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Non-volatile memories with larger capacity, faster operation speed, lower power consumption, smaller size and simpler fabrication process are strongly desired in the big data era. Recently, oxide-based random-access memories (OxRAMs) have been considered as a promising solution to meet these requirements. By achieving multiple resistance states in metal oxides, the memory capacity can be multiplied at the same cell size hence the development of metal oxide switching materials is important for achieving high-performance memory devices. In this thesis, a transparent metal oxide (SnO2) was selected for developing resistive switching-based RRAMs. Three strategies for improving the resistive switching behaviour were proposed and investigated, based on the solution-processed SnO2 thin films, which covered the following aspects:a. Defects engineering: to facilitate multi-level resistance states in metal oxides, defects engineering via cation doping has been investigated. The possibility of forming cationic and ionic defects in SnO2 by doping has been explored through density functional theory. Cationic defects – Mn3+ interstitials in Mn-doped SnO2 were synthesized through a new solution-processed approach and by altering the doping level, multi-resistance states in Mn-doped SnO2 have been achieved successfully. b. Layer design: to alter the migration and redox process of defects in metal oxides, an alternative multi-layer structure was designed. By inserting pure SnO2 layer as the ionic defects diffusion barrier, the migration and redox of ionic defects in the Mn-doped SnO2 layer can be modified. Stable multi-level resistive switching, high On/Off ratio, excellent retention and low operation voltage have been achieved. c. Graphene/metal oxide nanocomposites: graphene can be used as electrodes or buffer layer in RRAMs which can increase the device flexibility or modify the switching mechanism. However, due to the high hydrophobic behaviour of graphene, the fab

Ceramic electrolytes have attracted much interest in research, as they represent a safer alternative to flammable organic electrolytes. In particular, perovskite-type lithium lanthanum titanate (LLTO) is one of the most promising solid electrolytes because of its high ionic conductivity. However, it is a great challenge to synthesize LLTO nanomaterial with high purity at low temperature, which is essential for practical applications. In this dissertation, lanthanum titanate and lithium lanthanum titanate nanomaterials were successfully prepared by a modified hydrothermal process and their crystalline structures were characterized by X-ray diffraction and transmission electron microscopy. It has been found that both lanthanum titanate and lithium lanthanum titanate show layered structure, which can be attributed to the stratified monoclinic crystalline structure and weak bonding between layers. In addition, the effects of reaction parameters, including reaction time, surfactants and agitation on crystal growth, have been systematically investigated.Pure lanthanum titanate (LaTiO3) was used to fabricate resistive random access memory devices. The device shows excellent performance, such as the OFF / ON ratio of more than 100, over 200 cycles of resistance performance and a holding time longer than 105 s. A conductive filament model based on oxygen vacancies was proposed to explain the switching mechanismA number of different film preparation techniques were used to prepare LLTO films. The experimental results show that compared to drop coating and convective assembly, the layer-by-layer technique is superior for preparing nanoparticle films of structure in 2D layers. In addition, the LLTO was also combined with commercial LiCo1/3 Ni1/3Mn1/3O2 (CNM) for lithium battery applications, which indicated that the LLTO can facilitate the diffusion of lithium ions between active materials and electrolytes.This thesis demonstrated the great potential of the bottom up technology

Nowadays, enormous research efforts focus on the diagnosis and therapy of different types of sarcomas, which are rare but malignant cancers. The application of nano-science in cancer therapy has become one of the most attractive tools in scientific research because of its versatility in diagnosis and treatment. In particular, multifunctional and multimodal magnetic iron oxide nanoparticles can offer solutions in diverse areas of sarcoma, as one of the most desirable noninvasive magnetic resonance imaging (MRI) contrast agents, as well as drug, ligand and gene nanocarrier. It is also an outstanding hyperthermia agent via generating local heat under an alternative magnetic field. Iron oxide nanoparticles are renowned because of their low toxicity and suitability for treatment and diagnosis of different types of cancers; however, in some cases, iron oxide nanoparticles may result in severe damage of DNA, protein, and lipid. To our knowledge research investigating the cytotoxicity effect of iron oxide nanoparticles with different physiochemical characteristics in sarcoma is limited, which presents some major issues that need to be carefully considered. In this study, we initially prepared desirable iron oxide nanoparticles with hydrothermal synthesis and thermal decomposition methods. We modified the aforementioned methods in order to create a desirable range of size of magnetic nanoparticles for bio application (200, 100, 20 and 10 nm). We, also, modified the surface of nanoparticles with different types of coatings (polyethylene glycol (PEG), D-glucose (DG) and silica) under mild conditions to increase their bio-compatibility, bioavailability and colloidal stability. Various methods were used to illustrate and quantify cellular uptake of magnetic nanoparticles in sarcoma cell lines. Finally, the safety of the nanoparticles uptake on diverse human sarcoma cell lines was investigated and found that the readily available iron oxide nanoparticles can be safely taken up by

Fe-based amorphous/nanocrystalline alloys have become increasingly interesting for soft magnetic applications such as cores of transformers, motors, generators and toroidal wound cores. Basically, soft magnetic materials are characterized by low coercivity (Hc) and relatively high saturation flux density (Bs). Amorphous metals for soft magnetic applications are produced as thin ribbons with approximately 20mm thickness via rapid solidification method, such as melt-spinning process. The main advantage of the new amorphous/nanocrystalline system is its low coercivity, high permeability and low core loss as compared to conventional silicon steels counterpart. However, it suffers from relatively low saturation magnetic flux density. In the current work, a series of samples with different compositions (Fe-B-(Cu, Y, Si)) were prepared by single-roller melt-spinning method. It was found that Fe84.6B14.4 alloy annealed at 380°C for 5mins (around the first crystallization peak) possessed the highest saturation magnetic flux density (Bs=1.94T); however, annealing at higher temperature (440°C) degraded the soft magnetic properties mainly due to the precipitation of the phases with high magnetic anisotropic properties, such as Fe3B and Fe2B. In addition, it was evident that Cu-doping could facilitate the nucleation process of α-Fe, and thereby increasing the Bs value from 1.47 to 1.63 (T) in amorphous Fe84.2B14.8Cu1.0 alloy and reaching 1.81T after annealing at 400°C for 5mins. It was also observed that the coercivity was lowered owing to the refined microstructure and smaller grain size. In addition to Cu, the effect of yttrium addition on the soft magnetic properties was investigated and it was concluded that Y could effectively reduce the coercivity with scarification of high saturation magnetic flux density. Adding only 2 at.% yttrium decreased the Bs value from 1.81 to 1.32 (T) while significantly reducing Hc from 2708A/m to 172A/m. It was also found that silicon improved

Oxide thermoelectric materials have been drawing extensive attention as substitutes for conventional thermoelectric materials due to their low cost, nontoxicity, and high stability. Currently, the most promising p-type and n-type oxides are layered cobaltates (including NaxCoO2 and Ca3Co4O9) and donor-doped SrTiO3, respectively. Major enhancement of the thermoelectric properties of these materials relies on the reduction of thermal conductivity and the improvement of electrical conductivity through doping technology, compositing, nanotechnology, etc. We demonstrated the successful fabrication of p-type Na0.8Co1-xFexO2 and (1-x)Na0.77CoO2/xCa3Co4O9 composites by means of spark plasma sintering (SPS) technique. The thermoelectric properties were improved with small amount of Fe doping (x ≤ 0.01). A significant enhancement of Seebeck coefficient was achieved in (1-x)Na0.77CoO2/xCa3Co4O9 composites, approximately 17% higher than that of Ca3Co4O9 at 680 °C. The electrical resistivities of the composites were higher than the theoretical values. The increase in the Seebeck coefficient and the electrical resistivity of the composites is most likely associated with the compressive strain in Ca3Co4O9 grains due to the mismatch of thermal expansion coefficients between Na0.77CoO2 and Ca3Co4O9. Most importantly, the chemical stability of Na0.77CoO2 was improved by adding up to a 30 vol.% fraction of Ca3Co4O9 without deteriorating its thermoelectric performance. A typical thermoelectric generator consists of p-type and n-type semiconductors which form p-n junctions to convert the wasted heat from exhaust gases to useful electricity. Therefore, apart from the p-type thermoelectric oxides, we also investigated the thermoelectric performance of n-type SrTiO3. We examined the solubility of Y and La in Sr1-1.5xMxTiO3 (M = Y, La) and the corresponding thermoelectric properties. After determination of the proper amount of dopants (Y and La), the effects of Sr content on the phase compo