Vladimiros Nikolakis

	Principal Researcher FORTH/ICE-HT, Greece
Tel. : +30 2610-965 242   Email: vnikolak@iceht.forth.gr
Last updated: June 2008

Education:

PhD Chemical Engineering, University of Massachusetts Amherst
Diploma Chemical Engineering, Aristotle University of Thessaloniki, Greece

Previous Employment/Occupation:

2004-2008 Associate Researcher, FORTH/ICE-HT
2002-2004: Assistant Researcher, FORTH / ICE-HT
1996-2001: Research Assistant, Dpt Chemical Engineering, Univ. of Massachusetts Amherst .
1995-1996: Postgraduate Fellow, Chemical and Process Engineering Research Institute, Thessaloniki Greece.

Research Activities:

[1] Zeolite membrane synthesis, characterization and testing
The objective of this activity, in terms of application, is to synthesize supported polycrystalline zeolite membranes that can be used for the separation of gas or liquid mixtures. Such membranes must combine high permeation fluxes with high separation factors. To achieve this goal, membranes of the appropriate zeolite type and chemical composition need to be synthesized. In addition, the synthesis procedure needs to be tuned in order to minimize the number, and size of possible defects and grain boundaries. Adsorption/ diffusion models based on the Stefan-Maxwell formulation are used in order to understand the effect of host-guest, guest-guest interactions on the overall permeation flux and in order to make predictions about membrane permselective performance at different set of conditions.

[2] Investigation of zeolite nucleation and growth mechanisms
Despite the progress that has been achieved towards zeolite synthesis, the mechanisms of nucleation and growth remain elusive. This is partially due to the large number of chemical reactions, equilibria, and solubility variations that take place during the crystallization process. Furthermore, the colloidal nature and complex interactions between various species and zeolite crystals along with the disparity in length and time scales encountered in zeolite synthesis render a molecular understanding of growth as difficult. Research activities have been focused on studying zeolite nucleation and growth through the formation of a gel phase and from apparently clear solutions.

Zeolite crystals are usually synthesized hydrothermally, where an alkaline reaction mixture is prepared from silica and/or alumina sources, and sometimes a structure directing agent. Zeolites then nucleate and grow either directly from an apparently clear solution or through the formation of an amorphous gel phase. The most important factors that affect zeolite synthesis are (a) the nature of the reactants, (b) the alkalinity, (c) the degree of the reaction mixture homogeneity, (d) the silicon to aluminum ratio, (e) the aging of the gel, (f) possible seeding, (g) the existence of structure directing agents, and (h) the temperature and pressure. The factors mentioned above can affect zeolite synthesis by determining the type of zeolite structure, the growth and nucleation rates, the crystal shape, and the existence of defects (e.g. twinning).

[3] Development of zeolite-based composites for sensing applications
(In collaboration with D. Kouzoudis. Lecturer at the Polytechnic School of the University of Patras).
This activity aims at the development of composite materials consisting of a magnetoelastic material strongly bound to microporous inorganic films with selective adsorption properties. Magnetoelastic materials are ferromagnetic amorphous alloys that, when placed in a time varying magnetic field, transform magnetic energy into elastic energy, inducing an oscillating deformation of the material. The material vibrations generate a new magnetic flux that can be detected by using a pick-up coil. The resonance frequency of this oscillation depends on geometric parameters as well as on the density of the sensor. Even though the magnetoelastic alloy can be used for detecting changes in the pressure or in the velocity of a fluid, it cannot be used as is, for selective sensing of one compound in a mixture. On the other hand, zeolites have the ability to recognize molecules based on their size or polarity, a property that can be used in sensing applications if it can be transformed to a measurable signal. This transformation can be achieved by synthesizing zeolite - magnetoelastic alloy composite materials. The zeolitic part of the composite will provide the means for selective recognition of the analyte molecules (i.e. by selective adsorption) inducing changes in the resonant frequency of the magnetoelastic material with the concentration of the analyte of interest.

[4] Preparation modification and testing of mesoporous silica based adsorbents
The objective of this activity is the synthesis and modification of mesoporous silica materials that can be used as adsorbents of small volatile malodorous molecules. The physical properties (specific surface area, colour etc) of these materials are such that make them excellent candidate adsorbents for odour control. A twofold approach is followed, which consists of optimising synthesis parameters (composition, temperature, raw material sources, modification agents) as well as performing tests regarding the ability of the materials to selectively adsorb volatile organic molecules from vapour and aqueous environments.

Publications:

20 Refereed journal papers. 1 international refereed conference proceeding.

Conference Participation/Attendance:

Presentations in more than 30 national & international conferences.

Participation in Research Projects:

Professional Affiliations:

Technical Chamber of Greece
American Institute of Chemical Engineers (AIChE)
International Zeolite Association (IZA)

Prizes/Honours:

Scholarship from the Greek National Foundation of Scholarships 1990-1991.

Selected Publications:

• ‘"The effect of gas adsorption on the elastic properties of faujasite films measured using magnetoelastic sensors" Th. Baimpos, I. G. Giannakopoulos, V. Nikolakis, and D. Kouzoudis, Chemistry of Materials, 20 1470-1475, (2008)
• "Investigation of silicalite-1 crystallization using ATR/FT-IR spectroscopy", A. Patis, V. Drakopoulos, V. Nikolakis, Physical Chemistry C 111, 17478-17484, (2007)
• "Synthesis and characterization of a composite zeolite-metglasTM carbon dioxide sensor" I.G. Yiannakopoulos, D. Kouzoudis, C.A. Grimes, V. Nikolakis, Advanced Functional Materials 15, 1165-1170, (2005).
• "Separation of propane/ propylene mixtures using a FAU type zeolite membrane", I. G. Giannakopoulos, V. Nikolakis, Industrial and Engineering Chemistry Research, 44, 226-230, (2005).
• "Growth of a faujasite-type zeolite membrane and its application in the separation of saturated/unsaturated hydrocarbon mixtures", V. Nikolakis, G. Xomeritakis, A. Abibi, M. Dickson, D.G. Vlachos, M. Tsapatsis, Journal of Membrane Science, 184, 209-219, (2001).
• "Zeolite growth by addition of subcolloidal particles: Modeling and experimental validation", V. Nikolakis, E. Kokkoli, M. Tirrell, M. Tsapatsis, D.G. Vlachos, Chemistry of Materials, 12, 845-853, (2000).