Wyniki 1-10 spośród 17 dla zapytania: authorDesc:"MAREK NOWAK"

Nanoscale Ti-based hydrogen storage materials

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The major problem in a future world with renewable energies and less environmental pollution is energy storage. Novel nanostructured materials may successfully solve this problem [1÷6]. Term nanostructured is being used to denote different materials prepared by two different processes: i) by mechanical alloying (MA) or a high energy ball milling (HEBM) and ii) by the gas condensation of vapour in a partial vacuum. Among the different types of hydrogen forming compounds, Ti-based alloys are among the most promising materials for the electrode materials in nickel-metal hydride batteries [2]. Titanium and iron form two stable intermetallic compounds, TiFe and TiFe2. TiFe2 does not absorb hydrogen. The TiFe alloy, which crystallizes in the cubic CsCl-type structure, is cheaper and lighter than the LaNi5-type alloys and can absorb up to 2 H/f.u. at room temperature. To improve the activation of this microcrystalline alloy several approaches have been adopted. Recently, we have shown that the discharge capacity of TiFe increased from 0 to 64 mA·h·g-1 after high-energy ball-milling [2]. A fine nanostructure is known to improve greatly the kinetics and activation of hydrogen storage alloys, when compared with their conventional microcrystalline counterparts. On the other hand, the substitution of Fe by some amount of transition metals may improve the activation property of TiFe [6, 7]. As the continuation of our studies, in this paper the structural, electronic and electrochemical properties of nanocrystalline TiFe-based alloys were investigated, where the alloying elements of 3d transition metals, Ni, Mo, Cr and Co, are substituted for Fe atoms. The materials produced by MA and subsequent annealing with 10 wt. % addition of Ni powder, were subjected to electrochemical measurements as working electrodes. Additionally, the cyclic behavior of the some nanostructured Ti-based alloy anodes was examined in a sealed HB 116/054 ce[...]

Nanocomposite LaNi5/Mg2Ni- and ZrV2/Mg2Ni-type hydrides

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Nanostructured metal hydrides are a new class of materials in which outstanding hydrogen sorption may be obtained by proper engineering of the microstructure and surface [1]. These materials will play an important role in the field of hydrogen storage. For the vehicle application, depending on the temperature of hydrogen absorption/ desorption below or above 150°C, the alloy hydrides can be distinguished in high and low temperature materials. The principal disadvantages of alloy hydrides, apart from the cost, are the low hydrogen content at low temperature (e.g. La-based alloys) and the difficulty of reducing desorption temperature and pressure of alloy hydrides having high hydrogen storage capacity and fast rated (e.g. Mg-based materials). To solve the above mentioned problems, the use of composite materials, starting from La-based alloys and of catalyzed metal (C, Ni, Pd) or Mg-based alloy hydrides has been proposed [1, 2]. An important process on the surface of hydrogenated material is the splitting of the hydrogen molecule into atoms. Many clean transition metal surfaces have the capability of dissociating hydrogen, but lose this property upon oxidation. It is well known, that the oxidation process causes the sealing of the surface to H2 in metals and compounds such as Nb, V, Ta, FeTi, and others [3]. On the other hand, in a surface layer of LaNi5, La segregates and Ni forms ferromagnetic precipitation’s [3, 4]. The lanthanum atoms binds the impurities as oxide or hydroxide and keeps the Ni metallic, which then is able to split the hydrogen molecule. Therefore, the surface segregation process of lanthanum in the presence of O2 or H2O explained the excellent hydrogenation properties of LaNi5 [4, 5]. The nanocrystalline metal hydrides offer a breakthrough in prospects for practical applications. Their excellent properties (significantly exceeding traditional hydrides) are a result of the combined engineering of many fa[...]

Statistical analysis of the amount of the power generated by the wind power plant, according to weather conditions DOI:10.15199/48.2017.10.40

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The term atmospheric conditions is generally understood as weather phenomena occurring in a given area. If the observation is done over many years (at least 30 years) - the results of that observation can be generalized, and defined as the characteristic climate for given area. Atmospheric conditions considered in the analysis were: air temperature, humidity, atmospheric pressure, wind speed and direction, cloud cover and precipitation, their type and level. Observation and analysis of weather phenomena is an important issue, when considering the problems associated with renewable energy sources, especially with wind power. In [1] equation (1) was given. Based on this equation, the power of the wind turbine depends mainly on wind speed, and that relationship is strongly non-linear. (1) 2 3 8 Pw cp D v   where: cp - general conversion efficiency of wind energy into mechanical energy,  - air density [kg/m3], D - rotor diameter [m], v - wind speed [m/s]. Equation (1), does not include, among others, the minimum wind speed at which the turbine can successfully generate energy or the loss of energy within the mechanical components. For a certain range of wind speeds, the generated power is fixed. In addition, the wind turbine blade stops at high wind speeds, for safety reasons. In addition Formula (1) does not include some range of wind speed, for which, amount of the generated power is limited, and the maximum wind, when turbine must be stopped. The analysis was done using the Statistica program, based on real data from a real wind farm. It is an interesting example of the verification of a theory in practice. The aim of the analysis is the determination of a mathematical model, describing turbine power, which takes into account the real work conditions of wind turbines. In many articles, statistical analyses related to wind power can be found - for example [2] ÷ [8]. The material presente[...]

Simulation studies of the Proportional Resonant controller DOI:10.15199/48.2018.06.24

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The use of P or PI controllers, in rotating with the grid frequency dq frame is a common practice in regulation (current control) for the three phase converters in renewable energy systems "on grid". This method is developed and commonly used but it requires considerable amount of the equipment and software (filtration, elimination of fixed components in measuring signals, etc.). In the one phase, devices which are usually used are PI controllers with big gain and low integration time (in relation to basic waveform period), which operate on pre-filtered signals. The applied filtration limits the dynamics of such controllers. Because of that, new solutions are being sought that will allow to control one and three phase converters [1, 2]. The use of so-called Proportional-Resonant Controller (P+R) proposed by R. Teoderescu and his team [3] can be an alternative solution. It can be used in one and three phase systems, for converters which operates with fixed frequency of the output voltage e.g. grid tied converters. This controller is dedicated in principle for one phase systems [4, 5]. In the three phase devices, after transformation to two phase orthogonal αβ stationary frame, two identical controllers which operates in both axis, can be used [6]. Such a solution allows to control reactive current of the power line. The P+R controller can track sinusoidal signals and has selective amplitude and frequency response. In the literature, besides typical structure of the P+R controller, modified types of controller can be found. They allow to improve controller operation in grids with unstable voltage and frequency through different variants of the feedback loop and controller transmittance [7, 8, 9]. There are also solutions based on the combination of typical PI and P+R controllers, which operate in dq synchronous frame [10] and in αβ stationary frame [11].The P+R controller can operate with different types [...]

Comparative analysis of the indicators that concern power supply interruptions for electricity consumers for the selected distribution systems DOI:10.15199/48.2020.01.08

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Companies that are involved in the distribution of electricity are obliged to provide information to their customers, regulated by relevant regulations. Distributors, in the form of annual reports, provide information on the number of interruptions and their length, i.e. indicators of the duration of interruptions in the supply of electricity. Interruption duration indicators are SAIDI, SAIFI and MAIFI for example. These indicators show the average length of long breaks, the average number of breaks and the average number of short breaks per consumer. In addition to these three, there are a number of other indicators. The improvement of these indicators is in the interest of energy distributors and is the subject of research by many scientific teams. [1÷6] In terms of the area of electricity distribution, the territory of Poland was divided among 5 large DSO Distribution System Operators. There are also small companies dealing with the distribution of electricity, serving a much smaller number of customers. They are also obliged to provide information on selected indicators. The article presents the results of a comparative analysis of selected indicators characterizing the size of power supply interruptions for various distributors operating in Poland. The comparative analysis of indicators was carried out on the basis of generally available data on the Internet and on the basis of detailed information obtained directly from operators. A number of aspects have been taken into account, such as: the length and types of power lines, the amount of transmitted energy, the amount of investment funds, the multi-year time space, the division of indicators taking into account the types of interruptions. The results of the analysis were presented both in tabular and graphical form on charts, which constituted the basis for the formulation of final conclusions. Energy security One of the basic concepts inherent in energy quality is energy s[...]

Nanocrystallinie TiNi, Ti2Ni alloys for hydrogen storage

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In the last decade a great interest has been observed in the field of nanoscale materials. Mechanical alloying (MA) has been proved to be a novel and promising method for alloy formation, especially in the preparation of non-equilibrium materials of various systems [1÷7]. This technique has already succeeded in obtaining a wide range of alloy hydrides for energy storage or other energy related applications [2, 4÷11]. The advanced nanocrystalline intermetallics are representing a new generation of metal hydride materials with the following characteristics: high storage capacity, stable temperature- pressure cycling capacity during the life-time of the system, good corrosion stability and low costs. These materials exhibit quite different properties from both crystalline and amorphous materials, due to structure in which extremely fine grains are separated by what some investigators have characterized as "glass-like" disordered grain boundaries [3, 4]. Therefore, the hydrogenation behaviour of the amorphous structure is different than that of the crystalline material. Mechanical alloying has recently been used to make an amorphous and nanocrystalline TiFe, ZrV2-, LaNi5- and Mg2A-type alloys (A = Fe, Co, Ni, Cu) [6÷11]. These materials show substantially enhanced absorption and desorption kinetics, even at relatively low temperature [9, 10]. Among the different types of hydrogen forming compounds, Ti-based alloys are among the promising materials for hydrogen energy applications [6, 7, 12, 13]. For example, the TiNi alloy, which crystallizes in the cubic CsCl-type structure is lighter and cheaper than the LaNi5-type alloy. Nevertheless, the application of TiNi material in batteries has been limited due to poor absorption/ desorption kinetics in addition to a complicated activation procedure. To improve the activation of this alloy several approaches have been adopted. For example, ball milling of TiNi is effective for the improve[...]

Influence of surfactants on microstructure and corrosion resistance of Ni/Al2O3 coatings

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Composite coatings are one possibility to increase the durability and performance of materials for different applications and protect them from detrimental effect of the environment. Metal matrix composite reinforced with ceramic particles generally find wide range of engineering applications due to their enhanced hardness, better wear and corrosion resistance when compared to pure metals or alloys [1, 2]. The most sought after method of producing these kinds of composites is electrodeposition, owing to its advantages like low cost and the operating temperature. Electrodeposition of metals reinforced with dispersoids (mainly oxides or carbides) is an important technique for production of functional coatings. Such coatings are required in different fields of industry including: machinery and various device construction, machining tools, automotive and aircraft parts etc. Nickel composite coatings containing ceramic particles are used as protective coatings [3]. The plating bath for electrodeposition of Ni/Al2O3 composite coatings is frequently used a standard Watts solution with addition of alumina powder. The amount of ceramic particles incorporated into nickel affects the microstructure and properties of electrodeposited nickel composite coatings. The structure and properties of composite coatings depend not only on the concentration, size, distribution, and nature of the reinforced particles, but also on the type of used solution and electroplating parameters (current density, temperature, pH value etc.) [1, 4]. Although the Ni/Al2O3 composite coatings have been improved significantly, certain problems persist with respect to their preparation. The volume content of alumina particles in Ni/Al2O3 coating cannot be controlled quantitatively and the particles are frequently agglomerated in the composite [5]. The small inert particles like nanoalumina are difficult to embed into deposited layer because of their dispersion difficu[...]


  WPROWADZENIE Kompozytowe powłoki metalowe w tym m.in. niklowe, umacniane są poprzez zastosowanie różnego rodzaju fazy zbrojącej w postaci twardych cząstek dyspersyjnych. Do najczęściej stosowanych cząstek dyspersyjnych należą: tlenki, siarczki, borki, azotki, krzemki i węgliki [1, 2, 4, 5, 6, 7]. Dobierane są one w zależności od rodzaju osnowy. Charakteryzują się one wyższymi temperaturami topnienia oraz znacznie wyższą mikrotwardością w stosunku do osnowy. Równomierne rozmieszczenie fazy ceramicznej w powłoce kompozytowej wymaga użycia szeregu dodatków substancji organicznych, które wpływają na polepszenie jakości kąpieli galwanicznej oraz właściwości wytworzonych powłok. Wprowadzenie do kąpieli pewnej ilości substancji powierzchniowo czynnych ułatwia sporządzanie i utrzymanie stabilnej dyspersji cząstek ceramicznych w kąpielach, a modyfikacja ładunku powierzchniowego cząstki ułatwia jej transport i osadzenie na elektrodzie. Związki organiczne muszą być dobierane eksperymentalnie do danego typu cząstek oraz składu chemicznego użytej kąpieli galwanicznej. Jeżeli cząstki w zawiesinie mają duży ujemny, albo duży dodatni potencjał Zeta, będą odpychać się i nie będą miały skłonności do flokulacji (flokulacja - końcowy etap niektórych rodzajów koagulacji, to jest wypadania osadu z koloidów. Polega na tworzeniu się wiązań chemicznych między micelami, na skutek czego łączą się one w duże agregaty, które w widoczny[...]

Mg2Ni/M-type nanocomposites for hydrogen storage (M = C, Ni, Cu, Pd)

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Pure magnesium can store 7 wt% H2. Unfortunately MgH2 is too stable and too much energy has to be expended in realising the hydrogen. Alloying magnesium with other elements could lower the stability of the hydride. In this work, we have studied experimentally the structure and properties of Mg2Ni/M-type hydrogen storage nanocomposite materials (M=C, Ni, Cu, Pd). These materials were prepared[...]

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