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UNITHERM™ MODEL 1161V HIGH TEMPERATURE VERTICAL DILATOMETER

A high temperature furnace is constructed of low ther- mal mass insulation surrounding molybdenum disilicide heating elements. Four hairpin shaped elements act as eight linear heat sources equally spaced around the muffle tube (parallel to its axis). Length-to-diameter ra- tios are chosen to ensure excellent hot zone uniformity. The digital displacement transducer used in the system is an absolute device with no periodic calibration re- quirements. It is free of short term drift and long term changes, as its accuracy is based on a very stable in-ternal glass grating whose movement is optically moni- tored. The vertical configuration of this instrument makes it es-pecially suitable for testing ceramic materials where shrinkage often outweighs expansion. In a horizontal sample holder, shrinkage of a sample can cause it to pull away from the end plug, resulting in erroneous data. Vertical configurations are not subject to this problem. Pushrod tracking forces are governed by vari- able dead weight counter-balancing, and can be re- duced to very low values. Optionally, specific pushrod loading can also be applied through additional weights on a pan to operate it as a Thermo-Mechanical Ana-lyzer (TMA). Optional program modules allow softening point determination and controlled rate sintering cycles. The dilatometer head slides vertically on guide rods to extract the sample holder (dilatometer tube) from the furnace cavity. The smoothly functioning, head-lifting mechanism is counter-balanced with constant force springs. When inserted, sliding hermetic seals engage the muffle tube collar to provide a protective environ- ment for the specimen. Critical components, such as the ends of the muffle tube and the seals engaging it, along with the base of the dilatometer head, are water cooled. The standard alumina dilatometer tube and pushrod are readily interchangeable with a fused silica assembly. System correction for the tube is automatically made in software. The device automatically limits maximum fur- nace temperature when the fused silica tube is in place. A graphite system is also available, however tempera-ture is limited to 1400 Ambient to 1650
C Single or dual sample Research quality Absolute or differential Vertical model for sintering studies Vacuum, inert and hydrogen atmospheres Unitherm
TM Model 1161V is a fully computerized dila-tometer system designed to measure dimensional changes of a specimen brought about by changes in its thermal environment. Linear thermal expansion coefficient, shrinkage attendant to sintering, phase transformations, annealing characteristics, and other physical or chemical changes manifesting themselves in a change of a linear dimension can be precisely de- termined. Studies of processing parameters as re-flected by dimensional changes of the material can be studied in great detail through duplication of thermal cycles and rates used in the actual process. Due to the extensive programming available to produce ther- mal cycles, complex processes can easily be simu- lated.
C to prevent interaction with Type S thermocouple.
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