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By B. McFadzean, S. Pikinini, C. T. O’ Connor

Sperrylite (PtAs₂) comprises about 21% of the platinum group minerals (PGMs) in the Platreef ore and regularly reports to the tailings due to its poor floatability. Hence, improving its recovery will be of great economic value to the South African PGM industry. The reasons for its poor floatability are not yet clear. This paper seeks to understand the interactions occurring between PtAs₂ and common thiol collectors, viz. potassium normal butyl xanthate (PNBX), sodium normal dibutyl dithiophosphate (SNBDTP) and sodium normal mono butyl dithiocarbamate (SNBDTC). By understanding its interactions with these collectors, it is hypothesised that it will be possible to suggest ligands that may help improve the floatability of sperrylite. Mineral-collector interactions were studied by determining the molar energy of interaction using isothermal titration calorimetry and electrochemical techniques. The hydrophobicity of the mineral before and after adsorption of the collectors was determined by heat of immersion and its flotation response determined by microflotation tests. Microflotation tests using synthetic sperrylite at pH 9 showed low collectorless recovery of 34.8% and after adding the equivalent of one pseudo-monolayer of the PNBX collector, the recovery of 32.5% was obtained. Moreover, the addition of up to three pseudo-monolayers coverage of PNBX did not result in any increase in flotation recovery. A small recovery improvement was noted when synthetic plant water with the ionic strength of 0.0484 mol/L was used, but this did not hold for all collectors, with SNBDTP exhibiting higher recoveries in distilled water. Keywords: Sperrylite; flotation; recovery; adsorption energy; collectors; 2SPW (synthetic plant water)

Jan 1, 2020

By C. Karageorgos, J. Sakala, A. Prinsloo, B. Ngambi

The sulphide flotation circuit at First Quantum Minerals’ Kansanshi mine in Zambia produced over 100,000 t of copper in 2019. For this circuit, mineralogical analysis has shown that the majority of the copper lost is hosted in fine liberated chalcopyrite, which is a paramagnetic mineral. The objective of this work was therefore to improve fine chalcopyrite recovery in the sulphide flotation circuit at Kansanshi, using a magnetic conditioning technology to agglomerate fine paramagnetic minerals. This theoretically increases the probability of attachment during collision and therefore improves recovery. A four-month paired ‘t’ test plant trial was carried out and comprised of consecutive ON-OFF periods with and without magnetic conditioning in the rougher flotation bank of the sulphide circuit. The experimental design involved assessment of recovery by size based on daily and weekly composite samples of feed and tails, sized using both wet-screening and cyclosizer. Both the daily plant data and the sized samples showed an increase in Cu recovery with magnetic conditioning ON. A 0.56% copper recovery improvement was measured with magnetic conditioning at a 99.4% confidence level. Keywords: Flotation, fine mineral, chalcopyrite, magnetic aggregation

Jan 1, 2020

By J. Petersen, K. Shaik

The traditional route utilised for the recovery of Platinum Group Minerals (PGMs) in South Africa involves the concentration of ore by flotation, followed by smelting to produce a PGM rich matte, which is then digested hydrometallurgically to solubilise base metals and Platinum Group Elements (PGE). HCl/Cl2 is conventionally used for PGE dissolution from concentrated material, which is an aggressive reagent associated with high maintenance costs as well as environmental concerns. Of interest is the leaching of PGMs directly from mineral ores, low grade concentrates and tailings in a cyanide-ferricyanide system as a more sustainable alternative. This system has shown favourable Pt recoveries among the Pt minerals, but with sperrylite (PtAs2) displaying highly refractory behaviour. The dissolution of sperrylite is investigated in a cyanide-ferricyanide system in the context of an electrochemical study involving OCP, chrono-amperometry and cyclic voltammetry. This approach allows the assessment of leaching characteristics as well as the investigation of surface passivation, which is believed to contribute to poor Pt recoveries. Some evidence is presented that such passivation is related to the formation of arsenide species on the mineral surface. Keywords: Sperrylite, PGMs, cyanide, ferricyanide, electrochemistry

Jan 1, 2020

By D. Marcotte, R. V. Dutaut

In most exploration or mining grade data-sets, the presence of outliers or extreme values represents a significant challenge to mineral resource estimators. The most common practice is to cap the extreme values at a predefined level. A new capping approach is presented that uses QA/QC coarse duplicate data correlation to predict the real data coefficient of variation (i.e., error-free CV). The cap grade is determined such that the capped data has a CV equal to the predicted CV. The robustness of the approach with regard to original core assay length decisions, departure from lognormality, and capping before or after compositing is assessed using simulated data-sets. Real case studies of gold and nickel deposits are used to compare the proposed approach to the methods most widely used in industry. The new approach is simple and objective. It provides a cap grade that is determined automatically, based on predicted CV, and takes into account the quality of the assay procedure as determined by coarse duplicates correlation.

May 1, 2021

By M. Bryson, G. Marap, M. Ntlhane, M. D. Hlahane

This study investigated flotation of phosphate from a low-medium grade 8-12% P2O5, 65-73% SiO2 sedimentary phosphate ore from Kropz Elandsfontein (herein referred to as Elandsfontein) in South Africa. Quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) was used to determine apatite grain size distribution, liberation and mineral association in the F2 horizon sample. The mineralogy indicated that apatite was liberated and for the Elandsfontein plant to operate at the design throughput, the flotation feed has to be milled to a coarse grind ranging between 300 μm and 425 μm. Reverse flotation process routes using varying reagent dosages, and flotation feed top sizes that could possibly yield a final product of 31% P2O5,10% SiO2 at a reasonable +70% P2O5 recovery were investigated. Based on the results, a split circuit of coarse (-300+212μm) flotation and fine (-212+20μm) flotation, was mostly preferred as compared to treating the whole ore. A final combined concentrate of 31% P2O5 and 10% SiO2 with P2O5 recovery of 84% could be produced from the reverse split circuit. The robustness of reverse flotation for both coarse and fine fractions was further investigated. Reverse flotation of the fines fraction was found to be robust and produced a final product of 31% P2O5. It was however more challenging to achieve the required product grade and recoveries on the coarser fraction (-425+212μm), suggesting that reverse circuit was not adequately robust at fractions coarser than 300μm. Keywords: Phosphate, sedimentary, reverse flotation, particle size

Jan 1, 2020

Council and Standing Committees - 1982/83 President: Prof. A. N. Brown Vice Presidents: Prof. R. P. King and J. D. Austin Honorary Treasurer: Prof. D. G. Krige Immediate Past President: G. Y. Nisbet Members of Council: B. C. Alberts, R. H. English, P. T. Fewell, C. E. Fivaz, J. S. Freer, Prof. G. G. Garrett, J. J. Geldenhuys, Dr A. K. Haines, P. N. Harris, H. E. James, Dr B. K. Loveday, Dr J. Lurie, D. G. Malan, G. Pienaar, B. E. Protheroe, Dr 0. K. H. Steffen, G. C. Thompson, Dr H. Wagner, Dr P. T. Wedepohl. Chairman, Witbank/Middelburg Branch: H. C. van Zyl.

Jan 1, 1983

By P. C. Pistorius, D. Kruger, Y. Kacar

Because of its superior properties, stainless steel has been widely used for many applications. Nonmetallic inclusions can influence the quality of stainless steel products. A set of samples was used to track the response of inclusion composition during processing of a heat of titanium-bearing 18% chromium steel, from deoxidation after decarburization, to the solidified slab. The oxide inclusions responded as expected to additions of deoxidizers and calcium treatment, changing from silica to alumina and spinels, and then to calcium aluminates. The samples confirmed that titanium nitride can nucleate on liquid calcium aluminate during steel solidification.

Aug 1, 2021

By G. B. Abaka-Wood, J. Addai-Mensah, W. Skinner

Recently, coal fly ash has become a potential candidate as a secondary resource of rare earth elements (REE). In this investigation, we studied the recovery of REE from fly ash from a commercial power plant. The specific aim was to assess the technical feasibility of recovering REE from the coal fly ash using conventional preconcentration methods, including gravity separation, magnetic separation, and froth flotation. The experimental results revealed that flotation achieved major gains in REE recovery and upgrading. However, during gravity and wet magnetic separation tests, the bulk of REE reported to the tailings. The results showed significant variations in the performance of the various beneficiation methods investigated. This study has confirmed that existing physical separation methods could be used to recover REE from coal fly ash prior to hydrometallurgical and pyrometallurgical processing, although some challenges persist.

Jan 2, 2022

By F. Nakhaei, M. Le Roux, Q. P. Campbell, S. Botlhoko

The results of coal sink and float tests are plotted as washability curves. Analysis of these curves indicates the most effective method by which the coal can be cleaned. Sink and float experiments are samplingdependent, destructive, and use toxic chemicals. The present research introduces an alternative method based on a 3D imaging system called RhoVol, in which the density of individual particles is determined from mass and volume measurements. A quantitative error analysis was conducted on coal sample density measurements obtained by RhoVol, and the main factors influencing the errors identified and investigated. The results show that the drawback of this technique is related to its not being able to detect hidden concavities in the particle, resulting in an overestimation of particle volume. Furthermore, it is difficult to capture the impact of porosity and cracks on the volume of coal particles obtained from 3D silhouette images. This mismatch between the RhoVol data and sink and float test results has led to attempts to apply neural network (NN) and linear regression techniques to produce a fully reliable model for correction and estimation of coal density. The NN approach offers superior predictive capability over linear regression, and the estimated density distribution is in line with the sink and float analysis. The root mean square error in estimation of density using the NN model was less than 0.05 g/cm³.

Aug 2, 2022

By D. Skelton

The Renard kimberlite cluster is located in the Monts Otish region of Quebec, Canada. A Canadian National Instrument (NI) 43-101 compliant resource statement for the Renard kimberlites 2, 3, 4 and 9 and the Lynx kimberlite dyke was first issued in 2008 followed by a Preliminary Economic Assessment and the development of a conceptual mine plan. Following a successful drill program in 2009 that greatly expanded the amount of kimberlite in Renard 2, a revised resource statement was issued in December 2009 comprising 23 million carats of Indicated Mineral Resources and 13 million carats of Inferred Mineral Resources, a threefold increase on the previous estimate. The project is currently the focus of a second Preliminary Economic Assessment and it is expected that a full feasibility and permitting program will commence in 2010 leading to the creation of Quebec's first diamond mine by 2013.

Jan 1, 2010

The September General Meeting of the Institute was held in Kelvin House, Johannesburg, on 16th September, 1970, at 3.00 p.m. Mr V. C. Robinson (President) was in the Chair. There were also present one hundred and eighteen Fellows, including Dr J. M. Bereza, H. P. Carlisle, R. J. C. Goode, Dr J. P. Hugo, P. Lambooy, Prof R. P. Plewman, W. W. Malan, Dr J. T. McIntyre, Dr M. D. G. Salamon, L. W. P. Van den Bosch, P. A. von Wielligh (Council Members), A. Bain, G. P. Bennet, D. L. Carson, G. L. H. Diering, M. E. E. Douglas, F. A. B. Fouche, R. Fourie, A. R. C. Fowler, E. B. Gordon, J. S. Hay, G. H. Henderson, S. D. Hill, A. C. Hofmeyr, J. M. Jacobs, A. F. Lee, D. G. Malan, L. J. Prince, W. G. Pyne-Mercier, A. H. Mokken, Dr W. S. Rapson, R. R. Richardson, H. V. Solomon, C. G. Sowry, G. G. Stanley, G. R. Still, D. L. Starkey, D. L. Taylor, E. W. Thiel, I. E. Van Aswegan, M. van Ryneve1d Steyn, N. B. Vinson, H. Wheeler, Dr A. Whillier, R. A .Wilson, C. F. Ziervogel. Forty-two Members including R. C. Bertram, F. Collier, G. C. Currie, O. Davel, J. M. Gosnell, A. Hazell, Dr N. C. Joughin, F. Kleinschmidt, D. Love, R. B. Macgillivray, D. Mather, R. D. R. Munro, R. S. Pearson, J. J. Peisl, T. J. Pole, A. J. Rossouw, R. G. B. Skirving, G. S. Schwartz, K. Stee1e, H. A. G. Slater, A. Taylor, B. A. Thomas, P. L. Vaughan, D. T. Watt, W. Wilson. Nineteen Associates including R. K. Briggs, S. I. Du Preez, P. G. Gaylard, P. H. Hartslief, W. M. Mackay, A. D. Ross. Three Students: V. S. Care, R. J. Drummond, P. J. Pretorius. Thirty-one Visitors including C. P. S. Barnard, D. W. Bosch, M. Bain G. L. Brown, G. D. Behrens, C. Coetzer, D. M. Gilbart-Smith, R. L. Man, Dr G. J. Stander, M. W. L. Steinobel, R. H. E. Thorpe, T. D. van Wyk, P. H. van Zyl, E. Vereecken, J. J. H. Viljoen. Secretary, D. C. Visser. Total present: 215. OBITUARIES The President: "It is my sad duty to announce the death of the following: Bruce Donaldson Crawford, Fellow, who joined the Institute in 1951 and passed away on 29th April, 1970. Donald Joseph Powrie, Life Fellow, who joined the Institute in 1935 and passed away on 22nd July, 1970. As a mark of respect to the memory of the deceased and in sympathy with the bereaved I would ask you all to rise and observe a few moments' silence." MEMBERSHIP The President: "I have much pleasure in announcing that the names of the under-mentioned candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute in the following grades: Associate: WiIliam Norman Carter. Students: Roman Michael Dabrowski, Sean George Dean Eaton, Alan Philip Stonham Howard, Anton du Preez Roos, Richard Harold Tourle. MEMBERS TRANSFERRED TO A HIGHER GRADE From Graduate to Member: Terrance Alexander Ward. From Associate to Member: Bernard Andre Thomas. "I welcome the newly elected members to the Institute and congratulate the members who had been transferred to a higher grade." CO-OPTION The President: "I wish to advise members that, in terms of clause 3.9 of the Constitution, Mc. H. P. Carlisle had been co-opted to serve on Council." PAPERS FOR PRESENTATION The President: "We have two papers today, and I am first going to call on Dr Stander the Head of the Water Division of the C.S.I.R., who IS well known to many of you for his work and talks on pollution, who has had more than a little to do with this industry, and who has been I would say, of the greatest possible assistance to the mining industry in overcoming the problems of pollution which are so prevalent in industry of this nature. He, Mr Henzen and Mr Funke have written this paper, 'The disposal of polluted effluents from mining, metallurgical and metal-finishing industries, their effects on receiving water and remedial measures.' This is the Water Year, as you know, and it is most appropriate that we should have such an authority to talk to us on this very important topic. I now have much pleasure in asking Dr Stander to introduce his paper." After the presentation of the paper the President said, "Gentlemen, I am sure that you would like me on your behalf, to thank Dr Stander very sincerely for a paper which I think has enabled us to get a completely new slant on the Water Year. There are many people who have put their finger on this campaign and said, it is all a gimmick. There are others-I suppose notably some of the bridge clubs which operate on week-day afternoons in Parkview-who seem to think that this is a quick way of getting early rain. Of course, it is not. This is a most important paper which we have had given to us this afternoon. You probably found it here when you arrived and have not read it-I was very lucky to be able to read it last night, and there is an awful lot of meat in it. For as long as I have been associated with mining in any way, there has been a problem of polluted effluent-of effluents carrying a mineral load from mining, and I think Dr Stander is absolutely right-and, of course, the Commission is right when they say that this is not merely the problem of mine management or mine owners-this is a problem which affects every single human being in this country.

By S. Durapraj, R. T. Masethe, U. Maqina, A. C. Adoko

This study investigates seismicity and rockburst control within the Merensky Reef and UG2 orebody of an intermediate-depth platinum mine located in South Africa's Bushveld Complex. Utilising a mine-wide seismic monitoring system, over 1,900 seismic events were recorded between April 2023 and May 2024, revealing complex seismic patterns driven by mining-induced stress changes. The largest event, with a magnitude of ML 2.0, underscores the seismic risks associated with mining at increasing depths. Key findings include the spatial and temporal variability of seismic events, with high seismic activity observed near pillars and geological structures. A significant portion of events correlated with pillar and foundation failures. Moment tensor analysis identified dominant failure modes, such as stress-driven fracture closures and dynamic pillar failures. To mitigate risks, the study emphasises advanced support system redesign and rockburst risk assessment using the rockburst damage potential (RDP) method. The research highlights the importance of monitoring, geotechnical compliance, and adaptive designs in enhancing safety and reducing seismic hazards in underground mining operations. The study applied the RDP framework, classifying damage across R1 to R5 scales, where most instances fell into low-risk categories (R1 and R3), indicating minor to moderate damage. However, data limitations and the tabular stoping method's complexity led to inconclusive results, highlighting the need for more robust data and customised risk assessment tools. Despite these challenges, the RDP approach provided valuable insights into rockburst mechanisms and the effectiveness of existing support systems.

Jan 12, 2025

By F. L. D. Cloete, A. K. Haines, T. D. Sampson, T. H. Tunley, W. A. M. te Riele

The recovery of zinc from pickle liquors by ion exchange A. K. HAINES. Ph.D. (Visitor) T. H. TUNLEY. B.Sc;.(Chem.Eng.)(Visitor), W. A. M. TE RIELE. pr, Eng.. Ph. D. (Visitor), F. L. D. CLOETE. M.Sc. (Chem..Eng.)(Visitor), and T. P. SAMPSON. Pr. Eng.. BSc, (Chem.Eng,). B. Econ. (Visitor) Picklers and galvanizers in and around Johannesburg are encountering an ever-increasing problem in disposing of spent liquors from their hydrochloric acid pickling baths. Particularly troublesome is the zinc-contaminated liquor that is produced as a result of the clean-up of rejects from the galvanizing operation. Because of the volatility of zinc chloride. this liquor presents difficulties when processed in a conventional pyrohydrolysis acid-recovery unit. The paper describes the Metsep Process. developed by the National Institute for Metallurgy and Woodall-Duckham S.A. (Pty) Ltd. which involves the use of continuous ion exchange for the separation of the zinc from the pickle liquor. and the use of liquid-liquid extraction for the conversion of zinc chloride eluate to salable zinc sulphate. A description of laboratory and pilot-plant tests is given. and the approach used in the design of a full-scale continuous- ionexchange plant is outlined.

Jan 11, 1973

By N. Naudé, J. de Villiers, C. P. Bergmann

It is proposed that the physical and chemical composition of individual mineral particles are an appropriate basis from which to model the performance of minerals processing equipment. Such a particle-based approach enables modelling across disciplines such as comminution, classification and flotation and automatically generates the traditional mass and chemistry balances. The general approach followed is to generate full grade-recovery curves for a separator by sampling product and tailings at varying mass yields. AutoSEM characterisation of each sample provides particle data that is used to reconcile mineral deportment and liberation to the measured size and assay data. In this way, partition surfaces can be generated and modelled. In this paper, an empirical model for the performance of a gravity spiral concentrator treating fine chromite ore is proposed. The model is based on the combination of two partition surfaces and is able to accommodate both forward and reverse gravity concentration effects per size fraction. The results show that this approach is well suited to represent spiral performance for the cases evaluated. The effect of two feed particle size distributions on the performance of the Multotec SC21 and SC25 spirals is demonstrated. Simulations are run in an Excel environment, linked to Python-enabled routines for enhanced data management and calculation speed. Keywords: Spiral concentrator, gravity separation, particle-based modelling

Jan 1, 2020

It is widely accepted that the type of grinding media has an impact on the grinding chemistry and subsequent flotation behaviour of the sulphide minerals being separated. There are countless laboratory investigations demonstrating that inert grinding media produces more oxidizing pulp potentials, reduced levels of grinding media corrosion products, and superior concentrate grades and valuable metal recoveries. However, taking these results to industrial scale has proved difficult. This paper provides details of the protocol developed and used during a high-chrome grinding media plant trial. It describes the test regime employed to measure changes in pulp chemistry as well as concentrate grades and recoveries to produce a statistically meaningful result. The work also highlighted the need for close cooperation between the metallurgists on site and the researchers conducting the trial. To demonstrate the protocol, data gathered during a plant trail in a PGM concentrate will be presented describing the changes in pulp chemistry and metallurgical response observed.

Jan 1, 2012

By А. V. Aksenov, S. G. Rybkin, А. Y. Senchenko

For gold plants in Russia, it is very complicated and costly to use cyanide leaching for efficient processing of gold refractory ores, where gold is closely associated with sulphide minerals and the significant amount of natural carbonaceous matter present. Oxidative roasting of gold refractory concentrates is a well-known method, making it possible to obtain a high recovery rate of precious metals to a target product. The use of oxidative roasting is limited in general by the expense of capturing and neutralising the harmful components of roasted gas, mainly sulphur (SO2, SO3) and arsenic (As2O3) oxides. This paper addresses testing and development of an optimised technology to process gold refractory gravity and flotation concentrates by means of oxidative roasting which stabilises arsenic as calcium arsenate. The process involves roasting of a gravity or flotation refractory ore concentrate in a mixture with lime and calcium chloride, with a supply of oxygen, and at 600-700°С. During the roasting a carbonaceous matter of the concentrate burns out and sulphide components transform into harmless calcium sulphate (CaSO4) and calcium arsenate (Ca3(AsO4)2), and iron passes into the form of hematite (Fe2O3). After disintegration, the roasting cinder is concentrated on a table to obtain a high-grade gravity concentrate and gravity tailings. The high-grade gravity concentrate is subject to smelting in a mixture with fluxing agents, which results in alloyed gold and slag. The gravity tailings are ground and reported to cyanide leaching. In the case of a flotation concentrate, the roast cinder is ground to minus 30 μm and subject to sorption cyanide leaching. High gold recovery (90-95%) of the target product and environmental safety are typical of the improved technology under consideration. Two national patents were granted for the methods developed to treat refractory concentrates bearing precious metals. Keywords: Gold concentrates, oxidative roasting, cinder, cyanide leaching, smelting, alloyed gold

Jan 1, 2020

[Consider a square block W in an ore body S2, to be valued from one centre sample w, and one corner sample w2 (Fig. 9.1). The sample set is ws = Iw,;w21. We can estimate the block average µw by the average of the sample values x, and x2: µw = 'z (x, + xz). (9.1) The error made is measured by the estimation variance: o' (ws to W) = 2 - (ws; W) - - (ws;ws) - - (W; W). (9.2) However, we know that the centre sample w, gives more information about the block value than the corner sample w2. In the example studied in § 8.4, where w, and w2 were considered to be points, we found that of (w, to W) was nearly one third smaller than o2E (w2 to W), therefore when estimating W one should give more weight to w, than to w2. In general, when evaluating a block W from a set of n samples ws, where WS = l w;w2; ... wn1, a better estimator of µw can be obtained if we give different weights to the sample values, depending on the size and the positions of the samples. Some desirable properties of such an estimator µw are: ? It should be a linear function of the sample values xi: n µw = bi xi (9.3) =t where bi = weight given to sample x . ? It should be unbiased, i.e. its expected value should be equal to the true block value: E [µw - µw] = 0. (9.4) ? The mean squared error of estimation of µw should be a minimum E [(µw - µw)2] = a minimum. (9.5) The estimator which satisfies these properties is a minimum variance, linear and unbiased estimator, and is known as the kriging estimator. The corresponding error of estimation is the kriging error. This estimator is also known as the BLUE (for Best Linear Unbiased Estimator) estimator. This was named by Matheron in acknowledgement of the early work of Krige's in the optimization of the evaluation of the South African gold mines. The following notations will be used: µK kriging estimator. o2k = o2K (w,, to W) kriging error.]

Jan 1, 1978

By H. Jiang, W. Wang, Y. Zhao, J. Qiao, C. Duan

DEM simulations were used in this research to study the screening process of a novel variable amplitude equal thickness vibration screen (VAETVS). The response regularity of mass distribution and granular moving velocity at the different screen panels to feed rate was investigated and the predictive model for the unit area processing load was proposed. The influence of aperture size, the size variance, and the opening ratio on the mass passing-distribution and overall screening performance, respectively, were revealed. The results showed that the response model of the unit area load Ф to the feed rate Q can be concluded as Ф∝0.324×Q. The moving velocity of particles also showed a positive relevance to the feed rate, besides which the passing rate of fine-grained material at the feed end was negatively related to the aperture size, while the case was reversed in the feed end. The increase of aperture variance AV enhanced the passing ability of small particles at the feed end,and reduced the misplaced ratio of the large particles at the discharge end. A better screening efficiency can be obtained when the average aperture size of the entire sieve is 7.5 mm, with the aperture variance of 1 mm between the adjacent panels. When the combination of the opening ratio is 35-35-40, a better screening effect can be achieved. Keywords: Equal thickness screening, DEM, particulate velocity, mass distribution regulation

Jan 1, 2020

By E. Van Der Lingen

This paper provides a review on coloured gold, platinum, andpalladium intermetallic compounds, and discusses the models thatwere developed to obtain these materials. These compounds have acrystal structure of high symmetry, such as the CaF2or CsClstructures, ensuring distinct electron band structures. Variousexamples of coloured gold, platinum, and palladium intermetalliccompounds are provided. More in-depth discussion is provided on thepurple gold (AuAl2) and yellow platinum-aluminium (PtAl2)compounds with CaF2structure, as well as the purplish-pinkpalladium-indium (PdIn) compound with CsCl structure. Precious metal intermetallic compounds are used in jewellery andprovide a new dimension to design. Some of these compounds havealso found use as barrier coatings on turbine blades for jet engines,and more recently, research has been conducted into their potentialuse as catalysts, electro-catalysts, sensors, capacitors, and fordecorative coatings.

Jan 1, 2014

By J. W. van der Merwe, A. M. Maleka, V. J. Matjeke

The 10.5–12.5% chromium, titanium-stabilized ferritic stainless steel (FSS) plates used to fabricate coal line jumbo wagons is susceptible to undesirable chromium depletion during welding with 309L electrodes. In this work, non-stabilized FSS plates were welded using 308L welding electrodes. The objective was to weld non-stabilized FSSs using gas-shielded metal arc welding without causing sensitization. The welding process was optimized by lowering the heat input. Sensitization was assessed by rigorous etching techniques and anodic polarization scans. In addition, the welds were subjected to tensile testing, and their fracture surfaces were examined for intergranular cracking. Non-stabilized FSS plates were successfully welded using gas metal arc welding.

Apr 5, 2023