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EN
Novel silica aerogels were produced from carbon nanotubes/carbon black/polypyrrole (NTC/CB/PPy) blends, and their structure characterized by FT-IR analysis. X-ray diffraction analysis confirms the presence of amorphous silica and a new reflection at 2θ = 13°, which had not been reported before. SEM micrographs of the aerogels reveal the connectivity of the micropores of the material, along with the different fillers (NTC/CB/PPy), which allow to increase the water absorption of the aerogels and to increase thermal stability. The mechanical and thermal properties of the resulting aerogels are significantly better than those of similar materials reported in the literature.
PL
Otrzymano nowe aerożele krzemionkowe z wykorzystaniem mieszanin nanorurek węglowych, sadzy węglowej i polipirolu (NTC/CB/PPy). Strukturę wytworzonych aerożeli scharakteryzowano na podstawie widm FT-IR. Metodą dyfrakcji rentgenowskiej potwierdzono w nich obecność amorficznej krzemionki, stwierdzono też, wcześniej nieopisywane, odbicie przy 2θ = 13°. Mikrofotografie SEM aerożeli wykazały połączenia mikroporów krzemionki z cząstkami różnych napełniaczy (NTC/CB/PPy), pozwalające zwiększyć absorpcję wody przez aerożele i ich stabilność termiczną. Wykazano, że właściwości mechaniczne i termiczne powstałych aerożeli są znacznie lepsze niż właściwości podobnych materiałów opisanych w literaturze.
PL
W artykule przedstawiono ogólną charakterystykę aerożeli, ze zwróceniem uwagi na ich bardzo dobre właściwości izolacyjne w porównaniu z innymi materiałami. Wskazano zarówno zalety, jak i wady aerożeli. Przybliżono główne czynniki gorące występujące na stanowiskach pracy jak płomień, promieniowanie cieplne, rozpryski płynnego metalu, kontakt z gorącym przedmiotem i łuk elektryczny. Czynniki gorące sklasyfikowano jako czynniki szkodliwe wpływające na powstawanie mikroklimatu gorącego, na który narażeni są pracownicy instalacji przemysłowych, zajmujący się przerobem metali i stali, pracownicy odlewni szkła i ceramiki, pracownicy przemysłu spożywczego (piekarnie) oraz strażacy i spawacze. Omówiono przykłady zastosowania aerożeli w materiałach włókienniczych wykorzystywanych do ochrony przed czynnikami gorącymi. Dokonano analizy literatury pod kątem możliwości aplikacji aerożeli do włóknin i tkanin. Zamieszczono wybrane metody otrzymywania materiałów kompozytowych, najczęściej z udziałem aerożelu krzemionkowego o hydrofobowej powierzchni. Zwrócono uwagę na trwałość właściwości aerożelu po działaniu czynnika gorącego.
EN
The paper discusses the general characteristics of aerogels, with paying attention to very good insulation properties compared to other materials. Both the advantages and the disadvantages of aerogels were highlighted. The main heat factors occuring at workstations, such as a flame, thermal radiation, liquid metal splashes, contact with hot object and arcs, were approximated. Heat factors were classified as hazardous agents that affect the formation of hot microclimates, to which industrial workers, metal and steel workers, glass and ceramics workers, food service workers (bakeries) as well as firefighters and welders were exposed. Examples of aerogels used in textile materials for the protection against heat agents were discussed. Literature was analyzed for potential applications of aerogels to nonwovens and fabrics. Selected methods of obtaining composite materials, most commonly with silica aerogels with the hydrophobic surface. Attention was paid to the durability of aerogels properties after heat treatment with.
PL
W artykule omówiono nowoczesną izolację termiczną obecnie coraz częściej stosowaną w polskim budownictwie mieszkaniowym, dającą możliwość zdecydowanie szczelniejszej izolacji cieplnej niż tradycyjne materiały. Scharakteryzowano najbardziej dostępne na rynku materiały izolacyjne, takie jak aerożele i pianki poliuretanowe.
EN
In the article there has been presented modern thermal insulation used more and more often in Polish single-family housing, which gives the opportunity to insulate tighter with thermal insulation than traditional materials. The most accessible insulation materials on the market, such as aerogels and polyurethane foams, have been characterized.
4
Content available Photodegradation of organic compounds in water
EN
The application of photocatalytic processes for the decontamination treatment of polluted water has inspired very extensive studies. Titanium dioxide with its large band gap energy and appropriate redox potential was found as one of the most promising semiconductors for the photodegradation of pollutants in the water as well as in gas phase. The titania-silica aerogels obtained by a simple co-hydrolysis method was applied in the photodegradation of the model organic compound. Different ageing times and heat treatment temperatures were found to influence both the activity and the textural properties of the photocatalysts. The obtained aerogels are efficient photodegradation catalysts of methylene blue and allow a removal up to 98 and 78% of the model pollutant from 20 and 500 ppm solutions, respectively.
5
Content available remote SAXS from Particle and Disordered Systems
EN
SAXS studies were performed on different porous, disordered materials such as silica and zirconia aerogels, silica xerogels and carbonaceous materials (anthracite and shungite coals, coke, electrode material and activated carbon). These materials feature a variety of nanostructures. The relation between the profiles of the SAXS curves and the nanostructure of the materials was analysed. Fractal geometry proved to be very useful in this analysis. All types of fractality (mass, pore and surface fractality) were found in the materials studied. Porod plots appeared to be very sensitive to the structural details of the scattering objects.
PL
Badano efekt małokątowego rozpraszania promieni rentgenowskich (SAXS) od materiałów porowatych o złożonej, nieuporządkowanej strukturze. Badania wykonano dla krzemionkowych i cyrkonowych aerożeli, krzemionkowych kserożeli oraz różnych materiałów węglowych (węgle antracytowe i szungajskie, koksy, materiały elektrodowe, węgle aktywne). Analizowano zależność między profilem krzywych małokątowego rozpraszania a nanostrukturą badanych materiałów. Geometria fraktalna okazała się bardzo użyteczna w tej analizie. Stwierdzono dużą różnorodność nanostruktur badanych materiałów, którą można było opisać przy pomocy fraktali masowych, porowych i powierzchniowych. Stwierdzono również dużą czułość wykresów Poroda na zmiany w nanostrukturze materiałów rozpraszających.
6
Content available remote Aerożele organiczne i węglowe
EN
Aerogels are solid, organic (carbon) and inorganic porous materials of the exceptional properties such as very large specific surface area, low bulk density, low thermal and electric conductivity and superporous structure, obtained by sol-gel process. Numerous potential applications of aerogels as catalysts and catalyst supports, adsorbents, sensors, insulators, Cherenkov detectors and many others attract attention of many research laboratories. This review demonstrates selected routes to obtain organic and carbon aerogels. A special attention is given to the materials obtained by polycondensation of resorcinol with formaldehyde (RF aerogels). Some basis of the sol-gel processes as well as the influence of solvent on gelation time and shrinkage of the RF aerogels is presented. In the next part of the review the effect of the base preparation parameters i.e., resorcinol to formaldehyde (R/F) molar ratio and resorcinol concentration in solvent on textural properties on the final aerogel is discussed. Sol section of this paper is finished with information on the effect of catalyst concentration on particle size and shrinkage. Gel section contains informations about gelation time and aerogel properties dependence on it. Further sections are focused on drying step of the obtained gel, often found as the most important for the sake of final product characteristics. The reason why the drying step is so important is that solvent must be removed without destroying the gel matrix. Solvent removal methods are described with some principles of supercritical (low- and high-temperature) and freeze drying. Product obtained after supercritical or freeze drying step is called aerogel or cryogel respectively. Finally the effect of carbonization parameters on the carbon aerogels properties is described. Effect of other organic aerogel precursors such as cresol, phenol, furfural, melamine, PVC, MDI used in the sol-gel process of the preparation procedure of organic and carbon aerogels is described. Finally, selected technical applications of the carbon aerogels are presented.
EN
Nitrided silica aerogel was sintered at 1600 °C in vacuum or nitrogen atmosphere and the effect of densification was compared with that observed in silica aerogel. It has been shown that homogeneous oxynitride glasses containing 8.4–13 wt% can be obtained by densification of nitrided aerogels. The densification process of nitrided aerogels was simulated by computer modeling using classical molecular dynamics (MD) simulations. MD simulations have shown that densification process proceeds in a similar way as in the experiment. In addition, the simulations indicate that oxynitride glasses can be obtained by densification of Si–O–N system.
EN
Aerogel iron oxide (10, 30, 50 and 100 wt % of iron)-alumina based catalysts were prepared by: (I) co-gelation of alumina sol and complex iron compound followed by drying of the prepared gels under supercritical condition and (II) impregnation of the calcined alumina aerogel with isopropanol iron complex compound solution followed by drying of the obtained product under supercritical conditions and calcination. The influence of aerogel synthesis parameters on bulk density, total specific surface area and pore volume as well as activity of the obtained aerogel catalysts in Fischer-Tropsch synthesis was determined.
EN
In this paper, we firstly investigate the way the pores are created in silica gel during gelation. Then we show that the solid particle arrangement acts on the geometrical pore characteristics (pore volume and pore size distribution). According to the pore size value, the permeability of gels is quite low even if the value of the gel porosity exceeds 95%. Analogous properties can be extended to silica aerogels for which now the solvent is replaced by air. Consequently, and according to their low permeability, light weight aerogels exhibit very striking response to mechanical stresses. Here we report unusual experiments allowing us to estimate the mechanical properties of aerogels thanks to their low value of the average pore size. Moreover, one demonstrates that aerogels may be densified at room temperature using an external isostatic pressure. In that case, the pore size may be tailored with respect to the nature and the characteristics of the starting aerogel. The evolution of the textural properties such as the mean pore size and the specific surface area of these tailored aerogels is investigated as a function of isostatic pressure.
EN
The use of ammonium fluoride together with hydrochloric acid as a catalyst system for titania-silica mixed oxides markedly reduces the time of gelation and this has no detriomental effect on the porous texture of aerogels and their morphology in nanometer scales.
11
Content available remote The Effect of Drying on the Nanostructure of Sol-gel Solids
EN
It is demonstrated that different pore structures and morphologies in nanometer scales may be obtained using different strategies of drying of wet gels produced by the sol-gel method. The low temperature drying strategy (LTD), using supercritical carbon dioxide, gives similar nanopore structure as the high temperature supercritical drying (HTD) yet different morphology. Both methods lead to suppression of small mesopores. In the LTD method this effect can be minimized by replacement of the original interstitial liquid of alcogel by that exhibiting lower surface tension.
EN
Zirconia-sulfate aerogels obtained from the process with the molar hydrolysis ratio r=4 are more porous and active than those synthesized with r=2. Sulfate ions markedly hinder sintering of zirconia and structure consolidation during heat treatment and this process depends on their concentration. At a higher sulfate load (20 mol% of SO2-4 in Zro2) zirconia is amorphous upon calcinations at 773 K, irrespective of the water content in the synthesis, while at a lower load it can be crystalline. XRD analysis indicates that the crystalline phase of calcined zirconia-sulfate is cubic and not tetragonal, as observed in conventional zirconia, and reported in previous studies. Acid strength of ZrO2- SO2-4 system appears comparable to that of AlCl3/Al2O3, but lower than that of SbF5/Al2O3.
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