Search results for "Mole fraction"
showing 10 items of 62 documents
Formation of Laves phases in buoyancy matched hard sphere suspensions.
2018
Colloidal Laves phases (LPs) are promising precursors for photonic materials. Laves phases have not yet been observed to form in experiments on colloidal suspensions of hard spheres (HS), even though they have been reported in computer simulations. LP formation so far has been achieved only for binary mixtures of colloidal charged spheres or ligand-stabilized nano-particles after drying. Using static light scattering, we monitored LP formation and annealing in a binary mixture of buoyant hard sphere approximants (size ratio Γ = 0.77, number or molar fraction of small spheres xS = 0.76) for volume fractions in the fluid-crystal coexistence regions. All samples spontaneously formed MgZn2 type…
Oxidation of pentan-2-ol -Part II: Experimental and modeling study
2021
International audience; The oxidation of pentan-2-ol was investigated at high-pressure in a jet-stirred reactor and in a shock tube. Experiments in the JSR were carried out at 10 atm, between 500-1180 K, for five different equivalence ratios of = 0.35, 0.5, 1, 2, 4 and 1000 ppm of fuel, at a constant residence time of 0.7 s. Reactant, product and intermediate species mole fractions were quantified using Fourier transform infrared spectrometry (FTIR) and gas chromatography (GC). Ignition delay times were measured for pentan-2-ol/O 2 mixtures in argon in a shock tube at 20 and 40 bar, in a temperature range of 1070-1460 K and for equivalence ratios of = 0.5, 1 and 2. Ignition delay times of a…
Temperature and pressure dependence of quercetin-3-O-palmitate interaction with a model phospholipid membrane: film balance and scanning probe micros…
2004
The molecular interaction of quercetin-3-O-palmitate (QP) with dimyristoylphosphatidylcholine (DMPC) has been studied. Film balance measurements of the average molecular area vs QP molar fraction in DMPC/QP mixed monolayers showed that relevant positive deviations from ideality, i.e., a less dense monolayer packing, occurred for a temperature of 10 degrees C, below the critical melting transition temperature of DMPC monolayers T c m approximately equal 20 degrees C), while ideal behavior was observed at 37 degrees C, above this phase transition temperature. The positive deviation observed at low temperatures in the average molecular area increased with the surface pressure. Scanning probe m…
Dynamical Properties of Self-Assembled Surfactant-Based Mixtures: Triggering of One-Dimensional Anomalous Diffusion in Bis(2-ethylhexyl)phosphoric Ac…
2013
The dynamic features of bis(2-ethylhexyl)phosphoric acid (HDEHP)/n-octylamine (NOA) mixtures have been investigated as a function of the NOA mole fraction and temperature by (1)H NMR spectroscopy and rheometry. All data consistently suggest a composition-induced glass-forming behavior. The microscopic factors responsible for this behavior have been highlighted and have been explained in terms of driving forces given by HDEHP-to-NOA proton transfer, the tendency of the resulting species to establish H bonds and to spatially segregate the alkyl chains. The study sheds light on the molecular mechanism responsible for the peculiar behavior of transport properties in such systems and furnishes b…
Volumes and heat capacities of anionic-nonionic surfactant mixtures
1995
Density, heat capacity and surface tension measurements of sodium decylsulfate (NaDeS)-dodecyldimethylamine oxide (DDAO)-water mixtures were carried out as functions of the surfactants total molality mt at fixed stoichiometric mixture compositions XNaDeS. From the surface tension data, the critical micelle concentration of NaDeS-DDAO mixtures as a function of XNaDeS were obtained. From density and heat capacity data, the apparent molar volume VΦ,2 and heat capacity CΦ,2 of NaDeS-DDAO mixtures in water were calculated, respectively. At a given mole fraction, VΦ,2 and CΦ,2 monotonically increases and decreases, respectively, with increasing mt. However, anomalies were observed at XNaDeS=0.1 a…
Demixing of Mixed Micelles. Thermodynamics of Sodium Perfluorooctanoate−Sodium Dodecanoate Mixtures in Water
1997
Conductivity, density, heat capacity, enthalpy of dilution, and osmotic coefficient measurements of water−sodium perfluorooctanoate (NaPFO)−sodium dodecanoate systems were carried out as functions of the surfactants' total molality (mt) at different mole fractions (XNaPFO). From conductivity data, the critical micelle concentration (cmc) and the degree of ionization (β) of the micelles were derived. The cmc's of the micelles are higher than those of the pure surfactants while β depends linearly on XNaPFO. At a given mole fraction, the apparent molar volume (VΦ) and heat capacity (CΦ) of the mixture increases and decreases monotonically with mt, respectively. From data in the premicellar reg…
Thermodynamic Studies of Sodium Dodecyl Sulfate–Sodium Dodecanoate Mixtures in Water
1996
Abstract Conductivity, density, heat capacity, enthalpy of dilution, and osmotic coefficient measurements of water–sodium dodecyl sulfate (NaDS)–sodium dodecanoate systems were carried out as functions of the surfactants total molality ( m t ) at different mole fractions ( X NaDS ). From conductivity data, the critical micelle concentration (cmc) and the degree of ionization of the micelles (β) were calculated. The cmc vs X NaDS profile deviates negatively from that predicted on the basis of the Clint approach, while the β vs X NaDS profile deviates positively from the line correlating the values for pure surfactants. At a given mole fraction, the profiles of all the investigated properties…
A study of the refractive index and surface tension synergy of the binary water/ethanol: influence of concentration
2005
Pure alcohols or alcohols mixed with water are the most widely used solvents in a great variety of industrial applications, including the formulation of pharmaceutical and cosmetic products. As a result of water/alcohol molecular associations, variations result in the physico-chemical characteristics of the system, such as density, viscosity, refractive index and surface tension. The present study investigates the refractive index and the surface tension of ethanol and water mixtures at a temperature of 25°C, for different molar fractions. The data obtained allow us to study the corresponding refractive index and the surface tension synergies; in this sense, an absolute maximum refractive i…
Emissions and spatial variability of N2O, N2 and nitrous oxide mole fraction at the field scale, revealed with 15N isotopic techniques.
2006
Abstract The accurate measurement of nitrous oxide (N 2 O) and dinitrogen (N 2 ) during the denitrification process in soils is a challenge which will help to estimate the contribution of soil N 2 O emissions to global warming. Oxygen concentration, nitrate concentration and carbon availability are generally the main factors that control soil denitrification rate and the amount of N 2 O or N 2 emitted. The aim of this paper is to present a database of the N 2 O mole fraction measured at the field scale, and to test hypotheses concerning its regulation. A 15 N-nitrate tracer solution was added to 36 undisturbed soil cores on a 20 m×20 m cultivated field plot. Fluxes of CO 2 , N 2 O and N 2 f…
Nano-demixing as a novel strategy for magnetic field responsive systems: the case of dibutyl phosphate/bis(2-ethylhexyl)amine systems
2016
Pure surfactant liquids and their binary mixtures, owing to the amphiphilic nature of the molecules involved, can exhibit nano-segregation and peculiar transport properties. The possibility of opportunely choosing the amphiphiles should lead to the formation of anisotropic aggregates that can be oriented by an external factor like a magnetic field. In this case some properties, like optical birefringence, can be induced by the use of a magnetic field. Dynamic features of dibutyl phosphate (DBP)/bis(2-ethylhexyl)amine (BEEA) mixtures have been investigated by FT-IR, NMR, rheometry, Brillouin scattering, and magnetically-induced birefringence measurements as a function of the BEEA mole fracti…