KR20060000413A - Synthesis of surface controlled nickel-diamond composite powders by electroless plating method - Google Patents

Abstract

The present invention relates to a method for controlling the surface shape of a nickel-diamond composite powder by an electroless plating method. The object of the present invention is to provide a nickel-diamond composite powder manufacturing technique having a continuous needle shape on the diamond surface and a coating layer having excellent uniformity and adhesion. To provide an electroless nickel plating method to establish.

The composition of the present invention is a method for producing a nickel-coated composite powder on the surface of the synthetic diamond particles, the nickel sulfate salt coating solution containing NiSO _{4 ·} 6H ₂ O, Na acetate and Acetic acid is charged After adding to the incubator, adjusting the pH with hydrochloric acid, stirring and heating, and reducing the reaction by injecting at a constant rate while periodically reducing the reducing solution containing sodium hypophosphate and citric acid. Characterized in consisting of steps.

Composite powder, synthetic diamond, pretreatment, electroless nickel plating method, hypophosphorous acid

Description

Synthesis of surface controlled nickel-diamond composite powders by electroless plating method by electroless nickel plating method             

1 is an enlarged photograph of Example 1 of the present invention seen with a scanning electron microscope,

2 is an enlarged photograph of Example 2 of the present invention with a scanning electron microscope;

Figure 3 is an enlarged photograph of Example 3 of the present invention with a scanning electron microscope,

Figure 4 is an enlarged photograph of Example 4 of the present invention with a scanning electron microscope,

5 is a photograph of diamond powder without coating.

The present invention relates to a nickel-diamond composite powder manufacturing method, and more particularly, to a continuous needle shape by supplying at a constant speed while periodically changing the reducing agent by a semi-batch method using an electroless plating method The present invention relates to a method for producing a composite powder having nickel having a coating on a diamond particle surface.

Nickel-diamond composite powder is mixed with resin bond and attached to the cutting heel to be used for cutting or polishing stone. The reason why the nickel layer is applied to the diamond particles is to prevent the diamond from being easily detached from the base structure of the wheel by the heat generated during the polishing process, and the nickel surface layer has a larger specific surface area than the diamond to increase the base structure and adhesion of the wheel. Because.

Such composite powder production methods include electroless plating, hydrogen reduction, and electrolytic methods.However, when the nickel-diamond composite powder is prepared by the electrolytic method, the powder adheres to the agglomeration and plating electrodes, so that the recovery rate of the powder decreases and it is difficult to disperse the powder. The disadvantage is that the thickness control of the coating layer is difficult,

In the production of nickel-diamond composite powder by the hydrogen (pressurized hydrogen) reduction method, a high temperature and high pressure such as a reaction temperature of 100 ° C. or higher is required. Therefore, a special device such as an autoclave is required, and operating conditions are very demanding and diamond and coating layers There is a disadvantage of poor adhesion.

In addition, the conventional electroless plating method has a very smooth plating layer, which reduces adhesion to the base structure, and because the thickness of the plating layer is thin, it does not form a sufficient protective layer to prevent diamond from falling out. .

An object of the present invention for solving the above problems is to provide an electroless nickel plating method for establishing a nickel-diamond composite powder manufacturing technology having a continuous needle shape on the diamond surface and a coating layer having a uniform and excellent adhesion.

In addition, an object of the present invention is to serve as a support layer so that the diamond layer has a thick thickness on the surface of the diamond powder, so that the diamond powder can have a grinding ability, and the production cost is reduced by increasing the reaction efficiency by using a semi-batch constant temperature and humidity bath. To provide an electroless nickel plating method that can reduce the cost.

When described in detail with reference to the accompanying drawings, the configuration and the operation of the embodiment of the present invention to achieve the object as described above and to perform the task for eliminating the conventional drawbacks.

In the present invention, a semi-batch constant temperature that can control domestic synthetic diamond particles having a particle size of 140/170 mesh as a core material, hypophosphorous acid solution as a reducing agent, nickel sulfate as a nickel source, and a reducing agent injection rate as an experimental apparatus. It is an electroless nickel plating method using a semi-batch reaction bath.

When manufacturing nickel diamond composite powder by the electroless plating method, the nickel coating layer has the advantage of being dense and excellent bonding strength with the core particles, and it does not require a special device because the reaction occurs at a relatively low temperature by controlling the components of the reducing agent. In case of semi-batch application, various shape control of surface layer is possible.

Specifically, the plating method of the present invention comprises a pretreatment step of subjecting the surface of synthetic diamond particles (140/170 mesh) used as cores to sensitization (SnCl ₂ ) and activation (PdCl ₂ );

Adding the pre-treated diamond to a semi-batch incubator containing NiSO _{4 ·} 6H ₂ O, Na acetate, and Acetic acid-containing nickel sulfate coating solution, and heating and stirring the pH with hydrochloric acid;

It is a method of manufacturing composite powder coated with nickel on the surface of synthetic diamond particles through a reduction reaction step in which the reducing solution containing sodium hypophosphate and citric acid is changed at a constant rate while reacting at a predetermined rate when the reaction temperature is reached. .

The solution (l or 1000 ml) described below refers to the total mixed solution including the component elements mixed in distilled water.

In the pretreatment step of the diamond, it is subjected to sensitization with a 1% (weight fraction 10 g / l) SnCl ₂ solution.

In the pretreatment step, the sensitized diamond is further activated with 0.1% (weight fraction 1 g / L) PdCl ₂ solution.

The amount of diamond added is 25 g per 1000 ml.

The mixing ratio of NiSO _{4 ·} 6H ₂ O, Na acetate and Acetic acid constituting the nickel sulfate coating solution is 6-25 g (preferably 12.5 g) of NiSO _{4 ·} 6H ₂ O based on 1000 ml, 50 g of Na acetate, and Acetic. 4 ml of acid.

The reason for limiting the numerical value as above is that in case of NiSO _{4 ·} 6H ₂ O, less than 6g, electroless plating is not good, and wear resistance and adhesion to bond resin worsen. This is because the adhesion to the resin is deteriorated by forming a coating layer having a small surface area.

The pre-treated diamond is added to a pyrex semi-batch incubator and then stirred at a speed of 200-800 rpm, preferably at 200 rpm. In the case of less than 200 rpm, the coated nickel-diamond composite powder is agglomerated and the recovery rate is lower than 800 rpm. In the case of the diamond powder is not coated with nickel, the adhesive strength with the bond resin worsens. At this time, the reaction temperature is heated to 70 ℃.

In the electroless nickel reaction, the nickel coating salt solution is adjusted to pH 4.5-5.5 using hydrochloric acid, and preferably maintained at 5.0. If the pH is less than 4.5, the plating is not performed. This occurs and becomes difficult to use as a grinding material.

The composition of the reducing agent solution in the electroless nickel reaction is NaH ₂ PO ₂ and the mixing ratio of citric acid is 500g based on 1000ml, Citric acid 50g (However, when the amount of the reference solution is large or small, the same fluctuations It is continuously changed at a rate of 0.25-3 ml per minute, preferably 3.0 ml for the first 15 minutes, and 15 minutes after the injection into a semi-batch constant temperature reactor at a rate of 0.25 ml.

When generation of hydrogen gas was stopped in the semi-batch incubator, the semi-batch incubator was dismantled to collect the reaction product, and the residual nickel ion concentration in the solution was analyzed after solid and liquid separation.

Solid particles (nickel-based composite powder) were washed with distilled water, dried at a temperature of 80 ° C. in a vacuum oven for 24 hours, and then weighed, chemically analyzed, XRD and SEM were observed.

Hereinafter will be described a preferred embodiment according to the present invention.

Example 1

Synthetic diamond powder used as core particles is subjected to sensitization with 1% (weight fraction 10 g / L) SnCl ₂ solution and then activated with 0.1% (weight fraction 1 g / L) PdCl ₂ solution.

400 ml of nickel sulfate aqueous solution containing 6 g of NiSO ₄ · 6H ₂ O, 50 g of Na acetate, and 4 ml of Acetic acid in 1000 ml of distilled water was adjusted to pH 4.5 with hydrochloric acid and charged into a pyrex semi-batch reactor. And 10 g of the pretreated synthetic diamond powder is added.

The reaction solution is heated to the reaction temperature of 70 ℃ while stirring at 200rpm.

When the reaction temperature is reached, the mixing ratio of NaH ₂ PO ₂ and citric acid required for the experimental conditions is 500 g based on 1000 ml, and 50 g of citric acid is 3.0 ml for the first 15 minutes using a solution injection device. Thereafter, the mixture was injected into a semi-batch incubator at a rate of 0.25 ml and stirred at 200 rpm. The electroless plating reaction was carried out with a reaction time of 15 minutes in 1 step, 200 minutes in 2 steps, and 200 minutes in 3 steps. When the nickel sulfate solution was supplied again as described above, the experiment was performed. (3 coatings in total)

After the reduction reaction is completed, the reaction product is filtered to separate solid and liquid, and the recovered powder is washed five times with ethanol and distilled water.

The vacuum oven was dried at 80 ° C. for at least 24 hours, and the dried nickel-diamond composite powder was checked for coating state using SEM.

1 is an enlarged photograph of Example 1 seen with a scanning electron microscope. Comparing FIG. 1 with FIG. 5, it can be seen that a nickel coating layer is formed on the surface. XRD analysis confirmed that it is a nickel plated layer. The coating layer can be seen that the needle-like protrusions grow to a size of about 20 ㎛ and grown uniformly and densely on the entire surface of the diamond.

Example 2

Synthetic diamond powder used as core particles is subjected to sensitization with 1% (weight fraction 10 g / L) SnCl ₂ solution and then activated with 0.1% (weight fraction 1 g / L) PdCl ₂ solution.

400 ml of nickel sulfate aqueous solution in which 6 g of NiSO ₄ · 6H ₂ O, 50 g of Na acetate, and 4 ml of Acetic acid was dissolved in 1000 ml of distilled water was adjusted to pH 5.5 using hydrochloric acid and charged into a pyrex semi-batch reactor. And 10 g of the pretreated synthetic diamond powder is added.

The reaction solution is heated to the reaction temperature of 70 ℃ while stirring at 200rpm.

When the reaction temperature was reached, the mixture was stirred at 200 rpm and the mixing ratio of NaH ₂ PO ₂ and citric acid required for the experimental conditions was 500 g based on 1000 ml, and 50 g of citric acid was 3.0 g. After 15 minutes, it was injected into a semi-batch incubator at a rate of 0.25 ml and stirred at 200 rpm. The electroless plating reaction was carried out with a reaction time of 15 minutes for 1 step, 200 minutes for 2 steps, and 200 minutes for 3 steps, respectively. When the step of was completed, the nickel sulfate solution was again supplied as described above to perform the experiment. (3 coatings in total)

After the reduction reaction is completed, the reaction product is filtered to separate solid and liquid, and the recovered powder is washed five times with ethanol and distilled water.

The vacuum oven was dried at 80 ° C. for at least 24 hours, and the dried nickel-diamond composite powder was checked for coating state using SEM.

FIG. 2 is an enlarged photograph of Example 2 viewed with a scanning electron microscope. FIG. Comparing FIG. 2 with FIG. 5, it can be seen that a nickel coating layer is formed on the surface. XRD analysis confirmed that it is a nickel plated layer. The shape of the coating layer has almost no needle-like protrusions, and it can be seen that the size of the protrusions is very small as compared with FIG. 1. In addition, it can be seen that a lot of fine white projections on the surface of the nickel layer.

Example 3

Synthetic diamond powder used as core particles is subjected to sensitization with 1% (weight fraction 10 g / L) SnCl ₂ solution and then activated with 0.1% (weight fraction 1 g / L) PdCl ₂ solution.

400 ml of nickel sulfate aqueous solution in which 6 g of NiSO ₄ · 6H ₂ O, 50 g of Na acetate, and 4 ml of Acetic acid was dissolved in 1000 ml of distilled water was adjusted to pH 5.2 with hydrochloric acid, and charged into a pyrex semi-batch reactor. And 10 g of the pretreated synthetic diamond powder is added.

The reaction solution is heated to the reaction temperature of 70 ℃ while stirring at 200rpm.

When the reaction temperature is reached, stirring at 200rpm, the mixing ratio of NaH ₂ PO ₂ and citric acid required for the experimental conditions is 500g based on 1000ml, and 50g of Citric acid is 50g. Was proceeded for 30 minutes at 3 ml per minute, 2 minutes at 2 ml per minute for 30 minutes, and 3 steps at 1 ml per minute for 40 minutes. When each step was completed, the nickel sulfate salt solution was again supplied as described above. (Total 3 coatings).

After the reduction reaction is completed, the reaction product is filtered to separate solid and liquid, and the recovered powder is washed five times with ethanol and distilled water.

The vacuum oven was dried at 80 ° C. for at least 24 hours, and the dried nickel-diamond composite powder was checked for coating state using SEM.

Figure 3 is an enlarged photograph of Example 3 seen with a scanning electron microscope. Comparing FIG. 3 with FIG. 5, it can be seen that a nickel coating layer is formed on the surface. XRD analysis confirmed that it is a nickel plated layer. The shape of the coating layer has almost no needle-like protrusions, and the size of the protrusions is very small compared to FIG. 1, and it can be seen that many fine and white protrusions are seen on the surface of the nickel layer. In general, the surface of the nickel layer is round.

Example 4

Synthetic diamond powder used as core particles is subjected to sensitization with 1% (weight fraction 10 g / L) SnCl ₂ solution and then activated with 0.1% (weight fraction 1 g / L) PdCl ₂ solution.

400 ml of nickel sulfate aqueous solution in which 6 g of NiSO ₄ · 6H ₂ O, 50 g of Na acetate, and 4 ml of Acetic acid was dissolved in 1000 ml of distilled water was adjusted to pH 5.2 with hydrochloric acid, and charged into a pyrex semi-batch reactor. And 10 g of the pretreated synthetic diamond powder is added.

The reaction solution is heated to the reaction temperature of 70 ℃ while stirring at 200rpm.

When the reaction temperature is reached, the mixing rate of NaH ₂ PO ₂ and citric acid is 500g based on 1000ml and 50g of Citric acid is 50g. The step was carried out in three steps for a total of 200 minutes at 0.25ml per minute, and when each step was completed, the experiment was performed by supplying the nickel sulfate solution again as described above (total 3 coatings).

After the reduction reaction is completed, the reaction product is filtered to separate solid and liquid, and the recovered powder is washed five times with ethanol and distilled water.

The vacuum oven was dried at 80 ° C. for at least 24 hours, and the dried nickel-diamond composite powder was checked for coating state using SEM.

Figure 3 is an enlarged photograph of Example 3 seen with a scanning electron microscope. Comparing FIG. 3 with FIG. 5, it can be seen that a nickel coating layer is formed on the surface. XRD analysis confirmed that it is a nickel plated layer. The shape of the coating layer can be confirmed that the needle-like protrusions are larger than that of FIG. 3 and the size of the protrusions is larger than that of FIG. 3. On the other hand, it can be seen that many fine and white projections are seen on the surface of the nickel layer.

Table 1 Results of nickel content analysis of Examples 1 to 4

Example Nickel content (weight%) Remarks One 55.0% 2 57.7% 3 60.2% 4 54.2%

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

The electroless plating method of the present invention as described above is simple to operate by a semi-batch process, so that it is possible to manufacture nickel diamond powder having various shapes according to the acidity control of the plating liquid and the supply rate of the reducing agent. In the conditions where the reaction temperature is higher than 80 ° C., the reduction rate is high, but the reduced nickel is not coated on the surface of the core particles, but precipitates on the surface of the semi-batch reactor or on the sheet of nickel, and the aggregation phenomenon between the composite powders is improved. It is a new and very useful invention that can simplify the manufacturing process and save energy when manufacturing a composite powder by overcoming the shortcomings that are not caused by monodispersion.

Claims (10)

In the method for producing a composite powder coated with nickel on the surface of synthetic diamond particles, Adding the pre-treated diamond to a constant temperature reactor containing nickel sulfate coating solution containing NiSO _{4 ·} 6H ₂ O, Na acetate and Acetic acid, adjusting the pH with hydrochloric acid, stirring and heating, When the reaction temperature is reached, the nickel-diamond composite powder of the electroless nickel plating method is characterized in that it consists of a reduction reaction step of reacting the reducing solution containing sodium hypophosphate and citric acid at a constant speed while reacting it. Shape control manufacturing method. The method of claim 1, The constant temperature reaction tank is a semi-batch reaction bath (Semi-batch reaction bath) that can control the injection rate of the reducing agent, characterized in that the shape control manufacturing method of nickel-diamond composite powder by the electroless nickel plating method. The method of claim 1, In the pretreatment step of the diamond, the surface of the synthetic diamond particles (140/170 mesh) is sensitized with a 1% (weight fraction 10 g / L) SnCl ₂ solution, and then the sensitized diamond is again 0.1% (weight fraction 1 g / L). (1) A method for controlling the shape of a nickel-diamond composite powder by electroless nickel plating, characterized in that it is activated with a PdCl ₂ solution. The method of claim 1, The mixing ratio of NiSO _{4 ·} 6H ₂ O, Na acetate, and Acetic acid constituting the nickel sulfate coating solution is based on 1000 ml of 6-25 g of NiSO _{4 ·} 6H ₂ O, 50 g of Na acetate, and 4 ml of Acetic acid. A shape control manufacturing method of a nickel-diamond composite powder by an electroless nickel plating method. The method of claim 1, Shape control of the nickel-diamond composite powder by the electroless nickel plating method characterized by adjusting the pH to hydrochloric acid and adjusting the nickel coating salt solution to pH 4.5-5.5 using hydrochloric acid during the stirring and heating the electroless nickel reaction. Manufacturing method. The method of claim 1, The composition of the reducing agent solution during the electroless nickel reaction is 500 g of citric acid and 50 g of citric acid based on the mixing ratio of NaH ₂ PO ₂ and citric acid. The shape control manufacturing method of the nickel-diamond composite powder by the electroless nickel plating method characterized by the above-mentioned. The method according to any one of claims 1 to 6, The shape of the nickel-diamond composite powder by the electroless nickel plating method was injected into a semi-batch incubator continuously while periodically changing the reducing agent solution, and then injected into a solution of 0.25-3 ml per minute for a total of three coating reactions. Controlled manufacturing method. The method of claim 7, wherein When the coating is carried out once, the injection is divided into three stages and injected into a semi-batch constant temperature reaction tank to perform a reduction experiment. In the first step, inject 0.25 ~ 3.0ml per minute between 15 and 200 minutes, Step 2 inject 0.25 ~ 2.0ml per minute between 30 and 200 minutes, The third step is a shape control manufacturing method of nickel-diamond composite powder by electroless nickel plating method characterized in that the injection of 0.25 ~ 1.0ml per minute between 40 minutes and 200 minutes. The method of claim 7, wherein In the single coating, the injection is divided into three stages, but the initial 15 minutes are 3.0 ml and after 15 minutes, the nickel-diamond composite by the electroless nickel plating method is injected into a semi-batch constant temperature reactor at a rate of 0.25 ml. Shape control manufacturing method of powder. The method of claim 1, Forming method for controlling the shape of the nickel-diamond composite powder by the electroless nickel plating method characterized in that the heating temperature during the stirring is heated to 70 ℃.

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