Lead Free (BaZr0.2Ti0.8O3) and Lead Based (PbZr0.52Ti0.48O3) Flexible Thick Films: Structural Properties and Potential Use as Energy Storage and Energy Harvesting Systems

In the last year energy harvesters based on piezoelectricity from mechanical vibration has emerged as the very promising devices that are explored extensively for its functionality in energy technologies. In this paper a series of flexible lead- free BZT/PVDF and lead based PZT/PVDF piezocomposites with variable filler content up to 50 vol. % have been prepared by hot pressing method. Structure and morphology of BZT and PZT powders as well as distribution of piezo-active filler in obtained flexible films were characterized by XRD and SEM analysis. Total amoun of electro active phase (% FEA) of PVDF is higher in PZT-based films in comparison with BZT based ones but the contribution of more desirable β- phase is higher in BZT-PVDF films. In both composite dielectric permittivity's was increased in contrast to their polymer PVDF host matrix, but also displayed decreased breakdown strenght and raised energy loss. In addition, the remnant polarization (Pr) and leakage current were also investigated to evaluate the breakdown strength in both types of flexible films. Calculations of storage energies and output voltage obtained for the investigated materials revealed an increasing trend with increasing amount of BZT and PZT active phase. The maximum storage energy of 0.42 J/cm3 at 390 kV/cm3 was obtained for PZT-PVDF (40-60) films while the maximum output voltage of about 10 V was obtained for PZT-PVDF (50-50) flexible film. In addition, comparisons between properties of lead based and lead free flexible films as well as potential use of those films as energy storage and energy harvesting systems were considered

TWO-PHASE AND THREE-PHASE FLEXIBLE THICK FILMS: POTENTIAL USE AS ENERGY STORAGE AND ENERGY HARVESTING SYSTEMS

For the last decades, energy harvesters based on piezoelectricity from mechanical vibration (wind, human activities, vibrations of machines and traffic, ocean waves, and acoustic waves) are explored extensively for its functionality in energy technologies. Typical applications that could benefit from mechanical energy harvesting are that many sensors, alarms, LED lights, and other low-power and ultra-low-power devices can be driven energetically completely independently [1]. To fabricate a flexible piezoelectric energy harvester (FPEHs) that operates under various conditions, ceramic particles were blended with a polymer to form composite films. Two-phase lead-free BaZr0.2Ti0.8/PVDF and lead-based PbZr0.52Ti0.48/PVDF piezocomposites, as well as three-phase PbZr0.52Ti0.48/Ni0.7Zn0.3Fe2O4/PVDF composites films with variable filler content (up to 50 vol.%) have been prepared by hot pressing method. Structure and morphology of piezo-active phase powders as well as distribution of filler in obtained flexible films were characterized by XRD and SEM analysis. Total amount of electroactive phase (% FEA) of PVDF in all films were investigated by FTIR analysis. In all composites dielectric permittivities was increased in contrast to their polymer PVDF host matrix, but also displayed decreased breakdown strength and raised energy loss. In addition, the remnant polarization (Pr) and leakage current were also investigated to evaluate the breakdown strength in all types of flexible films. Also, ferromagnetic response was established in PZT/ferrite/PVDF films under magnetic field of 10 kOe. Calculations of storage energies and output voltage obtained for the investigated materials revealed an increasing trend with increasing amount of active phase. The maximum storage energy of 0.42 J/cm3 at 390 kV/cm3 was obtained for PZT-PVDF (40-60) films while the maximum output voltage of about 10 V was obtained for PZT-PVDF (50-50) flexible film. In addition, comparisons between properties of

LEAD BASED (PZT) AND LEAD FREE (BZT) COMPOSITES FLEXIBLE FILMS AS LOW-ENERGY PIEZOELECTRIC HARVESTERS

Various alternative renewable sources such as solar, wind, thermal energy and mechanical vibrations are available for the energy generations. For the last decades, energy harvesters based on piezoelectricity from mechanical vibration are explored extensively for its functionality in energy technologies [1,2]. Flexible piezoelectric energy harvesters (FPEHs) and energy storage system were fabricated by employing solid state synthesized lead-free BZT (BaZr0.2Ti0.8O3) and PZT (PbZr0.52Ti0.48O3) nanopowders prepared by autocombustion method with polyvinylidene fluoride (PVDF) in different volume percentage (xBZT/PZT-(1-x)PVDF, x=30, 40, 50). Both flexible films with quite homogeneous distribution of piezo-active filler were confirmed by XRD and SEM analysis. In addition, the remnant polarization (Pr) and dielectric constant are also investigated to evaluate the breakdown strength in flexible films. The improved dielectric loss tangent (< 0.02) and dielectric permittivity of 120 at room temperature and frequency 1 MHz of BZT-PVDF (50- 50) in comparison with neat PVDF films is found beneficial for both energy harvesting and storage. Calculations of storage energies obtained for the investigated materials revealed an increasing trend with increasing amount of active phase (BZT and PZT). The maximum storage energy of 0.11 J/cm3 and 0.13 J/cm3, and energy efficiency (η) of 72% and 39% was obtained for BZT-PVDF (50-50) and PZTPVDF (40-60) films, respectively. Test of the force impact showing similar output voltage of around 4 V for both, BZT and PZT flexible films

Conductivity of doped LaGaO3 prepared by citrate sol-gel method

Lanthanum-gallate powders (LSGM), with composition La1-xSrxGa1-yMgyO3-δ (0 ≤ x, y ≤ 0.2), were prepared using citrate solgel method. As-synthesized powders were calcined at 900°C, uniaxially pressed and sintered in air at different temperatures (up to 1450°C). Sintered samples contained cubic perovskite phase, while only pure LaGaO3 had small amount of the secondary orthorhombic phase. Sintering temperature of 1450°C with dwell time of 2 hours was sufficient to obtain samples with densities higher than 95% TD, with exception of pure LaGaO3. Impedance spectroscopy measurements confirmed that obtained LSGM ceramics have total conductivity an order of magnitude higher than zirconiabased electrolyte. Thus, citrate sol-gel method used in this work is a promising synthesis route for production of the doped lanthanum-gallate for intermediate temperature solid oxide fuel cells

Integration of Process Safety in Chemical Process Design: Initiating a Different Way of Thinking

Teaching process safety in Engineering curriculum in general and in Chemical Engineering curriculum in particular is becoming more crucial, giving the worldwide advancement and developments in process industries. Courses on chemical process safety usually involve, but are not limited to, the application of different principles and fundamentals studied in engineering courses (from mathematics and statistics up to transport phenomena and process design) to process safety. This paper discusses the experience gained from teaching chemical process safety courses to the senior students in chemical engineering department at Texas A&M University at Qatar (TAMU-Qatar). Significant efforts have been made to develop teaching programs supported by key activities and the use of relevant experimental facilities to improve the quality of the teaching and transmit Safety and Process Safety as a value to the students. Process design final year project is considered as an excellent opportunity for the students to apply the principles of process safety to their process design. For this particular activity the students are encouraged to thinking a different way beyond the achievement of predefined design goals and assess the risks associated to abnormal working conditions (operation under severe condition, loss of control, etc) and reduce these risks by application of the principles of inherent safety, and the addition of prevention and mitigation measures. In other words, the challenge lies in getting the student to switch from focusing only on the process design goals to integrating different process safety concepts during solving different design problems at early stages of the project