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    • 专利摘要:
    Nanostructured material, process of obtaining and using it. In the present document, a nanostructured material defined by an anodized alumina having a nanostructure having transverse pores crossing and connecting longitudinal pores grown on an aluminum substrate is detailed. This document also describes the procedure for obtaining said nanostructured material and its possible use as a template or mold for obtaining nanostructures formed by nanowires, which are generated in the pores or pores of the aforementioned nanostructure of the nanomaterial of the invention. This document also details the use of anodized alumina nanostructured material as a mold to produce nanostructures. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2559275A1
    申请号:ES201431048
    申请日:2014-07-11
    公开日:2016-02-11
    发明作者:Maria Soledad MARTÍN GONZÁLEZ；Jaime MARTÍN PÉREZ
    申请人:Consejo Superior de Investigaciones Cientificas CSIC；
    IPC主号:
    专利说明:

    Nanostructured MATERIAL, PROCESS FOR OBTAINING AND USING THE SAME
    D E S C R I P C I O N
    5 OBJECT OF THE INVENTION
    The object of the invention is an anodized aluminum nanostructured material, as well as its corresponding manufacturing process and possible uses of anodized aluminum nanostructured material, which is especially suitable as a mold for the production of 10 nanostructures.
    The material object of the invention is constituted by a homogeneous hexagonal network of parallel cylindrical nanotubes in formation perpendicular to the anodized surface and which are interconnected by pores located in planes parallel to the anodized surface.
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    BACKGROUND OF THE INVENTION
    Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. This technique is usually used on aluminum to generate an artificial protection layer by means of the protective oxide of aluminum, known as AAO by its acronym in English Anodic aluminum oxide or in Spanish anodic alumina. The layer is achieved by electrochemical methods, and provides an electrically insulating surface with greater chemical and mechanical resistance that increases the durability of aluminum. The name of the process derives from the fact that the piece to be treated with this material acts as an anode in the electrical circuit during the electrolltic process.
    Anodization is used to protect metals such as aluminum and titanium from abrasion and corrosion, and allows, apart from protection, to provide aesthetic advantages by means of surface coloration. Anodizing techniques have evolved a lot with the passage of
    time and range from a layer of aluminum oxide with the white color of this oxide to colors after the formation of the layer with colors such as gold, bronze, black and red.
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    10
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    In the processes of anodizing aluminum, pores are generated parallel to each other and perpendicular to the surface of the initial substrate. These pores are called longitudinal pores and are characterized by constituting a hexagonal network. In the state of the art the procedures for modulating in a controlled way the diameter of the longitudinal pores of the anodic alumina films are widely described. The longitudinal pores have diameters less than 0.5 pm, pores of submicron diameter, even reaching nanometric diameters, less than 100 nm. The diameter of the pores is controlled by the type of electrolyte used in the anodizing process. The microscopic modification of the pore is achieved by reproducing temperature conditions, electrolyte concentrations, voltages, agitation control, affected load surface and alloy characteristics.
    There are different methods of coloring the oxide layers formed during the anodizing process, consisting of coloring by inorganic or organic substances. The latest techniques based on optical interference processes can provide finishes such as blue, pearl gray and green. The finishes by optical interference are based on subsequent modifications of the pore of the aluminum oxide formed in the anodizing stage itself.
    At present, there is knowledge of the preparation of nanostructured AAO in the form of nanotubes and the characterization of various acidic media for anodization (H2SO4, H3PO4, H2C2O4), as well as the conditions of anodization (voltage, current density , temperature, etc.). In fact, in documents such as:
    • W. Lee; K. Schwirn; M. Steinhart; E. Pippel; R. Scholz; U. Gosele, (Nat Nano 2008, 3 (4), 234-239.25).
    • W. Lee; R. Scholz; U. GoEsele, (Nano Letters 2008, 8 (8), 2155-2160. 26. G. D. Sulka; A. Brzozka; L Liu, Electrochimica Acta 2011, 56 (14), 4972-4979)
    the differences and the possible advantages of the use of the conditions of soft anodization (Mild Anodisation, MA in English) and hard anodization (Hard Anodisation, HA in English) are reported alternately to internally configure the diameter of the nanotubes.
    In general, the processes of growth of the anodized aluminum sheet at lower potentials of anodizing, soft anodizing, AB, are slow and require several days of
    process for few tens of micrometers in thickness. In the employment of potential
    3
    higher anodization, hard anodization, AD, allow to increase the speed of growth and therefore achieve greater thicknesses. In hard anodization, higher electrical current densities are generally used than in soft anodization, so that the diameter of the longitudinal nanostructures is modified, producing larger pore diameters. It has also been described that the fabrication of porous films by pressing alternately, a process called pulsed anodization, periodically alternating stages of "soft anodization", AB, with pulses in the "hard anodizing" regime, AD, give pores that widen in hard anodizing areas versus the diameter of the soft anodizing zone. In this sense, document 10 is published as WO2008014977, which details, among other aspects, the application of alternating AB and AD stages in which different acidic media are used for anodization allowing the modulation of the nanotube diameter as the diameter obtained by AD is lower than that produced by AB.
    15 The document published as EP1884578A1 describes an anodization process based on oxalic acid for ordered alumina membranes, this can be easily implemented in nanotechnology, as! As in the industry. The process is an improvement of the so-called "hard anodization" that has been widely used since the 1960s in the industry for high-speed manufacturing of elements with good mechanical characteristics, high thickness (> 100 pm), and low anodic porosity of alumina films.
    On the other hand W. Lee et al. (Nanotechnology 21, 485304 (8pp), November 2010) already refers to the advantages of using pulses when configuring the nanotube diameter internally, although the procedure used does not resort to the same reactive medium or the other 25 reaction conditions specified in the base document. Obviously, despite knowing the different nanotube diameter results obtained by the different hard and soft anodizing regimes), this publication does not intend the formation of channels parallel to the anodized surface that interconnect the nanotubes.
    30 The sheets of anodized alumina can serve as well-defined nano-architectures in two dimensions, 2D, which can be applied in different nanotechnologies, such as photonic crystals, meta-materials, micromembranes, filters or molds for the manufacturing of nanostructures such as nanowires and nanotubes. Materials of very diverse nature.
    In other developments anodic aluminas have been used as standards or nanomolds for the fabrication of nanostructures; especially nanowires and nanotubes, an example is in Masuda, H. and K. Fukuda ,. (Science, 1995. 268 (5216): p. 1466-1468). The pores of the anodized alumina sheet are filled by various procedures consisting of electrodeposition processes, deposition of atomic layers, infiltration from melt, sol-gel, polymerization or crystallization in situ, vapor deposition, etc. Some examples of nanostructured materials obtained by means of the aforementioned procedures are metal nanowires, semiconductor nanowires, or polymers formed inside the longitudinal pores of the anodized alumina lamina. As a result, a set of nanowires or nanotubes perpendicular to the surface of the support substrate is obtained. In a subsequent process, the nanowires or nanotubes can be extracted from the matrix by selective dissolution of the aluminum sheet in acidic and basic media. As a result, dispersed and separated nanowires or nanotubes are obtained. Until now it has not been possible to interconnect the nanowires or nanotubes generated by using the anodized alumina sheet as a mold
    On the other hand, today there are materials with an ordered (periodic) and three-dimensional porous structure in the size range of the porous structure of the AAO, they are systems produced from continuous phases of block copolymers (CB) of type Gyroid, double 20 Gyroid, etc ... However, the use as nanomold of AAO materials has some advantages over the use of CB materials for the manufacture of ordered nanostructures:
    i) Many of the procedures for obtaining inorganic nanostructured materials that are interesting involve aggressive reaction conditions in terms of high temperatures, high vacuum, or the presence of highly reactive species (plasmas, ions, radicals ...), which are going to be hardly supported by the block copolymer, since it is composed of easily degradable organic molecules, typically polystyrene and ethylene polyoxide. Consequently, CBs are not compatible with many types of inorganic material growth methods. In contrast, AAO materials are 30 compounds of aluminum oxide, much more stable (thermally, mechanically, etc.) than the organic compounds that make up the porous system of the CB and, therefore, is compatible with many more growth methods , which leads to the fact that a greater number of materials can be used for nanostructures manufacturing.
    ii) The porous network of CB is composed of organic polymers such as polystyrene and ethylene polyoxide, which have a low surface energy (in the order of tens of mN / m). This can make it difficult to infiltrate other organic liquids such as polymer solutions, small molecules, or precursors, which complicate the fabrication of three-dimensional networks of organic compounds, such as polymers and other molecular materials. However, AAO materials, being composed of aluminum oxide, have a surface energy of the order of thousands of mN / m. This means that any organic liquid will wet the surface of AAO materials. Consequently, any organic liquid will be able to be infiltrated in the pore network, which means that practically any organic compound can be nanostructured using AAO materials.
    On the other hand, a limitation of the state of the art in coloration of layers of anodized alumina is that pigment colors look the same from all angles of vision since the sheets do not have structural type colors as a result of a reflection selective or iridescence phenomena that are characteristic of multi-layered structures; having a limitation in the aesthetic and optical properties derived from these materials. The different methods of coloring the oxide layers formed during the known anodization process are those consisting of coloring by inorganic or organic substances. In this way it is had that the techniques based on optical interference processes can provide finishes such as blue, pearl gray and green; However, optical interference finishes are based on subsequent modifications of the pore of the aluminum oxide formed in the anodizing stage itself.
    25 It would be desirable therefore to have a three-dimensional structures of porous alumina that allow, on the one hand, the growth of three-dimensional interconnected structures within its matrix that can serve as nanoarchitecture that promotes the interconnection of nanowires of various materials grown on the matrix and, on the other hand, that allow to obtain a variation in the optical properties that allows to obtain different finishes with 30 different optical characteristics and therefore a greater aesthetic variety.
    DESCRIPTION OF THE INVENTION
    A first aspect of the present invention relates to a nanostructured material that
    it comprises a porous sheet of anodic alumina, which in turn comprises preferably cylindrical pores and parallel to each other that are perpendicular to the substrate of the anodized surface called longitudinal pores, and also transverse pores in a plane parallel to the surface of the anodized alumina which interconnect the longitudinal pores 5.
    Another aspect of the invention relates to a process for obtaining the nanostructured material of the first aspect of the invention, anodized aluminum nanostructured material (AAO); said material is constituted by a homogeneous hexagonal network 10 of longitudinal pores that start from a substrate and that are arranged parallel to each other and in perpendicular formation to the anodized surface, and of longitudinal pores that are interconnected by transverse pores located with their longitudinal axes parallel to the substrate defining planes parallel to it.
    The first aspect of the present invention relates to the material itself, where in a preferred embodiment there is a porous sheet of anodic alumina comprising longitudinal pores perpendicular to the surface of the aluminum-containing substrate; and transverse pores in one or more planes parallel to the substrate, which interconnect the perpendicular pores, of cylindrical or elliptical section. In a preferred embodiment of the first aspect of the present invention the pores perpendicular to the surface of the anodic alumina film are parallel to each other and perpendicular to the anodized surface or substrate and lie along the entire thickness of the film of anodic alumina so that they cross the anodized alumina film and that is why they have been called "longitudinal pores" and have an ordering of adjoining outer walls, more specifically forming a hexagonal type network. The diameter of the longitudinal pores and the separation Typical among them are analogous to those formed in the porous films of anodic alumina described in the state of the art; in this preferred embodiment of the first aspect of the present invention the longitudinal pores have a diameter between 6 nm and 500 nm.
    30
    In a preferred embodiment of the first aspect of the invention, the transverse pores have a circular section with the axis aligned in the perpendicular direction and the axis aligned in the parallel direction, this being less than 100 nm; in other possible embodiments of the first aspect of the invention an ellipsoid section can be had that
    it is characterized by two axes, being at least one of them of nanometric dimensions, preferably less than 100 nm; so that there is an axis in the direction perpendicular to the longitudinal axis of the longitudinal pores and, therefore, of the longitudinal pores, and a second axis aligned in the direction parallel to said axis and of the 5 longitudinal pores. The transverse pores may have different values between the axes corresponding to the direction perpendicular to the longitudinal pores and to the direction parallel to the longitudinal pores.
    However, the dimension of the axes, the orientation of the axes and the relationship between the two 10 axes can be established in relation to the procedure for obtaining the described material as detailed in the description of the second aspect of the invention related to a procedure for obtaining the nanostructured material described here.
    In the first aspect of the invention, the nanostructured material described herein has the 15 transverse pores connecting the longitudinal pores perpendicularly; connection that is carried out through the first neighbors, as detailed above, that is, a transverse pore connects the longitudinal poles that are as short as possible between them at their location in the sheet of anodic alumina. The transverse pores are in planes parallel to the surface of the anodized layer, that is to say parallel to the substrate, and also have a hexagonal symmetry characterized in that the angle contained between two adjacent transverse pores is between 50 ° and 70 ° on average. As can be seen from a hexagonal arrangement, the number of transverse pores that connect longitudinal pores through their first neighbors is usually 6. In the situation of an anodic alumina with longitudinal pores hexagonally arranged, the shaft diameter aligned in the direction perpendicular to the longitudinal pores of the transverse pores will be less than 1,047 times the radius of the longitudinal pore.
    However, due to the nature of the invention, it is possible that the material described herein may have defects in the hexagonal arrangement of the longitudinal pores. The loss of the hexagonal symmetry allows the number of longitudinal pores considered as first neighbors to vary between 4, 5 or 7. The transverse pores connect the longitudinal pores through first neighbors, so in this situation of disorder the number can be given of transverse pores in a plane for a pore
    longitudinal vary between 4, 5 or 7, depending on the number of first neighbors of said longitudinal pore.
    In the preferred embodiment of the first aspect of the present invention, the anodic alumina film has at least one longitudinal pore, preferably several, defined in planes, interconnected by at least one transverse pore. As with longitudinal pores, a plurality of transverse pores defined in one or more planes is preferably preferred. The recently mentioned connection between the longitudinal pores and the transverse pores is preferably carried out by first neighbors, thus generating a three-dimensional porous network. The transverse pores laterally connect the longitudinal pores so that a three-dimensional network of cubic or prismatic cells is formed with nanometer-sized pore sections, that is, less than 100 nm. Thus, the material of the present invention has an advantage over those in the state of the art, because it has a three-dimensional nanometer porosity network that maintains the mechanical integrity of the anodized aluminum sheet.
    In an even more preferred embodiment of the first aspect of the present invention the material, that is to say the anodic alumina film, has a layer density that comprises the transverse pores less than that density of the layer that only contains longitudinal pores.
    The material of the first aspect of the invention described herein may have one or more planes of transverse pores, although with a single channel a three-dimensional internal nanostructure could be configured; The transverse pore planes are arranged at a distance that is modulable during the process of obtaining the material, that is, it can be defined by setting the parameters of the process described in another aspect of the present invention. Therefore, a flat set of transverse pores allows obtaining a three-dimensional network of nanometric pores in a sheet of the nanostructured material described herein; where you may have to:
    - the distance between the transverse pore planes is constant or periodic,
    - the distance between transverse pore planes is variable or aperiodic, and
    - a combination of transverse pore planes with constant distance and transverse pore planes with variable distance.
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    In that aspect of the present invention referred to the process of obtaining the aforementioned nanostructured material, said material with sheets of anodized alumina with the longitudinal pores and transverse pores mentioned above, it is necessary to obtain said material:
    a) prepare the metal surface to be anodized, the substrate; said preparation includes a cleaning of an aluminum metal substrate, electrochemical polishing, a first anodization and a chemical attack.
    b) Perform a pulsed anodizing process between a fixed soft anodizing potential and hard anodizing pulses limited in current to grow the anodized alumina layer, and
    c) Perform a chemical attack to reveal the porous structure.
    In a preferred embodiment of the aspect of the invention related to the process of obtaining the nanostructured material, once the surface is prepared as indicated, the anodizing process is started; however in other alternative embodiments, or when a preparation process becomes necessary, it may include cleaning and degreasing by sonication in acetone, distilled water, isopropanol and ethanol. The approximate time for each step is 4 minutes and, once the surface of the substrate has been cleaned and degreased, it is subjected to an electropolishing process in a solution of 20 perchloric acid and ethanol with a proportion of 1 volume of perchloric acid and 3 volumes of ethanol, under a constant voltage, such as that provided by 20 V for 4 minutes, although there are other alternative electropolished and mechanical polishing procedures that exist in the state of the art, which provide adequate surface finishes and which, by therefore, they are also applicable to the present invention.
    25
    Subsequently, the substrate is subjected to a process of first soft anodization to obtain a prior structuring of the surface thereof and, therefore, to improve the eventual hexagonal arrangement of the longitudinal pores that will give rise to the longitudinal pores themselves. The aluminum sheet subjected to a soft first anodizing process 30 is removed by a chemical attack in an aqueous solution of 7% by weight phosphoric acid and 1.8% by weight chromic oxide.
    The anodizing process of stage b) is a pulsed anodizing process that employs soft anodizing stages at fixed potential and hard anodizing pulses at a current
    limited In the soft anodizing stages, the nominal potential used is selected from 20-30 V, preferably 25 V. In the hard anodizing stage the current is limited to 60 mA, preferably 55 mA, as a result of which the peaks of Maximum voltage reached during hard anodization pulses is limited to 35 V, preferably 5 32 V. Hard anodization pulses are also temporarily limited and their
    Maximum duration is 5 seconds, preferably 3.5 seconds and, more preferably, 2 seconds. By limiting the maximum current and the duration of the hard anodizing pulses, a maximum voltage limitation is reached which, in turn, results in an effective control of the growth of the anodized alumina layer. The growth of the anodized alumina layer means the increase in its thickness. This process has an advantage over the processes described in the state of the art since it allows the hexagonal distribution of the longitudinal pores to be maintained without altering their diameter. The growth limitation of the anodized alumina layer during the hard anodization pulses limited in current allows to obtain 15 transverse channels that interconnect the longitudinal pores.
    The pulsing process with current limitation of the pulses in step b) produces a transverse pore plane for each hard anodizing pulse with current limitation. The distance between the transverse pore planes is directly related to the duration of the soft anodizing stages at constant potential; This distance between the planes can be defined and controlled by setting the soft anodizing time to constant potential. Therefore, structures can be designed that maintain a constant distance between transverse pore planes, thereby generating a set of transverse pore planes with a periodicity. Similarly, a variable distance between the different transverse pore planes can be established. Further, different combinations can be generated in the distances between transverse pore planes such as sets of transverse pore planes with a constant distance alternating with transverse pore planes at varying distances.
    30 The method described here allows the design of periodic, non-periodic and combination of periodic and non-periodic networks of transverse pore planes that, as will be seen later, allow to obtain optical reflection properties not described in the state of the art for this type of materials
    The pulsing process with current limitation of the pulses makes use of an electrolyte selected from sulfuric acid, oxalic acid and phosphoric acid, preferably 0.3 M sulfuric acid is used to obtain pores within the nanometric range, longitudinal pore diameters lower than 100 nm During the pulsed anodization process, agitation can be maintained to favor the homogeneity of the anodized alumina layer, likewise the pulsing process with current limitation of the pulses is carried out by means of a programmable power supply to adjust the distance between the transverse pore planes or between the sets of transverse pore planes. Likewise, the thickness of the anodized aluminum sheet is a function of the anodizing time used. The thicknesses of the layers of nanostructured material of anodized alumina have dimensions between 100 nm and 500 pm. The pulsing process with current limitation of the pulses is carried out at a temperature below 25 ° C, preferably at a temperature below 10 ° C, and more preferably at a temperature below 5 ° C. A lower temperature of the reaction favors a lower growth of the anodized aluminum sheet 15 which results in a better control of the cross-sectional sections, thus presenting an advantage for obtaining transverse pores.
    After steps a) and b), it is subjected to a chemical attack to reveal the three-dimensional porous structure. The formation of the transverse pores is carried out by subjecting the anodized alumina sheet to an acid attack, preferably using 5% by weight phosphoric acid in order to preferentially dissolve the alumina regions formed during the hard anodizing pulses with current limitation of stage b). The formation of pores takes place after an attack of 16-21.5 minutes at a temperature of 30-35 ° C. The acid attack process preferentially dissolves the material grown during the pulses of limited hard anodization in current, thus forming transverse pores that interconnect the longitudinal pores.
    In another preferred embodiment of the second aspect of the present invention, the aluminum foil with an anodized alumina layer obtained after step c) may have a three-dimensional porosity network comprising longitudinal circular section pores that are parallel to each other and pores transversal that interconnect the mentioned longitudinal pores.
    The previous steps generate an anodized alumina layer, the nanostructured material
    of the invention, which follows from the aluminum substrate that has not reacted either by physical means or by chemical means, for example with a solution of CuCl2 in hydrochloric medium, although not limited thereto; allowing the obtaining of self-supporting sheets of anodized alumina comprising a three-dimensional network of longitudinal pores and transverse pores.
    The result obtained can be subjected to a milling process following a process that can be a hammer mill grinding, ball mixer grinding, although not limited to these processes, so that discrete particles are obtained from the sheet . These particles retain the optical properties of the sheet thus presenting an advantage for its use as pigments.
    The nanomaterial obtained makes it possible to diffract light when it is done with the appropriate periodicity thus generating different colors depending on the angle of observation. This effect is a direct consequence of the diffraction network formed by the transverse pore planes and therefore can be modulated. The variation of the color for a coating according to the angle of observation thus presents an aesthetic advantage over the layers of anodic alumina described in the state of the art that goes beyond the interference colors by having a variable optical response of the layer of alumina originated by the 20 diffraction network formed by the transverse pore planes.
    A third aspect of the present invention relates to the use of the nanostructured material of the invention as a mold or pattern for the manufacture of networks of nanowires and / or three-dimensional nanotubes. The interconnected three-dimensional porosity structure is used as a mold or pattern to fill with a material selected from metallic, organic and inorganic materials. The procedures for filling the three-dimensional porous structure described in the present invention are selected from procedures described in the state of the art for the generation of nanometric structures in 2D porous alumina such as electrochemical deposition, sol-gel, in-situ polymerization, 30 deposition of atomic layers and any other that can be used with the porous alumina described in the state of the art and therefore, not limited thereto. The advantage presented by the present invention with respect to the state of the art is related to the existence of a three-dimensional network comprising the filling of the longitudinal pores and the filling of the transverse pore planes that interconnect the longitudinal pores
    for the material selected according to the procedure followed.
    In another preferred embodiment of the third aspect of the present invention the anodic alumina comprising an interconnected three-dimensional network filled with a material of different density that allows modifying the color of the sheet of anodized alumina containing a three-dimensional porous network.
    A fourth aspect of the present invention relates to the use of three-dimensional networks of nanotubes or nanowires with a nanometric section depending on their composition for application as thermoelectric elements, supercacitators, electronics, supports
    catalltics, filtration and separation membranes, drug release systems, scaffolds for cell growth, sensors, batteries, energy, optical devices and optoelectronic devices. Although it is not limited to other applications in which the porous alumina described in the state of the art has been used, but also has the advantage of nanostructuring the material in the form of networks.
    three-dimensional
    DESCRIPTION OF THE DRAWINGS
    20 To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of said description is attached, as an integral part of said description. Drawings where the following has been illustrated and not limited to:
    25
    Figure 1. It shows a diagram showing a sheet of material of the invention on aluminum, sheet comprising longitudinal pores perpendicular to the anodized alumina layer and planes of transverse pores parallel to the surface of the anodized alumina that interconnect the longitudinal pores in the direction perpendicular to them.
    30
    Figure 2. It shows a diagram of the internal three-dimensional network of the lamina of the invention showing the arrangement of the longitudinal pores and the cross-pore planes that interconnect them. The transverse pores interconnect the longitudinal pores through the first neighbors.
    Figures 3a, 3b. Figure 3a shows a scanning electron microscopy micrograph corresponding to a cross section of an anodized aluminum sheet in which the existence of longitudinal pores and planes of transverse pores that interconnect the longitudinal pores are observed. The distance between longitudinal pores is 65 nm and the distance between the planes of transverse pores is 320 nm. Figure 3b shows a scanning electron microscopy micrograph corresponding to a greater magnification of the cross section of (A) where the diameter of the longitudinal pores is 40 nm and the section of the cross pores is elliptical with at least one of its axes less than 20 nm aligned in the direction perpendicular to the longitudinal pores and an axis greater than 35 nm 10 aligned in the direction parallel to the longitudinal pores.
    Figures 4a-4c. It shows scanning electron microscopy micrographs corresponding to a cross-section of several sheets of material of the invention showing different distances between the cross-pore planes with a periodicity between the set of cross-pore planes. In Figure 4a, the distance between the transverse pore planes is 500 nm, in Figure 4b, the distance is 320 nm and in Figure 4c, 150 nm. The scale bars incorporated in the figures correspond to a length of 500 nm.
    Figure 5. It shows photographs of the sheet of the invention following the procedure described in the present invention, taken with a different angle of incidence of light and showing interference colors.
    Figure 6. Shows a scanning electron microscopy micrograph corresponding to a cross section of a sheet of the invention where the transverse pores have an aperiodic distance.
    Figures 7a and 7b. They show photographs of three-dimensional periodic networks of nanowires of conjugated polymers embedded in sheets of the invention taken when exposed to black light. The conjugated polymers infiltrated in the sheets of referred anodized alumina were in Figure 7a: PCDTBT, PFO-DTBT, P3EAT and PPV, In Figure 7b: The infiltrated polymer is PVDF-TrFE. The scale bars represent a length of 1 cm.
    Figure 8. Shows a scanning electron microscopy micrograph corresponding to a
    cross section of a three-dimensional periodic network of polystyrene nanowires. The scale bar of the interior image represents a length of 1 cm.
    Figure 9. It shows a scanning electron microscopy micrograph corresponding to a cross section of a three-dimensional periodic network of nanowires of Bi2Te3.
    Figure 10. It shows a graph where the optical properties of the material of the invention can be seen, in said graph a correlation between transmittance and wavelength for a pupil represented in a dark line and the material of the invention, three-dimensional alumina, represented. in lighter stroke.
    PREFERRED EMBODIMENT OF THE INVENTION
    As a practical case of realization of the invention, and without limitation thereof, several examples of embodiment of the three-dimensional nanostructured material (1) of one of the aspects of the invention shown in Figures 1 and 2 are described below. through anodization electrolysis processes, which simply implement the main concepts object of this invention.
    Example 1: Refers to a porous alumina sheet - three-dimensional nanostructured material (1) of the invention - on a substrate (4), laminates with at least one longitudinal pore (2), preferably several longitudinal pores (2), which they start from said substrate (4) with respective longitudinal axes essentially perpendicular to the substrate (4) and which are connected by at least one transverse pore (3), preferably 25 several transverse pores (3) defined in periodically spaced planes, as seen in Figures 4a-4c, although in other possible embodiments, as seen in Figure 6, the transverse pores (3) can be defined in planes that have periodic distances from each other as will be seen in a later example.
    30 It is based on a 1.6 cm diameter aluminum wafer that was first subjected to a cleaning process using acetone, water, isopropanol and ethanol sequentially. Next, the clean aluminum wafer was subjected to an electrochemical polishing process on an electrolyte composed of HClO4: EtOH (1: 3) at 20 V for 3 minutes. After the electrochemical polishing process, the wafer underwent a first reaction of
    anodizing at a voltage VAB, 25 V, to form an aluminum oxide film called alumina. This alumina layer was removed by dissolution in a mixture of 7% by weight phosphoric acid and 1.8% by weight chromic oxide for 24 h at 25 ° C.
    5 After the elimination of the first layer of alumina formed, the silicon wafer was subjected to a second anodizing process using anodizing pulses consisting of the application of a constant voltage of 25 V for 180 s and a pulse at nominal voltage 32 V for 2 s. The second pulsed anodizing process produced a growth of an anodic alumina layer. This second anodizing process was maintained until the thickness of said layer was 20 pm.
    In a process subsequent to the growth of the anodic alumina layer by pulsed anodization, the formed alumina layer is subjected to a chemical attack process using 5% H3PO4 by weight at a temperature of 30 ° C for 18 minutes.
    fifteen
    The resulting anodic alumina sheet whose microstructure is shown in Figure 3a is characterized by presenting longitudinal pores (2) and transverse pore planes (3) giving rise to the nanostructured material (1). The longitudinal pores (2) are characterized by having a hexagonal arrangement, a distance between the first 20 neighbors of 65 nm and a section of 40 nm. The transverse pores (3) are characterized by having an elliptical section with an axis aligned parallel to the longitudinal pores (2) of 35 nm and an axis aligned in the plane of the transverse pores (3) of 25 nm (see figure 3b). The transverse pore planes (3) are can have a periodic distance between planes of approximately 320 nm (see Figure 3a).
    25
    In another preferred embodiment of Example 1, the time of application of the pulsed anodizing process was maintained until a thickness of the anodized alumina sheet of 200 pm was reached. The anodized aluminum sheet thus obtained has the same characteristics described above that refer to the dimensions and arrangement of the longitudinal pores (2) and transverse pores (3).
    In another preferred embodiment of Example 1 in the second anodizing process using anodizing pulses at the time of application of the constant voltage of 25 V between pulses at nominal voltage of 32 V for 2 s, it was varied so that longer times
    between pulses increase the distance between the pianos of transverse pores (3) and shorter times decrease this distance. The distance between transverse pore planes (3) can be proportional to the application time of the constant voltage between the anodizing pulses limited in current.
    5
    The nanostructured material (1) of the invention, and therefore the anodic alumina sheet, can have a color that is variable depending on the angle of incidence of the light constituting an interference color.
    10 Example 2: Porous alumina sheet with longitudinal pores (2) connected with cross-sectional pore planes (3) spaced apart periodically.
    The porous alumina material of example No. 1 was processed following the procedure described in said example No. 1, which was repeated by modifying the application time at a constant voltage of 25 V between the anodizing pulses during the anodizing process 15 limited in current to a nominal voltage of 32 V. The resulting alumina sheet is characterized as shown in Figure 6 by presenting transverse pore planes (3) that are spaced apart periodically.
    Example 3. Porous alumina sheet with longitudinal pores (2) connected with transverse pore planes (3) filled with polymeric material seen in Figures 7a and 7b.
    The porous alumina material of example No. 1 was processed following the procedure described in said example No. 1 and the three-dimensional pore network was filled following an infiltration process with polymeric compounds of PCDTBT, PFO-DTBT, P3EAT and PPV. To fill the porous aluminas with longitudinal (2) and transverse (3) pores with these polymers, the following solutions were prepared: PCDTBT 4g / L in chloroform, PFO-DTBT 4g / L in chloroform, P3EAT 4g / L in chloroform and PPV 4g / L in tetrahydrofuran. At 30 continuation, sheets of anodized alumina with three-dimensional porosity were submerged in
    each of the solutions for 10 minutes. The sheets of anodized alumina with three-dimensional porosity were removed and the solvent contained in their pores was allowed to dry under ambient conditions.
    The nanostructured material (1) and, therefore, the porous alumina sheet with longitudinal pores (2) connected with transverse pore planes (3) filled with these polymeric materials, can have luminescent properties that vary depending on the polymer used.
    5
    In another preferred embodiment of example 3 the porous alumina nanostructured material (1) of example # 1 was processed following the procedure described in said example # 1 and the three-dimensional pore network was filled following an infiltration process with a polymeric compound of P (VDF-TrFE). To fill the nanostructured material (1) of 10 anodized alumina with three-dimensional porosity with this polymer, the following solution was prepared: P (VDF-TrFE) 5% by weight in dimethyl formamide. The AAO3D was then immersed in the solution for 10 minutes. The anodized alumina sheet was extracted with three-dimensional porosity and the solvent contained in its pores was allowed to dry under ambient conditions. The porous alumina sheet with longitudinal pores (2) 15 connected with transverse pore planes (3) filled with said polymeric materials has an advantage for having ferroelectric properties in addition to the luminescent ones that are also modified with the angle of incidence of light.
    Example 4. Procedure for obtaining interconnected three-dimensional polymer nanowire networks 20 as seen in Figure 8.
    The porous alumina nanostructured material (1) of example No. 1 was processed following the procedure described in said example No. 1 and the three-dimensional network of pores (2, 3) is filled with polystyrene, following an in situ polymerization process. Styrene was polymerized within the three-dimensional alumina using AIBN as an initiator in an N2 atmosphere for one hour. Subsequently, the anodized alumina nanostructured material (1) was selectively dissolved in a 10 M NaOH solution for 60 minutes. As a result, a network of polypropylene nanowires comprising longitudinal polystyrene wires connected by transverse planes of 30 polystyrene wires connecting the longitudinal wires through their first neighbors was obtained.
    Example 5. Procedure for obtaining interconnected three-dimensional networks of Bi2Te3 nanowires that can be seen in Figure 9.
    The three-dimensional porous alumina nanostructured material (1) of Example No. 1 was processed following the procedure described in said Example No. 1 and the three-dimensional network of pores (2, 3) was filled with Bi2Te3, following an electrochemical deposition process. For this, a metal layer was deposited on one of the surfaces of the 3D alumina that served as an electrode. This deposited electrode was used as a cathode of an electrochemical cell. The growth of Bi2Te3 within the three-dimensional porous network in the anodic alumina was carried out by electrodeposition in a three electrode electrochemical cell for 8 hours. The pulse conditions were: 20 mV for 0.1 s and 0 mA / cm2 for 0.1 s. The sheet of anodic alumina with three-dimensional porosity as! 10 obtained and filled by electrochemical deposition of Bi2Te3 is characterized by having a green color in contrast to the color of the Bi2Te3 compound which is dark gray.
    As a result, a network of nanowires from Bi2Te3 was obtained. An X-ray diffraction test confirmed the crystalline structure of Bi2Te3. This crystalline phase is characterized by presenting a semiconductor response that provides thermoelectric properties, therefore it can be used in energy generation devices.
    权利要求:
    Claims (21)
    [1]
    1. Nanostructured material (1) comprising a substrate (4), which in turn comprises aluminum, where on the substrate (4) at least a longitudinal pore (2) is disposed whose longitudinal axis is essentially perpendicular to said substrate (4) of which part, nanostructured material (1) characterized in that it comprises at least one transverse pore (3) whose longitudinal axis is essentially perpendicular to the longitudinal axis of the longitudinal pore (2).
    10 2.- Nanostructured material (1) according to claim 1 characterized in that the pore
    Longitudinal (2) has essentially circular cross section.
    [3]
    3. - Nanostructured material (1) according to claim 2 characterized in that the circular section of the longitudinal pore (2) has a diameter between 6 nm and 450 nm.
    fifteen
    [4]
    4. - Nanostructured material (1) according to claim 1 characterized in that the longitudinal pore (2) has an eKptic section.
    [5]
    5. - Nanostructured material (1) according to any one of claims 1 to 4, characterized in that the transverse pore (3) has an eKptic cross section.
    [6]
    6. - Nanostructured material (1) according to any one of claims 1 to 4 characterized in that the transverse pore (3) has a circular cross-section.
    25 7.- Nanostructured material (1) according to claim 6 characterized in that the section
    Circular transverse has a diameter of 100 nm.
    [8]
    8.- Nanostructured material (1) according to claim 5 characterized in that the ellipse of the cross section comprises:
    30 - a first axis of the ellipse with a direction perpendicular to the longitudinal axis of the
    longitudinal pore (2), and
    - a second axis of the ellipse aligned in a direction parallel to said longitudinal axis of the longitudinal pore (2).
    [9]
    9. - Nanostructured material (1) according to claim 8 characterized in that the optical section has at least one of its axes with a size of less than 100 nm.
    [10]
    10. - Nanostructured material (1) according to any one of the claims
    5 above characterized in that it comprises a plurality of transverse pores (3)
    defined with their longitudinal axes parallel to each other defining at least one plane parallel to the substrate (4).
    [11]
    11. - Nanostructured material (1) according to claim 10 characterized in that 10 comprises at least two transverse pore planes, wherein said planes are
    parallel to each other.
    [12]
    12. - Nanostructured material (1) according to claim 11 characterized in that the transverse pore planes are equidistant.
    fifteen
    [13]
    13. - Nanostructured material (1) according to any one of the claims
    anterior characterized in that it comprises a plurality of longitudinal and transverse pores, defining a three-dimensional network of pores where the longitudinal pores are perpendicular to the substrate (4) and the transverse pores (3) perpendicular to the
    20 longitudinal pores crossing the latter orthogonally crossing the
    respective longitudinal axes of the pores.
    [14]
    14. - Method of obtaining an anodized nanostructured material (1), a method characterized by comprising:
    A) preparing a substrate (4) comprising Al,
    b) perform an anodizing process on a surface of the substrate (4) and grow at least one layer of nanostructured anodized alumina on the substrate (4) this layer being corresponding to the nanostructured material (1) anodized, where said process process of anodized comprises a pulsed anodization which in turn
    30 comprises:
    • soft anodizing pulse stages with a fixed potential, and
    • hard anodizing pulse stages limited in current,
    c) perform a chemical attack to reveal the transverse pores.
    [15]
    15.- Method according to revindication 14 characterized in that the preparation step comprises: at least one cleaning of the substrate (4), an electrochemical polishing, a prior anodization and a chemical attack.
    5 16.- Method according to claim 14 characterized in that the fixed potential of the pulses
    Soft anodization is between 20-30 V, and the hard anodizing pulse current has a maximum Kmite value of 60 mA.
    [17]
    17. - Method according to claim 14 or 16, characterized in that the pulse stage of 10 anodization lasts for a maximum duration of 5 seconds.
    [18]
    18. - Method according to any one of claims 14 to 17 in which the hard anodization pulses have a fixed potential with a maximum value of 35 V.
    19. Method according to any one of claims 14 to 18 characterized in that
    at least the anodizing process is carried out at a temperature below 25 ° C.
    [20]
    20. - Method according to any one of claims 14 to 19 characterized in that the anodizing process is carried out with an electrolyte selected from the
    20 group consisting of: sulfuric acid, oxalic acid and phosphoric acid.
    [21]
    21. - Method according to any one of the preceding claims characterized in that it additionally comprises stirring the substrate (4) during the anodizing process by homogenizing the anodized layer of nanostructured material during its growth
    25 in the substrate (4).
    [22]
    22. - Method according to any one of claims 14 to 21 characterized in that it comprises performing a chemical attack on the alumina layer with 5% by weight phosphoric acid in order to generate pores by dissolving formed alumina regions
    30 during hard anodizing pulses with current limitation.
    [23]
    23. - Method according to claim 22 characterized in that the chemical attack is carried out for a time between 16 minutes and 21.5 minutes at a temperature between 30 ° C and 35 ° C.
    [24]
    24. - Nanostructured material (1) obtainable by the method described in any one of claims 14 to 23.
    [25]
    25. Use of the nanostructured material (1) according to any one of claims 1 to 13 or 24 as a mold for obtaining nanostructures.
    10 26.- Use of the nanostructured material (1) according to revindication 25 characterized in that
    The nanostructures comprise at least one of: nanowires and nanotubes.
    fifteen
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    同族专利:
    公开号 | 公开日
    US20170221597A1|2017-08-03|
    WO2016005636A1|2016-01-14|
    ES2559275B1|2016-11-22|
    CN107002273A|2017-08-01|
    EP3168331A1|2017-05-17|
    EP3168331A4|2018-02-07|
    引用文献:
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    US20050276743A1|2004-01-13|2005-12-15|Jeff Lacombe|Method for fabrication of porous metal templates and growth of carbon nanotubes and utilization thereof|
    CN100412237C|2005-03-18|2008-08-20|武汉大学|Manufacturing method of three dimensional aluminium oxide nanometer pattern plate|
    EP1884578A1|2006-07-31|2008-02-06|MPG Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V.|A method of manufacturing a self-ordered porous structure of aluminium oxide, a nanoporous article and a nano object|
    JP5294048B2|2007-12-05|2013-09-18|富士電機株式会社|Alumina nanohole array and method for producing magnetic recording medium|CN111024257B|2019-09-29|2021-12-24|株洲国创轨道科技有限公司|Metamaterial temperature sensing sensor, preparation method and application thereof|
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