Development of a portable time-of-flight mass spectrometer prototype using a cold electron source.

Fundamental obstacles toward the development of a portable time-of-flight mass spectrometer (TOF MS) are ionization sources and vacuum systems. To overcome these, a cold electron source (CES) and a pulse valve are introduced in this study to examine the possibility of developing a portable TOF MS. The CES is developed using a microchannel plate electron multiplier radiated by ultraviolet photons from a light-emitting diode. The CES is controlled using short pulses to generate accelerated electrons that ionize a substrate surface. A 10 ns CES pulse produces an electron flux density of 1013 to 1014 m-2 on the surface, and the short pulse minimizes the ionization time such that the resolution limit associated with a short drift tube is overcome. In addition, the injected 0.05 m3 quantitative sample reduces the vacuum exhaust load, and simultaneously, it is possible to temporarily form layers of the target molecules on the substrate. The possibility of immediate measurement by directly injecting benzene at ambient pressure was verified through repeated measurements; therefore, it is technically possible to use a CES to allow for a highly compact (and portable) TOF MS.

Synthesis and Hydrogen Desorption Properties of Aluminum Hydrides.

Aluminum hydride (AlH3 or alane) is known to store maximum 10.1 wt.% of hydrogen at relatively low temperature (< 100 degrees C), which partially fulfills the U.S. department of energy requirements for gravimetric loading capacity. However, its detailed mechanisms of appearing of different phases, structural stability, and dynamics of hydrogen desorption are still not clear. To understand the desorption properties of hydrogen in alane, thermodynamically stable α-AlH3 was synthesized by employing an ethereal reaction method. The dependence of pathways on phase formation and the properties of hydrogen evolution were investigated, and the results were compared with the ones for γ-AlH3. It was found that γ-AlH3 requires 10 degrees C higher than that of γ-AlH3 to form, and its decomposition rate demonstrated enhanced endothermic stabilities. For desorption, all hydrogen atoms of alane evolved under an isothermal condition at 138 degrees C in less than 1 hour, and the sample completely transformed to pure aluminum. Our results show that the total amount of desorbed hydrogen from α-AlH3 exceeded 9.05 wt.%, with a possibility of further increase. Easy synthesis, thermal stability, and a large amount of hydrogen desorption of alane fulfill the requirements for light-weight hydrogen storage materials once the pathway of hydrogen cycling is provided.

High Purity and Yield of Boron Nitride Nanotubes Using Amorphous Boron and a Nozzle-Type Reactor.

Enhancement of the production yield of boron nitride nanotubes (BNNTs) with high purity was achieved using an amorphous boron-based precursor and a nozzle-type reactor. Use of a mixture of amorphous boron and Fe decreases the milling time for the preparation of the precursor for BNNTs synthesis, as well as the Fe impurity contained in the B/Fe interdiffused precursor nanoparticles by using a simple purification process. We also explored a nozzle-type reactor that increased the production yield of BNNTs compared to a conventional flow-through reactor. By using a nozzle-type reactor with amorphous boron-based precursor, the weight of the BNNTs sample after annealing was increased as much as 2.5-times with much less impurities compared to the case for the flow-through reactor with the crystalline boron-based precursor. Under the same experimental conditions, the yield and quantity of BNNTs were estimated as much as ~70% and ~1.15 g/batch for the former, while they are ~54% and 0.78 g/batch for the latter.