Kompozitų, sudarytų iš polimerų ir organinių bei neorganinių nanodalelių, ultragarsinė ir dielektrinė spektroskopija

During the last decades nanotechnology has reached a great importance in the research world. The branch of technology is operating in various fields of application as communications and medicine. The main reason behind the use of nanocomposites is the enhancement of various properties when compared to individual components. Produced nanomaterials can display unique properties which are supported by morphological evidence at nanometer scale. For this reason, it is very important to understand, how properties of nano- and microcomposites depend on the ratio and type of its constituents. Moreover, it is important to determine the reliability and durability of a material prior to the massive production on the market. Therefore, conducted repetitive experiments under various conditions (e.g. increased temperature) could contribute to understanding the interfaces between various fillers and the surrounding medium within a nanocomposite. Polymer based composites with embedded solid fillers can incorporate mechanical and electrical properties of its constituents. In comparison with classical inorganic piezoelectrics, piezoelectric polymers have a number of advantages.On the frequency scale, acoustic waves of frequencies near to 10 MHz are commonly used in diagnostic ultrasound techniques (10 MHz). Therefore, results of ultrasonic investigation of pure P(VDF-TrFE) and its composites with BPZT at 10 MHz are of peculiar importance. In this work ultrasonic anomalies, related to the ferroelectric phase transitions in the materials under investigation, are discussed. Results of dielectric and differential scanning calorimetry (DSC) investigations of these new P(VDF-TrFE)/BPZT composites are also presented

Ultrasonic and dielectric spectroscopy of composites based on polymers and organic or inorganic nanoparticles

During the last decades nanotechnology has reached a great importance in the research world. The branch of technology is operating in various fields of application as communications and medicine. The main reason behind the use of nanocomposites is the enhancement of various properties when compared to individual components. Produced nanomaterials can display unique properties which are supported by morphological evidence at nanometer scale. For this reason, it is very important to understand, how properties of nano- and microcomposites depend on the ratio and type of its constituents. Moreover, it is important to determine the reliability and durability of a material prior to the massive production on the market. Therefore, conducted repetitive experiments under various conditions (e.g. increased temperature) could contribute to understanding the interfaces between various fillers and the surrounding medium within a nanocomposite. Polymer based composites with embedded solid fillers can incorporate mechanical and electrical properties of its constituents. In comparison with classical inorganic piezoelectrics, piezoelectric polymers have a number of advantages.On the frequency scale, acoustic waves of frequencies near to 10 MHz are commonly used in diagnostic ultrasound techniques (10 MHz). Therefore, results of ultrasonic investigation of pure P(VDF-TrFE) and its composites with BPZT at 10 MHz are of peculiar importance. In this work ultrasonic anomalies, related to the ferroelectric phase transitions in the materials under investigation, are discussed. Results of dielectric and differential scanning calorimetry (DSC) investigations of these new P(VDF-TrFE)/BPZT composites are also presented

Effect of open ultraviolet germicidal irradiation lamps on functionality of excimer lasers used in cornea surgery

We report on the impact of direct ultraviolet germicidal irradiation (UVGI) on reflective optics, used in the excimer laser system Allegretto Eye-Q. The aim of our work was to confirm our hypothesis based on long-rate observations of obtained anomalies in post-operative results that are attributed to degradation of reflective optics upon ultraviolet radiation. The presence of direct UVGI coupled with humidity in the operating environment caused merging anomalies and unwanted post-operative correction values. Ultraviolet-A radiation caused a similar effect on the reflective cover of the mirrors

Temperature and frequency dependence of the dielectric and piezoelectric response of P(VDF-TrFE)/CoFe2O4 magnetoelectric composites

CoFe2O4 nanoparticles embedded on polyvinylidene fluoride (PVDF) matrix shows suitable propertied for practical application as piezoelectric and magnetoelectric transducers. Essential for these applications is the knowledge about the dielectric, ferroelectric and piezoelectric responses of the multiferroic films at high frequencies and low temperatures. This work reports on the effect of ferrite content, temperature and frequency on the dielectric, ferroelectric and piezoelectric responses of magnetoelectric CoFe2O4 nanocomposites. It was observed that for frequencies lower than 100 kHz, no substantial differences are detected on the ɛ’ and ɛ’’ values from composites with CoFe2O4 contents ranging from 5 to 11 wt.%. For higher frequencies (100 kHz - 250 MHz) and at temperatures ranging from 150 K to 400 K the same trend is observed, the ɛ’ and ɛ’’ values are being higher for the composite with 5 wt.% of ferrite content and lower in the composites with 11 wt.%, indicating that after a critical filler loading, the e CoFe2O4 nanoparticles lead to a decrease the dielectric response of the composites at higher frequencies. For all composite compositions increasing temperature leads to lower coercive fields and higher piezoelectric and polarization values.FCT-Fundação para a Ciência e Tecnologia for financial support under grant SFRH/BPD/96227/2013. SLM thanks financial support from the Basque Government Industry Department under the ELKARTEK Program and the Diputación Foral de Bizkaia for finantial support under the Bizkaia Talent program; European Union’s Seventh Framework Programme; Marie Curie Actions – People; Grant agreement nº 267230info:eu-repo/semantics/publishedVersio