A method for preparing a bismuth-based color interference film material

Abstract

The application discloses a preparation method of a bismuth-based color interference film material, which comprises the following steps: under normal air conditions, high-purity metallic bismuth is heated, melted and then controlled-temperature oxidized, and a color film material is prepared by utilizing the interference effect of the spontaneously-formed oxidation film on the surface of the molten bismuth liquid, and the method comprises four steps of raw material melting, controlled-temperature impurity removal and oxidation film growth, color development and film layer adhesion forming and film taking, the film layer thickness can be controlled by adjusting the oxidation temperature and time, and full-spectrum interference color shades from blue-violet to purple-red can be obtained. The obtained bismuth-based color interference film comprises a solidified bismuth base and a surface color oxidation interference film layer, and can be subjected to artistic processing in modes such as cutting, bending, curling and local corrosion and the like, and is applied to artistic and creative carriers such as decorative pictures, sculptures, creative display articles, artistic ornaments, mounting processes and the like. The application has the advantages of simple equipment, low operation threshold, low cost, controllable and rich color.

Description

Technical Field

[0001] This invention relates to the fields of materials science and art and cultural creation, and in particular to a method for preparing a bismuth-based color interference film material. Background Technology

[0002] Thin-film interference is an optical phenomenon widely found in nature and artificial materials. When light waves are reflected from the upper and lower surfaces of a thin film and then superimposed, interference occurs due to the optical path difference, resulting in specific colors. Thin-film interference is widely observed in natural systems such as soap bubbles, oil films on water surfaces, and butterfly wings. Its vibrant colors change with the viewing angle, giving it high visual aesthetic value.

[0003] In the field of materials science, the fabrication of colored thin film materials using the principle of thin film interference has always been a research hotspot. Currently, the mainstream technical routes for fabricating colored interference films include physical vapor deposition (PVD), chemical vapor deposition (CVD), anodic oxidation, and sol-gel methods. Among them, physical vapor deposition requires a high vacuum environment, resulting in high equipment costs and harsh operating conditions, making it difficult to achieve large-area, low-cost mass production; chemical vapor deposition involves precise control of precursor gases, resulting in complex processes and safety hazards; anodic oxidation is mainly suitable for specific metals such as aluminum and titanium, and the electrolyte composition and process parameters have a significant impact on the final color, requiring precise control; the sol-gel method involves multiple chemical reactions, has a long process cycle, and is difficult to control the uniformity of the film layer.

[0004] Bismuth (Bi) is a low-melting-point heavy metal with a melting point of approximately 271°C, and it is chemically stable at room temperature. When heated above its melting point, bismuth melts into a highly fluid liquid metal. When this molten bismuth is exposed to an oxygen-containing atmosphere, a very thin oxide film spontaneously forms on its surface. This oxide film is transparent or translucent, and its thickness typically ranges from tens to hundreds of nanometers, perfectly meeting the conditions for thin-film interference. Since the oxidation process of bismuth can occur at relatively low temperatures, and the growth rate of the oxide film is relatively slow, with its thickness controllable by temperature and time, utilizing the surface oxidation of molten bismuth to prepare color interference films has inherent technological advantages.

[0005] However, there are no reports in the existing technology of systematically utilizing the oxide film on the surface of molten bismuth liquid to prepare color interference film materials and applying them to the field of arts and cultural creation. Furthermore, the aforementioned existing technologies generally suffer from the following common problems: First, they have high requirements for production equipment and environmental conditions, requiring specialized devices such as vacuum systems, precision temperature control systems, and electrolysis equipment, resulting in high equipment investment and maintenance costs; second, the process threshold is high, requiring operators to have professional materials science backgrounds and equipment operation experience; third, the process parameter window is narrow, requiring extremely high precision in controlling parameters such as temperature, pressure, atmosphere, and time, as even slight deviations can lead to uneven color or film defects; fourth, they are difficult to flexibly adapt to the personalized, small-batch, and multi-variety demands of the arts and cultural creation field, creating a contradiction between the existing industrialized production model and the flexibility and diversity of artistic creation. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a method for preparing bismuth-based color interference film materials.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing a bismuth-based color interference film material, comprising the following steps:

[0008] Step 1: Select high-purity metallic bismuth raw material and place it in a heating container. Heat the container to 260℃~350℃ to completely melt the metallic bismuth into a homogeneous molten bismuth liquid.

[0009] Step 2: Cool the molten bismuth liquid to a constant temperature range of 85℃~120℃ and let it stand. Scrape off the messy and uneven oxide film that spontaneously forms on the surface of the molten bismuth during the melting process. Maintain the gas atmosphere on the surface of the molten bismuth liquid containing 10%~30% oxygen by volume. Rely on the oxygen in the atmosphere to achieve uniform growth of the oxide film on the surface of the bismuth liquid. Adjust the thickness of the oxide film and the interference color by natural oxygen supply in the atmosphere. Wait until the oxide film on the liquid surface grows to present the target color interference color.

[0010] Specifically, during the oxide film growth process, when the oxide film on the liquid surface grows to a medium color, a scraping tool is used to selectively scrape away specific areas of the oxide film according to a preset pattern trajectory, exposing a bright new surface of molten bismuth liquid in the scraped area, forming a spatial alternation with the area where the oxide film is intact; the oxygen-containing atmosphere is maintained to continue supplying oxygen, allowing the oxide film to regrow in the scraped area, while the oxide film in the unscraped area continues to thicken. Due to the difference in oxidation initiation time and film thickness between the scraped and unscraped areas, the two types of areas form different oxide film thicknesses during the continued oxidation process, thereby producing a color abrupt change effect or a designable colored pattern; the oxide film thickness and interference color combination in each area of ​​the liquid surface reach the preset effect.

[0011] Step 3: Using a rigid heat-resistant component with a temperature range of 10℃~60℃, insert it obliquely into the molten bismuth liquid from the liquid surface. Utilize the low-temperature characteristics of the component itself to allow the molten bismuth liquid to spontaneously condense on the surface of the component to form a solid bismuth substrate. Slowly raise the component so that the colored oxide interference film already formed on the liquid surface can be completely adhered to the bismuth substrate by surface tension and be carried out as a whole.

[0012] Step 4: Cool the entire component, including the bismuth substrate and the surface color interference film, to 15°C~35°C, peel off the bismuth-based color interference film, which includes a solidified bismuth substrate and a color oxide interference film layer attached to the surface of the bismuth substrate, thus completing the preparation.

[0013] In a preferred embodiment of the present invention, the purity of the high-purity metallic bismuth raw material is 95% to 99.99% by mass.

[0014] In a preferred embodiment of the present invention, the heating container is a rigid container that does not deform within a temperature range of 260°C to 350°C.

[0015] In a preferred embodiment of the present invention, the molten bismuth liquid is cooled to a constant temperature range of 90°C to 115°C and left to stand.

[0016] In a preferred embodiment of the present invention, the gas atmosphere maintaining the surface of the molten bismuth liquid is a natural air atmosphere, wherein the oxygen volume fraction is 15%~25%.

[0017] In a preferred embodiment of the present invention, the rigid heat-resistant component has a melting point higher than 250°C, and the material, surface finish and shape of the rigid heat-resistant component are not limited.

[0018] In a preferred embodiment of the present invention, the angle of the oblique insertion is 15 degrees to 75 degrees, and the speed of the slow lifting is 0.5 cm / s to 5 cm / s.

[0019] In a preferred embodiment of the present invention, in step four, the cooling is natural cooling, and the cooling time is 10 min to 120 min.

[0020] In a preferred embodiment of the present invention, a bismuth-based color interference film is provided, which is prepared by the preparation method described above. The bismuth-based color interference film includes a solidified bismuth substrate and a color oxide interference film layer attached to the surface of the bismuth substrate. The color oxide interference film layer exhibits color produced by thin film interference effect.

[0021] In a preferred embodiment of the present invention, a method for applying bismuth-based color interference films in art and cultural creative products is also provided, comprising the following steps:

[0022] Step A: The bismuth-based color interference film is cut, divided, heated, bent, and rolled into shape; local interference color layers are selectively removed by local micro-etching to create local blank spaces and pattern texture effects;

[0023] Step B: Arrange, splice, and glue the processed bismuth-based color interference film and apply it to decorative paintings, sculptures, cultural and creative ornaments, art jewelry, or mounting art carriers. Combine it with the base, sealing layer, and frame to complete the overall art product.

[0024] In a preferred embodiment of the present invention, the local micro-corrosion in step A is carried out by using an acid solution with a concentration of 5% to 40% and applying the acid solution to the oxide film with a brush to perform selective corrosion.

[0025] In a preferred embodiment of the present invention, the heating temperature for the heating and bending in step A is 60°C to 150°C, and the bending angle is 5° to 170°.

[0026] In a preferred embodiment of the present invention, the finished artwork in step B further includes a superimposed combination of multiple bismuth-based color interference films, wherein the color interference colors of each bismuth-based color interference film are the same or different.

[0027] In a preferred embodiment of the present invention, the selective local scraping is performed when the oxide film on the liquid surface has grown to 30% to 80% of the target thickness; at this time, there is a thickness difference between the oxide film thickness formed after the scraped area is re-oxidized and the oxide film thickness that continues to thicken in the unscraped area, which is sufficient to produce a color contrast that can be recognized by the naked eye.

[0028] In a preferred embodiment of the present invention, the scraping tool is selected from one or more combinations of stainless steel scraper, bamboo scraper, hard template edge or ceramic needle tip; the selection of the scraping tool is determined according to the fineness of the preset pattern, wherein the linear pattern is preferably a thin stainless steel scraper or ceramic needle tip with sharp edges, and the large area color block pattern is preferably a rigid template edge or a wide bamboo scraper.

[0029] In a preferred embodiment of the present invention, the selective local scraping operation can be performed twice or more. That is, after a local scraping and subsequent differential re-oxidation, a specific area of ​​the oxide film on the liquid surface is scraped again, so that the newly scraped area can start growing an oxide film from the initial oxidation state, while the existing area continues to undergo differential oxidation, forming a composite color pattern effect with multiple superimposed patterns.

[0030] In a preferred embodiment of the present invention, the preset pattern trajectory includes straight lines, curves, geometric color blocks, text symbols, gradient transition areas, or any combination thereof; wherein the gradient transition area is formed by scraping at different depths or speeds during the scraping process, so that the edge of the scraped area presents an incompletely scraped transition zone, and the transition zone forms an intermediate thickness oxide film between the completely scraped area and the unscraped area during the continued oxidation process, thereby producing a gradient transition effect of interference colors.

[0031] In a preferred embodiment of the present invention, the selective local scraping operation needs to be completed within a few seconds, and the total duration of the scraping operation does not exceed 30 seconds; after the scraping is completed, the oxygen-containing atmosphere on the liquid surface is immediately restored to control the difference in oxidation time between the scraped area and the unscraped area, so as to ensure the clarity of the color contrast effect and the sharpness of the boundary.

[0032] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0033] (1) The preparation method described in this invention only requires conventional heating equipment (such as electric furnace, alcohol lamp, etc.) and rigid components, without the need for vacuum coating equipment, electrolysis equipment or precision temperature control system, which greatly reduces equipment investment and maintenance costs.

[0034] (2) The entire preparation process only includes four steps: melting, temperature-controlled oxidation, attachment molding and cooling. The operation process is clear and straightforward. No professional materials science background or equipment operation experience is required. It can be mastered after simple training and is suitable for studios, cultural and creative workshops and even individual enthusiasts.

[0035] (3) The raw material is high-purity metallic bismuth, which is widely available and reasonably priced; no expensive chemical reagents or protective gases are required during the process, and the normal air environment can meet the needs of oxide film growth; the rigid components have no special material requirements and can be reused.

[0036] (4) By adjusting the temperature of the molten bismuth liquid (85℃~120℃), oxidation time (several minutes to several hours) and oxygen content of the atmosphere, the thickness of the oxide film can be precisely controlled, thereby obtaining interference colors of the full spectrum from gold, orange, red, purple to blue, green, etc., with uniform color and high gloss.

[0037] (5) By using the method of slow lifting with oblique insertion, the surface tension is used to completely attach the formed oxide film to the bismuth substrate and bring it out. The film layer is undamaged and wrinkle-free, maintaining the integrity and uniformity of the liquid surface during oxidation.

[0038] (6) The shape of the rigid component determines the shape of the final film. Different components such as flat plate, arc surface, and irregular shape can be used to prepare bismuth-based color interference films of corresponding shapes as needed, which is extremely flexible.

[0039] (7) The bismuth-based color interference film of the present invention is thin and light but has a certain rigidity. It can be artistically shaped by secondary processing methods such as cutting, bending, rolling and etching. The interference color presents a dynamic visual effect as the viewing angle changes, providing a brand-new material selection and creative space for decorative paintings, sculptures, cultural and creative ornaments, and art ornaments.

[0040] (8) Bismuth metal and its oxides have extremely low toxicity, far lower than heavy metals such as lead and mercury, and are highly safe to use; no toxic or harmful waste liquids or gases are generated during the preparation process, which is environmentally friendly. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a flowchart of the method for preparing the bismuth-based color interference film according to the present invention;

[0043] Figure 2 This is a schematic diagram of the structure of the bismuth-based color interference film described in this invention;

[0044] Figure 3 This is a flowchart illustrating the application of the bismuth-based color interference film described in this invention in art and cultural creative industries.

[0045] Figure 4 Physical images of bismuth-based color interference film samples prepared with different process parameters at the first observation angle;

[0046] Figure 5 for Figure 4 A physical image of the bismuth-based color interferometer film sample group at the second observation angle;

[0047] Figure 6 The image shows a finished collage-style decorative painting made using the bismuth-based color interference film of this invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0050] Example 1: Basic preparation of bismuth-based color interference films

[0051] This embodiment describes the basic preparation process of a bismuth-based color interference film, and prepares a bismuth-based color interference film with a golden interference color. When understanding this embodiment, it is recommended to refer to... Figure 1 The flowchart shown illustrates the preparation method to clarify the sequential position of each step in the entire preparation process.

[0052] (1) Raw material melting

[0053] like Figure 1 The first step in the flowchart shown involves selecting approximately 200g of high-purity bismuth metallic raw material (99% by mass) and placing it in a stainless steel crucible. The crucible is then placed on a temperature-controlled electric furnace and heated to 280℃~300℃ at a heating rate of 5℃ / min~15℃ / min, and held at this temperature for 10min~20min to completely melt the bismuth metallic material into a homogeneous, highly fluid molten bismuth liquid. During this process, the bismuth metallic material gradually transforms from a silvery-white solid to a silvery-gray liquid, with a calm, bubble-free surface. This step corresponds to... Figure 1 The raw material melting process shown in the first box is the starting point of the entire preparation process.

[0054] (2) Temperature control for impurity removal and oxide film growth

[0055] like Figure 1 In the second step of the flowchart shown, the crucible containing molten bismuth is removed from the electric furnace and placed on a heat-insulated platform to cool naturally. An infrared thermometer is used to perform non-contact temperature measurement of the liquid surface, monitoring the surface temperature of the molten bismuth in real time. When the liquid surface temperature drops to the range of 90°C to 110°C, the crucible is transferred to a preheated constant-temperature heating plate and left to stand at a constant temperature. It should be noted that all temperature parameters described in this invention refer to the liquid surface temperature measured by the thermometer.

[0056] During the cooling process, a disordered and uneven oxide film will spontaneously form on the surface of the molten bismuth, appearing as dark gray spots. Gently scrape away this disordered oxide film with a stainless steel scraper to expose the bright surface of the molten bismuth. Maintain a normal air environment (oxygen volume fraction of approximately 21%), allowing the surface of the molten bismuth to be in natural contact with the air.

[0057] Under constant temperature conditions of 90℃ to 110℃, a uniform and dense oxide film begins to regrow on the surface of the molten bismuth liquid. Within this temperature range, the oxidation reaction rate is moderate, and the total duration of the entire oxidation cycle is approximately 1 to 2 minutes. As the oxidation time progresses, the liquid surface color gradually and rapidly changes from silvery-gray, with extremely short transition times between different interference colors, typically only a few seconds to 15 to 20 seconds. Operators must closely observe the color change of the liquid surface; when the liquid surface exhibits a uniform and stable golden-yellow interference color, it indicates that the oxide film has reached the target thickness. At this point, the oxide film thickness is approximately 100 nm to 150 nm, corresponding to a golden-yellow interference color.

[0058] It should be noted that in the oxidation process described in this invention, the oxidation time is directly related to the oxide film thickness, and the thickness of the oxide film is reflected in its surface microstructure: a longer oxidation time results in a thicker oxide film with a sparse wrinkled morphology on the film surface; a shorter oxidation time results in a thinner oxide film with a denser wrinkled morphology on the film surface. These wrinkled morphologies are natural surface textures formed by stress release during the growth of the oxide film. Different degrees of wrinkle density give the film layer different visual textures, which can be selectively controlled according to artistic effect requirements.

[0059] During this process, the oxide film layer formed on the surface of the molten bismuth liquid and the underlying bismuth substrate together constitute a structure such as Figure 2 The double-layer film structure shown consists of an upper layer of colored oxide interference film with a thickness of only about 100 nm to 150 nm, and a lower layer of solidified bismuth substrate with a thickness of about 0.3 mm to 0.8 mm. Figure 2 The diagram schematically illustrates that when incident light strikes the surface of the oxide film, part of the light is reflected from the upper surface of the oxide film, while the other part penetrates the oxide film and is reflected at the interface between the oxide film and the bismuth substrate. The two reflected beams interfere due to the optical path difference, thus exhibiting a golden interference color. This double-layer structure is the core feature of the product obtained by this invention.

[0060] (3) Color development and film adhesion formation

[0061] like Figure 1 The third step in the flowchart shown is to perform color development and film adhesion formation operations after the oxide film on the liquid surface has grown to the target golden color.

[0062] Select a 10cm×15cm stainless steel plate as a rigid heat-resistant component (the component temperature is about room temperature 20℃~25℃), and insert it obliquely into the molten bismuth liquid at an angle of about 30°~45° from the liquid surface, with an insertion depth of about 1cm~2cm.

[0063] Because the temperature of the stainless steel plate is much lower than that of the molten bismuth liquid (temperature difference of about 60℃~90℃), the molten bismuth liquid quickly condenses on the surface of the stainless steel plate, forming a solid bismuth substrate with a thickness of about 0.3mm~0.8mm.

[0064] Then, slowly and uniformly raise the stainless steel plate at a speed of approximately 1 cm / s to 2 cm / s, within the range of 0.5 cm / s to 5 cm / s. During the raising process, the golden-yellow oxide interference film already formed on the liquid surface adheres completely to the surface of the solid bismuth substrate due to surface tension and is carried out of the liquid surface as a whole along with the stainless steel plate. The raising speed should be kept uniform to avoid tearing the film due to excessive speed or redissolving the film due to excessively slow speed.

[0065] (4) Cooling and film removal

[0066] like Figure 1 In the fourth step of the flowchart shown, the stainless steel plate, including the bismuth substrate and the golden interference film on its surface, is placed in a ventilated area for natural cooling for approximately 30-60 minutes. Once the temperature has dropped to room temperature (20°C-25°C), the entire bismuth-based colored interference film is gently peeled off from the edge of the stainless steel plate. The resulting product is a thin film material with an area of ​​approximately 10cm × 15cm, and its structure is as follows... Figure 2 As shown, it includes a solidified bismuth substrate with a thickness of approximately 0.3 mm to 0.8 mm, and a golden-yellow oxide interference film layer with a thickness of approximately 100 nm to 150 nm attached to the surface of the bismuth substrate. The film surface is smooth and flat, with a uniform golden-yellow hue, and exhibits a fine wrinkle morphology corresponding to the oxidation time. When viewed from different angles, it displays a color change from golden yellow to orange-red. Thus, as... Figure 1 The complete four-step preparation process shown is now complete.

[0067] Example 2: Preparation of bismuth-based color interference films with different colors

[0068] This embodiment demonstrates the color controllability of the method of the present invention by preparing bismuth-based color interference films with different interference colors through controlling the oxidation temperature and oxidation time. When understanding this embodiment, it is recommended to combine it with... Figure 1 The four-step preparation flowchart shown illustrates the overall process route, and can be used as a reference. Figure 2 The schematic diagram of the double-layer film structure shown illustrates the basic principle that oxide films of different thicknesses produce different interference colors.

[0069] according to Figure 1 Step one, as shown, completes the melting of the raw materials, resulting in a homogeneous molten bismuth solution.

[0070] Molten bismuth was cooled to different temperatures within the range of 90℃ to 110℃ for isothermal oxidation. To systematically verify the effect of oxidation temperature on interference color and oxidation rate, the experiment was divided into 5 groups of different temperature conditions, numbered 2-1, 2-2, 2-3, 2-4, and 2-5. Group 2-1 corresponds to the lowest temperature (90℃~95℃), and group 2-5 corresponds to the highest temperature (105℃~110℃), with increasing numbers indicating progressively higher oxidation temperatures. Each group of experiments maintained a normal air environment (oxygen volume fraction of approximately 21%), and the liquid surface temperature was monitored using an infrared thermometer. The oxidation temperature range, total oxidation cycle time, resulting oxide film thickness range, film surface wrinkling characteristics, and final interference color of each group of experiments are summarized in the table below:

[0071] 2-1 90℃~95℃ 60s~120s 50nm~80nm blue-purple 2-2 95℃~100℃ 45s~90s 80nm~120nm blue-green 2-3 100℃~105℃ 30s~60s 100nm~150nm Golden yellow 2-4 105℃~108℃ 20s~45s 150nm~250nm Orange-red 2-5 108℃~110℃ 15s~30s 200nm~350nm purplish-red

[0072] The experimental conditions and results for each number are explained in detail below:

[0073] Step 2-1: The molten bismuth solution is cooled to a constant temperature between 90℃ and 95℃ and allowed to stand. After scraping off the impurity film, the oxidation cycle is maintained for approximately 60s to 120s. At this lower temperature, the oxidation rate of bismuth is slower, resulting in a thinner oxide film, approximately 50nm to 80nm thick. This corresponds to a smaller optical path difference, and the interference enhancement wavelength is located in the short-wavelength band of visible light, thus the film appears bluish-purple. The oxide film surface exhibits a fine, wrinkled morphology and a delicate texture. Figure 2 As shown, the thinner oxide film layer corresponds to a smaller optical path difference, which causes the wavelength of the interference enhancement to be biased towards the blue-violet end.

[0074] No. 2-2: The molten bismuth solution was cooled to a constant temperature between 95℃ and 100℃ and allowed to stand. After scraping off the impurity film, the oxidation cycle was maintained for approximately 45s to 90s. A slight increase in temperature accelerated the oxidation rate, resulting in an oxide film thickness of approximately 80nm to 120nm. The interference enhancement wavelength shifted towards longer wavelengths, and the film exhibited a blue-green hue. The surface wrinkle density was moderate. These conditions fall within the medium oxidation rate range, resulting in a natural color transition and representing an ideal preparation window for a blue-green hue. (Refer to...) Figure 2 The thin-film interference principle shown is such that the oxide film layer of this thickness range causes the interference enhancement wavelength to be located in the blue-green band.

[0075] Number 2-3: The molten bismuth solution is cooled to a constant temperature range of 100℃~105℃ and allowed to stand. After scraping off the impurity film, the oxidation cycle is maintained for approximately 30s~60s. This temperature range is similar to that of Example 1, and the oxide film thickness is approximately 100nm~150nm, exhibiting a golden-yellow color. The film surface has relatively fine wrinkles. The golden-yellow color has high brightness and strong visual impact, making it a commonly used and stable preparation condition in the method of this invention.

[0076] Number 2-4: The molten bismuth solution is cooled to a constant temperature between 105℃ and 108℃ and allowed to stand. After scraping off the impurity film, the oxidation cycle is maintained for approximately 20s to 45s. Further increasing the temperature significantly accelerates the oxidation rate, resulting in an oxide film thickness of approximately 150nm to 250nm. The interference enhancement wavelength shifts to the orange-red band, and the film appears orange-red. The wrinkles on the film surface gradually become less dense. Under these conditions, the oxidation time needs to be appropriately controlled to avoid an excessively thick film that results in a darker color.

[0077] Numbers 2-5: The molten bismuth solution was cooled to a constant temperature between 108℃ and 110℃ and allowed to stand. After scraping off the impurity film, the oxidation cycle was maintained for approximately 15-30 seconds. This group represents the highest temperature conditions, resulting in the fastest oxidation rate and the thickest oxide film, approximately 200nm-350nm thick. The corresponding interference enhancement wavelength is located in the long-wavelength visible light range or even the near-infrared region, and the film appears purplish-red. The film surface exhibits a distinct sparse wrinkled morphology. For example... Figure 2 As shown, a thicker oxide film corresponds to a larger optical path difference, causing the interference enhancement wavelength to shift towards the red-violet end. Under this condition, the oxidation time is the shortest, and the transition between different colors takes only a few seconds. It is necessary to closely observe the color change of the liquid surface and stop the oxidation in time to obtain the ideal purplish-red hue.

[0078] The five sets of experiments numbered 2-1 to 2-5 systematically demonstrate the complete color transition of the bismuth-based color interference film from blue-violet to purplish-red as the oxidation temperature increases from low to high within the range of 90℃ to 110℃. The bismuth-based color interference films with different colors obtained in each set of experiments were all produced using... Figure 1 The molding and film removal methods shown in steps three and four are used to prepare the product, and the resulting product is as follows. Figure 2 The diagram shows a bilayer structure consisting of a solidified bismuth substrate and a colored oxide interference film. It is particularly important to emphasize that, within the same temperature range, the oxidation rate is directly proportional to temperature: the higher the temperature, the faster the oxidation reaction and the shorter the time required to achieve the target color; conversely, the lower the temperature, the slower the oxidation reaction and the longer the time required to achieve the target color.

[0079] In practice, operators can select the appropriate oxidation temperature and time ranges according to the target color requirements, referring to the table above, and judge the oxidation process by directly observing the color change of the liquid surface with the naked eye (e.g., Figure 1 (Step 2 shows the color observation step). Since the conversion time between different interference colors within the temperature range of 90℃~110℃ described in this invention is typically only a few seconds to 15s~20s, operators must maintain high concentration and quickly proceed with subsequent adhesion and molding operations once the liquid surface displays the target color. Furthermore, if a finely textured, wrinkled texture is desired on the film surface, the oxidation time can be appropriately shortened; if a sparsely textured, wrinkled texture is desired, the oxidation time can be appropriately extended.

[0080] Example 3: Application of bismuth-based color interference films in arts and cultural creative products

[0081] This embodiment describes the complete process of applying the bismuth-based color interference films prepared in Examples 1 and 2 to the production of artistic decorative paintings. When understanding this embodiment, it is recommended to refer to... Figure 3 The flowchart shown illustrates the application of art and cultural creativity, allowing you to grasp the complete process from raw materials to the final artwork.

[0082] (1) Shaping and color changing processing

[0083] like Figure 3 The left side of the flowchart shows the process of shaping and color-changing the purplish-red bismuth-based color interference film prepared in Example 2 as the main material. First, according to the design pattern of the decorative painting, a large piece of bismuth-based color interference film is cut into the required shapes and sizes, including: main petal shapes (approximately 8cm × 12cm, 5 pieces), leaf shapes (approximately 5cm × 8cm, 3 pieces), and flower stem strips (approximately 0.5cm wide, length as needed). A sharp craft knife or scissors is used for cutting, cutting along the design outline in one go to avoid repeated cutting that could cause fraying at the film edges.

[0084] Heating and bending some of the petal components to create the desired shape: Place the cut petal-shaped membrane on a hot plate and heat it to 80℃~100℃. Hold the temperature for about 1min~2min to soften the membrane. Then, use tweezers to gently bend the edges of the petals upwards by about 30°~60° to form a three-dimensional petal shape. The bent petals, when viewed from different angles, exhibit a color gradient from purplish-red to pink, enhancing the three-dimensional effect. This step corresponds to... Figure 3 The process involves heating, bending, and curling to create the shape.

[0085] To create texture details, a micro-etching process is performed on one petal: a 10%–20% dilute nitric acid solution is used as the etching solution. A small amount of acid is applied to the petal surface with a fine brush, dotting several small dots. After etching for approximately 5–15 seconds, excess acid is absorbed with absorbent paper, and the petal is gently rinsed with water. The oxide film layer in the acid-etched area is selectively removed, exposing the underlying silvery-white bismuth substrate, creating a dewdrop or textured white-out effect on the petal. This step corresponds to… Figure 3 The localized micro-corrosion process is an optional fine processing step.

[0086] (2) Application of combination assembly

[0087] like Figure 3 The right side of the flowchart shows the assembly and application of the processed bismuth-based color interference film. A 30cm x 40cm black wooden frame is prepared as the base, lined with black velvet fabric as the background. The outlines of flower branches are pre-drawn on the background fabric as a reference for pasting and positioning.

[0088] Arrange the bent 3D petals, leaves, stems, and other components within the frame according to the design. The petals are arranged in a five-petal plum blossom shape, with a flat, unbent petal placed in the center as the stamen base. Secure the components together using transparent epoxy resin or double-sided tape, pressing from the center outwards to ensure a smooth, airtight finish. This step corresponds to... Figure 3 The middle stage involves arranging, splicing, and pasting to fix the parts.

[0089] Attach a transparent resin bead, approximately 0.5cm in diameter, to the center of the flower as a stamen embellishment, enhancing its three-dimensionality and gloss. After the entire decorative painting is completed, cover the surface with a transparent acrylic sheet approximately 2mm thick as a protective layer to protect the bismuth-based color interference film from mechanical damage and oxidation fading. Finally, fix the frame backing to complete the finished artwork. This step corresponds to... Figure 3 The process involves combining the base, protective layer, and frame to complete the final stage of creating the overall artwork.

[0090] The resulting decorative painting exhibits a dazzling array of color effects on its bismuth-based color interference film under different lighting conditions and viewing angles: the flowers appear purplish-red when viewed from the front, gradually transforming into blue and green when viewed from the side. This dynamic color change endows the artwork with unique visual appeal and artistic merit. The painting can be hung indoors for extended periods (temperature 15℃~30℃, relative humidity 40%~70%), maintaining stable colors and possessing excellent decorative and collectible value. Figure 3 As shown, this decorative painting falls under the application category of decorative painting as an art form.

[0091] Example 4: Multi-layered composite art ornaments

[0092] This embodiment describes the process of creating artistic earrings by stacking and combining multiple layers of bismuth-based color interference films of different colors. For understanding this embodiment, it is recommended to refer to... Figure 2 The schematic diagram of the double-layer membrane structure shown illustrates the basic structure of a single-layer membrane, and combines it with... Figure 3 The flowchart shown illustrates the application method, which involves multi-layered combinations and related steps of artistic ornaments.

[0093] Small bismuth-based color interference films in blue, green, and gold were prepared according to the method in Example 2, and each film was cut into a circle with a diameter of approximately 1.5 cm. The structure of each monolayer film is as follows... Figure 2 As shown, each consists of a solidified bismuth substrate and a colored oxide interference film.

[0094] Take a transparent acrylic disc (2cm in diameter) as the base substrate. On its surface, sequentially attach a blue film (bottom layer), a green film (middle layer, offset by 0.3cm), and a gold film (top layer, offset by another 0.3cm), forming a three-layered, staggered concentric circle structure. The three layers are bonded together with transparent optical adhesive, and each layer is cured by UV light for 30-60 seconds after bonding.

[0095] After multiple layers are stacked, light passes through interference films of different colors in sequence, producing a complex multi-beam interference effect, giving the jewelry a richer and deeper color gradation. When viewed from the front, gold is the dominant color; when viewed from the side, blue-green tones gradually emerge; and when the jewelry is rotated, the colors flow and change like a rainbow. This multi-layered structure can be viewed as three... Figure 2 The spatial combination of the basic bilayer film unit shown allows the interference colors of each layer of film to be superimposed and modulated, producing a composite color effect that cannot be achieved by a single film layer.

[0096] Drill a hole in the top of the acrylic substrate, insert a metal ear hook accessory, and secure it. This completes the creation of a pair of multi-layered, stacked art earrings. The entire piece is lightweight (approximately 3-5g total weight), comfortable to wear, and vibrantly colored, possessing high artistic value and market potential. Figure 3 As shown, these earrings fall under the category of art jewelry, an art form, and their production process encompasses... Figure 3 The flowchart shown illustrates the complete process route from shaping and color modification to assembly and application.

[0097] Example 5: Preparation of patterned bismuth-based color interference films by selective local scraping

[0098] This embodiment describes the complete process of preparing a patterned effect in situ on the surface of a bismuth-based color interference film using the selective local scraping technique in step two. This embodiment adds a selective local scraping step to the existing embodiments 1 and 2. Steps one, three, and four are the same as in embodiment 1 and will not be repeated here. The following focuses on the detailed operation of the selective local scraping in step two.

[0099] (1) Initial impurity removal and uniform oxidation

[0100] Following step one of Example 1, the raw material was melted, and the molten bismuth was cooled to a constant temperature between 100°C and 105°C and allowed to stand. A stainless steel scraper was used to gently remove the irregular oxide film that spontaneously formed on the surface of the liquid during cooling, exposing a bright molten bismuth surface. A normal air environment (oxygen volume fraction of approximately 21%) was maintained, allowing the surface of the molten bismuth to come into natural contact with the air.

[0101] Under constant temperature conditions of 100℃~105℃, a uniform and dense oxide film begins to regrow on the liquid surface. As oxidation time progresses, the liquid surface color gradually changes according to the following pattern: silver-gray → bluish-purple → bluish-green → golden yellow → orange-red → purplish-red. The entire oxidation cycle lasts approximately 30 to 60 seconds (corresponding to the golden yellow stage).

[0102] (2) Selective local scraping operation

[0103] In this embodiment, the target pattern is "blue-green tree branch texture on a gold background". The design concept is to use gold as the background color and blue-green as the tree branch texture pattern to form a distinct contrast between warm and cool colors.

[0104] Based on the above design objectives, the mid-course intervention mode will be selected for operation. The specific operation is as follows:

[0105] Determining the timing of scraping: Closely observe the color change of the liquid surface. When the oxide film on the liquid surface grows to a uniform and stable golden yellow color (at this point, the oxide film thickness is approximately 100nm~150nm, about 60%~70% of the total oxide film thickness), it is the optimal time to perform local scraping. Operators can directly observe the color of the liquid surface with the naked eye. When the golden yellow color reaches its highest brightness and best uniformity, preparations should be made immediately for the scraping operation.

[0106] Preparation of scraping tools: Select a thin stainless steel scraper with sharp edges as the scraping tool. The width of the scraper blade is about 3mm~5mm and the blade tip angle is about 30°~45°. Before use, wipe the blade with anhydrous ethanol to ensure that the blade is free of oil and impurities.

[0107] Scraping Procedure: Holding a stainless steel scraper, gently probe the oxide film surface from the edge of the liquid. Following the pre-set dendritic texture, scrape away the dendritic lines on the oxide film at a uniform speed and pressure. The scraping depth should be sufficient to completely remove the oxide film, exposing the bright, silvery-gray molten bismuth beneath. The scraping width should be controlled within the range of 1mm to 3mm. The entire dendritic line drawing process should be completed within 5 to 15 seconds.

[0108] After scraping, the liquid surface forms obvious spatial divisions: the dendritic lines are the bare bismuth liquid surface where the oxide film has been completely scraped off (exhibiting a silvery-gray luster), while the remaining areas are golden-yellow areas where the oxide film is completely preserved. The two types of areas are clearly alternating in space.

[0109] (3) Differentiated re-oxidation and pattern fixing

[0110] After the scraping operation is completed, maintain the normal air environment and constant temperature of 100℃~105℃ to continue oxygen supply and enter the differentiated re-oxidation stage.

[0111] Re-oxidation of the scraped area (dendritic region): The scraped dendritic region is re-oxidized from the bright new surface of the molten bismuth liquid, and the oxide film grows gradually from the initial thickness. During the continued oxidation process, the region first goes through a blue-violet stage (about 5 to 10 seconds), and then enters a blue-green stage (about 10 to 20 seconds).

[0112] Continued oxidation in the unscraped areas (base color areas): The oxide film in the unscraped golden yellow areas continues to thicken, and the golden yellow color gradually transitions towards orange-red.

[0113] Color contrast formation and pattern shaping: When the oxide film in the dendritic region grows to a uniform and stable blue-green color (at this time, the oxide film thickness in the dendritic region is approximately 80nm~120nm, corresponding to a continued oxidation time of approximately 10~20 seconds), while the oxide film in the base color region has thickened to an orange-red color (at this time, the oxide film thickness in the base color region is approximately 150nm~250nm), the adhesion and shaping operation in step three is immediately performed. At this point, the liquid surface presents a clear pattern effect of "blue-green dendritic texture on an orange-red base," with a sharp color contrast between the dendritic texture and the base color, and clear boundaries.

[0114] (4) Adhesion and removal of patterned film layers

[0115] Following the steps three and four of Example 1, a rigid heat-resistant component with a temperature of 10℃~60℃ is obliquely inserted into the molten bismuth liquid and slowly lifted so that the patterned color oxide interference film is completely attached to the bismuth substrate and is taken out as a whole. After cooling and peeling, the patterned bismuth-based color interference film is removed.

[0116] (5) Structural features and visual effects of the resulting product

[0117] The structure of the obtained bismuth-based color interference film is basically the same as that in Example 1, including a solidified bismuth substrate with a thickness of about 0.3 mm to 0.8 mm and a color oxide interference film layer attached to the surface of the bismuth substrate. The difference is that the color oxide interference film layer obtained in this example exhibits a spatially differentiated thickness distribution: the oxide film thickness in the dendritic region is about 80 nm to 120 nm, exhibiting a blue-green interference color; the oxide film thickness in the background region is about 150 nm to 250 nm, exhibiting an orange-red interference color.

[0118] Visually, when viewed from the front, the membrane presents a pattern of blue-green tree-like veins on an orange-red background, with clear lines and distinct boundaries. Due to the angle-dependent nature of interference colors, the pattern exhibits dynamic color changes when viewed from different angles: from the front, the contrast is predominantly orange-red / blue-green; when viewed at an angle, the background shifts towards purplish-red, and the veins shift towards blue-purple, resulting in a richer overall color gradation. The membrane surface displays varying degrees of wrinkles at different thicknesses, further enhancing the visual texture and depth of the pattern.

[0119] (6) Artistic Application

[0120] The partition-differentiated patterned bismuth-based color interferometer film prepared in this embodiment corresponds to... Figure 4 , Figure 5 , Figure 6 It can be used directly as the core substrate for artistic decorative paintings. Relying on the original partitioned interference colors and natural wrinkle texture of the film layer, a complete picture is formed without the need for additional ink printing, manual coloring, chemical overall corrosion and other secondary coloring processes, simplifying the artistic creation process.

[0121] The patterned film is cut to fit the artwork's design and assembled with a dark solid wood frame. A 2mm transparent acrylic sheet is then applied as a protective layer to isolate the film from air, moisture, and external abrasion, ensuring long-term color stability. The finished product has a metallic pearlescent texture. Utilizing the optical properties of thin-film interference, the background color and texture lines dynamically shift with changes in viewing angle and ambient light, creating a flowing, iridescent visual effect that cannot be replicated by ordinary pigments or metal patches, thus possessing both decorative and collectible value.

[0122] The pattern film can be shaped in three dimensions by combining the heating and bending process in Example 3: Place the cut pattern film on an electric heating plate at 80℃~100℃ to soften for 1~2 minutes, and use tweezers to bend and curl to shape petals, branches and leaves and other three-dimensional undulating structures, so that the pattern image has both planar texture and three-dimensional layers, and the color changing effect is richer when viewed from multiple angles.

[0123] It can be used in conjunction with the local micro-corrosion process described in Example 3: a 10%~20% dilute nitric acid solution is applied to a local area of ​​the film surface, and the local oxide film is removed by short-term corrosion to expose the silver-white bismuth base. On the basis of the original interference color pattern, white details such as dewdrops, leaf veins, and star points are added, and the warm and cool metallic colors complement each other to create a high-end artistic decorative material with more complex layers and more exquisite details.

[0124] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a bismuth-based color interference film material, characterized in that, Includes the following steps: Step 1: Select high-purity metallic bismuth raw material and place it in a heating container. Heat the container to 260℃~350℃ to completely melt the metallic bismuth into a homogeneous molten bismuth liquid. Step 2: Cool the molten bismuth liquid to a constant temperature range of 85℃~120℃ and let it stand. Scrape off the messy and uneven oxide film that spontaneously forms on the surface of the molten bismuth during the melting process. Maintain the gas atmosphere on the surface of the molten bismuth liquid containing 10%~30% oxygen by volume. Rely on the oxygen in the atmosphere to achieve uniform growth of the oxide film on the surface of the bismuth liquid. Adjust the thickness of the oxide film and the interference color by natural oxygen supply in the atmosphere. Wait until the oxide film on the liquid surface grows to present the target color interference color. Step 3: Use a rigid heat-resistant component with a temperature range of 10℃~60℃, and insert it obliquely into the molten bismuth liquid from the liquid surface. Utilize the low temperature characteristics of the component itself to cause the molten bismuth liquid to spontaneously condense on the surface of the component to form a solid bismuth substrate. The component is slowly raised so that the colored oxide interference film that has formed on the liquid surface is completely attached to the bismuth substrate by surface tension and is brought out as a whole. Step 4: Cool the entire component, including the bismuth substrate and the surface color interference film, to 15°C~35°C, peel off the bismuth-based color interference film, which includes a solidified bismuth substrate and a color oxide interference film layer attached to the surface of the bismuth substrate, thus completing the preparation.

2. The method for preparing a bismuth-based color interference film material according to claim 1, characterized in that: The purity of the high-purity metallic bismuth raw material is 95%~99.99% by mass.

3. The method for preparing a bismuth-based color interference film material according to claim 1, characterized in that: The heating container is a rigid container that does not deform within a temperature range of 260℃ to 350℃.

4. The method for preparing a bismuth-based color interference film material according to claim 1, characterized in that: The molten bismuth liquid is cooled to a constant temperature range of 90℃ to 115℃ and left to stand.

5. The method for preparing a bismuth-based color interference film material according to claim 1, characterized in that: The gas atmosphere maintaining the surface of the molten bismuth liquid is natural air atmosphere, in which the oxygen volume fraction is 15%~25%.

6. The method for preparing a bismuth-based color interference film material according to claim 1, characterized in that: The rigid heat-resistant component has a melting point higher than 250°C, and the material, surface finish, and shape of the rigid heat-resistant component are not limited.

7. The method for preparing a bismuth-based color interference film material according to claim 1, characterized in that: The angle of the oblique insertion is 15 degrees to 75 degrees, and the speed of the slow lifting is 0.5 cm / s to 5 cm / s.

8. The method for preparing a bismuth-based color interference film material according to claim 1, characterized in that: In step four, the cooling is natural cooling, and the cooling time is 10 min to 120 min.

9. A bismuth-based color interference film, characterized in that, The bismuth-based color interference film is prepared by any one of claims 1 to 8, comprising a solidified bismuth substrate and a color oxide interference film layer attached to the surface of the bismuth substrate, wherein the color oxide interference film layer exhibits color produced by thin-film interference effect.

Images