Ultrasonic speed of sound and derived thermodynamic properties of liquid 1, 1, 1, 2, 3, 3, 3-heptafluoropropane (HFC227ea) from 248 K to 333 K and pressures up to 65 MPa

This work reports experimental data of the speed of sound in liquid 1,1,1,2,3,3,3-heptafluoropropane (HFC227ea) from 248 K to 333 K and pressures up to 65 MPa, measured with a pulse-echo method. The results are fitted with a rational approximant. Derived thermodynamic properties are calculated, combining our experimental data with density and isobaric heat capacity values published by other authors. The results were compared with the data available in the literature.info:eu-repo/semantics/publishedVersio

Imidazolium-based ionic liquid type dependence of the bending response of polymer actuators

Actuators based on polymer blends of poly(vinylidene fluoride) (PVDF) with 40 % of different ionic liquids (IL) are prepared by solvent casting. [C2mim][Cl], [C6mim][Cl], [C10mim][Cl], [C2mim][NTf2], [C6mim][NTf2] and [C10mim][NTf2] were selected in order to evaluate the effect of anion and cation sizes in the bending properties. The microstructure, mechanical and electrical properties of the blend depend on the IL type, which in turn leads to a different bending response. In particular, the mechanical properties are independent on the IL type but the AC conductivity of the composites depend more on the anion type than on the size of the alkyl chain connected to the imidazolium based cation. Thus, the bending response of the IL/PVDF composites is correlated with the anion and cation sizes and a maximum bending response of 0.3 % is achieved for a 10 volts square signal in the IL/PVDF composite with 40 wt% content of [C2mim][NTf2].The authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under Strategic Funding UID/FIS/04650/2013, UID/Multi/04551/2013, UID/QUI/50006/2013, project PTDC/EEI-SII/5582/2014, a contract under Investigador FCT 2012 program (J.M.S.S.E.), and grants SFRH/BD/90215/2012 (JCD) and SFRH/BPD/112547/2015 (CMC). Financial support from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged. The authors (R. M. and S. B. H.) would like to thank the Tunisian Ministry of Higher Education and Research for its financial support. The authors thank the support of M. S. Martins (U. Minho) for supporting the electromechanical measurements

Unveiling the Temperature Influence on the Sorptive Behaviour of ZIF-8 Composite Materials Impregnated with [Cn MIM][B(CN)4 ] Ionic Liquids

LA/P/0008/2020 PTDC/CTM-CTM/ 30326/2017Composite sorbent materials (IL@MOF) with a metal-organic framework (MOF) ZIF-8 and [B(CN)4 ]−-based ionic liquids (ILs) were produced for the first time. Characterization results indicate the successful IL impregnation and conservation of the ZIF-8 crystalline structure and morphology. The data collected from the nitrogen (N2 ) physisorption at 77 K suggest that these IL@ZIF-8 materials are nonporous as their textural properties, such as BET specific surface area and total pore volume, are negligible. However, CO2, CH4, and N2 adsorption/desorption measurements in the IL@ZIF-8 composites at 303 and 273 K contradict the N2 data at 77 K, given that the obtained isotherms are Type I, typical of (micro)porous materials. Their gas adsorption capacity and ultramicroporous volume are in the same order of magnitude as the pristine microporous ZIF-8. The case study [C6 MIM][B(CN)4 ] IL revealed a high affinity to both CO2 and CH4 . This compromised the selectivity performance of its respective composite when compared with pristine ZIF-8. This work highlights the importance of accurate experimental gas adsorption/desorption equilibrium measurements to characterize the adsorption uptake and the porous nature of adsorbent materials.publishersversionpublishe

Carbon Materials Derived from Cyano-Based IL@ZIF-8 Composites for CO2 Sorption Separation Systems

Additionally, this work was partially supported by the Asso- ciate Laboratory for Green Chemistry, LAQV, which is funded by national funds from FCT/MCTES (LA/P/00 08/2020) .The sorption capacity and selectivity of pre- and post-carbonized cyano-based metal-organic framework (MOF) composite materials (cyano-based IL@ZIF-8) were investigated for the first time. The influence of the ionic liquid (IL) loading and number of cyano groups in the IL anion on a materials gas sorption separation performance was studied. Sorption-desorption equilibrium isotherms of CO2, CH4, and N2 were measured at 303 K in the ZIF-8, cyano-based IL@ZIF-8 composites and their derived carbon materials. The IL loading did not significantly affect the gas uptake of the carbon materials, while for the composites its main contribution was on the increase of the selectivity. The number of cyano groups in the anion played a key role in the sorption capacity and selectivity performance as it directly affects the N content and textural properties. The carbon material obtained from ZIF-8 (C_ZIF-8) precursor showed the best sorption capacity for all gases, just being surpassed by the C_15%[C6MIM][B(CN)4]@ZIF-8 carbon up to 1 bar. In terms of selectivity performance, carbons based on [C6MIM][B(CN)4]@ZIF-8 composites revealed to be equally or more selective than C_ZIF-8, increasing up to 65% between 0 and 1 bar depending on the mixture. The composites produced and their respective carbons demonstrated a promising application as sorbents for post-combustion CO2 separation systems.publishersversionpublishe

Synthesis and electrochemical characterization of aPEO-based polymer electrolyte

In this paper the preparation and purification of an amorphous polymer network, poly[oxymethylene-oligo(oxyethylene)], designated as aPEO, are described. The flexible CH2CH2O segments in this host polymer combine appropriate mechanical properties, over a critical temperature range from -20 to 60 ºC, with labile salt-host interactions. The intensity of these interactions is sufficient to permit solubilization of the guest salt in the host polymer while permitting adequate mobility of ionic guest species. We also report the preparation and characterization of a novel polymer electrolyte based on this host polymer with lithium tetrafluoroborate, LiBF4, as guest salt. Electrolyte samples are thermally stable up to approximately 250 ºC and completely amorphous above room temperature. The electrolyte composition determines the glass transition temperature of electrolytes and was found to vary between –50.8 and –62.4 ºC. The electrolyte composition that supports the maximum room temperature conductivity of this electrolyte system is n = 5 (2.10×10-5 S cm-1 at 25 ºC). The electrochemical stability domain of the sample with n = 5 spans about 5 V measured against a Li/Li+ reference. This new electrolyte system represents a promising alternative to LiCF3SO3 and LiClO4-doped PEO analogues.Fundação para a Ciência e Tecnologi

Structural, morphological, ionic conductivity, and thermal properties of pectin-based polymer electrolytes

New polymer electrolytes (PEs), potentially interesting for solid-state electrochemical devices applications, were synthesized by a solvent casting method using pectin and ionic liquid (IL) N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([N1 1 1 2(OH)][NTf2]. The resulting electrolytes besides being moderately homogenous and thermally stable below 155 ºC, they also exhibited good mechanical properties. The SPE membranes were analyzed by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and complex impedance spectroscopy.This work was supported by FEDER through the COMPETE Program and by Fundação para a Ciência e a Tecnologia (FCT) in the framework of the Strategic Projects PEST-C/QUI/UI0686/2013, grants FCT Investigator contract (J.M.S.S.E.). The authors are also indebted to CNPq (grant 201820/2014-5), FAPESP, and CAPES for the financial support given to this research. M.M. Silva acknowledges CNPq (PVE grant 406617/2013-9) for the mobility grant provided by these institutions. The authors are also acknowledges to Dra. Ivana for AFM data.info:eu-repo/semantics/publishedVersio

Electrochemical applications of electrolytes based on ionic liquids

The potential utility of room temperature ionic liquids as electrolytes in current electrochemical applications has been explored. Hence, the electrochemical behavior of [Ni(tmc)]Br2 complex at a glassy carbon electrode in the absence or in the presence of unsaturated halides in the ionic liquids, 1-ethyl-3- methylimidazolium ethylsulfate, [C2mim][C2SO4] and N,N,Ntrimethyl- N-(2-hydroxyethyl) ammonium bis(trifluoromethylsulfonyl)imide, [N1 1 1 2(OH)][NTf2], has been examined by cyclic voltammetry. It was observed that [Ni(tmc)]2+ complex is reduced in a reversible one-electron step and the electrogenerated [Ni(tmc)]+ complex catalytically reduces the carbon-halogen bond of unsaturated halides. The potencial use of natural ionic conducting polymer matrixes was also investigated. Samples of natural macromolecules-based electrolytes with the ionic liquid 1-ethyl- 3-methylimidazolium ethylsulfate, [C2mim][C2SO4], were prepared and characterized. The preliminary studies carried out with electrochromic devices (ECDs) incorporating optimized compositions have confirmed that these materials may perform as satisfactory multifunctional component layers in the field of ECD-based devices.Fundação para a Ciência e a Tecnologia (FCT

Acoustic determination of thermophysical properties and critical parameters for R404A and critical line of x CO2+(1− x) R404A

The thermophysical properties and critical parameters for the alternative refrigerant R404A (52 wt % of 1,1,1- trifluoroethane (R143a) + 44 wt % of pentafluoroethane (R125) + 4 wt % of 1,1,1,2-tetrafluoroethane (R134a)) were investigated using two different acoustic techniques. The critical behavior of the system xCO2 + (1 - x)R404A was also investigated. Experimental data of speed of sound in liquid R404A from 258 K to 338 K and pressures up to 65 MPa were measured using a pulse-echo method. Derived thermodynamic properties are calculated, combining our experimental data with density and isobaric heat capacity values published by other authors. Measurements of the critical temperature Tc and pressure pc on (R404A) and mixtures of xCO2 + (1 - x)R404A were performed using another simple ultrasonic time-delay technique. The binary critical line was determined over the whole composition range showing that this system deviates only slightly from ideality since the critical line is a continuous line. The Peng-Robinson equation of state with conventional mixing and combining rules was used to correlate the binary experimental data.info:eu-repo/semantics/publishedVersio

Polymer electrolytes for electrochromic devices through solvent casting and sol-gel routes

Ionically conductive membranes of gelatin and d-PCL(530)/siloxane doped with cyano-based ionic liquids (ILs) were prepared through solvent casting and sol-gel methods, respectively. The membranes were characterized in terms of ionic conductivity, thermal behavior, morphology, and structure. All samples, except the d-PCL(530)/siloxane matrix, exhibited a predominantly amorphous morphology. The samples prepared through solvent casting and sol-gel displayed a minimum thermal stability of 170 and 230 ºC, respectively. The ionic conductivity varied accordingly with the type, quantity, and length of the alkyl chain of the cation of the ILs. The sample with the highest ionic conductivity was gelatin0.5[C2mim][N(CN)2] with 2.40 x 10-3 S. cm-1 at 25 ºC and 1.68 x 10-2 S. cm-1 at 95 ºC. The good results of ionic conductivity encouraged the assembly and characterization of prototypes of electrochromic devices (ECDs). The best results were obtained with glass/ITO/WO3/gelatin1[C2mim][SCN]/CeO2-TiO2/ITO/glass configuration that showed a fast color switching time (~ 15 s) and a good open circuit memory (~ 4 hours). The ECD changed its color from pale blue to transparent, and its charge density decreased from -17.53 to - 2.71 mC. cm-2 during 640 color/bleaching cycles.This work was supported by Fundação para a Ciência e a Tecnologia (FCT) in the framework of the Research unit GREEN-it "Bioresources for Sustainability" (UID/Multi/04551/2013), Laboratório Associado para a Química Verde – Tecnologias e Processos Limpos-LAQV (UID/QUI/50006/2013), grant SRFH/BD/90366/2012 (R.L.) and a contract under Investigador FCT 2012 program (J.M.S.S.E.). It was also co-financed by FEDER through the COMPETE Program and PT2020 Partnership Agreement (POCI-01-0145-FEDER – 007265). M.M. Silva acknowledges CNPq (PVE grant 406617/2013-9) for the mobility grant provided by this institution. A. Pawlicka and R.C. Sabadini acknowledge CNPq (grant 305029/2013-4 and 152252/2016-9), and F.C. Sentanin acknowledges CAPES (grant PNPD20131739- 33002045017P6).info:eu-repo/semantics/publishedVersio