Synthesis of hybrid sol–gel materials and their biological evaluation with human mesenchymal stem cells

Surface engineering of biomaterials could promote the osseointegration of implants. In this work, two types of hybrid sol–gel materials were developed to stimulate cell attachment, proliferation and differentiation of osteogenic cells. One type was synthesised from vinyl triethoxysilane (VTES) and tetraethyl-orthosilicate (TEOS) at different molar ratios, while the other from VTES and hydroxyapatite particles (HAp). Hybrid materials were systematically investigated using nuclear magnetic resonance, Fourier transform infrared spectroscopy and contact angle metrology. The biocompatibility and osseoinduction of the coatings were evaluated by measuring mesenchymal stem cell proliferation using MTT assays and analysing the mineralised extracellular matrix production by quantifying calcium-rich deposits. The results highlighted the versatility of these coatings in obtaining different properties by changing the molar ratio of the VTES:TEOS precursors. Thus, mineralisation was stimulated by increasing TEOS content, while the addition of HAp improved cell proliferation but worsened mineralisation.     

Preparation and luminescence properties of ormosil hybrid materials doped with Tb(Tfacac)3phen complex via a sol–gel process

In this paper, silica-based transparent organic–inorganic hybrid materials were prepared via the sol–gel process. Tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were used as the inorganic and organic precursors, respectively. The terbium complex, Tb(Tfacac)₃phen (Tfacac=1,1,1-trifluoroacetylacetone, phen=1, 10-phenanthroline) was successfully doped into organically modified silicate (ormosil) matrix derived from TEOS and GPTMS, and the luminescent properties of the resultant ormosil composite phosphors [ormosil/Tb(Tfacac)₃phen] were investigated compared with those of the Tb(Tfacac)₃phen incorporated into SiO₂ derived from TEOS (labeled as silica/Tb(Tfacac)₃phen). Both kinds of the materials show the characteristic green emission of Tb³⁺ ion. The luminescence behavior of the resultant composite products was dependent on the matrix composition. The optimized lanthanide complex concentration in the ormosil/Tb(Tfacac)₃phen was increased compared with in silica/Tb(Tfacac)₃phen. Furthermore, the lifetime of Tb³⁺ in Tb(Tfacac)₃phen, silica/Tb(Tfacac)₃phen and ormosil/Tb(Tfacac)₃phen follows the sequence: ormosil/Tb(Tfacac)₃phen>silica/Tb(Tfacac)₃phen>pure Tb(Tfacac)₃phen.     

Synthesis and properties of chitosan/SiO2 hybrid materials

This study primarily aims to explore the strength and thermal properties of various hybrid materials that are made of tetraethoxysilane/vinyltriethoxysilane (TEOS/VTES) and chitosan in different weight ratios. It is confirmed, from micro Fourier transform infrared (micro FT-IR) and nuclear magnetic resonance (NMR) analysis, that hydrogen bonds emerge between chitosan and SiO₂ in hybrid materials. With the addition of more VTES and TEOS, the surface of the hybrid material features thick granules. In addition, the mechanical performance and thermostability of both types of hybrid are better than pure chitosan. The former is enhanced with an increasing amount of TEOS until it exceeds 2.4 g and the latter is also improved with an increasing amount of TEOS.     

Deposition of functional coatings on polyethylene terephthalate films by magnetron-plasma-enhanced chemical vapour deposition

Magnetron-plasma enhanced chemical vapour deposition (PECVD) is a process tool which allows the deposition of plasma polymer coatings at process pressures below 1 Pa. The striking features of this technology are the relatively easy realisation of large area deposition as well as the possibility of the combination with sputtering processes for multilayer coating designs. SiO_xC_y coatings were deposited on polymer film in a roll-to-roll deposition machine. Dynamic deposition rates as high as 120 nm?m/min were achieved. The process was set up with both the monomer hexamethyldisiloxane and the monomer tetraethylorthosilicate (TEOS) and with mixtures thereof. The coatings were analysed by Fourier transform infrared spectroscopy. This method identifies the existence of different types of Si-O bonding in the layer. The results show how the layer properties are linked to the plasma parameters of the deposition process. The properties were compared to sputtered SiO₂ and to layers obtained by other PECVD processes. Elastic recoil detection analysis (ERDA) was used in order to determine the composition of the samples. Both IR spectroscopy and ERDA revealed that the usage of TEOS provided more SiO₂-like layers. The process was applied to the deposition of optical multilayer coating in a roll-to-roll coating system.     

Biological characterization of a new silicon based coating developed for dental implants

Taking into account the influence of Si in osteoblast cell proliferation, a series of sol–gel derived silicon based coating was prepared by controlling the process parameters and varying the different Si-alkoxide precursors molar rate in order to obtain materials able to release Si compounds. For this purpose, methyltrimethoxysilane (MTMOS) and tetraethyl orthosilicate (TEOS) were hydrolysed together and the sol obtained was used to dip-coat the different substrates. The silicon release ability of the coatings was tested finding that it was dependent on the TEOS precursor content, reaching a Si amount value around ninefolds higher for coatings with TEOS than for the pure MTMOS material. To test the effect of this released Si, the in vitro performance of developed coatings was tested with human adipose mesenchymal stem cells finding a significantly higher proliferation and mineralization on the coating with the higher TEOS content. For in vivo evaluation of the biocompatibility, coated implants were placed in the tibia of the rabbit and a histological analysis was performed. The evaluation of parameters such as the bone marrow state, the presence of giant cells and the fibrous capsule proved the biocompatibility of the developed coatings. Furthermore, coated implants seemed to produce a qualitatively higher osteoblastic activity and a higher number of bone spicules than the control (uncoated commercial SLA titanium dental implant).     

Silica nanofilms deposited by atmospheric pressure plasma liquid deposition

Silica coatings were deposited onto pure silicon surfaces by a deposition technique known as atmospheric pressure plasma liquid deposition using liquid tetraethylorthosilicate (TEOS) as a precursor. Deposition parameters were varied, including power, TEOS flow rate, helium flow rate, and substrate distance, in order to assess their influence on the growth rates and refractive index as well as the formation of surface particulates and organic content of the coatings. Growth rates were accurately controlled in the range of 0.5 nm s^− 1 to 7.2 nm s^− 1, with thin-films having refractive indices ranging from 1.1 to 1.4, indicative of layers with different levels of porosity. The results suggest that, with careful selection of deposition parameters, this (atmospheric pressure) plasma-based deposition technique could be used to achieve coherent, particulate free, smooth dense inorganic silica coatings.     

Luminiscent dye Rhodamine 6G doped monolithic and transparent TEOS silica xerogels and spectral properties

Sol–gel process was used for the preparation of Rhodamine 6G (R6G) doped silica xerogels, using tetraethylorthosilicate [TEOS, Si(OC₂H₅)₄] as the precursor for the silica network. Silica alcosol was prepared by hydrolysis and polycondensation of ethanol (EtOH) diluted TEOS in the presence of citric acid (CTA) catalyst. The ethanolic R6G was added to the alcosol to trap R6G molecules inside the SiO₂ gel network during the gelation of the TEOS alcosol. The effect of CTA/TEOS molar ratio on the gelation time of the R6G doped TEOS alcosol, transparency and monolithicity of the R6G doped silica xerogel was studied by varying the CTA/TEOS molar ratio from 1.2 × 10^-4 to 180 × 10^-4 by keeping the molar ratios of TEOS:EtOH:H₂O:R6G constant at 1:5:7:9.2× 10^-6, respectively. It was found that the minimum (<70 h) gelation time was observed at higher and lower CTA/TEOS molar ratios of 72 × 10^-4 where as maximum (>180 h) gelation time was observed for CTA/TEOS molar ratio of 72 × 10²⁴. While opaque and monolithic R6G doped SiO₂ xerogels were obtained for <4.8 × 10^-4 CTA/TEOS molar ratios, whereas cracked and transparent xerogels were obtained for >120 × 10^-4 molar ratios of CTA/TEOS. Transparent, homogeneous and monolithic samples were obtained between 4.8 × 10^-4 and 120 × 10^-4 of CTA/TEOS molar ratios. Leaching out property was studied by using water, methanol and ethanol solvents for the R6G doped SiO₂ xerogels of 9.2 × 10^-6 and 12 × 10^-4 of R6G/TEOS and CTA/TEOS molar ratios, respectively, and found that R6G molecules were trapped in the pores of the SiO₂ network.

Bleaching out phenomena of the R6G doped SiO₂ xerogels was studied by focusing the high intensity light on some part of the samples for a period of 1 h and found that the pores were continuous in SiO₂ network. Visible spectra of R6G in water, ethanol, SiO₂ alcosol and xerogel were taken for 1.6 × 10^-4 M R6G andobserved that there were two absorption peaks at 499 and 525 nm in the spectrum of R6G in water due to dimerization of R6G molecules and only one absorption peak at 530 nm in the spectra of ethanol, SiO₂ alcosol and xerogel because of monomerization of R6G molecules. Visible spectra of the R6G doped silica xerogels for varying R6G/TEOS molar ratios from 9.2 × 10^-8 to 9.2 × 10^-5 were taken and found the red shift (5–10 nm) with increasing the R6G/TEOS molar ratio from 9.2 × 10²⁸ to 9.2 × 10^-5. The effect of temperature on these sample was studied by varying the temperature from 50 to 300 8C and found that the R6G doped silica samples were stable up to 200 8C. IR spectra were taken for pure R6G powder and R6G doped silica xerogels of 9.2 × 10^-8 and 9.2 × 10^-5 R6G/TEOS molar ratios and found that most of the peaks present in pure R6G powder spectrum were absent in the spectra of trapped R6G SiO₂ xerogels. This shows that, the SiO₂ network hinders the rotational and vibrational transitions of R6G when it is caged in the SiO₂ network. The peaks related to bending motion in R6G molecules were not disturbed by the SiO₂ network     

Luminiscent dye Rhodamine 6G doped monolithic and transparent TEOS silica xerogels and spectral properties

Sol–gel process was used for the preparation of Rhodamine 6G (R6G) doped silica xerogels, using tetraethylorthosilicate [TEOS, Si(OC₂H₅)₄] as the precursor for the silica network. Silica alcosol was prepared by hydrolysis and polycondensation of ethanol (EtOH) diluted TEOS in the presence of citric acid (CTA) catalyst. The ethanolic R6G was added to the alcosol to trap R6G molecules inside the SiO₂ gel network during the gelation of the TEOS alcosol. The effect of CTA/TEOS molar ratio on the gelation time of the R6G doped TEOS alcosol, transparency and monolithicity of the R6G doped silica xerogel was studied by varying the CTA/TEOS molar ratio from 1.2×10⁻⁴ to 180×10⁻⁴ by keeping the molar ratios of TEOS:EtOH:H₂O:R6G constant at 1:5:7:9.2×10⁻⁶, respectively. It was found that the minimum (<70 h) gelation time was observed at higher and lower CTA/TEOS molar ratios of 72×10⁻⁴ where as maximum (>180 h) gelation time was observed for CTA/TEOS molar ratio of 72×10⁻⁴. While opaque and monolithic R6G doped SiO₂ xerogels were obtained for <4.8×10⁻⁴ CTA/TEOS molar ratios, whereas cracked and transparent xerogels were obtained for >120×10⁻⁴ molar ratios of CTA/TEOS. Transparent, homogeneous and monolithic samples were obtained between 4.8×10⁻⁴ and 120×10⁻⁴ of CTA/TEOS molar ratios. Leaching out property was studied by using water, methanol and ethanol solvents for the R6G doped SiO₂ xerogels of 9.2×10⁻⁶ and 12×10⁻⁴ of R6G/TEOS and CTA/TEOS molar ratios, respectively, and found that R6G molecules were trapped in the pores of the SiO₂ network.Bleaching out phenomena of the R6G doped SiO₂ xerogels was studied by focusing the high intensity light on some part of the samples for a period of 1 h and found that the pores were continuous in SiO₂ network. Visible spectra of R6G in water, ethanol, SiO₂ alcosol and xerogel were taken for 1.6×10⁻⁴ M R6G and observed that there were two absorption peaks at 499 and 525 nm in the spectrum of R6G in water due to dimerization of R6G molecules and only one absorption peak at 530 nm in the spectra of ethanol, SiO₂ alcosol and xerogel because of monomerization of R6G molecules. Visible spectra of the R6G doped silica xerogels for varying R6G/TEOS molar ratios from 9.2×10⁻⁸ to 9.2×10⁻⁵ were taken and found the red shift (5–10 nm) with increasing the R6G/TEOS molar ratio from 9.2×10⁻⁸ to 9.2×10⁻⁵. The effect of temperature on these sample was studied by varying the temperature from 50 to 300 °C and found that the R6G doped silica samples were stable up to 200 °C. IR spectra were taken for pure R6G powder and R6G doped silica xerogels of 9.2×10⁻⁸ and 9.2×10⁻⁵ R6G/TEOS molar ratios and found that most of the peaks present in pure R6G powder spectrum were absent in the spectra of trapped R6G SiO₂ xerogels. This shows that, the SiO₂ network hinders the rotational and vibrational transitions of R6G when it is caged in the SiO₂ network. The peaks related to bending motion in R6G molecules were not disturbed by the SiO₂ network     

Influence of hydrophobic characteristic of organo-modified precursor on wettability of silica film

The objective of this study is to design new hybrid silica materials as templates with hydrophobic properties, prepared at room temperature by a base catalyzed sol–gel process. As silica sources, organoalkoxysilanes functionalized with short hydrophobic chains were used: tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES), vinyltriethoxysilane (VTES), octyltriethoxysilane (OTES) and isobutyltriethoxysilane (iTES). It was shown that hydrophobicity of the functionalized silica nanoparticles increased as a function of length of the aliphatic chains (MTES < iTES < OTES) or when, instead of a hydrophobic alkyl chains (substituting group of silica precursors), a monounsaturated group was used (VTES). It was observed that the samples responded in a specific way to each type (hydrophilic or hydrophobic) of the dropped liquid. Even though the experiments were limited to short hydrocarbon chains, they showed that there is a threshold to reach high hydrophobicity of the hybrid surface.     

Bioactive coatings obtained at room temperature with hydroxyapatite and polysiloxanes

Low temperature Hydroxylapatite (HA) coatings were obtained on metal substrates by depositing HA particles suspended in a ormosil polymer gel made of an equimolar mixture of amino and epoxy substituted silanes. The new coatings were analysed by thermal analysis, infrared and solid state NMR, as well as X-ray diffraction and SEM observations. Results show the HA powder conserves its characteristic physicochemical properties during the coating process. Furthermore, the coatings induce the formation of a biomimetic HA layer when soaked in simulated body fluids. This room temperature process may lead to novel calcium phosphate coatings with better control of crystallinity and porosity and with the possible incorporation of biofunctional organic molecules.     

LY12铝合金表面有机-无机杂化膜的防腐性能研究

以乙烯基三甲氧基硅烷(VMS)、γ-(甲基丙烯酰氧)丙基三甲氧基硅烷(MPMS)和γ-环氧丙基醚基三甲氧基硅烷(GPMS)三种硅烷偶联剂为前驱体,制备了正硅酸乙酯(TEOS)改性的有机-无机杂化膜.采用动电位极化曲线测试了膜层的防腐性能,考察了TEOS含量对其的影响.以腐蚀电流为指标,比较了三种体系杂化膜的防腐能力.利用盐雾试验和电子扫描照片研究了杂化膜耐长久腐蚀行为.结果表明,杂化膜的存在有效地抑制了腐蚀反应的发生,VMS和MPMS膜层可使腐蚀电流减小300多倍.当TEOS含量为15%～20%(质量分数,下同)时,膜层的腐蚀电流最小.比较而言,VMS-TEOS膜层的耐蚀能力最强,GPMS-TEOS膜层最差.VMS膜层和VMS 20%TEOS膜层耐盐雾腐蚀的能力最强,总体来说,杂化膜耐长久腐蚀的能力较差.     

Adsorptive properties of sol–gel derived hybrid organic/inorganic coatings

Hybrid organic-inorganic sol–gel derived coatings have been prepared by dip coating on glass substrates from alcoholic solutions of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), 3-aminopropyltriethoxysilane (APTES), 3-glycidoxypropyltrimethoxysilane (GPTMS) and phenyltriethoxysilane (PhTES). The hybrid materials have been fully characterized by means of solid state NMR spectroscopy and X-ray diffraction. The degree of cross-linking and the extent of interaction between silica and silsesquioxane phases appear dependent on the ratio between TEOS and organotrialkoxysilane and on the chemical features of the organic function linked to silicon, and influence the sorption ability towards aromatic compounds of hybrid films. The hybrid coatings have been put into an optical-grade quartz chamber placed into a UV–VIS–NIR spectrophotometer and the organic compounds have been allowed flowing through the chamber recording of molecule absorption spectra vs. time. Absorbance curves vs. time have also been collected at a fixed wavelength for different molecule-coating couples and simple kinetic models have been used for comparing the adsorption capability of the different films, which has been related to the chemical interactions between molecules and coatings.     

Studies on the effect of organic additives on the monolithicity and optical properties of the rhodamine 6G doped silica xerogels

Rhodamine 6G (R6G) laser dye doped silica xerogels were prepared by sol–gel processing using tetraethylorthosilicate [TEOS, Si(OC₂H₅)₄] precursor, citric acid (CTA) catalyst and ethanolic R6G in the presence of various organic additives such as formamide (FA), N′methylformamide (N′MF), dimethylformamide (DMF), acetamide (AA), glycerol (GLY), oxalicacid (OXA), ethyleneglycol (EG) and diethyleneglycol (DEG). The organic additive/TEOS molar ratio was varied from 0.001 to 0.1 by keeping the TEOS/EtOH/H₂O/CTA/R6G molar ratio constant at 1:5:7:1.2×10⁻³:9.2×10⁻⁶. It was found from the spectral studies of the additive modified R6G doped silica xerogels that the absorption maxima at 530 nm and emission maxima at 565 nm were increased with the addition of organic additive and with the increase of the additive/TEOS molar ratio. The transparency of the R6G doped silica xerogels was increased with the increase of additive/TEOS molar ratio from 0.001 to 0.1 with OXA, DEG and EG and in the case of DMF, N′MF, FA, AA and GLY, the transparency of the samples increased up to 0.014 of additive/TEOS molar ratio and then decreased for >0.014 of additive/TEOS molar ratio. Monolithic samples were obtained with all the organic additives. The percentage volume shrinkage of the samples was less EG and DEG and more with OXA additives.     

Effect of preparation conditions on the physical and hydrophobic properties of two step processed ambient pressure dried silica aerogels

The experimental results on the physical and hydrophobic properties of the ambient pressure dried silica aerogels as a function of sol-gel and drying conditions, are reported.The aerogels have been produced by a two stage (acidic and basic) catalytic sol-gel process using tetraethylorthosilicate (TEOS) precursor, oxalic acid (OXA) and ammonium hydroxide (NH₄OH) catalysts, ethanol (EtOH) solvent and hexamethyldisilazane (HMDZ) silylating agent at 200^∘C.The molar ratios of HMDZ/TEOS (M), OXA/TEOS (A) NH₄OH/TEOS (B), acidic H₂O/TEOS (Wa) basic H₂O/TEOS (Wb), EtOH/TEOS (S) were varied from 0.09 to 0.9, 3.115 × 10^{− 5} to 3.115 × 10⁻³, 4 × 10^{− 3} to 8 × 10^{− 2}, 2 to 9, 1.25 to 5 and 1 to 16 respectively. The physical properties such as the percentage (%) of volume shrinkage, density, thermal conductivity, percentage of porosity, the percentage of optical transmission and contact angle have been found to be strongly dependent on the sol-gel parameters. It was found from the FTIR spectra of the aerogels that with the increase of M, the bands at 3500 and 1600 cm^{− 1} corresponding to H-OH and Si-OH respectively decreased and the bands at 840 and 1250 cm^{− 1} due to Si-C and 2900 and 1450 cm⁻¹ due to C-H increased. The best quality silica aerogels in terms of low density, low volume shrinkage, low thermal conductivity, high hydrophobicity and high optical transmission have been obtained with the molar ratio of TEOS:EtOH:acidicH₂O:basicH₂O:OXA:NH₄OH:HMDZ at 1:8:3.75:2.25:6.23 × 10^{− 5}: 4 × 10^{− 2}:0.36 respectively, by ambient pressure dried method.     

Preparation of monodispersed spherical silicon carbide by the sol-gel method

Monodispersed spherical SiC gel powders were synthesized by hydrolysis and condensation of phenyltrimethoxysilane (PTMS) or a mixture of PTMS and tetraethylorthosilicate (TEOS) from a system of silane-H₂O-catalyst to which no co-solvent such as alcohol was added. The experiments were conducted through two routes; base catalysed and acid base catalysed routes. In each process, excess water was used as a dispersing medium in addition to a hydrolysing agent. In the base-catalysed route, monodispersed spherical gel powders were obtained regardless of NH₄OH content used in this experiment when the concentration of silane and the molar ratio of TEOS to PTMS were less than 0.5 mol l⁻¹ and 0.5, respectively. In the acid-base catalysed route, polydispersed powders were produced when the concentration of silane exceeded 0.25 mol l⁻¹. When heated above 1400°C, the initially monodispersed powders sustained their shape in the PTMS-TEOS system, but bulk and fibre phase were produced in the PTMS system.     

Preparation of nanoporous silica–zirconia layers by in situ sol–gel method

Abstract

Silica–zirconia membranes were prepared using a sol–gel process, never before used on this system. Thin layers of gel were grown on the outside of porous alumina support tubes using the permeation of water through pores of the tube to control the rate of hydrolysis with a reactive silica–zirconia alkoxide solution. A recipe was developed and optimum coating conditions were found to be the ratios of tetraethylorthosilicate (TEOS) to Zr propoxide to 1-propanol molar ratios (1:0·5:17), with a coating time of 300 s. The method allowed the formation of a membrane in a single step compared with repeated coating and firing. The coatings could be prepared adherent and without cracks when properly prepared.     

Silane-modified MWCNT/PMMA composites – Preparation, electrical resistivity, thermal conductivity and thermal stability

Multiwalled carbon nanotubes (MWCNT) were modified using 3-isocyanato- propyltriethoxysilane (IPTES). Crosslinkable PMMA was prepared from MMA monomer and Vinyltriethoxysilane (VTES) (PMMA–VTES). The IPTES-modified MWCNT (Si-MWCNT) was mixed with the PMMA–VTES copolymer and crosslinked with catalyst to form Si-MWCNT/PMMA–VTES composites. The degree of condensation of tri-distribution structure of the Si-MWCNT/PMMA–VTES composites decreases as the Si-MWCNT content increases. The morphology of the Si-MWCNT/PMMA–VTES composites was analyzed by SEM and TEM. The MWCNTs were well dispersed in the PMMA–VTES matrix. Surface and volume electrical resistivity decreased as the MWCNT content increased. The thermal conductivity of the PMMA–VTES composites increased by 87.5% when 0.99 wt% Si-MWCNT content was added to neat PMMA–VTES. The thermal stability of the PMMA–VTES in nitrogen and air increased significantly even when a small quantity (0.5 wt%) of Si-MWCNT was added.     

具有自洁和耐磨功能SiO2/TiO2减反膜的制备与研究

以正硅酸乙酯(TEOS)和钛酸正丁酯(TBOT)为原料,采用溶胶-凝胶法制备了SiO2溶胶和TiO2溶胶,利用浸渍提拉法制备了SiO2/TiO2双层减反膜.用紫外-可见分光光度计(UV-Vis)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)、椭圆偏振光谱仪和接触角测量仪等分析表征了薄膜的特性,以光催化降解甲基橙溶液实验来评价薄膜的自洁功能,考察了SiO2/TiO2双层减反膜的耐磨擦性.结果表明,SiO2/TiO2双层减反膜在400~800nm可见光波段的透光率最高可达97.2%,薄膜表面平整,结构致密且粗糙度小,经紫外灯照射后薄膜的水接触角接近0°,光催化2h后可将5mg/L的甲基橙溶液降解43.6%.SiO2/TiO2减反膜还具有优良的耐磨擦性能.     

溶胶-凝胶法制备抗原子氧涂层及性质研究

采用有机无机复合的溶胶-凝胶方法,合成了用于聚合物表面保护层的前驱溶液.采用旋转涂覆方法,将前驱溶液涂覆于聚酰亚胺基片上,制成了表面涂层.将所制得的相应涂层分别进行原子氧暴露试验,其表面形貌的变化通过扫描电镜观测.结果表明,在原子氧辐照下,无保护的聚酰亚胺表面已非常粗糙,与辐照前的光滑表面形成显著的对比.而涂覆有保护层的表面,原子氧辐照前后却没有变化.这表明使用这种有机无机复合的溶液涂层具有很好的抗原子氧能力.     

Surface properties of bioactive TEOS–PDMS–TiO2–CaO ormosils

Tetraethyl orthosilicate (TEOS)–polydimethyl siloxane (PDMS) ormosils with different amounts of Ti and Ca were prepared and characterized. Several surface properties such as specific surface area, porosity, fractality, dispersive and polar surface energies were determined and related with their in-vitro bioactivity. It has been found a dependence of the surface fractal dimension with the concentration of Ca²⁺ ions that induce the appearance of rough surfaces. The dispersive surface energy, γ _S ^d , increased with the incorporation of Ti or Ca and the presence of micropores, but Ca(NO₃)₂ precipitates in the surface coming from non-incorporated Ca lead to a decrease of the surface energy values. In relation with the polar surface energy, it has been observed that all ormosil materials presented amphoteric character with a larger presence of base surface sites than acid ones. The basicity of the surface increased with the concentration of Ti and Ca, while the acidity decreased. The in-vitro bioactivity of the surface was estimated by soaking samples in simulated body fluid (SBF) and afterwards characterized by means of X-ray diffraction (TF-XRD) and field emission scanning electron microscopy (FE-SEM). It has been observed that in vitro bioactivity is related with the polar surface characteristics of these materials, being necessary for the bioactivity, the presence of a highly polar surface with intermediate base/acid ratio and specific roughness.