Mixture Of Hexamethyldisiloxane Research Articles

Wettability of polypropylene films coated with SiO x plasma deposited layers

Surface wettability of polypropylene (PP) films has been significantly improved by the deposition of thin SiO x layers, elaborated from a mixture of hexamethyldisiloxane (HMDSO) and oxygen in a microwave DECR (distributed electron cyclotron resonance) plasma reactor (2.45 GHz, 400 W). Contact angle measurements, Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to study, respectively, the change in surface free energy, surface topography and chemical composition due to the deposition of thin SiO x layers. Contact angle measurements revealed that the water contact angle value is reduced from about 99° for untreated PP surface to nearly 30° for coated PP film. The polar component of the surface energy is considerably increased from 0.5 to 35 mJ/m 2. For films deposited in the presence of VUV photons, AFM images showed the growth of irregular structure due to substrate etching effect and the deconvolution results of the Si 2p XPS peaks indicated that the proportion of the partly oxidized silicon environment was the major component. However, for films deposited without the presence of VUV radiation, typical SiO 2 agglomerates can clearly be seen on PP surface at a thickness of about 29 nm and the proportion of the silicon dioxide was the major component.

Preparation of plasma-polymerized SiO x-like thin films from a mixture of hexamethyldisiloxane and oxygen to improve the corrosion behaviour

Chemical and electrochemical properties of plasma polymerized SiO x -like thin films have been studied to search for an alternative to the anticorrosive coatings produced by chromate conversion treatment. The films were deposited on steel substrates by means of hexamethydisiloxane/oxygen-fed plasmas ignited in an RF capacitive coupled parallel plates reactor. Their surface chemical characterization was carried out by means of X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FT-IR). The protective abilities of SiO x -like films as a function of RF power and gas feed composition in aerated 1 M Na 2SO 4 solution were examined by electrochemical methods. Alone and in combination, these techniques help us to understand the relationship between the deposition parameters and the properties of the deposited films.

Structural and chemical characterization of functional SiOxCy:H coatings for polymeric lenses

The deposition of suitable hard protective coatings onto organic substrates for ophthalmic applications faces several challenges, such as proper surface preparation to ensure the adhesion to the rigid substrate and a delicate balance between hardness and flexibility. In this work it is shown that SiOxCy:H-based protective coatings grown by plasma enhanced chemical vapor deposition (PECVD) from mixtures of hexamethyldisiloxane and oxygen, can be used as protective buffer coatings between the soft and easily scratchable substrate and the antireflection stack that might be applied on top of it. These coatings must show absence of optical absorption and require index matching with the substrate. To meet these conditions, a three-phase multifunctional coating PECVD deposition method has been developed, in which a progressive decrease towards the surface in the carbon content of the SiOxCy:H hard coat has been implemented. Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy characterization of the individual layers that compose the multilayer functional structure has been performed. The comparison of the results obtained from each spectroscopy shows the complementarity of these techniques and allows optimizing the protective coating performance from the optical and mechanical points of view.

Thermal stability of coatings prepared in atmospheric pressure glow discharge

In order to better understand the relations between the deposition conditions, the microstructure and hydrogen and/or nitrogen incorporation in polymeric films the thermal stability of coatings prepared in atmospheric pressure glow discharge was studied. The polymeric films were prepared from the mixture of hexamethyldisiloxane (HMDSO) or hexamethyldisilazane (HMDSZ) with nitrogen in atmospheric pressure glow discharge (APGD). The hydrogen and/or nitrogen evolved from polymeric films were studied by ther.

Heavy-ion ERDA and spectroscopic ellipsometry characterization of a SiOC:H layered structure as functional coating on polymeric lenses

In order to improve the optical and mechanical performance of plastic ophthalmic lenses the use of surface coatings is necessary. However, the application of such coatings can be limited by bad adhesion to the substrate. One way to overcome this drawback is the use of a layered structure consisting of an adherent layer, an abrasion resistant hard layer and an antireflective (AR) multilayer (ML) stack. In this work we study the preparation of SiO x C y :H layered coatings to increase the mechanical durability of polymeric substrates and to accommodate gradually an external dielectric SiO 2/TiO 2 AR-ML. The coatings were grown by plasma assisted chemical vapor deposition (PACVD) using a mixture of hexamethyldisiloxane (HMDSO) and O 2. The possibility of producing the whole layered stack by adjusting the HMDSO:O 2 ratio was demonstrated. The composition and elemental profiles of the different layers were measured by ERDA using 35 MeV Cl-ions. A polymeric-like gradient layer could be formed followed by a buffer layer Si 28O 47C 15H 10 with a nearly constant composition. The variation of the elemental composition does not affect significantly the optical properties, which are close to that of SiO 2.

Improvement of the efficiency of the silicon solar cells by silicon incorporated diamond-like carbon antireflective coatings

In order to obtain further improvement of the efficiency of the solar cells based on silicon we deposited upon the solar cells a silicon incorporated diamond-like carbon (DLC:Si) antireflective coating. Besides the improvement of the efficiency of the cells the DLC:Si coating serves as the hard protective coating. The films were prepared by plasma enhanced chemical vapour deposition (PECVD) technique from the mixture of hexamethyldisiloxane (HMDSO, C 6H 18Si 2O) and methane. The optical and tribological properties of prepared coatings could be easily changed by the percentage of HMDSO in the deposition feed.

Variable-energy positron lifetime study of silicon-oxide films plasma deposited from hexamethyldisiloxane and oxygen mixtures

Mixtures of hexamethyldisiloxane [HMDSiO, (CH3)3SiOSi(CH3)3] and oxygen are plasma polymerized at different oxygen pressures (P = 1.3–11.4 Pa) and a fixed monomer pressure (Pm = 2.6 Pa). The discharge power is kept at 100 W throughout the work. Nanometer-size holes in the deposited films are characterized by variable-energy positron annihilation lifetime spectroscopy (PALS). Additional information on the film composition and structure is obtained by X-ray photoelectron spectroscopy and IR absorption spectroscopy. The ortho-positronium lifetime τ3 and intensity I3 increase with the P up to 6.2 Pa and then decrease with the P. PALS measurements after annealing at 400°C show that films prepared at high oxygen pressure have a less stable structure than a film deposited at a lower oxygen pressure. These results are discussed in comparison with plasma deposition of pure HMDSiO, as are the possible effects of oxygen radicals on the film structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 974–980, 2001

Plasma deposited thin films suitable as moisture sensors

Plasma polymerized thin films from a mixture of hexamethyldisiloxane (HMDSO) and ammonia (NH3) deposited directly onto a microdielectrometer chip have been evaluated as moisture sensors. Microdielectrometry was chosen as the measuring technique because of its fast response and real time detection capability. The sheet resistance of the plasma polymerized film was found to decrease by eight orders of magnitude with an increase in relative humidity from 0 to 92%. The moisture effect on the sheet resistance was also found to be reversible. The composition and structure of the films deposited from various mixtures of HMDSO/NH3 have been elucidated by Electron Spectroscopy for Chemical Analysis (ESCA) and infrared spectroscopy.

A thermally stable porous material prepared by heating partially trimethylsilylated halloysite

Halloysite was trimethylsilylated in a mixture of hexamethyldisiloxane, 2-propanol and hydrochloric acid to the extent that small amounts of raw halloysite remained. The resulting product (PTSH) was heated in nitrogen and air. Heating in air scarcely influenced thermal degradation. The PTSH was in an amorphous state at 673–1273 K and crystallized into mullite at a higher temperature. The N 2-BET specific surface area (250 m 2/g) of the PTSH increased to 390 m 2/g after heating to 673 K and decreased to 270 m 2/g at 1073 K in nitrogen. The PTSH, regardless of heat-treatment temperatures, included extremely homogeneous pores of 1.7 nm. The number of acidic sites and their acidic strength were lower than those of commercially available catalysts.

Critical properties of mixtures containing siloxanes

The critical temperatures of mixtures of octamethylcyclotetrasiloxane with four hydrocarbons, hexafluorobenzene, perfluorocyclohexane and carbon tetrachloride and mixtures of hexamethyl-disiloxane with a hydrocarbon and hexafluorobenzene are reported. The results have been compared with the van der Waals model proposed by Rowlinson and coworkers. The unlike interactions derived are compared with those predicted by three combining rules and it is concluded that, for the hydrocarbon mixtures, the empirical van der Waals rule is superior to the geometric mean and Hudson and McCoubrey combining rules.The van der Waals model with the geometric mean rule predicts that there should be a maximum in the (critical temperature, composition) curve for some of the systems studied here. No definite maximum has been observed in these systems.