Preparation And Research Of Positive Temperature Coefficient Thermosensitive Materials

With the development of temperature control technology,the temperature requirement of electronic equipment is getting higher and higher.When the electronic instrument was in extremely low temperature environment,it is necessary to take timely heat treatment to make it stable in the normal working temperature range.The self-adaptive temperature control of electronic instruments can be realized by using the thermosensitive material with positive temperature coefficient effect?PTC?as the heater.When the temperature of the electronic instrument was lower than operating temperature,the PTC heater worked to restore the electronic instrument to the working temperature;When the temperature of electronic instrument exceeded working temperature,the resistance of the PTC heater would increase with the temperature of the electronic instrument,resulting in the decrease of heating power,and the electronic instrument would gradually stabilize to the working temperature.thus realizing automatic adjustment of temperature.The most suitable working temperature of electronic equipment is usually 0⁶0 degrees Celsius.However,Curie temperature of most PTC materials is far higher than 100 degrees Celsius,which doesn't meet the requirements of temperature control of electronic equipment.Aiming at decreasing Curie temperature point,reducing resistivity and increasing lift-drag ratio,Barium Titanate-based PTC ceramics and polymer PTC materials were prepared and characterized respectively.PTC materials with Curie temperature point between 0and 60 degrees Celsius were prepared.And using prepared samples conducted preliminary temperature control test.?1?Barium Titanate-based PTC ceramics were prepared by solid phase method.According to the doping modification mechanism,PTC materials with Curie temperature between 0 and 60 degrees Celsius were prepared.The sintering process of ceramics was discussed,and the preparation process of barium Titanate-based PTC ceramics with the best Resistance-Temperature was obtained.The results showed that the Curie temperature of barium Titanate-based PTC ceramics was 60 degrees Celsius and the PTC effect achieved the best when the sintering temperature was 1300degrees Celsius,the holding time was 4 hours,the doping ratio of elements were Nb₂O₅ 0.2 mole percent,Ce₂O₃ 0.3 mole percent and Mn?NO₃?₂ 0.08 mole percent.?2?Graphite powder/Carbon black as conductive particle and Paraffin/Polyethylene matrix composite polymer PTC materials were prepared by melt mixing method.The optimum doping concentration was obtained by adding different content of graphite powder and carbon black.The results showed that the Curie temperature of sample was 26 degrees Celsius,and the PTC performance achieved the best,when the content of graphite powder was 16.67 mass fraction percent and carbon black was 10 mass fraction percent.?3?Barium Titanate-based PTC ceramics and paraffin/polyethylene composite polymer PTC ceramics were used as heating sources respectively to test the temperature control of metal blocks of analog electronic equipment.Preliminary studies suggested that PTC thermosensitive material can adjust heating power according to its positive temperature coefficient characteristics,so as to achieving the purpose of self-adaptive temperature control.