Laboratory for Thermal Conductivity Studies, Institute of Mechanics – BAS
The laboratory carries out studies of the thermal conductivity, tribological and lubricating properties of new materials. Small solid and liquid samples are tested for thermal conductivity. Tribological studies are carried out on polymer specimens and foils, as well as on hard and superhard coatings. The relationship between the thermophysical properties, the resistance to friction and wear, and the structure of the materials is analysed. The lubricating properties of various lubricants are also determined.
Service Description
(1) Determination of the thermophysical properties of materials by the Light Flash method
Detailed description of the service: The Light Flash (LFA) technique is a fast, non-destructive and non-contact method for measuring the thermophysical properties of materials with the Light Flash LFA 467 HyperFlash® instrument (NETZSCH). Solid samples (polymers, metals, ceramics, building materials, thermal insulation materials, etc.) and liquid samples (water, oils, pastes, polymer melts, etc.) are studied. A range of characteristics is determined, such as thermal conductivity, thermal diffusivity and specific heat capacity. The principle of the Light Flash (LFA) method consists in heating the lower surface of a plane-parallel sample with a short pulse of light energy, while an infrared detector measures the temperature of the upper surface of the sample. The thermal diffusivity is measured, and the specific heat is determined using a reference specimen. Software calculates the thermal conductivity on the basis of models.
(2) Investigation of tribological properties under friction, wear and scratching. Visualisation of the microstructure
Detailed description of the service. A comprehensive study is carried out of the tribological properties and microstructure of composite surfaces, films, foils, and hard and superhard coatings under friction, wear and scratching. The friction and wear test is of the standard “pin on disk” and “ball on disk” type, with linear or rotary drive. The scratch test is carried out with a stylus (4 mm and 8 mm) under a variable or constant load of up to 100 N. The resistance to friction and scratching is determined, as well as the coefficient of friction. Scanning electron microscopy is used to examine the surface microstructure before and after the tribological test, which allows the friction resistance of the material and the wear depth to be determined precisely. For electrically conductive materials, a module for measuring electrical contact resistance in the range from 10 Ohm to 1 kOhm is used, which determines the electrical contact resistance during tribological tests and microindentation.
(3) Determination of the lubricating properties of oils and greases
Detailed description of the service. Lubricity test to determine the lubricating properties of oils and greases using rotating discs with a diameter of 7 mm, in accordance with an ASTM standard. Low- and high-viscosity oils and lubricants are studied and their lubricating properties determined. In addition, the laboratory offers measurement of the viscosity and thermal stability of oil-based lubricants and lubricating oils over a wide temperature range. This comprehensive assessment makes it possible to determine the quality, effectiveness and suitability of lubricants for various applications.
Equipment
THERMAL CONDUCTIVITY MEASUREMENT INSTRUMENT.
Light Flash LFA 467 HyperFlash® (NETZSCH)
The LFA 467 HyperFlash instrument measures the thermal conductivity, thermal diffusivity and specific heat capacity of solid and liquid samples of various materials over a wide temperature range (-100 to 500oC). Cooling is provided by liquid nitrogen. The instrument offers high measurement sensitivity and accuracy. The standard holders are designed for small specimens: round samples with a diameter of 10; 12.3 and 25 mm and square samples measuring 10 x 10; 12.3 x 12.3; 25 x 25 mm, with a sample height of 0.1 – 6 mm. It is also equipped with a holder for foils with a thickness of < 200 µm and a “PEEK” holder for liquid samples. Measurements are carried out in accordance with ISO 22007-4:2017.
MODULES FOR TRIBOLOGY AND LUBRICATION STUDIES
for the UMT-2 micromechanical testing instrument (Bruker)
The modules extend the research capabilities of the existing UMT-2 universal micromechanical testing apparatus (Bruker). (i) The linear-drive tribology module (Bruker) investigates the resistance to friction and wear and the coefficient of friction of hard surfaces and superhard coatings. It features an adjustable stroke from 0.1 to 25 mm and a linear drive speed of 0.1 – 25 Hz; (ii) the module for measuring electrical contact resistance in the range from 10 Ohm to 1 kOhm is used in the tribological study of electrically conductive materials; (iii) the lubrication module (Bruker) is used to study lubrication processes with oils and greases. The module consists of the following elements: a liquid container and a high-speed rotary drive mechanism with splash protection. It operates with discs 7 mm in diameter.
SCANNING ELECTRON MICROSCOPE. Tabletop SEM HIROX SH-4000M
The HIROX SH-4000M tabletop SEM enables the study of the structure and morphology of materials at the micro- and nanoscale. In tribological studies, the SEM is offered for visualising the track left after friction and scratch tests, which allows precise assessment of the friction resistance and wear depth of surfaces. Technical specifications: magnification 30x – 60 000x; resolution 15 nm; SE & BSE detectors, voltage 5 – 30 kV; multi-vacuum mode.
Contacts
Institute of Mechanics – BAS
Acad. Georgi Bonchev Str., Block 4, 1113 Sofia.
Assoc. Prof. Dr Vladimir Georgiev, e-mail: vladoferd@gmail.com
Access to the Laboratory for Thermal Conductivity Studies
The Laboratory for Thermal Conductivity Studies is part of the research infrastructure of the National Centre of Excellence “Mechatronics and Clean Technologies” and is located on the Geo Milev campus. Requests for access and for joint research are therefore handled centrally — see Contacts. In addition, a full overview of the Centre’s other laboratories is available on the Infrastructure and Laboratories page.
The equipment for thermal conductivity studies was established under project BG16RFPR002-1.014-0006, funded under the Research, Innovation and Digitalisation for Smart Transformation Programme 2021–2027, co-funded by the European Union through the European Regional Development Fund.