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Development of binderless ultra-tough titanium carbonitride (TiCN) using spark plasma sintering technique

  • 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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The evaluation of dendrimer encapsulated ruthenium nanoparticles, immobilised on silica, as catalysts in various catalytic reactions and the effect of ionic liquids on the catalytic activity

  • Authors: Antonels, Nathan Charles
  • Date: 2015-04-22
  • Subjects: Dendrimers , Catalysis , Nanostructured materials , Nanoparticles
  • Type: Thesis
  • Identifier: uj:13555 , http://hdl.handle.net/10210/13696
  • Description: Ph.D. (Chemistry) , This study discusses the preparation of various sized dendrimer encapsulated ruthenium nanoparticles (RuDEN) with the use of the generation 4 (G4), generation 5 (G5) and generation 6 (G6) hydroxyl-terminated poly(amidoamine) (PAMAM-OH) dendrimers as templating agents. The size of the nanoparticles ranges from 1.1-2.2 nm. The RuDENs were used as nanoparticle solutions in catalytic reactions or immobilised on amorphous silica 60 and silica 100 and subsequently referred to as RuSil catalysts. These catalysts were evaluated in the reduction of 4-nitrophenol, toluene hydrogenation, citral hydrogenation, cinnamaldehyde hydrogenation and styrene oxidation...
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Adsorption of arsenic on lanthanum and cerium nanoparticles adsorbents during hydrometallurgical extraction of copper

  • Authors: Bamidele, Emmanuel Anuoluwa
  • Date: 2019
  • Subjects: Lanthanum , Copper , Cerium , Nanoparticles , Extraction (Chemistry) , Arsenic - Absorption and adsorption
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/413042 , uj:34782
  • Description: M.Tech. (Extraction Metallurgy) , Abstract: Various activities of mining, mineral processing and extraction releases arsenic into the environment. The reported presence of high concentration of arsenic in lakes surrounding a selected silver, cobalt and copper mines has gained serious attention of the scientific community. This research encompasses the characterization of a low-grade copper oxide ore using atomic absorption spectrometer, x-ray fluorescence (XRF), x-ray diffractometer (XRD), SEM-EDS and Induced Coupled Plasma Mass Spectroscopy (ICP-MS). Leaching and adsorption of the copper ore sample was carried out using sulphuric acid of varying molarity -3M, 2M, 1.5M, 1M and 0.5M – and two Lanthanum and Cerium nanoparticles adsorbents were prepared for the adsorption of arsenic from the ore sample during the hydrometallurgical extraction of copper -leaching- process. This study revealed that there is a direct relationship between the concentration of acid and arsenic dissolution. The %As adsorption on Lanthanum nanoparticles adsorbent is lower at higher acid molarity and higher at lower sulphuric acid molarity. While in the case of Cerium adsorbent, there is a deviation. The Cerium ions were able to actively react with arsenic at higher acid molarity hence causing higher adsorption at higher molarity of acid than lower molar mass. Arsenate removal efficiency increases sharply with increasing adsorbent dosage, though there were some anomalies which were observed to be because of competing ions on the adsorption. The increase in temperature was found to reduce the adsorption efficiency of both the Cerium and Lanthanum nanoparticles adsorbents. The effect of acid molarity, adsorbent dosage and temperature were also studied on copper and iron dissolution in the extraction process. Low copper dissolution rate was achieved due to the activation of active binding sites by the Cerium and Lanthanum adsorbents which might have attracted some copper ions. The copper dissolution rate obtained when Cerium impregnated adsorbent was used gave better copper recovery than when Lanthanum adsorbents were applied. The values of RL obtained for each of the adsorption carried out shows that the nature of Langmuir model is unfavourable for Lanthanum nanoparticles, but the linear value obtained for RL in the case of Cerium nanoparticles makes it fit into the model. It is important to note that Cerium nanoparticles adsorbent performs better with increasing acid molarity while Lanthanum nanoparticles adsorbent performs better with increasing adsorbent dosage. Considering the findings obtained from studying different parameters such as acid molarity, temperature and adsorbent dosage, it can be concluded that Cerium nano adsorbent is a better adsorbent than Lanthanum nano adsorbent.
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Application of well-defined nanoparticles as catalysts for kinetic studies of model reactions, and their immobilization on mesoporous SBA-15 for olefin oxidation

Zinc oxide nanostructures with carbon nanotube and gold additives for co gas sensing application

  • Authors: Chauke, Hleko
  • Date: 2019
  • Subjects: Zinc oxide , Nanoparticles , Carbon nanotubes , Chemical vapor deposition , Gas detectors , Transmission electron microscopy
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/413090 , uj:34788
  • Description: Abstract: Zinc oxide (ZnO) nanostructures were synthesised for gas sensing application. In an attempt to improve the surface area and the electrical conductivity of the ZnO, nanomaterials such as the carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) were used separately to produce CNTs/ZnO and Au/ZnO nanocomposites, respectively. The addition of these nanomaterials onto the ZnO nanostructures significantly improved the gas sensing properties such as the sensitivity and response time. Synthesis of gold nanoparticles was successfully achieved via gold salt (HAuCl4.3H2O) reduction using the Turkevich method. Citrate molecules were used as the stabiliser and to systematically control the sizes of the AuNPs. The sizes of AuNPs were found to increase from 14 nm to 40 nm when the concentration of citrate ions was reduced from 1 mM to 0.3 mM. The size distribution of AuNPs was relatively wider as the particle size increased. The synthesized AuNPs were stable for over a period of 4 weeks. Carbon nanotubes synthesis was achieved using chemical vapour deposition (CVD) method using acetylene gas as the carbon source and ferrocene as the catalyst. An increase in the flowrate of the precursor gas (acetylene) yielded an increase in amorphous carbon, which was attached to the walls of the carbon nanotubes. The optimum flowrate of acetylene was found to be 150 m3/min that yielded CNTs with an average diameter of 95 nm and a relatively narrow size distribution. The hydrothermal chemical precipitation method was used to synthesise ZnO nanostructures. Zinc sulphate (ZnSO4) and sodium hydroxide (NaOH) were used as a metal precursor and reducing agent, respectively. The NaOH concentration of 0.3 M yielded ZnO nanosheets with relatively the highest surface area of 102 m2/g. Gas sensing analysis was conducted using carbon monoxide (CO) gas at 250°C. The sensitivity and response time were calculated to be 9.8% and 114 seconds, respectively, at a CO concentration of 200 ppm. The composites CNTs/ZnO and Au/ZnO were prepared, separately. The average surface area of the Au/ZnO composite was 131 m2/g and that of CNTs/ZnO composite was 153 m2/g. The CNTs/ZnO composite showed an optimum sensitivity of 9.9% and the response time of 49 seconds when exposed to 200 ppm of CO gas at 250°C. , M.Tech. (Chemical Engineering)
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Performance of bismuth based materials for electrochemical energy storage devices

  • Authors: Devi, Nishu
  • Date: 2019
  • Subjects: Bismuth , Nanoparticles , Supercapacitors , Electrochemistry
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/417075 , uj:35307
  • Description: Abstract: The efficient storage of electrical energy produced from renewable sources of energy is a crucial challenge and has attracted immense interests of the researchers. Electrochemical storage of the energy is proved to be an efficient and effective solution that suggests battery, supercapacitors and fuel cells. The lithium-ion battery is one of the most prominent existing solutions in the energy storage market which is being used in the technology devices. A supercapacitor is another alternative that evinces the potential to emulate battery technology in the upcoming years. To achieve this decisive task, electrode materials having high energy density and electrochemical stability are needed to be explored that should be environment-friendly and economical to be used. Carbonaceous materials, metal oxides, polymers, and their composites are being used for this purpose having a particle size in the nano range. Nanomaterials are proved to be an active candidate due to high surface area and a large number of active sites. Here, we synthesized and investigated bismuth nanomaterials that showed quite high energy density, power density and stability and can be used as electrode materials for supercapacitor applications. The thesis mainly focusses on bismuth-based materials, their synthesis and more concerned about the study of supercapacitive applications via electrochemical techniques. A facile synthesis method of nanoparticles at ambient conditions stabilized by organic matrix has been presented in this report... , Ph.D. (Chemistry)
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Bimetallic nanoparticles on carbon nanotubes and nanofibers copolymerized with ß-cyclodextrin for water treatment

Synthesis, functionalisation of sugars-capped water-soluble (Cd, Zn,Mn) metal oxides nanoparticles using conventional and single source precursor routes : application in toxicity studies

Spark plasma sintering of nanoceramics dispersion strengthened titanium aluminium vanadium alloy

The effects of succussion on nanoparticles in ferrum metallicum 30C

  • Authors: Hobson, Deborah Dawn
  • Date: 2019
  • Subjects: Homeopathic pharmacy , Nanoparticles , Nanostructured materials , Nanomedicine , Homeopathy
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/399657 , uj:33319
  • Description: Abstract : Nanoparticles are microscopic materials which range in length from 1-100 nanometres (nm). Nanoparticles have unique properties due to their size and shape, which include an increase in surface area, surface reactivity, thermal energy and diffusion rate. Nanomedicine refers to the application of nanoparticles in medicine, particularly in diagnostic techniques and as drug delivery systems. Nanoparticles are ideal for this as they provide greater bioavailability, are more easily absorbed by the body and produce a therapeutic effect with fewer side effects. Laboratory techniques to create nanoparticles include the top-down and bottom-up methods. Within these two methods are various synthesis techniques for creating nanoparticles, including solid phase synthesis, liquid phase synthesis, gas phase synthesis and green synthesis. Homoeopathy uses the top-down method by physically breaking down the starting substance via the process of potentization. Homoeopathy is a branch of complementary medicine (CM) founded by Dr Samuel Hahnemann in the late 1700’s. It is based on the principle similia similibus curantur, which translates to ‘like cures like’. Homoeopathic remedies are highly diluted substances which retain minute particles of the starting substance in the form of nanoparticles. The method used to make homoeopathic remedies is referred to as ‘potentization’ and includes trituration (grinding and serial dilution) of solid substances and succussion (violent shaking) of liquid substances. However, while homoeopathy has set guidelines for the trituration part of potentization, it lacks standardisation regarding the number of succussions which should be used. Iron (Fe) is a highly reactive silvery-white metal that easily forms compounds and alloys with other metals and has unique ferromagnetic properties which are stronger at lower temperatures. Ferrum metallicum, the homoeopathic remedy made from iron, can be used for a wide range of conditions when prepared in homoeopathic form. The aim of this study was to investigate the effect of succussion on the presence, size and distribution of nanoparticles in Ferrum metallicum 30C, when prepared with 0, 10 or 100 succussions, using transmission electron microscopy (TEM). iv This was a quantitative, experimental study performed at the Department of Chemistry, at the University of Johannesburg. Three batches of Ferrum metallicum 30C, with 0, 10 and 100 succussions respectively, and three controls of 43% ethanol with 0, 10 and 100 succussions respectively, were manufactured by the researcher. This was done at the laboratory of a registered manufacturer of homoeopathic medicines in Johannesburg. The researcher underwent training on the use of each of the laboratory analysis techniques. The sample preparation, experimental design and analysis of the samples was conducted by the researcher, under supervision and help of the laboratory technicians. Transmission Electron Microscopy (TEM) was conducted on two batches of samples. The first batch of samples showed contamination of the ethanol used to manufacture the test and control samples. The test samples were therefore manufactured a second time and TEM analysis conducted again. Additional analysis techniques were used to determine whether the first batch of test and control samples were contaminated and how the contamination had occurred. These analysis techniques included Energy Dispersive Spectroscopy (EDS), Inductively Couples Plasma Emission Spectroscopy (ICP-OES), Dynamic Light Scattering (DLS). An analysis for zeta potential of the samples and controls was conducted to explain the agglomeration of particles. TEM photographs were analysed by the researcher, under guidance of the co-supervisor, using the computer programme ImageJ. The results for EDS, ICP-OES, DLS and Zeta Potential were generated by the built-in software of the analysis machines, either as graphs or as numerical values. These were then analysed by the researcher under the guidance of the laboratory technicians. A total of five experimental procedures were conducted. The results of the experiments showed that the first batch of test and control samples was contaminated as the ethanol used to manufacture the samples contained traces of iron and unidentified particles. The additional analysis techniques helped confirm the contamination, and it was discovered that purified water, which was used to manufacture the ethanol used in the study, is not completely free of particles. The second batch of test and control samples, manufactured with distilled water, which is almost completely particle-free, showed positive results. The presence of spherically-shaped iron nanoparticles was confirmed for the test samples. Batch 1, Samples 1 and 2 (Ferrum v metallicum 30C with 0 and 10 succussions respectively), contained nanoparticles which were evenly distributed and unagglomerated. Batch 1, Sample 3 (Ferrum metallicum 30C with 100 succussions) had nanoparticles which were smaller in size, greater in number and agglomerated. Batch 2, Samples 1-2 (Ferrum metallicum 30C with 0 and 10 succussions respectively) contained nanoparticles which were more defined in shape, with similar numbers and sizes, and existed mainly as well-distributed, unagglomerated nanoparticles. Batch 2, Sample 3 (Ferrum metallicum 30C with 100 succussions) had nanoparticles which were slightly less in number and smaller, according to the automatic analysis by ImageJ, and which appeared to be distributed unevenly in smaller clusters. The first batch of control samples contained a large number of unidentified particles. The second batch of control samples also contained particles, although significantly less than the first batch of controls. Overall, the experiments showed that the number of succussions given does affect the number, size and distribution of nanoparticles in a homoeopathic remedy. The results of this experiment help to support the current research on nanoparticles in homoeopathic remedies and help to explain the effect of succussion on the nanoparticles within the remedies. , M.Tech. (Homoeopathy)
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Synthesis and application of monodisperse silver and gold nanoparticles as catalysts for kinetic investigations of model reactions

  • Authors: Ilunga, Ali Kabeya
  • Date: 2015
  • Subjects: Electrocatalysis , Nanoparticles , Gold , Catalysis
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/82587 , uj:18976
  • Description: Abstract:A hyperbranched polymers, dendrimers, synthesized for the first time by Tomalia and available in market in the form of poly-amidoamine (PAMAM) and poly-propylene imine (PPI) dendrimers are used as templates in the synthesis of metal nanoparticles to prevent agglomeration. Here, we study the synthesis of generation five amino-terminated poly(amidoamine) dendrimer encapsulated silver and gold nanoparticles. To avoid the intra-dendrimer stabilization, a spectrophotometric titration of the silver and gold ions into the dendrimer was performed. The results lead to the determination of the loading capacity of the dendrimers. The influence of temperature was evaluated by performing the titration at different temperatures. The colloidal metal nanoparticles were purified by dialyzing overnight against de-ionized water. The synthesis process of the silver and gold nanoparticles was monitored using UV-vis spectroscopy. The interaction of metal ions and tertiary amine group was assessed using a FTIR spectroscopy. TEM and EDX analysis were performed to obtain the distribution and average size of the metal nanoparticles, and to evaluate the purity of colloidal metal nanoparticles, respectively. The concentration of the metal nanoparticles in solution was determined by AAS. The specific surface area of silver and gold nanoparticles were estimated by self-assembled monolayer approach using the UV-photometric analysis to quantify the absorbed and unabsorbed organothiol. The catalytic activities of silver and gold nanoparticles were evaluated using the oxidation reaction of two different dyes, methylene blue and morin, as benchmark reactions. Hydrogen peroxide was used as an oxidizing agent and its stability during the catalytic process was assured by maintaining the pH constant using carbonate buffer. The Langmuir-Hinshelwood mechanism was applied to evaluate the catalytic performance of encapsulated silver and gold nanoparticles. This mechanism requires the adsorption of the reactants onto the catalyst surface prior to the start of the reaction. The catalytic process and the kinetic data set recorded were performed using UV-vis spectroscopy. The stability of the encapsulated metal nanoparticles during the reaction was evaluated by a three cycle runs using a dialysis bag. , M.Sc. (Chemistry)
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Facile extraction and characterization of silica nanoparticles from corn stalk by sol-gel hydrothermal methods

The acceleration of micro- and nano-particles in supersonic De-Laval-Type nozzle

The use of the conventional route and microwave technique on the synthesis of ZnO and CdSe/PbS core shell nanoparticles

  • Authors: Khoza, Phindile Brenda
  • Date: 2012-06-07
  • Subjects: Nanoparticles , Semiconductor nanoparticles , Zinc code
  • Type: Thesis
  • Identifier: uj:8719 , http://hdl.handle.net/10210/5070
  • Description: M.Sc. , ZnO nanostructures with different morphologies have been prepared by using microwave and conventional heating methods. The effect of solvent, zinc precursor, time and the concentration of sodium hydroxide on the morphology of zinc oxide were investigated, when different heating methods were employed. ZnO nanoparticles were prepared using the solvothermal method. Zinc precursor impact on the shape of zinc oxide nanoparticles formed depends on the solvent used during the synthesis. Different morphologies such as spheres, rods, hexagonal prisms, hexagonal plates, diamond-like and multipods were formed by a simple solution based method. The optical features for most of the formed shapes were typical of ZnO nanoparticles. The XRD patterns of the particles showed the most stable hexagonal phase with a high degree of crystallinity. A capping molecule has an impact on the shape of the nanoparticle. In this work, we also present the results from the study of the effect of the stabilizing molecule on the shape and formation of the core shell nanoparticles of CdSe/PbS. The capping molecules used were hexadecylamine (HDA), tri-n-octylphosphine oxide (TOPO) and stearic acid. The core shell nanomaterials were synthesized by using a method in which selenium powder was converted to TOPSe.Transmission electron microscopy was used to determine the morphology and the size of the ZnO and coreshell nanomaterials. Spherical particles were obtained when TOPO was used whereas the use of HDA induced the formation of non-spherical shapes. With both capping molecules, epitaxial shell growth was not achieved. The particles formed from both capping groups (HDA and TOPO) were large due to the long reaction time that instigates lager particle sizes. However, when stearic acid was used as a capping molecule, a perfect core shell arrangement was formed. The phase and the crystallinity of the formed particles were determined by the XRD.
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Plant components as low-cost alternatives to luminol for the detection of blood at crime scenes

  • Authors: Khunoana, Sewela
  • Date: 2019
  • Subjects: Plant luminescence , Chemiluminescence , Bloodstains , Crime scene searches , Gold , Nanoparticles
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/417470 , uj:35356
  • Description: Abstract: For decades, law enforcement officials have been using luminol as a tool to detect trace amounts of blood at crime scenes. Blood detection is accomplished through a chemiluminescence (CL) reaction between the iron in haemoglobin from human blood and the functional group (–COO– ) from the luminol molecule; the iron acts as a catalyst in this chemical reaction between the luminol and hydrogen peroxide (H2O2). With improvements in technology, luminol CL from the interaction with blood was also improved by enhancing its intensity with nanoparticles. Nanoparticles such as platinum (PtNPs), silver (AgNPs) and gold (AuNPs) have shown better improvements and more intense CL with luminol in blood detection. Thus, in this study, AuNPs were initially synthesised conventionally using chemicals such as sodium borohydride and many others added to luminol to improve the CL intensity. Again, with developing technologies, the green synthesis of these NPs including AuNPs is now possible. Several plant extracts from fruits, flowers, leaves and bulbs have been used in the synthesis of AuNPs but none of the AuNPs synthesised using green methods have been coupled with luminol in blood detection. Therefore, in this study, AuNPs were synthesised using the Crinum macowanii bulb water extract and added to luminol to compare the CL signals to those observed with AuNPs prepared by conventional methods. .. , Ph.D. (Chemistry)
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Synthesis, characterisation and catalytic activities of well defined gold nanoparticles

  • Authors: Khutlane, Tsepiso Joyce
  • Date: 2013-12-09
  • Subjects: Gold nanoparticles , Electrocatalysis , Catalysis , Nanoparticles
  • Type: Thesis
  • Identifier: uj:7842 , http://hdl.handle.net/10210/8737
  • Description: M.Sc. (Chemistry) , Loading gold nanoparticles (Au NPs) on mesoporous materials via different methods has been reported in the literature. However, the immobilisation of the dendrimer-encapsulated Au NPs on materials is still considered amongst the hot topics in chemistry. This study describes the synthesis, characterisation as well as catalytic evaluation of unsupported and supported Au NPs....
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Effect of anionic partial substitution on structural and luminescence properties of CaMoO4 : Eu3+color tunable phosphor compounds for white-light-emitting diode applications

  • Authors: Letswalo, Machaba Leanyatsa Abraham
  • Date: 2017
  • Subjects: Nanoparticles
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/279573 , uj:30026
  • Description: M.Sc. (Nanoscience) , Abstract: In this study, solid state method were used to synthesize calcium molybdate doped with Eu3+ ion and anionic groups (BO33-, PO43- and SO42-) for application in white light emitting diodes (LEDs) (solid state lighting) and display. Several sets of phosphor powder materials were prepared, namely CaMoO4:xEu3+, CaMoO4-BO3:xEu3+, CaMoO4-PO4:xEu3+ and CaMoO4-SO4:xEu3+ with various molar concentrations (0.5, 1.0, 1.5, 2.0 and 2.5 mol %). X-Ray diffraction (XRD) was used to identify the phase of the crystals, and subsequently to determine the average size of the phosphors and the degree of crystallinity. Scanning Electron Microscopy (SEM) was used to study the surface morphology (sizes and shapes) of the phosphors and elemental mapping. Elemental composition was determined using SEM and Energy Dispersion Spectroscopy (EDS). Fourier Transformation Infrared (FT-IR) was used for structural elucidation by identifying the stretching/bending mode frequencies. Lastly, surface states of the synthesised materials were studied using X-ray Photoelectron Spectroscopy. The diffuse reflectance and absorption edges were analysed using UV-Vis absorption spectroscopy. Photoluminescence (PL) was used to study the luminescence properties of the phosphor materials. The CaMoO4:xEu3+, CaMoO4-BO3:xEu3+, CaMoO4-PO4:xEu3+ and CaMoO4-SO4:xEu3+ XRD results indicated that the substitution of anions (BO33-,PO43-and SO42-) and Eu3+ dopant ions did not affect the crystal structure of the CaMoO4 phosphors, but greatly influenced the PL intensities of the CaMoO4:Eu3+ phosphors. According to Williamson-Hall equation, the crystallite sizes were ranging from 62 to 72 nm for CaMoO4-SO4:Eu3+phosphors, while for CaMoO4:Eu3+, CaMoO4-BO3:Eu3+ and CaMoO4-PO4:Eu3+ phosphors were ranging from 47 to 48 nm. The SEM images showed that the phosphors were made up of an agglomeration of irregular shaped particles. The luminescence spectra, excited at 395 nm using a monochromatized xenon lamp, for the four different anionic groups (BO33-, PO43- and SO42-) based CaMoO4:Eu3+ phosphors were recorded. The photoluminescent (PL) spectra showed an intense red emission at 615 nm belonging to the 5D0→7F2 electric dipole transition while the 5D0→7F1 was accountable to magnetic dipole. The highest PL intensity was observed for the CaMoO4-SO4:Eu3+ phosphor material. The calculated CIE (Commission Internationale de l’Eclairage) confirmed that the emission colour was lying in the red or orange region and the CIE coordinates changed from yellow to red, orange-red by varying the molar concentration of Eu3+ ion in CaMoO4-SO4:Eu3+ phosphors, while CaMoO4:Eu3+, CaMoO4-BO3:Eu3+ and CaMoO4-PO4:Eu3+ phosphors are stable at red region. The PL data suggested that our materials have potential applications as source of red light in red light emitting diodes.
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Fate and behavior of Bi₂O₃-BiVO₄ in wastewater treatment plant under an aerobic system

Synthesis of metal organic frameworks (MOF)/graphene oxide (GO) composites modified with Ag, Cu and Ag/Cu as nanoparticles for wastewater treatment

  • Authors: Makhetha, Thollwana Andretta
  • Date: 2019
  • Subjects: Organometallic polymers , Nanoparticles , Polymeric membranes , Factory trade and waste - Treatment , Water - Purification , Graphene
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/417542 , uj:35365
  • Description: Abstract: The intentional or unintentional release of wastewater containing dyes from the industries into the environment is a major challenge for municipalities, water practitioners and affected stakeholders. Conventional methods that are used somehow result in secondary pollution. Consequently, development of new or other treatment alternatives, such as membrane technology are required for the removal of these dyes from wastewater. Membrane technology has developed as a proficient method over conventional systems due to its high rejection capacity, ease in synthesis and operation, and cost effectiveness for the removal of dyes from wastewater. Polymeric membranes, such as those made of polyethersulfone (PES), are commonly used because of their higher flexibility, simple pore forming mechanism using phase inversion method, cost effective and require smaller space for synthesis as well as application in comparison to inorganic membranes. However, these polymeric membranes are susceptible to fouling because they are generally hydrophobic in nature. Fouling is a deposition of various colloidal particles, macromolecules (polysaccharides, proteins) and salts on membrane surface and within pores thus hinders membrane performance, reduces flux and results in high cost. As a result, modification of polymeric membranes is necessary to mitigate membrane fouling. Polymeric membranes are modified with nanomaterials owing to their altering ability; nanomaterials such as metal-organic framework (MOFs), graphene oxide (GO) and variety of metallic nanoparticles (e.g. AgNPs, CuNPs) results in polymeric nanocomposite membranes with high antifouling characteristics. Blending nanomaterials i.e. GO, MOFs and nanoparticles with polymeric membranes impart high selectivity, high permeability, high hydrophilicity, and antifouling properties to polymeric membranes... , Ph.D. (Chemistry)
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Synthesis and characterization of cerium (CE3+) doped alkaline sodium phosphate (NaMPO4 M= Mg/Ca/Sr/Ba) nano phosphors

  • Authors: Maleka, Prettier Morongoa
  • Date: 2018
  • Subjects: Phosphors - Synthesis , Phosphors - Spectra , Cerium , Nanoparticles
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/279485 , uj:30014
  • Description: M.Sc. (Nanoscience) , Abstract: Alkaline sodium phosphate (NaMPO4, M=Mg, Ca, Sr and Ba) phosphors doped with Ce3+ were prepared using combustion method. The effects of Ce3+ concentration on the optical and photoluminescence properties were investigated. The structure and particle morphologies of the phosphors were analysed using X-ray diffractometer (XRD) and field emission scanning electron microscopy (FE-SEM) respectively while the elemental composition of the phosphor were analysed using energy dispersive X-ray spectroscopy (EDS). X-ray photoelectron spectroscopy (XPS) was used to analyse the elemental composition, chemical and electronic states of the phosphors. The optical and luminescence properties were analysed by UV-Vis spectroscopy and photoluminescence spectroscopy respectively. The XRD results confirmed that the samples consisted of the expected crystalline phases found in the standard powder diffraction files. Energy band gaps were estimated from the diffuse reflectance data and were found to vary with the dopant content. SEM images indicated that the particles have irregular shape. FT-IR spectrum confirmed water impurities and symmetric, asymmetric and bending vibrations of the (PO4)3- ions in the prepared materials. The photoluminescence spectra recorded when the samples were excited using different wavelengths consisted of a broad and strong band ascribed to electronic transitions in Ce3+.
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