earlier for Li spectra with g > 2. Since experimentally observed Δ value was of the order of the Zeeman splitting parameter the spectra were analyzed using the full matrix of the spin Hamiltonian for the fivefold degenerate ground state. We found that angular dependencies of the spectra observed for the triplet and doublet states with g < 2 are well described by the solutions of the spin Hamiltonian with parameters λ and λ' obtained from our experimental data. At the same time, we are not able to find solutions that satisfy the data obtained for the spectra with g > 2.000 in previous studies.
Light-Element Impurities and their Reactions in Multicrystalline Si
Authors: Stavola Michael , Estreicher Stefan K. , Seacrist Mike
Published: October 2013

Vibrational spectroscopy has been used to investigate the properties of hydrogen in multicrystalline Si (mc-Si) and its interactions with carbon impurities that can be present with high concentration. The properties of point defects containing N and O have been investigated by way of their vibrational properties and their far-infrared electronic transitions.
Isotope-Dependent Phonon Trapping at Defects in Semiconductors
Authors: Estreicher Stefan K. , Gibbons T. Michael , Stavola Michael
Published: October 2013

Unexpectedly large isotope effects have been reported for the vibrational lifetimes of the H-C stretch mode of the CH2* defect in Si and the asymmetric stretch of interstitial O in Si as well. First-principles theory can explain these effects. The results imply that defects trap phonons for lengths of time that depend on the defect and sometimes on its isotopic composition. Some consequences of phonon trapping are discussed.
Charge Carrier Transport along Grain Boundaries in Silicon
Authors: Kittler Martin , Reiche Manfred , Krause Hans Michael
Published: October 2013

The influence of GBs contained in the channel of MOS-FETs - fabricated in thin SOI layers - is demonstrated. The drain current measured at room temperature increases about 50 times for nFETs and about 10 times for pFETs, respectively, as compared to reference devices. The observations might be interpreted as a strong increase of the mobility of charge carriers. Moreover, the observed stepwise changes of the drain current at 5 K may point to Coulomb blockades.
Precipitation of Interstitial Iron in Multicrystalline Silicon
Authors: Liu An Yao , Macdonald Daniel
Published: October 2013

The internal gettering of iron in silicon via iron precipitation at low processing temperatures is known to improve solar cell efficiencies. Studies have found that the optimal temperature lies in the range of 500°C-600°C. In this paper, we present experimental results on quantitatively analysing the precipitation of interstitial Fe in multicrystalline silicon wafers during the 500°C-600°C thermal annealing processes. The concentration and the spatial distribution of interstitial Fe in mc-Si were measured by the photoluminescence imaging technique. It was found that, apart from the processing temperature, the Fe precipitation time constant is highly dependent on the supersaturation ratio and the density and types of the precipitation sites.
Kinetics of Hydrogen Motion via Dislocation Network in Hydrophilically Direct Bonded Silicon Wafers
Authors: Loshachenko A.S. , Vyvenko Oleg F. , Kononchuk Oleg
Published: October 2013

The kinetics of hydrogen penetration through dislocation networks produced by silicon wafer bonding are investigated by means of reverse bias annealing (RBA) procedure. By using the combination of capacitance-voltage (CV) profiling of net-acceptor concentration and deep level transient spectroscopy (DLTS) the total concentration of H introduced in the samples during wet–chemical etching at room temperature was defined. Two processes with the different time constants τ1 and τ2 was found for the bonded sample. The slow process τ1 with an activation energy of (1.25±0.13) eV was analogous to that in the reference sample and corresponded to the dissociation of boron-hydrogen pairs. The fast process τ2 was found to exhibit a lower activation energy of (0.87±0.25) eV and was identified as the release of hydrogen bound at screw dislocations by their elastic strains.
Effect of Ultrasonic Treatment on the Defect Structure of the Si-SiO2 System
Authors: Kropman Daniel , Dolgov Sergei , Onufrijevs Pavel , Dauksta Edvins
Published: October 2013

The effect of ultrasonic treatment (UST) on the defect structure of the Si–SiO2 system is characterised by means of electron spin resonance (ESR), metallography, MOS capacitance measurements and secondary ion mass spectroscopy (SIMS). A non-monotonous dependence of the defect densities on the ultrasonic wave intensity has been observed. The influence of the UST frequency on the ESR signal intensity of the defect centres depended on the defect’s type and structure and may be caused by vibrational energy dissipation which is a function of the defect centre’s type. The influence of the UST on the Si–SiO2 interface properties depends on the oxide thickness and crystallographic orientation. The density of point defects and absorbed impurities at the Si–SiO2 interface can be reduced and its electrical parameters improved by an appropriate choice of UST and oxidation conditions.
Smoothening by Self-Diffusion of Silicon during Annealing in a Rapid Processing Chamber
Authors: Acosta-Alba Pablo Eduardo , Gourdel Christophe , Kononchuk Oleg
Published: October 2013

Atomic-scale mechanisms of thermal activated self-diffusion on crystal surfaces are investigated through AFM images. Surface evolution is studied by means of the Power Spectral Density (PSD) function over a large spatial bandwidth. We propose a parametric model based on the Mullins-Herring (MH) diffusion equation by adding two stochastic terms. Then, surface evolution during high temperature annealing in reducing ambient can be predicted. Very good agreement between experimental and theoretical roughness and diffusion parameters was observed. Origin and evolution of the stochastic terms, describing conservative and non-conservative noises, are discussed.
Unstable Luminescence and "Memory Effect" in Nitrides Irradiated by Electron Beam
Authors: Kuznetsova Yana V. , Zamoryanskaya Maria V.
Published: October 2013

In this paper the effect of unstable luminescence in nitrides was studied, notably the phenomena of cathodoluminescent intensity rising under stationery electron beam irradiation with typical times of tens up to hundreds of seconds. Long-lasting impact by electron beam leads to changes of cathodoluminescence properties of irradiated area. The changes still remain even after keeping structures at room temperature for several days. Reversibility of this "memory effect" was examined. A model of effect observed was proposed and experimentally verified.
Investigation of Point Defects Modification in Silicon Dioxide by Cathodoluminescence
Authors: Dementyeva Ekaterina , Zamoryanskaya M.V.
Published: October 2013

The aim of this work is study of point defects modification in silicon dioxide by a high power density electron beam. In this work we used the method which allows to estimate quantitative content of luminescent point defects by dependence of cathodoluminescence on current density. Content of point defects was evaluated and changing of point defect content in silicon dioxide under electron beam was assessed. It is shown that content of defect connected with silicon deficit decreases whereas content of defect connected with oxygen deficit increases. The model of point defects transformation was suggested on the basis of these results.