Piezoresistor-grade nickel protoxide and preparation method thereof
A method using metal hydroxide alkali leaching and controlled calcination produces varistor-grade nickelous oxide with low impurities and spherical shape, addressing the challenges of mesoporous structures and irregular shapes in traditional methods.
Patent Information
- Application Number
- CN202411381557.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2025-01-03
AI Technical Summary
Existing methods for preparing varistor-grade nickelous oxide often result in mesoporous structures with high impurity content and irregular shapes, making subsequent impurity removal difficult.
A method involving the use of an aqueous solution of metal hydroxide for alkali leaching nickel carbonate precursors at a pH of 8.5±0.5, followed by drying and calcination at specific temperatures to produce varistor-grade nickelous oxide with low impurity content and spherical morphology, without the addition of surfactants.
The method yields nickelous oxide with fewer surface pores, easier impurity removal, and improved spherical shape, reducing impurity content and enhancing the smoothness of the surface.
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Figure CN119240808A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of inorganic chemical technology, and in particular to a varistor-grade nickelous oxide and a preparation method thereof. Background Art
[0002] Varistor is an electric shock protection device made with zinc oxide nonlinear resistor element as the core. Nickelous oxide is its main additive and is the key material for realizing the nonlinear volt-ampere characteristics of the device. At present, the preparation method of varistor-grade nickelous oxide in industry mainly adopts the complexation method of nickel source and ammonia water to produce precursors such as nickel oxalate and nickel carbonate, and then obtains nickelous oxide by calcination. For example, the prior art reports that the nickel source after impurity removal is reacted with oxalic acid and ammonia water, and a surfactant is added to this system to obtain a precursor nickel oxalate powder with uniform shape and size. Alternatively, the nickelous oxide precursor is prepared by spray pyrolysis, and then calcined to obtain nickelous oxide, but the use of surfactants may cause the nickelous oxide to present mesoporous nickelous oxide, and the mesoporous nickelous oxide has a porous appearance, which makes subsequent impurity removal more difficult.
[0003] Chinese patent application 201610106501.7 discloses a method for synthesizing nickel carbonate, a precursor of nickelous oxide. The method for preparing nickel carbonate disclosed therein comprises the following steps:
[0004] Step 1: Parallel flow, low pH synthesis of crude nickel carbonate: Add water to the synthesis tank to submerge the stirring blades, start stirring, slowly introduce steam to raise the temperature to 70-80°C, and heat at 3m 3 / h、2m 3 / h flow rate, adding 40g / L nickel sulfate solution and 120g / L sodium carbonate solution in parallel, controlling the synthesis end point pH value to 6.9-7.1, filtering to obtain a filtrate and a filter cake;
[0005] Step 2: Slurrying and high pH alkaline leaching desulfurization: Add the filter cake from the previous step into the alkaline leaching tank, add water to immerse the stirring blades, start stirring, slowly introduce steam to raise the temperature to 80-90°C, continue to add water to slurry nickel carbonate at a ratio of 3:1 between water and filter cake for 30 minutes, add 120g / L sodium carbonate solution to adjust the pH value to 9.20-9.50, filter to obtain the filtrate and filter cake, and the excess sodium carbonate and SO4 entrained in the nickel carbonate filter cake 2- The reaction generates sodium sulfate solution to remove sulfur;
[0006] Step 3: Slurrying and washing to remove sodium: Add the filter cake from the previous step to the alkali leaching tank, add water to immerse the stirring blade, start stirring, slowly introduce steam to raise the temperature to 80-90°C, continue to add water to slurry nickel carbonate at a ratio of 5:1 between water and filter cake for 30 minutes, filter to obtain the filtrate and filter cake, and remove the Na contained in the nickel carbonate filter cake. + Remove into the filtrate;
[0007] First of all, the scheme has the characteristics of low processing cost, high metal recovery rate, low equipment material requirements, low investment cost, low technical threshold, simple and convenient method, good effect, and good quality of nickel carbonate. However, further observation of the scheme shows that, on the one hand, the scheme does not disclose the preparation process of nickel carbonate to nickelous oxide.
[0008] Chinese patent application 200710050492.5 discloses a method for preparing mesoporous nickelous oxide with high specific surface area. The method uses nickel chloride as a nickel source, sodium carbonate as a precipitant, and sodium dodecyl sulfate as a template to prepare mesoporous nickelous oxide. Specifically, an appropriate amount of sodium dodecyl sulfate is added to a nickel salt solution as a structure directing agent, and then a precipitation reaction is carried out with a sodium carbonate solution, and the pH value, temperature and aging conditions of the reaction are controlled. After aging, the precursor is washed and ground. The precursor is calcined and cooled under certain conditions to obtain mesoporous nickelous oxide. The process described in the method is easy to control, and the amount of precipitant and template is small. The nickelous oxide obtained has a mesoporous structure, a large specific surface area, no surfactant residue, and good thermal stability.
[0009] By observing this scheme, it can be seen that a surfactant is added during the preparation of nickel carbonate, and nickelous oxide with a mesoporous structure and a large specific surface area is prepared by using sodium dodecyl sulfate as a structure-directing agent; at the same time, in the subsequent calcination process, the calcination temperature is 350-400°C.
[0010] The problem that this scheme needs to solve is: how to propose a method for preparing nickelous oxide with low impurity content and a morphology that is closer to a spherical shape. Summary of the invention
[0011] The purpose of the present application is to provide a method for preparing varistor-grade nickelous oxide. The nickelous oxide prepared by the above preparation method has a low impurity content and a microscopic morphology that is closer to a spherical shape. In addition, the preparation method is different from the traditional preparation of nickelous oxide. No additional surfactant is added during the nickel deposition process to improve the smoothness of the nickelous oxide surface, thereby obtaining a nickelous oxide with fewer surface pores and easier subsequent impurity removal.
[0012] To achieve the above object, the present application provides a method for preparing varistor-grade nickelous oxide, comprising the following steps:
[0013] Step 1: adding a solution containing carbonate ions to a nickel sulfate solution until the pH value is 7 to 9 to obtain a nickel carbonate precursor;
[0014] Step 2: filter the nickel carbonate precursor obtained in step 1, alkali leaching and washing to obtain nickel carbonate;
[0015] Step 3: drying and calcining the nickel carbonate obtained in step 2 to obtain varistor-grade nickelous oxide;
[0016] In step 2, the nickel carbonate precursor after filter pressing is alkali leached by using an aqueous solution of a metal hydroxide as an alkali leaching solution, and the pH of the system during the alkali leaching process is 8.5±0.5.
[0017] The present application selects an aqueous solution of metal hydroxide for alkali leaching treatment. The reason is that, although it is traditionally known that all alkaline solutions can be used as alkali leaching solutions for alkali leaching treatment, during the experiment, when metal hydroxide is used as an alkali leaching solution, it exhibits better reaction activity with sulfur-containing impurities, thereby further reducing the sulfur content in nickel carbonate.
[0018] Preferably, the metal hydroxide is selected from at least one of sodium hydroxide, potassium hydroxide, magnesium hydroxide, lithium hydroxide and barium hydroxide.
[0019] Preferably, the nickel sulfate solution is selected from an aqueous solution of at least one of nickel sulfate, nickel chloride and nickel nitrate;
[0020] The solution containing carbonate ions is selected from an aqueous solution of at least one of sodium carbonate and potassium carbonate.
[0021] Preferably, step 1 is specifically as follows: adding a solution containing carbonate ions to the nickel sulfate solution, and while adding the solution containing carbonate ions, controlling the temperature of the system to be between 55 and 80° C., and stirring at a speed of 200 to 250 rpm / min until the pH value of the system is increased to 7 to 9, and then filtering to obtain a nickel carbonate precursor.
[0022] Preferably, step 3 specifically comprises: drying the nickel carbonate obtained in step 2, and then calcining it at 350-850° C. for 2-4 hours to obtain varistor-grade nickelous oxide.
[0023] Further preferably, step 3 specifically comprises: drying the nickel carbonate obtained in step 2, and then calcining at 600-850° C. for 2-4 hours to obtain varistor-grade nickelous oxide.
[0024] Preferably, the metal hydroxide is sodium hydroxide, and in the alkaline leaching process, the metal hydroxide is sodium hydroxide, and the concentration of sodium hydroxide in the alkaline leaching solution is 0.08 to 0.15 mol / L.
[0025] In addition, the present application also discloses a varistor-grade nickelous oxide, which is prepared by the above-mentioned preparation method of varistor-grade nickelous oxide.
[0026] The beneficial effects of this application are:
[0027] The nickelous oxide prepared in the present application has a low impurity content and good sphericity. In addition, unlike the traditional preparation of nickelous oxide, the present application does not add additional surfactants during the nickel deposition process to improve the smoothness of the nickelous oxide surface, thereby obtaining a nickelous oxide with fewer surface pores and a more fluid subsequent impurity removal. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 is a scanning electron microscope image of nickelous oxide obtained in Example 1;
[0029] Figure 2 is a scanning electron microscope image of nickelous oxide obtained in Example 4;
[0030] Figure 3 is a scanning electron microscope image of nickelous oxide obtained in Example 5;
[0031] Figure 4 This is the XRD pattern of nickelous oxide prepared in Example 1. DETAILED DESCRIPTION
[0032] In the description of the present invention, it should be noted that, if the specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.
[0033] Example 1
[0034] Step 1: adding a sodium carbonate solution with a concentration of 120 g / L to a nickel sulfate aqueous solution with a concentration of 53.5 g / L at a flow rate of 21.6 ml / min, controlling the temperature of the system to be stable at 55° C., stirring at a speed of 250 rpm / min until the pH value of the system is increased to 7.5±0.5, and then filtering to obtain a nickel carbonate precursor;
[0035] Step 2: The nickel carbonate precursor obtained in step 1 is filtered to obtain a filter cake, and then the filter cake is placed in a sodium hydroxide solution with a temperature of 65° C. and an initial concentration of 0.08 mol / L for alkali leaching for 0.5 h, and the pH value of the system is maintained within 8.5±0.5 during the alkali leaching process;
[0036] After the alkaline leaching is completed, the filter cake is washed with pure water at a volume ratio of 1:4 to obtain nickel carbonate;
[0037] Step 3: The nickel carbonate obtained in step 2 is placed in an environment of 70° C. for 10 hours for drying to obtain nickel carbonate having a water mass fraction of no more than 0.2%, and then the nickel carbonate is placed in an environment of 350° C. for 4 hours to obtain varistor-grade nickelous oxide.
[0038] Example 2
[0039] Step 1: Add a 200 g / L sodium carbonate solution to a 120 g / L nickel nitrate aqueous solution at a flow rate of 21.6 ml / min, control the temperature of the system to be stable at 80° C., and stir at a speed of 200 rpm / min until the pH value of the system is increased to 8.5±0.5, and then filter to obtain a nickel carbonate precursor;
[0040] Step 2: The nickel carbonate precursor obtained in step 1 is filtered to obtain a filter cake, and then the filter cake is placed in a potassium hydroxide solution with a temperature of 65° C. and an initial concentration of 0.15 mol / L for alkali leaching for 0.5 h, and the pH value of the system is maintained within 8.5±0.5 during the alkali leaching process;
[0041] After the alkaline leaching is completed, the filter cake is washed with pure water at a volume ratio of 1:4 to obtain nickel carbonate;
[0042] Step 3: The nickel carbonate obtained in step 2 is placed in an environment of 70° C. for 10 hours for drying to obtain nickel carbonate having a water mass fraction of no more than 0.2%, and then the nickel carbonate is placed in an environment of 850° C. for calcining for 2 hours to obtain varistor-grade nickelous oxide.
[0043] Example 3
[0044] Step 1: adding a 250 g / L potassium carbonate solution to a 150 g / L nickel chloride aqueous solution at a flow rate of 21.6 ml / min, controlling the temperature of the system to be stable at 65° C., stirring at a speed of 230 rpm / min until the pH value of the system is increased to 8±0.5, and then filtering to obtain a nickel carbonate precursor;
[0045] Step 2: The nickel carbonate precursor obtained in step 1 is filtered to obtain a filter cake, and then the filter cake is placed in a sodium hydroxide solution with a temperature of 65° C. and an initial concentration of 0.12 mol / L for alkali leaching for 0.5 h, and the pH value of the system is maintained within 8.5±0.5 during the alkali leaching process;
[0046] After the alkaline leaching is completed, the filter cake is washed with pure water at a volume ratio of 1:4 to obtain nickel carbonate;
[0047] Step 3: The nickel carbonate obtained in step 2 is placed in an environment of 70° C. for 10 hours for drying to obtain nickel carbonate having a water mass fraction of no more than 0.2%, and then the nickel carbonate is placed in an environment of 600° C. for calcination for 3 hours to obtain varistor-grade nickelous oxide.
[0048] Example 4
[0049] The method is basically the same as Example 1, except that step 3 is specifically as follows: the nickel carbonate obtained in step 2 is placed in an environment of 70° C. for 10 hours for drying to obtain nickel carbonate having a water mass fraction of not more than 0.2%, and then the nickel carbonate is placed in an environment of 600° C. for calcining for 4 hours to obtain varistor-grade nickelous oxide.
[0050] Example 5
[0051] The method is basically the same as Example 1, except that step 3 is specifically as follows: the nickel carbonate obtained in step 2 is placed in an environment of 70° C. for 10 hours for drying to obtain nickel carbonate having a water mass fraction of not more than 0.2%, and then the nickel carbonate is placed in an environment of 850° C. for calcining for 4 hours to obtain varistor-grade nickelous oxide.
[0052] Example 6
[0053] The method is basically the same as Example 1, except that the concentration of sodium hydroxide in the alkaline leaching solution is 0.03 mol / L.
[0054] Example 7
[0055] The same as Example 1, except that the concentration of sodium hydroxide in the alkaline leaching solution is 0.3 mol / L.
[0056] The method is basically the same as Example 1, except that ammonia water is used to replace the sodium hydroxide solution in step 2, and the pH value during the alkaline leaching process is still maintained within 8.5±0.5.
[0057] Comparative Example 2
[0058] The method is basically the same as Example 1, except that sodium carbonate solution is used to replace sodium hydroxide solution in step 2, and the pH value during the alkali leaching process is still maintained within 8.5±0.5.
[0059] Comparative Example 3
[0060] The method is basically the same as Example 1, except that step 2 is specifically as follows: the nickel carbonate precursor obtained in step 1 is filtered to obtain a filter cake, and then the filter cake is placed in a sodium hydroxide solution with a temperature of 65°C and an initial concentration of 0.08 mol / L for alkali leaching for 0.5 h, and the pH value of the system is maintained within 9.4±0.2 during the alkali leaching process.
[0061] Performance Test:
[0062] The sulfur content and metal impurity (Co, Cu, Fe, Zn, Cd, Ca, Mg, Na) content of the nickelous oxide synthesized in each embodiment and comparative example were tested with reference to "YS / T 277-2016". The results are shown in Table 1 below:
[0063] Table 1
[0064] Group Sulfur mass fraction Total mass of metal impurities Example 1 0.0275％ <1000ppm Example 2 0.0272％ <1000ppm Example 3 0.0269％ <1000ppm Example 4 0.0278％ <1000ppm Example 5 0.0264％ <1000ppm Example 6 0.0316％ <1000ppm Example 7 0.0351％ <1000ppm Comparative Example 1 0.0873％ 3649ppm Comparative Example 2 0.0880％ 3883ppm Comparative Example 3 0.0693％ 3051ppm
[0065] 1. As can be seen from Table 1, when the process parameters in the processing are slightly changed in Examples 1-3, the mass fraction of sulfur in the nickelous oxide obtained in Examples 1-3 fluctuates, but the amplitude is relatively small;
[0066] Further observation of Examples 4-5 shows that when the calcination temperature in step 3 is increased relative to that in Example 1, the sulfur content in Examples 4-5 does not show a significant change. Figure 1-3 It can be seen that Examples 4-5 have a more spherical morphology and a more uniform particle size distribution compared to Example 1;
[0067] 2. It can be seen from Table 1 that after the concentration of sodium hydroxide is adjusted in Examples 6-7, the sulfur content in Examples 6 and 7 has a certain upward trend relative to that in Example 1. The reason is that the reaction activity of low-concentration sodium hydroxide may be relatively low, which results in sulfur not being consumed as much as possible, while the reaction process of high-concentration sodium hydroxide is relatively more intense and the pH value fluctuates greatly, which results in sulfur not being consumed as much as possible;
[0068] 3. As can be seen from Table 1, when sodium hydroxide is replaced by ammonia water or sodium carbonate, even if the pH value of the alkali leaching process is still maintained in the range of 8.5±0.5, the sulfur content of both is increased relative to that of Example 1. It can be seen that in this scheme, the use of sodium hydroxide as the alkali leaching liquid has a stronger ability to remove sulfur;
[0069] Further observation of Comparative Example 3 shows that when the pH value during the alkaline leaching process is increased, the mass fraction of sulfur is increased relative to that of Example 1. The reason for this phenomenon may be that nickel carbonate reacts with alkali to generate soluble nickel salts, which in turn causes the mass fraction of sulfur to show a certain upward trend.
[0070] 4.Reference Figure 4 , observing the XRD spectrum of nickelous oxide prepared in Example 1, it can be seen that its half-peak width is about 0.5, which indicates that the nickelous oxide prepared in Example 1 has a relatively small porosity, and the relatively low porosity reduces the content of impurities attached to it, which is one of the reasons why it has a lower impurity content.
[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.
Claims
1. A method for preparing varistor-grade nickelous oxide, characterized in that: The following steps are involved: Step 1: adding a solution containing carbonate ions to a nickel sulfate solution until the pH value is 7 to 9 to obtain a nickel carbonate precursor; Step 2: filtering, alkali leaching and washing the nickel carbonate precursor obtained in step 1 to obtain nickel carbonate; Step 3: drying and calcining the nickel carbonate obtained in step 2 to obtain varistor-grade nickelous oxide; In step 2, the nickel carbonate precursor after pressure filtration is alkali leached using an aqueous solution of a metal hydroxide as an alkali leaching solution, and the pH value of the system during the alkali leaching process is 8.5±0.
5.
2. The method for preparing varistor-grade nickelous oxide according to claim 1, characterized in that: The metal hydroxide is selected from at least one of sodium hydroxide, potassium hydroxide, lithium hydroxide and barium hydroxide.
3. The method for preparing varistor-grade nickelous oxide according to claim 1, characterized in that: The solution containing carbonate ions is selected from an aqueous solution of at least one of sodium carbonate and potassium carbonate.
4. The method for preparing varistor-grade nickelous oxide according to claim 1, characterized in that: The step 1 specifically comprises: adding a solution containing carbonate ions to the nickel sulfate solution, and while adding the solution containing carbonate ions, controlling the temperature of the system to be between 55 and 80° C. and stirring at a speed of 200 to 250 rpm / min until the pH value of the system is increased to 7 to 9, and then filtering to obtain a nickel carbonate precursor.
5. The method for preparing varistor-grade nickelous oxide according to claim 1, characterized in that: Step 3 is specifically as follows: drying the nickel carbonate obtained in step 2, and then calcining it at 350-850° C. for 2-4 hours to obtain varistor-grade nickelous oxide.
6. The method for preparing varistor-grade nickelous oxide according to claim 5, characterized in that: The step 3 is specifically as follows: drying the nickel carbonate obtained in the step 2, and then calcining it at 600-850° C. for 2-4 hours to obtain varistor-grade nickelous oxide.
7. The method for preparing varistor-grade nickelous oxide according to claim 1, characterized in that: The metal hydroxide is sodium hydroxide, and in the alkali leaching process, the metal hydroxide is sodium hydroxide, and in the alkali leaching solution, the concentration of sodium hydroxide is 0.08-0.15 mol / L.
8. A varistor grade nickelous oxide, characterized in that: The method for preparing varistor-grade nickelous oxide is used.