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PL
Pomimo pojawienia się wielu nowych rodzajów fotoogniw słonecznych, fotogniwa krzemowe nadal odgrywają istotną rolę. Wysoki współczynnik załamania krzemu sprawia, że ponad 34% fotonów promieniowania słonecznego z zakresu absorpcji krzemu ulega od niego odbiciu i nie generuje w nim ekscytonów. Odbicie światła można istotnie zmniejszyć teksturując powierzchnię krzemu, wytwarzając na niej strukturę antyrefleksyjną albo stosując jednocześnie oba rozwiazania. Praca dotyczy jedno- i dwuwarstwowych struktur antyrefleksyjnych wywtarzanych metodą zol-żel i techniką dip-coating na podłożach krzemowych. Dla struktury jednowarstwowej osiągnięto ważony współczynnik odbicia fotonów Rw 9%, natomiast dla struktury dwuwarstwowej osiągnięto Rw<4%. W pracy przedstawiano optymalizację teoretyczną struktur antyrefleksyjnych, technologię ich wytwarzania oraz wyniki badań eksperymentalnych. Osiągnięto doskonałą zgodność wyników analizy teoretycznej z wynikami eksperymentalnymi.
EN
Besides many different types of photovoltaic solar cells, silicon solar cells are still of significant importance. Bare silica’s high refraction index leads to greater than 34% reflection of solar light photones, within silica’s absorption band, from its surface without generating excitons. Reflection loss can be significantly reduced with the use of surface texturing and/or antireflective coatings. The most beneficial effect is achieved when combinig both, surface texturing and antireflective coatings. This work presents single and double layer Anti Reflective Structures (ARS’s) derived from sol-gel process for application in silicon photovoltaic cells. Weighted average reflection of a single layer ARS is Rw 9%, whereas double layer ARS provides weighted average reflection Rw<4%. In this work theoretical optimization of ARS’s, technological process of structure fabrication as well as experimental results are demonstrated. Theoretical data shows excellent correlation with experimental results.
EN
Titania (TiO2) based coatings are ceramic products with unique properties that make them widely applicable (e.g. in automotive industry, optoelectronics, chemical processing or medicine). Atmospheric plasma spray process enables to deposit TiO2 with addition of NiAl feedstock material which has an influence on coating cohesion and adhesion to substrate. However, the literature and technical notes give little information about parameters of spraying of TiO2-10 wt.% NiAl feedstock powders enables producing coating without nonuniformities including cracks and delamination form substrate. The aim of the work was to verify the parameters of plasma spraying by evaluation of the morphology and properties of manufactured the TiO2-10 wt.% NiAl coatings. Titania based coatings were deposited by means of atmospheric plasma sprayed on steel substrate using TiO2-10 wt.% NiAl feedstock powders. Morphology and microstructure were examined using light optical microscope (LOM) and scanning electron microscope (SEM). Coating chemical composition were analysed by means of SEM-EDS method. Coating surface topography and Knoop microhardness were determined. Porosity and thickness were evaluated by using quantities image analysis programme. Plasma spraying parameters used in our research allow to obtain uniform coating without cracks and delamination at coating-substrate interface. It acknowledges that uniformity of coating technological properties as well manufactured coatings can be put to wear tests, such as high temperature oxidation, corrosion, erosion or cavitation erosion resistance evaluation.
PL
Metodą miękkiego odwzorowania zsyntezowano mezoporowate węgle z wykorzystaniem rezorcynolu i formaldehydu jako prekursorów węglowych w obecności nanocząstek dwutlenku tytanu oraz trójblokowego kopolimeru EO101PO56EO101 jako miękkiej matrycy. Do tych węgli wprowadzono dwie różne ilości (0,05 mol i 0,10 mol) dwutlenku ty-tanu o wymiarach nanocząstek 25 nm. Ponieważ dodanie dwutlenku tytanu zmniejsza właściwości adsorpcyjne materiału kompozytowego, dlatego do mieszaniny reakcyjnej wprowadzono TEOS (tetraetoksysilan), którego dodatek nie zaburza formowania mezofazy, natomiast pozwala rozwinąć dodatkową porowatość po roztworzeniu cząstek krzemionkowych utworzonych z TEOS. Otrzymane materiały kompozytowe miały dużą powierzchnię właściwą ok. 1000 m2/g i dużą całkowitą objętość porów ok. 1 cm3/g, z ok. 75÷80% mezoporowatością w całkowitej objętości porów. Krzywe rozkładu objętości porów potwierdziły obecność mikroporów o wymiarach ok. 2,0÷2,1 nm i mezoporów o wymiarach ok. 6,0÷7,0 nm. Dobrze rozwinięta struktura porowata otrzymanych materiałów węglowych zawierających nanocząstki dwutlenku tytanu wskazuje, że materiały te mogą być z powodzeniem stosowane w procesach katalitycznych i adsorpcyjnych.
EN
The soft-templated mesoporous carbons were successfully synthesized in the presence of titania nanoparticles, with resorcinol and formaldehyde as carbon precursors and triblock copolymer EO101PO56EO101 as a soft template. Two different loadings of 25 nm titania nanoparticles (0.05 or 0.10 mol) were introduced into the carbon framework. Since titania addition lowers the adsorption volume of the composite materials, the reaction mixture was supplied with TEOS (tetraethyl orthosilicate). Its addition improves porosity by removing the TEOS-generated silica species, without disturbing mesophase formation. The final composite materials exhibit a high surface area (~1000 m2/g) and a large total pore volume (~1 cm3/g), where mesoporosity accounts for ~75-80% of the total pore volume. Pore size distribution curves confirmed the presence of micropores (~2.0-2.1 nm) and mesopores (~6.0-7.0 nm). The well-developed porous structure with embedded titania nanoparticles substantiates the applicability of these composite materials in many catalytic and adsorption processes.
4
Content available remote Eu-doped titania nanofibers by electrospinning
EN
Pure and europium-doped titania nanofibers were successfully fabricated by the electrospinning technique, using a single multielement titanium/europium source. Eu content was 5 mol.%. Microstructure was studied by means of scanning electron microscopy (SEM), thermal behaviour followed by thermogravimetric and differential thermal analysis (TG-DTA). Phase analysis was performed by means of X-ray diffraction (XRD) and high temperature X-ray diffraction analysis (HT-XRD) up to 1100°C. Luminescence measurements were performed using a laser excitation source at 395 nm. All electrospun materials consisted of randomly oriented nanofibers of a fairly uniform diameter. The average fiber size was 80 š 20 nm and 40 š 10 nm for Eu-doped and undoped TiO2 calcinated at 500°C, respectively. The presence of europium shifted toward higher values either the crystallization temperature of anatase and the anatase to rutile phase transition, the latter being accompanied by the formation of the EuTi2O7 phase. The doped samples show a strong luminescence of Eu3+ ions. The emission spectra are dominated by the 5D0›7F2 emission, suggesting a notable distorsion around the Eu3+ ions. The broadening of the bands points to the presence of a relevant inhomogeneous disorder around the Eu3+ sites.
PL
Nanowłókna tlenku tytanu(IV), domieszkowane europem i bez domieszkowania, wytworzono z powodzeniem metodą przędzenia elektrostatycznego, wykorzystując pojedyncze, wielopierwiastkowe źródło tytan/europ. Zawartość europu wynosiła 5 % mol. Mikrostrukturę badano za pomocą skaningowej mikroskopii elektronowej (SEM), zachowanie podczas ogrzewania śledzono za pomocą analizy termograwimetrycznej i termicznej analizy różnicowej (TG-DTA). Analizę fazową przeprowadzono za pomocą dyfrakcji promieniowania X (XRD) i wysokotemperaturowej analizy dyfrakcyjnej promieniowania X (HT-XRD), aż do 1100°C. Pomiary luminescencyjne przeprowadzono wykorzystując laserowe źródło wzbudzenia przy 395 nm. Wszystkie elektrostatycznie przędzone materiały składały się z przypadkowo zorientowanych nanowłókien o raczej wyrównanej średnicy. W przypadku włókien TiO2 kalcynowanych w 500°C średni rozmiar wynosił 80 š 20 nm i 40 š 10 nm, odpowiednio dla włókien domieszkowanych Eu i bez domieszkowania. Obecność europu przesunęła w stronę wyższych wartości zarówno temperaturę krystalizacji anatazu, jaki i temperaturę przemiany anatazu w rutyl, której to towarzyszyło tworzenie się fazy EuTi2O7. Próbki domieszkowane pokazały mocną luminescencję jonów Eu3+. Widma emisyjne są zdominowane przez emisję 5D0›7F2, co sugeruje znaczące odkształcenie wokół jonów Eu3+. Poszerzenie pasm wskazuje na obecność odpowiedniego, niejednorodnego nieuporządkowania wokół miejsc przebywania Eu3+.
5
Content available remote Humidity sensing properties of TiO2-Sb2O5 nanocomposite
EN
The syntheses of TiO2-Sb2O5 (AT) composites were investigated by the conventional precipitation method and their use as humidity sensors. 2-50 wt. % of Sb2O5 was added to TiO2 and pellets were made under the pressure of 616 MPa a room temperature of 30°C. The pellets were annealed at various temperatures (200, 500, 700 and 800 °C) for 3 h and the humidity sensing properties of each pellet were studied. A saturated aqueous solution of potassium sulphate was used as the humidifier and a saturated solution of potassium hydroxide was used as the dehumidifier. Upon increasing relative humidity (RH) inside the test chamber, the resistance of each pellet decreased for the RH range from 10% to 95%. Samples of the sensor material, differing in the percentage of the additive, were subject to SEM and XRD analysis. The minimum grain size, estimated from SEM, was 30 nm and the minimum crystallite size from XRD data was 20 nm. The material was found to have suitable properties to be applied as a resistive humidity sensor operating over the entire humidity range.
6
EN
Embedded-style hydroxyapatite-titania nanotube arrays were successfully prepared by anodic oxidation of titanium substrate and centrifugal filling hydroxyapatite precursor sol into hollow nanotubes. The morphology, microstructure and thermal stability of the samples were characterized by X-ray diffraction, environmental scanning electron microscopy, and energy dispersive X-ray analysis. The results show that the structure of titania nanotube arrays is stable at 500 °C or below, and the crystallized hydroxyapatite could be formed from hydroxyapatite precursor sol after calcining at 500 °C for 4 h. The optimum calcining temperature for this material is 500 °C. An obvious apatite layer formed on the surface of the embedded- style material after soaking in simulated body fluid for 5 days, indicating that the material possesses a good in vitro apatite forming ability on its surface.
EN
In the present work, the titania nanotube arrays was fabricated by anodizing titanium in NH4F/H2SO4 electrolyte. The crystal structure and the apatite-forming ability of the titania nanotube arrays were investigated. The samples were examined by ESEM, XRD and FT-IR. The results indicate that the crystal structure of the titania nanotube arrays occurred transformation from amorphous to anatase and rutile as the annealed temperature rised. The surface structure of the nanotube could enhance the bioactivity of titania. The bioactivity of titania nanotube arrays lies on its the crystal structure, ranked in following series: mixture of anatase and rutile structure > anatase > amorphous.
8
Content available remote Ekologiczne pigmenty nośnikowe na bazie łyszczyków.
PL
Minerały łyszczykowe (miki), dzięki specyficznym właściwościom wynikającym z budowy strukturalnej są szeroko wykorzystywane w zastosowaniach praktycznych: w kondensatorach, filtrach optycznych, izolatorach, adsorbentach, betonach i pigmentach tzw. nośnikowych. Pigmenty nośnikowe stanowią środki barwiące, zbudowane z podłoża - nośnika, najczęściej mineralnego, na który nakładane są warstwy nieorganiczne składające się z materiałów o różnych gęstościach optycznych. To powoduje występowanie zjawisk interferencji, które nadają pigmentom swoiste barwy, perłowy połysk i brylantowy wygląd. Swoiste zabarwienie i połysk pigmentów pochodzi: od wielowarstwowej struktury nieorganicznego nośnika i chromoforu i zależy od rodzaju, wzajemnego położenia tych warstw i ich grubości na bazowym krysztale łyszczyku. W obrębie tej struktury, wielokrotne odbicie padającego światła powoduje efekt barwny zmienny, odpowiednio do kąta obserwacji. Blaszkowy pokrój łyszczyków, równoległe ułożenie płatków pigmentu w medium wzmacnia efekt interferencji światła odbitego. Ważną cechą pigmentów jest ich nietoksyczność wynikająca z mineralnego ekologicznego podłoża i znikomej zawartości składników chromoforowych.
EN
The mica-type minerals due to their specific properties resulting from the structure have many practical applications in condensers, optical filters, electrical insulators, adsorbents, concrete and so-called carrier pigments. The carrier pigments are colorizing agents consisted of a support - carrier, mostly the mineral one, on which inorganic layers of various optical densities are applied. This structure leads to the phenomena of interference, which gives to pigments specific colour, a pearl shinning and diamond appearance. These pigments properties can be modified by mutual sequence of layers and their thickness on the mica carrier. Within this multilayer structure the multiple light reflection causes a variable colour effect depending on the observation angle. The plate-like mica structure and the parallel stacking of pigment flakes reinforces interference. An important property of pigments is their non-toxicity as a result of mineral ecological carrier and very small content of chromophores.
9
Content available remote Preparation and structure of stable dispersions of uniform TiO2 nanoparticles
EN
A set of narrow fractions of anatase TiO2 nanocrystals was isolated by the stepped coagulation of polydisperse hydrosols using strong acids as coagulators. The sols and gels prepared from the fractions were studied by LAXS, SAXS, turbidimetry, dynamic light scattering, and other methods. The shape of uniform titania nanocrystals in the fractions was determined to be plate-like; thickness of the platelets was 2-3 nm and their lateral sizes differed considerably in the fractions. A rapid partial coagulation and slow sol separation processes were observed after the addition of HCl and KCl to the sols. The rapid coagulation threshold was shown to depend essentially on nanoparticles size; the rate of the slow process depended strongly on the electrolyte concentration. Some stable concentrated dispersions of nanometer periodicity were formed from the narrow titania fractions.
EN
Purpose: A dopant concentration higher than the optimum may reduce the number of mobile oxygen ions because of defect association causing conductivity degredation. In this study, the effect of TiO2 addition on the microstructure and electrical conductivity of cubic zirconia was investigated. Design/methodology/approach: The cubic zirconia powders with 0-10 wt% TiO2 were prepared by a colloidal processing and pressureless sintering. The effect of TiO2 addition on the microstructure and electrical conductivity of cubic zirconia was investigated. Sintered specimens were characterized by XRD, SEM and impedance spectroscopy. Findings: The experimental results showed that when the Ti02 amount was less than 5 wt %, the specimens were entirely single cubic phase; further addition of TiO2 (5 wt% or more) destabilized cubic zirconia phase and caused the formation of tetragonal phase. Grain size measurements for undoped and TiO2 doped cubic zirconia specimens showed that grain size decreased with increasing TiO2 content. The electrical conductivity of TiO2 doped cubic zirconia decreased with increasing TiO2 content and increased with increasing test temperature. Research limitations/implications: The measurement of electrical conductivity is one of the important requirements for the electrolyte in solid oxide fuel cells. Generally, the ac impedance of an ionic conductor contains the contributions from grain, grain boundary and electrode-electrolyte interface at high, intermediate and low frequencies, respectively, which can be reflected in a complex plane by three successive arcs. Originality/value: Determination of the microstructural and electrical conductivity properties of cubic zirconia doped with various amount of titania.
EN
Y2O3-TiO2-ZrO2 catalysts, where the contribution of oxide components ranges from 0 to 100 mol %, have been studied for their catalytic performance in methanol hydrosulfurization. Their activity and selectivity have shown a strong dependence on acid-base properties which, in turn, changed with catalyst composition. High yttria content favors selectivity to methanethiol, while catalysts highly active for the formation of dimethylsulfide were those containing 8 mol % Y2O3. The latter composition, which boosted selectivity to (CH3)2S, has created favorable conditions for the generation of acid centers in chemically mixed oxides as concluded on the ground of ESR studies and acidity measurements.
12
EN
In the present work an influence of heat treatment temperature on the morphology of TiO2 sol-gel coatings is presented. The sol-gel TiO2 coatings were deposited onto Co-Cr-Mo alloy substrate. Scanning electron microscopy examination revealed very good quality of the coatings treated up to 600ºC temperature. For higher heat treatment temperature cracks and pores appeared. The pores size increased with increasing heat treatment temperature.
EN
Al2O3 or TiO2 pillared montmorillonites modified with Cu or Co have been studied as catalysts for NO reduction with ammonia. The type of a pillaring agent, introduced transition metal, and preparation conditions strongly influenced catalytic performance of obtained materials. Among the studied samples, the highest catalytic activity was measured for Ti-pillared montmorillonites modified with copper. All studied catalysts were characterized by high selectivity towards N2.
EN
Montmorillonites, pillared with Al2O3 or TiO2, were modified by introduction of transition metal (Cu or Co) by ion exchange method. Pillaring of clay with alumina caused significant increase of surface area and micropore volume due to increase of interlayer distance. Modification of montmorillonite with titania also resulted in increase of surface area and porosity, however pillared material was characterized by delaminated structure. Additionally, part of TiO2 was deposited on the sample surface in form of separate phase. Among the studied catalysts, titania pillared montmorillonites modified with copper have shown the highest activity in reduction of NO with ethylene in flue gas purifn.
EN
Oxidation of methane over titania shows two parallel oxidation pathways, i.e., partial oxidation to CO + H2 + H2O and full oxidation to CO2 +2H2O. Both reactions proceed via a Mars van Krevelen mechanism with first order kinetics for methane and oxygen and are retarded by water. A mechanism is suggested in which methane is homolitically dissociated over O-(s) sites and via the formation and decomposition of a formaldehyde precursor reacted to CO, H2 and H2O. In parallel, CO2 is obtained from decomposition of bicarbonate that is formed via further oxidation of dioxymethylene.
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