Surface modified composite nanofibers for the removal of indigo carmine dye from polluted water

Surface coated magnetite nanoparticles (Fe(3)O(4) NPs) with 3-mercaptopropionic acid were immobilized on amidoximated polyacrilonitrile (APAN) nanofibers using electrospinning followed by crosslinking. The prepared composite nanofibers were characterized with Scanning Electron Microscopy (SEM), and Fourier Transform Infrared analysis (FTIR). The composite nanofiber was evaluated for the removal of indigo carmine dye from aqueous solutions. The effects of contact time, initial dye concentration, solution pH and adsorption equilibrium isotherms were studied. The adsorption of indigo carmine was found to be greatly affected by solution pH. The maximum loading capacity was determined to be 154.5 mg g(−1) at pH = 5. The experimental kinetic data were fitted well using a pseudo-first order model. The adsorption isotherm studies showed that the adsorption of indigo carmine fits well with the Langmuir model. The reuse of the composite nanofiber was also investigated in which more than 90% of indigo carmine was recovered in 5 min. The results of stability studies showed that the adsorption efficiency can remain almost constant (90%) after five consecutive adsorption/desorption cycles

Development and optimisation of incremental sheet forming of titanium grade 2: process mapping

Thesis (PhD)--Stellenbosch University, 2017.ENGLISH ABSTRACT: Manufacturing products ensure value creation from natural resources. The change in manufacturing systems to a greater emphasis on personalisation, increase the need for customised products. Manufacturing challenges are presented by the increasing instability in global markets, shorter innovation cycles, input cost pressures and generally expensive resources. Ever since the industrial revolution, the transformations in manufacturing from mass production and product variety and vice versa, were driven by market and societal transformations and the development of new enabling technologies. Single point incremental forming is a promising rapid prototyping technology for sheet metal applications. Titanium alloys are an attractive material for numerous applications, but its use has been mainly restricted by its material and manufacturing costs. Titanium alloys are also used in a variety of engineering applications, due to its high-strength to weight ratio, corrosion resistance and bio-compatibility. The alloy’s mechanical characteristics make it possible to reduce the application’s structural weight and increase its performance with thin-wall designs. Incremental sheet forming is characterised by its highly-localised deformation ability without drawing in material from a surrounding area. In this truly die-less configuration the sheet is shaped only by the action of a forming tool that has a single point of contact with the blank. Significant cost reductions can be realised from these flexible technologies devoted to reduce the buy-to-fly ratio and enlarge the scope of applications to small series titanium products. Although single point incremental sheet forming (SPIF) is an active research area, the process demands and limitations for forming of CP Grade 2 titanium alloy sheets are not clearly understood. Understanding the effects of these process variables to develop resource-efficient forming process chains of CP Grade 2 titanium sheets will make a significant contribution to manufacturing knowledge. In this dissertation, an efficient twostage process mapping approach is developed and validated. In order to characterise the SPIF conceptual processing space and to identify the key design factors, a systematic quantitative literature review has been undertaken analysing results from relevant publications. The design of experiments (DoE) and one factor at a time test (OFAT) experiments have been methodically implemented to verify the developed conceptual framework. The ultimate goal is to design aprocess suitable for incremental forming of CP Grade 2 sheets that can consistently deliver a product that meets the required quality attributes. The established approach involves mapping the SPIF of the CP Grade 2 in terms of the five key process variables. Once the behaviour of the SPIF process has been mapped, a thorough study of the role of a secondary process variable can be accomplished to evaluate its effect on the process across the full five-key-variables working window. The influence of SPIF factors on the formability of CP Grade 2 were investigated based on the forming forces, the forming temperature and the process productivity. The approach yields insight into the theory of the SPIF process, which deepens the understanding of the dependence of the process outcomes on different variables. The region of the SPIF process variable space, where successful forming of the CP Grade 2 titanium can be anticipated is identified throughout this process mapping approach. The processed data have been presented in a practical two-dimensional process map. The developed working window can be used as a design tool to understand the process demands and limitations for forming of CP Grade 2 titanium alloy sheets. This understanding of the effects of these process variables will enable the development of resource-efficient forming process chains for the CP Grade 2 titanium sheets. The approach as such, however, can be implemented for the establishing of process characteristics for other titanium alloys too.AFRIKAANSE OPSOMMING: Vervaardiging van produkte verseker die toevoeging van waarde tot natuurlike hulpbronne. Die verandering in vervaardiging stelsels om vir individue voorsiening te maak, verhoog die behoefte vir meer persoonlike produkte. Die uitdagings in vervaardiging word veroorsaak deur die toenemende variasie in wêreldmarkte, korter innovasie siklusse, toenemende insetkostes en duur hulpbronne. Sedert die Industriële Revolusie was die transformasie in vervaardiging van massaproduksie na produk verskeidenheid en omgekeerd, gedryf deur die mark, sosiale veranderinge en die ontwikkeling van nuwe tegnologie. Enkel punt inkrementele vervorming is 'n belowende snel vervaardiging tegnologie vir plaatmetaal toepassings. Titaan allooie is 'n gesogte materiaal vir talle toepassings, maar die gebruik daarvan is hoofsaaklik beperk deur die materiaal en vervaardigingskoste. Titaan allooie word ook gebruik in 'n verskeidenheid ingenieurstoepassings, as gevolg van sy hoë sterkte-tot-gewig verhouding, korrosie weerstand en biomediese aanvaarbaarheid. Die meganiese eienskappe van die allooie maak dit moontlik om die strukturele gewig van toepoasssings te verminder en hul prestasie met 'n dun-muur ontwerpe te verhoog. Inkrementele plaat vervorming word gekenmerk deur die hoogs gesentraliseerde vervorming vermoë, sonder om die nabye materiaal te betrek. In die werklike vormlose opstelling word die plaat gevorm slegs deur die beweging van die beitel wat 'n enkele kontakpunt met die plaat het. Beduidende kostes kan deur hierdie vervormings tegnologie gespaar word. Terselfdertyd kan die koop-tot-vlieg verhouding met titaan allooie verminder word en die toepoassings van klein reeks titanium produkte vermeerder. Hoewel enkele punt inkrementele plaat vervorming (SPIF) 'n aktiewe navorsing gebied is, is die proses vereistes en beperkings vir die vorming van CP Graad 2 titaan allooi plaatmateriaal nie duidelik bekend nie. Die verstaan van die gevolge van hierdie proses veranderlikes om hulpbrondoeltreffend vervorming proses kettings van CP Graad 2 titaan plate te ontwikkel, sal 'n belangrike bydrae tot vervaardiging kennis maak. In hierdie tesis word 'n doeltreffende twee fase proses kaart benadering ontwikkel en bevestig. Die SPIF konseptuele verwerking ruimte kon slegs ontwikkel word deur die sleutel ontwerp faktore te identifiseer. 'n Stelselmatige kwantitatiewe literatuuroorsig was onderneem om die resultate van relevante publikasies te ontleed. Die ontwerp van eksperimente (DOE) en een faktor op 'n tyd toets (OFAT) eksperimente was wetenskaplik geïmplementeer om die ontwikkelde konseptuele raamwerk te bevestig. Die doel is om 'n proses kaart vir die vervorming van CP Graad 2 plate te ontwikkel wat ‘n konstante kwaliteit produk kan verseker. Die benadering behels die kartering van die SPIF van die CP Graad 2 titaan allooi in terme van die vyf mees belangrikste prosesveranderlikes. Sodra die gedrag van die SPIF proses gekarteer is, kan 'n deeglike studie van die rol van 'n sekondêre proses veranderlike tot stand gebring word om die uitwerking daarvan op die proses oor die volle vyf sleutel-veranderlikes werk venster te evalueer. Die invloed van SPIF faktore op die vormbaarheid van CP Graad 2 titaan allooi is ondersoek en baseer op die vervorming kragte, die vervorming temperatuur en die produktiwiteit van die proses. Die benadering lewer insig in die teorie van die SPIF proses op, wat die begrip van die afhanklikheid van die proses uitsette op verskillende veranderlikes verdiep. Die area waar die SPIF proses veranderlikes suksesvolle vervorming van die CP Graad 2 titaan kan verwag word geïdentifiseer deur hierdie proses kartering benadering. Die verwerkte data is aangebied in 'n praktiese tweedimensionele proses kaart. Die ontwikkelde werk venster kan gebruik word as 'n ontwerp instrument om die proses vereistes en vervorming beperkings van CP Graad 2 titaan allooi plate te verstaan. Hierdie begrip van die gedrag van hierdie proses veranderlikes sal die ontwikkeling van die hulpbron-doeltreffende vervorming proses kettings vir CP Graad 2 titanium plate moontlik maak. Die benadering kan ook geïmplementeer word vir ander titaan allooie

Toward understanding the process limits of incremental sheet forming of titanium alloys

CITATION: Uheida, E. H., Oosthuizen, G. A. & Dimitrov, D. 2016. Toward understanding the process limits of incremental sheet forming of titanium alloys. In Competitive Manufacturing, International Conference on Competitive Manufacturing (COMA '16), 27-29 January 2016, Stellenbosch, Stellenbosch University, South Africa.The original publication is available at http://conferences.sun.ac.za/index.php/doie/coma16Incremental sheet forming (ISF) process is characterised by high flexibility at low cost, and short replacement time. ISF as a process has received global attention. Particular areas include the aerospace industries, customized products for biomedical applications and prototyping in the automotive industry. Most applications can become competitive due to the flexibility offered by this manufacturing process. In this work, a background study and review of state-of-the-art ISF have been undertaken with the aim of providing a better understanding of the process limitations. The critical factors of incremental sheet forming were discussed and the mechanical and thermal process demands were identified. This information provides the foundation for developing a forming optimisation map.Publisher's versio

Resource efficient process chain development of a modular CubeSat spaceframe

CITATION: Oberholzer, J. F., Uheida, E. H. & Oosthuizen, G. A. 2019. Resource efficient process chain development of a modular CubeSat spaceframe. Procedia Manufacturing, 35:917-928, doi:10.1016/j.promfg.2019.06.037.The original publication is available at https://www.sciencedirect.comA CubeSat is a 10×10×10 cm cube that can weigh up to 1.33 kg. This design offers a less expensive alternative for space enthusiasts to explore the cosmos, even though the total weight is very limited. For a CubeSat to be allowed to launch, it must adhere to certain specifications outlined in the CubeSat Design Specifications document. This places several restrictions on the satellite in terms of weight, size and center of gravity, and innovative solutions need to be explored during integration to meet these specifications. Having a spaceframe that can easily be assembled and disassembled will help smooth out the integration stage and save a significant time that can then be allocated elsewhere in the developmental stages. The increasing relevance of resource efficient manufacturing is prevalent through the continually rising costs of resources and energy. In order to stay competitive, manufacturers must develop resource efficient process chains to gain an advantage in the market. This study focused on developing a resource efficient process chain to manufacture a modular CubeSat spaceframe. This spaceframe must adhere to the CubeSat Design specifications, as well as meet the customer’s needs. A unique assembly process was designed that eliminated the need for screws structure together. Instead the spaceframe relies on interference fits, and utilizes the unique deployment method of the Poly-Picosatellite Orbital Deployer to ensure that the assembly does not fail. A material selection procedure was utilized, along with resource efficient manufacturing process chains to develop a CubeSat structure that is very cost effective to produce, easily assembled and disassembled and weighed less than most of the market leading CubeSat structures.https://www.sciencedirect.com/science/article/pii/S2351978919307620Publisher's versio

Investigating the impact of tool velocity on the process conditions in incremental forming of titanium sheets

CITATION: Uheida, E. H., Oosthuizen, G. A. & Dimitrov, D. 2017. Investigating the impact of tool velocity on the process conditions in incremental forming of titanium sheets. Procedia Manufacturing, 7:345-350, doi:10.1016/j.promfg.2016.12.085.The original publication is available at https://www.sciencedirect.comENGLISH ABSTRACT: This paper deals with a study focused on the single point incremental forming (SPIF) of titanium Grade 2 sheets. The direct impact of the sliding velocity of the forming tool on mechanical and thermal process loads was experimentally investigated. A wide range of spindle speeds and feed rates were examined at different forming conditions. The developed profiles of the mechanical and thermal demands during the SPIF of titanium sheets are presented and discussed. Forming temperature and force were directly related to the tool rotation speed, higher temperatures and lower reactional forces correspond to higher speeds. At very high rotation, failure conditions occurred and the ability to shape a CP Grade 2 sheet is decreased; these failures were mainly due to extreme heating, leading to termination of the tests concerned. The main objective of the study is to gain a better understanding of the combined effects that the varied relative motions at the tool/sheet contact zone have on the process conditions.https://www.sciencedirect.com/science/article/pii/S2351978916302487Publisher's versio

Visible light photocatalytic reduction of Cr(VI) by surface modified CNT/titanium dioxide composites nanofibers

In this work we report a highly efficient photocatalytic reduction of Cr(VI) based on PAN-CNT/TiO2-NH2 composite nanofibers fabricated by using electrospinning technique followed by chemical crosslinking of surface modified TiO2 NPs functionalized with amino group. The structure and morphology of the fabricated composite nanofibers were characterized by FTIR, SEM, TEM, TGA, and XPS. The results indicate that the composite nanofibers possess excellent photoreduction performance for Cr(VI) under visible light (125 W) after 30 min, which is much faster than previous reports. The effects of various experimental parameters such as catalyst dose, irradiation time, initial concentration of Cr(VI), and pH on the photoreduction efficiency of Cr(VI) were investigated. The highest photoreduction efficiency of Cr (VI) was obtained at low acidity and low amount of TiO2/CNT photocatalyst. The kinetic experimental data was attained and fitted well with a pseudo-first-order model. The UV–vis spectrophotometer and XPS analyses proved that chromate Cr(VI) was reduced to Cr(III). In addition, it can be concluded that the addition of the phenol enhances the photocatalytic reduction of Cr(VI). Furthermore, the photoreduction mechanism has also been discussed. Finally, the fabricated composite nanofibers were found to be stable after at least five regeneration cycles. © 201