Full range of wettability through surface modification of single-wall carbon nanotubes by photo-initiated chemical vapour deposition

Single-wall carbon nanotubes (SWCNTs) have various remarkable properties, which make them a promising candidate for many applications. However, their inherent hydrophobicity has limited their commercial use in optical, biological, and electrical applications. Photo-initiated chemical vapour deposition (PICVD) using syngas is proposed as a novel, affordable, and versatile method to tailor SWCNT wettability through the addition of oxygen-containing functional groups. Following PICVD surface treatment, X-ray photoelectron spectroscopy, water contact angle measurements (CA), thermogravimetric analysis, Raman spectroscopy and transmission electron microscopy confirm controlled oxygenation of the SWCNT surface. Indeed, this novel approach allows to reproducibly make SWCNTs having surfaces properties ranging from superhydrophilic (CA 150°), including any intermediate values, by simply varying operational parameters such as molar ratio of the syngas precursor, photo-polymerization time and reactor pressure (about normal conditions)

Phase transitions in the α–γ–β spodumene thermodynamic system and impact of γ-spodumene on the efficiency of lithium extraction by acid leaching

ABSTRACT: Heat-treatment of spodumene concentrate at 1323 K (1050 °C) for 30 min in a rotary kiln yielded a successful decrepitation. Particle size decreased from 2 cm to less than 425 µm for 80% of the initial mass. X-ray analysis of both fractions did not reveal the presence of α-spodumene or γ-spodumene. The coarse fraction was ground to less than 425 µm with minimal mechanical energy and mixed with the finer fraction to perform lithium extraction. The lithium extraction efficiency reached 98 wt% without the need for flotation. Some aspects of the thermodynamic behavior of the spodumene system were assessed. Results show that metastable γ-spodumene may hinder the formation of β-spodumene at lower heat treatment temperatures. Some heat-treated samples presented non-negligible γ-spodumene content and lithium extraction efficiency decreases as the γ content increases. Finally, the assumed irreversibility of the transformations was studied by analyzing heat-treated samples following long controlled-storage periods. The results show that concentrate composition is not static over the studied time. This suggests that the β formation is not as irreversible as claimed. It is recommended to avoid long periods between heat-treatment and extraction to avoid the slow conversion of β-spodumene to other allotropes, which are less susceptible to lithium extraction

Reaction kinetics and temperature effects in syngas photo-initiated chemical vapor deposition on single-walled carbon nanotubes

Photo-initiated chemical vapor deposition (PICVD) is a solvent-free process that can be used to produce thin films on a variety of substrates, with applications in fields ranging from biomedicine to optics and microelectronics. This study presents a kinetic analysis for this process using syngas (CO + H2) as a precursor for the surface treatment of single-walled carbon nanotubes (SWCNT) with average dimensions of 1.5 × 100 nm (diameter × length), and addresses the role of iron pentacarbonyl (Fe(CO)5), a photo-active contaminant found in CO. This work builds upon previously developed reaction schemes for PICVD, based mainly on surface characterizations, by coupling these analyses with gas-phase monitoring. This allows us to propose two separate reaction schemes for the gas and surface phase reactions and consider temperature effects. Online FTIR, offline GC-MS, and online GC characterized the gas phase, while for surface characterizations, XPS and TGA were used. Characterizations showed that a coating with a general formula of CnO3nFen was deposited, corresponding to 0.29 ± 0.04 mg carbon and 0.49 ± 0.03 mg iron on the SWCNT substrate over the course of treatment. The Fe(CO)5 was identified as the key reactant in syngas/PICVD reactions and was nearly completely consumed (94%). Mass balances derived from the gas phase characterization showed that Fe(CO)5 inputted to the plug flow reactor could potentially contribute all the amount of 0.49 ± 0.03 mg of Fe and 0.29 ± 0.04 mg of C to the coating on the SWCNT, indicating that syngas/PICVD can be optimized in the future to decrease gas throughput. Temperature did not show a significant effect in the case of PICVD. However, in the absence of ultraviolet light, its role becomes determinant, with rising temperatures causing more Fe deposition

Why some carbons may or may not graphitize? The point of view of thermodynamics

RÉSUMÉ: Not all carbons graphitize in equal measure. Some will develop a structure which approaches the one of perfect graphite (graphitizable carbons) upon heat treatment, while others will not (non-graphitizable carbons). The present work develops a phenomenological model for the conceptual understanding of graphitizability (capacity to graphitize). To support this model, a mathematical formalism, inspired from thermodynamics, is proposed to calculate the Ultimate Graphitizability (eta(g)) of some graphitizable and non-graphitizable carbon materials. eta(g) is the average interlayer spacing (d(002)) of a graphenic carbon following graphitization at similar to 3400 K. eta(g) can be estimated assuming a topological graphitization mechanism operating between 1700 K and 3400 K. Two independent variables define eta(g): d(002) (T alpha) and d(002) (T beta). T alpha and T beta are arbitrarily selected temperatures between 1700 K and 2550 K (the graphitization threshold). In order to better understand the parameters affecting d(002) (T-alpha) and d(002) (T-beta), new carbonization/ graphitization experimental results are presented. These suggest that d(002)(T-alpha) and d(002) (T-beta) are correlated to the oxygen/hydrogen composition ratio and the relative mesoscale crystallite orientation of some graphitizable carbons following the end of primary carbonization. (C) 2019 The Authors. Published by Elsevier Ltd

Rapid antibacterial activity of anodized aluminum-based materials impregnated with quaternary ammonium compounds for high-touch surfaces to limit transmission of pathogenic bacteria

Infections caused by multidrug-resistant bacteria are a major public health problem. Their transmission is strongly linked to cross contamination via inert surfaces, which can serve as reservoirs for pathogenic microorganisms. To address this problem, antibacterial materials applied to high-touch surfaces have been developed. However, reaching a rapid and lasting effectiveness under real life conditions of use remains challenging. In the present paper, hard-anodized aluminum (AA) materials impregnated with antibacterial agents (quaternary ammonium compounds (QACs) and/or nitrate silver (AgNO3)) were prepared and characterized. The thickness of the anodized layer was about 50 μm with pore diameter of 70 nm. AA with QACs and/or AgNO3 had a water contact angle varying between 45 and 70°. The antibacterial activity of the materials was determined under different experimental settings to better mimic their use, and included liquid, humid, and dry conditions. AA–QAC surfaces demonstrated excellent efficiency, killing >99.9% of bacteria in 5 min on a wide range of Gram-positive (Staphylococcus aureus, Clostridioides difficile, vancomycin-resistant Enterococcus faecium) and Gram-negative (streptomycin-resistant Salmonella typhimurium and encapsulated Klebsiella pneumoniae) pathogens. AA–QACs showed a faster antibacterial activity (from 0.25 to 5 min) compared with antibacterial copper used as a reference (from 15 min to more than 1 h). We show that to maintain their high performance, AA–QACs should be used in low humidity environments and should be cleaned with solutions composed of QACs. Altogether, AA–QAC materials constitute promising candidates to prevent the transmission of pathogenic bacteria on high-touch surfaces

Individual recovery expectations and prognosis of outcomes in non‐specific low back pain:prognostic factor review

BACKGROUND: Low back pain is costly and disabling. Prognostic factor evidence can help healthcare providers and patients understand likely prognosis, inform the development of prediction models to identify subgroups, and may inform new treatment strategies. Recent studies have suggested that people who have poor expectations for recovery experience more back pain disability, but study results have differed. OBJECTIVES: To synthesise evidence on the association between recovery expectations and disability outcomes in adults with low back pain, and explore sources of heterogeneity. SEARCH METHODS: The search strategy included broad and focused electronic searches of MEDLINE, Embase, CINAHL, and PsycINFO to 12 March 2019, reference list searches of relevant reviews and included studies, and citation searches of relevant expectation measurement tools. SELECTION CRITERIA: We included low back pain prognosis studies from any setting assessing general, self-efficacy, and treatment expectations (measured dichotomously and continuously on a 0 - 10 scale), and their association with work participation, clinically important recovery, functional limitations, or pain intensity outcomes at short (3 months), medium (6 months), long (12 months), and very long (> 16 months) follow-up. DATA COLLECTION AND ANALYSIS: We extracted study characteristics and all reported estimates of unadjusted and adjusted associations between expectations and related outcomes. Two review authors independently assessed risks of bias using the Quality in Prognosis Studies (QUIPS) tool. We conducted narrative syntheses and meta-analyses when appropriate unadjusted or adjusted estimates were available. Two review authors independently graded and reported the overall quality of evidence. MAIN RESULTS: We screened 4635 unique citations to include 60 studies (30,530 participants). Thirty-five studies were conducted in Europe, 21 in North America, and four in Australia. Study populations were mostly chronic (37%), from healthcare (62%) or occupational settings (26%). General expectation was the most common type of recovery expectation measured (70%); 16 studies measured more than one type of expectation. Usable data for syntheses were available for 52 studies (87% of studies; 28,885 participants). We found moderate-quality evidence that positive recovery expectations are strongly associated with better work participation (narrative synthesis: 21 studies; meta-analysis: 12 studies, 4777 participants: odds ratio (OR) 2.43, 95% confidence interval (CI) 1.64 to 3.62), and low-quality evidence for clinically important recovery outcomes (narrative synthesis: 12 studies; meta-analysis: 5 studies, 1820 participants: OR 1.89, 95% CI 1.49 to 2.41), both at follow-up times closest to 12 months, using adjusted data. The association of recovery expectations with other outcomes of interest, including functional limitations (narrative synthesis: 10 studies; meta-analysis: 3 studies, 1435 participants: OR 1.40, 95% CI 0.85 to 2.31) and pain intensity (narrative synthesis: 9 studies; meta-analysis: 3 studies, 1555 participants: OR 1.15, 95% CI 1.08 to 1.23) outcomes at follow-up times closest to 12 months using adjusted data, is less certain, achieving very low- and low-quality evidence, respectively. No studies reported statistically significant or clinically important negative associations between recovery expectations and any low back pain outcome. AUTHORS' CONCLUSIONS: We found that individual recovery expectations are probably strongly associated with future work participation (moderate-quality evidence) and may be associated with clinically important recovery outcomes (low-quality evidence). The association of recovery expectations with other outcomes of interest is less certain. Our findings suggest that recovery expectations should be considered in future studies, to improve prognosis and management of low back pain

Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease

Background: Experimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. Methods: We conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. RESULTS: At 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in the 300-mg group than in the placebo group. Canakinumab did not reduce lipid levels from baseline. At a median follow-up of 3.7 years, the incidence rate for the primary end point was 4.50 events per 100 person-years in the placebo group, 4.11 events per 100 person-years in the 50-mg group, 3.86 events per 100 person-years in the 150-mg group, and 3.90 events per 100 person-years in the 300-mg group. The hazard ratios as compared with placebo were as follows: in the 50-mg group, 0.93 (95% confidence interval [CI], 0.80 to 1.07; P = 0.30); in the 150-mg group, 0.85 (95% CI, 0.74 to 0.98; P = 0.021); and in the 300-mg group, 0.86 (95% CI, 0.75 to 0.99; P = 0.031). The 150-mg dose, but not the other doses, met the prespecified multiplicity-adjusted threshold for statistical significance for the primary end point and the secondary end point that additionally included hospitalization for unstable angina that led to urgent revascularization (hazard ratio vs. placebo, 0.83; 95% CI, 0.73 to 0.95; P = 0.005). Canakinumab was associated with a higher incidence of fatal infection than was placebo. There was no significant difference in all-cause mortality (hazard ratio for all canakinumab doses vs. placebo, 0.94; 95% CI, 0.83 to 1.06; P = 0.31). Conclusions: Antiinflammatory therapy targeting the interleukin-1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid-level lowering. (Funded by Novartis; CANTOS ClinicalTrials.gov number, NCT01327846.

Synthèse de poudres ultrafines de Si?N? par plasma inductif

L'objectif de cette thèse est d'étudier la synthèse de la poudre ultrafine de nitrure de silicium par plasma inductif à hautes fréquences (h.f.) à travers la réaction en phase gazeuse du SiCl₄ avec NH₃. Pour accomplir cet objectif, une étude thermodynamique du système Si-N-H-Cl-Ar a été complétée de même qu'une revue des théories sur la cinétique de ce système réactionnel. Par la suite, le développement du réacteur à plasma a été complété par une étude des phénomènes de mélange des gaz par spectrométrie de masse afin d'avoir une information complémentaire sur les profils de concentration. Les résultats obtenus avec les modes d'injection axiale et radiale ont montré que les conditions de mélange sous un plasma h.f. sont considérablement différentes de celles à température ambiante. Le mélange des gaz à hautes températures qui affectent les profils de concentration dépend fortement des débits des réactifs, de la pression du système, de la puissance du plasma, de la géométrie des brides d'injection et de la configuration du réacteur. Les phénomènes de transfert de masse dominent avec la présence du plasma. L'étude de synthèse a été réalisée en deux étapes. La première permet de vérifier l'approche proposée dans un réacteur à paroi froide utilisant un plasma d’Ar/N₂ à environ 25-35 kW. La poudre obtenue contenait une phase amorphe et/ou une petite quantité de la forme a ou du Si₃N₄. Des trichites ont pu être aussi observées. La poudre avait une couleur variant du blanc au brun et une surface spécifique de 60 m²/g. On observait des quantités fort appréciables du sous-produit NH₄Cl condensé avec la poudre et qui était éliminé par traitement thermique. La seconde étape basée sur les résultats de l'étude de mélange et les résultats de l'étude avec paroi froide, a été une étude avec paroi chaude pour vérifier si on pouvait augmenter la cristallinité de la poudre tout en évitant la condensation du NH₄Cl. Les résultats ont montré la capacité de réduire grandement le contenu de NH₄Cl de la poudre à moins de 1 % tout en obtenant une cristallinité de près de 30 %. La surface spécifique de la poudre a été réduite à 40 m²/g. Le développement des montages expérimentaux a été accompli par des études systématiques en étudiant les effets des paramètres comme la position de la sonde d'injection du SiCl₄, le ratio NH₃/SiCl₄, la puissance du plasma, les gaz de trempe et la composition des gaz plasmagènes et leurs débits. Une mesure de la composition de la phase gazeuse durant la réaction a été faite par spectrométrie de masse. Une caractérisation physico-chimique de la poudre a été réalisée avec plusieurs techniques comme la diffraction des rayons X, la surface spécifique, la microscopie électronique à transmission, l'analyse thermogravimétrique et la spectrométrie de dispersion d'énergie des rayons X