TEOS Precursor Research Articles

Characterization of SiO2 sol-gel coated Ti6Al4V alloy obtained by using TEOS and GPTMS

Synthesis of silicon oxide (SiO2) via the sol-gel method and SiO2 coating ability on to Ti6Al4V alloy were investigated, in the novel study. Ti6Al4V alloy is the most used alloy in biomedical applications due to its many advantages. However, it has a minor disadvantage like releasing ions into the human body. In this study, the substrate material Ti6Al4V alloy samples were coated using the sol-gel method with alkoxysilane solutions (tetraethyl orthosilicate, TEOS; Si(OC2H5)4 and glycidoxypropyltrimethoxysilane, GPTMS; C9H20O5Si) containing the unit of prepared Si(OR)n after the surface preparations were made. The prepared solutions were examined using thermal analysis methods and the process temperatures to be applied to the coatings were determined according to the results of the analysis. Coated samples were subjected to aging, drying, and sintering processes at specified temperatures. The morphologies and structures of the samples were investigated by using a scanning electron microscope with energy-dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The sol-gel coating ability of the silicon oxide on the surface of the Ti6Al4V alloys has been discussed. The results demonstrate that cracks were observed in coating produced by TEOS precursor whereas the coatings used GPTMS precursor exhibited crack-free surface independently of dipping number. The crack formation tended to reduce with increasing dipping number of coatings produced by TEOS precursor. Distances between coating islets gradually became smaller as the number of dippings increased, and the continuity of the coatings increased. It has been observed that SiO2 coating layers produced with GPTMS are obtained in a more continuous and crack-free form than the layers produced with TEOS.

Surface modification of blended fabrics by silica nanoparticles to improve their printability

The sol-gel technique offers an effective way of modifying fabrics, and has many advantages. In this paper, silica nano particles in the solid form were prepared from TEOS precursor; further application of these silica nanoparticles to polyester wool, and polyester cotton blends as well as polyester and cotton fabrics is carried out. Improved fabrics printability, as well as acquiring antibacterial properties were achieved. The basic idea for using sol-gel technology to modify fabric blend surfaces in order to solve their coloration problems and to attain solid shades using a single set of dyes.

Reinforcing effect of imidazole modified nanosilica on thermal and mechanical properties of anhydride based epoxy system

Abstract In this study, imidazole modified nanosilica (IS) was prepared from TEOS precursor by sol-gel via co-condensation method. The surface modification was confirmed by FTIR and SEM characterization. Further, epoxy nanocomposites were prepared using different content (0-3 wt %) of IS. TGA analysis demonstrated the significant effect of IS towards enhancement of thermal stability of epoxy composites at 1 wt% IS particle contents. The maximum enhancement in tensile strength of composites (1 wt% IS) was achieved by 45% with respect to neat epoxy. From these results, it confirms that the organic compatibility and chemical bonding at the interface around IS favours effective stress transfer to the matrix system. Thus, this work exposed the potential of imidazole modified nanosilica as a good choice of reinforcement in the field of composite industries.

The interaction characteristics controlling dispersion mode-catalytic functionality relationship of silica–modified montmorillonite-anchored Ni nanoparticles in petrochemical processes

This study has dealt with different interaction events during the synthesis of silica-modified montmorillonite (SMM) nanocomposites. TEOS precursor was intercalated into the clay (M) gallery (in M/TEOS mass ratios = 1:2 and 1:6), assisted by dodecylamine (DDA) or CTAB driving agents (at constant surfactant/M ratio = 1.8). Ni NPs (of 2, 4, 6 wt%) were immobilized into the gallery of H-SMM sample (M/TEOS = 1:6). Various characteristics were studied via XRD, EDX, FTIR, N2 physisorption, H2-pulse titration, DSC-TGA, TEM and DLS techniques. The formed Silica NPs were attached on platelet surface through the interaction with edge aluminol sites in octahedral sheet. Considerable delamination of clay platelets was observed by increasing the M/TEOS ratio and in presence of CTAB, exhibiting higher surface area and pore parameters. Ni NPs were anchored onto the bonded silica at clay layer edges through interactions involving DDA, interlayer sites and silica NPs. Ni nanocatalysts were tested in ethyl benzene (EB) conversion, considering possible reaction pathways according to various interaction events affecting the catalytic behavior. TOF of the reaction to selectively produce styrene remained constant with Ni loadings, suggesting that dehydrogenation pathway is structure insensitive. The constancy of TOF to produce optimized quantities of benzene favored the involvement of edge interlayer acid sites in cracking pathway, independent of Ni NPs content. TOF to selectively produce ethane in cracking pathway increased with Ni loading, where enlarged surface Ni NPs (reaching to 202 nm) seemed to control this structure sensitive pathway.

Comparative studies on the physical properties of TEOS, TMOS and Na2SiO3 based silica aerogels by ambient pressure drying method

In order to compare the various precursors of silica aerogels, three different precursors namely TMOS, TEOS and Na2SiO3 were studied in this paper. The property differences of the aerogels caused by the three precursors were discussed in terms of reaction process, gelation time, pore size distributions, thermal conductivity, SEM, hydrophobicity and thermal stability. It has been found that the gelation time of the silica gel is strongly dependent on the type of precursor used. During the surface modification process, organic groups were attached to the wet gel skeletons transforming the hydrophilic to the hydrophobic which were characterized by Fourier Transform Infrared spectroscopy (FTIR). It has been found that the contact angle of the Na2SiO3 and TMOS precursor based aerogels with water have the higher contact angle of 149° and whereas Na2SiO3 precursor based aerogel has the lower contact angle of 130°. The thermal conductivities of the Na2SiO3 and TMOS based aerogels have been found to be lower (0.025 and 0.030 W m−1 K−1, respectively) compared to the TEOS based (0.050 W m−1 K−1) aerogels. The pore sizes obtained from the N2 adsorption measurements varied from 40 to 180, 70 to 190, and 90 to 200 nm for the TEOS, TMOS and Na2SiO3 precursor based aerogels, respectively. The scanning electron microscopy studies of the aerogels indicated that the Na2SiO3 and TMOS based aerogels show narrow and uniform pores while the particles of SiO2 network are very small. On the other hand, TEOS aerogel show non-uniform pores such that the numbers of smaller size pores are less compared to the pores of larger size while the SiO2 particles of the network are larger as compared to both Na2SiO3 and TMOS aerogels. Hence, the surface are of the aerogels prepared using TEOS precursor has been found to be the lowest (~620 m2 g−1) compared to the Na2SiO3 (~868 m2 g−1) and TMOS (~764 m2 g−1) aerogels.

Study of thermal properties of mullite porous materials

Green ceramic bodies based on mullite were infiltrated with SiO2 (TEOS precursor) solution using a sol–gel technique and sintered at 1,300 °C. Previously, the green bodies had been prepared with the molding method, using corn flour as the pore-forming agent with a concentration in mass percent of 10, 15, and 20, and then they were sintered. Infiltrated ceramic material was evaluated to determine the relationship between, morphology, porosity, thermal properties, and crystalline characteristics by scanning electron microscopy, X-ray diffraction, porosimetry by N2 at 77 K, and thermal analysis using laser flash technique. The presence of SiO2 together with magnesium (talc powder) gives a cordierite crystalline phase, which is considered presenting thermal stability. Infiltration process changes the surface area, which is reduced by 93 %, and the pore size value reaches 1.98 nm, changing from open to closed structure. In spite of porosity change, thermal conductivity increases in the majority of the samples. This phenomenon obeys the complex system involved in the study, such as closed porosity, microstructure, tortuosity, geometry, and the anisotropy of mullite bonds, accompanied by the infiltrant liquid (SiO2).

Hydrophobic and low density silica aerogels dried at ambient pressure using TEOS precursor

Abstract In the conventional ambient pressure drying of silica aerogels, tedious repetitive gel washing and solvent exchange steps (∼6 days) are involved. Therefore, in the present studies, we intended to reduce the processing time of TEOS based ambient pressure dried silica aerogels. Solvents such as methanol, hexane and Hexamethyldisilazane (HMDZ) as surface chemical modification agents have been used. To get good quality aerogels in terms of low density, high porosity, high contact angle and low volume shrinkage in less processing time, we varied MeOH/TEOS, HMDZ/TEOS molar ratios, oxalic acid (A) and NH 4 OH (B) concentrations and stirring time from 1 to 27.7, 0.34 to 2.1, 0 to 0.1 M, 0 to 2 M and 15 to 90 min respectively. The transparent and low-density aerogels were obtained for TEOS:MeOH:acidic H 2 O:basic H 2 O:HMDZ molar ratio of 1:16.5:0.81:0.50:0.681 respectively. The thermal stability and hydrophobicity have been confirmed with Thermogravimetric and Differential Thermal (TG–DT) analyses and Fourier Transform Infrared Spectroscopy. Microstructural study was carried out by Scanning Electron Microscopy (SEM).

Effect of SC-1 Treatment in Thermal Wall Oxide on Nanoscale STI Gap-Filling by O<sub>3</sub>/TEOS CVD

The SC-1 treatment prior to the O3/TEOS CVD was a very effective method for gapfilling the nanoscale trench of the high aspect ratio by improving the adsorption of TEOS precursors onto the wall oxide. It was found that the interval duration after the SC-1 cleaning was a critical parameter for the contact angle and the gapfill performance of the O3/TEOS CVD.

The influence of the dielectric on the properties of dielectromagnetic soft magnetic composites. Investigations with silica and silica hybrid sol–gel derived model dielectric

Dielectromagnetics made from organic–inorganic hybrid silica-coated iron powders were characterised by determination of their physical, mechanical and magnetic properties. The influence of three main factors, dielectric composition, addition level and heat treatment conditions were investigated. Results showed that these factors have significant effects on the performance of the dielectromagnetics. Increase in the organic phase content in these dielectric coatings tends to increase both the electrical resistivity and magnetic permeability of dielectromagnetics, although the strength and density are slightly impaired. Increasing the coating thickness leads to improvements in resistivity and thus reduced eddy current losses, but these are offset by reductions in density, strength and particularly magnetic permeability. A hybrid organic–inorganic coating formulation based on 40 mol% MTMS and 60 mol% TEOS precursors was found to be the optimum composition investigated. Addition levels between 0.1% and 0.3% were found to offer a good compromise between maximum permeability ( μ max>400) and minimum loss (typically <8 W/kg) for operation at 50 Hz/1 T, and the system can be optimised within this range for the desired performance.

Evaluation of silicon oxide cleaning using F2∕Ar remote plasma processing

In this study, chamber cleaning experiments using a F2∕Ar remote plasma generated from a toroidal-type remote plasma source were carried out in a plasma enhanced chemical vapor deposition (PECVD) system. The cleaning processes for the various silicon oxide layers, including PE-oxide (deposited by PECVD using SiH4 and N2O), O3-TEOS oxide (deposited by thermal CVD using ozone and TEOS precursor), and BPSG (borophosphosilicate glass), were investigated by varying the various process parameters, such as the F2 gas flow rate, the F2∕(F2+Ar) flow ratio, and the cleaning temperature. The species emitted during cleaning were monitored by Fourier transformed infrared spectroscopy and residual gas analysis. Under the current experimental conditions, the cleaning rate of the BPSG was 4.1–5.0 and 3.9–7.3 times higher than that those of the PE-oxide and O3-TEOS oxide layers, respectively, at room temperature and an F2∕(F2+Ar) flow ratio of 28.5%–83%. As the cleaning temperature increased from 100 to 350 °C, the cleaning rates of the PE-oxide, O3-TEOS oxide, and BPSG layers were increased by factors of 2.0–3.0, 1.5–2.2, and 3.0–3.4, respectively, at an F2∕(F2+Ar) flow ratio of 28%–68%. The F2∕(F2+Ar) flow ratio and cleaning temperature were found to be the most critical parameters involved in determining the cleaning rate of the various oxide layers.

Comparative studies on the surface chemical modification of silica aerogels based on various organosilane compounds of the type RnSiX4−n

We report the experimental results dealing with the surface chemical modification of silica aerogels using various precursors and co-precursors based on mono-, di-, tri- and tetrafunctional organosilane compounds of the type RnSiX4−n (where R=alkyl or aryl groups, X=Cl or alkoxy groups, n=0–4). The precursors exhibit either tetrafunctional or trifunctional chemical functions while the co-precursors have a number of functional groups varying from 1 to 3. The organosilane based on the methyltrimethoxysilane (MTMS) can be used as a precursor as well as co-precursor. The chemically modified aerogels have been produced by (i) co-precursor, and (ii) derivatization methods. The co-precursor method results in aerogels with higher contact angle (θ≈136°) but the aerogels are opaque, whereas transparent (>80% optical transmission in the visible range) aerogels with lower contact angle (θ≈120°) are obtained using the derivatization method. The hydrophobicity of the phenyl-modified aerogels has been found to be thermally stable up to a temperature of 520°C. Using the MTMS precursor, aerogels with contact angles as high as 175° have been obtained, but the aerogels are opaque. The aerogels obtained using TEOS precursor along with the trimethylethoxysilane (TMES) co-precursor, show negligible volume shrinkage. Water intrusion into the MTMS-modified aerogels at pressures greater than the Laplace pressure exhibits hysteresis, as shown in the pressure-volume curves. Water droplets placed on surfaces coated with superhydrophobic aerogel powder with 8° of inclination showed velocities as high as 0.4ms−1. The results are discussed with respect to the ratios of organic and inorganic components of the organosilane compounds.

SILK compatibility with the IMD process using copper metallization

This work presents the results of SILK compatibility with the materials used in the damascene structure with copper metallization. Firstly, the thermal stability of the material was carefully evaluated; excellent stability at 450°C was confirmed. Moreover, 450°C is a good curing temperature for obtaining a low dielectric constant (2.7). The conventional PECVD hard masks, SiO 2 (from SiH 4 or TEOS precursors) and Si x N y do not affect the SILK properties. Finally, it was verified that an OMCVD TiN barrier is efficient in preventing copper diffusion. It was demonstrated that SILK should reach the performance requested for IMD materials in the damascene structure with Cu metallization.

Thermal Evolution of Hybrid Sol-Gel Silica Coatings: A Structural Analysis

The sol-gel method has been increasingly used to prepare organic-inorganic hybrid coatings with both glass and polymeric properties by including alkylalkoxides with one or more non-hydrolizable groups in the precursor alkoxide solution. When using MTES and TEOS precursors, it was found that the increase in Si–CH3 bond concentration in the coating augments the critical thickness, and strongly affects other properties. The final methyl content depends on both the composition of the precursor solution and the thermal treatment for densification. But little is known about the effect of this organic group on the hybrid structure and microstructure of the coatings. In this work, the effect of methyl content on the film structure and the evolution of porosity are analysed by using ellipsometry and infrared spectroscopy. A theoretical correction of the refractive index of the film and a description of the thermal evolution of the coating structure are also proposed.