Focused radiation heating for controlled high temperature chemistry, exemplified with the preparation of vanadium nitride nanoparticles

Abstract

A compact apparatus employing heating with concentrated light was designed for desktop laboratory application to run syntheses in the range 200–850 °C in short times under a satisfying control of the temperature, heating ramps, and adjustable chemical environments. The device is composed of 4 halogen lamps oriented to a centre point and allows fast heating rates up to 100 K min−1 of medium size scale samples (volume < 7 mL). This method can be proven to be more energetically efficient and allows for better temperature control over standard furnace methods. Herein we exemplify with a typical high temperature synthesis of non-oxide ceramic (vanadium nitride) nanoparticles. These nanoparticles can be obtained in different sizes and crystallinity ranges by varying the reaction conditions, following the urea glass route and applying the non-classical rapid heating method. Nanoparticles containing both carbon and nitrogen and showing the typical crystal structure of VN were obtained with sizes below 10 nm within a short reaction time (5 min at 750 °C) and in a fast heating procedure (50 K min−1). Moreover, quasi-quenching of samples through a fast cooling procedure allows the detection of various intermediate oxide species that otherwise were not observed.