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Al–C Aluminum–Carbon system
236 82kJ/mole [14] and the vaporisation heat of Al2Br6 is 54kJ/mole 110]. The heat of formation of AlBr3 is 520kJ/mole [7, 11, 15]. AlBr3 is monoclinic; 16 atoms in the unit cell; space group P2ja\ lattice parameters a= 10.20x 10~10m, b = 7.09 x 10"10m, c=7.48xlO- 1 0 m;/3 = 96° [16]. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 9b. 10. 11. 12. 13. 14. 15. 16.
N. Kameyama, etc., JIMMA 2, 524; 3, 208 E. Y. Gorenbein, CA 30, 7461 V. A. Plotnikov, etc., CA 31, 2106 C. C. Downie, JIMMA 5, 498 F. Irmann, CA 45,430 S. A. Semenkovich, CA 51, 16032 D. Rossini, etc., US Nat. Bur. Stds. Circ, 500, 1952 JANAF Thermochemical Tables, Dow Chemical Company, Midland, Michigan, 1960 A. F. Wells, Structural Inorganic Chemistry, Clarendon Press, 1962 W. Biltz, etc., Z. Anorg. Chem., 1923, 126, 39 W. Fisher, etc., Z. Anorg. Allgem. Chem., 1931, 200, 332; 1932, 205, 1 W. Klemm, etc., Z. Anorg. Allgem. Chem., 1932, 207, 186 L. Rotinjanz, etc., Z. Physik. Chem., 1914, 87,635 J. W. Johnson, etc., Met A I, \ 50964 T. G. Dunne, etc., CA 52, 13352 F. R. Bichowsky, etc., The Thermochemistry of the Chemical Substances, Reinhold, 1936 P. A. Renes, etc., Rec. Trav. Chim., 1945,64, 275
Al-C Aluminum-Carbon system Aluminum is produced, refined and often melted in contact with carbon-bearing materials; thus, carbon is a normal impurity of aluminum and its content can be expected to be close to saturation. Attempts to prepare graphite-containing aluminum alloys [1, 2] and alloys reinforced with carbon fibers [3-7] have been successful but these products are still experimental. The aluminum-carbon diagram is probably eutectic with the A1-C3A14 eutectic temperature and composition practically coinciding with those pure aluminum. The values of solubility of carbon in liquid aluminum of 0.32% C at 1 500 °K, decreasing to 0.10% C at 1 100 °K and extrapolating to 0.07% C at 933 °K, given by [8] are extremely high, probably by one order of magnitude [9-15]. The same is true for the solid solubility: the value of 0.02-0.04% C mentioned by [16] is probably too high by one order of magnitude. The carbide is solid up to 2 300 °K, and above 2 300 °K is reported as molten, sublimed, decomposed [17-19]. C3A14 (25.3%C) is rhombohedral [20,21J; parametersa = 8.55x 10- 10 m,a = 22° 28'; 7 atoms in the unit cell; space group R 3 m [22]; density 2 930-2 960kg/m3. The amorphous variety is less stable, and at 1 500 °K decomposes into aluminum and graphite [23]. The specific heat of the crystalline variety is given by [24]. All kinds of values can be found for the heat of formation of A14C3: from 90kJ/mole [25] to 280kJ/mole [26], with intermediate values [27-33]. For other thermodynamic data see [34, 35]. The carbide is yellow [36], with hardness similar to that of topaz [37] and forms hexagonal or triangular crystals [38]
237
(Figure 2.11). The presence of other carbides is reported—A13C (12.9% C) in equilibrium with Al and A1203 [39]; A12C6 (57.2%) [40], which is formed in iron-rich alloys and is the source for acetylene [41]; A1C2 (47.5% C); and A1C (30.7% C) [41b]—but their existence in aluminum alloys is doubtful.
Figure 2.11. Dross inclusions in aluminum; x 500, not etched. Dark crystals of carbide, grey carbonitride, light nitride. In center, crystal of carbide sheathed with carbonitride; at bottom right, oxide inclusions The reported effect of carbon on the properties of aluminum is very limited; however, there is no carbon-free aluminum and the zero point of all investigations is actually aluminum already saturated with carbon. Thus, the increase [42] or decrease [43] in electrical conductivity and the decrease in elongation at elevated temperatures [44] are only minor and probably due to entrapped carbides or reaction of the carbon with alloying elements. There is some evidence that small carbon additions enhance the grain refining effect of titanium and zirconium but that larger ones destroy it; for details see 'Aluminum-Boron-Titanium system'. Carbides, as well as nitrides, have been blamed for porosity and low quality in aluminum castings [45, 46], but the evidence is inconclusive. In carburising of aluminum there is no diffusion up to 650 °K [47], and below 1 000 °K carbide formation is very sluggish [26] unless the mixture of aluminum and carbon is subjected to explosive shock [48], or wetted with cryolite [49]. For information on oxycarbides and the carbothermic reduction of A1203 see [50]. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
F. A. Badia, etc., Met A 3, 510490 A. M. Patton, Met A 5, 510431 G. Blankenburgs, Met A 3, 620124 J. M. Evans, etc., Met A 5, 350109 Anon., Met A 5, 620010 R. C. Rossi, etc., Met A 4, 620150 A. N. Shurshakov, etc., Met A 5, 350850 I. Obinata, etc., Light Metals Tokyo, 1964, 14, 226 J. Czochralski, JIM 31, 362 H. Loewenstein, JIM 47, 577 L. Tronstad, JIMMA 3, 67, 203, 534
238 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 41b. 42. 43. 44. 45. 46. 47. 48. 49. 50.
J. Fischer, etc., JIMMA 23, 915 G. Long, as quoted in [50] Anon., JIMMA 8, 25 M. A. Sloman, J. Inst. Metals, 1945, 71,404 Elliott, 1965 M. P. Slavinski, etc., JIMMA 2, 461 O. Ruff, etc., Z. Anorg, Allgem. Chem., 1916, 97, 312; Z. Elektrochem., 1918, 24, 157 L. M. Foster, etc., Am. Mineral, 1958, 43, 285 M. L. Huggins, CA 18, 3128 J. H. Cox, etc., Canad.J. Chem., 1963,41, 1414 M. V. Stackelberg, etc., CA 29, 657 L. Wohler, etc., Z. Anorg. Allgem. Chem., 1933, 213, 249 S. Sato, CA 32, 3250 A. Meichsner, etc., CA 28, 2257 T. Takase, etc., LMJ1, 65 C. H. Prescott, Jr., etc., CA 22, 346 R. Brunner, CA 40, 6343 W. A. Roth, Z. Elektrochem., 1942, 48, 267 D. J. Meschi, etc., JIMMA 27, 430 P. Gross, C4 56, 13887 C. S. Campbell, Met. Soc. Conf., 1961, 7,412 R. O. G. Blachnik, etc., Met A 3, 151157 G. T. Furukawa, etc., MA 1, 1337 E. R. Plante, etc., MA 2, 832 H. Moissan,y5C/, 1895, 353 Gmelins Handbuch der Anorganische Chemie, System 35, Teil B, Lfg. 1, 287 M. Schippers, JIMMA 28, 583 E. Baur, etc., CA 28, 3974 M. Durand, Bull. Soc. Chim. France, 1924, 35, 1141 F. Roll, JIMMA 2, 146 C. A. Steams, etc., CA 78, 62510k R. Apt, CA 14,1291 H. Schmitt, etc., JIMMA 24, 855 I. Obinata, etc., JIMMA 22, 859 D. V. Ludwig, JIMMA 15, 228 F. A. Allen, JIMMA 16, 170 J. J. Trillat, etc., JIMMA 27,447; 28,441 ; 29, 223, 494 Y. Horiguchi, etc., MA 1, 607 R. C. Dorward, Met A 6, 340332; 7,430117 P. T. Stroup, AIME Tr., 1964, 230, 356
Al-Ca Aluminum—Calcium system Some of the uses suggested for calcium are: aluminum-calcium alloys as reducing agents for titanium oxide [1]; calcium additions to secondary metal to remove tin, bismuth, silicon, antimony and lead [2] which have proven ineffective [3], although [4] report that, in zone refining, calcium improves removal of tin and lead; additions to low-purity metal to insolubilise the silicon as Ca2Si and increase the electrical conductivity [5, 6] or to copper- and magnesium-bearing alloys to eliminate age hardening effects [7-9]; and as modifying agent in aluminum-silicon alloys, where it has proven more durable, but much less effective than sodium [6, 10]. Aluminum-calcium was also tried as intermediate layer in clad materials to act as a
N. Kameyama, etc., JIMMA 2, 524; 3, 208 E. Y. Gorenbein, CA 30, 7461 V. A. Plotnikov, etc., CA 31, 2106 C. C. Downie, JIMMA 5, 498 F. Irmann, CA 45,430 S. A. Semenkovich, CA 51, 16032 D. Rossini, etc., US Nat. Bur. Stds. Circ, 500, 1952 JANAF Thermochemical Tables, Dow Chemical Company, Midland, Michigan, 1960 A. F. Wells, Structural Inorganic Chemistry, Clarendon Press, 1962 W. Biltz, etc., Z. Anorg. Chem., 1923, 126, 39 W. Fisher, etc., Z. Anorg. Allgem. Chem., 1931, 200, 332; 1932, 205, 1 W. Klemm, etc., Z. Anorg. Allgem. Chem., 1932, 207, 186 L. Rotinjanz, etc., Z. Physik. Chem., 1914, 87,635 J. W. Johnson, etc., Met A I, \ 50964 T. G. Dunne, etc., CA 52, 13352 F. R. Bichowsky, etc., The Thermochemistry of the Chemical Substances, Reinhold, 1936 P. A. Renes, etc., Rec. Trav. Chim., 1945,64, 275
Al-C Aluminum-Carbon system Aluminum is produced, refined and often melted in contact with carbon-bearing materials; thus, carbon is a normal impurity of aluminum and its content can be expected to be close to saturation. Attempts to prepare graphite-containing aluminum alloys [1, 2] and alloys reinforced with carbon fibers [3-7] have been successful but these products are still experimental. The aluminum-carbon diagram is probably eutectic with the A1-C3A14 eutectic temperature and composition practically coinciding with those pure aluminum. The values of solubility of carbon in liquid aluminum of 0.32% C at 1 500 °K, decreasing to 0.10% C at 1 100 °K and extrapolating to 0.07% C at 933 °K, given by [8] are extremely high, probably by one order of magnitude [9-15]. The same is true for the solid solubility: the value of 0.02-0.04% C mentioned by [16] is probably too high by one order of magnitude. The carbide is solid up to 2 300 °K, and above 2 300 °K is reported as molten, sublimed, decomposed [17-19]. C3A14 (25.3%C) is rhombohedral [20,21J; parametersa = 8.55x 10- 10 m,a = 22° 28'; 7 atoms in the unit cell; space group R 3 m [22]; density 2 930-2 960kg/m3. The amorphous variety is less stable, and at 1 500 °K decomposes into aluminum and graphite [23]. The specific heat of the crystalline variety is given by [24]. All kinds of values can be found for the heat of formation of A14C3: from 90kJ/mole [25] to 280kJ/mole [26], with intermediate values [27-33]. For other thermodynamic data see [34, 35]. The carbide is yellow [36], with hardness similar to that of topaz [37] and forms hexagonal or triangular crystals [38]
237
(Figure 2.11). The presence of other carbides is reported—A13C (12.9% C) in equilibrium with Al and A1203 [39]; A12C6 (57.2%) [40], which is formed in iron-rich alloys and is the source for acetylene [41]; A1C2 (47.5% C); and A1C (30.7% C) [41b]—but their existence in aluminum alloys is doubtful.
Figure 2.11. Dross inclusions in aluminum; x 500, not etched. Dark crystals of carbide, grey carbonitride, light nitride. In center, crystal of carbide sheathed with carbonitride; at bottom right, oxide inclusions The reported effect of carbon on the properties of aluminum is very limited; however, there is no carbon-free aluminum and the zero point of all investigations is actually aluminum already saturated with carbon. Thus, the increase [42] or decrease [43] in electrical conductivity and the decrease in elongation at elevated temperatures [44] are only minor and probably due to entrapped carbides or reaction of the carbon with alloying elements. There is some evidence that small carbon additions enhance the grain refining effect of titanium and zirconium but that larger ones destroy it; for details see 'Aluminum-Boron-Titanium system'. Carbides, as well as nitrides, have been blamed for porosity and low quality in aluminum castings [45, 46], but the evidence is inconclusive. In carburising of aluminum there is no diffusion up to 650 °K [47], and below 1 000 °K carbide formation is very sluggish [26] unless the mixture of aluminum and carbon is subjected to explosive shock [48], or wetted with cryolite [49]. For information on oxycarbides and the carbothermic reduction of A1203 see [50]. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
F. A. Badia, etc., Met A 3, 510490 A. M. Patton, Met A 5, 510431 G. Blankenburgs, Met A 3, 620124 J. M. Evans, etc., Met A 5, 350109 Anon., Met A 5, 620010 R. C. Rossi, etc., Met A 4, 620150 A. N. Shurshakov, etc., Met A 5, 350850 I. Obinata, etc., Light Metals Tokyo, 1964, 14, 226 J. Czochralski, JIM 31, 362 H. Loewenstein, JIM 47, 577 L. Tronstad, JIMMA 3, 67, 203, 534
238 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 41b. 42. 43. 44. 45. 46. 47. 48. 49. 50.
J. Fischer, etc., JIMMA 23, 915 G. Long, as quoted in [50] Anon., JIMMA 8, 25 M. A. Sloman, J. Inst. Metals, 1945, 71,404 Elliott, 1965 M. P. Slavinski, etc., JIMMA 2, 461 O. Ruff, etc., Z. Anorg, Allgem. Chem., 1916, 97, 312; Z. Elektrochem., 1918, 24, 157 L. M. Foster, etc., Am. Mineral, 1958, 43, 285 M. L. Huggins, CA 18, 3128 J. H. Cox, etc., Canad.J. Chem., 1963,41, 1414 M. V. Stackelberg, etc., CA 29, 657 L. Wohler, etc., Z. Anorg. Allgem. Chem., 1933, 213, 249 S. Sato, CA 32, 3250 A. Meichsner, etc., CA 28, 2257 T. Takase, etc., LMJ1, 65 C. H. Prescott, Jr., etc., CA 22, 346 R. Brunner, CA 40, 6343 W. A. Roth, Z. Elektrochem., 1942, 48, 267 D. J. Meschi, etc., JIMMA 27, 430 P. Gross, C4 56, 13887 C. S. Campbell, Met. Soc. Conf., 1961, 7,412 R. O. G. Blachnik, etc., Met A 3, 151157 G. T. Furukawa, etc., MA 1, 1337 E. R. Plante, etc., MA 2, 832 H. Moissan,y5C/, 1895, 353 Gmelins Handbuch der Anorganische Chemie, System 35, Teil B, Lfg. 1, 287 M. Schippers, JIMMA 28, 583 E. Baur, etc., CA 28, 3974 M. Durand, Bull. Soc. Chim. France, 1924, 35, 1141 F. Roll, JIMMA 2, 146 C. A. Steams, etc., CA 78, 62510k R. Apt, CA 14,1291 H. Schmitt, etc., JIMMA 24, 855 I. Obinata, etc., JIMMA 22, 859 D. V. Ludwig, JIMMA 15, 228 F. A. Allen, JIMMA 16, 170 J. J. Trillat, etc., JIMMA 27,447; 28,441 ; 29, 223, 494 Y. Horiguchi, etc., MA 1, 607 R. C. Dorward, Met A 6, 340332; 7,430117 P. T. Stroup, AIME Tr., 1964, 230, 356
Al-Ca Aluminum—Calcium system Some of the uses suggested for calcium are: aluminum-calcium alloys as reducing agents for titanium oxide [1]; calcium additions to secondary metal to remove tin, bismuth, silicon, antimony and lead [2] which have proven ineffective [3], although [4] report that, in zone refining, calcium improves removal of tin and lead; additions to low-purity metal to insolubilise the silicon as Ca2Si and increase the electrical conductivity [5, 6] or to copper- and magnesium-bearing alloys to eliminate age hardening effects [7-9]; and as modifying agent in aluminum-silicon alloys, where it has proven more durable, but much less effective than sodium [6, 10]. Aluminum-calcium was also tried as intermediate layer in clad materials to act as a