Co-current co-precipitation method of CoNiO.SUB.2 .thermistor powders

Abstract

The disclosure relates to a co-current co-precipitation method of CoNiO.sub.2 thermistor powders. The method comprises the steps of mixing, stirring, precipitating, aging, suction filtration, washing and drying firstly using nickel nitrate and cobalt nitrate as raw materials to obtain cobalt hydroxide, and then calcining in a tubular furnace at an inert atmosphere to prepare CoNiO.sub.2 nano powders. The method has the advantages of simple operation, low cost, short cycle, high yield and no environmental pollution, and further oxidization of the CoNiO.sub.2 nano material into NiCo.sub.2O.sub.4 thermistor powders can be effectively avoided through selection and adjustment of calcination process parameters and inert atmosphere. A high-precision, fast-response and small-volume temperature sensor material can be prepared from CoNiO.sub.2 thermistor powders obtained by the method of the disclosure.

Claims

1. A co-current co-precipitation method of CoNiO.sub.2 thermistor powders, comprising the following steps: a, mixing raw materials Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 in a mole ratio of 1:1, and dissolving the obtained mixture into deionized water, so as to prepare a 0.5-3 mol/L mixed solution A; b, weighing Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 in a mole ratio of 1:(1.2-2.0), then weighing sodium hydroxide, oxalic acid, sodium carbonate, ammonium bicarbonate or ammonium hydroxide, and adding deionized water to the weighed Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 in the mole ratio of 1:(1.2-2.0) and the weighed sodium hydroxide, oxalic acid, sodium carbonate, ammonium bicarbonate or ammonium hydroxide, so as to prepare a 0.5-3 mol/L solution B; c, weighing polyvinylpyrrolidone, polyethylene glycol 400, polyethylene glycol 600, cetyltrimethyl ammonium bromide or triton X-100, and dissolving the weighed polyvinylpyrrolidone, polyethylene glycol 400, polyethylene glycol 600, cetyltrimethyl ammonium bromide or triton X-100 into deionized water, so as to prepare a dispersant solution C having a mass fraction of 0.5-10%; d, respectively putting the solution A and the solution B prepared in step a and step b in a dropping funnel, simultaneously dropwise adding the solution A and the solution B into the solution C in step c at a speed of 0.5-2 drop/s, and magnetically stirring the solution C after dropwise adding the solution A and the solution B for 1-4 hours to form a precipitate; e, standing and aging the precipitate formed in step d for 24-72 hours, subsequently carrying out suction filtration of the precipitate, and washing of the precipitate to have a neutral pH; and f, putting the precipitate obtained in step e into a vacuum drying oven for drying, then putting the dried precipitate into a tubular furnace, introducing inert gas argon or nitrogen to form an inert atmosphere, raising the temperature of the tubular furnace to 200-250° C. at a heating rate of 0.5-2° C./min, calcining the dried precipitate in the tubular furnace under the inert atmosphere at a constant temperature and preserving for 30-60 min, then heating to 300-600° C., then calcining the heated preserved calcined dried precipitate at a constant temperature and preserving for 1-4 hours, cooling to room temperature at a cooling rate of 0.5-2° C./min, calcining the cooled preserved precipitate, and subsequently carrying out dry ball milling for 2 hours, so as to obtain the CoNiO.sub.2 thermistor powders.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an SEM characterization of CoNiO.sub.2 powders prepared in example 2 of the disclosure; and

(2) FIG. 2 is an XRD characterization of CoNiO.sub.2 powders prepared in example 2 of the disclosure.

DESCRIPTION OF THE EMBODIMENTS

Example 1

(3) a, raw materials Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were mixed in a mole ratio of 1:1, and dissolved into deionized water, so as to prepare 0.5 mol/L mixed solution A;

(4) b, Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were weighed in a mole ratio of 1:1.2, then sodium hydroxide was weighed, and deionized water was added, so as to prepare 0.5 mol/L solution B;

(5) c, polyvinylpyrrolidone powders was weighed as a dispersant and dissolved into deionized water, so as to prepare dispersant solution C having a mass fraction of 0.5%;

(6) d, the solution A and solution B prepared in step a and step b were respectively put in a dropping funnel, simultaneously dropwise added into the solution C in step c at the speed of 0.5 drop/s, and magnetically stirred for 1 hour to form a precipitate;

(7) e, the precipitate formed in step d was stood and aged for 24 h, then subjected to suction filtration, and washed to be neutral; and

(8) f, the precipitate obtained in step e was put into a vacuum drying oven for drying, then put into a tubular furnace, inert gas argon or nitrogen was introduced, the temperature of the tubular furnace was raised to 200° C. at the heating rate of 0.5° C./min, calcination was carried out at a constant temperature and preservation was performed for 30 min, then the temperature was raised to 300° C., then calcination was carried out at a constant temperature and preservation was performed for 1 h, the temperature was reduced to room temperature at the cooling rate of 0.5° C./min, calcinination was carried out, and subsequently dry ball milling was carried out for 2 h, so as to obtain the CoNiO.sub.2 thermistor powders. The whole calcination process was protected by inert gas from beginning to end.

Example 2

(9) a, raw materials Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were mixed in a mole ratio of 1:1, and dissolved into deionized water, so as to prepare 1 mol/L mixed solution A;

(10) b, Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were weighed in a mole ratio of 1:1.4, then oxalic acid was weighed, and deionized water was added, so as to prepare 1 mol/L solution B;

(11) c, polyethylene glycol 400 was weighed as a dispersant and dissolved into deionized water, so as to prepare dispersant solution C having a mass fraction of 2%;

(12) d, the solution A and solution B prepared in step a and step b were respectively put in a dropping funnel, simultaneously dropwise added into the solution C in step c at the speed of 1 drop/s, and magnetically stirred for 2 h to form a precipitate;

(13) e, the precipitate formed in step d was stood and aged for 36 h, then subjected to suction filtration, and washed to be neutral; and

(14) f, the precipitate obtained in step e was put into a vacuum drying oven for drying, then put into a tubular furnace, inert gas argon or nitrogen was introduced, the temperature of the tubular furnace was raised to 210° C. at the heating rate of 1° C./min, calcination was carried out at a constant temperature and preservation was performed for 40 min, then the temperature was raised to 400° C., then calcination was carried out at a constant temperature and preservation was performed for 2 h, the temperature was reduced to room temperature at the cooling rate of 1° C./min, calcinination was carried out, and subsequently dry ball milling was carried out for 2 h, so as to obtain the CoNiO.sub.2 thermistor powders. The whole calcination process was protected by inert gas from beginning to end.

Example 3

(15) a, raw materials Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were mixed in a mole ratio of 1:1, and dissolved into deionized water, so as to prepare 1.5 mol/L mixed solution A;

(16) b, Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were weighed in a mole ratio of 1:1.6, then sodium carbonate was weighed, and deionized water was added, so as to prepare 1.5 mol/L solution B;

(17) c, polyethylene glycol 600 was weighed as a dispersant and dissolved into deionized water, so as to prepare dispersant solution C having a mass fraction of 4%;

(18) d, the solution A and solution B prepared in step a and step b were respectively put in a dropping funnel, simultaneously dropwise added into the solution C in step c at the speed of 1 drop/s, and magnetically stirred for 2 h to form a precipitate;

(19) e, the precipitate formed in step d was stood and aged for 48 h, then subjected to suction filtration, and washed to be neutral; and

(20) f, the precipitate obtained in step e was put into a vacuum drying oven for drying, then put into a tubular furnace, inert gas argon or nitrogen was introduced, the temperature of the tubular furnace was raised to 220° C. at the heating rate of 1° C./min, calcination was carried out at a constant temperature and preservation was performed for 40 min, then the temperature was raised to 400° C., then calcination was carried out at a constant temperature and preservation was performed for 2 h, the temperature was reduced to room temperature at the cooling rate of 1° C./min, calcinination was carried out, and subsequently dry ball milling was carried out for 2 h, so as to obtain the CoNiO.sub.2 thermistor powders. The whole calcination process was protected by inert gas from beginning to end.

Example 4

(21) a, raw materials Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were mixed in a mole ratio of 1:1, and dissolved into deionized water, so as to prepare 2 mol/L mixed solution A;

(22) b, Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were weighed in a mole ratio of 1:1.8, then ammonium bicarbonate was weighed, and deionized water was added, so as to prepare 2 mol/L solution B;

(23) c, cetyltrimethyl ammonium bromide was weighed as a dispersant and dissolved into deionized water, so as to prepare dispersant solution C having a mass fraction of 6.5%;

(24) d, the solution A and solution B prepared in step a and step b were respectively put in a dropping funnel, simultaneously dropwise added into the solution C in step c at the speed of 1.5 drop/s, and magnetically stirred for 3 h to form a precipitate;

(25) e, the precipitate formed in step d was stood and aged for 48 h, then subjected to suction filtration, and washed to be neutral; and

(26) f, the precipitate obtained in step e was put into a vacuum drying oven for drying, then put into a tubular furnace, inert gas argon or nitrogen was introduced, the temperature of the tubular furnace was raised to 230° C. at the heating rate of 1.5° C./min, calcination was carried out at a constant temperature and preservation was performed for 50 min, then the temperature was raised to 500° C., then calcination was carried out at a constant temperature and preservation was performed for 3 h, the temperature was reduced to room temperature at the cooling rate of 1.5° C./min, calcinination was carried out, and subsequently dry ball milling was carried out for 2 h, so as to obtain the CoNiO.sub.2 thermistor powders. The whole calcination process was protected by inert gas from beginning to end.

Example 5

(27) a, raw materials Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were mixed in a mole ratio of 1:1, and dissolved into deionized water, so as to prepare 2.5 mol/L mixed solution A;

(28) b, Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were weighed in a mole ratio of 1:1.8, then ammonium hydroxide was weighed, and deionized water was added, so as to prepare 2.5 mol/L solution B;

(29) c, triton X-100 was weighed as a dispersant and dissolved into deionized water, so as to prepare dispersant solution C having a mass fraction of 8.5%;

(30) d, the solution A and solution B prepared in step a and step b were respectively put in a dropping funnel, simultaneously dropwise added into the solution C in step c at the speed of 1.5 drop/s, and magnetically stirred for 3 h to form a precipitate;

(31) e, the precipitate formed in step d was stood and aged for 60 h, then subjected to filtered at reduced pressure, and washed to be neutral; and

(32) f, the precipitate obtained in step e was put into a vacuum drying oven for drying, then put into a tubular furnace, inert gas argon or nitrogen was introduced, the temperature of the tubular furnace was raised to 240° C. at the heating rate of 1.5° C./min, calcination was carried out at a constant temperature and preservation was performed for 50 min, then the temperature was raised to 500° C., then calcination was carried out at a constant temperature and preservation was carried out for 3 h, the temperature was reduced to room temperature at the cooling rate of 1.5° C./min, calcinination was carried out, and subsequently dry ball milling was carried out for 2 h, so as to obtain the CoNiO.sub.2 thermistor powders. The whole calcination process was protected by inert gas from beginning to end.

Example 6

(33) a, raw materials Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were mixed in a mole ratio of 1:1, and dissolved into deionized water, so as to prepare 3 mol/L mixed solution A;

(34) b, Co(NO.sub.3).sub.2 and Ni(NO.sub.3).sub.2 were weighed in a mole ratio of 1:2.0, then sodium hydroxide was weighed, and deionized water was added, so as to prepare 3 mol/L solution B;

(35) c, polyvinylpyrrolidone powders was weighed as a dispersant and dissolved into deionized water, so as to prepare dispersant solution C having a mass fraction of 10%;

(36) d, the solution A and solution B prepared in step a and step b were respectively put in a dropping funnel, simultaneously dropwise added into the solution C in step c at the speed of 2 drop/s, and magnetically stirred for 4 h to form a precipitate;

(37) e, the precipitate formed in step d was stood and aged for 72 h, then filtered at reduced pressure, and washed to be neutral; and

(38) f, the precipitate obtained in step e was put into a vacuum drying oven for drying, then put into a tubular furnace, inert gas argon or nitrogen was introduced, the temperature of the tubular furnace was raised to 250° C. at the heating rate of 2° C./min, calcination was carried out at a constant temperature and preservation was performed for 60 min, then the temperature was raised to 600° C., then calcination was carried out at a constant temperature and preservation was performed for 4 h, the temperature was reduced to room temperature at the cooling rate of 2° C./min, calcinination was carried out, and subsequently dry ball milling was carried out for 2 h, so as to obtain the CoNiO.sub.2 thermistor powders. The whole calcination process was protected by inert gas from beginning to end.

Example 7

(39) The CoNiO.sub.2 thermistor powders obtained in any one of examples 1-6 were subjected to X-ray diffraction and scanning electron microscope analysis characterization. The test showed that the CoNiO.sub.2 thermistor powders obtained by the method of the disclosure all formed the CoNiO.sub.2 cubic crystal phase whose morphology was basically hexahedral nano sheets.