Ανάπτυξη νανοσύνθετων υλικών για αποθήκευση υδρογόνου

Borohydrides are considered good candidates for low-pressure solid state hydrogen storage, as they have very high hydrogen content. However their high stability and decomposition temperatures hinder their practical use. An appealing approach for adjusting their thermodynamic properties is nano-sizing by confinement in nanometer-sized pores. The aim of this thesis has been to study the hydrogen storage-release properties of eutectic borohydride mixtures such as LiBH4 – NaBH4 (LiNa) and LiBH4 –KBH4 (LiK), after their incorporation (through melt infiltration) in mesoporous carbonaceous materials. It has been shown that the confinement of the borohydride mixtures into 5 and 25 nm diameter pores of a CMK-3 type carbon and a carbon aerogel (CA-20), respectively, improves the kinetics, also providing a partial reversibility of the dehydrogenation / rehydrogenation reaction for both eutectic mixtures after 5 cycles. While the dehydrogenation reactions of the bulk complex hydrides are irreversible, the nanoconfined systems exhibit a consistent reversible uptake of about 3.5-4 wt% H2 for the LiNa / CMK-3 and CA-20 composites and about 3 wt% H2 for the LiK ones. The same synthetic procedure was also followed to obtain composite materials with non-porous carbon disks (CD) and kinetic improvements in the hydrogen release properties of the borohydrides were also observed. These findings in the absence of porosity imply that the carbon surface may act catalytically and assist the decomposition of the borohydrides. However, the pore nanoconfinement seems to play a fundamental role in the reversibility of the hydrogenation reaction, at least for the case of the LiBH4 – KBH4 mixture. Overall, this thesis revealed that the increased reversibility and improved kinetics may be related to a combination of several phenomena such as the catalytic action of the carbon surface, the nano-sizing of the borohydride particles, and/or the abatement of irreversible side-reactions.Τα βοροϋδρίδια παρουσιάζουν ιδιαίτερο ενδιαφέρον για διεργασίες αποθήκευσης υδρογόνου σε χαμηλές πιέσεις, λόγω της πολύ υψηλής περιεκτικότητας σε υδρογόνο. Ωστόσο, η ιδιαίτερη σταθερότητά τους και οι υψηλές θερμοκρασίες που απαιτούνται για την διάσπασή τους δεν ευνοούν την πρακτική τους εφαρμογή. Μια ενδιαφέρουσα προσέγγιση για την κατάλληλη τροποποίηση των θερμοδυναμικών ιδιοτήτων τους σχετίζεται με την μορφοποίησή τους σε σωματίδια νανοκλίμακας μέσω περιορισμού σε νανοπόρους. Στόχος της παρούσας διατριβής ήταν η μελέτη των ιδιοτήτων αποθήκευσης-αποδέσμευσης υδρογόνου ευτηκτικών μιγμάτων βοροϋδριδίων, όπως LiBH4 – NaBH4 (LiNa) και LiBH4 – KBH4 (LiK), μετά την εισαγωγή τους (μέσω διήθησης τήγματος) στους πόρους μεσοπορωδών υλικών ανθρακικής βάσης. Παρατηρήθηκε ότι και για τα δύο ευτηκτικά μίγματα, η εισαγωγή τους στους πόρους άνθρακα τύπου CMK-3 και αερογέλης άνθρακα (CA-20) με διάμετρο 5 και 25 nm, αντίστοιχα, βελτιώνει την κινητική ενώ επιτρέπει και τη μερική αντιστρεψιμότητα της αντίδρασης αφυδρογόνωσης / υδρογόνωσης μετά από 5 κύκλους. Ενώ οι αντιδράσεις αφυδρογόνωσης των σύμπλοκων υδριδίων είναι μη αναστρέψιμες, τα σύνθετα συστήματα άνθρακα/βοροϋδριδίων παρουσιάζουν σταθερή αναστρέψιμη πρόσληψη H2 περίπου 3.5-4 wt% για τα σύνθετα LiNa / CMK-3 και CA-20 και περίπου 3 wt% H2 για τα αντίστοιχα υλικά με LiK. Η αντίστοιχη μελέτη σύνθετων υλικών με μη πορώδεις δίσκους άνθρακα (Carbon Disks, CD), επίσης έδειξε βελτίωση στις ιδιότητες απελευθέρωσης υδρογόνου από τα βοροϋδρίδια, υποδηλώνοντας ότι η επιφάνεια του άνθρακα μπορεί να δράσει καταλυτικά και να βοηθήσει την διάσπαση των βοροϋδριδίων. Ωστόσο, ο νανοπεριορισμός στους πόρους φαίνεται να παίζει θεμελιώδη ρόλο στην αντιστρεπτότητα της αντίδρασης υδρογόνωσης, τουλάχιστον για την περίπτωση του μείγματος LiBH4 – KBH4. Η συμπεριφορά αυτή μπορεί να σχετίζεται με έναν συνδυασμό φαινομένων όπως με την καταλυτική δράση της επιφάνειας του άνθρακα, τη νανοδιάσταση των σωματιδίων βοροϋδριδίου και/ή τον περιορισμό μη αντιστρέψιμων πλευρικών αντιδράσεων

Ammonia-free infiltration of NaBH4 into highly-ordered mesoporous silica and carbon matrices for hydrogen storage

In this work we focused on nanoconfiment of NaBH4 into highly-ordered Si-based and its carbon replica mesoporous scaffolds by ammonia-free wet chemical impregnation. Structural and morphological characterization, performed by X-ray diffraction and Transmission electron microscopy allowed to confirm the effectiveness infiltration procedure. Desorption properties tested by Temperature programmed desorption analyses highlighted a noticeable shift towards lower temperature than corresponding bulk material and literature data referred to similar systems.JRC.F.2-Cleaner energ

A Review of the MSCA ITN ECOSTORE Novel Complex Metal Hydrides for Efficient and Compact Storage of Renewable Energy as Hydrogen and Electricity

Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel, sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+, Mg2+ and Ca2+, while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials, the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore, it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Sklodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE, the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discusse

Clinical nutrition in surgical oncology: Young AIOM-AIRO-SICO multidisciplinary national survey on behalf of NutriOnc research group

Malnutrition is a common condition in cancer patients which is usually associated with functional limitations, as well as increased morbidity and mortality. Based on the support of the young sections of Italian Association of Medical Oncology (AIOM), Italian Association of Radiotherapy and Clinical Oncology (AIRO) and Italian Society of Surgical Oncology (SICO) merged into the NutriOnc Research Group, we performed a multidisciplinary national survey with the aim to define the awareness of nutritional issues among healthcare professionals delivering anticancer care. The questionnaire was organized in four sections, as follows: Knowledge and practices regarding Nutritional Management of cancer patients; Timing of screening and assessment of Nutritional Status; Nutritional Treatment and prescription criteria; Immunonutrition and educational topics. The modules focused on esophagogastric, hepato-bilio-pancreatic and colorectal malignancies. Overall, 215 physicians completed the survey. As regards the management of Nutritional Status of cancer patients, many responders adopted the ERAS program (49.3%), while a consistent number of professionals did not follow a specific validated nutritional care protocol (41.8%), mainly due to lack of educational courses (14.5%) and financial support (15.3%). Nearly all the included institutions had a multidisciplinary team (92%) to finalize the treatment decision-making. Cancer patients routinely underwent nutritional screening according to 57.2% of interviewed physicians. The timing of nutritional assessment was at diagnosis (37.8%), before surgery (25.9%), after surgery (16.7%), before radiochemotherapy (13.5%) and after radiochemotherapy (7%). Most of the responders reported that nutritional status was assessed throughout the duration of cancer treatments (55.6%). An important gap between current delivery and need of nutritional assessment persists. The development of specific and defined care protocols and the adherence to these tools may be the key to improving nutritional support management in clinical practice

Delayed colorectal cancer care during covid-19 pandemic (decor-19). Global perspective from an international survey

Background The widespread nature of coronavirus disease 2019 (COVID-19) has been unprecedented. We sought to analyze its global impact with a survey on colorectal cancer (CRC) care during the pandemic. Methods The impact of COVID-19 on preoperative assessment, elective surgery, and postoperative management of CRC patients was explored by a 35-item survey, which was distributed worldwide to members of surgical societies with an interest in CRC care. Respondents were divided into two comparator groups: 1) ‘delay’ group: CRC care affected by the pandemic; 2) ‘no delay’ group: unaltered CRC practice. Results A total of 1,051 respondents from 84 countries completed the survey. No substantial differences in demographics were found between the ‘delay’ (745, 70.9%) and ‘no delay’ (306, 29.1%) groups. Suspension of multidisciplinary team meetings, staff members quarantined or relocated to COVID-19 units, units fully dedicated to COVID-19 care, personal protective equipment not readily available were factors significantly associated to delays in endoscopy, radiology, surgery, histopathology and prolonged chemoradiation therapy-to-surgery intervals. In the ‘delay’ group, 48.9% of respondents reported a change in the initial surgical plan and 26.3% reported a shift from elective to urgent operations. Recovery of CRC care was associated with the status of the outbreak. Practicing in COVID-free units, no change in operative slots and staff members not relocated to COVID-19 units were statistically associated with unaltered CRC care in the ‘no delay’ group, while the geographical distribution was not. Conclusions Global changes in diagnostic and therapeutic CRC practices were evident. Changes were associated with differences in health-care delivery systems, hospital’s preparedness, resources availability, and local COVID-19 prevalence rather than geographical factors. Strategic planning is required to optimize CRC care