Hydrocarbon Matrix Research Articles

Analysis of Dimethylsiloxanes in Hydrocarbon Matrices like Marine Fuels Applying a Novel Enrichment Procedure and a Two-Column Gas Chromatography – Mass Spectrometry Measurement

Marine fuels are consumed worldwide in quantities of more than 200 million tons per year. It is not a uniform product, but rather heterogeneous mixtures of hydrocarbons with a wide range of viscosities. Due to the production processes, marine diesel contains dimethylsiloxanes. These lead to damage to marine exhaust catalysts in connection with combustion reactions in the ships’ engines. A novel analytical method, presented here, was developed that allows to investigate these processes and to monitor the dimethylsiloxane contents in complex marine fuel matrices. The key steps of the analytical procedure are analyte enrichment by solid phase extraction (SPE) using thermally activated silica gel and chromatographic separation and measurement by heart-cutting gas chromatography - mass spectrometry. Authentic reference substances for quantification by standard addition are used for the dimethylsiloxane analytes. The clean-up enabled a 90% reduction of the matrix content in the analysis solutions compared to the initial sample. Recovery rates in the range of 87.8% to 111.4% were determined for all analytes (Si3 to Si9). The detection limits of analytes ranged from 0.06 μg/L to 5.68 μg/L. Values of 0.71 μg/L to 23.6 μg/L were determined for the limits of quantification. The newly designed analytical method was successfully applied to real marine fuel samples. The analytical procedure is to be made available to commercial and industrial laboratories as a practical method for controlling siloxane contents in marine fuels to contribute this way to efficiently functioning marine exhaust gas purification.

Steam cracking of sulfur containing compounds: A fundamental modelling study

Sulfur-containing additives are commonly used in industrial steam cracking to mitigate carbon monoxide (CO) formation. Their impact on solid coke deposition in reactors is well-studied but not fully understood. This study investigates the decomposition of five common sulfur compounds (DMDS, DMS, DMSO, CS2, COS) in both inert and hydrocarbon environments within the steam cracking industry. To achieve this, an in-house automated network generation tool called Genesys and a validated ab initio methodology at the CBS-QB3 level are used. This combination generates a comprehensive kinetic model with precise thermodynamic and kinetic parameters. The kinetic model is rigorously validated against experimental data from prior studies under various conditions, including inert nitrogen atmospheres and hydrocarbon matrices (using ethane and heptane). Experimental setups involve bench-scale annular quartz reactors and pilot-scale stainless steel reactors. Remarkably, the kinetic model accurately predicts primary products and captures secondary product trends across diverse conditions without parameter adjustments. Rate of production analyses reveal critical decomposition pathways during sulfur-containing additive pyrolysis and the influence of hydrocarbon matrices. Notably, these additives primarily yield H2S upon decomposition, with CS2, SO2 and thiophene as minor products. In conclusion, the developed fundamental kinetic model accurately predicts product formation during the pyrolysis of DMS, DMDS, DMSO, CS2 and COS, whether in nitrogen or a hydrocarbon matrix, without altering core thermodynamic and kinetic parameters.

Alkaline pulping catalyzed ordered conversion of bark in supercritical water

The hydrophilicity of lignocellulosic biomass hinders the application of a high concentration slurry for supercritical water gasification, thereby reducing the gasification efficiency and energy self-sufficiency. A pretreatment method of alkaline pulping with KOH and NaOH was proposed to achieve the high feed concentration for continuous reactor and macromolecular simplification for barrier reduction of conversion. In this study, bark as an example of lignocellulosic biomass, whose 30 wt% and 40 wt% slurries with favorable rheology and stability, was prepared by alkaline pulping successfully. The minimum alkali consumption of NaOH and KOH pulping for 30 wt% and 40 wt% were 11%–14%, 16%–20%, and 16%–21%, 23%–28%, respectively. The most economical conditions were 180 °C and 24% KOH addition. All slurries prepared by NaOH and KOH at 180 and 200 °C could satisfy the industrial standard of coal-water slurry, and only 3–5 times higher than water viscosity. The bark macromolecules were restructured due to the hydrolysis of cellulose and lignin by breaking down the hydrogen bond and ether bond with trivial hydrocarbon matrix loss. The scattered crystal growth facilitated the uniform premixing of bark and water. Meanwhile, a surface particle charges potential increase leading to a heightened repulsive force by alkaline pulping furtherly enhanced the premixing effect. Additionally, metal ions could be deposited onto the bark surface during alkaline pulping. The chemical modification leading by alkaline pulping achieved the premixing of feedstock and water to form bark slurry. The conversion barrier was decreased to fulfill the ordered conversion, and 95.66% gasification efficiency for 40 wt% bark slurry was displayed at 600 °C with a preheated water of 6. Phenolic compounds and hydrocarbons were the most dominant components in liquid products. Polycyclic aromatic hydrocarbons in liquid products were detected at 620 °C with a preheated water of 4. The functional groups of organic matter in the slurry were significantly converted into the gas phase, and lattice oxygen was produced in the solid product. The alkali recovery was 65% at the optimal gasification condition, and achieved the maximum of 80% at 580 °C. The successful completion of this research affirms the dominance of the pulping-alkali recovery-gasification method for expanding the application of SCWG of lignocellulosic biomass in large engineering projects.

Late acquisition of the rTCA carbon fixation pathway by Chlorobi.

The reverse tricarboxylic acid (rTCA) cycle is touted as a primordial mode of carbon fixation due to its autocatalytic propensity and oxygen intolerance. Despite this inferred antiquity, however, the earliest rock record affords scant supporting evidence. In fact, based on the chimeric inheritance of rTCA cycle steps within the Chlorobiaceae, even the use of the chemical fossil record of this group is now subject to question. While the 1.64-billion-year-old Barney Creek Formation contains chemical fossils of the earliest known putative Chlorobiaceae-derived carotenoids, interferences from the accompanying hydrocarbon matrix have hitherto precluded the carbon isotope measurements necessary to establish the physiology of the organisms that produced them. Overcoming this obstacle, here we report a suite of compound-specific carbon isotope measurements identifying a cyanobacterially dominated ecosystem featuring heterotrophic bacteria. We demonstrate chlorobactane is 13C-depleted when compared to contemporary equivalents, showing only slight 13C-enrichment over co-existing cyanobacterial carotenoids. The absence of this diagnostic isotopic fingerprint, in turn, confirms phylogenomic hypotheses that call for the late assembly of the rTCA cycle and, thus, the delayed acquisition of autotrophy within the Chlorobiaceae. We suggest that progressive oxygenation of the Earth System caused an increase in the marine sulfate inventory thereby providing the selective pressure to fuel the Neoproterozoic shift towards energy-efficient photoautotrophy within the Chlorobiaceae.

Ion-beam deposited platinum as electrical contacting material in operando electron microscopy experiments at elevated temperatures.

Establishing a stable and well conducting contacting material is critical for operando electron microscopy experiments of electrical and electrochemical devices at elevated temperatures. In this contribution, the nanostructure and electrical conductivity of ion beam deposited Pt are investigated both in vacuum and in oxygen as a function of temperature. Its microstructure is relatively stable up to a temperature of approx. 800°C and up to an applied current density of approx. 100 kA/cm2 . Its conductivity increases with temperature, attributed to densification, with changes in the hydrocarbon matrix being less important. Recommendations are provided with respect to the Pt deposition parameters in terms of maximizing stability and minimizing electrical resistance. RESEARCH HIGHLIGHTS: It is feasible to use ion beam deposited Pt as electrical contacting material in operando electron microscopy. The deposited Pt is relatively stable up to 800°C and approx. 100 kA/cm2 . The resistivity can be reduced by increasing the applied ion current during deposition and by thermal annealing at a temperature of 500°C in a few mbar of oxygen.

Identification of sulfur mustard in complex environmental samples based on derivatization and LC-ESI-MS/MS analysis

A new analytical method to identify sulfur mustard (HD) using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC‒ESI‒MS/MS) after derivatization with diethanolamine was developed. The method has been successfully applied to identify HD spiked into both soil and asphalt extracts containing diesel, which resembles a diesel exhaust environment that may be encountered in battlefield conditions or in terror attacks. The LC-ESI-MS/MS method enables the sensitivity enhancement compared with conventional GC-EI-MS analysis and in addition, identifies HD in a complex hydrocarbon matrix. The calibration curve for the derivatization product was linear in the range of 50–5000 pg/mL with correlation coefficients (R2) greater than 0.99 and a LOI of 50 pg/mL. The recoveries (n = 3) were observed at >90% with soil and asphalt containing ∼10 mg/ml diesel. Thus, this method provides a robust evidence of HD use.

Chlorine speciation in complex hydrocarbon matrices using GC-ICP-MS/MS

In this study, the hyphenation of gas chromatography with ICP tandem mass spectrometry (GC-ICP-MS/MS) for the analysis of volatile organochlorides in complex hydrocarbon samples is described.

Analytics Driving Kinetics: Advanced Mass Spectrometric Characterization of Petroleum Products

The current state-of-the-art analysis techniques for petroleum fractions has progressed substantially during the past decade. This has helped to further improve the lumping procedures and modeling approaches of these complex systems. Recent advances in gas chromatography (GC), GC-field ionization mass spectrometry (GC-FIMS), and comprehensive gas chromatography (GC×GC) have made it possible to determine the compositions of fractions with up to 45 carbon atoms and in some cases up to C80. The combination of MS techniques with other selective detectors and reversed-phase column combinations has made it possible to quantify even traces of heteroatomic compounds in these complex hydrocarbon matrices. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), in some cases combined with GC×GC for the lighter part, has pushed the characterization of larger macromolecules in particular asphaltenes. Matrix-assisted laser desorption/ionization (MALDI) is also used widely for this purpose but has the disadvantage that quantification is not obvious. The development of more detailed characterization techniques has not remained unnoticed in the petrochemical society and more recently in the petrochemical kinetic modeling society. More detailed characterization of petrochemical fractions has made the implementation of detailed kinetic models for simulation and optimization possible including more and more molecular detail. Additionally, advances in photoionization mass spectrometry (PI-MS) have allowed the detection of reactive intermediates and direct kinetic measurements in time-resolved experiments. It can only be expected that this trend will continue and that the application field will move from now primarily petrochemistry (from catalytic cracking, over hydrotreating, and hydrocracking to pyrolysis, combustion, and steam cracking) to larger-scale chemical recycling and biomass conversion processes.

Particle motion artifacts in equilibrium magnetization measurements of large iron oxide nanoparticles

Iron oxide nanoparticles find many applications due to their response when subjected to externally applied magnetic fields. Equilibrium magnetization measurements (commonly known as magnetization curves) are an essential characterization tool to evaluate if particles display hysteresis, and to obtain magnetic properties such as the saturation magnetization. For superparamagnetic particles, one can obtain a magnetic size distribution by fitting the data to a theoretical model, such as the Langevin function, in what is called magnetogranulometric analysis. If one wishes to use the resulting size estimates as a predictor of particle performance in applications, magnetization data must be obtained under conditions that capture the response of the particles with minimal artifacts. In this paper, we used selected iron oxide nanoparticle batches with physical size ranging from 20 to 45 nm to demonstrate the influence of sample preparation methods on the magnetization data obtained. We show that measurements in powder form and in liquid solvents display varying degrees of particle interaction artifacts at low fields, depending strongly on particle size and on the thickness of the surface coating. In addition, measurements in ‘solid’ waxy hydrocarbon matrices are shown to be susceptible to particle rotation artifacts for large particle sizes. Hard crosslinked polymer matrices are shown to restrict particle motion completely, resulting in magnetization data that follows the Langevin function if the measurement is performed above the blocking temperature of the particles. We end with a discussion of how the presence of matrix-dependent measurement artifacts influence the magnetic diameter fits obtained using magnetogranulometry, and how measuring above and below the blocking temperature can affect fit results.

Detailed Group-Type Characterization of Plastic-Waste Pyrolysis Oils: By Comprehensive Two-Dimensional Gas Chromatography Including Linear, Branched, and Di-Olefins

Plastic-waste pyrolysis oils contain large amounts of linear, branched, and di-olefinic compounds. This makes it not obvious to determine the detailed group-type composition in particular to the presence of substantial amounts of N-, S-, and O-containing heteroatomic compounds. The thorough evaluation of different column combinations for two-dimensional gas chromatography (GC × GC), i.e., non-polar × polar and polar × non-polar, revealed that the second combination had the best performance, as indicated by the bi-dimensional resolution of the selected key compounds. By coupling the GC × GC to multiple detectors, such as the flame ionization detector (FID), a sulfur chemiluminescence detector (SCD), a nitrogen chemiluminescence detector (NCD), and a mass spectrometer (MS), the identification and quantification were possible of hydrocarbon, oxygen-, sulfur-, and nitrogen-containing compounds in both naphtha (C5–C11) and diesel fractions (C7–C23) originating from plastic-waste pyrolysis oils. Group-type quantification showed that large amounts of α-olefins (36.39 wt%, 35.08 wt%), iso-olefins (8.77 wt%, 9.06 wt%), and diolefins (4.21 wt%, 4.20 wt%) were present. Furthermore, oxygen-containing compounds (alcohols, ketones, and ethers) could be distinguished from abundant hydrocarbon matrix, by employing Stabilwax as the first column and Rxi-5ms as the second column. Ppm levels of sulfides, thiophenes, and pyridines could also be quantified by the use of selective SCD and NCD detectors.

Associations between Exposure to Organochlorine Chemicals and Endometriosis: A Systematic Review of Experimental Studies and Integration of Epidemiological Evidence.

Background:Growing epidemiological evidence suggests that organochlorine chemicals (OCCs), including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), may play a role in the pathogenesis of endometriosis.Objectives:We aimed to systematically review the experimental evidence (in vivo and in vitro) on the associations between exposure to OCCs and endometriosis-related end points.Methods:A systematic review protocol was developed following the National Toxicology Program /Office of Health Assessment and Translation (NTP/OHAT) framework and managed within a web-based interface. In vivo studies designed to evaluate the impact of OCCs on the onset or progression of endometriosis and proliferation of induced endometriotic lesions were eligible. Eligible in vitro studies included single-cell and co-culture models to evaluate the proliferation, migration, and/or invasion of endometrial cells. We applied the search strings to PubMed, Web of Science, and Scopus®. A final search was performed on 24 June 2020. Assessment of risk of bias and the level of evidence and integration of preevaluated epidemiological evidence was conducted using NTP/OHAT frameworkResults:Out of 812 total studies, 39 met the predetermined eligibility criteria (15 in vivo, 23 in vitro, and 1 both). Most studies () tested TCDD and other dioxin-like chemicals. In vivo evidence supported TCDD’s promotion of endometriosis onset and lesion growth. In vitro evidence supported TCDD’s promotion of cell migration and invasion, but there was insufficient evidence for cell proliferation. In vitro evidence further supported the roles of the aryl hydrocarbon receptor and matrix metalloproteinases in mediating steroidogenic disruption and inflammatory responses. Estrogen interactions were found across studies and end points.Conclusion:Based on the integration of a high level of animal evidence with a moderate level of epidemiological evidence, we concluded that TCDD was a known hazard for endometriosis in humans and the conclusion is supported by mechanistic in vitro evidence. Nonetheless, there is need for further research to fill in our gaps in understanding of the relationship between OCCs and their mixtures and endometriosis, beyond the prototypical TCDD. https://doi.org/10.1289/EHP8421

The Decade-long Evolution and Toxicity of Oil Transformation Compounds in Louisiana Salt Marsh Sediments Revealed by FT-ICR Mass Spectrometry

The 2010 explosion of the Deepwater Horizon (DWH) drilling rig provides a unique opportunity to advance the understanding of the evolution of lingering oil in Louisiana salt marshes for nearly a decade after the initial spill. After an oil spill, petroleum hydrocarbons undergo physical and chemical processes that transform the native oil composition to a polyfunctional oxygenated hydrocarbon matrix that contains ketones, hydroxyl, and carboxylic acid functional groups. Preliminary analysis of saltmarsh sediments impacted by the DWH spill between 2010–2014 identifies highly polar oxygenated hydrocarbons with carboxylic acid functionalities. These highly polar, high molecular weight compounds are not detectable by conventional gas chromatography (GC) based techniques. Here, we employ advanced analytical technologies such as targeted fractionation and isolation methods with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to document and catalog oil transformation compounds detected in oiled saltmarsh sediments. The toxicities of these environmental transformation products are determined by commercial Microtox bioassay. Samples have been continuously collected from 21 previously established sampling stations located in northern Barataria Bay for the past ten years post-spill. The concentration of oil contamination from heavily and moderately oiled sites exceed non-oiled reference sites for years after the spill. Combining chromatographic fractionation, conventional GC MS, and ultrahigh-resolution FT-ICR Mass Spectrometry analyses, we identified tens-of-thousands of biotic and abiotic crude oil transformation products that remain persistent and keep evolving in the environment. Heavily oxygenated transformation products, which are mostly only accessible by FT-ICR MS, span a wide range of chemical functionalities. Toxicity of the non-GC amenable fraction of oil contaminants was measured to determine the health risk of weathered oil residues left in the salt marsh environment. The current study creates a decade-long assessment record, and a comprehensive understanding of petroleum compounds evolution of oil-impacted wetlands ecosystem.

Catalytic Hydrodesulfurization of Gaseous Fuels with Autogenously Formed Hydrogen

AbstractHydrogen production from gaseous fuels, such as natural or liquefied petroleum gas, for fuel cell application requires feedstock free of catalyst poisons. As sulfur is one of the main poisons, different methods are employed to remove sulfur species. We propose a process not requiring external hydrogen feed to the feedstock. The hydrogen for the hydrogenation of the sulfur species is obtained directly from the hydrocarbon matrix reacting on a zeolite catalyst. The result is a desulfurization process with considerably simplified process management and a superior process startup.

Hydrocarbon transformations in sediments from the Cathedral Hill hydrothermal vent complex at Guaymas Basin, Gulf of California – A chemometric study of shallow seep architecture

Guaymas Basin isa submarine depression in the Gulf of California marking the northern end of the East Pacific Rise mid-oceanic spreading ridge.The basin receives high input of sedimentary organic matter (SOM) from elevated productivity in the overlying surface waters and runoff from the surrounding continent. This, coupled with high sedimentation rates, produces near-uniform compositions of SOM.Various hydrothermal vent complexes occur along this margin. One of these is Cathedral Hill, a hydrothermal mound with sulfide chimneys surrounded by mats dominated by sulfide-oxidizing Beggiatoa, covering sediments stained by locally produced oil. We collected four push cores along a transect at this site (4 m × 0.21 m) extending from near the vent center to the ambient sediment just outside the microbial mat cover. Porewater temperatures near the mound center were projected to reach 155 °C by 21 cm below the sea floor (cmbsf). Within these conditions, a kinetic model based on vitrinite reflectance equivalence (%Re) predicts petroleum formation as shallow as 15–18 cmbsf, with metagenesis commencing at <60 cmbsf. Bulk extract data (total lipid extracts as well as polar and apolar fractions), solvent-extracted sediment TOC (herein referred to as protokerogen TOC), and molecular thermal maturation parameters support these generation estimates. In recent years, the application of chemometric techniques tocomprehensive two-dimensional gas chromatographic (GC × GC) analyses has allowed comparison of thousands of unique hydrocarbons within oils. Here we reconstruct the shallow subsurface petroleum system by applying multiway principal component analysis (MPCA) and hierarchical cluster analysis (HCA)directly to GC × GC chromatograms. We then compare the resulting multivariate models to a systematic survey of subtracted GC × GC chromatograms, a transect heat map of sample hydrocarbon compound diversities, and profiles of various thermal maturation parameters to elucidate how these hydrocarbon matrices are attenuated by production, migration, and/or thermochemical oxidation. Sample matrices have up to 5800 unique compounds spanning a range ofnormal and branched alkanes, saturated and unsaturated biomarkers, substituted and unsubstituted polycyclic aromatic hydrocarbons (PAHs), perhydro-PAHs, and benzothiopheneswith up to six ring-cycles (i.e., benzoperylenes, dibenzopyrenes, dibenzochrysenes, and indenopyrenes). These matrices display systematic temperature-dependent trends. Generation likely begins in 6–10 and 15–18 cmbsf where sediments are exposed to ∼115 °C vent porewater temperatures, which is shallower than predictions based on our kinetic model. Independent of these sites of generation is ubiquitous staining of the sediments from advected oil that is heavily dominated by PAHs as well as two stratigraphic bandsof migrated oil that extend horizontally across the transect at 0–2 and ∼6–10 cmbsf, respectively.The MPCA models along with non-statistical validation techniques show evidence of decreasingdiversities and concentrations of alkylated aromatic hydrocarbons concomitant with elevated abundances of dealkylated PAHs and/or the migration of unsubstituted PAHs from deeper basin depths as sediments become exposed to more severe hydrothermal conditions. These results indicate that even at relatively small spatial scales, the petroliferous sediments at hydrothermal vent sites can be highly complex.

Specific Features of the Structure of Various Coal Ranks at the Nano Level

Structural factors and functions of radial distribution of atoms of different coal ranks have been calculated by X-ray diffraction analysis. This made it possible to establish that the main structural component is the clusters with graphite-like packing of atoms. The predominant size of these clusters (calculated from the peaks of small-angle X-ray scattering at 5° in CoKα-radiation) for coals with a carbon content of 83--95 % is within 2--3 nm. Fossil coal is an amorphous carbonaceous substance consisting of polymorphic modifications in the sp2- and sp3-states. According to the results obtained using Raman scattering spectroscopy, the physical properties of amorphous natural coals are strongly dependent on the ratio of sp2- and sp3-hybridization of atomic orbitals. Moreover, studies have shown that the carbon atoms of the coal matrix in the sp2-state are represented by both aromatic and aliphatic conjugated chain fragments. It was found that the degree of ordering in rank LF coals is higher than in coals of a higher stage of metamorphism. This is possible if the hydrocarbon matrix in rank LF coals can be represented as a polymer consisting of conjugated chains with periodicity. With an increase in the stage of coal metamorphism, starting with coal rank G, the transformation of the coal structure occurs with a violation of the periodicity of the conjugated fragments of the polymer matrix connecting graphite-like clusters, a decrease in their length, and an increase in randomness in their arrangement

Perfluorinated Anion Exchange Membranes for Alkaline Water Electrolysis

The anion exchange membranes (AEMs) contain positively charged functional groups in their polymeric matrices to selectively transport anions including hydroxide ion. The desirable AEMs should satisfy high chemical resistance and excellent anion conductivity. Commercially available AEMs are vulnerable to thermo-chemical attacks at the alkaline conditions and undesirable to anion transport owing to their hydrocarbon matrices’ characteristics. On the other hand, the use of perfluorinated backbones as AEM matrices can provide a route to avoid these negative issues, since the perfluorinated materials have excellent chemical resistance to alkaline atmospheres and well-developed morphologies. In this study, perfluorinated AEMs were synthesized via stepwise chemical substitution reactions of a perfluorinated sulfonic acid precursor membrane. The resulting membranes were evaluated as polymer electrolytes for alkaline water electrolysis.

Thermo-Chemically Durable Perfluorinated Anion-Conducting Ionomer Membranes for Advanced Alkaline Water Electrolysis

The state-of-the-art membrane for alkaline water electrolysis is porous Zirfon®. Unfortunately, Zirfon® has been suffering from the crossover of hydrogen gas permeated through the pores, inducing safety issues including explosion. To date, there have been approaches to solve this problem. One good example is to use anion-conducting ionomer membranes with dense structures. Generally, the membranes, which are made up of hydrocarbon matrices, experience severe degradation, when they are exposed under strong basic conditions at the temperatures higher than 50 oC for high electrochemical performances. In this study, perfluorinated ionomer membranes with extremely high thermo-chemical resistances are developed via the combination of architectural design and supercritical dispersion.

Investigation of Ag/a-C:H Nanocomposite Coatings on Titanium for Orthopedic Applications.

One of the leading causes of failure for any bone implant is implant-associated infections. The implant-bone interface is in fact the crucial site of infection where both the microorganisms and cells compete to populate the newly introduced implant surface. Most of the work dealing with this issue has focused on the design of implant coatings capable of preventing infection while ignoring cell proliferation or vice versa. The present study is therefore focused on investigating the antibacterial and biological properties of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) matrix containing silver nanoparticles (AgNPs). a-C:H coatings with varying silver concentrations were generated directly on medical grade titanium substrates using a combination of a gas aggregation source (GAS) and a plasma-enhanced chemical vapor deposition (PE-CVD) process. The obtained results revealed that the surface silver content increased from 1.3 at % to 5.3 at % by increasing the used DC magnetron current in the GAS from 200 to 500 mA. The in vitro antibacterial assays revealed that the nanocomposites with the highest number of silver content exhibited excellent antibacterial activities resulting in a 6-log reduction of Escherichia coli and a 4-log reduction of Staphylococcus aureus after 24 h of incubation. An MTT assay, fluorescence live/dead staining, and SEM microscopy observations of MC3T3 cells seeded on the uncoated and coated Ti substrates also showed that increasing the amount of AgNPs in the nanocomposites had no notable impact on their cytocompatibility, while improved cell proliferation was especially observed for the nanocomposites possessing a low amount of AgNPs. These controllable Ag/a-C:H nanocomposites on Ti substrates, which simultaneously provide an excellent antibacterial performance and good biocompatibility, could thus have promising applications in orthopedics and other biomedical implants.

A Qualitative Analysis of Different Types of Water Repellent Agent Used on Cotton Fabric

The existence of intermolecular attractive forces of polarity and hydrogen bond is imperative in providing strength, heat resistance and drycleaning resistance to cotton fabric. However, these forces enhance easy wetting of fiber by water offering little resistance to snow and rain for outerwear garments. This problem could be overcome by adding water repellent chemicals to the fabric either chemically or with mechanical coating which prevent penetration of water through the fabric without destroying comfort of the fabric. The aim of the work is to evaluate the effect of different types of water repellent agents used on cotton fabric and analyze different possible factors affecting the performance and quality of treated fabrics. For this purpose, three water repellent chemicals: Lurotex protector RP ECO is a product based on C6 technology, Rucostar EEE6 product consists of a hydrocarbon matrix and hyper-branched, star-shaped polymers(dendrimers) and Nuva TTC is a conventional fluorocarbon based water repellent chemicals were used in three different concentrations to find out an optimum chemical concentration. To judge the quality of the treated fabrics, spray test, air permeability test, strength test and abrasion resistance test were evaluated. The quality of treated fabrics for all three chemicals was very close to each other and if the process parameters is maintained successfully, desired results can be achieved.

Determination of Water Content in Liquid Insulation of High-Voltage Equipment by Different Methods

Control of the formation and behavior of water in a liquid dielectric during the operation of high-voltage equipment is of paramount importance because water provokes intensive oxidation and aging of the entire oil-solid insulation system. The electrophoretic ability of water has a strong effect on the insulating properties of dielectrics inside a high-voltage apparatus, and, in general, on its uninterrupted long-term operation. Problems associated with the determination of moisture in the complex hydrocarbon matrix of transformer oil by all available methods are considered. It is shown how different states of water in transformer oil of various grades can be determined by varying the temperature in the evaporator of the chromatographic unit. Chromatographic data are compared with data obtained by conventional methods (Karl-Fischer coulometric titration, calcium-hydride method, coulometric sensor based electrolysis).