The development of a novel reactive spray technology based on the well‐known gas‐phase metal oxide synthesis route provides innumerable opportunities for the production of non‐oxide nanoparticles. ...Among these materials, metal sulfides are expected to have a high impact, especially in the development of electrochemical and photochemical high‐surface‐area materials. As a proof‐of‐principle, MnS, CoS, Cu2S, ZnS, Ag2S, In2S3, SnS, and Bi2S3 are synthesized in an O2‐lean and sulfur‐rich environment. In addition, the formation of Cu2S in a single‐droplet combustion experiment is reported. The multiscale approach combining flame sprays with single‐droplet combustion is expected to pave the way toward a fundamental understanding of the gas‐phase formation of metal sulfides in the future. The knowledge acquired can open the possibility for the development of a next‐generation gas‐phase technology facilitating the scalable synthesis of functional binary/ternary metal sulfides.
As proof‐of‐principle, the preparation of various metal sulfides in a flame process using single‐droplet combustion and enclosed flame spray pyrolysis in O2‐lean condition is demonstrated. Using a large‐tube reactor MnS, CoS, Cu2S, ZnS, Ag2S, In2S3, SnS, and Bi2S3 are formed at a rate of 5 g h−1. The flame aerosol process is a key toward scalable synthesis of binary/ternary metal sulfides for next‐generation functional materials.
The progress in nanomedicine (NM) using nanoparticles (NPs) is mainly based on drug carriers for the delivery of classical chemotherapeutics. As low NM delivery rates limit therapeutic efficacy, an ...entirely different approach was investigated. A homologous series of engineered CuO NPs was designed for dual purposes (carrier and drug) with a direct chemical composition–biological functionality relationship. Model‐based dissolution kinetics of CuO NPs in the cellular interior at post‐exposure conditions were controlled through Fe‐doping for intra/extra cellular Cu2+ and biological outcome. Through controlled ion release and reactions taking place in the cellular interior, tumors could be treated selectively, in vitro and in vivo. Locally administered NPs enabled tumor cells apoptosis and stimulated systemic anti‐cancer immune responses. We clearly show therapeutic effects without tumor cells relapse post‐treatment with 6 % Fe‐doped CuO NPs combined with myeloid‐derived suppressor cell silencing.
A pharmacokinetic model: Dissolution kinetics from iron‐doped copper oxide nanoparticles were modelled to establish structure–release relationships. With those finely tuned kinetics, a cancer treatment orthogonal to conventional chemotherapy was achieved both in vitro and in vivo. Immunization of all animals occurred, rendering them protected against tumor relapse, even upon re‐engraftment of tumor cells.
Flame spray pyrolysis (FSP) has been employed for the syntheses of single crystalline WO3 nanoparticles using tungsten precursors with tungsten in usual (+6) and unusual (+4 and 0) oxidation states. ...The WO3 nanoparticles have been characterized by powder X-ray diffraction and the patterns have been refined using the Rietveld and the Le Bail method (space group P21/n, monoclinic system; the averaged lattice parameters of the three WO3: a = 7.3913(4) Å, b = 7.5630(5) Å, c = 7.6615(6) Å, β = 90.78(3)°, Z = 8, V = 423.19 Å3). Because of the very small crystallite sizes, non-Bragg scattering is observed. The crystallite sizes derived from Rietveld or Le Bail analyses were in the range of 6−8 nm, reasonably agreeing with the crystallite sizes (7−10 nm) determined from Brunauer−Emmett−Teller and microscopic analysis where each particle is basically a small single crystal. Well-developed lattice fringes of 3.860−3.994 Å were illustrated by high resolution transmission electron microscopy (HRTEM). Indexing of selected area electron diffraction (SAED) patterns of all WO3 revealed that the crystals are isostructural with the monoclinic phase having pseudocubic lattice parameters. The wide spot HRTEM image additionally examined in reciprocal space by calculating the corresponding power spectrum further proved the single-crystalline nature of the nanoparticles. The development of economic precursors and the systematic studies on the crystallization and assembly behavior of tungsten oxide products presented here now opens the door for the production of ultrafine single crystalline, single phase WO3 nanomaterial.
The spinel LiMn2O4 (LMO) is a promising cathode material for rechargeable Li-ion batteries due to its excellent properties, including cost effectiveness, eco-friendliness, high energy density, and ...rate capability. The commercial application of LiMn2O4 is limited by its fast capacity fading during cycling, which lowers the electrochemical performance. In the present work, phase-pure and crystalline LiMn2O4 spinel in the nanoscale were synthesized using single flame spray pyrolysis via screening 16 different precursor–solvent combinations. To overcome the drawback of capacity fading, LiMn2O4 was homogeneously mixed with different percentages of AlPO4 using versatile multiple flame sprays. The mixing was realized by producing AlPO4 and LiMn2O4 aerosol streams in two independent flames placed at 20° to the vertical axis. The structural and morphological analyses by X-ray diffraction indicated the formation of a pure LMO phase and/or AlPO4-mixed LiMn2O4. Electrochemical analysis indicated that LMO nanoparticles of 17.8 nm (d BET) had the best electrochemical performance among the pure LMOs with an initial capacity and a capacity retention of 111.4 mA h g–1 and 88% after 100 cycles, respectively. A further increase in the capacity retention to 93% and an outstanding initial capacity of 116.1 mA h g–1 were acquired for 1% AlPO4.
A mineral intermediate between sillimanite and mullite, tentatively designated as "sillimullite," was studied by electron microprobe analyses and single-crystal X-ray diffraction methods. The ...chemical compositions derived from the microprobe results and the crystal-structure refinement are Al7.84Fe0.18 Ti0.03Mg0.03Si3.92O19.96 and Al8.28Fe0.20Si3.52O19.76 (Fe is Fe3+) corresponding to x-values of 0.02 and 0.12, respectively, in the solid-solution series Al8+4xSi4-4xO20-2x assigning Fe3+, Ti, and Mg to the Al site. The composition derived from microprobe analysis is very close to a stoichiometric sillimanite (with Fe3+,Ti, and Mg assigned to Al sites), while the composition derived from diffraction data is midway between sillimanite and Si-rich mullites. The discrepancy is assumed to be caused by the occurrence of amorphous nano-sized SiO2 inclusions in the aluminosilicate phase not affecting the diffraction data but detected in the microprobe analysis. "Sillimullite" crystallizes in the orthorhombic space group Pnam with a = 7.5127(4), b = 7.6823(4), c = 5.785(3) Å, V = 333.88(4) Å3, Z = 1. It has a complete Si/Al ordering at tetrahedral sites like sillimanite but with neighboring double chains of SiO4 and AlO4 tetrahedra being offset by 1/2 unit cell parallel to C: relative to each other causing the change of the space-group setting from Pbnm (sillimanite) to Pnam. Difference Fourier calculations and refinements with anisotropic displacement parameters revealed the formation of oxygen vacancies and triclusters as known in the crystal structures of mullite. Final refinements converged at R1 = 5.9% for 1024 unique reflections with Fo > 4σ(Fo). Fe was found to reside predominantly in the octahedral site and with minor amounts in one of the T* sites. Mg and Ti were not considered in the refinements. The crystal studied here is considered to represent a new mineral intermediate between sillimanite and mullite, named "sillimullite."
Flame spray pyrolysis (FSP) is a novel technique for the fabrication of nanostructured catalysts with far-reaching options to control structure and composition even in cases where complex composites ...need to be prepared. In this study, we took advantage of this technique to synthesize highly dispersed pure and Pd-doped iron oxide nanoparticles and investigated them as Fischer−Tropsch (FT) catalysts. By systematically varying the Pd content over a large range from 0.1 to 10 wt %, we were able to directly analyze the influence of the Pd content on activity and selectivity. In addition to catalytic measurements, the structure and composition of the particles were characterized before and after these measurements, using transmission electron microscopy, adsorption measurements, X-ray diffraction, and EXAFS. The comparison revealed on the one hand that small Pd clusters (diameter: 1−2 nm) evolve from initially homogeneously distributed Pd and on the other hand that the iron oxide transforms into iron carbides depending on the Pd content. The presence of Pd influences the particle size in the pristine samples (8−11 nm) resulting in specific surface areas that increase as the Pd content increases. However, after activation and reaction the specific surface areas become similar due to partial agglomeration and sintering. In a fixed bed FT reaction test, enhanced FT activity was observed with increasing Pd content while the selectivity shifts to longer chain hydrocarbons, mainly paraffins. Mechanistic implications regarding the role of Pd for the performance of the catalysts are discussed.
Mullite and mullite-type crystal structures Fischer, Reinhard X.; Gaede-Köhler, Andrea; Birkenstock, Johannes ...
International journal of materials research,
04/2012, Letnik:
103, Številka:
4
Journal Article, Conference Proceeding
Recenzirano
Synthetic mullites (Al
Si
) belong to one of the most important groups of ceramic materials. Their crystal structure consists of chains of edge-sharing AlO
octahedra interconnected by tetrahedral ...double chains of
(
= Al, Si) tetrahedra. The occurrence of oxygen vacancies is associated with the formation of triclusters of
groups. The distribution of oxygen vacancies and the distribution of Al and Si on the tetrahedral sites are partially ordered yielding an incommensurately modulated crystal structure with satellite reflections in diffraction patterns. The number of symmetrically independent distribution patterns of oxygen vacancies is given for a 2 × 2 × 2 and a 3 × 3 × 2 superstructure model. Many other compounds have chain structures similar to mullite. These compounds are assigned to subgroups, all derived from a hypothetical tetragonal aristotype structure.
Flame Aerosol Synthesis
In article number 2211104, Lutz Mädler and co‐workers report a novel thermochemical process control with coordinated precursor design, which enables the establishment of a ...reactive spray process that produces binary metal sulfides with high surface area and crystallinity in the gas phase. Thus a breakthrough technology capable of producing multimetal sulfides (ternary, quaternary) is provided, which will play a key role in the field of non‐oxide materials.
The development and industrial application of advanced lithium based energy-storage materials are directly related to the innovative production techniques and the usage of inexpensive precursor ...materials. Flame spray pyrolysis (FSP) is a promising technique that overcomes the challenges in the production processes such as scalability, process control, material versatility, and cost. In the present study, phase pure anode material Li4Ti5O12 (LTO) was designed using FSP via extensive systematic screening of lithium and titanium precursors dissolved in five different organic solvents. The effect of precursor and solvent parameters such as chemical reactivity, boiling point, and combustion enthalpy on the particle formation either via gas-to-particle (evaporation/nucleation/growth) or via droplet-to-particle (precipitation/incomplete evaporation) is discussed. The presence of carboxylic acid in the precursor solution resulted in pure (>95 mass %) and homogeneous LTO nanoparticles of size 4–9 nm, attributed to two reasons: (1) stabilization of water sensitive metal alkoxides precursor and (2) formation of volatile carboxylates from lithium nitrate evidenced by attenuated total reflection Fourier transform infrared spectroscopy and single droplet combustion experiments. In contrast, the absence of carboxylic acids resulted in larger inhomogeneous crystalline titanium dioxide (TiO2) particles with significant reduction of LTO content as low as ∼34 mass %. In-depth particle characterization was performed using X-ray diffraction with Rietveld refinement, thermogravimetric analysis coupled with differential scanning calorimetry and mass spectrometry, gas adsorption, and vibrational spectroscopy. High-resolution transmission electron microscopy of the LTO product revealed excellent quality of the particles obtained at high temperature. In addition, high rate capability and efficient charge reversibility of LTO nanoparticles demonstrate the vast potential of inexpensive gas-phase synthesis for energy-storage materials.
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