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Biphenolate and cyclopentadienyl-derived complexes of zirconium and titanium as catalysts for the polymerisation of alpha olefins

- Van Zyl, Aletta

  • Authors: Van Zyl, Aletta
  • Date: 2012-09-04
  • Subjects: Oligomers , Polymerization , Zirconium , Alkenes , Titanium
  • Type: Thesis
  • Identifier: uj:3459 , http://hdl.handle.net/10210/6852
  • Description: M.Sc. , An annual production of approximately 46 million metric tons of polyolefins worldwide, emphasizes the industrial importance of this product and the polymerisation process. Olefins are the basic building block of the petrochemical industry and are therefore readily available and cheap. Reactivity of olefins decreases from ethylene to propylene to 1-octene and makes the study of polymerisation catalysts more complex, seeing that the activity of a catalyst differs from monomer to monomer. In this study zirconocene complexes with bridged cyclopentadienyl ligands have been prepared and investigated as , possible catalysts for the polymerisation of higher aolefins. Fulvenes have been reductively coupled and used as ligands for zirconium complexes. Steric bulk of the substituents on the ligand have been increased and changes in the polymeric products have been studied. The tacticty, endgroups and chain lengths of the polyolefins have been investigated. There is currently a considerable interest in the development of 'non-metallocene' catalysts as alternatives for the polymerisation and oligomerisation of a-olefins. Chelating diamide complexes of Group 4 metals have been the focus of much attention and these compounds have shown moderate to high reactivity. However, only a few examples of the corresponding chelating alkoxides are known. In this study, alkoxide complexes of zirconium and titanium have been prepared with Schiff bases as ligands. These complexes have been evaluated as polymerisation catalysts and the products have been studied. The titanium complexes were more active than the zirconium analogues. The narrow molecular weight distribution of the polyolefins gave evidence that these catalysts are single-sited catalysts.
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Characterization of functionally graded commercially pure titanium (CPTI) and titanium carbide (TiC) powders

- Akinlabi, Esther Titilayo, Akinlabi, Stephen A.

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2015-07-01
  • Subjects: Functional graded materials , Laser metal deposition , Titanium , Titanium carbide
  • Type: Article
  • Identifier: uj:5136 , ISBN 9789881404701 , http://hdl.handle.net/10210/14102
  • Description: Functionally Graded Materials (FGM) are advanced materials fabricated using additive manufacturing techniques. It belongs to a class of advanced material characterization in which the properties of the material composition is varied. The resulting property of the composite is always different from the properties of the individual material employed in the formation of the composite. They are known to also exhibit good mechanical and chemical properties and as such, are used for different industrial applications. One of the techniques employed in the fabrication of FGMs is called Laser Metal Deposition (LMD) technique. It uses laser beam to melt powder material on a substrate forming a melt pool that solidifies upon cooling. This paper reports on the material characterization of functionally graded Titanium and Titanium Carbide (TiC) powders deposited on Titanium substrate by laser metal deposition approach. The formed deposits were fabricated by varying the processing parameters such as laser power, scanning speed and the powder flow rate. From the result obtained, the microstructures showed that the laser power has much influence on the grain growth of the material. In addition, with the SEM analysis of the microstructure since the percentages of the titanium and titanium carbide were varied, it was observed that the sharp boundaries of the Titanium Carbide were reduced greatly and this resulting effect can be attributed to the thermal effect of the laser. The microstructures further revealed that as the percentage of TiC decreases, it becomes more difficult to see the TiC as a different material in the composite, emphasizing this as one of the best characteristics of functionally graded materials, which is the elimination of sharp interfaces and layers. Furthermore, it was observed that the laser power has great influence on the evolving hardness of the material compared to the TiC content.
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Development of binderless ultra-tough titanium carbonitride (TiCN) using spark plasma sintering technique

- Akinribide, Ojo Jeremiah

  • Authors: Akinribide, Ojo Jeremiah
  • Date: 2019
  • Subjects: Titanium , Sintering , Nanoparticles
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/443738 , uj:38757
  • Description: Abstract: Binderless ultra–tough titanium carbonitride (TiCN) was successfully consolidated by spark plasma sintering. The impact of blending and milling parameters on the formation of titanium carbonitride from milled titanium nitride, graphite and multiwalled carbon nanotube (MWCNTs) admixture were investigated. The effect of wet milling and dry milling on the phases and morphology of the developed composites were also studied. The morphology, microstructure and the chemical composition of as – received powders, admilled powders and the sintered compact were characterized by using energy dispersive Xray spectroscopy (EDS), X-ray diffractometer, and scanning electron microscopy respectively. The varying compositions of the ad-milled powders were sintered at 100 oC/min (heating rate), 10 mins (holding time), 50 MPa sintering pressure and 2000 oC (sintering temperature). Vickers hardness test, fracture toughness and modulus of elasticity were carried out on the sintered sample to evaluate the mechanical properties. The sintered TiN-based composites were completely formed without cracks, however with very fewer pores, an indication of a good metallurgical bonding quality achieved at the composite grain boundary interface. The structure of the grains has completely transformed to bimodal grains within the composites at 1 wt.% graphite in TiN for 40 h of milling, and subsequent composites developed was based on the result obtained at 1 wt.% graphite in TiN for 24 and 40 h of milling at different compositions. Much increment was observed in microindentation hardness and fracture toughness values of the sintered compact as the percentage graphite increased. The results show that grain size of the sintered sample decreases as the percentage composition of graphite/MWCNTs particles and milling time increases. Based on the results of the analysis, it was concluded that the incorporation of graphite/MWCNTs enhances the microstructures which ultimately are crucial to the mechanical behaviour of the sintered compacts. , D.Phil. (Metallurgical Engineering)
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Effect of build direction on the microhardness and dry sliding wear behaviour of laser additive manufactured Ti-6Al-4V

- Palanisamy, Chandramohan, Bhero, Shepherd, Obadele, Babatunde Abiodun, Olubambi, Peter Apata

Effect of built orientation on direct metal laser sintering of Ti-6Al-4V

- Chandramohan, P., Bhero, Shepherd, Obadele, Babatunde Abiodun, Olubambi, Peter Apata, Ravisankar, B.

Experimental and numerical analysis of geometrical properties of laser metal deposited titanium

- Akinlabi, Esther Titilayo, Tayob, Mohammed A., Pietra, Francesco

  • Authors: Akinlabi, Esther Titilayo , Tayob, Mohammed A. , Pietra, Francesco
  • Date: 2016
  • Subjects: Ansys , Heat-Affected zone , Laser metal deposition , Microhardness , Microstructure , Porosity , Powder flow rate , Titanium
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/93300 , uj:20330 , Citation: Akinlabi, E.T., Tayob, M.A. & Pietra, F. 2016. Experimental and numerical analysis of geometrical properties of laser metal deposited titanium.
  • Description: Abstract: Laser metal deposition (LMD) is a manufacturing process, which can be used to manufacture a complete, fully functional part by building it up layer-by-layer using the data from a Computer-Aided-Design (CAD) file. The layer-by-layer addition can also be used to rebuild worn-out sections of existing parts, as well as to deposit protective coatings to protect parts in surface engineering. The process involves laser heating a substrate, on which a metal powder is deposited. The powder solidifies, when mixed with the substrate, thereby creating a metallurgical bond. In order to produce parts with high geometrical tolerances and desirable material properties, the process parameters have to be carefully controlled. Since the LMD process requires the interaction of parameters, it is not always easy to predict the output geometry. In this paper, the laser metal deposition process was modelled in ANSYS Parametric- Design-Language (APDL), using a transient thermal analysis, in order to determine the geometrical properties of the clad, that is, the width and the height of the resulting clad. The simulated results were then compared experimentally by depositing Commercially Pure (CP) titanium powder onto a Ti-6Al-4V substrate, in order to verify the simulation. The varying parameter in the experimental process was the powder flow rate, which was varied between 0.5-2.5g/min. In addition to the geometrical properties, the microstructure, microhardness; and the porosity levels of the deposited clads were also analyzed, in order to better determine the clad quality and integrity. The model showed good agreement in predicting both the height and the width of the clads. Porosity was noticed in all the samples with the exception of the clad deposited at the lowest powder flow rate setting of 0.5 g/min. An increase in the powder flow rate also led to a smaller fusion zone, due to a lower laser-material interaction period, which was the result of the increase in the quantity of powder causing attenuation of the beam, and less laser power being absorbed by the substrate. The smaller fusion zone meant that the clads could not bond to the substrate properly, which led to the clad in the sample produced with the highest powder flow rate falling off the substrate. There was a significant increase in the microhardness of the clad zone, which was due to a combination of alloying with Ti- 6Al-4V and a change in the microstructure to an acicular alpha martensite microstructure; while the Heat-Affected-Zone (HAZ) in the substrate only showed a slight increase in microhardness.
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Experimental properties and simulated geometrical properties of Laser-metal-deposited Titanium

- Tayob, Mohammed Aqeel

  • Authors: Tayob, Mohammed Aqeel
  • Date: 2016
  • Subjects: Lasers - Industrial applications , Materials - Effect of radiation on , Titanium
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/82728 , uj:18994
  • Description: Abstract: Laser metal deposition (LMD) is a manufacturing process, which can be used to manufacture a complete, fully functional part – by building it up layer-by-layer using the data from a Computer-Aided-Design (CAD) file. The layer-by-layer addition can also be used to rebuild worn-out sections of existing parts, as well as to deposit protective coatings to protect parts in surface engineering. The process involves laser heating a substrate, on which a metal powder is deposited. The powder solidifies, when mixed with the substrate, thereby creating a metallurgical bond. In order to produce parts with high geometrical tolerances and desirable material properties, the process parameters have to be carefully controlled. Since the LMD process requires the interaction of parameters, it is not always easy to predict the output geometry. In this dissertation, the laser-metal-deposition process was modelled in ANSYS Parametric-Design-Language (APDL), using a transient thermal analysis, in order to determine the geometrical properties of the clad, that is to say, the width and the height of the clad. The simulated results were then compared experimentally by depositing Commercially Pure (CP) titanium powder onto a Ti-6Al-4V substrate, in order to verify the simulation. The varying parameter in the experimental process was the powder-flow rate, which varied between 0.5-2.5g/min. In addition, to the geometrical properties, the microstructure, microhardness; and the porosity levels of the deposited clads were also analyzed, in order to better determine the clad quality and integrity. The model showed good agreement in predicting both the height and the width of the clads. Porosity was noticed in all the samples – with the exception of the clad deposited at the lowest powder-flow rate setting of 0.5 g/min. An increase in the powder-flow rate also led to a smaller fusion zone, due to a lower laser-material interaction period, which was the result of the increase in the quantity of powder causing attenuation of the beam, and less laser power being absorbed by the substrate. The smaller fusion zone meant that the clads could not bond to the substrate properly, which led to the clad in the sample with the highest powder-flow rate falling off the substrate. There was a significant increase in the microhardness of the clad zone, which was due to a combination of alloying with Ti-6Al-4V and a change in the microstructure to an acicular alpha martensite microstructure; while the Heat-Affected-Zone (HAZ) in the substrate only showed a slight increase in microhardness. , M.Ing. (Mechanical Engineering Science)
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Fabrication and characterization of titanium-nickel-zirconia matrix composites prepared by spark plasma sintering

- Obadele, Babatunde Abiodun, Ige, Oladeji Oluremi, Olubambi, Peter Apata

Laser forming of titanium and its alloys – an overview

- Akinlabi, Esther Titilayo, Shukla, Mukul, Akinlabi, Stephen A.

Microstructural and mechanical evaluation of laser-assisted cold sprayed bio-ceramic coatings : potential use for biomedical applications

- Tlotleng, Monnamme, Akinlabi, Esther Titilayo, Shukla, Mukul, Pityana, Sisa

  • Authors: Tlotleng, Monnamme , Akinlabi, Esther Titilayo , Shukla, Mukul , Pityana, Sisa
  • Date: 2014
  • Subjects: Titanium , Laser power , Cold spray , Laser-assisted cold spray , Hydroxyapatite
  • Type: Article
  • Identifier: uj:5135 , ISSN 1544-1016 , http://hdl.handle.net/10210/14101
  • Description: Bio-composite coatings of 20 wt.%, HAP and 80 wt.%, HAP were synthesized on Ti-6Al-4V substrates using LACS technique. The coatings were produced with a laser power of 2.5 kW, powder-laser spot trailing by 5 s. The coatings were analyzed for the microstructures, microhardness, composition, and bio-corrosion using SEM-EDS, XRD, hardness tester, and Metrohm PGSTAT101 machine. SEM images indicated least pores and crack-free coating with dark-spots of Ti-HAP for the 20 wt.%, HAP as opposed to the 80 wt.%, HAP coating which was solid, porous and finely cracked and had semi-melted Ti-HAP particles. The EDS mappings showed high content of HAP for the 80 wt.%, HAP coating. The diffraction patterns were similar, even though the Ti-HAP peak was broader in the 80 wt.%, HAP coating and the HAP intensities were lower for this coating except for the (004) peak. The hardness values taken at the interface inferred that the 80 wt.%, HAP coating was least bonded. It was possible to conclude that when this phase material increased the hardness dropped considerably. The bio-corrosion tests indicated that the presence of HAP in coating leads to a kinetically active coating as opposed to pure titanium coating.
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Microstructure and wear properties of laser cladded cBN/Ti3Al on pure titanium

- Sobiyi, K. K., Akinlabi, Esther Titilayo

  • Authors: Sobiyi, K. K. , Akinlabi, Esther Titilayo
  • Date: 2017
  • Subjects: Titanium , Intermetallics , Laser cladding
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/233614 , uj:23856 , Citation: Sobiyi, K.K. & Akinlabi, E.T. 2017. Microstructure and wear properties of laser cladded cBN/Ti3Al on pure titanium.
  • Description: Abstract: In order to improve the tribological properties of titanium alloys at high temperature, the possibility of producing Ti3Al intermetallic with the addition of ceramics (cBN) coatings on titanium substrate using laser technique cladding was investigated. cBN is generally known for its high hot hardness, wear resistance and chemical stability. Laser cladding is an emerging material processing technique which is an efficient and cost effective technique for improving the surface properties of general metallic materials. This paper presents the effects of laser cladding on the phase combination, microstructure, hardness and wear resistance of titanium aluminide/cBN IMC composites at different variations in quantity of cBN in the composite. Optical microscopy, X-ray diffraction, and scanning electron microscopy (SEM) with EDX was used for characterizing the microstructure of the coating. In addition the composite coating was subjected to wear testing using the ball-on-disc, friction and wear apparatus. The XRD results revealed phases with small cBN, Ti2N and TiB2 peaks in addition to the rich γ-Ti, α2- Ti3Al and TiAl intermetallics phases in the coatings after cladding process. Whereas, the microstructure of the cBN cladded layer contained partially melted cBN grains evenly dispersed within the laths of alpha Widmanstätten phase in form of dendrites, precipitate of α2- Ti3Al and spherical shaped pure titanium. The effect of the addition of cBN into Ti3Al alloy at increasing weight percentages, showed an improvement in the hardness and wear resistance of the coatings. The increase is attributed to reacted boron nitrides particles with titanium, being distributed uniformly in the intermetallic matrix.
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On development of ultrahard hafnium and titanium carbide materials

- Maseko, Emily Tholakele

  • Authors: Maseko, Emily Tholakele
  • Date: 2012-09-10
  • Subjects: Hafnium , Titanium
  • Type: Thesis
  • Identifier: uj:9812 , http://hdl.handle.net/10210/7215
  • Description: M.Tech. , A mixture of HfC and TiC powders and a (Hf,Ti)C powder have been hot pressed with 4wt% Ni. In the absence of Ni the hot pressed temperature was 2000 °C and in the presence of Ni 1650 °C. The pressure of 30 MPa was applied in both cases. The starting powders were substoichiometric, as deduced from XRD spectra analyses, and the (Hf,Ti)C powders consisted of a range of compositions, as indicated by the width of the XRD peaks. In the absence of Ni the powders sintered without the formation of a liquid phase. In the case of HfC and TiC mixture, high- energy dry milled HfC + TiC +C black powder sintering occurred with simultaneous formation of (Hf,Ti)C solid solution. On account of mutual solid solubility of two carbides vacancy interdiffusion controlled the solution as well as the sintering process, assisted by the high concentration of vacancies in the starting powders. In the case of (Hf,Ti)C powder diffusion was also the controlling process because t he solid solution was not h omogeneous a nd the system t ended to homogenization, as shown by t he narrowing of t he XRD peaks after sintering. Since the diffusion of HfC into TiC did not occur at the same rate as the diffusion of TiC into HfC (as expected, on account of the different melting points of the two materials) diffusional porosity was observed in some of the (Hf, Ti) C grains. Grain growth was substantial but uniform. In the presence of Ni, sintering occurred with the formation of a liquid phase. The volume fraction of the liquid phase formed was sufficient to yield a low porosity. Grain growth was less than in the case of material sintered without Ni, probably just on account of lower sintering temperature. In the case of high- energy dry milled the reduction in particle size was observed.
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Residual stress distribution and the concept of total fatigue stress in laser and mechanically formed commercially pure grade 2 titanium alloy plates

- Mjali, Kadephi V., Els-Botes, Annelize, Mashinini, Peter M.

Sintering of nanostructured titanium carbonitride from carbonitrothermic reduced ilmenite

- Mojisola, Tajudeen

  • Authors: Mojisola, Tajudeen
  • Date: 2019
  • Subjects: Sintering , Nanostructured materials , Titanium , Nitrides , Ilmenite
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/418221 , uj:35451
  • Description: Abstract: In recent years, there has been concerted effort towards the synthesis of cermet materials from low grade titanium ore. This is because the reserve of high grade titanium containing ore, i.e. natural rutile, is fast depleting and rutile becoming more expensive across the globe. Today, titanium containing hard ceramic powders, e.g. TiC, TiN and their solid solution TiCN powders have become important reinforcement materials due to their suitable properties. Titanium carbonitride, which is a boundary solid solution of titanium carbide and titanium nitride combines the excellent properties of both TiC and TiN in one structure of TiCN. In order to make this special material readily available, various methods have been adopted to synthesize titanium carbonitride powder. Although, the synthesis of titanium carbonitride by carbothermic reduction of titanium dioxide (rutile) with carbon under nitrogen atmosphere has been the most widely used for the commercial production of titanium carbonitride. However, this process requires the extraction and purification of titanium dioxide from its ore e.g. ilmenite, which itself is a costly process, or the use of natural rutile, which is fast depleting and becoming more expensive across the globe. Ilmenite (FeTiO3), which is a mineral source of titanium dioxide, is abundantly found in many parts of the world, most especially in South Africa. South Africa, is a leading producer of ilmenite in the world, accounting for about 37% of 6.2 million metric tons of the global production. Hence sourcing and processing of TiCN powder directly from South African ilmenite will be an added advantage. It is on this premises that the urgency for the processing of South African ilmenite to its final products, e.g. titanium containing hard ceramic products, such as TiC, TiN and/or TiCN powders or composite, and titanium metal, is being hung. Hence, this study develops a mechano-chemical processing route for the synthesis of titanium containing hard ceramic powders from ilmenite concentrate, which could be used for the production of cutting tools made of TiC and TiCN composite materials. The study also determines the possibility of sintering bulk TiCN based cermets with different metal matrices. For the synthesis of titanium carbide and titanium nitride/carbonitride powders, mixtures of ilmenite concentrate and graphite were milled in a planetary ball mill (PM 100) for different time intervals of 0, 30, 60 and 120 min, and carbo(nitro)thermally reduced under argon and nitrogen gas in a high temperature laboratory furnace (Thermal Tech., USA), respectively. These carbo(nitro)thermic reductions of mixtures of ilmenite concentrate and graphite result in the formation of Fe –TiC and Fe – TiCN powder composites in which globules of TiC and TiCN particles are embedded in the iron matrix,.. , Ph.D. (Engineering Metallurgy)
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Surface morphology characterisation : magnetron sputtering of nanostructured titanium carbide thin films on titanium and its alloys

- Abegunde, Olayinka Oluwatosin

  • Authors: Abegunde, Olayinka Oluwatosin
  • Date: 2020
  • Subjects: Titanium , Titanium alloys , Sputtering (Physics)
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/480476 , uj:43497
  • Description: Abstract: The selection process for functionally engineered materials cannot only rely on the physical appearance of the materials, texture, aesthetic and bulk properties but also on the surface characteristics composition especially in the area of applications where surface contact is of high priority. The behaviour of a material is greatly dependent on the surface properties of the material. Functionally engineered materials must be able to satisfactorily perform desired functions completely and effectively, under various conditions in aggressive environments without failing or yielding into a disastrous catastrophe when in service. Savaging, protecting and optimizing scarce natural materials like Titanium from surface defects and deformation like corrosion and wear is a major problem around the world. Titanium alloys are reactive materials and have a high affinity for oxygen, resulting in the formation of protective oxide film spontaneously in the presence of oxygen. However, it can give rise to disruption in the mechanical properties when the system is suffering from starvation of oxygen to form the protective layer. Also, titanium exhibits low wear and abrasion resistance, which can result in reduced service life... , Ph.D. (Mechanical Engineering Science)
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Surface texture assessment of commercially pure titanium dental implants

- Rogers, Rowan Mark

  • Authors: Rogers, Rowan Mark
  • Date: 2015
  • Subjects: Titanium - Industrial applications , Aluminum oxide - Surfaces , Dental implants , Titanium
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/213584 , uj:21170
  • Description: Abstract: An investigation into the surface texture evaluation of titanium dental implants was carried out. Surface modifications of dental implants are commonplace, albeit by different mechanisms and processes (machining, blasting, coatings, etc.), with the purpose of optimising and/or enhancing implant performance. Regardless of the reasoning behind surface modification, reliable and consistent evaluation techniques and methodologies are required by both researchers and manufacturers of the implants. Researchers would require consistent evaluation methods for comparative purposes, and manufacturers in order to produce surfaces that meet certain texture descriptor targets or fall within a specified texture descriptor ranges. Following a similar train of thought; perhaps even more fundamental is the concept of surface texture evaluation and its applicability to surface texture, and how the required/desired surface texture descriptor values were established in the first place. Commercially pure grade 4 titanium (cpTi‐Gr4) dental implants that featured surfaces modified by an aluminium oxide blasting process were selected for use as tangible samples for the purposes of carrying out the investigation. A review of the recent published literature specifically relating to titanium dental implants and their surface texture was conducted – a total of 57 journal articles were identified for the period between 2001 and 2015. It was found that while standards do exist for roughness evaluation, there were no set standards used in the texture evaluation of dental implants. The standards referred to in some of the articles specified ranges of evaluation parameters based upon a range of length scales, however there were neither agreed upon nor stated length scales set by researchers for dental implant texture evaluations. This observation implied that evaluation parameters are required to explicitly state the conditions under which roughness descriptors are measured and determined, however it is apparent that this is not a requirement for many publications. It was noted that only 1 out of the 57 reviewed articles gave enough evaluation parameter information to repeat the measurement methodology it followed. As a consequence it follows that many of the published research articles gave texture quantities which are difficult, if not impossible, to meaningfully relate to one another. Even in the cases where identical roughness descriptor results were published, information regarding the acquisition of the surface descriptors was generally absent. Equivalence of surface descriptor values across articles was therefore tenuous at best. It was concluded that most authors used standards (ISO) in their evaluations, and as such a filtering cut‐off length of 800 μm (λc = 0.8 mm) was the ‘default’. To complicate the issue further, it was found that most authors gave profile roughness results, while some gave areal roughness results. Profile roughness descriptors are suitable for isotropic surfaces, however areal descriptors are better suited for anisotropic surfaces. Areal analysis is the preferred regime in this research. A related topic to the reviewed articles was the instrumentation used to carry out surface texture evaluations of the titanium dental implants. Scanning electron microscopy (SEM) (single image) was the most popular tool, followed by atomic force microscopy (AFM) and contact stylus profilometry (CSP). It is noted that single image SEM has primarily been used as qualitative tool since the images generally do give a surface height, whereas the AFM and CSP output height values which are easily converted into texture descriptors by modern instrument control software. Advantages and disadvantages of the instruments were identified; SEM (single image) could examine a wide range of... , M.Ing. (Mechanical Engineering)
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Synthesis and characterization of commercial pure titanium-nickel alloy behavior reinforced with titanium diboride

- Falodun, Oluwasegun Eso, Oke, Samuel Ranti, Olubambi, Peter Apata

  • Authors: Falodun, Oluwasegun Eso , Oke, Samuel Ranti , Olubambi, Peter Apata
  • Date: 2020
  • Subjects: Titanium , Nickel , TiB2
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/458331 , uj:40705 , Falodun, O.E., Oke, S.R., Olubambi, P.A.: Synthesis and characterization of commercial pure titanium-nickel alloy behavior reinforced with titanium diboride.
  • Description: Abstract: Commercial pure titanium alloy with Ni-TiB2 ceramic additions (5, 10, 15 and 20 vol.%) were synthesized through the spark plasma sintering approach with sintering temperature of 1000 oC, the heating rate of 100 oC/min, holding time of 5 min at a constant pressure of 50 MPa. The study investigated the effect of Ni-TiB2 on the densification, phase change, microhardness, microstructure, and wear properties of the sintered titanium-based composites. Results showed that Ti-Ni-TiB2 composites relative density ranges from 97 to 99 %, while microhardness values increase with addition of nickel and titanium diboride from 228 to 587 HV0.1. The microstructural evolution shows that pure titanium transformed from lamellar phase to equiaxed alpha phase upon addition of nickel alloy and further get refined with a distinct grain boundary comprises of titanium diboride around the boundaries. The average coefficient of friction for the titanium-based composite was higher for commercially pure titanium (0.73) while the addition of TiB2 exhibit (0.66, 0.63, 0.58, 0.55 and 0.46 respectively) improvement in the wear behavior.
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Synthesis and characterization of mesoporous silica/titania nanocomposites : potential additives for dye sensitized solar cells (DSSCs)

- Akawa, Mpingana Ndilimeke

  • Authors: Akawa, Mpingana Ndilimeke
  • Date: 2017
  • Subjects: Dye-sensitized solar cells , Nanostructured materials , Mesoporous materials , Silica , Titanium
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/235628 , uj:24100
  • Description: M.Sc. (Nanoscience) , Abstract: The photoanode is an important part of the DSSCs as it is the medium for dye adsorption, electron transport and electrolyte diffusion. The composition and morphology of the photoanode therefore directly influences the performance of the cell. Optimising the morphology of the photoanode is therefore one of the key factors in improving the performance of the DSSCs. This work entailed the synthesis of titania supported on silica nanocomposites for use as light scattering materials in the photoanode with the motivation of optimising the morphology of the photoanode and further enhance the energy conversion efficiency of the DSSCs. The silica support materials, specifically mesoporous silica, SBA-15 and non-mesoporous SiO2 were synthesized through the soft-template acid catalyzed sol-gel method and base catalyzed sol-gel method respectively. Two SBA-15 nanomaterials were synthesized by varying the hydrolysis and aging times which resulted in materials of different textural and morphological properties. These silica support materials (SiO2, SBA-15 A1 and SBA-15 A2) were used as support materials for the synthesis of TiO2 supported on silica nanocomposites. Also, TiO2 nanoparticles of size 19.32 ±3.70 nm (n = 193) were synthesized for use as active site of the photoanode. The physical, chemical and optical properties of the nanoparticles and nanocomposites were studied using FTIR, TEM, Nitrogen Sorption, SEM-EDS, XRD, and diffuse reflectance Ultraviolet-Visible (DR-UV-VIS) spectroscopy. The nitrogen desorption results of the 10 wt% TiO2 / SBA-15 nanocomposites just like the parent SBA-15 support, revealed the Type IV isotherms with H1 hysteresis loops which indicated that the support materials did not lose their mesoporosity and uniform pore size arrangement upon incorporation of TiO2 nanocrystals. This finding was supported by the TEM results. The energy band gaps of TiO2 supported on the mesoporous silica (SBA-15) (3.60 eV) were blue shifted relative to the unsupported TiO2 (3.44 eV) and TiO2 supported on the non-mesoporous SiO2 (3.55 eV). These results confirmed the XRD results which indicated smaller TiO2 crystallite sizes for TiO2 crystals supported on the SBA-15 support materials which were 10.60 nm as compared to the unsupported TiO2 and TiO2 supported on the non-mesoporous SiO2 (15.89 nm). The band gap increased as the crystallite sizes decreased...
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Synthesis and photocatalytic performance of Ag-TiVOX nanocomposite

- Ntobeng, Mahubedu Khutso, Imoisili, Patrick Ehi, Jen, Ten-Chien

  • Authors: Ntobeng, Mahubedu Khutso , Imoisili, Patrick Ehi , Jen, Ten-Chien
  • Date: 2020
  • Subjects: Titanium , Nanocomposite , Methylene blue
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/458235 , uj:40693 , Ntobeng, M.K., Imoisili, P.E., Jen, T.: Synthesis and photocatalytic performance of Ag-TiVOX nanocomposite. DOI: https://doi.org/10.1016/j.jksus.2020.08.021
  • Description: Abstract: A silver, vanadium and silver/vanadium doped titanium dioxide (TiO2, Ag-TiO2, V-TiO2 and Ag-TiVOX) nanocomposite photocatalyst was achieved via a modify sol–gel and hydrothermal method. Structural analysis by X-Ray Diffraction (XRD) depicted the lattice fringes for both anatase and rutile in its crystalline phase in the synthesized nanocomposites. Surface areas (SBET) analysis shows that surface area of synthesized Ag-TiVOX is 46.01 m2/g, compare to TiO2 64.75 m2/g, Ag-TiO2 61.33 m2/g and V-TiO2 62.73 m2/g. Optical absorption results demonstrated by UV–Visible Spectroscopy (UV–Vis) shows that the effects of Ag and V doping was a shift in spectrum to the visible light region, enhancing the visible light absorption capacity of the synthesized photocatalyst. The optical absorption of Ag-TiVOX achieved a reduced bandgap energy of 2.2 eV, as compared to Ag-TiO2 (2.8 eV), V-TiO2 (2.3 eV) and TiO2 (2.9 eV). Morphological characterization by Transition Electron Microscope (TEM) and Scanning Electron Microscope (SEM), depicting a cluster composed of spherical aggregates particles of non-uniform diameter nanoparticles with particle size ranging between 10 and 50 nm. Synthesized Ag-TiVOx demonstrated remarkable photocatalytic capabilities under visible light irradiation, as 99.83 percent of methylene blue (MB) degradation was accomplished during the first 15 min. Impact of Ag and V doping of TiO2 showed enhancement in the photocatalytic activity, reporting excellent removal rates and achieving well desirable decline in the band gap energy.
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The influence of scanning speed on laser metal deposition of Ti/TiC powders

- Sobiyi, K. K., Akinlabi, Esther Titilayo, Akinlabi, Stephen A.

  • Authors: Sobiyi, K. K. , Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2017
  • Subjects: Titanium , Lasers , Metal deposition
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/241302 , uj:24840 , Citation: Sobiyi, K.K. 2017. The influence of scanning speed on laser metal deposition of Ti/TiC powders.
  • Description: Abstract: This paper describes the experimental work performed on laser metal deposition (LMD) of titanium carbide powders on pure titanium substrate. The understanding the effect of LMD processing parameters is vital in controlling the properties of the final product fabricated from the LMD process. The objective of the study is to characterize the influence of laser scanning speed of metal deposition of titanium and titanium carbide powders on pure titanium substrate. Microstructural characterization results showed that the substrate is characterized by two-phase morphology; alpha and beta phase. Deposit zone microstructures showed that the grains are of continuous columnar in nature. Heat affected zone region grain areas appear to decrease with increasing in scanning speed for different samples at different scanning speeds. The height of samples at different scanning was observed to decrease with increase in scanning speed. Microhardness results showed that the hardness of the deposits is greater than the hardness of the substrate. Wear resistance performance results showed that the coefficient of friction of substrate is greater than the coefficient of friction of the deposit samples. Wear volume loss of material of the substrate is higher than the deposits. The deposit contains titanium carbide and, as such, this powder has improved the wear resistance performance of the substrate.
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