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Synthesis of nanostructured tetragonal ZrO2 of enhanced thermal stability

100%

Adamski A. , Jakubus P. , Sojka Z.

2006

tom Vol. 51,suppl.1

27-33

Hydrous zirconia particles of nanometric dimensions were synthesized via forced hydrolysis of zirconyl chloride. Prolonged aging at 100°C in the mother liquor and subsequent calcination produced a single-phase tetragonal ZrO2 of enhanced thermal stability with the narrow size and pore distributions. The influence of the preparation conditions on the phase composition of the resultant zirconium dioxide was examined using structural (XRD, SEM/TEM) and spectroscopic (Raman) methods, supported by thermal analysis (DTA/TG, DSC) and N2-porosimetry. The nature of the parent salt, pH of the solution, the temperature of precipitation and aging, were found to be the key parameters of the successful synthesis. The sequence of mechanistic steps invoked to account for the formation of t-ZrO2 was rationalized using the concepts of zirconium aquatic chemistry.

Aquatic chemistry in correlation with water level in the Kasprowa Niznia Cave [Tatra Mts]

100%

Dumnicka E. , Galas J. , Wojtan K.

Acta Hydrobiologica

1995

tom 37

nr 3

The values of conductivity, total hardness, alkalinity, total residue, total fixed residue, and calcium concentration measured at the times of low water level in the Kasprowa Niżnia Cave were distinctly higher than those measured during high water level. Silicate values had the opposite pattern. Means of the above chemical factors were significantly different (p < 0.05 or p < 0.005). No dependence between the remaining parameters measured and water level in the studied cave was observed.

Przy niskich stanach wody wartości przewodnictwa elektrolitycznego, twardości ogólnej i węglanowej oraz całkowitej suchej pozostałości i jej części mineralnej, a także koncentracja jonów Ca były wyraźnie wyższe, a koncentracja krzemionki - niższa. Różnice średnich były statystycznie istotne na poziomie p < 0.05 lub p < 0.005. Pozostałe badane parametry nie wskazywały zróżnicowania zależnego od poziomu wody.

Seasonal variability of aquatic chemistry and phytoplankton communities in a shallow floodplain lake of the Daugava River, Latvia

67%

Gruberts D. , Druvietis I. , Klavins M.

tom 05

nr 2

Seasonal changes of water level, aquatic chemistry and phytoplankton composition of the Daugava’s floodplain lake Grīvas was studied in 1999. Significant influence of the Daugava’s floods on the lake’s water level was found. Filling, drainage and isolation phases in hydrological regime of the lake were distinguished. The Daugava’s floodwater influx in April caused considerable water level rising and dilution of the lake’s water column. Small diatoms and greens formed the spring maximum at the highest water level. After the floods, concentration of total diluted solids and nutrients increased, typical planktonic algae species were replaced by epiphytic and benthic species and rich macrophyte vegetation developed as in other shallow lakes.