Termometru de temperatura maxima pe baza de materiale inteligente (Smart materials based MAXIMUM THERMOMETER)

Project Director: Dr. Felicia Tolea

The project aims to develop a "maximum thermometer" (i.e. for recording the maximum temperature reached during a certain process / in a given period of time) entirely made of Shape Memory Alloys (SMA). The idea is based on the thermal memory effect exhibited by SMA, making it possible for a single piece of material to perform tasks of conventional thermometers, but without toxicity hazard and with higher compactness and mechanical robustness. In order to record an overheating episode, a SMA must be in martensite phase at room temperature and the overheating to be in the range of the solid state phase transition (the martensite - austenite transition). Subsequently, the maximum overheating temperature can be determined in the laboratory and manifests as a dip in the calorimetric signal on heating. Since an alloy's "sensitivity" is in the range of its phase transition, one must combine different type of alloys for a wide range of thermometer usefulness. The materials we have in mind are based on Heusler type Ni-Fe-Ga and Ni-Mn-Ga alloys, prepared by melt-spinning technique, with various substitutions (e.g. Co), and also subjected to thermal treatments. Complex experimental characterizations will be performed and also supportive numerical simulations. The main deliverable will be a compact thermometer fully tested in laboratory, consisting in a small aluminum pan lid (i.e. a crucible of about 5 mm diameter) encapsulating 30-50 mg of SMAs of different compositions. The envisaged temperature range is 20-60 C, with main applications in the food producing/transportation/storage industry, pharmaceutical or space industries, where the recording of accidental overheating is of high importance.

Project objectives:
1. Obtaining SMA ribbons with desired range of phase transition (MT) temperatures. We aim to obtain
SMA ribbons with the compositions Ni-Mn-Ga and Ni-Fe-Ga, stoichiometric and off- stoichiometric, with and
without addition of Co, by melt-spinning technique. Structural, magnetic and calorimetric characterization will
be performed, in particular to check the range of the phase transitions. Thermal treatments will be performed
which are expected to tune the MT by structural relaxation.
2. Highlighting single and multiple arrest temperatures recording on the prepared samples. Thermal
memory recording of various temperatures will be checked on each alloy to determine the range of optimal
effect (a more pronounced dip). Multiple temperatures recording will be performed as well. From compositions
with overlapping transformation temperatures, the one with better memory potential will be chosen.
3. Theoretical simulation of the thermal memory effect. This objective is a continuation of a previous
theoretical work by our group [14, 20]. If successful, it is expected to shed light on the relation between
transition temperatures and compositions/thermal treatments in the context of single or multiple arrest
4. Building and testing the thermometer. Several compositions of ribbons will be chosen to cover the
desired range of transformation temperatures ( 20-60 C). The encapsulated thermometer must be also tested the
same as the individual ribbons to give its full functioning characteristics. Thermometers recording higher
temperatures may be also proposed, depending on the experimental results obtained. A very important aspect
will be the calibration of the thermometer and addressing accuracy issues.

Articole ISI:

Magnetic and Magnetostrictive Properties of Ni50Mn20Ga27Cu3 Rapidly Quenched Ribbons,M. Sofronie, M. Tolea, B. Popescu, M. Enculescu, F. Tolea, MATERIALS Volume 14 Article Number 5126, DOI10.3390/ma14185126 SEP 2021, Document Type Article WOS:000700294200001

The Effect of the In-Situ Heat Treatment on the Martensitic Transformation and Specific Properties of the Fe-Mn-Si-Cr Shape Memory Alloys Processed by HSHPT Severe Plastic Deformation, C. Gurau, G. Gurau, F. Tolea, B. Popescu, M. Banu, LG Bujoreanu, MATERIALS Volume 14 Article Number 4621, DOI10.3390/ma14164621, AUG 2021 Document Type Article WOS:000689390200001

Long- and short-range order in the Ni52Co2Fe20Ga26 ferromagnetic Heusler alloy D. Macovei, F. Tolea, JOURNAL OF APPLIED CRYSTALLOGRAPHY Volume 54
Page 1207-1216, Part 4, DOI10.1107/S1600576721006415,Published AUG 2021 Document Type Article WOS:000683118400019

Martensitic Transformation and Magnetic Properties of Ni57Fe18Ga25 Shape Memory Alloy Subjected to Severe Plastic Deformation B. Popescu, C. Gurau, G. Gurau, M. Tolea, M. Sofronie, F. Tolea, TRANSACTIONS OF THE INDIAN INSTITUTE OF METALS, DOI 10.1007/s12666-021-02293-8. Early Access MAY 2021 Document Type Article; WOS:000655084100001

Multifunctional GaFeO3 Obtained via Mechanochemical Activation Followed by Calcination of Equimolar Nano-System Ga2O3-Fe2O3 L. Diamandescu, F. Tolea, M. Feder, F. Vasiliu, I. Mercioniu, M. Enculescu, T. Popescu, B. Popescu, NANOMATERIALS Volume 11, Article Number 57, DOI 10.3390/nano11010057 JAN 2021, Document Type Article. WOS:000610651200001

Structural, magnetic and magnetostrictive properties of the ternary iron–palladium–silicon ferromagnetic shape memory ribbons M. Sofronie, B. Popescu, M. Enculescu, Applied Physics A (2021) 127:168, https://doi.org/10.1007/s00339-021-04315-0 Conferinta internationala ICAME 2021, desfasurata in perioada 5 - 10 septembrie 2021, la Brasov:

Prezentarea orala:

Unidirectional Magnetic Anisotropy in Molibden Dioxide – Hematite Mixed Oxide Nanostructures, Felicia Tolea* ,Lucian Diamandescu, Monica Sorescu, Mihaela Valeanu, Mugurel Tolea,Victor Kuncser

Prezentare poster:

Specific behaviour of the fe-Ni-Co-Ti shape memory ribbons evidenced by Mössbauer spectroscopy, Felicia Tolea, Mihaela Sofronie, Bogdan Popescu, Mugurel Tolea*, Victor Kuncser, Mihaela Valeanu


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