Temperature-Dependent 4‑, 5- and 6‑Fold Coordination of Aluminum in MOCVD-Grown Amorphous Alumina Films: A Very High Field 27Al-NMR study

The only easy way to prepare amorphous alumina is via thin film deposition. For this reason, the disorder in amorphous alumina has not yet been fully investigated. We have used very high-field (20 T) solid state 27Al NMR spectroscopy to analyze the structural modifications of amorphous alumina thin films with deposition temperature (Td). The films were deposited by metalorganic chemical vapor deposition in the Td range of 360−720 °C. Depending on Td, film composition is either AlO1+x(OH)1−2x (0 ≤ x ≤ 0.5) or Al2O3. From 27Al 1D magic angle spinning(MAS) and 2D multiple-quantum magic angle spinning (MQMAS) NMR analyses, the films grown between 360 and 600 °C contain between 38 and 43 atom % of 5-fold coordinated aluminum sites ([5]Al). The percentages of [6]Al and [4]Al sites vary spectacularly, reaching their respective minimum (5 atom %) and maximum (54 atom%) around 515 °C. The analysis of a very thin film (85 nm) of Al2O3 reveals the presence of metallic aluminum at the interface with the substrate and suggests that the respective percentages of [n]Al sites slightly differ from those in thicker films. The observed Td dependence of amorphous alumina structure can be correlated with that of film properties previously reported,namely, Young’s modulus, hardness, and corrosion protection

Temperature Dependent 4-, 5- and 6-Fold Coordination of Aluminum in MOCVD-Grown Amorphous Alumina Films: From Local Coordination to Material Properties

Aluminum 5-fold coordination coexisting with 4-and 6-fold coordination structurally characterizes amorphous aluminum oxide. For nearly 30 years now, 27Al MAS NMR has enabled to detect and later on to quantify this feature thanks to advances in high-resolution instrumentation. The Introduction shortly reviews the results of investigations of 5-coordinate aluminum in amorphous alumina through NMR analysis. Aluminum oxide is not a glass-forming oxide. A convenient way to obtain the amorphous state is by thin film deposition. We present here 27Al NMR analysis of a series of thin films of aluminum oxide prepared by metalorganic chemical vapor deposition (MOCVD) in the temperature range 360 ≤ Td ≤ 720 °C. In this range, low Td yield OH-containing films, while high Td yield nanocrystallites-containing films. The variation of the [4]Al, [5]Al and [6]Al content with Td is presented and discussed. It is correlated with the Td dependence of mechanical and corrosion protection properties. These properties are optimal when the structural disorder is to the utmost. Al coordination dependence on film thickness and the formation of metallic aluminum during the deposition process are also presented

Atomic scale structure of amorphous aluminum oxyhydroxide, oxide and oxycarbide films probed by very high field 27Al nuclear magnetic resonance

The atomic scale structure of aluminum in amorphous alumina films processed by direct liquid injection chemical vapor deposition from aluminum tri-isopropoxide (ATI) and dimethyl isopropoxide (DMAI) is investigated by solid-state 27Al nuclear magnetic resonance (SSNMR) using a very high magnetic field of 20.0 T. This study is performed as a function of the deposition temperature in the range 300–560 °C, 150–450 °C, and 500–700 °C, for the films processed from ATI, DMAI (+H2O), and DMAI (+O2), respectively. While the majority of the films are composed of stoichiometric aluminum oxide, other samples are partially or fully hydroxylated at low temperature, or contain carbidic carbon when processed from DMAI above 500 °C. The quantitative analysis of the SSNMR experiments reveals that the local structure of these films is built from AlO4, AlO5, AlO6 and Al(O,C)4 units with minor proportions of the 6-fold aluminum coordination and significant amounts of oxycarbides in the films processed from DMAI (+O2). The aluminum coordination distribution as well as the chemical shift distribution indicate that the films processed from DMAI present a higher degree of structural disorder compared to the films processed from ATI. Hydroxylation leads to an increase of the 6-fold coordination resulting from the trend of OH groups to integrate into AlO6 units. The evidence of an additional environment in films processed from DMAI (+O2) by 27Al SSNMR and first-principle NMR calculations on Al4C3 and Al4O4C crystal structures supports that carbon is located in Al(O,C)4 units. The concentration of this coordination environment strongly increases with increasing process temperature from 600 to 700 °C favoring a highly disordered structure and preventing from crystallizing into γ-alumina. The obtained results are a valuable guide to the selection of process conditions for the CVD of amorphous alumina films with regard to targeted applications

Fluidized Bed CVD of [5]Al-rich amorphous alumina on powders for catalysis applications

Producing alumina catalysts containing high amounts of penta-coordinated aluminum sites ([5]Al) is of main interest to develop a green production of olefins from biomass. Inspired from an original process developed on planar substrates at low pressure, a Fluidized Bed Chemical Vapor Deposition (CVD) process coupled to a DLI (Direct Liquid Injection) system has been studied at atmospheric pressure to deposit amorphous alumina on soluble NaCl powders, using dimethyl aluminum isopropoxide (DMAI) as precursor. A set of experiments has been performed at 310°C, showing the good reproducibility of the deposition process in terms of deposit morphology, mass and chemical composition. Nuclear Magnetic Resonance of aluminum-27 probing the structure at atomic scale of the deposit indicates the presence of high contents of penta-coordinated aluminum, as it was the case on planar substrates. This demonstrates that this DLI-CVD route from DMAI is robust. Coupled with a fluidized bed, it could lead to massive production of high specific surface area amorphous alumina with high content of penta-coordinated aluminum environments

Atomic Insights into Aluminium-Ion Insertion in Defective Anatase for Batteries

International audienceAluminium batteries constitute a safe and sustainable high‐energy‐density electrochemical energy‐storage solution. Viable Al‐ion batteries require suitable electrode materials that can readily intercalate high‐charge Al3+ ions. Here, we investigate the Al3+ intercalation chemistry of anatase TiO2 and how chemical modifications influence the accommodation of Al3+ ions. We use fluoride‐ and hydroxide‐doping to generate high concentrations of titanium vacancies. The coexistence of these hetero‐anions and titanium vacancies leads to a complex insertion mechanism, attributed to three distinct types of host sites: native interstitial sites, single vacancy sites, and paired vacancy sites. We demonstrate that Al3+ induces a strong local distortion within the modified TiO2 structure, which affects the insertion properties of the neighbouring host sites. Overall, specific structural features induced by the intercalation of highly polarising Al3+ ions should be considered when designing new electrode materials for polyvalent batteries

Network hydration, ordering and composition interplay of chemical vapor deposited amorphous silica films from tetraethyl orthosilicate

The chemical or mechanical performance of amorphous SiO2 films depend on intrinsic physicochemical properties, which are intimately linked to atomic and molecular arrangements in the Si–O–Si network. In this context, the present work focuses on a comprehensive description of SiO2 films deposited from a well-established chemical vapor deposition process involving tetraethyl-orthosilicate, oxygen and ozone, and operating at atmospheric pressure in the range 400–550 °C. The connectivity of the silica network is improved with increasing the deposition temperature (Td) and this is attributed to the decreased content of hydrated species through dehydration-condensation mechanisms. In the same way, the critical load of delamination increases with increasing Td thanks to the silicon substrate oxidation. The utilization of a O2/O3 oxidizing atmosphere involving the oxidation of intermediates species by O2, O3 and O., allows increasing the deposition rate at moderate temperatures, while minimizing carbon, H2O and silanol contents to extremely low values (4.5 at.% of H). The SiOx stoichiometry and Td interplay reveals two distinct behaviors before and above 450 °C. The best corrosion resistance of these films to standard P-etching test is obtained for the minimum silanol content and the best network molecular ordering, with an etching rate of 4.0 ± 0.1 Å/s at pH = 1.5. The elastic modulus and hardness of the films remain stable in the investigated range of deposition temperature, at 64.2 ± 1.7 and 7.4 ± 0.3 GPa respectively, thanks to the low content in silanol groups

Magnetism: Molecules to Build Solids

The seminal discovery in 1981 of bimetallic ferrimagnetic chains, based on the synthetic use of the concept “complex as ligand”, can be considered as a significant step on the way from molecules to more and more complex materials. We describe the chemistry, the structures, the magnetic properties of these 1D materials, together with the new theoretical models created to understand them. We then give an overview of some original creative ideas, which have irrigated the synthetic chemistry of brand‐new molecular materials, room temperature magnets, photomagnetic and chiral magnets or functional surfaces. The review emphasizes that the celebrated individual “wins” are indeed the fruit, along the years, of the constructive multidisciplinary collaboration of many scientists, theoreticians and experimentalists, chemists and physicists. Difficulties, dead‐end hypotheses, mistakes which represent a significant exciting part of any scientific endeavour, are not put under the rug

The Drosophila junctophilin gene is functionally equivalent to its four mammalian counterparts and is a modifier of a Huntingtin poly-Q expansion and the Notch pathway

[EN] Members of the Junctophilin (JPH) protein family have emerged as key actors in all excitable cells, with crucial implications for human pathophysiology. In mammals, this family consists of four members (JPH1-JPH4) that are differentially expressed throughout excitable cells. The analysis of knockout mice lacking JPH subtypes has demonstrated their essential contribution to physiological functions in skeletal and cardiac muscles and in neurons. Moreover, mutations in the human JPH2 gene are associated with hypertrophic and dilated cardiomyopathies; mutations in JPH3 are responsible for the neurodegenerative Huntington's disease-like-2 (HDL2), whereas JPH1 acts as a genetic modifier in Charcot-Marie-Tooth 2K peripheral neuropathy. Drosophila melanogaster has a single junctophilin (jp) gene, as is the case in all invertebrates, which might retain equivalent functions of the four homologous JPH genes present in mammalian genomes. Therefore, owing to the lack of putatively redundant genes, a jp Drosophila model could provide an excellent platform to model the Junctophilin-related diseases, to discover the ancestral functions of the JPH proteins and to reveal new pathways. By up-and downregulation of Jp in a tissue-specific manner in Drosophila, we show that altering its levels of expression produces a phenotypic spectrum characterized by muscular deficits, dilated cardiomyopathy and neuronal alterations. Importantly, our study has demonstrated that Jp modifies the neuronal degeneration in a Drosophila model of Huntington's disease, and it has allowed us to uncover an unsuspected functional relationship with the Notch pathway. Therefore, this Drosophila model has revealed new aspects of Junctophilin function that can be relevant for the disease mechanisms of their human counterparts.This work was supported by project grants from Association Francaise contre les Myopathies [AFM 18540 to M.I.G.], Instituto de Salud Carlos III (ISCIII) [PI12/000453 and PI15/000187 to C.E.], Generalitat Valenciana [PROMETEOII/2014/067 to R.A. as partner], and a collaborative grant from the International Rare Diseases Research Consortium (IRDiRC) and ISCIII [IR11/TREAT-CMT to M.I.G. (partner 12) and C.E. (partner 6)]. C.E. has a 'Miguel Servet' contract funded by the ISCIII and Centro de Investigacion Principe Felipe [CPII14/00002]; M.C. was the recipient of a Santiago Grisolia award from Generalitat Valenciana [GrisoliaP/2013/A/044].Calpena-Corpas, E.; Lopez Del Amo, V.; Chakraborty M; Llamusi, B.; Artero R; Espinos, C.; Galindo, MI. (2018). The Drosophila junctophilin gene is functionally equivalent to its four mammalian counterparts and is a modifier of a Huntingtin poly-Q expansion and the Notch pathway. Disease Models & Mechanisms. 11(1). https://doi.org/10.1242/dmm.029082S11