News Column

Patent Issued for Electrochemical Methods for Making Silicon Nanopowder, Silicon Nanowires and Silicon Nanotubes

July 25, 2014



By a News Reporter-Staff News Editor at Health & Medicine Week -- According to news reporting originating from Alexandria, Virginia, by NewsRx journalists, a patent by the inventors Lu, Shigang (Beijing, CN); Yang, Juanyu (Beijing, CN); Zhang, Xiangjun (Beijing, CN); Kan, Surong (Beijing, CN), filed on May 2, 2011, was published online on July 8, 2014 (see also General Research Institute for Nonferrous Metals).

The assignee for this patent, patent number 8771498, is General Research Institute for Nonferrous Metals (Beijing, CN).

Reporters obtained the following quote from the background information supplied by the inventors: "The unique electrical and optical properties and high surface activity feature of one-dimensional nanowires (tubes) materials have attracted great interest in recent years. There are many ways to fabricate Si nanowires (tubes) at present, including a laser ablation (Morales A M, Lieber C M. Science, 1998, 279(9):208.about.211; Lee C S, Wang N, Tang Y H, et al. MRS. Bulletin., 1999:36.about.41), a chemical vapor deposition (CVD) (Wang N L, Zhang Y J, Zhu J. Journal of Materials Science Letters, 2001, 20:89.about.91), a plasma enhanced chemical vapor deposition (PECVD) (Zeng X B, Xu Y Y, Zhang S B, et al. Journal of Crystal Growth, 2003, 247 (1):13.about.16), a thermal vapor deposition (Feng S Q, Yu D P, Zhang H Z, et al. Journal of Crystal Growth, 2000, 209:513.about.517), a solution technique (Holmes J D, Johnston K P, Doty R C, et al. Science, 2000, 287:1471.about.1473), a selective plating (Lew K K, Redwing J M. Journal of Crystal Growth, 2003, 254(1):14.about.22) and a hydrothermal deposition (Pei L Z, Tang Y H, Chen Y W, et al. Journal of Crystal Growth, 2005, 289:423.about.427). Nanowires produced by a laser ablation method have high yield and high purity. But its shortcoming is high costs for expensive equipments. On the contrary, chemical vapor deposition (CVD) and thermal chemical vapor deposition techniques are relatively low costs, but the products' diameters vary over a wide range. The products also contain plentiful nano-chains. Solution-grown technique can produce nanowires with high length-diameter ratio, but requires using noble metals as catalyst. In addition, the organic and toxic solution has to be recycled, since it will pollute the environment. Other techniques, such as selective plating etc., the yields of nanowires are quite low. The shortcomings of all the above-mentioned techniques hamper the industrial use of nanowires.

"In molten salt studies, the electrochemical method of fabricating metal, alloy and non-metal directly from solid compounds by electrolysis has been provided by Fray Derek John, Farthing Thomas William and Chen Zheng of Cambridge GB, therefore this method is also called FFC Cambridge techniques. The FFC Cambridge method has advantages over other methods. It uses solid compounds to fabricate metal, alloy and non-metal by a one-step electrolysis, thereby it shortens the production process, saves energy and reduces pollution and costs. Since the composition and the reduction level of the materials can be controlled, this method is used in functional materials production. Both international publications 'Removal of oxygen from metal oxides and solid solutions by Electrolysis in a fused salt' (WO1999/064638) and 'Metal and alloy powders and powder fabrication' (WO2002/040725) by this Cambridge team claimed the technique for fabricating silicon powder directly from solid SiO.sub.2 powder. Japanese patent (JP2006/321688) also discloses a method for producing silicon powder by using silicon dioxide powder mixed with silicon or single crystal silicon wafer as conductor, and electrolyzing high-purity quartz. Micron silicon powder is produced by using the methods disclosed by above three patents. However, electrochemical methods for fabricating silicon nanopowder, silicon nanowires (tubes) from silicon compound SiX or silicon mixture comprising silicon compound SiX have not been published."

In addition to obtaining background information on this patent, NewsRx editors also obtained the inventors' summary information for this patent: "One aspect of an embodiment of the present invention provides an electrochemical method for producing one or more of silicon nanopowder, silicon nanowires and nanotubes directly from silicon compound SiX powder or a powdered mixture containing silicon compound SiX and other species. The method has many advantages: 1) shorter production processing, 2) inexpensive equipment, 3) convenient operation, 4) reduction of contaminate, 5) easily available feed materials, and 6) easy to achieve continuous production.

"Another aspect of an embodiment of the present invention describes the electrochemical method for making Si nanopowder, Si nanowires or Si nanotubes directly from silicon compound SiX powder. The electrochemical method uses an electrolysis cell which comprises a silicon compound SiX as a cathode, an anode, and a molten salt electrolyte which may contain metal compound. Electrolysis occurs when a potential is applied between the cathode and the anode. Products including Si nanopowder, Si nanowires and/or Si nanotubes can be obtained on the cathode. In the formula SiX, X can be O, S, C or N.

"By using a method of the present invention, the following types of nano materials can be produced: (1) silicon nanowires and silicon nanotubes, (2) only silicon nanowires, (3) silicon nanopowder, silicon nanowires and silicon nanotubes, or (4) only silicon nanopowder on the cathode.

"According to the present invention, the electrochemical method for producing nanopowder, nanowires and/or nanotubes containing silicon directly from a powder mixture containing silicon compound SiX. This method may comprise a silicon compound SiX cathode, an anode and a molten salt electrolyte containing metal compound. Electrolysis occurs when a potential is applied between the anode and the cathode. The obtained electrolysis products on the cathode include at least one of Si nanopowder, Si nanowires and Si nanotubes, wherein X in the formula SiX can be O, S, C or N.

"By using a method of this invention, the electrolysis products on the cathode include 1) silicon nanowires and silicon nanotubes; 2) only silicon nanowires; 3) silicon nanopowder, silicon nanowires and silicon nanotubes; or 4) only silicon nanopowder.

"According to the method of the invention, the average diameter of the silicon compound SiX powder may be less than 1 .mu.m.

"According to the method of the invention, the mixture containing silicon compound SiX may be a mixture prepared by adding a metal, an alloy, a metal compound M.sup.1Y and/or a nonmetal into the silicon compound SiX powder, wherein the metal, the alloy, the metal compound M.sup.1Y and the nonmetal are in powder forms.

"According to the method of the invention, the metal may be Au, Pt, Ag, Cu, Fe, Co, Ni, Cr, Mo, Zr. Ti, Al, Mg and/or Nb.

"According to the method of the invention, the mentioned alloy may comprise at least two metals selected from the group of Au, Pt, Ag, Cu, Fe, Co, Ni, Cr, Mo, Zr. Ti, Al, Mg and Nb.

"According to the method of the invention, M.sup.1 in the metal compound M.sup.1Y may be Au, Pt, Ag, Cu, Fe, Co, Ni, Cr, Mo, Zr, Ti, Al, Mg or Nb; and Y may be O, S, C or N.

"According to the method of the invention, the non-metal may be C, Si, Ge, S, P and/or B.

"According to the method of the invention, the metal compound of the metal compound of the molten salt may be represented by formula MY.sup.1, wherein M is Ca, Ba, Li, Al, Cs, Na, K or Sr; and Y.sup.1 is Cl or F.

"According to the method of the invention, the molten salt electrolyte containing metal compound may contain one or more electrolyte salt

"According to the method of the invention, the electrolyte may comprise CaO, which is produced by hydrolyzing fused CaCl.sub.2 at high temperature.

"According to the method of the invention, the potential applied between the cathode and the anode is preferably less than 3.2 v.

"According to the method of the invention, the potential applied between the cathode and the anode is preferably less than the decomposition potential of electrolyte.

"According to the method of the invention, the temperature range for the electrolysis is preferably between 500.degree. C. and 1000.degree. C.

"According to the method of the invention, the average diameter of the silicon nanopowder is preferably less than 100 nm.

"According to the method of the invention, the diameter of the silicon nanowires is preferably less than 100 nm.

"According to the method of the invention, the diameter of the silicon nanotubes is preferably less than 100 nm.

"According to the method of the invention, the electrolysis products comprise Si nanopowder having a diameter less than 100 nm, Si nanowires having a diameter less than 100 nm and/or Si nanotubes having a diameter less than 100 nm.

"According to the method of the invention, the electrolytic products comprise one or more species selected from the group of Si nanopowder, nanowires and nanotubes.

"The main characteristics of this invention are:

"(1) The feed materials has rich resources; no pollution during preparation and production.

"(2) Since the silicon nanopowder, nanowires and/or nanotubes are prepared in electrolyte, there is no problem of tangled and intertwist.

"(3) The shape of products of silicon nanopowder, nanowires and/or nanotubes can be controlled and the difference in size of electrolytic products is in a narrow range.

"(4) The production and equipments are easy to install and operate.

"(5) Since the feed materials and the products are all in solid state, it is easy to achieve continuous production."

For more information, see this patent: Lu, Shigang; Yang, Juanyu; Zhang, Xiangjun; Kan, Surong. Electrochemical Methods for Making Silicon Nanopowder, Silicon Nanowires and Silicon Nanotubes. U.S. Patent Number 8771498, filed May 2, 2011, and published online on July 8, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8771498.PN.&OS=PN/8771498RS=PN/8771498

Keywords for this news article include: Chemistry, Electrolytes, Legal Issues, Crystal Growth, Nanotechnology, Electrochemical, Silicon Compounds, Inorganic Chemicals, Emerging Technologies, Chemical Vapor Deposition, General Research Institute for Nonferrous Metals.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Health & Medicine Week


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters