by Keyword: Challenges
Arnau, Marc, Sans, Jordi, Turon, Pau, Aleman, Carlos, (2024). Establishing ultraporous permanently polarized hydroxyapatite as a green and highly efficient catalyst for carbon dioxide conversion in continuous flow under mild conditions Rsc Sustainability , 
We present the use of an ultraporous permanently polarized hydroxyapatite (upp-HAp) catalyst for continuous and highly efficient production of formic acid (predominant) and acetic acid using wet CO2 (i.e. CO2 bubbled into liquid water) as a reagent. In all cases, reactions were conducted at temperatures ranging from 95 to 150 degrees C, using a CO2 constant flow of 100 mL s(-1), and without applying any external electric field and/or UV radiation. Herein, we study how to transfer such a catalytic system from batch to continuous reactions, focusing on the water supply (proton source): (1) wet CO2 or (2) liquid water in small amounts is introduced in the reactor. In general, the reduction of CO2 to formic acid predominates over the C-C bond formation reaction. On the other hand, when liquid water is added, two interesting outcomes are observed: (1) the yield of products is higher than in the first scenario (>2 mmol g(c)(-1)min(-1)) while the initial liquid water remains largely available due to the mild reaction temperature (95 degrees C); and (2) a high yield of ethanol (>0.5 mmol g(c)(-1)min(-1)) is observed at 120 degrees C, as a result of the increased efficiency of the C-C bond formation. Analysis of kinetic studies through temporal and temperature dependence shows that CO2 fixation is the rate limiting step, ruling out the competing effect of proton adsorption on the binding sites and confirming the crucial role of water. The activation energy for the CO2 fixation reaction has been determined to be 66 +/- 1 kJ mol(-1), which is within the range of conventional electro-assisted catalysts. Finally, mechanistic insights on the CO2 activation and role of the binding sites of upp-HAp are provided through isotopic-labeling ((CO2)-C-13) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) studies.
JTD Keywords: Butano, Challenges, Co2 reduction, Fuels, Hydrogenation, Mechanism, Nanomaterials, Noble-metal
Planell, J. A., Navarro, M., (2009). Challenges in bone repair 
Bone repair biomaterials (ed. Planell, J. A., Lacroix, D., Best, S., Merolli, A.), Woodhead (Cambridge, UK) , 3-24
A fundamental aspect of the rapidly expanding medical care sector, bone repair continues to benefit from emerging technological developments. This text provides researchers and students with a comprehensive review of the materials science and engineering principles behind these developments. The first part reviews the fundamentals of bone repair and regeneration. Further chapters discuss the science and properties of biomaterials used in bone repair, including both metals and biocomposites. Final chapters analyze device considerations such as implant lifetime and failure, and discuss potential applications, as well as the ethical issues that continually confront researchers and clinicians.
JTD Keywords: Social impact of musculoskeletal disease, Economic burden of musculoskeletal disease, Social aspects of dental and maxillofacial conditions, Some clinical challenges of bone repair, Conclusions and future trends, Sources of further information and advice