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  • Polymer and Materials Science  (11)
  • Small Scale Mining  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 43 (1992), S. 131-135 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Die gegen Spannungsrißkorrosion beständigen austenitischen Mangan-Chrom-StähleDer Grundtyp der MnCr-Stähle (0,05Mn19Cr13) hat sich als gegen Chloride hochbeständig erwiesen. Zusatz von Titan, Niob und Vanadium beeinträchtigt die Beständigkeit gegen Spannungsrißkorrosion nicht, während Zusatz von mehr als 0,5% Nickel die Beständigkeit deutlich verschlechtert. Die chemische Zusammensetzung der stabilisierten Stähle wurde so gewählt, daß der Ferritgehalt so niedrig wie möglich gehalten wurde. Die beiden stabilisierten Stahlsorten ließen sich nur schlecht passivieren, was u.a. der Anwesenheit von Mangan zuzuschreiben ist. Aus diesem Grunde sind diese Typen nur für weniger aggressive Bedingungen geeignet. Um die Korrosionsbeständigkeit bei niedrigem Ferritgehalt oder erhöhtem Chromgehalt zu verbessern, muß man weitere wirksame Austenitbildner zusetzen. Angesichts des ungünstigen Effekts von Nickel auf die Beständigkeit gegen Spannungsrißkorrosion wurden die mit Stickstoff und Molybdän modifizierten Mangan-Chrom-Stähle besonders berücksichtigt.
    Notes: The basic type of MnCr steels (composition 0.05Mn19Cr13) was found to be highly resistant to chlorides. Additions of titanium, niobium and vanadium did not impair resistance to stress corrosion cracking, but addition of nickel in excess of 0.5% appreciably impaired the resistance. The chemical composition of the stabilized steels was selected in such a way as to make the ferrite content as low as possible. The two stabilized steel grades ability to passivate was limited, also because of the presence of manganese; this makes these grades suitable only for less aggressive environments.The ferrite content can be controlled, or the chromium content increased for better corrosion resistance, only by adding another strong austenite-former. Considering the adverse effect of nickel on the resistance to stress corrosion cracking, attention was given to manganese-chromium grade modified with nitrogen and molybdenum.
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  • 2
    Publication Date: 2021-03-29
    Description: After a long decline of gold production in Ghana since 1986 the gold mining sector is recovering and mainly foreign investment led to substantial exploration efforts as well as to the opening up of new mines and/or rehabilitation and expansion of the existing mines after their divestiture (privatization). Foreign junior exploration and mining companies and established international mining houses are currently exploring the country in search of large, therefore commonly low-grade gold deposits which are amenable to highly mechanized open pit mining. Beside such orebodies of the disseminated type or in granites, Ghana is endowed with many occurrences of gold quartz veins and banket reefs, which vary in width from a few centimetres to several metres and have striking length from a few 10 meter to several kilometer. Whilst such larger orebodies with ore reserves of above 1 Mio. tons are a target for industrial mining operations, the smaller "stringer"-occurrences are not of interest, if not only as indicators in prospection for possible adjacent disseminated mineralization. Such restricted orebodies could offer investment and employment opportunities for Ghanaian owned mining groups and companies and should therefore contribute also to economic development of the hinterland. Some of these orebodies as well as the ubiquitous gold bearing alluvials are currently mined by artisanal small scale miners, commonly called "galamsey", which use manual labour only and employ simple handtools in their operations. A visit to such operations will convince any observer that in almost all cases the operations are either inefficient, including the skimming of orebodies, or dangerous, or environmentally unsound or a combination of these. This is due to the long oppression of small scale mining activities first by the Colonial Government from about 1920 ongoing, later by the Ghanaian authorities after Independence. Only in 1986 under the Minerals and Mining Law, PNDC-Law 153 was the small miner legally recognized and a basis laid for his operations. Vast experience in narrow vein mining, which was available among African small scale miners before and around the advent of this century has been lost. To prove this point, mention should be made of the African engineer T.B.F. Sam, who managed and operated singlehandedly the Adja Bippo Mine near Tarkwa before 1900, the only mine of all the mines in operation since 1880 which was profitable and declared dividends (Rosenblum, 1974). Today it can still be assumed that there will be no re-juvenation of skilfull vein mining by African small scale miners as long as it has not been proved to Ghanaian investors that such operations could be viable. The proof can be presented best by a few reference operations applying durable, locally available machinery, simple and sound mining and extraction methods, basic safety standards and bearable working conditions as well as in their effect on the environment controlled operations. Such reference mines could also provide the necessary information in respect of day-to-day running problems, required amounts of investment, minimum working capital, maintenance and repair needs and problems with unskilled labour drawn from the surroundings of such small mines, to mention only a few areas of missing experience.
    Description: My brother still wanted to publish this magazine article at the 15.05.2001 before his death. Unfortunately, it was not granted to him any more to do this. I have sighted his estate and processed according to these as his brother. Therefore I am publishing the last work of my brother Dipl engineer Winfried Peters now, too, so that his bequest is filled. I unfortunately can not guarantee for the scientific correctness of the work, however, have revised this work after best knowledge and conscience.
    Description: research
    Keywords: 622 ; ZU 000 ; Bergbau {Technik} ; Ghana ; Tetrem ; Small Scale Mining ; Gold
    Type: article , draft
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  • 3
    Publication Date: 2021-03-29
    Description: This publication is the continuation of a previous presentation of the operation and cost analysis of the partly mechanised Tetrem small scale gold mine which discussed in detail the mining, safety and environmental aspects of the venture. At Tetrem, various experiments with different machinery for crushing and grinding the ore in preparation for gravity separation (sluicing) were carried out and the results are presented. The trials led to the construction and application of suitable, locally obtainable equipment for such milling operations. Continuous weighing and sample checks at the different stages of the comminution and gravity separation provided interesting production and recovery data which could be of help for similar operations. Trials for improved recovery of gold from sulphidic ores were carried out and showed the restrictions of gravity separation when confronted with such „fresh ores“. The amalgamation process, recirculation of tailings, special handling of tailings for recovery improvements are described. An overview about the results obtained during six months of operation is presented. Improvements for the locally produced machines and problems with maintenance and repairs of the equipment as well as strategies to solve them are discussed. The experiences obtained in the marketing of the final gold product are critically outlined.
    Description: My brother still wanted to publish this magazine article at the 15.05.2001 before his death. Unfortunately, it was not granted to him any more to do this. I have sighted his estate and processed according to these as his brother. Therefore I am publishing the last work of my brother Dipl engineer Winfried Peters now, too, so that his bequest is filled. I unfortunately can not guarantee for the scientific correctness of the work, however, have revised this work after best knowledge and conscience.
    Description: research
    Keywords: 622 ; ZU 000 ; Bergbau {Technik} ; Ghana ; Small Scale Mining ; Gold Ore Treatment
    Type: article , draft
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  • 4
    Publication Date: 2021-03-29
    Description: The economically successful operation of partly mechanized small scale mines in Ghana could fill the gap between large scale, industrial and foreign controlled mining operations and the artisanal (or "galamsey") small scale operations which use only manual labour and simple tools and are mainly confined to alluvial gold deposits and on limited scale to hard rock occurrences. The need to initiate and operate partly mechanized small scale mines stems from the existence of many small orebodies spread all over Ghana which are in their extent and amount of available ore reserves too small to be of interest to medium or large scale mining companies. In this presentation one of these small auriferous orebodies is described and the operation of a small mine is outlined. The employed mining methods during start up and throughout production phases are described. Special attention is given to safety aspects of such operations. A mechanised plant for crushing and grinding the ore in preparation for gravity separation (sluicing) was set up by using locally obtainable or manufactured crushing, seeving and milling equipment. The extraction results over 6 month operation are presented and discussed. The total investment for the small mine and the production costs are presented giving an overview on the economics for such operation. Factors to be observed to safeguard a small mine from causing adverse environmental effects are discussed. Finally, an outlook in respect of multiplication of such operations in Ghana is presented.
    Description: My brother still wanted to publish this magazine article at the 15.05.2001 before his death. Unfortunately, it was not granted to him any more to do this. I have sighted his estate and processed according to these as his brother. Therefore I am publishing the last work of my brother Dipl engineer Winfried Peters now, too, so that his bequest is filled. I unfortunately can not guarantee for the scientific correctness of the work, however, have revised this work after best knowledge and conscience.
    Description: research
    Keywords: 622 ; ZU 000 ; Bergbau {Technik} ; Ghana ; Small Scale Mining ; Gold Mine
    Type: article , draft
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  • 5
    Publication Date: 2021-03-29
    Description: With reference to various publications in newspapers on Small Scale Mining or Galamsey or activities of illegal small miners in Ghana and sometimes very agressive comments or demands voiced by representatives of industrial mining companies the following is to convey some thoughts on this subject and to submit some possible solutions in regard of the administration of the Small Scale Mining Sector in general.
    Description: My brother still wanted to publish this magazine article at the 15.05.2001 before his death. Unfortunately, it was not granted to him any more to do this. I have sighted his estate and processed according to these as his brother. Therefore I am publishing the last work of my brother Dipl engineer Winfried Peters now, too, so that his bequest is filled. I unfortunately can not guarantee for the scientific correctness of the work, however, have revised this work after best knowledge and conscience.
    Description: research
    Keywords: 622 ; ZU 000 ; Bergbau {Technik} ; Ghana ; Galamsey ; Illegal mining ; Small Scale Mining ; Gold
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 351-356 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymerization of ethylene was carried out in toluene using the homogeneous catalytic system Cr[OC(CH3)3]4/Al(C2H5)2Cl, combined with various metal chlorides (MtClx). The polymerization activity was found to be strongly dependent upon the MtClx used. A clear correlation was found between the activity and the elctronegativity X(Mtx+) of the metal ion in MtClx. MtClx containing metal ions with X(Mtx+) 〈 8,5 (electronegativity of the active Cr2+) show a markedly increased activity, whereas those with X(Mtx+) 〉 8,5 have a rather decreased activity. Thus, for example, the catalyst combined with MgCl2 shows very high activity to give a linear polyethylene with a remarkably high molecular weight and narrow molecular weight distribution. A plausible mechanism for the enhancement of the activity by suitable MtClx is proposed on the basis of these results.
    Additional Material: 2 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 883-897 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Interfaces of evaporated viterous selenium and various organic polymeric resins of both the thermosetting and thermoplastic type have been studied by ultra-thin sectioning and transmission electron microscopy techniques. Epoxy, phenoxy, polyamide, butadien-styrene copolymer, vinyl-toluene-butadiene copolymer, resins as well as polyethylene are among those organic polymers studied. Interfaces prepared by vaccum evaporation of selenium onto the various substrates and under varying processing conditions were examined. Intermixing and interdiffusion of the inorganic and organic polymers in the interfacial region were observed in certain cases when selenium was evaporated onto incompletely curved epoxy or lower viscosity polymers. These occurrences were found to contribute significantly to the mechanical strength of the assembly. Electrical properties of certain specific systems have also been investigated.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 2831-2856 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The data for the calculation of tensions and bendings of sandwich structures show that in case of bending loads, which are not free from transverse forces, shearing stress occurs in the core, and this stress influences the bending properties of polyethylene compound cores provided with aluminum facings. This influence is due to the viscoelastic properties of the polymers participating in the compound, dependent on the temperature and the load duration. Additives mixed into the core material produce, besides increased rigidity of the core itself, a more favorable bending behavior provided it has been possible at the same time to improve the firmness of the adhesive effect between the plates and the core by means of the additive. In this case the influence of the production conditions must be taken into consideration.
    Additional Material: 20 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 201-213 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Miscibility and crystallization of poly-p-phenylene terephthalamide (PPTA)/nylon 6 and nylon 66 composites prepared by coagulation of isotropic ternary sulfuric acid solutions were studied. The apparent crystallinity of nylon 6 and nylon 66 in molecular composites was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The solvation of nylon 6 crystals in PPTA matrix was observed when the PPTA content exceeds 70 wt%. Cross-hydrogen bonding seems to be responsible for the virtual disappearance of nylon 6 crystals. Specific interaction between PPTA and nylon 6 macromolecules and phase separation during thermal treatment has been discussed.
    Additional Material: 10 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 22 (1991), S. 289-300 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Characterization of the Tribological Behaviour of Ceramic Sliding Couples with Modern Surface Analysis MethodsDry friction and wear tests were performed in ambient atmosphere with various self-mated couples of SiC, Al2O3, Si3N4 and ZrO2. The temperature was varied between 22 °C and 1000 °C and the sliding velocity between 0.03 m/s and 5 m/s. Normal force, temperature and sliding velocity are kept constant during the tests.The materials and wear mechanisms were characterized by various surface analytic methods - optical microscopy, scanning electron microscopy, transmission electron microscopy, electron microprobe analysis, IR-spectroscopy, X-ray diffraction, auger electron spectroscopy and X-ray photoelectron spectroscopy. High wear/low wear transitions could be explained. On the basis of these results new ceramic materials with lower friction and/or wear were selected or successful developed.
    Notes: Es werden Ergebnisse von Modellverschleißprüfungen an artgleichen keramischen Gleitpaarungen in einer Stift/Scheibe-Anordnung bei Festkörperreibung vorgestellt. Die Temperatur wurde zwischen 22 °C und 1000 °C und die Gleitgeschwindigkeit zwischen 0,03 m/s und 3 m/s variiert. Die Versuche wurden in Laboratmosphäre unter konstanten Lasten von 1 N und 10 N durchgeführt. Für die Charakterisierung der Ausgangswerkstoffe, zur Aufklärung von Verschleißhochlage/-tieflage-Übergängen sowie der Verschleißmechanismen und der Verschleißerscheinungsformen wurden verschiedene oberflächenanalytische Verfahren - u. a. Lichtmikroskopie. Rasterelektronenmikroskopie. Transmissionselektronenmikroskopie. Infrarot-Spektroskopie. Elektronenstrahl-Mikroanalyse, Röntgenbeugung. Auger-Elektronen-Spektroskopie und Röntgen-Photoelektronen-Spektroskopie - eingesetzt.Auf der Grundlage oberflächenanalytischer Untersuchungen wurden die Werkstoffe tribologisch optimiert. Mit den neu entwickelten Werkstoffen konnten die Reibungszahlen und/oder die Verschleißraten auf Werte gesenkt werden, Wie sie vor allem bei extremen Beanspruchungsbedingungen (hohe Temperatur, aggressives Umgebungsmedium und Festkörperreibung) von anderen Werkstoffgruppen nicht erreicht werden.
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