SiOSi Bonds Research Articles

Structural study and ion-beam channelling in Si 〈1 0 0〉 modified by Kr+, Ag+, 2+ and Au+, 2+ ions

A Si-crystal layer on SiO2/Si was irradiated using 0.4 MeV Kr+, Ag+, Au+ and 5.0 MeV Ag2+, Au2+ at ion fluences of 0.5 × 1015–5.0 × 1015 cm−2. The induced structural modification in a Si crystal strongly influences ion-beam channelling phenomena through the introduced point defects, damage accumulation and induced internal strain. He+ ion channelling in the ion-implanted Si structure was studied, simultaneously with the structure and surface-morphology characterization of Si-irradiated layers, in connection with the ion-implantation parameters and prevailing energy-stopping type. The dislocated atom-depth profiles in the Si layer and the Si sub-surface layer were extracted from Rutherford backscattering spectrometry in the channelling mode (RBS-C). RBS-C shows the density of gradually displaced atoms as a function of ion fluence and ion mass for 5.0-MeV-ion implantation. The relative disorder grows more progressively for Au-ion implantation, where the thicker disordered layer was also observed in connection to the higher density collision cascade comparing to Ag+ ions. This phenomenon was discussed in the frame of the structural RBS-C and surface morphological data from AFM. The axial channelling effect of He+ ions measured in the 5.0-MeV-ion-implanted Si layer is varying during 2.0-MeV-He+ channelling in consequences of the various implantation fluences. The narrowing of axial channels observed in RBS-C was correlated to the number of produced vacancies in the Si layer after ion implantation and compared to MC simulations performed by FLUX. Nanostructured surface morphology modification has been detected mainly in 0.4-MeV-implanted Si layers using atomic force microscopy (AFM) studies, where the nuclear stopping is a prevalent phenomenon. Fourier transformation infrared spectroscopy (FTIR) has shown SOI modification mainly done by Si rearrangement and modified by possible SiOSi bonds creation.

Oxidative desulfurization of dibenzothiophene and diesel by hydrogen peroxide: Catalysis of H3PMo12O40 immobilized on the ionic liquid modified SiO2

Here we reported an oxidative desulfurization system for oxidation of sulfur-containing compounds in model oil and diesel by catalysis using SiO2-supported phosphomolybdate hybrid material with 30% H2O2 aqueous solution as the oxidant. Firstly, The SiO2 was modified with 1-propyl-3-triethoxysilyl 3-methylimidazolium chlorid by grafting method. We used the 29Si MAS NMR to demonstrate that the organic silane group was attached to the SiO2 surface by one or two SiOSi bonds. Secondly, the phosphomolybdate was immobilized onto the modified SiO2 to prepare the hybrid material catalyst. The FT-IR, UV–vis, and TG characterization results indicate that the Keggin structure of the [PMo12O40]3− and imidazole ring were remained. The catalyst was used to oxidative desulfurization of dibenzothiophene by H2O2 as the oxidant. Maximum oxidation activity was observed at a loading of 30 wt.% H3PMo12O40 which can complete oxidation 0.2 wt.% of dibenzothiophene at 50 °C and an O/S molar ratio of 3.0 in 30 min. The catalyst could be easily separated by centrifugation and reused for seven times without any deactivation. The high performance of this oxidative desulfurization system was verified in the sulfur removal from a real diesel oil by oxidation followed by dimethylformamide extraction.

Synergistic effect of microwave rapid heating and weak mineralizer on silica-stabilized tetragonal zirconia nanoparticles for enhanced photoactivity of Bisphenol A

Silica-doped tetragonal mesoporous zirconia nanoparticles (SZ) were successfully synthesized with various concentrations of ammonia solution(NH4OH) using microwave-assisted method for photodegradation of Bisphenol A (BPA). The phase of SZ catalyst was pure mesoporous tetragonal ZrO2 with nano in size (5–10nm). The increasing concentration of NH4OH solution enhanced the hydrolysis and condensation process, as confirmed by formation of additional ZrOZr, SiOSi and SiOZr bonds. The formation of oxygen vacancy (Vo) and Zr3+ surface defects (ZSD) also increased proportionally with the concentration of NH4OH solution. Both properties and the SiOZr bond are supposed to play important roles in stabilizing the tetragonal phase of ZrO2. The Vo and ZSD also lowered the band-gap energy (from 4.35eV to 3.05eV) and act as electron acceptors. Catalytic testing showed that 8-SZ gave the highest initial rate (0.372× 10−3mMmin−1) of 10mgL−1 BPA at pH7 using 0.5gL−1 catalyst within 4h while under similar conditions, 5-SZ, 3-SZ, 0-SZ, ZrO2 and TiO2 only gave 0.263×10−3, 0.211×10−3, 0.145× 10−3, 0.026× 10−3 and 0.305×10−3mMmin−1, respectively. These results demonstrate that higher numbers of SiOZr, Vo, and ZSD seemed to be the main factors in the high photoactivity of SZ prepared in 8M NH4OH solution (8-SZ). A kinetic study demonstrated that the photodegradation followed the pseudo-first-order Langmuir-Hinshelwood model. The mechanism study using scavenging agents proved that photogenerated hole was the main active species, thus led more hydroxyl radicals formed to degrade the BPA. The 8-SZ also exhibited a great potential on degradation of various phenols and dyes in wastewater.

Facile synthesis of novel fibrous silica@apatite@Au composites with superior photo-catalytic activity

Novel fibrous silica@apatite@Au composites with superior photo-catalytic activity were facilely synthesized through combination of electrospinning technique, bio-mineralization, and in situ immobilization. Silica nanofibers with the diameter of 486±60nm were synthesized through electrospinning of the sol-gel mixture of gelatin, tetraethoxysilane, acetic acid, water, and calcium chloride followed by sintering process. After bio-mineralization in the Kokubo's simulated body fluid, silica nanofibers supported in situ deposition of fibrous apatite nanosheet flowers to produce fibrous silica@apatite composites. SEM observations showed that the silica@apatite composites had the fibrous feature with the diameter of 2498±608nm and their surface was very rough and constructed by numerous apatite nanosheets with the thickness around 10nm. XRD patterns showed that the fibrous silica@apatite composites presented the characteristic diffraction peaks at 26° and 32° assigned to apatite components. FT-IR spectra revealed that silica@apatite composites contained both SiOSi bonds and POP groups. After immersion in the suspension of Au nanoparticles, the silica@apatite composites supported the in situ immobilization of Au nanoparticles to produce silica@apatite@Au composites. When incubated in the aqueous mixture of 4-nitrophenol and NaHB4, the fibrous silica@apatite@Au composites presented a superior photo-catalytic activity and rapidly catalyzed the reduction of 4-nitrophenol to 4-aminophenol.

First principles band gap engineering of [1 1 0] oriented 3C-SiC nanowires

Silicon carbide nanowires offer excellent opportunities for technological applications under harsh environmental conditions, however, the 3C-SiC polytype nanowires, grown along the [1 1 0] crystallographic direction, have been rarely studied, as well as the effects of the surface passivation on their physical properties. This work addresses the effects of hydrogen passivation on the electronic band gap of silicon carbide nanowires (SiCNWs) grown along the [1 1 0] direction by means of Density Functional Theory. We compare the electronic properties of fully hydrogen-passivated SiCNWs in comparison to those of SiCNWs with a mixed passivation of oxygen and hydrogen by changing some of the surface dihydrides with SiOSi or COC bonds. The results show that regardless of the diameter and passivation, most of the nanowires have a direct band gap which suggests an increased optical activity. The surface COC bonds reduce the electronic band gap energy compared to that of the fully H-terminated phase, while the nanowires with SiOSi bonds have a larger band gap. The calculation of formation energies shows that the oxygen increases the chemical stability of the SiCNWs. These results indicate the possibility of band gap engineering on SiC nanostructures through surface passivation.

The key for sodium-rich coal utilization in entrained flow gasifier: The role of sodium on slag viscosity-temperature behavior at high temperatures

Tremendous sodium-rich coal in China has unique ash compositions, and the entrained flow gasification is one of the best choices to use sodium-rich coal for coal chemical industry. The entrained flow gasifiers require smooth slag tapping for long term and safe running, but the viscosity-temperature behavior of high-sodium slags is unknown, which limits the utilization of sodium-rich coal. In this study, viscosity-temperature behavior of high-sodium coal ash slags was revealed for the first time, and the parameter of slag network structure and index of slag crystallization tendency is raised for slag viscosity evaluation. The results show that Na2O provides O2− ions which break SiOSi bonds and slag network structure. However, Al3+ ions are absorbed into silicate network, acting as a network former with the ionic charge-compensation effect of Na+. The classic structural parameter (fraction of non-bridging oxygen, NBO) is modified to evaluate the high-sodium slag viscosity accurately by taking Al3+ into account. NBO fraction decreases as Na2O content increases, leading to the decrease of slag viscosity. Below Tliq, slags are prone to be crystalline slag with increasing Na2O content or glassy slag with increase in SiO2/Al2O3 ratio (S/A). A novel index, namely glassy slag formation ability (G), is established to quantitatively evaluate the crystallization tendency of coal ash slags. G is the ratio of activation energy for viscous flow (Eη) to Tliq. The slag will exhibit the glassy behavior when G is higher than 0.16kJ/(mol·K). The results enhance the knowledge of viscosity-temperature behavior of high-sodium coal ash slags and will be helpful for coal selection and blending to avoid slag blockage in entrained flow gasification.

Directly grafting octa(aminophenyl) polyhedral oligomeric silsesquioxane onto carbon fibers for superior interfacial strength and hydrothermal aging resistance of silicone resin composites

Introducing nano-scale reinforcements into carbon fiber (CF)-matrix interface is a useful method to enhance interfacial strength of composites. In this work, we demonstrated a facile and high efficient strategy of preparing octa(aminophenyl) polyhedral oligomeric silsesquioxane (OapPOSS)/CF hierarchical reinforcements (CF-g-POSS) by directly grafting OapPOSS on CFs by covalent bonding. OapPOSS distributed on fiber surfaces uniformly, and enhanced surface polarity as well as roughness significantly. CF-g-POSS exhibited a low contact angle and high surface free energy, which helped to change the wettability between CF and the matrix. Simultaneous enhancements of interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CF-g-POSS/methylphenylsilicone resin (MPSR) composites were achieved, increasing 47.83% in IFSS and 59.04% in ILSS compared to those of untreated composites. These enhancements could be attributed to OapPOSS interface with providing sufficient covalent bonding and strong mechanical interlocking. Additionally, anti-hydrothermal aging behaviors were also increased obviously owing to the introduction of SiOSi bonds at the interface.

Synthesis and characterization of ZnS@Fe3O4 fluorescent-magnetic bifunctional nanospheres

Herein, we synthesized and characterized fluorescent and super paramagnetic ZnS@Fe3O4 nanospheres. First, (3-mercaptopropyl) trimethoxysilane (MPS) capped ZnS quantum dots (QDs) and SiO2 coated Fe3O4 nanoparticles were synthesized separately by using solution growth and co-precipitation techniques. After synthesis and characterization of these two nanoparticles, they were conglutinated together in a nano sized sphere. The QDs were attached to the surface of the Fe3O4 nanoparticles by SiOSi bonds and so SiOSi bonds created a SiO2 network around the nanoparticles during the formation of the ZnS@Fe3O4 nanospheres. The synthesized MPS capped ZnS fluorescent QDs, SiO2 coated magnetite super paramagnetic nanoparticles and ZnS@Fe3O4 fluorescent-magnetic bifunctional nanospheres were characterized by using UV–Vis Absorption Spectroscopy, Fluorescence Spectroscopy, X-ray analysis, Vibrating Sample Magnetometer analysis, Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope and Energy-dispersive X-ray spectroscopy. ZnS@Fe3O4 bifunctional nanospheres were shown to retain the magnetic properties of magnetite, while exhibiting the luminescent optical properties of ZnS nanoparticles. The combination of fluorescent and magnetic behaviors of nano composites make them useful for potential applications in the field of bio-medical and environmental.

SiO2-coated pure anatase TiO2 catalysts for enhanced photo-oxidation of naphthalene and anthracene

Our current efforts reveal the preparation of SiO2@TiO2 nanocomposites having different thicknesses of silica shell and the relationship to photocatalytic activity (PCA) for the photo-oxidation of naphthalene and anthracene. The presence of SiO2 coating over TiO2 surface was demonstrated by FT-IR analysis, with peaks corresponding to SiOSi (1081cm−1) and SiOTi (950cm−1) bonds observed. High-resolution transmission electron microscopy analysis confirmed the presence of SiO2 in the as-prepared nanocomposites and the amount of Si, Ti, and O was determined by energy dispersive X-ray spectroscopy analysis. Increasing the SiO2 shell thickness increases the surface area of the nanocomposites (69–235m2/g), which enhances naphthalene/anthracene adsorption. However, the observed PCA trend presents an inverse correlation to the adsorption studies, where the as-prepared samples possessing the highest surface areas exhibited the least PCA, while catalysts having lower surface areas (among silica coated samples) displayed the highest PCA in the degradation of naphthalene and anthracene to CO2. Despite complete degradation of naphthalene and anthracene, incomplete mineralization occurred, ascribed to the formation of various intermediates, identified by GC–MS analysis.

Well-dispersed Ni nanoclusters on the surfaces of MFI nanosheets as highly efficient and selective catalyst for the hydrogenation of naphthalene to tetralin

One of the challenges in material science has been to design and prepare highly efficient and selective catalysts for target reactions. Here we demonstrate a one-pot hydrothermal synthesis of hierarchical MFI nanosheets with nickel species chemically bonded on the outer surfaces. It turns out that the growth and morphologies of self-pillared MFI nanosheets are affected by Ni content, and the thickness of MFI nanosheets are determined to be 2.3nm or 3.0nm. Specially, the bonded Ni on the outer surfaces can effectively prevent adjacent nanosheets from forming new SiOSi bonds, and in conjunction with the self-pillared structure, can hamper complete collapse of Ni-MFI-NSs during calcination. In naphthalene hydrogenation, the separated Ni species are previously reduced to highly-dispersed metallic Ni nanoclusters with size below 1.6nm, which are highly active for hydrogenation. And the hierarchical porosity of Ni-MFI-NSs significantly enhances the diffusion of substrates and the accessibility of active sites. As a result, Ni-MFI-NSs achieve 100% selectivity for tetralin and 84.9% conversion of naphthalene with Ni content of only 4.2wt%. Furthermore, the gradually enlarged Ni nanoparticles cause the decline of catalytic activities of catalysts.

Synthesis of an alumina enriched Al2O3-SiO2 aerogel: Reinforcement and ambient pressure drying

An alumina enriched Al2O3-SiO2 aerogel was successfully synthesized using an inexpensive inorganic aluminum salt Al(H2O)9(NO3)3 as the precursor and tetraethoxysilane (TEOS) as the framework reinforcing agent via a sol-gel process followed by ambient pressure drying. In order to show the enhanced effect of TEOS on aerogel, its structure and properties were detected by FESEM, TEM and BET. Furthermore, FTIR and Raman spectra were collected to explain the enhancement mechanism of TEOS to Al2O3-SiO2 aerogel at the molecular level. The FTIR spectra showed that some AlOSi and AlOSiOSiOAl bonds gradually formed during the reinforcement process. These long AlOSiOSiOAl chains supported and strengthened the alcogel skeleton and effectively avoided potential shrinkage and cracking during the ambient pressure drying process. In addition, Raman spectra supported this conclusion by verifying that AlOSi and SiOSi bonds were present. Moreover, the Raman spectra indicated that with the increase of the Si/Al mole ratio from 0 to 3.0, the primary gel skeleton of AlOAl bonds was gradually transformed to SiOSi bonds. When the Si/Al mole ratio was greater 3.0, SiOSi bonds became the primary bonds in the final aerogel.

Identification of double four-ring units in germanosilicate ITQ-13 zeolite by solid-state NMR spectroscopy

Well-crystallized Ge-free and Ge-ITQ-13 were successfully obtained by solid state synthesis method. The Ge/Si ratio and the water content that are the two important factors in the synthesis of germanosilicate zeolites were explored for the formation of ITQ-13. The effect of the mineralizing agents (NH4F and NH4Cl) on the ITQ-13 synthesis was investigated as well. The obtained pure silica ITQ-13 and Ge-ITQ-13 were characterized by one- and two-dimensional solid- state NMR techniques. One-dimensional (1D) 19F MAS, 1H→29Si CP/MAS and 19F→29Si CP/MAS NMR spectroscopy evidenced the formation of pure Si-D4R (double four ring) and Ge-D4R units, with the latter being generated by substitution of Si atom from the former units. The detailed configurations of the Ge-D4R units in ITQ-13 was revealed by two-dimensional (2D) 29Si{19F} HETCOR NMR spectroscopy. With the help of theoretical calculations on the 19F and 29Si NMR chemical shifts, six types of D4R units were determined. The formation of the specific D4R unit confirms the structural directing roles of Ge atom and F ions in the formation of the D4R units in zeolite framework. The identification of the SiOSi bonds in the D4R units that connects the layers of ITQ-13 framework provided rationale for the high stability of the ITQ-13 in the degermanation treatment.

Roles of texture and acidity of acid-activated sepiolite catalysts in gas-phase catalytic dehydration of glycerol to acrolein

In the search for novel solid acid catalysts for the gas-phase catalytic dehydration of glycerol to acrolein, sepiolite clay minerals were activated with hydrochloric acid to produce acid-activated sepiolite catalysts. The effects of the activation process on the texture and acidity of acid-activated sepiolite, and their roles in gas-phase catalytic dehydration of glycerol to acrolein, were then investigated. A series of acid-activated sepiolite catalysts were made from purified natural sepiolite treated with hydrochloric acid of different concentrations (0–8mol/L) at 80°C, followed by drying at 100°C. The acid-activated sepiolite catalyst samples were characterized using X-ray diffraction, X-ray fluorescence analysis, scanning electronic microscopy, thermogravimetric analysis, N2 adsorption-desorption isotherms, NH3-temperature-programmed desorption. Fourier transform-infrared spectroscopy and pyridine adsorption followed by in situ infrared spectroscopy. The catalytic performances in gas-phase catalytic dehydration of glycerol to acrolein were studied using a vertical fixed-bed reactor. Typically, a glycerol conversion of 92.9%, an acrolein selectivity of 59.4%, and a yield of acrolein of 55.2% were achieved when the gas-phase catalytic dehydration of glycerol was conducted over HCl (2mol/L) acid-activated sepiolite catalyst at 320°C with an aqueous glycerol solution (20wt.%) at a rate of 0.10ml/min as the feedstock and air as the carrier gas at a flow rate of 20ml/min. The activation of the sepiolite with hydrochloric acid followed by drying can eliminate a portion of the zeolitic water in the tunnels, remove part of the magnesium and aluminum cations in the octahedral sheets of sepiolite, unbundle aggregated sepiolite fibers, and partly break the Si-O-Si in the tetrahedral sheets of sepiolite. These factors increased the porosity, the specific surface area and the acidity of the sepiolite. The partial leaching of magnesium and aluminum ions in the octahedral sheet generated octahedral vacancies and created MgOAl+ sites in the octahedral sheets, thereby increasing the amount of Lewis acid sites. Along with penetration of H+ cations into the interlayered space of the sepiolite by an ion-exchange reaction and physicochemical surface adsorption, some breakage of the SiOSi bonds in the tetrahedral sheets generated more SiOH+, thus increasing the quantity of Brønsted acid sites. Furthermore, the strength of acidity of the hydrochloric acid-activated sepiolite was significantly changed after the acid activation. The medium-strong Brønsted acid sites (SiOH+ and H+ adsorbed on the surface) appeared to be beneficial for the high conversion of glycerol and the selectivity to acrolein. Lewis acid sites could facilitate the formation of acetol. Under the reaction conditions mentioned above, the coking on the hydrochloric acid-activated sepiolite catalysts readily occurred, rapidly leading to the decrease of the yield of acrolein.

From illite/smectite clay to mesoporous silicate adsorbent for efficient removal of chlortetracycline from water

A series of mesoporous silicate adsorbents with superior adsorption performance for hazardous chlortetracycline (CTC) were sucessfully prepared via a facile one-pot hydrothermal reaction using low-cost illite/smectite (IS) clay, sodium silicate and magnesium sulfate as the starting materials. In this process, IS clay was “teared up” and then “rebuilt” as new porous silicate adsorbent with high specific surface area of 363.52m2/g (about 8.7 folds higher than that of IS clay) and very negative Zeta potential (−34.5mV). The inert SiOSi (Mg, Al) bonds in crystal framework of IS were broken to form Si(Al) O− groups with good adsorption activity, which greatly increased the adsorption sites served for holding much CTC molecules. Systematic evaluation on adsorption properties reveals the optimal silicate adsorbent can adsorb 408.81mg/g of CTC (only 159.7mg/g for raw IS clay) and remove 99.3% (only 46.5% for raw IS clay) of CTC from 100mg/L initial solution (pH3.51; adsorption temperature 30°C; adsorbent dosage, 3g/L). The adsorption behaviors of CTC onto the adsorbent follows the Langmuir isotherm model, Temkin equation and pseudo second-order kinetic model. The mesopore adsorption, electrostatic attraction and chemical association mainly contribute to the enhanced adsorption properties. As a whole, the high-efficient silicate adsorbent could be candidates to remove CTC from the wastewater with high amounts of CTC.

Tunable synthesis of hierarchical mesoporous silica via porogen-carrying organosilicates

We describe the synthesis and characterization of hierarchically porous organic-inorganic hybrid silica with periodic 2-D hexagonal order and tunable location of secondary nanopores through co-condensation of tetraethylorthosilicate (TEOS) and a new type of amphiphilic organosilicate precursors. Our amphiphilic organosilicates offer unique tunability of secondary micropores by carefully controlled bond molecular structure and number of bonds between hydrophobic adamantylphenols pore-generating moieties and siloxane precursors. Small angle X-ray scattering (SAXS) and microscopy results show a good structural order of the organic-inorganic hybrid silica. In addition, 29Si CP-MAS NMR spectra confirm the successful incorporation of organosilicate precursors into a silica framework. The primary cylindrical mesopores (∼6.4 nm) were originated from the cooperative self-assembly of Pluronic P123 triblock copolymer templates while smaller meso-/micropores were derived from adamantylphenols groups. We have previously demonstrated that adam-graft SQ had an affinity for hydrophobic PO core blocks to be located close to PO segment, which resulted in small pores next to primary mesopores and the resultant increment of mesopore size as well as wrinkled silica walls. On the contrary, the secondary small pores were mainly generated within a silica network while the size of the primary mesopores unaffected with the addition of adam-bridge SQ due to its selective incorporation into a silica framework. Moreover, the organic-inorganic hybrid silica prepared with adam-bridge SQ showed higher thermal stability than that of adam-graft SQ and SBA-15 type mesoporous silica. It is attributed to more SiOSi bonds formed from the bridged structure as well as enhanced hydrogen-bonding interaction between adam-bridge SQ hybrid silica and P123 templates.

Delamination of bonding Interface between benzocyclobutene (BCB) and silicon dioxide/silicon nitride

BCB is emerging as an attractive bonding adhesive for wafer bonding in 3-D integration. Although the bonding strength of BCB is satisfactory with the assist of adhesion promoter, it is found that BCB suffers from interface delamination in harsh chemical or thermal conditions. This paper proposes, at chemical bond level, that the mechanism of interface delamination in KOH solution is attributed to the decomposition of SiOSi bonds at the interface between substrates and AP3000 adhesion promoter as a result of hydrolysis. Silicon dioxide and silicon nitride films with various densities of SiH and SiN bonds are prepared, and the bond densities are measured using infrared spectroscopy. The corresponding interface delamination rates of these films and BCB in KOH solution are measured, and the relations between the bond densities and the delamination rates are obtained for silicon dioxide and silicon nitride. It shows that the delamination rates decrease with the increase in the densities of SiOSi. These results demonstrate that the decomposition of SiOSi in KOH is the main reason for BCB delamination, and increase in the density of SiOSi improves the bonding strength.

From naturally low-grade palygorskite to hybrid silicate adsorbent for efficient capture of Cu(II) ions

A new eco-friendly hybrid Mg, Al-silicate adsorbent with superior adsorption properties for Cu(II) was prepared by a one-step hydrothermal process using earth-abundant low-grade palygorskite (PAL) as the starting materials and non-toxic sodium carbonate as the assistant. The structural characterizations by scanning electronic microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), BET adsorption-desorption isotherms and Zeta potential analyses confirm that part of rod-like PAL crystals were in-situ transformed as smectite sheets, and the hybrid silicate adsorbents with rod/sheet transition formulation were formed. Under the action of alkaline, some inert SiOSi(or M) bonds were broken as –Si–O− groups, which not only make the adsorbent having extremely negative surface charge (−46.4mV), but also strengthen the chelating and holding capability of the adsorbent to Cu(II). The silicate adsorbent shows high adsorption capacity of 229.9mg/g for Cu(II), which can capture 98.95% of Cu(II) from 200mg/L of Cu(II) solution at the dosage of 2.6g/L (only 64.5% for raw PAL). The intensified electrostatic attraction, ion-exchange, and chemical association of Si-O− surface groups with Cu(II) primarily contribute to the improved capture capability for Cu(II).

Microstructure and electrochemical behavior of cerium conversion coating modified with silane agent on magnesium substrates

The cerium conversion coating with and without different concentrations of silane agent bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) modification is obtained on magnesium alloys. Detailed properties of the coatings and the role of BTESPT as an additive are studied and followed with careful discussion. The coating morphology, wettability, chemical composition and corrosion resistance are characterized by scanning electronic microscope (SEM), water contact-angle, X-ray photoelectron spectroscopy (XPS), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of the coatings is investigated using EIS. The results indicate that the coating morphology and composition can be controlled by changing silane concentration. The combination of cerium ions and silane molecules could promote the formation of more homogenous and higher hydrophobic coating. The coating turns to be more compact and the adhesive strength between the coating and the magnesium substrate are strongly improved with the formation of SiOSi and SiOM chemical bonds. The optimum corrosion resistance of the coating in the corrosive media is obtained by 25mlL−1 BTESPT modification. This whole study implies that the cerium conversion coating modified with certain silane agent deserves cautiousness before its application for corrosion resistance.

Effect of 750 keV Argon ion irradiation on nc ZnO[sbnd]SiOx thin films

Nanocomposite (nc) ZnOSiOx thin films were grown using rf magnetron sputter deposition technique and post-deposition annealing at 750°C. These films were irradiated with 750keV Argon ions at fluences in the range from 1×1015 to 1×1017ions/cm2, using Low Energy Ion Beam Facility (LEIBF) at IUAC. X-ray diffraction (XRD) patterns of the as-deposited irradiated films show decrease in intensity of ZnO peaks relative to pristine film. Fourier transform infrared (FT-IR) spectroscopy measurements of the as-deposited irradiated films indicate the breakage of ZnO, ZnOSi and SiOSi bonds in them, which is substantiated by FT-IR measurements of 750°C annealed films that were irradiated at a fluence of 1016ions/cm2. Photoluminescence (PL) measurements show drastic decrease of visible PL emission from as-deposited irradiated films. Current−Voltage (I–V) measurements show decrease in surface resistance of irradiated films by three orders of magnitude. The results suggest that 750keV argon ion irradiation of nc ZnO−SiOx films has resulted in the formation of non-radiative defects in ZnO phase and damage in SiOx, and amorphization in Zinc silicate phase. These results are explained on the basis of the dominant energy loss mechanism of low energy ions in materials.

Tailoring the metal introduction sequence onto mesostructured silica nanoparticles framework: Effect on physicochemical properties and photoactivity

Cu with variable weight loading (1–5wt%) was introduced to 5wt% Zn mixed mesostructured silica nanoparticles (MSN) via an electrochemical method to synthesize CuO–ZnO/MSN (C-ZM) catalysts. The physicochemical properties of the catalysts were characterized by XRD, FTIR, XPS, N2 adsorption–desorption, ESR, and cyclic voltammetry. 3wt% Cu and 5wt% Zn were also introduced alternately to MSN (3C-ZM and Z-3CM) to study the metal introduction sequence effect on the properties and catalytic activity. The characterization data showed that an altered arrangement of the silica network was observed with a different structure, particularly in the numbers of SiOSi, SiOZn, and SiOCu bonds as well as oxygen vacancies. The catalytic activity regarding the photodecolorization of methyl orange (MO) was in the following order: 3C-ZM>5C-ZM>Z-3CM>1C-ZM. The higher numbers of SiOZn, oxygen vacancies, and the higher pore volume of the 3C-ZM catalyst seemeed to be the main factors behind its higher photoactivity compared to the other catalysts. Further optimization by response surface methodology (RSM) with a central composite design (CCD) model was performed for the decolorization of MO. RSM demonstrated that the experimental value (99.89%) was reasonably close to the predicted value (99.99%) with only 0.1% error for MO decolorization at pH 3.5 using 1.6gL−1 catalyst with 4wt% Cu loading.