CN1308016A

CN1308016A - Preparation of low temperature sinterable hydroxyapatite powder

Info

Publication number: CN1308016A
Application number: CN 00127421
Authority: CN
Inventors: 高濂; 李蔚
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2000-11-10
Filing date: 2000-11-10
Publication date: 2001-08-15
Anticipated expiration: 2020-11-10
Also published as: CN1105678C

Abstract

The preparation method of low-temp. sintered nanometer hydroxyapatite powder belongs to the field of fine chemicals, and the cheap commercially available calcium nitrate and ammonium dihydrogen phosphate are used as raw material, and by precipitation, ageing, washing and drying to prepare said powder. It is mainly characterized by that before ageing process the dispersing agent is added or after ageing process the ultrasonic dispersion process is used to reduce agglomeration so as to make the temp. of obtained powder be 950 deg.C, and after 2 hr. of heat insulation and having been sintered its relative density can be up to 98%, and everage grain size is less than 140 nm.

Description

Preparation method of nano hydroxyapatite powder capable of being sintered at low temperature

The invention relates to a preparation method of nano hydroxyapatite powder, belonging to the field of fine chemical engineering.

Hydroxyapatite (HAp) is a material with great application prospect. It is the main inorganic component of human skeleton tissue, contains calcium and phosphorus elements necessary for human tissue, and contains no other harmful elements. After being implanted into the body, under the action of body fluid, calcium and phosphorus are dissociated from the surface of the material, absorbed by body tissues and grow new tissues. Hydroxyapatite can form chemical bond with human bone tissue and is a typical bioactive material. The research shows that: the finer the grains of the hydroxyapatite material, the higher its biological activity. In addition, the hydroxyapatite is an excellent humidity sensitive material, and a humidity sensitive element prepared from the hydroxyapatite has good ageing resistance. In the current international market, the price of hydroxyapatite powder exceeds $ 1000 per kilogram.

Hydroxyapatite is mainly obtained by artificial synthesis because it is not a natural mineral. At present, a plurality of methods for preparing hydroxyapatite powder are available, and a precipitation method, a hydrolysis method, a hydrothermal method, a solid phase method and the like are common. The hydrothermal method requires complex and expensive equipment, the solid phase method has large energy consumption, and the precipitation method is widely applied due to simple process, cheap equipment and large yield. However, the precipitation method has some disadvantages, such as easy agglomeration of the powder, unstable quality, etc.

The present invention is an improvement over the conventional precipitation method. Aims to provide a method for preparing nano hydroxyapatite powder which can be produced in large scale, has less agglomeration and can be sintered at low temperature to obtain fine-grained hydroxyapatite material. The method has the advantages of simple process, stable product quality and low cost.

The preparation method provided by the invention takes inorganic calcium salt and phosphate as raw materials, and the HAp powder with small crystal grains and less agglomeration is obtained by precipitation reaction under a certain pH value, addition of a proper amount of dispersant, aging, washing and drying. The process flow diagram is shown in fig. 6.

The respective processes will now be described in detail as follows:

1. selection of inorganic salt raw materials: selecting cheap and easily available calcium nitrate Ca (NO) on the market₃)₃And ammonium dihydrogen phosphate NH₄H₂PO₄. The reaction equation is:

2. selection of inorganic salt concentration: both raw materials are controlled between 1 and 2 mol/L, and the yield is low when the concentration is too low. While mechanically stirring, dropwise adding an aqueous solution of ammonium dihydrogen phosphate into a solution of calcium nitrate to react and precipitate.

3. pH value in precipitation: controlling the temperature between 9 and 11, and stirring.

4. Selection of a dispersant: polyacrylic acid, polyethylene glycol (molecular weight 2000), etc. may be selected, and the amount of the dispersant added is 0.5 to 4%, preferably 2 to 3% (mass percentage) with respect to the precipitate.

5. Aging temperature and time: the temperature is controlled between 60 ℃ and 80 ℃ and the time is controlled between 12 hours and 24 hours. The most critical process of the invention is to add a dispersant before aging or to perform ultrasonic dispersion after aging to reduce agglomeration.

6. Washing of the precipitate: the precipitate was washed with distilled water to remove impurity ions.

7. Desorbing water: in order to save time and cost, the invention adopts a common oven to dry and dehydrate the precipitate. The drying temperature was 120 ℃ and the time was 12 hours.

From the above, it can be seen that the outstanding features of the present invention are:

1. the preparation process is simple, the process parameters are easy to control, and the large-scale industrial production is easy to realize.

2. The invention adopts the method of adding thedispersing agent before aging or ultrasonic dispersing after aging to reduce agglomeration, thereby avoiding the process of eluting water by alcohol in the general powder preparation process and saving the cost.

3. The powder obtained by the invention can be directly molded and sintered without calcination, and has excellent sintering performance. The relative density of the obtained HAp can reach about 98% under the condition of 950 ℃/2h, and the average grain size is less than 140 nm.

FIG. 1 is an electron micrograph of a powder of HAp prepared by the method of the present invention. It is clear from the photographs that the powder prepared by the method provided by the invention has less agglomeration.

Fig. 2 is an XRD spectrum of a hydroxyapatite block material prepared from the powder obtained by the method provided by the invention after sintering at 1100 ℃/2 h. As can be seen from FIG. 2, after sintering at 1100 deg.C for 2 hours (without protection of water vapor), the phase composition of the material is still hydroxyapatite, and no decomposition occurs, indicating that the obtained powder has good stability.

Fig. 3 is a graph showing the sintering properties of the hydroxyapatite powder (a) obtained without washing with alcohol in the presence of a dispersant, compared with the hydroxyapatite powder (B) obtained without washing with alcohol in the presence of a dispersant. The abscissa in the figure represents the sintering temperature and the ordinate represents the relative density of the resulting sample.

Fig. 4 is a comparison of sintering performance of hydroxyapatite powder (a) prepared according to the present invention and commercial hydroxyapatite powder. The abscissa and ordinate have the same meaning as in fig. 3.

FIG. 5 is an XRD spectrum of a powder obtained by washing with water without aging and by adding a dispersant directly, after calcining at 1100 ℃ for 2 hours.

The salient features of the invention are further illustrated by the following examples, which are intended to be illustrative only and in no way limiting of the invention, i.e. the salient features and the marked improvements of the invention are in no way limited to the examples described below.

Example 1:

the pH of a 1.5 mol/l calcium nitrate and 1.5 mol/l ammonium dihydrogen phosphate solution was adjusted to greater than 9, and ammonium dihydrogen phosphate was added dropwise to the calcium nitrate solution while mechanically stirring. Separating the precipitate generated by the reaction into two parts for reaction, adding 2 percent (mass percent) of dispersant polyethylene glycol (with the molecular weight of 2000) into one part, and directly drying at 120 ℃ after aging and water washing; the other part is not added with the dispersing agent, is aged and washed by water, is washed for 3 times by absolute ethyl alcohol and is dried at 120 ℃. And carrying out dry pressing on the obtained powder, and carrying out isostatic pressing at 450MPa to obtain a biscuit. And carrying out pressureless sintering (without water vapor protection) on the obtained biscuit at a preset temperature, wherein the heat preservation time is 2 hours. The sintered density is shown in FIG. 3: the hydroxyapatite powder (A) not subjected to alcohol washing with the dispersant added has a higher sintered density than the powder (B) subjected to alcohol washing under the same conditions. Fig. 4 is a sintering curve of the hydroxyapatite powder (a) prepared by the present invention and a commercial hydroxyapatite powder (C, manufactured by university of sichuan) sintered after molding under the same conditions, and it can be seen that the sintering performance of the powder obtained by the method of the present invention is significantly superior to that of the commercial hydroxyapatite powder.

Example 2:

the precipitate obtained after the reaction of calcium nitrate and ammonium dihydrogen phosphate was divided into 11 parts. Five parts are added with dispersant polyethylene glycol (molecular weight is 2000) with the addition amount of 0.5, 1, 2, 3 and 4 percent (mass percentage relative to the precipitate, the same below), five parts are added with polyacrylic acid with the addition amount of 0.5, 1, 2, 3 and 4 percent, and the other part is not added with dispersant. After all precipitates were aged for 12 hours, washed with water and dried, and then dehydrated at 120 ℃/1 hour, the specific surface area of the powder was measured by the BET method, and the results showed that the specific surface area after addition of the dispersant was increased as compared to that without addition of the dispersant, as shown in table 1.

TABLE 1 relationship between the amounts of polyethylene glycol and polyacrylic acid added and the specific surface area of the powder

Polyethylene glycol (%)	0.5	1	2	3	4
Polyethylene glycol (%)	0.5	1	2	3	4	Specific surface area (m) of powder²/g)	85	101	103	104	107	105
Polyacrylic acid (%)	0.5	1	2	3	4	Specific surface area (m) of powder²/g)	85	101	103	104	107	105
Polyacrylic acid (%)	0.5	1	2	3	4	Specific surface area (m) of powder²/g)	85	100	102	105	104	103

Example 3:

dividing calcium nitrate and ammonium dihydrogen phosphate into 3 parts, adding polyethylene glycol into one part before reaction, adding polyethylene glycol into the other part before aging, and adding polyethylene glycol into the other part after aging, wherein the addition amount is 3%. After all the precipitates were water-washed and dried and then dehydrated at 120 c/1 hour, the specific surface area of the powder was measured by BET method, and the result showed that the specific surface area was the highest after adding the dispersant before aging, as shown in table 2.

TABLE 2 Effect of different time additions of dispersant on surface area

Time of addition	Before reaction	Before aging	After aging
Time of addition	Before reaction	Before aging	After aging	Specific surface area (m) of powder²/g)	100	107	95

Example 4:

dividing the precipitate obtained after the reaction of calcium nitrate and ammonium dihydrogen phosphate into two parts, and directly washing one part after aging at 70 ℃ for 12 hours; the other part was aged and then subjected to ultrasonic treatment for 1 hour and then washed with water. After drying, dehydration was carried out at 120 ℃/1 hour, and the specific surface area of the powder was measured by the BET method, and the results showed that the specific surface area of the powder subjected to ultrasonic treatment was significantly higher than that of the powder not subjected to ultrasonic dispersion, as shown in table 3.

TABLE 3 influence of ultrasonic Dispersion on powder specific surface area

Processing method	Direct water washing	Ultrasonic dispersion
Processing method	Direct water washing	Ultrasonic dispersion	Specific surface area (m) of powder²/g)	85	103

Example 5:

dividing the precipitate obtained after the reaction of calcium nitrate and ammonium dihydrogen phosphate into two parts, and aging one part at 70 ℃ for 12 hours and then washing with water; the other part is directly added with a dispersant for water washing without aging. And (3) calcining the powder obtained by drying and grinding the two precipitates obtained after water washing at 1100 ℃ for 2 hours. Figure 5 is an XRD spectrum of two powders after calcination. From the spectrum, it can be seen that: the aged hydroxyapatite powder does not undergo any decomposition under the condition of 1100 ℃/2h, and the unaged powder can undergo severe thermal decomposition.

Claims

1. A preparation method of nano hydroxyapatite powder capable of being sintered at low temperature comprises the processes of precipitation, aging, washing, dehydration and drying, and is characterized in that:

(1) selecting cheap calcium nitrate and ammonium dihydrogen phosphate which are sold on the market as raw materials, and controlling the concentration of the raw materials within the range of 1-2% mol/liter;

(2) dropwise adding ammonium dihydrogen phosphate into a calcium nitrate solution while mechanically stirring for reaction and precipitation, wherein the pH value iscontrolled to be 9-11 in the reaction process;

(3) the aging temperature is controlled to be 60-80 ℃, the aging time is 12-24 hours, and the agglomeration is reduced by adding a dispersing agent such as polyacrylic acid, polyethylene glycol and the like before aging or carrying out ultrasonic dispersion after aging;

(4) washing the precipitate with water;

(5) dehydrating and drying at 120 deg.C for 12 hr.

2. The process according to claim 1, wherein the dispersant is added before the aging of the precipitate, in an amount of 0.5 to 4% with respect to the precipitate, preferably in an amount of 2 to 3% by mass.

3. The process of claim 1, wherein the polyethylene glycol used as the dispersant has a molecular weight of 2000.

4. The process according to claim 1 or 2, wherein the washing of the precipitate is performed with distilled water instead of alcohol.

5. The preparation method according to claim 1 or 4, characterized in that the obtained hydroxyapatite powder can be directly formed and sintered without calcination, the sintering temperature is 950 ℃ and 1100 ℃, the temperature is kept for 2 hours, when the sintering temperature is 950 ℃, the relative density can reach 98%, and the average grain size is less than 140 nm.