Structural and spectroscopic characteristics of synthetic hydrohaematite

In order to investigate the identity of water-containing haematite, a method of preparation has been elaborated which leads to samples of hydrohaematite which are structurally pure and free of amorphous iron hydroxide. Differential thermal analysis by a lack of endothermic effect at 423 to 473 K on the DTA-curves and by a steady fall of the TG curves up to 1150 K revealed that water in the preparations must be tightly held in the lattice of haematite. Measurements of intensities of X-ray reflections of the (1 0 4) and (0 2 4) planes in relation to the (1 1 3) plane confirmed Fe³⁺-deficiency in the haematite cationic sublattice brought about by the presence of OH^– ions in the anionic sublattice. The infrared spectrum of hydrohaematite, in addition to six bands from Fe-O variations, exhibits three bands from hydroxyl groups. The effect of silicates on the pattern of the infrared spectra of natural and synthetic hydrohaematites and the discrepancies in the infrared spectra of haematites published to date are discussed.     

A low noise, high resolution silicon temperature sensor

High resolution temperature measurement is essential for determination of blood perfusion in biomaterials. A compact, low noise, high resolution temperature sensor designed for use in an invasive tissue property measurement probe is presented. The circuit is based on traditional proportional-to-absolute-temperature (PTAT) principles. A feedback technique is used to improve linearity and reduce noise. Data from test chips shows temperature resolution of 3 m°C. The chips were fabricated using a 1.75 μm double poly, single metal modified CMOS process designed for this project