Projects / Programmes
Hibridni nanomateriali za samo-mazalne kompozite in za pretvorbo energije (Slovene)
| Code |
Science |
Field |
Subfield |
| 1.02.01 |
Natural sciences and mathematics |
Physics |
Physics of condesed matter |
| Code |
Science |
Field |
| 1.03 |
Natural Sciences |
Physical sciences |
Researchers (17)
Organisations (2)
Significance for science
The project enabled research of new nanohybrids based on MoS2 and WS2 nanotubes, which have been synthesized at Jozef Stefan Institute for the first time. Their synthesis has been successfully patent protected by international patents. These are completely unique structures, lik eWS2 nanobuds, where WS2 nano-onions grow on the WS2 nanotubes, or MoS2 "mama"-tubes, where Mos2 nano-onions are incorporated inside MoS2 nanotubes, co-axial MoS2 nanotubes, where nanotubes are inside nanotubes, or size controlled Mos2 nanotubes, which show metallic behaviour due to high density of structural defects, in contrary with otherwise semiconductive MoS2. The main goal of the project was understanding of growth processes of hybrid nanomaterials, their interaction with polymer matrix and evaluation of possible application for energy saving with reduction of friction, for energy production through photovoltaics or for energy storage with hydrogen or lithium intercalation. All this goals have been achieved and directions of further research have been designed.
Friction is an old subject of research and its control is of a great technological importance, especially in recent attempts of energy saving and higher fuel economy. While macroscopic friction can be related to the collective action of small asperities and those studies were traditionally attributed to faculties of mechanical engineering, use of an atomic force microscopy (AFM) enables a focus on a single asperity and demands knowledge of nano-physics. Atomic resolution in measuring the friction forces reveals a detailed structure of an investigated sample and indirectly it controls a time dependent quality of the AFM tip, which represents a dynamic probe in the system. While the conventional interest of friction measurements with AFM was to focus on phenomena such as local wear, which are not accessible with macroscopic apparatus, nanomaterials in a role of lubricants opened a new challenge of measuring friction on a surface of a single nanotube or fullerene-like particle.
And this goal was achieved. We have measure friction on a surface of a single MoS2 nanotube and single MoS2 nano-onion for the first time in general. We have confirmed more than quarter of century old statement phenomena that intra-crystalline friction is higher than inter crystalline one. Use of an ultra-high vacuum experimental environment enabled elimination of humidity or risks of oxidation, which can blur a basic process of friction during sliding.
Knowledge on mutual interaction of nanoobject and different polymers for special purposes is important for development of multi-functional coatings. We have prepared coatings based on water soluble and biocompatible polyethylene oxide (PEO), where we have experimentally obtained 75 % wear reduction at 25 Wt.% of the MoS2 nanotubes related to the mass of the polymer. The MoS2 nanotubes mixed into chemical and temperature resistant PVDF caused stabilization of a new conformation of this polymer, which was unknown although PVDF belongs to the most studied polymers in general. Only 1 wt.% of PVDF decreases friction of PVDF for 50 %. We have evidenced growth of tribo-film during mechanical shear load using PAO oil with added MoS2 nanotubes. Wear at the metal contact has been reduced for 90 % with respect to pure oil.
Exfoliation of the nanotubes at mechanical contact is a mechanical equivalent to chemical exfoliation, which was used for synthesis of MoS2 monolayers as graphene analogy. We have chosen MoS2 nanotubes for exfoliation and not usual platelets. This enabled us to prepare material with a low degree of restacking and research on single monolayers. We have found a strong quantum effect due to small thickness of a monolayer. Raman shift revealed a similar quantum confinement effect in layers consisted tribo-film.
We participated in construction of the first field effect transistor based on thin flakes of our MoS2 and WS2 nanomaterials.
Significance for the country
Project was important for better understanding of new nanomaterials, which have been discovered in our group in Slovenia and appropriately patent protected in Europe and US. Besides promotion of Slovenia at technologically important field sof nanotechnology and nanoelectronics, , the results of the project are applicable for evaluation of possible directions of applied research of MoS2 nanotubes. Particularly strongly enhanced self-lubricative function of technological polymers with added MoS2 nanotubes. like PVDF, PEO and iPP is important. With atomic force microscopy studies we have evidenced lower friction on the tubes than on flat plate like crystals and in collaboration with the faculty for Mechanical Engineering performed friction testing in oils and greases. The material is unique and ready for technological utilization. Two further steps are necessary: development of scale up production and development of a final product. Both steps are beyond the limits of current project and wait for a new applied oriented call or an investment.
The project is interdisciplinary, because it combined researchers form technique with those from natural science, but it is centered in physics, which is therefore involved into the most recent development of materials important for industrial applications. The collaboration with the Faculty for Mechanical Engineering was based on very fruitful cooperation with dr. Kalin, who is internationally recognized expert in tribology and a co-editor of a book: Tribology of mechanical systems : a guide to present and future technologies. New York: ASME Press, 2004. Informal cooperation formalized in this project and hopefully will last also after the project end. One PhD student defended his PhD from the topic of the project, other two PhD students still work in the topic, and three diploma works were completed.
Most important scientific results
Annual report
2009,
2010,
2011,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2009,
2010,
2011,
final report,
complete report on dLib.si
