• Energy Research
• 7. Clean energy close
• IT close
• EU close
• ES close
• CNR ExploRA close

Dielectric and anelastic spectroscopies are complementary techniques and their combination allows valuable information to be obtained in the field of multifunctional materials. Whereas the dielectric spectroscopy measures the dielectric susceptibility ?(?,T) and it is sensitive to fluctuations of electric dipoles, the anelastic spectroscopy measures the elastic compliance or elastic susceptibility s(?,T) and it is sensitive to fluctuations of elastic dipoles. Both susceptibilities are complex, their immaginary part being due to the delayed response of the mobile defects coupled to the electric field/stress. The great advantage of using a combination of both techniques is that the anelastic measurements are insensitive to free charges, therefore it is possible to measure the dynamics of ions also in the presence of free charges. Two main types of investigations have been pursued by the combination of these techniques: the study of structural phase transitions and the study of microscopic mechanisms associated with the presence of defects, both important for the knowledge and development of multifunctional materials. We have applied this approach for different functional materials with perovskite framework: multiferroic, ferroelectric and relaxor ferroelectric ceramics, and organic-inorganic perovskite photovoltaics. Thanks to the combination of the two spectroscopies, it has been possible to probe more accurately the structural transitions involving the antiferrodisortive tilt modes of the octahedra in PZT [1] and NBT-BT [2]. It was also possible to evidence incipient phase separation in lead titanate-based multiferroics [3]. Moreover, since the elastic response is insensitive to free charges, it has been used to probe the piezoelectric response even in unpoled ceramics [4] and for the study of coexisting ferroelectric and metallic states [5]. The combination of the two techniques allowed also new features to be revealed on the reorientation dynamics of the organic molecules in MAPbI3 photovoltaic organic-inorganic perovskites and the hindrance of their ferroelectric order by coupling with the tilt modes [6]. 1. F. Cordero, F. Trequattrini, F. Craciun, C. Galassi, Phys. Rev. B, 87 (2013) 094108 2. F. Cordero, F. Craciun, F. Trequattrini, et al., Phys. Rev. B, 81 (2010) 144124 3. F. Craciun, F. Cordero, B. Vasile, et al., Phys. Chem. Chem. Phys., 20 (2018) 14652 4. F. Cordero, F. Craciun, F. Trequattrini, C. Galassi, Phys. Rev. B, 93 (2016) 174111 5. F. Cordero, F. Trequattrini, F. Craciun, et al., Phys. Rev. B, 99 (2019) 064106 6. F. Cordero, F. Craciun, F. Trequattrini, et al., J. Phys. Chem. Lett., 9 (2018) 4401

Dielectric and anelastic spectroscopies are complementary techniques and their combination allows valuable information to be obtained in the field of multifunctional materials. Whereas the dielectric spectroscopy measures the dielectric susceptibility ?(?,T) and it is sensitive to fluctuations of electric dipoles, the anelastic spectroscopy measures the elastic compliance or elastic susceptibility s(?,T) and it is sensitive to fluctuations of elastic dipoles. Both susceptibilities are complex, their immaginary part being due to the delayed response of the mobile defects coupled to the electric field/stress. The great advantage of using a combination of both techniques is that the anelastic measurements are insensitive to free charges, therefore it is possible to measure the dynamics of ions also in the presence of free charges. Two main types of investigations have been pursued by the combination of these techniques: the study of structural phase transitions and the study of microscopic mechanisms associated with the presence of defects, both important for the knowledge and development of multifunctional materials. We have applied this approach for different functional materials with perovskite framework: multiferroic, ferroelectric and relaxor ferroelectric ceramics, and organic-inorganic perovskite photovoltaics. Thanks to the combination of the two spectroscopies, it has been possible to probe more accurately the structural transitions involving the antiferrodisortive tilt modes of the octahedra in PZT [1] and NBT-BT [2]. It was also possible to evidence incipient phase separation in lead titanate-based multiferroics [3]. Moreover, since the elastic response is insensitive to free charges, it has been used to probe the piezoelectric response even in unpoled ceramics [4] and for the study of coexisting ferroelectric and metallic states [5]. The combination of the two techniques allowed also new features to be revealed on the reorientation dynamics of the organic molecules in MAPbI3 photovoltaic organic-inorganic perovskites and the hindrance of their ferroelectric order by coupling with the tilt modes [6]. 1. F. Cordero, F. Trequattrini, F. Craciun, C. Galassi, Phys. Rev. B, 87 (2013) 094108 2. F. Cordero, F. Craciun, F. Trequattrini, et al., Phys. Rev. B, 81 (2010) 144124 3. F. Craciun, F. Cordero, B. Vasile, et al., Phys. Chem. Chem. Phys., 20 (2018) 14652 4. F. Cordero, F. Craciun, F. Trequattrini, C. Galassi, Phys. Rev. B, 93 (2016) 174111 5. F. Cordero, F. Trequattrini, F. Craciun, et al., Phys. Rev. B, 99 (2019) 064106 6. F. Cordero, F. Craciun, F. Trequattrini, et al., J. Phys. Chem. Lett., 9 (2018) 4401

Dolomite-based binders are characterised by interesting technical and environmental features. For their synthesis, sources of both CaO and MgO are required. The idea developed in this work is to couple the synthesis of dolomite-based binders, starting from a natural dolomite, through the concept of concentrated solar energy (needed to drive the endothermal dolomite calcination process) in fluidised bed reactors. To this end, a fluidised bed system, where the concentrated solar radiation is mimicked by the use of Xe-lamps (short-arc), has been set up and operated. Natural dolomite (sieved in the 420-590 ?m size range) was calcined at a nominal temperature of 850 °C, and bed temperature profiles during solar-driven calcination were investigated. Then, four binders were prepared by mixing slaked dolomite (obtained from the hydration of solar calcined dolomite) with either blast furnace slag or coal fly ash as supplementary cementitious materials. The binders were hydrated for curing times ranging from 7 to 56 days. X-ray fluorescence, X-ray diffraction and combined differential thermal and thermogravimetric analyses were employed as characterisation techniques both to analyse the chemical composition of starting materials and to investigate the evolution of the hydration in the four systems.

Dolomite-based binders are characterised by interesting technical and environmental features. For their synthesis, sources of both CaO and MgO are required. The idea developed in this work is to couple the synthesis of dolomite-based binders, starting from a natural dolomite, through the concept of concentrated solar energy (needed to drive the endothermal dolomite calcination process) in fluidised bed reactors. To this end, a fluidised bed system, where the concentrated solar radiation is mimicked by the use of Xe-lamps (short-arc), has been set up and operated. Natural dolomite (sieved in the 420-590 ?m size range) was calcined at a nominal temperature of 850 °C, and bed temperature profiles during solar-driven calcination were investigated. Then, four binders were prepared by mixing slaked dolomite (obtained from the hydration of solar calcined dolomite) with either blast furnace slag or coal fly ash as supplementary cementitious materials. The binders were hydrated for curing times ranging from 7 to 56 days. X-ray fluorescence, X-ray diffraction and combined differential thermal and thermogravimetric analyses were employed as characterisation techniques both to analyse the chemical composition of starting materials and to investigate the evolution of the hydration in the four systems.

The effect of external EGR on knock was evaluated using a CFR engine. Combustion pressure was sampled on a time basis. A band pass filter in the time domain was applied to the pressure cycles. Five knock indices were calculated for each combustion cycle. The problem to quantify knock intensity was focused. At this extent, measurements were carried out on standard iso-octane-n-heptane blends in the test conditions used for the determ of the Motor Method Octane Number (MON). Knock intensity was varied acting on compression ratio. For each index, the conditions of absence of knock were determined using motored cycles. The indices were compared and one of them, showing the lowest C.O.V., was selected for further measurements. The effect of EGR on test fuels having different composition was evaluated varying the compression ratio, at fixed ignition timing. In this way, the same level of detonation, obtained in the absence of EGR, was realized with different amounts of external EGR. Percent variation of compression ratio was used to compare the ability of fuels, having different octane number, to tolerate compression ratio increase in presence of EGR. In particular, the tests were carried out on a matrix of twelve fuels with three levels of EGR. The results show that with all tested fuels the percent increase of compression ratio is strongly dependent on EGR.

The effect of external EGR on knock was evaluated using a CFR engine. Combustion pressure was sampled on a time basis. A band pass filter in the time domain was applied to the pressure cycles. Five knock indices were calculated for each combustion cycle. The problem to quantify knock intensity was focused. At this extent, measurements were carried out on standard iso-octane-n-heptane blends in the test conditions used for the determ of the Motor Method Octane Number (MON). Knock intensity was varied acting on compression ratio. For each index, the conditions of absence of knock were determined using motored cycles. The indices were compared and one of them, showing the lowest C.O.V., was selected for further measurements. The effect of EGR on test fuels having different composition was evaluated varying the compression ratio, at fixed ignition timing. In this way, the same level of detonation, obtained in the absence of EGR, was realized with different amounts of external EGR. Percent variation of compression ratio was used to compare the ability of fuels, having different octane number, to tolerate compression ratio increase in presence of EGR. In particular, the tests were carried out on a matrix of twelve fuels with three levels of EGR. The results show that with all tested fuels the percent increase of compression ratio is strongly dependent on EGR.

In the present work, an experimental study on a lab-scale adsorption refrigerator, based on activated carbon/ethanol working pair is reported. An extensive testing campaign has been carried out at the CNR ITAE laboratory, with multiple aims. First, the performance has been evaluated in terms of both COP and Specific Cooling Power (SCP), under different boundary conditions, including both air conditioning and refrigeration applications. Attractive SCPs, up to 180 W/kg and 70 W/kg for air conditioning and refrigeration, respectively, were measured. Under the same conditions, COP between 0.17 and 0.08 were obtained. In addition, different management strategies, namely, heat recovery between adsorbers and re-allocation of phase durations, were evaluated to identify their influence on the system. Both strategies confirmed the possibility of increasing COP and SCP up to 40% and 25%, respectively. Moreover, a design analysis based on the experimental results has been carried out, to suggest possible improvements of the system. The obtained results demonstrated the possibility of employing a non-toxic refrigerant like ethanol reaching performance comparable with other harmful refrigerants like ammonia and methanol.

In the present work, an experimental study on a lab-scale adsorption refrigerator, based on activated carbon/ethanol working pair is reported. An extensive testing campaign has been carried out at the CNR ITAE laboratory, with multiple aims. First, the performance has been evaluated in terms of both COP and Specific Cooling Power (SCP), under different boundary conditions, including both air conditioning and refrigeration applications. Attractive SCPs, up to 180 W/kg and 70 W/kg for air conditioning and refrigeration, respectively, were measured. Under the same conditions, COP between 0.17 and 0.08 were obtained. In addition, different management strategies, namely, heat recovery between adsorbers and re-allocation of phase durations, were evaluated to identify their influence on the system. Both strategies confirmed the possibility of increasing COP and SCP up to 40% and 25%, respectively. Moreover, a design analysis based on the experimental results has been carried out, to suggest possible improvements of the system. The obtained results demonstrated the possibility of employing a non-toxic refrigerant like ethanol reaching performance comparable with other harmful refrigerants like ammonia and methanol.