Sintering behaviour of cobalt ferrite ceramic

Pure cobalt ferrite ceramic powder was prepared using standard solid-state ceramic processing. Uniaxially pressed pure cobalt ferrite discs, sintered under isothermal ramp rate and single dwell time conditions, yielded a maximum theoretical density (%Dth) of <90%. Discs made from finer particle size powder yielded a %Dth of 91.5%. Based on dilatometry analysis, a sintering profile comprising non-isothermal sintering, and two-step sintering was devised, yielding discs with %Dth of 96%. Cylindrical rods of pure cobalt ferrite were cold iso-statically pressed and sintered according to the revised sintering profile. Pycnometry analysis was used to quantify the percentages of open and closed pores in the rods after sintering

Calibration and characterisation with a new laser-based magnetostriction measurement system

A laser-based magnet measurement system has been developed to measure the magnetostrictive strain of large cylindrical samples. The measurement system incorporates a solenoid capable of generating a maximum magnetic field intensity of 3000 Oe and a laser displacement sensor. For calibration and evaluation purposes, the positive magnetostrictions of two different types of giant magnetostrictive Tb–Dy–Fe-based materials were accessed with this system. A magnetostrictive strain of 622 ppm was obtained at 3000 Oe for TbxDy1-xFe2-y, compared with 725 ppm for Tb0.27Dy0.73Fe2. A rod of sintered cobalt ferrite was also measured. This exhibited negative magnetostriction, with a maximum contraction of 260 ppm at 3000 Oe

An investigation of co-fired varistor-ferrite materials

The purpose of this work was to co-fire crack-free varistor-ferrite ceramic multilayers fabricated via a dry pressing route. Multilayers were sintered using a standard industrial grade varistor sintering regime. Sinter shrinkages of both varistor and ferrite materials were measured using dilatometry and showed that the varistor shrunk significantly more than the ferrite material. X-ray diffraction analysis indicated that no significant phase changes occurred in the materials under investigation as a result of the sintering process. Scanning electron microscopy observations of the dry-pressed co-fired varistor-ferrite revealed vertical cracking in the ferrite due to thermal expansion mismatch between the materials. By pressing a mixed composition interlayer in the ratio 50:50, between the varistor and ferrite materials, a crack-free multilayer structure could be obtained. Energy dispersive X-ray analysis of the co-fired ferrite and varistor confirmed diffusion of Fe and Ni components from the ferrite into the varistor material. The degree of diffusion was reduced by using 50:50 ratio mixed composition interlayers

Partially Oxidised Boron Nitride As A 2D Nanomaterial For Nanofiltration Applications

Access to clean water has become increasingly scarce in recent years due to various factors, such as increasing population density, urbanisation, and inequality, among others.1 The development of new, inexpensive, and reliable methods for the removal of various impurities and toxins from water is therefore vital. In recent years, the emergence of nanofiltration (NF) membranes has become an exciting prospect for water purification. NF can be described as a type of filtration which exhibits separation characteristics in between reverse osmosis and ultrafiltration, and typically has molecular weight cut-offs in the region of 200–1000 Daltons.2,3 Various nanomaterials have been implemented in NF membranes, such as metal organic frameworks (MOFs), metal oxide nanoparticles and nanotubes.4–6 NF membranes based on 2D nanomaterials such as graphene and boron nitride (BN) have attracted significant interest due to the unique properties of 2D nanomaterials, most importantly their high surface-to-volume ratio, which leads to high adsorption capacity. In particular, BN is an attractive candidate for use in NF membranes as it is mechanically strong, inexpensive, and environmentally friendly. BN-based membranes have been the subject of numerous studies, with BN shown to be very effective in the removal of several water pollutants, including various dyes, that often can be leached into wastewater, from the textile industry

Activated Carbon Cloth Electrodes for Capacitive Deionization: A Neutron Imaging Study

&lt;p&gt;Neutron images of capacitive deionization&nbsp;by activated carbon cloths.&lt;/p&gt;&lt;p&gt;Corresponding readouts from potentiostat.&lt;/p&gt;&lt;p&gt;Nitrogen gas adsorption data of the activated carbon cloths.&lt;/p&gt

Tantalum-Containing Meso-Porous Glass Fibres for Hemostatic Applications

Novel tantalum-containing meso-porous bioactive glass (Ta-MBG) powders, developed via the sol-gel process, have demonstrable hemostatic properties. However, powders can create dust in the operating environment and may be washed away if profuse bleeding occurs. Powders may not adequately compress wound tissue, and in certain circumstances, a thick callus can form, which is challenging to remove. Fibrous forms of MBGs offer advantages over powders for hemostatic applications, yet they appear comparatively under-researched. In this study, Ta-MBG compositions were successfully designed and fabricated into fibrous mats using electrospinning. State-of-the-art imaging techniques were used to investigate the mats. The individual fibres were ∼300 nm in diameter and contained porosity (1−50 nm). There was also micrometre-sized -porosity (1−2 μm) – this constituted the pore space between the matted fibres, unlike the Ta-MBG powders, which comprised of uni-modal channels (pore size: 4 nm) within the particles themselves. Hierarchical micro-nano porosity is known to enhance the activation of coagulation proteins. The surface area and pore volume of the fibrous mats were a maximum of 61 m2 g−1, 0.23 cm3 g−1 compared to 374 m2 g−1, 0.27 cm3 g−1 for powders. The surface area is an important property facilitating blood fluid sorption and enhancing clotting. The measured zeta potential of the fibres was more highly-negative than that of powder; a highly-negative zeta potential can provide a stable matrix for hemostasis. Overall, the texture of the fibrous mats, the easily-accessible micron-sized pores, the presence of tantalum, the hierarchical porosity, the favourable zeta potential, and the naturally biomimetic architecture are important attributes which make the fibrous mats developed here an attractive alternative for hemostatic applications

High-Performance Boron Nitride-Based Membranes for Water Purification

In recent years, nanotechnology-based approaches have resulted in the development of new alternative sustainable technologies for water purification. Two-dimensional (2D) nanomaterials are an emerging class of materials for nanofiltration membranes. In this work, we report the production, characterisation and testing of a promising nanofiltration membrane made from water-exfoliated boron nitride (BN) 2D nanosheets. The membranes have been tested for water purification and removal of typical water-soluble dyes such as methyl orange, methylene blue and Evans blue, with the water-exfoliated BN membranes achieving retention values close to 100%. In addition, we compared the performance of membranes made from water-exfoliated BN with those produced from BN using sonication-assisted liquid exfoliation in selected organic solvents such as 2-propanol and N-methyl-2-pyrrolidone. It was found that membranes from the water-exfoliated BN showed superior performance. We believe this research opens up a unique opportunity for the development of new high-performance environmentally friendly membranes for nanofiltration and new sustainable separation technologies