A versatile chemical vapor synthesis reactor for in situ x-ray scattering and spectroscopy.

We describe a versatile reactor system for chemical vapor synthesis of nanoparticles, which enables in situ investigations of high temperature gas phase particle formation and transformation processes by x-ray scattering and x-ray absorption spectroscopy. The system employs an inductively heated hot wall reactor as the energy source to start nanoparticle formation from a mixture of precursor vapor and oxygen. By use of a modular set of susceptor segments, it is especially possible to change solely the residence time of the gas mixture while keeping all other process parameters (temperature, gas flow, pressure) constant.

Formation of polymorphs and pores in small nanocrystalline iron oxide particles.

A novel chemical vapor synthesis reactor design is used to control the pore-particle mesostructure and investigate the pore formation mechanism through the variation of residence time in oxygen. This enables the exploitation of the Kirkendall effect at the nanoscale to generate ultrasmall pores in small nanocrystalline iron oxide particles. Detailed structural characterization and quantitative data analysis of complementary high resolution transmission electron microscopy images, X-ray diffractograms, nitrogen sorption isotherms and X-ray absorption spectra provide a consistent comprehensive picture of the hollow nanoparticles from the local to the microstructure.

In situ cell for x-ray absorption spectroscopy of low volatility compound vapors.

Technologically relevant gas phase processes rely on reactants in vapor form for the production of thin films and nanoparticles. An instrument is described which enables the investigation of such vapors by x-ray absorption spectroscopy. Corresponding in situ studies provide information about gas phase precursor chemistry and optimized synthesis processes.

Laser synthesis, structure and chemical properties of colloidal nickel-molybdenum nanoparticles for the substitution of noble metals in heterogeneous catalysis.

Platinum and iridium are rare and expensive noble metals that are used as catalysts for different sectors including in heterogeneous chemical automotive emission catalysis and electrochemical energy conversion. Nickel and its alloys are promising materials to substitute noble metals. Nickel based materials are cost-effective with good availability and show comparable catalytic performances.