Non-Isothermal Crystallization Kinetics of PBSu/Biochar Composites Studied by Isoconversional and Model Fitting Methods

Non-isothermal crystallization of Poly(butylene succinate) (PBSu)/biochar composites was studied at various constant cooling rates using differential scanning calorimetry. The analysis of the kinetics data revealed that the overall crystallization rate and activation energy of the PBSu polymer were significantly influenced by the addition of biochar. Specifically, the PBSu/5% biochar composite with a higher filler content was more effective as a nucleation agent in the polymer matrix, as indicated by the nucleation activity (ψ) value of 0.45. The activation energy of the PBSu/5% biochar composite was found to be higher than that of the other compositions, while the nucleation activity of the PBSu/biochar composites decreased as the biochar content increased. The Avrami equation, which is commonly used to describe the kinetics of crystallization, was found to be limited in accurately predicting the non-isothermal crystallization behavior of PBSu and PBSu/biochar composites. Although the Nakamura/Hoffman–Lauritzen model performed well overall, it may not have accurately predicted the crystallization rate at the end of the process due to the possibility of secondary crystallization. Finally, the combination of the Šesták–Berggren model with the Hoffman–Lauritzen theory was found to accurately predict the crystallization behavior of the PBSu/biochar composites, indicating a complex crystallization mechanism involving both nucleation and growth. The Kg parameter of neat PBSu was found to be 0.7099 K2, while the melting temperature and glass transition temperature of neat PBSu were found to be 114.91 °C and 35 °C, respectively, very close to the measured values. The Avrami nucleation dimension n was found to 2.65 for PBSu/5% biochar composite indicating that the crystallization process is complex in the composites

The Effect of Biochar Addition on Thermal Stability and Decomposition Mechanism of Poly(butylene succinate) Bionanocomposites

In the present study, poly(butylene succinate) (PBSu) and its bionanocomposites containing 1, 2.5, and 5 wt.% biochar (MSP700) were prepared via in situ melt polycondensation in order to investigate the thermal stability and decomposition mechanism of the materials. X-ray photoelectron spectroscopy (XPS) measurements were carried out to analyze the surface area of a biochar sample and PBSu/biochar nanocomposites. From XPS, it was found that only physical interactions were taking place between PBSu matrix and biochar nanoadditive. Thermal stability, decomposition kinetics, and the decomposition mechanism of the pristine PBSu and PBSu/biochar nanocomposites were thoroughly studied by thermogravimetric analysis (TGA) and pyrolysis–gas chromatography/mass spectrometry (Py−GC/MS). TGA thermograms depicted that all materials had high thermal stability, since their decomposition started at around 300 °C. However, results indicated a slight reduction in the thermal stability of the PBSu biochar nanocomposites because of the potential catalytic impact of biochar. Py−GC/MS analysis was employed to examine, in more detail, the thermal degradation mechanism of PBSu nanocomposites filled with biochar. From the decomposition products identified by Py−GC/MS after pyrolysis at 450 °C, it was found that the decomposition pathway of the PBSu/biochar nanocomposites took place mainly via β-hydrogen bond scission, which is similar to that which took place for neat PBSu. However, at higher biochar content (5 wt.%), some localized differences in the intensity of the peaks of some specific thermal degradation products could be recognized, indicating that α-hydrogen bond scission was also taking place. A study of the thermal stability and decomposition pathway of PBSu/biochar bionanocomposites is crucial to examine if the new materials fulfill the requirements for further investigation for mulch films in agriculture or in electronics as possible applications

Sol-Gel Derived Mg-Based Ceramic Scaffolds Doped with Zinc or Copper Ions: Preliminary Results on Their Synthesis, Characterization, and Biocompatibility

Glass-ceramic scaffolds containing Mg have shown recently the potential to enhance the proliferation, differentiation, and biomineralization of stem cells in vitro, property that makes them promising candidates for dental tissue regeneration. An additional property of a scaffold aimed at dental tissue regeneration is to protect the regeneration process against oral bacteria penetration. In this respect, novel bioactive scaffolds containing Mg2+ and Cu2+ or Zn2+, ions known for their antimicrobial properties, were synthesized by the foam replica technique and tested regarding their bioactive response in SBF, mechanical properties, degradation, and porosity. Finally their ability to support the attachment and long-term proliferation of Dental Pulp Stem Cells (DPSCs) was also evaluated. The results showed that conversely to their bioactive response in SBF solution, Zn-doped scaffolds proved to respond adequately regarding their mechanical strength and to be efficient regarding their biological response, in comparison to Cu-doped scaffolds, which makes them promising candidates for targeted dental stem cell odontogenic differentiation and calcified dental tissue engineering

GALVANOMAGNETIC PROPERTIES OF INTERCALATED COMPOUNDS BI2SE3

ΤΟ BI2SE3 ΕΙΝΑΙ ΕΝΑΣ ΦΥΛΛΟΜΟΡΦΟΣ ΗΜΙΑΓΩΓΟΣ, ΣΤΕΝΟΥ ΕΝΕΡΓΕΙΑΚΟΥ ΧΑΣΜΑΤΟΣ. ΣΕ ΜΟΝΟΚΡΥΣΤΑΛΛΟΥΣ BI2SE3 ΕΓΙΝΕ ΠΑΡΕΝΘΕΣΗ ΜΕ ΟΡΓΑΝΙΚΑ ΚΑΙ ΑΝΟΡΓΑΝΑ ΜΟΡΙΑ, ΟΠΩΣ Η ΥΔΡΑΖΙΝΗ, Η ΦΑΙΝΥΛΥΔΡΑΖΙΝΗ, Η ΑΜΜΩΝΙΑ ΚΑΙ Η ΜΕΘΥΛΥΔΡΑΖΙΝΗ. ΣΤΗ ΣΥΝΕΧΕΙΑ ΕΓΙΝΕ ΑΠΟΠΑΡΕΝΘΕΣΗ ΣΤΟ ΠΕΡΙΒΑΛΛΟΝ ΚΑΙ ΣΕ ΠΕΡΙΒΑΛΛΟΝ ΑΛΚΟΟΛΗΣ. ΚΑΤΑ ΤΗΝ ΔΙΑΡΚΕΙΑ ΤΗΣ ΠΑΡΕΝΘΕΣΗΣ ΚΑΙ ΑΠΟΠΑΡΕΝΘΕΣΗΣ ΜΕΛΕΤΗΘΗΚΑΝ Η ΜΕΤΑΒΟΛΗ ΤΗΣ ΑΓΩΓΙΜΟΤΗΤΑΣ ΚΑΙ ΤΟΥ ΣΥΝΤΕΛΕΣΤΗ HALL. ΕΠΙΣΗΣ ΕΓΙΝΑΝ ΜΕΤΡΗΣΕΙΣ ΣΤΗ ΠΕΡΙΟΧΗ ΘΕΡΜΟΚΡΑΣΙΩΝ ΑΠΟ 20 - 300 K. ΤΑ ΣΥΜΠΕΡΑΣΜΑΤΑ ΤΑ ΟΠΟΙΑ ΠΡΟΕΚΥΨΑΝ ΑΠΟ ΤΗΝ ΘΕΩΡΗΤΙΚΗ ΕΠΕΞΕΡΓΑΣΙΑ ΤΩΝ ΠΕΙΡΑΜΑΤΙΚΩΝ ΔΕΔΟΜΕΝΩΝ ΕΙΝΑΙ: Α) ΤΟ ΜΗ ΠΑΡΑΒΟΛΙΚΟ ΠΡΟΤΥΠΟ KANE ΙΚΑΝΟΠΟΙΕΙ ΤΑ ΔΕΔΟΜΕΝΑ ΜΑΣ. Β) ΟΙ ΓΑΛΒΑΝΟΜΑΓΝΗΤΙΚΕΣ ΙΔΙΟΤΗΤΕΣ ΠΕΡΙΓΡΑΦΟΝΤΑΙ ΓΙΑ ΤΟ ΚΑΘΑΡΟ ΥΛΙΚΟ ΚΑΙ ΤΑ ΠΡΩΤΑ ΣΤΑΔΙΑ ΤΗΣ ΠΑΡΕΝΘΕΣΗΣ ΑΠΟ ΣΥΝΔΥΑΣΜΟ ΣΚΕΔΑΣΗΣ ΑΠΟ ΑΚΟΥΣΤΙΚΑ ΦΩΤΟΝΙΑΚΑΙ ΑΤΕΛΕΙΕΣ (ΔΥΝΑΜΙΚΟ ΜΑΚΡΑΣ ΕΜΒΕΛΕΙΑΣ ΤΗΣ ΠΡΟΣΜΙΞΗΣ). ΣΤΑ ΤΕΛΙΚΑ ΣΤΑΔΙΑ ΤΗΣ ΠΑΡΕΝΘΕΣΗΣ ΕΙΣΑΓΕΤΑΙ ΝΕΟΣ ΜΗΧΑΝΙΣΜΟΣ ΣΚΕΔΑΣΗΣ ΑΠΟ ΤΟ ΔΥΝΑΜΙΚΟ ΜΙΚΡΗΣ ΕΜΒΕΛΕΙΑΣ ΤΟΥ ΙΟΝΤΟΣ. Γ) Η ΤΙΜΗ ΤΟΥ ΕΝΕΡΓΕΙΑΚΟΥ ΧΑΣΜΑΤΟΣ ΕΙΝΑΙ EG=.229 EV ΚΑΙ ΤΗΣ ΕΝΕΡΓΟΥ ΜΑΖΑΣ M*D5,0=.16 M0.BI2SE3 IS A LAMELLAR COMPOUND WITH NARROW ENERGY GAP. BI2SE3 SINGLE CRYSTALS WERE INTERCALATED WITH ORGANIC AND INORGANIC MOLECULES SUCH AS HYDRAZINE, PHENYLHYDRAZINE AMMONIA AND METHYLHYDRAZINE. DEINTERCALATION OF THE SAMPLES WAS DONE IN ALCOHOL. CHANGES IN CONDUCTIVITY AND HALL COEFFICIENT WERE STUDIED DURING BOTH INTERCALATION AS WELL AS DURING DE - INTERCALATION. THE ELECTRICAL PROPERTIES WERE ALSO STUDIED AT THE TEMPERATURE RANGE OF 20 - 300 K. ANALYSIS OF THE ELECTRICAL PROPERTIES CAN BE SUMMARIZED AS: A. THE NON - PARABOLIC KANE MODEL SEEMS TO DESCRIBE OUR EXPERIMENTAL DATA. B. THE GALVANOMETRIC PROPERTIES BOTH FOR THE PRISTINE MATERIAL AND DURING THE FIRST STATES OF INTERCALATION CAN BE DESCRIBED AS DUE TO A MIXED SCATTERING BY ACOUSTIC PHONONS AND IMPURITIES (LONG RANGE COULOMBIC INTERACTION). AT THE LATER STATES OF INTERCALATION A NOVEL MECHANISM SHOULD BE TAKEN INTO ACCOUNT RESULTING FROM SHORT RANGE COULOMBIC INTERACTIONS. C. THE ENERGY GAP AS DETERMINED IN THIS WORK IS EG=.229 EVAND THE EFFECTIVE MASS MD5,0=.16M0

CORRELATION BETWEEN TEACHING PRACTICES IN PHYSICS WITH ATTITUDES AND PERCEPTIONS OF STUDENTS TOWARDS PHYSICS

According to the extensive literature, the learning process in which students participate plays a very important role in shaping a positive attitude towards physics. This paper presents the findings of a research study focusing on the identification and investigation of student attitudes towards the subject and the science of physics. The results were derived from 686 students who attended the first grade of Lyceum – elected Direction Group 2 – in eight different Lyceums of Cyprus public schools. The students participated in the research process at the beginning of their enrolment in the Lyceum. The Group 2 direction includes physics and mathematics as elective subjects. The findings of the research reveal that students who elected Direction Group 2 show a positive attitude towards the subject of physics to a great extent and over time. This element could be used in the educational design addressed to this specific group of students. The research tool used was an appropriately designed questionnaire, tested for its reliability and validity. The questionnaire included closed-ended questions related to the students’ demographics and the determination of their attitudes towards the subject and the science of physics. It also included an open-ended question in which students expressed their views, opinions and suggestions on the subject of physics as well as a specific question dedicated to the teaching practices and approaches of physics at Gymnasium according to the students’ opinions. The emerging correlation of these practices or approaches with the levels of attitudes developed by the students towards the subject and the science of physics verify the prevailing view of the related literature that proposes a significant relationship between the teaching process and the attitudes of students towards the subject of physics. Moreover, the computation of ANOVA p-value produced several statistically significant approaches

Bio-economy in Greece: Current trends and the road ahead

Economic activity that takes environmental protection into account and uses the environmental benefits of an area or country may continuously combine growth with sustainability thereby providing prosperity and societal quality. This paper aims to complement European research on Bioeconomy by reviewing current situation and future trends in Greece. Current data testify that there are significant opportunities for Greece to progress towards a lucrative economy based on renewable resources. The effective growth of such Bioeconomy in Greece depends on the successful cooperation of all stakeholders (state, business, citizens). This is the first study that provides a numerical analysis of the Bio-economy opportunities for Greece and may constitute the foundation for future research, suggestions for policy measures and strategic plannin

Kinetics of Crystallization and Thermal Degradation of an Isotactic Polypropylene Matrix Reinforced with Graphene/Glass-Fiber Filler

Polypropylene composites reinforced with a filler mixture of graphene nanoplatelet-glass fiber were prepared by melt mixing, while conventional composites containing graphene nanoplatelet and glass fiber were prepared for comparative reasons. An extensive study of thermally stimulated processes such as crystallization, nucleation, and kinetics was carried out using Differential Scanning Calorimetry and Thermogravimetric Analysis. Moreover, effective activation energy and kinetic parameters of the thermal decomposition process were determined by applying Friedman’s isoconversional differential method and multivariate non-linear regression method. It was found that the graphene nanoplatelets act positively towards the increase in crystallization rate and nucleation phenomena under isothermal conditions due to their large surface area, inherent nucleation activity, and high filler content. Concerning the thermal degradation kinetics of polypropylene graphene nanoplatelets/glass fibers composites, a change in the decomposition mechanism of the matrix was found due to the presence of graphene nanoplatelets. The effect of graphene nanoplatelets dominates that of the glass fibers, leading to an overall improvement in performance