Publications by authors named "Jawwad Darr"

A novel eco-friendly high throughput continuous hydrothermal flow system was used to synthesise phase pure ZnO and doped ZnO in order to explore their properties for tissue engineering applications. Cerium, zirconium, and copper were introduced as dopants during flow synthesis of ZnO nanoparticles, Zirconium doped ZnO were successfully synthesised, however secondary phases of CeO and CuO were detected in X-ray diffraction (XRD). The nanoparticles were characterised using X-ray diffraction, Brunauer-Emmett-Teller (BET), Dynamic Light scattering Measurements, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and RAMAN spectroscopy was used to evaluate physical, chemical, and structural properties.

View Article and Find Full Text PDF

The development of oxidation catalysts that are resistant to sulfur poisoning is crucial for extending the lifespan of catalysts in real-working conditions. Herein, we describe the design and synthesis of oxide-metal interaction (OMI) catalyst under oxidative atmospheres. By using organic coated TiO , an oxide/metal inverse catalyst with non-classical oxygen-saturated TiO overlayers were obtained at relatively low temperature.

View Article and Find Full Text PDF

When polymer composites containing magnetic nanoparticles (MNPs) are exposed to an alternating magnetic field, heat is generated to melt the surrounding polymer locally, partially filling voids across any cracks or deformities. Such materials are of interest for structural applications; however, structural polymers with high melting temperatures pose the challenge of generating high localised temperatures enabling self-healing. A method to prepare a multiferroic-Polyamide 6 (PA6) nanocomposite with tuneable magnetocaloric properties is reported.

View Article and Find Full Text PDF

Synchrotron high-energy X-ray diffraction computed tomography has been employed to investigate, for the first time, commercial cylindrical Li-ion batteries electrochemically cycled over the two cycling rates of C/2 and C/20. This technique yields maps of the crystalline components and chemical species as a cross-section of the cell with high spatiotemporal resolution (550 × 550 images with 20 × 20 × 3 µm voxel size in ca. 1 h).

View Article and Find Full Text PDF

α-VO has been extensively explored as a Mg intercalation host with potential as a battery cathode, offering high theoretical capacities and potentials vs. Mg/Mg. However, large voltage hysteresis is observed with Mg insertion and extraction, introducing significant and unacceptable round-trip energy losses with cycling.

View Article and Find Full Text PDF

Developing large-scale and high-performance OER (oxygen evolution reaction) and ORR (oxygen reduction reaction) catalysts have been a challenge for commercializing secondary zinc-air batteries. In this work, transition metal-doped cobalt-nickel sulfide spinels are directly produced a continuous hydrothermal flow synthesis (CHFS) approach. The nanosized cobalt-nickel sulfides are doped with Ag, Fe, Mn, Cr, V, and Ti and evaluated as bifunctional OER and ORR catalyst for Zn-air battery application.

View Article and Find Full Text PDF

A library of 66 perovskite BaSrCaTiO ( + + = 1) samples (ca. three grams per sample) was made in ca. 14 h using a high-throughput continuous hydrothermal flow synthesis system.

View Article and Find Full Text PDF

V2O5 is of interest as a Mg intercalation electrode material for Mg batteries, both in its thermodynamically stable layered polymorph (α-V2O5) and in its metastable tunnel structure (ζ-V2O5). However, such oxide cathodes typically display poor Mg insertion/removal kinetics, with large voltage hysteresis. Herein, we report the synthesis and evaluation of nanosized (ca.

View Article and Find Full Text PDF

While commercial Li-ion batteries offer the highest energy densities of current rechargeable battery technologies, their energy storage limit has almost been achieved. Therefore, there is considerable interest in Mg batteries, which could offer increased energy densities in comparison to Li-ion batteries if a high-voltage electrode material, such as a transition-metal oxide, can be developed. However, there are currently very few oxide materials which have demonstrated reversible and efficient Mg insertion and extraction at high voltages; this is thought to be due to poor Mg diffusion kinetics within the oxide structural framework.

View Article and Find Full Text PDF

Thermal control in low-emission windows is achieved by the application of glazings, which are simultaneously optically transparent in the visible and reflective in the near-infrared (IR). This phenomenon is characteristic of coatings with wide optical band gaps that have high enough charge carrier concentrations for the material to interact with electromagnetic radiation in the IR region. While conventional low-E coatings are composed of sandwiched structures of oxides and thin Ag films or of fluorinated SnO coatings, ZnO-based glazing offers an environmentally stable and economical alternative with competitive optoelectronic properties.

View Article and Find Full Text PDF

Photo-electrochemical (PEC) hydrogen generation is a promising technology and alternative to photovoltaic (PV)-electrolyser combined systems. Since there are no commercially available PEC cells and very limited field trials, a computer simulation was used to assess the efficacy of the approach for different domestic applications. Three mathematical models were used to obtain a view on how PEC generated hydrogen is able to cover demands for a representative dwelling.

View Article and Find Full Text PDF

Chromium oxides with the spinel structure have been predicted to be promising high voltage cathode materials in magnesium batteries. Perennial challenges involving the mobility of Mg2+ and reaction kinetics can be circumvented by nano-sizing the materials in order to reduce diffusion distances, and by using elevated temperatures to overcome activation energy barriers. Herein, ordered 7 nm crystals of spinel-type MgCr2O4 were synthesized by a conventional batch hydrothermal method.

View Article and Find Full Text PDF

The Li ion diffusion characteristics of V- and Nb-doped LiFePO were examined with respect to undoped LiFePO using muon spectroscopy (µSR) as a local probe. As little difference in diffusion coefficient between the pure and doped samples was observed, offering D values in the range 1.8-2.

View Article and Find Full Text PDF

Nanomaterials are at the leading edge of the emerging field of nanotechnology. Their unique and tunable size-dependent properties (in the range 1-100 nm) make these materials indispensable in many modern technological applications. In this Review, we summarize the state-of-art in the manufacture and applications of inorganic nanoparticles made using continuous hydrothermal flow synthesis (CHFS) processes.

View Article and Find Full Text PDF

Nano-sized Mo-doped titania (MoTiO) and Nb-doped titania (NbTiO) were directly synthesized via a continuous hydrothermal flow synthesis process. Materials characterization was conducted using physical techniques such as transmission electron microscopy, powder x-ray diffraction, x-ray photoelectron spectroscopy, Brunauer-Emmett-Teller specific surface area measurements and energy dispersive x-ray spectroscopy. Hybrid Li-ion supercapacitors were made with either a Mo-doped or Nb-doped TiO negative electrode material and an activated carbon (AC) positive electrode.

View Article and Find Full Text PDF

High-throughput continuous hydrothermal flow synthesis was used to generate a library of aluminum and gallium-codoped zinc oxide nanoparticles of specific atomic ratios. Resistivities of the materials were determined by Hall Effect measurements on heat-treated pressed discs and the results collated into a conductivity-composition map. Optimal resistivities of ∼9 × 10 Ω cm were reproducibly achieved for several samples, for example, codoped ZnO with 2 at% Ga and 1 at% Al.

View Article and Find Full Text PDF

Copper oxide modified electrodes were investigated as a function of applied electrode potential using in situ infrared spectroscopy and ex situ Raman and X-ray photoelectron spectroscopy. In deoxygenated KHCO electrolyte bicarbonate and carbonate species were found to adsorb to the electrode during reduction and the CuO was reduced to Cu(i) or Cu(0) species. Carbonate was incorporated into the structure and the CuO starting material was not regenerated on cycling to positive potentials.

View Article and Find Full Text PDF

Metal sulfides are commonly used in energy storage and electrocatalysts due to their redox centers and active sites. Most literature reports show that their performance decreases significantly caused by oxidation in alkaline electrolyte during electrochemical testing. Herein, S and N co-doped graphene-based nickel cobalt sulfide aerogels are synthesized for use as rechargeable alkaline battery electrodes and oxygen reduction reaction (ORR) catalysts.

View Article and Find Full Text PDF

Lithium sulfur (Li-S) batteries offer higher theoretical specific capacity, lower cost and enhanced safety compared to current Li-ion battery technology. However, the multiple reactions and phase changes in the sulfur conversion cathode result in highly complex phenomena that significantly impact cycling life. For the first time to the authors' knowledge, a multi-scale 3D in-situ tomography approach is used to characterize morphological parameters and track microstructural evolution of the sulfur cathode across multiple charge cycles.

View Article and Find Full Text PDF

A series of LiMnFeVPO (LMFVP) nanomaterials have been synthesized using a pilot-scale continuous hydrothermal synthesis process (CHFS) and evaluated as high voltage cathodes in Li-ion batteries at a production rate of 0.25 kg h. The rapid synthesis and screening approach has allowed the specific capacity of the high Mn content olivines to be optimized, particularly at high discharge rates.

View Article and Find Full Text PDF

Lithium-ion battery performance is intrinsically linked to electrode microstructure. Quantitative measurement of key structural parameters of lithium-ion battery electrode microstructures will enable optimization as well as motivate systematic numerical studies for the improvement of battery performance. With the rapid development of 3-D imaging techniques, quantitative assessment of 3-D microstructures from 2-D image sections by stereological methods appears outmoded; however, in spite of the proliferation of tomographic imaging techniques, it remains significantly easier to obtain two-dimensional (2-D) data sets.

View Article and Find Full Text PDF

A high-throughput optimization and subsequent scale-up methodology has been used for the synthesis of conductive tin-doped indium oxide (known as ITO) nanoparticles. ITO nanoparticles with up to 12 at % Sn were synthesized using a laboratory scale (15 g/hour by dry mass) continuous hydrothermal synthesis process, and the as-synthesized powders were characterized by powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray photoelectron spectroscopy. Under standard synthetic conditions, either the cubic In2O3 phase, or a mixture of InO(OH) and In2O3 phases were observed in the as-synthesized materials.

View Article and Find Full Text PDF

Hydroxyapatite is used extensively in hard tissue repair due to its biocompatibility and similarity to biological apatite, the mineral component of bone. It differs subtly in composition from biological apatite which contains other ions such as magnesium, zinc, carbonate and silicon (believed to play biological roles). Traditional methods of hydroxyapatite synthesis are time consuming and require strict reaction parameter control.

View Article and Find Full Text PDF

In this work, the photocatalytic disinfection of Escherichia coli (E. coli) using dual layer ceramic wafers, prepared by a simple and low-cost technique, was investigated. Heterojunction wafers were prepared by pressing TiO2 and WO3 powders together into 2 layers within a single, self-supported monolith.

View Article and Find Full Text PDF

In this paper, we demonstrate the use of continuous hydrothermal flow synthesis (CHFS) technology to rapidly produce a library of 56 crystalline (doped) zinc oxide nanopowders and two undoped samples, each with different particle properties. Each sample was produced in series from the mixing of an aqueous stream of basic zinc nitrate (and dopant ion or modifier) solution with a flow of superheated water (at 450 °C and 24.1 MPa), whereupon a crystalline nanoparticle slurry was rapidly formed.

View Article and Find Full Text PDF