22 results on '"Ihor Z. Hlova"'
Search Results
2. A New Complex Borohydride LiAl(BH4)2Cl2
- Author
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Oleksandr Dolotko, Takeshi Kobayashi, Ihor Z. Hlova, Shalabh Gupta, and Vitalij K. Pecharsky
- Subjects
hydrides ,X-ray diffraction ,crystal structure ,solid-state NMR ,hydrogen storage ,Inorganic chemistry ,QD146-197 - Abstract
A new mixed alkali metal–aluminum borohydride LiAl(BH4)2Cl2 has been prepared via mechanochemical synthesis from the 2LiBH4–AlCl3 mixture. Structural characterization, performed using a combination of X-ray powder diffraction and solid-state NMR methods, indicates that the LiAl(BH4)2Cl2 phase adopts a unique 3D framework and crystallizes in an orthorhombic structure with the space group C2221, a = 11.6709(6) Å, b = 8.4718(4) Å, c = 7.5114(3) Å. The material shows excellent dehydrogenation characteristics, where hydrogen evolution starts at Tons = 70 °C, releasing approximately 2 wt.% of nearly pure (99.8 vol.%) hydrogen and a very small amount (~0.2 vol.%) of diborane. When compared to halide-free mixed alkali metal–aluminum borohydrides, the presence of Al‒Cl bonding in the LiAl(BH4)2Cl2 structure likely prevents the formation of Al(BH4)3 upon decomposition, thus suppressing the formation of diborane.
- Published
- 2021
- Full Text
- View/download PDF
3. Unusual first-order magnetic phase transition and large magnetocaloric effect in Nd2In
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Anis Biswas, Rajiv K. Chouhan, Alex Thayer, Yaroslav Mudryk, Ihor Z. Hlova, Oleksandr Dolotko, and Vitalij K. Pecharsky
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Physics and Astronomy (miscellaneous) ,General Materials Science - Published
- 2022
4. Depolymerization of polystyrene under ambient conditions
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Scott L. Carnahan, Mastooreh Seyedi, Aaron J. Rossini, Ihor Z. Hlova, Igor Luzinov, Oleksandr Dolotko, and Viktor P. Balema
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Depolymerization ,General Chemistry ,Photochemistry ,Catalysis ,law.invention ,Styrene ,Metal ,chemistry.chemical_compound ,Monomer ,chemistry ,law ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Addition polymer ,Polystyrene ,Electron paramagnetic resonance ,Bond cleavage - Abstract
Depolymerization of the addition polymer polystyrene to monomeric styrene is facilitated by mechanochemical processing at room temperature under ambient atmosphere. The reaction occurs in metal-based milling media in concert with scission of macromolecular chains that generates carbon-centered free-radicals detectable by EPR spectroscopy, even though the processing is performed in air.
- Published
- 2021
5. Incommensurate transition-metal dichalcogenides via mechanochemical reshuffling of binary precursors
- Author
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Raymundo Arroyave, Roman V. Gamernyk, Viktor P. Balema, Vitalij K. Pecharsky, Arjun K. Pathak, Ihor Z. Hlova, Duane D. Johnson, Oleksandr Dolotko, Prashant Singh, and Serhiy Z. Malynych
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Materials science ,Condensed matter physics ,General Engineering ,Binary number ,Bioengineering ,Heterojunction ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Transition metal ,Homogeneous ,General Materials Science ,Direct and indirect band gaps ,Density functional theory ,0210 nano-technology ,Joint (geology) - Abstract
A new family of heterostructured transition-metal dichalcogenides (TMDCs) with incommensurate (“misfit”) spatial arrangements of well-defined layers was prepared from structurally dissimilar single-phase 2H-MoS2 and 1T-HfS2 materials. The experimentally observed heterostructuring is energetically favorable over the formation of homogeneous multi-principle element dichalcogenides observed in related dichalcogenide systems of Mo, W, and Ta. The resulting three-dimensional (3D) heterostructures show semiconducting behavior with an indirect band gap around 1 eV, agreeing with values predicted from density functional theory. Results of this joint experimental and theoretical study open new avenues for generating unexplored metal-dichalcogenide heteroassemblies with incommensurate structures and tunable physical properties.
- Published
- 2021
6. Unprecedented generation of 3D heterostructures by mechanochemical disassembly and re-ordering of incommensurate metal chalcogenides
- Author
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Scott L. Carnahan, Arjun K. Pathak, Prashant Singh, Vitalij K. Pecharsky, Viktor P. Balema, Yaroslav Mudryk, Ihor Z. Hlova, Oleksandr Dolotko, Lin Zhou, Aaron J. Rossini, Emily A. Smith, Ely M. Eastman, Jingzhe Li, Brett W. Boote, and Duane D. Johnson
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Chemical process ,Materials science ,Annealing (metallurgy) ,Metal chalcogenides ,Science ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,Condensed Matter::Materials Science ,Nanoscience and technology ,Monolayer ,lcsh:Science ,Alternative methods ,Multidisciplinary ,Synthesis and processing ,Heterojunction ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,0104 chemical sciences ,lcsh:Q ,0210 nano-technology - Abstract
Three-dimensional heterostructures are usually created either by assembling two-dimensional building blocks into hierarchical architectures or using stepwise chemical processes that sequentially deposit individual monolayers. Both approaches suffer from a number of issues, including lack of suitable precursors, limited reproducibility, and poor scalability of the preparation protocols. Therefore, development of alternative methods that enable preparation of heterostructured materials is desired. We create heterostructures with incommensurate arrangements of well-defined building blocks using a synthetic approach that comprises mechanical disassembly and simultaneous reordering of layered transition-metal dichalcogenides, MX2, and non-layered monochalcogenides, REX, where M = Ta, Nb, RE = Sm, La, and X = S, Se. We show that the discovered solid-state processes are rooted in stochastic mechanochemical transformations directed by electronic interaction between chemically and structurally dissimilar solids toward atomic-scale ordering, and offer an alternative to conventional heterostructuring. Details of composition–structure–properties relationships in the studied materials are also highlighted., 3D heterostructures offer properties that are inaccessible in bulk single-phase solids, but synthetic approaches are limited. The authors use mechanochemical reshuffling of binary precursors and subsequent annealing to design structurally aligned misfit heterostructures with well-defined atomic arrangements.
- Published
- 2020
7. Mechanochemical synthesis, luminescent and magnetic properties of lanthanide benzene-1,4-dicarboxylate coordination polymers (Ln0.5Gd0.5)2 (1,4-BDC)3(H2O)4; Ln = Sm, Eu, Tb
- Author
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Vitalij K. Pecharsky, Tao Ma, Viktor P. Balema, Anja-Verena Mudring, Lin Zhou, Ihor Z. Hlova, Anis Biswas, Shalabh Gupta, and Tarek Alammar
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Lanthanide ,Paramagnetism ,Crystallography ,Chemistry ,Ligand ,Yield (chemistry) ,Materials Chemistry ,Infrared spectroscopy ,Quantum yield ,General Chemistry ,Isostructural ,Luminescence ,Catalysis - Abstract
Mechanochemical reactions of benzene-1,4-dicarboxylate (BDC2−) and lanthanide carbonates, Ln2(CO3)3·xH2O (Ln = Sm, Eu, Gd, Tb) yield phase pure lanthanide coordination polymers, (Ln0.5Gd0.5)2(1,4-BDC)3(H2O)4 with Ln = Sm, Eu, Tb, which are isostructural with Tb2(1,4-BDC)3(H2O)4 as confirmed by powder X-ray diffraction and vibrational spectroscopy. Upon excitation with UV light all three compounds display strong emissions, characteristic for the respective optically active lanthanide ion, namely, red for Eu3+, green for Tb3+ and orange-red for Sm3+. In case of the Tb3+-containing compound, the energy difference between the triplet energy level of benzene-1,4-dicarboxylate ligand (BDC2−) allows for the most efficient BDC2−–Tb3+ energy transfer. As a consequence, an intense green luminescence with rather long lifetime (0.81 ms) and high quantum yield (22%) is observed after allowed excitation of the BDC2− ligand. The compounds are paramagnetic with no onset of long range magnetic ordering down to liquid He temperatures.
- Published
- 2020
8. A New Complex Borohydride LiAl(BH4)2Cl2
- Author
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Takeshi Kobayashi, Vitalij K. Pecharsky, Shalabh Gupta, Ihor Z. Hlova, and Oleksandr Dolotko
- Subjects
crystal structure ,Materials science ,hydrides ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Borohydride ,01 natural sciences ,0104 chemical sciences ,X-ray diffraction ,hydrogen storage ,chemistry.chemical_compound ,Hydrogen storage ,Crystallography ,chemistry ,X-ray crystallography ,solid-state NMR ,Dehydrogenation ,Orthorhombic crystal system ,0210 nano-technology ,Powder diffraction ,Inorganic chemistry ,Diborane ,QD146-197 - Abstract
A new mixed alkali metal–aluminum borohydride LiAl(BH4)2Cl2 has been prepared via mechanochemical synthesis from the 2LiBH4–AlCl3 mixture. Structural characterization, performed using a combination of X-ray powder diffraction and solid-state NMR methods, indicates that the LiAl(BH4)2Cl2 phase adopts a unique 3D framework and crystallizes in an orthorhombic structure with the space group C2221, a = 11.6709(6) Å, b = 8.4718(4) Å, c = 7.5114(3) Å. The material shows excellent dehydrogenation characteristics, where hydrogen evolution starts at Tons = 70 °C, releasing approximately 2 wt.% of nearly pure (99.8 vol.%) hydrogen and a very small amount (~0.2 vol.%) of diborane. When compared to halide-free mixed alkali metal–aluminum borohydrides, the presence of Al‒Cl bonding in the LiAl(BH4)2Cl2 structure likely prevents the formation of Al(BH4)3 upon decomposition, thus suppressing the formation of diborane.
- Published
- 2021
- Full Text
- View/download PDF
9. Mechanochemical reactions and hydrogen storage capacities in MBH4–SiS2 systems (M Li or Na)
- Author
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Ihor Z. Hlova, Eric McDonald, Eric H. Majzoub, Oleksandr Dolotko, Vitalij K. Pecharsky, Viktor P. Balema, Takeshi Kobayashi, Shalabh Gupta, and Marek Pruski
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,Sorption ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Amorphous solid ,Hydrogen storage ,chemistry.chemical_compound ,Fuel Technology ,Solid-state nuclear magnetic resonance ,chemistry ,Mechanochemistry ,Desorption ,Physical chemistry ,Dehydrogenation ,0210 nano-technology ,Diborane - Abstract
The hydrogen storage properties, and phase compositions of mechanochemically prepared mixtures of xMBH4-SiS2 (x = 2–8), where M = Li or Na, were investigated using gas sorption analysis, powder X-ray diffraction, and infrared and solid-state NMR spectroscopic methods. The 2LiBH4:1SiS2 system forms an amorphous product that releases ca. 4.3 wt % of H2 below 385 °C with a Tonset of 88 °C without detectable diborane emission. The dehydrogenated sample reversibly absorbs 1.5 wt % of H2 at 385 °C under 160 bar pressure. The H2 release from materials with varying LiBH4:SiS2 ratios peaks at 8.2 wt % for the 6LiBH4:1SiS2 composition, with a reversible hydrogen storage capacity of 2.4 wt %. The H2 desorption capacities of the Li-containing systems surpass those of Na-containing systems. Solid-state NMR studies indicate that products of mechanochemical reactions in the LiBH4 SiS2 system consist of one-dimensional chains of edge-sharing SiS4/2 tetrahedra in which the non-bridging S-ends are terminated with Li+, which are further coordinated to the [BH4]− anions. A variety of possible polymorphs in the Li Si S-(BH4) composition space have been identified using first principles and thermodynamic modeling that supports the likelihood of formation of such novel complexes.
- Published
- 2019
10. Incommensurate transition-metal dichalcogenides
- Author
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Ihor Z, Hlova, Prashant, Singh, Serhiy Z, Malynych, Roman V, Gamernyk, Oleksandr, Dolotko, Vitalij K, Pecharsky, Duane D, Johnson, Raymundo, Arroyave, Arjun K, Pathak, and Viktor P, Balema
- Abstract
A new family of heterostructured transition-metal dichalcogenides (TMDCs) with incommensurate ("misfit") spatial arrangements of well-defined layers was prepared from structurally dissimilar single-phase 2H-MoS
- Published
- 2021
11. Luminescence properties of mechanochemically synthesized lanthanide containing MIL-78 MOFs
- Author
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Ihor Z. Hlova, Tarek Alammar, Anja-Verena Mudring, Viktor P. Balema, Vitalij K. Pecharsky, and Shalabh Gupta
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Lanthanide ,Materials science ,Ligand ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Resonance (chemistry) ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Excited state ,Physical chemistry ,Trimesic acid ,Triplet state ,0210 nano-technology ,Luminescence - Abstract
Three metal-organic framework (MOF) compounds, Ln0.5Gd0.5{C6H3(COO)3}; Ln = Eu, Tb, and Dy with a MIL-78 structure, have been synthesized by a solvent-free mechanochemical method from stoichiometric mixtures of benzene 1,3,5-tricarboxylic acid, C6H3(COOH)3, also known as trimesic acid, and the respective lanthanide carbonates, Ln2(CO3)3·xH2O, Ln = Eu, Gd, Tb and Dy. MIL-78 (Ln0.5Gd0.5) shows the characteristic red, green, and yellow luminescence of Eu3+, Tb3+, and Dy3+, respectively. Efficient intramolecular energy transfer from the ligand triplet state to the excited states of Ln3+ ions can be observed. The lifetimes and quantum yields of these compounds are studied and discussed in detail. Among the three compounds, the Tb3+ containing compound shows the longest lifetime and highest quantum yield due to a smaller contribution from non-radiative decay pathways and better matching of the lowest triplet energy level of the benzenetricarboxylate ligand and the resonance level of Tb3+.
- Published
- 2018
12. A benign synthesis of alane by the composition-controlled mechanochemical reaction of sodium hydride and aluminum chloride
- Author
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Takeshi Kobayashi, Marek Pruski, Vitalij K. Pecharsky, Shalabh Gupta, Ihor Z. Hlova, and Jennifer F. Goldston
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integumentary system ,Mechanical Engineering ,Inorganic chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Decomposition ,Chloride ,0104 chemical sciences ,Sodium hydride ,Hydrogen storage ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Mechanochemistry ,Yield (chemistry) ,medicine ,General Materials Science ,0210 nano-technology ,Selectivity ,Stoichiometry ,medicine.drug - Abstract
Solid-state mechanochemical synthesis of alane (AlH3) starting from sodium hydride (NaH) and aluminum chloride (AlCl3) has been achieved at room temperature. The transformation pathway of this solid-state reaction was controlled by a stepwise addition of AlCl3 to the initial reaction mixture that contained sodium hydride in excess of stoichiometric amount. As in the case of previously investigated LiH–AlCl3 system, complete selectivity was achieved whereby formation of unwanted elemental aluminum was fully suppressed, and AlH3 was obtained in quantitative yield. Reaction progress during each step was investigated by means of solid-state NMR and powder X-ray diffraction, which revealed that the overall reaction proceeds through a series of intermediate alanates that may be partially chlorinated. The NaH–AlCl3 system presents some subtle differences compared to LiH–AlCl3 system particularly with respect to optimal concentrations needed during one of the reaction stages. Based on the results, we postulate that high local concentrations of NaH may stabilize chlorine-containing derivatives and prevent decomposition into elemental aluminum with hydrogen evolution. Complete conversion with quantitative yield of alane was confirmed by both SSNMR and hydrogen desorption analysis.
- Published
- 2017
13. Correction: Depolymerization of polystyrene under ambient conditions
- Author
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Ihor Z. Hlova, Aaron J. Rossini, Scott L. Carnahan, Viktor P. Balema, Oleksandr Dolotko, Mastooreh Seyedi, and Igor Luzinov
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chemistry.chemical_compound ,Chemical engineering ,Chemistry ,Depolymerization ,Materials Chemistry ,General Chemistry ,Polystyrene ,Catalysis - Abstract
Correction for ‘Depolymerization of polystyrene under ambient conditions’ by Viktor P. Balema et al., New J. Chem., 2021, 45, 2935–2938, DOI: 10.1039/D0NJ05984F.
- Published
- 2021
14. Solvent- and catalyst-free mechanochemical synthesis of alkali metal monohydrides
- Author
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Vitalij K. Pecharsky, Timothy E. Prost, Andra Castle, Takeshi Kobayashi, Marek Pruski, Ihor Z. Hlova, Shalabh Gupta, Jennifer F. Goldston, and L. Scott Chumbley
- Subjects
Alkaline earth metal ,Materials science ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,Hydride ,Continuous reactor ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Alkali metal ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Metal ,chemistry ,visual_art ,visual_art.visual_art_medium ,General Materials Science ,Cold welding ,0210 nano-technology - Abstract
Alkali metal monohydrides, AH (A = Li–Cs) have been synthesized in quantitative yields at room temperature by reactive milling of alkali metals in the presence of hydrogen gas at 200 bar or less. The mechanochemical approach reported here eliminates problems associated with the malleability of alkali metals — especially Li, Na, and K — and promotes effective solid–gas reactions, ensuring their completion. This is achieved by incorporating a certain volume fraction of the corresponding hydride powder as a process control agent, which allows continuous and efficient milling primarily by coating the surface of metal particles, effectively blocking cold welding. Formation of high-purity crystalline monohydrides has been confirmed by powder X-ray diffraction, solid-state NMR spectroscopy, and volumetric analyses of reactively desorbed H2 from as-milled samples. The proposed synthesis method is scalable and particularly effective for extremely air-sensitive materials, such as alkali and alkaline earth metal hydrides. The technique may also be favorable for production in continuous reactors operating at room temperature, thereby reducing the total processing time, energy consumption and, hence, the cost of production of these hydrides or their derivatives and composites.
- Published
- 2016
15. Mechanochemical recovery of Co and Li from LCO cathode of lithium-ion battery
- Author
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Yaroslav Mudryk, Ihor Z. Hlova, Viktor P. Balema, Shalabh Gupta, and Oleksandr Dolotko
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Battery (electricity) ,Chemical substance ,Materials science ,Mechanical Engineering ,Metals and Alloys ,Magnetic separation ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cathode ,Lithium-ion battery ,0104 chemical sciences ,law.invention ,Chemical engineering ,chemistry ,Mechanics of Materials ,law ,Reagent ,Materials Chemistry ,Lithium ,0210 nano-technology ,Ball mill - Abstract
Increasing demand for lithium-ion batteries (LIBs) that serve as power source for diverse electronic devices, electrical propulsion systems and other applications, calls for economical and environmentally benign recycling of spent LIBs and recovery of critical elements such as Co and Li from rapidly growing volumes of battery wastes. The presented study explores mechanochemical extraction of Co and Li from lithium cobaltate (LiCoO2), which serves as cathode material in commercial LIBs. Our investigation reveals that solvent-free mechanochemical processing can successfully convert pure, reagent grade LiCoO2 into metallic Co and Li-derivatives that are suitable for the further recovery of Li. We also show that the proposed approach can be successfully applied to reclaiming these critical elements from commercial LIBs. Due to its magnetic nature, metallic Co is easy to separate from non-magnetic components of mechanochemically generated powder mixtures using an appropriate magnetic separation technique, while Li can be reclaimed as Li2CO3 after an additional liquid-phase processing. The recovery rates achieved during our experiments with pure LiCoO2 are ∼90% for Co and ∼70% for Li.
- Published
- 2020
16. Multi-principal element transition metal dichalcogenides via reactive fusion of 3D-heterostructures
- Author
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Vitalij K. Pecharsky, Arjun K. Pathak, Emily A. Smith, Viktor P. Balema, Oleksandr Dolotko, Ihor Z. Hlova, and Brett W. Boote
- Subjects
Fusion ,Reaction mechanism ,Materials science ,Metals and Alloys ,Heterojunction ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Exfoliation joint ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Chemical engineering ,Transition metal ,Materials Chemistry ,Ceramics and Composites ,Principal element ,0210 nano-technology - Abstract
Transition metal dichalcogenides combining multiple principal elements in their structures are synthesized via mechanochemical exfoliation and spontaneous reassembly of binary precursors into 3D-heterostructures that are converted into single-phase layered materials by high-temperature reactive fusion. Physical and chemical events enabling these transformations are summarized in the form of a conceivable reaction mechanism.
- Published
- 2018
17. Mechanochemical synthesis of hydrogen-storage materials based on aluminum, magnesium and their compounds
- Author
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Ihor Z. Hlova
- Subjects
Hydrogen storage ,Materials science ,chemistry ,Hydrogen ,Chemical engineering ,Hydride ,Magnesium ,Desorption ,Metallurgy ,chemistry.chemical_element ,Gravimetric analysis ,Halide ,Ball mill - Abstract
Over the last few decades, interest in hydrogen-storage materials as an alternative high-efficiency and safe, green energy carriers is steadily increasing. Among numerous hydrides scrutinized for the purpose over the past 10-15 years, aluminumand magnesiumbased systems attract continued attention, mainly because of their high gravimetric capacity and low cost. However, difficulties associated with facile synthesis and hence the reversibility, relatively high desorption temperatures, and sluggish kinetics in many of these systems are still of great concern and hold them back from broad, large-scale applications, e.g. in automotive industry. Our research was devoted to studies of mechanochemical activation and synthesis of nanostructured hydride systems of aluminum and magnesium by solid-state mechanical milling techniques. The structural and desorption properties of milled powders were examined by powder X-ray diffraction (XRD), solid-state nuclear magnetic resonance (NMR) spectroscopy and desorption analysis in a Sieverts-type apparatus. The primary focus of this study was to investigate a number of aluminum-based hydride systems to develop advanced synthesis procedures for AlH3 (alane) using solventfree solid-state mechanical milling under moderate hydrogen pressures at room temperature. The findings reported in this dissertation, may provide the much needed basic scientific insight necessary for the development of an approach for direct mechanochemical hydrogenation of metallic aluminum which still remains elusive despite numerous efforts worldwide. Here, we have demonstrated a mechanochemical approach for synthesis of alane via metathesis reactions between hydride sources and aluminum halides. Reaction pathways
- Published
- 2018
18. Solvent-free mechanochemical synthesis of alane, AlH3: effect of pressure on the reaction pathway
- Author
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Vitalij K. Pecharsky, Marek Pruski, Jennifer F. Goldston, Ihor Z. Hlova, Shalbh Gupta, and Takeshi Kobayashi
- Subjects
Aluminium chloride ,Argon ,Hydrogen ,Thermal desorption spectroscopy ,Metallurgy ,Analytical chemistry ,chemistry.chemical_element ,Lithium aluminium hydride ,Pollution ,chemistry.chemical_compound ,chemistry ,Aluminium ,medicine ,Environmental Chemistry ,Inert gas ,Bar (unit) ,medicine.drug - Abstract
Nearly quantitative mechanochemical synthesis of non-solvated AlH3 from lithium aluminium hydride (LiAlH4) and aluminium chloride (AlCl3) has been achieved at room temperature under reasonably low pressure of hydrogen (210 bar) or inert gas (125 bar for He or 90 bar for Ar). X-ray diffraction, solid-state 27Al NMR spectroscopy, and temperature programmed desorption analyses of as-milled materials reveal a nearly complete conversion of a 3 : 1 (molar) mixture of LiAlH4 and AlCl3 to a 4 : 3 (molar) mixture of AlH3 and LiCl in ca. 30 min. By applying pressure of 210 bar or less (depending on the gas: hydrogen, helium, or argon), competing reactions leading to formation of metallic aluminium can be completely suppressed. X-ray diffraction and NMR analyses of products extracted at various stages of the mechanochemical reaction between LiAlH4 and AlCl3 reveal, for the first time, that the solid-state transformation proceeds with LiAlCl4 as an intermediate. Evidently, the critical pressure required to suppress the formation of metallic aluminium depends on the rate at which mechanical energy is supplied during milling. For example, the critical pressure is reduced from 210 bar to 1 bar of hydrogen when the milling speed of a standard planetary mill is reduced from 300 rpm to 150 rpm, although at the expense of sluggish kinetics and much longer reaction time.
- Published
- 2014
19. Dry mechanochemical synthesis of alane from LiH and AlCl3
- Author
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Takeshi Kobayashi, Vitalij K. Pecharsky, Marek Pruski, Shalabh Gupta, Jennifer F. Goldston, and Ihor Z. Hlova
- Subjects
Aluminium chloride ,Thermal desorption spectroscopy ,Inorganic chemistry ,chemistry.chemical_element ,Reaction intermediate ,Metal ,chemistry.chemical_compound ,chemistry ,Aluminium ,Lithium hydride ,visual_art ,visual_art.visual_art_medium ,medicine ,Physical and Theoretical Chemistry ,Diethyl ether ,Stoichiometry ,medicine.drug - Abstract
A mechanochemical process for the synthesis of alane (AlH3) starting from lithium hydride (LiH) and aluminium chloride (AlCl3) at room temperature and the underlying reaction pathway have been studied. In contrast to a conventional process using the same two reactants dissolved in diethyl ether, our approach enables a solvent-free synthesis, thereby directly leading to adduct-free alane. The method described here is quick and efficient, resulting in the quantitative conversion of all aluminium in the starting mixture to alane. Both the intermediate compounds formed during the reaction and the final products have been characterized by powder X-ray diffraction, solid-state27Al NMR spectroscopy, and temperature programmed desorption analysis of the as-milled mixtures. We show that excess LiH in the starting mixture (with an optimal ratio of 9LiH : 1AlCl3) is essential for the formation and stability of Al–H bonds, initially in the form of alanates and, eventually, as alane. Further processing of this mixture, gradually adding AlCl3to reach the ideal 3LiH : 1AlCl3stoichiometry, appears to restrict the local accumulation of AlCl3during the ball-milling process, thereby preventing the formation of unstable intermediates that decompose to metallic Al and molecular hydrogen. We also demonstrate that under the milling conditions used, a moderate hydrogen pressure ofca.300 bar is required to suppress competing reactions that lead to the formation of metallic Al at room temperature. The identification of the reaction intermediates at each stage of the synthesis provides significant insight into the mechanism of this solid-state reaction, which may potentially afford a more rational approach toward the production of AlH3in a simple solvent-free process.
- Published
- 2014
20. Solid-State NMR Study of Li-Assisted Dehydrogenation of Ammonia Borane
- Author
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Marek Pruski, Niraj K. Singh, Ihor Z. Hlova, Takeshi Kobayashi, and Vitalij K. Pecharsky
- Subjects
Reaction mechanism ,Hydrogen ,Inorganic chemistry ,Ammonia borane ,chemistry.chemical_element ,Nuclear magnetic resonance spectroscopy ,Inorganic Chemistry ,Hydrogen storage ,chemistry.chemical_compound ,chemistry ,Solid-state nuclear magnetic resonance ,Lithium ,Dehydrogenation ,Physical and Theoretical Chemistry - Abstract
The mechanism of thermochemical dehydrogenation of the 1:3 mixture of Li(3)AlH(6) and NH(3)BH(3) (AB) has been studied by the extensive use of solid-state NMR spectroscopy and theoretical calculations. The activation energy for the dehydrogenation is estimated to be 110 kJ mol(-1), which is lower than for pristine AB (184 kJ mol(-1)). The major hydrogen release from the mixture occurs at 60 and 72 °C, which compares favorably with pristine AB and related hydrogen storage materials, such as lithium amidoborane (LiNH(2)BH(3), LiAB). The NMR studies suggest that Li(3)AlH(6) improves the dehydrogenation kinetics of AB by forming an intermediate compound (LiAB)(x)(AB)(1-x). A part of AB in the mixture transforms into LiAB to form this intermediate, which accelerates the subsequent formation of branched polyaminoborane species and further release of hydrogen. The detailed reaction mechanism, in particular the role of lithium, revealed in the present study highlights new opportunities for using ammonia borane and its derivatives as hydrogen storage materials.
- Published
- 2012
21. ChemInform Abstract: Facile Synthesis and Regeneration of Mg(BH4)2by High Energy Reactive Ball Milling of MgB2
- Author
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Fu Chen, Vitalij K. Pecharsky, Ihor Zavaliy, Marek Pruski, Ihor Z. Hlova, Takeshi Kobayashi, Shalabh Gupta, and Roman V. Denys
- Subjects
chemistry.chemical_compound ,Hydrogen storage ,chemistry ,Chemical engineering ,Magnesium ,chemistry.chemical_element ,General Medicine ,Borane ,Borohydride ,Ball mill ,Isothermal process ,Ion ,Bar (unit) - Abstract
We report direct hydrogenation of MgB2 in a planetary ball mill. Magnesium borohydride, Mg(BH4)2, and various polyhedral borane anion salts have been synthesized at pressures between 50 and 350 bar H2 without the need for subsequent isothermal hydrogenation at elevated temperature and pressure. The obtained products release ∼4 wt% H2 below 390 °C, and a major portion of Mg(BH4)2 transforms back to MgB2 at around 300 °C, demonstrating the possibility of reversible hydrogen storage in an Mg(BH4)2–MgB2 system.
- Published
- 2013
22. Facile synthesis and regeneration of Mg(BH4)2 by high energy reactive ball milling of MgB2
- Author
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Roman V. Denys, Fu Chen, Ihor Z. Hlova, Marek Pruski, Vitalij K. Pecharsky, Shalabh Gupta, Ihor Zavaliy, and Takeshi Kobayashi
- Subjects
Materials science ,Magnesium ,Metallurgy ,Metals and Alloys ,chemistry.chemical_element ,General Chemistry ,Borane ,Borohydride ,Catalysis ,Isothermal process ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,chemistry.chemical_compound ,Hydrogen storage ,chemistry ,Chemical engineering ,Materials Chemistry ,Ceramics and Composites ,Ball mill ,Bar (unit) - Abstract
We report direct hydrogenation of MgB(2) in a planetary ball mill. Magnesium borohydride, Mg(BH(4))(2), and various polyhedral borane anion salts have been synthesized at pressures between 50 and 350 bar H(2) without the need for subsequent isothermal hydrogenation at elevated temperature and pressure. The obtained products release ∼4 wt% H(2) below 390 °C, and a major portion of Mg(BH(4))(2) transforms back to MgB(2) at around 300 °C, demonstrating the possibility of reversible hydrogen storage in an Mg(BH(4))(2)-MgB(2) system.
- Published
- 2012
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