Wyniki wyszukiwania - BazTech

1

New composite materials prepared by high-pressure infiltration of superionic glasses into diamond powder compacts

Foltyn M., Zgirski M., Garbarczyk J., Wasiucionek M., Pałosz B., Gierlotka S., Nowiński J.L.

Materials Science Poland

|

2006

|

Vol. 24, No. 1

141--146

EN

Glassy-crystalline composites have been prepared by infiltrating highly conducting silver vanadate glasses into diamond powder compacts. The process of infiltration was carried out at a high isostatic pressure (from 1.5 to 8 GPa) and temperatures up to 800 °C. The resulting composites have conductivities comparable to those of glasses used for infiltration, but exhibit a wider range of thermal stability (up to 300 °C) than glasses. Additionally, they have much better mechanical properties, in particular, being less brittle and exhibiting higher microhardness than glasses.

2

EXAFS/XANES studies of the local structure of amorphous ionic and electronic-ionic conductors

Wasiucionek M., Garbarczyk J., Bacewicz P., Jóźwiak J, Nowiński J.L.

Materials Science Poland

|

2006

|

Vol. 24, No. 1

181--186

EN

X-ray absorption spectroscopy methods such as EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure) are sophisticated and effective tools for studying the local structure of many solids and liquids. Their use is particularly valuable in the case of amorphous systems, in which due to the absence of long-range order the possibilities of structure determination by diffraction methods are limited. EXAFS and XANES have been extensively used to study the local structure of many electrically conducting (via ions, electrons, or both electrons and ions) solids. The special merit of the latter studies is that their results reveal the short-range structure of these conductors, which is an important factor determining their transport properties. The paper reports recent results of EXAFS/XANES studies on the local structure of selected electrically conducting glasses of the Li2O-V2O5-P2O5 system and their silver analogues. All spectra were acquired at the K-edge of vana

3

Crystallization processes in superionic AgI-Ag2O-P2O5 ([Ag2O]/[P2O5] = 3) glasses

Nowiński J.L., Mroczkowska M., Garbarczyk J.E., Wasiucionek M.

Materials Science Poland

|

2006

|

Vol. 24, No. 1

161--167

EN

Crystallization processes in superionic AgI-Ag2O-P2O5 ([Ag2O]/[P2O5] = 3) glasses were investigated by X-ray, DSC, SEM, and impedance spectroscopy. It was found that the crystallization process depended on the total concentration of the AgI dopant in the material and on the thermal treatment of the glass. During quenching of the glass melt, the following phases are successively formed with increasing total AgI concentration: pure glass without detectable (XRD) traces of crystalline phases, glasses containing ß-AgI and some other, unidentified crystallites precipitated on the surface, and finally a composite material, namely a glass matrix in which ß/gamma-AgI inclusions are embedded. Glasses containing x < 50 mol % of AgI do not crystallize during annealing. Two bulk crystallization processes were identified in solid glasses with 50 < x < 75 mol %. During annealing, the initial product of crystallization transforms to the final one. There is an evidence that crystallization is preceded by a pre-crystallization stage, in which the glass matrix becomes inhomogeneous, forming nano-sized volumes.

4

Crystallization processes in silver-ion conducting borate and phosphate glasses

Nowiński J.L.

Materials Science Poland

|

2006

|

Vol. 24, No. 1

169--179

EN

Crystallization processes in silver-ion conducting superionic borate and phosphate glasses are presented. Experimental evidence indicates that these processes are determined by the dopant concentration x, glass former, molar ratio of modifier to former eta = [Ag2O]/[P2O5], cooling rate of the molten glass during preparation, and by the thermal history of the glass. A crystal-free material is produced by the press-quenching method, in which the total concentration of AgI does not exceed 64-65 mol %. Rapid quenching of highly-doped borate glasses results in the formation of alfa-AgI crystallites in the glass. The phase deteriorates when stored for a long time or after pressure operation. Annealing prompts crystallization in solid glasses when they contain 40 < x < 65 mol % of dopant. Only surface crystallization takes place when 0 < ? < 1. In the 1 < eta < 2 range, the surface crystallization of gamma-AgI dominates, provided the annealing time is not too long. When the concentration of the modifier Ag2O is high eta > 2), the crystalline phases precipitate in the glass bulk. Investigations point to the key role of a rigid substructure in crystallization. Some of the results indicate that primary crystallization is preceded by a precrystallization stage.

5

Nanokrystalizacja szkieł o wysokiej przewodności elektrycznej.

Garbarczyk J.E., Nowiński J.L., Wasiucionek M., Jóźwiak P., Latuch J., Wnętrzewski B.

Archiwum Nauki o Materiałach

|

2003

|

T. 24, nr 4

583-596

PL

W pracy przedstawiono wyniki badań nanomateriałów szklisto-krystalicznych na bazie szkieł układów AgI-Ag2O-V2O5, AgI-Ag2O-P2O5 i Li2O-V2O5-P2O5. Nanomateriały otrzymywano dwoma metodami - przez wygrzewanie wyjściowych szkieł w temperaturze zbliżonej do temperatury krystalizacji, oraz przez ultraszybkie chłodzenie roztopionych mieszanin zawierających dużą nadwyżkę jednego ze składników (AgI), która przy typowej szybkości chłodzenia prowadziłaby do masowej krystalizacji próbki. Stwierdzono, że wygrzewanie wyjściowych szkieł w temperaturze krystalizacji, wyznaczonej z pomiarów DSC, prowadzi do wyraźnej poprawy przewodności elektrycznej materiałów. Podwyższeniu ulega także górna granica temperatury, w której właściwości próbek są stabilne. Obserwowana wyraźna korelacja między temperaturami, w których mają miejsce zmiany przewodnictwa elektrycznego i wyznaczonymi z termogramów DSC temperaturami przejścia szklistego i krystalizacji jednoznacznie wskazuje na wpływ struktury materiału na transport ładunku elektrycznego. Badania rentgenograficzne potwierdziły amorficzność wyjściowych szkieł oraz pozwoliły prześledzić proces tworzenia się krystalitów w matrycy szklistej w trakcie nanokrystalizacji. Rozmiary powstałych ziaren krystalicznych wynosiły od 20 nm do ponad 100 nm (zależnie od składu i etapu procesu nanokrystalizacji). Zaproponowano model opisujący związek między ilością i wielkością krystalitów w nanomateriałach układu Li2O-V2O5-P2O5 a obserwowanymi zmianami przewodności elektrycznej.

EN

Results of studies of glass-crystalline nanomaterials based on glasses of the AgI-Ag2O-V2O5, AgI-Ag2O-P2O5 and Li2O-V2O5-P2O5 systems are presented. These nanomaterials were prepared by two methods: annealing of initial glasses at crystallization temperature and ultrafast quenching of molten mixtures containing an excess of one component (AgI). It was found that the annealing of glasses at crystallization temperature (determined from DSC thermograms) leads to a considerable increase in electrical conductivity of the annealed materials. Also the upper thermal stability limit of the samples increases. The correlation between temperatures at which conductivity of the samples undergo noticeable changes and glass transition and crystallization temperatures, determined from DSC scans, indicate the influence of material's structure on transport of electrical charges. X-ray diffraction studies confirmed amorphous state of as-obtained glasses and showed the formation of crystallites during nanocrystallization. Dimensions of these crystallites were from 20 nm to above 100 nm. A model explaining the effect of concentration and dimensions of crystallites on observed changes of electrical conductivity was proposed.