Free Volume Space Research Articles

Segregation and Migration of the Oxygen Vacancies in the Σ3 (111) Tilt Grain Boundaries of Ceria

In nanocrystalline materials, defect–grain boundary (GB) interactions play a key role in determining structural stability, as well as size-dependent ionic, electronic, magnetic, and chemical properties. In this study, using density functional theory, we systematically investigated the segregation and migration of oxygen vacancies at the Σ3 [110]/(111) grain boundary of ceria. Three oxygen layers near the GB are predicted to be segregation sites for oxygen vacancies. Moreover, the presence of oxygen vacancies stabilizes this tilt GB at a low Fermi level and/or under oxygen-poor conditions. An atomic strain model is proposed to rationalize the layer dependency of the relaxation energy for a 2+-charged oxygen vacancy. The structural origin of the large relaxation energies at layers 1 and 2 was determined to be free-volume space, which induces ion relaxation toward the GB. Our results not only pave the way for improving oxygen transport near GBs in ceria, but also provide important insights into the engineer...

Structural transformations in crystals induced by radiation and pressure. Part 5. The influence of pressure on the course of the photochemical reaction in crystals of 2,6-difluorocinnamic acid

The [2 + 2] photodimerization of 2,6-difluorocinnamic acid was gradually induced in crystals by UV radiation at 0.5, 1.1 and 2.1 GPa. The crystal and molecular structures were determined before the photochemical reaction and for many of its steps. For the pure monomer structures, the following parameters were analyzed in order to gain knowledge of the influence of pressure on the reaction environment: (a) the volume of free space, (b) the geometry of close intermolecular interactions, including hydrogen bonds and (c) the geometry of intermolecular reactivity parameters. The following structural changes brought about by the [2 + 2] photodimerization at high pressure were monitored step-by-step: (a) the cell parameters and the cell volume, (b) the content of the monomer and the dimer, (c) the distance between the reactive carbon atoms in adjacent monomer molecules and (d) the geometry of mutual orientation of molecules in the crystals. The rate of the [2 + 2] photodimerization of 2,6-difluorocinnamic acid increased as follows: 0.1 MPa < 0.5 GPa < 1.1 GPa ≤ 2.1 GPa. This was rationalized by the decrease in the volume of free space columns protecting the intermolecular geometry suitable for the reaction and by the decrease of the distance between the reactive carbon atoms of adjacent monomer molecules.

Scale-up in centrifugal partition chromatography: The “free-space between peaks” method

Centrifugal Partition Chromatography (CPC) is a purification technique using a biphasic liquid system. As a preparative separation technique, scale-up is of primary concern. Once the separation is optimized on a lab-scale instrument, the scale-up transfer is quite straightforward simply using the instrument volume ratio as the linear transfer factor, thanks to the absence of solid support. Such linear transfer underestimates the performances of large-scale CPC rotors that are usually better than that of small rotors. It means that more material than predicted by the linear estimation could be purified. A fully practical method based on experimental observations is proposed. The first step is to determine experimentally the free space volume available between the two peaks of interest doing two analytical separations, one with the small analytical CPC instrument, giving ΔV1, and the second with the large preparative one, giving ΔV2. The second step is to determine on the small CPC instrument how much material can be loaded to reach the maximum mass load still giving the required purity and recovery ratio of the desired compound. Then, an accurate prediction of the maximal quantity of sample that the large-scale rotor can purify is simply obtained by multiplying the maximum mass load on the analytical CPC instrument by the free-space between peaks ΔV2/ΔV1 ratio. For demonstration purposes, the method is applied to the transfer of the CPC separation of a synthetic three-GUESS-compound mixture from a 35mL-rotor to a semi-prep 239-mL rotor. The paper addresses also the operating condition optimization depending on industrial production strategy (maximal load per run or maximal productivity).

Influence of pressure on molecular packing and photochemical properties in three chalcone analogs

Abstract The structures of 1-(4-methylphenyl)-3-(2-thienyl)prop-2-en-1-one, (I), 1-(5-bromo-2-hydroxyphenyl)-3-(2-furyl)prop-2-en-1-one, (II), and 1-(3-furyl)-3-[3-(trifluoromethyl)phenyl]prop-2-en-1-one, (III), were determined in ambient and high pressure conditions. The values of the intermolecular geometrical parameters describing possibilities of execution of [2+2] photodimerization were calculated and analysed. In the case of ambient pressure, for (I) they are close to the border valid for photoreactive compounds and for (II) and (III) they exclude the photochemical reaction in crystals. High pressure hardly changed the mutual orientation of adjacent molecules and largely the distance between them: in the case of (I), the distance was far below limits for compounds undergoing [2+2] photodimerization. The volume of free space was calculated for the studied compounds for different values of pressure and analysed in the context of possibilities of the [2+2] photodimerization.

Feasibility assessment of pervaporation for desalinating high-salinity brines

Pervaporation, which is a non-pressure driven membrane process, was evaluated to determine its viability for desalinating high-salinity source waters like those originating from oil and natural gas development (produced water). Two types of membrane material chemistries were studied in order to identify the optimal properties for maximizing the permeate flux under a given set of operating conditions. Permeate flux was determined to be a significant function of membrane thickness and the diffusion coefficient of water through the membrane. The diffusion coefficient is in turn a function of the membrane's affinity for water (hydrophilicity) and its fractional free volume space. A cellulose triacetate membrane (Membrane B) achieved fluxes of 0.06 m3m–2day–1 when treating solutions having salt concentrations of 100 g L–1, comparable to fluxes achieved by other types of non-pressure driven membrane processes. The flux increased in a linear fashion with decreasing ionic strength and improved through increases in the vapor pressure gradient and/or inclusion of a feed channel spacer into the test cell. Salt rejection efficiencies by all membranes were &amp;gt;99%; however, co-ions were able to penetrate into the membrane material matrix over time.

Pyrolysis of coal in TGA: Extent of volatile condensation in crucible

Thermal gravimetric analysis (TGA) with crucibles of different shapes and sizes are used to evaluate reactions of volatiles generated from pyrolysis of two coals based on the understandings obtained from decomposition of CaCO3 and Polyvinylpyrrolidone. The TGA experiments were carried out in a flow of argon at a heating rate of 10°Cmin−1. The decomposition of CaCO3 shows an increase in derivative thermal gravimetric (DTG) peak temperature with an increase in the sample height or in the free space volume in the crucibles, which are attributed to the reverse reaction between the volatile product CO2 and the solid product CaO. The depolymerization of Polyvinylpyrrolidone supported on a coal-derived coke shows a decrease in DTG peak depth with an increase in the sample height or in the free space volume of the crucibles, indicating that the volatile intermediates generated from the deploymerization are reactive to form solid. The DTG curves of the two coals are very similar. They show a main pyrolysis peak which varies little with changes in the sample height and in the free space volume in the crucibles, suggesting that the extent of volatiles' reaction to form solid in the crucibles is very limited.

Electrostatic Potential within the Free Volume Space of Imidazole-Based Solvents: Insights into Gas Absorption Selectivity

In this work, a variety of molecular simulation tools are used to help characterize the selective absorption of CO2 and CH4 in imidazole-based solvents. We focus our efforts on a series of 1-n-alkyl-2-methyl-imidazoles and ether-functionalized imidazoles, over a temperature range from 293 to 353 K, and we perform detailed analysis of the free volume. We find that the electrostatic potential within the solvent free volume cavities provides a useful indication of the selective absorption of CO2 and CH4. The electrostatic potential calculation is significantly faster than the direct calculation of the chemical potential, and tests with the 1-n-alkyl-2-methyl-imidazoles and the ether-functionalized imidazoles indicate that this may be a useful screening tool for other solvents.

Rejection of small and uncharged chemicals of emerging concern by reverse osmosis membranes: The role of free volume space within the active skin layer

Free-volume hole-radii of the active skin layer of one seawater and two low pressure reverse osmosis (RO) membranes – namely SWC5, ESPAB, and ESPA2 respectively – were evaluated using positron annihilation lifetime spectroscopy (PALS) with a slow positron beam. The results were related to the rejection of boric acid and eight N-nitrosamines to provide insights to the transport of these small solutes through RO membranes. At pH 8 (which is the experimental pH in this study), these solutes are uncharged. PALS analysis showed that the SWC5 has the smallest mean free-volume hole-radius (0.259nm) among the three RO membranes investigated here. Correspondingly, the SWC5 membrane exhibited the highest rejection of boric acid and all N-nitrosamines. Results reported here also showed that the rejection of these chemicals increased in the order of increasing molecular volume. In addition, the difference in their rejection amongst the three RO membranes investigated here was most apparent for those (i.e., boric acid and N-nitrosodimethylamine (NDMA)) with a small molecular volume. The EPSA2 and ESPAB were determined to have mean free-volume hole-radius of 0.289nm. However, the ESPAB membrane had lower water permeability and showed considerably higher rejection of boric acid and NDMA than the ESPA2 membrane. These results suggest that in addition to the mean free-volume hole-radius, other membrane parameters and properties such as the free-volume hole-radius distribution and thickness of the active skin layer can also play a role in governing the rejection of small and uncharged solutes by RO membranes.

Influence of Free-space Volume in Ampoule on Defects of CdZnTe Crystal Grown by Bridgman Method

CdZnTe crystal was grown by Bridgman method. The relationship between the free-space volume in the ampoule and the defects in CZT, such as Te inclusion and Cd vacancy, was studied by IR transmission microscopy and positron annihilation technique (PAT). With the decrease of the free-space volume in the ampoule, the density reduced from 6.67×10/cm to 2.36×10/cm with the reduction of Te inclusions. The average positron lifetime decreased from 325.4 ps to 323.4 ps with the decrease of the free-space volume, indicating a reduction of Cd vacancies. The improvement of IR transmittance and resistivity of CZT further demonstrates that lowing the free-space volume in the ampoule can effectively depress the defects in CZT crystal.

Effect of the nature of a porogen on the porous structure of monolithic polydivinylbenzene sorbents

In quartz capillaries, macroporous monolithic sorbents based on divinylbenzene are synthesized and their porous structure is studied via inverse size-exclusion-hydrodynamic chromatography. Either a single-component porogen (a higher alcohol) or a two-component porogen (a mixture of a higher alcohol and mesitylene) is used for the synthesis of monoliths. The removal of a solvent good for a polymer from a porogen results in an increase in the size of flow-through channels and a decrease in the free-space volume inside the monolith; this space is used for the separation of polymer sorbates (the working volume of a column). At the same time, the volume of micro- and mesopores in the monolith structure is practically independent of the content of the good solvent in the porogen. It is inferred that the good porogen plays an active role in formation of the macroporous structure of monoliths. The structure of monoliths obtained on the basis of the two-component porogen with the use of nonanol and mesitylene or toluene is optimum for the molecular-mass analysis of polymers.

Effect of deposition temperature on the bonding configurations and properties of fluorine doped silicon oxide film

In our study, fluorine-doped silicon oxide (SiOF) films were prepared using a mixture of SiH 4, N 2O, and CF 4 in a conventional plasma enhanced chemical vapor deposition system at various deposition temperatures. Deposition behaviors are determined by the deposition temperature. Our results show that for temperatures below 300 °C the process is surface-reaction-limited controlled, but becomes diffusion-limited when the deposition temperature exceeds 300 °C. The surface topography images obtained using an atomic force microscope show that a large amount of free volume space was created in the film with a low temperature deposition. The optical microscope and secondary ion mass spectrometer analyses show that precipitates were produced at the near-surface at the deposition temperature of 150 °C with a higher fluorine concentration of 2.97 at.%. Our results show that the properties of the SiOF film are controlled not only by the free volume space but also by the fluorine concentration. An optimal SiOF film prepared at a temperature of 200 °C shows a low dielectric constant of 3.55, a leakage current of 1.21 × 10 − 8 A/cm 2 at 1 MV/cm, and a fluorine concentration of 2.5 at.%.

Gel polymer electrolyte based on poly(methyl methacrylate-maleic anhydride)-poly(ethylene glycol) monomethyl ether and organophilic rectorite clay

AbstractA grafted polymer (P(MMA-MAh)-PEGME)) was synthesized by reacting poly(ethylene glycol) monomethyl ether (PEGME) with copolymer of poly(methyl methacrylate-maleic anhydride) (P(MMA-MAh)and end-capping the residual carboxylic acid with methanol. Natural rectorite (REC) was made organophilic by modification with the surfactant dodecyl benzyl dimethyl ammonium chloride. The organoclay was termed OREC and was used as a filler additive to modify gel polymer electrolytes (GPEs) which consisted of the grafted polymer (used as a polymer matrix), propylene carbonate (PC) as a plasticizer and LiClO4 as a lithium ion producer.The temperature dependence of the ionic conductivity of the GPEs agreed well with the VTF (Vogel-Tamman-Fulcher) relation. 5 phr doses of OREC resulted in the highest ionic conductivity. Using OREC also considerably improved the plasticizer retention levels. As a consequence of OREC occupation of the free volume space in the polymer matrix of GPEs, the bulk resistance of the GPEs was reduced and the glass transition temperature (Tg) increased. From the present research, it can be concluded that the incorporation of PEGME into the copolymer of P(MMA-MAh) produced a great improvement in ionic conductivity, plasticizer retention capability and movement of carrier charge of Li+.

High ionic transfer of a hyperbranched-network gel copolymer electrolyte for potential electric vehicle (EV) application

Hyperbranched network-based gel copolymer electrolytes are synthesized by in situ free radical polymerization. This research is separated into two parts: the first is an investigation of modified bismaleimide oligomer (MBMI) as a free volume additive, and the second investigates the salt concentration effect on high power application. A polymer electrolyte with MBMI additive provided more free volume space, and the ionic conductivity of gel copolymer electrolytes was measured as a function of the salt concentration of lithium hexafluorophosphate (LiPF 6). The highest ionic conductivity and the lowest activation energy of hyperbranched-network gel copolymer electrolytes were determined to be 7.72 × 10 −3 S/cm at 23 °C and 5.41 kJ/mol, respectively. Furthermore, the MBMI additive and the optimal concentration of lithium salt increased the free space for carrier ions and contributed to increasing capacity and working voltage at a high rate discharge (8C). The reliability and cycling ability of lithium polymer batteries are as good as lithium ion batteries for potential electric vehicle (EV) application.

Proton Conduction Properties of Sulfonicacid Type Polymer Gel Electrolytes

Conduction properties of the proton conductive polymer gel electrolytes were investigated by the measurements of the sulfonicacid site concentration, proton concentration after the dissociation from the site, proton conductivity, and diffusion coefficient of the 1H species. The proton mobility, μH+, estimated from the conductivity and proton concentration, as a function of the water fraction of the gel, showed a change with a maximum. At the higher water content over the maximum point, μH+ converged to the proton mobility in the bulk water. This changing feature reveals that there is an optimum concentration of the gel ([H+]/[H2O]) responsible for the μH+ maximum. A specific region at the interface between the polymer chains and water molecules could be formed which permits the efficient proton hopping. This is confirmed by the measurement of the 1H relaxation time, T1. Correlated with the μH+ increase with increasing the water content of the gel, T1’s increase is restricted, showing the T1-flat region. This anomalous region would be associated with the structural features of the polymer. One is the nanolevel feature, concentration of the acid site at which the sulfonate group after the proton dissociation would play the part of the base for keeping the water molecules close to the chains. The other is the macroscopic aspect of the polymer, the free volume space of the polymer molecules. Associated with the size and form of the space, the layered region of the water molecules around the polymer chains could be formed, which is effective for proton hopping transport taking advantage of the mobile water and sulfonate groups.

Effect of meta-Carborane on Segmental Dynamics in a Bimodal Poly(dimethylsiloxane) Network

Bimodal networks of polydimethylsiloxane (PDMS) filled with varying amounts of icosahedral meta-carborane (m-CB) have been developed and characterized by broadband dielectric spectroscopy (BDS) and static 1H multiple quantum nuclear magnetic resonance (MQ NMR). Both BDS and MQ NMR showed evidence for a decrease in the polymer chain dynamics. BDS spectra quantified a normal-mode relaxation near 40 Hz at 40 °C. The frequency maximum observed for filled samples decreased with increasing m-CB content until contents greater than 5 wt %. The width of the relaxation spectrum increased with the addition of small quantities of filler and decreased with filler contents greater that 5 wt %. Agglomeration effects were observed at loadings greater than 5 wt % as manifest by the onset of low frequency Maxwell−Wagner−Sillars (MWS) processes. The MQ NMR data allowed the characterization of distributions of the residual dipolar couplings, <Ωd> and, thus, in the dynamic order parameter, Sb, consistent with the bimodal network architecture expected from the synthesis protocol used. Upon addition of less than 10 wt % m-CB filler, the mean <Ωd> for the longer chains increased by 46% and the width of the distribution increased by 33%. The mean <Ωd> for the shorter chains increased by much less, indicative of preferential dispersion of the filler particles in the long chain domains of the network structure. We conclude that the mechanism of reinforcement is likely free volume space filling at low loadings transitioning to complex molecular filler and polymer chain interaction phenomena at higher loadings.

Gel polymer electrolyte based on the synthesized co-polymer of poly(methyl methacrylate-maleic anhydride)

AbstractIn this study, poly(methyl methacrylate-maleic anhydride) (P(MMA-MAh)) was synthesized in toluene from methyl methacrylate (MMA) and maleic anhydride (MAh) monomers via free radical polymerization, in the presence of 2,2′-Azo-bis-isobutyronitrile (AIBN), as initiator at 80ºC for 8 h. The molar ratio of monomers was found to be 1 MAh:8 MMA using hydrolysis and titration. The molecular weight of co-polymer was determined to be of the order of 104 (g/mol) by gel permeation chromatography. The co-polymer was characterized using Fourier transform infrared and nuclear magnetic resonance spectroscopy. Thermogravimetric analysis indicated the initial decomposition temperature was ~270ºC. Differential scanning calorimetry indicated that the glass transition temperature was near 126ºC.Rectorite modified with benzyldimethyldodecylammonium chloride (OREC) was used as an additive to modify gel polymer electrolytes (GPEs) which consisted of P(MMA-MAh) used as a polymer matrix, propylene carbonate (PC) as a plasticizer and LiClO4 as the lithium ion source. X-ray diffraction analysis indicates that OREC can exfoliate well in GPEs when the amount of clay is suitable. The temperature dependence of the ionic conductivity of the resulting GPEs agreed well with the VTF (Vogel-Tamman-Fulcher) relation. OREC doses of 5 phr resulted in the greatest ionic conductivity. This OREC addition considerably improved the plasticized retention levels. As a consequence of OREC occupying the free volume space in the polymer matrix of GPEs, the bulk resistance of the GPEs was reduced and the glass transition temperature (Tg) increased.

Causes and consequences of errors in determining sorption capacity of coals for carbon dioxide at high pressure

Abstract Recent comparisons of CO2 sorption by coals at high pressures have shown major differences between the results obtained by different laboratories. These need to be resolved for laboratory estimation of CO2 sequestration in coal seams to be useful. A compilation of potential sources of error in determination of sorption characteristics and their impact on sorption measurements is provided here. A series of tests is also provided that can be used to identify and reduce such errors in measurement. For example, an error in temperature produces a characteristic distortion of the sorption curve for carbon dioxide, which can be corrected to some extent. A negative value for excess sorption at high pressure is almost certainly diagnostic of either a cell volume that has been overestimated or that some part of the substrate that is inaccessible to the gas is accessible to helium. The major source of variation between results from the different laboratories that supplied the closest sorption values was found to be variations in the assumed free space volume, which could be due to discrepancies in determined helium density or measured cell volume. Including a term in the sorption model that is proportional to gas density will markedly reduce the influence of such errors in estimating sorption capacity or heats of sorption. The influence of swelling and moisture on sorption isotherms is also quantified here. Correction for swelling of coals in carbon dioxide changes the estimated sorption capacity by less than 1%, if a term that is proportional to gas density is included as a free parameter in the model fitting the isotherm.

Robot programming using augmented reality: An interactive method for planning collision-free paths

Current robot programming approaches lack the intuitiveness required for quick and simple applications. As new robotic applications are being identified, there is a greater need to be able to programme robots safely and quickly. This paper discusses the use of an augmented reality (AR) environment for facilitating intuitive robot programming, and presents a novel methodology for planning collision-free paths for an n-d.o.f. (degree-of-freedom) manipulator in a 3D AR environment. The methodology is interactive because the human is involved in defining the free space or collision-free volume (CFV), and selecting the start and goal configurations. The methodology uses a heuristic beam search algorithm to generate the paths. A number of possible scenarios are discussed.

AN ABJS BEST PAPER: Analysis of Anatomic Periarticular Tibial Plate Fit on Normal Adults

Implant manufacturers are producing anatomically contoured periarticular plates to improve the treatment of proximal tibia fractures. We assessed the accuracy of the designation anatomic. We applied eight-hole medial and lateral anatomically contoured periarticular plates to 101 cadaveric tibiae. The tibiae and the plate fits were mapped, quantified, and analyzed using a MicroScribe G2LX digitizer, Rhinoceros software, and MATLAB software. By corresponding the clinical appearance of good fit with our digital findings, we created numerical criteria for plate fit in three planes: coronal (volume of free space between the plate and bone), sagittal (alignment with the tibial plateau and shaft), and axial (match in curvature between the proximal horizontal part of the plate and the tibial plateau). An anatomic fit should mirror the shape of the tibia in all three planes, and only four medial and four lateral plate fits qualified. Recognizing and understanding the substantial variations in fit that exist between anatomically contoured plates and the tibia may help lead to a more stable fixation and prevent malreduction of the fracture and/or soft tissue impingement.

Preparation and characterization of organic rectorite composite gel polymer electrolyte

AbstractIn liquid-filled batteries, the liquid electrolytes may escape or present a fire hazard and an inert spacer is needed to separate the electrodes. Alternative polymer-based electrolytes are of current technological interest. Solid polymer electrolytes are non-volatile, non-corrosive materials, which can readily be processed into any shape or size. However, despite possessing the required mechanical properties, they have inherently lower conductivity. Gel-based systems are an attempt to strike a balance between the high conductivity of organic liquid electrolytes and the dimensional stability of a solid polymer.Rectorite was modified with dodecyl benzyl dimethyl ammonium chloride to form organic-modified rectorite (OREC). OREC was used as a filler additive to modify gel polymer electrolytes (GPEs) and prepare composite gel polymer electrolytes (CPEs) which consisted of polymethyl methacrylate (PMMA) used as a polymer matrix, propylene carbonate (PC), used as a plasticizer, and LiClO4, used as a lithium ion producer. A variety of physical and chemical techniques was used to characterize the CPEs. The interlayer d spacing of OREC was much larger than that of the initial rectorite (2.22 nm). OREC also possesses a fine microscopic structure, and has a hydrophobic surface. Molau and XRD analysis of CPEs indicate that OREC has good compatibility with the components of CPEs and can be dispersed well. The effects of temperature and OREC dose on properties were studied. The temperature dependence of ionic conductivity of CPEs is well fitted by the VTF (Vogel-Tamman-Fulcher) relation. OREC doses of 5 phr gave the greatest ionic conductivity. This amount also greatly increased the plasticizer maintenance levels. Due to the occupancy of free volume space in the polymer matrix of CPEs by OREC, the bulk resistance of the CPEs was lowered and the glass transition temperature (Tg) increased. The sheet structure of OREC is thought to improve the decomposition temperature of CPEs.