Ceria-Based Dual-Phase Membranes for High-Temperature Carbon Dioxide Separation: Effect of Iron Doping and Pore Generation with MgO Template

Dual-phase membranes for high-temperature carbon dioxide separation have emerged as promising technology to mitigate anthropogenic greenhouse gases emissions, especially as a pre- and post-combustion separation technique in coal burning power plants. To implement these membranes industrially, the carbon dioxide permeability must be improved. In this study, Ce0.8Sm0.2O2−δ (SDC) and Ce0.8Sm0.19Fe0.01O2−δ (FSDC) ceramic powders were used to form the skeleton in dual-phase membranes. The use of MgO as an environmentally friendly pore generator allows control over the membrane porosity and microstructure in order to compare the effect of the membrane’s ceramic phase. The ceramic powders and the resulting membranes were characterized using ICP-OES, HSM, gravimetric analysis, SEM/EDX, and XRD, and the carbon dioxide flux density was quantified using a high-temperature membrane permeation setup. The carbon dioxide permeability slightly increases with the addition of iron in the FSDC membranes compared to the SDC membranes mainly due to the reported scavenging effect of iron with the siliceous impurities, with an additional potential contribution of an increased crystallite size due to viscous flow sintering. The increased permeability of the FSDC system and the proper microstructure control by MgO can be further extended to optimize carbon dioxide permeability in this membrane system.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Hydrogenation of Carbon Dioxide to Dimethyl Ether on CuO–ZnO/ZSM-5 Catalysts:Comparison of Powder and Electrospun Structures

The promising direct dimethyl ether (DME) production through CO2 hydrogenation was systematically analyzed in this research by synthesizing, characterizing, and testing several catalytic structures. In doing so, various combinations of precipitation and impregnation of copper- and zinc-oxides (CuO–ZnO) over a ZSM-5 zeolite structure were applied to synthesize the hybrid catalysts capable of hydrogenating carbon dioxide to methanol and dehydrating it to DME. The resulting catalytic structures, including the co-precipitated, sequentially precipitated, and sequentially impregnated CuO–ZnO/ZSM-5 catalysts, were prepared in the form of particle and electrospun fibers with distinguished chemical and structural features. They were then characterized using XRD, BET, XPS, ICP, TGA, SEM, and FIB-SEM/EDS analyses. Their catalytic performances were also tested and analyzed in light of their observed characteristics. It was observed that it is crucial to establish relatively small-size and well-distributed zeolite crystals across a hybrid catalytic structure to secure a distinguished DME selectivity and yield. This approach, along with other observed behaviors and the involved phenomena like catalyst particles and fibers, clusters of catalyst particles, or the whole catalytic bed, were analyzed and explained. In particular, the desired characteristics of a CuO–ZnO/ZSM-5 hybrid catalyst, synthesized in a single-pot processing of the precursors of all involved catalytically active elements, were found to be promising in guiding the future efforts in tailoring an efficient catalyst for this system.</p

A 3D Cu‐Naphthalene‐Phosphonate Metal–Organic Framework with Ultra‐High Electrical Conductivity

A conductive phosphonate metal–organic framework (MOF), [{Cu(H2O)}(2,6‐NDPA)0.5] (NDPA = naphthalenediphosphonic acid), which contains a 2D inorganic building unit (IBU) comprised of a continuous edge‐sharing sheet of copper phosphonate polyhedra is reported. The 2D IBUs are connected to each other via polyaromatic 2,6‐NDPA's, forming a 3D pillared‐layered MOF structure. This MOF, known as TUB40, has a narrow band gap of 1.42 eV, a record high average electrical conductance of 2 × 102 S m−1 at room temperature based on single‐crystal conductivity measurements, and an electrical conductance of 142 S m−1 based on a pellet measurement. Density functional theory (DFT) calculations reveal that the conductivity is due to an excitation from the highest occupied molecular orbital on the naphthalene‐building unit to the lowest unoccupied molecular orbital on the copper atoms. Temperature‐dependent magnetization measurements show that the copper atoms are antiferromagnetically coupled at very low temperatures, which is also confirmed by the DFT calculations. Due to its high conductance and thermal/chemical stability, TUB40 may prove useful as an electrode material in supercapacitors.TU Berlin, Open-Access-Mittel – 202

Textured dense Zinc Oxide layers for active noise cancelling windows

Dense ZnO films with a strong c-axis texture have been deposited on TCO-Glass, Glass and Si wafers, respectively, with a two-step pressureless wet chemical method using zinc Acetatedihydrate as Zn-precursor. The crystallographic structure of the films has been studied with XRD and SEM. Optical measurements reveal a high transparency of the ZnO films with a thickness of up to 10 µm. This new cost effective route for ZnO film deposition does not require expensive sophisticated equipment and is easily upscaled

Metastable Phase Formation, Microstructure, and Dielectric Properties in Plasma-Sprayed Alumina Ceramic Coatings

The need for new solutions for electrical insulation is growing due to the increased electrification in numerous industrial sectors, opening the door for innovation. Plasma spraying is a fast and efficient way to deposit various ceramics as electrical insulators, which are used in conditions where polymers are not suitable. Alumina (Al2O3) is among the most employed ceramics in the coating industry since it exhibits good dielectric properties, high hardness, and high melting point, while still being cost-effective. Various parameters (e.g., feedstock type, spray distance, plasma power) significantly influence the resulting coating in terms of microstructure, porosity, and metastable phase formation. Consequently, these parameters need to be investigated to estimate the impact on the dielectric properties of plasma-sprayed alumina coatings. In this work, alumina coatings with different spray distances have been prepared via atmospheric plasma spray (APS) on copper substrates. The microstructure, porosity, and corresponding phase formation have been analyzed with optical microscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Moreover, we present an in-depth analysis of the fundamental dielectric properties e.g., direct current (DC) resistance, breakdown strength, dielectric loss tangent, and permittivity. Our results show that decreasing spray distance reduces the resistivity from 6.31 &times; 109&Omega;m (130 mm) to 6.33 &times; 108&Omega;m (70 mm), while at the same time enhances the formation of the metastable &delta;-Al2O3 phase. Furthermore, space charge polarization is determined as the main polarization mechanism at low frequencies

Rechargeable Magnesium Ion Batteries Based on Nanostructured Tungsten Disulfide Cathodes

Finding effective cathode materials is currently one of the key barriers to the development of magnesium batteries, which offer enticing prospects of larger capacities alongside improved safety relative to Li-ion batteries. Here, we report the hydrothermal synthesis of several types of WS2 nanostructures and their performance as magnesium battery cathodes. The morphology of WS2 materials was controlled through the use of sodium oxalate as a complexing agent and different templating agents, including polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and hexadecyltrimethyl ammonium bromide (CTAB). A high capacity of 142.7 mAh/g was achieved after 100 cycles at a high current density of 500 mA/g for cathodes based on a nanostructured flower-like WS2. A solution consisting of magnesium (II) bis(trifluoromethanesulfonyl)imide (MgTFSI2) and magnesium (II) chloride (MgCl2) in dimethoxyethane (DME) was used as an effective electrolyte, which contributes to favorable Mg2+ mobility. Weaker ionic bonds and van der Waals forces of WS2 compared with other transition metal oxides/sulfides lay the foundation for fast discharge/charge rate. The enhanced surface area of the nanostructured materials plays a key role in enhancing both the capacity and discharge/charge rate

Rechargeable Magnesium Ion Batteries Based on Nanostructured Tungsten Disulfide Cathodes

Finding effective cathode materials is currently one of the key barriers to the development of magnesium batteries, which offer enticing prospects of larger capacities alongside improved safety relative to Li-ion batteries. Here, we report the hydrothermal synthesis of several types of WS2 nanostructures and their performance as magnesium battery cathodes. The morphology of WS2 materials was controlled through the use of sodium oxalate as a complexing agent and different templating agents, including polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and hexadecyltrimethyl ammonium bromide (CTAB). A high capacity of 142.7 mAh/g was achieved after 100 cycles at a high current density of 500 mA/g for cathodes based on a nanostructured flower-like WS2. A solution consisting of magnesium (II) bis(trifluoromethanesulfonyl)imide (MgTFSI2) and magnesium (II) chloride (MgCl2) in dimethoxyethane (DME) was used as an effective electrolyte, which contributes to favorable Mg2+ mobility. Weaker ionic bonds and van der Waals forces of WS2 compared with other transition metal oxides/sulfides lay the foundation for fast discharge/charge rate. The enhanced surface area of the nanostructured materials plays a key role in enhancing both the capacity and discharge/charge rate

Hydrogenation of Carbon Dioxide to Dimethyl Ether on CuO–ZnO/ZSM-5 Catalysts: Comparison of Powder and Electrospun Structures

The promising direct dimethyl ether (DME) production through CO2 hydrogenation was systematically analyzed in this research by synthesizing, characterizing, and testing several catalytic structures. In doing so, various combinations of precipitation and impregnation of copper- and zinc-oxides (CuO–ZnO) over a ZSM-5 zeolite structure were applied to synthesize the hybrid catalysts capable of hydrogenating carbon dioxide to methanol and dehydrating it to DME. The resulting catalytic structures, including the co-precipitated, sequentially precipitated, and sequentially impregnated CuO–ZnO/ZSM-5 catalysts, were prepared in the form of particle and electrospun fibers with distinguished chemical and structural features. They were then characterized using XRD, BET, XPS, ICP, TGA, SEM, and FIB-SEM/EDS analyses. Their catalytic performances were also tested and analyzed in light of their observed characteristics. It was observed that it is crucial to establish relatively small-size and well-distributed zeolite crystals across a hybrid catalytic structure to secure a distinguished DME selectivity and yield. This approach, along with other observed behaviors and the involved phenomena like catalyst particles and fibers, clusters of catalyst particles, or the whole catalytic bed, were analyzed and explained. In particular, the desired characteristics of a CuO–ZnO/ZSM-5 hybrid catalyst, synthesized in a single-pot processing of the precursors of all involved catalytically active elements, were found to be promising in guiding the future efforts in tailoring an efficient catalyst for this system

NaGdSi2_2O6_6 – A novel antiferromagnetically coupled silicate with Vierer chain structure

Ceramics based on pyroxenes and pyroxenoids present new pathways towards diverse functional materials. In this study, a novel sodium gadolinium pyroxene of the composition NaGdSi$_2$O$_6$ was successfully synthesised via a chelation-polymerization based sol-gel method and its crystal structure was determined by Rietveld refined synchrotron X-ray powder diffraction. NaGdSi$_2$O$_6$ crystallises in monoclinic symmetry with space group P2$_1$/c and unit cell parameters of a ​= ​5.44069(8) Å, b ​= ​13.83410(17) Å, c ​= ​7.66897(9) Å and β ​= ​109.9929(6)° (Z ​= ​4). The structure has been identified to be an inosilicate with a strongly undulated single tetrahedral chain along c with a chain periodicity of 4 (Vierer chain). Vierer chain-type NaGdSi$_2$O$_6$ shows a weak antiferromagnetic coupling, however there is no evidence for long-range magnetic order above 2 ​K