EP2566995A1 - Procédé d'élaboration d'une couche superficielle cristalline - Google Patents

Procédé d'élaboration d'une couche superficielle cristalline

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Publication number
EP2566995A1
EP2566995A1 EP11777643A EP11777643A EP2566995A1 EP 2566995 A1 EP2566995 A1 EP 2566995A1 EP 11777643 A EP11777643 A EP 11777643A EP 11777643 A EP11777643 A EP 11777643A EP 2566995 A1 EP2566995 A1 EP 2566995A1
Authority
EP
European Patent Office
Prior art keywords
metal
substrate
gold
crystals
liquid phase
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11777643A
Other languages
German (de)
English (en)
Other versions
EP2566995A4 (fr
Inventor
Karl-Olof Axelsson Wadell
Eric Wadell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wadell Karl-Olof Axelsson
WADELL, NINA
Original Assignee
Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP2566995A1 publication Critical patent/EP2566995A1/fr
Publication of EP2566995A4 publication Critical patent/EP2566995A4/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/02—Alloys based on gold
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G15/00—Compounds of gallium, indium or thallium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G7/00—Compounds of gold
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C23C2/29—Cooling or quenching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • C23C4/08—Metallic material containing only metal elements
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM

Definitions

  • the present invention relates to a process for producing a crystalline surface layer essentially consisting of gold and a second metal selected from the group consisting of Bi, Ga, In and Te on a surface of the substrate.
  • the substrate with the surface layer is intended for use in jewellery applications or other aesthetic applications, such as pieces of jewellery, watches, exclusive casings for business or credit cards and caps for exclusive perfume bottles or the like.
  • AuAI 2 which has a purple colour and is often referred to as "purple gold”.
  • AuAI 2 comprises about 79% by weight of gold.
  • the intermetallic compound is provided as a surface coating.
  • the intermetallic compound AuAI 2 can be produced by vacuum melting gold and aluminium in the correct ratio and casting, by thermal spraying of molten gold-aluminium powder, by physical vapour deposition or by thermal diffusion.
  • the intermetallic compounds Auln 2 which has a blue colour
  • AuGa 2 which has a bluish colour
  • US 4,91 1 ,792 discloses various intermetallic compounds for use in jewellery, such as AuAI 2 , AuGa 2 and Auln 2 .
  • the compounds are produced by powder metallurgy.
  • AuGa2 and Auln 2 are described as soft and thus have a low resistance to abrasion, and their use is therefore limited to non-exposed parts of jewellery.
  • AuAI 2 , AuGa 2 and Auln 2 for jewellery applications are also disclosed in Koltz, "Metallurgy and processing of coloured gold intermetallics - Part I:
  • Koltz discusses liquid metal dip-coating as an alternative for producing AuGa 2 and Auln 2 due to it being a simple and easy to use technique.
  • the experiments could not be repeated successfully because of poor wetting of gold by gallium and oxidation of gallium.
  • the object of the present invention is to achieve an attractive surface of coloured gold on a substrate.
  • the process according to the invention results in a crystalline surface layer comprising gold and a second metal selected from the group consisting of Bi, Ga, In and Te.
  • the crystalline surface layer comprises more than 10 carat gold.
  • the obtained crystals are facetted and relatively large thus enabling a glittering appearance of the surface.
  • the process may typically result in about 50 000 - 5 000 000 crystals/cm 2 and each crystal is facetted giving about 200 000- 20 000 000 facets/cm 2 .
  • the process results in intermetallic crystals, the surface has a higher hardness compared to if it had not been crystalline.
  • the process is based on the discovery that it is possible to obtain a surface layer essentially consisting of intermetallic crystals of AU2B1, AuGa2, Auln 2 or AuTe2 on the surface of a substrate by allowing gold to react with a second metal selected from the group consisting of Bi, Ga, In and Te under certain conditions, followed by removal of any non-reacted part of said second metal.
  • the process for producing a crystalline surface layer essentially consisting of gold and a second metal selected from the group consisting of Bi, Ga, In, and Te on a substrate comprises providing a substrate having a substantially oxide free and clean surface, the surface consisting of 18 to 24 carat gold, optionally coating said surface with a coating layer of said second metal, exposing said surface to a liquid phase of said second metal, said liquid phase optionally further comprising gold, at a temperature where there is equilibrium between solid and liquid phases for an intermetallic phase selected from the group consisting of AU2B1, AuGa2, Auln 2 and AuTe2 depending on the selected second metal, such that crystals of said intermetallic phase are formed on the surface of the substrate, optionally subjecting the substrate to a heat treatment at a temperature where there is equilibrium between solid and liquid phase for said intermetallic phase, removing any excess of said second metal not reacted with gold from said surface by etching, such that the surface of the substrate essentially consists of crystals of said intermetallic phase.
  • the exposure of the surface to a liquid phase of said second metal is achieved by submersing the substrate in a melt of said second metal.
  • the exposure of the surface to a liquid phase of the second metal is conducted at a temperature of 230-365 °C in case the second metal is Bi, 50-340 °C in case the second metal is Ga, 165-450 °C in case the second metal is In or 400-450 °C in case the second metal is Te.
  • the heat treatment after said exposure may preferably be made at a lower temperature than the preceding step of exposing said surface to a liquid phase of said second metal.
  • smaller crystals are allowed to be formed in the interface between the substrate and the already formed outer surface crystals, resulting in increased bonding strength of the larger crystals to the substrate. This is especially advantageous in case of the outermost crystals being relatively large.
  • the process further comprises a heat treatment prior to the removal of excess metal, said heat treatment being conducted at a temperature where all phases are solid.
  • the purpose of such a heat treatment is to allow further diffusion of the second metal into the surface of the substrate thereby further improving the adhesion of the outermost crystals to the substrate.
  • the removal of excess of said second metal from the surface of the substrate after formation of the intermetallic crystals is performed by etching in order to avoid affecting the geometrical form of the crystals.
  • the etching process step comprises contacting the substrate with a remote piece of said second metal via connecting means such that a galvanic circuit is formed in the etching solution.
  • the coating of the second metal on the surface of the substrate may suitably be made by electroplating or physical vapour deposition.
  • the thickness of the coating layer, when made by electroplating should preferably be at least 0.5 ⁇ in order to ensure that the coating is coherent and essentially free from defects.
  • the coating layer can be considerably thinner as long as the coating layer is coherent and covers the surface.
  • the process may further comprise a heat treatment after the removal of excess of said second metal such that the second metal is diffused into the substrate, thus altering the composition of the crystal while essentially preserving the size thereof.
  • This may increase the amount of gold in the crystalline surface layer and may also result in a surface layer having a higher hardness, thus making it more scratch-resistant.
  • Figure 1 a shows a binary phase diagram of Au and In Figure 1 b shows a binary phase diagram of Au and Ga
  • Figure 1 c shows a binary phase diagram of Au and Bi
  • Figure 1 d shows a binary phase diagram of Au and Te
  • Figure 2 shows a photograph taken in SEM of an Auln 2 surface obtained by an embodiment of the process according to the invention
  • Figure 3 shows a photograph taken in SEM of an AU2B1 surface obtained by an embodiment of the process according to the invention
  • the process for producing a crystalline surface layer essentially consisting of gold and a second metal on a substrate comprises providing a substrate having a substantially oxide free and clean surface, the surface consisting of 18 to 24 carat gold, optionally coating said surface with a coating layer of said second metal, exposing said surface to a liquid phase of said second metal, said liquid phase optionally further comprising gold, at a temperature where there is equilibrium between solid and liquid phases for an intermetallic phase of gold and the second metal, such that crystals of said intermetallic phase are formed on the surface of the substrate, optionally subjecting the substrate to a heat treatment at a temperature where there is equilibrium between solid and liquid phases for said intermetallic phase, removing any excess of said second metal not reacted with gold from said surface by etching such that the surface of the substrate essentially consists of crystals of said internnetallic phase.
  • the second metal is selected from the group consisting of bismuth (Bi), gallium (Ga), indium (In) and tellurium (Te); and the resulting intermetallic phase is thus Au 2 Bi, AuGa2, Auln 2 or AuTe 2 .
  • Bismuth, gallium, indium and tellurium all have a relatively low melting temperature and are able to form intermetallic compounds with gold. Furthermore, such intermetallic compounds have an attractive colour thus making them suitable for jewellery applications. Moreover, these metals do not require increased pressure for formation of intermetallic phase with gold.
  • a substrate which has a surface of 18 to 24 carat gold.
  • the entire substrate may be made of gold, but it is also possible to use substrates having a surface coating or surface layer of 18 to 24 carat gold.
  • the reason for the substrate having at least 18 carat gold is to ensure that there will be a sufficient amount of gold which may be reacted with the second metal and also avoid impurities in the crystalline surface layer.
  • other alloying elements of gold, other than Ga, In, Bi and Te, in the surface of 18 to 24 carat gold, such as Ag, Cu, Ni and Pd may influence the formation of the desired crystalline surface layer by forming unwanted intermetallic phases.
  • the surface of the substrate consists of 20 to 24 carat gold, most preferably 23-24 carat gold.
  • the surface of the substrate is free from surface oxides and impurities. Therefore, the surface should be treated to remove any surface oxides and thoroughly cleaned before the subsequent steps of the process. If the surface of the substrate is not oxide free and properly cleaned, the adhesion of the crystalline surface layer may be insufficient. Furthermore, there is a risk of defects in the crystalline surface layer. In most cases, it is also preferred that the surface is relatively smooth even though this is not necessary.
  • the process according to the present invention results in crystals of an intermetallic compound selected from the group consisting of Au 2 Bi, AuGa2, Auln 2 and AuTe 2 .
  • the crystals should preferably be at least 5 ⁇ in order to achieve the glittering appearance and may be produced up to a size of at least 150 ⁇ by means of the process according to the invention.
  • the crystals should have a size of 5-100 ⁇ , more preferably 10-100 ⁇ .
  • the substrate having a surface consisting of 18 to 24 carat gold is firstly coated with a coating layer of the second metal.
  • the layer should be coherent, essentially free from impurities and cover the surface. For this reason, it is preferred that the coating layer has a thickness of at least 0.5 ⁇ if electroplating is used to form the coating layer. If for example physical vapour deposition is used, a much thinner coating layer can be used as long as it covers the surface.
  • the purpose of the coating layer is to ensure that the liquid phase of the second metal wet the surface completely in the subsequent step of the process.
  • the coating layer may be applied with any conventional method resulting in a coherent and substantially dense coating layer covering at least the part of the surface of the substrate on which the crystalline surface is to be formed. Examples of suitable methods for coating the substrate with said coating layer are
  • the coating layer should be at least 0.5 ⁇ , preferably 1 -100 ⁇ , more preferably 1 -20 ⁇ .
  • the surface of the substrate is exposed to a liquid phase of the second metal.
  • the purpose of this step is to allow formation of stoichiometric intermetallic crystals of gold and the second metal on the surface of the substrate. Therefore, the step is performed at a temperature where there is equilibrium of liquid and solid phases under formation of the intermetallic compound. These temperatures are directly derivable from the binary phase diagrams of gold and the second metal. These binary diagrams are shown in Figures 1 a-1 d.
  • Figure 1 a shows the binary phase diagram of gold and indium and the temperature range where there is equilibrium between solid and liquid phase for Auln 2 is marked by the arrows.
  • the second metal is In
  • the temperature should preferably be maximally 450 °C in order to ensure that only Auln 2 is formed on the surface.
  • the second metal is Ga
  • the second metal being selected from Bi and Te
  • the entire temperature interval where there is equilibrium between the solid and liquid phase for the intermetallic phase can be used since these elements only have one
  • the suitable temperature ranges for the different second metals, as well as the intermetallic compound formed and their colours respectively are shown in Table 1 .
  • the size of the crystals obtained generally increases with increasing temperature within the specified intervals. Very large crystals may suffer from poor adhesion to the surface of the substrate. Moreover, in order to avoid any problems with possible fluctuations of temperature during the steps, it is generally advisable not to use a temperature too close to the end values of the interval of the broadest possible temperature range.
  • Table 1 also specifies the preferred ranges of the temperature during the exposure of the surface of the substrate to the liquid phase of the second metal.
  • the metals are not oxidised, and the exposure of the surface of the substrate to the liquid phase of the second metal is therefore preferably conducted in a non-oxidising environment.
  • This may suitably be achieved by using an argon protective atmosphere or vacuum. It has to be noted that in some cases, this step may be conducted without protective atmosphere or vacuum.
  • the liquid phase is only formed in the interface between the substrate and a possible coating layer, the outermost part of the coating layer being solid and wherein the coating layer is so thick that a possible surface oxide on the coating layer will not risk affecting the formation of
  • the exposure may preferably be made at about atmospheric pressure. It will be readily apparent to the skilled person that an increased or reduced pressure will alter the suitable temperatures of the exposure of the surface to the liquid phase since the above specified temperatures are based on atmospheric pressure. The temperatures for cases where the pressure is not atmospheric should be adjusted to the corresponding temperatures according to binary phase diagrams for such pressures.
  • Exposing the surface of the substrate to a liquid phase of the second metal may be achieved by different process steps. For example, it may be achieve by contacting the surface with a solid foil, or the like, of the second metal and heating to a temperature where the foil is melted such that a liquid phase of the second metal is formed on the surface of the substrate. It is also possible to apply a coating layer of the second metal and heating to a temperature where the coating layer is melted such that a liquid phase is formed on the surface of the substrate.
  • the exposure is performed by submersing the substrate in a melt of the second metal.
  • This embodiment is applicable to the cases when the second metal is selected from the group consisting of Bi, Ga and In.
  • the second metal is Te
  • such an embodiment is not practically applicable since the melting temperature of Te is equal to the maximal temperature where there is equilibrium between solid and liquid phases under formation of the intermetallic phase.
  • Alloying of the second metal with gold reduces the liquidus temperature of the second metal in case the second metal is Bi or Te.
  • the second metal is In or Ga
  • the liquidus temperature increases when the second metal is alloyed with gold.
  • a two phase is created for all cases, wherein a solid phase comprising the intermetallic compound and a liquid phase comprising the second metal and optionally gold are formed. Therefore, the temperature of the exposure of the surface of the substrate to the liquid phase of the second metal is not necessarily a temperature above the melting temperature of the pure second metal.
  • the second metal is Ga or In
  • the temperature of the exposure of the surface to the liquid phase is above the melting temperature of the second metal.
  • the second metal is Bi
  • Te the temperature of the exposure is in fact equal to or below the melting temperature of Te.
  • the second metal When the surface is in contact with the liquid phase of the second metal, the second metal will diffuse into the surface consisting of 18 to 24 gold and react with the gold. By the fact that the temperature is kept within the interval where there is equilibrium between solid and liquid phase for the intermetallic compound, crystals of the intermetallic compound will be formed.
  • the surface of the substrate should be in contact with the liquid phase of the second metal for a sufficient period of time for formation of the desired amount and size of crystals of the intermetallic compound on the surface. It will be readily apparent to the skilled person that the appropriate time depends on the
  • the substrate is thereafter heat treated at a temperature where there is equilibrium between solid and liquid phase for said intermetallic phase, but preferably at a lower temperature than the step at which the exposure of the liquid phase of the second metal and the surface of the substrate was conducted.
  • the purpose of such a heat treatment is to improve the bonding of the obtained crystals to the surface of the substrate.
  • Such a heat treatment is especially advantageous when relatively large crystals were formed in the preceding step as such large crystals sometimes may have a low adhesion to the substrate.
  • the second metal will diffuse into the substrate and react with gold under formation of more crystal. This will in turn lead to formation of relatively small crystals in the interface of the substrate and the already formed larger crystals at the outer surface, and thus improved adhesion of the outermost crystals of the surface to the substrate.
  • the above described heat treatment can be performed in a non-oxidising atmosphere in order to ensure that the metals are not oxidised during the heat treatment.
  • the heat treatment can be made after the substrate has been allowed to cool to room temperature, or in the same furnace as the preceding step and directly thereafter but at a lower temperature.
  • a second heat treatment may suitably be performed at a temperature where all phases are solid.
  • a heat treatment is suitably performed at a temperature below 230 °C when the second metal is Bi, below 50 °C when the second metal is Ga, below 156 °C when the second metal is In, and below 400 °C when the second metal is Te.
  • the removal of excess non-reacted second metal from the surface after formation of the crystals is an essential part of the process in order to achieve an outermost surface layer of intermetallic crystals and avoid any alteration of the appearance of the surface during use.
  • the removal of excess of said second metal is made by etching in order not to destroy the geometrical form of the crystals.
  • the etching may be performed by any etching solution that is able to etch the second metal.
  • etching of the intermetallic crystals starts which quickly alters the composition of the crystals and may thus almost immediately alter the surface appearance of the substrate.
  • the surface of the substrate almost instantaneously changes from the clear blue colour to a brownish colour as soon as all of the non-reacted indium has been etched from the surface.
  • the substrate is connected to a remote piece made of the second metal via a connection means, such as a gold wire or the like, the remote piece of said second metal being submersed in the same etching solution as the substrate.
  • a galvanic circuit is formed by the substrate and the remote piece of the second metal in the etching solution.
  • the substrate with the intermetallic crystals on the surface thereof may be exposed to further process steps if desired.
  • the substrate may be subjected to a heat treatment after the non-reacted part of the second metal has been removed from the surface.
  • the purpose of such a heat treatment may be to allow said second metal to diffuse from the intermetallic crystals into the substrate, thereby increasing the gold content of the crystals.
  • Such a heat treatment should be conducted in a non-oxidising atmosphere and preferably at a temperature below the melting point of at least the stoichiometric intermetallic phase.
  • the size and the geometry of the crystals on the surface are
  • a heat treatment after the removal of excess indium on the surface of the substrate may be performed in order to allow indium to diffuse into non-reacted gold of the substrate whereas gold will diffuse out towards the surface.
  • a heat treatment after the removal of excess indium on the surface of the substrate may be performed in order to allow indium to diffuse into non-reacted gold of the substrate whereas gold will diffuse out towards the surface.
  • the Auln crystals are more stable and have a considerably higher hardness than Auln 2 crystals, about 250 Hv compared to about 40-45 Hv for Auln 2 .
  • an outermost surface of Auln which is highly scratch resistant may be obtained and which has an excellent adhesion to the substrate.
  • Such a surface would be highly suitable for example for exposed parts of jewellery.
  • the colour of the Auln surface will be bluish.
  • Such a subsequent process may also be conducted in case of the second metal being Ga, and the crystalline surface formed on the surface of the substrate thus essentially consisting of AuGa2, which would then result in crystals of AuGa on the surface.
  • the coated substrate was then placed in an indium melt in an argon atmosphere at atmospheric pressure and at a temperature of about 275 °C for about 30 minutes. This resulted in formation of relatively large crystals of Auln 2 on the surface of the substrate. The substrate was then removed from the melt and allowed to cool to room temperature.
  • the substrate was heated to about 200 °C for about 10 hours without any additional melt being provided to the substrate than the already present melt resulting from the not reacted indium on the surface from the preceding step.
  • relatively small crystals of Auln 2 were formed under the surface layer of the relatively large crystals of Auln 2 . These smaller crystals thus improve the adherence of the large crystals to the surface of the substrate.
  • the substrate was then removed from the furnace and allowed to cool down to room temperature.
  • the substrate was etched with a HCI-solution.
  • a piece of indium was connected to the substrate through a gold wire in order to create a galvanic circuit.
  • the remote piece of indium was further etched instead of the crystals of Auln 2 on the surface of the substrate.
  • Figure 2 shows a photograph taken in SEM of the surface of the substrate after indium had been etched from the surface. It is clear from the figure that facetted crystals with a size in the order of tens of micrometers were formed. The facetted crystals resulted in a glittering appearance of the surface and the colour was blue.
  • a surface of a 24 carat gold substrate was polished and thoroughly cleaned.
  • the substrate was then placed in a bismuth melt, without any prior coating of the surface, in an argon atmosphere at atmospheric pressure and at a temperature of about 300 °C for about 60 minutes. This resulted in formation of relatively large crystals of AU2B1 on the surface of the substrate.
  • the substrate was then removed from the melt and allowed to cool to room temperature.
  • the substrate was etched with a HNO3-solution.
  • a piece of bismuth was connected to the substrate through a gold wire in order to create a galvanic circuit.
  • the remote piece of Bi was further etched instead of the crystals of AU2B1 on the surface of the substrate.
  • Figure 3 shows a photograph taken in SEM of the surface of the substrate after the non-reacted bismuth had been removed.
  • the crystals obtained had sharp corners and the surface layer was found to have a hardness in the order of about 200 Hv and should therefore be fairly scratch resistant.
  • the colour of the surface was white-pink.
  • a surface of a 24 carat gold substrate was polished and thoroughly cleaned.
  • the substrate was dipped in molten gallium at about 40 °C in order to achieve a coating layer and allowed to cool to room temperature. Thereafter, the substrate was heated to 225 °C during 60 minutes such that a liquid phase of gallium was present on the surface. This resulted in formation of crystals of AuGa2 on the surface of the substrate. The substrate was then allowed to cool to room temperature.
  • the substrate was etched with a HCI-solution.
  • a piece of gallium was connected to the substrate through a gold wire in order to create a galvanic circuit.
  • the remote piece of gallium was further etched instead of the crystals of AuGa2 on the surface of the substrate.
  • the colour of the surface was bluish.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Thermal Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Plasma & Fusion (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • ing And Chemical Polishing (AREA)

Abstract

L'invention concerne un procédé d'élaboration d'une couche superficielle cristalline composée d'Au2Bi, AuGa2, AuIn2 ou AuTe2. Le procédé consiste à exposer une surface d'or à une phase liquide de Bi, Ga, In ou Te à une température prédéterminée pour que des cristaux intermétalliques se forment, et à retirer tout le Bi, Ga, In ou Te n'ayant pas réagi de la surface. Le procédé permet d'obtenir un substrat ayant une surface d'or colorée avec une apparence brillante, le substrat étant ainsi approprié pour des applications de joaillerie.
EP11777643.5A 2010-05-04 2011-04-11 Procédé d'élaboration d'une couche superficielle cristalline Withdrawn EP2566995A4 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1050446A SE534817C2 (sv) 2010-05-04 2010-05-04 Förfarande för att producera ett kristallint ytskikt
PCT/SE2011/050437 WO2011139206A1 (fr) 2010-05-04 2011-04-11 Procédé d'élaboration d'une couche superficielle cristalline

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EP2566995A1 true EP2566995A1 (fr) 2013-03-13
EP2566995A4 EP2566995A4 (fr) 2014-02-19

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4911762A (en) * 1987-03-10 1990-03-27 Samuel Steinemann Intermetallic compound, method for producing the compound, and use of the compound

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0006050D0 (en) * 2000-03-14 2000-05-03 Johnson Matthey Plc Liquid gold compositions

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4911762A (en) * 1987-03-10 1990-03-27 Samuel Steinemann Intermetallic compound, method for producing the compound, and use of the compound

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
"Handbook of Metal Etchants", 1991, CRC Press, XP002717914, ISBN: 0-8493-3623-6 page 156, 405, 643, * Pages 156, 405, 643 * *
CHRISTOPHER W. CORTI: "Blue, black and purple! The special colours of gold" In: "CONFERENCE PROCEEDINGS OF INTERNATIONAL JEWELLERY SYMPOSIUM", 2006, St. Petersburg, XP002717915, * page 2, paragraph 3 - paragraph 8 * * page 6, paragraph 4 - paragraph 6 * *
CRETU C ET AL: "Coloured Gold Alloys", GOLD BULLETIN, WORLD GOLD COUNCIL, LONDON, GB, vol. 32, no. 4, 1 January 1999 (1999-01-01), pages 115-126, XP002535888, ISSN: 1027-8591 *
See also references of WO2011139206A1 *
ULRICH E KLOTZ: "Metallurgy and processing of coloured gold intermetallics Part I: Properties and surface processing", GOLD BULLETIN, SPRINGER, LONDON, UK, vol. 43, no. 1, 1 March 2010 (2010-03-01), pages 4-10, XP008159694, ISSN: 0017-1557, DOI: 10.1007/BF03214961 [retrieved on 2011-03-29] *

Also Published As

Publication number Publication date
EP2566995A4 (fr) 2014-02-19
WO2011139206A1 (fr) 2011-11-10
SE534817C2 (sv) 2012-01-10
SE1050446A1 (sv) 2011-11-05

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