Polymer-derived ceramic thin film thermocouple and preparation method thereof

A method for preparing a polymer-derived ceramic thin film thermocouple configured for monitoring a surface temperature of a hot component;

• wherein the polymer-derived ceramic thin film thermocouple comprises an A electrode (31) and a B electrode (32);
• wherein one end of the A electrode (31) and one end of the B electrode (32) intersect and overlap to form hot junctions (33), wherein an other end of the A electrode (31) away from the hot junctions (33) and an other end of the B electrode (32) away from the hot junctions (33) are provided with solder joints (34);
• wherein the A electrode (31) is prepared by mixing a polysilazane solution, nanocomposite powder and a xylene solution;
• the B electrode (32) is prepared by mixing a polysilazane solution, indium oxide nanopowder, and a xylene solution;
• and
• wherein the nanocomposite powder is prepared by mixing indium oxide nanopowder, zinc oxide powder and anhydrous ethanol;
• wherein each solder joint (34) is connected to a lead wire (35) and the lead wire (35) is configured for outputting a signal;
• wherein the method comprises:
• S1, pretreatment:
• cleaning and drying alumina ceramic sheets;
• S2, preparation of the nanocomposite powder:
• mixing the indium oxide nanopowder and the zinc oxide powder according to a first preset mass ratio k1 to obtain a mixed powder, mixing the mixed powder and the anhydrous ethanol according to a second preset mass ratio k2 to obtain a mixture and placing the mixture in a ball milling tank of a ball mill;
• controlling the ball mill to grind, and drying the mixture to obtain the nanocomposite powder;
• wherein a rotational speed of the ball mill during grinding is a preset rotational speed n, and a grinding duration is a first preset duration t1;
• and a temperature at a time of drying is a first preset temperature T1;
• wherein the k1, k2, n, t1 and T1 satisfy:
• 3≤k1≤5, 0.1≤k2≤1, 1600 rpm≤n≤2400 rpm, 4 h≤t1≤6 h, 80° C.≤T1≤120° C.;
• S3, preparation of an A mixed slurry and a B mixed slurry, comprising:
• mixing the polysilazane solution, the nanocomposite powder and the xylene solution according to a third preset mass ratio k3 to obtain the A mixed slurry;
• mixing the polysilazane solution, the indium oxide nanopowder and the xylene solution according to a fourth preset mass ratio k4 to obtain the B mixed slurry;
• wherein the k3 and k4 satisfy:
• 1:1:3≤k3≤1:1:1, 1:1:3≤k4≤1:1:1;
• S4, preparation of a polymer-derived ceramic A slurry and a polymer-derived ceramic B slurry, comprising:
• magnetically stirring the A mixed slurry at a room temperature to obtain the polymer-derived ceramic A slurry;
• magnetically stirring the B mixed slurry at the room temperature to obtain the polymer-derived ceramic B slurry;
• S5, preparation of the A electrode (31) and the B electrode (32) comprising:
• directly writing the polymer-derived ceramic A slurry on the alumina ceramic sheets and directly writing the polymer-derived ceramic B slurry on the alumina ceramic sheets by adopting a Weissenberg direct writing process;
• then, placing the alumina ceramic sheets directly written with the polymer-derived ceramic A slurry and the polymer-derived ceramic B slurry in a vacuum drying oven for heating and curing treatment, and then placing the alumina ceramic sheets directly written with the polymer-derived ceramic A slurry and the polymer-derived ceramic B slurry in a vacuum tube furnace for sintering to obtain the A electrode (31) and the B electrode (32);
• wherein, in S5, the placing the alumina ceramic sheets directly written with the polymer-derived ceramic A slurry and the polymer-derived ceramic B slurry in the vacuum tube furnace for sintering comprises:
• firstly, raising a temperature to a third preset temperature T3 at a preset heating rate 11, and maintaining the temperature for a third preset duration t3, wherein, in this process, the polymer-derived ceramic A slurry and the polymer-derived ceramic B slurry undergo organic to inorganic transformation, and amorphous ceramic is generated;
• secondly, raising the temperature to a fourth preset temperature T4 at the preset heating rate v1, and maintaining the temperature for a fourth preset duration t4, wherein, in this process, the amorphous ceramic undergoes phase separation and crystallization to generate a polycrystalline ceramic;
• and
• finally, cooling the temperature to room temperature at a preset cooling rate 12;
• wherein v1 and v2 satisfy:
• 3° C./min≤v1≤7° C./min, 3° C./min≤v2≤7° C./min;
• the T3 and t3 satisfy:
• 900° C.≤T3≤1100° C., 3 h≤t3≤5 h;
• the T4 and t4 satisfy:
• 1400° C.≤T4≤1800° C.;
• 3 h≤t4≤5 h;
• S6, preparation of the solder joints (34) comprising:
• mixing titanium diboride nanopowder and polysilazane solution according to a fifth preset mass ratio k5 to obtain a conductive slurry, applying the conductive slurry on the alumina ceramic sheets and sintering to obtain the solder joints (34);
• electrically connecting the solder joints (34) and lead wires (35) and placing them in the vacuum tube furnace for sintering;
• wherein the k5 satisfies:
• 1:3≤k5≤1:1;
• and
• S7, preparation of a protective layer precursor layer:
• mixing the titanium diboride nanopowder and yttriastabilized zirconia (YSZ) nanopowder according to a sixth preset mass ratio k6, incorporating into the polysilazane solution, and placing into the vacuum drying oven for heating and curing treatment, and then obtaining a protective layer precursor;
• wherein a temperature at a time of the heat and curing treatment is a seventh preset temperature T7, and a duration for the heat and curing treatment is a seventh preset duration t7;
• masking the alumina ceramic sheets directly written with the A electrode (31) and the B electrode (32), taking the protective layer precursor as a target material, depositing the protective layer precursor on a top surface of the A electrode (31) and a top surface of the B electrode (32) by pulsed laser, and then vacuum pyrolyzing to obtain the protective layer precursor layer;
• and, during vacuum pyrolysis, raising the temperature to an eighth preset temperature T8 at the preset heating rate v1 and maintaining the temperature for an eighth preset duration t8;
• wherein the k6 satisfies:
• 3:1≤k6≤5:1;
• the Ty and t satisfy:
• 100° C.≤T1≤300° C., 0.4 h≤t7≤0.6 h;
• the v1 satisfies:
• 3° C./min≤v1≤7° C./min;
• T8 and t8 satisfy:
• 1400° C.≤T8≤1800° C., 3 h≤t8≤5 h.