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INVENTION
Patent of the Russian Federation RU2051864
METHOD OF OBTAINING THE SYNTHETIC GREECE OPALE
The applicant's name: Samoylovich Lidia Alexandrovna; Marin Anatoly Alexandrovich; Samoilovich Mikhail Isaakovich
The name of the inventor: Samoylovich Lidia Alexandrovna; Marin Anatoly Alexandrovich; Samoilovich Mikhail Isaakovich
The name of the patent owner: Samoylovich Lidia Alexandrovna; Marin Anatoly Alexandrovich; Samoilovich Mikhail Isaakovich
Address for correspondence:
Date of commencement of the patent: 1991.07.26
Use: jewelry industry .
SUMMARY OF THE INVENTION: partial softening is introduced into the opal structure due to the layered formation of the opal deposit from silica globules characterized by particle sizes in alternating layers of 10-15% , and giving globules a polygonal shape by dehydration treatment at 100-150 ° C and subsequent pneumatolytic annealing At 350-400 ° C and a pressure of 80-200 atm for 2-10 hours . To fill the interglobular space, it has been proposed to use silica gel, which is converted into a glassy state by heat treatment at 400-600 ° C for 1 to 2 hours .
DESCRIPTION OF THE INVENTION
The invention relates to the synthesis industry of mineral raw materials and can be used to produce a synthetic noble opal analog of natural noble opal used in the jewelry industry.
Natural noble opal is one of the most expensive and beautiful stones. A variety of color games (orisation) in noble opals is caused by the diffraction of light from a spatial lattice formed by one-dimensional globules of amorphous silica, predominantly polygonal forms, the space between them is filled with a cementitious substance (in natural opal silica), slightly different ( 0.01-0.02 ) By the refractive index of the refractive index of the globules themselves. The color of the irradiation depends on the size of the globules (150 nm blue, 450 nm red), and the intensity of the game depends on the degree of orderliness of the structure, on the composition and structure of the substance filling the interglobular space. According to the nature of the pattern, the color spots in natural opals are diverse and depend on the domain structure and the degree of its disorder. The microstructure of natural noble opal is represented by the densest hexagonal or cubic packing of polygonal deformed spherical single-dimensional (within one domain) amorphous silica globules contacting each other along segments; Interglobular space is filled partially or completely with a monolithic, non-scattering glassy silica; At the same time, there is an iris in different parts of the spectrum. The refractive indices are 1.41-1.46 , the microhardness is 4.5-6 units . Mohs, according to the chemical composition of SiO 2 nH 2 O , with SiO 2 ~ 90%
A method is known in which noble opal is obtained from monodisperse suspensions with amorphous silica particles of 150-450 nm in size , the particles are packed by centrifugation or sedimentation into an ordered structure, diffracted light, opal sediment is dehydrated in air first at 100 ° C. , then at 400-900 ° C. The interglobular space is filled with silica from smaller globules of SiO 2 or another substance with a refractive index that differs from the refractive index of globules by 0.01-0.1 .
A disadvantage of this method is that the opal sediment obtained using a suspension with globules of the same size and spherical forms does not give multi-colored spots under a certain illumination; The filling of the interglobular space with silicasols consisting of fine silica particles leads to the scattering of light on these particles, which reduces the transparency of opal and the brightness of the colors of irradiation; Dehydration in air at 100 ° C slightly strengthens the structure, since the particles have only a point contact with each other, the opal material is brittle, and dehydration itself at 100 ° C is accompanied by a strong fracturing; High-temperature treatment in air at 400-900 ° C gives relatively weak hardening, since globules remain almost spherical and have only point contacts. Microhardness of such samples does not exceed 4 units. On the Mohs scale. In general, the synthetic noble opal obtained by the method described above does not have bright spotted iris, transparency and microhardness in the case of the filling of the interglobular space with silica, and when filled with organic matter, the opal material is qualified as an imitation of noble opal. The absence of polygonal forms of globules and a certain disorder in the structure makes such an opal quite different in terms of jewelry characteristics from natural.
The object of the invention is to obtain a noble opal , which is as close to the natural opal as possible in terms of jewelry characteristics.
This object is achieved in that, in a known method for producing a noble opal, comprising obtaining monodisperse suspensions from spherical globules of amorphous silica, packing them in an ordered structure, heat treating and filling the interglobular space with silica, the following additional operations are performed, which are the hallmarks of the invention. The structure of the opal sediment is formed layer by layer, a monodisperse suspension with a predetermined particle size is used to deposit each layer, and each subsequent layer of the precipitate is formed from the suspension with particle sizes of ± 10-15% different from the previous suspension; The opal sediment is dehydrated in two stages, namely by drying at 100-150 ° C and then subjected to pneumatolytic annealing at 350-400 ° C and a pressure of 80-200 atm for 2-10 hours ; Interglobular space is filled with impregnation, which is a silica powder of such composition that during the subsequent heat treatment, the glass transition gel sol is carried out.
The difference in the sizes of the globules in each layer is 10-15% due to the fact that when the sizes of globules differ less than 10%, the effect in the color of the irradiation of the precipitate is negligible, and if the size of globules is larger than 15%, a transient disordered layer is formed which does not give irisation, which violates Decorative and artistic appearance of opal.
Partial disordering of the structure due to the polygonization of spherical globules due to their splicing strengthens the opal and is carried out in two stages by dehydration in a temperature range of 100-150 ° C for 10-30 h and subsequent pneumatolytic annealing at 350-400 ° C and a water vapor pressure of 80-200 Atm for 2-20 hours . The lower limit of dehydration of 100 ° C is determined by the boiling point of water in pores of large diameter, and the upper 150 ° C by the boiling point of water in smaller pores.
This treatment promotes the transfer of SiO 2 to the contact point of the globules and, in addition, creates an external pressure that reduces capillary forces in the pores and thereby prevents cracking of the sample. The dehydration treatment time of 10-13 hours is determined experimentally. At processing less than 10 hours polygonization of globules does not occur, and at processing more than 30 hours this effect does not increase.
The time of pneumatolytic annealing is determined experimentally. Optimal processing time is 5 hours , at a time less than 2 hours, the polygonization of the globules is negligible, and when processed for more than 10 hours the globules are strongly deformed, the structure becomes sintered, the porosity necessary to fill the interglobular space disappears, and the material becomes unsuitable for impregnation with silica powders.
The parameters of pneumatolytic annealing determined experimentally ( 350-400 о С and 80-200 atm ) are interrelated, as they are determined by the temperature-pressure-density relations of water vapor. At parameters below 350 ° C and 80 atm, the globular polygonization effect is insignificant, the hardening is weak, and at 400 ° C and 200 atm , on the contrary, the globular structure is highly distorted, the globules strongly cake, the material becomes unsuitable for silica impregnation.
The glassy state of silica in the interglobular space provides a bright color iris, since the scattering from the monolithic, transparent mass decreases. Its amount of 5-15% is determined by the fact that at an amount below 5%, the iris is weak, since in this case only 20% of the interglobular space is filled with glass, the remaining 80% by air or water vapor, and at 15% of the glass 60% of the interglobular space is filled with glass . To achieve a higher filling of the interglobular space (it is 25% of the total system) is practically impossible, since the size of the interglobular space is too small ( ~ 1/4 of the globule size), and decreases with silica.
The interval of heat treatment of the material impregnated with silica is 400-600 о С due to the fact that it is in this interval that the sol turns into the vitreous state, and the refractive index of the resulting glass (depending on the processing temperature) creates the effect of light diffraction. At temperatures below 400 ° C , the transition to the glass does not take place, and above 600 ° C the positive effect does not increase.
The time of heat treatment of 1-2 hours is established almost less than 1 hour, a complete transition to the glass is not carried out, and with a treatment time of more than 2 hours there is no positive effect.
As a result, an ordered structure is formed, with elements of disordering inherent in natural noble opal: globules of silica are tightly connected, they have contact areas in the form of segments, globules of spherical ones themselves become polygonal; Interglobular space is partially filled with transparent vitreous silica having a refractive index different from globules; The opal sediment has a textured structure, spotted in color and shape. According to physical characteristics, the resulting noble opal is identical to natural: microhardness of the order of 5-6 units. Moos, blocking and includes 2-3 or more colors of the visible spectrum, transparency, microstructure (according to EM data) the closest hexagonal or cubic package of polygonal globules with touching areas and silica-filled interglobular space.
Advantages of the proposed method as compared with the method set forth in the prototype are as follows: by chemical composition ( SiO 2 nH 2 O ), microstructure, physical microhardness ( 5-6 Mohs ), refractive index ( 1.43-1 , 45 ), density ( 2.0-2.1 g / cm 3 ), intensity of irradiation, and the shape of color spots, the noble opal obtained by the proposed method is an analog of natural noble opal, and even exceeds it by some secondary characteristics (stability of irradiation Time, mechanical strength, resistance to fracturing). Such opals are practically indistinguishable from natural ones and are highly valued in the world market.
EXAMPLE 1 (prototype). A monodisperse suspension consisting of spherical particles of amorphous silica with a size of predominantly 250 nm is prepared from which a sediment having an ordered diffractive structure is obtained by sedimentation or centrifugation. Then, the precipitate is hardened first by drying at room conditions for a week, then at 100 ° C. in air for several hours, and then at 600 ° C. for 2 hours . After that, the samples are impregnated with 1% fresh silica gel, consisting of particles of ~ 10 mmq in size, and dried until the difference in the index of refraction of spheres and silica in the interglobular space is 0.01-0.1. The operations of impregnating silica powder and drying are repeated several times until the interglobular space is partially or completely filled with silica (up to 40-50 times). The obtained material has an ordered structure consisting of spherical silica particles having point contacts with each other, the substance in the interglobular space is in the form of a xerogel that diffuses light, the iris is weak, mainly in green tones, other colors of the spectrum are barely noticeable, the spotting is absent, the samples are porous And opaque, density 1.9 g / cm 3 , microhardness 3.9 Mohs.
EXAMPLE 2 A suspension is prepared by the hydrolysis of tetraethoxysilane ( TEOS ) in an alcohol-ammonia medium. To do this, mix 100 ml of C 2 H 5 OH with 2.2 ml of a 30% aqueous solution of ammonia and 4 ml of TEOS, the mixture is placed for 30 minutes on an AVU-6s shaker and then left for 1.5-2 h at rest. A suspension with spherical globules of amorphous silica 200 nm in size is obtained. The suspension is poured into a centrifuge tube and centrifuged at a value of g = 500 for 1 hour. The gyrolyzate is drained, the opaline wet sediment remains at the bottom of the tube. A new portion of the suspension prepared by the described method is then poured into this tube, except that the component ratio is changed: 100 ml of C 2 H 5 OH, 2.5 ml of 30% NH 4 OH and 4 ml of TEOS (particle size 225 nm , Ie 12% more than in the 1st case), and again it is centrifuged to obtain the second layer of opal sediment. Similarly, 3 and 4 layers are deposited, while 3.0 and 3.5 ml of ammonia are taken respectively to the third and fourth layers at the same TEOS and alcohol ratios, respectively. The particle size will then be 250 nm and 280 nm. Then, the moist opal sediment is dried at room temperature before separation from the tube, placed on the holder and transferred to a special hermetically sealed container and heat treated at 120 ° C in a thermostat for 20 hours with the lid closed. After cooling to room temperature, the samples are removed and subjected to pneumatolytic annealing in an autoclave. To do this, water is poured into the autoclave at the rate of 5% of the free volume, the autoclave is hermetically sealed and placed in a heating furnace. The temperature is 375 о С, the pressure is 140 atm, the holding time is 5 hours. Then the furnace is switched off, the autoclave is cooled, it is opened, the samples are taken out for the next procedure of impregnation with silica.
Kremnesol with a concentration of 10-20 wt. Is prepared as a hydrolyzate by sol-gel-glass method. The starting components are: TEOS, ethanol, distilled water and hydrochloric acid. The molar ratio of TEOS: C 2 H 5 OH: H 2 O: HCl 1: 4: 4: 0.7. The components are stirred for 0.5 hours. The disintegrating precipitate is placed in a heat-resistant beaker, filled with the obtained silica gel and placed in a thermo cabinet. Next, gelation is carried out at 50 ° C., then the temperature rises at a rate of 100 ° C./h to 500 ° C. and held for 1.5 hours. The furnace is turned off, the samples are cooled to room temperature and cleaned from impregnation, which easily flakes from the samples. The impregnation and heat treatment procedure is repeated 4 times. The samples obtained have a bright irisation of blue and green, when spotted (the shape of the spots and their size depend on the direction of the cut and the thickness of the layers). Microhardness on the Mohs scale is 5-6 units. Density 2 g / cm 3 , translucent, microstructure in the form of polygonal globules arranged in a cubic lattice, SiO 2 content of glass 9 wt.
EXAMPLE 3 The operations for obtaining a noble opal are the same as in Example 2, but suspensions with particle sizes differing by 5% in each layer of opal sediment are used. The result is the same as in Example 2, except that the iris is in blue tones without blotchiness.
EXAMPLE 4 The operations for obtaining a noble opal are the same as in Example 2, but suspensions with particle sizes differing by 20% in each layer are used. The result is similar to the result of Example 2, but there are disordered non-infusible regions 1.0-1.5 mm thick between the iris layers , Which impair the decorative qualities of the final product.
EXAMPLE 5 The operations are the same as in Example 2, but the dehydration treatment is carried out at 90 ° C. As a result, a brittle material is obtained, the globules are spherical, and in subsequent operations the material is cracked.
EXAMPLE 6 The operations for obtaining a noble opal are the same as in Example 2, but suspensions are used that differ in particle size by 10%. The result is the same as in Example 2, but separate color spots were observed from violet to yellow.
EXAMPLE 7 The operations are the same as in Example 2, but the dehydration treatment is carried out at 160 ° C. The result is similar to Example 2, but more electricity is expended.
EXAMPLE 8 The operations for producing noble opal are the same as in Example 2, but suspensions are used that differ in particle size by 15%. The result is similar to Example 2, but there were color spots from violet to red.
EXAMPLE 9 The operations are the same as in Example 2, but the dehydration treatment is carried out at 100 ° C for 30 hours. As a result, the globules are polygonized, the material is strengthened and is suitable for further operations.
EXAMPLE 10 The operations are the same as in Example 2, but the dehydration treatment is carried out for 8 hours. As a result, the globules are spherical, the hardening is weak, unsuitable for further operations.
EXAMPLE 11 The operations are the same as in the example, but the dehydration treatment is carried out for 10 hours. As a result, the globules are polygonized, the material is strengthened for further operations.
EXAMPLE 12 The operations are the same as in Example 2, but the dehydration treatment is carried out for 32 hours. The result is similar to Example 2, but more electricity is expended and with increasing processing time, labor costs increase without a positive effect.
EXAMPLE 13 The operations are the same as in Example 2, but pneumatolytic annealing is carried out at 340 ° C. As a result, the particles are slightly deformed, the final microhardness is below 4 units. Mohs and the material has increased brittleness.
EXAMPLE 14 The operations are the same as in Example 2, but pneumatolytic annealing is carried out at 350 ° C and 100 atm pressure for 7 hours. The result is similar to the result of Example 2, namely the same effect was obtained, but over a longer period of time.
EXAMPLE 15 The operations are the same as in Example 2, but pneumatolytic annealing is carried out at 400 ° C and a pressure of 200 atm for 2 hours. The result is similar to the result of Example 14, namely the same effect was obtained, but in a shorter time interval.
EXAMPLE 16 The operations are the same as in Example 2, but pneumatolite annealing is conducted at 410 ° C. As a result, the spheres are strongly sintered, the structure becomes unsuitable for the impregnation step.
EXAMPLE 17 The operations are the same as in Example 2, but pneumatolytic annealing is carried out at a pressure of 70 atm and 400 ° C. As a result, the globules are not subjected to the polyglylation, the structure is fragile, unsuitable for the impregnation step.
EXAMPLE 18 The operations are the same as in Example 2, but pneumatolytic annealing is carried out at 210 atm and 350 ° C. As a result, the globules are strongly deformed, the structure becomes non-porous and, therefore, unsuitable for the impregnation step.
EXAMPLE 19 The operations are the same as in Example 2, but pneumatolytic annealing takes 1 hour. As a result, the globules are polygonized, the material is slightly hardened.
EXAMPLE 20 The operations are the same as in Example 2, but the processing time is 2 hours. As a result, the globules are polygonized, the material is suitable for subsequent impregnation with silica.
EXAMPLE 21 The operations are the same as in Example 2, but the treatment takes 10 hours. As a result, the globules are polygonized and the material is suitable for subsequent impregnation with silica.
EXAMPLE 22 The operations are the same as in Example 2, but pneumatolytic annealing takes 11 hours. As a result, the globules strongly deform, the material is non-porous and is not suitable for subsequent impregnation with silica.
EXAMPLE 23 The operations are the same as in Example 2, but heat treatment is carried out at 390 ° C. As a result, silica in the interglobular space does not go over into a glassy state. Samples are dim, the iris is not bright.
EXAMPLE 24 The operations are the same as in Example 2, but the heat treatment is carried out at 400 ° C. As a result, silica in the interglobular space becomes a glassy state. Irisation is normal, the samples are translucent.
EXAMPLE 25 The operations are the same as in Example 2, but heat treatment is carried out at 600 ° C. As a result, silica in the interglobular space passes into a glassy state, the iris is bright, the samples are transparent.
EXAMPLE 26 The operations are the same as in Example 2, but the heat treatment is carried out at 620 ° C. The result is similar to Example 2, but more electricity is expended and labor costs increase without a positive effect.
EXAMPLE 27 The operations are the same as in Example 2, but the heat treatment is 0.5 h. As a result, the silica in the interglobular space remains in the form of a xerogel that dissipates light. The samples are dim, the iris is not bright.
EXAMPLE 28 The operations are the same as in Example 2, but the heat treatment is carried out for 1 hour. As a result, the silica in the interglobular space becomes a glassy state. The iris is average, the samples are semitransparent.
EXAMPLE 29 The operations are the same as in Example 2, but the heat treatment is 2 hours. As a result, all the silica in the interglobular space is in a glassy state. Samples with bright iris were obtained, transparent.
EXAMPLE 30 The operations are the same as in Example 2, but the heat treatment is carried out for 3 hours. The result is similar to Example 23, but more electricity is expended and with increasing heat treatment time, labor costs increase without a positive effect.
EXAMPLE 31 The operations are the same as in Example 2, but the silica is impregnated once. As a result, the silica of the whole system is in the vitreous state, the iris is weak, the samples are opaque, porous.
EXAMPLE 32 The operations are the same as in Example 2, but the impregnation and heat treatment procedure is repeated twice. As a result, 5% of the silica of the whole system is in a vitreous state, the iris is normal, the samples are semitransparent, weakly porous.
EXAMPLE 33 The operations are the same as in Example 2, but the impregnation and heat treatment procedure is carried out 7 times. As a result, 15% of the silica of the entire system is in a glassy state. The iris is bright, the samples are non-porous, transparent.
EXAMPLE 34 The operations are the same as in Example 2, but the impregnation and heat treatment procedure is carried out 10 times. The results are similar to those described in Example 33, but more electricity and labor are consumed without a positive effect.
The proposed method of obtaining a noble opal makes it possible to obtain a synthetic noble opal that is practically non-distinguishable from natural opal. According to the conclusion of American experts from the New York Gemological Institute ( USA ), the opal synthesized by us is qualified as natural. The cost of natural opals on the world market is 80-800 US dollars per carat (depending on the type and quality). Therefore, obtaining a noble opal is an extremely profitable object of production, since the cost of production of one carat does not exceed 20-80 rubles (depending on the type and quality), and the experience of the world trade in synthetic jewelery raw materials shows that the price for it is 10-30% of the cost Natural raw materials of similar quality and type.
CLAIM
- METHOD FOR OBTAINING A SYNTHETIC MAGNIFICENT OPAL , comprising depositing a opal precipitate from a previously obtained monodisperse suspension containing spherical globules of amorphous silica, drying, heat treatment of the precipitate and subsequent impregnation with silica, characterized in that the deposition step is carried out layer by layer, and to form each successive layer, a slurry containing Globules of a size 10-15% different from the previous ones, the heat treatment is carried out by pneumatolytic annealing in the presence of water vapor for 2-10 hours at a temperature of 350-400 ° C and a pressure of 80-200 atm , after the impregnation step with silica refining at 400- 600 ° C for 1-2 hours, and for impregnation, silica is used in an amount that provides the content of vitreous silica in the product after repeated heat treatment of 5-15% by volume of total silica.
- Method according to claim 1, characterized in that the drying is carried out at 100-150 ° C for 10-30 hours .
print version
Date of publication 31.10.2006гг
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