Temperature-programmed Desorption Mass Spectrometry Research Articles

Hydration–Dehydration of Acetonitrile and Methanol in Amorphous Solid Water

The interactions of two model dipolar molecules (acetonitrile (ACN) and methanol (MeOH)) with amorphous solid water (ASW) were investigated using temperature-programmed desorption and temperature-dependent secondary ion mass spectrometry of a series of mixed adlayer thin film systems comprising different configurations of monolayers and thin films of ACN, MeOH, and ASW as well as a nonpolar probe molecule, CO2, deposited on a Ni(111) substrate. The temperature-dependent desorption rates and surface compositions of these systems were found to be consistent with the hydrophobic hydration of ACN, wherein the ACN is caged by water molecules, likely in clathrate-like structures. Consequently, the ACN–water hydrogen bonds are limited to the interior surfaces of the cages. The ACN is not incorporated into the ASW hydrogen bonding network, and it does not modify the crystallization kinetics of the ASW. In contrast, MeOH incorporates into the hydrogen bonding network and modifies the water crystallization kinetics...

In English

The coordination compound EuL 3 Phen (where L – = N-{bis[methyl(phenyl)amino]phosphoryl}-benzenesulfoneamidate anion) has been synthesized and studied by laser-desorption and temperature-programmed mass spectrometry in the condensed phase and on the surface of a standard metal substrate. The temperature dependence of the main mass spectrum components in the method of temperature-programmed desorption mass spectrometry (TPD MS) is defined and interpreted, components of the laser desorption/ionization (LDI) mass spectrum of the synthesized substance have been identified. A comparative analysis of mass spectra obtained by both methods for the studied coordination compound has been carried out. A possibility of both mass spectrometric methods using for the investigation of metal-containing polymer components is discussed.

Influence of the Si/Al ratio and Al distribution on the H-ZSM-5 lattice and Brønsted acid site characteristics

An experimentally-guided theoretical study was conducted to investigate H-ZSM-5 aluminosilicate lattice intrinsic Brønsted acid site properties and reactive functionalities. The variation of intrinsic parameters, including Si/Al ratio and Al distribution, were probed with VASP fully-minimized periodic atomic models, and compared to characterization results. Isopropylamine (IPA) and pentane adsorption and protonation were predicted at selected Brønsted acid sites in these H-ZSM-5 configurations. The following trends were observed with decreasing Si/Al ratio: The predicted H-ZSM-5 lattice parameters increased, consistent with H-ZSM-5 X-ray diffraction measurement trends. The Brønsted acid site O–H distance was predicted to increase and the proton charge to decrease. This trend was explained by increased lattice covalency in the predicted electronic density of states. Temperature programmed desorption–mass spectrometry showed that the H-ZSM-5 IPA cracking reactivity increased with Brønsted acid site density, utilizing a reduced fraction of total Al sites. The IPA adsorption with spontaneous protonation was predicted to increase in favorability. Pentane physisorption electron transfer and favorability was also predicted to increase. However, the favorability of activated pentane protonation decreased, due to poor charge accommodation in the increasingly covalent lattices. Thermochemical analyses predicted decreased H-ZSM-5 deprotonation energies, DPEH-ZSM-5, but also decreased stabilization interactions of deprotonated H-ZSM-5 with protonated products. On the other hand, Al substitution in next–next nearest-neighbor T-sites at a low Si/Al ratio was shown to increase lattice and Brønsted acid site polarization, facilitating both proton transfer and protonated product stabilization. This configuration was predicted to reduce both the DPEH-ZSM-5 and increase the stabilization interaction for protonated adsorbates.

Study on Reactivity of HgO over Activated Carbon with HCl and SO2 in the Presence of Moisture by Temperature-Programmed Decomposition Desorption Mass Spectrometry

Reactivities of mercury compounds over mercury sorbents with HCl and SO2 are very important to the design of a solid sorbent for mercury vapor removal from coal-derived flue gases. However, presently available data on the reactivity of mercury oxide over mercury sorbent is insufficient. This study investigated the reactivity of mercury oxide with HCl and SO2 using a temperature-programmed decomposition and desorption technique and a mass spectrometer (TPDD-mass) method. Mercury desorption from HgO over activated carbon (HgO/AC) was observed at the same temperature range as from HgO/SiO2, but the mercury desorption peak from the HgO/AC was observed at a higher temperature than from the HgO/SiO2, indicating that some of the HgO was stabilized by the AC surface. When the HgO/AC was pretreated with HCl–H2O, the formation of HgCl2 was suggested by the mass spectra of m/z = 272 and 270. The mercury desorption temperatures in the TPDD spectra were lower than those of nonpretreated samples. On the basis of the sh...

Scandium functionalized carbon aerogel: Synthesis of nanoparticles and structure of a new ScOCl and properties of NaAlH4 as a function of pore size

A new method for scandium-functionalization of carbon aerogels forming nanoparticles of a new scandiumoxochloride, ScOCl is presented. Sodium aluminiumhydride, NaAlH4, is successfully melt infiltrated into the nano porous scaffolds with pore sizes of Dmax=7, 10, 13, 21, 26 and 39nm, containing scandium based nano particles (<2.9wt%) confirmed by elemental analysis and scanning electron microscopy. A systematic study of hydrogen storage properties of the nano composite materials is presented. An aqueous solution of ScCl3 was initially infiltrated and formed nanoconfined [Sc(OH)(H2O)5]2Cl4(H2O)2, which transforms to nanoparticles of a new scandium oxochloride, ScOCl at 192°C and to Sc2O3 at 420°C. ScOCl crystallizes in an orthorhombic unit cell a=3.4409(8), b=3.9613(6) and c=8.178(2)Å, space group Pmmn, and is built from layers of [ScO4Cl2] octahedra forming neutral ScOCl layers. Temperature programmed desorption mass spectroscopy shows slightly improved kinetics for release of hydrogen with decreasing pore size. Continuous cycling of hydrogen release and uptake measured by the Sieverts' method reveal a larger preserved hydrogen storage capacity for scandium-functionalized aerogel with the larger pores (39nm).

Electrochemical Synthesis of Carbon Fluorooxide Nanoparticles from 3C-SiC Substrates

Chemical nature of products, formed during electrochemical dissolution of polycrystalline 3C-SiC substrate in HF:ethanol mixture, was studied by means of FTIR spectroscopy, temperature-programmed desorption mass spectrometry (TPD-MS), 1H, 13C, and 19F NMR (solution as well as MAS), XPS, AFM, and other characterization methods. Simultaneous formation of two major products, porous SiC and carbon fluorooxide (CFO) nanoparticles (NPs) with sizes of 1–10 nm, is described. CFO NPs easily dissolve in polar organic solvents (ethanol, CH2Cl2, etc.); their solutions demonstrate intense yellowish-green photoluminescence under UV excitation. A model of the CFO chemical structure based on relatively small graphene domains interconnected with partially fluorinated hydrocarbon groups and terminated by carboxylic acid (−CO2H), ethyl ester (−CO2C2H5), perfluorinated functional groups, and polycarboxylated alkyl chains is proposed. Presence of carboxylates allows easy functionalization of the CFO NPs via amide chemistry. I...

Chemisorption and thermally induced transformations of polydimethylsiloxane on the surface of nanoscale silica and ceria/silica

Compositions of polydimethylsiloxane (PDMS) polymer with nanosized silica and ceria/silica were prepared. The influence of these nano-fillers on the thermal stability and degradation mechanism of silicone polymer was investigated using Thermogravimetric Analysis (TGA) and Temperature Programmed Desorption Mass Spectrometry (TPD MS). The results showed that thermal decomposition of pure and adsorbed PDMS differs significantly. The three main stages of the PDMS thermal transformations in the adsorbed state were determined to be: 1) chemisorption of PDMS chains involving the terminal trimethylsilyl groups of the polymer and silanol groups of the silica surface; 2) formation and desorption of cyclic oligomers; 3) high temperature radical degradation of the polymer accompanied by the formation of methane and ethylene. The kinetic parameters of the corresponding reactions were calculated from the TPD MS data. It was found that nanoparticles of cerium dioxide strongly influence the degradation pattern, lower the decomposition temperature and catalyze the formation of methane.

Vacuum thermal decomposition of polyethylene containing antioxidant and hydrophilic/hydrophobic silica

Temperature-programmed desorption mass spectrometry has been used to study vacuum thermolysis of high-density polyethylene (HDPE) and its composites with hydrophilic or hydrophobic nanosilica in the presence or absence of butylated hydroxytoluene (BHT). It has been found that both surface chemistry of silica filler and the presence of immobilized BHT affect the pathway of HDPE thermal decomposition. Volatility of BHT antioxidant was shown to decrease in the following sequence: free BHT > HDPE–BHT > HDPE–hydrophobic silica/BHT > HDPE–hydrophilic silica/BHT, and the capability of the additives to inhibit chain scission reaction during thermal decomposition of HDPE in vacuum was as follows: hydrophobic silica/BHT > BHT > hydrophobic silica > hydrophilic silica/BHT > hydrophilic silica ≈ no additives.

Study of Thermolysis of Hydrogenated Carbon Molecules as Products of Fullerenization of Benzene, Xylene, Ethanol and Pyridine

Novel essentially distinct from already known (methods of hydrogenation of fullerenes (C60 and C70) or fullerite) method for the synthesis of highly hydrogenated carbon molecules is developed; such approach is perspective hydrogen capacity accumulators. First, the reactionary conditions are created for the realization of the process of fullerenization as direct transformation of molecules of aromatic hydrocarbons, pyridine and ethanol into carbon molecules, fulleranes (С60Н8-С60Н60 and С70Н8-С70Н44) and quasi-fulleranes (CnHn-6-CnHn-2 (n = 20 - 46)) containing up to 5.7 wt% hydrogen. X-ray amorphous powders of hydrogenated carbon molecules in gram amounts are obtained. Appreciable dehydrogenation of such samples of fulleranes and quasi-fulleranes at ~50&degC is began, while dehydrogenation of synthesized from fullerene (or fullerite) fulleranes is observed only at temperatures above 400&degC. Methods of NMR, IR spectroscopy, mass spectrometry MALDI and temperature-programmed desorption mass spectrometry EI are used for the study of condensed products of fullerenization of precursors molecules.

Inorganic-organic thin implant coatings deposited by lasers.

The lifetime of bone implants inside the human body is directly related to their osseointegration. Ideally, future materials should be inspired by human tissues and provide the material structure-function relationship from which synthetic advanced biomimetic materials capable of replacing, repairing, or regenerating human tissues can be produced. This work describes the development of biomimetic thin coatings on titanium implants to improve implant osseointegration. The assembly of an inorganic-organic biomimetic structure by UV laser pulses is reported. The structure consists of a hydroxyapatite (HA) film grown onto a titanium substrate by pulsed-laser deposition (PLD) and activated by a top fibronectin (FN) coating deposited by matrix-assisted pulsed laser evaporation (MAPLE). A pulsed KrF* laser source (λ = 248 nm, τ = 25 ns) was employed at fluences of 7 and 0.7J/cm(2) for HA and FN transfer, respectively. Films approximately 1500 and 450 nm thick were obtained for HA and FN, respectively. A new cryogenic temperature-programmed desorption mass spectrometry analysis method was employed to accurately measure the quantity of immobilized protein. We determined that less than 7 μg FN per cm(2) HA surface is adequate to improve adhesion, spreading, and differentiation of osteoprogenitor cells. We believe that the proposed fabrication method opens the door to combining and immobilizing two or more inorganic and organic materials on a solid substrate in a well-defined manner. The flexibility of this method enables the synthesis of new hybrid materials by simply tailoring the irradiation conditions according to the thermo-physical properties of the starting materials.

Hydrogen storage properties of nanoconfined LiBH4–Ca(BH4)2

The hydrogen storage properties of the eutectic melting metal borohydrides, 0.7LiBH4–0.3Ca(BH4)2, nanoconfined in two carbon aerogel scaffolds with different surface areas and pore volumes (pristine and CO2-activated) are presented and compared to the bulk properties. The temperature of hydrogen release investigated by temperature programmed desorption mass spectroscopy is reduced by 83°C for nanoconfined LiBH4–Ca(BH4)2 in the pristine scaffold and by 95°C in the CO2-activated scaffold, compared to that of the bulk. This corresponds to apparent activation energies, EA, of 204, 156 and 130kJ/mol. Several cycles of reversible, continuous release and uptake of hydrogen is investigated by the Sieverts׳ method. Nanoconfined LiBH4–Ca(BH4)2 in the CO2-activated scaffolds demonstrate high degree of stability, releasing 80% and 73% of the original hydrogen content in the second and third hydrogen release cycle, respectively. However most importantly, this study shows that CO2-activated carbon aerogel, CA-6, is more stabile against reaction with the metal hydride and a lower amount of borates and oxides are formed during melt infiltration and hydrogen release and uptake cycling. We conclude that the CO2-activated scaffold is more inert, provides faster kinetics and higher stability over several cycles of hydrogen release and uptake and has the potential to provide useful hydrogen storage densities in the range ~12wt% H2.

Stability of functionalized activated carbon in hot liquid water

Acidity and stability of activated carbon-based solid acid catalysts for aqueous-phase reactions are investigated. Carbon is acidified with liquid and gas phase methods, using nitric and sulfuric acid, hydrogen peroxide and calcination in air at 300 and 400°C. Modified carbons are characterized by nitrogen physisorption, scanning electron microscopy (SEM), point of zero charge (PZC) measurements, Boehm titration, temperature-programmed desorption–mass spectrometry (TPD–MS), and X-ray photoelectron spectroscopy (XPS). Stability of acid functional groups under typical reaction conditions for biomass conversion is investigated by exposing carbons to hydrothermal treatment (i.e. hot liquid water). Special attention was devoted to elucidating the effect of the temperature (150–225°C) and time of exposure (0–24h) on the hydrothermal stability of different surface functional groups. Carbon modification by sulfuric acid generates strong acid sites in higher concentration, compared to carbon modified by nitric acid, calcination and hydrogen peroxide. In contrast to the other treatments, calcination at 400°C increases carbon basicity. Although the concentrations of all surface acid sites decrease upon the hydrothermal treatment, this effect is not uniform. Stability of acid sites with different strengths and their chemical nature are dependent on the modification method. Strong acid sites formed by sulfuric acid treatment show a much higher stability than those formed by the other acidification procedures. The H2SO4-treated material retains ca. 40% of strong acid sites even after exposure to hot liquid water at 200°C for more than 4h. Only such strong acid sites remain on the carbon surface after exposure to hot liquid water at 225°C.

Investigation of chemical transformations of thiophenylglycoside of muramyl dipeptide on the fumed silica surface using TPD-MS, FTIR spectroscopy and ES IT MS.

In this study, chemical transformations of benzyl ester of О-(phenyl-2-acetamido-2,3-dideoxy-1-thio-β-d-glucopyranoside-3-yl)-d-lactoyl-l-alanyl-d-isoglutamine (SPhMDPOBn) on the fumed silica surface were examined, and the surface complex structure was characterized by temperature-programmed desorption mass spectrometry (TPD-MS), infrared spectroscopy (FTIR) and electrospray ion trap mass spectrometry (ES IT MS). Stages of pyrolysis of SPhMDPOBn in pristine state and on the silica surface have been determined. Probably, hydrogen-bonded complex forms between silanol surface groups and the C = O group of the acetamide moiety NH-(CH3)-C = O…H-O-Si≡. The thermal transformations of such hydrogen-bonded complex result in pyrolysis of SPhMDPOBn immobilized on the silica surface under TPD-MS conditions. The shifts ∆ν of amide I band (measured from 1,626 to 1,639 cm−l for SPhMDPOBn in pristine state) of 33 and 35 cm−l which occurred when SPhMDPOBn was immobilized on the silica surface may be caused by a weakening of the intramolecular hydrogen bonding of the SPhMDPOBn because the interaction with the silica surface as hydrogen bond with silanol groups is weaker than that in associates.

Advanced surface and microstructural characterization of natural graphite anodes for lithium ion batteries

Natural graphite powders were subjected to a series of thermal treatments to improve the anode irreversible capacity loss and capacity retention during long-term cycling of lithium-ion batteries. A baseline thermal treatment in inert Ar or N2 atmosphere was compared to cases with a proprietary additive to the furnace gas. This additive substantially altered the surface chemistry of the uncoated natural graphite powders and resulted in significantly improved long-term cycling performance of the lithium ion batteries over the commercial, carbon-coated natural graphite baseline. Different heat-treatment temperatures were investigated ranging from 950 to 2900°C to achieve the desired long-term cycling performance with a significantly reduced thermal budget. A detailed summary of the characterization data is also presented, which includes X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and temperature-programmed desorption-mass spectroscopy. Characterization data was correlated to the observed capacity fade improvements over the course of long-term cycling at high charge–discharge rates in full lithium-ion cells. It is believed that the long-term performance improvements are a result of forming a more stable solid electrolyte interface (SEI) layer on the anode graphite surfaces, which is directly related to the surface chemistry modifications imparted by the proprietary gas environment during thermal treatment.

Processing-phase diagrams: a new tool for solution-deposited thin-film development applied to the In5O(OPri)13–In2O3 system

Understanding processing–property relationships of a precursor is important for achieving the desired properties in opto-electronic thin-films. This work highlights the construction of a processing-phase diagram of the novel In2O3 precursor In5O(OPri)13 for transparent conducting oxide applications. The decomposition behavior of the precursor was profiled with thermogravimetry, differential scanning calorimetry, and temperature programmed desorption mass spectroscopy. Decomposition occurred at 150–230 °C. Higher temperature exothermic reactions were identified as structural rearrangement/ordering processes. The precursor powder was found to crystallize into the bixbyite structure at 300–350 °C, presenting a non-crystalline phase-processing window for the material. Crystallization of a film was monitored with in situ X-ray diffraction annealing, which showed a markedly higher crystallization onset of 500 °C and a much larger non-crystalline oxide window. The decomposition and crystallization behavior of the precursor powders and films were combined into a master processing-phase diagram. Solution deposited, crystalline In2O3 films annealed under Ar–4%H2 achieved a conductivity of 165 S cm−1 with high visible transparency (80%) and exhibited a mobility of 9.6 cm2 V−1 s−1 with a carrier concentration of 1.1 × 1020 cm−3.

Interfacial reaction of water ice on polycrystalline vanadium and its effects on thermal desorption of water

Thermal desorption and decomposition of water ice deposited onto a polycrystalline V surface were investigated using temperature-programmed desorption and secondary ion mass spectrometry. The water molecules in multilayer films dissociate preferentially at the interface, whereas water desorption from the surface is depressed considerably. The oxygen atoms (hydrogen molecules) formed at the interface are incorporated into the substrate (released into the gas phase) sequentially at temperatures higher than 140 K. The crystallization kinetics of water multilayers is not influenced by the interfacial reaction, but the water desorption rate is depressed by the interfacial reaction even after crystallization. Consequently, thermal desorption of water from the surface and its reaction at the interface are found to be correlated across thin films. This behavior is explainable as dynamic heterogeneity of water in the deeply supercooled region and premelting of metastable ice Ic, where mobile water molecules play a dominant role in both thermal desorption and the interfacial reaction.

Hydrogenated Molecules of Carbon as Products of New Pyrolysis Method of Toluene, Xylene and Ethanol

In contrast to previously known methods of fullerenes and fulleranes producing, firstly the reaction conditions of direct conversion of toluene, xylene and ethanol molecules into molecules of not only fulleranes (C60H4-C60H60 and C70H10-C70H42), but also into quasi-fulleranes (CnHn-6-CnHn-2 (n = 20-42)) were created. The substances containing small molecules of carbon C3-C17 were synthesized from vapors of toluene, xylene and ethanol under the conditions excluding sublimation of carbon. Firstly the volatile products of thermolysis of hydrogenated molecules of carbon are investigated in all an interval of temperatures 50-750°C by means of mass spectrometric method. It is established, that the evolution of hydrogen from given hydrogenated molecules of carbon with so low (~ 50°C) temperature is starting off. Earlier by anybody yet not synthesized an equiatomic composition fullerane C60H60 was synthesized, the thin structure of its mass spectrum completely coincides with natural isotope distribution in a molecule C60H60. The substances synthesized were characterized by temperature-programmed desorption mass spectrometry, matrix-activated laser desorption/ionization mass spectrometry, IR spectroscopy and chemical analysis.

Pretreatment of cylindrical coconut activated carbon and performance as catalyst support

Cylindrical coconut activated carbon(CCAC) support was graphitized at a high temperature(1900 °C) in argon, then oxidized with an O2-N2-H2O mixture, and treated with nitric acid. Pretreatment of carbon support on its mechanical strength, physical structure, chemical composition and surface properties of cylindrical CCAC support was investigated by X-ray diffraction(XRD), surface area analysis, scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), thermogravimetric-differential thermogravimetric(TG-DTG) analysis and temperature programmed desorption-mass spectrometry(TPD-MS), and the effect of CCAC support on the catalytic activities was also studied. The results show that the degree of graphitization, the purity(phosphorus, sulphur), pore structure(micropore, mesopore) and oxygen-containing functional groups(—COOH, —OH, —COOR) of carbon supports are obviously different, which have a great influence on the performance of Ru-based catalysts. After a series of pretreatments, the surface physical and chemical properties of the commercial CCAC are modified and improved, and the activity of as-prepared Ru/AC catalyst is increased significantly.

Effects of graphitic carbon nitride on the dehydrogenation of ammonia borane

By ball milling carbon nitride (C 3 N 4 ) and ammonia borane (AB), the AB-C 3 N 4 system was successfully synthesized. It is shown that the dehydrogenation temperature of the AB-C 3 N 4 system was obviously decreased. However, the concentration of byproduct ammonia was much higher than that of pristine AB. Thus, LiBH 4 -modified C 3 N 4 (LC 3 N 4 ) was produced and employed to synthesize a AB-LC 3 N 4 system. The dehydrogenation of the AB-LC 3 N 4 system was investigated using X-ray diffraction, temperature-programmed desorption-mass spectrometry, thermogravimetry-differential thermal analysis, and nuclear magnetic resonance. The results show that the dehydrogenation temperatures of the AB-LC 3 N 4 systems were reduced to a lower region compared with pristine AB. Moreover, byproduct borazine and the induction period were significantly suppressed. After LiBH 4 modification on C 3 N 4 , the other byproduct ammonia was also reduced in the dehydrogenation process. Dynamic analysis and NMR characterization results show that the decomposition mechanism of AB-LC 3 N 4 still follows the self-decomposition of AB, which is induced by the formation of NH 3 BH 2 NH 3 BH 4 . The dehydrogenation temperature of C 3 N 4 -modified ammonia borane was reduced to lower region with depression of byproduct and induction period compared with pristine ammonia borane.

Thermal Stability of Li2B12H12and its Role in the Decomposition of LiBH4

The purpose of this study is to compare the thermal and structural stability of single phase Li2B12H12 with the decomposition process of LiBH4. We have utilized differential thermal analysis/thermogravimetry (DTA/TGA) and temperature programmed desorption-mass spectroscopy (TPD-MS) in combination with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy to study the decomposition products of both LiBH4 and Li2B12H12 up to 600 °C, under both vacuum and hydrogen (H2) backpressure. We have synthesized highly pure single phase crystalline anhydrous Li2B12H12 (Pa-3 structure type) and studied its sensitivity to water and the process of deliquescence. Under either vacuum or H2 backpressure, after 250 °C, anhydrous Li2B12H12 begins to decompose to a substoichiometric Li2B12H12-x composition, which displays a very broad diffraction halo in the d-spacing range 5.85-7.00 Å, dependent on the amount of H released. Aging Pa-3 Li2B12H12 under 450 °C/125 bar H2 pressure for 24 h produces a previously unobserved well-crystallized β-Li2B12H12 polymorph, and a nanocrystalline γ-Li2B12H12 polymorph. The isothermal release of hydrogen pressure from LiBH4 along the plateau and above the melting point (Tm = 280 °C) initially results in the formation of LiH and γ-Li2B12H12. The γ-Li2B12H12 polymorph then decomposes to a substoichiometric Li2B12H(12-x) composition. The Pa-3 Li2B12H12 phase is not observed during LiBH4 decomposition. Decomposition of LiBH4 under vacuum to 600 °C produces LiH and amorphous B with some Li dissolved within it. The lack of an obvious B-Li-B or B-H-B bridging band in the FTIR data for Li2B12H(12-x) suggests the H poor B12H(12-x) pseudo-icosahedra remain isolated and are not polymerized. Li2B12H(12-x) is persistent to at least 600 °C under vacuum, with no LiH formation observable and only a ca. d = 7.00 Å halo remaining. By 650 °C, Li2B12H(12-x) is finally decomposed, and amorphous B can be observed, with no LiH reflections. Further studies are required to clarify the structural symmetry of the β- and γ-Li2B12H12 polymorphs and substoichiometric Li2B12H(12-x).