Preparation of high silica microporous zeolite SSZ-13 using solid waste silica fume as silica source

Silica fume (SF) is a kind of solid waste that produced in the process of industrial silicon smelting. The disposal of SF for environmental problem is of great urgency. Here, a facile and novel one-step approach of high silica microporous materials SSZ-13 (SF-SSZ-13) were hydrothermally synthesized using silica fume (SF) as silica source. This method requires significantly shorter reaction times (48?h) compared to conventional SSZ-13. The as-synthesized SF-SSZ-13 exhibited high purity structure, popcorn-like morphology, and a large BET surface area of 545.74?m²?g^?1. Additionally, on the basis of controlled growth under different hydrothermal times, the formation mechanism of the SF-SSZ-13 outlined for further extension to other materials. The results on time- and energy-efficient of SF-based preparation of SSZ-13 pave the way for the reducing the cost of production of raw materials and decreasing environment load of solid waste, and also extend the application of silica fume.     

Adsorption and thermochemical data of divalent cations onto silica gel surface modified with humic acid at solid/liquid interface

Humic acid immobilized onto silica gel surface was studied by the calorimetric titration of divalent cations in aqueous solution. The adsorption isotherms were obtained by the batchwise method and were fitted to a modified Langmuir equation. The maximum number of moles per gram of the material gave: 10.42 ± 0.75, 13.16 ± 0.58, 7.87 ± 0.58 for copper, nickel and zinc, respectively. Gibbs free energies were negative for all systems and the adsorption interactions calorimetrically followed presented endothermic enthalpic values: 6.24 ± 0.47, 6.75 ± 0.74, 6.97 ± 0.58 kJ mol⁻¹ for the same sequence of divalent cations. All liquid/solid interface adsorptions were entropically driven.     

The luminescent properties, thermal stability of phthalic acid and energy transfer from phthalic acid to Tb in sol—gel derived silica xerogels

In recent years, the energy transfer between different rare earth ions and the luminescent properties of rare earth ions have been studied extensively. However, the research of luminescent properties, thermal stability and structural variations of organic compounds, as well as their energy transfer to rare earth ions in silica xerogel, have not been reported. Organic—inorganic composites have even more efficient luminescence than pure rare earth ions. We describe the fabrication of silica xerogels doped with phthalic acid and Tb³⁺, their luminescent properties and thermal stability. The results show that, in silica xerogels, phthalic acid can exist steadily at 300 °C, and it can transfer the energy that it has absorbed to Tb³⁺.     

Synthesis and conductivity of solid high-proton conductor H5GeW10MoVO40·21H2O

A new solid high-proton conductor decatungstomolybdovanadogermanic heteropoly acid (HPA) H₅GeW₁₀MoVO₄₀·21H₂O has been synthesized for the first time by stepwise acidification and stepwise addition of solutions of the component elements. The product was characterized by chemical analysis, potentiometric titration, IR, UV, XRD and TG-DTA. The IR, UV and XRD indicate that H₅GeW₁₀MoVO₄₀·21H₂O possesses the Keggin structure. The TG-DTA curve shows the sequence of water loss in the acid, the amount of the loss, as well as the thermostability. The results of AC impedance measurement show that its proton conductivity is 3.58 × 10⁻⁴ S cm⁻¹ at 18 °C and the activation energy for proton conduction is 31.82 kJ/mol.     

Effects of preparation methods on structure,ionic conductivity and dielectric relaxation of solid polymeric electrolytes

The solid polymer electrolytes (SPEs) consisted of poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO₄) (PEO₂₀–LiClO₄ and PEO₈–LiClO₄ electrolytes of composition stoichiometric ratios EO:Li⁺ = 20:1 and 8:1) have been prepared by various blending methods. The simple solution casting, solution–cast hot pressed, dry blended melt pressed, high intensity ultrasonic assisted, microwave irradiated, and both the ultrasonicated and microwave irradiated solution–cast followed by their remelt with hot pressed methods have been used for preparation of the SPEs films. The complex formation between etheric oxygen (EO) of PEO and cation (Li⁺) of LiClO₄ is confirmed by relative changes in amorphous phase of these electrolytes which is investigated by X-ray diffraction measurements. It is found that the amount of amorphous phase of these SPEs is strongly influenced by their preparation methods and the salt concentration. The complex dielectric function, ac electric conductivity, electric modulus and impedance spectra of the electrolytes are studied over the frequency range of 20 Hz to 1 MHz by dielectric relaxation spectroscopy at ambient temperature. The dc ionic conductivity of PEO₈–LiClO₄ electrolytes is found two to three orders of magnitude higher than that of the PEO₂₀–LiClO₄ electrolytes, which is significantly affected by their preparation methods. The cations coupled PEO chain segmental dynamics and its correlation with the ionic conductivity of these electrolytes has been explored by considering the values of relaxation times and dielectric relaxation strength. Results reveal that the ionic conductivity of PEO₈–LiClO₄ electrolytes can be tuned over two orders of magnitude by adopting different blending methods with a state-of-the-art engineering.     

Preparation and antibacterial character of a water-insoluble antibacterial material of grafting polyvinylpyridinium on silica gel

Micron-sized silica gel particles were modified with the coupling agent of 3-methacryloylpropyl trimethoxysilane (MPS), then the copolymer of 4-vinyl pyridine and acrylamide (P (4VP-co-AM), PVA) was grafted onto the surface of modified silica gel particles by adopting the “grafting from” way, and the grafted particles PVA/SiO₂ were obtained. Finally, PVA on the particles PVA/SiO₂ were quaternarized by using benzyl chloride or dimethyl sulfate as quaternization reagents, and a kind of water-insoluble antibacterial material QPVA/SiO₂ with pyridinium-type was prepared. In this paper, the antibacterial property of QPVA/SiO₂ was mainly investigated by using Escherichia coli (E. coli) as model bacterium and by the colony count method, the effects of the grafting degree of pyridinium and the variety of quaternization reagents on the antibacterial property of QPVA/SiO₂were examined, and the antibacterial mechanism of QPVA/SiO₂ was explored using the method of measuring the activities of β-d-galactosidase and TTC-dehydrogenase. The experiment results show that QPVA/SiO₂ possesses strong antibacterial ability, and the antibacterial ratio of QPVA/SiO₂ with 2.3 mmol/g of grafting degree of pyridinium can reach 100% for bacterium suspension of 10⁹ CFU/mL with the dosage of 20 g/L and for 10 min of contact time. The greater the grafting degree of pyridinium is, the stronger the antibacterial ability, and the antibacterial property of the QPVA/SiO₂ prepared using benzyl chloride as quaternization reagent is stronger than that of the QPVA/SiO₂ prepared using dimethyl sulfate. The experimental results of two kinds of enzyme activity measurements reveal that the antibacterial effect of QPVA/SiO₂ is based on a sterilization process and not only based on a restraining action.     

Proton conducting composite materials containing heteropoly acid and matrices

The composite materials were prepared by 90 wt.% tungstovanadophosphoric heteropoly acids with Dawson structure (H₇P₂W₁₇VO₆₂·nH₂O and H₉P₂W₁₅V₃O₆₂·nH₂O, abbreviated as P₂W₁₇V and P₂W₁₅V₃), 5 wt.% silica gel (SiO₂) and 5 wt.% organic polymers (polyvinylpyrrolidone, PVP or polyethylene glycol, PEG). The products were characterized by the infrared (IR), X-ray powder diffraction (XRD) and electrochemical impedance spectroscopy (EIS). EIS measurements show that the conductivity values PVP/P₂W₁₇V/SiO₂, PVP/P₂W₁₅V₃/SiO₂ and PEG/P₂W₁₅V₃/SiO₂ are 1.89 × 10⁻², 2.32 × 10⁻² and 2.67 × 10⁻² S cm⁻¹ at 26 °C and 75% relative humidity, which increase with higher temperature. They exhibit low activation energies of 16.12, 16.85 and 14.02 kJ mol⁻¹ for proton conduction, respectively. The mechanisms of proton conduction of the composite materials are also proposed.     

Preparation and characterization of silica aerogels from oil shale ash

The silica aerogels were successfully synthesized using oil shale ash which is a by-product of oil shale processing via ambient pressure drying. The physical and textural properties of the silica aerogels have been investigated and discussed. The results showed that the organic modification of hydrogels was a crucial step during the processing which preserved mesopores in ambient pressure drying. The unmodified hydrogel underwent tremendous shrinkage during the drying and yielded microporous silica aerogel. Using this novel route, it could produce silica aerogel with low tapping density of 0.074 g/cm³, high specific surface (909 m²/g) and cumulative pore volume of 2.54 cm³/g. From the industrial point of view, the present process is quite suitable for a large scale production of powdered silica aerogel. Furthermore, it provides a new way to solve the problem of oil shale ash pollution.     

Preparation, characterization and photocatalytic activity of manganese doped TiO(2) immobilized on silica gel

A series of Mn-TiO(2)/SiO(2) (silica gel loaded with manganese doped TiO(2)) photocatalysts have been prepared by sol-gel method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activities were enhanced in photocatalytic degradation of methyl orange over Mn-TiO(2)/SiO(2). XPS analysis shows that a Ti-O-Si or Ti-O-Mn bond is formed on the surface of photocatalyst. Mn is doped as a mixture of Mn(2+) and Mn(3+) on the surface of 1.0mol% Mn-TiO(2)/SiO(2). Mn(3+) appears to trap electrons and prohibit the electron-hole recombination. The electrons trapped in Mn(3+) site are subsequently transferred to the adsorbed O(2). As a result, the combination of the electron-hole pair was reduced.     

Microstructure and high temperature deformation characteristics of sol–gel derived aluminium titanate–mullite composites

Aluminium titanate (AT)–mullite composites with varying compositions were processed by sol–gel technique. The influence of mullite on the microstructure and creep deformation of AT–mullite composites was investigated. In the composites mullite addition was varied from 0 to 100 vol.%. The AT-80 vol.% mullite composite sintered at 1600 °C resulted in fine-grained microstructure with an average grain size of 2.5 μm. From the steady-state creep analysis of the different AT–mullite composites, the activation energies for the creep deformation and stress exponents were determined. The activation energies in the range 655–874 kJ mol⁻¹ were obtained for various the sol–gel derived AT–mullite composites. Similarly stress exponent values were found in the range 1.5–1.9.     

Preparation of DNA–cyclodextrin–silica composite by sol–gel method and its utilization as an environmental material

A DNA–cyclodextrin–silica composite was prepared by the sol–gel method. This composite possessed the bi-functions of double-stranded DNA, such as intercalation into DNA, and cyclodextrin, such as inclusion into its intramolecular cavity. Therefore, we demonstrated the accumulation of harmful compounds from an aqueous multi-component solution using a DNA–cyclodextrin–silica composite column. As a result, the DNA–cyclodextrin–silica composite column can effectively accumulate not only planar structure-containing harmful compounds, such as dioxin and polychlorobiphenyl (PCB) derivatives, but also non-planar structure containing compounds, such as bisphenol A and diethylstilbestrol, from an aqueous multi-component solution. The accumulated amount of these harmful compounds was more than 90%. Additionally, the DNA–cyclodextrin–silica composite column was recycled by the application of methanol. Therefore, the DNA–cyclodextrin–silica composite may have the potential to be used as an environmental material for the accumulation of harmful compounds from industrial or experimental waste.     

硅胶固载酸功能化离子液体催化剂的制备和应用

将带有酸官能团的离子液体固载到具有高表面积的硅胶上,制备的硅胶固载酸功能化离子液体可作为催化剂用于多种有机反应。该新型催化剂具有高效、高选择性、离子液体用量少、产品易分离和催化剂易回收等优点,因有望用于化工过程的固定床反应器而受到关注。     

Preparation of surface-silvered graphene-CNTs/polyimide hybrid films: Processing,morphology and properties

Silver nanoparticles modified graphene-carbon nanotubes/polyimide (Gr-CNTs/PI) films have been prepared by electrochemical reduction of silver nitrate on potassium hydroxide hydroxylated of Gr-CNTs/PI films surface. The as-prepared nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction analyzer and semiconductor characterization system. The lower content of Gr-CNTs (≤10 wt. %) doping in PI matrix can improve the conductivity of PI films more clearly than pure CNTs. The conductivity can be regulated by controlling Gr-CNTs content in PI matrix. These silver nanoparticles into Gr-CNTs/PI films presented here can act as deposition seeds which can initiate subsequent electroless silver or copper or electrodeposition other metal.     

Anomalous steam oxidation behavior of a creep resistant martensitic 9 wt. % Cr steel

The efficiency of thermal power plants is currently limited by the long-term creep strength and the steam oxidation resistance of the commercially available ferritic/martensitic steel grades. Higher operating pressures and temperatures are essential to increase efficiency but impose important requirements on the materials, from both the mechanical and chemical stability perspective. It has been shown that in general, a Cr wt. % higher than 9 is required for acceptable oxidation rates at 650 °C, but on the other hand such high Cr content is detrimental to the creep strength. Surprisingly, preliminary studies of an experimental 9 wt. % Cr martensitic steel, exhibited very low oxidation rates under flowing steam at 650 °C for exposure times exceeding 20,000 h. A metallographic investigation at different time intervals has been carried out. Moreover, scanning transmission electron microscopy (STEM) analysis of a ground sample exposed to steam for 10,000 h at 650 °C revealed the formation of a complex tri-layered protective oxide comprising a top and bottom Fe and Cr rich spinel layer with a magnetite intermediate layer on top of a very fine grained zone.     

Organic/inorganic flame retardants containing phosphorus,nitrogen and silicon: Preparation and their performance on the flame retardancy of epoxy resins as a novel intumescent flame retardant system

This paper presents the preparation of novel organic/inorganic flame retardants containing phosphorus, nitrogen and silicon (organic/inorganic FRs). The organic/inorganic FRs were highly water resistant, as suggested by the water contact angle and water solubility tests. The organic/inorganic FRs were then incorporated into epoxy resins (EP) at different phosphorus/nitrogen ratios and the flame retardancy of EP/FRs composites was characterized. The results showed that synergistic effects on the flame retardancy of EP composites existed between the DOPO-VTS and TGIC-KH. The char residues for EP/FRs composites were increased, and the highest char residues were obtained in air atmosphere (3.8 wt.%) when the DOPO-VTS/TGIC-KH is 4/1. The MCC results also showed that the THR of epoxy resins were also decreased when the DOPO-VTS/TGIC-KH is 4/1, which was in accordance with the highest LOI and UL-94 results. The SEM, FTIR, XPS and TG-FTIR results of pyrolysis products in both condensed and gases phases indicated that the strategy of organic/inorganic FRs combined condensed phase and gases phase flame retardant strategies such as the phosphorus–nitrogen synergism systems, the silicon reinforced effects in the condensed phase and DOPO flame retardant systems in the gases phase, resulting in significant improvements in the flame retardancy of epoxy resins.     

Effect of thermo mechanical treatments and aging parameters on mechanical properties of Al–Mg–Si alloy containing 3 wt.% Li

In the present work, microstructure and mechanical properties of 3 wt.% Li addition in a Al–Mg–Si alloy of target composition 0.5 wt.% Mg and 0.2 wt.% Si in W (solution heat treated), T6 (solution heat treated and artificially aged) and T8 (solution heat treated, cold worked and artificially aged) conditions was studied. The age-hardening response of the alloy was determined after systematic cold reductions from 10%, 20%, 30%, 40%, 50% and 60% in quenched condition followed by aging at 175 °C (448 K) for 2, 4, 6, 8, 10 and 12 h (T8 condition). The results were compared with samples aged in the same conditions with 0% cold reduction (T6 condition). The alloy displayed a strong artificial aging response and maximum hardness value achieved was after 60% cold work and 10 h of aging time. Furthermore, the yield strength and the ultimate tensile strength were increased from 123 MPa to 224 MPa and 356 MPa to 540 MPa respectively with a slight decrease in ductility. Scanning electron microscopy (SEM) based fractography showed a uniform network of bigger and deeper dimples with round morphology in T6 condition while a ductile tearing with few discernable cleavage planes was observed in T8 condition. The interplay of various precipitation hardening mechanisms and relevant phases was established by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was concluded that the enhancement in mechanical properties, with the degree of cold work, was attributed due to a possible refinement of δ′ (Al₃Li) precipitates resulted after aging.     

Phase transformations of Ni-15 wt.% B powders during mechanical alloying and annealing

The formation of Ni-B binary intermetallic compounds was investigated by mechanical alloying (MA) of the Ni-15 wt.% B (≈ Ni-48 at.% B) powder mixture and subsequent heat treatment. It was found that an interstitial Ni(B) solid solution was formed at the early stage of milling, followed by the formation of Ni₃B intermetallic compound after 25 h of milling. On further milling, the Ni₃B transformed to Ni₂B and o-Ni₄B₃ (orthorhombic). Phase transformation during heating of Ni(B) solid solution phase up to 800 °C could be represented by Ni(B) → Ni₃B → Ni₂B. Other intermetallics can be formed by heat treatment of Ni(B) solid solution at temperatures above 800 °C.     

Correlation between ionic conductivity and fluidity of polymer gel electrolytes containing NH4CF3SO3

Nonaqueous polymer gel electrolytes containing ammonium triflate (NH₄CF₃SO₃) and dimethylacetamide (DMA) with polymethylmethacrylate (PMMA) as the gelling polymer have been synthesized which show high value of conductivity (~ 10^-2 S/cm) at 25°C. The conductivity of polymer gel electrolytes containing different concentrations of NH₄CF₃SO₃ shows a small decrease with the addition of PMMA and this has been correlated with the variation of fluidity of these gel electrolytes. The small decrease in conductivity with PMMA addition shows that polymer plays the role of stiffener and this is supported by FTIR results which also indicates the absence of any active interaction between polymer and NH₄CF₃SO₃ in these gel electrolytes.     

Preparation and characterization of water-borne epoxy shape memory composites containing silica

Shape memory silica/epoxy composites were successfully prepared by hydrolysis of tetraethoxysilane (TEOS) within the epoxy matrix via latex, freeze-drying, and hot-press molding method. The silane coupling agent 3-triethoxysilylpropylamine (KH550) was introduced to improve the interfacial properties between the in-situ generated silica particle and epoxy matrix. The morphology structure and the effect of the content of the in-situ formed silica on the mechanical and shape memory properties of the silica/epoxy composites were studied. The experimental results indicated that the silica particles were homogenously dispersed and well incorporated into the epoxy matrix. Significant improvements were achieved in the mechanical property of the organic–inorganic hybrid materials. The silica/epoxy composites exhibited high shape recovery and fixity ratio approximately 100% even after 10 thermo-mechanical cycles.