On-Line Monitoring of Sintering Process using Ultrasounds

为了对陶瓷烧结过程进行超声在线监测，研制了可在1273K高温环境下提供脉冲回波测量的高性能超声传感器和实时数据采集系统。进行了可行性研究和几项基础性实验，并利用研制的传感器和采集系统对723K下的氧化铝烧结过程进行了监测。研究结果表明：(1)高密度细晶氧化铝具有良好的导波性能，可作为高温超声传感器的缓冲棒材料。由锥形缓冲棒和水冷却系统组成的超声传感器在1123K下也能很好地工作。(2)在723K的等离子烧结机上，利用研制的传感器和采集系统对氧化铝粉末的烧结过程进行了实验验证，测得炭模中氧化铝粉末的超声信号具有较低的S/N比。因此，所开发的超声缓冲棒技术在粉末烧结过程的在线监测中是一种有前途的候选技术，实际应用还需要进一步的研究。

High performance ultrasonic sensors that provide pulse echo measurements in a high temperature environment up to 1273 K and a real-time data acquisition system have been developed in order to make ultrasonic on-line monitoring for ceramic sintering processes. Feasibility study and several fundamental experiments have been carried out and an attempt to monitor an alumina sintering process at 723 K has been made using the developed sensors with the acquisition system. The obtained results are the following:(1) A high density alumina with fine grains has been chosen as a buffer rod material used for high temperature ultrasonic sensors, because of its superior wave guidance ability. It has been shown that the developed ultrasonic sensor consisting of a tapered buffer rod and water cooling system works well even at 1123 K.(2) Laboratory validation of the use of the developed sensor and acquisition system for sintering monitoring of alumina powders has been demonstrated using a plasma sintering machine at 723 K. An ultrasonic signal with poor S/N ratio has been measured from alumina powders packed in a carbon die.It is therefore considered that the developed ultrasonic buffer rod technique is a promising candidate for on-line monitoring during powder sintering processes and further studies are needed for practical use.