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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]

The working fluids at supercritical pressures will experience abnormal heat transfer compared with those in a sub-critical state. In particular, the heat transfer deterioration (HTD) can make the wall temperature increase sharply in the tube, posing a challenge for the design of heat exchangers in the supercritical organic Rankine cycle (SORC). It is generally acknowledged that the effects of buoyancy and flow acceleration lead to abnormal heat transfer. However, a clear understanding of the interactions between the turbulent flow and heat transfer characteristics still needs to be further improved by obtaining the internal flow mechanism. The current study analyses the contours of the turbulent flow information under the different boundary conditions by means of validated CFD numerical simulation based on the previous experimental data and reveals the main causes of HTD and the impact mechanism of boundary conditions. The results reveal that two deteriorated extreme points are generated in a vertical upward tube with uniform heat flux for hexamethyldisiloxane at supercritical pressures. The buoyancy and flow acceleration effects caused by the drastic variation in fluid density near the pseudo-critical temperature can deform the velocity profile, thus reducing the local shear stress and turbulence intensity, and leading to the HTD. Moreover, HTD gets worse with the increase in heat flux and moderate with the rise in supercritical pressure. This study should support the data and theory for the refined design of heaters applied to the SORC in the future.

The working fluids at supercritical pressures will experience abnormal heat transfer compared with those in a sub-critical state. In particular, the heat transfer deterioration (HTD) can make the wall temperature increase sharply in the tube, posing a challenge for the design of heat exchangers in the supercritical organic Rankine cycle (SORC). It is generally acknowledged that the effects of buoyancy and flow acceleration lead to abnormal heat transfer. However, a clear understanding of the interactions between the turbulent flow and heat transfer characteristics still needs to be further improved by obtaining the internal flow mechanism. The current study analyses the contours of the turbulent flow information under the different boundary conditions by means of validated CFD numerical simulation based on the previous experimental data and reveals the main causes of HTD and the impact mechanism of boundary conditions. The results reveal that two deteriorated extreme points are generated in a vertical upward tube with uniform heat flux for hexamethyldisiloxane at supercritical pressures. The buoyancy and flow acceleration effects caused by the drastic variation in fluid density near the pseudo-critical temperature can deform the velocity profile, thus reducing the local shear stress and turbulence intensity, and leading to the HTD. Moreover, HTD gets worse with the increase in heat flux and moderate with the rise in supercritical pressure. This study should support the data and theory for the refined design of heaters applied to the SORC in the future. [ABSTRACT FROM AUTHOR]

The combustion-synthesized silica particles possess low metal impurity and present excellent surface properties. In this paper, silica particles were first prepared by hexamethyldisiloxane (HMDSO) combustion and then SEM, XPS, XRD and ICP were used to characterize the surface characteristics of silica particle. Finally, ReaxFF molecular dynamics simulations were conducted to investigate the formation mechanism of particle surface groups during HMDSO combustion. Effects of the temperature on surface group formation were also investigated. High-purity and spherical silica nanoparticles were prepared. The experimental and simulation results show that the type of surface groups at silica particle surface included the methyl group (-CH3), aminocarbonyl group (-O-C-OR), hydroxyl group (-OH), carbonyl group (-CO) and aldehyde group (-CHO). The hydroxyl and methoxyl groups were formed at oxygen sites of the silica particle by adsorption of free radicals H and CH3. The adsorptions of free radicals CH3 and CHO as well as carbon monoxide molecule at silicon sites lead to the formation of methyl group, aldehyde group and carbonyl group. The results of ReaxFF simulations also showed that the hydrophobic groups were dominant at low temperatures such as 500 K, and hydrophilic groups played more important role at high temperatures such as 1300 K. [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]

Graphene oxide (GO) membranes show good separation performance in membrane distillation processes, which require at least a single-sided hydrophobic surface to resist liquid penetration, but such hydrophobic GO membrane cannot be facilely prepared by conventional wet chemical processes. Here, a pulsed plasma hexamethyldisiloxane (HMDSO) process was investigated, with the highest surface contact angle of 124° obtained. The results demonstrate that a plasma deposition process can provide a proper route to prepare surface-selective hydrophobic GO films, which facilitates their applications for membrane distillation processes and related fields. [ABSTRACT FROM AUTHOR]

The paper was devoted to the results of the study of methods to obtain superhydrophobic film based on the plasma polymerisation of hexamethyldisiloxane (HMDSO) inside the plasma jet at atmospheric pressure. The 3D printing technology was intended for film deposition, which has the advantage of producing superhydrophobic surfaces over a wide range of scales. The effect of synthesis parameters on the hydrophobic properties of the film has been studied. The obtained superhydrophobic films demonstrated stability and resistance in chemical solutions, at high temperatures, under the influence of UV-irradiation and in various weather conditions. The results can be used in various fields, including automotive, construction, electronics, medicine and others, where surface protection against moisture, contamination and corrosion is required.

Volatile methyl siloxanes (VMS), which are considered to be the most troublesome impurities in current biogas-cleaning technologies, need to be removed. In this study, we fabricated a series of Fe3O4–urea-modified reduced graphene-oxide aerogels (Fe3O4–urea–rGOAs) by using industrial-grade graphene oxide as the raw material. A fixed-bed dynamic adsorption setup was built, and the adsorption properties of the Fe3O4–urea–rGOAs for hexamethyldisiloxane (L2, as a VMS model pollutant) were studied. The properties of the as-prepared samples were investigated by employing various characterization techniques (SEM, TEM, FTIR, XRD, Raman spectroscopy, and N2 adsorption/desorption techniques). The results showed that the Fe3O4–urea–rGOA–0.4 had a high specific surface area (188 m2 g−1), large porous texture (0.77 cm3 g−1), and the theoretical maximum adsorption capacity for L2 (146.5 mg g−1). The adsorption capacity considerably increased with a decrease in the bed temperature of the adsorbents, as well as with an increase in the inlet concentration of L2. More importantly, the spent Fe3O4–urea–rGOA adsorbent could be readily regenerated and showed an excellent adsorption performance. Thus, the proposed Fe3O4–urea–rGOAs are promising adsorbents for removing the VMS in biogas. [ABSTRACT FROM AUTHOR]

Volatile methyl siloxanes (VMS) must be removed because the formation of silica in the combustion process seriously affects the resource utilization of biogas. Herein, a series of APTMS ((3–aminopropyl)trimethoxysilane)-modified activated porous carbon (APC) adsorbents (named APTMS@APC) were prepared for VMS efficient removal. The as-prepared adsorbents were characterized using SEM, FTIR, Raman, X-ray diffraction analyses, and N2 adsorption/desorption. The results showed that the surface modification with APTMS enhanced the hydrophobicity of APC with the water contact angle increasing from 74.3° (hydrophilic) to 127.1° (hydrophobic), and meanwhile improved its texture properties with the SBET increasing from 981 to 1274 m2 g−1. The maximum breakthrough adsorption capacity of APTMS@APC for hexamethyldisiloxane (L2, model pollutant) was 360.1 mg g−1. Effects of an inlet L2 concentration (31.04–83.82 mg L−1) and a bed temperature (0–50 °C) on the removal of L2 were investigated. Meanwhile, after five adsorption–desorption cycles, the APTMS@APC demonstrated a superior cycling performance. This indicated that the hydrophobic APTMS@APC has a great significance to remove VMS. [ABSTRACT FROM AUTHOR]

Organosiloxanes are industrially produced worldwide in millions of tons per annum and are widely used by industry, professionals, and consumers. Some of these compounds are PBT (persistent, biaccumulative and toxic) or vPvB (very persistent and very bioaccumulative). If organosiloxanes react at all in the environment, Si–O bonds are hydrolyzed or Si–C bonds are oxidatively cleaved, to result finally in silica and carbon dioxide. In strong contrast and very unexpectedly, recently formation of new Si–CH3 bonds from siloxanes and methane by the action of microorganisms under mild ambient conditions was proposed (in landfills or digesters) and even reported (in a biotrickling filter, 30 °C). This is very surprising in view of the harsh conditions required in industrial Si–CH3 synthesis. Here, we scrutinized the pertinent papers, with the result that evidence put forward for Si–C bond formation from siloxanes and methane in technical microbiological systems is invalid, suggesting such reactions will not occur in the environment where they are even less favored by conditions. The claim of such reactions followed from erroneous calculations and misinterpretation of experimental results. We propose an alternative explanation of the experimental observations, i.e., the putative observation of such reactions was presumably due to confusion of two compounds, hexamethyldisiloxane and dimethylsilanediol, that elute at similar retention times from standard GC columns. [ABSTRACT FROM AUTHOR]

Since its introduction, about 15 years ago, the cyclic siloxane Cyclomethicone D5 has become increasingly used in the conservation of Cultural Heritage. In free form it allows the temporary hydrophobization of sensitive surfaces that must be treated in an aqueous environment; in the commercially available gelled form it allows the formulation of water-in-oil particle emulsions for surface cleaning or removal of film-forming substances, depending on the conditions of the aqueous phase. Over time, doubts have arisen about the real inertness of this solvent towards modern oil media. In addition, European regulations have restricted its use in consideration of its environmental impact, and so the already difficult availability of the material could further complicate; this advises the search for a substitute solvent. These two arguments motivated this study, conducted on two modern oil paintings: one unvarnished on paper, the other varnished on canvas. Samples of these paintings were treated under different conditions with D5 and the potential substitute chosen: dodecamethylpentasiloxane. The GC–MS and SEM-EDS analysis of the treated samples made it possible to evaluate and compare the degree of interaction with the oil binder in terms of leaching and topographic alterations of the surface, for both the free solvents and their gelled forms. Tests conducted on specially prepared paint samples also made it possible to evaluate the degree of solvation and consequent swelling produced by the two solvents on the different binders. [ABSTRACT FROM AUTHOR]

The utilisation of activated porous carbon (APC) for the removal of volatile methyl siloxane (VMS) has attracted significant research attention. However, the development of materials with high adsorption capacity remains a challenge. In this study, we successfully developed a high-specific-surface-area (2551 m2 g−1) APC material with a large porous texture (1.30 cm3 g−1) using coconut shell waste and NaOH as the activating agent. The performance of the APC material in the removal of hexamethyldisiloxane (L2) was evaluated using a fixed-bed dynamic adsorption setup. Notably, at 0 °C, the APC demonstrated a remarkable L2 removal ability, achieving a breakthrough adsorption capacity of 898.6 mg g−1. By increasing the inlet concentration of L2 and decreasing the temperature appropriately, the L2 adsorption capacity could be further improved. One advantage of APCs is their simple recycling process, which allows for sustained adsorption performance even after five consecutive cycles of adsorption and desorption. Therefore, the prepared APC material holds great promise as an efficient adsorbent for the removal of VMS. [ABSTRACT FROM AUTHOR]

In protecting cultural heritage, deacidification is used to stabilize acidic papers, ensuring the neutralization of acids present in the paper. But in the process of aging, several mechanisms of degradation occur simultaneously. Therefore, substances used to stabilize the paper should contain an antioxidant component in addition to the deacidifying component. The effect of the antioxidant (hindered amine light stabilizers—HALS type) on the stabilization of lignin-containing acid papers during accelerated aging was studied in this work. The effective deacidification component was magnesium; the solvent was hexamethyldisiloxane (HMDSO). The 4-amino-2,2,6,6-tetramethylpiperidine series of hindered amine light stabilizers (HALS) was selected as appropriate for creating a modifying system based on HMDSO. The modification system was tested on samples of a model test acid lignin-containing paper (NOVO) and naturally aged acidic paper from the real book. The addition of substances to the proposed deacidification system has a favorable effect on stabilizing the pH during aging and provides the inhibition of the oxidative degradation products and stabilization of the cellulose degree of polymerization. It was confirmed that the application of the system containing deacidification and an antioxidant component may increase the effectiveness of the protection of acid groundwood paper heritage objects. Adding a tested antioxidant to the proposed deacidification system has a favorable effect on stabilizing the pH value for a long time in accelerated aging. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of hexamethyldisiloxane (HMDSO) plasma on the fabrics surface to produce masks. Samples of 400-thread count cotton fabric were used. The fabrics was covered with a layer of HMDSO employing plasma enhanced chemical vapor deposition. Optical Microscopy, helium ion beam microscopy (HIM) and atomic force microscopy (AFM) were used for topographic analysis. Fourier transformed infrared spectroscopy technique was used to analyze the chemical modifications on surface. The level of hydrophobicity was evaluated using contact angle measurements. To evaluate the effect of washing cycle on the plasma coating, a protocol proposed by the World Health Organization was used. All experiments were performed in triplicate. For the statistical analysis, the Mann–Whitney, Kruskal–Wallis and Dunn tests were used. AFM showed that, after HMDSO plasma coating, a layer of small granules agglomerated on the original surface of the fabric was visualized. The fabric, which initially had a 0° contact angle value, presented angles of 120° after the plasma coating. It was concluded that the use of cotton fabric coated with HMDSO plasma proved to be adequate for the manufacture of protective masks, since the coating made the surface hydrophobic and this property is maintained even after washing cycles.

Published data on the effect of low-temperature plasma on polydimethylsiloxane have been analyzed. Changes in the contact properties, chemical structure, and morphology of the modified polymer surface have been revealed using modern research techniques (contact angle measurement, X-ray photoelectron spectroscopy, Fourier-transform IR spectroscopy, atomic force and scanning electron microscopy). It has been shown that modification by plasma results in the formation of a hybrid material that has the surface layer consisting mainly of silicon oxide. Plasma-enhanced chemical vapor deposition processes of hexamethyldisiloxane polymerization on various substrates are considered and the formation of similar hybrid materials containing a significant amount of silicon oxide is shown. Data on the use of such materials in biology, medicine, membranes, humidity sensors, and other fields of science and technology are presented. [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]

In this study, functional nanocoatings for water-repellent footwear leather materials were investigated by chemical plasma polymerisation by implanting and depositing the organosilicon compound hexamethyldisiloxane (HMDSO) using a low-pressure plasma system. To this end, the effect of monomers on leather plasma deposition time was evaluated and both the resulting plasma polymers and the deposited leather samples were characterised using different experimental techniques, such as: Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). In addition, leather samples were tested by standard tests for color change, water resistance, surface wetting resistance and dynamic water contact angle (DWCA). The resulting polysiloxane polymers exhibited hydrophobic properties on leather. Furthermore, these chemical surface modifications created on the substrate can produce water repellent effects without altering the visual leather appearance and physical properties. Both plasma coating treatments and nanocoatings with developed water-repellency properties can be considered as a more sustainable, automated and less polluting alternative to chemical conventional processing that can be introduced into product-finishing processes in the footwear industry. [ABSTRACT FROM AUTHOR]

Volatile methyl siloxanes (VMS) must be removed because the formation of silica in the combustion process seriously affects the resource utilization of biogas. Herein, a series of APTMS ((3–aminopropyl)trimethoxysilane)-modified activated porous carbon (APC) adsorbents (named APTMS@APC) were prepared for VMS efficient removal. The as-prepared adsorbents were characterized using SEM, FTIR, Raman, X-ray diffraction analyses, and N2 adsorption/desorption. The results showed that the surface modification with APTMS enhanced the hydrophobicity of APC with the water contact angle increasing from 74.3° (hydrophilic) to 127.1° (hydrophobic), and meanwhile improved its texture properties with the SBET increasing from 981 to 1274 m2 g−1. The maximum breakthrough adsorption capacity of APTMS@APC for hexamethyldisiloxane (L2, model pollutant) was 360.1 mg g−1. Effects of an inlet L2 concentration (31.04–83.82 mg L−1) and a bed temperature (0–50 °C) on the removal of L2 were investigated. Meanwhile, after five adsorption–desorption cycles, the APTMS@APC demonstrated a superior cycling performance. This indicated that the hydrophobic APTMS@APC has a great significance to remove VMS.

Volatile methyl siloxanes (VMS), which are considered to be the most troublesome impurities in current biogas-cleaning technologies, need to be removed. In this study, we fabricated a series of Fe3O4–urea-modified reduced graphene-oxide aerogels (Fe3O4–urea–rGOAs) by using industrial-grade graphene oxide as the raw material. A fixed-bed dynamic adsorption setup was built, and the adsorption properties of the Fe3O4–urea–rGOAs for hexamethyldisiloxane (L2, as a VMS model pollutant) were studied. The properties of the as-prepared samples were investigated by employing various characterization techniques (SEM, TEM, FTIR, XRD, Raman spectroscopy, and N2 adsorption/desorption techniques). The results showed that the Fe3O4–urea–rGOA–0.4 had a high specific surface area (188 m2 g−1), large porous texture (0.77 cm3 g−1), and the theoretical maximum adsorption capacity for L2 (146.5 mg g−1). The adsorption capacity considerably increased with a decrease in the bed temperature of the adsorbents, as well as with an increase in the inlet concentration of L2. More importantly, the spent Fe3O4–urea–rGOA adsorbent could be readily regenerated and showed an excellent adsorption performance. Thus, the proposed Fe3O4–urea–rGOAs are promising adsorbents for removing the VMS in biogas.

In this study, β-cyclodextrin-modified reduced graphene oxide aerogels (β-CD-rGOAs) were synthesized via a one-step hydrothermal method and were used to remove hexamethyldisiloxane (L2) from biogas. The β-CD-rGOAs were characterized by the Brunner–Emmet–Teller technique, using Fourier-transform infrared spectroscopy, Raman spectrometry, scanning electron microscopy (SEM), contact angle measurements, and X-ray diffraction. The results of the characterizations indicate that β-CD was grafted onto the surface of rGOAs as a cross-linking modifier. The β-CD-rGOA had a three-dimensional, cross-linked porous structure. The maximum breakthrough adsorption capacity of L2 on β-CD-rGOA at 273 K was 111.8 mg g−1. A low inlet concentration and bed temperature facilitated the adsorption of L2. Moreover, the β-CD-rGOA was regenerated by annealing at 80 °C, which renders this a promising material for removing L2 from biogas. [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]

The development and efficient production of effective bioplastics is a hot topic, required to face up to the issue of the difficult disposal of plastics derived from oil. Among the different natural sources of bioplastics, starch is one of the most promising. However, for most applications, the proper mastering of the surface properties of bioplastic is necessary. We report about the surface modification of extruded corn starch films by means of cold plasma based on helium (He) and hexamethyldisiloxane (HMDSO). The differently treated surfaces were functionally characterized in wettability and water absorption. The nanoscale morphology was assessed by scanning electron microscopy and atomic force microscopy. The obtained images were analyzed by advanced figures describing both texture and amplitude parameters, including fractal behavior. The combined treatment (He/HMDSO) resulted in more homogeneous films with smaller, better-distributed grains compared to the case wherein He was not used. Despite the different morphologies observed, starch coated by HMDSO alone and by He/HMDSO presented similar hydrophobic character, with contact angles higher than 110°. Plasma treatment with HMDSO and He/HMDSO resulted in a significant reduction of absorbed water content without reduction of water vapor permeability. The nanotexture of the films did not present statistically significant differences, in terms of spatial complexities, dominant spatial frequencies, homogeneous void distribution, and surface percolation. [ABSTRACT FROM AUTHOR]

In order to make cotton spunlaced nonwoven keeping well air permeability and a certain waterrepellent effect at the same, atmospheric pressure plasma technology was adopted. Hexamethyldisiloxane was used as monomer for the study of cotton spunlaced nonwoven single water-repellent modification experiment. After modification, hydrophobic surface layer was formed on the surface of nonwoven sample. water-repellent theory of modified nonwoven surface was analyzed combining with lotus effect. Infrared spectroscopy test results showed that hydrophobic groups like Si--CH3, Si--C and so on were generated on the modified surface. Water contact angle of the modified nonwoven was tested and it could be reached 157° on the treated surface in maximum. The surface without treatment were infiltrated and showed excellent single water-repellent effect. When modified nonwoven sample was treated by friction and placed for different time, the water contact angle was not changed too much. The water-repellent property of modified nonwoven was stable. It is considered that cotton spunlaced nonwoven after modified by atmospheric pressure plasma technology with hexamethyldisiloxane as monomer has excellent single water-repellent property. [ABSTRACT FROM AUTHOR]

Antimicrobial textiles are helpful tools to fight against multidrug-resistant pathogens and nosocomial infections. The deposition of silver nanoparticles (AgNPs) onto textiles has been studied to achieve antimicrobial properties. Yet, due to health and environmental safety concerns associated with such formulations, processing optimizations have been introduced: biocompatible materials, environmentally friendly agents, and delivery platforms that ensure a controlled release. In particular, the functionalization of polyester (PES) fabric with antimicrobial agents is a formulation in high demand in medical textiles. However, the lack of functional groups on PES fabric hinders the development of cost-effective, durable systems that allow a controlled release of antimicrobial agents. In this work, PES fabric was functionalized with AgNPs using one or two biocompatible layers of chitosan or hexamethyldisiloxane (HMDSO). The addition of organo-matrices stabilized the AgNPs onto the fabrics, protected AgNPs from further oxidation, and controlled their release. In addition, the layered samples were efficient against Staphylococcus aureus and Escherichia coli. The sample with two layers of chitosan showed the highest efficacy against S. aureus (log reduction of 2.15 ± 1.08 after 3 h of contact). Against E. coli, the sample with two layers of chitosan showed the best properties. Chitosan allowed to control the antimicrobial activity of AgNPs, avoid the complete loss of AgNPs after washings and act in synergy with AgNPs. After 3 h of incubation, this sample presented a log reduction of 4.81, and 7.27 of log reduction after 5 h of incubation. The antimicrobial results after washing showed a log reduction of 3.47 and 4.88 after 3 h and 5 h of contact, respectively. Furthermore, the sample with a final layer of HMDSO also presented a controlled antimicrobial effect. The antimicrobial effect was slower than the sample with just an initial layer of HMDSO, with a log reduction of 4.40 after 3 h of incubation (instead of 7.22) and 7.27 after 5 h. The biocompatibility of the composites was confirmed through the evaluation of their cytotoxicity towards HaCaT cells (cells viability > 96% in all samples). Therefore, the produced nanocomposites could have interesting applications in medical textiles once they present controlled antimicrobial properties, high biocompatibility and avoid the complete release of AgNPs to the environment. [ABSTRACT FROM AUTHOR]

Volatile methyl siloxanes (VMSs) as a trace impurity in biogas decreases its energy utilization, and thus need to be removed. In this paper, a one-step hydrothermal reduction was performed to produce three-dimensional reduced graphene oxide aerogels (rGOAs) using industrial-grade graphene oxide (IGGO) as raw material and vitamin C (VC) as a reductant to facilitate the fabrication of rGOAs. The synthesis of rGOAs was a simple, green, and energy-efficient process. The developed rGOAs were characterized using the Brunauer–Emmett–Teller method, Raman spectrometry, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction measurements and contact angle. The results obtained showed that rGOA-1 with a VC/IGGO ratio of 1/1 (m/m) exhibited a hierarchical porous structure and super-hydrophobicity, yielding a high specific surface area (137.9 m2 g−1) and superior water contact angle (143.8°). The breakthrough adsorption capacity of rGOA-1 for hexamethyldisiloxane (L2, a VMS model) was 11 times higher than that of IGGO. Low inlet concentration and bed temperature were considered beneficial for the L2 adsorption. Interestingly, rGOA-1 was less sensitive to water, and it was readily regenerated for reuse by annealing at 80 °C. The rGOAs have been demonstrated to have great potential for the removal of siloxanes from biogas. [ABSTRACT FROM AUTHOR]

This paper presents the investigation of zeotropic binary fluid mixtures containing cyclohexane (critical temperature above 200 °C) as the base fluid with R600, R600a, R601, R601a, R1336mzz(Z), R1234ze(Z), R1233zd(E) and cyclopropane (critical temperatures between 100 °C and 200 °C). For pure components and their mixtures, the performance of the vapor compression system with an internal heat exchanger was analysed at 50 °C and 80 °C heat source and sink inlet, respectively. Variation of the heat source temperature difference and the internal heat exchanger pinch point temperature difference at supply temperatures (140–170 °C) were also investigated. A pinch point temperature difference of 5 K was maintained for the evaporator and condenser. An increase of 6.59 % in COP was obtained with the zeotropic mixture of cyclohexane/cyclopropane compared to that of pure cyclopropane. The design point analysis showed that increasing the heat source temperature difference and internal heat exchanger pinch point temperature difference reduces the COP. The adopted mixture criteria increased the performance between 3.23 % and 3.91 % with respect to standard working fluids like R1233zd(E) and R601, for a 170 °C supply temperature. With this promising thermodynamic analysis in a subcritical operation, the cyclohexane/cyclopropane mixture has prospect of full integration heat pump design. • Siloxane and cyclic hydrocarbon mixtures are suitable for heat pump (up to 170 °C). • Cyclohexane/cyclopropane mixture improved the COP of R601a heat pump by 7.16%. • COP increased at lower heat exchanger pinch point temperature difference. • Increased source temperature glide amounted to reduction in COP. • Heat pump performance strongly correlates with heat exchanger exergy destruction. [ABSTRACT FROM AUTHOR]

• Silicon oxide films have attracted much attention to its practical applications. • We used hexamethyldisiloxane (HMDSO) as a source material. • A methodology for fabricating silicon oxide films using HMDSO was presented. • Silicon oxide films were formed when 100 eV O+ ions were irradiated in conjunction with HMDSO. We attempted to form silicon oxide films by spraying hexamethyldisiloxane (HMDSO) to a substrate together with low-energy O+ ion beam injections. The energy of O+ ions was 100 eV. The substrate temperature was set at room temperature. After the trial, we found a film deposited on the substrate. X-ray photoelectron spectroscopy (XPS) measurements of the film showed that the film was silicon dioxide. The XPS spectra of the film also showed that the film contained almost no carbon atoms. For comparison, 100 eV SiO+ ion beams were injected into a substrate at room temperature in conjunction with HMDSO. XPS results of the deposited film showed that the film was silicon oxide and the atomic concentration ratio of oxygen to silicon was 1.35. In this case, however, a relatively large amount of carbon atoms (12 atomic%) was included in the film. In conclusion, we confirmed that the 100 eV O+ ion beam induced deposition using HMDSO is useful for the silicon dioxide film formation. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate the application of an atmospheric pressure plasma brush (APPB) reactor for improving the hydrophobic properties of leather surfaces treated with organo-silane precursors for the first time. A comprehensive investigation was conducted to analyze the influence of various process parameters, including plasma access current, treatment duration, nozzle height, and gas flow rate, on the observed outcomes effects. The dispersion of active particles in the APPB was scrutinized using an Optical Emission Spectrometer (OES), while the underlying reaction mechanism was elucidated through the integration of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), cross-sectional Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) analysis. The findings unveiled that the resultant polysiloxane polymers bestowed a remarkable degree of hydrophobicity upon the leather, persisting steadfastly even following a 90-day aging period (WCA >140°). This APPB treatment combined with organosilane strategy may open a new design avenue for the development of surface treatments for intricate and temperature-sensitive substrates materials. • Novel reactor designed with simple structure and capable of generating large-area plasma. • Interpretation of silicon distribution during discharge by OES. • Tested for aging effects with WCA above 140°. • Silicon oxide structure in the coating facilitates hydrophobicity. [ABSTRACT FROM AUTHOR]

In this study, β-cyclodextrin-modified reduced graphene oxide aerogels (β-CD-rGOAs) were synthesized via a one-step hydrothermal method and were used to remove hexamethyldisiloxane (L2) from biogas. The β-CD-rGOAs were characterized by the Brunner–Emmet–Teller technique, using Fourier-transform infrared spectroscopy, Raman spectrometry, scanning electron microscopy (SEM), contact angle measurements, and X-ray diffraction. The results of the characterizations indicate that β-CD was grafted onto the surface of rGOAs as a cross-linking modifier. The β-CD-rGOA had a three-dimensional, cross-linked porous structure. The maximum breakthrough adsorption capacity of L2 on β-CD-rGOA at 273 K was 111.8 mg g−1. A low inlet concentration and bed temperature facilitated the adsorption of L2. Moreover, the β-CD-rGOA was regenerated by annealing at 80 °C, which renders this a promising material for removing L2 from biogas.

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]

Plasma enhanced chemical vapor deposition is a promising process for the generation of tailor-made polymer coatings on medical devices in order to improve their implant/ host interaction. The ultra-thin coatings can fulfil a variety of purposes, depending on the monomers used, the process conditions and the location of the coated implants in the human body. In addition, even complex geometries can be coated easily and without the application of solvents. Particularly hydrophilic and hydrophobic plasma polymer coatings can improve biocompatibility, especially in blood contact. Furthermore, the selection of the monomers used enables the generation of specific functional groups for further surface immobilization of drugs, such as proteins, by chemical crosslinking. The release of toxic residues from polymeric implants, such as monomers, additives or degraded components, can also be avoided. The aim of our investigation was the generation of plasma polymer films, their characterization and application as coatings for biodegradable metallic biomaterials in order to retard the degradation process. Metallic biomaterials, in various forms are frequently used in orthopaedics, dentistry, cardiovascular and neurosurgical equipment, because of their tensile strength, fracture toughness, fatigue strength and electrical conductivity. Plasma polymerization was performed using the monomers hexamethyldisiloxane and allylamine. The resulting plasma polymers were analysed in an accelerated degradation test. Both plasma polymers appear to be promising, while polyHMDSO appears to degrade over time and polyallylamine indicates to be stable.

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]

Surface properties of SiO2-like films deposited from plasma polymerization of HMDSO + O2 mixture have been investigated. Plasma of the gas mixture was produced using repetitive high voltage pulses at − 3 kV with varied frequency from 100 to 500 Hz. The films were characterized by means of atomic force spectroscopy, spectroscopic ellipsometry, contact angle measurement, and X-ray photoelectron spectroscopy. The film thickness increased linearly with the pulse frequency in the range of 100–400 Hz where the system was in energy-deficient domain. A further increase in the pulse frequency led to the monomer-deficient domain and the linear dependence of the deposition rate terminated. Refractive index of the films were similar to that of SiO2. Refractive index and extinction coefficient values suggested that the films had high density which is related to high fraction of suboxide structure. The total surface energy of the films was not significantly different when varied pulse frequency was used. The surface energy contained high polar component indicating that the polar Si–O groups were dominant in the structure. [ABSTRACT FROM AUTHOR]

• Hexamethyldisiloxane (HMDSO) has been employed for the deposition of silicon dioxide (SiO 2) films. • We proposed a methodology for SiO2 formation with the ion beam deposition with HMDSO. • We obtained SiO+ ion beams by the mass-selection, and then irradiated the SiO+ ions to substrates. • After the completion of experiment, we discovered SiO 2 films deposited on the substrate. In this work, low-energy fragment-ion beams were produced from hexamethyldisiloxane (HMDSO) used as a source material and substrates were irradiated by these beams with supplemental oxygen gas for the formation of silicon dioxide (SiO 2) film. During this process, SiO+ ions having an energy of 50 eV were mass-selected from various fragments derived from the decomposition of HMDSO. These ions were subsequently transferred to a Si substrate at room temperature in conjunction with a supplemental oxygen flow. The resulting film was assessed by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy to confirm SiO 2 deposition. The bonding of incident SiO+ ions with a quartz crystal microbalance (QCM) was assessed at ion energies of 50, 100 and 200 eV, and the sticking probability of incident SiO+ ions to the QCM crystal substrate was found to decrease monotonically with increasing energy. [ABSTRACT FROM AUTHOR]

A polyorganosiloxane thin film was deposited on an optically transparent poly(ethylene 2,6-naphthalate) (PEN) film using plasma-enhanced chemical vapor deposition (PECVD) at room temperature to improve the moisture barrier property of the PEN film. In the PECVD process, hexamethyldisiloxane (HMDSO) was used as the monomer. Argon or oxygen and their mixture gases were used as the plasma carrier gas. Poly(HMDSO) thin film was successfully deposited through plasma-induced radical polymerization reaction on the surface of PEN film. It was observed that the mixture ratio of argon-oxygen carrier gas significantly affected the surface and the moisture barrier properties of the resulting poly(HMDSO) film. Chemical structures of the poly(HMDSO) were confirmed using FT-IR analysis. Surface properties of the poly(HMDSO) thin film were investigated by water contact angle measurement and atomic force microscopy (AFM). Water vapor transmission rate (WVTR) value was obtained by an electrical calcium test (Ca test) at 85 °C and 85% relative humidity condition. It was confirmed that the poly(HMDSO) thin film exhibited excellent water vapor barrier capability. WVTR value of the PEN film coated with poly(HMDSO) deposited with a mixture of argon and oxygen (Ar: O2 = 2: 8) was 5.09 g/m2-day, which is much lower than 18.4 g/m2-day of a bare PEN film. [ABSTRACT FROM AUTHOR]

Siloxanes are a significant impurity in syngas feedstocks and an important source of silicon in combustion synthesis applications. However, little is known regarding the fundamental combustion chemistry of siloxane compounds. The impact of two organic silicon species with different but related chemical structures, trimethylsilanol (TMSO) and hexamethyldisiloxane (HMDSO), on syngas auto-ignition behavior was investigated in this study using physical and computational experiments. A rapid compression facility (RCF) was used to create temperatures of 1010–1070 K and pressures of 8–10.3 atm for auto-ignition experiments. Experiments with trace concentrations of TMSO (100 ppm, mole basis) or HMDSO (100 ppm) were added to a surrogate syngas blend (CO and H 2 with a molar ratio of 2.34:1, air levels of dilution, with molar equivalence ratios of ϕ = 0.1). The measured ignition delay times showed both siloxane species promote ignition behavior with TMSO yielding faster ignition delay times by approximately 37% and HMDSO yielding faster times by approximately 50% compared with the reference syngas mixture which contained no siloxanes. A computational study was conducted to interpret the results of the ignition experiments. Because detailed chemistry does not exist for these organo-silicon compounds, the effects of the addition of CH 3 , H, and OH radicals to H 2 and CO mixtures were explored to simulate the potential rapid decomposition of the siloxanes in the H 2 and CO system. Addition of the radicals decreased the predicted ignition delay times when compared with the H 2 and CO mixture simulations without the radical species, but the simulations did not fully capture the behavior observed in the experiments, indicating the siloxane chemistry is more complex than providing a rapid source of radicals. [ABSTRACT FROM AUTHOR]

Chitosan–silica hybrid aerogel [(CS) h A] was prepared using sol-gel method by combining an inorganic network in the presence of an organic polymer. Chitosan biopolymer and silica (SiO 2) which are obtained from agricultural waste of crab shell and bamboo leaves are the primary precursors used in the sol-gel reaction and hexamethyldisiloxane applied for hydrophobicity. The derived aerogel has been characterized using Fourier transform infrared (FTIR), scanning electron microscope (SEM), energy dispersive X-ray (EDX), and thermogravimetric analysis (TGA). Sears method was used to determine surface area. The FTIR spectrum shows presence of organic and inorganic entities which are also seen on the EDX chart. TGA provides information on the thermal stability of the derived aerogel. The SEM analysis shows clearly the surface morphology and roughness of (CS) h A. The calculated pore volume, bulk density, surface area, and porosity is 0.286 cm3 g−1, 0.441 g cm−3, 237.4 m2 g−1 and 0.126. [ABSTRACT FROM AUTHOR]

Volatile methyl siloxanes (VMSs) as a trace impurity in biogas decreases its energy utilization, and thus need to be removed. In this paper, a one-step hydrothermal reduction was performed to produce three-dimensional reduced graphene oxide aerogels (rGOAs) using industrial-grade graphene oxide (IGGO) as raw material and vitamin C (VC) as a reductant to facilitate the fabrication of rGOAs. The synthesis of rGOAs was a simple, green, and energy-efficient process. The developed rGOAs were characterized using the Brunauer–Emmett–Teller method, Raman spectrometry, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction measurements and contact angle. The results obtained showed that rGOA-1 with a VC/IGGO ratio of 1/1 (m/m) exhibited a hierarchical porous structure and super-hydrophobicity, yielding a high specific surface area (137.9 m2 g−1) and superior water contact angle (143.8°). The breakthrough adsorption capacity of rGOA-1 for hexamethyldisiloxane (L2, a VMS model) was 11 times higher than that of IGGO. Low inlet concentration and bed temperature were considered beneficial for the L2 adsorption. Interestingly, rGOA-1 was less sensitive to water, and it was readily regenerated for reuse by annealing at 80 °C. The rGOAs have been demonstrated to have great potential for the removal of siloxanes from biogas.

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 Silver nanoparticles (NPs) are known to provide antimicrobial properties for surfaces. However, there are environmental concerns due to reports of toxicity after exposure to the environment during or after end-use. Immobilizing silver NPs to the surface of substrates could ensure that particles are readily available for antibacterial activity with limited environmental exposure. A plasma coating on top of silver NPs could improve the adhesion of NPs to a substrate, but it could also impede the release of silver NPs completely. Furthermore, silver has been shown to require direct contact to demonstrate antibacterial activity. This study demonstrates immobilization of silver NPs with plasma coating onto a surface while maintaining its antibacterial properties. Silver NPs are simultaneously synthesized and deposited onto a surface with liquid flame spray aerosol technique followed by hexamethyldisiloxane plasma coating to immobilize the NPs. Atomic force microscope scratch testing is used to demonstrate improved nanoparticle adhesion. Antibacterial activity against gram-negative Escherichia coli is maintained even for plasma coating thicknesses of 195 nm. NP adhesion to the surface is significantly improved. Gram-positive Staphylococcus aureus was found be resistant to all the plasma-coated samples. The results show promise of using plasma coating technology for limiting NP exposure to environment. Highlights • Roll-to-roll synthesis of silver nanoparticles using Liquid flame spray • Plasma coating for improved nanoparticle adhesion to substrate • Antibacterial properties of silver nanoparticles across plasma layer • Limited environmental exposure of silver nanoparticle [ABSTRACT FROM AUTHOR]

Abstract The surface modification in order to obtain hydrophobic cotton fabrics was carried out using air/HMDSO Gliding Arc plasma discharge. The dependence of the surface wettability on used process parameters, such as air flow, sample distance and treatment time were investigated. The wettability of cotton fabrics was evaluated by the drop test method by measuring the time of droplet absorption and water contact angle (WCA). The changes in the surface morphology were examined by optical microscopy and scanning electron microscopy (SEM). The treated hydrophobic fabrics were subjected to the analysis of chemical composition of the applied coatings using the ATR-FTIR spectroscopy. Hydrophobic cotton fabrics were obtained, especially with a high resistance to static wetting. In addition, the treated cotton fabrics were tested using a spray test measurement and were subjected to multiple washing. Highlights • The use of simple method based on atmospheric plasma discharge for cotton fabric treatment affects surface wettability. • Treated cotton fabrics exhibit high hydrophobicity with water contact angle up to 143° and good resistance to static wetting. • Gliding Arc plasma treatment has a potential as an alternative method for fabric hydrophobization. [ABSTRACT FROM AUTHOR]

To expand the applications of graphene-based materials to biogas purification, a series of reduced graphene oxide aerogels (rGOAs) were prepared from industrial grade graphene oxide using a simple hydrothermal method. The influences of the hydrothermal preparation temperature on the textural properties, hydrophobicity and physisorption behavior of the rGOAs were investigated using a range of physical and spectroscopic techniques. The results showed that the rGOAs had a macro-porous three-dimensional network structure. Raising the hydrothermal treatment temperature reduced the number of oxygen-containing groups, whereas the specific surface area (SBET), micropore volume (Vmicro) and water contact angle values of the rGOAs all increased. The dynamic adsorption properties of the rGOAs towards hexamethyldisiloxane (L2) increased with increasing hydrothermal treatment temperature and the breakthrough adsorption capacity showed a significant linear association with SBET, Vmicro and contact angle. There was a significant negative association between the breakthrough time and inlet concentration of L2, and the relationship could be reliably predicted with a simple empirical formula. L2 adsorption also increased with decreasing bed temperature. Saturated rGOAs were readily regenerated by a brief heat-treatment at 100 °C. This study has demonstrated the potential of novel rGOA for applications using adsorbents to remove siloxanes from biogas.