A new method of preparation of nanocrystalline zinc aluminate (ZnAl2O4) powder is described in this paper. Different organic acids are used as template material and nitric acid as an oxidant. Single phase ZnAl2O4 spinel can be formed at a much lower temperature through this route which gives nanocrystalline powder with uniform particle size and morphology. The powders are characterized by thermo gravimetric analysis (TGA), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area analysis and field emission scanning electron microscopy (FE-SEM). The average crystallite size of the single phase material was of 20 to 30 nm and the surface area was found to be 21 to 27 m2g−1.
S. Sadana, S. Yadav, N. Jha, V. Gupta, R. Agarwal, A. Bandyopadhyay and T. Saxena
A Computer Controlled Precision High Pressure Measuring System
A microcontroller (AT89C51) based electronics has been designed and developed for high precision calibrator based on Digiquartz pressure transducer (DQPT) for the measurement of high hydrostatic pressure up to 275 MPa. The input signal from DQPT is converted into a square wave form and multiplied through frequency multiplier circuit over 10 times to input frequency. This input frequency is multiplied by a factor of ten using phased lock loop. Octal buffer is used to store the calculated frequency, which in turn is fed to microcontroller AT89C51 interfaced with a liquid crystal display for the display of frequency as well as corresponding pressure in user friendly units. The electronics developed is interfaced with a computer using RS232 for automatic data acquisition, computation and storage. The data is acquired by programming in Visual Basic 6.0. This system is interfaced with the PC to make it a computer controlled system. The system is capable of measuring the frequency up to 4 MHz with a resolution of 0.01 Hz and the pressure up to 275 MPa with a resolution of 0.001 MPa within measurement uncertainty of 0.025%. The details on the hardware of the pressure measuring system, associated electronics, software and calibration are discussed in this paper.