Dali Zhou

Synthesis and characterization of tungsten carbide and application to electrocatalytic hydrogen evolution

Tungsten carbide was synthesized and further hydrogen treated to remove excess carbon. The obtained WC with different carbon contents was investigated by XRD, TG, SEM, EDS, BET and Raman. This work evaluated the effect of excess carbon on the properties of WC as a support for platinum. The hydrogen evolution reaction (HER) activity was used as a metric to test the effect of excess carbon on the electrochemical activity in 0.5 M sulfuric acid using a linear sweep voltammogram (LSV). Pt deposited on WC after hydrogen treatment exhibited a better electrocatalytic performance than Pt deposited on untreated WC. The investigations show that the presence of excess carbon is harmful to HER activity.

Study on transformation mechanism of lithium titanate modified with hydrochloric acid

The effects of the concentration of hydrochloric acid and treatment time on the transformation of Li2TiO3 were studied in detail. The results demonstrate that lithium ions are easily removed from the (−133) and (−206) planes. In contrast, Li+ extraction requires a longer time for the (002) and (−131) planes. A mixture of the anatase and rutile phases, pure rutile, and pure anatase can be generated by treating Li2TiO3 with a suitable concentration of hydrochloric acid for an appropriate amount of time. The phase(s) that are present significantly affect the cyclic adsorption performance of a titanium lithium ion sieve and the dissolution of Ti. The transformation from H2TiO3 particles to TiO2 primarily occurs via the dissolution-recrystallization process. The electrophilic H+ and highly electronegative Cl− affect the Ti–O bond, resulting in the destruction of the Ti–O bond in TiO6 octahedrons, promoting the structural rearrangement of anatase to rutile TiO2.

Immobilization of RGD peptide onto the surface of apatite-wollastonite ceramic for enhanced osteoblast adhesion and bone regeneration

The arginine-glycine-aspartic (RGD) acid peptide was grafted to the surface of apatite-wollastonite (AW) ceramic in an effort to improve its cell adhesion, proliferation and osteoinduction. RGD peptide was covalently immobilized onto the surface of AW ceramic via the synthetic cross linker AAPTS-E and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC). The modified surfaces were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The chemical analysis indicated that RGD peptide had been immobilized onto the AW surface successfully. The growth of osteoblast-like cells (MG63) showed that modifying the AW surface with RGD peptide enhanced the cell adhesion and proliferation. And the histological evaluation of RGD-AW showed that the bone regeneration and remodeling process were significantly enhanced compared to the original AW ceramics after 2, 4 and 8 weeks implantation in rabbit’s femoral condyles.

Preparation of ceramic foams suitable for aircraft arresting by the airport runway based on a protein foaming agent

Crushable ceramic foams are more suitable to be used as an arrestor material applied in engineered materials arresting system (EMAS) for airport runway for their properties of widely controllable strength, negligible crushing-rebounding behavior, durability, and chemically-inert composition, comparing with traditional concrete foams. The synthesis of ceramic foams adopted direct-foaming method and used an animal protein as foaming agent. Kaolin, talc powder and alumina were the main raw materials. Effects of the ratios of raw materials, calcination temperatures, heating rates, holding time, viscosities of polyvinyl alcohol (PVA) solution as well as the amounts of protein foaming agent and water on microscopic structure, densities, compressive strength and open porosities of ceramic foams were investigated systematically. The results indicate that ceramic foams with typical pore sizes 100–300 μm, open porosities from 73.1% to 91.5%, densities from 0.25 to 0.62 g·cm−3, compressive strength from 0.19 to 4.89 MPa, are obtained by properly adjusting the parameters mentioned above. And the mechanical strength meets the requirement for the EMAS for airport runway. In addition, good correlations are observed among compressive strength, open porosity, microscopic structure, and crystal phase. Furthermore, the possibility of producing the general dimensions of such aircraft arresting components with the proposed method was also discussed.

Surface modification of apatite-wollastonite glass ceramic by synthetic coupling agent

In this study, lysine was introduced into the surface of apatite—wollastonite glass ceramic (AW-GC) to improve its cytocompatibility by two steps reaction procedure. Firstly, lysine connected to N-β-(aminoethyl)-γ-aminopropyl trimethoxy silane (A-1120) by covalent binding of amide group. Secondly, the lysine-functionalized A-1120 was deposited on the surface of AW-GC through a silanization reaction involving a covalent attachment. FTIR spectra indicated that lysine had been immobilized onto the surface of AW-GC successfully. Bioactivity of the surface modified AW-GC was investigated by simulated body fluid (SBF), and the in vitro cytocompatibility was evaluated by coculturing with human osteosarcoma cell MG63. The results showed that the process of hydroxyapatite layer formed on the modified material was similar to AW-GC while the mode of hydroxyapatite deposition was changed. The growth of MG63 cells showed that modifying the AW-GC surface with lysine enhances the cell adhesion and proliferation.

Extraction Difficulty of Lithium Ions from Various Crystal Planes of Lithium Titanate

To study the extraction difficulty of lithium ions from various crystal planes of Li2TiO3, according to the first principle, four representative crystal surfaces of Li2TiO3 (precursor), (-133), (-206), (002) and (-131), were selected to establish a model and to calculate the surface energy, bond length and population using Materials Studio 5.5 (MS 5.5). The results demonstrate that there is no direct relationship between the surface energy and the order of disappearance of the four diffraction peaks when lithium titanate is treated with hydrochloric acid, instead, the difficulty of Li+ extraction from various crystal faces corresponds to the Li-O bond strength. Lithium ion is easy to remove from (-133) and (-206) due to the relatively weak Li-O bond strength. In contrast, Li+ extraction requires a longer time for (002) and (-131).