In-vitro viability of bone scaffolds fabricated using the adaptive foam reticulation technique.

The adaptive foam reticulation technique combines the foam reticulation and freeze casting methodologies of fabricating bone reparative scaffolds to offer a potential alternative to autografts. For the first time this paper studies the effect of processing on the mechanical properties and in-vitro cell growth of controllably generating a hierarchical structure of macro- (94 ± 6 to 514 ± 36 µm) and microporosity (2-30 µm) by the inclusion of camphene as a porogen during processing. Scaffolds were produced with porogen additions of 0-25 wt%. Porosity values of the structures of 85-96% were determined using the Archimedes technique and verified using X-ray Computed Tomography. The strength of the hydroxyapatite scaffolds, 5.70 ± 1.0 to 159 ± 61 kPa, correlated to theoretically determined values, 3.71 ± 0.8 to 134 ± 12 kPa, calculated by the novel incorporation of a shape factor into a standard equation. Fibroblast (3T3) and pre-osteoblast (MC3T3) cell growth was found to be significantly (P < 0.005) improved using 25 wt% porogen. This was supported by increased levels of alkaline phosphatase and was thought to result from greater dissolution as quantified by increased calcium levels in incubating media. The combination of these properties renders adaptive foam reticulation-fabricated scaffolds suitable for non-structural bone regenerative applications in non-load bearing bone defects.

Mechanism of gelation in high nickel content cathode slurries for sodium-ion batteries.

Sodium-ion batteries are a prospective sustainable alternative to the ubiquitous lithium-ion batteries due to the abundancy of sodium, and their cobalt free cathodes. The high nickel O3-type oxides show promising energy densities, however, a time dependency in the rheological properties of the composite electrode slurries is observed, which leads to inhomogeneous coatings being produced. A combination of electron microscopy and infra-red spectroscopy were used to monitor the O3-oxide surface changes upon exposure to air, and the effect upon the rheology and stability of the inks was investigated. Upon exposure to air, NaOH rather than Na2CO3 was observed on the surfaces of the powder through FTIR and EDS. The subsequent gelation of the slurry was initiated by the NaOH and dehydrofluorination with crosslinking of PVDF was observed through the reaction product, NaF. Approximately 15% of the CF bonds in PVDF undergo this dehydrofluorination to form NaF. As observed in the relaxation time of fitted rheological data, the gelation undergoes a three-stage process: a dehydrofluorination stage, creating saturated structures, a crosslinking stage, resulting in the highest rate of gelation, and a final crosslinking stage. This work shows the mechanism for instability of high nickel containing powders and electrode slurries, and presents a new time dependent oscillatory rheology test that can be used to determine the process window for these unstable slurry systems.

On the Solubility and Stability of Polyvinylidene Fluoride.

This literature review covers the solubility and processability of fluoropolymer polyvinylidine fluoride (PVDF). Fluoropolymers consist of a carbon backbone chain with multiple connected C-F bonds; they are typically nonreactive and nontoxic and have good thermal stability. Their processing, recycling and reuse are rapidly becoming more important to the circular economy as fluoropolymers find widespread application in diverse sectors including construction, automotive engineering and electronics. The partially fluorinated polymer PVDF is in strong demand in all of these areas; in addition to its desirable inertness, which is typical of most fluoropolymers, it also has a high dielectric constant and can be ferroelectric in some of its crystal phases. However, processing and reusing PVDF is a challenging task, and this is partly due to its limited solubility. This review begins with a discussion on the useful properties and applications of PVDF, followed by a discussion on the known solvents and diluents of PVDF and how it can be formed into membranes. Finally, we explore the limitations of PVDF's chemical and thermal stability, with a discussion on conditions under which it can degrade. Our aim is to provide a condensed overview that will be of use to both chemists and engineers who need to work with PVDF.

Nanozeolite ZSM-5 electrolyte additive for long life sodium-ion batteries.

A novel low cost sodium-ion battery electrolyte additive ZSM-5 nanozeolite, which improves cycle life, is demonstrated in a Na-ion cell. The addition of this zeolitic small molecule scavenger removes electrolyte decomposition products, and has beneficial properties compared to traditional organic additives such as fluoroethylene carbonate (FEC). Capacity retention after 480 cycles improves from 40% (none) compared to 62% (ZSM-5). This is due to the enhanced interface stability over the cell life-time, as shown by XPS.

Electrochemical formation protocols for maximising the life-time of a sodium ion battery.

Electrochemical protocols for reducing formation time and maximising cycle life in a sodium ion battery are proposed. The formation protocols comprise low current cycles within a targeted voltage window. After accelerated cell aging tests, the impedance and cycle life are evaluated. Maximum life time is obtained for formation within the 3.6-3.8 V window. 250 cycles are observed to 80% of initial capacity with accelerated ageing, compared to 90 cycles with no formation.

Facile silane functionalization of graphene oxide.

The facile silane functionalization of graphene oxide (GO) was achieved yielding vinyltrimethoxysilane-reduced graphene oxide (VTMOS-rGO) nanospheres located in the inter-layer spacing between rGO sheets via an acid-base reaction using aqueous media. The successful grafting of the silane agent with pendant vinyl groups to rGO was confirmed by a combination of Fourier-transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The structure and speciation of the silane-graphene network (nanosphere) and, the presence of free vinyl groups was verified from solid-state magic angle spinning (MAS) and solution 13C and 29Si nuclear magnetic resonance (NMR) measurements. Evidence from Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and TEM-High-Angle Annular Dark-Field (TEM-HAADF) imaging showed that these silane networks aided the exfoliation of the rGO layers preventing agglomeration, the interlayer spacing increased by 10 Å. The thermal stability (TGA/DTA) of VTMOS-rGO was significantly improved relative to GO, displaying just one degradation process for the silane network some 300 °C higher than either VTMOS or GO alone. The reduction of GO to VTMOS-rGO induced sp2 hybridization and enhanced the electrical conductivity of GO by 105 S m-1.