Low Additive Concentrations Research Articles

Retention in high-performance liquid chromatography at −196 °C

Recently, we have developed ultralow-temperature high-performance liquid chromatography (HPLC) at −196°C using liquid nitrogen-based mobile phases. In this study, a retention model for ultralow-temperature HPLC, in which adsorption exchange and “pseudo partition” modes are combined, is proposed to describe the effect of the mobile phase composition on the retention of analytes. The experimental results agreed well with the equation of the proposed model. It was revealed that, in the low and high additive concentration regions, adsorption exchange and pseudo partition retention, respectively, dominate the analyte retention. The difference in the retention behavior between bare-silica and octadecylsilyl-modified silica (ODS) columns was also studied. Retention of alkanes in the ODS column was greater than that in the bare-silica one. Addition of both ethane and ethylene to the mobile phase in the ODS column afforded the elution of propylene, which was not eluted with the bare-silica column at −196°C.

Anisotropic Overgrowth of Palladium on Gold Nanorods in the Presence of Salicylic Acid Family Additives

We explored the use of salicylic acid (SA) and its derivatives 5-formylsalicylic acid (FSA) and 5-sulfosalicylic acid (SSA) as organic additives to cetyltrimethylammonium bromide (CTAB) in synthesizing gold nanorods (AuNRs) followed by palladium (Pd) capping at the ends of AuNRs. In the AuNR synthesis step, SA family additives in the presence of low concentration of CTAB (50 mM) serve as both the prereducing agent and the cofactor in nanorod growth. At an optimum additive/CTAB ratio (0.1–0.2), AuNRs grow to the longest length. At low additive concentrations, the gold seeds do not grow. At high concentrations, the longitudinal growth of AuNRs is disrupted because the excessive additive disturbs the ligand structure, leading to more isotropic growth. In the Pd overgrowth step, Pd starts to grow from both ends for AuNRs synthesized at optimum additive/CTAB ratios. Feeding more Pd grows the particles into a core–shell structure, possibly because there lacks a tight ligand layer on Pd that favors the longitudinal growth. For AuNRs synthesized at high additive/CTAB ratios, Pd growth loses preference, showing randomized Pd nucleation on AuNR surface. Finally, the palladium-end-capped–AuNRs’ catalytic activity was tested using the resazurin reduction reaction. This study shows a new way to produce controllable deposition of Pd on AuNRs.

Synergistic Blend Based on Glycol Ethers as Antiknock Additives to Motor Fuels

The expediency and effectiveness of use of composite compositions for raising the octane number of straight-run gasoline fraction are proved. It is shown that cellosolves and carbitols tested as oxygenate additives improve the antiknock properties of narrow gasoline fraction selectively, depending on their fractional composition, and significantly raise the octane number of a straightrun gasoline fraction. A synergistic blend of glycol ethers at determined optimal ratios can be used to get high-octane gasoline with an octane number not lower than 93, which is of interest as a highoctane component for compounding motor fuel. The low composite additive concentration (1 vol. %) in gasoline hardly has any influence on change in the basic performance properties of motor fuel and primarily on the fractional composition. Use of such an additive is preferred to existing antiknock additives for solving important economic, technological, and ecological aspects of the use of motor fuels in modern automotive engines

Engineering of Piroxicam Agglomerates by Additives Using Wet Agglomeration Technique

Background: Wet agglomeration is a method wherein the crystals of dispersion are held together in aggregates by small amount of a liquid acting as an intercrystal binder. In present study, in order to study the possible modification of agglomerate structure, low concentrations of additives (0.1-1%) were added to binder liquid. Methods: Piroxicam agglomerates were produced by wet agglomeration method by three solvent systems including a good solvent (dimethylformamide or acetone), antisolvent (water) and a binder liquid (ethylacetate or isopropylacetate). Span 80, talc, ethylcellulose and Eudragit RS in different concentrations were used as additives. The agglomerates were evaluated for production yield of agglomerates, size, friability and drug release properties. Results: The results showed that formation of agglomerates was possible in presence of span and talc. However, no agglomerates could be obtained with polymers tested (ethylcellulose and Eudragit RS). Talc increased agglomerate size, whereas the obtained agglomerates were more susceptible to breakup. However, using span as opposed to talc resulted in agglomerates with higher strength but smaller particle size. The dissolution tests showed that both additives adversely affected the dissolution rate of piroxicam from the agglomerates. Conclusion: Result of this study suggested that additives even in small amounts played a major role in agglomerate properties.

Effect of additive concentration during copper deposition using EnFACE electrolyte

Copper deposition from solutions using high concentration of acid, metal ions and polyethylene glycol (PEG), and bis-(3-sulphopropyl) disulphide (SPS) and chloride ions (Cl–) is well known. A recent maskless micropatterning technology, which has the potential to replace the traditional photolithographic process, called EnFACE, proposed using an acid-free, low metal ion solution which is in direct contrast to those used in standard plating technology. In this work copper has been deposited using both standard electroplating solutions and those used in the EnFACE process. In the standard electrolyte 0.63 M CuSO4 and 2.04 M H2SO4 has been used, along with Gleam additives supplied by Dow Chemicals. For the Enface electrolyte, copper deposition has been carried out without any acid, and with different concentrations of additives between 17% - 200% of those recommended by suppliers. 25 µm of metal has been plated on stainless steel coupons as suggested by ASTM, peeled off and subjected to ductility and resistance measurements. Scanning electron microscopy and electron back scatter diffraction have been carried out to determine the deposit morphology. It was found that copper deposits obtained from acid-free solutions containing low concentration of metal ion and additives produced copper deposits with properties which are comparable to those obtained from standard electrolytes. The optimum additive concentration for the EnFACE electrolyte was 50% of the supplier recommended value.

Confining Liquids on Silicon Surfaces to Lubricate MEMS

Liquid lubrication may provide a solution to the problem of high friction and wear in micro-electro-mechanical systems. Although the effectiveness of this approach has been demonstrated in laboratory-based friction tests, practical constraints prevent it from being applied in commercial devices. The main problem is how to position the lubricant on a silicon surface in order to limit spreading and evaporation. This paper describes two techniques to address this issue. First, low concentrations of additives are used to promote autophobic behaviour. Tests’ results show that certain concentrations of both multiply alkylated cyclopentane and amine additives are effective in halting the spread of hexadecane on silicon, and, in the latter case, cause the hexadecane drop to subsequently retract. The second approach involves applying a micro-contact printing technique previously used on gold surfaces. Here, silicon surfaces are coated with octadecyltrichlorosilane mono-layers that are then selectively removed, using oxygen plasma, to leave regions of contrasting surface energy. Results from spin tests show that surfaces treated in this way can anchor 1 μl drops of hexadecane and water when forces of up to 22 and 230 μN, respectively, are applied.

Modifying polyester surfaces with incompatible polymer additives

Surface modification of amorphous PET in incompatible blends is demonstrated using fluorocarbon end-functional polystyrenes. Contact angles with water and decane were consistent with high levels of surface fluorocarbon, even for spin-cast films with no further processing required. Hydrophobicity and lipophobicity were further increased by annealing above the glass transition temperature. High resolution depth profiling using complementary ion beam analysis and specular neutron reflectometry has enabled accurate characterisation of the composition profile of the additive including the minimum in additive concentration found just below the surface enriched layer. This analysis quantified the very low compatibility between the modifying polymer and the amorphous PET and was consistent with the highly segregated nature of the adsorbing species and its sharp interface with the subphase. For these incompatible polymer blends, surfaces enriched with the surface active polymer could coexist at equilibrium with extremely low (∼0.4%) bulk loadings of the additive. This suggests that for thicker films at even lower additive concentrations than the minimum 1% that we studied, it may be possible to achieve efficient surface modification. However, at this concentration, the efficiency of surface modification is limited by the processing conditions. Finally we note that in higher loadings of surface active additive there is clear evidence for lateral phase separation into patterned domains of differing composition. The enhancement in surface properties is due to local reorganisation rather than bulk redistribution of the components within the film, as the composition versus depth distributions of the polymer blend components was observed to be relatively unaffected by annealing.

Absorption of carbon dioxide into sterically hindered amines: Kinetics analysis and the influence of promoters

AbstractThe sterically hindered amines 2‐amino‐2‐methyl‐1‐propanol (AMP) and 2‐piperidineethanol (PE) are promising candidate absorbents for CO2 capture. Although reaction kinetics of the CO2‐AMP system is extensively studied, there exists some deviations in the reported kinetic parameters and there is some uncertainty about the reaction mechanism. Contrarily, kinetic data on the CO2‐PE reaction system is scarce. In this work, these reaction systems were revisited to set right the discrepancy of previous works and facilitate and deepen fundamental understanding of these reaction systems. Kinetic data were obtained experimentally at 298, 303, and 308 K by using a stirred‐cell reactor. The molarities of AMP and PE in the aqueous solutions were varied from 1 to 3 M and 0.05 to 0.25 M. Second order rate constants for the reactions with AMP and PE were equal to 809 and 899 m3/(kmol s) at 303 K. The increase in temperature and amine concentration caused the expected increase in the values of the observed pseudo‐first order reaction rate constants. Finally, it was found that the investigated reactions were accelerated by the addition of two sterically hindered secondary amines comprising an alkyl group, viz., N‐methyl‐ and N‐ethyl‐monoethanolamine, even at low additive concentrations (0.05–0.1 M).

Crystallographic orientations and twinning of electrodeposited nickel—a study with complementary characterization methods

A series of nickel layers was electrodeposited at different current densities from a Watts type electrolyte containing the additive 2-butyne-1,4-diol in various concentrations. The internal structure of the nickel electrodeposits was systematically investigated applying complementary microscopic and diffraction based characterization methods involving both surface and cross section investigations with different resolution and statistics. The complementary information gathered from combining the various techniques of microstructure characterization, in particular, supported the investigation of twins and the preferred crystallographic orientations of grains in the electrodeposits. Additive-free deposition results in relatively large columnar grains with numerous growth twins of nanoscale dimensions. The presence of the additive in the electrolyte yields considerable grain refinement already at low additive concentration, but the preferred crystallographic orientation of grains changes gradually with increasing additive concentration and twins with nanoscale dimensions are detected also in these samples.

High Polymer/Fullerene Ratio Realized in Efficient Polymer Solar Cells by Tailoring of the Polymer Side‐Chains

The introduction of “double aromatic side-chains” to the existing polymer backbone is an effective approach to obtain high performance polymer solar cells with low fullerene and additive concentrations, leading to improved absorbance for thin film and more environment-friendly processing. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Tribological behaviors of some novel dimercaptothiadiazole derivatives containing hydroxyl as multifunctional lubricant additives in biodegradable lithium grease

Purpose – In order to meet the requests of exploring environmental-friendly and multifunctional lubricant additives, some novel dimercaptothiadiazole derivatives containing hydroxyl are prepared and used as antiwear (AW) and extreme-pressure (EP) additives in biodegradable lithium grease. The paper aims to discuss these issues. Design/methodology/approach – The tribological performances of the grease samples containing these derivatives are evaluated by using a four-ball tester. X-ray absorption near edge structure (XANES) spectroscopy is used to analyze the chemistry of tribofilms under AW/EP regime, and thermal films are also considered for comparison. Findings – The tribological tests show that these derivatives are all effective in reducing wear, especially at lower additive concentrations, but they are basically failed in reducing friction. They are also helpful in improving the EP characteristic of the base grease. The thermal films generated by these derivatives are composed of adsorbed organic sulfide and ferrous sulfate, though for short-chain derivatives, organic sulfide is the only component at 5.0 wt.%. Ferrous sulfide is the main component of the tribofilms formed by these derivatives at various additive concentrations. But for short-chain derivatives, these tribofilms consist of ferrous sulfide and ferrous disulfide at 5.0 wt.%, and the appearance of disulfide suggests that the interfacial temperature between the upper ball and three lower balls under these conditions is considerably low. The EP films generated by short-chain derivatives are all composed of organic sulfide and ferrous sulfide, while for long-chain derivatives, ferrous sulfide is the main component. Originality/value – These low-toxic and oil-soluble dimercaptothiadiazole derivatives are effective in improving the tribological characteristic of the biodegradable lithium grease, and these heterocyclic derivatives may be good substitutes for some harmful traditional additives.

Permeability thickening fluids for improved secondary oil recovery

Waterflooding is limited by zones of spatially varying permeability which cause channelling. More crude oil could be produced by a more uniform water/brine front across layers of different permeabilities. Novel non-polymeric water additives (CTAB+NaSal in brine) are used to selectively slow down flow of water in high permeability zones. In order to isolate rheological effects from rock fluid interactions, we have carried out experiments on inert glass cores. A monotonic increase of viscosity as function of permeability is observed for the range 45–2200 mD (covering typical reservoir ranges). This effect can be referred to as permeability thickening. This result opens up the possibility of tunable fluid engineering for any given permeability distribution of reservoirs. Low additive concentrations (<1000 ppm) yield in-situ permeability dependent viscosities up to 40 times that of brine. Flow in high permeability zones is retarded more than in low permeability ones which results in typically 15–36% extra sweep area based on single phase experiments.

Nanostructured composites based on carbon nanotubes and epoxy resin for use as radar absorbing materials

Nanostructured polymer composites have opened up new perspectives for multifunctional materials. In particular, carbon nanotubes (CNTs) present potential applications in order to improve mechanical and electrical performance in composites with aerospace application. The combination of epoxy resin with multiwalled carbon nanotubes results in a new functional material with enhanced electromagnetic properties. The objective of this work was the processing of radar absorbing materials based on formulations containing different quantities of carbon nanotubes in an epoxy resin matrix. To reach this objective the adequate concentration of CNTs in the resin matrix was determined. The processed structures were characterized by scanning electron microscopy, rheology, thermal and reflectivity in the frequency range of 8.2 to 12.4 GHz analyses. The microwave attenuation was up to 99.7%, using only 0.5% (w/w) of CNT, showing that these materials present advantages in performance associated with low additive concentrations.

Fabrication of porous Al2O3 ceramics by rapid gelation and mechanical foaming

Abstract

Effects of solvent additive on inverted structure PCPDTBT:PC71 BM bulk heterojunction organic solar cells

This work investigates the effects of the solvent additive, 1,8-octanedithiol (1,8-ODT), on solution-processed inverted bulk heterojunction (BHJ) organic solar cells based on a thin film blend of poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl]] (PCPDTBT) and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM). In this work, varying concentrations of 1,8-ODT were added into the polymer solution in order to optimise the device performance. The UV–Vis spectrometer measurements showed that adding 1,8-ODT can improve the magnitude of light absorption in the blend film, as well as inducing an ∼40 nm red shift for long wavelengths. External quantum efficiency (EQE) measurements displayed improvements at all wavelengths for 1–4 vol% 1,8-ODT concentration, when compared to the reference device. Current density–voltage (J–V) measurements confirmed this addition of photocurrent, as the short circuit current density (Jsc) increases by 23%, from 9.89 mA cm−2 for the reference to 12.14 mA cm−2 for the 1 vol% additive cell. The highest average device efficiency of 2.59% was obtained using a 1,8-ODT concentration of 3 vol%. Further increasing additive concentration caused a reduction in efficiency. Additionally, the effect of drying the additive processed films in a vacuum was investigated. Drying in a vacuum had little effect on films processed with low additive concentration. However, the vacuum drying process led to a significant efficiency enhancement for high 1,8-ODT concentrations. The efficiency of the 4 vol% 1,8-ODT devices increased by 25% as a result of drying in a vacuum. This was due to the removal of excess residual additive from the active layer.

A Conventional Surfactant Becomes CO2‐Responsive in the Presence of Switchable Water Additives

We have developed a new benign means of reversibly breaking emulsions and latexes by using "switchable water", an aqueous solution of switchable ionic strength. The conventional surfactant sodium dodecyl sulfate (SDS) is not normally stimuli-responsive when CO2 is used as the stimulus but becomes CO2 -responsive or "switchable" in the presence of a switchable water additive. In particular, changes in the air/water surface tension and oil/water interfacial tension can be triggered by addition and removal of CO2 . A switchable water additive, N,N-dimethylethanolamine (DMEA), was found to be an effective and efficient additive for the reversible reduction of interfacial tension and can lower the tension of the dodecane/water interface in the presence of SDS surfactant to ultra-low values at very low additive concentrations. Switchable water was successfully used to reversibly break an emulsion containing SDS as surfactant, and dodecane as organic liquid. Also, the addition of CO2 and switchable water can result in aggregation of polystyrene (PS) latexes; the later removal of CO2 neutralizes the DMEA and decreases the ionic strength allowing for the aggregated PS latex to be redispersed and recovered in its original state.

The condensation of steam containing low concentrations of trimethylamine

This report describes the condensation of steam, on a horizontal tube, when the steam contains a low concentration of trimethylamine. Previous tests in this programme have studied the addition of ammonia and methylamine; all of these tests were conducted at similar or identical operating conditions. The most significant difference in properties of these ammonia series additives is the magnitude of the surface tension variation that develops when their mass fractions are increased. All of the vapour additives generate Marangoni instabilities in the condensate film; the type of instability depends on the additive but at very low additive concentrations the rates of heat transfer through the film will be higher than those found when pure steam condenses.The morphology of the films formed during the condensation of steam, containing a low mass fraction of trimethylamine, are very different from those described in the earlier parts of this test series and the dynamic nature of this film morphology does not appear to have been previously reported. The video analysis of these films suggests that at low concentrations they form a very thin continuous film, which moves with a rapid circumferential velocity. At higher concentrations this film supports condensate drops that are rapidly formed at the top of the tube. These drops do not grow or move relative to each when they are conveyed down the tube and take time to be incorporated into the base layer at the bottom of the tube. It is not clear what influence these drops have on the rates of condensation. The size distribution of the drops tends to become more uniform at higher trimethylamine concentrations. Measurements of the drop velocities suggest that they and the base layer moves with a velocity of 0.1m/s. The maximum heat transfer rate through these films is four times greater than that predicted by the Nusselt equation and it occurs with a trimethylamine mass fraction of 0.0003.

Preparation, thermal stability and electrical properties of PMMA/functionalized graphene oxide nanosheets composites

In this investigation, graphene oxide nanosheets (GONs) were made from expandable graphite after thermal shock in air and supersonic bath. SEM (scanning electron microscope), TEM (transmission electron microscope) and XRD (X-ray diffraction) were used to characterize the structure of GONs, and then were functionalized using a coupling agent, 3-aminopropyltriethoxsilane (APTS), to produce covalent bonds between the organic and inorganic phases, enhancing the thermal stability of the composites. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectra (XPS) were adopted to characterize the functionalization reaction between APTS and GNOs. It is affirmed that APTS has reacted with GONs. The functionalized GONs (FGONs) had –OEt functional groups that reacted with silane modified methyl methacrylate through the sol–gel reaction. The results of thermogravimetric analysis (TGA), integral procedure decomposition temperature (IPDT) and thermogravimetric difference (TGΔ) reveal that FGONs can improve the thermal stability of composites. The four-point probe was used to measure the surface resistivity of composites. The results showed the PMMA/FGONs composites which contained low concentration of additives possess excellent electrical property. This kind of composites can be used in antistatic application to prevent fire accident happen.

Tribological behaviors of three novel imidazoline-type thiadiazole derivatives as multifunctional lubricant additives in biodegradable lithium grease

Three novel imidazoline-type thiadiazole derivatives are prepared and used as antiwear and extreme-pressure additives in biodegradable lithium grease, and their tribological performances are evaluated using a four-ball tester. Tribological tests show that all derivatives are effective in reducing wear, especially at lower additive concentrations. Oleic acid-imidazoline-type thiadiazole derivative is a preferred additive to reduce wear. For the friction-reducing property of base grease, improvements after using these derivatives are not remarkable. On the other hand, these derivatives are also effective extreme-pressure additives. In order to understand the friction process further, chemical composition of tribofilms under antiwear/extreme-pressure regime is analyzed by X-ray absorption near edge structure spectroscopy, and thermal films are also considered for comparison. Thermal films formed by these imidazoline-type thiadiazole derivatives consist of adsorbed organic sulfide and ferrous sulfide. Sulfur presents several chemical valences in the antiwear regime, and tribofilms generated by stearic acid and lauric acid-imidazoline-type thiadiazole derivatives at 1.0 wt% are composed of ferrous disulfide, ferrous sulfide and ferrous sulfate. The appearance of disulfide suggests that the interfacial temperature between the upper ball and three lower balls under antiwear conditions is considerably low. Composition of extreme-pressure films generated by oleic acid and lauric acid-imidazoline-type thiadiazole derivatives is only ferrous sulfide, and the extreme-pressure film for stearic acid imidazoline-type thiadiazole derivative is a mixture of ferrous sulfide, ferrous sulfate, and adsorbed organic sulfide.

Evaluation of new mixed-mode UHPLC stationary phases and the importance of stationary phase choice when using low ionic-strength mobile phase additives

In this study, the selectivity, retention properties, peak shape and loading capacity for bases were practically evaluated using two UHPLC mixed-mode hybrid CSH stationary phases modified by C18 or Phenyl group. The data were compared with the data obtained on other UHPLC hybrid stationary phases (BEH C18, BEH C8, BEH Phenyl and BEH Shield RP18) at both basic and acidic conditions using conventional HPLC buffers (50mM ammonium formate/acetate) as well as low ionic-strength additives such as, e.g. 0.1–0.01% formic/acetic acid and 1mM solution of ammonium formate/acetate, which are widely used in LC–MS applications.Ten pharmaceutically important compounds encompassing acids, bases and neutral were included into the study. Due to properties of CSH sorbent (which possess positively charged surface besides RP group), much improved peak shapes and weaker retention was obtained for bases even at very low concentration of acidic additives. Such conditions are ideally suited for LC–MS analysis of bases, where typical RP chromatographic separation (retention and good selectivity at basic pH) and LS–MS conditions (efficient ionization at acidic pH) are not in agreement. On the other hand, acids were more strongly retained and for some compounds the peak shape was influenced negatively due to ion-exchange mechanism. Further, the behavior of acidic, basic and neutral solutes is discussed using various additives at both basic and acidic pH for all above stated columns. The robustness of retention times after pH change from basic to acidic was also evaluated. The new CSH stationary phases represent an interesting selectivity tool preferably for separation of basic compounds.