High-resolution Thermogravimetric Analysis Research Articles

Non-freezing water sorbed on microcrystalline cellulose studied by high-resolution thermogravimetric analysis

Non-freezing water sorbed on microcrystalline cellulose studied by high-resolution thermogravimetric analysis

Water based quad acrylic copolymer/cloisite 30B nanocomposite heat resistant adhesive: thermal and rheological properties

In this study, a quad acrylic copolymer composed of four monomers namely acrylic acid, methacrylic acid, butyl acrylate, and methyl methacrylate/cloisite30B(C30B) nanocomposites with different loading of nanoclay (0.5–3.0%) is prepared by the in-situ method for heat resistant adhesive application. Different parameters like solid content, solubility, appearance, acid value, and pH values are measured for each nanoclay filled copolymer. For dispersion and thermal characterization of nanocomposite X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) are performed. Epoxy resin along with curing agent is added to the acrylic copolymer/C30B nanocomposite to prepare adhesive. The rheological properties for amplitude sweep, frequency sweep, and temperature scan are analyzed. The nanoclay content doesn’t affect the shear-thinning component significantly but improves the complex viscosity and elastic behavior of the adhesives. The crossover point shows good dispersion of C30B up to 2.0% in nanocomposite adhesive. Peel strength is found to be increased with an increase in nanofiller content up to 2.0%. A significant improvement in peel strength is observed when exposed to 150 °C for 45 min. Temperature sweep study by rheology and peel strength results at high temperature suggest that these adhesives can be used in high-temperature resistance adhesive application areas like heat seal packaging and fabric lamination.

Polythiophene/Zinc Oxide/Graphene Oxide Ternary Photocatalyst: synthesis, characterization and application

ABSTRACT In this study, polythiophene-zinc oxide-graphene oxide (PTh-ZnO-GO) nanocomposite photocatalysts have been successfully synthesized via a green method followed by in-situ chemical polymerization. The catalysts were characterized by Fourier transform infrared analysis, powder x-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Thermogravimetric analysis, four-point probe and UV-vis diffuse reflectance spectrum. FT-IR bands confirmed the presence of PTh, ZnO and GO in the PTh-ZnO-GO nanocomposites. The PTh-ZnO-GO composites exhibit higher photocatalytic activities compared to pure ZnO and GO and also binary PTh-GO and ZnO-GO composite under irradiation and degradation ability of PTh-ZnO-GO is about 38 times higher than that pure component such as GO. Thermogravimetric analysis and electrical conductivity measurement also showed that degradation temperature improved about 20◦ C in ternary hybrids and electrical conductivity increased in the range of one order of magnitude. Therefore, PTh-ZnO-GO nanocomposite is a solar light-active photocatalyst which can be used in the degradation of organic pollutants.

Online monitoring of reactive compatiblization of poly(lactic acid)/polyamide 6 blend with different compatibilizers

ABSTRACTImprovement of poly(lactic acid)/polyamide 6 (PLA/PA6) miscibility is approached by reactive compatibilization with using different reactive agents. Specifically, compatibilizing efficiency of commercially available Joncryl ADR‐4368 (Joncryl) and free‐radical initiator 2,5‐dimethyl‐2,5‐bis(tert‐butylperoxy)hexane (L101) is compared to that of laboratory synthesized compatibilizers (poly(lactic acid) grafted with itaconic anhydride (PLA‐g‐IAH) and poly(itaconic anhydride) (PIAH) by online rheology monitoring in internal mixer and oscillatory rheometer. The change of morphology and particle‐size distribution is evaluated by scanning electron microscopy (SEM), the extent of PLA‐PA6 miscibility is determined by differential scanning calorimetry (DSC), and newly formed polymer phases are identified by high‐resolution thermogravimetric analysis (HR‐TGA) and solvent extraction in formic acid. Although Joncryl exhibits the most promising results in PLA‐PA6 compatibility, other compatibilizers also exhibit specific benefits for PLA/PA6 blend or individual polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48005.

Nanostructure and reactivity of nascent carbon particles from 2,5-dimethylfuran/n-heptane swirling inverse diffusion flames

Carbon particles (Soot) have been the one of primary pollutants inevitably with the combustion of fossil fuels. A better understanding on incipient soot was useful to build the models of soot formation and even control soot emissions. The present work focuses on the nanostructure and oxidation reactivity of nascent carbon particles (soot) formed from 2,5-dimethylfuran (DMF)/n-heptane non-swirling and swirling inverse diffusion flames (IDFs). The nascent soot samples were derived from three different fuels: 100% n-heptane, 50% n-heptane/50% DMF and 100% DMF. In addition, the effects of swirling combustion and collection time on characteristics of nascent soot were investigated in detail using the high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Results demonstrated that nascent soot from pure n-heptane flames presented the film-like morphology and nanostructure of amorphous nature, while the nearly primary particles with more well-organized nanostructure were found in pure DMF soot. Swirling combustion increased the entire flame front areas and diameters due to the existence of tangential velocity at the outlet of burner. Moreover, swirling combustion could enhance the mixability of the oxidizer stream and fuel stream, leading to more young soot within the fuel stream being oxidized in the inception stage. However, the collection time on soot characteristics exhibited quite negligible impacts in comparison to the swirling effects.

Imaging carbon nanostructures' reactivity: a complementary strategy to define chemical structure.

In the search for the integration of carbon nanostructures in composite and functional materials, covalent organic reactions are successfully performed. This approach resulted in the construction of tailored chemical interfaces facilitating incorporation of nanocarbons. By a combination of different characterization techniques, such as high-resolution X-ray photo-spectroscopy, thermogravimetric analysis, Raman spectroscopy, UV-vis-nIR, and fluorescence spectroscopies, it is possible to identify and quantify the functional moieties covalently attached to the carbon frame. However, the determination of the structural conformation of functionalized nanostructures remains a difficult task. In this work, we present a straightforward methodology to visualize by transmission electron microscopy the functional moieties covalently attached to the carbon network in carbon nanotubes and graphene. The identification of the functionalities occurs in colloidal dispersions by using gold nanoparticles (AuNPs) as discriminating markers by molecular recognition or by the direct growth of AuNPs on the oxygenated moieties. This methodology, in combination with other characterization analysis, is expected to improve the design of hierarchical interfaces by the spatial localization of the functionalities responsible for colloidal stabilization in solvents with different polarities, different from their homogeneous incorporation into different matrices.

Influence of octadecylammonium, N,N-dimethylhexadecylammonium, and 1-hexadecyltrimethylammonium chloride upon the fractionated montmorillonite

Various alkyl-amines (ammoniums) salts were reacted with fractionated sodic montmorillonite (FNa-MMT) to prepare the organomontmorillonites. The interlayer d-spacing obtained by X-ray diffraction analysis of FNa-MMT was increased after the alkylammonium cations intercalation. The FTIR spectrograms indicate the presence of the different surfactant agents in the montmorillonite interlayer space. High-resolution thermogravimetric analysis reveals that the thermal decomposition of the modified montmorillonite occurs in three steps. For the surface morphologies examined by atomic force microscopy, the measured root-mean-square roughness was increased after the reaction of the FNa-MMT (< 2 µm) with the different surfactants.

Nafion/(WO3)x] hybrid membranes for vanadium redox flow batteries

Nafion‑tungsten oxide hybrid membranes, [Nafion/(WO3)x], with varying loading levels of WO3 nanofiller (x = 0, 0.024, 0.329) are prepared and investigated as candidates for application as solid electrolytes in vanadium redox flow batteries (VRFBs). The thermal properties of [Nafion/(WO3)x] hybrid membranes are probed both by high-resolution thermogravimetric analysis (HR-TGA) and by modulated differential scanning calorimetry (MDSC). Vibrational spectroscopy studies are carried out by: (i) Attenuated Total Reflectance - Fourier Transform Infrared spectroscopy (ATR-FTIR); and (ii) Raman spectroscopy, to elucidate the secondary structure of [Nafion/(WO3)x] and study the interactions taking place between the nanofiller and the Nafion matrix. The electrical response of [Nafion/(WO3)x] is determined by Broadband Electrical Spectroscopy (BES) and the permeability towards VO2+ is measured by UV-VIS spectrometry. It is demonstrated that the [Nafion/(WO3)x] hybrid membranes exhibit a high ion selectivity (up to 10.6∙103 S∙min∙cm−3 for [Nafion/(WO3)0.329]) that is much improved in comparison with that characterizing recast Nafion (6.5∙103 S∙min∙cm−3). A structural model and a conductivity mechanism for the [Nafion/(WO3)x] hybrid membranes are proposed, in order to rationalize the experimental results and correlate the electrical response with the transport properties.

Contributions of environment and genotype to variation in shrub willow biomass composition

Yield improvement of woody bioenergy crops has been the major focus of breeding programs, but biomass quality is also important for conversion to biofuels. Using high-resolution thermogravimetric analysis, the composition of biomass samples from two shrub willow (Salix spp.) yield trial networks representing two distinct datasets were examined. Dataset 1 consisted of 12 yield trials containing 10 genotypes that mainly represented early cultivars from the US breeding program. Dataset 2 consisted of five trial locations containing 19 genotypes from later breeding efforts. Variation in ash and hemicellulose content were largely controlled by genetic factors, while cellulose and lignin content were heavily influenced by environmental effects. Mean biomass composition traits for dataset 1 were 2.1% ash, 42.4% cellulose, 18.7% hemicellulose and 25.5% lignin. For dataset 2 mean traits were 1.9% ash, 43.2% cellulose, 17.7% hemicellulose and 25.7% lignin. Yield was negatively correlated with lignin content and positively correlated with cellulose content at the level of environment. Elite triploid hybrid cultivars have the potential to produce more cellulose per unit area because of higher yields and/or greater cellulose content. These findings suggest that selection of genotypes for improved yield, as well as selection of growing environment, can improve feedstock quality for biofuel production.

Poly(diallyldimethylammonium chloride)/clay nanocomposites: effect of molecular weight and concentration of polymer on the structural, thermal, and dielectric properties

Poly(diallyldimethylammonium chloride), PDADMAC, with low and high molecular weight and with concentrations 0.5, 1, and 2 times the cation exchange capacity (CEC) of the clay was used to modify sodium bentonite clay to prepare hybrid PDADMAC/clay nanocomposites using solution-intercalation method. The prepared hybrids were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Data analysis showed that PDADMAC/clay nanocomposites have intercalated structure. The results showed also that the nanocomposite prepared using high molecular weight PDADMAC with concentration one times the CEC of the clay has the most intercalated structure and the highest thermal stability between the prepared nanocomposites. The room temperature dielectric properties were studied as a function of frequency in which the values of real (e 1) and imaginary (e 2) parts of relative permittivity are calculated and discussed. Higher values of e 1 and e 2 are obtained using PDADMAC with high molecular weight. Increasing the concentration of polymer affects the values of e 1 and e 2 towards lower values.

Fe-carbon nitride “Core-shell” electrocatalysts for the oxygen reduction reaction

In this report, the preparation of Fe-carbon nitride (CN)-based electrocatalysts (ECs) with a “core-shell” morphology for the oxygen reduction reaction (ORR) is described. The ECs consist of spherical XC-72R carbon nanoparticles, the “cores”, that are covered by a CN matrix, the “shell”, that embeds Fe species in “coordination nests”. The latter consist of hollow cavities in the CN matrix, whose internal surface is covered by N- and C-ligands able to stabilize alloy nanoparticles or active sites. Two families of CN-based ECs are prepared, which are grouped on the basis of the concentration of N atoms in the CN “shell”. Each group comprises of both a “pristine” and an “activated” EC; the latter is obtained from the “pristine” EC by a suitable series of treatments (A) devised to improve the ORR performance. The chemical composition of the CN-based ECs is determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and microanalysis. The thermal stability under both inert and oxidizing atmospheres is gauged by High-Resolution Thermogravimetric Analysis (HR-TGA). The structure is probed by powder X-ray diffraction, and the morphology is inspected by Scanning Electron Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM). The surface area of the CN-based ECs is determined by nitrogen physisorption techniques, and the surface composition is probed by X-ray Photoelectron Spectroscopy (XPS). The electrochemical performance and reaction mechanism of the CN-based ECs in the ORR is investigated in both acid and alkaline environments by cyclic voltammetry with the Thin-Film Rotating Ring-Disk Electrode setup (CV-TF-RRDE). The influence of the preparation parameters and of the treatments on the physicochemical properties, the ORR performance, and reaction mechanism is studied in detail. In the alkaline environment the FeFe2-CNl 900/CA“core-shell” EC shows a remarkable ORR onset potential of 0.908V vs. RHE which, with respect to the value of 0.946V vs. RHE of the Pt/C ref., classifies the proposed materials as very promising “Platinum Group Metal-free” ECs for the ORR.

(Invited) 3D-Catenated EMImCl/(TiCl4)1.4/(δ-MgCl2)x Ionic Liquid Electrolyte for Mg Secondary Batteries

The rapid advance in the fields of portable electronics, load leveling and peak shaving for the power grid and zero-emission automotive applications require the development of new and improved electrical energy storage systems [1,2]. Since the 90’s major improvements have been achieved in magnesium battery technology [3-6]. In comparison to Li, Mg offers the following advantages: (i) a higher volumetric capacity (3832 vs. 2062 mAh·cm-3); (ii) far greater abundance in the Earth’s crust, lowering the costs; (iii) a safer operation and a better compatibility with the environment; and (iv) an acceptable standard reduction potential (-2.36 vs. -3.04 V) [7-9]. The main roadblock for these devices is the development of an efficient and stable electrolyte that is able to reversibly deposit and strip magnesium. Although Grignard and other organo-magnesium compounds exhibit good electrochemical performances [9], they do not exhibit an optimal stability due to their high vapor pressure and flammability. Ionic liquids dissolving a Mg salt with a high crystalline disorder were proposed as promising alternative electrolytes to organo-Mg systems owing to their good electrochemical performance and lack of flammability and thermal stability issues [10]. In the present work a new family of electrolytes is proposed, based on 1-ethyl-3-methylimidazolium chloride (EMImCl), titanium(IV) chloride (TiCl4) and increasing amounts of δ-MgCl2. Specifically, four EMImCl/(TiCl4)1.4/(δ-MgCl2)xelectrolytes, with 0.00 ≤ x ≤ 0.23 are prepared and extensively characterized. The chemical composition was determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The thermal stability was gauged using High-Resolution Thermo Gravimetric Analysis (HR-TGA) and the phase transitions are highlighted with Modulated Differential Scanning Calorimetry (MDSC). Chemical interactions were studied through Fourier-Transform spectroscopy in the medium and far infrared (FT-MIR and FT-FIR) regions and confocal micro-Raman spectroscopy. The electrochemical performance was studied with: (i) Cyclic Voltammetry (CV), to probe Mg deposition and stripping (Fig. 1); (ii) Linear Sweep Voltammetry (LSV), to evaluate the electrochemical stability window; (iii) Chronopotentiometry (CP) experiments coupled with ICP-AES, to confirm and quantify the Mg deposition; and (iv) Broadband Electrical Spectroscopy (BES), to elucidate the long-range charge migration mechanisms of the electrolytes. High level density functional theory (DFT) based electronic structure calculations were undertaken to elucidate structures and vibrational frequency assignments. References 1 M. Armand and J. M. Tarascon Nature 451, 652-657, (2008). 2 B. Dunn, H. Kamath and J. M. Tarascon Science 334, 928-935, (2011). 3 V. Di Noto and M. Fauri, Batterie Primarie (Non Ricaricabili) e Secondarie (Ricaricabili) a Base di Elettroliti Polimerici Basati su Ioni Magnesio, PD99A000179, (1999). 4 V. Di Noto and M. Fauri, Magnesium-based Primary (Non Rechargeable) and Secondary (Rechargeable) Batteries, PCT/EP00/07221, (2000). 5 V. Di Noto, M. Fauri, G. De Luca and M. Vidali, (1998). 6 V. Di Noto, S. Lavina, D. Longo and M. Vidali Electrochim. Acta 43, 1225-1237, (1998). 7 D. Aurbach, G. S. Suresh, E. Levi, A. Mitelman, O. Mizrahi, O. Chusid and M. Brunelli Adv. Mater. 19, 4260-4267, (2007). 8 T. D. Gregory, R. J. Hoffman and R. C. Winterton J. Electrochem. Soc. 137, 775-780, (1990). 9 J. Muldoon, C. B. Bucur, A. G. Oliver, T. Sugimoto, M. Matsui, H. S. Kim, G. D. Allred, J. Zajicek and Y. Kotani Energy and Environmental Science 5, 5941-5950, (2012). 10 F. Bertasi, C. Hettige, F. Sepehr, X. Bogle, G. Pagot, K. Vezzù, E. Negro, S. J. Paddison, S. G. Greenbaum and M. Vittadello ChemSusChem 8, 3069-3076, (2015). Figure 1

N-Functionalised Polyketone Ion Exchange Membranes for Aemfcs

Anion-exchange membrane fuel cells (AEMFCs) provide significant advantages over their proton-exchange membrane counterparts. In the alkaline environment, the oxygen reduction reaction (ORR) is more facile, there is diminished fuel crossover, and a greater flexibility regarding fuel and catalyst choice. The membrane at the heart of AEMFCs not only facilitates the ion exchange but also separates the fuel feedstocks and acts as a support for the membrane-electrode assembly (MEA). However, to date there are still no membrane materials that satisfy all the needs (long-term stability in alkaline environment, high ionic conductivity, low swelling and good structural integrity) for use in AEMFCs and this remains one of the larger obstacles for further AEMFC development. The amination and subsequent quarternisation of polyketone leads to a new family of ionomers containing N-substituted pyrrole moieties. The degree of amination can be controlled by manipulating reaction conditions, allowing the composition and resulting structural properties of the polymer to be tuned. Membrane fabrication results in thermally stable (TD > 250 oC), structurally robust polymer electrolytes that exhibit ionic conductivity ( > 10-3 S cm-1). These new solid-state ion conducting materials have the potential to be used in a variety of applications including AEMFCs. Here we present an in-depth study focusing on the structure-property relationships of this new polypyrrole/polyketone polymer. A variety of analytical techniques are used to probe the thermal and structural properties of the polymers, these include high-resolution thermogravimetric analysis, modulated differential scanning calorimetry, dynamic mechanical analysis, vibrational, NMR and UV-Vis spectroscopies. In addition, broadband electrical spectroscopy is used to gauge the interplay between the structural properties and electrical response. Figure 1

Graphene-Supported Au-Ni Carbon Nitride Electrocatalysts for the ORR in Alkaline Environment

This study reports the preparation and characterization of a new family of electrocatalysts (ECs) for the oxygen reduction reaction (ORR) exhibiting a “core-shell” morphology. The “core” consists of graphene sheets, which are covered by a carbon nitride (CN) “shell” embedding Au and Ni active sites. The investigated ECs are labeled AuNi10-CNl 600/Gr and AuNi10-CNl 900/Gr. The chemical composition and thermal stability are studied by inductively-coupled plasma atomic emission spectroscopy (ICP-AES), elemental analysis and by high-resolution thermogravimetric analysis (HR-TGA). The morphology of the ECs is probed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction (XRD). The ORR performance of the ECs is studied both in acid (0.1 M HClO4) and in alkaline medium (0.1 M KOH) by Cyclic Voltammetry with the Thin-Film Rotating Ring-Disk Electrode (CV-TF-RRDE) method. Both ECs exhibit a promising performance in the ORR in the alkaline medium.

Single-Ion-Conducting Nanocomposite Polymer Electrolytes for Lithium Batteries Based on Lithiated-Fluorinated-Iron Oxide and Poly(ethylene glycol) 400

A poly(ethylene glycol) 400 (PEG400) matrix doped with different amounts of a fluorinated Fe2O3-based nanofiller (LiFI) featuring a Li+-functionalised surface gives rise to nanocomposite polymer electrolytes (nCPEs) that demonstrate single-ion conduction. A family of nCPEs with general formula [PEG400/(LiFI)y] and y=nFe/nPEG400 ranging from 0 to 8.15 are prepared; they are characterized by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), High-Resolution Thermogravimetric Analysis (HR-TGA), Differential Scanning Calorimetry (DSC), and Fourier-transform vibrational spectroscopy in both the medium (MIR) and far (FIR) infrared. The Li+ transference number, tLi+,is determined and Broadband Electrical Spectroscopy (BES) is used to elucidate the electrical response of the materials in terms of polarization and relaxation events. The combination of the information obtained by all the aforementioned techniques enables us to present a possible conduction mechanism for these nCPEs single-ion conducting systems.

Use of high-resolution thermogravimetric analysis (HRTG) technique in spent FCC catalyst/Portland cement pastes

Thermogravimetric analysis is one of the most common instrumental techniques used for the characterization of pastes, mortars and concretes based on both calcium hydroxide and Portland cement. Important information about pozzolanic materials can be assessed concerning calcium hydroxide consumption and the formation of new hydrated products. Nevertheless, in some cases, problems associated with the overlapped decomposition processes for hydrates make the analysis of obtained data difficult. In this paper, the use of high-resolution thermogravimetric analysis, a powerful technique that allows separating decomposition processes in analysis of hydrated binders, was performed for spent FCC catalyst—Portland cement pastes. These pastes were monitored for 1, 4, 8 h and 1, 2, 3, 7 and 28 curing days. In order to study the influence of the pozzolanic material (spent FCC catalyst), Portland cement replacements of 5, 15 and 30 % by mass were carried out. The presence of spent FCC catalyst in blended pastes modified the amount and the nature of the formed hydrates, mainly ettringite and stratlingite.

Near-infrared investigation of folding sepiolite

Sepiolite is an industrially important clay mineral of the palygorskite-sepiolite group with alternating 2:1 ribbons and hydrated tunnels. Dry sepiolite, Mg 8 Si 12 O 30 (OH) 4 (OH 2 ) 4 , loses half of its OH 2 content upon further heating and undergoes a structural collapse known as folding. This treatment is considered essential for enhancing the absorptive properties of the clay. In this paper, the folding process is studied by near-infrared (NIR) spectroscopy, mid-infrared attenuated total reflectance (ATR), and thermogravimetric analysis (TGA). The folded state, Mg 8 Si 12 O 30 (OH) 4 (OH 2 ) 2 , reveals a new spectrum of fundamental and higher-order OH 2 vibrations, as well as systematically split doublets of structural and surface O-H vibrations. Detailed assignments for the stretching, combination, and overtone O-H modes are proposed on the basis of the two non-degenerate populations of Mg 3 OH (and SiOH) present in the folded state. It is demonstrated that NIR is of particular diagnostic value in monitoring conveniently and non-invasively the folding process, which appears as a simple transition between well-defined dry- and folded-structures. At the level of elementary sepiolite particles (laths), folding is described as a cooperative process requiring the integrity of the ribbons and the inter-ribbon linkages (moderately acid-leached sepiolite does not fold). This is opposed to the skewed and sometimes complex OH 2 desorption trace observed by high-resolution TGA, which appears to indicate a multimodal distribution of laths. It is proposed that the rate-determining step for a sepiolite (also, palygorskite) lath to fold is the creation of a critical zone at mid-particle length, which is OH 2 -deficient and contains unstable, fivefold-coordinated Mg 2+ .

Mesoporous-structure-tailored hydrothermal synthesis and mechanism of the SrTiO3 mesoporous spheres by controlling the silicate semipermeable membranes with the KOH concentrations

Mesoporous structure-tailored SrTiO3 mesoporous spheres have been hydrothermally realized by controlling the silicate semipermeable membranes with KOH concentration. The phase and microstructures were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis and N2-physisorption techniques, respectively. Because the high KOH concentration lowers the polymerization degree of the silicate anion species, the silicate semipermeable membranes become thinner with increasing KOH concentration. Whereas the attenuated silicate semipermeable membranes favour the penetration of the metal ions, the primary SrTiO3 nanocrystallites for the self-assembly of the SrTiO3 mesoporous spheres grow larger as the KOH concentration increases. As a consequence, the mesoporous structures of the self-assembled SrTiO3 mesoporous spheres can be simply tailored by adjusting the KOH concentration of the hydrothermal reaction system. Moreover, because the attenuation of the silicate membrane facilitates the orientation attachment of the primary nanocrystallites, the self-assembled SrTiO3 mesoporous spheres trend to single-crystal-like with the increasing KOH concentration.

Iodide-conducting plastic crystals based on N,N-dimethyl-2-(methylsilyloxy) ethanaminium cations (MESEAn+) for application in dye-sensitized solar cells

This report describes the synthesis and the properties of twelve iodide-conducting Plastic Crystal Electrolytes (PCEs) based on N,N-dimethyl-2-(methylsilyloxy) ethanaminium cations (MESEAn+) and I−/I3− anions for application in dye-sensitized solar cells (DSSCs).The PCEs are obtained in three steps. In the first, the MESEAn+(Cl−)n precursor is prepared by reacting different chlorosilanes (CH3)4−nSiCln with 1 ≤ n ≤ 4 with N,N-dimethyl ethanolamine (DMEA). In the second step, the MESEAn+(I−)n PCEs are obtained by treating MESEAn+(Cl−)n with CH3I. In the final step, the MESEAn+(I−)n are doped with different aliquots of I2 to obtain blends of MESEAn+(I−)n and MESEAn+(I3−)n PCEs bearing the active I−/I3− redox couple. Twelve PCEs based on siloxane cations, with general formula {[MESEAn+(I3−)n]ρ%·[MESEAn+(I−)n]100−ρ%} with 1 ≤ n ≤ 4 and 0 ≤ ρ% ≤ 8.3 are obtained. ρ% is the percentage of I3− on the total anions included in the PCEs.The properties of the PCEs are investigated by vibrational spectroscopy (MIR FT-IR), high-resolution thermogravimetric analysis (HR-TGA), differential scanning calorimetry (DSC) and broadband electrical spectroscopy (BES) in order to study the correlations between the structural features, the conductivity and the composition of the proposed electrolytes. Results show that the PCEs with n = 3 and ρ% = 3.7 exhibit: (a) a melting temperature below 100 °C, which is typically observed in room-temperature ionic liquids; (b) a thermal stability up to 200 °C and (c) a conductivity of 0.8·10−4 S cm−1 at 50 °C.

Thermal stability and hot-stage Raman spectroscopic study of Ca-montmorillonite modified with different surfactants: A comparative study

Three long chain cationic surfactants were intercalated into Ca-montmorillonite through ion exchange and the obtained organoclays were characterized by X-ray diffraction (XRD), high resolution thermogravimetric analysis (TG) and Raman spectroscopy. The intercalation of surfactants not only changes the surface properties of clay from hydrophilic to hydrophobic but also greatly increases the basal spacing of the interlayers based on XRD analysis. The thermal stability of organoclays intercalated with three surfactants (TTAB, DTAB and CTAB) and the different arrangements of the surfactant molecules intercalated into Ca-montmorillonite were determined by TG-DTG analysis. A Raman spectroscopic study on the Ca-montmorillonite modified by three surfactants prepared at different concentrations provided the detailed conformational ordering of different intercalated long-chain surfactants under different conditions. The wavenumber of the antisymmetric stretching mode is more sensitive than that of the symmetric stretching mode to the mobility of the tail of the amine chain. At room temperature, the conformational ordering is more easily affected by the packing density in the lateral model. With the increase of the temperature, the positions of both the antisymmetric and symmetric stretching bands shift to higher wavenumbers, which indicates a decrease of conformational ordering. This study offers new insights into the structure and properties of Ca-montmorillonite modified with different long chain surfactants. Moreover, the experimental results confirm the potential applications of organic Ca-montmorillonites for the removal of organic impurities from aqueous media.