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The perovskite-type oxides LaCoO (LCO) with and without substitution of Co by Pd and/or Zn are studied for steam reforming of methanol (SRM). The catalysts LaCoPdZnO are synthesized by amorphous citrate method and subjected to calcination at 800 °C for 2 h. The catalysts are characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), N-physisorption (BET), X-ray diffraction (XRD) and tested in SRM reaction. The surface area of the catalysts is around 9 (±1) m/g. The XRD patterns of the catalysts reflect only rhombohedral crystal structure, indicating the phase purity of the perovskites. The SRM performance of the catalysts, especially the CO selectivity below 275 °C, is strongly dependent on the catalyst composition and reaction temperature. The CO selectivity profile of Pd and Zn containing LaCoPdZnO consists of two distinct maxima, one at 225 °C and the other above 375 °C. The former is missing on un-substituted LCO or mono metal substituted LaCoPdO and LaCoZnO, which is attributed to CO selective phase related to Pd and Zn. The high temperature CO selectivity maximum of the catalysts is not dependent on the Co substitution by Pd and/or Zn and is ascribed, in general, to the bulk catalyst composition. [ABSTRACT FROM AUTHOR]

(Ti/Zr/Hf)CoSb 0.8 Sn 0.2 compounds are promising p -type thermoelectric materials. In this work, excessive Ga and Co deficiencies were introduced into Ti 0.2 Hf 0.8 CoSb 0.8 Sn 0.2 compounds. The microstructure, electrical, and thermal transport properties were investigated in the temperature range of 300 K < T < 1000 K. The excessive Ga formed nanoinclusions with Ti and Sn at the grain boundaries. The Co deficiencies lowered the thermal conductivity and simultaneously improved the electrical conductivity. As a result, the power factor was enhanced to 3.2 mW/m K2, and the maximum Z.T. of ∼0.93 at 988 K was obtained in the Ti 0.2 Hf 0.8 Co 0.99 Sb 0.8 Sn 0.2 –0.01Ga sample, which is an increase of ∼48% compared to that of the pristine Ti 0.2 Hf 0.8 CoSb 0.8 Sn 0.2 sample. [ABSTRACT FROM AUTHOR]

Half-Heusler (HH) alloys have attracted considerable interest as promising thermoelectric (TE) materials in the temperature range around 700 K and above, which is close to the temperature range of most industrial waste heat sources. The past few years have seen nanostructuing play an important role in significantly enhancing the TE performance of several HH alloys. In this article, we briefly review the recent progress and advances in these HH nanocomposites. We begin by presenting the structure of HH alloys and the different strategies that have been utilized for improving the TE properties of HH alloys. Next, we review the details of HH nanocomposites as obtained by different techniques. Finally, the review closes by highlighting several promising strategies for further research directions in these very promising TE materials. [ABSTRACT FROM AUTHOR]

Investigates the thermal extraction of zinc from the zinc silicate ore willemite. Overview on the condensed product phases of zinc sulfide dissociation; Dissociation reaction of natural zinc ores in the solar furnace; Kinetics and mechanism governing the reduction of zinc ore to the metal.

Layered TiS 2 is of great potential in thermoelectrics for room temperature and medium temperature applications due to its tunable transport properties, low environmental impact, low cost, and lightweight. Herein, we prepared Fe x TiS 2– δ with x varying from 0 to 0.05 through a two-step process, involving initial synthesis in sealed tubes followed by spark plasma sintering. Mössbauer spectroscopy indicated that Fe atoms occupy the octahedral sites in the van der Waals gaps and exist in the form of Fe2+ with a high spin state. Fe x TiS 2– δ with x ≤ 0.02 exhibit high in-plane power factors, reaching an average of ∼ 1.2 mWm–1K–2. The structural disorder caused by Fe intercalation leads to a significant decrease in out-of-plane lattice thermal conductivity. The anisotropy in the figure of merit, ZT , of Fe x TiS 2– δ is suppressed due to Fe intercalation. Fe 0.01 TiS 2– δ possesses the highest ZT of 0.39 at 625 K along the in-plane direction. [ABSTRACT FROM AUTHOR]

Mixed ionic‐electronic conducting (MIEC) membranes have gained growing interest recently for various promising environmental and energy applications, such as H2 and O2 production, CO2 reduction, O2 and H2 separation, CO2 separation, membrane reactors for production of chemicals, cathode development for solid oxide fuel cells, solar‐driven evaporation and energy‐saving regeneration as well as electrolyzer cells for power‐to‐X technologies. The purpose of this roadmap, written by international specialists in their fields, is to present a snapshot of the state‐of‐the‐art, and provide opinions on the future challenges and opportunities in this complex multidisciplinary research field. As the fundamentals of using MIEC membranes for various applications become increasingly challenging tasks, particularly in view of the growing interdisciplinary nature of this field, a better understanding of the underlying physical and chemical processes is also crucial to enable the career advancement of the next generation of researchers. As an integrated and combined article, it is hoped that this roadmap, covering all these aspects, will be informative to support further progress in academics as well as in the industry‐oriented research toward commercialization of MIEC membranes for different applications. [ABSTRACT FROM AUTHOR]

The structure of strontium niobium dioxygen nitride, SrNbO2N, has been solved by powder neutron diffraction at room temperature and 1.5 K. SrNbO2N crystallizes in the tetragonal space group I4/mcm, with a = 5.7056 (4) and c = 8.1002 (9) Å at room temperature, and a = 5.6938 (4) and c = 8.0974 (8) Å at 1.5 K. The crystal structure is derived from the cubic perovskite archetype by a slight rotation of the Nb(O,N)6 octahedra with respect to the tetragonal axis. A partially ordered distribution of oxygen and nitrogen on the anionic sites was found. [ABSTRACT FROM AUTHOR]

The integration of membrane separation processes with chemical reactions through oxygen transport dual‐functional membrane reactors has attracted significant attention due to the potential for process intensification, which also can create a synergy between the two units. This approach holds promise for promoting green chemistry principles by reducing energy consumption and environmental pollution. Despite its potential, a comprehensive review of recent advancements exploring the full potential of oxygen transport dual‐functional membrane reactors (coupling two distinct reactions) in enhancing membrane performance is currently lacking. To address this gap, this perspective article presents various concepts and principles of oxygen transport dual‐functional membrane reactors and provides an overview of recent advances and applications. Additionally, the challenges and opportunities for future research to enhance the efficiency of the process toward industrialization are discussed and highlighted. These include developing novel oxygen transport membrane materials, optimizing membrane engineering, innovating membrane reactor design, and exploring new applications and reaction mechanisms. [ABSTRACT FROM AUTHOR]

Oxynitrides such as LaTa(O,N)3 are attractive materials as photoelectrodes for photoelectrocatalytic solar water splitting. The potential anionic ordering in their perovskite-type structure has been shown to impact the materials' properties. Given the importance attributed to it, the present study reports a detailed experimental analysis supported by simulations of the anionic ordering of La1−xYxTa(O,N)3. The influence of O/N and yttrium content on the anionic order was assessed. Neutron diffraction analysis was performed on four different nominal compositions—LaTaON2, LaTaO2N, La0.9Y0.1TaON2, and La0.9Y0.1TaO2N—at 10 K and 300 K to study potential long-range ordering. Neutron pair distribution function (PDF) analysis was performed on all samples at 10 K and on non-Y-substituted samples at 300 K to evaluate short-range ordering. There was no evidence of long-range O/N order in any of the compounds. In contrast, at a short range (1.5 Å ≤ r < 6 Å), a Pnma (a−b+a−) tilting pattern and local cis-ordering of the anions were seen. The latter faded rapidly, leaving the Pnma tilting pattern in a 6 Å ≤ r ≤ 11 Å range. At higher distances, the PDF analysis agreed with the Imma (a−b0a−) O/N disordered long-range structure. As the O/N content changed, not much difference in behavior was observed. Yttrium substitution introduced some disorder in the structure; nonetheless, it showed marginal influence on octahedral tilting and anionic ordering. [ABSTRACT FROM AUTHOR]

Ruddlesden‐Popper‐type oxides exhibit remarkable chemical stability in comparison to perovskite oxides. However, they display lower oxygen permeability. We present an approach to overcome this trade‐off by leveraging the anisotropic properties of Nd2NiO4+δ. Its (a,b)‐plane, having oxygen diffusion coefficient and surface exchange coefficient several orders of magnitude higher than its c‐axis, can be aligned perpendicular to the gradient of oxygen partial pressure by a magnetic field (0.81 T). A stable and high oxygen flux of 1.40 mL min−1 cm−2 was achieved for at least 120 h at 1223 K by a textured asymmetric disk membrane with 1.0 mm thickness under the pure CO2 sweeping. Its excellent operational stability was also verified even at 1023 K in pure CO2. These findings highlight the significant enhancement in oxygen permeation membrane performance achievable by adjusting the grain orientation. Consequently, Nd2NiO4+δ emerges as a promising candidate for industrial applications in air separation, syngas production, and CO2 capture under harsh conditions. [ABSTRACT FROM AUTHOR]

Ruddlesden‐Popper‐type oxides exhibit remarkable chemical stability in comparison to perovskite oxides. However, they display lower oxygen permeability. We present an approach to overcome this trade‐off by leveraging the anisotropic properties of Nd2NiO4+δ. Its (a,b)‐plane, having oxygen diffusion coefficient and surface exchange coefficient several orders of magnitude higher than its c‐axis, can be aligned perpendicular to the gradient of oxygen partial pressure by a magnetic field (0.81 T). A stable and high oxygen flux of 1.40 mL min−1 cm−2 was achieved for at least 120 h at 1223 K by a textured asymmetric disk membrane with 1.0 mm thickness under the pure CO2 sweeping. Its excellent operational stability was also verified even at 1023 K in pure CO2. These findings highlight the significant enhancement in oxygen permeation membrane performance achievable by adjusting the grain orientation. Consequently, Nd2NiO4+δ emerges as a promising candidate for industrial applications in air separation, syngas production, and CO2 capture under harsh conditions. [ABSTRACT FROM AUTHOR]

Single-source-precursor derived ceramics exhibit advantages for the preparation of Si-based ceramics with controllable phase composition and adjustable functional/mechanical properties, which has significant potential for (ultra)high temperature ceramic materials. Within the present work, a series of hafnium/boron-containing Si 3 N 4 -based ceramics (SiHfBCN) are prepared upon pyrolysis/annealing of the corresponding single-source-precursors in N 2 atmosphere at different temperatures ranging from 1000 °C to 1700 °C. The high-temperature (micro)structural evolution with respect to the annealing temperatures and boron concentration was studied using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The results show that the amorphous SiHfBCN ceramics convert upon crystallization into ceramic nanocomposites consisting of a α-Si 3 N 4 matrix with embedded Si, HfB 2 , and HfB x C y N 1– x – y. The formation and stability of HfB x C y N 1– x – y solid solution were discussed in detail. Finally, the oxidation resistance of the obtained α-Si 3 N 4 /HfB 2 /HfB x C y N 1– x – y ceramic nanocomposites was investigated by thermal gravimetric analysis in air. [ABSTRACT FROM AUTHOR]

Magnetic properties in perovskite titanates ATiO3‐δ (A = Ca, Sr, Ba) were investigated before and after arc melting. Crystal structure analysis was conducted by powder synchrotron X‐ray diffraction with Rietveld refinements. Quantitative chemical element analysis was carried out by X‐ray photoelectron spectroscopy. Magnetic measurements were conducted by vibrating sample magnetometer and X‐ray magnetic circular dichroism (XMCD). The magnetic properties are found to be affected by impurities of 3d elements such as Fe, Co, and Ni. Depending on the composition and crystal structure, the occupation of the magnetic ions in perovskite titanates is selectively varied, which is interpreted to be the origin of the different magnetic behaviors in arc‐melted perovskite titanates ATiO3‐δ (A = Ca, Sr, Ba). In addition, both formation of oxygen vacancies and the reduction of Ti4+ to Ti3+ during arc‐melting also play a role as proven by XMCD. Nevertheless, preferential site occupation of magnetic impurities is dominant in the magnetic properties of arc‐melted perovskite ATiO3‐δ (A = Ca, Sr, Ba). [ABSTRACT FROM AUTHOR]

In this work, Si3N4 and Zr(NO3)4 were used as raw materials to prepare ZrN/ZrO2‐containing Si3N4‐based ceramic composite. The processing, phase composition, and microstructure of the composite were investigated. Hardness and fracture toughness of the ceramics were evaluated via Vickers indentation in Ar at 25°C, 300°C, 600°C, and 900°C. During spark plasma sintering, Zr(NO3)4 was transformed into tetragonal ZrO2, which further reacted with Si3N4, resulting in the formation of ZrN. The introduction of ZrN enhanced the high‐temperature mechanical properties of the composite, and its hardness and fracture toughness reached 13.4 GPa and 6.1 MPa·m1/2 at 900°C, respectively. The oxidation experiment was carried out in air at 1000°C, 1300°C, and 1500°C for 5 h. It was shown that high‐temperature oxidation promoted the formation and growth of porous oxide layers. The microstructure and phase composition of the formed oxide layers were investigated in detail. Finally, it was identified that the obtained composite exhibited a higher thermal diffusivity than that of monolithic Si3N4 in the temperature range of 100°C–1000°C. [ABSTRACT FROM AUTHOR]

The article presents an introduction to the special section on materials for energy production, including topics such as quantitative microscopy of materials and thermoelectrics research.

The transformation towards a circular economy based on sustainable technologies requires future-oriented materials development, which considers materials recycling with a minimum environmental impact (EI). This demands a holistic approach towards materials design, including a combined assessment of functional and environmental performance. Scientific methods for environmental assessment, e.g., life cycle assessment (LCA), are well established but rarely integrated into the chemical process development at early stages. Consequently, sustainability claims often lack scientific verification. Here, we test the approach of integrating a screening LCA into the development of a chemical (recycling) process. As a relevant use case, we selected the recently developed oxygen transport membrane (OTM) material (La0.9Ca0.1)2Ni0.75Cu0.25O4±δ (LCNC). An initial LCA identified the consumption of primary metal nitrates as a major contributor to the EI of the primary synthesis. To address this issue, a Pechini-based chemical recycling process for LCNC was developed, which involves microwave-heated dissolution and subsequent re-gelation. Experimental results demonstrate the synthesis of recycled LCNC powder with primary-like properties, similar reaction behaviour, and >96% yield. Based on the LCA results, the EI of recycling is reduced by up to 76% compared to the primary synthesis in 12 of 14 impact categories. Measures for the simultaneous improvement of the process functionality and environmental performance were identified. The approach of integrating LCA in chemical process development is discussed critically based on the given use case. The results strongly encourage the integration of LCA as a standard method into the future development of sustainable chemical processes. [ABSTRACT FROM AUTHOR]

The title perovskite-type compound is prepared by ammonolysis of LaVO4 in a NH3 stream (1123 K, 6 h). [ABSTRACT FROM AUTHOR]

Thermoelectric conversion may take a significant share in future energy technologies. Oxide‐based thermoelectric composite ceramics attract attention for promising routes for control of electrical and thermal conductivity for enhanced thermoelectric performance. However, the variability of the composite properties responsible for the thermoelectric performance, despite nominally identical preparation routes, is significant, and this cannot be explained without detailed studies of thermal transport at the local scale. Scanning thermal microscopy (SThM) is a scanning probe microscopy method providing access to local thermal properties of materials down to length scales below 100 nm. To date, realistic quantitative SThM is shown mostly for topographically very smooth materials. Here, methods for SThM imaging of bulk ceramic samples with relatively rough surfaces are demonstrated. "Jumping mode" SThM (JM‐SThM), which serves to preserve the probe integrity while imaging rough surfaces, is developed and applied. Experiments with real thermoelectric ceramics show that the JM‐SThM can be used for meaningful quantitative imaging. Quantitative imaging is performed with the help of calibrated finite‐elements model of the SThM probe. The modeling reveals non‐negligible effects associated with the distributed nature of the resistive SThM probes used; corrections need to be made depending on probe‐sample contact thermal resistance and probe current frequency. [ABSTRACT FROM AUTHOR]

In the present work, bulk Si3N4/HfBxN1‐x ceramic nanocomposites were successfully fabricated via a polymer‐derived ceramic approach. The chemical reaction to form the single‐source precursor was confirmed by FT‐IR and XPS, in which both Si−H and N−H groups of perhydropolysilazane react with borane dimethyl sulfide complex and tetrakis(dimethylamido) hafnium(IV). The investigation of the polymer‐to‐ceramic transformation of the synthesized precursors indicates that Hf‐ and B‐modified PHPS exhibits high ceramic yields of up to 100 wt % after pyrolysis at 1000 °C under ammonia. Moreover, XRD and TEM results show that the SiHfBN ceramics with a molar ratio of B : Hf=5 and 10 resist crystallization at temperatures up to 1500 °C and separate after annealing at 1700 °C into nanocomposites comprising of an α‐Si3N4 matrix with embedded ternary HfBxN1‐x phases, solid solutions of rock salt‐type HfN and HfB. Based on the investigation, warm‐pressing was applied to fabricate bulk SiHfBN specimens, and the oxidation behavior of samples annealed at 1700 °C was recorded at 1500 °C over a range of oxidation times between 1 and 50 h. The weight changes of Si3N4/HfBxN1‐x ceramics with B : Hf molar ratios of 2 : 1, 5 : 1 and 10 : 1 are 4.31 %, 4.37 % and 2.57 %, respectively. The formation of HfSiO4, B2O3 and SiO2 during oxidation plays a crucial role for the improvement of the oxidation resistance of the Si3N4/HfBxN1‐x ceramics. [ABSTRACT FROM AUTHOR]

Within the present work, additive-free amorphous bulk SiHfN ceramics with excellent mechanical properties were prepared by a resource-efficient low-temperature molding method, namely warm-pressing. As densification mechanism viscous flow has been identified based on cross-linking reaction. The critical problems concerning gas evolution and crystallization inducing bloating and cracking are addressed through controlled thermolysis and pressure. The microstructural evolution of the SiHfN ceramics indicates that the incorporation of Hf in perhydropolysilazane not only increases the ceramic yield (97.4 wt%) and crystallization resistance (1300 °C), but also suppresses the transformation from α-Si 3 N 4 to β-Si 3 N 4 at high temperatures (1700 °C). Especially, HfN/α-Si 3 N 4 nanocomposites converted by the SiHfN ceramics at 1500 °C show a slight weight loss of 3.13 wt%, indicating the high temperature resistance of the ceramic nanocomposites. The method proposed in this work opens a new strategy to fabricate additive-free polycrystalline Si 3 N 4 - and amorphous Si 3 N 4 -based (nano)composites. [ABSTRACT FROM AUTHOR]

Boron and boron containing materials have created a new class of catalysts for the highly selective conversion of light alkanes to building block olefins. Boron oxide species seem to play an essential role for the oxidative dehydrogenation of propane. For boron nitride they are created through an induction process under reaction conditions. It is still not obvious how different kinds of oxidative pre‐activation influences the observed activity and selectivity. Here we compare two different oxygen activation strategies of boron nitride, a classical activation by calcination at different temperatures and ball‐milling with varying rotation velocity. These treatments allow to control the amount of introduced boron oxide species from 0.2 to 17.5 wt.‐%, as quantified by alkalimetric titration. The catalytic experimental data together with the pre, post as well as in situ characterization, give insights how the catalyst's surface changes under reaction conditions. On this backdrop it can be deduced that molten boron oxide predominantly acts as catalyst under reaction conditions, and boron nitride as catalyst support. [ABSTRACT FROM AUTHOR]

Ceramic SiCN nanocomposites modified with nanocellulose derived defect-rich carbon nanofibers (CNFs-SiCN) were developed by thermolysis of nanocelulose-polysilazane single-source precursors (SSPs). Multi-loss mechanisms (i.g. polarization loss and conductive loss) were established in the SiCN ceramic nanocomposites by employing the defect-rich structure of CNFs. Cole-Cole circle plots indicate that the CNFs-SiCN ceramics possess strong polarization capability due to the defect-rich structure of the CNFs. Dielectric loss values fitted by the Debye theory showed that the proportion of polarization loss reaches an unprecedented high value, accounting for 52.1% of the total dielectric loss. When the content of nanocellulose is 10 wt% of SSPs, the minimal reflection coefficient (RC min) and effective absorption bandwidth (EABs) of CNFs-SiCN ceramic can reach −36.3 dB and 3.0 GHz, respectively. This work may contribute new ideas for establishing multi-loss mechanisms in ceramic-based materials, finding a new application for nanocellulose, and shaping the design of novel absorbents. [Display omitted] [ABSTRACT FROM AUTHOR]

The misfit-layered cobalt oxide [Ca2CoO3-δ][CoO2]1.62 is a promising material for high-temperature thermoelectric heat recovery. Here, we show that discrepancies in the numerously reported thermoelectric performances can result from Co3OM4 impurities or a change of the defects, i.e., the relative Co content in the [Ca2CoO3-δ][CoO2]1.62 phase. We observe that increasing the relative Co content in the [Ca2CoO3-δ][CoO2]1.62 phase leads to a larger figure of merit ZT. We attribute this increase of ZT to additional p-type charge carriers introduced by Ca vacancies and the resulting reduction of the electrical resistivity. For Co/Ca ratios above the miscibility limit, the increase in thermal conductivity due to the formation of Co3OM4 impurities leads to a reduction of ZT when the volume fraction of the Co3OM4 phase is increased from 1% to 3%. Hence, the best figure of merit is expected close to the upper phase boundary of the [Ca2CoO3-δ][CoO2]1.62 phase. [ABSTRACT FROM AUTHOR]

Co-substitution of Eu and Nb into insulating CaTiO 3 can make it a good n-type potential thermoelectric (TE) material. In the present work, solid solution compounds with the nominal composition Ca 0.8 Eu 0.2 Ti 1– x Nb x O 3– δ (x = 0.05, 0.08, 0.1, 0.12) were synthesized and sintered in different atmospheres, including argon (Ar) and forming gas (5 vol% H 2 in Ar). Notably, the different reduction effects of these atmospheres resulted in significant differences in phase formation, grain size, oxygen deficiency, and TE properties of the synthesized samples. Introducing additional electrons to the system by donor substitution of Ti with Nb leads to significant changes in the electrical conductivity and Seebeck coefficient. The most favorable TE performance of the prepared samples was found in the sample with x = 0.05, primarily attributed to its proper charge carrier concentration. This work highlights the crucial role of the sintering atmosphere in manipulating the TE performance of n-type CaTiO 3 -based ceramics, an effect similar to donor doping. [Display omitted] • Sintering atmospheres play a vital role in determining thermoelectric transport properties of titanate perovskites. • Nb is an efficient electron donor in the titanate perovskite system. • Tungsten carbide impurity can significantly enhance the thermal conductivity. [ABSTRACT FROM AUTHOR]

The article titled "Multiplying Oxygen Permeability of a Ruddlesden–Popper Oxide by Orientation Control via Magnets" discusses the magnetic anisotropy and oxygen transport anisotropy of the Ruddlesden–Popper oxide Nd2NiO4+δ. The study found that by aligning the (a,b)-plane of the oxide perpendicular to the gradient of oxygen partial pressure using a magnetic field generated by permanent magnets, the oxygen flux of the membrane can be increased five times compared to a randomly oriented membrane. This research was conducted by Zhijun Zhao, Armin Feldhoff, and their colleagues. [Extracted from the article]

The article titled "Multiplying Oxygen Permeability of a Ruddlesden-Popper Oxide by Orientation Control via Magnets" discusses the magnetic anisotropy and oxygen transport anisotropy of the Ruddlesden-Popper oxide Nd2NiO4+δ. The study shows that by aligning the (a,b)-plane of the oxide perpendicular to the gradient of oxygen partial pressure using a magnetic field generated by permanent magnets, the oxygen flux of the membrane can be increased five times compared to a randomly oriented membrane. The research, conducted by Zhijun Zhao, Armin Feldhoff, and their colleagues, provides valuable insights into enhancing the oxygen permeability of oxide membranes. [Extracted from the article]

[Display omitted] Hierarchically cellular, stiff, and lightweight niobium carbide (NbC)-pyrolytic carbon (PyC) monolithic foam composites possessing excellent electromagnetic interference shielding effectiveness (EMI SE) were developed via a natural wood template-based method. Pyrolytic carbon derived from the decomposed cellulose in the wood worked as the carbon source for the growth of NbC phase, and the NbC-PyC heterogeneous nano-interface formed between the residual PyC and the freshly formed NbC. Multi-loss mechanisms (e.g. conductive loss, dipole polarization loss, and especially interface polarization loss) were established by controlling the NbC content and residual PyC phase in the NbC-PyC foams, which significantly improved the absorption capability. Compared to 28.0 dB of PyC monolith, the EMI SE of NbC-PyC foam can reach 54.8 dB when the thickness is 0.5 mm, which outperforms the other porous-based shielding materials. Due to the highly porous structure of pristine wood, the resulting NbC-PyC foam exhibited a low density of 0.48 g/cm3, which is ~ 1/16 of dense NbC (7.78 g/cm3). Generally, this work introduces innovative ideas for designing novel and advanced transition metal carbide–carbon composite materials. [ABSTRACT FROM AUTHOR]

Abstract: We report on the design of a solar cavity-receiver packed with an array of thermoelectric converter (TEC) modules, which enables efficient capture of concentrated solar radiation entering through a small aperture. A 1kW demonstrator (proof-of-concept) containing 18 TEC modules, each consisting of Al2O3 absorber/cooler plates, and p-type La1.98Sr0.02CuO4 and n-type CaMn0.98Nb0.02O3 thermoelements, was subjected to peak solar concentration ratios exceeding 600 suns over its aperture. The TEC modules were operated at 900K on the hot side and 300K on the cold side. The measured solar-to-electrical energy conversion efficiency was twice that of a directly irradiated TEC module. A heat transfer model was formulated to simulate the solar cavity-receiver system and experimentally validated in terms of open-circuit voltages measured as a function of the mean solar concentration ratio. Vis-à-vis a directly irradiated TEC module, the cavity configuration enabled a reduction of the re-radiation losses from 60% to 4% of the solar radiative power input. Theoretical considerations for TEC with figure-of-merit higher than 1 indicate the potential of reaching solar-to-electrical energy conversion efficiencies exceeding 11%. [Copyright &y& Elsevier]

The structural and microstructural evolution of microwave plasma nitrided SrTiO3 was studied by scanning, high-resolution transmission electron microscopy (STEM, HRTEM), electron energy loss spectroscopy, and energy dispersion X-ray spectroscopy (EELS/EDX) combined with elemental mapping at the nanometer scale. EELS/EDX mappings show the SrTiO3−xNy single crystal formation as well as the TiN1−xOy nanograin layer formation on the surface, which depends on the plasma treatments. Stacking faults were the most common defects found in single crystal SrTiO3−xNy, either with SrO plane-excess or TiO2 plane-excess. The excess of SrO was integrated as Ruddlesden−Popper planar faults, showing an arrangement of the three-dimensional nanostructure, and the excess of TiO2−xNy was integrated as crystallographic shear defects. Nitrogen incorporation into the structure is not homogeneous at the atomic level, and a high concentration of nitrogen was found in Sr-deficient planar defects. TEM and STEM-EDX-EELS elemental mapping has been applied to investigate microwave plasma nitrided STO. The plasma treatment at NH3 ≤ 100 mL/min produces SrO etching and the formation of Ti and N rich islands in the near surface region (<150 nm). The plasma treatment at NH3 > 100 mL/min produces defects such as stacking faults near the surface, free from TiN1−xOy nanocrystals. [ABSTRACT FROM AUTHOR]

A heat transfer model that couples radiation/conduction/convection heat transfer with electrical potential distribution is developed for a thermoelectric converter (TEC) subjected to concentrated solar radiation. The 4-leg TEC module consists of two pairs of ptype La1.98Sr0.02CuO4 and n-type CaMn0.98Nb0.02O3 legs that are sandwiched between two ceramic Al2O3 hot/cold plates and connected electrically in series and thermally in parallel. The governing equations for heat transfer and electrical potential are formulated, discretized and solved numerically by applying the finite volume (FV) method. The model is validated in terms of experimentally measured temperatures and voltages/power using a set of TEC demonstrator modules, subjected to a peak radiative flux intensity of 300 suns. The heat transfer model is then applied to examine the effect of the geometrical parameters (e.g. length/width of legs) on the solar-to-electricity energy conversion efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Nanopowders of TiO2:N were synthesized in a two step process. At first, TiO2 was prepared from titanium tetraisopropoxide (TTIP) in form of crystalline powder by flame spray synthesis (FSS). In a second step TiO2-FSS with a specific surface area (SSA) of 54m2/g and TiO2-P25 as a reference material were ammonolysed in a rotating tube furnace. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to investigate crystallinity before and after ammonolysis. Based on the X-ray photoelectron spectroscopy (XPS) studies it has been established that the N 1s peak at 395.9eV can be assigned to substitutional nitrogen. New electron transitions and resulting band gap changes in respect to undoped sample have been observed in TiO2−x N x . Diffusive reflectance and the resulted band gap energy were determined by diffuse reflection spectroscopy (DRS), where the correlation between differential reflectance and Tauc plot, known as a second method of the band gap determination, is discussed for pure and N-doped TiO2 nanopowders. The photocatalytic performance of the nanopowders under visible light irradiation (400–500nm) was studied by the degradation of methylene blue (MB) in aqueous suspensions. [Copyright &y& Elsevier]

Abstract: Thin films of La x Sr1−x TiO3+x/2 (x =0, 0.25, 0.5, 0.75, 1) were grown by laser ablation on two different kinds of substrates (SrTiO3 (STO) and MgO) and were subsequently ammonolysed to yield the corresponding oxynitrides La x Sr1−x Ti(O,N)3. For both substrates all films were found to grow epitaxially to the (100) direction of the cubic perovskite structure, except for x =0.5 that grew parallel to the (110) direction. For some of the films TiN was detected as impurity phase. Scanning electron microscopy revealed that the films are dense and homogeneous with thicknesses around 350nm. Atomic force microscopy showed that the surface roughness of the films varied between 4.2 and 14.1nm. The employed substrate had a strong influence on the electrical properties. Films grown on STO exhibited a metallic behaviour, in contrast to the films grown on MgO, which were insulating. [Copyright &y& Elsevier]

Abstract: Thick films of the perovskite-related oxynitrides LaTiO2N, NdTiO2N, SrNbO2N and SrTaO2N were synthesised by nitridation of single crystals of the corresponding oxides with general composition ABO3.5. The oxide crystals were obtained by optical floating zone growth. They correspond to n =4 member of the AnBn O3n+2 family of layered perovskites and were reacted at temperatures between 900°C and 1050°C to form the oxynitrides. Electron probe microanalysis proved the presence of nitrogen in a surface layer of a few micrometer thickness. Cross-section SEM revealed additional thin stripes of oxynitride within the bulk of the crystals, indicating that nitrogen is incorporated preferably parallel to the perovskite-type layers, which in turn are connected in a zipper-type mechanism. The formation of the desired perovskite-type oxynitrides was confirmed by X-ray diffraction. Pole figure measurements proved an epitaxial orientation ABO2N (110)[001]‖ ABO3.5 (001)[100]. The mosaicity of the oxynitrides both in polar and azimuthal direction was very small (<2°) indicating a nearly single crystalline quality of the surface layer. The nitridation of the crystals results in a dramatic change in colour. Optical spectroscopy revealed shifts of the absorption edge by more than 200nm to longer wavelengths with respect to the parent oxides, corresponding to a reduction of the band gap energies by 1.4–1.8eV. [Copyright &y& Elsevier]

Abstract: Oxynitride perovskites with bright and variable colour have the potential to be employed as non-toxic pigments, and to substitute colourants that contain harmful heavy metals. For this application it is extremely important to have a precise knowledge about the materials stability. The thermal stability of oxynitride perovskites in different atmospheres was measured by thermogravimetry in combination with mass spectroscopy (MS). The studied compounds, namely LaTiO2N, SrNbO2N and SrTaO2N, were heated up to 1200°C in argon–oxygen mixtures with varying oxygen contents. It was found that the thermal behaviour of the studied oxynitrides changes drastically with the oxygen concentration. When heated up in pure argon the oxynitrides transform to oxides containing transition metals of lower oxidation state and/or binary nitrides. For oxygen contents between 0.5% and 20% the samples were completely oxidised. The oxidation rate increases with oxygen content. MS analysis of the gaseous products (including N2, NO and NO2) reveals a complex reaction mechanism, which is strongly modified by the composition of the atmosphere. [Copyright &y& Elsevier]

Ternary metal oxynitrides have attracted considerable attention because of their bright colouring, while oxide perovskites are usually colourless. In this report some technically relevant properties for the application of these materials as pigments, such as colour and thermal stability, have been measured. The crystal structure and phase purity of the samples were analysed by X-ray diffraction. The accurate colours were determined using a colorimeter. The selected oxynitrides possess a variety of different colours like yellow, orange, red, brown, green and black. In addition, the thermal stability of the compounds was investigated. All studied samples are stable in air, water and diluted acids at room temperature and start to decompose in air only above 400°C. This high thermal and chemical stabilities make oxynitrides promising candidates to be employed in rubbers, thermoplastics, paints, etc. as ceramic pigments to substitute dyes, which contain toxic metals. [Copyright &y& Elsevier]

A novel and sustainable paper template-based method was developed for the fabrication of advanced niobium carbide (NbC)-based free-standing films for electromagnetic interference (EMI) shielding application. Through employing the porous structure of paper template, the simultaneous optimization of thickness, flexibility, density and shielding effectiveness (SE) of NbC-based films was facilely achieved. The pyrolytic carbon (PyC) derived from paper worked as a carbon source for the growth of the NbC phase. A hierarchically porous structure with a porosity of ∼80 vol % was established to optimize the flexibility and density of the resultant films. Adjusted heterogeneous NbC-PyC nano-interfaces were formed by controlling the amount of NbC and the remaining PyC phase in the films, which significantly improved the absorption capability of EM waves. At the highest NbC content, the film possesses shielding effectiveness of 50 and 86 dB when the sample thickness is ∼55 and ∼220 μm, respectively compared to 32 dB of pristine paper-derived PyC film (∼55 μm). These results provide guidance to explore more eco-friendly and commercially effective routes for the recycling of used paper through developing their application in the EM field. [Display omitted] [ABSTRACT FROM AUTHOR]

In view of rising ecological awareness, materials development is primarily aimed at improving the performance and efficiency of innovative and more elaborate materials. However, a materials performance figure of merit should include essential aspects of materials: environmental impact, economic constraints, technical feasibility, etc. Thus, we promote the inclusion of sustainability criteria already during the materials design process. With such a holistic design approach, new products may be more likely to meet the circular economy requirements than when traditional development strategies are pursued. Using catalysts for water electrolysis as an example, we present a modelling method based on experimental data to holistically evaluate processes. [ABSTRACT FROM AUTHOR]

Angesichts des steigenden ökologischen Bewusstseins zielt die Materialentwicklung in erster Linie auf die Verbesserung der Leistung und Effizienz innovativer und komplexerer Materialien ab. Eine Leistungsbewertung von Werkstoffen sollte jedoch wesentliche Aspekte von Materialien einbeziehen: Umweltauswirkungen, wirtschaftliche Zwänge, technische Machbarkeit usw. Daher wollen wir die Einbeziehung von Nachhaltigkeitskriterien bereits während des Materialdesignprozesses anstoßen. Mit einem solchen ganzheitlichen Designansatz ist es wahrscheinlicher, dass neue Produkte die Anforderungen der Kreislaufwirtschaft erfüllen, als wenn traditionelle Entwicklungsstrategien verfolgt werden. Am Beispiel von Katalysatoren für die Wasserelektrolyse präsentieren wir eine auf experimentellen Daten basierende Modellierungsmethode zur ganzheitlichen Bewertung von Prozessen. [ABSTRACT FROM AUTHOR]

New ceramic Ca3Co3.9O9+δ ?/CaMn0.97W0.03O3-δ thermoelectric generators with different cross section areas Ap and An of the p- and the n-type leg are fabricated, characterized, and tested at high temperatures in long-term tests. The variation of the measured power output and the efficiency with changing Ap/An ratio is discussed and compared with calculations based on the measured material properties. The highest conversion efficiencies are reached for ratios close to the one predicted by the compatibility approach, whereas an improper choice of Ap/An leads to a strong reduction of the efficiency. A volume power density of 1.4?W/cm3 and an efficiency of 1.08% are found for the most promising generator (temperature difference ΔT = 734?K and Ap/An = 1.12). The results reveal the major importance of the Ap/An ratio for the conversion efficiency and subsequently cost and weight reduction issues, both crucial for a large scale application of thermoelectric converters. Additionally, the oxide generators proved to be very reliable, as after more than 110?h of high temperature energy conversion, no degradation is observable. [ABSTRACT FROM AUTHOR]

Electronic and transport properties of Bi2S3 with various dopants are studied using density functional theory and experimental characterizations. First, principle calculations of thermoelectric properties are used to evaluate the thermoelectric potential of the orthorhombic Bi2S3 structure. The computational screening of extrinsic defects is used to select the most favorable n-type dopants. Among all the dopants considered, hafnium and chlorine are identified as prospective dopants, whereas, e.g., germanium is found to be unfavorable. This is confirmed by experiment. Seebeck coefficient (S) and electrical conductivity (σ) measurements are performed at room temperature on pellets obtained by spark plasma sintering. An increase of power factors (S2·σ) from around 50 up to 500 μW K-2m-1 is observed for differently doped compounds. In several series of samples, we observed an optimum of power factor above 500 μW K-2m-1 at room temperature for a chlorine equivalence of 0.25 mol. % BiCl3. The obtained results are plotted on a semilogarithmic log (r) versus S graph to demonstrate that a very strong linear trend that limits the power factor around 500 μW K-2m-1 exists. Further improvement of Bi2S3 as thermoelectric material will require finding new doping modes that will break through the observed trend. The results of stability tests demonstrate that properties of optimally doped Bi2S3 are stable. [ABSTRACT FROM AUTHOR]

For the synthesis of perovskite-type oxynitrides AB (O,N) 3 in most cases cationic substitution is applied for charge compensation, while anionic substitution, e.g., using fluoride is by far less investigated. Herein, we have investigated the possibility to use sequential double anionic substitution for charge compensation while forming perovskite-type oxynitride fluorides AB (O,N,F) 3 with A = Ca, Sr, Ba and B Ti, Zr. As expected from Goldschmidt's tolerance factor, the cubic SrTi(O,N,F) 3 and BaZr(O,N,F) 3 were found to be easily formed. The synthesis required a lower number of rigorous thermal treatment cycles to obtain single-phase materials. The non-cubic crystal structures favored a factor six to ten higher nitrogen content of e.g., up to 0.06 per formula unit in SrZr(O,N,F) 3 , while the fluoride content did not change within measurement uncertainty. Overall, the amount of anionic substitution remained low and a presence of oxygen vacancies in the range of 0.1 per formula unit was indicated in all cases. In comparison to the corresponding oxides the double anionic substituted oxynitride fluorides displayed a band gap reduction by about 0.7 eV on average, however, the obtained band gap values of around 3 eV were still too large for a potential application in solar water splitting (SWS). Nonetheless, a clear correlation of the nitrogen content and the band gap reduction was obtained, e.g., SrZr(O,N,F) 3 revealing the highest nitrogen content also showing the highest band gap reduction. While no band gap change was observed in CaZr(O,N,F) 3 showing a negligible nitrogen amount. The main drawback of a sequential double anionic substitution strategy using consecutive heterovalent substitution by F− and N3− is found to be the need of intermediate charge compensation. In parallel the Fermi level is altered. Both allowed only for a very limited substitution of the anionic sublattice. Instead, alternative synthesis pathways enabling a simultaneous anionic double substitution will be needed to realize increased partial substitution of nitride and fluoride in perovskite-type AB (O,N,F) 3 reducing the band gaps to values suitable for SWS. [Display omitted] • Cubic SrTi(O,N,F) 3 & BaZr(O,N,F) 3 are easier to synthesize, but have lower N content. • The higher the N content, the higher the band gap reduction. • Non-cubic structures helped to stabilize higher anionic substitution degree. • Intermediate charge compensation during sequential synthesis limits anionic substitution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bimetallic Co-Ni catalysts were firstly developed by a molecular-level engineering strategy. • The superior performance of bimetallic catalysts is unprecedentedly pinpointed via DFT calculations. • The specific yields of carbon nanocomposites and H 2 are outstanding compared to the reported work. • The carbon nanocomposites exhibited excellent electromagnetic absorption performance. The advancement in the pyrolysis-catalysis conversion of waste plastics is currently limited by three problematic issues, namely lack of efficient catalysts, ambiguous catalytic mechanism, and identification of a dedicated application of carbon nanocomposites. Herein, advanced bimetallic NiCo/MnO catalysts were developed via a molecular- and macroscale-level engineering strategy. The best conversion performance among all batches was achieved for a Co:Ni molar ratio of 1:1. When the plastic-to-catalyst ratio is 10.7:1, the H 2 and carbon yields of polyethylene conversion reached 29.8 mmol/g plas and 42.2 wt%, respectively. Density functional theory simulations rationalized the activity of NiCo/MnO catalysts in the dehydrogenation of hydrocarbons. The resulting carbon nanocomposites demonstrated excellent electromagnetic absorption performance with an effective absorption bandwidth of the representative carbon nanocomposites/wax composite of 5.12 GHz and a minimal reflection loss lower than −45 dB. This work provides novel insights for developing advanced catalysts for the pyrolysis-catalysis conversion of waste plastics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bridging the gap between laboratory research and industrial applications. • Up-carbonization of process not only limited to De-carbonization. • Focusing on physico-chemical mechanisms to achieve energy-efficient, low-carbon-emissions, scalable processes. • Discussion on engineering challenges and opportunities for translational research towards commercial applications. A global transition to a hydrogen economy requires widespread adoption of clean hydrogen energy. Methane cracking is one of the most viable technologies for producing clean hydrogen, nearing the ultimate zero-carbon-emissions targets. While major progress has been made in the lab-scale development of high-performance reactors and catalysts for methane pyrolysis, research focusing on industry-relevant scale and process conditions is in its infancy. Herein, recent advances in fundamental and applied research in methane pyrolysis are critically examined, focusing on physico-chemical mechanisms to achieve energy-efficient, low-carbon-emission, scalable processes. The highlighted recent efforts to bridge the gap between laboratory research and industrial applications reveal rapid advances in practical applications based on synergistic chemical engineering, catalysis, and materials science research. Perspectives, challenges, and opportunities for translational research towards commercial applications of methane cracking are discussed aiming at clean hydrogen production. [ABSTRACT FROM AUTHOR]

N-type half-Heusler NbCoSn is a promising thermoelectric material due to favourable electronic properties. It has attracted much attention for thermoelectric applications while the desired p-type NbCoSn counterpart shows poor thermoelectric performance. In this work, p-type NbCoSn has been obtained using Sc substitution at the Nb site, and their thermoelectric properties were investigated. Of all samples, Nb0.95Sc0.05CoSn compound shows a maximum power factor of 0.54 mW/mK2 which is the highest among the previously reported values of p-type NbCoSn. With the suppression of thermal conductivity, p-type Nb0.95Sc0.05CoSn compound shows the highest measured figure of merit ZT = 0.13 at 879 K. [ABSTRACT FROM AUTHOR]

Perovskite-type oxynitrides hold great potential for optical applications due to their excellent visible light absorption properties. However, only a limited number of such oxynitrides with modulated physical properties are available to date and therefore alternative fabrication strategies are needed to be developed. Here, we introduce such an alternative strategy involving a precursor microstructure controlled ammonolysis. This leads to the perovskite family member LaTa(IV)O2N containing unusual Ta4+ cations. The adjusted precursor microstructures as well as the ammonia concentration are the key parameters to precisely control the oxidation state and O:N ratio in LaTa(O,N)3. LaTa(IV)O2N has a bright red colour, an optical bandgap of 1.9 eV and a low (optically active) defect concentration. These unique characteristics make this material suitable for visible light-driven applications and the identified key parameters will set the terms for the targeted development of further promising perovskite family members. Perovskite-type oxynitrides hold great potential for optical applications due to their excellent visible light absorption properties. Here, a defined precursor microstructure is used to modulate the oxidation state of tantalum during ammonolysis leading to a bright red perovskite containing tantalum in a rare 4+ -state. [ABSTRACT FROM AUTHOR]

The thermoelectric performance of Ta substituted (ZrHf)NiSn-based half-Heusler compounds is studied. Here, Ta is used on the Hf site for controlling the charge carrier concentration in contrast to the widely used Sb substitution on the Sn site. The influence of the Ta content on the thermoelectric and transport properties of (Zr0.3Hf0.7-xTax)NiSn (x=0, 0.01, 0.05) is investigated by means of Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall coefficient measurements. The results are analyzed in context of the single parabolic band model. Ta substitution increases the charge carrier concentration and suppresses the influence of impurity band, which is present in the pristine (Zr0.3Hf0.7)NiSn. Moreover, Ta substitution decouples and simultaneously increases the density-of-states effective mass (m*) and the charge carrier mobility (μ), leading to a larger weighted mobility μ·(m*)3/2. The lattice thermal conductivity is slightly suppressed due to increased point defect scattering. As a result, a Figure of Merit of 0.85 is achieved for (Zr0.3Hf0.65Ta0.05)NiSn compound at 870 K, ca. 180% improvement over the unsubstituted sample. [ABSTRACT FROM AUTHOR]

The thermoelectric performance of Ta substituted (ZrHf)NiSn-based half-Heusler compounds is studied. Here, Ta is used on the Hf site for controlling the charge carrier concentration in contrast to the widely used Sb substitution on the Sn site. The influence of the Ta content on the thermoelectric and transport properties of (Zr0.3Hf0.7-xTax)NiSn (x=0, 0.01, 0.05) is investigated by means of Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall coefficient measurements. The results are analyzed in context of the single parabolic band model. Ta substitution increases the charge carrier concentration and suppresses the influence of impurity band, which is present in the pristine (Zr0.3Hf0.7)NiSn. Moreover, Ta substitution decouples and simultaneously increases the density-of-states effective mass (m*) and the charge carrier mobility (μ), leading to a larger weighted mobility μ(m*)3/2. The lattice thermal conductivity is slightly suppressed due to increased point defect scattering. As a result, a Figure of Merit of 0.85 is achieved for (Zr0.3Hf0.65Ta0.05)NiSn compound at 870 K, ca. 180% improvement over the unsubstituted sample. [ABSTRACT FROM AUTHOR]