Thermal characteristics of Ni–Ti SMA (shape memory alloy) actuators

Degeratu, Sonia; Rotaru, P.; Manolea, Gh.; Manolea, Horia Octavian; Rotaru, Andrei

doi:10.1007/s10973-009-0215-0

Cited by 32 publications

(16 citation statements)

References 15 publications

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“…Thermal analysis of materials is a very important tool for finding their stability in order to understand the structure [34][35][36], the interactions within components [37][38][39][40] and to know the applicability domains [41,42]. The kinetic studies of the thermal decompositions were usually used for performing lifetime predictions [43,44], for comparative purposes [45,46] or for better understanding of the structural dynamics [47].…”

Section: Investigation Techniquesmentioning

confidence: 99%

Thermal and kinetic study of hexagonal boric acid versus triclinic boric acid in air flow

Rotaru

2016

J Therm Anal Calorim

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Boric acid is a very important inorganic material with diverse uses in optoelectronics, petroleum industry, medicine, agriculture, etc. Recently, it was reported on the modification of the crystallization system of the triclinic boric acid (TBA) to hexagonal boric acid (HBA), when a special obtaining procedure is applied. In this paper, the thermokinetic stability of HBA novel material was comparatively studied with respect to the well-known TBA, in air flow atmosphere. Both HBA and TBA undergo a threestep overall thermal decomposition reaction (dehydration), following similar pathways; from the thermodynamic point of view HBA is more stable-decomposition temperatures and DH are higher in this case compared to those of TBA. The kinetic analysis was performed by means of the isoconversional methods, for each step of dehydration observing different thermokinetic regions. Higher thermal stability for HBA enables it to be employed at higher temperatures instead of TBA, explaining why the triclinic symmetry enhances the formation actually of the pseudohexagonal crystals as crystal habit at the macroscopic scale. Lower thermodynamic and kinetic stability of HBA makes it easier to be activated and thus more instable at the microstructural scale: this is an indirect proof of the TBA presence in the usual surrounding conditions and in the same time raises the probability for HBA molecules to slide onto their crystalline layers due to the lability of hydrogen bonds keeping them and thus increased potential to intercalate with other molecules. The present results open the possibility for promising applications of HBA as a better lubricant for various industries, while in the medical sector superior cleanser, antifungal and antibacterial properties may be foreseen.

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Section: Investigation Techniquesmentioning

confidence: 99%

Thermal and kinetic study of hexagonal boric acid versus triclinic boric acid in air flow

Rotaru

2016

J Therm Anal Calorim

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“…Thermal analysis is frequently used to determine the thermal stability and phase transformations of organic and inorganic materials [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”

Section: Resultsmentioning

confidence: 99%

Thermal properties, texture, second-order stress, and magnetic susceptibility of the Bi1.8Pb0.3Sr2Ca2Cu3.3Ox

Harabor

Rotaru

Harabor

2014

J Therm Anal Calorim

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Mono-phase high critical temperature (Bi,Pb)-2223 superconductor from the off-stoichiometric Bi 1.8 Pb 0.3 Sr 2 Ca 2 Cu 3.3 O x belonging to the tetragonal system, has been obtained. We studied the crystalline structure, the stress of second order, and the texture of the surface pellet, in the framework of XRD diffractometry. Results of the thermal measurements made in the nitrogen, with a heating rate of 10 K min -1 , from room temperature (RT) to 1273.15 K, show a slow mass decrease of 1.25 % from RT to 1003.15 K probably due to the elimination of water, oxygen, and of the other gases accumulated on the crystallite surface through chemical adsorption. Two endothermic processes were evidenced on DSC, and DTG curves: the first in the range of 1135.15-1193.15 K (melting and slow decomposition), and another after 1217.45 K (decomposition). The contribution of crystal lattice to the estimated specific heat capacity was in conformity with the Einstein model, giving for the Einstein temperature a value of 1297.5 K. In conformity with the Müller critical state model, we found linear dependences for intragrain critical transition temperature, T g , and intergrain coupling temperature, T p , versus the amplitude of the external AC magnetic fields. There was evidenced that intergrain critical currents are five orders smaller than the intragrain critical currents.

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“…The SMA formed actuator can be applied to wind direction adjusting mechanism for an air conditioner, Micropump, Microvalve, thermostatic mixing valve, fire resistant valve for gas pipeline, sprinkler fire extinguishing system, robot hand derived by shape memory alloy actuator, auto thermostat, automobile fan clutch and automatic actuator for fog lamp cover etc. [3][4].…”

Section: Introductionmentioning

confidence: 99%