US 20130045152A1 (19) United States (12) Patent Application Publication (10) Pub. N0.: US 2013/0045152 A1 Neelameggham (43) Pub. Date: Feb. 21, 2013 (54) ELEMENTAL BORON BY REDUCTION OF (52) us. c1. ...................................... .. 423/298; 205/615 BORON HALIDES BY METALS AND THEIR BORIDES (57) ABSTRACT (75) Inventor: Ramaswaml Neelameggham’ South The quest for making pure boron has been continuing for over Jordan’ UT (Us) 200 years. Most common method has been by hydrogen (73) AssigneeZ IND LLC’ South Jordan’ UT (Us) reduction of boron halides on a hot ?lament, and this has not been an economical approach. Other techniques using mag (21) Appl. No.: 13/209,610 nesiothermic reduction or electrolysis of oxide compounds of . boron P roduced imP ure boron. Present invention describes (22) Flled? Aug- 15’ 2011 techniques of making pure boron in the amorphous as Well as Publication Classi?cation crystalline formiapplying thermochemical principles in an e?icient manner. The present invention shoWs that boron (51) Int Cl halides can be reduced by alkali metal, alkaline earth metal, C023 3'5/02 (2006 01) aluminum or silicon, as Well as by alkaline earth borides, C253 1/00 (200601) aluminum borides, silicon borides into pure elemental boron. US 2013/0045152 A1 Feb. 21,2013 ELEMENTAL BORON BY REDUCTION OF and alkali metal ?uoborate using a boron carbide anode and a BORON HALIDES BY METALS AND THEIR cathode. D. R. Stern also patented an electrolytic method BORIDES Which made boron of purity to 91% in melts of B203 With alkaline oxides or ?uoborates [U.S. Pat. No. 3,030,284]. BACKGROUND OF THE INVENTION Recently, P. Taylor applied for a patent [U.S. Patent Applica [0001] Production of elemental boron in a high purity form tion 2010/0294670 A1] Wherein, a less than 90% pure boron Was made by electrolyZing B203 in an electrolyte of MgFzi has been a dif?cult and not an economical process for over NaFiLiF. In 2006, H. Yldiran and S. D. Guler disclosed a 200 years. The present invention sets out to see the causes and novel approach of electrolyZing sodium tetraborate at 10000 come up With logical economic methods. C. [WO 2006/135350]. BRIEF SUMMARY OF THE INVENTION [0007] Prior art also shoWed the folloWing metallothermic approaches. In 1958, J. M. Finn Jr, described a method Where [0002] A comprehensive thermochemical study Was made metallic Zinc is used as the reductant to react With boron to delineate methods of making high purity elemental boron. halides [U.S. Pat. No. 2,850,494]. This method did not get The study revealed that the conditions applied to making the pursued for economic production of elemental boron. In US. elemental boron thus far have been inadequate in overcoming Pat. No. 2,897,056, N. P. Nies and E. W. Fajans, describes a the oxide and stable metal borides inclusions With the magnesiothermic method of making boron from B2O3. The elemental boron. The present invention found that boron tri purity obtained Was about 92%; this Was further processed by halides can be reduced by metals as Well as metal borides in reacting the resultant impure boron in a melt of potassium a controlled fashion giving high purity boron, hitherto ?uoborate and potassium chloride [U.S. Pat. No., 2,893,842] . thought not feasible. [0008] Almadari, et al., describe a mechanochemical reac tion of boron oxide or borate compounds With metal granules PRIOR ART such as magnesium, aluminum or calcium in a high speed ball [0003] The initial discovery of elemental boron by Hum mill in Canadian patent [CA 2365641]. The examples shoWn phrey Davy and by Gay Lussac in 1808 Was later proven by in this give a measured purity of about 85% for the resultant acid Washed boron poWder. several others to be an impure material contaminated With oxides, and borides Which Were quite inseparable from the PRESENT INVENTION boron material. In 1892, Moisson came up With a magnesium reduction method of boron oxides Which produced about 90% [0009] The present invention discloses methods of making pure boron. In the early tWentieth century, Weintraub pat pure boron by metallothermic reaction of boron halide vapors ented [U.S. Pat. Nos. 1,019,165; 1,074,672 and 1,306, 568] using alkali metals, alkaline earth metals or aluminum or methods Wherein boron trichloride vapors Were reduced on silicon as Well as their borides. None of the prior art disclosed hot ?laments by hydrogen gas giving 99.0% plus pure such methods. They either disclosed metallothermic reduc elemental boron. Even though this produced purer boron, this tion of boron oxide solids, or boron oxide or its compounds continues to be a costly method even to date, as the reaction contained in melts or fusions by metal or by electrolysis. This temperatures are very high and the elemental boron tended to invariably introduced oxygen impurities in the boron product, react With the ?lament material. In US. Pat. No. 1,774,410 Which also continued to be held together With other solid Van Arkel describes a method of self dissociation of boron oxide products such as magnesium oxide [if magnesiother bromide on a surface Which is chemically inert to boron mic]. The product elemental boron in most cases reacted With bromide at temperature suf?ciently elevated to cause the dis the reductant forming stable metal borides, Which prevented association of boron bromide solely by heat. the formation of high purity boron. Thus, the prior art for [0004] During 1940 through mid 1960s several other pat making boron from boron halides utiliZed mostly hydrogen as ents described preparation of elemental boron from boron the reducing agent [Weintraub patents] or Zinc as the reducing containing oxides. US. Pat. No. 2,465,989 by SoWa disclosed agent [Finn patent]. Finn’s patent noted that the boron prod that amorphous boron can be made from a fusion of a metallic uct Was substantially pure and Was scarped from the tube; ?uoborate reacting With alkali or alkaline earth metals. He While the product Zinc chloride vapor Was condensed sepa obtained boron of 70 to 84% purity using sodium ?uoborate rately as Was the unreacted BCl3 and Zinc vapors. It is not or potassium ?uoborate reduced by metallic sodium. In 1951, knoWn Whether this process Was ever commercially practised H. S. Cooper, described a method Where a molten mixture of or not. Finn’ s patent notes that hydrogen reduced boron prod potassium chloride [4000 g] and potassium ?uoborate [1500 uct Was prone to boron hydride contamination, and he noted g] Was used as an electrolyte to dissolve boron oxide [500 g] that alkali metal and alkaline earth metals are not used as Which Was electrolyZed onto a molybdenum cathode [U.S. reductants on a contention of contamination With borides. Pat. No. 2,572,249]. [0010] It is knoWn that boron trichloride reductions using [0005] Richard B. Ellis made boron by electrolysis of a hydrogen is endothermic at room temperatures, and can be fused mixture of boron and phosphate compounds, indicating carried out only at temperatures higher than 16000 C.ire that his invention [U.S. Pat. No. 2810683] Was less cumber quiring exotic metal ?laments and this process is expensive. some than hydrogen reduction of boron trichloride. HoWever, Since the melting point of boron is 20760 C., the poWdery the purity of boron Was loW. deposit tend to stay amorphous. [0006] US. Pat. No. 2, 832, 730 by N. N. Perry, et al, [0011] Present invention, overcomes these obstacles, by describes the electrolysis of 60% KCl, 25% KF and 15% careful thermochemical analysis of reduction processes of B2O3. N. P. Murphy, et al, utiliZed the electrolysis of alkali boron halides. The comparison is shoWn in Table 1 for boron metal oxides and boron compounds [U.S. Pat. No., 2,848, trichloride [one of the halides] reduction With metals and 396] to make boron. D. R. Stern and Q. H. Mckenna described hydrogen. It is discovered that reductions of boron halides by the electrolysis [up to 10000 C.] using alkali metal chloride, alkali metals, alkaline earth metals, aluminum and silicon are US 2013/0045152 A1 Feb. 21,2013 exothermic and have negative free energies of reaction at 298 TABLE 3 K [room temperature 25° C]. Thus, these reactions can start at near room temperature provided the rate of reaction is favor Boride reduction of boron trihalides able. Higher temperatures caused by the exothermic reaction Free energy Will favor higher rates of conversion. But the boron tri-chlo Ht. of Reaction of Reaction ride reaction With hydrogen or iron has a positive free energy Reaction at 298 K, kcal at 298 K, kcal of reaction and does not happen at room temperature, and in BC13 + FeB = 2B + FeCl3 +75 +124 addition the heat of reaction is positive, making the reaction 3siB3 + 413013 = 3sic14 + 13B —334 —206 endothermic. This is Well knoWn that hydrogen reduction of 213013 + 3MgB2 = 8B + 3Mgc12 —843 -732 A113l2 +BC13 =AlC13 + 13B -102 —35 boron tri -chloride requires very high temperature and high A1132 + 13013 =A1c13 + 3B —236 -177 energy inputithus this process is expensive. [0012] The thermochemical analysis should also carryout [0015] From Table 3, it can be inferred that iron borides are the equilibrium reaction analysis to see What other contami very stable and are not reduced by boron trichlorides as noted nant side reactions take place. In the case of magnesiotherrnic by positive free energy of reaction and endothermic heat of reductions and aluminothermic reductions We can see that reaction. On the other hand, above table, generated as part of boride formations can occur as shoWn in Table 2. The boride the present invention, notes that When using silicon, magne formation staying as an impurity in the elemental boron is sium .or aluminum as the reducing agent for boron halides, Well knoWn.