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A new and more ecologically sound cementing material known as "bio-cement" has been found to have the capacity to consolidate loose gravel into sand columns offering a certain degree of strength, and to fill and repair cracks in concrete to restore resilience. The typical representative is the microbial induced calcium carbonate deposition technology(MICP) and enzyme induced calcite precipitation (EICP). As part of this research, EICP with soybean urease as the core was studied. The test results show that soybean urease activity is significantly affected by pH and urea concentration values, while the external nickel source is not found to impair a stimulating effect on activity. When the concrete specimens were immersed in the composite solution of soybean urease, urea, and calcium chloride after having been subjected to a high temperature, a continuous layer of white precipitations quickly appeared on the surface of the specimens. Measured using a metalloscope, the thickness of the precipitations was found to reach up to 2.0 mm, while the surface water absorption rate was reduced by 70%. The effects of this combined outcome are believed to significantly protect and improve the durability of the concrete specimens previously subjected to a high temperature. At the same time, the composite solution is shown to be capable of cementing fly ash, with the cubic strength of the finished samples reaching 4.0 MPa after 3 days. Results from the use of a scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction(XRD), reveal that both the white precipitations on the surface of the concrete specimens and the cement binding the fly ash particles are calcite crystals. It is concluded from these preliminary study results that the use of soybean urease as a bio-cement had proved successful. [ABSTRACT FROM AUTHOR]

Photocatalytic removal of hexavalent chromium (Cr(VI)) based on semiconductor is important under visible light for environment and energy. Herein, a visible light-responsive heterojunction composed of molybdenum disulfide and zinc indium sulfide was synthesized through a simple one-pot hydrothermal method to ensure full contact between the two components to efficiently improve the Cr(VI) reduction. The MoS2/ZnIn2S4 composites build heterojunctions between MoS2 and ZnIn2S4 to inhibit recombination of photogenerated holes and electrons and provide the reaction sites to trap photogenerated electrons to participate in the reduction of Cr(VI). The highly efficient reduction of Cr(VI) was obtained by adjusting the proportion of molybdenum disulfide. It demonstrates that the 0.5 wt% MoS2/ZnIn2S4 composite microstructures show the highest degradation rate of 0.1989 s−1 under visible light irradiation, 1.7 times of bare ZnIn2S4. Moreover, the MoS2/ZnIn2S4 showed excellent stability during photocatalytic recyclable processes. This work encourages researchers to remove Cr(VI) by constructing effective heterojunction structures. [ABSTRACT FROM AUTHOR]

The C60 concrete blocks with surface crack damage under high temperature environment were soaked by adding appropriate amount of soybean urease into the CO(NH2)2-CaCl2 solution, the soybean urease mineralized calcium carbonate were characterized, and the effect of repairing concrete surface crack damage were evaluated by the surface sedimentation of C60 concrete blocks in the study. The experimental results showed that the activity of soybean powder was statistically significant, and its productivity of urease was comparable with that of urease-producing bacteria. After immersion in a soybean solution, a layer of complete and continuous white sediment covered the concrete surface. The cracks on the concrete surface were completely shielded, and the rising temperature on infrared thermal image of the concrete after repair was lower than before. Besides, through analysis by SEM, EDS, and XRD, the products formed after repair were found to be calcite-type CaCO3 with high purity, and the crystals exhibited different morphological features. The above results indicate that soybean urease can regulate and induce the formation of calcium carbonate, and the precipitate is innocuous and harmless, suitable for a new type of concrete crack repair material. [ABSTRACT FROM AUTHOR]

With the application of X-ray computed tomography (CT) technology of C80 high-strength concrete with polypropylene fiber at elevated temperatures, the microscopic damage evolution process observation and image building could be obtained, based on the statistics theory and numerical analysis of the combination of concrete internal defects extension and evolution regularity of microscopic structure. The expermental results show that the defect rate has changed at different temperatures and can determine the concrete degradation threshold temperatures. Also, data analysis can help to establish the evolution equation between the defect rate and the effect of temperature damage, and identify that the addition of polypropylene fibers in the high strength concrete at high temperature can improve cracking resistance. [ABSTRACT FROM AUTHOR]

Using the detection principle of infrared thermal imaging technique and the detection principle of DRH thermal conductivity tester laboratory, we investigated the infrared thermal image inspection, coefficient of thermal conductivity, apparent density, and compressive strength test on C80 high-strength concrete(HSC) in the presence and absence of polypropylene fibers under completely heated conditions. Only slight damages were detected below 400 °C, whereas more and more severe deterioration events were expected when the temperature was above 500 °C. The results show that the elevated temperature through infrared images generally exhibits an upward trend with increasing temperature, while the coefficient of thermal conductivity and apparent density decrease gradually. Additionally, the addition of polypropylene fibers with appropriate length, diameter, and quantity contributes to the improvement of the high-temperature resistance of HSC. [ABSTRACT FROM AUTHOR]

The electroactive polyaniline (PANI) and manganese oxide (MnO) were integrated with titanium nitride (TiN) nanowire array (NWA) to form PANI/MnO/TiN ternary nanocomposite for supercapacitor application. TiN NWA was prepared via a seed-assisted hydrothermal synthesis and ammonia nitridization process. The electroactive MnO and PANI was layer-by-layer coated on TiN NWA to form heterogeneous coaxial structure through a stepwise electrodeposition process. Scanning electron micrographs revealed that the well-separated TiN NWA was composed of well-distributed nanowires with diameters in the range of 10-30 nm and a total length of 1.5 μm. A villiform MnO layer with a thickness of 10-20 nm covered on TiN NWA to form MnO/TiN NWA composite. The coral-like PANI layer with thicknesses in the range of 20-50 nm covered on the above MnO/TiN NWA to form PANI/MnO/TiN NWA. Electrochemical measurements showed that a high specific capacitance of 674 F g at a current density of 1 A g (based on total mass of PANI/MnO) was obtained for PANI/MnO/TiN NWA ternary nanocomposite, which was much higher than that of PANI/MnO/carbon-cloth composites reported previously. This ternary nanocomposite also showed a good rate and cycling stability. Moreover, in comparison with PANI/TiN NWA or MnO/TiN NWA, the specific capacitance of PANI/MnO/TiN NWA was obviously enhanced due to the extra pseudocapacitance contribution and the effective surface area of coral-like PANI layer, showing the advantage of manipulating the heterogeneous coaxial configuration between PANI and MnO for fundamentally improved capacitive performance. These results demonstrated that PANI/MnO/TiN NWA ternary nanocomposite was a promising candidate electrode material for supercapacitor application. [ABSTRACT FROM AUTHOR]

We report on a new nanocomposite material for electrochemical sensing of hydrogen peroxide using a titanium dioxide nanotube arrays modified with reduced graphene oxide onto which silver nanoparticles (AgNPs) were chemically deposited. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray and Raman spectroscopy were used to characterize its microstructure and morphology. The results demonstrated that the AgNPs were uniformly dispersed on the surface of the modified electrode which was investigated with respect to capability for sensing hydrogen peroxide (HO). Under optimized experimental condition, the electrode responds to HO with a sensitivity of 1152 μA mM cm at a working potential of −0.6 V. The current response is linearly related to the concentration of HO in the range from 50 to 15.5 mM (with a correlation coefficient of 0.9997), and the detection limit is 2.2 μM. The sensor exhibits good stability and excellent selectivity for HO. By immobilizing glucose oxidase on the surface of this electrode, a glucose biosensor was obtained that responds to glucose in the 0.5 to 50 mM concentration range. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A glucose biosensor has been fabricated by immobilizing glucose oxidase (GOx) on unhybridized titanium dioxide nanotube arrays using an optimized cross-linking technique. The TiO nanotube arrays were synthesized directly on a titanium substrate by anodic oxidation. The structure and morphology of electrode material were characterized by X-ray diffraction and scanning electron microscopy. The electrochemical performances of the glucose biosensor were conducted by cyclic voltammetry and chronoamperometry measurements. It gives a linear response to glucose in the 0.05 to 0.65 mM concentration range, with a correlation coefficient of 0.9981, a sensitivity of 199.6 μA mM cm, and a detection limit as low as 3.8 µM. This glucose biosensor exhibited high selectivity for glucose determination in the presence of ascorbic acid, sucrose and other common interfering substances. This glucose biosensor also performed good reproducibility and long-time storage stability. This optimized cross-linking technique could open a new avenue for other enzyme biosensors fabrication. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A polyaniline/titanium nitride (PANI/TiN) nanotube hybrid was prepared and used for an electrochemical supercapacitor application. Firstly, the well-aligned TiN nanotube array was prepared by anodization of titanium foil and subsequent nitridation through ammonia annealing. Then, PANI was deposited into TiN nanotube through the electrochemical polymerization process. The obtained PANI/TiN nanotube hybrid had an ordered porous structure. A high specific capacitance of 1,066 F g was obtained at the charge-discharge current density of 1 A g when only the mass of PANI was considered. The specific capacitance can even achieve 864 F g at 10 A g and still keep 93 % of the initial capacity after 200 cycles. An aqueous supercapacitor, consisting of two symmetric PANI/TiN nanotube hybrid electrodes and 1.0 M HSO electrolyte solution, showed the specific capacitance of 194.8 F g, energy density of 9.74 Wh kg, and power density of 0.3 kW kg. [ABSTRACT FROM AUTHOR]

In this study, the polypyrrole-titania nanotube hybrid has been synthesized for an electrochemical supercapacitor application. The highly ordered and independent titania nanotube array is fabricated by an electro-oxidation of titanium sheet through an electrochemical anodization process in an aqueous solution containing ammonium fluoride, phosphoric acid and ethylene glycol. The polypyrrole-titania nanotube hybrid is then prepared by electrodepositing the conducting polypyrrole into well-aligned titania nanotubes through a normal pulse voltammetry deposition process in an organic acetonitrile solution containing pyrrole monomer and lithium perchlorate. The morphology and microstructure of polypyrrole-titania nanotube hybrid are characterized by scanning electron microscopy, infrared spectroscopy and Raman spectroscopy. The electrochemical capacitance performance is determined by cyclic voltammetry and charge/discharge measurement. It indicates that the polypyrrole film can been uniformly deposited on both surfaces of titania nanotube walls, demonstrating a heterogeneous coaxial nanotube structure. The specific capacitance of polypyrrole-titania nanotube hybrid is determined to be 179 F g based on the polypyrrole mass. The specific energy and specific power are 7.8 Wh kg and 2.8 kW kg at a constant charge/discharge current of 1.85 mA cm, respectively. The retained specific capacitance still keeps 85% of the initial capacity even after 200 cycle numbers. This result demonstrates the satisfying stability and durability of PPy-TiO nanotube hybrid electrode in a cyclic charge/discharge process. Such a composite electrode material with highly ordered and coaxial nanotube hybrid structure can contribute high energy storage for supercapacitor applications. [ABSTRACT FROM AUTHOR]