One‐step synthesis of ordered Sn‐substituted SBA‐16 mesoporous materials using prepared silica source of rice husk and their selectively catalytic activity

Highly ordered SBA‐16 silica mesoporous materials were synthesised hydro‐solvothermally under the acidic medium using SiO₂/F127/BuOH/HCl/H₂O gel. Pure SiO₂ powders were prepared from inexpensive and environmentally friendly silica source of rice husk. The pore size of the materials could be optimised by using a blend of P123 and F127 templates. Sn‐substituted SBA‐16 mesoporous materials were yielded via the direct injection of stannic chloride into the fixed gel in acidic medium. X‐ray diffraction, N₂ adsorption, scanning electron microscope/transmission electron microscope results suggest that tin ions were incorporated into the Si‐SBA‐16 framework by isomorphous substitution between Sn and Si ions. Elemental analysis indicates that tin can be substituted in the range of Si/Sn = 21.4–10.5. UV–vis, XPS, TPR‐H₂, TPD‐NH₃ results reveal that tin atoms are highly dispersed in 4+ oxidation state and mostly occupy in the silica framework. The degree of tin incorporation into silica framework can easily be controlled by a simply adjustment of the H₂O and HCl molar ratios. The mesoporous Sn‐SBA‐16 materials were an active benzylation catalyst with almost 100% selectivity to monoalkylated product in alkylation of aromatics with benzyl chloride. © 2011 Canadian Society for Chemical Engineering     

Influence of water addition on the structure of plasma-deposited allyl alcohol polymer films

One hundred and fifty nanometre thick polymer films made of allyl alcohol and H₂O addition were deposited onto aluminium substrates using the radio-frequency (rf) pulsed plasma mode. The structure–property relationships of polymer films were studied in dependence on the precursor ratio allyl alcohol-water. Both the regularity of structure and composition of such thin films in comparison to chemically polymerized allyl alcohol were investigated using by bulk-sensitive Fourier transform infrared spectroscopy (FTIR) in the spectral range of 4000–500 cm^?1 as well as surface-sensitive X-ray photoelectron spectroscopy (XPS). The intention of this work was to increase the yield in OH groups by addition of water to the allyl alcohol precursor. For an unambiguous identification of the functionality of the deposited films, the OH groups were labelled with trifluoroacetic anhydride and subsequently measured by XPS as well as quantitatively by FTIR. As expected, the O/C ratio grew with increasing water admixture by oxidation of both the plasma polymerized allyl alcohol layer to preferably aldehyde and/or carboxylic acid groups. In contrary, the concentration of OH groups in the deposited polymer film decreases dramatically with increasing admixture of water to the allyl alcohol plasma. It has been shown that the additional water has produced preferably higher oxidized C-O_x species with two or three C–O bonds. This fits also very well with the observation that almost no deuterium is introduced into the surface of plasma polymer if D₂O was added instead of H₂O.     

Surface modification of ABS by photocatalytic treatment for electroless copper plating

Surface roughness of acrylonitrile–butadiene–styrene (ABS) resin prior to metallization is treated generally with sulphuric/chromic acid system. However, the presence of chrominum (VI) ion imposes serious environmental problems. In this work, TiO₂ photocatalytic treatment was used to enhance the adhesion strength between the ABS surface and the electroless copper film. Effects of the TiO₂ content, irradiation time and UV power upon the surface topography, surface characterization and the adhesion strength were investigated. The results indicated that the surface hydrophilicity of ABS resin and the adhesion strength between the electroless copper film and ABS surface increased with an increase in the UV power and a prolongation in irradiation time, and did not increase linearly with an increase of TiO₂ content. Though the surface topography of ABS changed little, the adhesion strength reached 1.25?kN/m, which was higher than that in the optimal H₂SO₄–MnO₂ colloid. The surface chemistry results indicated that –COOH and –OH groups formed with the photocatalytic treatment and the absorption strengths increased with the UV power. XPS analysis results further demonstrated that the contents of C=O and –COOH reached 6.4 and 4.9% with the photocatalytic treatment, which was much higher than that of the H₂SO₄–MnO₂ colloid (3.9 and 3.1%). The high contents of C=O and –COOH groups enhanced the surface hydrophilicity of the ABS resin and improved the adhesion strength between the electroless copper film and ABS resin. The results indicated that the photocatalytic treatment was an environment-friendly and effective method to replace the commercial wet chemical process for ABS surface modification.     

Combined XPS and TPD study of oxygen-functionalized carbon nanofibers grown on sintered metal fibers

A composite material consisting of carbon nanofibers (CNFs) grown on sintered metal fiber filters was modified by H₂O₂ or plasma-generated O₃. Coupling temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) techniques in the same UHV apparatus allowed the direct correlation of the nature of the created O-functional groups and their evolution as CO and CO₂ upon heating. The two oxidative treatments yielded different distributions of O-containing groups. The relative contribution of oxidized carbon was very low in the C1s region, hence the functional groups were more robustly analyzed through the O1s region. The comparison of the released oxygen by integration of the TPD CO, CO₂ and H₂O spectra with the intensity loss of the XPS O1s spectra showed good agreement. In order to fit the data adequately, the set of O1s spectra was deconvoluted in at least four peaks for the differently activated samples. Finally, it was shown that functional groups formed by H₂O₂-treatment (mostly non-phenolic OH groups) are more thermally stable than those formed by O₃-treatment. The latter treatment increases the concentration of carboxylic functionalities, which decompose at temperatures < 800 K; O₃-activated CNFs should therefore show a more pronounced acidic behavior.     

New route to the preparation of carboxymethylchitosan hydrogels

A new method to prepare CM–chitosan hydrogels was introduced with the use of steam. The procedure was simple and economical, with no toxic chemicals involved. The steam‐induced crosslinking of CM–chitosan sodium salt involved the –NH₂ and –COONa groups, forming amide linkages (–CONH–), evidently supported by FTIR spectroscopy and other techniques. The hydrogels instantly imbibed a great deal of water. The degree of swelling (DS) of the hydrogels was found to be up to 36, depending on the harshness of steaming conditions used. Likewise, the coloration of the samples increased from light beige to brown with increasing temperature and duration of steam exposure. The overall efficiency of the steam method for the crosslinking of CM–chitosan sodium salt was quite high. The percentage weight loss was found to be less than 10 to obtain hydrogels with DS values around 20. No weight loss in the dry weight of the fractionated hydrogels was observed when the samples were steamed at 115°C or higher for 15 min or longer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4016–4020, 2003     

Treatment of PET nonwoven with a water vapor or carbon dioxide plasma

Gas plasma treatment of poly(ethylene terephthalate) nonwoven (NW–PET) was used to increase the hydrophilicity of single‐ and multilayer NW–PET. NW–PET was treated with a pulsatile CO₂ or with a pulsatile H₂O glow discharge. X‐ray photoelectron spectroscopy (XPS) showed significantly more oxygen with CO₂ glow‐discharge‐treated NW–PET than with H₂O glow‐discharge‐treated‐NW–PET surfaces. Moreover, the introduction rate of oxygen at a single layer of NW–PET was higher for a CO₂ than for a H₂O glow‐discharge treatment. Titration data revealed significantly higher surface concentrations of carboxylic groups for CO₂ glow‐discharge NW–PET than for H₂O glow‐discharge‐treated NW–PET. Mass spectrometry analysis revealed that the entire internal surface of a single layer of NW–PET was modified. XPS and contact measurements confirmed the modification of the internal surface of multilayers of NW–PET. H₂O and CO₂ glow‐discharge‐treated substrates consisting of six layers of NW–PET had a nonuniform surface concentration of carboxylic acid groups as determined with titration experiments. The outside layers of the substrate contained a higher surface concentration of carboxylic acid groups than did the inside layers. XPS analysis and titration data showed that the rinsing of H₂O and CO₂ glow‐discharge‐treated NW–PET with water changed the surface composition considerably. Part of the carboxylic acid group‐containing species were washed off. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 480–494, 2000     

Structure and in vivo anticalcification properties of a polymeric calcium–sodium–phosphocitrate organic–inorganic hybrid

This paper describes the synthesis, characterization and crystal structure of an organic–inorganic polymeric hybrid composed of Ca, Na, and phosphocitrate (CaNaPC). CaNaPC is synthesized by reaction of CaCl₂·2H₂O and Na₄(HPC)·3H₂O in water, at pH 2. Its structure is polymeric with Ca(PC)₂(H₂O) “monomers” connected through Na⁺ bridges. The 9-coordinate Ca occupies the center of an irregular polyhedron defined by four phosphate, four carbonyl, and one H₂O oxygens. CaO(C) distances are in the 2.446(2)–2.586(2) Å range. There is a short distance of 2.477(1) Å between Ca and the ester O from C–O–PO₃H₂. All –COOH groups are protonated. There are three dissociated protons per two PC molecules, all coming from –PO₃H₂. Na ions are six-coordinate surrounded by –COOH’s. The anticalcification properties of CaNaPC on plaque growth were studied in vivo using rats as model systems. Na–phosphocitrate is an effective inhibitor, but its effectiveness diminishes when a lower dose is used (9.7 mg as H₅PC), resulting in only 30% plaque reduction. Superior inhibition activity becomes evident by following treatment with CaNaPC, at an equal dose (9.6 mg as H₅PC) giving nearly quantitative (95%) plaque inhibition.     

Effect of salts on soy storage proteins defatted with supercritical CO2 and alcohols

The primary objective was to determine whether salts will stabilize soy storage proteins against the denaturing effects of alcohols or the heat and pressure used in supercritical CO₂ during the defatting process. Nitrogen solubility index (NSI) and differential scanning calorimetry (DSC) were used to monitor the denaturation of proteins. A variety of salt solutions used to hydrate full-fat soy grits increased the thermal stability of both 7S and 11S storage proteins. DSC was used to monitor their denaturation temperature. Neutral salt hydrations followed the lyotropic series for protein stabilization. Of the salts evaluated, the test results indicate that the reducing salt, sodium sulfite, and the neutral salt, sodium sulfate, when used to steep beans, yielded significantly higher NSI than did the water-steeped controls or other salt treatments after partial defatting with absolute isopropanol or ethanol and supercritical CO₂. However, these same salt treatments did not as effectively stabilize the proteins against the denaturing effects of ethanol more aqueous than 84% when these alcohols were used as the defatting medium.     

Reduction of solubilized multi-walled carbon nanotubes

In this paper, the chemical reduction of solubilized multi-walled carbon nanotubes by LiAlH₄ was investigated. The amide groups on the nanotubes could be reduced to hydroxyl groups, which was confirmed by FTIR and XPS studies. The Raman spectroscopic investigation showed that the morphology of the nanotubes did not change after the reduction.     

Synthesis and thermal stability properties of boron‐doped silicone resin

In this article, a novel boron‐doped silicone resin (BSR) was synthesized by hydrolysis‐polycondensation method, with propyl‐triethoxysilane (PTES), dimethyl‐diethoxysilane (DMDES), and boric acid (BA) as starting materials, using absolute ethyl alcohol as solvent and hydrochloric acid as catalyst. The structures of the BSR were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X‐ray photoelectron spectroscopy (XPS), and gel permeation chromatography (GPC). FTIR spectra showed characteristic B? O? Si and Si? O? Si stretching modes. XPS and NMR results confirmed further that boron element was doped successfully into the main chains of the silicone resin as Si? O? B bond motifs, and hydroxyl groups from BA were condensed properly with Si? OH or Si? OR to form cross‐linked structure of BSR with narrowed molecular weight distributions in optimum experimental condition. The thermal stability of the BSR was studied by thermogravimetry analysis and derivative thermogravimetry. The thermal degradation temperature of the silicone resin improved greatly after doping element boron into the main chain, and the thermal stability of the BSR was influenced by the content of boron. The thermal degradation mechanism of this BSR was also discussed. The degradation process can be divided into two stages, the weight loss in the first stages may be corresponding to the loss of the small groups and weaker bonds in the chains, such as ? CH₃, and ? C₃H₇, the weight loss in the second stage may be corresponding to the loss of the group as ? OC₂H₅. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40934.     

The influence of fuel type on carbon deposition over precious metal containing motorcycle catalysts

The influence of fuel type on carbon deposition over precious metal containing motorcycle catalysts was studied by SEM, EPMA, XPS, TG-DTA and FTIR. The results show that the carbonaceous species are in the form of C_xH_y if the vehicle is fueled with MTBE blended gasoline, whereas the carbonaceous species are C_xH_yO for blended ethanol fuel. The majority of the carbonaceous species are deposited on the PM sites. Further, aromatic rings, alkyl groups and their partial oxidation products are found in the carbonaceous deposit.     

Crystallinity and surface state of cellulose in wet ball‐milling process

We report the effect of wet ball‐milling process under mild neutral salt conditions on the alteration of crystallinity and surface state of microcrystalline cellulose (MC). The ball‐milling experiments were performed when the MC was immersed in H₂O, NaCl aqueous solution, and KCl aqueous solution. Two collation groups, i.e., MC immersed in H₂O₂ and nonimmersed MC were additionally investigated for comparison. Except when H₂O₂ was present, the highest decrease in the cellulose crystallinity index (CI) was observed in dilute KCl. On the other hand, the CI of wet‐milled MC/NaCl was greater than that of the wet‐milled MC/H₂O, however, still lower than that of the non‐immersed MC. XPS results showed that the carbonization progressed in dry‐milled MC and wet‐milled MC/NaCl surfaces. Though, the surface oxidization progressed in wet‐milled MC/H₂O and wet‐milled MC/KCl. Lastly, the ball‐milling processes in different solutions led to various decreases of the crystallinity and the surface degradation due to carbonization and/or oxidization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44903.     

Functional biodegradable protein-based matrices as a potential candidate for micronutrients and water supply

The excessive use of fertilizers in horticulture applications generates subsoil and groundwater contamination due to their high solubility. A possible solution to this problem is the incorporation of nutrients in biodegradable matrices, allowing nutrients to be released in a controlled manner depending on the needs of the crops. The principal objective of this work was the evaluation of the incorporation of different salts into soy protein-based matrices to develop devices that could release micronutrients in a controlled manner. Thus, the processability of matrices with different incorporated salts such as zinc sulfate heptahydrate (ZnSO₄·7H₂O), zinc sulfate monohydrate (ZnSO₄·H₂O), zinc carbonate (ZnCO₃), and zinc perchlorate (Zn(ClO₃)₂), as well as their integrity and functionality have been evaluated. Results show the great potential of soy protein-based matrices for the incorporation of micronutrients such as zinc. However, salt incorporation has a detrimental effect on the water uptake capacity of the matrices.     

Preparation of shish‐kebab and nanofiber polyethylene with chromium/Santa Barbara amorphous silica‐15 catalysts

Cr/SBA‐15 catalysts were prepared by the grafting of chromium nitrate nonahydrate [Cr(NO₃)₃·9H₂O] complexes onto SBA‐15 mesoporous materials. Shish‐kebab and nanofiber polyethylenes (PEs) were prepared under different temperatures via ethylene extrusion polymerization with the Cr(NO₃)₃·9H₂O catalytic system. The diameter of a single nanofiber was 100–250 nm. Scanning electron microscopy images showed that the polymer obtained from the SBA‐15‐supported catalyst under different polymerization temperatures produced nanofiber and/or shish‐kebab morphologies. X‐ray diffraction and differential scanning calorimetry were used to characterize microstructures of the materials. Polymers obtained with all of the catalysts showed a melting temperature, bulk density, and high load melt index; this indicated the formation of linear high‐density PE. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Magnesium chloride precipitation from mixed salt solution using 1,4-dioxan

This paper deals with the preparation of magnesium chloride hydrate from a mixed salt solution containing, besides MgCl₂, substantial quantities of undesired substances such as alkali metal chlorides and magnesium sulphate. Magnesium chloride extraction was done using dioxan. In particular, it was found that this salt precipitate as the ternary compound MgCl₂·6H₂O·C₄H₈O₂. Reaction equilibrium is reached after 40 min. It was shown that solid phase MgCl₂·6H₂O·C₄H₈O₂ conversion into MgCl₂·6H₂O is feasible by a drying carried out at constant temperature chosen in the range (70-110 °C). Physico-chemical properties of the final product are determined using XRD, complexometry, potentiometry, gravimetry and FAAS. Prepared MgCl₂·6H₂O purity is upper than 99%. Its X-ray diffractogram is impurity free.     

Effect of Na2O on the High‐Temperature Thermal Conductivity and Structure of Na2O–B2O3 Melts

The effect of Na₂O and temperature on the thermal conductivity of the Na₂O–B₂O₃ binary system has been measured using the hot‐wire method to examine the relationship between the thermal conductivity and structure in high‐temperature melts. The thermal conductivity of the binary melt is measured from 1173 to 1473 K in the fully liquid state. The thermal conductivity slightly increases with Na₂O content up to 20 wt%. Above 20 wt% Na₂O, the thermal conductivity decreases with increasing Na₂O. The network structure of molten glass was analyzed using Fourier transform infrared (FTIR), Raman spectroscopy, and XPS. The FTIR analysis shows that 3‐D complex borate structures, such as tri‐, tetra‐, and pentaborate are made by [BO₄] tetrahedral units interconnected with 2‐D structure boroxol rings in the low Na₂O region. Above 20 wt% Na₂O content, nonbridged oxygen in [BO₂O^?] units and diborate groups increase with increase in Na₂O. The same tendency is shown by the Raman spectroscopy and XPS analyses. The Raman analysis shows that boroxol rings disappeared with large [BO₄] groups, such as tri‐, tetra‐, and pentaborate structures, which increase at low Na₂O content. Isolated diborate groups and nonbridged oxygen in [BO₂O^?] units increase at high Na₂O content. It can be inferred that single structure units, such as isolated diborate groups, interfere with conduction. The XPS analysis results show that free oxygen produced by the interconnection of Na₂O in the borate structure does not cause significant changes to O^2? in the low Na₂O region, but increases the O^o and decreases the O^?. Above 20 wt% Na₂O, O^? slightly increases and O^o shows a decreasing trend.     

HYDROTHERMAL SYNTHESIS AND ION EXCHANGE PROPERTIES OF THE NOVEL FRAMEWORK SODIUM AND POTASSIUM NIOBIUM SILICATES

ABSTRACT

Two novel metastable sodium niobium silicates of the empirical formula: Na_l+x?yH_y(Nb_1?xSi_x)O₃ nH₂O, where x=0.33?0.38, y<l+x, n=0,7-l.l (NbSi-Na, 6.0 Å phase), and Na_3-x H_xNb₃Si₂O₁₃ nH₂O, where x<1.5, n=2.5?3.5 (NbSi-Na, 12.6 Å phase), and two novel potassium niobium silicates: K_4?xH_xNb₄SijO₂₂nH₂O, where x<l, n=3.5-4.0 (NbSi-K., 10.0 Å phase), and K_1?xH_xNbSi₄O₁₁nH₂O, where x<0.2, n=0.4-0.5 (NbSi-K, 6.05 Å phase), were synthesized in the homogeneous alkaline reaction system NbCl₅ - SiO₂ - NaOH (KOH) -H₂O₂ - H₂O under mild hydrothermal conditions. The compounds were characterized by elemental analysis, FTIR, TGA, MAS ²⁹Si NMR and X-ray diffraction. It was found that alkali metal niobium silicates have open framework structures. Their ion exchange affinity towards alkali, alkaline earth and some transition metal ions was studied. All alkali metal niobium silicates are moderately acidic ion exchangers. Both sodium niobium silicates show a distinct affinity for Cs⁺ ion among alkali metal ions, whereas potassium niobium silicate, the NbSi-K, 10.0 Å phase, exhibits affinity for Rb⁺ ion. The affinity of the sodium niobium silicate, NbSi-Na, 6.0 Å, toward strontium ion in neutral solutions is equal or superior to the best Sr-selective inorganic ion exchangers. The sodium niobium silicate (NbSi-Na, 12.6 Å phase) exhibits extremely high affinity for Pb²⁺ ion in acidic and neutral media, and both sodium niobium silicates also show a moderate affinity for Hg²⁺ ion in neutral and highly alkaline media. These exchangers could be promising for the treatment of some specific nuclear waste and contaminated environmental and biological liquors containing lead, mercury and radioactive strontium.     

Square-planar nickel(II) complexes with a tridentate Schiff base and monodentate heterocycles: self-assembly to dimeric and one-dimensional array via hydrogen bonding

Two nickel(II) complexes having the general formula [Ni(bhac)L] with tridentate ONO-donor acetylacetone benzoylhydrazone (H₂bhac) and monodentate N-donor heterocycles (L=3,5-dimethylpyrazole (Hdmpz) and imidazole (Himdz)) are reported. The complexes were synthesized in ethanol media by reacting Ni(O₂CCH₃)₂·4H₂O, H₂bhac and L in 1:1:1 mole ratio and characterized by analytical, magnetic and spectroscopic methods. X-ray crystal structures of both complexes have been determined. In each complex, the metal ion is in square-planar N₂O₂ coordination geometry. In the solid state, a one-dimensional assembly of the [Ni(bhac)(Himdz)] molecules is formed via intermolecular hydrogen bonds between the imidazole N–H groups and the uncoordinated N-atoms of the deprotonated amide functionalities. On the other hand, two [Ni(bhac)(Hdmpz)] molecules are involved in a pair of complementary hydrogen bonds between the pyrazole N–H groups and the coordinated O-atoms of the deprotonated amide functionalities forming a dinuclear species.     

A facile pot synthesis of (Ti3AlC2) MAX phase and its derived MXene (Ti3C2Tx)

Various processing techniques reported in the literature for synthesizing the Ti₃AlC₂ MAX phase involve high calcination temperature, expensive equipment, and inert environmental requirement. Here, we report a cost-effective, solid-state, single-step synthesis route of the Ti₃AlC₂ MAX phase. Optimizing the stoichiometry of the precursors and controlling the thermal treatment, the desired MAX phase has been attained, as confirmed by XRD analysis. Further, Ti₃C₂T_x (where, T_x: O, OH, F functional groups) MXene was prepared from this one-pot synthesized MAX phase. FESEM, TEM, and Raman spectroscopy were used to ensure that the hexagonal structure of the MAX phase was retained in as-synthesized MXene. Further, XPS was employed to detect the presence of surface functional groups (-O, –OH, and –F) on the MXene surface. UV–vis spectroscopy shows a strong absorption peak in the NIR region.     

Hydrogen production from CO2 reforming of methane over high pressure H2O2 modified different semi-cokes

H₂O₂ was used under different temperatures and pressures to activate three kinds of different semi-cokes. FTIR, BET, SEM and Boehm titration were used to analyze properties of the semi-cokes surfaces, finding that catalytic activities of these semi-cokes after modification by high temperature and high pressure H₂O₂ were improved. FTIR shows that the characteristic infrared absorption peak of functional groups on the semi-cokes surface does not change, but the absorption peak intensity of some functional groups is increased. The strength of OH absorption peak of Hongce lignite (HCL) semi-coke at 3444 cm⁻¹, carboxyl CO at 1598 cm⁻¹, aliphatic ether, cyclic ether and other organic functional groups at 1023 cm⁻¹ in the modified Shenmu bituminous(SMB) semi-coke and Jincheng anthracite (JCA) semi-coke are increased significantly. BET finds that the specific surface area and pore volume of three semi-cokes are increased after modification. Boehm titration shows that the basic functional group content in semi-coke is increased after modification, and the net alkali content is increased significantly. Compared with the raw semi-coke, SEM shows that the surface of semi-coke modified with H₂O₂ becomes rough. Modified JCA semi-coke surface pitted with holes, modified HCL and SMB semi-coke surface present porous.