Lucie Kullová

A study on the relationship between preparation condition and properties/performance of polyamide TFC membrane by IR, DSC, TGA, and SEM techniques

Abstract High-performance thin-film composite polyamide membranes for inorganic solute separation were prepared by the interfacial polymerization of trimesoyl chloride (TMC) with diethylenetriamine, 1,3-cyclohexanebis(methylamine), 2,3-diaminopyridine (DAP), m-phenylenediamine (MPD), piperazine (PIP) or a mixture of MPD and PIP/DAP, on the surface of a reinforced microporous polyethersulfone (PES) membrane support. The polyamide skin layers were isolated by dissolving the PES support in dichloromethane and the characteristics of the free skin layers were studied by infrared spectroscopy (IR), differential scanning calorimetry, thermogravimetric analysis (TGA), and scanning electron microscope (SEM) techniques. It was attempted to correlate the observed flux and rejection properties of the membranes with their preparation conditions such as reactant concentrations, reaction time, curing temperature etc. The glass transition temperatures (T gs) of PES and polyamide blends are dependent on the concentration ...

Production of refractory chamotte particle-reinforced geopolymer composite

Geopolymer resins are obtained by alkaline activation of aluminosilicate sources where raw calcined clays are one of the suitable potentialities. Besides the fact that chemical composition has an essential effect on final properties of the geopolymer binder, the type of filler strongly affected resulting properties of such granular composite. However, very few comparative studies have been done on detail description of composite systems: binder - granular filler, in relation to aggregate gradation design and rheology properties of the mixture. The aim of this work is to develop and describe granular composite concerning workability of the mixture and kinetics of geopolymerization/polycondensation through flow behaviour. The rheological measurements indicated that initial viscosities of the mixtures and their evolution are different for various proportions of the filler. Moreover, it was demonstrated that increase in complex viscosity responds to the creation of chemical bonds and the formation of structural network. Finally, a correlation of the mechanism of geopolymer formation was carried out by differential scanning calorimetry (DSC).

Modification of gas diffusion layers properties to improve water management

In this paper we report an approach to improve water management of commercial GDLs by introducing hydrophobicity patterns. Specifically, line and grid patterns have been created in the MPL side by laser radiation. For an in-depth investigation of these modified GDLs the current density distribution was monitored during fuel cell operation. Additionally, the physical properties of these materials were investigated by a number of ex situ methods such as Fourier transform infrared microscopy, electrochemical impedance spectroscopy and water vapor sorption. Furthermore, a comparison of the physical properties of the patterned GDLs with chemically modified GDLs (treated in H2SO4 and H2O2) is provided. Our results show a clearly improved homogeneity of current density distribution of the patterned GDLs compared to untreated GDLs. This observation is likely due to a reduced local hydrophobicity which facilitates water diffusion along the flow field of the fuel cell. However, performance of the fuel cell was not affected by the MPL irradiation.Graphical Abstract

Mechanically activated fly ash as a high performance binder for civil engineering

This study is aimed for investigation of fly ash binder with suitable properties for civil engineering needs. The fly ash from Czech brown coal power plant Prunerov II was used and mechanically activated to achieve suitable particle size for alkaline activation of hardening process. This process is driven by dissolution of aluminosilicate content of fly ash and by subsequent development of inorganic polymeric network called geopolymer. Hardening kinetics at 25 and 30 °C were measured by strain controlled small amplitude oscillatory rheometry with strain of 0.01 % and microstructure of hardened binder was evaluated by scanning electron microscopy. Strength development of hardened binder was investigated according to compressional and flexural strength for a period of 180 days. Our investigation finds out, that mechanically activated fly ash can be comparable to metakaolin geopolymers, according to setting time and mechanical parameters even at room temperature curing. Moreover, on the bases of long time strength development, achieved compressional strength of 134.5 after 180 days is comparable to performance of high grade Portland cement concretes.

Characterization of Heat-Resistant Geocement Based on Potassium Silica Solution

The aim of this paper is detailed description of synthesis geocement composite material based on K2O-Al2O3-SiO2 system and characterization its thermal properties. The series of analytic tools were used (XRF, XRD, SEM, BET, particle-size distribution) for accurate identification of chemical and physical properties of raw material. Optimum technological prescription was determined and geocement specimens were tested for identification of mechanical and thermal properties. Three series of specimens were heated up to 1000, 1100 and 1230°C and flexural strength was determined. The thermal analysis TMA and DMA were used for characterization of heat-resistant properties. The maximum shrinkage in the range 30-1000°C was for the first run in temperature rate 20°C/min. only 3%. The heating exposure at slower rate (3°C/min.) caused reduction of shrinkage up to 1.5% at 1000°C. Geocement represents attractive thermal properties.