Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl
Ograniczanie wyników
Czasopisma help
Lata help
Autorzy help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 83

Liczba wyników na stronie
first rewind previous Strona / 5 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  nanosilica
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 5 next fast forward last
EN
More and more attention is paid nowadays to the quality and durability of the applied cement slurries. Apart from the appropriate rheological, technological and strength parameters, the slurry should be resistant to the strongly mineralized reservoir waters. Appropriate phase composition of cement slurries, especially high CSH content is responsible for the change of pore structure in the cement slurry; the number of fine gel pores which are not available for the fluid increases and the number of capillary pores responsible for the transport of corrosive factors inside the cement slurry decreases.The use of nanosilica as an additive improving the properties of cement slurries has recently gained popularity. Bearing in mind these properties of nSiO2, there were conducted laboratory experiments on the use of organic nanosilica for cement slurries based on Portland cement CEM I 52.5 R.
EN
The present study investigated the effect of the surface functional groups of nanosilica on the interfacial, crystallization, and thermal stability of polyamide 6/SiO2 (PA6/SiO2) nanocomposite, in which nanosilica was modified in situ with both 3-triethoxysilylpropylamine and 3-methacryloxypropyltrimethoxy silane¬ (KH-550 and KH-570). The FTIR analysis results showed the chemical bonding action between the reacting amino groups of nanosilica and end carboxyl groups of polyamide 6 enhanced with increasing the ratio of KH-550 and KH-570. The XRD spectrum indicated that the crystal structure of PA6/SiO2 nanocomposites tended to form α crystal type that was beneficial to an improvement of mechanical properties, and which was in agreement with the results of mechanical strength measurements. It was also found that crystallization temperature and crystallization rate of PA6/SiO2 nanocomposites were lower than that of neat polyamide 6.
EN
Nanocomposite materials can be used in many application. In this study polymer–based nanocomposites modified with carbon nanotubes (CNTs) and ceramic silica nanoparticles (nSiO2) were used. Size and shape of nanoparticles were observed using transmission electron microscope (TEM). It was shown that, this parameter changes during mixing of nanoparticles with solvent or polymer solution. Dispersion of nanoparticles depends on their chemical composition. The CNTs are more compatible with polymer (PLDL) than nSiO2. Nanoparticles influence rheological parameters of the polymer solution (increase of viscosity). Distribution of nanoparticles within the polymer matrix was determined using DLS method. Nanocomposites in the form of thin foils were used for mechanical tests which show that small amount of nanoparticles increases tensile strength (Rm) and Young’s modulus (E) of the material. The biological properties of the polymer-based nanocomposite materials like viability and proliferation were measured using osteoblast-like human cells MG63. Results of these investigations show that both types of the nanocomposites are suitable for promoting bone tissue for faster regeneration process.
EN
Applicability of the sol-gel method to fabricate polymer-silica composites has been briefly reviewed. The sol-gel method has been applied for synthesis of nanosilica in mineral and naphthenic oils and also in latexes of diene copolymers. A new silane precursor of nanosilica was prepared by transesterification of tetraethoxysilane with n-decyl alcohol and (aminopropyl)trimethoxysilane, in the presence of an emulsifier and a stabilizer. Transparent sols of nanosilica in oils were obtained as the main product, accompanied by few % of dispersions of SiO2. Microscope and AFM studies confirmed the presence of particles of nanometric size. The studies are continued in order to optimize reaction conditions and minimize the size of SiO2 particles. Nanosilica sols are applied for modification of properties of elastomers and other polymers. New hybrid modifiers of general formula X(Me2SiO)4R have been prepared. Their chemical structures were confirmed by spectroscopic methods: FT-IR and NMR (1H, 29Si-). These New products have been applied for synthesis of modified silica nanoparticles in elastomers matrices (in situ).
EN
The paper presents the results of physical and mechanical tests of cement composites that include small amounts of nanosilica, as well as systems of nanosilica with less commonly used iron and nickel nanooxides. In the work, a physicochemical analysis of the nanooxides was performed to compare their morphological and structural properties, to determine their temperature stability and to assess their behavior in the cement matrix environment. Particle distribution analysis indicated a tendency for nanooxide particles to aggregate and agglomerate, with nickel nanooxide showing the highest degree of homogeneity. For iron nanooxide, the largest size scatter and the largest particle aggregates were observed. As expected, the nanosilica displayed the highest specific surface area, whereas, both nickel and iron nanooxide exhibited higher electrokinetic and temperature stability compared to nanosilica, which guarantees their durability in high pH cement matrixes. Cement composites with oxide additions had slightly lower density and comparable absorbability after 28 days of curing, as compared to pure mortar. In the case of nanosilica, after 7 days of curing, a significant increase in compressive strength was observed in comparison with pure mortar, while the strengths were slightly lower at a later time. Synergistic application of nanosilica with nickel or iron nanooxide resulted in significant increases in strength after 28 and 90 days of curing, where the effect of nanosilica alone was not as spectacular.
EN
The rapid civilizational progress forces us care more about the natural environment. A huge population produces immeasurable amounts of waste, including vast amounts of waste glass. Therefore, the recycling of waste glass is a challenge that has to be taken on to preserve the balance in our environment. The development of the nanomaterial technology, allowed us to obtain the cement mortars with similar or even enhanced parameters compared to the ordinary ones. These two aspects have become an inspiration for the research, in which waste glass was used along with modern nanomaterial technology. Three groups of mortars, where the natural aggregate was replaced by waste glass (100% – WG, 50% – RWG, 0% – R) were prepared. Each group of mortars was modified with nanosilica admixture of 0%, 1% and 3% (of cement mass). Superplasticizer was incorporated in order to improve the workability of mortars. The workability and density of fresh mortar were determined. The specimens were cured for 7, 28 and 365 days, after which their freeze-thaw resistance and abrasion resistance were evaluated. The study showed that the waste glass aggregate might find application in the construction industry as the mortars produced with the waste glass and nanosilica exhibited improved mechanical properties. The analysis of the results of this experimental research allowed for determining the influence of grain shape of waste glass aggregate on the properties of cement mortar.
EN
The present study investigated the effect of the surface functional groups of nanosilica on the interfacial, crystallization, and thermal stability of polyamide 6/SiO2 (PA6/SiO2) nanocomposite, in which nanosilica was modified in situ with both 3-triethoxysilylpropylamine and 3-methacryloxypropyltrimethoxy silane¬ (KH-550 and KH-570). The FTIR analysis results showed the chemical bonding action between the reacting amino groups of nanosilica and end carboxyl groups of polyamide 6 enhanced with increasing the ratio of KH-550 and KH-570. The XRD spectrum indicated that the crystal structure of PA6/SiO2 nanocomposites tended to form α crystal type that was beneficial to an improvement of mechanical properties, and which was in agreement with the results of mechanical strength measurements. It was also found that crystallization temperature and crystallization rate of PA6/SiO2 nanocomposites were lower than that of neat polyamide 6.
EN
The photocatalytic process of phenol oxidation and Cr(VI) reduction in the presence of nano-silica modified titania was carried out. The activity of composites was tested using two different light sources. The photocatalysts with 10% of nanosilica showed the highest activity. The calcination temperature (200–800 °C) significantly determined the sensitivity of the obtained materials to the light source used. Photocatalysts alternately adsorbed and desorbed Cr(VI) ions from the reaction mixture during irradiation. In the one-component mixture, complete oxidation of phenol was observed using material calcined at 650 °C, after 3 h of UV-VIS irradiation. In the reaction mixture of Cr(VI) and phenol, the highest activity was demonstrated by photocatalyst calcined at 300 °C. The concentration of phenol decreased in proportion to the decrease of chromium ions. The obtained titania-silica composites showed oxidizing properties towards phenol and reductive properties toward Cr(VI) ions.
9
80%
EN
The agglomeration trend of nanosilica particles was found to significantly affect the properties of cement-based materials. The influence of nanosilica suspension on the fluidity, setting time, and compressive strength of cement-based grouts were studied. The hardened pastes were characterized by thermogravimetric (TG) analysis and scanning electron microscopy (SEM). The results showed that the fluidity of cement-based grouts with nanosilica suspension had obviously improved. The setting time was obviously decreased, compared with the reference sample. The compressive strengths for 1 day, 3 days, and 28 days were 12.8%, 14.3%, and 10.1% higher than that of the reference group, respectively. This paper may provide a novel route to improve the mechanical properties of cement-based materials without affecting their workability.
EN
The possibility of producing protective coatings by the sol-gel process is discussed. Metaloorganic complexes open new possibilities for the syntheses of ceramic materials. The most important applications of Si alkoxides for the synthesis of inorganic-inorganic composites are presented. The SiO2 protective coatings on surgical stainless steel 316L have been synthesized by the sol-gel techniques. The multi-layer coatings were deposited by the dip method using sols containing appropriate molar ratios of the prekursor (tetraethoxysilan), anhydrous ethanol, nitric acid and acetic acid. Nanosilica with the surfactant didodecyldimethyl- ammonium bromide were added to the sols applied. Coatings were annealed from 200 st.C to 300 st.C. The electrochemical characterization by dc measurements of the protective coatings in Ringer's solutions is reported. The coatings performance has been compared using polarization characteristics. Two arbitrarily chosen values were taken: the current density at -750 mV and the potential corresponding to the current density of 2 A/cm2. The coatings were chosen and ranked with regard to additional parameters: the polarization resistance and the through-coating porosity. It has been established that the way of applying of the coatings had an influence on the protective properties. The best protective properties have the coatings obtained from sols consisting of three SiO2 layers with nanosilica and three SiO2 layers without nanosilica. The positive effect of nanosilica on the protective properties of the coatings was determinated. Small changes in the preparation process can often have disproportionate large effects on the quality of the coatings.
PL
W pracy przedstawiono wyniki badań wpływu napełniaczy proszkowych na procesy uwalniania fluoru z kompozytowych materiałów na stałe wypełnienia stomatologiczne. Oceniano wpływ fluorku strontu oraz nanokrzemionki na ilość uwalnianego fluoru. Emisję jonów fluorkowych analizowano przy pomocy metody potencjometrii bezpośredniej z zastosowaniem fluorkowej elektrody jonoselektywnej. Badano także chropowatość powierzchni oraz mikrotwardość analizowanych kompozytów.
EN
This work presents results of research of the influence two filler powders on fluorine release from composite materials for dental fillings. The influence of fluoride strontium and nanosilica on fluorine release was investigated. Fluorine release was measured using direct potentiometry method with fluoride electrode. The surface roughness and microhardness were also analyzed.
EN
The requirements for the performance of 2-pack polyurethane clear coatings are increasing constantly: In many high performance applications the use of nanosized silica particles is an answer to these demands.2-pack polyurethane coatings can be formulated by using polyols with various chain length and oh-values and different isocyanate crosslinker to create different mechanical properties.by adding nanosilica composites coating properties like scratch and abrasion resistance can be improved dramatically. A correlation between nanosized silica particles and the content was found without any influence to gloss and transparency.new coating systems can be developed by incorporating nanosilica technology into traditional binders for 2-pack polyurethane coatings. This is a reliable solution to formulate resistant and clear coatings.
13
Content available remote Wpływ nanokrzemionki na strukturę i właściwości poliolefin
60%
PL
Zbadano wpływ zawartości, wielkości cząstek nanokrzemionki i rodzaju wprowadzonych grup funkcyjnych oraz kompatybilizatora na strukturę, właściwości mechaniczne i barierowe kompozytów poliolefin wytworzonych metodą wytłaczania dwuślimakowego współbieżnego.
EN
The effects of silica's content, size and functionality, as well as compatibilizer on the structure, mechanical and barrier properties of polyolefines composites obtained by my melt compounding was investigated.
15
Content available Nowoczesne materiały do szybkiego prototypowania
60%
PL
Niektóre spośród projektów naukowych wymagają nieszablonowego podejścia do problemu oraz nietypowego sprzętu laboratoryjnego. Stworzenie nowych prototypowych urządzeń coraz częściej staje się warunkiem koniecznym dla przeprowadzenia badań. Dzięki szybkiemu rozwojowi technologii projektowania i druku 3D możliwe jest rozbudowanie zaplecza technologicznego placówek badawczych. Podczas prac skupiono się na skonstruowaniu komory ciśnieniowej, która ma wiele zastosowań. Wspomniana komora (Rys. 1) została zaprojektowana przy pomocy oprogramowania CAD Autodesk Inventor Professional 2015. Komora składa się jedynie z kilku elementów, co ułatwia jej późniejsze złożenie przy pomocy prostych powszechnie dostępnych narzędzi. Komora ciśnieniowa jest zbudowana z poliwęglanu zmodyfikowanego różnymi dodatkami zmieniającymi właściwości filamentu. Jedną z możliwych modyfikacji jest dodatek nanokrzemionki, który posiada właściwości antybakteryjne. Umożliwia to wykonanie komory próżniowej wykorzystywanej np.: do sterylizacji narzędzi chirurgicznych. Wszystkie próbki użyte w tym projekcie przeszły testy szczelności wykonane metodą PALS (z ang. Positron Annihilation Lifetime Spectroscopy).
EN
Some of the scientific projects require outside the box approach to the problem and non-standard laboratory equipment. Creating a new prototype devices are increasingly becoming a prerequisite to conduct the research. Thanks to the rapid development of technology, design and 3D printing, make it possible to develop the technological facilities of research institutes. During the studies the main focus was on building the pressure chamber, which has various applications. Mentioned pressure chamber (Figure 1) was designed by the use of Autodesk Inventor Professional 2015 CAD software. The chamber consists of only few elements which facilitates the future assembling by using simple and commonly available tools. The pressure chamber is made of polycarbonate modified by various additives which change properties of filament. One of the possible modifications is nanosilicon additive which have antibacterial properties. It allows to use vacuum chamber for sterilization e.g. surgical instruments. All samples used in this project passed the tightness test associated with Positron Annihilation Lifetime Spectroscopy (PALS).
PL
W ostatnich latach szczególną uwagę poświęca się cząstkom o wymiarach nano, które mają szeroki zakres zastosowań w przemyśle spożywczym, medycznym, ceramicznym i innych. Jedną z takich nanocząstek jest nanokrzemionka, której synteza biometodami zyskuje coraz większe zainteresowanie ze względu na ich ekonomiczność oraz neutralność wobec środowiska. W niniejszej publikacji przedstawiono formy występowania nanokrzemionki wykorzystywane podczas biokonwersji roślin, które są bogate w ten cenny składnik. Zaprezentowano również mechanizm jej biopozyskiwania w porównaniu z metodami chemicznymi i fizycznymi.
EN
In recent years special attention has been paid to nanoscale particles that have a wide range of applications in the food, medical, ceramic and other industries. Such a nanoparticle is nanosilica, which biosynthesis is gaining increasing interest due to its economics and environmental neutrality. This publication presents the forms of nanosilica used during the bioconversion of plants that are rich in this valuable product. The bioacquisition mechanism is also presented in comparison with chemical and physical methods.
EN
Nanosilica as a commercial product dedicated to construction remains a relatively expensive chemical admixture for concrete and cement mortars. Economic considerations are a major barrier to the industrial use of nanosilica in the building materials industry. With respect to nanosilica, the following have been confirmed: accelerating the effect of C3S hydration, accelerated C-S-H gel formation, modification of the mixture viscosity, improvement of cement matrix tightness, also at high temperature. The efficiency of nanosilica depends on its even distribution in the composite, therefore disagglomeration is necessary for the proper design of mortar or concrete. The article presents the results of tests on cement mortars modified with different amounts of colloidal nanosilica. It is an nano-SiO2 admixture in the form of an aqueous dispersion containing up to 50% pure nanosilica, which is produced on an industrial scale as an admixture for concrete and cement mortars. Dispersions of nanosilica in composite using ultrasound were used. The possibilities of using nanosilica as an admixture improving the early strength of cement composites were pointed out.
PL
Nanokrzemionka jako produkt komercyjny dedykowany dla budownictwa pozostaje nadal stosunkowo drogą domieszką chemiczną do betonów i zapraw cementowych. Względy ekonomiczne są główną barierą w przemysłowym zastosowaniu nanokrzemionki w przemyśle materiałów budowlanych. W odniesieniu do nanokrzemionki potwierdzono: przyspieszające działanie na hydratację C3S, przyspieszone tworzenia się żelu C-S-H, modyfikację lepkości mieszanki, poprawę szczelności matrycy cementowej, także w warunkach wysokiej temperatury. Wydajność nanokrzemionki zależy od jej równomiernego rozmieszczenia w kompozycie, dlatego dezaglomeracja jest niezbędna do prawidłowego zaprojektowania zaprawy lub betonu. W artykule przedstawiono wyniki badań zapraw cementowych modyfikowanych różną ilością nanokrzemionki koloidalnej. Jest to domieszka nano-SiO2 w postaci wodnej dyspersji zawierającej do 50% czystej nanokrzemionki, która produkowana jest na skalę przemysłową jako domieszka do betonów i zapraw cementowych. W badaniach zastosowano dyspersję nanokrzemionki w kompozycie z wykorzystaniem ultradźwięków. Wskazano na możliwości zastosowania nanokrzemionki jako domieszki poprawiającej wczesną wytrzymałość kompozytów cementowych.
EN
At world-wide production over 30 billion of tones, concrete is one of the most popular construction materials, at the same time the amount of carbon dioxide derived from cement industry is estimated to 5-7% of world annual CO2 emissions. By enhancing concrete’s properties, the application of nanoparticles to cement composites production could diminish the carbon footprint of the industry. Nanosilica is researched with an aim to enhance mechanical properties and durability of concrete. The aim of this study is to assess the influence of nano-silica on compressive strength, density and water absorption of cement paste with an addition of two plasticizers with different chemical base. The consistency of fresh cement paste with plasticizers was measured. The dosage of nano-silica was 1%, 2% or 3% of binder mass. The addition of nano-silica severely reduced the consistency of cement paste. The enhancement of early compressive strength was observable.
EN
In this paper, commercial nano zinc oxide (nano-ZnO) and nanosilica (nano-SiO2) were employed as fillers to improve the properties of abrasion and UV resistance in a waterborne polyurethane coating. Various dispersion techniques were studied to prevent the aggregation of primary nanoparticles in the polyol mixture. The nanoparticles dispersion was studied by OM and SEM. Polyols containing nanoparticles were mixed with the suitable isocyanate amount to obtain a polyurethane water based coatings. The resultant polyurethane nanocomposite was characterized according to abrasion resistance (ASTM D 4060) and QUV resistance (ASTM D 4587). Abrasion resistance was improved adding different percentages of nanosilica nanoparticles but no improvement was obtained regarding UV resistance. Nano zinc oxide nanoparticles contributed to enhance neither abrasion nor UV resistance, maybe due to catalytic reaction of nano-ZnO over PUR matrix.
20
Content available remote Antibacterial Fibers Containing Nanosilica with Immobilized Silver Nanoparticles
60%
EN
The main aim of the presented research was to obtain antibacterial fibers containing nanosilica with immobilized silver nanoparticles. The nanomodifier in an amount of 250 ppm, 500 ppm, 1,000 ppm, and 2,000 ppm were introduced into the cellulose fiber matrix during the cellulose dissolution process. In order to assess the influence of the nanomodifier's amount in the fiber on the antibacterial activity of modified fiber, a quantitative test of the antibacterial activity of the fibers was performed. The basic parameters of modified fibers, such as the mechanical and hygroscopic, were estimated. The size and shape of the nanomodifier in the selected fibers, as well as microanalysis of the polymer matrix, were examined. The investigations were conducted by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy Dispersive Spectrometry (EDS). The obtained results allowed the selection of optimal fibers with strong antibacterial properties that can be potentially used for personal protection or medical purposes.
first rewind previous Strona / 5 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.