Method for aluminum electroless deposition

Abstract

A method for electroless deposition of aluminum or an aluminum alloy on a substrate surface is provided. The method includes activating the surface of the substrate to be coated by applying a coating of a catalyst metal; preparing a mixture of urea (NH2CONH2) and anhydrous aluminum chloride (AlCl3) having a 2:1 molar ratio of AlCl3:NH2CONH2 to obtain a Lewis acid room temperature ionic liquid (RTIL) optionally containing an alloy metal salt; dissolving a hydride reducing agent in an aprotic anhydrous solvent to obtain a hydride solution; mixing the hydride solution and the AlCl3:NH2CONH2 RTIL to obtain an electroless Al solution; exposing the activated surface of the substrate to the electroless Al solution; and removing the electroless Al solution from the substrate surface; wherein upon exposure of the activated substrate surface to the electroless Al solution, an Al or Al alloy coating is obtained on the activated substrate surface.

1 . A method for electroless deposition of aluminum or an aluminum alloy on a substrate surface, comprising:
 activating the surface of the substrate to be coated by applying a coating of a catalyst metal;   preparing a mixture of urea (NH 2 CONH 2 ) and anhydrous aluminum chloride (AlCl 3 ) wherein a molar ratio of AlCl 3 :NH 2 CONH 2  is 2:1 to obtain a Lewis acid room temperature ionic liquid (RTIL) comprising Al 2 Cl 7   −  and [AlCl 2 ·(Urea) n ] +  ions,   wherein n is 1;   dissolving LiAlH 4  in an aprotic anhydrous solvent to obtain a hydride solution;   optionally, when an Al alloy coating is to be deposited, adding an anhydrous alloy metal salt as a solution to the RTIL;   mixing the LiAlH 4  solution and the AlCl 3 :NH 2 CONH 2  RTIL to obtain an electroless Al solution;   exposing the activated surface of the substrate to the electroless Al solution; and   removing the electroless Al solution from the substrate surface;   wherein upon exposure of the activated substrate surface to the electroless Al solution, an Al or Al alloy coating is obtained on the activated substrate surface by reduction of the Al 2 Cl 7   −  and [AlCl 2 ·(Urea) n ] +  ions and by decomposition of the LiAlH 4 .   
     
     
         2 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the aprotic anhydrous solvent is selected from the group consisting of tetrahydrofuran (THF), diethyl ether, dibutyl ether, dioxane, toluene and hexane. 
     
     
         3 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein an anhydrous alloy metal salt is added to the RTIL by a method comprising dissolving the alloy metal salt in an aprotic solvent; and
 adding the solution to the RTIL;   wherein the metal salt is selected from the group consisting of a halide salt of zinc, chromium, iron, nickel, tin, lead, copper, silver, gold and combinations thereof.   
     
     
         4 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the catalyst metal is selected from the group consisting of iron, palladium, silver, gold, platinum, and combinations thereof. 
     
     
         5 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the catalyst metal is palladium. 
     
     
         6 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 5 , wherein the activation of the surface of the substrate to be coated comprises:
 treating the surface with a colloidal solution of palladium-tin (Pd—Sn) nanoparticles in the presence of HCl and water to cover the surface of the substrate with a layer of adsorbed catalytic Pd—Sn nanoparticles comprising stannous hydroxide covered on their surface;   cleaning the substrate surface from the residues of the colloidal solution; and   placing the substrate in an acidic accelerator solution wherein the excess stannous hydroxide layer is removed from the surface of the substrate for an increased catalytic activity.   
     
     
         7 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 6 , wherein the substrate surface is non-reactive to Al deposition and/or non-conductive. 
     
     
         8 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 6 , wherein the substrate is a nanostructure. 
     
     
         9 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 8 , wherein the nanostructure is selected from the group consisting of a nanofiber, a nanoparticle, a nanotube, a nano-rod and a quantum dot. 
     
     
         10 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 8 , wherein the nanostructure is a carbon nanotube (CNT). 
     
     
         11 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 8 , wherein the nanostructure is a multi-wall carbon nanotube (MWCNT) or a single-wall carbon nanotube (SWCNT). 
     
     
         12 . An aluminum or aluminum alloy coated carbon nanotube obtained according to  claim 10 . 
     
     
         13 . An aluminum or aluminum alloy coated multiwall carbon nanotube obtained according to  claim 11 . 
     
     
         14 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the substrate is a metal coated polymer. 
     
     
         15 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the substrate is selected from the group of fibers consisting of a glass fiber, an aramid fiber and a carbon fiber. 
     
     
         16 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the substrate is selected from the group of yarns consisting of a glass fiber yarn, a Kevlar fiber yarn and a carbon fiber yarn. 
     
     
         17 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the substrate is selected from the group consisting of a fullerene, a Bucky paper and a Bucky sheet. 
     
     
         18 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the substrate is selected from the group of 2-D materials consisting of graphene, molybdenum disulfide (MoS 2 ), tungsten disulfide (WS 2 ), tungsten diselenide (WSe 2 ), and zinc oxide(ZnO). 
     
     
         19 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the substrate is selected from the group consisting of graphene powder and graphene nanoparticles. 
     
     
         20 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the substrate is selected from the group consisting of a ZnO microtube and a ZnO nanowire. 
     
     
         21 . The method for electroless deposition of aluminum or an aluminum alloy according to  claim 1 , wherein the substrate is selected from the group consisting of steel, a steel alloy, glass and a ceramic. 
     
     
         22 . A method for coating a substrate with an anodized aluminum oxide layer, comprising:
 activating the surface of the substrate to be coated by applying a coating of a catalyst metal;   preparing a mixture of urea (NH 2 CONH 2 ) and anhydrous aluminum chloride (AlCl 3 ) wherein a molar ratio of AlCl 3 :NH 2 CONH 2  is 2:1 to obtain a Lewis acid room temperature ionic liquid (RTIL)) comprising Al 2 Cl 7   −  and [AlCl 2 ·(Urea) n ] ions, wherein n is 1;   dissolving LiAlH 4  in an aprotic anhydrous solvent to obtain a hydride solution;   mixing the LiAlH 4  solution and the AlCl 3 :NH 2 CONH 2  RTIL to obtain an electroless Al solution;   exposing the activated surface of the substrate to the electroless Al solution; and   removing the electroless Al solution from the substrate surface to obtain an electroless aluminum plated substrate;   submerging the electroless aluminum plated substrate in an electrolytic solution;   applying an anode current to the aluminum coat to form an aluminum oxide coat comprising a barrier layer; and   treating the aluminum oxide coat comprising a barrier layer to form pores in the aluminum oxide coat structure.