Evaporation Of Hexane Research Articles

Условия и режимы обработки технологического процесса маслонаполнения полимерных деталей

A large number of polymer parts, used in railway transport, operating in difficult conditions, significantly wear off caused by conditions in open friction units, having dust loading and other contamination without any liquid lubrication. Existing technologies, used for solving this problem, aimed at making just the material of the part, which results in a change in the operational properties of the whole part, but there is no technology that will be useful in changing the operational properties of the surface layer itself. In order for a decision to be adopted on, a new procedure specification is being developed to improve the performance characteristics of ready-made polymer parts. This technology consists in filling their surface layer with an oil mixture to a given depth of approved wear. One of the most important stages in the development of this technological process is the determination of various conditions and operating modes necessary to ensure the parameters of this operating procedure. For that purpose, the objective function of two parameters is formed in the work. In this paper, the criteria for evaluating the parameters of the specification procedure of oil filling are determined. The analytical calculations and experimental studies are performed for the boundary delimination of the parameters and temperature limits for the application of the filling mixture based on the temperature of its boiling and evaporation of hexane. Due to certain initial and boundary conditions, the recommended operating modes for performing the specification procedure of oil filling are determined. The result of the work was the determination of the specific boundaries of the objective function of two parameters and the order of the stages of the procedure, which allows ensuring its stability and performance.

Fluorine-Free Extinguishing of a Hydrocarbon Pool Fire with a Suspension of Glass Bubbles Grafted with Nanoscale Polymer Layers.

The current most efficient solution to extinguish liquid hydrocarbon (class B) pool fires involves fire-fighting foams containing fluorinated surfactants. However, fluorocarbon surfactants are unsafe due to their environmental persistence and negative toxicological/bioaccumulative impact. To this end, we show that fluorine-free aqueous suspensions of Glass Bubbles (GB) modified with hydrophilic polymer grafted layers can efficiently extinguish hydrocarbon pool fires. Namely, GB grafted with poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA), GB-G was fabricated employing "grafting-through" and "grafting-from" methods and used to obtain the suspensions. It was found that the GB suspension, with a grafted layer of higher molecular weight and lower grafting density (GB-GL), proved superior to the more densely grafted GB-GH and nongrafted GB-0 system. The GB-GL suspensions displayed less negative spreading coefficients and viscosities lower than those of GB-GH/GB-0 compositions. When siloxane-polyoxyethylene surfactant was added to all GB suspensions, the interfacial properties were dominated by the surfactant, with all suspensions having the same positive spreading coefficient. However, the GB-GL-surfactant composition had the lowest viscosity among the suspensions studied in this work. Specifically, the viscosity of GB-GH and GB-0 suspensions at a shear rate of 77 s-1 was ∼110% and 70% higher than that of GB-GL. Due to the lower viscosity, the GB-GL suspension demonstrated the most efficient spreading over model hydrocarbon solid (polyethylene) and liquid (hexadecane) surfaces when the surfactant was added. The suspension also showed the best performance in the retardation of hexane evaporation when placed over the heated hexane pool. After 50 min, the amount of hexane that evaporated through GB-GH and GB-0 suspensions was ∼8 and 11 times higher, respectively, compared to the GB-GL suspension. We found that the GB-GL-surfactant system was the most efficient GB suspension in extinguishing the fire due to its superior spreading and sealing ability. It was within 10% of fluorine-containing foam's fire extinguishment performance. The GB suspensions are much safer in terms of burnback resistance as a torch applied directly to the suspension after extinguishment could not reignite the fire. The GB material is recyclable, since it can be collected and reused after application to a fire.

Construction of Millimeter-Wide Monolayers of Ordered Nanocubes as a Stain of “Wineglass Tears” Driven by the Marangoni Flow

We constructed millimeter-wide monolayers consisting of tetragonally ordered BaTiO3 (BT) nanocubes through the liquid film formation caused by the Marangoni flow in a toluene-hexane binary liquid containing oleic acid. A thin liquid film containing BT nanocubes was overspread on a standing silicon substrate through the condensation of toluene at the advancing front after the preferential evaporation of hexane. Then, the oscillatory droplet formation like "wineglass tears" occurred on the substrate. Finally, two-dimensionally ordered BT nanocubes were observed as a stain of "wineglass tears" on the substrate after the liquid film receded through evaporation. The presence of a thin liquid film in the binary system is essential for the production of millimeter-wide monolayers on the substrate because multilayer deposition occurs without the formation of a thin liquid film in monocomponent systems. We improved the regularity of the ordered arrays of nanocubes by adjusting the liquid component and evaporation conditions.

Continuous separation and recovery of high viscosity oil from oil-in-water emulsion through nondispersive solvent extraction using hydrophobic nanofibrous poly(vinylidene fluoride) membrane

Membrane separation has been considered as a promising technology for oily wastewater treatment. However, membrane fouling significantly limited its practical applications especially for oils with high viscosity and concentration. In this study, we propose membrane based nondispersive solvent extraction for continuous separation and recovery oils with high viscosity and concentration from oil-in-water emulsion. In this process, oil-in-water emulsion and extraction solution (hexane) was separated by a porous hydrophobic poly (vinylidene fluoride) (PVDF) nanofibrous membrane and flowed on each side of the membrane. The strong affinity of PVDF membrane and high solubility of hexane towards oil (e.g., lubricant oil) endowed continuous transfer of oil from emulsion side to hexane side. Different from conventional physical sieving, fouling enhanced transfer of lubricant oil in this process. Lubricant oil flux was up to about 336 g/m2 when 1% lubricant oil-in-water emulsion was used and increased to 935 g/m2 in case of 10%. Moreover, lubricant oil can be easily recovered through hexane evaporation both in low (17oC) and relative high temperature (67oC). Water content of recovered oil (0.10 ± 0.02%) was almost the same as original samples (0.11 ± 0.02%). Strategy proposed in the current study offers an effective way for treating oil-in-water emulsion with high viscosity and concentration.

Cuticular Hydrocarbon Trails Released by Host Larvae Lose their Kairomonal Activity for Parasitoids by Solidification

Successful host search by parasitic wasps is often mediated by host-associated chemical cues. The ectoparasitoid Holepyris sylvanidis is known to follow chemical trails released by host larvae of the confused flour beetle, Tribolium confusum, for short-range host location. Although the hexane-extractable trails consist of stable, long-chain cuticular hydrocarbons (CHCs) with low volatility, the kairomonal activity of a trail is lost two days after release. Here, we studied whether this loss of kairomonal activity is due to changes in the chemical trail composition induced by microbial activity. We chemically analyzed trails consisting of hexane extracts of T. confusum larvae after different time intervals past deposition under sterile and non-sterile conditions. GC-MS analyses revealed that the qualitative and quantitative pattern of the long-chain CHCs of larval trails did not significantly change over time, neither under non-sterile nor sterile conditions. Hence, our results show that the loss of kairomonal activity of host trails is not due to microbially induced changes of the CHC pattern of a trail. Interestingly, the kairomonal activity of trails consisting of host larval CHC extracts was recoverable after two days by applying hexane to them. After hexane evaporation, the parasitoids followed the reactivated host trails as they followed freshly laid ones. Cryo-scanning electron microscopy showed that the trails gradually formed filament-shaped microstructures within two days. This self-assemblage of CHCs was reversible by hexane application. Our study suggests that the long-chain CHCs of a host trail slowly undergo solidification by a self-assembling process, which reduces the accessibility of CHCs to the parasitoid’s receptors as such that the trail is no longer eliciting trail-following behavior.

Direct Observation of Homogeneous Cavitation in Nanopores.

We report on the evaporation of hexane from porous alumina and silicon membranes. These membranes contain billions of independent nanopores tailored to an ink-bottle shape, where a cavity several tens of nanometers in diameter is separated from the bulk vapor by a constriction. For alumina membranes with narrow enough constrictions, we demonstrate that cavity evaporation proceeds by cavitation. Measurements of the pressure dependence of the cavitation rate follow the predictions of the bulk, homogeneous, classical nucleation theory, definitively establishing the relevance of homogeneous cavitation as an evaporation mechanism in mesoporous materials. Our results imply that porous alumina membranes are a promising new system to study liquids in a deeply metastable state.

In situ monitoring of the morphology evolution of interfacially-formed conductive nanocomposite films and their use as strain sensors

HypothesisUnderstanding and monitoring the film formation of interfacially formed layered films allows for the design of conductive nanocomposite films suitable for strain sensing. ExperimentsTo understand the mechanism of interfacial film formation, the hexane/water interface was monitored during the evaporation process via confocal laser scanning microscopy. Scanning electron microscopy and atomic force microscopy were utilized to investigate final film morphology. Tensile testing was used to determine their mechanical properties under uniaxial strain. FindingsConductive nanocomposite films were formed at the hexane/water interface. Due to their low colloidal stability in hexane, the Vulcan carbon (VC) nanoparticles settled to the hexane/water interface prior to the onset of paraffin wax precipitation. Consequently, after the evaporation of hexane a two-layer structured film was formed. The bottom (water-facing, VC-rich) layer was conductive due to the existence of a percolated network of nanoparticle aggregates, while the top (hexane facing, paraffin-rich) layer was not conductive. The films showed high sensitivity for strains between 1% and 10%. We propose that the mechanism of strain sensing is similar to that of layer-structured sensors fabricated through embedding conductive nanofillers onto flexible polymeric substrates. The advantage of the films derived by the method proposed here is their ease of fabrication as well as their low cost.

Chemical profile of organic residues from ancient amphoras found in Pyrgi and Castrum Novum, Tyrrhenian Sea (Italy)

The organic residues in the form of black layer spots inside amphoras found on the sites of the former ancient ports of Pyrgi and Castrum Novum on the coast of the Tyrrhenian Sea were investigated using GC–MS and HPLC with fluorimetric detection. According to our hypothesis, the residues could be from waterproofing materials from pine trees, which ensured that amphoras could be used for transportation and the storage of liquids. Samples of the residues were removed, extracted with hexane and separated into three parts. The first part served directly for GC–MS analysis of hydrocarbons. The second part after the evaporation of hexane and silylation of the residue with MSTFA was used for the analysis of fatty and resin acids. Finally, the third part after evaporation of hexane and dilution of the residue with methanol was used for HPLC analysis of pinosylvin mono methyl ether and confirmation of retene presence using a fluorimetric detector. 18-Norabieta-8,11,13-triene, 19-norabieta-8,11,13-triene and 1,2,3,4-tetrahydroretene were found in the hexane extract, which are intermediates from the tar/pitch production process. The most abundant peak in the chromatogram of the hexane extract was dehydroabietic acid and retene. The latter is considered to be a marker for pine pitch. The most abundant compound in the derivatized hexane extract was also dehydroabietic acid, which occurs only as a minor component in fresh resins. This molecule is formed during the oxidative dehydrogenation of abietic acid, which predominates in original resins. Pinosylvin mono methyl ether was found in the methanolic extract using HPLC with fluorimetric detection and, to the best of our knowledge, it is the first finding of this substance in archaeological samples. Together with the abovementioned compounds, it supports the hypothesis of the resin's origin from trees of the Pinaceae family.

An Inexpensive, Single Use Carbon-Based Sensor for the Rapid and Early Detection of Hydrocarbon Leaks

A novel fabrication process for a single use, low-cost organic solvent sensor has been developed. The process is simple, and the materials are readily available. Carbon nanomaterials are self-assembled at a water/hexane interface, where the hexane phase contains dissolved paraffin wax. Upon the controlled evaporation of hexane, the paraffin wax precipitates, trapping the carbon nanoparticles at the surface in a paraffin wax backbone, realizing a carbon-nanoparticle-decorated film. The film is hydrophobic and highly electrically conductive. When exposed to hydrocarbons or a mixture of hydrocarbons, the conductive carbon network deteriorates and an increase in film resistivity is monitored. The rate of change in resistivity is proportional to the concentration and composition of organic molecules in contact with the film.

Controllable photo-physical and aggregating properties of D–π–A perylene diimide derivatives by introducing soft/hard substituent on the bay position

Comparative discussions on photo-physical and aggregating properties of D–π–A perylene diimide derivatives with soft n-octylamine (PDI-soft) and hard quinoidal (PDI-hard) substituents on the bay position were put forward to reveal structure–property relations. UV–vis spectrometer and fluorospectro photometer were used to characterize the absorption and emission properties of derivatives in various solutions. The PDI-hard aggregated in both Hexane and THF/water systems and showed an interesting time-dependent aggregation-induced enhanced emission (AIEE) phenomenon. PDI-soft also aggregated in poor solvents as Hexane or Acetonitrile and exhibited broad light absorption range making PDI-soft a candidate for photoelectric materials. Morphologies of solid aggregations formed from solutions were observed by means of scanning electron microscopy. Results showed that PDI-hard molecules aggregated to sheets structure after the evaporation of Hexane while PDI-soft obtained a wire-like structure through a slipped π-π stacking in the system of THF and water. The comparison of photo-physical properties and morphologies between PDI-hard and PDI-soft suggests that a subtle choice of the bay substituents makes the controllable photo-physical and aggregating properties possible.

Small Angle X-ray Scattering of Iron Oxide Nanoparticle Monolayers Formed on a Liquid Surface

In situ small-angle X-ray scattering (SAXS) is used to show that iron oxide nanoparticles (NPs) of a range of sizes form hexagonally ordered monolayers (MLs) on a diethylene glycol liquid surface, after drop-casting the NPs in hexane and subsequent hexane evaporation. The formation of the ordered NP ML is followed in real time by SAXS when using a heptane solvent. During drying, the NPs remain in the hexane or heptane layer, and an ordered structure is not formed then. After drying, the NPs are farther apart than expected from only van der Waals attraction between the NP cores and Brownian motion considerations, which suggests the importance of ligand attraction in binding the NPs.

Simultaneous enhancement in both large-area coatability and photovoltaic performance of inverted organic solar cells with co-solvent

We report our observation of simultaneous enhancement in large-area coatability and photovoltaic performance for blade-coated inverted P3HT:PCBM organic solar cells with DCB:hexane co-solvent. The addition of hexane improves greatly the wettability of P3HT:PCBM blend layer on Cs2CO3 treated ITO and leads to excessively higher P3HT surface concentration due to the incongruent evaporation of hexane and DCB. A post-processing light soaking was found to further improve the photovoltaic performance for blade-coated devices prepared with co-solvent by adjusting the P3HT surface concentration ratio for more favorable carrier transport, as evidenced by the disappearance of current suppression at forward bias and significant increase in Voc after light soaking. Since large-area manufacturing is the key to full commercialization of organic solar cells, the use of co-solvent, combined with light soaking, may be crucial for the development of inverted organic solar cells.

Monolayers of spin-coated L10 FePt nanoparticles

Monolayers of FePt nanoparticles were synthesized on SiO2/Si substrates by spin-coating method. The effects of spin-coating conditions on surface morphology of FePt system was studied with FE-SEM. A high temperature annealing on the FePt monolayer films resulted in phase transition from fcc into fct (L10 phase), while preventing nanoparticles from sintering. Furthermore, L10 FePt nanoparticles with an average size of 15 nm are coated on SiO2/Si surface. Uniform nanoparticle monolayer was obtained by optimizing the experiment parameters such as spin time and controlling hexane evaporation rate.

Analysis of Polychlorinated Biphenyls in Transformer Oil by Using Liquid–Liquid Partitioning in a Microfluidic Device

Polychlorinated biphenyls (PCBs) that are present in transformer oil are a common global problem because of their toxicity and environmental persistence. The development of a rapid, low-cost method for measurement of PCBs in oil has been a matter of priority because of the large number of PCB-contaminated transformers still in service. Although one of the rapid, low-cost methods involves an immunoassay, which uses multilayer column separation, hexane evaporation, dimethyl sulfoxide (DMSO) partitioning, antigen-antibody reaction, and a measurement system, there is a demand for more cost-effective and simpler procedures. In this paper, we report a DMSO partitioning method that utilizes a microfluidic device with microrecesses along the microchannel. In this method, PCBs are extracted and enriched into the DMSO confined in the microrecesses under the oil flow condition. The enrichment factor was estimated to be 2.69, which agreed well with the anticipated value. The half-maximal inhibitory concentration of PCBs in oil was found to be 0.38 mg/kg, which satisfies the much stricter criterion of 0.5 mg/kg in Japan. The developed method can realize the pretreatment of oil without the use of centrifugation for phase separation. Furthermore, the amount of expensive reagents required can be reduced considerably. Therefore, our method can serve as a powerful tool for achieving a simpler, low-cost procedure and an on-site analysis system.

Formation of Close-Packed Nanoparticle Chains

The self-assembly of CoPt(3) particles (diameter 6 nm) into low-dimensional ordered arrays results from phase separation in a hexane solution containing nanoparticles, hexadecylamine, and water. The evaporation of hexane from the thin film of solution initiates the formation of a water layer on the solid substrate. Subsequent dewetting of this water layer leads to the formation of water droplets. The nanoparticles follow the motion of the contact line of the dewetting water layer and thus assemble into ordered arrays at the periphery of the water droplets.

Characterization of silica-coated Ag nanoparticles synthesized using a water-soluble nanoparticle micelle

This article describes the synthesis of silica-coated Ag nanoparticles using a water-soluble nanoparticle micelle under basic conditions. Monodispersed Ag nanoparticles with a mean particle size of 7 nm were synthesized using AgNO 3 in the presence of ascorbic acid as a reducing agent. The Ag nanoparticles were easily re-dispersed into an aqueous solution by surface adsorption of surfactant molecules, indicating formation of water-soluble nanoparticle micelles. Silica-coated Ag nanoparticles ranging in size from 50 to 100 nm were obtained by controlling the surfactant, Ag nanoparticle and tetraethylortho silicate (TEOS) concentrations. Adsorbed surfactant monolayers on Ag nanoparticles were used as a template for the silica shell because of the hydrophobicity of TEOS. In all cases, the size of the resulting particles increased linearly as these concentrations increased. Based on transmission electron microscopy, all the Ag nanoparticles were completely covered with a silica shell. In most samples, however, Ag nanoparticle size increased from 7 to 50 nm due to evaporation of hexane by heating. Although mean particle size of silica-coated Ag nanoparticles was drastically altered, characteristic absorption peaks were observed at approximately 410 nm.

Effects of variable density for film evaporation on laminar mixed convection in a vertical channel

A numerical investigation was conducted to study mixed convection in a vertical parallel-plate channel with evaporation of thin liquid films on wetted walls. Air–water vapor and air–hexane vapor mixtures, assumed as ideal gases, are considered under various boundary conditions. Steady laminar, two-dimensional flows are examined in detail for large mixture density changes between the inlet and outlet sections of the channel. Comparisons with the usual problem formulations based on the Boussinesq approximation are discussed. The elliptic flow model used allow to predict flow reversal as well as recirculation cells in the entrance region. The evaporation of water and hexane into a downward laminar stream of dry air leads to various flow structures according to the interfacial mass fraction, W v,w , and differences in the molecular weights of the species. For water evaporation, the thermal and solutal forces are opposing. In the entrance region, evaporation produces a significant increase in axial velocity at the core region in comparison with pure forced flow. For W v,w larger than ≈0.2, upward velocities may be observed in the wall regions due to solutal buoyancy forces near the wetted surfaces. For hexane evaporation, the solutal force acts downward. Mass diffusion produces both a strong flow acceleration in the boundary layers and flow recirculations at the channel center for large mass evaporation rates.

Synthesis and Characterization of Paramagnetic Microparticles through Emulsion-Templated Free Radical Polymerization

A novel method is described for the preparation of high-magnetization paramagnetic microparticles functionalized with a controlled density of poly(ethylene glycol) (PEG) and carboxyl groups. These microparticles were synthesized using four steps: (1) creation of an oil-in-water emulsion in which hydrophobic iron oxide nanoparticles and a UV-activated initiator were distributed in hexane; (2) formation of uniform microparticles through emulsion homogenization and evaporation of hexane; (3) functionalization of the microparticle with a PEG-functionalized surfactant and acrylic acid; and (4) polymerization of the microparticles. Characterization of the microparticles with electron microscopy and light scattering revealed that they were composed of densely packed iron oxide nanoparticles and that the size of the microparticles may be controlled through the pore size of the membrane used to homogenize the emulsion. The concentration of surfactant and acrylic acid used in the third processing step was found to determine the surface chemistry, iron content, and magnetization of the microparticles. Increasing the PEG surfactant to acrylic acid ratio resulted in higher PEG surface densities, lower iron content, and lower magnetization. The resulting microparticles were readily functionalized with antibodies and showed a low propensity for nonspecific protein adsorption. We believe that these microparticles will be useful for magnetic tweezers measurements and bioanalytical devices that require microparticles with a high magnetization.

An Inexpensive Method for Applying Nitrogen Evaporation to Hexane-containing 24- or 96-well Plates

A method is described for assembling an evaporation manifold from a cell culture flask, which allows for efficient nitrogen evaporation of hexane from 24- and 96-well plates. The precursor parts are readily available in most research laboratories. The nitrogen evaporation manifold is inexpensive, could possibly be used with other organic solvents, and appears ideal for a small number of samples in a multi-well format.

New concept for the preparation of potassium sodides: the use of hexane as a non-polar solvent

NaK alloy in contact with 15-crown-5 hexane solution became potassium sodide K +(15-crown-5) 2Na −. After the evaporation of hexane the crystalline solid product was analyzed by X-ray diffraction and the lattice parameters were calculated. The potassium sodide thus obtained could be easily dissolved in tetrahydrofuran. A deep blue solution containing sodium anions and complexed potassium cations was formed with a very low concentration of solvated electrons, i.e. of the order of 10 −7 M. Potassium anions were not detected in this case. A new crystalline potassium sodide K +(DCH-24-crown-8) 2Na − was obtained using NaK alloy and dicyclohexano-24-crown-8 hexane solution.