Inorganic Polycondensation Research Articles

Mesoporous crystalline Ti1-xSnxO2 (0 < x < 1) solid solution for a high-performance photocatalyst under visible light irradiation.

We report a facile and effective inorganic polycondensation combined with aerosol-spray strategy towards high-performance photocatalyst by fabricating mesoporous Ti1-xSnxO2 (0 < x < 1) solid solution. Such Ti1-xSnxO2 nanocrystals with high Sn-doped contents are self-assembled into mesoporous spheres can effectively promote visible-light harvest and high quantum yield, leading a longer lifetime of the photoelectron-hole pairs and less recombination. Such the photocatalysts enhanced photocatalytic activity for the degradation of Rhodamine B (RhB). The representative Ti0.9Sn0.1O2 and Ti0.8Sn0.2O2 compounds reach an optimum degradation of ≈50% and 70%, respectively, after 120min irradiation under visible irradiation. The mesoporous Ti1-xSnxO2 solid solution could inhibit the recombination of electron-hole pairs, which promote reaction thermodynamics and kinetics for RhB degradation.

Hybrid Epoxy-Alkyl Sol-Gel Coatings Reinforced with SiO2 Nanoparticles for Corrosion Protection of Anodized AZ31B Mg Alloy.

AZ31B Mg alloys were anodized at different potentials using an alkaline electrolyte. Then, an epoxy-alkyl silane sol reinforced with SiO2 nanoparticles was prepared by sol–gel and deposited on top of the optimized anodic layers. 1-Methyl imidazole was added to the sol to promote a partial epoxy ring aperture and improve the condensation degree of the inorganic network. The results showed the curing temperature affects the inorganic polycondensation of the organic-inorganic network; this effect was analyzed by 29Si and 13C solid-state NMR spectroscopy. Electrochemical impedance spectroscopy in 3.5 wt% NaCl solution revealed that the corrosion resistance is enhanced by the anodized process obtained for Mg alloy anodized at 100 V/2 min. However, a quick deterioration of the oxide film with immersion time was evident, showing a reduction of the protection efficiency (ηE%) of 76.5% after 16 h/immersion. The deposition of an epoxy-alkyl coating improved the ηE% up to 98.6% after 72 h/immersion. The proposed hybrid coating used for post-sealing the porous anodized Mg alloy looks like a good alternative protective barrier to control the corrosion process of Mg alloys. A suitable compromise between cross-linking network and curing temperature is necessary to obtain a good barrier coating.

Comparative study on Phosphate-Powder as Partial-Replacement in conventional concrete and PrimeMaterials in GeopolymerConcrete

Phosphate is mined rock, which contains lime, silica, with high amount of phosphorus penta-oxide; this rock is pulverized and utilized for several purposes in various food industries as preservatives or used as fertilizers for crops. Due to the high carbon footprint from construction industries, so far many alternative materials have come through researchers as a cement replacement, either partially or fully. In this effort, phosphate powder (PP) was utilized (for its lime and silica present in its chemical composition) as a binder replacement in conventional mortar and one of the source material in geopolymer mortar. This paper includes the study conducted with PP as partial replacement of cement with various mix proportions. Also phosphate powder was synthesized as one of the source material in geopolymer concrete incorporated with flyash and Ground-granulated-blast-furnace-slag (GGBS) as binder material for 12-Molarity under three-combinations. In both cases, copper-slag (waste extracted from copper industry) was used as the partial replacement of fine-aggregate, and the compression behavior was compared with the control specimens. Both type of concrete under various proportions were casted and strength behavior was analyzed with microstructural studies of the optimized mix for the detailed study of the binding matrix. Specimen with 30% of PP + 35% Flyash + 35% of GGBS gave optimum results in compression result with 50% replacement of fine-aggregate with copper-slag under 12-Molarity alkaline-solution. It was found that the PP does not give desirable results under hydration process of conventional mortar. Whereas under the inorganic poly-condensation process of PP + flyash + GGBS as prime-materials gave better results under compression tests. Therefore PP has pozzolanic property and it can be activated only by adding alkaline-liquids.

Geopolymer bricks made from less active waste materials

The current study aims at investigating the production feasibility of the geopolymer bricks using the waste materials emanated from the washing process of sand and gravel in aggregate industries. Geopolymer is a material originated by inorganic polycondensation as a result of the alkali activation of aluminosilicate materials. Geopolymer bricks seem to be advantageous due to the low demand for energy and the significant incorporation of wastes. The production of geopolymers from pozzolanic or aluminosilicate rich materials is very common. However, few studies have been carried out on the less-active materials such as waste materials of aggregate industries as raw materials for producing geopolymers. For this purpose, the influence of three parameters, sodium hydroxide concentration (4, 8 and 12 M), calcium hydroxide content (5%,10%, and 15%), and curing temperature (70 °C and 105 °C), on the physical and mechanical properties of geopolymer bricks was investigated using compressive strength, SEM micrographs, XRD analysis, water absorption, and bulk density. The results indicate that higher sodium hydroxide concentration caused forming a less porous and a more amorphous microstructure, and yielded higher strengths and lower water absorption. The mixtures with higher calcium hydroxide content had higher compressive strengths (up to 75 MPa and 36 MPa at dry and wet conditions, respectively) and a more stable microstructure, however, incorporation of calcium hydroxide at levels higher than 20% results in lower compressive strengths, lower densities, and higher water absorption contents. Increasing curing temperature from 70 °C to 105 °C increased significantly the compressive strength.

Carbon dioxide sealing-based inhibition of coal spontaneous combustion: A temperature-sensitive micro-encapsulated fire-retardant foamed gel

In order to enhance the inhibition efficiency of inhibitor on spontaneous combustion of coal and optimize the grouting process of traditional foamed gel, a temperature-sensitive retardant microcapsule (TSRM) was prepared via encapsulation of polyphenols with paraffin. Using composite surfactant (CFA) as a foaming agent and Carbon dioxide (instead of the traditional N2) as the gas source, a small amount of TSRM was incorporated into the water glass solution as base material to prepare microcapsuled retardant foamed gel (CDSFG-TSRM). TSRM temperature sensitivity allows melting at 60 °C followed by the release of tea polyphenols, which extends the effective period of tea polyphenols and improves the inhibitory effect on spontaneous coal combustion. Due to the inorganic polycondensation reaction between carbon dioxide and water glass solution, the preparation process of the material reduces carbon dioxide emission as a greenhouse gas and achieves a rapid gelation process of the mixed solution without the addition of a crosslinking agent, hence simplifying the preparation process of foam gel. The combination of in-situ FTIR and TG-IR indicated that the extent of oxidation on the surface hydroxyls of the coal sample treated with CDSFG-TSRM was low and the concentration of ether bond was high. The characteristic absorption peak intensity of C–H structure and Carbon dioxide were obviously weakened, and the characteristic absorption peak of Carbon dioxide appears at a higher temperature. In addition, CDSFG-TSRM has the advantages of shorter extinguishing time, higher retardant efficiency and difficulty in re-ignition.

Functionalized superhydrophobic coatings with micro-/nanostructured ZnO particles in a sol–gel matrix

Among the methods to create superhydrophobic surfaces by wet chemistry, one of the strategies consists in coating the substrate with a hydrophobic polymer with specific morphology. Such elaborated surfaces are largely developed and can present complex architectures but are generally fragile. Ceramic-based coatings show better durability. In this work, a new route associating inorganic and polymeric parts is used. Surfaces with superhydrophobic properties are prepared with a mixture of zinc oxide (ZnO) particles in a hybrid organic inorganic matrix prepared via sol–gel route. ZnO particles were synthesized by the inorganic polycondensation route and exhibit an appropriate micro-/nanostructure for superhydrophobicity. Sol–gel matrix is obtained by the alkoxide route with aluminum-tri-sec-butoxide (ASB) and (3-glycidoxypropyl)trimethoxysilane (GPTMS). A step of octadecylphosphonic acid (ODP) functionalization on ZnO particles and on film surfaces was employed to considerably improve hydrophobic properties. This new route enables to obtain superhydrophobic coatings that exhibit water contact angles superior to 150°. These coatings show a homogeneous and smooth coverage on aluminum alloy substrate. Results attest the significance of the synergy for superhydrophobic coatings: a micro-/nanostructured surface and an intrinsic hydrophobic property of the material. The durability of the coatings has also been demonstrated with only a slight decrease in hydrophobicity after erosion.

Microstructural and optical properties of spinel oxide MxCo2 − xMnO4 (M = Ni, Zn or Cu; 0 < x < 1) thin films prepared by inorganic polycondensation and dip-coating methods

Spinel oxide nanoparticles of MxCo2−xMnO4 (M=Ni, Zn, Cu; 0<x<1) were prepared at 120°C by the inorganic polycondensation method. Phase composition and microstructure of each sample powder thus obtained were characterized by X-ray diffraction, X-ray fluorescence and scanning electron microscopy. Nanoparticles are well crystallized and uniformly distributed in both shape and size. Colloidal dispersions were stabilized in a low cost and environmentally friendly solvent solution. Spinel oxide thin films were then deposited on glass substrates by using the dip-coating technique. Their optical properties were measured in the 300–1100nm wavelength range. Thin films show extremely good absorbance in the ultra-violet and blue regions. The highest absorbance observed in the red region was for x=0.15 in zinc. A smaller direct band gap was determined when a low amount of doping M element was introduced in the cobalt and manganese spinel oxide material.

Room temperature inorganic polycondensation of oxide (Cu2O and ZnO) nanoparticles and thin films preparation by the dip-coating technique

Oxide thin solid films were prepared by dip-coating into colloidal dispersions of oxide nanoparticles stabilized at room temperature without the use of chelating or complex organic dispersing agents. Crystalline oxide nanoparticles were obtained by inorganic polycondensation and characterized by X-ray diffraction and field emission gun scanning electron microscopy. Water and ethanol synthesis and solution stabilization of oxide nanoparticle method was optimized to prepare two different structural and compositional materials, namely Cu2O and ZnO. The influence of hydrodynamic parameters over the particle shape and size is discussed. Spherical and rod shape nanoparticles were formed for Cu2O and ZnO, respectively. Isoelectric point values of 7.5 and 8.2 were determined for cuprous and zinc oxides, respectively, after zeta potential measurements. A shear thinning and thixotropic behavior was observed in both colloidal sols after peptization at pH ~6 with dilute nitric acid. Every colloidal dispersion stabilized in a low cost and environmentally friendly azeotrope solution composed of 96vol.% of ethanol with water was used for the thin film preparation by the dip-coating technique. Optical properties of the light absorber cuprous oxide and transparent zinc oxide thin solid films were characterized by means of transmittance and reflectance measurements (300–1100nm).

Foam drainage study during plateau border mineralisation

We investigate the drainage of a foaming solution during inorganic polycondensation by macroscopic measurements and local observations. We reveal an original mineralisation mechanism starting from Plateau border interfaces. This slow process is not able to counteract the destabilizing effects of foam drainage and we therefore propose a new strategy in which mineralisation is assisted by a biopolymer.

Sol–gel processes at the droplet interface: hydrous zirconia and hafnia nanocapsules by interfacial inorganic polycondensation

We report a simple method to prepare nanocapsules of hydrous zirconia and hafnia by interfacial precipitation in water-in-oil miniemulsions. We show that the sol–gel precipitation of transition metal hydroxides, exemplified for the cases of zirconium and hafnium, can be driven to the droplet interface by addition of an organic base. The prompt addition of triethylamine generates hydroxide ions at the interface, which initiate a polycondensation of the metal hydroxo species. Electron and X-ray diffractions indicate that the resulting materials are amorphous, but can be transformed to monoclinic ZrO2 or HfO2 upon thermolytic treatment. Mixed oxides of Hf and Zr with different compositions (HfxZr1−xO2) can also be formed by using the desired ratios of precursors. Furthermore, the ability of the hollow particles to encapsulate efficiently hydrophilic materials without leakage has been proven with the example of a water-soluble dye (fluorescein isothiocyanate).

Viscoelasticity and morphological modulation of silicon alkoxide-based systems by selective catalysts

We have studied the formation of three-dimensional silicon alkoxide-based network resulting from an inorganic polycondensation based on hydrolysis and condensation reactions. Using mechanical spectroscopy, small-angle X-ray scattering, and penetration measurements, we have shown that viscoelastic and morphological properties of gelling soft matter systems can be modulated according to the nature of a catalyst by modifying the rate of the hydrolysis and condensation reactions. The description of the network build up in terms of a continuous transition between three viscoelastic states leads us to obtain new information on the viscoelastic properties determined up to now only at the sol–gel transition.

TTCP-DCPA Based Calcium Phosphate Cements Containing Hybrid Microparticles as Drug Carriers

In recent years, considerable attention has been focused on the development of new composite materials for application as drug delivery systems. In this field, calcium phosphate cements (CPCs) are often employed as support to delivery of drugs, but their behavior has some drawback related to the so-called burst effect. The aim of this work was to develop new CPCs formulations from synthesized tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous TTCP and drug-containing hybrid microparticles (DCHM). The main function of these DCHM is providing nuclei of high concentration of drugs into the CPCs. The DCHM were synthesized via the sol-gel method from a bridged precursor of the type (H3CO)3 – Bridge – (OCH3)3 and aspirin (AS) as model drug. The inorganic polycondensation reached 89.5 % as calculated by 29Si NMR. The analysis by small angle X-ray scattering (SAXS) reveled a short range structural ordering in the DCHM at molecular level. Effective incorporation of AS inside the microspheres was detected by FTIR spectroscopy. In vitro tests of DCHM according to ISO 10993-5 revealed non-cytotoxic behavior. Four CPCs formulations containing 0, 1, 5 and 10 wt % of DCHM, were evaluated. The presence of DCHM did not modify neither the degree of conversion to low-crystallinity HA nor the measured setting times of the CPCs, however, the amount of incorporated microparticles considerably affected the degree of porosity (macropores of 200 µm) and interconnectivity of the cement matrix.

Individualized Silica Nanohelices and Nanotubes: Tuning Inorganic Nanostructures Using Lipidic Self-Assemblies

Diverse chiral nanometric ribbons and tubules formed by self-assembly of organic amphiphilic molecules could be transcribed to inorganic nanostructures using a novel sol-gel transcription protocol with tetraethoxysilane (TEOS) in the absence of catalyst or cosolvent. By controlling parameters such as temperature or the concentration of the different reactants, we could finely tune the morphology of the inorganic nanostructures formed from organic templates. This fine-tuning has also been achieved upon controlling the kinetics of both organic assembly formation and inorganic polycondensation. The results presented herein show that the dynamic and versatile nature of the organic gels considerably enhances the tunability of inorganic materials with rich polymorphisms.

Photoluminescence of Bridged Silsesquioxanes Containing Urea or Urethane Groups with Nanostructures Generated by the Competition between the Rates of Self-Assembly of Organic Domains and the Inorganic Polycondensation

The aim of this study was to investigate the changes produced in the nanostructures and the photoluminescence spectra of bridged silsesquioxanes containing urea or urethane groups, by varying the relative rates between the self-assembly of organic domains and the inorganic polycondensation. Precursors of the bridged silsesquioxanes were 4,4‘-[1,3-phenylenebis(1-methylethylidene)]bis(aniline) and 4,4‘-isopropylidenediphenol, end-capped with 3-isocyanatopropyltriethoxysilane. The inorganic polycondensation was produced using either high or low formic acid concentrations, leading to transparent films with different nanostructures as revealed by FTIR, SAXS, and 29Si NMR spectra. For the bridged silsesquioxanes containing urea groups the self-assembly of organic domains was much faster than the inorganic polycondensation for both formic acid concentrations. However, the arrangement was more regular and the short-range order higher when the rate of inorganic polycondensation was lower. The photoluminescence spe...

Solutions of hybrid silica microgels as precursors of sol–gel coatings

A two-step process to synthesize a new type of organic–inorganic hybrid sol, that may be used for a variety of processes related to sol–gel chemistry, is analyzed. The first step consisted of a typical inorganic polycondensation of tetraethoxysilane (TEOS) and 3-methacryloxypropyl-trimethoxysilane (MPMS) leading to a conventional sol. In the second step a convenient amount of a solvent (isopropanol), and a vinyl co-monomer (2-hydroxyethylmethacrylate, HEMA) were added. The free-radical co-polymerization of the CC groups of MPMS and those of the co-monomer was carried out by using a suitable initiator (2,2′-azobis(isobutyronitrile), AIBN). The advance in the organic and inorganic polymerizations was followed employing different experimental techniques: FTIR, 13C NMR, 29Si NMR and viscosity measurements. The key to the new process was the amount of solvent added before the second stage such that gelation did not occur after complete consumption of CC groups. This led to a solution of hybrid microgels (a hybrid sol) that was characterized by scanning electron microscopy (SEM) and exhibited the following characteristics: a) it could be stored for prolonged periods at room temperature without gelation, b) it led to extremely fast gelation by solvent evaporation and c) it had a high wettability that allowed the production of coatings over different substrates. Besides, in this new process it is possible to add co- and ter-monomers in the second step to provide a desired functionality to the resulting coating. These concepts may be used to synthesize a variety of sols for the extended field of sol–gel processes.

Controlling the Thermal Polymerization Process of Hybrid Organic−Inorganic Films Synthesized from 3-Methacryloxypropyltrimethoxysilane and 3-Aminopropyltriethoxysilane

An important step in the synthesis of hybrid materials is the control of organic chains formation when the organically modified alkoxides are bearing polymerizable groups, such as acrylate or epoxy. Control of the process can be achieved through a deep understanding of the correlation between the synthesis parameters and the final structure. In this paper we have used 3-methacryloxypropyltrimethoxysilane (MPTMS) co-hydrolyzed with tetraethyl orthosilicate (TEOS) using 3-aminopropyltriethoxysilane (APTS) as basic catalyst and network modifier of the structure. The acrylate function in MPTMS has been thermally polymerized and the process has been tuned, with the purpose to reach the highest polymerization efficiency, by controlling the synthesis parameters. The synthesis has been followed in solution by 13C and 29Si nuclear magnetic resonance (NMR) spectroscopy, and the structural changes in the films have been studied by Fourier transform infrared spectroscopy (FTIR) as a function of the thermal treatment. Multinuclear solid state NMR spectroscopy on related bulk materials has provided supplementary information on the hybrid network formation. As-deposited films are not fully condensed but a very large conversion of the CC double bonds (up to 98% of polymerization degree) is achieved during thermal curing by the simultaneous inorganic polycondensation and organic polymerization.

Highly Stable Metal Hydrous Oxide Colloids by Inorganic Polycondensation in Suspension.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Highly Stable Metal Hydrous Oxide Colloids by Inorganic Polycondensation in Suspension

Hybridische Kern-Kranz-Nanoarchitekturen (siehe Schema, Mitte) eignen sich als supramolekulare Vorstufen für beständige Metallhydroxid-Kolloide (rechts). Die hydrophilen anionisch-neutralen Blockcopolymere ermöglichen Metallhydrolyse und -kondensation in Suspension. Die Größe der Partikel und ihre Morphologie können über das Ausmaß der Metallkomplexierung eingestellt werden.

Highly stable metal hydrous oxide colloids by inorganic polycondensation in suspension.

Highly stable metal hydrous oxide colloids by inorganic polycondensation in suspension.

Role of double-hydrophilic block copolymers in the synthesis of lanthanum-based nanoparticles

The formation of nanosized lanthanum hydroxide particles in aqueous medium was studied in the presence of double-hydrophilic block copolymers (DHBC). These copolymers contain a polyacrylic acid (PAA) block as an ionizable block, and a polyacrylamide (PAM) or a polyhydroxyethylacrylate (PHEA) block as a neutral block. The nanoparticles are synthesized by a two-step procedure. Firstly, the complexation of lanthanum ions in water by the polyacrylate blocks induced the formation of star-shaped micelles stabilized by the PAM or PHEA blocks. The micelles were characterized by dynamic light scattering (DLS), small-angle neutron scattering (SANS) and transmission electron microscopy (TEM). Secondly, the inorganic polycondensation of lanthanum ions led to the formation of organic–inorganic nanohybrids. Hairy needle-like colloids were obtained. The size of the sterically stabilized colloids was controlled by adjusting the polymer-to-metal ratio.