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Ultrafine one-dimensional LaFe1-xMnxO3 (0.00 ≤ x ≤ 0.15) nanofibers were prepared by electrospinning. The X-ray diffraction pattern of Mn-doped LaFeO3 nanofibers showed orthorhombic perovskite crystalline structure of LaFeO3. Transmission electron microscopy (TEM) images revealed that the nanofibers were composed of fine particulates with diameter of about 50 ± 5 nm in pure LaFeO3 and 35 ± 5 nm in 15 mol% Mn-doped nanofibers. The chemical state of Mn3+ and Mn4+ in Mn-doped LaFeO3 nanofibers were confirmed from curve fitting after X-ray photoelectron spectroscopy (XPS) measurement. The optical energy bandgap decreased with increasing Mn-doping, which can be ascribed to Mn dopant levels near the conduction band. A clear hysteresis loop can be observed for Mn-doped LaFeO3 nanofibers. With increasing Mn concentration, remnant magnetization linearly increased from 0.098 to 0.289 emu/g at 10 K, which is due to uncompensated spin moment at the surface and the differences of spin magnetic moments between Fe and Mn ions. The coercivity is decreased from 632 to 190 Oe, following an increasing trend with increase of particles size up to a critical particle size. The present work shows that Mn doping in LaFeO3 nanofibers is a very effective method for having enhancement of magnetic property in antiferromagnetic LaFeO3.

Nanofibers of titania and composite nanofibers of titania and multiwall carbon nanotubes were synthesized by electrospinning using a sol-gel process combined with activated carbon nanotubes. The relationships of treatment temperature, carbon nanotube content on the crystal phase, fiber morphology, and electric properties are reported. It is found that the rutile phase becomes more prominent at low heat treatment temperatures with an increase of carbon content in nanofibers, be it for higher amount of carbon due to reducing atmosphere or due to an increase in MWCNT. Atmospheric control and lower heat treatment temperatures enable crystalline nanocomposite fibers of anatase where the level of rutile is below the detection limit of XRD or Raman spectroscopy. This work provides a new path to fabricate electrospun TiO2/MWCNT nanocomposite nanofibers with limited C-induced rutile phase.

The increasing demand for sustainable energy results in the development of new technologies of energy generation. The key objective of hydrogen economy is the introduction of hydrogen as main energy carrier, along with electricity, on a global scale. The key goal is the development of hydrogen-related technologies needed for hydrogen generation, hydrogen storage, hydrogen transportation and hydrogen distribution as well as hydrogen safety systems. It is commonly believed that hydrogen is environmentally clean since its combustion results in the formation of water. However, the technology currently employed for the generation of hydrogen from natural gas, does in fact lead to the emission of greenhouse gases and climate change. Therefore, the key issues in the introduction of hydrogen economy involve the development of environmentally clean hydrogen production technology as well as storage and transport. The clean options available for hydrogen generation using nuclear energy; such as advanced nuclear fission and, ultimately, nuclear fusion, are discussed. The latter, which is environmentally clean, is expected to be the primary approach in the production of hydrogen fuel at the global scale. The present work considers the effect of hydrogen on properties of TiO2 and its solid solutions in the contexts of photocatalytic energy conversion and the effect of tritium on advanced tritium breeders.

Zinc oxide nanoparticles (ZnO) were prepared via a sol–gel method, and a photo-assisted deposition method was used to prepare platinum on zinc oxide nanoparticles (Pt/ZnO). Several techniques were used to characterize these enhanced photocatalysts: XRD, TEM, UV–vis spectra, PL spectra, XPS, and BET surface area analysis. As-prepared samples’ photocatalytic performances were studied via degradation of malachite green dye under various visible-light-only irradiation scenarios. Results demonstrated the following: platinum (Pt) was well dispersed on and in ZnO's surfaces and pores; as such, Pt/ZnO had less surface area than pure ZnO due to pore blockage; however, advantages gained from enhanced electron-hole separation and decreased band gap width more than made up for this negative effect; moreover, Pt/ZnO prepared with 0.3 wt% Pt exhibited the lowest band gap and the highest photocatalytic activity of the various samples with a solids loading of 0.8 g/l; finally, such samples were recyclable, i.e., photocatalytic performance remained stable even after five uses.

Enhanced visible-light absorption of 4 at% fluorine (F) doped zinc oxide (ZnO) nanowires (F:ZnO) produced via a hydrothermal method with 15 M sodium hydroxide (NaOH) is explored with various characterization techniques: XRD, TEM, UV–vis spectra, Pl spectra, XPS, and surface area analysis. Moreover, photocatalytic performance of as-prepared samples is studied via degradation of malachite green dye under visible light irradiation. Finally, the photocatalyst’s optimal amount to use is determined as well as its recyclability. Results show that band gaps of ZnO nanostructures depend on NaOH concentration, doping 15 M NaOH resultant ZnO nanowires with 4 at% F further narrows the band gap, F:ZnO nanowires perform 1.6 times better than the pure ZnO nanowires in malachite green dye (MG) degradation tests, overloading the solution with the photocatalyst actually hinders degradation performance, and the F:ZnO photocatalyst remains a robust performer even after five cycles.

Organic dyes used by food and textile industries, e.g. Malachite green dye (MG), contaminate surface and ground waters. Photocatalysis with ultraviolet light (UV) irradiation of zinc oxide (ZnO) nanoparticles can remove such industrial effluents. However, to more efficiently use solar energy, a photocatalyst active over a wider range of the visible light spectrum remains desirable for environmental remediation. Thus, we synthesized visible light photoactive cobalt/zinc oxide hollow sphere nanostructures with a hydrothermal process, and we used a number of characterization techniques to confirm that doped cobalt (Co) ions replace some zinc (Zn) ions in the lattice. The as-prepared Co doped hollow spheres performed 55.9 times better in Malachite green dye visible light photodegradation tests than similar ZnO nanoparticles. Furthermore, the Co/ZnO hollow spheres are recyclable.

Silicon is one of many materials whose surface will oxidize in ambient conditions. However it is one of few materials whose native oxide will self-limit its growth in a matter of hours at a thickness of ∼2 nm. In this work, we show through the theory of repulsive van der Waals forces that this self-limitation is due, at least in part, to the interaction between the inherent material properties of a native silicon oxide film on silicon and oxidizing molecules. These molecules are not just hindered from even entering the system at all, but those that do enter the native oxide film are repelled away from the silicon – silicon oxide interface, preventing additional growth by oxidation. We also show how this repulsion is overcome by increasing ambient temperatures to subsequently increase the kinetic energy of the oxidizing molecules, calculated by the Boltzmann-Maxwell distribution, and allow oxidation to continue.

The recent climate change agreement in Paris highlights the imperative to aggressively decarbonize the energy economy and develop new technologies, especially for the generation of electrical energy that are environmentally clean. This challenge can only be addressed by a multi-pronged approach to research and education of the next generation of scientists and engineers as well as informed public discourse. Consequently this requires the introduction of new and comprehensive education programs on sustainable energy technologies for universities and, possibly, high schools. Among others, the new programs should provide in-depth knowledge in the development of new materials for more efficient energy conversion systems and devices. The enhanced level of education is also needed for properly assessing the competing technologies in terms of their economic and social benefits. The increasing recognition of the significance of clean and efficient energy conversion indicates the need for a comprehensive education program to be developed. The purpose of the present work is to consider the structure of both an education program and the related textbook where the energy-related fundamental and applied subjects are presented in a concentrated and uniform manner. Such a textbook could be an education aid for students of energy-related courses as well as the teachers involved in the formulation of the education programs. The textbook, which should be dedicated mainly for students at the undergraduate levels at universities, and possibly high schools, should include in-depth interdisciplinary sections dedicated to energy experts and graduate students. This paper considers the present international efforts in reducing the impact of climate change and the need to develop new technologies for clean energy generation. It is argued that progress in this area requires recognition of hydrogen as the main energy carrier of the future. This work also delineates the goals of the Sustainable Energy Network, SEN, involved in the UN program of Future Earth.

TiO 2 is one of the most exciting anode candidates for safe application in lithium ion batteries. However, its low intrinsic electronic conductivity limits application. In this paper, a simple sol–gel based route is presented to produce nanosize TiO 2 fibers with 119 ± 27 nm diameters via electrospinning. Subsequent calcination in various atmospheres was applied to achieve anatase and anatase-rutile mixed phase crystallites with and without carbon coating. The crystallite size was 5 nm for argon calcined fibers and 13–20 nm for air calcined fibers. Argon calcined TiO 2 nanofibers exhibited electronic conductivity orders of magnitude higher than those of air-calcined samples. Lithium diffusivity was increased by one time and specific capacity by 26.9% due to the enhanced conductivity. It also had a different intercalation mechanism of lithium. Hydrogen post heat-treatment was found to benefit electronic conductivity (by 3–4.5 times), lithium diffusivity (1.5–2 times) and consequently the high rate performance of the TiO 2 nanofibers (over 80%). The inner mechanism and structure-property relations among these parameters were also discussed.

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The adhesion force between ceria and polyurethane (PU) pad was controlled to remove the step height from cell region to peripheral region during Shallow Trench Isolation Chemical Mechanical Planarization (STI-CMP) for NAND flash. Picolinic acid was found to be adsorbed on ceria particles at pH 4.5 following a Langmuir isotherm with the maximum adsorbed amount of 0.36 mg/m2. The ceria suspension with full surface coverage of picolinic acid showed a threefold increase in the number of adhered ceria particles on the PU pad over non-coated ceria particles. It was shown that the coverage percent of picolinic acid on ceria corresponds well with the amount percent of adsorbed ceria on PU pad. The change in adsorbed particles was directly reflected in the CMP polishing process where significant improvements were achieved. Particularly, convex areas on the chip experienced higher friction force from the attached abrasives on the PU pad than concave areas. As a result, the convex areas have increased removal rate of step height compared to the ceria suspension without picolinic acid. The changing profiles of convex areas are reported during the step height reduction as a function of polishing time.

A sol–gel based route was used to produce TiO 2 based nanocomposites. Sols were electrospun into continuous nanofibers and calcined to get rutile phase. Fibers with diameter around 100 nm and crystallites size between 10 and 50 nm were obtained. The morphological impact and crystallites size dependence of the electrochemical performance for as-synthesized materials are reported. Enhancements using inert calcination atmosphere and incorporation of multi-wall carbon nanotubes (MWCNT) into the system are also presented.

Magnetic photocatalysts were successfully prepared by coating titania–silica (TiO 2 –SiO 2 ) on cobalt ferrite (CoFe 2 O 4 ) nanoparticles. A simple organic acid precursor method was employed to prepare the magnetic part, while the TiO 2 –SiO 2 was synthesized and coated onto CoFe 2 O 4 by the sol–gel technique. Controlling the modification process of TiO 2 –SiO 2 with CoFe 2 O 4 nanoparticles is a key factor for obtaining appropriate catalytic performance. Under optimized conditions, a core–shell structure could be obtained in which CoFe 2 O 4 is a core while TiO 2 –SiO 2 forms a shell. The current photocatalyst exhibits remarkable catalytic activity for the degradation of methylene blue dye in water under UV irradiation. It was demonstrated that the catalyst could remove as high as 98.3% of the organic dye in just 40 min. The degradation efficiency was found to depend essentially on initial dye concentration, solution pH and the catalyst loading. The as-synthesized catalyst was characterized by different techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and N 2 adsorption–desorption isotherm. The photocatalyst could be removed from the reaction mixture and its recyclability remains effective and active after six cycles.

We investigated the effect of poly (ethyleneimine) (PEI)-modified silica abrasive on the removal rate and the degree of dishing during Cu chemical mechanical planarization (CMP). The PEI-modified silica abrasive was prepared by mutually attractive electrostatic forces between PEI and silica abrasive. The physico-chemical behaviors between PEI and the silica abrasive were evaluated by total organic carbon (TOC), force-separation measurements using atomic force microscopy (AFM) with molecular weight of PEI, which was found to adsorb on silica at pH 7.0 following a Langmuir isotherm. The maximum adsorbed amounts of low and high molecular weight PEI were 0.195mg/m^2 and 0.228mg/m^2, respectively. AFM results showed the repulsive force of the adsorbed PEI layers on the silica surface and the adsorption thickness of PEI on silica vary with the molecular weight of PEI. A twofold change was observed in the AFM analysis. First, the increased areal density of adsorbed PEI caused a higher zeta-potential and longer reaching repulsive force. Second, the adsorption thickness was also significantly enlarged. High molecular weight showed increased adsorption thickness under similar conditions compared to low molecular weight of PEI. These changes of silica abrasive such as electrostatic forces and steric interaction vary with molecular weight of PEI reduced the dishing of Cu pattern film from 50 to 20nm.

a b s t r a c t Nanosize LiNixFe1−xPO4 solid solution and LiNixFe1−xPO4/C nanocomposites were prepared via a solid state reaction method under argon atmosphere. A single phase olivine-type structure with Pnma space group was determined by X-ray diffraction. Crystallite sizes were found to be around 50 nm. A linear relationship was observed between lattice parameters and chemical composition which follows Veg- ard's law. Synthesized materials displayed electronic conductivity similar to previous reported values of LiFePO4. Carbon coating further increased the overall conductivity of nanocomposites to the order of 10 −3 S/cm. Chemical delithiation via NO2BF4 oxidant extracted more than 95% of lithium from the solid solution material accompanied by a decrease in lattice parameters.

Hybrid nanofibers of polyaniline/polyoxometalate are synthesized via a facile interfacial polymerization method for the first time, and evaluated as a cathode material for lithium ion batteries. The hybrid nanofibers with 100 nm diameter consisted of phosphomolybdic acid polyanion, [PMo12O40]3–, and polyaniline matrix. Their 1D geometry improves the utilization of electrode materials and accommodates the volume change during cycling, which enables the significant improvement in lithium storage capacity and capacity retentions. The phosphomolybdic acid polyanions not only exhibit a large theoretical capacity of about 270 mAh g–1, but also reduce the charge transfer resistance of electrode leading to the enhanced reversible capacity and rate capability. The polyaniline/polyoxometalate nanofibers delivered a remarkably improved electrochemical performance in terms of lithium storage capacity (183.4 mAh g–1 at 0.1C rate), cycling stability (80.7% capacity retention after 50 cycles), and rate capability (94.2 ...

A series of CexZr1−xO2 nanoparticles were synthesized by reverse micelle method that acted bi-functionally as either photocatalysts or free radical scavengers. The switch was realized by illumination with light at different wavelengths. Dye degradation method was used to evaluate their photocatalytic activity compared to Aeroxide® TiO2 P25. The free radical scavenging capability was examined by photocatalysis of mixed particles. Our results demonstrated their ability to effectively remove free radicals created by the best photocatalysts in the UV-B region. When the excitation wavelength decreased to 302 nm CexZr1−xO2 nanoparticles acted as photocatalysts. This opens possible applications such as selectively killing of the disease cells with bi-functional particles using light as a switch. Dark sections will be protective to tissues via free radical scavenging while illuminated sections will be free radical formers that may cause cell death. Particle characterization revealed that the bandgap played a major role in the selectivity of light wavelength while bi-functionality should be attributed to the exchange between [Ce3+] and [Ce4+] valence state. We also conclude that ceria must be a superior free radical former at 302 nm compared to titania since it is capable of surpassing its own free radical scavenging ability. Further tuning of the bandgap is predicted to produce bi-functionality with longer wavelengths.

The response time (to change from maximum to minimum contact angle—CA for a drop of water) on the electrospun poly(N-isoporpylacrylamide) (PNIPA)/polystyrene (PS) fiber mats of 380, 990, and 1500 nm diameter fibers was found to be 4–5 s; whereas, on the 16 µm diameter fiber it was more than five times slower. While the reported switching times were limited by the experimental design, they are in the micro- to millisecond for fiber diameters ranging between 100 and 500 nm, in theory. The temperature-dependent-switch in CA values is attributed to the hydrogen bonding capability of PNIPA with water. The closer to superhydrophobic CA values at 65 °C was successfully described by the Cassie–Baxter (CB) state equation. The superhydrophilicity at RT was explained by hydrogen bonding as well as capillary forces provided by the fiber mat. The variations in the larger fibers' changes are attributed to lower surface area with reduced capillary driving forces for droplet spread.

Tin oxide (SnO2) is a promising candidate as an anode for lithium ion batteries because of its high theoretical capacity. However, poor capacity retention caused by large volume changes during cycling, large initial irreversible capacity, and low rate capability frustrate its practical application. We have developed a ternary nanocomposite based on tin indium oxide (SnO2–In2O3) and graphene nanosheet (GNS) synthesized via a facile solvothermal method. The incorporation of In2O3 into SnO2 can improve the electrochemical property of SnO2 and reduce the charge transfer resistance of electrode leading to the enhanced reversible capacity and rate capability. The graphene nanosheet in the composite electrode can accommodate high volume expansion/contraction during cycling resulting in excellent capacity retention. As an anode for lithium ion batteries, the SnO2–In2O3/GNS nanocomposite exhibits a remarkably improved electrochemical performance in terms of lithium storage capacity (962 mAh g−1 at 60 mA g−1 rate), initial coulombic efficiency (57.2%), cycling stability (60.8% capacity retention after 50 cycles), and rate capability (393.25 mAh g−1 at 600 mA g−1 rate after 25 cycles) compared to SnO2/GNS and pure SnO2–In2O3 electrode.

This work considers the equilibration kinetics of Nb-doped TiO2 single crystal (0.066 atom % Nb) during oxidation and reduction within a wide range of temperature (1073-1298 K) and oxygen activity (10(-14)-10(5) Pa). The associated semiconducting properties were determined using simultaneous measurements of both electrical conductivity and thermoelectric power. It is shown that the chemical diffusion coefficient in the strongly reducing regime, p(O2)10(-5) Pa, is 4 orders of magnitude larger than that in the reducing and oxidizing regimes, 10 Pap(O2)22 kPa. The derived theoretical model considers the gas/solid kinetics for the TiO2/O2 system in terms of two diffusion regimes: the fast regime related to fast defects (oxygen vacancies and titanium interstitials) and leading to quasi-equilibrium, and the slow regime associated with slow defects (titanium vacancies) resulting in the gas/solid equilibrium. It has been shown that incorporation of donor-type elements, such as niobium, and imposition of oxygen activity above a certain critical value, results in a substantial reduction in the concentration of high mobility defects and leads to slowing down the equilibration kinetics. In consequence, the fast kinetic regime is not observed. Comparison of the kinetic data for Nb-doped TiO2 single crystal (this work) and polycrystalline Nb-doped TiO2 (reported before) indicates that the gas/solid kinetics for the polycrystalline specimen at higher oxygen activities is rate controlled by the transport of oxygen within individual grains.

Flexible ceramic nanofibers have been electrospun from a novel TiO 2 –SiO 2 aqueous sol. The nanofibers obtained have an average diameter of around 150 nm and are amorphous even after heat treatment at 600 °C for 3 h in air. Since the material is amorphous it may be considered as electrospun glass nanofiber. Fracture in glass usually initiates from surface defects and in the absence of any preferred plane propagates perpendicular to the surface. The presence of surface defects on the heat treated nanofibers could not be detected on SEM and TEM images. It is hypothesized that the observed flexibility is due to significant reduction in surface defects.

Superhydrophobic surfaces have received tremendous attention in the last decade, owing to the number of emerging applications in conservation of environment. These surface properties are based on physio-chemical principles and can be transferred into technical “biomimetic” materials, as successfully done for the Lotus leaves. This article provides a review of the most recent development in superhydrophobic surfaces. Examples of superhydrophobic surfaces from nature are presented. It focuses on the hairy exterior of many different plant and animal species which renders them water repellent for protecting and maintaining crucial life functions. The classical Wenzel and Cassie–Baxter models along with manufacturing and understanding of the wettability of flexible hairy structures are reviewed.

Crystal-growth-related microstructures and the length-to-diameter ratio of a single-crystal-type α-Al 2 O 3 nanofiber were examined using HR-TEM techniques. The fibers exhibited diameters ranging from 50 to 100 nm and lengths of several tens of micrometers. During thermal treatments, the alumina fiber went through phase transformations similar to boehmite. Therefore, the phase evolution, especially the final θ- to α-Al 2 O 3 stage of the phase transformation, may be the determining factor in the microstructural evolution of the nanofibers. HR-TEM techniques were utilized to demonstrate that the single crystals were formed by the coalescence of well-elongated α-Al 2 O 3 colonies. The fibers grew in the [1 1 0] or [1 1 2] direction instead of [0 0 1]. A thermodynamic analysis revealed that if the α-Al 2 O 3 nanofiber that transformed from θ-Al 2 O 3 behaved in a stable manner, there could be a size ratio limit for the length and diameter of each α-Al 2 O 3 colony. The smallest potential diameter was calculated to be around 17 nm.

Force interactions of porous silica particles against mirror-polished stainless steel surfaces were quantified in the presence of various solvents to facilitate processing of ceramics with less reliance on organic aids which subsequently need to be burned off. The results were compared to and found to be in good agreement to idealized models of van der Waals force interactions. Significantly, van der Waals attractive forces between steel surfaces and silica surfaces were minimized through the use of tetrahydrofuran and enhanced using methanol. The solvent selections were further extended to settling behavior and were found to follow the general trends determined by Stokes law. The methods presented herein can be extended to other real-world systems.

Long-length nanofibers are able to form porous networks with high surface-area-to-volume ratios, and decrease diffusion lengths. While there are numerous techniques to create nanostructures, electrospinning is the only technique that allows fabrication of nanofibers at long-length scales. These uniquely shaped fibers are applied to several energy-related devices. This review is an in-depth summary of the uses of electrospun fibers in dye-sensitized solar cells (DSSCs), batteries, capacitors, fuel cells, and hydrogen storage devices. Developments in electrospinning technologies to create novel fiber morphologies are also discussed.

Superhydrophobic membranes have the potential to protect devices from incidental exposure to water. This paper reports on the processing of Teflon AF fluoropolymers through electrospinning. Teflon AF is difficult to electrospin due to its low dielectric constant and the low dielectric constants of the liquids in which it is soluble. The two approaches that have been utilized to produce fibers are direct electrospinning in Novec engineering liquids and core-shell electrospinning. Both methods produced superhydrophobic membranes. Fibers with an average diameter of 290 nm and average water contact angle of 151° were obtained by core-shell electrospinning. One suggested application for electrospun superhydrophobic membranes is the lithium-air battery.

Nanocrystalline octahedra of cobalt ferrite CoFe 2 O 4 powders were synthesized using the organic acid precursor route. The effect of the calcination temperature, Fe 3+ /Co 2+ molar ratio, calcination time and type of organic acid (oxalic, benzoic and tartaric acids) on the formation, crystallite size, microstructure and magnetic properties was studied systematically. The Fe 3+ /Co 2+ molar ratio was varied from 2 to 1.739 while the annealing temperature was controlled from 400 to 1000 °C for various periods from 0.5 to 2 h. The resulting powders were investigated using X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). XRD results indicate that a well crystallized, single spinel cobalt ferrite phase was formed for the precursors annealed at 600–800 °C for 2 h, using oxalic and tartaric acids as precursors for Fe 3+ /Co 2+ molar ratio 1.818. The crystallite size of as-formed powders was in the range of 38.0–92.6 nm at different operating conditions. The calcination temperature and Fe 3+ /Co 2+ molar ratio have a significant effect on the microstructure of the produced cobalt ferrite. The microstructure of the produced powders was found to be octahedra-shaped. The crystalline, pure cobalt ferrite powders with magnetic properties having a maximum saturation magnetization (76.1 emu/g) was achieved for the single phase at Fe 3+ /Co 2+ molar ratio 1.818 and annealing temperature of 600 °C for 2 h using tartaric acid precursor.

Airborne biological agents, albeit intentionally released or naturally occurring, pose one of the biggest threats to public health and security. In this study, a microwave assisted nanofibrous air filtration system was developed to disinfect air containing airborne pathogens. Aerosolized E. coli vegetative cells and B. subtilis endospores, as benign surrogates of pathogens, were collected on nanofibrous filters and treated by microwave irradiation. Both static on-filter and dynamic in-flight tests were carried out. Results showed that E. coli cells were efficiently disinfected in both static and in-flight tests, whereas B. subtilis endospores were more resistant to this treatment. Microwave power level was found to be the major factor determining the effectiveness of disinfection. Both thermal and non-thermal effects of microwave irradiation contributed to the disinfection. Reducing flow velocity to decrease heat loss yielded higher disinfection efficiency.

Changes in the surface chemistry of LiFePO4 cathodes in an aqueous medium for lithium ion battery are investigated based on a quantitative evaluation of surface functional groups of LiFePO4 as a function of pH. It is found that, while the dissolution of Li ions from LiFePO4 increases the number of acidic surface groups, the dissolution of Fe ions reduces the number of basic surface groups. The pKa values for various processing conditions are calculated. Interestingly, none of the investigated processing conditions changes the characteristic acid moieties on the particles (pKa ∼ 2.8). However, the processing condition strongly impacts the chemistry of the basic surface groups showing three distinct basic surface groups with pKb values of 0.1, 0.9, and 1.5, respectively. Correlation is made between dissolution behavior, surface groups, dispersion properties, and electrochemical properties. It is found that Li-and Fe-ion depleted LiFePO4 powder increases the viscosity in N-methylpyrrolidone pastes 5-fold and...

Nanofiber filtration is drawing great interest nowadays because of its large surface collection area as well as low air resistance. In this study, electrospun nanofiber mats of different thicknesses were evaluated for their filter quality factors. Shorter-term electrospun fiber mats exhibited a better quality factor than those longer-term electrospun ones. Multiple thin layers of nanofiber mats to improve the filter quality of the nanofiber filters were then evaluated. Filtration test results showed that the filter made up of multiple thin layers of nanofiber mats had a filter quality factor much higher than the single thick layer nanofiber mat. Better thickness uniformity in the multi-layer structure due to stacking compensation and smaller fiber diameters in nanofibers of short-term deposition time are two possible reasons for the improvement of the filter quality.

Aims: Fluorescent cerium oxide (ceria) nanoparticles were developed through incorporation of erbium into the lattice. Catalytic properties and luminescent behavior are examined. Materials & methods: Cerium–erbium mixed oxide nanoparticles were synthesized by the reverse micelles route. Purity, size, and composition were characterized. Catalytic properties were measured using a hydrogen peroxide assay, and the luminescence properties were determined by confocal microscopy. Results: The nanoparticles exhibited enhancement of the catalytic properties with increasing erbium content to 10 mole% in the cerium oxide lattice; and they demonstrated emission at 515 nm and 572.5 nm under 405 nm UV excitation in aqueous conditions. Conclusion: Erbium incorporation into ceria-based nanoparticles were developed, having catalytic properties similar to and better than purely synthesized ceria and luminescent properties under UV irradiation by confocal microscopy.

The literature and advances in photocatalysis based on the combination of titania (TiO2) and carbon nanotubes is presented. The semiconductor basis for photocatalysis is introduced for anatase and rutile. Furthermore, the proposed mechanisms of catalytic enhancement resulting from the pairing of the titania semiconductor with either metallic, semiconducting, or defect-rich carbon nanotubes (CNT) is discussed. Differences are apparent for the mixtures and chemically bonded CNT–TiO2 composites. The article then highlights the recent advances in the synthesis techniques for these composites and their photocatalytic reactions with organic, inorganic, and biological agents. Finally, various applications and challenges for these composite materials are reported.

Aims: The hypothesis that an increase in defects in cerium oxide (CeO2) nanoparticles induced by solid solutions with differences in valency and ionic radius of the solute will yield superior reactive oxygen species (ROS) scavengers at room temperature will be tested. Methods: Solid solutions of zirconium in CeO2, that is, CexZr1-xO2 nanoparticles, were synthesized by a reverse micelle method. Their crystal structures, particle sizes and level of agglomeration were characterized. The nanoparticles’ activities to scavenge ROS were tested in response to hydrogen peroxide at physiological levels and room temperature using an enzyme peroxidase-based assay. Results: Solid solutions of Zr in CeO2 nanoparticles enhanced ROS scavenging fourfold. The hypothesis is confirmed that more defects are formed and that the scavenging activities of CexZr1-xO2 correlate to the nanoparticles’ oxygen-storage capacity. Conclusions: The antioxidant efficacy of CeO2 nanoparticles can be enhanced by dissolving zirconium in the CeO2 lattice. The CexZr1-xO2 nanoparticles act as an enhanced catalyst at room temperature that scavenges ROS. Increased efficacy will enable lower nanoparticle dosages to protect cells from ROS, thus increasing the therapeutic width of these compounds.

This work expands the field of view in ceramic fiber electrospinning, wherein ceramic fibers of hydrous alumina are directly electrospun from alkoxide-based precursors. The continuous fibrous bundles are produced with consistent tubular structures. The stability of the drawn fibers is dominated by the hydrolysis and condensation kinetics of the sol–gel precursor, which in parallel changes the processing parameter relationships found in traditional electrospinning. Here, we explore the nature and introduce the processing development of the sol–gel based fibers through electrospinning.

Electrospinning is a versatile process for drawing fibers of diverse materials including polymers, ceramics, and composites. We demonstrate here its application in the synthesis of complex ceramic oxide materials. The phase formation and morphology of BaTiO 3 nanofibers synthesized via electrospinning is investigated as a function of heat treatment conditions. Fully crystallized BaTiO 3 nanofibers with the perovskite structure are obtained after annealing at 750 °C and show an average grain size of about 30 nm. Tetragonal crystal structure of the fibers is indicated by XRD peak splitting (calculated c / a ratio=1.007), and confirmed by Raman spectroscopy. Furthermore, the advancement in heat treatment of the electrospun fibers yields single crystalline BaTiO 3 nanofibers with 50 nm in diameter and lengths up to 1 μm.

Electrospinning is a versatile and straight forward process for synthesizing one-dimensional (1D) nanostructures of diverse materials. Recently, a large variety of oxide ceramics have been synthesized in combination with conventional sol-gel processing. Here, the synthesis of BaTiO3 nanofibers via electrospinning is reported. The structural evolution from amorphous to crystalline is presented under various heat treatment conditions. Nanofibers with well-defined perovskite tetragonal phase were achieved with an average crystallite size of about 20 nm. Furthermore, single crystalline BaTiO3 nanofibers with 50 nm in diameter and lengths up to 1 μm were found, which is a novelty in electrospinning of ferroelectrics. XRD peak splitting confirmed the tetragonal perovskite structure, and this was fully supported by further evidence from selected area electron diffraction and Raman spectroscopy.

This tutorial review considers defect chemistry of TiO2 and its solid solutions as well as defect-related properties associated with solar-to-chemical energy conversion, such as Fermi level, bandgap, charge transport and surface active sites. Defect disorder is discussed in terms of defect reactions and the related charge compensation. Defect equilibria are used in derivation of defect diagrams showing the effect of oxygen activity and temperature on the concentration of both ionic and electronic defects. These defect diagrams may be used for imposition of desired semiconducting properties that are needed to maximize the performance of TiO2-based photoelectrodes for the generation of solar hydrogen fuel using photo electrochemical cells (PECs) and photocatalysts for water purification. The performance of the TiO2-based semiconductors is considered in terms of the key performance-related properties (KPPs) that are defect related. It is shown that defect engineering may be applied for optimization of the KPPs in order to achieve optimum performance.

Silicon is one of the most studied materials, yet questions remain unanswered about its unusual property of growing a self-limiting native oxide that attains its final thickness in a matter of hours yet months later has not grown further. For the first time, we have explored this self-limiting growth in terms of repulsive van der Waals (vdW) forces generated by the combination of material properties inherent to the system. These repulsive forces represent an energy barrier preventing additional oxidizing chemicals, mainly oxygen and water, from adsorbing on the surface as well as hindering diffusion of those that do adsorb toward the interface. We have also proven that this native oxide can be increased in thickness at room temperature and without reactive species by changing the oxidation environment to one predicted by theory to result in attractive vdW forces, thus allowing oxygen/water to interact with the surface more freely.

Hard magnetic composite photocatalytic particles—barium ferrite (magnetic core)/silica (intermediate layer)/titania (photoactive shell) (B/S/T) were prepared by wet-chemical methods. Anatase titania nanoparticles were directly coated on the silica-coated barium ferrite forming photoactive titania shell by hydrolysis and condensation of titanium n -butoxide. The prepared hard magnetic composite photocatalyst can be magnetically fluidized and recovered by an applied magnetic field enhancing both the separation and mixing efficiency for remediating fluids. The prepared composite particles were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), BET specific surface area measurement and inductively coupled plasma (ICP) spectroscopy. The photocatalytic activity of the synthesized composite particles was tested by photodegradation of Procion red MX-5B dye under UV illumination (302 nm) and compared with that of titania nanoparticles. The as-prepared composite particles were photoactive, with enhanced photocatalytic activity after the heat-treatment at 500 °C for 1 h. The reusability of the composite photocatalytic particles was also tested and the recycled composite particles presented the photocatalytic activity comparable to the fresh composite particles.

During the last years, several groups across the world have concentrated on the adaptation and further development of electrospinning (e-spinning) to enable ceramic fiber synthesis. Thus far, more than 20 ceramic systems have been synthesized as micro- and nanofibers. These fibers can be amorphous, polycrystalline, dense, porous, or hollow. This article reviews the experimental and theoretical basis of ceramic e-spinning. Furthermore, it introduces an expanded electro hydrodynamic (EHD) theory that allows the prediction of fired fiber diameter for lanthanum cuprate fibers. It is hypothesized that this expanded EHD theory is applicable to most ceramic e-spinning systems. Furthermore, electroceramic nanofibers produced via e-spinning are presented in detail along with an overview of electrospun ceramic fibers.

There has been growing interest in new ways to produce composite nanofibers. Continuous TiO2 (anatase phase) nanofibers with silver nanoparticles were prepared successfully via sol-gel and electrospinning. A sol containing poly(vinyl pyrrolidone), titanium tetraisopropoxide, and silver nitrate was injected through a conductive capillary where high voltage was applied. As a result of electrospinning, continuous composite nanofibers were collected and they were calcined in air at 500 degrees C in order to complete the crystallization of anatase phase. The anatase-silver nanocomposite fibers were characterized with X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy.