Significant Increase In Specific Surface Area Research Articles

Size-related mineralogical and surface physicochemical properties of the mineral particles from the recent sediments of the Eastern Adriatic Sea

The mineral composition and surface physico-chemical properties, i.e., specific surface area (SSA), cation exchange capacity (CEC), and surface charge of recent sediments and their submicron mineral fractions from different sedimentological environments of the Eastern Adriatic were investigated. The influence of organic matter on these properties was also investigated. It was shown that illite and mixed-layered clay minerals (MLCM) were ubiquitous and showed no size-related preferences while the occurrence of smectites, chlorites, and kaolinites varied. The smectites content increased and the chlorites decreased slightly with decreasing particle size. The sediments from the carbonate-rich environment contained no smectites or chlorites and had the highest kaolinite content. For the first time, in the recent sediments of the Adriatic Sea the poorly- and the well-crystallised kaolinite (Kl and KlD) were distinguished. While Kl predominates in the submicron-sized fraction, KlD occurred only in micron-sized fractions. Authigenic aragonite of submicron-sized was determined in a distinct environment of the semi-enclosed marine lake. The differences in mineral composition and particle size of sediments and their separated fractions were reflected in a wide range of the SSA and CEC values obtained. The highest values of SSA and CEC were determined in the phyllosilicates-rich submicron-sized fractions range, 109 m2g-1 and 87.4 cmol+kg−1, respectively. The submicron-sized fraction from aragonite-rich marine lake showed the lowest values of SSA (56.4 m2g-1) and CEC (38.8 cmol+kg−1), which are still unexpectedly high for carbonate-rich environments. The removal of organic matter resulted in a significant increase in SSA and CEC, up to 150% and 76%, respectively.

Влияние отжига на структурные, текстурные, термические, магнитные и люминесцентные свойства наночастиц фторида кальция

Mesoporous nanocrystalline CaF2 powder was obtained by pulsed electron beam evaporation (PEBE) in vacuum. The specific surface area (SSA) of the nanopowder (NP) of CaF2 reached 88.7 m2g. The effect of thermal annealing in air in the temperature range 200–900 oC on particle size, morphology, textural, thermal, magnetic, and luminescent properties of NP was studied. A strong deviation of the obtained nanoparticles from stoichiometry and a significant increase in SSA after annealing at 200 ° C was observed. The obtained CaF2 NP showed ferromagnetic (FM) behavior. The appearance of the FM response can be explained by the formation of structures and radiation defects. An analysis of the pulsed cathodoluminescence (PCL) curves and the magnetization of NP CaF2 allows us to draw conclusions about their relationship.

Electrical double layer capacitors with sucrose derived carbon electrodes in ionic liquid electrolytes

Activated carbons were prepared via a pyrolysis of sucrose followed by activation in the stream of CO 2 gas for 2–6 h at 900 °C to tune the pore size distribution (PSD) and increase the specific surface area (SSA). The porosity of the activated sucrose derived carbons (ASCs) has been characterized using N 2 sorption measurements. Increasing activation time led to the significant increase in SSA and pore volume of ASCs, among which sucrose derived carbon with 6 h activation time (ASC-6 h) exhibited the highest SSA of 1941 m 2 g −1 and the highest micropore volume of 0.87 cm 3 g −1. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge cycle tests have been applied to investigate the capacitive performance of the ASC electrodes in ionic liquids (ILs) at room and elevated temperatures. The ASC-6 h electrodes in ethyl-dimethyl-propyl-ammonium bis (trifluoromethylsulfonyl) imide (EdMPNTf 2N) showed specific capacitance in excess of 170 F g −1 at 60 °C, whereas the same electrodes in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF 4) showed slightly lower capacitance but significantly better rate performance.