3,784,682 United States Patent Office Patented Jan. 8, 1974

feet the true density. That is, by this method only theo- 3,784,682 retical or near theoretical densities can be obtained by DENSIFYING METAL HYDRIDES WITH HIGH making the material quite free from porosity (p. 354). TEMPERATURE AND PRESSURE The true density remains the same. Leonard M. NiebylsM, Birmingham, Mich., assignor to Ethyl Corporation, Richmond, Va. SUMMARY OF THE INVENTION No Drawing. Continuation-in-part of abandoned applica- tion Ser. No. 392,370, Aug. 24, 1964. This application The process of this invention provides a practical Apr. 9,1968, Ser. No. 721,135 method of increasing the true density of hydrides of Int. CI. COlb 6/00, 6/06 metals of Groups II-A, II-B, III-A and III-B of the U.S. CI. 423—645 8 Claims Periodic Table. More specifically, true densities of said 10 metal hydrides may be substantially increased by subject- ing a hydride to superatmospheric pressures at or above ABSTRACT OF THE DISCLOSURE fusion temperatures. When beryllium hydride is subjected A method of increasing the density of a hydride of a to this process, a material having a density of at least metal of Groups II-A, II-B, III-A and III-B of the 0.69 g./cc. is obtained. It may or may not be crystalline. Periodic Table which comprises subjecting a hydride to 15 a pressure of from about 50,000 p.s.i. to about 900,000 DESCRIPTION OF THE PREFERRED p.s.i. at or above the fusion temperature of the hydride; EMBODIMENT i.e., between about 65° C. to about 325° C. Beryllium According to the method of this invention, when a hydride obtained from this process has a density of at 20 metal hydride, such as beryllium hydride, in an amorphous least 0.69 g./cc. form, is subjected to superatmospheric pressures at the fusion temperature or higher, the true density of the hy- This application is a continuation-in-part of my co- dride is increased appreciably over the true density of said pending application Ser. No. 392,370, filed Aug. 24, hydride in its original amorphous form. 1964, now abandoned. 25 The metal hydrides whose densities can be increased according to this invention are hydrides of the elements BACKGROUND OF THE INVENTION of Groups II-A, II-B, III-A and III-B, including the lan- thanum series of rare earth elements; that is, those ele- Metal hydrides find use in many applications. For ex- ments having an atomic number between 58 and 71 inclu- ample, reaction with water allows their use as a ready 30 sive. Thus, among the metal hydrides that can be used means for hydrogen generation. Densification of a metal are the hydrides of the elements of Group II-A of the hydride allows a greater amount of hydrogen to be evolved Periodic Table; that is, beryllium hydride, magnesium hy- per unit volume of hydride. dride, calcium hydride, strontium hydride, and barium Certain metal hydrides, notably beryllium hydride, findhydride . Likewise, the hydride can be zinc hydride, cad- use as rocket fuel components because of their uniquely 35 mium hydride or mercury hydride; that is, a hydride of high specific impulse. However, because beryllium hy- an element of Group II-B of the Periodic Table. Simi- dride, for example, has a relatively low specific density, larly, the hydride of an element of Group III-A of the propellants containing beryllium hydride as a fuel also Periodic Table can be employed. Thus, boron hydride, have a low specific density, resulting in relatively low de- aluminum hydride, gallium hydride, indium hydride, and livered impulse per unit volume. Therefore, increasing 40 thalium hydride can be used. Also, the hydride of an ele- the density of beryllium hydride would aid in producing ment of Group III-B of the Periodic Table can be used; an even greater delivered impulse per unit volume and to wit: scandium hydride, yttrium hydride, lanthanum hy- allow greater flexibilityi n the construction of rocket dride and the hydrides of elements of the lanthanide and motors. actinide series of rare earth elements; that is, those ele- Beryllium hydride has been synthesized by Coates and 45 ments having atomic numbers from 58 to 71 inclusive. Glockling, J. Chem. Soc. 25-26 (1954), by the pyrolysis Accordingly, cerium hydride, praseodymium hydride, neo- of di-tertiary butyl beryllium etherate and by Head, dymium hydride, promethium hydride, samarium hydride, Holley and Rabideau, J. Am. Chem. Soc. 29, 3687 (1957),europiu m hydride, gadolinium hydride, terbium hydride, using ether-free di-tertiary butyl beryllium. More re- dysprosium hydride, holmium hydride, erbium hydride, cently, a superior product has been obtained by the py-50 thulium hydride, ytterbium hydride, and lutecium hydride rolysis of tertiary butyl beryllium etherate dissolved in a can be used in accordance with this invention. high-boiling inert solvent (co-pending application Ser. No. The hydrides of beryllium and aluminum are preferred 176,865, filedFeb . 26, 1962). However, the beryllium in this invention as they are most susceptible to the proc- hydride products of the above synthetic processes are ess described herein. Beryllium hydride is most highly pre- without exception amorphous in structure, and as a re- 55 ferred as its density is particularly increased by the tech- sult are characterized by a relatively low density, 0.57 3 niques of this invention. to 0.67 gram per cm. , which limits their suitability for The density increase is accomplished by fusing the this application. particles of a hydride. The term "fusing" as used here Methods of increasing the density of a material are means that the particles of a hydride flow into one another known in the metallurgical art. For example, Jones, Fun60- or coalesce forming a coherent structure. The temperature damental Principles of Powder Metallurgy, Edward Ar- at which this takes place is called fusion temperature. nold (Publishers) Ltd., London (1960), in the chapter Definite changes in the physical properties of the ma- on pressing discusses increasing the density of a metal terial take place at the point of fusion. For example, while powder by hot-pressing (pp. 351-355). However, this prior to fusion the amorphous hydride is opaque, at the method increases only the bulk density and does not af- 65 point of fusion, this material becomes clear and trans- 3,781,545 3 4 parent similar to glass. The degree of clarity depends on slurry wasfiltered, th efilter cake washed with hexane or the degree of purity of the hydride. That is, if beryllium petroleum ether and then dried. The products were white hydride is contaminated with beryllium metal or beryllium to a somewhat gray in appearance and had densities of oxide, then the degree of clarity of the fused hydride will from 0.63 to 0.67 g./cc. The following table summarizes be directly proportional to the amount of the impurities g the conditions and results of several runs, since these impurities themselves do not undergo fusion. TABLE I Fusion of the metal hydride is readily accomplished by [Solution pyroiysis] control of the temperature and pressure imposed on the - material. The pressure can be either mechanical, gas pres- Hati0 BeH2> sure or hydrostatic. Gas pressures generally have to be io solvent/ time, Temp., wt! Density, quite a bit higher at any particular temperature than is Bun Solvent PTBBEi mm. ° c. percent g./cc. necessary with mechanical or hydrostatic pressure. Simi- l Dodecane... 3/t 20 195 93.4 0.65 larly, hydrostatic pressures should be somewhat higher g- do"""" 1.5/1 so 195 92!? 0.65 than mechanical pressures. 4=11IIIIIIII-I IdoIIIIIII 1! 5/1 20 210 92! 9 0^63 The greater the pressure, the lower the temperature re- 15 f^SV" 3/1 30 "7-202 90.? a w quired to accomplish fusion of a metal hydide. The reverse 7 do 3/1 60 191-196 93.5 0.0a is also true. However, no fusion can be obtained at the s'lIIIIIIIIIIdoIIIIIII !/i 100 19^200 94.3 o'.es atmospheric pressure or at the room temperature. Thus, a i6riIIIIIIIIIdoIIII-.- 3/1 90 197-200 94.8 0.65 pressure of at least 50,000 p.s.i. and a temperature of at , Di.tert-butyi beryllium etherate. least 65° C. is required to accomplish fusion and the 20 ' -A. refined kerosene with a boiling range or about 200-250° C. increase in density according to the process of this inven- , ... ^ . ,, , ., . . ... tion. For beryllium hydride, preferably a pressure of over J? h}s manneTJ flet^yIalummT 75,000 p.s.i. and most preferably over 100,000 p.s.i., and cally decomposed to aluminum hydride Similarly di- a temperature of over 100° G. and most preferably over ,., - . . .. , , " 135° C. is employed. 25 Als0' dibutylcadmium is pyrolyticalln y decomposed to The particular temperature-pressure relationship at cadmium hydride, which a particular metal hydride is fused depends on txample 2 several factors, among which are purity of the metal Beryllium hydride was obtained by neat pyroiysis of di- hydride, and origin of the metal hydride; that is, whether tert-butyl beryllium etherate as follows, it was formed pyrolytically or metathetically. Pyrolytically 30 Di-tert-butyl beryllium etherate was added to a vessel and metathetically formed beryllium hydride is generally equipped with heating means, temperature measuring readily fused at a temperature of from 135° to 210° C. means, vacuum creating means and pressure measuring and under a pressure of at least 50,000 p.s.i. means. The vessel was heated and the pressure was In order to pyrolytically prepare a metal hydride, an brought down to 60 mm. Hg at 170° C. At 170-175° C. appropriate organometallic compound is heated and de- 35 the pressure was dropped to 15-20 mm. Hg and to 1 mm. composed to the hydride. For example, di-tert-butyl beryl- Hg at 180-195° C. The temperature was raised to about lium etherate can be heated by solution pyroiysis at 190- 200° C. and held there for about 2Vi hours. It was then 200° C. for two to four hours to form beryllium hydride. raised to about 205-211° C. over a one-hour period, with Solution pyroiysis can be accomplished by separately 40 concurrent lowering of pressure to below 1 mm. Hg, and heating a high boiling saturated hydrocarbon, for example, was maintained at that temperature for less than one hour to about 190-200° C., heating an organometallic com- or until the pressure rose to 1 mm. Hg. The purity of pound (e.g. to about 135° C.) and contacting the two, beryllium hydride obtained by this method varied torn resulting in decomposition of the organometallic com- 74.8 to 77%. pound to BeH2. Good purities can be obtained. For ex- In like manner, triethylgallium is pyrolytically decom- ample, when using an organoberyllium, purities of BeH2 45 posed to gallium hydride. Similarly, trimethylindium of about 90 weight percent can be obtained. yields indium hydride. Also, diisobutylmercury is pyro- Pyrolysis to the metal hydride will also take place when lytically decomposed to mercury hydride, an organometallic is heated, e.g., as a vapor or liquid, for Example 3 several hours; e.g., an organoberyllium (neat) can be heated at 185-195° C. for 3 to 4 hours to form BeH2. 50 Beryllium hydride was obtained by neat pyroiysis of With the preparations described, pyroiysis can be cata- di-tert-butyl beryllium etherate, catalyzed by the presence lyzed; e.g., by dissolving an alkyl 'lithium in the hydro- of one of dimethyl beryllium, beryllium borohydride, carbon. Other such catalysts include organic derivatives lithium hydride and tert-butyl lithium. The procedure of of the Group I metals, such as sodium and potassium. Example 2 was otherwise followed. The products obtained Pyroiysis can also be accomplished in a hydrogen at- 55 by this method range in purity from about 75 to about mosphere. For example, diethylberyllium can be pyrolyzed 95 percent beryllium hydride. by heat under hydrogen pressure to form beryllium In like manner, triethylthallium is pyrolytically decom- hydride. Examples of such preparation are as follows: posed to thallium hydride. Similarly, di-n-butylzinc yields Example 1 zinc hydride. Also, triphenyl aluminum is pyrolytically 60 decomposed to aluminum hydride. Beryllium hydride was obtained by solution pyroiysis of Beryllium hydride was also obtained by hydrogenolysis di-tert-butyl beryllium etherate as follows. of diethyl beryllium. Reactions were run in an autoclave A reactor equipped with heating means, temperature without agitation. The diethyl beryllium was charged into measuring means, a stirrer, a reflux condenser having its a glass vial which was placed in the autoclave. The pres- outlet vented through a bubbler, and a feed line was 65 sure was raised to 9,000 p.s.i. H2 by a pump. On heating, flushed with an inert gas (nitrogen or argon) and heated. the pressure rose to about 11,000 p.s.i. A high-boiling liquid hydrocarbon was charged to the In like manner, magnesium benzoate is pyrolyzed, with reactor in a ratio of 1.5 to 3 times the volume of di-tert- heat and hydrogen pressure to yield magnesium hydride, butyl beryllium etherate to be pyrolyzed. When the solvent Similarly, calcium benzoate is pyrolyzed, under hydrogen, reached a temperature of 195-200° C., addition of the 70 to yield calcium hydride. Also, strontium acetate yields, di-tert-butyl beryllium etherate was started. Pyroiysis on such pyroiysis, strontium hydride. Other compounds occurred very rapidly and beryllium hydride precipitated that can be so used to yield metal hydrides include: barium immediately. After completion of the addition, gas evolu- malonate, scandium oxalate, lanthanum acetate, cerium tion dropped off rapidly and ceased after from about 5 benzoate, praseodymium acetate, neodymium acetate, to 10 minutes. Immediately thereafter, the resultant hot 75 samarium acetate, gadolinium acetate, dysprosium acetate, 3,784,682 6 erbium acetate, thulium oxalate, ytterbium acetate and with diethyl aluminum hydride to form calcium hydride. thallium phenoxide. Still other organometallic compounds Strontium iodide etherate can similarly be used to meta- that can be used include cyclomatic compounds of the thetically form strontium hydride. Examples of other Groups II-A, II-B, III-A and DI-B metals as found in compounds that metathetically form the corresponding U.S. Pat. 2,818,416, which compounds are incorporated - hydride, as above, include bariumfluoride etherate , ra- herein by reference. dium chloride etherate, scandium bromide etherate, yt- Among the organoberyllium compounds that can be trium iodide etherate and lanthanumfluoride etherate . used are various dialkyl beryllium compounds such as di- As pointed out, the method of this invention increases isopropyl beryllium or di-tert-butyl beryllium. Diethyl the true density of metal hydrides mentioned above. True beryllium, however, is uniquely useful since it has a low JQdensity , as used herein, means the highest theoretical molecular weight, it is readily obtainable in pure ether- density of a substance in a particular form. This is con- free condition and it is a liquid at room temperature, per- trasted with bulk density which almost always will be mitting visual estimation of the progress of the hydro- lower than true density because of the presence of some genolysis reaction as solid BeH2 is produced. air pockets in a bulk. In other words, true density is the As noted, the meal hydride can also be prepared meta- 15 highest density of a material which cannot be further in- thetically; the following general reactions, among others, creased by physical means, such as pressure. can be used: By employing the method of this invention unex- pectedly the true density of metal hydrides may be in- (1) NRmM1H+MR11^MHn-f2Rln+1M1 creased. To illustrate the difference between increasing (2) NRmMiH+MXn+NRaO^-MHn+NRmMX-RaO 20 the bulk density and the true density of beryllium hydride, where M is a metal for which the hydride is desired, Mj there is presented the following example. is a Group II, III or IV metal, which may include M, n and N are both the major valence of M ion, m is one less Example 6.—Comparison of density increases than the valence of Mt ion, R is an organic radical that doesn't form a chelate with M and X is halogen such as 25 Beryllium hydride, prepared by one of the methods chlorine, bromine, iodine orfluorine. Example s of useable described above had a density between 0.64 and 0.65 organic radicals can include alkyl, aryl, alkaryl and ethers,g./cc . Using a mechanical press having pressure measur- including such groups containing inorganic substituents ing means, the hydride was subjected for one-half hour such as amino. In general, alcohols, esters, acetones and to 75K p.s.i. at a temperature which was below fusion. aldehydes should be avoided as they tend to form chelates 30 The resulting beryllium hydride had a density between or alkoxides which tend to interfere with the reaction. Ex- 0.66 and 0.67 g./cc. amples of usable metals include aluminum and boron. This operation was repeated using beryllium hydride The following examples illustrate metathetical prepara- from the same source, but in this case, while the pressure tions. was applied, the hydride was heated to 135-145° C., that Example 4 35 is, about 10° C. above the fusion temperature. The re- sulting density of most of the sample was between 0.69 To a reaction vessel equipped with heating means, tem- and 0.70 g./cc., and part of the sample had a density perature measuring means and reagent adding means are between 0.70 and 0.71 g./cc. In both instances, the densi- added 100 parts by weight of diethyl aluminum hydride ties were determined by the same method; i.e., by the sink- and 50 parts by weight of diethyl beryllium. The vessel is 4float0 method as described below. It should be noted that heated to 130° C. and maintained at that temperature the method of this invention does not cause decomposi- for several hours. Diethyl ether is then added and solids tion of the hydride. Thus, the increase in density is not due containing beryllium hydride are precipitated. These solids to the oxidation of the hydride to the free metal. arefiltered, washe d with ether and dried under reduced From the above it is clear that by merely applying a pressure. Analysis of a similar preparation shows the pressure to the hydride, the density did not go over 0.67 solids to contain 65.7 weight percent beryllium hydride. 45 g./cc., which is approximately the theoretical density of In a similar manner, triethyl aluminum is reacted with an amorphous beryllium hydride in its original state. diethyl boron hydride to yield aluminum hydride. Like- However, when the same pressure was applied, but above wise, dimethyl borane yields boron hydride on reaction the fusion temperature, the density increased substantially with diethyl aluminum hydride. Also, dibutylcadmium over the theoretical density of the starting material. Thus, can be similarly metathetically converted to cadmium 50 the increase of density of beryllium hydride above 0.69 hydride. Likewise, a metathetical reaction, as above, of g./cc. was not due merely to the physical compaction of triethylgallium yields gallium hydride. Other compounds the material, but due to some type of change in the molec- that can be metathetically reacted to form the correspond- ular structure. That is, it is quite apparent that under the ing hydride include dibutylzinc, triethylthallium, dibutyl- fusion conditions, the molecules rearranged themselves, at mercury, and trimethylindium. 55 least partially, from a random array to a more orderly space array, thereby resulting in a more compact structure Example 5 (thus, of higher density). To a reaction vessel equipped with heating means and Fusion of metal hydrides generally can be accomplished temperature measuring means and containing toluene as at pressures of from 50,000 p.s.i. to 350,000 p.s.i. or a solvent are added 50 parts by weight of beryllium chlo- f,900,00o 0 p.s.i., or higher, at a temperature of from about ride dietherate and 100 parts by weight of diethyl alumi- 65° C. to about 325° C., depending on the hydride and num hydride. The vessel is heated to 130° C. and main- method of preparation. The following examples describe tained at that temperature for one hour, during which the fusion of metal hydrides whereby a material having time solids form. The solids arefiltered of f and dried an increased density is obtained. for an hour at 130-150° C. at 1-5 mm. pressure. Solids 65 from a similar preparation have been found to comprise, Example 7 by weight, 71.9 percent beryllium hydride, 2.4 percent beryllium metal, 10.1 percent ethyl groups, 5.1 percent Using a mechanical press having heating means, tem- chlorides, 6.0 percent aluminum, no ether and 3.8 percent perature measuring means and pressure measuring means, unknown material. 70 0.1 g. samples of pyrolytically formed beryllium hydride, By other similar reactions, beryllium hydride was ob- having purities of more than 95 percent, were subjected, tained having from 71.8-77.3 weight percent purity. for one-half hour each, to pressures and temperatures Similarly, magnesium chloride etherate is reacted with sufficient to cause the samples to fuse. The following table diethyl aluminum hydride to yield magnesium hydride. summarizes the pressure and temperature ranges used to Likewise, calcium bromide etherate metathetically reacts 75 obtain fusion. 3,778,6210 6 7 TABLE II will shatter into splinters much as will glass. Its strength Fusion temperature is increased with an increase in annealing time. Pressure, p.s.i.: range, ° C. As noted, fusion of metal hydrides can be accom- 50,000 130-140 plished by subjecting it to certain temperature-pressure 75,000 130-140 - conditions. Temperatures in excess of the minimum 90,000 130-140 needed at any specific pressure can also be used. How- 350,000 About 65 ever, the temperature should not be so high as to cause In a similar manner, scandium hydride and gallium decomposition of the hydride. Thus, it can be seen that hydride are fused when individually subjected to 60,000 the maximum temperature will vary with the particular p.s.i. and a temperature of 170° C. Likewise, cerium hy- 10hydride , but it will generally be between 65° C. and dride, gadolinium hydride, and ytterbium hydride are 325° C. Likewise, pressures in excess of the minimum fused when subjected to 300,000 p.s.i. at 85° C. needed for any specific temperature can be used. Gener- ally, fusion will take place much faster at higher tem- Example 8 peratures and pressures. Using a mechanical press similar to that of Example 7, 15 By fusing a metal hydride as described, and controlling samples of aluminum hydride, obtained from three the temperature and pressure, the density of the metal sources, were subjected to pressures between 50,000 p.s.i. hydride can be increased. Thus, by maintaining the metal and 100,000 p.s.i. at temperatures between 65° C. and hydride in the fused state under pressure, for a short time, 125° C. which caused the samples to fuse. The time of and then releasing the pressure without the temperature fusion varied from 5 minutes to 60 minutes. 20bein g above the decomposition point of the fused metal hydride, metal hydrides of greater density are obtained. Example 9 In general, the higher the pressure, at any particular tem- Using the mechanical press of Example 7, 50 mg. perature, the denser the metal hydride produced. Sim- samples of metathetically formed beryllium hydride were ilarly, the higher the temperature, but subject to the above subjected, for one-half hour each, to pressures and tem- 25limitation , at any particular pressure, the denser the metal peratures sufficient to cause the samples to fuse. Two hydride produced. The following example illustrates the methods were used to prepare the samples. Those samples effect of pressure with respect to the density of the fused designated "A" in the following table were prepared by hydride. the method described in Example 6 by reaction of diethyl Example 10 beryllium with diethyl aluminum hydride. Those samples designated "B" were prepared by the method described in Using the mechanical press of Example 7, 50 mg. Example 7 by reaction of beryllium chloride dietherate samples of beryllium hydride, prepared pyrolytically as and diethyl aluminum hydride. The pressure and tempera- in Example 3 and having a purity of about 95 weight ture ranges used are as follows. percent, were subjected, for one-half hour each, to pres- sures and temperatures sufficient to cause the samples to 35 TABLE III fuse. Densities of the fused material were measured by the "sink orfloat" method ; that is, the samples were BeHj prepa- Pressure, Tempera- placed in pure hydrocarbons of calibrated densities to Hun ration p.s.i. ture,0 C. determine whether they would sink orfloat. Th e density :— 40 3 0 A 50,000 141-154 ranges obtained at various pressures are given in the 3 1 A 75,000 141-154 following table. 3 2 A 90,000 125-128 3 3 B 35,000 132-140 TABLE IV 3 4 B 75,000 96-104 3 5 B 75,000 77-85 [Bella density change with pressure] Density range of fused material, g./cc. Similarly, pyrolytically prepared aluminum hydride, 45 indium hydride, and lutetium hydride are each fused at a Pressure, p.s.i. Sink Float pressure of 70,000 p.s.i. at 135° C. Likewise, meta- 10,000 0.641 0.651 35,000 0.651 0.661 thetically prepared praseodymium hydride and aluminum 50,000. 0.670 0.675 hydride are each fused at 95,000 p.s.i. at 100° C. Also, 75,000 0. 701 0. 708 50 90,000 0.701 0.708 pyrolytically prepared magnesium hydride and terbium 100,000_ 0.718 0.731 hydride are each fused at 50,000 p.s.i. at 130° C. Further, yttrium hydride is fused at 280,000 p.s.i. at 85° C. Similarly, other metal hydrides of increased densities are Regardless of the method of preparation of the metal provided by the above procedure. Thus, several samples hydride, the rate of fusion is somewhat dependent on theg g each of aluminum hydride, strontium hydride and zinc temperature at which pressure is applied to the specimen. hydride are subjected to different pressures for one-half Generally, and particularly with beryllium hydride, if hour at temperatures sufficient to cause the samples to pressure is not applied until the hydride has been, sub- stantially heated, fusion takes place very rapidly. fuse. Increases in density for each hydride are found with As noted, the metal hydride can be fused using hydro- samples subjected to increased pressures. Likewise, when static pressure. This method involves pressure-treating a go several samples of holmium hydride are subjected to in- powdered metal hydride suspension in a saturated high creased pressures for the same .period of time, increases boiling hydrocarbon. For example, Bayol-90 or dodecane in densities for the hydride are observed. can be used. The liquid-solid mixture can be placed in a Not only can the density of a metal hydride be increased hardened steel bomb, for example, and pressure can be by the above fusion techniques, but the carbon content applied with a plunger. Generally, and particularly with 65 of carbon-contaminated metal hydrides can be reduced by beryllium hydride, it is important that the volume of solids annealing the metal hydride in its fused state. The carbon comprising the unfused metal hydride suspension be at content comprises elemental carbon and/or chemically least as great as one-half the volume of the liquid and, combined carbon, such as organic materials. If an unfused preferably, as great as the volume of the liquid. hydride is heated without fusion, its carbon content is not Fusion generally changes the physical appearance of 70 lowered but is actualdly relatively increased due to the the metal hydride. For example, freshly fused beryllium decomposition of the metal hydride to metal. By fusing hydride is generally a transparent yellow-glassy mass the metal hydride, and maintaining it in a fused state which on aging will gray. It is generally sufficiently clear under controlled temperature and pressure, the carbon so as to allow printed matter to be clearly viewed through content of the metal hydride is reduced substantially with- it. The fused beryllium hydride is hard but brittle and 75 out increasing or changing the hydrogen content. Further, 9 10 no metal is generally detected in such fused and annealed conditions sufficient to cause their fusion to denser ma- material, nor generally, does such annealing produce a terial than heretofore existed. color change. The following example illustrates such For example, to obtain a higher density aluminum hy- annealing. dride, it is fused for about one-half hour at about 65° Example 11 C. at a pressure of 75,000 p.s.i. Similarly, aluminum hy- dride of increased density is obtained when it was kept Five samples of pyrolytically formed beryllium hydride for about 15 minutes at a temperature of about 125° C. having purities of 95.6 weight percent were heated to under a pressure of 250,000 p.s.i. Preferably, when higher 175° C. for varying amounts of times. Three of the sam- temperatures are employed with aluminum hydride, the ples were subjected to mechanical pressures, during heat- 10 fusion is carried out under inert gas to minimize the ing, of 16,000 p.s.i., using the mechanical press of possibility of oxidation to aluminum oxide. Example 7. The following table summarizes the condi- Without limiting this invention to any one theory, it is tions and analyses of the products. believed that the increase of density accomplished by TABLE V the instant invention results from a change in molecular Sample treatment Analysis 15 arrangement of a metal hydride from a random array to a more regular space array. Pres- Carbon, Hydro- BeH2 sure, Temp., Time, Physical wt. gen, wt. purity, Metal hydrides having increased densities obtained by p.s.i. 0 C. hrs. percent percent percent the method of this invention may or may not be crystal- Original specimen Not fused... 2.83 17.9-18.0 95.6 line. When amorphous hydrides are subjected to the 15 175 18 do 2.90 17.8-17.9 94.9 fusion process herein described, the metal hydride 15 175 Ti do 13.20 116.4-16.6 87.1 20 16,000 175 18 Fused 2.00 17.8-17.9 95.8 molecules start arranging themselves into a more orderly 16,000 175 36 do 1.87 17.7-17.9 95.8 array. The orderly arrangement of molecules may be in 16,000 175 72 do 1.12 17.5-17.6 95.2 one dimension, two dimensions or three dimensions. True i Metal detected by X-ray diffraction. crystallinity does not result in a hydride unless a three Similarly, when aluminum hydride, barium hydride and2 5 dimensional ordering is achieved. However, density in- boron hydride are each fused and held at fusion temper- creases as soon as a molecular order in only one dimen- ature for 12 hours, the carbon content of each is signifi- sion is achieved. cantly lowered. Likewise, the carbon contents of cadmium Beryllium hydride having the density between 0.69 and hydride, samarium hydride and erbium hydride are effec- 0.88 g./cc. prepared by the method of the invention exists tively lowered by maintaining each hydride in the fusion3 0 in both crystalline and non-crystalline forms as discussed. state for 40 hours. Also, the carbon contents of uranium Table VI below gives average ^-values obtained by X-ray hydride and californium hydride are similarly lowered diffraction using a beryllium hydride sample which was by maintaining each hydride in a fused state for 90 hours. fused by the method of this invention. As the values Generally fusions will occur with any pure metal hy- clearly indicate, this particular sample was crystalline and dride as described. The lower purity samples, e.g., 803 5 has a density of 0.80-0.88 g./cc. percent, will generally lack strength and be difficult to TABLE VI prepare. Quite often brown carbonaceous materials will be interspersed on the surface of fused hydrides from Average d-values for phase 332 from sedimented fraction such impure samples. These carbon spots become less 40 of 0.80-0.88 g./cc. density apparent as hydride purity increases. By conducting the fusion process just described, metal d: I/I d: I/I hydrides of increased density are provided. Thus, beryl- 7.06 w 1.474 ___ S lium hydrides are produced having a density of from 0.69 4.59 w 1.341 s to 0.88 g./cc. Accordingly, an embodiment of this inven- 3.80 . MS 1.287 w 3.30 . WS 1.263 MW tion is the provision of such denser metal hydrides and 45 particularly the provision of beryllium hydrides having 3.05 _ MW 1.163 - MW a density of 0.69 to 0.88 g./cc. 2.89 _ MW 1.111 W 2.79 _ Using the mechanical press of Example 7, 50 mg. of 90 MW 1.099 M 2.58 _ MW 1.043 ___ MS weight percent pure pyrolytically formed beryllium hy- 2.47 _ dride is subjected to a pressure of 50,000 p.s.i. at a tem- M 1.020 VW 50 2.33 VS 0.995 MW perature of 190 C. for an hour during which time the 2.20 _ beryllium hydride is fused. The resultant fused beryllium w 0.953 W 3 2.09 _ hydride has a density of 0.69 g./cm. . MW 0.916 — MW 1.981 M 0.897 W In like manner, 50 mg. of 85 weight percent pure meta- 1.898 S 0.881 M thetically formed beryllium hydride is subjected to 90,00055 1.788 w 0.858 . — VW p.s.i. pressure at a temperature of 135° C. for 45 minutes. 1.723 vw 0.825 Fusion occurs and portions of the resultant fused beryl- VW 1.649 M 0.802 . „ MW lium hydride have a density as high at 0.76 g./cc. with 1.510 an average density of 0.73 g./cc. MW 0.799 .. MW Similarly, 50 mg. of 95 weight percent pure pyrolyt- 60 Having fully described the process and novel composi- ically formed beryllium hydride is subjected to a pressure tions of this invention, it is desired that this invention be of 900,000 p.s.i. at a temperature of 135° C. The resultantlimite d only by the lawful scope of the appended claims. beryllium hydride is fused and has a density of 0.88 3 I claim: g./cm. . 1. A method of increasing the density of a hydride of Beryllium hydride having densities between 0.69 and 65 a metal by fusion, said metal being a member of one of 0.88 g./cc. are also obtained when amorphous beryllium Groups II-A, II-B, III-A and III-B of the Periodic hydride is heated from 5 minutes to two hours at tem- Table, said method comprising subjecting said hydride peratures between 100° C. and 325° C. under pressures to a pressure of from about 50,000 p.s.i. to about of between 100,000 p.s.i. and 350,000 p.s.i. 900,000 p.s.i. at a temperature from about 65° C. to Similarly, aluminum hydride, radium hydride, neptu-70 about 325° C., said pressure and temperature being nium hydride and mercury hydride are subjected to and sufficient to fuse said hydride. held at pressures and temperature conditions sufficient to 2. The method of claim 1 wherein said hydride is cause their fusion. The resultant hydrides are denser ma- beryllium hydride. terial than heretofore existed. Likewise, thulium hydride 3. The method of claim 1 wherein said hydride is are subjected to and held at pressure and temperature 75 aluminum hydride. 3,784,682 11 12 4. The method of claim 1 wherein said hydride is un- 8. Beryllium hydride having a density of at least 0.69 fused beryllium hydride, said pressure is from 50,000 to g./cc. prepared by the method of claim 1. 900,000 p.s.i. and said temperature is from about 135° References Cited C. to about 210° C., such that said pressure and tem- perature are sufficient to fuse said unfused beryllium 5 UNITED STATES PATENTS hydride. 1,130,533 3/1915 Pictet 264—65 5. The method of claim 4 wherein said unfused OTHER REFERENCES beryllium hydride is pyrolytically-formed unfused Kingery, Densification During Sintering in the Presence beryllium hydride. 6. The method of claim 4 wherein said unfused of a Liquid Phase, Jour, of Applied Physics. beryllium hydride is metathetically-formed unfused LELAND A. SEBASTIAN, Primary Examiner beryllium hydride. 7. The method of claim 4 wherein said pressure is U.S. CI. X.R. from about 75,000 p.s.i. to about 350,000 p.s.i. 23—293 R; 149—109; 423—263, 646, 647