JP2007126689A - Functional noble metal product and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a functional noble metal product capable of exhibiting an effect of promoting the circulation and flow of blood while obviating the necessity of crystalline silica having carcinogenicity and also to provide its manufacturing method. <P>SOLUTION: The functional noble metal product comprises: a noble metal selected from the group consisting of gold, silver, platinum and alloys thereof; and amorphous silica particles dispersed in a matrix of the noble metal. This functional noble metal product can be obtained by preparing mixed powder particles of noble metal powder particles and amorphous silica particles weighed in a prescribed proportion, filling a die with the mixed powder particles and then carrying out heating and sintering in this state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a functional noble metal product having a blood circulation / blood flow promoting effect and containing no crystalline silica having carcinogenicity to a human body and a method for producing the same.

  Precious metals such as gold, platinum, white gold, and silver are widely used in jewelry, ornaments, arts and crafts, watches, rings, necklaces, pendants, tableware, etc. due to their sparkle. Recently, there are known precious metals whose main purpose is to promote physical health and therapeutic / healing effects, and health-oriented precious metals that have secondary effects.

For example, Japanese Patent Application Laid-Open No. 2000-144283 (Patent Document 1) proposes a jewelry that exhibits a far-infrared effect by containing appropriate amounts of germanium and indium in silver. Japanese Patent Application Laid-Open No. 11-56425 (Patent Document 2) proposes a noble metal jewelry containing ceramics that generates negative ions. Furthermore, Japanese Unexamined Patent Application Publication No. 2002-283491 (Patent Document 3) proposes a decorative article in which an ore that generates negative ions is applied to the surface.
JP 2000-144283 A JP-A-11-56425 JP 2002-283491 A

In the noble metal products disclosed in the above-described prior art, silica (silicon oxide: SiO ₂ ) particles or ores containing the main component thereof (for example, Guiyang) are used as one of the substances having far-infrared effect and negative ion generation effect. Stone, tourmaline, Io stone, barley stone, silica black, Inada stone, Ono ore). Any silica used is crystalline silica.

  According to the International Agency for Research on Cancer (IARC), it has been reported that "crystalline silica is carcinogenic to the human body (Group 1)". For this reason, the use of crystalline silica may be restricted against the background of the recent asbestos problem. On the other hand, amorphous (non-condensed) silica is classified into Group 3 in the survey conducted by the same institution, and no carcinogenicity to the human body has been pointed out.

  In conventional noble metal products, there is a concern about the influence on the human body as a carcinogenic substance when handling crystalline silica as a raw material in the process of producing the noble metal or the noble metal product.

  An object of the present invention is to provide a functional noble metal product capable of exhibiting blood circulation and blood flow effects without containing any carcinogenic crystalline silica and a method for producing the same.

  The functional noble metal product according to the present invention comprises a noble metal selected from the group consisting of gold, silver, platinum and alloys thereof, and amorphous silica particles dispersed in the base of the noble metal.

  Here, as used herein, the term “functional precious metal product” includes products such as jewelry, arts and crafts, watches, rings, necklaces, pendants, tableware using precious metals. However, it should be understood as including precious metal materials as materials for making such products.

  Preferably, the content of the amorphous silica particles contained in the base of the noble metal is 1% or more and 20% or less in volume fraction, and more preferably 3% or more and 12% or less in volume fraction.

  Preferably, the silica content in the amorphous silica particles is 90% or more on a weight basis, and more preferably 95% or more on a weight basis.

  Preferably, the amorphous silica particles have a particle size of 50 nanometers or more and 500 microns or less, and more preferably 500 nanometers or more and 200 microns or less.

  The functional noble metal product can be used as the entire article or the entire material, or can be used as a part of the article.

The manufacturing method of the noble metal product according to the present invention in one aspect includes the following steps.
(A) A step of preparing powder particles of noble metal selected from the group consisting of gold, silver, platinum, and alloys thereof, and amorphous silica particles.
(B) A step of weighing the noble metal powder particles and the amorphous silica particles at a predetermined ratio.
(C) A step of mixing the noble metal powder particles and the amorphous silica particles in a predetermined ratio to obtain mixed powder particles.
(D) A step of dispersing amorphous silica particles in a precious metal substrate by heating and sintering the mixed powder particles filled in a mold.

  Preferably, when the melting point of the noble metal powder particles is Tm, the heating and sintering temperature for the mixed powder particles is in the range of 0.9 Tm to 1.2 Tm.

  In one embodiment, the mixed powder particles are heated and sintered while applying pressure to the mixed powder particles in the mold. In this case, preferably, when the melting point of the noble metal powder particles is Tm, the heating and sintering temperature for the mixed powder particles is in the range of 0.8 Tm to 1.2 Tm.

  Preferably, the mixed powder particles are heated and sintered in a vacuum or in an inert gas atmosphere.

    The manufacturing method of the noble metal product according to the present invention in another aspect includes the following steps.

(E) A step of preparing powder particles of noble metal selected from the group consisting of gold, silver, platinum, and alloys thereof, and amorphous silica particles.
(F) A step of weighing the noble metal powder particles and the amorphous silica particles at a predetermined ratio.
(G) A step of mixing the noble metal powder particles and the amorphous silica particles in a predetermined ratio to obtain mixed powder particles.
(H) A step of producing a powder compact by pressurizing the mixed powder particles after filling the mold.
(I) A step of dispersing amorphous silica particles in a base material of a noble metal by subjecting the above-mentioned powder solidified body to hot plastic processing to make it dense.

  Preferably, the green compact is heated in a vacuum or in an inert gas atmosphere prior to the above hot plastic working. Preferably, when the melting point of the noble metal powder particles is Tm, the heating temperature of the above-mentioned powder compact is within a range of 0.5 Tm to 1.0 Tm.

  The hot plastic working for the compacted body is, for example, extrusion, rolling, forging, swaging, pressing or drawing.

  The significance and operational effects of the above defined contents will be described in detail below.

  The present invention provides a functional noble metal product that exhibits a blood circulation / blood flow promoting effect without containing any carcinogenic crystalline silica and a method for producing the same. Specifically, the use of amorphous silica particles as the starting raw material powder prevents adverse effects on the human body in the production process of noble metals and noble metal products.

(1) Content of amorphous silica particles in functional precious metal product In the functional precious metal product according to the present invention, amorphous (non-crystalline) is present in the base of precious metal selected from the group consisting of gold, silver, platinum and their alloys. Quality) Silica (SiO ₂ ) particles are dispersed. A preferable content of the amorphous silica particles is 1% or more and 20% or less in terms of volume fraction. When the content is less than 1%, the blood circulation / blood flow promoting effect of the functional precious metal product is not sufficiently exhibited. On the other hand, when the content rate exceeds 20%, the toughness of the functional noble metal material is lowered, and thus the material is cracked, cracked, broken or the like during the plastic processing in the subsequent process.

  A more preferable content of amorphous silica particles is 3% or more and 12% or less in terms of volume fraction. By making the content rate 3% or more, a more remarkable blood circulation / blood flow effect appears. Even if the amorphous silica particles are added in excess of 12%, the blood circulation / blood flow effect is not significantly improved, and the appearance of the noble metal may be impaired by the silica particles added in a large amount.

(2) Silica content (silica purity) in amorphous silica particles
Preferably, the silica content in the amorphous silica particles is 90% or more on a weight basis. When the silica content is less than 90%, the above blood circulation / blood flow effect cannot be sufficiently obtained even if the amorphous silica particles are dispersed in the noble metal substrate. On the other hand, as impurities, besides oxides such as alumina (Al ₂ O ₃ ), potassium oxide (K ₂ O), iron oxide (Fe ₂ O ₃ ), calcium oxide (CaO), magnesium oxide (MgO), Carbon (C) and the like are included, but these have very little influence on the human body and are not a problem.

  A more preferable silica content is 95% or more. When silica particles with few impurities and high purity are used, a functional noble metal product having the above-mentioned blood circulation / blood flow effect can be produced by adding less silica particles. As a result, there is an advantage that plastic workability such as forging and rolling of the noble metal material is improved.

(3) Particle size of amorphous silica particles The preferable particle size of amorphous silica particles is 50 nanometers or more and 500 microns or less. If the particle diameter is less than 50 nanometers, silica particles aggregate and form large defects in the substrate, so that the strength and plastic workability of the functional noble metal product are lowered. On the other hand, when the particle diameter exceeds 500 microns, the coarse silica particles similarly become defects or stress concentration portions.

  The particle diameter of the amorphous silica particles is more preferably 500 nanometers or more and 200 microns or less. If the particle diameter is 500 nanometers or more, the above-mentioned problem of aggregation does not occur, the silica particles are uniformly dispersed in the substrate, and the price of the silica particles is reduced, so that it is excellent in terms of economy. On the other hand, if the particle diameter is 200 microns or less, there is no defect or stress concentration part, and the mixing property with the raw material powder constituting the substrate is good, so that the particle dispersibility in the substrate is good. improves.

  There is no provision for the purity of noble metal powders composed of gold, silver, platinum or their alloys that constitute the base of functional noble metal products. There is no particular problem as long as the purity is within a range that does not impair the appearance of jewelry or decorative items such as rings and necklaces. The particle diameter of the noble metal powder is not particularly limited. However, in the method for producing a noble metal product according to the present invention, the powder for a substrate having a size in the range of about 100 microns to 3 mm is formed and solidified. Is preferable in terms of heat resistance and sinterability.

  Amorphous silica particles can be obtained by various production methods. For example, there are a method of pulverizing quartz glass to obtain a powder having a predetermined particle diameter described above, and a method of extracting amorphous silica contained in biomass such as wood and agricultural products by acid treatment and baking. Furthermore, fine amorphous silica particles generated when a high melting point iron-based compound such as ferromolybdenum (FeMo) or ferrosilicon (FeSi) is produced can also be used.

(4) Production method of functional noble metal product (a) Preparation of input raw material As a starting material, precious metal powder particles selected from the group consisting of gold, silver, platinum and their alloys and amorphous silica particles are prepared. Both are weighed in the above-mentioned predetermined appropriate ratio, and this is uniformly mixed by a conventional dry mixing method using a ball mill, a V-type mixer, a rocking mill or the like to obtain a mixed powder. This mixed powder is used as the raw material powder.

(B) In-mold sintering method Amorphous silica particles are precious metal by heating and sintering in a vacuum or in an inert gas atmosphere, preferably in a state where the raw material powder of (a) is filled in the mold. To produce functional precious metal products dispersed in the substrate. As the material of the mold, carbon is mainly used in terms of heat resistance, but depending on the temperature condition, steel material or carbide can be applied.

  Regarding the heating and sintering conditions, assuming that the melting point of the noble metal powder particles used is Tm, the temperature of the raw material powder in the mold during heating and sintering is preferably 0.9 Tm to 1.2 Tm. When the heating / sintering temperature is less than 0.9 Tm, a sufficient diffusion phenomenon does not proceed between the noble metal powder particles, so that the strength of the material after sintering becomes low. As a result, defects such as cracks, cracks, and defects occur in the noble metal material in the rolling process and forging process in the subsequent process. Heating and sintering are preferably performed in a vacuum or in an inert gas atmosphere in order to suppress a decrease in sintering phenomenon between particles due to oxidation of noble metal powder particles.

  When the heating and sintering temperature exceeds 1.2 Tm, a liquid phase is generated in the entire noble metal powder particles, and the viscosity thereof is lowered, so that a problem arises that the noble metal melted out from the gaps in the mold. Note that a liquid phase is generated on the surface of the noble metal powder particles from the time when the heating and sintering temperature reaches the melting point Tm of the noble metal powder particles, but the liquid phase does not completely transform into the powder and the liquid phase diffusion on the surface. Thus, a sintered body can be obtained while maintaining the shape. In other words, a good noble metal sintered material using such a liquid phase diffusion phenomenon can be obtained when the heating / sintering temperature is Tm or more and 1.2 Tm or less.

(C) In-mold pressurization / sintering method In the state where the input raw material powder of (a) is filled in the mold, preferably heating and firing simultaneously while applying pressure in a vacuum or in an inert gas atmosphere. As a result, a functional precious metal product in which amorphous silica particles are dispersed in a precious metal substrate is produced. As the material of the mold, carbon is mainly used in terms of heat resistance, but depending on the temperature condition, steel material or carbide can be applied.

  Regarding the heating / sintering conditions, if the melting point of the noble metal powder particles used is Tm, the temperature of the raw material powder in the mold when heated and sintered while being pressurized in the mold is preferably 0.8 Tm to 1.2 Tm. Here, unlike (b) above, by applying pressure to the noble metal particles during the heating process, the diffusion phenomenon between the particles is more likely to proceed. Therefore, if the heating / sintering temperature is 0.8 Tm or more, a good noble metal sintered material can be obtained. On the other hand, as for the upper limit value of the heating / sintering temperature, when it exceeds 1.2 Tm, a liquid phase is generated in the entire noble metal powder particles, and the viscosity thereof is lowered. There arises a problem that the melted noble metal oozes out from.

(D) Powder molding / hot plastic working method After the raw material powder of the above (a) is filled in a mold, a predetermined pressure is applied and the raw material powder is compacted. The obtained powder solidified body is heated in an inert gas atmosphere, and immediately subjected to hot plastic working to be densified, thereby producing a functional noble metal product in which amorphous silica particles are dispersed in the substrate. As the material of the mold, in order to produce a denser compacted solidified body, a steel material or carbide that can apply a high pressure is used.

  Regarding the heating / sintering conditions, assuming that the melting point of the precious metal powder particles to be used is Tm, the temperature of the raw material powder in the mold at the time of heating / sintering is preferably 0.9 Tm to 1.2 Tm. Further, as a hot plastic working method, an extruding process, a rolling process, a forging process, a swaging process, a pressing process or a drawing process is applied to further refine the noble metal material.

  First, when the input raw material powder is pressed with a mold, it is usually desirable to apply a molding pressure of 400 MPa or more in order to obtain a dense compacted body. On the other hand, the upper limit of the molding pressure is usually 1000 MPa or less. When the molding pressure exceeds 1000 MPa, mold defects, adhesion (seizure) phenomenon between noble metal powder particles and the mold wall surface occur.

  Next, heating and sintering of the obtained powder solidified body is preferably performed in a vacuum or in an inert gas atmosphere, which suppresses a decrease in sintering phenomenon between particles due to oxidation of noble metal powder particles. Because. Regarding heating and sintering conditions, 0.9 Tm to 1.2 Tm are selected as appropriate conditions for obtaining a good precious metal sintered material for the same reason as in (b) above.

  By applying extruding, rolling, forging, swaging, pressing, drawing, etc. as the subsequent hot plastic working method, the relative density of the precious metal sintered material is densified to 99% or more. In order to reduce the deformation resistance of the precious metal sintered material and facilitate the processing in each processing, it is necessary to heat the precious metal sintered material again before processing. The heating temperature at that time is preferably 0.5 Tm to 1.0 Tm. When the heating temperature before hot plastic working is less than 0.5 Tm, the deformation resistance of the raw material is not sufficiently low, and thus the noble metal material is cracked, cracked, broken, etc. during the plastic working process. On the other hand, if the heating temperature before the hot plastic processing exceeds the melting point Tm of the noble metal powder particles, the processing heat generated in the hot plastic processing process is added, so that the liquid phase of the material becomes prominent and the material melts. Problem arises.

(E) Secondary processing of functional precious metal material The functional precious metal obtained by the production methods (b) to (d) above is again heated in an inert gas atmosphere and immediately subjected to hot plastic working. Thus, a functional noble metal product in which amorphous silica particles are dispersed in the substrate is produced. Here, it aims at further densifying the precious metal sintered material and forming the shape of the final product by the above hot plastic working.

  By applying extruding, rolling, forging, swaging, pressing, drawing, etc. as the hot plastic working method, the relative density of the precious metal sintered material is densified to 99% or more. In order to reduce the deformation resistance of the precious metal sintered material and facilitate the processing in each processing, it is necessary to heat the precious metal sintered material again before hot plastic working. The heating temperature at that time is 0.5 Tm to 1.0 Tm. The reason for setting the heating temperature is the same as (d) above.

(5) Use of functional noble metal product The functional noble metal product having the effect of promoting blood circulation and blood flow may be used as an article or the whole material, or may be used as a part of the article.

  The uses of functional noble metal products are listed below as an example.

  a) A material mainly composed of precious metals.

  b) Jewelery and ornaments.

  c) Art crafts.

  d) Writing instruments such as fountain pens and ballpoint pens.

  e) Accessories that come into contact with the body, such as key holders, nets, watches, watch belts, glasses frames, glasses chains, cellphone straps, dog tags, and pet jewelry.

  f) Underwear fittings, clothing fittings, sandal fittings, shoe fittings, footwear fittings, belt fittings, etc.

  g) Bedding and clothing that come into contact with the body, such as bedclothes, pillows, mufflers, gloves, hats, hair bands, supporters, underwear and clothes.

  As raw materials constituting the base of the noble metal material, 18 gold powder, silver powder, platinum powder, and white gold powder having an average particle diameter shown in Table 1 were prepared.

  As the amorphous silica particles, a sample obtained by washing and hydrolyzing rice husks in a dilute hydrochloric acid aqueous solution and firing the husks at 1000 ° C. for 5 minutes was pulverized to a predetermined particle size with a ball mill. The purity of the silica powder was 99.6%. The particle diameter was adjusted to the value shown in Table 1 by controlling the grinding conditions.

  Each base constituent raw material and amorphous silica particles were dry-mixed at a ratio shown in Table 1 (indicated by volume fraction) using a V-type mixer.

  When each input raw material powder is sintered and solidified, each raw material powder is filled in a carbon mold having an inner diameter of 30 mmΦ using a discharge plasma sintering apparatus, and a pressure of 50 MPa is applied to the raw material powder in a vacuum atmosphere from room temperature. The temperature was raised to a predetermined temperature shown in Table 1, and maintained at that temperature for 15 minutes. Thereafter, the furnace was cooled, and a sintered body sample having a diameter of about 30 mm and a thickness of about 3 to 4 mm was taken out.

  The obtained noble metal sintered material was subjected to twin roll rolling to produce a functional noble metal material having a thickness of 0.3 mm.

  In addition, the heating temperature of the sample at the time of rolling was 0.6 to 0.7 Tm when the melting point of the substrate was Tm, and after heating at that temperature for 5 minutes, the rolling was performed immediately.

  About each sample, the occurrence condition of a crack, a crack, etc. was evaluated by external observation. In addition, in order to evaluate the blood circulation / blood flow promoting effect, each sample was placed on the palm, and after 5 minutes, the temperature distribution of the entire palm was measured by thermography, and the temperature change of the fingertip before and after placing the sample was investigated. The evaluation results are summarized in Table 1.

  As shown in Table 1, sample No. 1 to 17, since the amorphous silica particles have an appropriate particle size and content and are pressurized and heated at an appropriate temperature, the amorphous silica particles are uniformly dispersed in the substrate. A noble metal composite was obtained. Furthermore, by rolling the composite material under appropriate conditions, a functional noble metal product that is good as a decorative product in terms of appearance free from cracks, cracks, and defects was obtained. The blood circulation and blood flow promoting effects were also confirmed by the fact that the temperature rise at the fingertips could be demonstrated.

  On the other hand, sample No. which is a comparative example. In 18-26, the following problems occurred. Sample No. In No. 18, since the maximum silica particle diameter was as large as 800 μm, cracks and cracks occurred in the material during the rolling process. Sample No. 19 and sample no. In No. 25, since the minimum silica particle diameter was as small as 35 nm, the particles aggregated and existed in spots, which was not preferable in terms of appearance as a decorative article or jewelry. Sample No. 20 and sample no. In No. 21, since the silica content was small, a sufficient blood circulation / blood flow promoting effect could not be obtained. Sample No. 22 and sample no. In No. 26, since the silica content was higher than 20%, cracking / cracking occurred in the raw material during the rolling process. Sample No. In No. 23, since the heating / sintering temperature was as low as 0.7 Tm, the strength of the precious metal sintered material was lowered, and cracks / cracks were generated in the rolling process. Sample No. In No. 24, since the heating / sintering temperature was as high as 1.3 Tm, the liquid phase of noble metal (silver) flowed out of the mold, and a good sample material could not be obtained.

  A silver powder having an average particle size of 220 μm was prepared as a raw material constituting the base of the noble metal material. Amorphous silica particles having a maximum particle size of 320 μm and a minimum particle size of 3.2 μm were used. Silver powder and silica particles were weighed and mixed so that the silica particle content was 10% by volume.

  The obtained mixed powder is filled in a carbon mold having an inner diameter of 30 mmΦ, and the temperature is raised in an argon gas atmosphere while the upper and lower sides are held down by a similar carbon disk-shaped jig (outer diameter 29.8 mmΦ, thickness 5 mm). -Heated and held. The heating rate was 1 ° C./second, and the heating and holding temperature was as shown in Table 2. Tm means the melting point of the silver powder used. The holding time was 15 minutes for all.

  After the heating, the sample was gradually cooled to room temperature in a furnace, and then a sintered body sample having a diameter of about 30 mm and a thickness of about 3 mm was taken out.

  The obtained precious metal sintered material was subjected to twin roll rolling to produce a functional precious metal material having a thickness of 0.4 mm. In addition, the heating temperature of the sample at the time of rolling was set to 0.7 Tm when the melting point of the substrate was Tm, and after heating at that temperature for 10 minutes, the rolling was performed immediately.

  About each sample, the occurrence condition of a crack, a crack, etc. was evaluated by external observation. The results are shown in Table 2. As for the precious metal sintered material, as in Example 1, the temperature distribution of the entire palm was measured by thermography 5 minutes after placing the sample on the palm, and the temperature change of the fingertip before and after placing the sample was investigated. .

  Sample No. which is an example of the present invention. In Nos. 27 to 31, the diffusion phenomenon sufficiently progressed between the silver powder particles by maintaining the raw material powder in the mold at an appropriate heating temperature. As a result, a functional noble metal material excellent in appearance as a decorative product was obtained in which no cracks or cracks were generated in the subsequent rolling process. Further, as a result of temperature measurement by thermography, a temperature increase of 8.0 to 8.4 ° C. could be demonstrated at the fingertip, and the blood circulation / blood flow promoting effect of these functional precious metals was confirmed.

  On the other hand, sample No. which is a comparative example. For 32-35, the following problems occurred. Sample No. 32 and sample no. In No. 33, since the heating and holding temperature was lower than 0.8 Tm, sufficient sintering did not proceed, and the strength of the silver powder sintered body was lowered. As a result, cracks occurred in the material during the rolling process. Sample No. 34 and sample no. In No. 35, since the heating and holding temperature exceeded 1.2 Tm, the liquid phase of silver flowed out of the mold and a good sample material could not be obtained.

  The raw material powder (base: silver powder, amorphous silica content: 10% by volume) used in Example 2 was filled into a SKD11 mold (inner diameter: 30 mmΦ) at room temperature, and an outer diameter of 30. A compacted green body having a diameter of 1 mm and a thickness of 3.2 mm was produced.

The obtained compacted solid body was held in a vacuum atmosphere (10 ⁻³ torr) under the temperature conditions shown in Table 3 for 30 minutes, and then cooled to room temperature in the same atmosphere to have a diameter of about 30 mm and a thickness of about 3 mm. A silver sintered material in which silica particles were dispersed was prepared. Tm means the melting point of the silver powder used.

  The obtained disc-shaped sintered material was heated and held at the temperature shown in Table 3 for 10 minutes, and then immediately put into a coin-shaped mold having an inner diameter of 31 mmΦ, and a surface pressure of 800 MPa was applied in the upper and lower punch directions to Densification was performed by forging. The sintered material was heated in an argon gas atmosphere, and the forging die temperature was 500 ° C.

  Sample No. which is an example of the present invention. In 36 to 40, an appropriate heating and holding temperature was applied in the sintering process, and the heating temperature of the sintered material before hot forging was also within an appropriate range. Therefore, in any sample after forging, a fine functional noble metal material having a good appearance and a relative density of 99.9% or more is obtained in terms of appearance without cracks, cracks and damage. It was.

  On the other hand, sample No. which is a comparative example. In 41-46, the following problems occurred. Sample No. 41 and sample no. In No. 42, since the heating and holding temperature in the sintering process was less than 0.8 Tm, sufficient sintering did not proceed, and the strength of the silver powder sintered body was lowered. As a result, cracks occurred in the material during the forging process. Sample No. 43 and Sample No. In No. 44, since the heating and holding temperature in the sintering process exceeded 1.2 Tm, the liquid phase of silver flowed out from the mold, and a good sample material was not obtained, so that forging was not performed. Sample No. In No. 45, since the temperature before hot forging was below 0.5 Tm, the deformation resistance was large, and cracks and cracks occurred in the sintered material during forging. Sample No. In No. 46, since the temperature before hot forging exceeds Tm, a liquid phase was generated during forging and a good forging material could not be obtained.

  Amorphous silica powder having the silica purity shown in Table 4 was prepared by adjusting the concentration of dilute hydrochloric acid and the immersion time when the rice husk was acid-treated. In all cases, the particle diameter was in the range of 150 nm to 280 μm. Further, silver powder having an average particle diameter of 315 μm was prepared as a raw material constituting the base of the noble metal material. Both powders were weighed and mixed so that the silica powder content was 10% in terms of volume fraction.

  When the obtained mixed powder is sintered and solidified, each raw material powder is filled into a carbon mold having an inner diameter of 30 mmΦ using a discharge plasma sintering apparatus in the same manner as in Example 1, and the raw material powder is pressurized to 50 MPa in a vacuum atmosphere. The temperature was raised from room temperature to 0.9 Tm (Tm: melting point of the used silver powder) and maintained at that temperature for 15 minutes. Thereafter, furnace cooling was performed, and a sintered body sample having a diameter of about 30 mm and a thickness of about 3 mm was taken out.

  In order to evaluate the blood circulation / blood flow promoting effect, each sintered body sample was placed on the palm, and after 5 minutes, the temperature distribution of the entire palm was measured by thermography, and the temperature change of the fingertip before and after placing the sample was investigated. The evaluation results are shown in Table 4.

  Sample No. which is an example of the present invention. In 47 to 51, amorphous silica particles having a purity of 90% or more are used. In these samples, as a result of temperature measurement by thermography, a temperature increase of 7.0 to 8.5 ° C. could be demonstrated at the fingertip. Thereby, in the functional noble metal material using the amorphous silica powder having an appropriate purity, a sufficient blood circulation / blood flow promoting effect was confirmed.

  On the other hand, it is a comparative example and sample no. In 52 to 55, silica particles having a purity of less than 90% are used. As a result, it was confirmed that the blood circulation / blood flow promoting effect was small as compared with the examples of the present invention.

  Sample No. described in Example 1 When the functional noble metal material No. 8 (Example of the present invention) was used for a spectacle frame, pain due to stiff shoulders was resolved. When the same material was used for the belt buckle, the back pain was resolved. Furthermore, when the same material was pulverized into powder and sewed onto a muffler and gloves, the heat retaining effect was confirmed. Thus, the same effect | action and effect were confirmed by applying to the products and articles | goods other than jewelry / decoration using the blood circulation / blood flow promotion effect which the functional noble metal material of this invention has.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the thing of embodiment mentioned above. Various modifications and variations can be made to the above-described embodiment within the same range or equivalent range as the present invention.

The present invention can be advantageously used as a functional noble metal product that exhibits blood circulation and blood flow promoting effects.

Claims (17)

A precious metal selected from the group consisting of gold, silver, platinum and their alloys;
A functional noble metal product comprising amorphous silica particles dispersed in the noble metal substrate. The functional precious metal product according to claim 1, wherein the content of the amorphous silica particles contained in the base of the precious metal is 1% or more and 20% or less in terms of volume fraction. The functional precious metal product according to claim 1, wherein the content of the amorphous silica particles contained in the base of the precious metal is 3% or more and 12% or less in terms of volume fraction. The functional noble metal product according to any one of claims 1 to 3, wherein a silica content in the amorphous silica particles is 90% or more on a weight basis. The functional noble metal product according to any one of claims 1 to 3, wherein a silica content in the amorphous silica particles is 95% or more by weight. The functional noble metal product according to any one of claims 1 to 5, wherein a particle diameter of the amorphous silica particles is 50 nanometers or more and 500 microns or less. The functional noble metal product according to any one of claims 1 to 5, wherein the amorphous silica particles have a particle diameter of 500 nanometers or more and 200 microns or less. An article comprising the functional noble metal product according to any one of claims 1 to 7. Preparing powder particles of a noble metal selected from the group consisting of gold, silver, platinum and their alloys, and amorphous silica particles;
A step of weighing the noble metal powder particles and the amorphous silica particles at a predetermined ratio;
Mixing the noble metal powder particles and the amorphous silica particles in a predetermined ratio to obtain mixed powder particles, and heating and sintering the mixed powder particles in a mold filled state, And a step of dispersing silica particles in the base of the noble metal. The method for producing a functional precious metal product according to claim 9, wherein the mixed powder particles are heated and sintered in a vacuum or in an inert gas atmosphere. The method for producing a functional noble metal product according to claim 9 or 10, wherein the mixed powder particles are heated and sintered while applying pressure to the mixed powder particles in the mold. The method for producing a functional noble metal product according to claim 9 or 10, wherein a heating and sintering temperature for the mixed powder particles is within a range of 0.9 Tm to 1.2 Tm, where Tm is a melting point of the noble metal powder particles. . The method for producing a functional noble metal product according to claim 11, wherein a heating and sintering temperature for the mixed powder particles is in a range of 0.8 Tm to 1.2 Tm, where Tm is a melting point of the noble metal powder particles. Preparing powder particles of a noble metal selected from the group consisting of gold, silver, platinum and their alloys, and amorphous silica particles;
A step of weighing the noble metal powder particles and the amorphous silica particles at a predetermined ratio;
Mixing the noble metal powder particles and the amorphous silica particles in a predetermined ratio to obtain mixed powder particles;
A step of producing a powder solidified body by pressurizing after filling the mixed powder particles into a mold, and applying a hot plastic working to the powder solidified body to densify the amorphous silica particles. A method for producing a functional noble metal product, comprising a step of dispersing in a base of a noble metal. The method for producing a functional noble metal product according to claim 14, wherein the green compact is heated in vacuum or in an inert gas atmosphere prior to the hot plastic working. The method for producing a functional noble metal product according to claim 15, wherein the heating temperature of the powder compact is within a range of 0.5 Tm to 1.0 Tm, where Tm is a melting point of the noble metal powder particles. The hot plastic working for the powder compacted body is an extrusion process, a rolling process, a forging process, a swaging process, a pressing process, or a drawing process, and manufacturing a functional noble metal product according to any one of claims 14 to 16. Method.