In situ FTIR investigation on phase transformations in BN nanoparticles

Fourier transformation infrared spectrum (FTIR) was employed to investigate phase transformation of nanoparticle BN, containing eBN, rBN, wBN and cBN, in which eBN and rBN are the main components. We found that part of eBN was converted into rBN at 200―350℃. At and above 400℃, eBN transformed into wBN, and some of wBN were converted into cBN simultaneously. This conclusion is supported by the results from high- resolution transmission electron microscopic (HRTEM) and Raman spectroscopic measurements. In this work, the converting processes be- tween different BN phases were continuously monitored by in situ FTIR spectroscopy. The results will be helpful for synthesis of cBN at moderate conditions.

Investigation on the key factors in the hydrothermal synthesis of BN: The way of introducing sodium azide

The way of introducing sodium azide (NaN_3) into the reaction solution played an important role in the preparation of cBN by hydrothermal synthesis method. The results showed that both cBN content and crystalline perfection of the samples improved with increasing R_N value, and pure cBN could be obtained at 300℃ and 10 MPa when R_N increased to 3:1. Here R_N is defined as R_N =NaN_3(I)/NaN_3(II), wherNaN_3(I) denotes the amount of NaN_3 (in molar) that is added into the autoclave at the beginning of threaction process, and NaN_3(II) is the amount of NaN_3 (also in molar) introduced into the autoclave ahigh temperature and high pressure (i.e. 300℃ and 10 MPa). In order to explain the experimental results, a preliminary model was proposed in this paper.

Pressure-sensitive Transistor Fabricated from an Organic Semiconductor 1,1＇-Dibutyl-4,4＇-bipyridinium Diiodide

Although organic semiconductors have attracted extensive interest and been utilized to fabricate a variety of optoelectronic devices, their electrical transportation characteristics under high pressure have rarely been investigated. However, the weak intermolecular interaction of organic semiconductors endows them with a pressure-sensitive crystal structure and electrical transportation performance, especially the latter. Herein, a new pressure-sensitive transistor was fabricated from an organic semiconductor 1,1＇-dibutyl-4,4＇-bipyridinium diiodide. It was found that this transistor exhibited increasing resistance as the pressure gradually increased and that it eventually shut off under a pressure of 288 MPa. Such a characteristic makes this organic semiconductor a potential candidate for the use in the fabrication of pressure-sensitive switches and regulators. In addition, these results shed light on the electrical performance of flexible organic optoelectronic devices working under high pressure levels resulted from the bending force.