Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie最新文献

{"title":"Effects of combined alkali treatment and clay nanoparticle infusion on thermo-mechanical response of kenaf/PLA biocomposites","authors":"M. Moyo, K. Kanny, T. Mohan","doi":"10.36303/satnt.2021cosaami.27","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.27","url":null,"abstract":"Fibre-reinforced biocomposites have inherently low thermo-mechanical properties and hence require some treatments or modifications during the fabrication process in order to enhance these properties. In this work, a combination of alkalization and nanoparticle infusion was used in enhancing thermo-mechanical properties of kenaf fibre-reinforced polylactic acid biocomposites. The biocomposites were made using sodium hydroxide (NaOH) treated kenaf nonwoven mats and polylactic acid infused with clay nanoparticles. Fabrication of the biocomposites was done using the prepreg method and curing at high temperature. Investigation of the thermo-mechanical properties were performed using a thermogravimetric analyser (TGA) and dynamic mechanical analyser (DMA). Results showed that a combination of alkalization and nanoparticle infusion improves the thermal stability of the biocomposites, loss modulus and damping. However, alkalization and nanoparticle infusion decreased the glass transition temperature of the biocomposites. The study shows that combined treatment of biocomposites with sodium hydroxide and clay nanoparticles significantly improves their performance properties. Therefore, this expands the application capabilities of natural fibre reinforced biocomposites. Best results were obtained by a combination of NaOH treatment and infusion with 5 wt% clay nanoparticles.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74637817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of Mo on microstructure and nanoindentation hardness of Ti-Al-Si-xMo alloy processed by Laser Engineered Net Shaping (LENS)","authors":"S. Raji, A. Popoola, S. Pityana, OM Popool, N. Arthur, M. Tlotleng","doi":"10.36303/satnt.2021cosaami.18","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.18","url":null,"abstract":"In this work, the microstructure and nanoindentation hardness properties of Ti-Al-Si-xMo alloys produced through laser in-situ alloying using laser engineered net shaping (LENS) technology were investigated. The microstructures and phases present were examined by means of scanning electron microscopy (SEM) equipped with an electron dispersion spectrometer (EDS), while the mechanical properties were studied using a nanoindentation tester. The microstructures exhibited fine lamellar α2-Ti3Al/γ-TiAl colonies surrounded with ζ-Ti5Si3 and ordered β0-TiAl phase in the as-produced state; while after heat treatments coarse β0-phase was observed to be embedded within the lamellae colonies. Microstructural analysis showed that β0-phase precipitated not only at the α2/γ lamellae colony boundaries but also inside the lamellae owing to the relatively high content of the β0-phase present. Nanoindentation testing showed that the indentation hardness of this current alloy is comparable to most TiAl alloys. This study also reveals that Mo additions generally increase hardness values, but only minor effects on hardness are observed at 1400 oC heat treatment temperature. Thus, Mo additions for TiAl alloys demonstrate positive effects on mechanical properties when less than 5 at.% of the alloy composition but the mechanical properties would either reduce or remains unchanged with further increase in Mo.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75716375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermo-mechanical processing and phase analysis of titanium alloys with copper additions","authors":"K. Ukabhai, K. Nape, L. Spotose, M. Mavundla, IA Mwamba, MO Bodunrin, L. Chown, L. Cornish","doi":"10.36303/satnt.2021cosaami.17","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.17","url":null,"abstract":"In dentistry and orthopaedics, to replace and mend broken bones, any replacement material needs to have: low density, high strength, good biocompatibility and must be able to integrate closely with the bone. Titanium-based alloys have these properties, although currently used alloys contain toxic elements, and commercially pure Ti does not have sufficient strength. Within ten years, 7% of dental implants have complete failure, mainly from bacterial infection. Therefore α + β type Ti-alloys were developed by adding b stabilisers, with similar phase proportions to Ti-6Al-4V without the toxic elements, with Cu additions for antibacterial properties and Ru for corrosion resistance. Deformation behaviour of Ti-6Al-4V and Ti-Ta-Nb Zr alloys were also studied using a Gleeble thermomechanical simulator. The compositions of the new alloys were derived using Thermo-Calc. Ti-8Nb-4Zr alloys had bimodal microstructures and the addition of Cu formed the Ti2Cu phase. The Ti-6Ta-1.5Zr and Ti-6Ta-1.5Zr-0.2Ru alloys with no Cu had coarse α lamellae, whereas the alloys with Cu had parallel α plates. The Gleeble results showed that higher flow stresses were obtained at higher strain rates and lower temperatures, agreeing with literature. At 850 °C, the Ti-6Al-4V alloy had higher flow stresses than Ti-10.1Ta-1.7Nb-1.6Zr. The Ti-6Al-4V and Ti-10.1Ta-1.7Nb-1.6Zr alloys had steady-state flow stresses at 950 °C, and continuous flow softening at 850 °C for both strain rates.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"68 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90350207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A case for establishment of the Ferrous Materials Development Network (FMDN) in South Africa","authors":"M. Phasha, J. Moema, J. Papo","doi":"10.36303/satnt.2021cosaami.36","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.36","url":null,"abstract":"South Africa is known to be one of the mineral endowed countries in the world, bearing large quantities of iron, chrome, manganese and vanadium reserves that are key to iron and steel industries. It is thus vital to leverage on this natural resource endowment to build a dynamic industrial economy capable of creating sustainable jobs. Central to achieving this goal is the need to derive greater economic value from these natural resources, which will reduce import levels and create export opportunities. Currently, however, the local iron and steel industry is forced to navigate some of the known challenges such as the cost of energy, transportation, labour and steel, in order to remain competitive and operational. These matters which hamper the realization of beneficiation aspirations do not only have a huge impact on the downstream value-adding steel industry but also make the cost of doing business in SA unattractive.\u0000\u0000Consequently, based on its capability, relevancy and experience in supporting the iron and steel sector for many years, Mintek has been entrusted with the responsibility to host the Ferrous Materials Development Network (FMDN) by government through advanced materials initiative (AMI) programme to coordinate research on ferrous materials in the country.\u0000\u0000The purpose of this paper is to illustrate the need for interdependent research activities in ferrous materials in South Africa, which is underpinned by collaborative research, development and innovation (RDI) efforts between science councils, academia and industry. These activities are aimed at generating local know how, fostering local and international collaboration, development of human capital (HCD), supporting job creation through beneficiation, identification of relevant advanced technologies to improve competitiveness, localization of designated castings, design and development of new ferrous materials with enhanced properties to enable access to niche export markets as well as improving local capability to produce high-end ferrous products for critical sectors of the economy such as petrochemical, energy generation, transportation, mining, etc.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83452477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of hydrothermal grown zinc oxide nanoparticles as seeds on the properties of nanoripples in zinc oxide thin films","authors":"M. Seabi, T. Muller, S. Bolokang, F. Cummings, C. Arendse","doi":"10.36303/satnt.2021cosaami.13","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.13","url":null,"abstract":"This work reports on a simple approach to improving the optoelectronic properties of Wurtzite ZnO nanoripples by means of incorporating hydrothermally synthesised ZnO nanoparticles under controlled synthesis temperature. Initially, ZnO nanoparticles were investigated and subsequently utilised as seeds to induce ripple growth in spin-coated ZnO thin films. TEM images illustrated the development of nanospheres at 140°C. The yield of ZnO NPs at 180°C increased and consisted of a combination of nanorods and nanospheres. Morphologically, seedless ZnO nanoripples showed rugged ends of the nanoripple structures. The SEM images illustrated that the layers uniformly formed on the substrates, and seeding the ZnO nanoripples caused the nanoripples to elongate. The thickness of the nanoripples thin films showed a decrease with the incorporation of hydrothermally synthesised ZnO seeds from 134 nm for unseeded ZnO nanoripples to 96 nm at 180°C. The incorporation of ZnO NPs seeding treatment increased the transmission of ZnO nanoripples from 82% to 92%, leading to untreated ZnO nanoripples exhibiting a direct band gap of 3.19 eV that increased after seeding to 3.36 eV. The change in the band gap to a higher value(s) and increased transparency confirms the progressive improvement of the thin films due to incorporating ZnO seeding for optoelectronic and photovoltaic applications.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87253604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational fluid dynamics evaluation of conditions before impact of particles in plasma spraying process","authors":"KJ Mbwebwe, A. Kolesnikov, I. Van der Walt, H. Bissett","doi":"10.36303/satnt.2021cosaami.04","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.04","url":null,"abstract":"Plasma Spraying is one of the most sophisticated and versatile thermal spray techniques. In Plasma Spraying, powdered material is injected into a plasma jet, which is generated from a plasma torch. Upon contact with the plasma jet, the particles are melted and propelled forward onto a substrate to form an adherent coating which modifies the properties of the substrate. The modifications to the substrate can, for example, increase its resistance to other extreme operating conditions such as wear, abrasion, and corrosion. However, the phenomena governing the formation of the plasma jet inside the plasma torch and its subsequent interaction with injected particles are not fully understood. This paper provides a detailed report on steps taken for the development of a comprehensive numerical model to simulate plasma jet development inside a direct current plasma torch. The heat flow and mass exchange of ionized gas with injected solid particles were followed in three dimensions by using a Computational Fluid Dynamics (CFD) method. A cylindrical energy source term which was defined as an increasing linear function dependent on time as a variable, was included to reproduce the effects of an electric arc on the gas flow. For optimization purposes, it was sought to investigate the effects of the particles’ injection angle and inlet velocity, as well as the effects of particle size distribution on the particle temperature and velocity histories.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72738079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of substrate heating on the microstructure and hardness of TiB/Ti6Al4V-ELI during laser in-situ metal deposition","authors":"PM Lekoadi, M. Tlotleng, B. Masina","doi":"10.36303/satnt.2021cosaami.12","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.12","url":null,"abstract":"This work investigated the influence of heating temperature (°C) on the microstructure and microhardness of TiB/Ti6Al4V-ELI composite clads that were produced via in-situ alloying using laser metal deposition technique. The samples were produced on a Ti6Al4V base plates which were heated at different temperatures (25°C, 200°C, 300°C, 400°C and 500°C) before they were characterised for microstructure and hardness. It was found that the TiB/Ti6Al4V-ELI sample that was produced on a non-pre-heated base plate was characterized by TiB particles and had the lowest hardness of 511 ± 66 HV. Base plate heating resulted in the formation of TiB whiskers that were dispersed within the titanium matrix. 200°C led to a microstructure with clusters of TiB whiskers hence it had an increased hardness of 651 ± 40 HV. A fine microstructure with homogeneous distribution of the TiB whiskers was obtained at 500°C base plate heating temperature and had hardness of 565 ± 14 HV.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"333 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73895171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling and simulation of the fatigue usage factor of γ-TiAl alloy fabricated through Laser Additive Manufacturing (LAM)","authors":"S. Raji, A. Popoola, S. Pityana, O. Popoola, N. Arthur, M. Tlotleng","doi":"10.36303/satnt.2021cosaami.30","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.30","url":null,"abstract":"Recently, laser additive manufacturing (LAM) technologies are increasingly being applied for producing components with excellent physical and mechanical properties in the aerospace, automotive and energy industries. This work is aimed at modelling the fatigue usage factor of γ-TiAl alloy fabricated through LAM. The modelling and simulation were performed using the COMSOL Multiphysics 5.4 software by developing a y-TiAl alloy microstructure. This was modelled to generate the material properties (density, heat capacity at constant pressure and thermal conductivity) from the microstructure of a unit cell as a general representation of the alloy. The computed properties were used in modelling the LAM process to fabricate γ-TiAl alloy part with subsequent fatigue simulation to determine the usage factor (Ke). From the models, the maximum Von Mises stress and transient temperature were 2.88 x108 Nm-2 and 1510 K respectively, for the LAM fabrication process; while the fatigue usage factor model showed a maximum Von Mises stress of 2.91 x108 Nm-2 and a fatigue usage factor of 0.35.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87394012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In-situ synthesis of TiC/Ti-6Al-4V-ELI composite by laser","authors":"P. Ramasobane, P. Mashinini, B. Masina","doi":"10.36303/satnt.2021cosaami.14","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.14","url":null,"abstract":"Titanium-based alloys are reported to offer up to 50% strength to weight ratio. These lands titanium-based alloys as a preferred material over steel and nickel-base super-alloys, where strength and stiffness are required. Regardless titanium-based alloys are prone to losing strength and stiffness at elevated temperature applications such as jet engines. This prompted a need for titanium matrix to be braced with a material with superior properties, such as ceramic. In-situ synthesis with laser metal deposition (LMD) of Ti-6Al-4V-ELI braced with discontinuous particulates of TiC resulted in improved hardness and microstructure. It is reported that an increase in the feed rate of TiC during the LMD process directly increases the hardness of the TiC/Ti-6Al-4V-ELI composite and refine the grain size of Ti-6Al-4V-ELI. Various fabrication methods and properties of Ti-6Al-4V are well documented in the literature. This paper focuses on the effect of TiC on the microstructure and hardness of Ti-6Al-4V-ELI.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"106 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76717519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterisation of Spheroidised tungsten carbide metco 32c powder using radio frequency plasma","authors":"R. Dire, H. Bissett, D. Delport, K. Premlall","doi":"10.36303/satnt.2021cosaami.22","DOIUrl":"https://doi.org/10.36303/satnt.2021cosaami.22","url":null,"abstract":"Metco 32C is a coarse grey powder, which mostly consists of tungsten carbide and cobalt; with small traces of nickel, chromium, boron, iron silicon and carbon. Metco 32C powder has the role of supporting oxidation and corrosion resistance at high temperatures as well as increasing the hardness of the coated materials.\u0000\u0000The spheroidal morphology of Metco 32C improves flowability during layer application methods such thermal spraying. There has been a growing interest in the development / improvement of methods producing powders of cast tungsten carbide and other high-melting-point materials of uniform composition, characterised by a high sphericity of the particles and having higher physical-mechanical properties. Spherical particles are generally preferred in the additive manufacturing process as they pack together for uniform powder bed density, better flowability in machinery, eliminate internal cavities and fractures resulting in a better quality of final product. Similarly, thermal spraying processes also require dense, spherical particles to ensure consistency and reproducibility of the feeding mechanism as well as interaction between the feedstock and thermal spraying heat source. The process of transforming irregularly shaped powder particles into spherical shapes is known as the spheroidisation process and this can be achieved by plasma spheroidisation.\u0000\u0000It was found that the spheroidisation ratio of the powder increased as the plasma plate power increased. A decrease in density was observed as plasma power increased. The spheroidised powders have a smaller particle size distribution (PSD) than the feed powders (un-spheroidised). The XRD results showed that as the plasma plate power increased the WC phase composition decreased, subsequently the phase composition of W2C increased.","PeriodicalId":22035,"journal":{"name":"Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73476345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}