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DOI: 10.22184/1993-7296.FRos.2020.14.4.368.374
The paper presents the research of the properties of light-absorbing coatings based on nickel-phosphorus alloy. The spectral characteristics of reflection of the coatings were analyzed at different stages of their manufacture. The reason of the super-absorption of the NiP alloy is established and the possibility of its use as a material suppressing the scattered light inside the optical path of optoelectronic devices is described, for example, in blends of stellar sensors of a spacecraft orientation system, is described.
The paper presents the research of the properties of light-absorbing coatings based on nickel-phosphorus alloy. The spectral characteristics of reflection of the coatings were analyzed at different stages of their manufacture. The reason of the super-absorption of the NiP alloy is established and the possibility of its use as a material suppressing the scattered light inside the optical path of optoelectronic devices is described, for example, in blends of stellar sensors of a spacecraft orientation system, is described.
Теги: light-absorbing coatings nip alloy super-absorption сверхпоглощение. светопоглощающие покрытия сплав nip
Super Absorbing Properties of Nickel-Phosphorus Alloy
D. V. Marusev
Joint Stock Company “Science research institute Micro Devises-С”, Moscow, Russia.
The paper presents the research of the properties of light-absorbing coatings based on nickel-phosphorus alloy. The spectral characteristics of reflection of the coatings were analyzed at different stages of their manufacture. The reason of the super-absorption of the NiP alloy is established and the possibility of its use as a material suppressing the scattered light inside the optical path of optoelectronic devices is described, for example, in blends of stellar sensors of a spacecraft orientation system, is described.
Keywords: NiP alloy, light-absorbing coatings, super-absorption.
Received: 25.03.2020
Accepted: 10.05.2020
Introduction
Improving the optical information systems used on board spacecraft is relevant in the modern aerospace industry. One of the reasons that reduces image quality is the scattered light background in the optical path of optoelectronic devices. To suppress it, a hood with diaphragms located inside it is installed in front of the entrance pupil of the optical system [1]. An additional way to suppress scattered radiation is to blacken the inner surface of the hood by applying special coatings with the function of light absorption. Moreover, the higher their absorption indices, the lower the overall dimensions of the equipment. The use of light-absorbing coatings improves the signal-to-noise ratio of optoelectronic receivers and, accordingly, the modulation transmission function of optical information systems operating in polychrome or hyperspectral modes.
At the moment, there is a large selection of light-absorbing coatings that differ from each other by the type of radiation absorption mechanism, manufacturing technology, resistance to external factors, cost, etc. The criterion characterizing the absorbing ability of coatings is the coefficient of diffuse reflection of electromagnetic radiation from their surface. The lower it is, the more efficient is the absorption of light.
The most common light-absorbing material is matte black enamel. For a long time, they were used to suppress scattered radiation in optical devices of a spacecraft, but the insufficiently low reflectivity of electromagnetic radiation from their surface (diffuse reflectance ≈ 5%) and the sensitivity of their optical and physical properties to external factors compel us to look for alternative ink technologies.
One such method is the deposition of a nickel-phosphorus alloy. Special processing in an acid solution (etching) of chemically or galvanically deposited NiP films creates a developed surface morphology, in the form of many cone-shaped funnels, which provides ultra-low reflectivity of electromagnetic radiation from their surface in the wavelength range from UV to near IR (NIR) [2, 3]. In addition to this, the increased resistance of nickel-phosphorus coatings to external factors allows them to be used to suppress scattered radiation in optical information systems of a spacecraft. Furthermore, unlike enamels, they have high conductive properties, which eliminates the possibility of accumulation of static charge on the structural elements of optical devices. The uniqueness of the properties of light-absorbing coatings based on a nickel-phosphorus alloy is of interest in their further study.
The paper presents the results of studies of the spectral characteristics of the reflection of the NiP alloy at different stages of the manufacture of light-absorbing coatings, their resistance to various destabilizing factors, and the possibility of using as a material that suppresses the scattered light background inside the optical path of spacecraft optoelectronic devices.
Object of Research
The study of light-absorbing nickel-phosphorus coatings was carried out on round test samples with a diameter of 30 mm and a thickness of 1 mm, from steel 35, stainless steel 12X18H10T, duralumin AMg6, titanium VT1–0 and invar 36N.
The manufacturing technology of light-absorbing coatings obtained by the galvanic method consists of three stages, shown in Fig. 1.
The deposition process was carried out from an electrolyte containing sodium hypophosphite, nickel sulfate and boric acid. Etching took place in aqueous solutions of nitric acid and sulfuric acid with sodium nitrate. Chemical pretreatment is a standard operation for surface preparation before galvanic deposition of nickel films.
Research Methods
The absorption properties of the nickel-phosphorus alloy were studied by measuring its spectral coefficients of total and diffuse reflections on a Lambda 1050 spectrophotometer with a 150 mm Integrating Sphere attachment.
The morphology of the surface of light-absorbing nickel-phosphorus coatings was studied using a FEI Helios 650 Nanolab double-beam scanning electron-ion microscope.
A statistical analysis of the values of the input diameters of the funnels of light-absorbing coatings was carried out using a programmed calculation of their average values of the Feere diameters from images of developed surface morphology obtained using an electron microscope.
Research Results
Electroplated nickel-phosphorus films (after the 2nd stage of the process) are externally shiny, due to their high reflectivity. They acquire the properties of superabsorption of electromagnetic radiation after etching in oxygen-containing acids (stage 3 of the process). This is due to the fact that, as a result of etching, a developed surface morphology is formed, in the form of many conical depressions of different sizes, which are effective light traps. Multiple reflection of electromagnetic radiation inside the funnels makes the coatings optically black. The appearance of the surface morphology of the light-absorbing nickel-phosphorus alloy is shown in Fig. 2.
The optical properties of the NiP alloy (spectral coefficients of total and diffuse reflections) at different stages of the manufacture of light-absorbing coatings are shown in Fig. 3. The developed surface morphology makes it possible to reduce the spectral coefficient of total reflection of coatings of the 2nd stage of the manufacturing process on average from 70% (curve 1, Fig. 3) to tenths of a percent (curve 3, Fig. 3). It also changes the nature of reflection.
Electromagnetic radiation diffusely scatters from the surface of the light-absorbing coating. Its spectral characteristics of total and diffuse reflections are almost identical (curves 3 and 4, Fig. 3), in contrast to films after the 2nd stage of the process, which have an average reflection coefficient of 60%.
The dimensions of the funnels of light-absorbing coatings affect the efficiency of absorption of electromagnetic radiation in different spectral wavelength ranges. The control of technological modes of the 2nd stage of the technological process – the composition of the electrolyte, the pH value and the current density during alloy deposition, as well as the 3rd stage – the concentration of acid solutions, time and etching temperature, allows to optimize their absorption capacity for specific observation tasks. In fig. Figure 4 shows the statistical distributions of the input diameters of the light traps of coatings for different types of spectral characteristics of reflection, which are presented in Fig. 5.
Coatings with a funnel diameter distribution corresponding to the Gaussian distribution (Fig. 4b) have values of the total reflection coefficient almost independent of the wavelength (curve 2, Fig. 5).
Light-absorbing nickel-phosphorus coatings are resistant to various types of external factors. This is evidenced by the test results in accordance with GOST RV 20.39.304–98 for equipment group 5.3, which approximately simulate their presence in the spacecraft equipment: mechanical loads, solar and radiation, low atmospheric pressure, high and low ambient temperatures, and its cyclical change. According to the test results, the values of the diffuse reflection coefficient remained unchanged.
The characteristics of light-absorbing nickel-phosphorus coatings remain unchanged regardless of the type, area and configuration of the substrate on which they are applied. Fig. 6 presents structural details of various shapes with areas of up to 100 and 1000 sq.cm.
Nickel-phosphorus alloy, it is possible to blacken the structural details of the optical path of optoelectronic devices made of various types, steel, alloys of aluminum, titanium and invar. Figure 7 shows an image of blend samples with a light-absorbing nickel-phosphorus coating of stellar sensors of the spacecraft orientation system.
Conclusions
The super-absorbing properties of the nickel-phosphorus alloy are formed due to the presence of developed morphology on its surface in the form of many conical funnels that determine the diffuse nature of the reflection of electromagnetic radiation.
Technological control of the input diameters of the funnels of the developed surface morphology of the light-absorbing coatings allows you to influence their spectral characteristics of the reflection of electromagnetic radiation.
The resistance of light-absorbing nickel-phosphorus coatings to external factors allows them to be used for operation in outer space.
The manufacturing technology of light-absorbing nickel-phosphorus coatings allows you to apply them to the structural parts of the optical path from different types of materials, various configurations with an area of up to 1000 sq.cm or more.
We are grateful for the help in carrying out research S. N. Khakhanov and employees of Systems for Microscopy and Analysis LLC, Moscow, Skolkovo Innovation Center.
AUTHOR
D. V. Marusev, engineer, JSC “Scientific research Institute of micro instruments-K”, marusev.niimpk@gmail.com, Moscow, Russia.
ORCID ID: 0000-0003-0325-2003
D. V. Marusev
Joint Stock Company “Science research institute Micro Devises-С”, Moscow, Russia.
The paper presents the research of the properties of light-absorbing coatings based on nickel-phosphorus alloy. The spectral characteristics of reflection of the coatings were analyzed at different stages of their manufacture. The reason of the super-absorption of the NiP alloy is established and the possibility of its use as a material suppressing the scattered light inside the optical path of optoelectronic devices is described, for example, in blends of stellar sensors of a spacecraft orientation system, is described.
Keywords: NiP alloy, light-absorbing coatings, super-absorption.
Received: 25.03.2020
Accepted: 10.05.2020
Introduction
Improving the optical information systems used on board spacecraft is relevant in the modern aerospace industry. One of the reasons that reduces image quality is the scattered light background in the optical path of optoelectronic devices. To suppress it, a hood with diaphragms located inside it is installed in front of the entrance pupil of the optical system [1]. An additional way to suppress scattered radiation is to blacken the inner surface of the hood by applying special coatings with the function of light absorption. Moreover, the higher their absorption indices, the lower the overall dimensions of the equipment. The use of light-absorbing coatings improves the signal-to-noise ratio of optoelectronic receivers and, accordingly, the modulation transmission function of optical information systems operating in polychrome or hyperspectral modes.
At the moment, there is a large selection of light-absorbing coatings that differ from each other by the type of radiation absorption mechanism, manufacturing technology, resistance to external factors, cost, etc. The criterion characterizing the absorbing ability of coatings is the coefficient of diffuse reflection of electromagnetic radiation from their surface. The lower it is, the more efficient is the absorption of light.
The most common light-absorbing material is matte black enamel. For a long time, they were used to suppress scattered radiation in optical devices of a spacecraft, but the insufficiently low reflectivity of electromagnetic radiation from their surface (diffuse reflectance ≈ 5%) and the sensitivity of their optical and physical properties to external factors compel us to look for alternative ink technologies.
One such method is the deposition of a nickel-phosphorus alloy. Special processing in an acid solution (etching) of chemically or galvanically deposited NiP films creates a developed surface morphology, in the form of many cone-shaped funnels, which provides ultra-low reflectivity of electromagnetic radiation from their surface in the wavelength range from UV to near IR (NIR) [2, 3]. In addition to this, the increased resistance of nickel-phosphorus coatings to external factors allows them to be used to suppress scattered radiation in optical information systems of a spacecraft. Furthermore, unlike enamels, they have high conductive properties, which eliminates the possibility of accumulation of static charge on the structural elements of optical devices. The uniqueness of the properties of light-absorbing coatings based on a nickel-phosphorus alloy is of interest in their further study.
The paper presents the results of studies of the spectral characteristics of the reflection of the NiP alloy at different stages of the manufacture of light-absorbing coatings, their resistance to various destabilizing factors, and the possibility of using as a material that suppresses the scattered light background inside the optical path of spacecraft optoelectronic devices.
Object of Research
The study of light-absorbing nickel-phosphorus coatings was carried out on round test samples with a diameter of 30 mm and a thickness of 1 mm, from steel 35, stainless steel 12X18H10T, duralumin AMg6, titanium VT1–0 and invar 36N.
The manufacturing technology of light-absorbing coatings obtained by the galvanic method consists of three stages, shown in Fig. 1.
The deposition process was carried out from an electrolyte containing sodium hypophosphite, nickel sulfate and boric acid. Etching took place in aqueous solutions of nitric acid and sulfuric acid with sodium nitrate. Chemical pretreatment is a standard operation for surface preparation before galvanic deposition of nickel films.
Research Methods
The absorption properties of the nickel-phosphorus alloy were studied by measuring its spectral coefficients of total and diffuse reflections on a Lambda 1050 spectrophotometer with a 150 mm Integrating Sphere attachment.
The morphology of the surface of light-absorbing nickel-phosphorus coatings was studied using a FEI Helios 650 Nanolab double-beam scanning electron-ion microscope.
A statistical analysis of the values of the input diameters of the funnels of light-absorbing coatings was carried out using a programmed calculation of their average values of the Feere diameters from images of developed surface morphology obtained using an electron microscope.
Research Results
Electroplated nickel-phosphorus films (after the 2nd stage of the process) are externally shiny, due to their high reflectivity. They acquire the properties of superabsorption of electromagnetic radiation after etching in oxygen-containing acids (stage 3 of the process). This is due to the fact that, as a result of etching, a developed surface morphology is formed, in the form of many conical depressions of different sizes, which are effective light traps. Multiple reflection of electromagnetic radiation inside the funnels makes the coatings optically black. The appearance of the surface morphology of the light-absorbing nickel-phosphorus alloy is shown in Fig. 2.
The optical properties of the NiP alloy (spectral coefficients of total and diffuse reflections) at different stages of the manufacture of light-absorbing coatings are shown in Fig. 3. The developed surface morphology makes it possible to reduce the spectral coefficient of total reflection of coatings of the 2nd stage of the manufacturing process on average from 70% (curve 1, Fig. 3) to tenths of a percent (curve 3, Fig. 3). It also changes the nature of reflection.
Electromagnetic radiation diffusely scatters from the surface of the light-absorbing coating. Its spectral characteristics of total and diffuse reflections are almost identical (curves 3 and 4, Fig. 3), in contrast to films after the 2nd stage of the process, which have an average reflection coefficient of 60%.
The dimensions of the funnels of light-absorbing coatings affect the efficiency of absorption of electromagnetic radiation in different spectral wavelength ranges. The control of technological modes of the 2nd stage of the technological process – the composition of the electrolyte, the pH value and the current density during alloy deposition, as well as the 3rd stage – the concentration of acid solutions, time and etching temperature, allows to optimize their absorption capacity for specific observation tasks. In fig. Figure 4 shows the statistical distributions of the input diameters of the light traps of coatings for different types of spectral characteristics of reflection, which are presented in Fig. 5.
Coatings with a funnel diameter distribution corresponding to the Gaussian distribution (Fig. 4b) have values of the total reflection coefficient almost independent of the wavelength (curve 2, Fig. 5).
Light-absorbing nickel-phosphorus coatings are resistant to various types of external factors. This is evidenced by the test results in accordance with GOST RV 20.39.304–98 for equipment group 5.3, which approximately simulate their presence in the spacecraft equipment: mechanical loads, solar and radiation, low atmospheric pressure, high and low ambient temperatures, and its cyclical change. According to the test results, the values of the diffuse reflection coefficient remained unchanged.
The characteristics of light-absorbing nickel-phosphorus coatings remain unchanged regardless of the type, area and configuration of the substrate on which they are applied. Fig. 6 presents structural details of various shapes with areas of up to 100 and 1000 sq.cm.
Nickel-phosphorus alloy, it is possible to blacken the structural details of the optical path of optoelectronic devices made of various types, steel, alloys of aluminum, titanium and invar. Figure 7 shows an image of blend samples with a light-absorbing nickel-phosphorus coating of stellar sensors of the spacecraft orientation system.
Conclusions
The super-absorbing properties of the nickel-phosphorus alloy are formed due to the presence of developed morphology on its surface in the form of many conical funnels that determine the diffuse nature of the reflection of electromagnetic radiation.
Technological control of the input diameters of the funnels of the developed surface morphology of the light-absorbing coatings allows you to influence their spectral characteristics of the reflection of electromagnetic radiation.
The resistance of light-absorbing nickel-phosphorus coatings to external factors allows them to be used for operation in outer space.
The manufacturing technology of light-absorbing nickel-phosphorus coatings allows you to apply them to the structural parts of the optical path from different types of materials, various configurations with an area of up to 1000 sq.cm or more.
We are grateful for the help in carrying out research S. N. Khakhanov and employees of Systems for Microscopy and Analysis LLC, Moscow, Skolkovo Innovation Center.
AUTHOR
D. V. Marusev, engineer, JSC “Scientific research Institute of micro instruments-K”, marusev.niimpk@gmail.com, Moscow, Russia.
ORCID ID: 0000-0003-0325-2003
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