Characteristics of colored inorganic–organic hybrid materials

Inorganic–organic hybrid glasses are relatively new nanometric materials of Ormosil’s group (organic modified silicates). There co-existence, on a molecular scale, exists between inorganic structures in the form of silica-oxide network and organic structures based on carbon links. Properties of these materials are intermediate between those of inorganic glasses (hardness, chemical and thermal resistance) and organic polymers (low temperature of obtaining, elasticity of structure). The hybrid materials are compatible matrices for organic compounds such as organic dyes, laser dyes, photo-chromic compounds, etc. Inorganic–organic hybrid glasses are usually produced in the form of thin coatings on various bases using a low-temperature sol-gel process. These coatings, depending on the kind and amount of units, building their structure, show various properties: refractive index changing in a wide range, anti-static properties, anti-reflection, corrosion protection, intensive color, luminescence and others. That is why these materials found application as protective and colored covering of glass articles as well as in new technical areas. The aim of this paper is obtaining and characterizing colored inorganic–organic coatings on glass, considering both protective and colored properties. These materials have been produced from phenyltriethoxysilane (PhTES), 3-glycidoxypropyltrimethoxysilane (GPTMS), aluminium tri-sec-butylate (TBA); (PGT matrix). The structure of PGT matrix was determined using the FTIR, ²⁹Si MAS NMR and ²⁷Al MAS NMR examinations. It has been found that chemical bonds occur between structural units. The two groups of organic dyes were used for coloring the coatings. The first group consisted of ORASOL dyes, chiefly based on various metal complexes. These dyes have a wide range of commercial utilization. The second group included the organic, intensive dyes obtained in the laboratory and are inaccessible for sale. The coloring coatings were coated on flat glass using the dip-coating method. The samples were submitted for thermal treatment at temperatures of 100 and 200 °C. Investigation of chemical resistance (boiling in water for 1 h) was made for coated materials after thermal treatment at 100 °C. UV–VIS transmission of colored coatings was examined after each stage of thermal treatment and also after hydrolytic resistance examination. The quality of the coatings and their thickness were estimated by SEM observations. The obtained, inorganic–organic coatings were characterized by good chemical resistance and stability of color.     

Vegetal nanoclusters in hybrid silica films prepared by sol-gel spin coating technique

Hybrid sol-gel films containing Rosemary extract nanoclusters embedded into hybrid silica network have been successfully synthesized using the sol-gel procedure by exploiting the template route, in association with an adequate spin-coating method. Formation of film precursor sols and effect of selected amounts of octyl trimethoxysilane and ethyl oleate succinic anhydride into the starting acid sols on the sol-gel product size have been evaluated by dynamic light scattering technique. The spectral characteristics of hybrid organic-inorganic films have shown that the multiple functional groups from Rosemary extract associated with residual Si-OH groups can cause the increase in the degree of physical interaction. The effect of hybrid sols meaning the silica precursors molar ratio and template concentration on the fluorescence of hybrid films has been also investigated. The fluorescence properties of synthesized films were found to be dependent on template and natural extract concentration. A higher amount of template resulted in doubling the fluorescence intensity in the 400-480 nm domain. The microstructural characteristics of the hybrid films revealed by atomic force microscopy have shown a homogeneous surface morphology with cluster-like structure. Hybrid silica films exhibit a periodic structure with cluster size less than 150 nm.     

Preparation of alumina fibers by sol-gel method

The shape of particles present in the alumina sols prepared from inorganic salts was examined by transmission electron microscopic observation and related to the rheological property and fiber drawing behavior of the sols. It was found that fibers could be drawn in the viscosity range of 1–100 Pa·s from the sols in which long-shaped particles were found, while no fibers could be drawn from the sols containing round particles. It was also found that non-spinnable sols showed relatively large structural viscosity, whereas spinnable sols showed Newtonian flow or very little structural viscosity.     

Formation of nanoporous and nanocrystalline anatase films by pyrolysis of PEO–TiO2 hybrid films

Poly(ethylene oxide)–titania (PEO–TiO₂) organic–inorganic hybrid films were synthesized through a sol–gel process and spin coating. The mixed precursor sols were aged for 6 and 12 h, respectively, prior to the spin coating. Hybrid films were crystallized to the anatase phase first and then further heat treated at elevated temperatures for different time periods to analyze the anatase-to-rutile phase transformation. Quantitative X-ray diffraction (Q-XRD) results were employed for Johnson–Mehl–Avrami (JMA) kinetic analyses and the Avrami exponent (n) was determined for each film. The Arrhenius plots were created based on the JMA plots and the activation energy (Q) values for the phase transformation were determined for each film. The difference in the phase transformation kinetics in the films was discussed based upon the difference in the activation energy values and thus the molecular structures of each hybrid film. Nanoporous and nanocrystalline anatase films were successfully achieved through the retarded phase transformation during the pyrolysis of the organic–inorganic hybrid films. Owing to the maximized surface area these nano-structured anatase films are highly expected to show the enhanced photocatalytic efficiency compared to common TiO₂ films as well as sintered bulk forms.     

Highly Electrical Conductivity of Hybrid Langmuir-Blodgett Films of Transition Metal Dichalcogenide and Amphiphilic Compounds

Abstract

Hybrid alternate layered films of transition metal dichalcogenides and amphiphilic compounds were prepared by Langmuir-Blodgett (LB) technique. The conductivity at room temperature depended on the transition metal dichalcogenide species, showing the highest value for the hybrid LB films of MoS₂ system. This methodology was successfully applied to the fabrication of the hybrid LB films using various organic amphiphiles such as cyanine dyes, phthalocyanines, azobenzene, and ferrocene derivatives. The conductivity depended on the interlayer spacing: the conductivity decreased with increasing interlayer spacing of the film. The highest electrical conductivity of the hybrid LB films was over 100 Scm^?.     

The novel use of organo alkoxy silane for the synthesis of organic–inorganic hybrid coatings

UV-curable, organic–inorganic hybrid coatings based on a UV-curable epoxyacrylate resin (EA) and methacryloxypropyl trimethoxysilane were prepared by the sol–gel method. 2,2′-Bis(4-β-hydroxy ethoxy) phenyl propane was modified by a coupling agent, 3-isocyanato propyl triethoxy silane, to improve the compatibility of the organic and inorganic phases. The formulations were applied onto Aluminum panels and cured by UV light to obtain a hard and clear coating with a good adhesion. The structural characterization of cured hybrid materials was performed using solid state ²⁹Si NMR spectroscopy. The real time infrared technique was used to follow the degree of double bond conversion and photopolymerization rate. The thermal properties of the coatings are improved depends on the ‘component A’ composition in hybrid mixture which was composed of methacryloxy propyl trimethoxysilane (MAPTMS) and trimethoxysilane terminated HEPA urethane (TMSHU). The char yield of pure epoxy acrylate resin was 0.7 wt% and that of 30 wt% of component A containing hybrid coating was 4.6 wt% at 900 °C in air atmosphere. The morphology of the hybrid materials was examined by scanning electron microscopy. The hybrids were nanocomposites.     

Preparation of organic-inorganic nano-composites for antireflection coatings

In this research, bi-layer thin film stacks that served as an antireflective coating were developed. The top layer was synthesized using tetraethoxysilane and 3-(trimethoxysilyl) propyl methacrylate by the well-known sol-gel technique. Its refractive index was lower than that of the bottom layer, which was prepared by reaction between tetrabutoxyltitanium and γ-glycidoxy propyl trimethoxysilane. Antireflective coatings were obtained by spin-coating of the synthesized sols on a glass substrate, followed by pre-drying, UV-curing, and post-baking. Fourier transform infrared spectrometer was employed to investigate the evolution of chemical bonds during the UV-curing and the sol-gel processes. The size of the inorganic/organic hybrid particles in the sol was found to be less than 10 nm, as measured by transmission electron microscope and dynamic light scattering. Thermo gravimetric analyzer was used to find out the thermal degradation temperature of the two layers and the effect of post-baking. The results indicated that the thermal stability increased after post-baking at 200 °C for 15 min. The reflectance of the antireflection coating was controlled by the relative refractive indices and the thickness of the top and bottom layers. Under optimal synthesis condition, we obtained an antireflection coating, exhibiting a low reflection, 1% at 550 nm, in the visible range.     

Spinnablity and structure characterization of mullite fibers via sol–gel-ceramic route

Viscosity and rheology behaviors of the mullite sols prepared from aqueous solution of aluminum nitrate, aluminum isopropoxide and tetraethylorthosilicate has been investigated. Rheological measurement suggested that mullite sols exhibited good spinniabilty when the evaporation of the solvent is allowed during sol–gel process. Spinnable sols showed shear-thinning flow behavior with high viscosity to the time of gelation. By adjusting temperature, the gelation degree and viscosity of the sol could be stabilized at a certain value and the sol–gel transition could be transferred to the spinning line of a laboratory dry-spinning apparatus. Continuous mullite fibers were obtained from such sols using sol gel dry-spinning method. The final ceramic fibers had smooth surfaces with an average diameter of 50 μm. Structure evolution of mullite ceramic fibers were characterized by MAS NMR and specific surface area analyses.     

Colloidal sol/gel processing of ultra-low expansion TiO2/SiO2 glasses

A series of titania-silica glasses with 0–9% TiO₂ were fabricated using a sol/gel process. The sol was prepared by dispersing colloidal silica fume in an aqueous solution of titania which was synthesized through the acid-catalyzed hydrolysis of titanium isopropoxide. The sols gelled in 2–4 days, and then were dried for 6–8 days. The dry gels were sintered at 1450–1500°C to produce clear, dense, microstructure-free glasses. The gels underwent a total shrinkage of 50% to yield glass rods about 50 mm long and 5 mm in diameter, or glass discs about 4 cm in diameter and 5 mm thick. The drying step was most critical in the production of crack-free specimens.

In the gel, the transmission electron microscope (TEM) revealed the presence of 1–5 nm rutile microcrystallites uniformly distributed within a network of colloidal silica particles. After sintering to 1450–1500°C, though, a dense, transparent, microstructure-free glass was created. Fourier transform infrared spectroscopy (FTIR) verified the formation of an amorphous solid-solution of titania and silica after sintering.

The thermal expansion of the glasses was measured using a differential dilatometer. The average linear coefficients of thermal expansion (CTE @ 25–675°C) varied between +5 × 10⁻⁷ and −0.2 × 10⁻⁷°C⁻¹ in the range 0 to 9% TiO₂. The glass with 7.2% TiO₂ exhibited a zero thermal expansion coefficient at 150–210°C. The hysteresis in CTE on heating and cooling was of the order of 0.01–0.02 ppm.     

非水解溶胶-凝胶法制备硅酸锆薄膜及抗碱腐蚀性能

以正丙醇锆和正硅酸乙酯分别为锆源和硅源,结合非水解溶胶-凝胶法和提拉镀膜工艺制备出硅酸锆(ZrSiO4)薄膜.采用XRD、FTIR、SEM、AFM等分析测试手段研究了前驱体浓度、提拉速度对ZrSiO4合成、ZrSiO4薄膜形貌及显微结构的影响,并研究薄膜的抗碱液腐蚀性能.结果表明:当前驱体浓度为0.1 mol/L、提拉速度为1 mm/s时可以在单晶硅片获得表面光滑、平整致密、无开裂的ZrSiO4薄膜.镀有ZrSiO4薄膜的单晶硅片在浓度为40;NaOH溶液中40℃条件下浸泡42 h,表面只发现有较小的坑蚀,且质量随腐蚀时间延长变化很小,质量损失仅为0.17;,表明该ZrSiO4薄膜具有较好的抗碱液腐蚀性能.     

Continuous preparation of decorated nano zinc oxide organic sols with intense luminescence

A sort of decorated nano ZnO organic sols have been successively prepared by pulsed laser ablation at the interface of ZnO target and a flowing liquid containing polymers. It is found that the decorated nano ZnO ethanol sols, the decorated nano ZnO-PS (polystyrene) cyclohexane sols and the decorated nano ZnO-PMMA (polymethyl methacrylate) ethyl butyrate sols all have strong fluorescence emission at 329 nm and 411 nm, 308 nm and 317 nm, and at 330 nm and 400 nm, respectively. The results show the decorating for nano ZnO will intensely affect their luminescence, and the wavelength and intensity of luminescence can be adjusted or controlled by the different decoration.     

Formation of silica/epoxy hybrid network polymers

Epoxy-based inorganic–organic hybrid polymers, for use as a matrix in coatings, have been prepared from 3-glycidoxypropyltrimethoxysilane by a sol–gel process. The precursor molecule possesses both epoxy and silicon alkoxide functionality and so interlinked inorganic–organic networks can be formed. Diethylenetriamine was used to open the epoxy rings and form the organic network to an extent determined by the initial ratio of amine to epoxy groups. The materials were cured either at room temperature or with an additional heat treatment at 150 °C. Structural characterisation of the cured hybrid materials was performed using a combination of Raman, and ²⁹Si and ¹³C MAS NMR spectroscopies. These show that the formation of the two networks does not occur independently and the rate or extent of organic cross-linking has a direct effect on the extent of the inorganic network formation, and vice-versa.     

Synthesis via sol–gel process and characterization of novel organic–inorganic coatings

Organic–inorganic coatings were synthesized from tetraethoxysilane (TEOS) and vinyltriacetoxysilane (VTAS) via dual process involving sol–gel reaction and radical polymerization. The deposition of the films was carried out using the spin-coating technique with the sample holder spinning at 1500 rpm. In order to determine the nature of products formed during the sol–gel reaction (i.e. polymerization) and to study the kinetics of this reaction, Fourier transform infrared (FTIR) spectroscopy experiments were performed. This technique allows also determining the optimal temperature of the final heat treatment. Thermogravimetric analysis (TGA) was used to study the influence of the ratio of organic and inorganic components on the thermal stability of the organic–inorganic hybrid, while differential scanning calorimetry (DSC) was used to determine its glass transition temperature. The chemical structure of this prepared hybrid material is also studied using FTIR with attenuated total reflection (ATR) device.Finally, the homogeneity of the chemical composition of the synthesized materials was checked by using the elemental distributions obtained by an energy dispersive spectrometer (EDS) attached to a scanning electron microscope (SEM). Moreover, nanoindentation measurements on thin films show enhanced hardness and elastic modulus with increasing silicate network.     

Investigation on sol–gel silica coatings for the protection of ancient glass: Interaction with glass surface and protection efficiency

To hinder the phenomenon of weathering of ancient stained glass, the present work proposes the application of sol–gel coatings to the glass surface. Previous investigations [1], [2], [3], [4], [5] and [6], in fact, show that sol–gel silica coatings do not change the appearance of artistic glasses when deposited on their surface. Moreover, the film thickness is so small (around 200 nm) and its composition and structure so compatible with that of the original glass, that the characteristics of the coating and original glass are not distinguishable. In this work, several recipes used to produce sol–gel coatings have been tested in order to understand their behavior when adopted for covering ancient weathered glass. The coatings are made of sol–gel silica prepared with two different catalysts: H⁺, Pb²⁺ and without catalyst. All the investigated samples show a good adhesion of the coating to the glasses used to simulate the behavior of ancient artefacts. The sol–gel silica coatings have been studied before and after accelerated ageing to test the resistance of the protective coatings to weathering. Another important index to test of the efficiency of the sol–gel coatings for the protection of an ancient glass is the lead ion mobility. In ancient stained glass, in fact, this element is present in the metallic lead network, in the grisaille paintings and constitutes a main component of many glass tesserae. The action of water on this highly mobile ion involves the degradation of the glass itself and the release of the ion in the rain solution. Ageing tests show the efficiency of H⁺ and Pb²⁺ catalyzed coatings and the inefficiency of the non-catalyzed sol–gel layers.     

Microporous and mesoporous 8YSZ materials derived from polymeric acetylacetone-modified precursors for inorganic membrane applications

Both microporous and mesoporous 8% mol-yttria-stabilized zirconia (8YSZ) material can be prepared from the same 8YSZ sols. Stable 8YSZ sols with particle sizes smaller than 10 nm were prepared by using acetylacetone as a precursor modifier in combination with carboxylic acids. Nonanic and caproic acids are preferred due to their higher stability in combinations of highly concentrated sols. Cubic 8YSZ microporous material can be prepared by using acetylacetone as a precursor modifier with caproic acid as the catalyst. These materials can be transformed into mesoporous material composed of crystalline primary cubic YSZ nanoparticles by simply mixing with structure-directing agents. Use of the block copolymer F127 resulted in the largest specific surface area of 100 m²/g. Thin 8YSZ layers of these sols can be prepared on glass slips and on graded porous alumina supports with thicknesses between 20 and 100 nm.     

Design of hybrid organic–inorganic materials through their structure control: The case of epoxy bearing alkoxides

Hybrid organic–inorganic materials from (3-glycidoxypropyl)methyldiethoxysilane (GPMD) and [3-(2-aminoethyl)aminopropyl]trimethoxysilane (AEAPTMS) have been synthesized. The structure of the hybrid material has been studied as a function of AEAPTMS content by a combination of vibrational and nuclear magnetic resonance spectroscopies. The amine groups in AEAPTMS have shown to be very effective epoxy curing agents and the degree of condensation inside the hybrid material can be finely tuned with the amount of AEAPTMS. Fourier transform near infrared spectroscopy coupled with 2D infrared analysis has been used to elucidate the role of amines in epoxy curing. Several reactions of the amines with the epoxies have been observed, via tertiary, secondary and primary amines. At low AEAPTMS contents the hybrid material exhibits a residual mobility of the organic species, as revealed by solid state NMR spectroscopy. This property has been evaluated comparing qualitatively the residual mobility in hybrid materials synthesized with different types of organically modified alkoxides containing epoxy functional groups.     

AES and FTIR characterization of sol–gel alumina films

In this work we obtained sol–gel alumina coatings on AISI 304 stainless steel substrates. Alumina sols were prepared by using aluminum isopropoxide (AI) as precursor, acetic acid (HOAc) as catalyst, ethanol (C₂H₅OH) or isopropanol (C₃H₈O) as solvent, and water. The as-prepared solutions were deposited on stainless steel substrates by means of the dip-coating technique. The obtained composites were characterized by Fourier transform infrared spectroscopy (FTIR) and Auger electron spectroscopy (AES). We observed that the concentration of AlO type bonds in the obtained alumina coatings depends on the solvent type used, temperature and peptization state of the sol, withdrawal speed, and number of dipping cycles. AES experiments showed that the interface formed between the alumina coating and substrate surface is in general formed by several layers of different chemical compositions.     

Production and shaping of high performance phosphors by using the sol–gel process: Yttrium aluminum garnet (Y3Al5O12)

Luminescent Y₃Al₅O₁₂:Tb³⁺ (YAG:Tb³⁺) phosphor thin films and powders have been successfully prepared by the sol–gel route from alkoxide precursors. Advanced coatings were produced by spray and dip-coating from stabilized sols. X-ray diffraction (XRD), attenuated total reflectance/Fourier transform infrared spectroscopy (ATR/FTIR) and atomic force microscopy (AFM) were used to investigate the structure and morphology of layers. YAG phases of high purity were obtained for both powders and films. AFM study revealed coatings of homogeneous topography, whatever the deposition technique. However, dip-coated samples exhibited a much smoother topography, characterized by a root mean square (rms) roughness much lower than that of spray-coated ones. Laser induced emission spectra and decay times of Tb³⁺ ions in a spray-coated film were recorded. Measurements exhibit the characteristic green emission of Tb³⁺. Effectiveness of the Tb³⁺ doped coatings under UV excitation is also illustrated by pictures.     

Ca0.6Mg0.4Zr4(PO4)6涂层改善堇青石陶瓷

本文采用溶胶-凝胶法和浸渍涂覆技术在致密堇青石陶瓷表面制备了Ca0.6Mg0.4Zr4(PO4)6(C0.6M0.4ZP) 涂层,采用XRD、SEM等分析手段研究了涂层的相组成和微观结构,并通过分别测定涂覆和未涂覆涂层试样在1000℃下受腐蚀后的质量损失和强度变化,对涂层的耐碱腐蚀性能进行了表征.结果表明,在堇青石表面制备的涂层均匀致密,由单相的C0.6M0.4ZP组成.SEM分析表明涂层与堇青石基体间结合良好.C0.6M0.4ZP涂层具有较好的耐碱腐蚀性能,可显著提高堇青石陶瓷的高温耐碱腐蚀性能.     

Corrosion behavior of solid solution (Ti,Al) N as a function of Al concentration

In this work, a series of (Ti, Al) N coatings with different Al contents were deposited on 304 stainless steel substrates by Hollow Cathode Discharge (HCD) method. The coatings were grown on 304 stainless steel substrates at 400 °C. The coatings were characterized using energy dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), atomic force microscopy (AFM), and microhardness test. The XRD confirmed the transition from TiN phase to (Ti, Al) N phase and then to AlN phase with increasing Al concentration in the solid solution. It was found that with increasing Al concentration the hardness of the coatings initially increased up to a maximum value of about 30 GPa at around 32 at.% of Al and then the coating hardness decreased rapidly with further increase of Al content (Al > 32 at.%). The potentiodynamic polarization analysis was carried out in 3.5 wt.% NaCl solutions to study the corrosion resistance of the coatings. From the corrosion test it can be inferred that the amount of Al atoms in the coatings plays an important role for reducing the corrosion.