Showing papers on "Diborane published in 2010"
TL;DR: In this article, the role of Li2B12H12 for the sorption of LiBH4 is analyzed by in situ X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy.
Abstract: By in situ X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy, the role of Li2B12H12 for the sorption of LiBH4 is analyzed. We demonstrate that Li2B12H12 and an amorphous Li2B10H10 phase are formed by the reaction of LiBH4 with diborane (B2H6) at 200 °C. Based on our present results, we propose that the Li2B12H12 formation in the desorption of LiBH4 can be explained as a result of reaction of diborane and LiBH4. This reaction of the borohydride with diborane may also be observed for other borohydrides, where B12H12 phases are found during decomposition.
146 citations
TL;DR: In this paper, nanometer-thick amorphous boron (?-B) layers were formed on (100) Si during exposure to diborane (B2H6) in a chemical vapor deposition (CVD) system, either at atmospheric or reduced pressures, at temperatures down to 500°C.
Abstract: Nanometer-thick amorphous boron (?-B) layers were formed on (100) Si during exposure to diborane (B2H6) in a chemical vapor deposition (CVD) system, either at atmospheric or reduced pressures, at temperatures down to 500°C. The dependence of the growth mechanism on processing parameters was investigated by analytical techniques, such as transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS), in conjunction with extensive electrical characterization. In particular, devices fabricated by B deposition effectively demonstrated that p + doping of the silicon substrate can be achieved within 10 nm from the surface in a manner that is finely controlled by the B2H6 exposure conditions. High-quality, extremely ultrashallow, p + n junctions were fabricated, and their saturation current was tuned from high Schottky-like values to low deep pn junction-like values by the increasing of the deposited B layer thickness. This junction formation exhibited high selectivity, isotropy, spatial homogeneity, and compatibility with standard Si device fabrication.
104 citations
TL;DR: Al-Li-borohydride decomposes at approximately 70 degrees C, forming LiBH(4), and the high mass loss during the decomposition indicates the release of not only hydrogen but also diborane.
Abstract: The new double-cation AlLi-borohydride is an attractive candidate material for hydrogen storage due to a very low hydrogen desorption temperature (-70°C) combined with a high hydrogen density (17.2 wt%). It was synthesised by high-energy ball milling of AlCl3 and LiBH4. The structure of the compound was determined from image-plate synchrotron powder diffraction supported by DFT calculations. The material shows a unique 3D framework structure within the borohydrides (space group = P-43n, a = 11.3640(3) A). The unexpected composition Al3Li4(BH 4)13 can be rationalized on the basis of a complex cation [(BH4)Li4]3+ and a complex anion [Al(BH 4)4]-. The refinements from synchrotron powder diffraction of different samples revealed the presence of limited amounts of chloride ions replacing the borohydride on one site. In situ Raman spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TG) and thermal desorption measurements were used to study the decomposition pathway of the compound. Al-Li-borohydride decomposes at -70°C, forming LiBH4. The high mass loss of about 20 % during the decomposition indicates the release of not only hydrogen but also diborane. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
70 citations
TL;DR: Structural data, experimental electron density analysis, and computational studies confirm the 3-fold bonding between the two boron atoms incorporating the two bridging hydrogen atoms.
Abstract: In contrast to the common multiple bonding between carbon atoms, multiply bonded boron compounds have still been a synthetic challenge due to the electron deficiency of boron. We now report that a stable doubly hydrogen-bridged diborane(4), EindB(μ-H)2BEind, is produced by the two-electron oxidation of a hydrogen-substituted diborane(4) dianion [Li+(thf)]2[Eind(H)BB(H)Eind]2−, where Eind denotes the 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl. The X-ray crystallography reveals a short B−B distance of 1.4879(7) A in comparison with the normal B−B single bond length (1.72 A), the presence of two hydrogen atoms bridged perpendicular to the B−B bond with a butterfly shape having a dihedral angle of the two BHB triangles of 113(1)°, and a linear geometry around the B−B bond with a C−B−B bond angle of 178.92(4)°. These structural data, experimental electron density analysis, and computational studies confirm the 3-fold bonding (a σ and two π-like bonds) between the two boron atoms incorporating the two bridgin...
69 citations
TL;DR: In this article, boron layers fabricated by exposing silicon to diborane (B2H6) gas in an atmospheric-pressure chemical vapor deposition reactor are investigated with respect to their electrical properties.
Abstract: Deposited boron layers fabricated by exposing silicon to diborane (B2H6) gas in an atmospheric-pressure chemical vapor deposition reactor are investigated with respect to their electrical properties. At the applied temperatures from 500°C to 700°C, the deposition forms a nanometer-thick layer stack of amorphous boron (α-B) and boron-silicon compound (BxSiy), whereas the crystalline Si substrate is p-doped to depths below 10 nm, depending on the temperature and exposure time. The as-deposited layers can be used to fabricate high-quality p+n diodes with low series resistance and low saturation current values that are comparable with those of conventional deep p+ junctions. By investigating p-n-p structures with p+ B-deposited emitters, it is shown that the presence of the α-B layer increases the effective Gummel number of the diffused emitter up to about a factor of 60. The α-B layer is also demonstrated to be a stable and controllable supply of B for the formation of deep p-type regions by thermal drive-in.
55 citations
TL;DR: It is proposed that diborane is an intermediate compound for the hydrogen sorption in borohydrides and may be the key for a reversible hydrogen ab- and desorption reaction under moderate conditions.
Abstract: We describe a new method for the solvent-free synthesis of borohydrides at room temperature and demonstrate its feasibility by the synthesis of three of the most discussed borohydrides at present: LiBH4, Mg(BH4)2 and Ca(BH4)2. This new gas–solid mechanochemical synthesis method is based on the reaction of metal hydrides with diborane to form the corresponding borohydrides. The synthesis will facilitate the preparation of a wide range of different borohydrides, including mixed borohydride systems, with tuneable sorption properties. We propose that diborane is an intermediate compound for the hydrogen sorption in borohydrides and may be the key for a reversible hydrogen ab- and desorption reaction under moderate conditions.
55 citations
TL;DR: Its crystal structure has been determined and contains disordered BH(4)(-) ions in 2 distinct sites and Hydrogen release is similar to that from NH(3)BH(3), but with faster kinetics.
54 citations
TL;DR: In this article, the authors report on new experiments on the catalytic dehydrogenation of [H 2 B(μ-hpp)] 2 leading to the doubly base-stabilized diborane(4) [HB(μ)-hpp] 2 featuring two hpp bridges (hpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) under mild conditions.
Abstract: In this work we report on new experiments on the catalytic dehydrogenation of [H 2 B(μ-hpp)] 2 leading to the doubly base-stabilized diborane(4) [HB(μ-hpp)] 2 featuring two hpp bridges (hpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) under mild conditions. Several dehydrogenation (pre)catalysts were tested. The best one turned out to be Ru 3 (CO) 12 , allowing quantitative dehydrogenation already at 60 °C. Subsequently we subjected [HB(μ-hpp)] 2 to reactions with S 8 and disulfides (Ph 2 S 2 and Bn 2 S 2 , Bn = benzyl). Reaction with S 8 leads to oxidative insertion of one sulfur atom into the B―B bond and formation of [HB(μ-hpp)] 2 (μ-S). In the case of disulfides, substitution reactions leading to the doubly base-stabilized diborane(4) species [RSB(μ-hpp)] 2 and HB(μ-hpp) 2 BSR (R = Ph or Bn) compete with sulfuration again leading to [HB(μ-hpp)] 2 (μ-S).
54 citations
TL;DR: In this article, the authors presented enhanced dehydrogenation of solid ammonia borane (AB, NH3BH3) at 85 °C after it was preheated at 80 °C for 2−4 h.
Abstract: This paper presents enhanced dehydrogenation of solid ammonia borane (AB, NH3BH3) at 85 °C after it was preheated at 80 °C for 2−4 h. Thermal treatments and subsequent hydrogen release experiments were carried out in a Hastelloy cell mounted on a high-pressure differential scanning calorimeter. With increased preheating durations, not only does the induction period for hydrogen release shorten but also the hydrogen release becomes fast. It is deduced that diammoniate of diborane (DADB, [(NH3)2BH2]+[BH4]−), oligomers or polymers, and AB form a solid solution, shifting the melting temperature of AB to a low value. Hydrogen evolution, as the result of the initial stage of oligomerization, is observed after maintaining pristine AB at 80 °C for 20 min. FTIR-ATR spectra of thermally treated AB indicated that only linear dimers of aminoborane (LDAB, NH3BH2NH2BH3) are detected for preheating periods shorter than 3 h, whereas other oligomers and polymers form for the longer thermal treatment at 80 °C.
44 citations
TL;DR: The surface oxidation induces the formation of a Li(2)O layer on LiBH(4), significantly reduces the desorption of diborane, and enhances the rate of hydrogen Desorption.
Abstract: The surface oxidation behavior of LiBH4 and NaBH4 was investigated in view of the formation and structure of the surface oxidation and its effect on the hydrogen desorption kinetics. The sample surfaces were intentionally modified by exposure to oxygen in the pressure range from 10−10 mbar up to 200 mbar. The induced surface changes were systematically studied by means of X-ray photoelectron spectroscopy. NaBH4 shows a low reactivity with oxygen, while LiBH4 oxidizes rapidly, accompanied by surface segregation of Li. The hydrogen desorption kinetics of LiBH4 were studied by thermal desorption spectroscopy with particular emphasis on the analysis of the desorbed gases, i.e. diborane and hydrogen. The surface oxidation induces the formation of a Li2O layer on LiBH4, significantly reduces the desorption of diborane, and enhances the rate of hydrogen desorption.
39 citations
TL;DR: In this paper, the authors used 11B magic angle spinning (MAS) solid state NMR spectroscopy, TGA/DSC/MS with 15N-labeled ammonia borane, and solution 11B NMR analyzer to characterize the release of hydrogen from AB/nano-BN mixtures.
Abstract: Ammonia borane (AB) is under significant investigation as a possible hydrogen storage material. While chemical additives have been shown to lower the temperature for hydrogen release from ammonia borane, many provide additional complications in the regeneration cycle. Mechanically alloyed hexagonal boron nitride (nano-BN) has been shown to facilitate the release of hydrogen from AB at lower temperature, with minimal induction time and less exothermicity, and inert nano-BN may be easily removed during any regeneration of the spent AB. The samples were prepared by mechanically alloying AB with nano-BN. Raman spectroscopy indicates that the AB/nano-BN samples are physical mixtures of AB and h-BN. The release of hydrogen from AB/nano-BN mixtures as well as the decomposition products was characterized by 11B magic angle spinning (MAS) solid state NMR spectroscopy, TGA/DSC/MS with 15N-labeled AB, and solution 11B NMR spectroscopy. The 11B MAS solid state NMR spectrum shows that diammoniate of diborane (DADB) is...
TL;DR: In this paper, the synthesis and chemical properties of some binuclear and oligonuclear compounds of boron-and magnesium-containing bridging guanidinate ligands were reported.
Abstract: Herein we report on the synthesis and chemical properties of some binuclear and oligonuclear compounds of boron- and magnesium-containing bridging guanidinate ligands. These species were prepared by reaction of the bicyclic guanidine hppH (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) and BCl3, the diborane(4) B2Cl2(NMe2)2 or the Grignard compound MeMgBr. The experimental results are complemented by quantum chemical (DFT) calculations.
TL;DR: The photoelectron spectra indicate essential differences between the amines and phosphines toward borane complexation, while the dative bond is more stable in the studied amine-boranes than in phosphines, and the sigma(B-H) orbitals are morestable in the latter compounds.
Abstract: Borane complexes of aziridine, phosphirane, cyclopropylamine, cyclopropylphosphine, cyclopropylmethylamine, and cyclopropylmethylphosphine have been prepared by the reaction at low temperatures of a borane complex or diborane on the free phosphine or amine. The products characterized by NMR spectroscopy and mass spectrometry have then been investigated by photoelectron spectroscopy and B3LYP/aug-cc-pVTZ quantum chemical study. The complexation led to rotamers with structures similar to the ones of the corresponding free systems. The main geometry change with the complexation is the P−C bond elongation and the N−C bond shortening, which can be rationalized by the charge transfer attached to the electron donation. The calculated relative stability order of the conformers changes with the complexation only in the case of cyclopropylamine. The calculated complexation energies are higher for the amines, in accord with the differences observed in the flash vacuum thermolysis of methylamine-, methylphosphine-, a...
TL;DR: The energy decomposition analysis using the density functional theory-symmetry adopted perturbation theory (DFT-SAPT) method confirms the predominant role played by the dispersion interaction in the stabilization of the various complexes when compared to the electrostatic interaction.
Abstract: The gas phase interaction between borazine (IBz) and diborane (DB) has been investigated using MP2/6-311++G** and M05-2X/6-311++G** methods. The calculations have also been carried out at the same levels on the intermolecular complex formed between benzene (Bz) and DB to compare the modes of interaction. The complexation pattern found in IBz···DB is similar to that of Bz···DB due to their structural similarity. The calculated stabilization energies (SEs) at the MP2/6-311++G** level of theory for IBz···DB and Bz···DB complexes are 1.67 and 3.06 kcal/mol, respectively. The corresponding values obtained from the M05-2X/6-311++G** level of calculation are 2.55 and 3.43 kcal/mol. The variation in the SEs between IBz···DB and Bz···DB is due to the differences in the π-electron distributions of IBz and Bz rings. Since, DB contains a three center−two electron (3c−2e) electron deficient bond, the substitution of nonbridge hydrogen atoms (H) by different functional groups may influence the nature of interaction bet...
TL;DR: A core shell structure of the grains, in which LiBD(4) forms a passivation layer on the surface of the LiD grains, was found in the subsequent microstructural and chemical analysis of the final product.
Abstract: The formation of LiBD4 by the reaction of LiD in a diborane/hydrogen atmosphere was analysed by in situ neutron diffraction and subsequent microstructural and chemical analysis of the final product. The neutron diffraction shows that nucleation of LiBD4 already starts at temperatures of 100 °C, i.e. in its low temperature phase (orthorhombic structure). However, even at higher temperatures the reaction is incomplete. We observe a yield of approximately 50% at a temperature of 185 °C. A core shell structure of the grains, in which LiBD4 forms a passivation layer on the surface of the LiD grains, was found in the subsequent microstructural (electron microscopy) and chemical (electron energy loss spectrometry) analysis.
TL;DR: In this paper, a low temperature growth of germanium (Ge) on silicon dioxide (SiO 2 ) is demonstrated using a diborane pretreatment technique using SiH 4 and B 2 H 6 precursors, using Si 1-x B x layers are deposited on Si0 2 to seed the chemical vapor deposition growth of Ge films.
Abstract: Low temperature (<350°C) growth of germanium (Ge) on silicon dioxide (SiO 2 ) is demonstrated using a diborane pretreatment technique. Using SiH 4 and B 2 H 6 precursors, Si 1-x B x layers are deposited on Si0 2 to seed the chemical vapor deposition growth of Ge films. In the SiH 4 :B 2 H 6 system, the binary deposition mechanism of the Si 1-x B x film is explained by the "enhancement" model. In situ doping of Ge films is also investigated. In situ boron activation is achieved during the crystallization of the Ge films at 310°C. Device applicability of the doped Ge film growth on oxide is demonstrated in a low temperature (350°C) Si p-channel metal-oxide-semiconductor field-effect transistor, in which the Ge layer is used as a gate electrode. The low temperature Ge growth technique can be used for low thermal budget processes, e.g., monolithic three-dimensional integrated circuits.
TL;DR: The formation of hydrogen-content-controlled B(12)H(n) (+) clusters is presented through the decomposition and ion-molecule reactions of the decaborane and diborane molecules in an external quadrupole static attraction ion trap.
Abstract: We present the formation of hydrogen-content-controlled B12Hn+ clusters through the decomposition and ion-molecule reactions of the decaborane (B10H14) and diborane (B2H6) molecules in an external quadrupole static attraction ion trap. The hydrogen- and boron-contents of the B10−yHx+ cluster are controlled by charge transfer from ambient gas ions. In the process of ionization, a certain number of hydrogen and boron atoms are detached from decaborane ions by the energy caused by charge transfer. The energy caused by the ion-molecule reactions also induces H atom detachment. Ambient gas of Ar leads to the selective generation of B10H6+. The B10H6+ clusters react with B2H6 molecules, resulting in the selective formation of B12H8+ clusters. Ambient gas of Ne (He) leads to the generation of B10−yHx+ clusters with x=4–10 and y=0–1 (with x=2–10 and y=0–2), resulting in the formation of B12Hn+ clusters with n=4–8 (n=2,4–8). The introduction of ambient gas also increases the production of clusters. PBE0/6-311+G(d)...
Proceedings Article•
24 May 2010TL;DR: In this article, a deposited boron layer is investigated as a diffusion barrier between Al and Si, and it is demonstrated that the normally observed spiking behaviour of Al on Si can be prevented and a perfect spike- and precipitate-free interface can be achieved.
Abstract: A deposited boron layer is investigated as a diffusion barrier between Al and Si. The doping reaction of diborane B 2 H 6 on Si(100) substrates forms an ultra-shallow p+-doped region and amorphous boron layer, the barrier properties of which are tested at different thicknesses. Experimental data obtained from extensive microscopy analyses are used to asses the topography and chemical properties of the silicon/boron surface when in contact with pure aluminium. In this study it is demonstrated that the normally observed spiking behaviour of Al on Si can be prevented and a perfect, spike- and precipitate-free interface can be achieved.
TL;DR: The diborane B 2 (NMe 2 ) 2 Fc 2 (3) adopts an unstrained geometry and features notable molecular ring strain manifested in the tilt-angle a = 10.5(2)° as discussed by the authors.
Abstract: The new [2]boraferrocenophane derivative [Fe(η 5 -C 5 H 4 )-B(Mes)-B(Mes)-(η 5 -C 5 H 4 )] (2) was prepared by reaction of 1,1'-dilithioferrocene with B 2 (Mes) 2 Cl 2 . In addition, the diborane(4) B 2 (NMe 2 ) 2 Fc 2 (3) was isolated from the reaction of B 2 (NMe 2 ) 2 Cl 2 and monolithioferrocene. Both species were fully characterized including X-ray diffraction analyses. While B 2 (NMe 2 ) 2 Fc 2 (3) adopts an unstrained geometry, [2]boraferrocenophane 2 features notable molecular ring strain manifested in the tilt-angle a = 10.5(2)°.
TL;DR: In this paper, electrical and structural characterizations of a-Si:H layers prepared by plasma enhanced chemical vapor deposition (PECVD) method at 540k on glass substrates at different diborane (B2H6) flow ratios (500, 250, 150 and 50 sccm).
Abstract: Hydrogenated amorphous silicon (a-Si:H) has found applications in flat panel displays, photovoltaic solar cell and recently has been employed in boron doped microbolometer array. We have performed electrical and structural characterizations of a-Si:H layers prepared by plasma enhanced chemical vapor deposition (PECVD) method at 540 K on glass substrates at different diborane (B2H6) flow ratios (500, 250, 150 and 50 sccm). Fourier transform infrared spectroscopy (FTIR) measurements obtained by specular reflectance sampling mode, show Si–Si, B–O, Si–H, and Si–O vibrational modes (611, 1300, 2100 and 1100 cm−1 respectively) with different strengths which are associated to hydrogen and boron content. The current–voltage curves show that at 250 sccm flow of boron the material shows the lowest resistivity, but for the 150 sccm boron flow it is obtained the highest temperature coefficient of resistance (TCR).
TL;DR: In this paper, a nanocrystalline MgB2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH4 with MgH2 at temperatures as low as 450°C.
Abstract: Magnesium diboride (MgB2) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH4 with MgH2 at temperatures as low as 450°C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K.
25 May 2010
TL;DR: In this paper, the role of diborane in the sorption of LiBH_4 is analyzed by in situ X-ray diffraction and nuclear magnetic resonance (NMR) spectroscopy.
Abstract: By in situ X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy, the role
of Li_2B_(12)H_(12) for the sorption of LiBH_4 is analyzed We demonstrate that Li_2B_(12)H_(12) and an
amorphous Li_2B_(10)H_(10) phase are formed by the reaction of LiBH_4 with diborane (B_2H_6) at 200 °C
Based on our present results, we propose that the Li -2B - (12)H_(12) formation in the desorption of LiBH_4 can
be explained as a result of reaction of diborane and LiBH_4 This reaction of the borohydride with
diborane may also be observed for other borohydrides, where B_(12)H_(12) phases are found during
decomposition
Patent•
18 Feb 2010
TL;DR: In this article, a plasma doping method capable of uniformly introducing impurities into an object to be processed is described, which is called p-type impurity diffusion (PVD).
Abstract: Disclosed is a plasma doping method capable of uniformly introducing impurities into an object to be processed. A plasma of diborane gas that contains boron, which is a p-type impurity, and argon gas, which is an inert gas, is generated, and boron radicals (21) within said plasma are deposited on the surface of a silicon substrate (13) by a bias potential not being applied to the silicon substrate (13). Then, the supply of diborane gas is stopped and the surface of the silicon substrate (13) is irradiated with the argon ions (22) within the plasma by a bias potential being applied to the silicon substrate (13). When the irradiating argon ions (22) collide with the boron radicals (21), the boron radicals (21) are introduced into the silicon substrate (13). The boron radicals (21) which have been introduced are activated by heat treatment, thus forming a p-type impurity diffusion layer (23) in the silicon substrate (13).
TL;DR: In this article, the magnetic properties of the boron-oxide-coated iron nanocapsules were compared and discussed in terms of the particles' sizes, the phase components, and the surface structures.
TL;DR: In this article, the vibrational spectra of 1,2-tetramethylenediborane (B2C4H12), 1, 2:1, 2-bis(tetramerethylene)diboranes (B 2C8H18), and 1, 1:2, 2 -bis (tetamethylene)-dibarane were studied using quantum computational density functional B3LYP and B3PW91 methods and 6 -31G*, 6-31G** and 6 −31++G** basis sets
Abstract: Molecular structure and vibrational spectra of 1,2-tetramethylenediborane (B2C4H12), 1,2:1,2-bis(tetramethylene)diborane (B2C8H18), 1,1-tetramethylenediborane (B2C4H12) and 1,1:2,2-bis(tetramethylene)diborane (B2C8H18), have been studied using quantum computational density functional B3LYP and B3PW91 methods and 6-31G*, 6-31G** and 6-31++G** basis sets. Natural bond orbital analyses have been carried out to study in detail the nature of the B—C, C—C and B—H bonds in these molecules. This study showed that all these compounds are thermodynamically stable in the gas phase, but bicyclic structures are more stable than monocyclic structures.
Patent•
11 Oct 2010
TL;DR: In this article, a microwave plasma chemical vapor deposition process that uses Nitrogen and Diborane simultaneously in combination along with the Methane and Hydrogen gases to grow white color diamonds is described.
Abstract: The present application discloses the details of a microwave plasma chemical vapor deposition process that uses Nitrogen and Diborane simultaneously in combination along with the Methane and Hydrogen gases to grow white color diamonds. The invention embodies using nitrogen to avoid inclusions and impurities in the CVD diamond samples and Diborane for the color enhancement during the growth of diamond. It is also found that heating of the so grown diamonds to 2000 C results in significant color enhancement due to the compensation of Nitrogen and Boron centers in the samples. The origin of the various colors in diamond is explained on the basis of the band diagram of CVD diamond.
TL;DR: In this article, three new diborane(4) derivatives, 1,2-bis(2,4,6-trimethylanilide)-1, 2-bis (dimethyamido)diboranes(4), (1), (2) and (3) have been synthesized and characterized by means of elemental analysis, IR, 1H, 13C and 11B NMR spectroscopy.
Dissertation•
01 Jul 2010
TL;DR: In this article, a study has been made into the mechanical milling of metal chlorides with sodium borohydride to try to form homoleptic borhydrides.
Abstract: With relatively high gravimetric and volumetric hydrogen storage capacities, borohydride compounds are being investigated for their potential use as hydrogen storage media. A study has been made into the mechanical milling of metal chlorides with sodium borohydride to try to form homoleptic borohydrides. Mechanical milling of zinc chloride with sodium borohydride resulted in the formation of a covalent complex NaZn\(_2\)(BH\(_4\))\(_5\). Thermal decomposition occurred at 80°C with a mass change of 12 wt.%, associated with the evolution of hydrogen and diborane. A composite mixture with magnesium hydride a reaction between diborane and magnesium hydride was observed form magnesium borohydride. Mechanical milling of calcium chloride or magnesium chloride with sodium borohydride did not produce calcium borohydride and magnesium borohydride, but rather resulted in solid solutions where chlorine ions substitute for borohydride ions within the cubic sodium borohydride lattice. Thermal decomposition of milled calcium chloride and sodium borohydride occurs at a similar manner to that of Ca(BH\(_4\))\(_2\) (from Sigma-Aldrich). Milled magnesium chloride and sodium borohydride thermally decomposes via several unknown phases with a weight loss of 4.4 wt.% yielding Mg, MgB\(_2\), B, and [B\(_{12}\)H\(_{12}\)]\(^{2-}\). Lithium borohydride investigated using Raman spectroscopy. After heating lithium borohydride through its orthorhombic to hexagonal phase change (118°C) and melting point (280°C), shifts in Raman peak position and peak width were measured as a function of temperature. This work shows the in-situ decomposition of LiBH\(_4\) observing formation of lithium dodecaborane (Li\(_2\)B\(_{12}\)H\(_{12}\)) at 340°C and amorphous boron from liquid lithium borohydride.
01 Jan 2010
TL;DR: In this paper, the authors investigated the use of a chemical hydride, ammonia borane (AB), as a potentially efficient material for hydrogen storage and developed new efficient methods for increasing the rate and extent of H2-release from AB and elucidate the important mechanistic pathways and intermediates in these reactions.
Abstract: Development of a safe and efficient storage medium for hydrogen is integral to its use as an alternative energy source. The overall goal of the studies described in this dissertation was to investigate the use of a chemical hydride, ammonia borane (AB (19.6 wt% H2)), as a potentially efficient material for hydrogen storage. The specific goals of this study were both to develop new efficient methods for increasing the rate and extent of H2-release from AB and to elucidate the important mechanistic pathways and intermediates in these reactions. Significant achievements that resulted from this work are that AB H2-release is activated in the presence of either ionic liquids or bases. For example, an AB H2-release reaction carried out at 110 °C in 50 wt% ionic liquid liberated over 2 equivalents H2 in 15 minutes. Reducing ionic liquid loading to 20 wt% at 110 oC yielded a higher materials weight percent (11.4 mat wt%), while still having fast release rates: 2 equivalents in ~2.5 hours. The addition of the strong nitrogen base 1,8-bis(dimethylamino)naphthalene, Proton Sponge™, to ionic liquid solutions of AB increased the AB H2release rate at 85 °C, with over 2 equivalents of H2 achieved within 3 h. Additional Proton Sponge increased the rate of release; however, the mat wt% of H2 decreased since the Proton Sponge added significant weight to the system. Solid state and solution 11B NMR and DSC studies of reactions in progress allowed the identification of initial and final products in the H2-release reactions and helped elucidate the overall reaction pathway. The initial formation of diammoniate of diborane, the key intermediate in dehydropolymerization of ammonia borane, was promoted by the addition of ionic liquids. Subsequent H2-release resulted in the formation of polyaminoborane then polyborazylene. Proton Sponge increased the release rate of the second equivalent of H2 by a newly proposed anionic polymerization mechanism. The final product was identified by solid-state 11B NMR and proved to be a sp2-framework of polyborazylene which formed regardless of base additive or amount/type of ionic liquid.
Patent•
08 Jul 2010
TL;DR: In this article, the boron doped semiconductor nanowire of a uniform diameter in the direction of growth axis is manufactured by manufacturing steps including: a step (1) in which group IV semiconductor nano-nodes are grown on a substrate using semiconductor material gas; step (2) in where a bboron film is deposited on the surface of the semiconductor micro-wires by introducing only diborane gas; and step (3), in which the semiconducting material is thermally annealed at the temperature of melting point
Abstract: PROBLEM TO BE SOLVED: To provide a boron doped semiconductor nanowire whose diameter is uniform in the direction of growth axis, and also to provide its manufacturing method. SOLUTION: The boron doped semiconductor nanowire of a uniform diameter in the direction of growth axis is manufactured by manufacturing steps including: a step (1) in which group IV semiconductor nanowire is grown on a substrate using semiconductor material gas; a step (2) in which a boron film is deposited on the surface of the semiconductor nanowire by introducing only diborane gas; and a step (3) in which the semiconductor nanowire with the boron film on the surface of which the boron film is deposited is thermally annealed at the temperature of melting point of semiconductor nanowire (main body) or lower. COPYRIGHT: (C)2010,JPO&INPIT