WO2021124356A1

WO2021124356A1 - A process and device for fabrication of high temperature superconductors

Info

Publication number: WO2021124356A1
Application number: PCT/IN2020/051035
Authority: WO
Inventors: Guru Pratheep RAJASEKAR; Arindam Ghosh; Anshu Pandey; Satish Patil; Rekha Mahadevu
Original assignee: Indian Institute Of Science
Priority date: 2019-12-18
Filing date: 2020-12-18
Publication date: 2021-06-24

Abstract

Processes and devices for fabrication of nanostructured superconductors are provided. A precursor of a first material is dispersed into a carrier gas to obtain a first aerosol. The first aerosol is contacted with a substrate. Decomposition of the first material is caused on contacting the first aerosol with the substrate to deposit the nanoparticles of the first material on the substrate to obtain a partially covered substrate. A second material is deposited on the partially covered substrate to form nanoclusters comprising the second material embedded in the first material to obtain the nanostructured superconductors.

Description

A PROCESS AND DEVICE FOR FABRICATION OF HIGH TEMPERATURE

SUPERCONDUCTORS

TECHNICAL FIELD

[0001] The present subject matter relates to superconductors and, in particular, to a process for fabrication of nanostructured superconductors.

BACKGROUND

[0002] Superconductors are conductors that carry electrical current with no measurable energy dissipation. Superconductors that are resistant to high magnetic fields have seen widespread applications in medical diagnostics and research sectors. Nanostructured superconductors provide several advantages, such as high surface area-to-volume ratio, improved physical properties (melting point and hardness), and tunable electronic properties. Nanostructured superconductors have to be obtained in a form that can be employed in various applications, such as interconnects in electronics, cables in electrical appliances, coils in high field magnets, shields against electromagnetic interference, and many other domestic, and technological uses.

BRIEF DESCRIPTION OF DRAWINGS

[0003] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0004] Fig. 1 illustrates an example process for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. [0005] Fig. 2 illustrates another example process for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. [0006] Fig. 3 illustrates another example process for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. [0007] Fig. 4 illustrates another example process for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. [0008] Fig. 5(a) illustrates an example assembly for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. [0009] Fig. 5(b) illustrates a schematic of an example assembly for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter.

[00010] Fig. 5(c) illustrates a schematic of an example assembly for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter.

[00011] Fig. 5(d) illustrates a schematic of an example assembly for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter.

[00012] Fig. 6(a)-(c) depicts results of absorbance spectra study, in accordance with an implementation of the present subject matter.

[00013] Fig. 7(a)-(f) depict HAADF STEM images of nanostructured superconductor film, in accordance with an implementation of the present subject matter.

[00014] Fig. 8(a)-8(c) depicts results of elemental mapping of the HAADF image, in accordance with an implementation of the present subject matter. [00015] Fig. 9(a) depicts EELS spectrum, in accordance with an implementation of the present subject matter.

[00016] Fig. 9(b) depicts inelastic scattering by a nanostructured superconductor film, in accordance with an implementation of the present subject matter.

[00017] Fig. 10(a)-(b) depict Transmission Electron Microscopy (TEM) images of the samples, in accordance with an implementation of the present subject matter.

[00018] Fig. 1 l(a)-(b) show HAADF images taken over a few regions where individual nanoparticles were visible, in accordance with an implementation of the present subject matter. [00019] Fig. 12(a) depicts three-dimensional (3D) topography of deposited film on quartz, in accordance with an implementation of the present subject matter.

[00020] Fig. 12(b) and 12(c) depicts height profile obtained from AFM images, in accordance with an implementation of the present subject matter. [00021] Fig. 12(d) depicts surface topography obtained from AFM image, in accordance with an implementation of the present subject matter.

[00022] Fig. 13(a)-(b) depict results of magnetic AFM study, in accordance with an implementation of the present subject matter.

[00023] Fig. 14(a)-(b) depict results of magnetic AFM study, in accordance with an implementation of the present subject matter.

[00024] Fig. 15(a) illustrates the topography of the film, in accordance with an implementation of the present subject matter.

[00025] Fig. 15(b) represents the thickness of the film across the line drawn in the image, in accordance with an implementation of the present subject matter. [00026] Fig. 16(a) illustrates the topography of the film, in accordance with an implementation of the present subject matter.

[00027] Fig. 16(b) represents the thickness of the film across the line drawn in the image, in accordance with an implementation of the present subject matter.

[00028] Fig. 17(a) and 17(b) depict images of the fluorescent microscopy, in accordance with an implementation of the present subject matter.

[00029] Fig. 18(a) and Fig. 18(b) depict results of photoluminescence and decay kinetics study, in accordance with an implementation of the present subject matter.

DETAILED DESCRIPTION

[00030] The present subject matter provides methods fabrication of the nanostructured superconductors and nanostructured superconductors obtained therefrom. Further, the present subject matter also provides an assembly for fabrication of the nanostructured superconductors. [00031] A superconductor is a material that can conduct electricity or transport electrons from one atom to another with no resistance. Nanostructured superconductors provide advantages, such as high surface area-to-volume ratio, improved physical properties, and tunable electronic properties. Nanostructured superconductors can be fabricated or assembled by several techniques, for example, nanoparticles which form the nanostructured superconductors can be assembled using chemical means onto pre existing nanoparticle templates or else precipitated from solution using a combination of chemical and gravimetric methods and/or size sorting; concentrated and subsequently used as inks for film casting. These methods are invariably time consuming and unsuitable for a continuous flow process.

[00032] In another method, by the process of manufacture, anisotropy was demonstrated across a nanostructured superconductor film. This anisotropy was attributed to differential removal of surfactants across the nanostructured superconductor film, as well as due to inhomogeneity in distribution of nanoparticles which forms the nanostructured superconductor film that arises during film casting. Further, deterioration in nanostructured superconductor film was also found to occur during the process of surfactant removal, that leads to buckling effects, as well as the formation of porosity, indentations and breaks in the film from points where surfactants are removed. [00033] Further, most conventional methods teach the use of millimolar or even lower concentrations of precursors in solutions for the fabrication of the nanostructured superconductors. This essentially implies that in molar terms roughly 10000 moles of solvent can be consumed per mole of conductor deposited, thereby translating to about 10 kg of solvent consumed per gram of active material deposited. In addition, the higher reliability solution-based methods also utilize large amounts of surfactant, typically 100-1000 times more than the mass of the active material deposited. This translates to about 1 kg of surfactant utilized per gram of active material. Hence, there is a need for a process that reduces this waste greatly. [00034] Another known method of preparation of superconductors is through simultaneous evaporation of two different metals. However, this method has been shown to work only sporadically. Another method includes ion beam implantation growth of nanoparticles in a preexisting film. However, the ion beam implantation has been shown to fabricate or use materials that exhibit superconductor-like behavior at extremely low, i.e. less than 10K temperatures.

[00035] Thus, the method of fabrication of nanostructured superconductors generally are associated with limitations, such as usage of large amounts of surfactants and solvents, difficulty in scale-up and roll-to-roll processing, unstable nature of nanomaterial used for fabrication of the nanostructured superconductors which causes coagulation over time, high sensitivity to parameters of chemical purity, anisotropy in obtained nanostructured superconductors, and non-uniformity over deposition area. [00036] The present subject matter addresses these and other problems of conventional methods of fabricating nanostructured superconductors. The present subject matter provides a process for fabrication of nanostructured superconductors. The process helps in minimizing solvent wastage.

[00037] A precursor of a first material is dispersed into a carrier gas to obtain a first aerosol. The first aerosol is contacted with a substrate. Decomposition of the first material is caused to deposit the nanoparticles of the first material on the substrate. A partially covered substrate is obtained. A second material is deposited onto the partially covered substrate to form nanoclusters comprising the second material embedded in the first material to obtain the nanostructured superconductor.

[00038] In one example, the decomposition of the first material is caused by heating the substrate prior to contact with the first aerosol to cause decomposition of the first material on contacting of the first aerosol with the substrate. Thus, when the first aerosol makes contact with the substrate volatiles in the first aerosols are removed and, thereby, chemical transformation is facilitated. In another example, the decomposition of the first material is caused by heating the first aerosol prior to contacting the first aerosol with the substrate. As will be understood, in other examples, both the substrate and the first aerosol may be heated. Other methods of decomposition, such as, photochemical, electrochemical, and the like are possible.

[00039] The second material may be deposited in a manner similar to the deposition of the nanoparticles of the first material, i.e., a precursor of the second material can be dispersed into a carrier gas to form a second aerosol, the second aerosol can be contacted with the substrate partially covered with nanoparticles of the first material, and decomposition of the second material may be caused on contacting the second aerosol of the second material to embed the nanoparticles of the second material in the nanoparticles of the first material. In other examples, the second material may be deposited by thermal sputtering, electron beam sputtering, evaporation/ condensation sputtering, electrochemical deposition, atomic layer deposition, chemical bath deposition and combinations thereof.

[00040] Thus, the present subject matter provides a predominantly physical method for fabrication of nanostructured superconductors that reduces or minimizes usage of solvents and surfactants. The process is economical and provides reliable and isotropic products. The process can be scaled-up and provides roll-to-roll process ability. [00041] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components. [00042] Fig. 1 illustrates an example process 100 for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. The nanostructured superconductors, in one example, comprises nanoclusters of a first material and a second material. In one example, the second material embedded in the first material to obtain the nanostructured superconductor. The first material or the second material are formed into nanoclusters with particle size in the range of 0.2 nm to 2.5 nm without using surfactants. In one example, the obtained nanostructured superconductor exhibits low or vanishing resistivity of less than 10⁸ Ohm-m over a range of temperatures from 0.0001 K to 1000 K and pressures ranging from 10²⁰ GPA to 10 GPA. Therefore, the nanostructured superconductor fabricated from the process 100 exhibits low resistance over a wide range of temperature and pressure.

[00043] The first material and the second material may be selected such that there are electrochemical potential differences between the materials. In one example, the first material may be gold, and the second material may be silver. While the process 100 has been explained with reference to gold as the first material and silver as the second material, other variations are possible. For example, first material may be silver, and the second material may be gold. Further, one of first material and second material may be copper and the other is gold, platinum, palladium, and the like.

[00044] At step 102, the process 100 comprises dispersing a precursor of a first material into a carrier gas to obtain a first aerosol. The first aerosol may comprise a liquid, a solid, or a colloid of the precursor and the carrier gas. The first aerosol may be obtained, for example, by using an atomizer by a hybrid-spray pyrolysis -based synthesis. The first material may be a metal which may be selected from the group consisting of alkali metals, alkaline earth metals, transitional metals, post transitional metals, coinage metals, noble metals, metalloids, and lanthanoids. In one example, the precursor of the first material comprises a metal salt.

[00045] The carrier gas may be selected from air, hydrogen, nitrogen or any other inert gas and combinations thereof. The carrier gas may be selected based on the precursor of the first material. For example, an aqueous solution of silver nitrate may be dispersed in argon; a solution of gold compound, such as tetrachloroauric acid may be dispersed into a mixture of hydrogen and nitrogen; a colloid of silver compound, such as silver chloride nanoparticles in a solvent, such as chloroform may be dispersed in air. The dispersion of the precursor of the first material may be achieved by various means, for example, by using an ultrasound transducer, passing the precursor of the first material in a solvent through an orifice, and the like.

[00046] Concentration of the precursors of the first material in the dispersion may be tuned, for example, based on droplet size in the first aerosol, number of atoms of first material per nanoparticle, size of nanoparticles to be deposited, and the like. For example, when 20 - 30 atoms are required per nanoparticle, droplet size of 3 pm may be required. In another example, for the formation of nanoparticles of 0.6 - 25 nm, ~ 10 microns sized droplets may be required. For this, a 10⁵ molar concentration i.e. 10 micro-molar concentration of the first precursor may be used. In this case, the first precursor moles may be identical with moles of the metal. Appropriate corrections may be made when the first precursor is a compound with more than one active atom per mole of precursor (e.g. Ag₂S0₄).

[00047] At block 104, the process 100 comprises contacting the first aerosol with a substrate. The substrate may serve as a receptacle to enable the formation of the nanostructured superconductor. On the substrate, the nanostructured superconductor may be obtained in the form of a large, free-standing bulk. The free-standing bulk can be wire, pellet, sheet, or macroscopic grains. The substrate may be, for example, glass, quartz, silicon, metal foil, and the like.

[00048] At block 106, the process 100 comprises causing decomposition of the first material to deposit the nanoparticles of the first material on the substrate to obtain a partially covered substrate. The decomposition of the first material may be by thermal, electrochemical, photochemical, electrochemical process, and combination thereof. [00049] In one example, causing the decomposition of the first material comprises heating the substrate prior to contact with the first aerosol to cause decomposition of the first material on contacting of the first aerosol with the substrate. The heating of the substrate helps in removal of volatiles in the first aerosol and also assists in chemical transformation of the first precursor to form the nanoparticles on the substrate. In one example, the substrate is held at an electrical potential between 100 V to 1 MV relative to other parts of a set-up, for example, a chamber where the process 100 is conducted. [00050] In another example, causing the decomposition of the first material comprises heating the first aerosol prior to contacting the first aerosol with the substrate. The heating of the first aerosol may be achieved by mixing the first aerosol with a pre heated gas, ultrasonic heaters, by using a spray gun, and the like. The heating of the first aerosol helps in removal of volatiles in the first aerosol and also assists in chemical transformation of the first precursor to form the nanoparticles on contact of the first material with the substrate. In one example, both the substrate and the first aerosol may be heated. On decomposition, nanoparticles of the first material of size 0.2 - 2.5 nm may partially cover the substrate to obtain a partially covered substrate.

[00051] In another example, causing the decomposition of the first material comprises subjecting the first aerosol to light from a light source, for example, a laser source, to cause photochemical decomposition of the first material. In another example, causing the decomposition of the first material comprises causing electrothermal decomposition by generating an electric arc, for example, by using an electrode. [00052] At step 108, the process 100 comprises depositing a second material onto the partially covered substrate to form nanoclusters. The nanoclusters comprise the second material embedded in the first material to obtain the nanostructured superconductor. The second material comprises a metal salt with metal selected from the group: alkali metals, alkaline earth metals, transitional metals, post transitional metals, coinage metals, noble metals, metalloids, and lanthanoids. [00053] In one example, the second material may be deposited in a similar manner as the first material. For example, a precursor of the second material may be dispersed in a carrier gas to form a second aerosol. Similar to the first material, concentration of the precursor of the second aerosol may be a function of the droplet size. The second aerosol may comprise a liquid, a solid, or a colloid of the precursor of the second material in the carrier gas. The second aerosol may be contacted with the substrate partially covered with nanoparticles of the first material.

[00054] Decomposition of the second material may be caused, in one example on contacting the second aerosol with the substrate to embed nanoparticles of the second material in the nanoparticles of the first material. In one example, causing the decomposition of the second material is by thermal, electrochemical, photochemical, electrothermal decomposition and combination thereof.

[00055] In one example, to facilitate thermal decomposition of the second material, the substrate may be heated, or the second aerosol may be heated or both may be heated to help in removal of volatiles and facilitate chemical transformation of the second material. In other examples, causing the decomposition of the first material comprises subjecting the first aerosol to light from a light source, for example, a laser source, to cause photochemical decomposition of the first material. In another example, causing the decomposition of the first material comprises causing electrothermal decomposition by generating an electric arc, for example, by using an electrode.

[00056] In another example, depositing the second material is by thermal sputtering, electron beam sputtering, evaporation/ condensation sputtering, electrochemical deposition, atomic layer deposition, chemical bath deposition and combinations thereof. [00057] The steps 102-108 may be carried out multiple times to achieve the desired thickness of the nanostructured superconductors. In one example, the steps of deposition, i.e., causing decomposition of the first material on the substrate to obtain the partially covered substrate and depositing the second material onto the partially covered substrate, may be repeated to obtain the desired thickness of the film of a superconductor with a transition at the desired temperature to a state with low or vanishing resistance.

[00058] The transition temperature to the superconductive state may be tuned by varying the relative amounts of components, component identities and nanoparticle size, and density of incorporation, among other methods such as but not limited to film aging, thermal, electrical or microwave annealing, oxygen exposure, and so forth. This may be accomplished by either changing the amounts of material in each solution, by altering the exposure times e.g. by pulsed flows, or by regulating the stream density or through a combination of these and other methods.

[00059] The desired thickness may be empirically determined, for example, based on application of the obtained nanostructured superconductors, reactor parameters for fabrication of the nanostructured superconductors, and the like. The obtained nanostructured superconductors may be in the form of wire, pellet, sheet, macroscopic grain, film, and the like.

[00060] Fig. 2 illustrates another example process 200 for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. At block 202, a precursor of the first material is dispersed into a first solvent and a carrier gas. The solvent may be an aqueous or organic solvent, such as acetone, hexane, methanol, chloroform, and the like. The carrier gas may be nitrogen, hydrogen inert gases, air, and combinations thereof to obtain a first aerosol as shown in block 204.

[00061] At block 206, the first aerosol obtained at block 204 can be heated. Heating the first aerosol of the first material may be carried out by using an ultrasonic heater or infrared heated or mixing the first aerosol with pre -heated gas. At block 208, heated first aerosol is contacted with the substrate to facilitate formation and deposition of nanoparticles of the first material on the substrate. In one example, the substrate is heated to facilitate volatilization of the solvents and chemical transformation. [00062] At block 210, a second material is supplied for deposition on the substrate partially covered with nanoparticles of the first material. At block 212, the nanoparticles of the second material are deposited on the substrate by either evaporative or sputter deposition leading to formation of nanoclusters of the first material and the second material where the second material is embedded in the first material. The process steps as provided by blocks 202 - 212 may be repeated to obtain the nanostructured superconductors at block 214.

[00063] Fig. 3 illustrates another example process 300 for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. At block 302, a precursor of the first material is dispersed into a first solvent and a carrier gas. The solvent may be an aqueous or organic solvent, such as acetone, hexane, methanol, chloroform, and the like. The carrier gas may be nitrogen, hydrogen inert gases, air, and combinations thereof to obtain a first aerosol as shown in block 304. [00064] At block 306, the first aerosol obtained at block 304 can be heated. Heating the first aerosol of the first material may be carried out by using an ultrasonic heater or mixing the first aerosol with pre -heated gas. At block 308, heated first aerosol is contacted with the substrate to facilitate formation and deposition of nanoparticles of the first material on the substrate. In one example, the substrate is heated to facilitate volatilization of the solvents and chemical transformation.

[00065] At block 310, a second material is supplied for deposition on the substrate partially covered with nanoparticles of the first material. At block 312, the nanoparticles of the second material are deposited on the substrate by electrochemical deposition leading to formation of nanoclusters of the first material and the second material where the second material is embedded in the first material. The process steps as provided by blocks 302 - 312 may be repeated to obtain the nanostructured superconductors at block 314. [00066] Fig. 4 illustrates another example process 400 for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. A precursor 402 of the first material is dispersed within a carrier gas 404 to obtain the first aerosol 406. As will be understood, the precursor 402 may be dissolved in a solvent prior to dispersion in the carrier gas 404. The obtained first aerosol may be heated as shown at block 408.

[00067] Similarly, a precursor 410 of the second material is dispersed within a carrier gas 412 to obtain the second aerosol 414. As will be understood, the precursor 410 may be dissolved in a solvent prior to dispersion in the carrier gas 412. The obtained second aerosol 414 may be heated as shown at block 416. The heated first aerosol and the heated second aerosol are contacted with a substrate 418. The substrate 418 may be heated to deposit nanoparticles of the first material and the second material on the substrate 418 to obtain the nanoclusters. Contacting of the first aerosol and the second aerosol may, in one example, be sequential to obtain the nanostructured superconductors at block 420.

[00068] Fig. 5(a) illustrates an example assembly 500 for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. The assembly 500 for fabrication of nanostructured superconductors can comprise at least an atomizer 502, a decomposition unit 503, and a deposition unit 504. While Fig. 5 has been explained with reference to a single atomizer 502, a single decomposition unit 503, and a single deposition unit 504, it is to be understood that multiple atomizers, decomposition units and deposition units may be included in the assembly 500. In one example, the atomizer 502, the decomposition unit 503, and the deposition unit 504 are enclosed in a chamber 506. The assembly 500 can also comprise a power source 511 to supply power for the functioning of the various components of the assembly 500. [00069] The atomizer 502, in one example, may be used for dispersing a precursor of a first material into a carrier gas to obtain a first aerosol. The first aerosol is for being contacted with a substrate. In one example, the substrate may be placed on a base 508. [00070] The decomposition unit 503 can cause decomposition of the first material to deposit the nanoparticles of the first material on the substrate to obtain a partially covered substrate. The decomposition unit 503 may be one of: a heating element to cause thermal decomposition of the first material, an electrode to cause electrochemical decomposition of the first material, an electrode for forming an electric arc to cause electrothermal decomposition of the first material, a light source to cause photochemical decomposition of the first material, and combination thereof.

[00071] For example, the heating element may be coupled to the atomizer 502 to cause evaporation of volatiles in the first aerosol; the heating element may be coupled to the base 508 to heat the substrate to cause evaporation of volatiles in the first aerosol on contact of the first aerosol with the substrate; or the heating element may be coupled to the chamber 506 to heat the first aerosol and the substrate.

[00072] In another example, for electrochemical decomposition, the electrode to cause electrochemical decomposition of the first material may be placed in the chamber 506 in a first aerosol stream. In another example, for electrothermal decomposition, the electrode to cause electrothermal decomposition of the first material may be placed in the chamber 506 such that an electric arc is produced in the first aerosol stream. In another example, for photochemical decomposition, the light source may be placed in the chamber 506 to subject the first aerosol stream to light or to decompose the first material on contact of the first aerosol on the substrate.

[00073] In one example, the deposition unit 504 is to deposit the second material on the substrate partially covered with nanoparticles of the first material. The deposition unit 504 is one of: at least one atomizer, evaporator, sputterer, electrochemical deposition setup, chemical bath, and atomic layer depositor. [00074] The deposition unit 504 may be one of: a heating element to cause thermal decomposition of the second material, an electrode to cause electrochemical decomposition of the second material, an electrode for forming an electric arc to cause electrothermal decomposition of the second material, a light source to cause photochemical decomposition of the second material, and combination thereof. [00075] For example, the heating element may be coupled to the atomizer to cause evaporation of volatiles in the second aerosol; the heating element may be coupled to the base 508 to heat the partially covered substrate to cause evaporation of volatiles in the second aerosol on contact of the second aerosol with the partially covered substrate; or the heating element may be coupled to the chamber 506 to heat the second aerosol and the partially covered substrate.

[00076] In another example, for electrochemical decomposition, the electrode to cause electrochemical decomposition of the second material may be placed in the chamber 506 in a second aerosol stream. In another example, for electrothermal decomposition, the electrode to cause electrothermal decomposition of the second material may be placed in the chamber 506 such that an electric arc is produced in the second aerosol stream. In another example, for photochemical decomposition, the light source may be placed in the chamber 506 to subject the second aerosol stream to light or to decompose the second material on contact of the second aerosol on the partially covered substrate. [00077] The deposition unit 504 can comprise other ancillary components. For example, when the deposition unit 504 is an evaporator or sputterer based deposition unit, the chamber 506 may be maintained under low pressure. This can be achieved by using an overall evacuated chamber 506.

[00078] In another example, when the deposition unit 504 is the electrochemical deposition setup, the substrate may be used as an electrode for metal deposition. The chamber 506 may comprise other electrodes may or may not serve as active electrodes. For example, copper metal may be very conveniently deposited in an aqueous environment using an active copper electrode and a copper-based electrolyte such as copper sulfate. For other metals, passive platinum electrodes may be required. The electrochemical deposition may be accomplished either by sequentially moving the substrate from the aerosol deposition to the electrochemical deposition region of the chamber 506 or else by the use of a compact moving electrochemical reactor.

[00079] Similarly, when the deposition unit 504 is a chemical bath, the substrate may be moved within the chemical bath, for example, by using a movement unit 509 couple to the base 508. In other examples, the movement may be by using a mobile reactor. [00080] In another example, when the deposition unit 504 is the atomic layer depositor, the pressure in the chamber 506 may be maintained at about 100 mtorr so that flow of gas is laminar. The second aerosol may be introduced such that deposition of an atomic layer thickness of the nanoparticles of the second material is achieved on the substrate partially covered with nanoparticles of the first material.

[00081] To cause different depositions of the nanoparticles of the first material and the second material on the substrate, the assembly 500 may include the movement unit 509 coupled to the base 508. The movement unit 509 may be used to cause movement of the substrate relative to the atomizer 502, the decomposition unit 503, and the deposition unit 504.

[00082] Fig. 5(b) illustrates a schematic of an example assembly for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. In the assembly as shown in Fig. 5(b), the decomposition unit 503 is a heating element 510 and the deposition unit 504 is the heating element 510 in combination with an atomizer 514. While the heating element 510 is shown to be coupled to a substrate 512, the heating element 510 may be coupled to the base 508 or to the chamber 506 to heat the substrate 512, the first aerosol or both.

[00083] In operation, with reference to Fig. 5(b), the precursor of the first material may be atomized by the atomizer 502 and introduced as a first aerosol stream in the chamber 506 via a first gas inlet. The precursor of the second material may be atomized by the atomizer 514 and introduced as a second aerosol stream in the chamber 506 via a second gas inlet. The chamber 506 may comprise an exhaust valve (not shown) to exhaust any residual first aerosol and second aerosol. [00084] On introducing the first aerosol stream and the second aerosol stream within the chamber 506, the first aerosol stream and the second aerosol stream may heated by the heating element 510 to cause decomposition of the first material and the second material to cause deposition of nanoparticles of first material and the second material on the substrate 512 to obtain the nanostructured superconductors. In one example, the first aerosol stream and the second aerosol stream may be introduced in the chamber 506 simultaneously. In other examples, the first aerosol stream and the second aerosol stream may be introduced sequentially.

[00085] Fig. 5(c) illustrates a schematic of an example assembly for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. In the assembly as shown in Fig. 5(c), the decomposition unit 503 is a heating element 510 in combination with a light source 516, and the deposition unit 504 is the heating element 510 in combination with the atomizer 514 and the light source 516. While the heating element 510 is shown to be coupled to a substrate 512, the heating element 510 may be coupled to the base 508 or to the chamber 506 to heat the substrate 512, the first aerosol or both. The light source 516 may be coupled substantially towards the base 508 to expose the substrate 512 or the first aerosol stream or the second aerosol stream to light for photochemical decomposition of the first material and the second material to form nanoclusters comprising the second material embedded in the first material to obtain the nanostructured superconductor.

[00086] In operation, with reference to Fig. 5(c), the precursor of the first material may be atomized by the atomizer 502 and introduced as a first aerosol stream in the chamber 506 via a first gas inlet. The precursor of the second material may be atomized by the atomizer 514 and introduced as a second aerosol stream in the chamber 506 via a second gas inlet. The chamber 506 may comprise an exhaust valve (not shown) to exhaust any residual first aerosol and second aerosol.

[00087] On introducing the first aerosol stream and the second aerosol stream within the chamber 506, the first aerosol stream and the second aerosol stream may be heated by the heating element 510 and be exposed to light from the light source 516 to cause decomposition of the first material and the second material to cause deposition of nanoparticles of first material and the second material on the substrate 512 to obtain the nanostructured superconductors. In one example, the first aerosol stream and the second aerosol stream may be introduced in the chamber 506 simultaneously. In other examples, the first aerosol stream and the second aerosol stream may be introduced sequentially.

[00088] Fig. 5(d) illustrates a schematic of an example assembly for fabrication of nanostructured superconductors, in accordance with an implementation of the present subject matter. In the assembly as shown in Fig. 5(d), the decomposition unit 503 is a heating element 510 and the deposition unit 504 is the heating element 510 in combination with an electrode 518 to cause electrochemical decomposition. In the assembly as shown in Fig. 5(d), the base 508 may be conveyor belt on which the substrate 512. [00089] As shown in Fig. 5(d), the substrate 512 may first receive the first aerosol, for example, via pipe 520 of the chamber 506. The heating element 510 may then cause decomposition of the first aerosol to partially cover the substrate 512. The partially covered substrate 512 may be then transported along the conveyor belt for deposition of nanoparticles of the second material on the partially covered the substrate 512. The precursor of the second material may be pumped into the chamber 506, for example, by a pump 521 , to obtain the second aerosol. The second aerosol formed may be applied by an applicator 522 on the partially covered substrate 512.

[00090] The electrode 518 creates a potential difference between the pump 521 and the substrate and causes electrochemical decomposition of the second material to obtain nanoparticles of the second material to obtain the nanostructured superconductors.

[00091] The present subject matter will now be illustrated with working examples, which are intended to illustrate the working of disclosure and not intended to be taken restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. It is to be understood that this disclosure is not limited to the particular methods and experimental conditions described, as such methods and conditions may vary depending on the process and inputs used as will be easily understood by a person skilled in the art.

EXAMPLES

EXAMPLE 1 : PREPARATION OF THE NANOSTRUCTURED SUPERCONDUCTORS EXAMPLE lA: PREPARATION OF SILVER AND GOLD BASED NANOSTRUCTURED SUPERCONDUCTORS

[00092] Silver nanoclusters was prepared by volatilizing an aqueous solution of silver nitrate using an ultrasonic transducer and following the steps outlined below. The aerosolized solution was guided by a carrier gas comprising of high purity nitrogen (preheated to 1501C) to a heated substrate (Heated to 2001C). At these temperatures, first water evaporated leaving behind an aerosol of silver nitrate nanoparticles; these in turn were deposited onto the substrate and were eventually decomposed to form silver clusters. Gold deposition was carried out simultaneously by the deposition of another colloid formed by aerosolizing an aqueous solution of tetrachloroauric acid that was then mixed with high purity nitrogen at 1501C. The entire process was carried out in a reactor vessel in a nitrogen atmosphere with a 5 psi overpressure relative to the ambient.

EXAMPLE IB: PREPARATION OF GOLD AND SILVER BASED NANOSTRUCTURED SUPERCONDUCTORS

[00093] Silver nanoclusters were prepared by volatilizing an aqueous solution of silver nitrate using an ultrasonic transducer and following the steps outlined below. The aerosolized solution was guided by a carrier gas comprising of high purity nitrogen (preheated to 150 “C) to a heated substrate (heated to 300 C). A locally reducing environment at the substrate was created by directing a flow of an H2:N2 stream (1:99 molar ratio) at the substrate. At these temperatures, first water evaporated leaving behind an aerosol of silver nitrate nanoparticles which in turn was deposit onto the substrate and eventually decomposed to form silver clusters. Gold deposition was carried out simultaneously by the deposition of another colloid formed by aerosolizing an aqueous solution of tetrachloroauric acid which was then mixed with high purity nitrogen at 150 C. EXAMPLE 1C: PREPARATION OF COPPER AND MANGANESE BASED NANOSTRUCTURED SUPERCONDUCTORS

[00094] Copper nanoclusters were prepared by volatilizing an aqueous solution of Cupric Chloride using an ultrasonic transducer and following the steps outlined below. The aerosolized solution was guided by a carrier gas comprising of high purity nitrogen (preheated to 150¾3) to a heated, electrically conductive substrate (heated to 400 C). A locally reducing environment at the substrate was created by directing a flow of an H2:N2 stream (2:98 molar ratio) at the substrate. At these temperatures, first water evaporated leaving behind an aerosol of cupric chloride nanoparticles; these in turn were deposited onto the substrate and were eventually decomposed to form copper clusters. The substrate coated with copper clusters was subsequently placed in an electrochemical bath for manganese metal deposition. The substrate formed the cathode for Mn deposition.

EXAMPLE ID: PREPARATION OF COPPER AND MANGANESE BASED NANOSTRUCTURED SUPERCONDUCTORS

[00095] Copper nanoclusters were prepared by volatilizing an aqueous solution of Cupric Chloride using an ultrasonic transducer and following the steps outlined below. The aerosolized solution was guided by a carrier gas comprising of high purity nitrogen (preheated to 1501C) to a heated, electrically conductive substrate (heated to 4001C). A locally reducing environment at the substrate was created by directing a flow of an H2:N2 stream (2:98 molar ratio) at the substrate. At these temperatures, first water evaporated leaving behind an aerosol of cupric chloride nanoparticles; these in turn were deposited onto the substrate and were eventually decomposed to form copper clusters. The substrate coated with copper clusters was subsequently placed in an electrochemical bath for manganese metal deposition. The substrate formed the cathode for Mn deposition. EXAMPLE IE: PREPARATION OF SILVER AND GOLD BASED NANOSTRUCTURED SUPERCONDUCTORS

[00096] Silver nanoclusters were prepared by spraying an aqueous 0.001 M solution of silver nitrate using an atomizer and following the steps outlined below. The aerosolized solution was guided by a carrier gas comprising of high purity nitrogen (preheated to 1501C) to a heated substrate (heated to 3001C). At these temperatures, first water evaporated leaving behind an aerosol of silver nitrate nanoparticles, which in turn was deposited onto the substrate and eventually decompose to form silver clusters. Gold deposition is carried out simultaneously by the deposition of another colloid formed by spraying an aqueous solution of tetrachloroauric acid that is then mixed with 5:95 HydrogemNitrogen mixture at 1501C..

EXAMPLE 2: ABSORBANCE SPECTRA

[00097] Samples of nanostructured superconductors of silver and gold were prepared. 10 m M AgNCE and HAuCU solutions were prepared separately to obtain their respective vapors. The obtained vapors were passed through T-Joint and allowed to mix in the middle by passing inert gas. The mixed vapor was deposited on a Quartz substrate which was pre heated to -230-250 °C. The absorbance spectra of the sample were studied. Fig(s) 6(a), 6(b), and 6(c) depicts results of absorbance spectra study, in accordance with an implementation of the present subject matter. Figs. 6(a) - (c) shows different optical density, the thickness of the film depends on the amount of vapor generation and deposition time.

EXAMPLE 3: STEM IMAGES OF NANOSTRUCTURED SUPERCONDUCTOR FILM DEPOSITED

IN GLOVE BOX [00098] High-angle annular dark-field scanning transmission electron microscopy

(HAADF STEM) images of nanostructured superconductor film deposited on carbon coated copper grid (20 min deposited) were obtained. Fig(s). 7(a)-(c) depict HAADF STEM images of nanostructured superconductor film, in accordance with an implementation of the present subject matter. From Fig(s). 7(b) and 7(c) it can be observed that the nanostructured superconductor film spars and is not continuous in most of the region. It conveys the homogeneous distribution of gold and silver. [00099] A second set of HAADF STEM images of film deposited on carbon coated copper grid (20 min deposited) were obtained. Fig(s). 7(d)-(f) depict HAADF STEM images of nanostructured superconductor film, in accordance with an implementation of the present subject matter. As can be observed from Fig(s). 7(e) - 7(f), the nanostructured superconductor film includes both gold and silver.

[000100] Elemental mapping of the HAADF images was performed using Electron Energy Loss Spectroscopy (EELS). Fig(s) 8(a)-8(c) depicts results of elemental mapping of the HAADF image, in accordance with an implementation of the present subject matter. As can be observed from Fig(s) 8(a)-8(c) there was a distribution of silver and gold nanoparticles for the particular area analyzed through EELS.

[000101] EELS spectrum and Annular Dark Field (ADF) images of samples were obtained. Fig. 9(a) depicts EELS spectrum and Fig. 9(b) depicts inelastic scattering, in accordance with an implementation of the present subject matter. To obtain the EELS spectrum and ADF images, the samples of the nanostructured superconductors were kept under an electron beam with 80 kV accelerating voltage (Technical details: FWHM of the Zero loss peak is 0.23 eV. Here, the Gaussian-Lorentzian zero loss model was been used). In Fig. 9(c) black solid lines (inelastic scattering) showed no plasmon resonances at 2.3 eV (Au) and 3.1 eV (Ag). This indicated the unconventional nature of the gold and silver nanoparticles of the nanostructured superconductors. [000102] Fig(s). 10(a) and 10(b) depict Transmission Electron Microscopy (TEM) images of the samples, in accordance with an implementation of the present subject matter. TEM images as shown in Fig(s) 10(a) and 10(b) correspond to nanostructured superconductor film deposited on a carbon coated copper grid (2 min deposited, separate set up). As can be observed from Fig(s). 10(a) and 10(b), the grid contained micron sized blocks of metals. The nanostructured superconductor film was too thick to be analyzed further by using TEM. However, at few regions existence of individual nanoparticles was also observed.

[000103] Energy-dispersive X-ray spectroscopy (EDS) study was performed. Fig(s). 11(a) and 11(b) depict EDS spectra of nanostructured superconductor film, in accordance with an implementation of the present subject matter. Insets of Fig(s). 11(a) and 11(b) show HAADF images taken over a few regions where individual nanoparticles were. EDS spectra showed the presence of gold and silver.

[000104] Atomic force microscopy (AFM) of the sample nanostructured superconductor film was performed. Fig. 12(a) depicts three-dimensional (3D) topography of deposited film on quartz, in accordance with an implementation of the present subject matter. Fig. 12(a) indicates layered deposition. [000105] Fig(s). 12(b) and 12(c) depicts height profile obtained from AFM images, in accordance with an implementation of the present subject matter. The height profile shows the deposited nanostructured superconductor having thickness of 2 microns. [000106] Fig. 12(d) depicts surface topography obtained from AFM image, in accordance with an implementation of the present subject matter. The surface roughness of the selected regions was found to be about 184 nm.

[000107] Magnetic AFM was performed of nanostructure superconductors deposited outside of a glove box. For this, Au/Ag nanostructured superconductor films were deposited on a pre-deposited thin Ag film. For this purpose, 50 nm of Ag was thermally evaporated on quartz. Fig(s). 13(a), 13(b), 14(a), 14(b) depict results of magnetic AFM study, in accordance with an implementation of the present subject matter.

[000108] Fig. 13(a) shows the topography of obtained filed over 25x25 micrometer area. Fig. 13(b) represents the thickness of the film across the line drawn in the image. Fig. 14(a) represents the magnetic phase image of the same 25x25 micrometer area. Fig. 14(b) represents a large positive phase shift (11.55°) in the oscillation of AFM tip over a particular region. This observation infers the strong diamagnetic nature of the deposited film in that concerned region.

[000109] Fig. 15(a) illustrates the topography of the film, in accordance with an implementation of the present subject matter. The topography is over the same 25x25 micrometer area as Fig(s). 13 and 14. Fig. 15(b) represents the thickness of the film across the line drawn in the image.

[000110] Similar to Fig(s). 15(a) and 15(b), Fig. 16(a) represents the magnetic phase image of a 35x35 micrometer area, in accordance with an implementation of the present subject matter. Fig 16(b) represents a large positive phase shift (55.32°) in the oscillation of AFM tip over the particular region. This observation infers the strong diamagnetic nature of the deposited film in that concerned region.

[000111] Fluorescent microscopic study of nanostructured superconductor films was performed. Fig(s). 17(a) and 17(b) depict images of the fluorescent microscopy, in accordance with an implementation of the present subject matter. From Fig(s). 17(a) and 17(b), it can be observed that the deposited Au/Ag films show luminescence when excited by 405nm pulsed wave laser source. Fig. 17(a) depicts lifetime imaging of vapor deposited Au/Ag film on quartz, i.e., when both first and second material are deposited by way of respective aerosol contact with quartz. Fig. 17(b) depicts lifetime imaging of nanostructured superconductor film wherein the Ag nanoparticles were deposited after synthesizing the Au nanoparticles via colloidal route.

[000112] Photo luminescence and decay kinetics were studied. Fig. 18(a) and Fig. 18(b) depict results of photoluminescence and decay kinetics study, in accordance with an implementation of the present subject matter. Generally, the Au/Ag film shows a broad luminescence throughout the visible range optical frequencies (Fig. 18(a) solid lines), where the Au film also shows similar broad luminescence over the same energy range (Fig. 18(a) dashed lines). Fig. 18(b) represents the decay kinetics where Au/Ag film shows a slower decay ~40ns compare to Au film ~25ns.

[000113] The present subject matter, thus, provides a process for fabrication of nanostructured superconductors which is devoid of anisotropy, that show low resistance over a wide range of temperature and pressure. The process is predominantly a physical method for fabrication of nanostructured superconductors that reduces or minimizes usage of solvents and surfactants. The process is economical and provides reliable and isotropic nanostructured superconductors.

[000114] Although the subject matter has been described in considerable detail with reference to certain examples and implementations thereof, other implementations are possible. As such, the scope of the present subject matter should not be limited to the description of the preferred examples and implementations contained therein.

Claims

I/We claim:

1. A process for fabrication of a nanostructured superconductor comprising: dispersing a precursor of a first material into a carrier gas to obtain a first aerosol; contacting the first aerosol with a substrate; causing decomposition of the first material in the first aerosol to deposit nanoparticles of the first material on the substrate to obtain a partially covered substrate; and depositing a second material onto the partially covered substrate to form nanoclusters comprising the second material embedded in the first material to obtain the nanostructured superconductor.

2. The process as claimed in claim 1, wherein the first aerosol comprises a liquid, a solid, or a colloid of the precursor of the first material in the carrier gas.

3. The process as claimed in claim 1, wherein the precursor of the first material comprises a metal salt with the metal selected from the group comprising of alkali metals, alkaline earth metals, transitional metals, post transitional metals, coinage metals, noble metals, metalloids, and lanthanoids.

4. The process as claimed in claim 1, wherein the second material comprises a metal selected from the group comprising of alkali metals, alkaline earth metals, transitional metals, noble metals, coinage metals, post transitional metals, metalloids, and lanthanoids.

5. The process as claimed in claim 1, wherein one of first material and second material is silver and other is gold.

6. The process as claimed in claim 1, wherein one of first material and second material may be copper and the other is gold, platinum, palladium.

7. The process as claimed in claim 1, wherein causing the decomposition of the first material is by thermal, electrochemical, photochemical, electrothermal decomposition and combination thereof.

8. The process as claimed in claim 1, wherein causing the decomposition of the first material comprises heating the substrate prior to contact with the first aerosol to cause decomposition of the first material on contacting of the first aerosol with the substrate.

9. The process as claimed in claim 1, wherein causing the decomposition of the first material comprises heating the first aerosol prior to contacting the first aerosol with the substrate.

10. The process as claimed in claim 1, wherein depositing the second material comprises: dispersing a precursor of the second material into a carrier gas to form a second aerosol; contacting the second aerosol with the partially covered substrate; and causing decomposition of the second material on contacting the second aerosol of the second material with the substrate to embed nanoparticles of the second material in the nanoparticles of the first material.

11. The process as claimed in claim 10, wherein the second aerosol comprises a liquid, a solid, or a colloid of the precursor of the second material in the carrier gas.

12. The process as claimed in claim 1, wherein depositing the second material is by thermal sputtering, electron beam sputtering, evaporation/ condensation sputtering, electrochemical deposition, atomic layer deposition, chemical bath deposition and combinations thereof.

13. The process as claimed in claim 10, wherein causing the decomposition of the second material is by thermal, electrochemical, photochemical, electrothermal decomposition and combination thereof.

14. The process as claimed in claim 10, wherein causing the decomposition of the second material comprises heating the partially covered substrate prior to contact of the second aerosol to cause decomposition of the second material on contacting of the second aerosol with the partially covered substrate.

15. The process as claimed in claim 10, wherein causing the decomposition of the second material comprises heating the second aerosol prior to contacting the second aerosol with the partially covered substrate.

16. The process as claimed in claim 1, wherein the process comprises forming an aerosol by at least an atomi er.

17. The process as claimed in claim 1, wherein the depositing of the second material is by a deposition unit.

18. The process as claimed in claim 17, wherein the deposition unit is one of: at least one atomizer, evaporator, sputterer, electrochemical deposition setup, chemical bath, and atomic layer depositor.

19. The process as claimed in claim any one of claims 16 and 17, wherein the atomizer and the deposition unit are enclosed in a chamber.

20. An assembly for fabrication of nanostructured superconductors, the assembly comprising: at least an atomizer for dispersing a precursor of a first material into a carrier gas to obtain a first aerosol, wherein the first aerosol is for being contacted with a substrate; a decomposition unit to cause decomposition of the first material to deposit the nanoparticles of the first material on the substrate to obtain a partially covered substrate; a deposition unit to deposit a second material onto the partially covered substrate to form nanoclusters comprising the second material embedded in the first material to obtain the nanostructured superconductor; and a base to hold the substrate.

21. The assembly as claimed in claim 20, wherein the decomposition unit comprises one of: a heating element to cause thermal decomposition of the first material, an electrode to cause electrochemical decomposition of the first material, an electrode for forming an electric arc to cause electrothermal decomposition of the first material, a light source to cause photochemical decomposition of the first material, and combination thereof.

22. The assembly as claimed in claim 20, wherein the deposition unit comprises one of: a heating element to cause thermal decomposition of the second material, an electrode to cause electrochemical decomposition of the second material, an electrode for forming an electric arc to cause electrothermal decomposition of the second material, a light source to cause photochemical decomposition of the second material, and combination thereof.

23. The assembly as claimed in claim 20, wherein the deposition unit is one of: at least one atomizer, evaporator, sputterer, electrochemical deposition setup, chemical bath, and atomic layer depositor.

24. The assembly as claimed in claim 20, wherein at least the atomizer, the decomposition unit, and the deposition unit are enclosed in a chamber.

25. The assembly as claimed in claim 20 comprising a movement unit coupled to the base to cause movement of the substrate relative to the at least the atomizer, the decomposition unit, and the deposition unit.

26. A nanostructured superconductor formed by the process as claimed in any one of the preceding claims, wherein the nanostructured superconductor comprises: nanoparticles of a first material partially covering a substrate, wherein the nanoparticles are formed by contacting a first aerosol of a precursor of the first material dispersed in a carrier gas with the substrate; and nanoparticles of a second material deposited in the substrate partially covered with nanoparticles of the first material, wherein the second material is embedded in the first material.