Vislielākais burtu izmērs
Lielāks burtu izmērs
Burtu standarta izmērs
Achievements 2003 - 2017
Last Update
  • Obtained hematite thin film coatings with different impurity metals using advanced spray pyrolysis process; thin films possesses high photo-conductivity and appropriate width of forbidden gap for photocatalytic water splitting
  • Simple method is developed to obtain nanostructured multilayer graphene and modify it with metals/cations for application as electrode material in supercapacitor and for solid state hydrogen storage
  • Self-oriented nanostructured titanium dioxide nanotube coatings are obtained in anodization process, and research performed on influence of various parameters on the formation of this coating at the very beginning.
  • In collaboration with the designer created a prototype of Solar Tree to demonstrate united principle of Solar energy harvesting, storage and usage for installation in public areas of the urban environment.
  • Original composite has been developed (composite from milled glass and AB5 metal hydride catalyst) for efficient hydrogen storage.
  • The following mechanism is proposed to explain the hydrogen absorption in such composite material: hydrogen molecules are split in atoms by catalyst and spills from AB5 nanoparticles to inert carrier substrate (silica particle), the so-called hydrogen “spillover” effect which allows the use of hydrogen accumulation on the surface of a carrier material activated by catalyst nanoparticles
  • Research was carried out on the hydrogen adsorption/desorption capacity of palladium and platinum activated natural zeolite using gravimetric and volumetric methods, concluding that zeolite, pre-treated with temperature pulses in inert atmosphere, can be used for hydrogen storage in solid state material (up to 5% by weight).
  • An electric-hydrogen car has been developed in cooperation with IEEI RTU on go-kart construction basis. The concept of this H2-car is based on a hydrogen fuel cell (1.2 kW), supercapacitor (160 F), solar PV panel (26 W) and a small starting battery. The car has improved charge-discharge characteristics, and it collects regenerative power from braking. At the rated load (33 A) the fuel cell (FC) consumes 12 liters of H2 gas per minute. The 10 liter fuel tank and 200 bars hydrogen gas cylinder provides 167 minutes of engine power only from the FC, while working with supercapacitor there is enough fuel energy produced to ensure 5 hours of continuous running at a speed of 22 km/h. Thanks to the pilot studies using a real fuel cell system (Nexa Power Module) in the hydrogen car it was concluded that the design of fuel cell power converters must take into account the dynamic volt-ampere characteristics of the FC in order to provide a stable electric motor power in a relatively wide range. It was also concluded that the dynamic V-A characteristics of FC can be explained with the constant of electrochemical polarization transient time of much larger value than the expected electrical load transient time constant value.
  • We are also conducting research on proton-conducting membranes and catalytic materials for fuel cells and electrolysers. New method to manufacture membrane from PEEK polymer has been developed (patented in Latvia). The new membrane shows high conductivity and, most importantly, increased stability in the fuel cell’s operating environment. A study has been launched on PEEK polymer composite formation using oxide nanopowders and ionic liquids. Mixed-conductivity polymer is synthesized from electron-conducting (poli-anilin) and proton-conducting (sulfonated polyether-ether ketone) polymers that can be applied to the electrode-membrane assembly (MEA) of fuel cells. Using electrochemical impedance and spectrophotometric methods, the presence of proton and electron transfer mechanisms for obtained polymer composites has been detected.
  • To explain the pulse electrolysis experiment results a theoretical model has been proposed which assumes that no mass transfer occurs in the vicinity of electrodes during a very short pulse time (microseconds) and that electrolysis cell behaves as an ideal capacitor which can be charged with energy. During the pause following the pulse power supply circuit is disconnected, while the pulse energy stored discharges initiating water electrolysis. This allows you to create an efficient electrolysis system without heat loss during the operation process.
  • A relatively simple production method of nano-structured titanium dioxide coatings has been presented, and coating activation using nano-catalysts has been acquired. In collaboration with theoreticians work is in progress to find an explanation for the stability of anatase phase in formation of self-oriented hexagonal nanotube coatings and for their high photocatalytic activity. These coatings are necessary to form air-cleaning surfaces of buildings, significantly reducing environmental pollution, and for water splitting using only solar energy. Various oxide and ferrite nanopowders and coatings are synthesized to initiate water photo-catalysis in sunlight.
  • In the field of bio-hydrogen production it has been found that C.sporogenes bacteria is capable of forming hydrogen gas in dark fermentation by processing various biomass production residues (whey from dairy and crude glycerol from bio-diesel plants in Latvia) with the hydrogen production rate of 1.5 mmol H2/l/h. Studies have shown that the use of micro-organisms from our own collection can successfully ferment various food residues, yielding hydrogen in gas phase. By increasing efficiency of the process it will be possible to transfer biomass residue into valuable energy carrier, hydrogen, which can be further used for electricity generation in food and chemical industries.
  • Prototype bioreactor has been created for pilot studies with hydrogen (and methane) production in bacterial fermentation process, also providing process control and reliable data acquisition. Micro-sensors, as well as optical sensors, are built in the bioreactor to test gas environment. It has been found that mixing and aeration with an inert gas increases the release of hydrogen in gas phase.

Functionalization of Glass and Natural Fiber Textile Materials

Studies are carried out on E-glass [(1-2)(Na2O-K2O)(16-25)CaO(12-16)Al2O3(3-5)MgO(52-56)SiO2] and K-glass [(18-22)Na2O(3-5)Al2O3(73-79)SiO2] fiber modification and nanostructuring technologies, and research has been started on hemp fiber modification and nanostructuring.

The most effective method for heightening thermal strength of glass fibers is the combination of leaching in sulfuric acid and coating with TiO2 in sol-gel process. By the leaching and coating the glass fibers breaking temperature can be increased 100÷200 °C. The thermo mechanical strength at 280 °C of hemp yarn coated with Cu and CuO particles are increased by 13% and 42% of the yarn without coating.

Water in K-glass fabric is located in leachable substances and in pores of elementary glass fibers. Conductivity of glass fabric has a sharp decrease when the surface of elementary glass fibers loses water (electrolyte). A method has been proposed to determine the volume of pores based on water content and electrical conductivity measurements.

Functional Coating Technologies

For fiber surface modification and nanostructuring purposes a method has been developed for stimulating leaching process with ultrasound, and an ion gun unit has been created for surface treatment with argon plasma and incorporated with coating magnetron.

An electrophoresis equipment and technology for metal ceramic coatings of solar energy collectors are being developed. Homogeneous TiO2 films are produced by sol and suspension electrophoresis, and the method is promising in applications on metal substrates and fibers. It has been detected that thin films, crystallized at 500 °C, are mainly composed of anatase form, while in thicker films the proportion of rutile forms will increase. TiO2 thin layer photo activity varies significantly depending on the surface area and dopants (Fe2O3, WO3).

Cathode and Anode Materials for Li-ion Batteries

A new method of magnetron sputtering of high charge capacity has been developed for production of cathode thin film material, based on LiFePO4/C, for lithium-ion batteries. Electrochemical parameters of cathode material/Li-ion electrolyte boundary have been defined for cathode material charge - discharge states. It has been found that the largest double layer capacitance and the smallest charge transfer resistance is in the discharged state, but Li-ion diffusion coefficient minimum value is reached at the equilibrium state. Electrophoretic deposition method is elaborated for obtaining thin films of LiFePO4. New model describing extraction and injection mechanism of lithium ions in LiFePO4 thin films has been developed.

The electrophoretic deposition (EPD) method has been developed to obtain multilayer reduced graphene oxide (rGO) films as anode material. High charge capacity of films is ensured by lamellar structure and large surface area of electrode. Composite anode material TiO2/Fe2O3/rGO obtained by EPD showed very high charge capacity and cycling stability.

Raman Spectroscopy and Lattice Dynamics Analytical Modeling

Analysis of AlF3 and WoCl4 lattice vibrations symmetry has been performed. Using CRYSTAL09 program package, the structure of the crystal lattice parameters defined for equilibrium state and calculated lattice fluctuations at different symmetrical Brillouin zone points.