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This study presents a source for studying thin‐film deposition utilizing vacuum UV (VUV) radiation from a remote argon or helium atmospheric plasma to initiate photochemistry in the precursor gas. We aim to assess how this radiation affects the deposition process and film structure while avoiding deposition inside the plasma source or particle formation. Deposition occurs where radiation interacts with the precursor and the growing film, as well as further downstream. The measured film properties clearly show that photon interaction with the film has a significant effect. Using hexamethyldisiloxane (HMDSO) as a precursor, we achieved nearly carbon‐free silicon dioxide (SiO2 ) film growth due to photodesorption of hydrocarbons from the growing film, as confirmed by infrared spectra and positive ion mass spectrometry. [ABSTRACT FROM AUTHOR]

Hexamethyldisiloxane (HMDSO) is one of the main impurities in the syngas produced from sewage and landfill plants. In order to utilize this syngas or control the characteristics of the generated silica particles, it is crucial to understand the chemical kinetics of HMDSO combustion. This study investigated the process of HMDSO combustion using synchrotron radiation mass spectrometry (SRMS), gas chromatography (GC), and ReaxFF molecular dynamics simulations. First, the force field used for ReaxFF simulation was validated by comparing the energies of different bond lengths, bond angles, and dihedral angles with the ones from DFT calculations. Good agreements were found. Then, ReaxFF simulations of HMDSO combustion with this force field were conducted under various conditions, which include different equivalence ratios (0.67, 1.0, and 1.5) and temperatures ranging from 2000 to 3500 K. The oxidation characteristics of HMDSO were analyzed, including the evolution of gas products and particle formation. Finally, based on the results from experiments and ReaxFF simulations, the reaction pathways, reaction lists, and reaction kinetics data during HMDSO combustion were obtained. A detailed reaction mechanism was proposed and validated by applying it in modeling the H2/HMDSO/O2 combustion systems. The temperature and part of the gas products such as CO and CO2 as well as SiO could be well predicted. [ABSTRACT FROM AUTHOR]

Thermoplastic starch (TPS) films underwent casting and plasma coating with Hexamethyldisiloxane (HMDSO) gas at various self‐bias voltages. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging revealed slight swelling and grain structures in untreated TPS films due to starch dissolution. However, the HMDSO plasma treatment had minimal impact, with swollen grains still present beneath a layer of small granules. Contact angle measurements demonstrated that untreated films had an initial water contact angle of 32°, gradually decreasing over time. Conversely, HMDSO‐coated films exhibited stable hydrophobic behavior, with contact angles exceeding 100°. Statistical analysis confirmed TPS films' lower average roughness, while modified films showed no significant difference in height parameters. Higher self‐bias voltages correlated with larger grain sizes. Notably, experimental treatments decreased long‐range spatial correlations, as indicated by Hurst's exponent. [ABSTRACT FROM AUTHOR]

In a high‐rise building, due to the risk of flame spread and strict regulations associated, wood use is limited for interior finishes. This study aimed to evaluate the effect of a thin organosilicon layer (∼500 nm) prepared by atmospheric pressure plasma on the fire behavior of a wood substrate. The coating was deposited from hexamethyldisiloxane in argon on both untreated wood and wood with a preparatory coating of primer. The primer reduces the presence of cracks in the plasma layer and ensures more homogenous coverage of the substrates. Finally, the flame retardancy analysis highlights an improvement in fire behavior only when the primer is used. Our study suggests that plasma thin deposition has a synergic effect with primer to fireproof wood. [ABSTRACT FROM AUTHOR]

The pyrolysis kinetics of hexamethyldisiloxane (HMDSO) at various temperatures was studied using the reactive force field (ReaxFF) molecular dynamics simulations. Reaction rate constants and the main pyrolysis pathways were explored at the initial decomposition stage of HMDSO and intermediates decomposition stage. The activation energy and pre‐exponential factor describing the reaction rate constants were obtained and further validated by experimental data and DFT theoretical calculations. The formation of C5H15OSi2 fragment by Si–C bond dissociation was dominant at the initial decomposition stage of HMDSO at the simulation temperatures of 2500–4000 K. The subsequent reaction pathways involved the formation of C5H14OSi2 and C4H11OSi2. After that, the pathways were different for 2500 and 3000 K. At 4000 K, small silicon‐containing fragments were formed, including CH3Si, CH4Si, and C3H9Si, etc. The simulations also revealed that the major hydrocarbons generated during HMDSO pyrolysis were CH3 and CH4. Also, CH4 formation was more important in the end of HMDSO pyrolysis when simulation temperature was over 3500 K. [ABSTRACT FROM AUTHOR]

One interesting category of nano‐ and micro‐engineered surfaces is surface gradients, which allow the controlled optimization of biointerfaces at a small scale in an extended area length. Plasma coatings offer a large diversity of functionalities at the nanoscale, accompanied by high chemical stability and adhesion on a variety of substrates at ambient temperature. Atmospheric‐pressure plasma‐assisted deposition could be employed for the generation of surface gradients on thermosensitive materials. In this study, a corona plasma jet is used to deposit polydimethylsiloxane/SiO2‐like surface gradients on polyethylene foil by varying the O2 concentration in the discharge during the movement of the plasma source. We obtained, in a single‐step approach, gradient coatings along a length of ∼10 cm, with a gradual variation of both chemistry and surface energy. [ABSTRACT FROM AUTHOR]

A plasma probe and measuring method were developed to simultaneously determine both the electron density, ne, and floating potential in plasma‐enhanced chemical vapor deposition (PECVD) coating processes within low‐pressure plasmas. The functionality of the probe with a high deposition rate is demonstrated on the basis of examples using hexamethyldisiloxane as a precursor gas. The results show that the developed probe can determine both the ne (∼1015 m−3) and the time‐varying floating potential. The results also indicate that the probe is effective for monitoring the changes in the plasma condition caused by the pressure and the gas flow rate during the coating process. This method can contribute to confirm the process and chamber conditions in PECVD processes. [ABSTRACT FROM AUTHOR]

The short residence time of Ar–HMDSO (Ar–hexamethyldisiloxane) gas mixtures rapidly flowing across atmospheric‐pressure, glow‐type, single‐filament dielectric barrier discharges is utilized to accomplish thin‐film deposition via a purely ionic route. A comparison of thin‐film volumes obtained from profilometry, on the one hand, and from the transferred charge, on the other hand, enables to evaluate the mass of the ions contributing to the film growth. For HMDSO fractions at the lower end of the studied range of molar fractions, 50 ppm, pentamethyldisiloxanyl cations (Me3SiOSiMe2+, PMDS+), generated from the monomer via Penning ionization by Ar(1s) species, are mainly responsible for film formation. For HMDSO fractions growing beyond 1,000 ppm, ionic oligomerization processes by reactions of PMDS+ with HMDSO molecules result in a 2.5‐fold increase of the average deposited ion mass. [ABSTRACT FROM AUTHOR]

Plasma‐polymerized hexamethyldisiloxane (pp‐HMDSO) thin films have been deposited in a radiofrequency (RF) remote plasma‐enhanced chemical vapor deposition (PECVD) system, on different types of substrates: silicon wafers, glass, quartz crystals, and chemiresistor structure. The as‐grown thin films have been post treated in two types of reactive plasmas produced in SF6 and O2 gases. The effect of this surface modification on different properties of the as‐grown pp‐HMDSO thin film (chemical structure, elemental composition, surface morphology, film density and thickness, optical bandgap, and electrical resistivity) has been investigated. It is found that SF6 plasma and O2 plasma surface modifications of the as‐grown pp‐HMDSO thin film induce property changes different from each other. SF6 plasma converted the as‐grown pp‐HMDSO film to a more porous material and caused a narrowing of its optical band gap of about 33%, while O2 plasma induced a lowering of film electrical resistivity of about two orders of magnitude. [ABSTRACT FROM AUTHOR]

Abstract: The versatility of the fiber reinforced composites has significantly replaced some of the sophisticated metal components in certain sectors of industries. The matrix could be altered to improve self‐properties via silane modifiers by forming chemical linkages with the matrix in harmony with the reinforcing agents. This research work is an endeavor to enhance the traits of Vinyl ester by scrutinizing the influence of silane chemical agents using Hexamethyldisiloxane (HMDS). The dispersion time and concentration of these chemicals in matrix were optimized and henceforth a natural reinforcement, Abaca fabric was incorporated to constitute Natural fiber composite via Vacuum Assisted Resin Transfer Molding (VARTM) technique. The effect of resin modification on mechanical, thermal, and physical properties of Vinyl ester/Abaca (VE/AF) composite was examined. HMDS resin modified composite showed an improvement in the mechanical and flame retardant properties when compared to the pristine composite due to the formation of siloxane bonding which is compatible with the functional groups of both the matrix and the fabric. FT‐IR and FESEM characterizations have showed imperative evidences to support the results. This investigation provides a channel for enhancing the properties of natural fiber composites via chemical modification technique. [ABSTRACT FROM AUTHOR]

Atmospheric‐pressure dielectric barrier discharges (DBDs) in argon with admixtures of small amounts of hexamethyldisiloxane (HMDSO) have been analysed by means of numerical modelling. A time‐dependent, spatially one‐dimensional fluid‐Poisson model has been used, which takes into account the spatial variation of the discharge plasma between the plane‐parallel dielectrics covering the electrodes. Main features of the model, including the reaction kinetics for HMDSO, are given. Good agreement with related experimental studies of the ignition voltage for HMDSO amounts of up to 200 ppm and the temporal course of the discharge current for conditions typical of deposition experiments is obtained by the model calculations when assuming that 30% of the reactions of HMDSO with excited argon atoms, with a rate coefficient of 5.0 × 10−10 cm3/s, lead to the production of electrons due to Penning ionization. The modelling results for constant frequency f = 86.2 kHz and applied voltage Ua = 4 kV show that the electrical energy dissipated in the DBD decreases with an increasing amount of HMDSO and enable the determination of the energy absorbed per HMDSO molecule on the basis of their energy balance. The analysis of the plasma–chemical processes also makes clear that collision processes of HMDSO with excited argon atoms and molecules leading to neutral reaction products are essential for the formation of thin polymer films. [ABSTRACT FROM AUTHOR]

Nanoparticles can be produced by plasma polymerization from different precursors at low or atmospheric pressure. The polymers produced by plasma polymerization are not chemically regular as conventional polymers; they are complex and rich in functional groups. The variety of chemical groups is due to the fragmentation of the precursor as well as other gases present during the reaction. The concentration of these groups on the nanoparticle surface can be tuned by changing plasma polymerization variables. In this work we demonstrate the preparation of nanoparticles by plasma polymerization of poly(ethylene glycol), poly(ethylene glycol) copolymerized with pyrrole, and hexamethyldisiloxane. Nanoparticles were characterized by transmission electron microscopy and infrared spectroscopy. [ABSTRACT FROM AUTHOR]

We evaluate the use of p-type silicon oxide (p-SiO x) dielectric layers as a boron diffusion source for n-type crystalline silicon (c-Si) substrates. The p-SiO x layers grown on n-type c-Si substrates by plasma enhanced chemical vapor deposition using a gas mixture of He/hexamethyldisiloxane/CO2/B2H6 are thermally stable and do not peel off during annealing up to 1050 °C, making them effective diffusion sources. The layers were examined before and after annealing with characterization techniques including spectroscopic ellipsometry and secondary ion mass spectrometry. We observe that there is a reduction in the thickness of the p-SiO x layer after annealing by about 50%, and that boron diffuses into the n-type c-Si substrate, forming a p+ layer, limited by the formation of a carbon-rich layer above the c-Si surface. The concentration of holes in the diffused region was measured by the electrochemical capacitance-voltage technique, and it was found that essentially all the boron that diffused into the n-type c-Si was active, unaffected by the presence of carbon and oxygen atoms. The concentration of carriers can be controlled by the initial thickness of the p-SiO x layers and the depth of the p+/n junction can be controlled by the time of annealing. A surface carrier concentration of 3 × 1019 at cm−3 and a sheet resistance of the order of 120 Ω sq−1 was obtained upon annealing at 1050 °C for 30 min. [ABSTRACT FROM AUTHOR]

Bilayer plasma polymer (PP) films were examined using a combination of X-ray and neutron reflectometery and X-ray photoelectron spectroscopy to gain an understanding of the interfacial structures that form between the films. Three different PP films were produced from the monomers hexamethyldisiloxane (HMDSO), di(ethylene glycol) dimethyl ether (DG), and allylamine (AA) at different load powers. These films were used as 'substrates' for the subsequent deposition of a deuterated DG (dDG) PP top film. The width of the interfacial region was found to be strongly dependent on the chemical and physical properties of the substrate film. These findings have relevance to the general use and application of plasma polymer films. [ABSTRACT FROM AUTHOR]

In the present work two thin films, fabricated by plasma-polymerization of hexamethyldisiloxane (HMDSO) monomer, were studied by a combination of electron (ESID) and photon (PSID) stimulated ion desorption techniques. The organic character of the polymer film is evidenced by the high contribution of C2H n+ species and the absence of high mass fragments in its ESID spectrum. On the other hand, the inorganic character is elucidated by the presence of high mass silicon ionic fragments. NEXAFS and PSID spectra also show clear differences between organic and inorganic films. The marked reduction of CH3+ species for PSID spectra of the organic-polymeric film is in accordance with ESID analysis and may be interpreted by a screening effect of its cross-linked organic structure. [ABSTRACT FROM AUTHOR]

An overview and evaluation of different technologies is presented, which can be applied to remove problematic silane and siloxane compounds from exhaust air. In a lab screening, 96 % H2SO4 was identified to be the most efficient and practical absorbent to remove hexamethyldisiloxane (HMDSO) from exhaust air. Lab scale results were transferred to pilot scale, where the superiority of 96 % H2SO4 in comparison with a previously used scrubber solution (NaOH/MeOH) was demonstrated. In several large scale experiments, the elimination factors of HMDSO from different exhaust airs by 96 % H2SO4 and the capacity of the absorbent were determined. The practicability and robustness of the developed scrubber system using 96 % H2SO4 will allow its easy applicability in API production processes. [ABSTRACT FROM AUTHOR]

MQ silicone resins, which represent a broad range of hydrolytic condensation products of monofunctional silane (M) and tetrafunctional silane (Q), were synthesized by reaction of water glass with hexamethyldisiloxane. The optimum reaction time and the optimal reaction temperature is 30 min and 30-40°C, respectively. Concentrated hydrochloric acid is the best one among those catalysts tested. In large-scale experiments (420-1680 mL), the favorable feeding order is catalyst first, and then water glass, the mixture of hexamethyldisiloxane and ethanol last and most MQ silicone resin was observed. The structure of MQ silicone resin was characterized by FT-IR and GPC spectra. The MQ silicone resin shows narrow molecular weight distribution and the number average molecular weight of MQ silicone resin is 2917. The silicone pressure sensitive adhesive prepared from as-synthesized MQ resin has good tack (29#) and 180° peel adhesion (5.630 N/20 mm). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Quantitative mapping of oxygen tension (pO2), noninvasively, could potentially be beneficial in cancer and stroke therapy for monitoring therapy and predicting response to certain therapies. Intracellular pO2 measurements may also prove useful in tracking the health of labeled cells and understanding the dynamics of cell therapy in vivo. Proton Imaging of Siloxanes to map Tissue Oxygenation Levels (PISTOL) is a relatively new oximetry technique that measures the T1 of administered siloxanes such as hexamethyldisiloxane (HMDSO), to map the tissue pO2 at various locations with a temporal resolution of 3.5 minutes. We have now developed a siloxane‐selective Look‐Locker imaging sequence equipped with an echo planar imaging (EPI) readout to accelerate PISTOL acquisitions. The new tissue oximetry sequence, referred to as PISTOL‐LL, enables the mapping of HMDSO T1, and hence tissue pO2 in under one minute. PISTOL‐LL was tested and compared with PISTOL in vitro and in vivo. Both sequences were used to record dynamic changes in pO2 of the rat thigh muscle (healthy Fischer rats, n = 6), and showed similar results (P > 0.05) as the other, with each sequence reporting a significant increase in pO2 (P < 0.05) under hyperoxia compared with steady state normoxia. This study demonstrates the ability of the new sequence in rapidly and accurately mapping the pO2 changes and accelerating quantitative 1H MR tissue oximetry by approximately 4‐fold. The faster PISTOL‐LL technique could enable dynamic 1H oximetry with higher temporal resolution for assesing tissue oxygentation and tracking the health of transplanted cells labeled with siloxane‐based probes. With minor modifications, this sequence can be useful for 19F applications as well. [ABSTRACT FROM AUTHOR]