Thick lanthanum zirconate buffer layers from water-based precursor solutions on Ni-5%W substrates

In this work, water-based precursor solutions suitable for dip-coating of thick La₂Zr₂O₇ (LZO) buffer layers for coated conductors on Ni-5%W substrates were developed. The solutions were prepared based on chelate chemistry using water as the main solvent. The effect of polymer addition on the maximum crack-free thickness of the deposited films was investigated. This novel solution preparation method revealed the possibility to grow single, crack-free layers with thicknesses ranging 100–280 nm with good crystallinity and an in-plane grain misalignment with average FWHM of 6.55°. TEM studies illustrated the presence of nanovoids, typical for CSD–LZO films annealed under Ar-5%H₂ gas flow. The appropriate buffer layer action of the film in preventing the Ni diffusion was studied using XPS. It was found that the Ni diffusion was restricted to the first 30 nm of a 140 nm thick film. The surface texture of the film was improved using a seed layer.     

Optimum sol viscosity for stable electrospinning of silica nanofibres

Silica nanofibres have, due to their excellent properties, promising characteristics for multiple applications such as filtration, composites, catalysis, etc. Silica nanofibres can be obtained by combining electrospinning and the sol–gel process. To produce silica nanofibres most of the time organic solutions are applied containing a carrying polymer, which is afterwards removed by a thermal treatment to form pure ceramic nanofibres. Although electrospinning of the pure silica precursors without carrying polymer is preferred, the parameters influencing the stability of the electrospinning process are however largely unknown. In addition, this knowledge is essential for potential upscaling of the process. In this study, the optimum viscosity to electrospin in a stable manner is determined and the way to obtain this viscosity is evaluated. Sols with a viscosity between 120 and 200 mPa.s could be electrospun in a stable way, resulting in uniform and beadless nanofibres. Furthermore, this viscosity region corresponded with nanofibres having the lowest mean nanofibre diameters. Electrospinning with diluted sols was possible as well, but electrospinning of the fresh sols was more stable. These results illustrate the importance of the viscosity and degree of crosslinking of the sol for the stable electrospinning of silica nanofibres and demonstrate that upscaling of the electrospinning process of silica nanofibres is feasible.     

Determination of the electron temperature of a shocktunnel-produced Ar-Cs plasma by the line reversal method using non-resonance lines of Cs

It is shown that the influence of the temperature boundary layer on the measured population temperature of Cs, of a shocktunnel-produced, low-temperature Ar-Cs plasma, can be neglected in measurements where the line reversal method is used with non-resonance lines of Cs.Owing to Ar-Cs collisions and radiation losses, a decrease in population density of the levels concerned in the transition occurs. This decrease is calculated in comparison with LTE and results in a population temperature of Cs which is less than 8 per cent lower than the electron temperature.Because of a test time of 5 msec in our shocktunnel experiment, use is made of a chopper to measure the radiation intensity of the plasma and the radiation intensity of the reference source in interaction with the plasma alternately. From these two radiation intensities and the radiation intensity of the reference source, we calculate the population temperature of Cs and the ratio of the concentration of Cs-atoms and the concentration of Ar-atoms, which is called the seed ratio. Comparison of the measured population temperature and the calculated electron temperature at a gas temperature and pressure of 2000 K and 5 atm, respectively, shows agreement within 10 per cent.     

Ammonothermal Synthesis,Crystal Structure,and Vibrational Properties of the Doubly Deprotonated Calcium Guanidinate,CaC(NH)3

We report the synthesis of the doubly deprotonated calcium guanidinate, CaC(NH)₃, from liquid ammonia and its crystal structure as determined from powder X-ray and neutron diffraction, and confirmed using CNH elemental analysis and infrared (IR) spectroscopy data. CaC(NH)₃ crystallizes in the hexagonal system with space group P6₃/m (no. 176) with Z = 2 and a = 5.2666(13) Å, c = 6.5881(6) Å and V = 158.25(4) ų. We also compare the structural similarities and differences of this phase with the isotypical strontium and ytterbium compounds.     

Analysis of the vibration correlation diagram of base · HCl(DCl) H-bonded complexes in Ar matrices: Type II and intermediate type I → II systems

The Fourier transform infrared spectra of the H-bonded complexes between HCl and 4-aminopyridine, 4-aminopyrimidine, 4-hydroxypyridine, 2-hydroxypyridine, benzimidazole and purine were investigated in Ar matrices. From the analysis of these spectra, the H-bonds N HCl appear to be of the pseudosymmetric type II for 4-aminopyridine, 4-aminopyrimidine and 4-hydroxypyridine, while benzimidazole forms a slightly weaker complex. H-bonding of HCl with the bases 2-hydroxypyridine and purine is of the intermediate type I → II. In the case of 4-aminopyrimidine, additional bonding of the Cl atom of HCl to an amino N---H bond yields a closed complex which explains the type II behaviour. In all other cases, bonding of additional HCl molecules to the 1:1 complexes results in proton transfer towards N---H⁺…Cl⁻(HCl)_π species, but n is much lower for type II than for the intermediate type I → II complexes. The results allow us to investigate the vibration correlation diagram and the isotopic ratio ν(HCl)/ν(DCl) for B - HCl complexes in Ar matrices into more detail.