Research Outputs

2013 2013 2012 2012 2011 2011 2010 2010 2009 2009 2008 2008 2007 2007 0.0 0.0 1.0 1.0 2.0 2.0 3.0 3.0 4.0 4.0 5.0 5.0
Now showing 1 - 10 of 20
  • Publication
    Optimization of a container design for depositing uniform metal coatings on glass microspheres by magnetron sputtering
    (Elsevier, 2010-08-24)
    Schmid, G. 
    ;
    Eisenmenger-Sittner, C. 
    ;
    Hell, J. 
    ;
    Horkel, M. 
    ;
    ;
    Mahr, H. 
    Coating granular substrates by PVD methods like magnetron sputtering is a very challenging process. Although many of such substrates may also be coated by other means like the sol gel method, there are coating materials (e. g. refractory metals) for which PVD processes are the method of choice. One of these substrates is hollow glass microspheres with 2–80 μm diameter which can be used for hydrogen storage if a proper catalytic film is applied. To achieve a uniform film by magnetron sputtering on all the spheres a special apparatus was used which basically consists of rotating vessels positioned beneath the target. The arising problems of agglutination of the powdery substrate were solved by designing a special coating vessel, where the spheres are contained during deposition. For testing the system first copper was used as a target material, which was then replaced by platinum since the glass microspheres are used for a catalytic application. The film thickness on the spheres was determined by optical absorption and matches well with the thickness calculated for the special vessel geometry. Additionally it is shown that the glass microspheres can be coated with a uniform layer by magnetron sputtering whereas coatings produced by a chemical deposition process are not continuous.
      70Scopus© Citations 17
  • Patent
      185  232
  • Publication
    Development of a µ-scale Turbine Expander for Energy Recovery
    (American society of mechanical engineers, 2009) ;
    Dudzinski, Piotr 
    ;
    Tajmar, Martin 
    ;
    Willinger, Reinhard 
    ;
    Käfer, Klaus 
    Waste heat is a primary source of energy loss in many applications. A number of developments around a micro rocket engine at the Austrian Research Centers (ARC) promise innovative energy recovery and micro power generation solutions. Here we focus on the investigation of micro technologies for application in HVAC (heating, ventilating, and air conditioning) systems. The use of μ-scale turbine expanders for work recovery in transcritical CO2 heat pump processes has been identified as most interesting and promising for the application in HVAC cases. One of the main drawbacks of transcritical CO2 heat pumps is the lower COP (coefficient of performance) compared to conventional heat pump systems which originates from the non isothermal heat rejection in the gas cooler. This drawback can be compensated by utilizing the pressure difference between the high pressure and low pressure part of the heat pump for work recovery. This is feasible as the pressure difference is considerably larger in case of CO2 heat pumps compared to conventional systems. Work recovery can be realized by substituting the expansion valve between the high and low pressure side by an expansion machine. Due to the low flow rate of the working fluid, the turbine type is based on the Pelton turbine with specific two phase flow turbine blades. In addition to the turbine part a magnetic coupling, miniature bearings and a small scale generator are important parts of the system. Thermodynamic simulations showed an absolute microturbine power yield between 60 W and 150 W for a 2 kW heating system.
      109
  • Publication
    Neutron transmission measurements on hydrogen filled microspheres
    (Elsevier, 2013-10-26)
    Dyrnjaja, Eva 
    ;
    Hummel, Stefan 
    ;
    ;
    Smolle, Marie-Theres 
    ;
    Gerger, Joachim 
    ;
    Zawiswky, Michael 
    Hollow microspheres are promising candidates for future hydrogen storage technologies. Although the physical process for hydrogen diffusion through glass is well understood, measurements of static quantities (e.q. hydrogen pressure inside the spheres) as well as dynamic properties (e.g. diffusion rate of hydrogen through glass) are still difficult to handle due to the small size of the spheres (d ! 15 lm). For diffusion rate measurements, the long-term stability of the experiment is also mandatory due to the relatively slow diffusion rate. In this work, we present an accurate and long-term stable measurement technique for static and dynamic properties, using neutron radiography. Furthermore, possible applications for hydrogen filled microspheres within the scope of radiation issues are discussed.
      65Scopus© Citations 1
  • Publication
    Development of Innovative Micro Power Converter Technologies at the Austrian Institute of Technology
    (American Institute of Aeronautics and Astronautics, 2009-08) ;
    Vasiljevich, Ivanhoe 
    ;
    Dudzinski, Piotr 
    ;
    Tajmar, Martin 
    ;
    Gerger, Joachim 
    Waste heat is a primary source of energy loss in many aerospace and terrestrial applications. The Austrian Institute of Technology (AIT) is presently developing two different types of micro power converters, promising high efficiencies in their respective application areas. The first converter is based on an innovative thermoacoustic Stirling engine concept without moving parts. Such a maintenance-free engine system would be particularly suitable for advanced Stirling radioisotope space power systems. The second converter is based on microturbines to use exhaust-gases for improving the overall efficiency for a number of applications. This paper will summarize our efforts on micro power converter technologies.
      104Scopus© Citations 1
  • Publication
    Characterization of the Reversible Hydrogenation Properties of Sodium Alanate under various contaminated Hydrogen Conditions
    (2013-06-17)
    Reissner, Alexander 
    ;
    ;
    Hummel, Stefan 
    ;
    Scharlemann, Carsten 
    ;
    Tajmar, Martin 
      122
  • Publication
    Micro-Propulsion and Power Developments at AIT
    (2009-01-12) ;
    Tajmar, Martin 
    ;
    Scharlemann, Carsten 
    The increasing application of micro-satellites (from 10 kg up to 100 kg) as well as CubeSats for a rising number of various missions demands the development of miniaturized propulsion systems. The Austrian Institute of Technology is developing a number of micropropulsion technologies including both electric and chemical thrusters targeting high-performance at small scales. Our electric propulsion developments include FEEP thrusters with thrust ranges from μN to mN using highly-integrated clusters of indium Liquid-Metal-Ion Sources providing ultralow thrust noise and long-term stability, as well as the development of a micro PPT thruster enabling pointing capabilities for CubeSats. For chemical thrusters, we are developing novel micro-monopropellant thrusters with several hundred mN as well as a 1-3 N bi-propellant micro rocket engine using green propellants and high specific impulse performance. This paper will give an overview of our micropropulsion developments highlighting performance as well as possible applications.
      102
  • Publication
    Novel Hydrogen Storage Solutions for Space and Aerospace Applications
    (2011-05-15) ;
    Reissner, A. 
    ;
    Bichler, D. 
    ;
    Tajmar, M. 
    Novel hydrogen storage solutions are increasingly important for a number of future aerospace and space applications. The Aerospace Engineering Group of the fotec Forschungs- und Technologietransfer GmbH is presently developing an innovative hydrogen storage system based on high pressure hydrogen storage in microspheres. The hollow glass microspheres are loaded with up to 700 bar of hydrogen gas with a thermal process. The gas was released with a special heating wire. Such a system could be used as safety gas generator on satellites and airplanes. An additional space application for hydrogen filled microspheres seemed to be the use as additive in cryogenic liquid storage systems to enlarge the longtime durability. Further projects deals with new energy storage solutions to replace secondary batteries on satellites. We decided to approach this topic by directly coupling a fuel cell with a metal hydride based on Ti-doped sodium alanate. The power dissipation of the fuel cell can be used for desorption of hydrogen where heat is required, instead of being rejected by a heavy thermal control system. This advantage would be very interesting in order to obtain higher weight efficiencies which are especially important for space and submarine applications.
      197  510
  • Publication
    Development of a Ti-doped Sodium Alanate Hydrogen Storage System
    (2009) ;
    Reissner, Alexander 
    ;
    Dudzinski, Piotr 
    ;
    Tajmar, Martin 
    A trade-off analysis regarding power supply on satellites, which was performed for the European Space Agency (ESA), suggested that fuel cells might be an interesting candidate to replace secondary batteries on satellites. The Austrian Research Centers (ARC) decided to approach this topic by combining a fuel cell with innovative chemical hydrogen and oxygen storage as well as integrating the oxygen storage system into a form that can be used as a structural element. Also an integration of the fuel cell into the hydrogen tank, and the resulting storage of dissipation heat, results in a reduction of the necessary thermal control system. These advantages are very interesting in order to obtain higher weight efficiencies, which are especially important for space and automotive applications. The complete system includes a hydrogen storage tank based on Ti-doped sodium alanate and a novel oxygen tank based on YBaCo4O7 developed at ARC. Water tanks and a micro-fluidic system connected to the fuel cell have been considered as well in order to provide a completely reversible system, competitive to batteries. For the hydrogen storage, a finite elements model has been developed, implementing the reaction kinetics of the storage process, in order to predict the thermal mechanisms during adsorption and desorption of hydrogen in sodium alanate. The present paper discusses these simulations, the development of an experimental hydrogen storage tank and the proposed concepts of a battery replacement system.
      97