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NiAl alloy sheet was successfully prepared using current-assisted sintering, thus verifying the possibility of preparing a NiAl thin-wall component by current-assisted sintering and foil/foil reaction synthesis. Ni/Al laminated sheets were obtained by annealing at 550 °C at 5 MPa for 0.5 h; uniform NiAl alloy sheets were fabricated by annealing at 1150 °C at 15 MPa for 20 min. The experimental results showed that current-assisted sintering significantly reduced the reaction temperature and reaction time. Microstructural characterization revealed that the inter-diffusion ability of Al atoms is considerably weaker than that of Ni atoms. Molecular dynamics simulation confirmed these experimental results and showed that this difference becomes significant under the action of an electric field. The mechanism of synthesis of Ni/Al laminated sheets using current sintering is mainly determined by the diffusion behavior of Ni atoms. [ABSTRACT FROM AUTHOR]

Composite particles composed of SiO nanoparticles and polystyrene (PS) spheres with a raspberry-like structure were successfully synthesized by a PVP-assistant sol-gel method. The as-prepared products were systemically characterized by FT-IR, TGA, SEM and TEM. The characterization results indicated that the amount of polyvinyl pyrrolidone (PVP) and concentration of ammonia solution played key roles in tailoring the structure of the composite particles, including size and surface density of SiO nanoparticles on the surface of PS spheres. During the PVP-assisted sol-gel process, the synthesized nano-sized SiO particles were favorably deposited on the surface of PS spheres to form hierarchical composite particles. By adjusting the amount of PVP and pH value of reaction system, the typical raspberry-like particles with controllable coverage of SiO nanoparticles on PS spheres were obtained. Subsequently, the composite particles with well controllable morphology were modified with OcTMS and orderly deposited on the substrate. The effect of the composite particles with different morphologies on the wetting property was investigated. Finally, superhydrophobic surface was generated and the water contact angle was up to 154°. Graphical Abstract: PS-SiO composite particles with hierarchical structure were successfully prepared by a PVP-assisted sol-gel method, which exhibited a superhydrophobic property after surface modification with OcTMS.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A novel core-shell-structured Ag-based magnetic functional polymer nanocatalyst, i.e., FeO@SN/GLA@chitosan-Ag (SN represents animo-functionalized SiO, GLA signifies glutaraldehyde), was fabricated via a simple and environmentally friendly method. The magnetic separation property of FeO, the protection effects of SiO, the reduction and stabilization activities of chitosan, and the catalytic property of Ag nanoparticles (NPs) in the multifunctional catalyst system were efficiently combined using glutaraldehyde as bridging agent. The Ag NPs with average diameter about 2-11 nm were generated in situ and stabilized by chitosan, which acted as reducing agent and stabilizer in the absence of other potentially toxic reagents. Furthermore, the reduction, chelation ability of chitosan, and the size of Ag NPs were found to be tunable, thereby enabling the preparation of other noble metal catalysts with tailored properties. Most importantly, the as-prepared catalyst exhibited superior catalytic performance (the reduction reaction was finished within 3 min) and reusability (reusable for at least six times) in the reduction of 4-nitrophenol. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A one-pot method was introduced to fabricate Ag-SiO hollow composite spheres with developed porosity by employing monodisperse carboxylic-capped polystyrene (PS-COOH) spheres as a hard template. During the synthetic process, Ag ions were immediately anchored on the surface of the PS-COOH spheres via electrostatic interaction and readily reduced by employing polymethylhydrosiloxane (PMHS) as a reducing agent. At the same time, silica oligomers derived from the hydrolysis of PMHS and TEOS were slowly deposited on the PS-COOH spheres to form solid silica shells. Subsequent decomposition of the PS-COOH spheres in air induced the formation of Ag-SiO hollow spheres. The as-prepared products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and N absorption-desorption study. The results show that the well-designed composite spheres featured thin and spherical silica shell (~10 nm), large surface area (>240 m g) and mesopore (6.0-9.0 nm). In addition, the Ag-SiO hollow composite spheres exhibited high catalytic performance toward the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Graphical Abstract: A one-pot method was reported to prepare Ag-SiO hollow spheres with well-developed porosity, which exhibited high catalytic performance and durable activity for the reaction of 4-NP to 4-AP.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This work presented a novel, facile, cost-effective and environmentally friendly approach for the preparation of magnetic core-shell structured catalyst i.e. FeO@SN-Ag (abbreviation of FeO@SiO-NH-Ag). During the process of preparation, Ag nanoparticles were in situ generated with amino groups in the surface of FeO@SN serving as green reductant and stabilizer in the absence of any additional toxic reductant or organic reagent. Magnetic core, FeO, was easily prepared through solvothermal method. The subsequent coating and surface amino functionalization of SiO was accomplished via one-pot sol-gel method, which was green and time-saving. What's more, the resulting catalyst exhibited excellent catalytic property (the reaction was finished within 2 min) and reusability (reused at least seven times) in the reduction of 4-nitrophenol. [ABSTRACT FROM AUTHOR]

A newly designed two-step acid-base sol-gel method for the synthesis of Ag-doped hybrid materials with tailored physicochemical properties is presented. In the proposed protocol, Ag is in situ reduced by Si-H bonds of polymethylhydrosiloxane (PMHS) in the absence of an additional reductant. Hydrolysis of the alkyloxysilane groups of tetraethoxysilane and PMHS or 3-mercaptopropyltrimethoxysilane (MPTMS) can be promoted by the release of H due to complexation between Ag/Ag and thiol groups. Newly formed nanosilver can be fully stabilized by a sol-gel reaction and embedded parallel to the skeletons. The MPTMS dosage used during synthesis has a significant impact on the textural characteristics of the final products. The properties of as-prepared materials are characterized by Brunauer-Emmett-Teller analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy. This study presents a novel method for the synthesis of Ag-doped hybrid materials using the synergetic effects of common organosilane precursors. [ABSTRACT FROM AUTHOR]

Multifunctional nanomaterials with task-specific physicochemical properties, especially core-shell nanostructures with FeO core and NH-functional shells (FeO@SiO-NH), have been extensively investigated as high-performance adsorbents, catalysts and catalyst supports; and in most cases the controllable sol-gel technique is the choice for fabrication of this kind of widely applied materials. Herein, we demonstrated that mono-dispersed and spherical FeO@SiO-NH nanomaterials with magnetic response core, NH-functional shell structure can be facilely prepared by co-condensation of TEOS with APTMS using a versatile sol-gel process. It was shown that the proper usage of APTMS and appropriate pre-hydrolysis time of TEOS were crucial and key steps for formation of highly uniform and desirable amino loading FeO@SiO-NH materials. The TEOS pre-hydrolysis and the critical time (around 90 min) before the addition of APTMS prove to be vital for uniform structure evolution, while the appropriate concentration of APTMS (~2.28 mmol L in our system) leads to well-dispersed materials with relatively high loading of amino functionality. The as-prepared FeO@SiO-NH magnetic nanoparticles prepared under optimum conditions possessing superparamagnetic behavior, uniform core-shell structure (~200 nm in diameter), relatively large BET surface area (~138 m/g) and high incorporation of amino-functionality (~2.90 wt %). [ABSTRACT FROM AUTHOR]

A facile sol-gel route to the fabrication of size-controllable nanosilver embedded hybrid materials at room-temperature is presented. The preparation process involves using three kind of organosilica precursors, i.e. tetraethoxysilane, 3-mercaptopropyltrimethoxysilane and polymethylhydrosiloxane, which behaved as framework constructor, complexing agent toward metal ions and in situ reducing agent for Ag ions, respectively, under alcohol-rich synthesis conditions. The prepared hybrid materials were characterized by Ultraviolet-visible diffuse reflectance spectra, Fourier transform infrared, transmission electron microscopy, X-ray diffraction, nitrogen adsorption-desorption measurements. It was shown that well-dispersed silver nanoparticles (AgNPs) with small particle size were successfully embedded in the hybrid skeleton, and the mean particle size of AgNPs could be controlled at ca. 2-5 nm. [ABSTRACT FROM AUTHOR]

Adsorption of heavy metal ions from aqueous solutions on tri-amino-functionalized silica hybrids with tailored structural characteristics was investigated. The adsorbents were prepared using a controllable sol-gel method with (3-aminopropyl)trimethoxysilane or 3-[2-(2-aminoethylamino)ethylamino] propyltrimethoxysilane, polymeric polymethylhydrosilane and tetraethoxysilane as co-precursors in the absence of traditional surfactant aggregates. These as-prepared hybrids possess tailored structures with high specific surface area, large pore volumes and relatively narrow pore diameter as confirmed by transmission electron microscopy and nitrogen sorption results. The elemental analysis and FT-IR indicated that amino groups had been successfully introduced into the opened skeletons. The loadings of amino moieties of the amino-functionalized gels could be tuned from 5 to 40% by adjusting the molar ratio of organoalkoxysilane/silica in the synthesis system. The heavy metal adsorption experiments have been examined for Cu(II), Pb(II), Ni(II), Cd(II) and Zn(II) from aqueous solution employing batch method. The results showed that the adsorption capacity of the tri-amino-functionalized adsorbents was higher than that of the mono-amino-functionalized counterparts, illustrating a good potential for environmental remediation in virtue of the combination of selective adsorption performance and large-scale synthesis character. [ABSTRACT FROM AUTHOR]

Thiol-functionalized sol-gel materials with porous structures were successfully prepared via co-condensation of tetraethoxysilane, (3-mercaptopropyl)-trimethoxysilane, polymeric polymethylhydrosiloxane in the absence of traditional structure-directing agents under proposed basic conditions. The dependence of textural characteristics on the preparation parameters were investigated employing various techniques as such N adsorption/desorption isotherms, SEM, TG-DTG, FT-IR and solid state Si MAS NMR measurements. It was shown by these characterizations that thiol-functional groups have been successfully introduced into the porous network and the loadings could be tuned by adjusting the content of corresponding precursor in the gel system. Besides, the as-prepared samples exhibited high surface areas, large pore volume, tunable pore diameters and favorable thermal stability. Adsorption experiments indicated that thiol-incorporated materials have selective adsorption ability toward heavy metal ions from aqueous solutions, and a high capacity in adsorbing heavy metal ion of Pb (up to 99.4%) was observed under optimized experimental conditions. [ABSTRACT FROM AUTHOR]

Hybrid materials based on tetraethoxysilane (TEOS) and polymethylhydrosiloxane (PMHS) have been prepared employing sol-gel synthesis pathway, and the effects of preparation parameters such as PMHS concentration, water and NaOH amount on the structural characteristics were detailed investigated based on various techniques. It is illustrated that structural characteristics especially pore size can be tuned readily by adjusting the amount of PMHS during the sol-gel reaction. Furthermore, pore size increases with water amount and contrarily is almost independent on the amount of sodium hydroxide (NaOH) added in the sol-gel process. Typical hybrid sample prepared with desirable preparation parameters presents disordered wormhole structure with uniform mesopores, developed porosity with high specific surface area and pore volume and stable framework. In virtue of facileness and tunable composition, this synthesis pathway can be favorably applied for the preparation of other fascinating materials, i.e. porous ceramics, hydrophobic coatings and aerogels as well. [ABSTRACT FROM AUTHOR]