JP4476393B2 - Synthesis confirmation method - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a synthesis confirmation method capable of knowing the degree of progress of synthesis in producing a composite such as an inorganic material typified by a ceramic material.
[0002]
[Prior art]
Conventionally, when a synthetic product is produced by chemical synthesis, in order to know whether or not the synthesis is completed, the pH of the product is measured.
[0003]
In the synthesis of ceramics, a slurry-like product is sampled in the middle of synthesis, and after drying the sample, it is fired to obtain a powder, and the composition of the powder is examined to determine whether the synthesis is completed. I was judging.
[0004]
However, the presence of impurities contained in the powder, in particular, the remaining unreacted substances (starting materials, etc.) and secondary reaction products cannot be detected with high accuracy. There was a drawback that it could not be grasped accurately.
[0005]
In some cases, the confirmation method based on pH is such that in the case of a neutralization reaction, the amount of change around pH 7 is abrupt, and even at the same pH, the composition differs depending on the raw material concentration, synthesis speed, synthesis temperature, etc. As a result, the progress of the synthesis cannot be accurately determined.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a synthesis confirmation method capable of knowing the progress of synthesis with high accuracy and high sensitivity.
[0007]
[Means for Solving the Problems]
Such an object is achieved by the present inventions (1) to ( 9 ) below.
[0008]
(1) Drop a phosphoric acid aqueous solution into calcium hydroxide and mix it to react calcium hydroxide and phosphoric acid to produce hydroxyapatite as a composite thereof , and confirm the progress of the synthesis. A method,
The sample containing the composite is molded into a shape having at least a detection surface, the molded body is fired, and CaO and tricalcium phosphate present on the detection surface of the obtained sintered body are used by X-ray diffraction. By analyzing the above, it is possible to know that the synthesis has not been completely completed when CaO is detected, and that the synthesis has passed when the tricalcium phosphate substance is detected. A composite confirmation method characterized by
In this method, it is possible to grasp the progress of synthesis by identifying substances other than the target compound (especially precipitates). In particular, since the substance precipitates at a high concentration, The degree can be known with high accuracy and high sensitivity.
[0009]
(2) The composition confirmation method according to (1), wherein the detection surface is a flat surface.
Thereby, the detection accuracy of a substance improves more.
[0010]
(3) The synthetic confirmation method according to (1) or (2), wherein the molded body is manufactured by compression molding.
As a result, the sintered body is densified, and precipitation (uneven distribution) on the detection surface is promoted, thereby further improving the substance detection accuracy.
[0011]
(4) The composition confirmation method according to (3), wherein the compression molding is performed by isotropic pressure.
Thereby, a dense molded body can be molded by a simple method.
[0012]
(5) The synthesis confirmation method according to the above (3) or (4), wherein the molding pressure is 1.0 to 2.5 ton / cm ² .
As a result, the compact can be densified, and the resulting sintered body becomes denser, so that precipitation on the detection surface is promoted, and thus the substance detection accuracy is further improved.
[0013]
(6) the detection plane, after compression molding is a surface which is flat by machining the above (3) to the synthesis confirmation method according to any one of (5).
Thereby, a detection surface, in particular, a flat detection surface can be easily formed.
[0014]
(7) The temperature during firing is at 1050-1400 ° C., and synthesis confirmation method according to any one of from the compound is (1) to less than thermal decomposition temperature (6).
Thereby, the detection accuracy of a substance improves more.
[0015]
(8) Surface roughness Ra of the detection surface of the sintered body, the synthesis confirmation method according to any one of from the above (1) to 0.01~120μm (7).
Thereby, the detection accuracy of a substance improves more.
[0016]
(9) Synthesis confirmation method according to any one of from the relative density of the sintered body is above (1) to a 95% to 98% (8).
Thereby, the sintered body is densified and the precipitation on the detection surface is promoted, so that the substance detection accuracy is further improved.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the synthesis confirmation method of the present invention will be described in detail.
[0024]
The present invention is a method for confirming the degree of progress of synthesis when producing a composite product by reacting a first raw material and a second raw material. The synthesized product (hereinafter referred to as “target synthesized product”) may be either an organic material or an inorganic material, but an inorganic material is preferable, and a ceramic material is particularly preferable because it is a substance having sinterability.
[0025]
Examples of the ceramic material include ceramics such as alumina, silica, titania, zirconia, yttria, and calcium phosphate compounds, nitride ceramics such as silicon nitride, aluminum nitride, titanium nitride, and boron nitride, and carbides such as graphite and tungsten carbide. Ceramics and other materials such as ferroelectric materials such as barium titanate, strontium titanate, PZT, PLZT, and PLLZT can be used.
[0026]
Here, the calcium phosphate compound is used in, for example, biomaterials, chromatography and the like, and specific examples thereof include apatites such as hydroxyapatite, fluorapatite, carbonate apatite, dicalcium phosphate, tricalcium phosphate, Examples include tetracalcium phosphate and octacalcium phosphate. Among these, hydroxyapatite is rich in biocompatibility and is used for biomaterials, in particular, for medical and dental fillers, artificial bones, and artificial tooth roots.
[0027]
In this embodiment, hydroxyapatite is typically described as the target compound. However, it goes without saying that the present invention is not limited to this.
[0028]
1. Synthesis of Hydroxyapatite Hydroxyapatite (HAp) is synthesized, for example, by dropping a phosphoric acid (H ₃ PO ₄ ) aqueous solution into calcium hydroxide (Ca (OH) ₂ ) and mixing in a container. The reaction is as shown in the following formula (I).
[0029]
10Ca (OH) ₂ + 6H ₃ PO ₄ → 2Ca ₅ (PO ₄ ) ₃ (OH) + 18H ₂ O (I)
[0030]
Here, if the synthesis is insufficient, a large amount of unreacted calcium hydroxide is present in the mixture (in the sample).
[0031]
Further, when the synthesis proceeds further, the produced hydroxyapatite (HAp) further reacts with phosphoric acid to produce tricalcium phosphate (TCP) as a secondary reaction product. The reaction is as shown in the following formula (II).
[0032]
3Ca ₅ (PO ₄ ) ₃ (OH) + H ₃ PO ₄ → 5Ca ₃ (PO ₄ ) ₂ + 3H ₂ O (II)
[0033]
In this embodiment, for example, the progress of the reaction is confirmed by detecting the amount of calcium hydroxide, hydroxyapatite, tricalcium phosphate, or the reaction product produced by firing.
[0034]
2. Molding (Manufacture of molded products)
A. Compression molding The mixture in the container is, for example, in the form of a slurry. At least a part of the mixture is taken out as a sample (sample) and formed into a desired shape. Note that the sample may be dried prior to molding. At this time, the sample may be powdered by granulation and drying in order to improve handling. The average particle diameter of this powder is, for example, about 10 to 30 μm, more preferably about 18 to 23 μm. The obtained powder may be pulverized by, for example, a jet mill or a turbo mill so as to easily obtain a denser compact, and may have an average particle size of 15 to 20 μm.
[0035]
As shown in FIG. 1A, the molding is performed by compression molding (in the case of powder, compacting). The compression molding may be performed by isostatic pressing (HIP, CIP) in which pressure is applied isotropically, for example, in one direction (one axis) in a molding die (not shown) like press molding. In the direction).
[0036]
When isotropically pressurized, as in isostatic pressing, a compact with a uniform density is obtained, so when sintered, substances other than the target compound are the same on all surfaces of the sintered body. Therefore, no matter how the detection surface is set, there is no difference in the degree of precipitation, and the precipitate detection accuracy is improved. In addition, in order to set it as the flat detection surface 3 with respect to such a molded object 1, machining, such as a cutting | disconnection, cutting, grinding, and grinding | polishing, can be given. In particular, it is preferable to perform such machining on a molded body compression-molded by isotropic pressure.
[0037]
Molding pressure in the compression molding is not particularly limited, but is preferably 1 ton / cm ² or more, more preferably 1.5~2.5ton / cm ^2, is about 1.9~2.1ton / cm ² Is more preferable. Thereby, since the density of the molded body 1 is increased and a more dense sintered body 2 is obtained, precipitation on the detection surface 3 is promoted, and detection accuracy is improved.
[0038]
Moreover, the temperature at the time of shaping | molding (molding temperature) is although it does not specifically limit, It is preferable that it is about 10-70 degreeC. Usually, it may be about room temperature.
[0039]
In the illustrated example, the molded body 1 has a cylindrical shape (disc shape). However, in the present invention, the shape, dimensions, and the like of the molded body 1 are not particularly limited, and have a detection surface 3. Any thing can be used.
[0040]
The detection surface 3 may be a surface having minute irregularities, but is preferably a flat surface as shown. This is because the detection accuracy of the precipitate (substance) can be improved.
[0041]
B. Other Molding Methods Molding of the sample may be performed by a method other than the compression molding. For example, a method of densifying a known powder, such as a method of unevenly distributing a solid content by centrifugation on a slurry sample, can be mentioned.
[0042]
3. Firing of the molded body The molded body 1 molded as described above is fired in, for example, a furnace to obtain a sintered body 2 (see FIG. 1B). When the molded body 1 is sintered, it shrinks and densifies. Presuming this densification, the target compound (hydroxyapatite) and other substances (CaO, TCP, etc.) are considered to have different firing rates. It is thought that it is deposited on the surface of the sintered body 2, particularly on the detection surface 3 so as to be extruded from
[0043]
The temperature during firing (firing temperature) is not particularly limited, but is preferably 1050 ° C. or higher and lower than the temperature at which the target compound is thermally decomposed. In the case of synthesizing hydroxyapatite, about 1100 to 1400 ° C is preferable, and about 1200 to 1250 ° C is more preferable. If the firing temperature is too low, the density of the sintered body 2 will not be high, and if the firing temperature is too high and thermal decomposition of the target compound occurs, the detection accuracy cannot be improved, and the degree of synthesis progress is judged. May be affected.
[0044]
Moreover, although baking time is not specifically limited, either about 0.1 to 6 hours are preferable and about 2 to 4 hours are more preferable when baking in the said temperature range.
The firing atmosphere is preferably in the air when the target compound is calcium phosphate.
[0045]
In the case of other target compounds, the firing atmosphere can be in a vacuum or under reduced pressure, or in an inert gas such as argon gas, helium gas, or nitrogen gas.
[0046]
The obtained sintered body 2 is preferably as dense as possible. When the density of the sintered body 2 is high, substances other than the target compound are likely to be precipitated (locally distributed) on the detection surface 3 and the detection accuracy is increased. Therefore, the relative density of the sintered body 2 is preferably 95% or more (= porosity is less than 5%), more preferably 97% or more.
[0047]
Moreover, although the property of the detection surface 3 of the sintered compact 2 is not specifically limited, It is preferable that surface roughness Ra is 120 micrometers or less, and it is more preferable that it is about 0.01-50 micrometers. When the surface roughness of the detection surface 3 is within this range, the detection accuracy in the analysis of the detection surface 3 described later can be improved.
[0048]
4). Analysis of the detection surface The detection surface 3 of the sintered body 2 obtained by firing is analyzed to analyze substances (particularly precipitates) present on the detection surface 3 (see FIG. 1C).
[0049]
The method for analyzing the substance is not particularly limited, and examples thereof include X-ray analysis, Auger analysis, ESCA analysis, and the like, and a method based on the X-ray diffraction method is particularly preferable. According to this method, each crystal can be identified by the diffraction pattern, and high-precision analysis can be easily performed.
[0050]
When producing hydroxyapatite (HAp) as the target compound, the reaction proceeds with the above formulas (I) and (II).
[0051]
When the analysis shows that CaO (calcium hydroxide reaction product by firing) is detected on the detection surface 3, the reaction of the formula (I) has not progressed sufficiently, and thus the synthesis is still completely completed. You can see that they are not.
[0052]
In the analysis, when a large amount of hydroxyapatite is detected on the detection surface 3 and other substances (impurities) such as calcium hydroxide and tricalcium phosphate (TCP) are hardly detected, the above formula (I) It can be seen that the reaction is complete.
[0053]
When the analysis results in detecting tricalcium phosphate (TCP), which is a secondary reaction product of the target compound, on the detection surface 3, the reaction of the above formula (II) has occurred, and thus the synthesis is completed. You can see that it has passed.
[0054]
【Example】
Next, specific examples of the present invention will be described.
[0055]
Example 1
Calcium hydroxide was hydrated, placed in a beaker, an aqueous phosphoric acid solution (phosphoric acid concentration 10%) was dropped into the beaker, and sufficiently stirred and mixed to synthesize hydroxyapatite (target compound).
[0056]
When the pH of the mixture (slurry) reached 7.7, a part of the slurry in the beaker was sampled, and this sample was spray-dried to obtain a powder having an average particle size of 23 μm.
[0057]
Next, this powder is solidified into a cylindrical shape with a compression molding machine, and then packed in a plastic bag and vacuum-packed, and is hydrostatically pressurized at room temperature (24 ° C.) at a pressure of ² ton / cm ² . Compression molding was performed to obtain a cylindrical molded body having a diameter of 15 mm and a height of 8 mm. Furthermore, the surface of the molded body was ground by a lathe process or the like, and further polished to form a flat detection surface.
[0058]
Next, the molded body was fired to obtain a sintered body. Firing was performed in the atmosphere at 1200 ° C. for 4 hours.
[0059]
The relative density of the obtained sintered body was about 98% (porosity 2%).
The surface roughness Ra of the detection surface of the sintered body was 0.7 μm.
[0060]
(Example 2)
A molded body was manufactured and fired in the same manner as in Example 1 except that the sample sampled when the pH of the mixture (slurry) reached 7.6 was used.
[0061]
The relative density of the obtained sintered body was about 97% (porosity 3%).
The surface roughness Ra of the detection surface of the sintered body was 0.7 μm.
[0062]
(Example 3)
A molded body was manufactured and fired in the same manner as in Example 1 except that the sample sampled when the pH of the mixture (slurry) reached 7.5 was used.
[0063]
The relative density of the obtained sintered body was about 97% (porosity 3%).
The surface roughness Ra of the detection surface of the sintered body was 0.7 μm.
[0064]
(Comparative Example 1)
Calcium hydroxide was hydrated, placed in a beaker, and an aqueous phosphoric acid solution (the same concentration as in Example 1) was dropped therein, and the mixture was sufficiently stirred and mixed to synthesize hydroxyapatite.
When the pH of the mixture (slurry) reached 8.0, a part of the slurry in the beaker was sampled, and this sample was spray-dried to obtain a powder having an average particle size of 23 μm.
[0065]
Next, this powder was fired. Firing was performed in air at 1200 ° C. for 30 minutes.
[0066]
(Comparative Example 2)
A calcined powder was obtained in the same manner as in Comparative Example 1 except that the sample sampled when the pH of the mixture (slurry) reached 7.6 was used.
[0067]
(Comparative Example 3)
A calcined powder was obtained in the same manner as in Comparative Example 1 except that the sample sampled when the pH of the mixture (slurry) reached 7.3 was used.
[0068]
<Analysis of components>
About each sintered compact of Examples 1-3, the component analysis (analysis) by the X-ray diffraction of a detection surface was performed using the X-ray-diffraction apparatus (the Rigaku company make, type | mold RINT2200). 2, 4 and 6 are graphs (X-ray diffraction patterns) showing the analysis results of the sintered bodies of Examples 1, 2 and 3, respectively.
[0069]
3, FIG. 5, and FIG. 7 are diagrams in which the vertical axis (strength) of FIG. 2, FIG. 4, and FIG.
[0070]
On the other hand, for each powder (sintered) of Comparative Examples 1 to 3, component analysis (analysis) by X-ray diffraction of the powder was performed using the same X-ray diffraction apparatus as described above. 8, 10 and 12 are graphs (X-ray diffraction patterns) showing the analysis results of the powders of Comparative Examples 1, 2, and 3, respectively. 9, FIG. 11, and FIG. 13 are diagrams in which the vertical axis (strength) of FIG. 8, FIG. 10, and FIG.
[0071]
<Discussion of analysis results>
As shown in FIGS. 2 and 3, in Example 1, in addition to the main peak of HAp, a main peak of CaO is observed at a diffraction angle 2θ = 37.36 (intensity: about 100). Therefore, in Example 1, it turns out that reaction of the said formula (I) has not fully advanced, and the synthesis | combination of a hydroxyapatite is not complete | finished completely yet.
[0072]
As shown in FIGS. 4 and 5, in Example 2, the HAp main peak is observed at 2θ = 31.77, and the CaO main peak and the TCP main peak are not observed. Therefore, in Example 2, it turns out that the synthesis | combination of a hydroxyapatite just complete | finished. That is, it can be seen that high-purity hydroxyapatite containing less than 0.3% of impurities such as CaO and TCP was synthesized.
[0073]
As shown in FIGS. 6 and 7, in Example 3, in addition to the main peak of HAp, a main peak of TCP is recognized at a diffraction angle of 2θ = 30.7 (intensity: about 1900). Therefore, in Example 3, it can be seen that the reaction of the formula (II) has occurred and the end of the synthesis of hydroxyapatite has been passed.
[0074]
On the other hand, in Comparative Example 1, the degree of progress of synthesis is not advanced from Example 1 due to the pH at the time of sampling, that is, the main peak of CaO should be clearly recognized from Example 1, but in actuality, In Example 1, the main peak of CaO is hardly recognized in FIG. 8 as well as in FIG.
[0075]
In Comparative Example 2 in which the degree of progress of synthesis is estimated to be the same as in Example 2, the main peak of HAp is recognized in both FIGS. 10 and 11, and the main peak of CaO and the main peak of TCP are not recognized.
[0076]
In Comparative Example 3, the degree of progress of synthesis is higher than that in Example 3 from the pH at the time of sampling. In other words, the main peak of TCP should be clearly recognized from Example 3. In FIG. 12, the TCP main peak is not recognized, and in the enlarged FIG. 13, the TCP main peak is slightly recognized (intensity: about 40).
[0077]
As can be seen from the above results, in Examples 1 to 3 of the present invention, the progress of the synthesis of hydroxyapatite can be accurately grasped, whereas in Comparative Examples 1 to 3, almost no analysis results are obtained. There is no difference, and the progress of the synthesis of hydroxyapatite cannot be accurately grasped.
[0078]
【The invention's effect】
As described above, according to the present invention, the progress of synthesis of the target compound can be known with high accuracy and high sensitivity, and the operation is extremely simple.
Thereby, for example, a high-purity target compound can be produced.
[Brief description of the drawings]
FIG. 1 is a diagram showing the steps of a synthesis confirmation method of the present invention.
2 is a graph showing the result of component analysis by X-ray diffraction in Example 1. FIG.
FIG. 3 is a graph showing the result of component analysis by X-ray diffraction in Example 1 (the vertical axis is enlarged to 10).
4 is a graph showing the result of component analysis by X-ray diffraction in Example 2. FIG.
5 is a graph showing the result of component analysis by X-ray diffraction in Example 2 (the vertical axis is enlarged to 10). FIG.
6 is a graph showing the result of component analysis by X-ray diffraction in Example 3. FIG.
7 is a graph showing the result of component analysis by X-ray diffraction in Example 3 (the vertical axis is enlarged to 10). FIG.
8 is a graph showing the result of component analysis by X-ray diffraction in Comparative Example 1. FIG.
9 is a graph showing the result of component analysis by X-ray diffraction in Comparative Example 1 (the vertical axis is enlarged to 10). FIG.
10 is a graph showing the result of component analysis by X-ray diffraction in Comparative Example 2. FIG.
11 is a graph showing the result of component analysis by X-ray diffraction in Comparative Example 2 (the vertical axis is enlarged to 10). FIG.
12 is a graph showing the result of component analysis by X-ray diffraction in Comparative Example 3. FIG.
13 is a graph showing the results of component analysis by X-ray diffraction in Comparative Example 3 (the vertical axis is enlarged to 10). FIG.
[Explanation of symbols]
1 Molded body 2 Sintered body 3 Detection surface

Claims (9)

This is a method of confirming the degree of synthesis when a hydroxyapatite is produced by reacting calcium hydroxide and phosphoric acid by dropping and mixing an aqueous solution of phosphoric acid into calcium hydroxide. And
The sample containing the composite is molded into a shape having at least a detection surface, the molded body is fired, and CaO and tricalcium phosphate present on the detection surface of the obtained sintered body are used by X-ray diffraction. By analyzing the analysis, it can be found that when CaO is detected, the synthesis has not been completely completed, and when the tricalcium phosphate substance is detected, it can be known that the synthesis has passed. Characteristic composition confirmation method.   The method according to claim 1, wherein the detection surface is a flat surface.   The synthesis confirmation method according to claim 1, wherein the molded body is manufactured by compression molding.   The composition confirmation method according to claim 3, wherein the compression molding is performed by isotropic pressure. The synthesis confirmation method according to claim 3 or 4, wherein the molding pressure is 1.0 to 2.5 ton / cm ² . The detection surface is the synthesis confirmation method according to any one of claims 3 to 5 after compression molding is a surface which is flat by machining. The temperature during firing is at 1,050 to 1400 ° C., and synthesis confirmation method according to any one of the compounds is claims 1 is less than thermal decomposition temperature 6. Surface roughness Ra of the detection surface of the sintered body, the synthesis confirmation method according to any one of claims 1 to 7 is 0.01～120Myuemu. Synthesis confirmation method according to any one of the sintered to a relative density of sintered body is no claim 1 wherein 95% to 98% 8.

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