Greener Chemistry for Hybrid Materials,Alcohol‐Free Synthesis with an Epoxy‐Cyclohexyl Precursor

Green synthesis is one of the hot topics in the chemistry of hybrid organic–inorganic materials. A alcohol‐free sol–gel process has been developed to prepare optically transparent hybrid films from an epoxy bearing alkoxide, [2‐(3,4‐epoxy‐cyclohexyl)‐ethyl]‐trimethoxysilane (ECTMS). The synthesis is simple and effective because only two components, ECTMS and an aqueous solution of NaOH, are employed. Infrared spectroscopy has been used to monitor the reactivity of the precursor sol as a function of the aging time. Organic–inorganic hybrid films have been then prepared with the different sols via spin‐coating. The presence of the cyclohexyl ring slows down dramatically both the epoxide opening and the capability of the resulting diols in forming a tricyclic dioxane derivative. The highly basic conditions employed in the synthesis favor the formation of the cyclohexyl rings and cage‐ and ladder‐like silica structures. The hybrid films have shown a high transmittance in the visible range and a thermal stability up to 200 °C.

     

Development of flame retardancy properties of new halogen‐free phosphorous doped SiO2 thin films on fabrics

In this study, flame retardancy properties of fabrics treated with phosphorous (P) doped and undoped SiO₂ thin films were developed by sol–gel technique. As to this aim, P‐doped and undoped SiO₂ film were coated on cotton fabric from the solutions prepared from P, Si‐based precursors, solvent, and chelating agent at low temperature in air using sol–gel technique. To determine solution characteristics, which affect thin film structure, turbidity, pH values, and rheological properties of the prepared solutions were measured using a turbidimeter, a pH meter, and a rheometer machines before coating process. The thermal, structural, and microstructural characterization of the coating were done using differential thermal analysis/thermograviometry, fourier transform infrared spectroscopy, X‐ray diffractometry, and scanning electron microscopy. In addition, tensile strength, wash fastness, flame retandancy, and lightness properties of the coated fabrics were determined. To compensate the slight loss of tensile strength of samples, which occurred at the treated fabrics with P‐doped Si‐based solutions, the cotton fabrics were coated with polyurethane films during second step. In conclusion, the flame retardant cotton fabric with durability of washing as halogen‐free without requiring after treatment with formaldehyde was fabricated using sol–gel processing for the first time. Moreover the cotton fabrics, which were treated with P‐doped Si‐based solutions and then coated with polyurethane at second step, still has got nonflammable property. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Fabrication and Ultraviolet Absorption of Sol–Gel-Derived Germanium Oxide Glass Thin Films

Germanium oxide glass thin films were prepared by the sol–gel method and annealed under reduced atmosphere to create more oxygen-deficient defects. The densification and crystallization were examined depending on sintering and annealing conditions. Thus, homogeneous germanium oxide thin films with a high content of oxygen vacancies were fabricated. Ultraviolet absorption and oxygen vacancies of the films were investigated as a function of annealing temperature and time. Optical absorption in the 5-eV region due to the formation of oxygen vacancies is enhanced with increasing annealing temperature and time. The formation energy of oxygen vacancies is calculated to be about 1.0 eV.     

Tailoring of elastomeric grafted coating via sol–gel chemistry of crosslinked polymethylhydrosiloxane

Thin coating of crosslinked polymethylhydrosiloxane are grafted on silica using sol–gel process that leads to polymer layers tailored in term of thickness and elasticity. The degree of crosslinking is tuned by sol–gel polycondensation of a mixture of methyldiethoxysilane(DH) HSi(CH₃)(OCH₂CH₃)₂ and triethoxysilane (TH) HSi(OCH₂CH₃)₃, yielding triethoxysilane‐based networks. Samples with well‐defined thicknesses from nanometer to micrometer range are prepared by sol–gel dip‐coating method on silicon surface. Homogeneous or gradient‐thickness coating can be produced in this way. It results in surface‐attached networks bearing Si? H functionalities covalently anchored to the substrate. Powdered gels of DH/TH composition from 50/50 to 95/5 (mol %) were also prepared for a comparison purpose. The structure of the gels was investigated by NMR and FTIR, showing that DH/TH mixtures react totally to yield homogeneous matrix. The surface‐attached polymer films are very stable and present high hydrophobicity as evidenced by contact angle measurements. Their surface and mechanical properties have been qualitatively studied using the atomic force microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1504–1516, 2007     

PH sensitive structural uniformity of rice husk ash‐derived MCM‐41 silica

In this study, highly uniform MCM‐41 mesoporous silica was synthesised from rice husk ash‐derived sodium silicate using cetyltrimethyl ammonium chloride (CTAC) as a template. The chemical composition of the gel mixture was based on a SiO₂:CTAC:H₂O molar ratio of 1:0.5:75. When the pH value was initially controlled at ranges of 5.0–10.5 for 5 h and then immediately adjusted to 11.25 for the next 1 h, the structural uniformity of MCM‐41 was abruptly increased by 3.3–7.5 times of the single pH value at 11.25, respectively. Moreover, thermal and hydrothermal stabilities at 900 and 250°C were clearly observed. © 2012 Canadian Society for Chemical Engineering     

铜锌锡硫半导体薄膜材料的制备与表征

采用水热法成功制备了Cu2ZnSnS4(CZTS)半导体材料,通过浸涂法制备了相应的薄膜,并在N2气氛中于400℃对薄膜进行了退火处理.用X射线荧光光谱分析了所得CZTS粉末中各组成元素的含量,并分别用X射线衍射、扫描电子显微镜和紫外-可见-近红外光谱对CZTS薄膜样品的晶体结构、表面形貌和带隙进行了表征.结果表明:所...     

Sol–gel derived CeO2/α‐Al2O3 bilayer thin film as an anti‐coking barrier and its catalytic coke oxidation performance

A CeO₂/α‐Al₂O₃ bilayer was coated on a high temperature alloy (Incoloy 800H) by sol–gel dip‐coating and was evaluated for its potential as an anticoking barrier and coke oxidation catalyst. The bilayer effectively functioned as a barrier to metal surface catalyzed coking. The film prevented filamentous catalytic coking via blocking surface active metallic sites on the Incoloy substrate. Furthermore, the bilayer reduced the oxidation temperature of pyrolytic coke deposited on the film surface as compared to a bare oxidized Incoloy substrate, mostly owing to the oxidation catalytic activity of the CeO₂ layer. Finally, it is demonstrated that the presence of the α‐Al₂O₃ buffer layer is critically important to the overall performance. Without the α‐Al₂O₃ layer, a CeO₂ layer nearly completely lost both its barrier and oxidation catalytic functions. It is presumed that metallic species migrating from the substrate during high temperature treatments are responsible for the CeO₂ deactivation, likely by blocking catalytic sites on the CeO₂ surface. © 2018 American Institute of Chemical Engineers AIChE J, 64: 4019–4026, 2018     

Antibacterial activity and antistatic composites of polyester/Ag‐SiO2 prepared by a sol–gel method

Poly(butylene adipate‐co‐terephthalate) (PBAT) composites containing silver‐silica (Ag‐SiO₂) were prepared using an in‐situ sol–gel process. Maleic anhydride‐grafted PBAT (PBAT‐g‐MA) and multihydroxyl‐functionalized Ag‐SiO₂ were used to improve the compatibility and dispersibility of Ag‐SiO₂ within the PBAT matrix. The composites were characterized morphologically using transmission electron microscopy and chemically using Fourier transform infrared spectrometry. The existence of Ag‐SiO₂ nanoparticles on the substrate was confirmed by the ultraviolet–visible absorption spectra. The antibacterial and antistatic properties of the composites were evaluated whether SiO₂ enhanced the electrical conductivity was tested as well as whether Ag enhanced the antibacterial activity of the PBAT‐g‐MA/SiO₂ or PBAT/SiO₂ composites. The PBAT‐g‐MA/SiO₂ or PBAT/SiO₂ composite that contained Ag had better antibacterial activity (more than 1.3‐fold). The functionalized PBAT‐g‐MA/Ag‐SiO₂ composite can markedly enhanced antibacterial and antistatic properties due to the carboxyl groups of maleic anhydride, which acted as coordination sites for the Ag‐SiO₂ phase, allowing the formation of stronger chemical bonds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of core–shell glass bead/polysulfone microspheres with two‐step sol–gel process

Core–shell microspheres made from glass beads as the core phase and polysulfone (PSf) as the shell phase can act as an absorbent in the separation process or a supporter for chemical reactions. Based on phase‐inversion principles, a two‐step sol–gel method was developed in this work in which ether was added first and H₂O was added second to a PSf‐containing dimethyformamide (DMF) solution to help PSf solidify on the surface of glass beads. The results from scanning electron microscopy, Fourier transform IR, and X‐ray photoelectron spectroscopy showed that a dense layer of PSf (thin to several microns) was coated on the glass beads and the core–shell microspheres were almost monodispersed. The utilization percentages of the glass beads and PSf were high as 100 and 80%, respectively. The thickness of the PSf membrane was calculated to be about 4.3 μm. To obtain well‐monodispersed microspheres, the practical volume ratio of ether to DMF was recommended to be larger than 4.5. The results suggested that the two‐step sol–gel method is a highly efficient process for preparation of glass bead/PSf core–shell microspheres. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3365–3369, 2006     

Comparative studies on corrosion protection properties of polyimide‐silica and polyimide‐clay composite materials

Comparative studies on corrosion protection properties of polyimide‐silica‐clay composites were studied in this article. A series of polyimide‐silica (PIS), polyimide‐clay (PIC), and polyimide‐silica‐clay composites (PISC) materials, consisting of an organo‐soluble polyimide (ODA‐BSAA) matrix, inorganic silica particles prepared through the sol–gel reaction of tetraethyl orthosilicate (TEOS) and dispersed nanolayers of inorganic montmorillonite clay, were successfully prepared by solution dispersion technique. Then, all samples were characterized by FTIR, powder X‐ray diffraction patterns, transmission electron microscopy, and ²⁹Si solid‐state NMR. The main focus of this article is the comparison of the corrosion protection properties of PIS, PIC, and PISC composite materials. Normally, the aspect ratio of clay is higher than silica. Superior dispersion of clay platelets into a polymer matrix may effectively increase the length of diffusion pathways for oxygen and water. The effects of the materials composition on the corrosion protection performance, gas barrier, and optical properties, in the form of both coating and film, were also studied by electrochemical corrosion measurements (e.g., corrosion potential, polarization resistance, corrosion current, and impedance spectroscopy), gas permeability analysis, and UV‐visible transmission spectroscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of rigid‐rod polyimide/silica hybrid materials by sol–gel process

Polyimide (PI) materials with a low coefficient of thermal expansion (CTE) while still retaining high strength and toughness are desirable in various applications. In this study a sol–gel process was used to incorporate silica into homopolyimides and copolyimides with highly rigid structures in an attempt to pursue this aim. A number of highly rigid monomers were used, including pyromellitic dianhydride (PMDA), p‐phenylene diamine (PPA), m‐phenylene diamine (MPA), benzidine, 2,4‐diaminotoluene, and o‐toluidine. No homopolyimide flexible films were obtained. However, it was possible to obtain flexible films from the copolyimides. Therefore, a copolyimide based on PPA, MPA, and PMDA (PPA/MPA = 2/1 mol) was then chosen as the matrix to prepare the PI/silica hybrids. Flexible films were obtained when the silica content was below 40 wt %. The hybrid films possessed low in‐plane CTEs ranging from 14.9 to 31.1 ppm with the decrease of the silica content. The copolyimide film was strengthened and toughened with the introduction of an appropriate amount of silica. The thermal stability and the Young's modulus of the hybrid films increased with the increase of the silica content. The silica particle size was assessed by scanning electron microscopy and was about 100 nm for the hybrids containing 10 and 20 wt % silica and 200–500 nm for the hybrids containing 30 and 40 wt % silica. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 794–800, 2001     

Preparation and Characterization of Trialkoxysilane‐Containing Acrylic Resin/Alumina Hybrid Materials

Summary: In the present study (3‐methacryloxypropyl)trimethoxysilane (MPMS) containing acrylic resin/alumina hybrid materials with various alumina contents were prepared. The effects of ethylacetoacetate (EAA) content, catalyst type, and water content during sol–gel process for alumina sols on the microstructure and properties of the hybrid materials were investigated by SAXS, AFM, DSC, TGA, and nano‐indentation tester, respectively. It was found that the hybrid materials exhibited a homogeneity and the alumina phase of the hybrids had mass fractal dimension and open structure. The thermal and mechanical properties of the hybrid materials were obviously improved when alumina was incorporated. The EAA contents, catalyst type, and water content during sol–gel process for alumina sols had obvious effects on the microstructure and properties of the hybrid materials.

Typical load–displacement curves of the pure acrylic resin and hybrid materials with increasing alumina content.     

铜、锌共掺杂二氧化钛薄膜的制备及光催化活性

以钛酸丁酯为钛源,采用溶胶-凝胶法制备了Cu2+、Zn2+共掺杂TiO2薄膜,通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见吸收光谱(UV-Vis)对其进行表征.结果表明,Cu2+、Zn2+掺杂促进了TiO2晶相的转变,引入铜锌离子之后TiO2的禁带宽度由3.37 eV减少至3.28 eV.SEM表明Cu2+、Zn2+共掺杂TiO2薄膜晶粒比纯TiO2更加细小.XPS分析证实了制备的铜锌共掺杂TiO2,锌以二价氧化价态存在.以亚甲基蓝为模拟污染物,对其进行光催化降解实验,结果表明:Cu2+、Zn2+共掺杂的协同作用使TiO2薄膜的光催化活性显著提高.     

Morphology of Organic–Inorganic Hybrid Composites in Thin Films as Multichip Packaging Material

Silica–polyimide hybrid composites were prepared via a sol–gel process and thermal imidization. Two different types of soluble precursors, poly(amic acid) (PAA) and poly(amic diethyl ester) (ES), chemically convertible to poly(p-phenylene biphenyltetracarboximide), were used as organic polymer matrix component, and tetraethoxysilane (TEOS), convertible to silica, as the inorganic component. The structure of composites prepared as thin films was investigated by means of small-angle X-ray scattering, scanning electron microscopy and atomic force microscopy. Nanometre-scale composites were successfully obtained for ≤30wt% TEOS-loaded mixtures with ES and PAA. It was considered from the microstructural investigation that the composite films based on ES were not significantly affected by the inorganic particles generated, maintaining the structure of the homopolyimide, while those based on PAA did not preserve the structure due to the nanoparticles grown in situ during the sol–gel process. © 1997 SCI.     

A Facile Synthesis of PdO‐Decorated SnO2 Nanocomposites with Open Porous Hierarchical Architectures for Gas Sensors

PdO‐decorated SnO₂ nanocomposites with open porous hierarchical architectures are fabricated through a facile biotemplating sol–gel technique. The sol–gel soakage process is carried out by immersing the templates butterfly wings in Sn‐ and Pd‐ impregnants successively to generate a uniform colloid layer. PdO and SnO₂ nanocrystallites come into being with subsequent calcination treatment, and PdO‐decorated SnO₂ nanocomposites further construct the parallel main ridges with connective pillars and vertical struts, finally present a 3‐D open porous hierarchical architecture. Benefiting from unique ingredients and structure hierarchy, the nanocomposites give enhanced acetone‐sensing performance of high sensitivity and rapid response/recovery rate     

Temperature dependence of gel properties of two‐component physical gels

The cascade model for mixed gels developed by the author in a previous work is extended to describe the temperature‐dependent gel properties. The equilibrium constant of the association between component polymers is assumed to depend on temperature via a van't Hoff‐type equation. The temperature variation of the network structure and gel modulus is presented and discussed at different parameters such as enthalpy change per crosslink ΔH°, entropy change per crosslink ΔS°, functionality ratio s, and concentration ratio r. It is demonstrated that the model agrees reasonably well with the experimental data obtained from the rheological gelling for galactomannan/xanthan and glucomannan/xanthan mixed gels. However, the resulting model parameters are not consistent with those obtained from the concentration dependence study. A further investigation on the calorimetric thermogram of the glucomannan/xanthan mixed gel reveals that the gelling process involves an association reaction followed by a structural rearrangement, which is beyond the scope of this work. Finally, the cascade model is shown to be consistent with the Eldridge–Ferry equation. It is also demonstrated that the sol–gel behavior of the galactomannan/xanthan mixed gel follows the Eldridge–Ferry relationship, but the calculated melting enthalpy is composition‐dependent, contrary to the assumption made in the cascade model. This discrepancy is due to the self‐association of xanthan when xanthan is present in excess amounts. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 663–673, 2006     

Fabrication and Characterization of the Piezoelectric Ceramic–Polymer Composites

The modified sol–gel method was used to synthesize lead zirconate titanate nanoparticles, and the lead zirconate titanate nanoparticles and polyvinylidene fluoride were used to prepare piezoelectric nano‐ceramic–polymer composites with 0–3 connectivity type. The composites were successfully prepared by cold‐pressing and curing‐molding methods. X‐ray diffraction and scanning electron microscopy were adopted to characterize the microstructure of the obtained lead zirconate titanate nanoparticles and composites. The normal vibration modes of the lead zirconate titanate nanoparticles were investigated by Fourier transform infrared spectroscopy. The dielectric and piezoelectric properties of the composites were analyzed in detail with respect to different volume fractions of the lead zirconate titanate nanoparticles. It demonstrated that the values of d₃₃ and ε increased with the increase in the content of lead zirconate titanate. The results here pointed to potential and simple methods to fabricate the lead zirconate titanate nanoparticles and the piezoelectric ceramic–polymer composites for piezoelectric applications.     

Preparation of Sn‐Doped Zinc Phosphate Amorphous Thin Film and its Emission Properties

Using liquid‐phase synthesis, SnO – ZnO – P₂O₅ amorphous coating films exhibiting broad emission of Sn²⁺ center were prepared. It is found that the P – O – Zn bonds of the film were generated during the heat‐treatment. The emission property due to Sn²⁺ depended on the heat‐treatment temperature, which correlated with the residual chloride ion content. Although the peak position of the photoluminescence (PL) excitation band was almost constant, that of PL red‐shifted with increasing amount of SnO, which was quite different from the result observed for SnO – ZnO – P₂O₅ bulk glass containing Sn²⁺ center.     

Microencapsulated melamine phosphate via the sol–gel method and its application in halogen‐free and intumescent flame‐retarding acrylonitrile‐butadiene‐styrene copolymer

In this paper, a facile method is introduced to modify melamine phosphate (MP) via the sol–gel process. The aim was simultaneously to increase the water resistance of MP and improve the dispersion and compatibility of MP in acrylonitrile‐butadiene‐styrene copolymer (ABS). In addition, the incorporation of SiO₂ particles into the MP/dipentaerythritol (DPER) system can further ameliorate the char‐forming ability and enhance the flame retardant properties of polymer composites. The chemical structure and surface morphology of SiO₂@MP were confirmed and observed by Fourier transform infrared (FTIR) spectroscopy, SEM and TEM, respectively. The results demonstrate that ABS/SiO₂@MP/DPER (3/1) at a loading of 30 phr reaches 31.2% limiting oxygen index and achieves a UL‐94 V‐0 rating. Moreover, FTIR spectra indicate that the main char‐forming process of the SiO₂@MP/DPER system occurs at 365–420 °C. A potential condensed flame retardant mechanism of SiO₂@MP and DPER in ABS composites is proposed via the systematic analysis of char residue after combustion by FTIR spectroscopy, SEM and X‐ray photoelectron spectroscopy. © 2015 Society of Chemical Industry