Materials Science and Engineering
http://repository.aust.edu.ng/xmlui/handle/123456789/354
This collection contains the theses of Materials Science and Engineering Students from 2012-20222024-03-29T07:18:17ZBiomass Valorization: Assessment and Characterization of Biomass Waste for Valuable Products.
http://repository.aust.edu.ng/xmlui/handle/123456789/5113
Biomass Valorization: Assessment and Characterization of Biomass Waste for Valuable Products.
Ezealigo, Uchechukwu
Research in the use of biomass residues has a huge interest as their potentials span a wide range of applications. Processed residues are useful as green energy such as biofuel (pellets and briquettes), animal feed, antioxidants, and activated charcoal for filtration and even carbon capture. With this in mind, my doctoral research covers the assessment of biomass residues generated in Nigeria for bioenergy. Also, Ficus benjamina fruit, identified as a biomass waste, was characterized for its value addition in bioenergy application. The latter fruit was further characterized for its value as a potential feed substrate for animals as well as the chemical source for industrial applications. The results from the research within this framework include the following. First, a proper bio-resource assessment, particularly, biomass residues availability and potential were investigated. This is a key requirement for an efficient and functional bioenergy sector in Nigeria, proposing to generate biofuel from agro-waste materials. In this study, computational
and analytical approaches with mild assumptions were employed to evaluate the bioenergy potential in agricultural residues, including municipal solid and liquid waste. This assessment was performed using data from 2008 to 2018. The available technical potential of 84 Mt yielded cellulosic ethanol and biogas of 14,766 ML/yr (8 Mtoe) and 15,014 Mm3/yr (13 Mtoe), respectively. The residues gave more biogas than cellulosic ethanol from the same amount of residue potential. The energy potential from residues in Nigeria may be tailored towards biogas production for diverse applications ranging from heat to electric power generation and therefore holds great potential in solving the current electricity crisis in Nigeria. It will also position the nation towards achieving the 7th sustainable development goal (SDG 7) on clean and affordable energy Secondly, having identified that some residues may be limited in supply due to seasonality and
multiple applications for various purposes, there is a need to continue a search for more plant waste that is resourceful as a potential feedstock. Ficus benjamina (FB) is an ornamental plant that produces nonedible fruits considered as waste. These fruits have no defined application, hence, identifying the potential in these fruits for possible valorization is necessary. Detailed preliminary characterization was performed to determine its suitability as a biofuel feedstock. The whole fruit (pulverized) was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDS), thermogravimetric analysis (TGA), Fourier transform infrared
spectroscopy (FTIR), X-ray diffraction (XRD), and bomb calorimeter. In addition, the physical, thermal, and chemical properties of FB fruits for potential biofuel application was determined using the proximate and ultimate analyses. Pulverized Ficus benjamina fruits
(PFB) have a porous morphology that makes them less dense and a crystallinity index of 25.5%. The moisture, ash, volatile matter, and fixed carbon contents were 9.29, 6.26, 64.35, and 20.10%, respectively. The higher and lower heating values are 19.74 and 18.55 MJ/kg, respectively, and are comparable to other biomass feedstock. The results establish the possibility of using PFB as a solid biofuel.
Thirdly, another possible approach in valorizing FB fruit focuses on other value products and benefits for livelihood. On this basis, the nutritional analysis, as well as the identification and quantification of micro and macro-nutrients and amino acid profile, were performed. HPLC and GC-MS were used to investigate the sugar profile of the water extract and the chemical content on the extracts obtained with solvents (ethanol, n-hexane, and ethyl-acetate), respectively. Found in FB fruits were: eighteen (18) amino acids, diverse micro- and macro mineral content, metabolizable sugars (such as galactose and glucose), and other chemicals,
including phytochemicals. In addition, these fruits showed low anti-nutritional factors such as phytate and tannins. From these findings, FB fruits offer diverse biological potential and functions and may be a prospective bio-resource for animal feed. The high fiber content reveals rich lignocellulose for bowel bulkiness. This result indicates that the fruits of FB can offer health benefits and can serve as a biomaterial. Thus, FB fruits may possess the potential as an additive material for animal feed, and phytochemicals for industrial and pharmaceutical uses.
Main Thesis
2022-04-15T00:00:00ZValorization of Agro-Waste for Mechanical Properties’ Improvement of Lateritic Soil for Sustainable Construction
http://repository.aust.edu.ng/xmlui/handle/123456789/5102
Valorization of Agro-Waste for Mechanical Properties’ Improvement of Lateritic Soil for Sustainable Construction
Obianyo, Ifeyinwa Ijeoma
This study presents the results of a combined theoretical, experimental and statistical study of the mechanical performance of stabilized lateritic soil for sustainable construction applications. The lateritic soil was stabilized with different percentage of bone ash (5%, 10%, 15% and 20%),hydrated lime (3%, 9% and 15%) for the project I whereas four different matrices with bone ash content of 0, 3, 6 and 9% of the weight of lateritic soil were used for the lateritic soil stabilization in project II. The bone ash and palm bunch ash were added to the soil sample in equal proportion at a varying proportion of 0%, 2%, 4% and 6% by weight of the soil in project III. Lateritic brick
samples obtained were cured at different temperature and ages. The effects of these stabilizers on the morphology and mechanical properties of the composite were investigated using Scanning Electron Microscopy and Universal Testing Machine respectively. The microstructural analysis gave a morphology with reduced porosity for the stabilized soil samples whereas, the results of the compressive strength tests indicated that the compressive strength of the lateritic soil was improved by the addition of the different stabilizers. The study also presents the prediction of compressive strength of stabilized bricks using Multivariate statistical models. Non-linear and mixed models with higher R2 performed better than the linear model in predicting the compressive strength of the stabilized bricks. The mixed model with R2 of 97% was identified as the best-fit model in predicting the compressive strength of the stabilized bricks. The results indicate that agro waste (cow bone and palm bunch) can be valorized through conversion to ash which can be used as an effective stabilizer for lateritic soil. Also, it can be used for making bricks with higher compressive strength compared to conventional stabilizers. The implications of the results for potential applications in the making of lateritic bricks for the construction of
sustainable and affordable buildings include lower building costs, bricks with high compressive strength and reduction in the use of cement for building construction.
Main Thesis
2020-09-06T00:00:00ZStructure and Properties of Organic and Inorganic Composites Materials: From Organic Photovoltaic Cells to Aerospace Materials
http://repository.aust.edu.ng/xmlui/handle/123456789/5101
Structure and Properties of Organic and Inorganic Composites Materials: From Organic Photovoltaic Cells to Aerospace Materials
Agyei-Tuffor, Benjamin
Pressure and contacts in materials and systems play crucial roles in their performance and also their eventual failures. Pressure application closes voids, bridges gaps and improves transport across interfaces. In thin film technology of multiple layers which are usually stacked together, photonic and electrical charge transports across the interfaces can have direct consequences on the performance and failures. This study explores the effects of pressure and contacts in bulk heterojunction organic, inorganic and hybrid materials used in photovoltaic applications. We present a review of the state-of-the-art in the theoretical study of the structure of the photovoltaic cells. It involves the application of pressure on contacts between the layers of the organic photo voltaic cells with poly (3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as the active layer. The contacts between the layers were modeled using analytical concepts and finite element models. The potential effects of surface roughness and dust particles were mod eled along with the effects of lamination pressure and adhesion energy. The results show that, increased pressure is associated with decreased void length or increased contact length. The con tacts associated with the interfaces between the active layer and the hole/electron injection layer poly(3,4-ethylenedioxythiophene: poly styrenesulphonate (PEDOT.PSS) and Molybdenum triox ide (MoO3) are also compared. The implications of the results are discussed for the design of stamping/lamination processes for the fabrication of organic photovoltaic cells. The morphology of active layers of organic photovoltaic cells plays crucial roles in achiev ing good performing devices with longer life span. The study of the active layer materials there fore explored an improved way of processing the active layer to enhance charge transport and lifetime of the conjugated polymer blends. The process of fabricating these devices included post
deposition thermal annealing, which increases the crystallinity and enhances phase-separated domains of deposited active layer components. A blended composite of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) used as the active layer in this Bulk heterojunction (BHJ) photovoltaic cell and annealed at different temperatures coupled with the application of pressure. AFM, SEM and GIWAXS techniques were employed to observe the nano- and micro- structures of the various active layers after quenching to room temperature. A better understanding of the correlation between the observed microstructures and
electrical characteristic of the active layers are therefore used to explain the performance of or ganic photovoltaic cells. Finally, Silicon carbide-fiber-reinforced silicon carbide matrix composites (SiC/SiC CMCs) have been proven to possess greater high-temperature strength and durability. These materials are usually used in air breathing engines due to their unique properties. However, the application of SiC/SiC CMCs is ineffective in combustion environment due to oxidation and surface recession. Efforts to improve service of SiC/SiC CMCs in combustion environments require knowledge of their long-term stability in combustion environments, volatility, phase stability, and thermal con ductivity. Therefore in this chapter, the design of a reliable EBC for SiC/SiC CMCs with excellent corrosion, recession and thermal shock resistance is proposed. This design consists of a three-multilayer; yttrium disilicate/mullite/ytterbium disilicate (Y2Si2O7/ 3Al2O3. 2SiO2 /Yb2Si2O7) system. Also, finite element models (FEMs) are used to predict the thermal residual stresses within the proposed multilayers under operating conditions. The implications of the results are discussed for potential application of this EBC system in aerospace engines
Main Thesis
2017-11-15T00:00:00ZDiffusion Kinetics for Drug Release and Food Preservation
http://repository.aust.edu.ng/xmlui/handle/123456789/5100
Diffusion Kinetics for Drug Release and Food Preservation
Aina, Toyin
This thesis presents silica nanoparticles for the controlled release of AMACR-conjugated doxorubicin for the inhibition of prostate cancer cell growth. Inorganic MCM-41 silica nanoparticles were synthesized, functionalized with phenylboronic groups (MCM-B), and capped with dextran (MCM-B-D). The nanoparticles were then characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), zeta potential analysis, N2 sorption, X-ray diffraction, and thermogravimetric analysis before exploring their potential for drug loading and controlled drug release. This was done using a model prostate cancer drug, doxorubicin (DOX), and a targeted prostate cancer biomarker to facilitate the localized delivery of the drug, α-Methyl Acyl-CoA racemase (AMACR)-conjugated DOX, which attaches specifically to receptors that are overexpressed on the surfaces of prostate cancer cells. The kinetics of controlled drug release over 30 days was then studied using zeroth order, first order, second order,
Higuchi, and the Korsmeyer-Peppas models, while the thermodynamics of drug release was elucidated by determining the entropy and enthalpy changes. The flux of the released DOX was also simulated using the COMSOL Multiphysics software package. Generally, the
AMACR-conjugated DOX drug-loaded nanoparticles were more effective than the free DOX drug-loaded formulations in inhibiting the growth of prostate cancer cells (PC-3 cell line) in vitro over a 96-h period. Furthermore, the effectiveness of DOX-A cancer drug for the
targeted treatment of prostate cancer was explored in vivo. AMACR-conjugated drug (AMACR-doxorubicin) and free doxorubicin drug injections into groups of 4-week-old athymic male nude mice were discovered to target and shrink tumors without any apparent cytotoxicity, as shown by ex vivo toxicity histopathology studies. Our findings demonstrate that prostate cancer cells/tumors with overexpressed AMACR receptors act as binding sites vi for AMACR-conjugated drugs, which in both in vitro and in vivo tests prevented the growth of prostate cells/tumors. The ability to restrain the growth of prostate cancer cells/tumors effects are due to the adhesive contacts between the overexpressed AMACR receptors on the prostate cancer cells/tumors and the AMACR molecular recognition units on the drug doxorubicin, DOX and DOX-A. The implications of the results are then discussed for the development of drug-eluting structures for the localized and targeted treatment of prostate cancer. The second phase of the work, presents the release kinetics (RK) of a fungicidal antimicrobial agent (AMA), potassium sorbate (PS), that prolongs the shelf life of packaged food. The effects of PS release are explored on peanuts and fresh bread to determine the effects of PS on Aspergillus niger (A. niger) microbial growth. The A. niger was cultured in a potato dextrose agar (PDA) medium to obtain AMA activity on the film. AMA activity of PS incorporated into cellulose acetate (CA) based film was tested on peanuts and fresh bread for an extended period of time. The RK of PS from the films was obtained by studying the de swelling properties of PS loaded film at room temperature (24°C) and at elevated temperature (37°C). The diffusion coefficients of PS released through the film network were obtained to be between 8.32 × 10−10 to 7.3 × 10−7 m2/s. The release exponents (n) of PS from the film occurred by anomalous transport with n values ranging from 0.13 to 0.16 at 24°C and 0.5 to 0.89 at 37°C. The average flux released from the CA film was consistent with the percentage PS release from the CA film showing that modelling the effective diffusion of PS from a porous media is feasible. The released PS was potent enough to inhibit the growth of A. niger for a week then over a period of 2 years. Thereafter, the implications of the results in designing smart food packaging for enhanced food preservation were discussed
Main Thesis
2022-10-05T00:00:00Z