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Polymer electrolyte films based on poly(trimethylene carbonate) (PTMC) mixed with LiTFSI salt in different compositions were synthesized and investigated as electrolytes for lithium ion batteries, where the ionic conductivity is the most interesting material property. Electrochemical impedance spectroscopy (EIS) and DSC were used to measure the ionic conductivity and thermal properties, respectively. Additionally, FTIR and Raman spectroscopy were used to examine ion coordination in the material. Additives of nanosized TiO2 and powders of superionically conducting Li1.3Al0.3Ti1.7(PO4)3 were investigated as enhancers of ionic conductivity, but no positive effect could be shown. The most conductive composition was found at a [Li+]:[carbonate] ratio of 1, corresponding to a salt concentration of 74 percent by weight, which showed an ionic conductivity of 2.0 × 10–6 S cm–1 at 25 °C and 2.2 × 10–5 S cm–1 at 60 °C, whereas for even larger salt concentrations, the mechanical durability of the polymeric material was dramatically reduced, preventing use as a solid electrolyte material. Macroscopic salt crystallization was also observed for these concentrations. Ion coordination to carbonyls on the polymer chain was examined for high salt content compositions with FTIR spectroscopy, where it was found to be relatively similar between the samples, possibly indicating saturation. Moveover, with FTIR, the ion-pairing was found to increase with salt concentration. The ionic conductivity was found to be markedly lower after 7 weeks of aging of the materials with highest salt concentrations.

No / As the weakest zone in concrete, the interfacial transition zone (ITZ) between aggregates and cement mortars has important effects on the properties of concrete. This paper aims to investigate the effects and mechanisms of nanofillers on the bond strength and interfacial microstructures between aggregates and cement mortars. A total of 8 representative types of nanofillers (namely nano-SiO2, nano-TiO2, nano-ZrO2, untreated multi-walled carbon nanotubes (MWCNTs), hydroxyl-functionalized MWCNTs, nickel-coated MWCNTs, multi-layer graphenes (MLGs), and nano boron nitride (nano-BN)) were selected to fabricate specimens with scale-up aggregate-cement mortar interface that can be characterized by the three-point bend test. The experimental results indicate that all types of nanofillers can enhance the bond strength between aggregates and cement mortars. The highest relative/absolute increases of 2.1 MPa/35.1%, 2.32 MPa/38.8% and 2.56 MPa/42.8% in interfacial bond strength are achieved by incorporating 2 wt% of nano-ZrO2, 0.3 wt% of nickel-coated MWCNTs, and 0.3 wt% of nano-BN, respectively. Scanning electron microscope observations show the presence of nanofillers can improve hydration products and increase interfacial compactness. Energy dispersive spectrometer results suggest that local content of nanofillers in the ITZ is higher than that in the bulk cement mortars. These findings indicate the nanofillers can transfer with water migration toward aggregates and enrich in ITZ, thus improving the bond strength and interfacial microstructures between aggregates and cement mortars through the nano-core effect. / National Science Foundation of China (51978127 and 51578110), and the Fundamental Research Funds for the Central Universities in China(DUT18GJ203)

Yes / This study investigates the interfacial characteristics between aggregates and cement paste matrix in nanofillers modified concrete. A three-point bend test on the specimens composed of two pieces of aggregates bonded with a thin layer of cement pastes with/without nanofillers was carried out to characterize the interfacial bond strength of the composites. The scanning electron microscope observations and energy dispersive x-ray spectrometry analysis were also performed to characterize the interfacial microstructures and compositions of the composites. The experimental results indicated that the nanocomposites have higher interfacial bond strength and narrower interfacial transition zone thickness as well as more optimized intrinsic compositions and microstructures than that of composites without nanofillers. Specifically, the interfacial bond strength of nanocomposites can reach 7.67 MPa, which is 3.03 MPa/65.3% higher than that of composites without nanofillers. The interfacial transition zone thickness of nanocomposites ranges from 9 μm to 12 μm, while that of composites without nanofillers is about 18 μm. The ratio of CaO to SiO2 in the interface of composites without nanofillers is 0.69, and that of nanocomposites increases to 0.75–1.12. Meanwhile, the nanofiller content in nanocomposite interface is 1.65–1.98 times more than that in the bulk matrix. The interfacial microstructures of nanocomposites are more compact and the content and crystal size of calcium hydroxide were significantly reduced compared with that of composites without nanofillers. / The National Science Foundation of China (51978127 and 51908103), and the China Postdoctoral Science Foundation (2019M651116).

No / This study investigates the interfacial characteristics between aggregates and cement paste matrix in nanofillers modified concrete. A three-point bend test on the specimens composed of two pieces of aggregates bonded with a thin layer of cement pastes with/without nanofillers was carried out to characterize the interfacial bond strength of the composites. The scanning electron microscope observations and energy dispersive x-ray spectrometry analysis were also performed to characterize the interfacial microstructures and compositions of the composites. The experimental results indicated that the nanocomposites have higher interfacial bond strength and narrower interfacial transition zone thickness as well as more optimized intrinsic compositions and microstructures than that of composites without nanofillers. Specifically, the interfacial bond strength of nanocomposites can reach 7.67 MPa, which is 3.03 MPa/65.3% higher than that of composites without nanofillers. The interfacial transition zone thickness of nanocomposites ranges from 9 μm to 12 μm, while that of composites without nanofillers is about 18 μm. The ratio of CaO to SiO2 in the interface of composites without nanofillers is 0.69, and that of nanocomposites increases to 0.75–1.12. Meanwhile, the nanofiller content in nanocomposite interface is 1.65–1.98 times more than that in the bulk matrix. The interfacial microstructures of nanocomposites are more compact and the content and crystal size of calcium hydroxide were significantly reduced compared with that of composites without nanofillers. / National Science Foundation of China (51978127 and 51908103), and the China Postdoctoral Science Foundation (2019M651116).

Yes / This paper investigated the bond characteristics between eight types of nanofillers modified reactive powder concrete (RPC) and plain steel bars, aiming to explore the modifying mechanisms and establish a bond-slip relationship model for nanofillers modified RPC and steel bar interface. The experimental results indicated that the incorporation of nanofillers can increase the bond strength and reduce the slip between RPC and plain steel bars. It was shown that a 2.15 MPa/20.5% of absolute/relative increase in cracking bond strength, a 1.25 MPa/10.3% of absolute/relative increase in ultimate bond strength, a 2.35 MPa/22.4% of absolute/relative increase in residual bond strength, a 0.592 mm/56.5% of absolute/relative reduction in ultimate bond slip, and a 1.779 mm/52.1% of absolute/relative reduction in residual bond slip were the best achieved due to the addition of various nanofillers. The enhancement of nanofillers on RPC-steel bar interface has been mainly attributed to RPC microstructure improvement, optimization of intrinsic compositions, and elimination of defects in the interface, especially the underside near steel bar, due to the nano-core effect of nanofillers enriched in the interface. In addition, the bond-slip relationship of nanofillers modified RPC-steel bar interface can be accurately described by the proposed model considering an initial branch. / The authors would like to thank the funding offered by the National Science Foundation of China (51978127 and 51908103), and the Fundamental Research Funds for the Central Universities (DUT21RC(3)039).

La morphologie et les propriétés de sorption d’eau et d’éthanol de films extrudés minces de polyamide 6 ont été étudiées pour différentes conditions de mise en oeuvre (température de chill roll (TCR) de 50 et 125°C et taux d’étirage compris entre x et y). L’influence de l’ajout de faibles taux de nanocharges lamellaires (montmorillonite (MMT) ou phosphate de Zirconium (ZrP)) a également été évaluée. L’étirage n’a, dans la gamme étudiée, aucun effet sur la morphologie et les propriétés de sorption des films. Les films de PA6 préparés à une température de chill roll de 50°C présentent en revanche une proportion de phase cristalline g plus faible que les films préparés à une TCR de 125°C. L’épaisseur des lamelles cristallines y est plus fine et la mobilité des chaînes de la phase amorphe y est réduite. L’ajout de faibles taux de montmorillonite à une TCR de 50°C modifie significativement la mobilité des chaînes de la phase amorphe, les proportions des phases cristallines a et g et l’orientation des lamelles cristallines, contrairement à une TCR de 125°C où l’impact de la MMT n’a été observé qu’au niveau de l’orientation de la phase cristalline g. Les mécanismes de sorption de vapeur d’eau et d’éthanol ont été étudiés pour l’ensemble des films. Les isothermes de sorption ont été modélisées afin d’étudier plus particulièrement les phénomènes d’agrégation observés à haute activité. Une modélisation des courbes cinétiques a également été proposée sur la base de l’approche de Berens et Hopfenberg. La confrontation des données thermodynamiques et cinétiques de sorption et des paramètres morphologiques caractéristiques des matériaux a permis de conclure à un rôle prépondérant des interfaces entre zone amorphe et zone cristalline sur le transport / The morphology and water and ethanol sorption properties of thin films made of polyamide 6 were studied in relation to different transformation conditions, namely chill roll temperature (TCR) (50 and 125°C) and stretching ratio (between 6 and 10.8). The influence of nanofillers (montmorillonite (MMT) and zirconium phosphate (ZrP)) was also investigated. It was observed that stretching has no influence on neither the morphology nor the sorption properties in the studied range. In contrast unfilled films prepared at a chill roll temperature of 50°C have a lower amount of g crystalline phase, thinner cristalline lamellae and reduced amorphous phase mobility than films prepared at a chill roll temperature of 125°C. Adding low amounts of MMT at a TCR of 50°C has a remarkable impact on chain mobility, a and g crystalline phase fractions and lamellar orientation whereas the nanoparticules added at a TCR of 125°C only affect the crystalline orientation. Vapor sorption mechanisms were studied for both filled and unfilled films. The sorption isotherm curves were modelled to obtain a deeply understanding of the aggregation phenomena observed at high activity. Modelling of the kinetics was proposed according to Berens and Hopfenberg approach. Coupling the thermodynamics and kinetics of sorption with the morphological data leads to the conclusion that the interfaces between the amorphous and crystalline domains play a critical role on transport properties

Les nanocomposites polymères diélectriques ayant une constante diélectrique élevée et une faible perte diélectrique ont reçu un grand intérêt pour une utilisation dans le domaine du condensateur électrostatique. De manière générale, les performances diélectriques améliorées des nanocomposites sont déterminées par le type et la nature des polymères et des nanocharges sélectionnés, ainsi que par l'effet de couplage interfacial entre les matrices et les nanocharges. Parmi ces facteurs, les propriétés physiques, les géométries et les structures des composants des nanocharges jouent un rôle essentiel dans la détermination des performances diélectriques des nanocomposites. Selon les conductivités des nanocharges, les nanocomposites polymères diélectriques peuvent être classés en deux types: les nanocomposites polymères diélectriques conducteurs (CDPN) et les nanocomposites polymères diélectriques-diélectriques (DDPN). Cependant, la perte diélectrique élevée accompagnée au voisinage du seuil de percolation pour les CDPN et la charge élevée de nanocharges en céramique entravent le développement de nanocomposites polymères diélectriques à haute performance.Tout d'abord, des nanocomposites ternaires BNNS/CNT/PVDF ont été fabriqués. L'incorporation de BNNS dans les nanocomposites binaires CNT/PVDF a amélioré la dispersion des NTC et optimisé le réseau conducteur. La connexion directe entre les CNT pourrait être entravée en augmentant le contenu de BNNS.Deuxièmement, des hybrides CNT@AC à structure cœur-coquille ont été préparés par méthode CVD. La couche de carbone amorphe entrave non seulement le contact direct des NTC, mais améliore également la dispersibilité des NTC dans la matrice de PVDF. Le seuil de percolation augmente avec la prolongation du temps de dépôt du carbone. Plus important encore, la perte diélectrique a subi une forte diminution après le processus de revêtement. Troisièmement, les hybrides BNNSs@C avec des teneurs en carbone différentes ont été synthétisés par la méthode CVD. La fraction de carbone dans les hybrides BNNSs@C pourrait être ajustée avec précision en contrôlant le temps de dépôt de carbone. Les propriétés diélectriques des nanocomposites BNNSs@C/PVDF pourraient être ajustées avec précision en ajustant la teneur en carbone. Les polarisations interfaciales améliorées des interfaces BNNS/C et C/PVDF ont doté les nanocomposites de performances diélectriques améliorées.Quatrièmement, les hybrides TiO2@C NW structurés en noyau et en coquille ont été synthétisés par une combinaison d'une réaction hydrothermale et du procédé CVD. L'épaisseur de la couche de carbone dans les hybrides TiO2@C NW obtenus pourrait être précisément ajustée en contrôlant le temps de dépôt du carbone. De plus, les propriétés diélectriques des nanocomposites TiO2@C NWs/PVDF pourraient être ajustées avec précision en ajustant l'épaisseur de la coque en carbone. Les polarisations interfaciales améliorées des interfaces TiO2/C et C/PVDF ont doté les nanocomposites d'excellentes performances diélectriques.Enfin, des nanofils structurés de TiO2@C@SiO2 structurés à double coques ont été synthétisés par une combinaison de réactions hydrothermales modifiées, de CVD et de réactions sol-gel. L'introduction de carbone comme enveloppe interne entre le noyau de TiO2 et l'enveloppe externe de SiO2 a induit deux types supplémentaires de polarisation interfaciale. Les nanocomposites de PVDF obtenus avec TiO2@C@SiO2 NWs présentaient simultanément une constante diélectrique améliorée et des caractéristiques de perte diélectrique supprimées. La constante diélectrique et la perte de nanocomposites ont augmenté avec l'augmentation de l'épaisseur de la couche interne de carbone et ont diminué avec l'augmentation de l'épaisseur de la couche externe de SiO2. La relation entre la perte diélectrique et l'épaisseur de l'enveloppe extérieure en SiO2 a été démontrée par les résultats de la simulation finie. / Dielectric polymer nanocomposites with a high dielectric constant and low dielectric loss have received broad interest for use in the field of the electrostatic capacitor and they are usually composed of dielectric polymers as matrix and inorganic or organic nanofillers as the reinforcement. Generally, the improved dielectric performance of nanocomposites is decided by the type and nature of selected polymers and nanofillers as well as interfacial coupling effect between matrices and nanofillers. Among these factors, the physical properties, geometries, component structures of nanofillers play a critical role in deciding the dielectric performance of nanocomposites. According to the conductivities of nanofillers, the dielectric polymer nanocomposites can be classified into two types: conductive-dielectric polymer nanocomposites (CDPNs) and dielectric-dielectric polymer nanocomposites (DDPNs). However, the accompanied high dielectric loss in the vicinity of the percolation threshold for CDPNs and high loading of ceramic nanofillers hinders the development of high performance dielectric polymer nanocomposites.Firstly, ternary BNNSs/CNTs/PVDF nanocomposites were fabricated. The incorporation of BNNSs into the binary CNTs/PVDF nanocomposites improved the dispersion of CNTs and optimized the conductive network, which contributed to the enhanced dielectric constant. The direct connection between CNTs could be hindered by increasing the content of BNNS.Secondly, core-shell structured CNTs@AC hybrids were prepared by CVD method. The amorphous carbon layer not only hindered the direct contact of CNTs but also improved the dispersibility of CNTs in the PVDF matrix. The percolation threshold increased with the prolongation of carbon deposition time. More importantly, the dielectric loss underwent a sharp decrease after the coating process, which was attributed to the decrease in leakage current. The results suggested that the influence of AC interlayer on the final dielectric performance after percolation was much more obvious than that before percolation.Thirdly, BNNSs@C hybrids with different carbon contents were synthesized by the CVD method. The carbon fraction in the BNNSs@C hybrids could be accurately adjusted through controlling the carbon deposition time. The dielectric properties of BNNSs@C/PVDF nanocomposites could be accurately tuned by adjusting the carbon content. The improved interfacial polarizations of BNNSs/C and C/PVDF interfaces endowed the nanocomposites with enhanced dielectric performance.Fourthly, core-shell structured TiO2@C NW hybrids were synthesized by a combination of a hydrothermal reaction and the CVD method. The carbon shell thickness in the obtained TiO2@C NW hybrids could be precisely tuned by controlling the carbon deposition time. The TiO2@C NWs/PVDF nanocomposites exhibited a percolative dielectric behavior. Moreover, the dielectric properties of the TiO2@C NWs/PVDF nanocomposites could be accurately adjusted by tuning the carbon shell thickness. The enhanced interfacial polarizations of the TiO2/C and C/PVDF interfaces endowed the nanocomposites with excellent dielectric performance.Lastly, core@double-shells structured TiO2@C@SiO2 nanowires were synthesized by a combination of modified hydrothermal reaction, CVD, and sol-gel reaction. The introducing of carbon as an inner shell between the TiO2 core and SiO2 outer shell induced two additional types of interfacial polarization. The obtained PVDF nanocomposites with TiO2@C@SiO2 NWs exhibited simultaneously enhanced dielectric constant and suppressed dielectric loss characteristics. The dielectric constant and loss of nanocomposites increased with the increase of carbon inner shell thickness and decreased with the increasing of SiO2 outer shell thickness. The relationship between the dielectric loss and SiO2 outer shell thickness was further demonstrated by the finite simulation results.

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Fuel cell technology is a promising clean energy source compared to internal combustion engines and electricity generating plants which are associated with high emissions of greenhouse gases. The aim of this study was to modify chitosan into polymer electrolyte membranes suitable for use in PEMFC and DMFC fuel cells. Chitosan modification was done with 2-aminoethanesulfonic acid (2-AESA), dimethylformamide (DMF) and silica nanoparticles. The effect of the modification on the properties of the developed chitosan membranes was studied using FTIR, XRD, SEM-EDS and TGA. The performance of the membrane electrode assemblies was investigated. The formation of electrostatic interactions in the developed sulfonated chitosan membranes was confirmed via the Fourier transform infrared (FTIR) analysis, indicating a shift in the wavenumber of the N-H bonds from 1581 cm-1 on the chitosan spectrum to a lower wavenumber of 1532 cm-1 in the FTIR spectra of the membranes and by the new peak at the wavenumber of ~1260 cm-1 attributed to the asymmetric O=S=O stretching vibrations of the sulphate groups and sulfonic acid groups from the cross-linking sulphuric acid solution and 2-aminoethanesulfonic acid incorporated on the chitosan polymer chain during the modification. Notably, the FTIR spectra of the developed sulfonated chitosan membranes lacked the peak at the wavenumber of ~1153 cm-1 attributed to the stretching of C-O-C bonds of the polysaccharide ring of chitosan. A reaction mechanism was proposed in this study illustrating the possible conversion of the polysaccharide rings of chitosan into a poly (cyclohexene-oxide) thermoplastic rings in the developed membranes. The TGA/DTGA results of the developed sulfonated chitosan membranes showed three degradation stages. The initial weight loss occurred at temperatures ˂100 °C due to the evaporation of volatile components and water molecules inside the membranes. The second degradation phase of the membranes occurred at 208 ℃ with a loss in weight of >30% resulting from the decomposition of cross-linking networks. The third degradation stage was associated with the decomposition of the main polymer backbone of the membranes and occurred at 263°C for the chitosan membranes modified with 2-aminoethanesulfonic acid and at 266 °C for the chitosan membrane modified with silica nanofiller. The TGA/DTGA curves of Nafion 117 showed a small loss in weight of ~ 5% before a sharp decomposition that occurred between 346–505 °C. The XRD diffractograms of the developed sulfonated chitosan membranes showed amorphous phases, the crystal peaks of chitosan at 2theta of 10° and 20° were flattened on the membranes. The SEM images showed a homogenous surface morphology for the sulfonated chitosan membrane with a higher weight percentage of 2-aminoethanesulfonic acid (13,6 wt.%). The SEM images performed on the surface of the sulfonated chitosan membrane modified silica nanoparticles showed a slight agglomeration associated with the migration of the unbonded silica to the surface. The methanol permeability coefficient of the developed sulfonated chitosan membrane modified with 2-aminoethanesulfonic acid was calculated to be 2.29x10-6 cm2/s. This value was close to the methanol permeability coefficient of 2.33x10-6 cm2/s associated with unfavourable depolarisation at the cathode in direct methanol fuel cells when using Nafion 117. The proton diffusion coefficient of Nafion 117 was calculated to be 1.64x10-5 cm2/s and that of the developed sulfonated chitosan membrane modified with 2-aminoethanesulfonic acid was found to be 6.56x10-6 cm2/s, respectively. The fuel cell performance of the developed sulfonated chitosan membrane modified with 2AESA was investigated in a hydrogen fuel cell (PEMFC) supplied with H2 and O2 directly from the electrolyser. The sulfonated chitosan membrane modified with 2-aminoethanesulfonic acid (13.6 wt.%) achieved an open-circuit voltage of ~0.9 V and a maximum power output of 64.7 mW/cm2 at a maximum current of 70 mA. The current produced by the developed chitosan membrane was applied into the load and was able to turn (power) the electric fan. The sulfonated chitosan membrane modified with silica nanoparticles (2 wt.%) yielded an open-circuit voltage of ~0.9 V and attained a maximum power output of 58 mW/cm2 at a maximum current output of 60 mA/cm2. The current generated by the membrane was also able to turn the electric fan. The Nafion 117 membrane was also investigated under similar conditions and obtained an open-circuit voltage of 0.6 V and a maximum power output of 130 mW/cm2 at the maximum current output of 308 mA. The current produced by Nafion 117 was supplied into the load and was able to turn the electric fan.

Dissertation offers a plan for air – conditioning equipment of library building in Brno and it involves air filter experimental measurement. The proposal is divided into three parts. The first part explains air filter theory with detailed description of atmospheric air filters for separation of particles for general ventilation - filter parameter determination. Theory part ends specifically with pocket air filters and their construction. The second part focuses on experimental pocket air filter measurement execution, which calculates with variable filter cartridges and pocket count. Measurement also evaluates pressure drop and their efficiency. The last part of the dissertation looks at air – conditioning equipment design for specified building, concretely library building. The project solves fresh air traffic into interior of selected library rooms and it counts with thermal heat gain in summer season, heat loss in winter season and air humidity modification.