In situ deposition of iron nanoparticles on transmission electron microscopy grid in furnace aerosol reactor
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In the current work, a device was proposed for the first time to deposit the particles in situ on a transmission electron micrography grid within furnace aerosol reactors. The device was successfully tested on iron particles produced by thermal decomposition of Fe(CO)5 at 600 °C in a quartz tube heated by an electric heater. The particle depositions were made at four different spatial locations in the axial direction and investigated by transmission electron microscopy. At the reactor inlet, chain agglomerates of 2–3-nm particles were observed. At 19 cm from the inlet, the particles within the agglomerate structures fully coalesced by sintering, and at 32 cm (reactor outlet), polyhedral particles of about 100 nm in diameter emerged from the sintered body.
Numerous studies have been made for vapor-phase synthesis of nanoparticles of metals and ceramics using furnace aerosol reactors or tubular reactors heated by electric heaters.1–3 The precursor is fed to the reactor in vapor and converted by chemical reaction to condensable product molecules. These molecules self-nucleate to form nuclei or smallest particles. As they travel suspended in the carrier gas toward the outlet, the particles grow by coalescence or form fractal-like agglomerates. Neck formation and coalescence may occur for particles within the agglomerate structures. Transmission electron microscopy (TEM) has widely been used for the measurement of particle shape, size, and distribution, although potential biases introduced in representing the whole spectrum of particles is a problem. Previously, the particles were deposited on TEM grids after they had left the reactor, and no information was obtainable on the history of particle formation and growth inside the reactor. In the current work, a device was proposed for the first time to deposit the particles in situ on a TEM grid within the reactor as shown in Fig. 1. The device is composed of a protection tube and a TEM grid holding tube. The protection tube is of stainless steel, 16 mm in outside diameter, 1.2 mm in thickness, and 97 cm in length. A 16-mm disk with a 9-mm hole is welded on the front end of the tube. The hole is closed with a blind film that will be destroyed later to have the TEM grid exposed to the particle-laden gas; this by fixing the film on the disk
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e-mail: [email protected] J. Mater. Res., Vol. 18, No. 10, Oct 2003
http://journals.cambridge.org
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with four small bolts. The protection tube is closed at the rear end but for the TEM grid-holding tube. A nitrogen purge line is connected to the tube near the rear end. The grid-holding tube is 9.6 mm in outside diameter and 110 cm in length and is tapered toward the front end at which it is closed with a disk 7.5 mm in diameter. A shallow well 5 mm in diameter and 1 mm in depth is formed in the disk. A TEM grid 3 mm in diameter is mounted on the bottom of the well and fixed by forcing a flat ring into the well to push the grid frame against the disk. A knife with two legs is welded on the ring. A photograp
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