Wyniki wyszukiwania - Biblioteka Nauki

1

Effects of Metal Oxides on the Thermal Decomposition Kinetics and Mechanisms of HAN/PVA Based Propellants

100%

Hu S.-q. , Liu X.-l. , Liu L.-L. , Kang B. , Zhang Y.

Central European Journal of Energetic Materials

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2021

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tom Vol. 18, no. 3

322-338

EN

The thermal decomposition processes of HAN/PVA-based propellants have been investigated using a simultaneous thermogravimetric analysis (TGA) – differential scanning calorimetry (DSC), coupled with Fourier-Transform Infrared Spectroscopy (FTIR) and Mass Spectrometry (MS) system. The activation energy (Ea), pre-exponential factor A and reaction mechanism function f(α) of the decomposition processes have been determined by non-isothermal and Malek methods. The results showed that the decomposition process of an HAN/PVA sample occurs mainly in the temperature range 202.2~220.1 °C, with a mass loss, heat release and Ea of about 84.8%, 1474.18 and 88.76 kJ·mol–1, respectively. Of the seven metal oxides studied as catalysts, Al2O3, V2O5 and Fe2O3 have significant catalytic effects on an HAN/PVA-based propellant, in lowering the decomposition temperature, with Ea changing from 88.8 to 83.7, 85.6 and 113.6 kJ·mol–1, respectively. The f(α) of both HAN/PVA and HAN/PVA/Al2O3 samples can be expressed as f(α) = (1 – α)2, whereas f(α) = α or f(α) = α/2 fit well for the HAN/PVA/V2O5 and HAN/PVA/Fe2O3 samples.

2

Density functional simulation of metal oxides: Al2O3 and Fe3O4

100%

Łodziana Z.

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tom Vol. 8, No 4

561-572

EN

The study of the metal oxides is a rapidly developing area of research. Below a theoretical method based on the density functional theory, common in studying ceramics, is briefly presented. Application of the theory to the surface and the bulk properties of alumina and magnetite are presented. Relaxation mechanism of two different surfaces of alumina and the (100) surface of Fe3O4 are shown. The mutual stability of the ? and ? phases of Al2O3 is calculated.

3

Diagramy stężenia defektów punktowych dla tlenków Ni1-δO, Co1-δO, Mn1šδO i Cu2šδO

100%

Stokłosa A.

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2012

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tom T. 64, nr 1

4-10

PL

W pracy przedstawiono diagramy stężenia defektów punktowych dla tlenków metali Ni1-δO, Co1-δO, Mn1šδO i Cu2šδO, uwzględniając wszystkie defekty w podsieci kationowej. Obliczenia diagramów przeprowadzono nową metodą. Opiera się ona na zależności opisującej równoczesne tworzenie się i zanik poszczególnych defektów i wiąże standardowe entalpie swobodne tworzenia wakancji kationowych, defektów samoistnych jonowych i elektronowych oraz prężności tlenu przy której tlenek osiąga skład stechiometryczny. Obliczenia przeprowadzono wykorzystując doświadczalne wartości odstępstwa od stechiometrii i przewodnictwa elektrycznego uzyskane przez szereg autorów.

EN

Diagrams of point defects concentration in metal oxides Ni1-δO, Co1-δO, Mn1šδO and Cu2šδO, covering all the types of defects in the cation sublattice, are presented in this work. A new method was used for the calculation of the diagrams. It is based on an equation describing the formation and decay of determined quantities of point defects and derived standard Gibbs energy of formation of cation vacancies, intrinsic ionic and electronic defects, oxygen pressure at which the oxide attained stoichiometric composition. The calculations were performed using the results of studies of deviation from stoichiometry and electrical conductivity obtained by several authors.

4

Activated Carbon as a Support of Catalysts for the Removal of Nitrogen Oxides

88%

Białas A. , Szlendak J. , Czosnek C. , Motak M.

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tom Vol. 51, iss. 1

9--16

EN

Activated carbon was oxidised with concentrated nitric acid and impregnated with urea to form nitrogen-containing groups. Such a support was impregnated with cobalt, copper or silver nitrates to obtain catalysts for the selective catalytic reduction of nitrogen oxides with ammonia. Infrared spectra confirmed the formation of carboxylic and other organic oxygen-containing groups during oxidation. Nitrogen-containing species resulted from urea thermal decomposition. The metal-containing samples were hydrophilic. Cobalt and copper were present in the samples as small Co3O4 and CuO crystallites, while silver occurred in the form of large metallic crystallites, as seen from the X-ray diffraction patterns. Low temperature N2 sorption revealed that all samples were microporous solids, and the chemical and thermal treatment did not change their textural properties. The copper admixture caused the highest NO conversion, but worsened the selectivity and thermal stability of functionalised carbon support.

5

Direct synthesis as a new approach to heteropolynuclear complexes

88%

Kokozay V. N. , Shevchenko D. V.

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tom Vol. 23, No. 1

287--312

EN

The idea of direct synthesis of coordination compounds - use of elemental metals or their oxides as starting materials - has been developed into "Salt route", "Ammonium salt route" and "Direct template synthesis", methods to synthesize heteropolynuclear complexes. The advantages of this approach in obtaining heterobi-, heterotrimetallic and mixed-anion heteropolynuclear coordination compounds are shown taking complexes of transition metals (Cu, Ni, Co, Mn, Zn, Cd) with aminoalcohols and ethylenediamine ligand as an example. The results of the X-ray crystal structure analysis and magnetic properties of the most interesting complexes are presented.

6

Preparation and characterization of cobalt and copper oxide nanocrystals

88%

Moharram A. H.

Materials Science Poland

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2019

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tom Vol. 37, No. 3

347--352

EN

Copper oxide and cobalt oxide (Co3O4, CuO) nanocrystals (NCs) have been successfully prepared using microwave irradiation. The obtained powders of the nanocrystals (NCs) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric (TGA) analysis and Fourier-transform infrared spectroscopy. The obtained results confirm the presence of both nanooxides which have been produced during chemical precipitation using microwave irradiation. TEM micrographs have shown that the obtained nanocrystals are characterized by high dispersion and narrow size distribution. The results of X-ray diffraction confirmed those obtained from the transmission electron microscope. Optical absorption analysis indicated the direct band gap for both kinds of the nanocrystals.

7

Modyfikacja właściwości nieliniowych ceramiki warystorowej.

75%

Mielcarek W. , Nowak-Woźny D. , Prociów K. , Marycha J.

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2006

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tom Vol. 44, nr 18

21-24

PL

Typowe warystory ZnO produkuje się prasując mieszaninę ZnO z matą ilością (poniżej 3wt%) innych tlenków metali. Podczas procesu spiekania ziarna ZnO są otaczane izolującą warstwą międzyziarnową a na granicy ziaren tworzy się bariera potencjału odpowiedzialna za własności warystorowe. Warstwa międzyziarnową, której głównym składnikiem jest Bi2O3 ma tendencję do aglomeracji. Poprawę dystrybucji fazy międzyziarnowej, a tym samym własności warystorowych ceramiki ZnO otrzymano modyfikują Bi2O3 tlenkami innych metali. Biorąc jako kryterium wartość współczynnika nieliniowości w zakresie prądów 10-6 A - 10-2 A uszeregowanie stosowanych modyfikatorów Bi2Oi, od najgorszego do najlepszego, wyglądałoby następująco: Sb2O3-MnO-PbO-SrO- Co2O3.

EN

Varistor ceramics based on ZnO its non-linear current-voltage characteristics possesses due to small amount of other metal oxide and micro structure developed during sintering. Bi2O3 segregating at the ZnO grain boundaries relates directly to the value of the non-linearity coefficient a. Modifying Bi2O3 with other metal oxides appeared effective for imposing the better varistors property into the ZnO ceramics.

8

Effects of ZnO, CuO, Au, and TiO2 nanoparticles on Daphnia magna and early life stages of zebrafish danio rerio

51%

Liu J. , Fan D. , Wang L. , Shi L. , Ding J. , Chen Y. , Shen S.

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tom Vol. 40, nr 1

139--149

EN

The effects of four different kinds of nanoparticles (NPs), namely, CuO, ZnO, TiO2, and Au, of the sizes ranging from <20 nm to 50 nm on Daphnia magna, early life stage of zebrafish, and various enzymes have been investigated. The experimental results showed that the NPs inhibited both the body length and hatching rate of zebrafish larvae; the small nanoparticles exhibited more toxicity. In a 21 day chronic toxicity test, metal ions of higher concentrations significantly reduced the number of Daphnia magna offspring. Studies on enzyme activity showed that the NPs reduced the glutathione content and inhibited catalase and superoxide dismutase activities, resulting in shorter body length, lower hatching success, and lower reproduction of zebrafish larvae. Therefore, studies should focus more on the potential toxicity of smaller NPs.

9

Antimicrobial Characteristics of Pulsed Laser Deposited Metal Oxides on Polypropylene Hydroentangled Nonwovens for Medical Textiles

51%

Ramamurthy P. , Chellamani K. P. , Dhurai B. , ThankaRajan S. P. , Subramanian B. , Santhini E.

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tom Vol. 25, no. 2 (122)

112--119

EN

In this study, an attempt was made to investigate the antimicrobial activity on polypropylene (PP) hydroentangled nonwoven fabrics coated with transition metal oxides. After etching the nonwoven fabrics with RF plasma, nano-scale coatings of ZnO and CuO were done using the KrF excimer based pulsed laser deposition technique (PLD). Morphological and antimicrobial studies were carried out to elucidate the mechanism of antibiocidal behaviour of the coated fabrics. Results showed significant antibacterial activity of ZnO and CuO coated PP hydroentangled nonwovens with a better activity against gram positive S.aureus than gram negative E.coli. Inherently non-toxic, PP has excellent chemical resistance and the use of specialised PP fibres for hydroentangled nonwovens could offer scope in addition to metal oxide coatings; nano-scale biological materials such as enzymes and drugs could add specific functionality for their use as medical textiles.

PL

W pracy podjęto próbę zbadania aktywności przeciwdrobnoustrojowej polipropylenowych włóknin pokrytych tlenkami metali. Przeprowadzono badania morfologiczne i przeciw- drobnoustrojowe powlekanych włóknin. Wyniki wykazały znaczną aktywność antybakteryjną włóknin pokrytych ZnO i CuO, przy czym wyższą aktywność antybakteryjną zaobserwowano wobec bakterii Gram-dodatnich (Staphylococcus ureus), niż wobec Gram-ujemnych (Escherichia coli). Stwierdzono, że zastosowanie nietoksycznego polipropylenu, który charakteryzuje się bardzo dobrą odpornością chemiczną, do wytwarzania włóknin powlekanych tlenkami metali pozwala na otrzymanie funkcjonalnych produktów medycznych.

10

Badania nanocząstek metali/tlenków metali i ich przemian w roślinach przy wykorzystaniu technik spektrometrii mas

51%

Wojcieszek J.

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2022

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tom nr 4

26--31

PL

Opracowana metodologia analityczna, oparta na różnych technikach spektrometrii mas, dała możliwość śledzenia losów nanocząstek NPs od momentu rozpoczęcia hodowli po ich akumulację i transport w obrębie analizowanej rośliny.