Low Miscibility Research Articles

Analysis of combustion characteristics, engine performances and emissions of long-chain alcohol-diesel fuel blends

Petroleum-based fuels have been one of the most in demand energy source for various purposes and application. However, rigorous emissions from petroleum-based fuels have forced many governments to introduce stringent regulations and concerns over energy security. Alternative fuel such as short-chain alcohol (methanol and ethanol) had been used as an oxygenated element to increase oxygen content in diesel fuel (DF). However, short-chain alcohol-diesel blends have disadvantages such as low cetane number, low heating value, increase of hydrocarbons (HC) and low miscibility with DF. Recently, researchers have shown interest on long-chain alcohols which have better physicochemical properties than short-chain alcohol. In this experiment, 5%, 10% and 20% of 2-ethyl 1-hexanol (2-EH) was added into DF to produce long-chain alcohol-diesel fuel blends. The fuel blends were prepared by using Hielscher UP400S ultrasonic emulsifier machine at 20% Hz stirring speed. The discussion will focus on combustion characteristics, engine performance and exhaust emissions of single cylinder diesel engine YANMAR TF120M at constant engine speed of 1800 rpm under various loads (0%, 25%, 50%, 75%, and 100%). The results show that HE5 has the preeminent properties among fuel blends in terms of calorific value (45.87 MJ/kg), density (806.1 kg/m3) and viscosity (3.02 mPa·s). Performance analysis shows BTE had increased by 91.72%, while BSFC had decreased by 45.22% for 5% 2-EH (HE5).

Synthesis, properties of pentaalkylguanidinium-based magnetic room temperature ionic liquids (MRTILs) and the mutual solubility of (MRTILs + cyclohexane) and (MRTILs + n-octane) binary systems

The application of guanidinium-based ionic liquids (ILs) is a newly emerging area in the fields of extraction desulfurization. Herein, four novel pentaalkylguanidinium-based magnetic room temperature ionic liquids (MRTILs) [CnTMG][FeCl3Br] (n = 2, 4, 6, 8) were synthesized and characterized by FT-IR, Raman and HRMS (ESI) spectra. The physical properties including thermal stability, density, viscosity, conductivity and magnetic properties were determined and revealed that the MRTILs were liquids at room temperature and have good thermal stability (Td > 250 °C), high magnetic susceptibility (>3.8 × 105 emu·g−1) and low viscosities (<160 mPa·s, 25 °C). Moreover, the mutual solubility behaviors for binary systems of MRTILs with representative non-polar organic solvents (cyclohexane, n-octane) were measured at temperatures from 5 to 65 °C, showed a low miscibility between MRTILs and organic solvents and a typical lower critical solution temperature (LCST) phenomenon. The results are supposed to provide useful information for further application as “green” liquid desulfurization extractants or others potential dispersive liquid-liquid microextraction applications.

Partial deoxygenation of biomass derived pyrolysis liquids

Biomass pyrolysis liquids (also known as bio-oil), are derived from renewable lignocellulosic biomass residues by fast pyrolysis process. These second-generation oxygenated hydrocarbon resources have the potential to partially substitute for petroleum-derived feedstocks and thus enhance the economic and environmental sustainability of our natural resources. However, in contrast to petroleum fuels, biomass-derived pyrolysis liquids contain a large amount of oxygen, usually 40-50% wt% (wet basis). This undesirable high oxygen content in pyrolysis liquids is considered as the primary reason for its high polarity, high acidity, lower stability, lower energy density and very low miscibility with conventional crude refining feedstocks. There are two major pathways for upgrading the pyrolysis liquids. While hydrodeoxygenation route is one of the most explored options, it requires production and supply of large amounts of expensive hydrogen at high pressures, mandating large and centralized upgrading plants, and thus large capital investment. In this paper, we discuss an alternative method of pyrolysis liquid upgrading, using cheap and affordable hydrogen donor additives and catalysts to promote partial deoxygenation at near atmospheric pressure. This approach is preferably to be used as a pre-treatment and stabilizing method for pyrolysis liquids in the close vicinity of remote biomass pyrolysis plants. The pre-treated oil, then can be shipped for further hydrocracking process in a centralized co-processing facility. Preliminary results from the initial proof of concept experiments involving a 200 g/h gas-phase continuous fast catalytic cracking system with continuous coke removal to enhance deoxygenation performance are presented. These results indicate positive impact of catalyst bed on quality and yield of the upgraded bio-oil product in terms of pH, viscosity, degree of deoxygenation, oil yield and concentration of hydrogen in the off gases.

Utilisation of recycled thermoplastics sourced from rejected-unused disposable diapers as polymer blends

The blending of two or more thermoplastics could produce polymer blends, which are preferable compared to developing a new type of plastic. This paper presents the study on the utilisation of recycled thermoplastic polymers which are recovered from rejected-unused disposable diapers. The aim of study is to characterise the effect of manufacturing temperature on the tensile and morphological properties of recycled plastic blend. Besides that, the polymer blend sourced from virgin materials was also prepared to compare the properties. The recycled and virgin materials were blended by using an internal mixer with fixed parameters. Later, the blended materials were crushed and moulded using hot compression moulding with temperature variations of 180 °C, 190 °C and 200 °C. The tensile tests were conducted in accordance with the ASTM D638 using a universal testing machine, followed by scanning electron morphological analysis. The results showed that as temperature increases, tensile strength decreases and tensile strain increases for both recycle and virgin blends. Tensile strength and strain for the recycled blend were also lower than the virgin blend at all temperatures, due to low miscibility in the recycled blend compared to the virgin one. The low miscibility caused more macrophase separation and resulted in poor adhesion between the polymer components. Also, the increase of temperature caused the tensile modulus to be reduced for the recycled blend. Meanwhile for the virgin blend, the modulus reduced at 190 °C but increased suddenly at temperature of 200 °C.

Phase equilibrium measurements and thermodynamic modelling of {water + phenol + [Hmim][NTf 2 ]} ionic liquid system at several temperatures

Abstract Experimental liquid–liquid equilibrium (LLE) data of the ternary chemical system of {water + phenol + 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Hmim][NTf2], ionic liquid (IL)} were obtained under different temperatures of (293.2, 298.2 and 308.2) K and ambient pressure of 81.5 kPa. The cloud point method, based on refractive index measurement, was employed. The results indicate that the solubility of phenol in the IL is considerably higher than in water, especially at high level concentrations. Meanwhile, due to very low miscibility of the IL in water and strong hydrogen bonding between the IL and phenol, high level solute distribution coefficient and separation factor were obtained within (5.586–25.001) and (105.05–1476.23), respectively. The reliability of the tie-line data was examined with Hand and Bachman equations. Further, the well-known NRTL and UNIQUAC models were used to correlate the experimental data. For this aim, the thermodynamic properties of the IL were determined by the Density Functional Theory (DFT) calculations, carried out at the M05-2X/6-311++G∗∗ level of theory. Low levels of root mean square deviations indicate the capability of the both models to correlate data with a preference for NRTL model.

Antibiofilm activity of nanoemulsions of Cymbopogon flexuosus against rapidly growing mycobacteria

Rapidly growing mycobacteria (RGM) are opportunistic microorganisms that can cause both local and disseminated infections. When in biofilm, these pathogens become highly resistant to antimicrobials used in clinical practice. Composed abundantly of polymeric substances, biofilms delay the diffusion of antimicrobials, preventing the drug from penetrating the deeper layers and having an effective action. Therefore, the search for new and alternative therapeutic options has become of fundamental importance. Natural products fall into these options, especially essential oils. However, these oils present problems, such as low miscibility in water (which decreases its bioavailability) and degradation by light and temperature. Thus, the objective of this work was to explore the action of free essential oil and nanoemulsions of Cymbopogon flexuosus on strains of RGM, in planktonic and sessile forms. In this work, standard strains of Mycobacterium fortuitum (ATCC 6841), Mycobacterium massiliense (ATCC 48898) and Mycobacterium abscessus (ATCC 19977) were used. The susceptibility of the microorganisms in planktonic form was obtained by conventional microdilution techniques and by cell viability curve. The analysis of the antibiofilm activity was performed by a semi-quantitative macrotechnique. The nanoemulsion exhibited significant antimicrobial activity, with minimum inhibitory concentration values lower than those presented by the free essential oil, against strains in the planktonic state. However, both were efficient in destroying the already formed biofilm, whereas only the free oil inhibited the formation of mycobacterial biofilm. This study demonstrated the therapeutic potential of C. flexuosus essential oil, especially in its nanostructured form, which can be demonstrated against infections caused by rapidly growing mycobacteria.

(Invited) Challenges to Implement Resistive Memory Cells in the CMOS BEOL

The paper reviews the manifold challenges of implementing resistive switching memory cell into back-end-of-line of CMOS. The challenges include not only the choice of materials of a stand-alone CBRAM cell, but also the way the cell is embedded in BEOL. In case of the inert electrode, a composite electrode is required with appropriate glue layer, heat transport layer, and inert metal proper with sufficient thermal conductivity, low miscibility with, and low surface diffusivity of the active metal atoms. The active metal is required to allow for a copious redox reaction but simultaneously to prevent reactions with the dielectric. A dielectric is preferred with a moderate level of defects which may be controlled by deposition processes. Finally, the choice of the materials is gated by the material and process compatibility with BEOL, as well as by the dynamics of resistive switching operations, including Joules heat during SET and RESET operations.

Reformulation of Gasoline To Replace Aromatics by Biomass-Derived Alkyl Levulinates

In the search for a “green gasoline”, a new reformulation strategy, having no or reduced amount of aromatics, is proposed. Biomass-derived alkyl levulinates (ALs) are prospected as oxygenated additives as well as blending components to circumvent the use of aromatics and methyl tertiary butyl ether (MTBE) in gasoline. By utilizing molecular dynamics (MD) simulations, the thermophysical and dynamical behavior of gasoline blends with four alkyl levulinates, viz. methyl levulinate (ML), ethyl levulinate (EL), propyl levulinate (PL), and butyl levulinate (BL), was scrutinized and compared with those of MTBE–gasoline mixtures. It is shown that, at 300 K and 1 atm, ALs in conventional gasoline can be used for reformulation with amounts up to 18 mol % while maintaining the density, viscosity, and compressibility within the recommended limits. However, this amount can be further increased to 35 mol % by modification of aromatic content. Among the studied oxygenates, BL was observed to have the lowest miscibility in water as compared to other ALs studied. The methodology may be applied to study similar biomass-derived oxygenates for their applicability as a fuel additive or blend.

A renewable lipid source for biolubricant feedstock oil from housefly (Musca domestica) larva

Biolubricants are gaining increased attention because of their low toxicity, high biodegradability, and miscibility with additives. These features render them ideal for lubrication, especially in total-loss processes. In this study, housefly (Musca domestica) larvae were used as low-cost, non-food biolubricant feedstock. A larval lipid with high acid value (AV) of 63 mg KOH/g was used as feedstock for esterification to produce 2-ethylhexyl fatty acid esters (2-EH esters). We developed a method of producing high-purity 2-EH esters in which housefly larva free fatty acids (HLFFAs) were derived from larvae fed with kitchen waste. HLFFAs were esterified with 2-ethyl-1-hexanol (2-EHOH) catalysed with benzenesulfonic acid (BSA). The optimum esterification conditions were as follows: catalyst loading, 0.5 wt%; 2-EHOH-to-HLFFAs molar ratio, 3:1; temperature, 130 °C; and reaction time, 2 h. These conditions yielded 98.6% esterification rate. Excess 2-EHOH was removed by molecular distillation at 80 Pa and 110 °C. Residual fatty acids were neutralised by alkali refining. The chemical and physical properties, including the tribological properties, of the produced high-purity 2-EH esters (>99.7%) were also tested.

Structure–property relationships of Thai silk–microcrystalline cellulose biocomposite materials fabricated from ionic liquid

Biomaterials made from natural proteins and polysaccharides have become increasingly popular in the biomedical field due to their good biocompatibility and tunable biodegradability. However, the low miscibility of polysaccharides with proteins presents challenges in the creation of protein-polysaccharide composite materials. In this study, neat 1-allyl-3-methylimidazolium chloride (AMIMCl) ionic liquid was used to regenerate Thailand gold Bombyx mori silk and microcrystalline cellulose blended films. This solvent was found to not only effectively dissolve both natural polymers, but also preserve the structure and integrity of the polymers. A single glass transition temperature for each blend was found in DSC curves, indicating good miscibility between the Thai silk and cellulose molecules. The structural composition as well as the morphology and thermal stability of blend films were then determined using FTIR, SEM and TGA. It was found that by varying the ratio of Thai silk to cellulose, the thermal and physical properties of the material could be tuned. Blended films tended to be more thermally stable which could be due to the presence of hydrophobic–hydrophobic or electrostatic interactions between the silk and cellulose. These studies offered a new pathway to understand the tunable properties of protein-polysaccharide composite biomaterials with controllable physical and biological properties.

(Invited) Contactless Photo-Electrochemistry of Dye-Sensitized TiO2 Nanoparticles Floating at Electrified Water-Oil Interfaces

Certain soft interfaces formed between aqueous and organic electrolyte solutions of low miscibility (e.g., trifluorotoluene) are electrochemically active in the sense that it is possible to precisely control the Galvani potential difference between the two adjacent liquids (i.e., to “polarise” or electrify the interface), and thus drive charge transfer reactions. In comparison to solid electrode-electrolyte interfaces, where typically only electron transfer may be probed, charge transfer reactions at soft interfaces may include simple ion transfer, assisted ion transfer, heterogeneous electron transfer, or photoinduced heterogeneous electron transfer (PET), see Figure 1 [1]. PET represents a novel method of potentially harnessing solar energy at electrified soft interfaces. By exploiting (i) energy trapped from visible light by a photoactive interfacial film (e.g., a porphyrin dye or a dye-sensitized TiO2 nanoparticle) and (ii) the electrochemical driving force provided by electrification of the soft interface, a solar fuel such as H2 or H2O2 may be evolved by PET across the soft interface using a weak electron donor in the oil phase, e.g., ferrocene. Crucially, all photo-electrochemical techniques applied at traditional solid electrode-electrolyte interfaces (voltammetry, impedance, photo-current transients, etc.) are applicable at polarised soft interfaces [2-3]. The photochemical properties of TiO2 nanoparticles have been extensively studied in homogeneous phases for a variety of processes including water splitting and the photocatalytic destruction of pollutants. Mesoporous films based on TiO2 nanoparticles have also been studied as photoactive materials. In this regard, dye sensitization of wide bandgap semiconductors has been extensively studied in the field of photovoltaics. Despite the overwhelming literature on the photochemistry of TiO2 colloids, little is yet known about the properties of these particles floating as “photo-electrodes” at molecular water-oil interfaces, with only a small number of published articles on the topic [4-7]. In this presentation the photo-electrochemistry of TiO2 nanoparticles floating at electrified water-oil interfaces under blue LED illumination will be detailed. The experimental techniques employed (cyclic voltammetry, photocurrent transient data) will be able to provide valuable fundamental information on the rates of charge transfer between redox species in solution and the semiconductors floating at the interface. The studies will explore new possibilities for contactless photo-electrochemistry of nanoparticles in the presence of a static electric field, with potential applications in solar energy conversion to solar fuels and storage (ECS) and photocatalytic pollutant degradation.

Abnormal strong burn-in degradation of highly efficient polymer solar cells caused by spinodal donor-acceptor demixing

The performance of organic solar cells is determined by the delicate, meticulously optimized bulk-heterojunction microstructure, which consists of finely mixed and relatively separated donor/acceptor regions. Here we demonstrate an abnormal strong burn-in degradation in highly efficient polymer solar cells caused by spinodal demixing of the donor and acceptor phases, which dramatically reduces charge generation and can be attributed to the inherently low miscibility of both materials. Even though the microstructure can be kinetically tuned for achieving high-performance, the inherently low miscibility of donor and acceptor leads to spontaneous phase separation in the solid state, even at room temperature and in the dark. A theoretical calculation of the molecular parameters and construction of the spinodal phase diagrams highlight molecular incompatibilities between the donor and acceptor as a dominant mechanism for burn-in degradation, which is to date the major short-time loss reducing the performance and stability of organic solar cells.

Agglomeration of celecoxib by quasi-emulsion solvent diffusion method without stabilizer: effect of good solvent

Aim: The aim of the present research is to investigate the feasibility of agglomeration of crystals by the quasi-emulsion solvent diffusion method without using a stabilizer.Method: Two solvent systems comprising a solvent and an antisolvent (water) were used to prepare celecoxib agglomerates. To this end, seven solvents including propanol, methyl acetate, methyl ethyl ketone, butanol, ethyl acetate, isopropyl acetate, and pentanol were examined. The agglomerates were evaluated by micromeritic properties (e.g., size, density, flowability), yield, drug physical state, friability, and dissolution behavior.Results: In the present study the clear trend was observed experimentally in the agglomerate properties as a function of physical properties of the solvent such as miscibility with water. Solvents with high water miscibility (25% v/v) resulted in sticky and hollow particles, while solvents with low water miscibility (3%v/v) led to the formation of agglomerates with low strength. However, the agglomerates made from the solvents with intermediate water miscibility (10% v/v), may reflect a greater integrity of the agglomerates regarding yield and strength.Conclusion: Results of this study offer a useful starting point for a conceptual framework to guide the selection of solvent systems for the quasi-emulsion solvent diffusion method without using a stabilizer.

Designing an antibacterial acrylic resin using the cosolvent method -Effect of ethanol on the optical and mechanical properties of a cold-cure acrylic resin.

Antimicrobial cetylpyridinium chloride (CPC) has low miscibility with acrylic resin monomer but can be homogeneously mixed using ethanol as a cosolvent. This study investigated the effects of ethanol addition on the properties of a cold-cure acrylic resin. Ethanol was an excellent cosolvent for CPC and methyl methacrylate monomer (MMA), but the cured resin exhibited a strong change in coloration to yellow (ΔE*ab>8) and a drastically reduced bending strength (from 97 to 25 MPa) and elastic modulus (from 2.7 to 0.6 GPa) when equal volumes of ethanol and monomer were used together, possibly due to the solvation and deactivation of radicals by ethanol. However, these unfavorable effects diminished when the ethanol/MMA ratio was reduced to 0.25, and became smaller when each specimen was depressurized and excess ethanol was removed. Thus, it may be possible to develop a molecularly uniform antibacterial acrylic resin with acceptable color and strength using this simple technique.

Microstructure and nanomechanical properties of pulsed excimer laser deposited DLC:Ag films: Enhanced nanotribological response

Diamond-like carbon:silver (DLC:Ag) thin films, with metal contents as high as 16.8at.%, have been deposited on silicon substrates using pulsed excimer laser deposition; the produced DLC:Ag films sustain a substantial sp3 content (36%) in the DLC matrix even for the highest Ag content (~16.8at.%), in contrast to previous reports. The morphological, topographical, crystallographic, compositional and mechanical/tribological characteristics of the films have been studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and nanoindentation/nanoscratch tests, respectively. The low miscibility between carbon and silver leads to a nanocomposite material that exhibits a reduced elastic modulus and hardness that scale inversely with the silver content. The mechanical capacity reduction is attributed to the incorporation of the soft/compliant silver phase and the subsequent graphitization of the amorphous carbon matrix, as quantified through XPS. This mechanical softening response, however, is coupled with an increased ductility and an enhanced tribomechanical response (70% increase in the critical load to film failure), making this class of DLC-metal nanocomposites of great interest for protective coatings and other functional applications.

Design and Optimization of Carbon Foam Electrode for Local Confinement of Bromine in Non-Flowing Single-Chamber Zinc Bromine Batteries

Zinc Bromine redox flow batteries are well studied, quite inexpensive, and have reasonably high power and energy densities. However, there has been limited commercial implementation of bromine bearing systems in general, and the Zn-Br2 systems in particular, due to the following premises: i) Br2(l), generated at the cathode during charging, can diffuse through the electrolyte and react with Zn deposited at the anode (crossover), leading to self-discharge; ii) Repeated electroplating and dissolution of zinc leads to dendrite formation, which can form a conductive bridge between the electrodes (shorting), and iii) Br2(l) has low miscibility in aqueous solutions (~2.8 vol%) and tends to stratify, resulting in non-uniform concentration distributions. Standard Zn-Br2 flow-cell designs alleviate these limitations with bromine-complexing agents to improve Br2(l) solubility, separation membranes to prevent crossover and shorting, and flowing electrolyte to remove bromine and to minimize dendrite formation. In the membrane-free, non-flowing single-chamber zinc-bromine (SC-Zn-Br2) battery design zinc dendrites are allowed to form freely and Br2(l) is allowed to stratify; expensive membranes, complexing agents, and pumps are eliminated; and yet overall energy efficiency is improved and cost is lowered. This is achieved by using a highly-porous carbon foam electrode (CFE) for local containment of Br2 generated during cycling, thus preventing crossover. Zinc dendrites are allowed to grow, but react with the highly corrosive Br2(l) on the surface of the CFE and dissolve back into the electrolyte as Zn2+ and Br-ions. This prevents shorting. Here, we discuss the design, composition, and fabrication of the CFE, and its effects on the performance of SC-Zn-Br2 battery. In particular, we demonstrate the optimization of CFE porosity through processing parameters to maximize the coulombic and energy efficiencies of the cell. We also introduce a color tracking and feedback monitoring scheme to actively control the active species (deep red Br2(l), yellow Br2(aq), and colorless ZnBr2 electrolyte) transport and prevent self-discharge. Finally, we demonstrate the effect of prolonged exposure to Br2(l) after multiple cycles on various CFE compositions using XPS analysis, and the potential degradation mechanisms. We show coulombic and energy efficiencies of 95% and 75%, respectively, for over 1000 cycles for SC-Zn-Br2 cells, with improvements possible with further optimization of the CFE.

Exploiting Zinc Dendrite Formation and Bromine Transport Properties to Build a Safer, More Reliable Zn-Br2 Battery

In order to address inefficiencies that exist in our electrical grid, low cost grid scale electrochemical energy storage (EES) systems, such as zinc bromine batteries, are being researched extensively. Zinc bromine batteries, however, have issues at both the anode and the cathode that affect the reliability of the cell as well as present hazardous conditions of operation. At the anode, current density localization from the inhomogeneity of the zinc surface leads to the formation of dendritic structures. These dendritic structures can grow to the point of touching the other electrode, causing shorting of the cell. At the cathode, bromine contamination into the electrolyte can lead to issues of bromine corrosion at the anode as well as safety concerns of corrosive, vapor phase bromine escaping from the system.Standard Zn-Br2 flow-cell designs alleviate these limitations with bromine-complexing agents to improve Br2(l) solubility, separation membranes to prevent crossover and shorting, and flowing electrolyte to remove bromine and to minimize dendrite formation. These approaches are implemented at the expense of cell resistance, performance efficiency, system size, and especially capital costs. However, if constructed properly, the cell design could be used to address the issues at the anode and cathode without the added cost and complexity of complexing agents, membranes, or flow systems. Here, we show a simple and scalable, low-cost, membrane-free, non-flowing single-chamber zinc-bromine (SC-Zn-Br2) secondary battery design that utilizes the physical properties of liquid bromine and a highly-porous carbon foam electrode, and also allows zinc dendrites to form freely. We demonstrate the local containment of Br2 in the carbon foam electrode, and discuss a color tracking and feedback monitoring scheme to actively control the reactive species transport and improve reliability.To take advantage of the density and low miscibility of Br2, an anodic carbon current collector is placed on top of the cell. During charging, metallic Zn gets plated onto the carbon cloth electrode, while Br2(l) is generated at a carbon foam cathode. If dendrites form and creep towards this carbon foam electrode (CFE), Zn(s) will react with Br2(l) on the surface of the foam and dissolve back into the electrolyte as Zn2+ and Br- ions. This spontaneous process can prevent short circuiting, as the Zn(s) + Br2(l) reaction occurs faster than zinc deposition at low charging currents. Thus, the Br2(l) loosely held on the CFE surface acts as a natural protection from shorting, and can be exploited for ‘self-maintenance’, removing the need for separation membranes or protective coatings.We also take advantage of the distinct colors of the ZnBr2(aq) electrolyte, Br2(l), and dissolved Br2(aq): clear, red, and yellow, respectively. By calibrating the solution color with Br2(l,aq) concentration, we can track the generation, consumption, and transport of bromine in real time to improve battery performance and prevent unwanted processes (i.e., crossover). In addition, we can use this color tracking technique to prevent bromine escape from the system and thus alleivate safety concerns of operating with voliltite bromine. To optimize performance, a feedback loop is written into the cycling control algorithm to stop the charge step at this point. This optical visualization, tracking, and in operando feedback technique has never been used for any bromine-based electrochemical cells, to the best of our knowledge.

SOLUBILITY AND MISCIBILITY OF REFRIGERANTS R407C AND R410A WITH SYNTHETIC COMPRESSOR OILS

In this paper, solubility and low temperature miscibility of refrigerants R407C and R410A in four different commercial Polyolester (POE) lubricants, produced by the same company but with different ISO standard viscosity grade, are measured with the aim to evaluate the possible correlation of solubility and miscibility with standard viscosity of the lubricant. Vapor pressure (solubility) is measured using calibrated, constant volume cells at oil mass fractions 30, 50, 70, 80, and 90% over a temperature range from -20 to 100 °C, and pressures up to 5 MPa. The measurements of low temperature miscibility limit (lower critical solution temperature LCST) were made using high-pressure sapphire cell. LCST was directly obtained by visual observation of a «milky haze» followed by a phase separation. Miscibility data were obtained at oil mass fractions from 5 to 50% over a temperature range from -60 to 0 °C. A set of simple equations was derived to describe the experimental results. Analysis of the obtained results showed that the solubility of refrigerant/lubricant mixtures depends weakly on the viscosity grade of the oil. At the same time, the miscibility gap (LCST) differ much bigger for various refrigerant/lubricant mixtures. The lower viscosity grade of the oil, the lower LCST of the refrigerant/lubricant mixture. LCSTs for the mixtures of R407C with the lubricants with the viscosity grades 32 and 220 differ by 30-45 °С.

Hydrogen-Bonded Liquid Crystal Nanocomposites.

Nanoparticle-liquid crystal (NP-LC) composites based on hydrogen bonding were explored using a model system. The ligand shells of 3 nm diameter zirconium dioxide nanoparticles (ZrO2 NPs) were varied to control their interaction with 4-n-hexylbenzoic acid (6BA). The miscibility and effect of the NPs on the nematic order as a function of particle concentration was characterized by polarized optical microscopy (POM), fluorescence microscopy and (2)H NMR spectroscopy. Nonfunctionalized ZrO2 NPs have the lowest miscibility and strongest effect on the LC matrix due to irreversible binding of 6BA to the NPs via a strong zirconium carboxylate bond. The ZrO2 NPs were functionalized with 6-phosphonohexanoic acid (6PHA) or 4-(6-phosphonohexyloxy)benzoic acid (6BPHA) which selectively bind to the ZrO2 NP surface via the phosphonic acid groups. The miscibility was increased by controlling the concentration of the pendant CO2H groups by adding hexylphosphonic acid (HPA) to act as a spacer group. Fluorescence microscopy of lanthanide doped ZrO2 NPs showed no aggregates in the nematic phase below the NP concentration where aggregates are observed in the isotropic phase. The functionalized NPs preferably concentrate into LC defects and any remaining isotropic liquid but are still present throughout the nematic liquid at a lower concentration.

Photoprecursor Approach Enables Preparation of Well-Performing Bulk-Heterojunction Layers Comprising a Highly Aggregating Molecular Semiconductor.

Active-layer morphology critically affects the performance of organic photovoltaic cells, and thus its optimization is a key toward the achievement of high-efficiency devices. However, the optimization of active-layer morphology is sometimes challenging because of the intrinsic properties of materials such as strong self-aggregating nature or low miscibility. This study postulates that the "photoprecursor approach" can serve as an effective means to prepare well-performing bulk-heterojunction (BHJ) layers containing highly aggregating molecular semiconductors. In the photoprecursor approach, a photoreactive precursor compound is solution-deposited and then converted in situ to a semiconducting material. This study employs 2,6-di(2-thienyl)anthracene (DTA) and [6,6]-phenyl-C71-butyric acid methyl ester as p- and n-type materials, respectively, in which DTA is generated by the photoprecursor approach from the corresponding α-diketone-type derivative DTADK. When only chloroform is used as a cast solvent, the photovoltaic performance of the resulting BHJ films is severely limited because of unfavorable film morphology. The addition of a high-boiling-point cosolvent, o-dichlorobenzene (o-DCB), to the cast solution leads to significant improvement such that the resulting active layers afford up to approximately 5 times higher power conversion efficiencies. The film structure is investigated by two-dimensional grazing-incident wide-angle X-ray diffraction, atomic force microscopy, and fluorescence microspectroscopy to demonstrate that the use of o-DCB leads to improvement in film crystallinity and increase in charge-carrier generation efficiency. The change in film structure is assumed to originate from dynamic molecular motion enabled by the existence of solvent during the in situ photoreaction. The unique features of the photoprecursor approach will be beneficial in extending the material and processing scopes for the development of organic thin-film devices.