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Apical left ventricular (LV) aneurysms in hypertrophic cardiomyopathy (HCM) are associated with adverse outcomes. The reported frequency of mid-LV obstruction has varied from 36% to 90%. The authors sought to ascertain the frequency of mid-LV obstruction in HCM apical aneurysms. The authors analyzed echocardiographic and cardiac magnetic resonance examinations of patients with aneurysms from 3 dedicated programs and compared them with 63 normal controls and 47 controls with apical-mid HCM who did not have aneurysms (22 with increased LV systolic velocities). There were 108 patients with a mean age of 57.4 ± 13.5 years; 40 (37%) were women. A total of 103 aneurysm patients (95%) had mid-LV obstruction with mid-LV complete systolic emptying. Of the patients with obstruction, 84% had a midsystolic Doppler signal void, a marker of complete flow cessation, but only 19% had Doppler systolic gradients ≥30 mm Hg. Five patients (5%) had relative hypokinesia in mid-LV without obstruction. Aneurysm size is not bimodal but appears distributed by power law, with large aneurysms decidedly less common. Comparing mid-LV obstruction aneurysm patients with all control groups, the short-axis (SAX) systolic areas were smaller (P < 0.007), the percent SAX area change was greater (P < 0.005), the papillary muscle (PM) areas were larger (P < 0.003), and the diastolic PM areas/SAX diastolic areas were greater (P < 0.005). Patients with aneurysms had 22% greater SAX PM areas compared with those with elevated LV velocities but no aneurysms (median: 3.00 cm2 [IQR: 2.38-3.70 cm2] vs 2.45 [IQR: 1.81-2.95 cm2]; P = 0.004). Complete emptying occurs circumferentially around central PMs that contribute to obstruction. Late gadolinium enhancement was always brightest and the most transmural apical of, or at the level of, complete emptying. The great majority (95%) of patients in the continuum of apical aneurysms have associated mid-LV obstruction. Further research to investigate obstruction as a contributing cause to apical aneurysms is warranted. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract A series of polyaluminosilazanes was synthesized by reaction of dimethylethylamine alane complex with polysilazanes. Starting from different dichlorosilanes, polysilazanes were obtained by means of ammonolysis. The latter reacted with the alane complex and led to solid polyalumino(carbo)silazanes that can be described as "custom-made" polymers since all the steps were monitored and controlled (from the choice of the molecular precursor to the polymerization and the functionalization with aluminum) in order to study the effect of the introduction of Al on the different reactive sites of the Si- backbone in the polysilazanes. Detailed information on the polymer structures were obtained by FTIR and multinuclear solid state NMR spectroscopies. The transition from the polymeric state to the ceramic inorganic state was investigated by means of solid-state NMR spectroscopy and finally the structural evolution of the final ceramics by high angle XRD, Raman spectroscopy and TEM imaging. It is noted that the polymer-derived SiAlCN ceramics are X-ray amorphous even at high temperature under nitrogen with some local crystallization. Upon further heating these materials tend to further crystallize into thermodynamically stable phases at a given chemical composition, such as SiC, Si 3 N 4 , free C, or AlN. Finally, the present study shows that the amorphous-to-crystalline transition is closely related to the nature and structure of the preceramic polymer. [ABSTRACT FROM AUTHOR]

Summary The hematopoietic system seeds the CNS with microglial progenitor cells during the fetal period, but the subsequent cell generation dynamics and maintenance of this population have been poorly understood. We report that microglia, unlike most other hematopoietic lineages, renew slowly at a median rate of 28% per year, and some microglia last for more than two decades. Furthermore, we find no evidence for the existence of a substantial population of quiescent long-lived cells, meaning that the microglia population in the human brain is sustained by continuous slow turnover throughout adult life. [ABSTRACT FROM AUTHOR]

Summary Because human white adipocytes display a high turnover throughout adulthood, a continuous supply of precursor cells is required to maintain adipogenesis. Bone marrow (BM)-derived progenitor cells may contribute to mammalian adipogenesis; however, results in animal models are conflicting. Here we demonstrate in 65 subjects who underwent allogeneic BM or peripheral blood stem cell (PBSC) transplantation that, over the entire lifespan, BM/PBSC-derived progenitor cells contribute ∼10% to the subcutaneous adipocyte population. While this is independent of gender, age, and different transplantation-related parameters, body fat mass exerts a strong influence, with up to 2.5-fold increased donor cell contribution in obese individuals. Exome and whole-genome sequencing of single adipocytes suggests that BM/PBSC-derived progenitors contribute to adipose tissue via both differentiation and cell fusion. Thus, at least in the setting of transplantation, BM serves as a reservoir for adipocyte progenitors, particularly in obese subjects. [ABSTRACT FROM AUTHOR]

Abstract: In chemical hydrogen storage, nanoconfinement (or nanoscaffolding) is an efficient approach to reduce the size of the particles of boron hydrides such as ammonia borane (AB, NH3BH3) at nanoscale while destabilizing its molecular network. It involves the dehydrogenation of AB at temperatures lower than 100 °C and hinders the formation of undesired gaseous by-products such as borazine. Herein, commercial activated carbon (AC) with a specific surface area of 716 m2 g−1 and a porous volume of 0.36 cm3 g−1 was used as host material for AB nanoconfinement. A composite activated carbon-ammonia borane (AC@AB) was successfully prepared by infiltration in cold conditions (0 °C). Its dehydrogenation was followed by volumetric method, FTIR, XRD, TGA, DSC, GC–MS and 11B MAS NMR. The most striking result is that the nanoconfined AB, being highly destabilized, dehydrogenates in ambient conditions, even at 3–4 °C. It is demonstrated that dihydrogen is formed according to two pathways that simultaneously take place. The first one is the dehydrogenation through inter- and/or intra-molecular reactions between protonic H and hydridic H of AB, and the second one is the acid-base reaction between protonic H of COO−H groups present on the AC surface and hydridic H of AB. [Copyright &y& Elsevier]

Abstract: Human tissues continually replace dying cells with newborn cells. However, the rate of renewal varies by orders of magnitudes between blood cells, which are renewed every day and neurons, for which renewal is non-existent or limited to specific regions of the brain. Between those extreme are many tissues that turnover on a time scale of years, although no direct measurements have been done. We present here a mathematical method to estimate cell turnover in slowly renewing biological systems. Age distribution of DNA can be estimated from the integration of radiocarbon derived from nuclear bomb-testing during the cold war (1955–1963). For slowly renewing tissues, this method provides a better estimate of the average age of the tissue than direct estimates from the bomb-curve. Moreover, death, birth and turnover rates can be estimated. We highlight this method with data from human fat cells. [Copyright &y& Elsevier]

The development of efficient and cost-effective catalysts for the oxygen electrocatalysis is crucial for advancing renewable energy technologies, such as fuel cells, electrolyzers and metal-air batteries. Herein, we report the high efficiency of Co nanoclusters generated on porous silicon oxycarbonitride (SiCN(O)) fibre mats towards Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER) in alkaline medium. Porous SiCN(O) ceramic fibrous supports were synthesized via electrospinning of a blend of oligosilazane Durazane 1800, polyacrylonitrile and polystyrene followed by an appropriate heat-treatment. Co nanoparticles with a remarkably low mass loading (4 wt%) were immobilized on the SiCN(O) fibres for efficient bifunctional catalytic activity towards OER/ORR. The catalysts exhibited ORR activity (onset potential (E 0) of 0.83 V vs. RHE) and excellent stability (80 h) in alkaline medium. Concomitantly, the catalyst required only 1.67 V to drive a current density of 10 mA cm−2 in 1 M KOH for OER. • Co nanoclusters on SiCN(O) fibre mats for ORR/OER in alkaline medium. • Ultra-low mass loading of Co offers high ORR/OER activity with excellent durability. • Nitrogen-doped carbon layers stabilize Co nanocrystals. • Synergistic Co/CoO and N-doped carbon layer promotes the electron transfer. [ABSTRACT FROM AUTHOR]

The first demonstration of a nanoscaled titanium zirconium nitride (TiZrN 2) single-phase isolated during the preparation of polymer-derived silicon nitride (Si 3 N 4) matrix nanocomposites is discussed. We employed a polysilazane, which was chemically modified with Zr[N(CH 2 CH 3) 2 ] 4 and Ti[N(CH 3) 2 ] 4 then ammonolyzed before a pyrolysis step under ammonia (1000 °C) and a heat-treatment in flowing nitrogen (1000–1700 °C). Based on a careful control of the precursor chemistry in the early stage of the process and nano-/microstructural investigations of the material performed during its preparation, we were able to identify TiZrN 2 nanocrystals with a size as low as 9 nm distributed in α- and β-Si 3 N 4 phases at a temperature as low as 1500 °C. We particularly proved that the TiZrN 2 nanophase could be generated because of the use of the polysilazane evoluting towards a covalently-bonded Si 3 N 4 matrix. This unique nanostructure is expected to provide particular functionality to Si 3 N 4 as noble metal-free catalysts and components with high plasmonic quality. [ABSTRACT FROM AUTHOR]

Patients with intermediate-risk pulmonary embolism (PE) commonly present with a significantly reduced cardiac index (CI). However, the identification of this more severe profile requires invasive hemodynamic monitoring. Whether inferior vena cava (IVC) contrast reflux, as a marker of worse right ventricular function, can predict invasive hemodynamics has not been explored. This was a single-center retrospective study over a 3-year period of consecutive patients with PE undergoing mechanical thrombectomy and simultaneous pulmonary artery catheterization. CT pulmonary angiograms were reviewed, and contrast reflux was graded as no/minimal reflux (limited to the IVC) or substantial (opacification including hepatic veins) based on an established scale. Substantial contrast reflux was present in 29 of 85 patients (34 %) and associated with a lower CI (1.8 ± 0.4 L/min/m2 v. 2.6 ± 1.0 L/min/m2, p < 0.001), higher pulmonary artery systolic pressure (53.2 ± 19.5 mmHg v. 44.0 ± 12.1 mmHg, p = 0.025), and worse right ventricular systolic function. An IVC contrast reflux grade > 3 was a significant predictor for a CI ≤2.2 L/min/m2 (OR: 22.5, 95 % CI: 4.8, 104.4, p < 0.001). Sensitivity, specificity, positive predictive value, and negative predictive value for substantial contrast reflux for a CI ≤2.2 L/min/m2 were 62.6 %, 93.1 %, 94.6 %, and 56.2 %, respectively. These findings remained significant in a multivariable model and were similar when isolating for intermediate-risk patients (n = 72, 85 %). The degree of contrast reflux is highly specific for a reduced cardiac index in PE even when isolating for intermediate-risk patients. Real-time prediction of a hemodynamic profile may have added value in the risk-stratification of PE. [Display omitted] • Higher grades of contrast reflux on CT are specific for a low cardiac index in PE. • Contrast reflux predicts worse RV function and higher PA pressures. • Contrast reflux may aid in risk stratification and identification of occult shock. [ABSTRACT FROM AUTHOR]

• First demonstration of the low temperature formation of a rock salt ZrN nanophase within a surrounding Si 3 N 4 matrix. • The structure of ZrN/Si 3 N 4 nanocomposites is finely tailored through the chemistry of Zr-modified organosilicon polymers. • Nanocomposites propose promising optical properties as photocatalysts. ZrN/Si 3 N 4 nanocomposites have been prepared by chemically crosslinking two polysilazanes with a zirconium-based compound and subsequent heat-treatment at temperatures ranging from 1000 to 1600 °C. The polymer synthesis has been systematically investigated using FT-IR, solid-state NMR, and elemental analyses. Then, the pyrolysis under ammonia at 1000 °C trigering the thermo-chemical polymer-to-ceramic conversion was examined, leading to X-ray amorphous ceramics with yields governed by the chemistry of the neat polysilazane. Investigations of the structural evolution of the single-phase amorphous ceramic network above 1000 °C by X-ray diffraction and Raman spectroscopy pointed out that the ZrN phase already segregated at 1400 °C and formed highly crystalline ZrN/Si 3 N 4 nanocomposites at 1600 °C. HRTEM investigations validated the unique nanostructural feature of the nanocomposites made of ZrN nanocrystals distributed in α- and β-Si 3 N 4 phases. Our preliminary investigations of the optical properties showed that these structural changes allowed tuning the optical properties of ZrN/Si 3 N 4 nanocomposites. [ABSTRACT FROM AUTHOR]

Open-Celled silicon carbide (SiC) foams were prepared from a mixture of a boron-modified polycarbosilane as a preceramic polymer and poly(methymetacrylate) (PMMA) microbeads as sacrificial agents. The process consists in the cross-linking of the liquid allylhydridopolycarbosilane (AHPCS, SiC precursor) with borane dimethylsulfide (BDMS, boron source) to form a solid boron-modified polycarbosilane with an adjusted cross-linking degree. The latter is mixed with PMMA microbeads (25 μm) in a 20:80 ratio and the mixture is warm-pressed at 120 °C forming consolidated green bodies to be pyrolyzed at 1000 °C under argon and to deliver open-celled SiC foams with an interconnected porosity of 73.4 vol %. These foams combine a low density with a compressive strength of 3.49 ± 0.56 MPa and a thermal and mechanical stability under argon up to 1300 °C. Ageing and microfiltration tests in the conditions of a primary loop of coolant in a Pressurized Water Reactor (PWR) showed that foams display a relatively high stability while retaining particles of 5 μm in diameter making these materials as appropriate candidates to work in separation techniques under harsh environments. [ABSTRACT FROM AUTHOR]

The in-situ immobilization of cobalt (Co) or nickel (Ni) nanoparticles (NPs) in a polymer-derived silicon nitride (Si 3 N 4) matrix is firstly reported. It is accomplished by the coordination of a polysilazane with metal chlorides (CoCl 2 or NiCl 2) followed by the subsequent pyrolysis of the metal:organosilicon polymer coordination complex in the temperature range 700–1000 °C in flowing ammonia. By coupling X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) on powders, it has been shown that the phase composition and crystallinity (NPs and matrix) as well as the crystal size of the NPs can be finely tuned through the synthesis parameters including the type of metals, the Si:metal ratio, the reaction time, the self-crosslinking ability of the considered polysilazane in the presence of the metal salts and the heat-treatment temperature. Then, the micro-/mesoporosity of the Si 3 N 4 matrix has been developed using a nano-casting approach to exploit the catalytic activity of NPs towards the hydrolysis of sodium borohydride (NaBH 4). Hence, compounds with a matrix delivering BET specific surface areas (SSA) as high as 921.5 m2 g and supporting the NPs have been investigated to evaluate their potential for catalysis. [Display omitted] • In-situ formation of Ni or Co nanoparticles in a micro-/mesoporous Si 3 N 4 matrix from polysilazanes coordinated with TMCl 2 (TM = Co, Ni). [ABSTRACT FROM AUTHOR]

Abstract Herein, we provide a detailed insight into the precursor chemistry, precursor-to-material transformation and characterization of nanocomposites made of a TiN nanophase and a Si-O-C-N ceramic. The polymer-derived ceramics (PDCs) route applied to synthesize these nanocomposites resulted in the formation of nanocrystals less than 4 nm in size and the calculated lattice parameter value for the nanocrystals (a = 0.4239 nm) matched the theoretical value of TiN (a = 0.4241 nm). The Si-O-C-N ceramic served as a platform for anchoring TiN nanocrystals. As a proof of concept, we have attempted to exploit the plasmonic properties of nanocomposites to achieve photocatalytic degradation of organic dyes. The absorption spectra clearly showed plasmonic resonance in the visible region with peak positioned around 670 nm according to the presence of TiN nanocrystals which resulted in the enhancement of dye degradation. Graphical abstract Unlabelled Image Highlights • Controlled size and in situ crystallization of TiN nanocrystals in an amorphous Si-O-C-N matrix is achieved through PDC route. • Plasmonic properties of TiN nanocrystals were exploited towards degradation of organic dyes in visible light for the first time. • The photodegradation rate constant was found to be 4.2 x 10-3 min-1. • Reactive species trapping experiments suggests that hydroxyl radicals play a major role in the degradation of MB. [ABSTRACT FROM AUTHOR]

The scientific and technological challenges of energy-related fields are mainly associated with the emergence of new, advanced knowledge and fundamental understanding of materials. In the different categories of materials, ceramics offer a unique combination of physical and chemical properties making them key contributors for energy production/conversion and storage applications. The Polymer-Derived Ceramics (PDC) route enables the synthesis of such materials with an excellent control of the porosity at mesoscopic length scale offering potentialities as support materials to anchor and disperse active metals or for a direct use as catalysts. This review proposes an overview of the works related to the design of mesoporous PDC in the last 15 years. A particular focus is made on the forming methods which have been associated with the PDC route to engineer the mesoporosity and the shape of ceramics derived from preceramic polymers. The main topics reviewed are related to the processing of tailor-made polymeric precursors to mesoporous components, and to the characterization of the material properties. The two strategies adopted for the development of the catalytic activity of mesoporous PDC, i.e., deposition of metal nanoparticles on the mesoporous network or in-situ generation of the catalytically active phase in the mesoporous PDC matrix, are presented. Their recent application in various catalyst-assisted reactions is then discussed. Additionally, we outline the current challenges on the field of mesoporous PDC and provide perspectives on the need for further advances in mesoporous PDC. [ABSTRACT FROM AUTHOR]

Commercially available polycarbosilane has been chemically modified with primary and secondary amino silane derivatives in order to provide amine-functionalized polycarbosilane as hydrophobic solid sorbent capable of reversibly capturing CO 2 from flue gas streams. CO 2 uptake by the samples was investigated at the molecular level using thermogravimetric analysis under CO 2 atmosphere, in situ DRIFTS analysis, and CO 2 sorption isotherm. The reaction paths and sorption mechanisms were examined by comparing with the CO 2 adsorbing behaviors previously studied for amine-functionalized SiO 2 , and proven to be related to the presence of adsorbed water, as well as the nature of the grafted amino silanes. With effective CO 2 adsorption rate, regeneration capacity at 40–50 °C, and lesser sensitivity to moist due to its hydrophobic Si-C backbone, secondary amine-functionalized polycarbosilane hybrids have potential applications in membrane gas separation through facilitated transport of CO 2 . [ABSTRACT FROM AUTHOR]

The high temperature crystallization behavior of polytitanosilazane-derived amorphous SiTiN ceramics was investigated in a nitrogen atmosphere using XRD, Raman spectroscopy, TEM, SEM and BET. At 1400 °C, TiN is the first phase to nucleate in SiTiN ceramics forming nanocomposites with a homogeneous distribution of TiN nanocrystals within an amorphous Si 3 N 4 matrix. Above 1400 °C, XRD indicates that the temperature at which Si 3 N 4 crystallizes depends on the volume fraction of TiN present in nanocomposites. This is closely related to the chemistry of the polyorganosilazanes used to synthesize polytitanosilazanes. The use of perhydridopolysilazane, the most reactive polyorganosilazane, allows preparing TiN/Si 3 N 4 nanocomposites with a remarkable stability of the amorphous matrix up to 1800 °C as mesoporous materials and powders. Dense monoliths crystallize earlier than the powder analogs because of the use of an ammonia pre-treatment before polymer warm-pressing. [ABSTRACT FROM AUTHOR]

This paper describes the fabrication of Si-C-Ti ceramics from titanium nanoparticle filled allylhydridopolycarbosilanes (Ti NP-filled AHPCS) using a casting/curing technique followed by pyrolysis at 1000 °C under argon. TGA and XRD have been applied to investigate the mass loss behaviour during ceramization and to gain structural information on the decomposition process of Ti NP-filled AHPCS. TiC is the first phase to nucleate in an amorphous SiC matrix around 800 °C, whereas titanium silicide and MAX phases grow between 800 and 1000 °C. Densities measurements have been done and structural characterization of the final specimens is carried out using XRD and Raman spectroscopy. The process leads to (nano)composites with a density increasing from 2.45 to 2.90 g/cm 3 and a Vickers hardness ranging from 17 to 20.9 GPa according to the AHPCS:Ti ratio fixed in the early stage of the process. The titanium silicide and MAX phases are decomposed during a further heat-treatment between 1000 and 1400 °C to generate TiC/SiC (nano)composites. [ABSTRACT FROM AUTHOR]

Herein, mesoporous 3D silicon carbide (SiC), carbonitride (Si C N) and nitride (Si 3 N 4 ) structures have been synthesized by nanocasting and pyrolysis using commercial organosilicon polymers as precursors of the different compositions. Detailed characterizations by BET and XRD allowed us to fix the most appropriate parameters to design mesoporous 3D structures with high specific surface areas and high pore volume. Then, the series of 3D structures has been used as supports to grow platinum nanoparticles (Pt NPs) by wet impregnation followed by reduction in hydrogen/argon flow. The Pt-supported mesoporous 3D supports kept the mesoporosity of the virgin supports to be used for catalytic hydrolysis of sodium borohydride (NaBH 4 ). A hydrogen generation rate of 24.2 L min −1 g Pt −1 is measured for the Pt-supported mesoporous 3D Si 3 N 4 structure, which is notably higher than the catalytic hydrolysis using Pt-supported mesoporous 3D SiC and Si C N structures. HRTEM investigations demonstrated the homogeneous distribution of Pt NPs over the Si 3 N 4 support. [ABSTRACT FROM AUTHOR]

The present paper reports the preparation of sintering additive-free Si-B-C-N monoliths by spark plasma sintering (SPS) under nitrogen of polymer-derived Si-B-C-N powders. Powders are synthesized in nitrogen or ammonia atmosphere to modify their carbon content. The nitrogen-treated powders sintered in the temperature range 1500-1900 °C lead to monoliths with a density increasing from 2.4 to 2.6 g/cm³, Vickers harness and Young's modulus ranging from 0.7 to 5.4 GPa and 48 to 102 GPa, respectively. SiC was the first phase to nucleate around 1700 °C, whereas Si3N4 grew at 1800 °C. At this temperature, monoliths are pure electrical conductor nanocomposites mainly composed of Si3N4 and SiC nanophases embedded in a turbostratic BN(C) matrix. Above 1800 °C, Si3N4 was not identified. In comparison, ammonia-treated powders sintered at 1800 °C represent dense insulator composites mainly composed of Si3N4 and BN with a Vickers hardness as high as 15 GPa and an excellent stability in air. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, the vacuum-assisted polyborazylene transfer molding (VAPTM) followed by pyrolysis at 1450°C under nitrogen was successfully applied to prepare C/BN composites with a relative density of 94.7%, and an open porosity of 5.1vol%. Rheology measurements combined with TG experiments and measurement of the weight gain of the composites after each polymer impregnation pyrolysis (PIP) cycles allowed fixing elaboration parameters (10 PIP cycles using two types of polyborazylene) to generate C/BN composites as high temperature vacuum compatible materials which demonstrate potentialities for vacuum technology and space applications. Scanning electron micrographs of composites demonstrated that the BN matrix appropriately filled the space between the fibers with a low fiber-matrix bonding which affects the compressive modulus. The thermal diffusivity and electrical conductivity of the BN matrix have been measured and showed that carbon fibers have poor effects on the intrinsic properties of BN. [Copyright &y& Elsevier]

Abstract: Ordered two-dimensional (2D) mesoporous silicoboron carbonitride (SiBCN) ceramics were prepared by a nanocasting approach of a boron-modified polysilazane of the type [B(C2H4SiCH3NH)3] n (C2H4 =CHCH3, CH2CH2) ([Si3B1.1C10.5N3.0H25.5] n ) using mesoporous CMK-3 carbon as hard template. The polymer was synthesized according to a monomer route by hydroboration of CH2 =CHSiCH3Cl2 followed by reaction of the as-made tris(dichloromethylsilylethyl)borane (B(C2H4SiCH3Cl2)3 (TDSB, C2H4 =CHCH3, CH2CH2) with lithium amide (LiNH2). It was generated as a highly soluble compound which could easily impregnate mesoporous CMK-3 carbon. The derived [B(C2H4SiCH3NCH3)3] n -carbon composite was directly pyrolyzed in flowing nitrogen at 1000°C to generate a SiBCN-carbon composite. The carbon template was subsequently removed through thermal treatment at 1000°C in a mixture of ammonia and nitrogen to generate ordered mesoporous Si3.0B1.0C4.2N2.4 structures. XRD and TEM analyses revealed that the obtained amorphous mesoporous ceramic exhibits open, continuous, and ordered 2D hexagonal frameworks which are strongly dependent on the number of impregnation cycles and the carbon removal step. Using a double impregnation cycle combined with a pyrolysis process up to 1000°C in flowing nitrogen and a carbon removal step at 1000°C for 3h in a volumetric flow ratio between ammonia and nitrogen of 1, the ordered mesoporous SiBCN ceramic displays high surface area (630m2 g−1), high pore volume (0.91cm3 g−1), and narrow pore-size distribution (around 4.6nm) with a thermal stability which extends up to 1180°C under nitrogen. [Copyright &y& Elsevier]

Abstract: The present paper is focused on the synthesis of a series of poly[N-(alkylimino)alanes] of the type [HAlNR] n as preceramic polymers for the preparation of aluminum nitride (AlN). Polymers were characterized by means of Fourier transform infrared spectra (FT-IR), liquid-state 1H and 13C NMR spectrometry and elemental analyses. The polymers were prepared in different physical states going from viscous liquid to solid (soluble and/or fusible) compounds with the decrease of the carbon content in the polymer chain. Such properties offer potentialities in the preparation of complex forms of ceramics including thin coatings and 1D nanostructures. AlN thin coatings and 1D nanostructures were obtained from a solution of poly[N-(isopropylimino)alane] in toluene followed by heat-treatment in flowing ammonia up to 1000°C resulting in a ceramic yield of 50.6%. Subsequent heat-treatment to 1800°C in flowing nitrogen allowed the production of crystalline AlN coatings and nanorods identified by Raman spectrometry and X-ray diffraction. [Copyright &y& Elsevier]

Abstract: The thermal behaviour of a series of poly[B-(methylamino)borazine] prepared at various temperatures ranging from 140 to 200°C is studied in the present paper as potential BN fiber precursors. It was shown that the softening capability of poly[B-(methylamino)borazine] can be tailored by controlling the temperature at which polymers were prepared to achieve melt-spinning and produce high quality green fibers. Thus as-spun fibers could be next converted into boron nitride fibers using ammonia (25–1000°C) and nitrogen (25–1800°C) atmospheres. The quality of boron nitride fibers was shown to depend on the first part of the pyrolysis step (25 and 1000°C; ammonia atmosphere) in which the great majority of the weight loss necessary for boron nitride production occurs. Ideal poly[B-(methylamino)borazine] as BN fiber precursors are those prepared between 170 and 180°C. They display appropriate melt-spinnability and ceramic conversion capability. [Copyright &y& Elsevier]

Silicon carbide (SiC) filters and porous membranes is a growing industry with deployment for gas and liquid separation processes. In view of its importance, the research efforts into the development of SiC filters and membranes are of growing interest around the world. Therefore, this review paper is focused on the latest advancements in SiC and SiC composites used for the preparation of substrates and thin films in filters and membranes. There is a multitude of methods used to prepare filters and membranes of different shapes (tubular, honeycomb, flat sheets and multi-channel), which are influenced by precursor mixture and sintering conditions. In turn, these processing conditions affect porosity and pore size, which affects the transport and separation properties of SiC filters and membranes. SiC particles size and distribution allow for the precise control of pore size in membranes, leading to high gas separation factors. In addition, SiC has strong thermal stability properties that are very desirable for high temperature gas cleaning. Together with gas and liquid transport and separation properties, this review also addresses the potential applications in gas and liquid separation processes, coupled with thermal/chemical stability properties. Future challenges are highlighted towards further research efforts. Image 1 • Silicon carbide (SiC) - flexible material for the preparation of filters and membranes. • SiC substrates - varied shapes as tubular, honeycomb, flat sheets and multi-channel. • SiC filters - high filtration efficiency of ~99% plus operating in catalytic mode. • SiC membranes - very high He/Ar selectivity of 465, precise pore size control. • SiC membranes - commercially available for micro and ultrafiltration processes. [ABSTRACT FROM AUTHOR]

• In-situ crystallization of N-doped TiO 2 nanocrystals in amorphous Si-O-C-N matrix. • Mesoporous nanocomposite exhibited ultra-high adsorption capacity . • Nitrogen atoms in the TiO 2 lattice facilitated visible light photocatalysis. • Synergistic effect of nanoscaled heterojunctions and radicals enhanced catalysis. • Photodegradation rate constant was found to be 8.3 × 10−3 min−1. The mesoporous N-doped TiO 2 /Si-O-C-N ceramic nanocomposites has been revealed to be a potential candidate towards visible light photocatalytic degradation of organic dyes. The polymer-derived ceramic route was implemented to prepare uniformly distributed in-situ crystallized N-doped TiO 2 nanocrystals in a mesoporous amorphous siliconoxycarbonitride matrix. This chemical approach assisted by the hard template pathway resulted in a high surface area (186 m2/g) nanocomposite exhibiting predominantly mesoporous structure with an average pore size of 11 nm. The two-step process involved pyrolysis of the polyhydridomethyilsiloxane impregnated in CMK3 (hard template) under argon generating SiOC-C composites and functionalizing it with titanium n -tetrabutoxide to be pyrolyzed under ammonia to form the titled nanocomposite. Interestingly, pyrolysis in a reactive ammonia atmosphere resulted in the incorporation of nitrogen in the titania lattice while decomposing the template. The Si-O-C-N support on which N-doped TiO 2 exhibited superior adsorption of organic dye molecules and photocatalytically active in the visible wavelength. The nanoscaled heterojunctions reduced the recombination rate and the presence of superoxide anions/hydroxyl radicals was found to be responsible for the dye degradation. [ABSTRACT FROM AUTHOR]