Special electric furnaces
Published: 17 December, 2014
Two specially designed CARBOLITE electric furnaces integrated with a pair of hydraulic presses are reported to be providing sophisticated thermal processing facilities for Infrared Integrated Systems Ltd (Irisys), a specialist in people counting and queue management systems based in Northampton.
Irisys systems are used by many of the world’s leading retailers, banks, transport hubs and leisure facilities to improve customer service, operational efficiency and profitability. Some 80 % of its products are exported, and in 2011 the company was awarded The Queen’s Award for Enterprise. At the heart of the Irisys systems are small wafers of specially formulated lead zirconate titanate (PZT), a pyro-electric ceramic that develops a voltage difference across two of its faces when it experiences a temperature change. As a result, when bonded to a read-out circuit, it can be used as a sensor to identify and count people.
PZT is produced initially in powder form and then subjected by Irisys to a two-stage process to densify and compress it so that it will provide the required performance. The first stage involves cold-pressing the powder and then sintering in one of six Carbolite chamber furnaces at the site at temperatures above 1000 ºC for several hours to form discs 50mm or 75mm diameter.
After cooling, the discs are pressed at up to 40 tonne in conjunction with precisely controlled temperatures in the Carbolite furnaces. This involves using the inbuilt process controller to ramp the furnace temperature between ambient and up to 1200ºC, dwell for a number of hours, followed by a controlled cool to ambient.
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