Hongqiang Ru

Toughening mechanisms in iron-containing hydroxyapatite/titanium composites.

Pure hydroxyapatite (HA) is brittle and it cannot be directly used for the load-bearing biomedical applications. The purpose of this investigation was to develop a new iron-containing HA/titanium composite via pressureless sintering at a relatively low temperature with particular emphasis on identifying the underlying toughening mechanisms. The addition of iron to HA/titanium composites led to a unique and favorable core/shell microstructure of Ti-Fe particles that consisted of outer titanium and inner iron, and good interfacial bonding with HA matrix. While the relative density, hardness and Youngs modulus reduced, the flexural strength, fracture toughness, fatigue resistance, and the related fracture surface roughness increased significantly with increasing amount of Ti-Fe particles. Different toughening mechanisms including crack bridging, branching and deflection were observed in the composites, thus effectively increasing the crack propagation resistance and resulting in a substantial improvement in the mechanical properties of the composites.

Facile preparation and new formation mechanism of plugged SBA-15 silicas based on cheap sodium silicate

It is for the first time demonstrated that the plugged hexagonal-templated silicas can be facilely and controllably prepared from cheap sodium silicate without using any additives. The formation of constricted/plugged mesostructures is attributed to the non-uniform/ill-templating behaviours between silicate oligomers and P123 molecules under the synthesis conditions employed.

A simple ternary non-ionic templating system for preparation of complex hierarchically meso–mesoporous silicas with 3D-interconnected large mesopores

This work for the first time demonstrated that hierarchically meso–mesoporous silicas can be facilely prepared in a simple ternary non-ionic surfactant templating system (TEOS/HCl(aq.)/P123) based on a previously reported partitioned cooperative self-assembly (PCSA) principle. As a result, unique clew-like hierarchically meso–mesoporous (HMM) silica particles with the first mode of worm-like mesostructures (3D-interconnected wormholes with pore size of 7–10 nm) and the second mode of 3D-interconnected intra-particulate mesochannels (16–32 nm in sizes) can be obtained in a controllable way without resorting to complicated synthesis procedures or special additives or multi-templates. Associated with the large mesopore sizes in both modes, very large mesoporosity (up to 2.37 cm3 g−1) can be achieved. Based on systematic investigations on the synthesis conditions, synthesis domains for preparation of such HMM silicas were also presented. It is proposed that the formation of two mode mesoporosities follows different mechanisms: the first mode mesoporosity results from the self-assembly between P123 and silicate, though it is shown to be disordered due to the partitioning effect, while the formation of the second mode mesoporosity starts from loosely packed silicate/P123 hybrid aggregates/flocs formed upon the 1st addition of TEOS, and then is initiated and finished by the 2nd TEOS addition. This synthesis protocol therefore constitutes a new, simple and reliable pathway to prepare HMM silicas.

Partitioned cooperative self-assembly process: taking the mesopore swelling strategy one step further for the preparation of mesocellular foams

This work demonstrates that the combination of recently developed partitioned cooperative self-assembly (PCSA) process with the conventional mesopore swelling strategy can take the preparation of mesocellular foams (MCFs) one step further based on cheap sodium silicate precursor. Compared with conventional method derived MCFs, such synthesized MCFs show more uniform cell size distributions without using commonly employed additives, i.e., NH4F. Furthermore, when prepared with aging at 120 °C via the PCSA process, MCFs with large uniform cells (38.3 nm) and enlarged windows up to 7.9 nm can be obtained, resembling the conventional MCFs based on TEOS/P123/NH4F system. Moreover, a simple adjustment in the order of addition of trimethylbenzene in the PCSA process produces unique bimodal meso-mesoporous MCFs with ordered normal SBA-15 regions dispersed in the matrix.

An in-vitro investigation of iron-containing hydroxyapatite/titanium composites

The in-vitro biological behavior of a newly-developed iron-containing hydroxyapatite/titanium (HA/Ti) composite was investigated by immersing the composites in the simulated body fluid (SBF) for up to 5 weeks. The addition of iron was observed to have a significant influence on the in-vitro biological behavior of the composites. The obtained results revealed that the stability of the composites in the physiological solution was markedly improved. The solubility decreased in the order of pure HA, HA/5%(Ti-33%Fe), and HA/15%(Ti-33%Fe). Precipitation occurred on the surface of HA/5%(Ti-33%Fe) composite, showing a good combination of physiostability with bioactivity, while HA/15%(Ti-33%Fe) composite exhibited superior physiostability since there was no obvious change on the surface of HA/15%(Ti-33%Fe).

Extraction of Ce(IV) from sulphuric acid solution by emulsion liquid membrane using D2EHPA as carrier

In order to provide a potential method for extracting Ce(IV), the extraction of Ce(IV) from sulphuric acid solution by an emulsion liquid membrane using D2EHPA as a carrier was investigated. The ELM system consisted of sulfonated kerosene as diluent, Span 80 as surfactant, liquid paraffin as intensifier and hydrochloric acid containing hydrogen peroxide as the inner aqueous solution. The influences of various parameters on the extraction of Ce(IV) were investigated. The optimum conditions for Ce(IV) extraction can be summarized as follows: D2EHPA concentration, 12% (v/v); Span 80 concentration, 2–3% (v/v); liquid paraffin concentration, 2–4% (v/v); hydrochloric acid concentration in the internal phase, 4–5 mol l−1; hydrogen peroxide concentration, 0.02 mol l−1; volume ratio of membrane phase to internal phase (Roi), 1.5; external phase acidity, 0.4–0.5 mol l−1; volume ratio of external phase to membrane phase (Rwe), 2; extraction time, 15 min; and stirring speed, 250 rpm. Experiments in which Ce(IV) was separated from RE(III) were then carried out under the optimum conditions, and the results indicated that the system is extremely selective for Ce(IV). The mechanism of Ce(IV) extraction has also been discussed. The loss for the experimental process was within 3%. The results reveal that the ELM method is a clean and cost-effective process for the extraction of Ce(IV) from sulphuric acid solution.

High temperature and water-based evaporation-induced self-assembly approach for facile and rapid synthesis of nanocrystalline mesoporous TiO2

Various appealing applications of mesoporous TiO2 continuously spur research on related mesostructural design as well as innovations in preparation. This paper reports a novel high temperature and water-based evaporation-induced self-assembly (HW-EISA) approach based on a simple ternary templating system (peroxotitanic acid/P123/H2O), enabling the facile and rapid synthesis of nanocrystalline mesoporous TiO2 with unusual structures: high surface areas (140–240 m2 g−1), ultra-large mesopores (20–30 nm)/pore volumes (0.7–1.0 cm3 g−1) and tunable bicrystallinity (anatase plus rutile). The unusual templating and subsequent decomposition behaviors of P123 were newly unveiled to play crucial and multiple roles in inducing self-assembly between peroxotitanic acid and P123 for final meso-TiO2 with ultra-large mesopores/pore volumes during the HW-EISA and helping preserve the integrity of mesostructures during calcination and rendering bicrystallinity in the titania frameworks as well. Other PEO-based nonionic surfactants were also demonstrated to be applicable in producing similar mesostructures. The photocatalytic testing results showed that both high surface areas and the synergistic effects of bicrystallinity of anatase plus rutile are of great significance in enhancing the photocatalytic properties of meso-TiO2.

Separation of fluorine/cerium from fluorine-bearing rare earth sulfate solution by selective adsorption using hydrous zirconium oxide

Separation of fluorine/cerium from fluorine-bearing rare earth sulfate solution using selective adsorption was studied using hydrous zirconium oxide as an adsorbent. The relevant parameters studied for fluoride adsorption were the effects of contact time, pH, nF/nCe ratio, initial fluoride concentration and coexisting ions. The material was characterized using XRD, SEM, EDS, Raman, FTIR and XPS. The Raman, FTIR and XPS spectra suggest that an ion-exchange reaction between the hydroxyl ion on hydrous zirconium oxide and fluoride is involved. Most of the fluoride adsorption takes place in the first 3 min. The adsorption capacities of fluoride and cerium both increase with an increase in solution pH, and the optimum pH is suggested to be 0.3–0.6. The loss of cerium is higher at a low nF/nCe ratio. High initial fluoride concentration is unfavorable for the separation. The accompanied rare earth ions have no significant influence on the adsorption of fluoride. The adsorbed fluoride can be desorbed effectively with 0.1 mol l−1 NaOH which shows utility of the adsorbent in a sustainable manner. In addition, the effectiveness of the method was also evaluated using real bastnaesite sulfuric acid leaching solution. This work presents a potential use of hydrous zirconium oxide for adsorption and separation of fluorine from cerium in fluorine-bearing rare earth sulfate solution and it is expected to eliminate the influence of fluorine on the extraction separation of rare earths.

Water-deficient templating system: a general, versatile and efficient synthetic approach for mesoporous silicas†

Controlled synthesis of mesoporous silicas with tailorable mesostructures and particle morphologies has always been the research target of many materials scientists since the breakthrough in ordered mesoporous silicates in 1992, while the synthesis methodology is the key. Though standing out as a versatile and convenient approach, current non-ionic block copolymer (NBC) surfactant templating systems themselves in a broad sense polarize the two ‘extremes’: either being performed in far too diluted surfactant solution (DSS approach) or in much concentrated ones, i.e., liquid crystal phases (LCP approach). As a result, some limitations associated with each ‘extreme’ are also apparent: low silica content in synthesis mixture and therefore low synthesis efficiency and environmental unfriendliness mainly due to the high acid consumption for the DSS approach, while added synthesis complexity plus restricted functions for the LCP approach. Herein, we report a general, versatile and efficient synthetic approach, called water-deficient templating (WDT) system, bridging the above two ‘divided’ templating approaches based on the commonly used and commercially available NBCs, yet bearing some unusual characteristics in the templating manner that is different from those currently known. This approach to greater extent combines the advantages of both DSS and LCP approaches, enabling the facile engineering on the mesopore arrangements (wormhole-like, 2D-hexagonal or cubic), and effective adjustment in the mesopore sizes and facile tailoring in particle morphologies and even hierarchically macro–mesoporous monoliths. Moreover, significantly reduced synthesis volume and acid consumption in the WDT system re-assure that the NBC templated self-assembly process can be performed in this efficient and green way.

Oxidation protection of (ZrTa)B2–SiC–Si coating for graphite materials

ABSTRACT To protect graphite materials from oxidation, a dense (ZrTa)B2–SiC–Si coating was for the first time prepared on graphite substrate by slurry dipping and vapour silicon infiltration process. (ZrTa)B2 phase was synthesised by in-situ reaction using ZrC, TaC, B4C, phenolic resin and Si as raw materials. The phase compositions and microstructure of the obtained coating were analysed by XRD and SEM. The isothermal oxidation tests demonstrated that the in-situ coating had excellent oxidation resistance ability, after oxidation for 468 and 347 h at 1273 and 1773 K, respectively, the weight gains were 0.07% and 0.33%, respectively. No signs of oxidation of graphite substrate were found after oxidation, and two layers could be observed in the coating, namely, oxide layer containing Zr and Ta oxides and (ZrTa)B2–SiC–Si layer. A model for the evolution of the oxide layer was proposed to interpret the oxidation failure mechanism of the coating.