Energy Consumption During Nanoparticle Production: How Economic is Dry Synthesis?

The production of oxide nanoparticles by selected wet-chemistry or dry processes is compared in terms of energy requirements. Clear differences arise for production using electricity-intensive plasma processes, organic- or chloride-derived flame synthesis and liquid based precipitation processes. In spite of short process chains and elegant reactor design, many dry methods inherently require vastly bigger energy consumption than the multi-step wet processes. Product composition strongly influences the selection of the preferred method of manufacturing in terms of energy requirement: Metal oxide nanoparticles of light elements with high valency, e.g. titania demand high volumes of organic precursors and traditional processes excel in terms of efficiency. Products with heavier elements, more complex composition and preferably lower valency such as doped ceria, zirconia, and most mixed oxide ceramics may be readily manufactured by recently developed dry processes.     

Flame spray synthesis under a non-oxidizing atmosphere: Preparation of metallic bismuth nanoparticles and nanocrystalline bulk bismuth metal

Metallic bismuth nanoparticles of over 98% purity were prepared by a modified flame spray synthesis method in an inert atmosphere by oxygen-deficient combustion of a bismuth-carboxylate based precursor. The samples were characterized by X-ray diffraction, thermal analysis and scanning electron microscopy confirming the formation of pure, crystalline metallic bismuth nanoparticles. Compression of the as-prepared powder resulted in highly dense, nanocrystalline pills with strong electrical conductivity and bright metallic gloss.     

Preparation of nano-gypsum from anhydrite nanoparticles: Strongly increased Vickers hardness and formation of calcium sulfate nano-needles

The preparation of calcium sulfate by flame synthesis resulted in the continuous production of anhydrite nanoparticles of 20–50 nm size. After compaction and hardening by the addition of water, the anhydrite nanoparticles reacted to nano-gypsum which was confirmed by X-ray diffraction, diffuse reflectance IR spectroscopy and thermal analysis. Mechanical properties were investigated in terms of Vickers hardness and revealed an up to three times higher hardness of nano-gypsum if compared to conventional micron-sized construction material. The improved mechanical properties of nano-gypsum could in part be due to the presence of calcium sulfate nano-needles in the nano-gypsum as showed by electron microscopy.     

Fluorescence reagents. I. Derivatization of carboxylic acids,imides and alcohols with 1-chloromethylbenz[c,d]indol-2(1H)-one (CMBI)

The derivatization and fluorodensitometric determination of carboxylic acids (CA), imides and alcohols with 1-chloromethylbenz[c,d]indol-2(1H)-one ( 19 , CMBI) have been studied. Out of a series of fluorescent fused lactams 9-11, 13-15 and 17 , benzindolone 17 was selected and transformed via hydroxymethylbenzin-dolone 18 into CMBI 19. CMBI reacts with CA, diCA and alcohols respectively to yield strongly fluorescent benz[c,d]indol-1-ylmethyl esters 20, 21 (BIM esters) and BIM ethers 22. Phenobarbital is transformed by action of CMBI into fluorescent 1,3-bisBIM phenobarbital 25. Studies on the applicability of the derivatization reactions to the fluorodensitometric determination of CA, alcohols and imides showed that CA with more than 3 carbon atoms can be determined via BIM esters down to the low picomole range. In the case of alcohols and imides the results were not satisfying. The ir, uv, fluorescence, nmr and mass spectra of the prepared benzindole derivatives are also presented.     

Glass and bioglass nanopowders by flame synthesis

The preparation of amorphous nanopowders by flame synthesis opens access to common soda-lime, metal-doped glasses or bioglasses in the range of 20-80 nm and offers an alternative to conventional wet-phase preparation, solid state reactions or melting.