FeGa 2 Se 4 single crystals belonging to the promising class of diluted magnetic semiconductors of the AB 2 X 4 type (A is Mn, Fе, Co, or Ni; B is Ga or In; and X is S, Sе, or Te) are investigated; this compound is currently used for designing solid-state magnetically controlled devices.Optically homogeneous bulk FeGa 2 Se 4 single crystals ~14 mm in
Проведен послойный анализ металлов и сплавов, а также изучена возможность напыления нанопленок, содержащих в своем составе олово, на различных видах поверхностей (металл, стекло) при воздействии сдвоенных лазерных импульсов на мишень в атмосфере воздуха. Эксперименты проводились с помощью лазерного двухимпульсного атомно-эмиссионного многоканального спектрометра LSS-1. Достоинствами импульсного лазерного напыления как метода получения кластеров, фракталов являются: универсальность по отношению к материалу, возможность исключения посторонних примесей, гибкость метода, возможность контроля образования пленочных структур. Выполненные спектроскопические исследования лазерной плазмы, образованной при воздействии двух последовательных импульсов на мишень, иллюстрируют развитие методов получения нанокластеров различных химических элементов. Данным способом можно получать нанопленки не только чистых металлов, но и композиционных сплавов. Показана возможность напыления нанопленок для создания газочувствительных сенсоров. A layer-by-layer analysis of metals and alloys has been carried out, and the possibility of deposition of nanofilms containing tin in their composition on various types of surfaces (metal, glass) under the action of dual laser pulses on a target in an air atmosphere has been studied. The experiments were carried out using the laser two-pulse multichannel atomic emission spectrometer LSS-1. The advantages of the pulsed laser deposition as a method for producing clusters and fractals are: versatility in relation to the material, the ability to exclude impurities, the flexibility of the method, and the ability of controlling the formation of film structures. The performed spectroscopic studies of the laser plasma formed by the action of two successive pulses on a target illustrate the development of methods for obtaining nanoclusters of various chemical elements. This method can be used to obtain nanofilms of not only pure metals, but also composite alloys. The possibility of obtaining nanofilms for creating gas-sensitive sensors is shown.
Spectroscopic studies of the surface of a porous solid containing micro amounts of uranyl nitrate hexahydrate using irradiation by two sequential pulses with pulse-to-pulse intervals in the range 4-12 μs have shown that laser chemical synthesis of uranium and uranium oxide nanoclusters within the interior of a porous solid is a promising technique, with the possibility at the same time of determining the uranium content with good sensitivity (~10 -10 g). Introduction. Research in the field of nanoclusters and nanosystems provides a basis for designing new 21stCentury technology: nanotechnology. Thus, for example, cluster catalysts make it possible to develop new directions in control of conversions and selectivity of catalytic reactions as a result of the cluster size and its interaction with the matrix [1]. Uranium oxides are quite attractive for catalysis due to the possibility of varying their stoichiometry over a broad range and varying the valence state of uranium depending on external conditions (temperature, amount of oxygen). In [2,3], it is shown that catalysts based on uranium oxides are active in reactions of exhaustive oxidation of hydrocarbons at low temperatures, and are resistant to the action of such catalytic poisons as sulfur, water, and halogens. We know that uranium oxide catalysts can also be used in partial oxidation processes [4,5]. Mixed Ni-U oxide systems are efficient in processes of conversion of methane to synthesis gas [1,6]. Uranium catalysts in the original state can contain compounds of the 3-, 4-, 5-, or 6-valent metal. This provides more diversity in the composition of active sites than when using derivatives of lanthanides, which generally have a trivalent state [7].
Spectroscopic studies of the surface laser plasma formed by the action of sequential high-power double laser pulses close to a porous body containing microquantities of ammonium polyuranates showed that the intensities of uranium spectral lines that are proportional to the elemental content in the plasma depend significantly on the physicochemical properties of the uranium compounds. The line intensities increase by several times with almost the same increase in the formation enthalpy of the compounds.Introduction. Uranium oxides are key intermediates in the processing of natural uranium, spent nuclear fuel, and weapons-grade uranium in nuclear power plant fuel into uranium fluorides and metallic uranium. Uranium oxides are highly attractive for catalysis because of the ability to vary their stoichiometry over wide ranges and to change the uranium valence state depending on the temperature and amount of oxygen. It was shown [1-3] that catalysts based on uranium oxides are active for extensive oxidation of hydrocarbons at low temperatures and are resistant to the action of catalyst poisons such as sulfur, water, and halogens. It is known that uranium-oxide catalysts can be used for partial oxidation [4,5]. Mixed Ni-U oxides are effective in the conversion of methane to synthesis gas [1,6].One of the principal current industrial methods for manufacturing uranium oxides is chemical denitration of uranyl nitrate using ammonium hydroxide. Thermal dissociation of ammonium uranates is an exceedingly complex process and, despite volumes of data on the process, there are still not generally accepted principles that describe it. Therefore, the study of thermal decomposition of ammonium polyuranates formed upon precipitation of uranium from uranyl-nitrate solutions by ammonium hydroxide has important theoretical and practical value [7][8][9]. This process has been used in industry for over 60 years. However, much published data on the preparation and properties do not agree with each other, despite the large number of investigations [10][11][12][13][14][15][16][17][18][19][20]. This indicates firstly that this system is complicated. However, it is impractical to replace it by a more tenable version, for example, alkali-metal uranates. Uranium oxides are preferentially prepared as ammonium uranates because the only non-volatile component in them is uranium. All other uranates give mixed oxides of uranium and alkali metals.The advantages of ammonium diuranate as a precipitate include the simplicity of producing a uranium-containing solid by ammonia precipitation of practically any solution; the completeness of converting uranium into a precipitate; the comparatively low cost and availability of ammonia, the ability to regenerate ammonia by calcining ammonium diuranate; and the production of mother liquors of uranium [7]. Ammonium diuranate can be converted to either uranium trioxide or mixed-valence uranium oxide depending on the calcination temperature. The composition of mixed-valence uranium oxide varies depending on the c...
Проведено исследование процессов образования нанопорошков AlO и AlN при воздействии сдвоенных лазерных импульсов энергией 52 мДж и между импульсным интервалом 10 мкс на алюминиевую мишень, помещенную в закрытую стеклянную прямоугольную кювету, в зависимости от количества импульсов. Установлено, что наибольшая интенсивность полос субоксида AlO и молекул AlN наблюдается при 40 - 50 последовательных сдвоенных импульсов в серии. Размер первичных частиц, оцененный с помощью электронной микроскопии высокого разрешения, преимущественно составил 30 - 40 нм, частицы собраны в агломераты. Методом комбинационного рассеяния показана возможность получения активных форм оксидов алюминия и продуктов взаимодействия их с кислородом и азотом воздуха в лазерной плазме, осаждаемых на стеклянную поверхность. A study of the AlO and AlN nanopowder formation under the influence of twin laser pulses with an energy of 52 mJ and between the pulse interval of 10 microseconds on an aluminum target placed in a closed glass rectangular box, depending on the number of pulses. It was found that the highest intensity of the bands of AlO suboxide and AlN molecules is observed at 40 - 50 consecutive double pulses in a series. The size of the primary particles estimated using the high-resolution electron microscopy was mainly 30 - 40 nm, the particles were collected in agglomerates. The possibility of obtaining active forms of aluminum oxides and products of their interaction with oxygen and air nitrogen in a laser plasma deposited on a glass surface is shown by RAMAN methods.
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