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Wang H.,South China University of Technology | Zhong H.,Xiamen University of Technology | Ouyang L.,South China University of Technology | Liu J.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | And 3 more authors.
Journal of Physical Chemistry C | Year: 2014

This paper presents a new approach to tune the de/hydriding thermodynamic properties of Mg via forming reversible Mg base solid solutions in the Mg-In and Mg-In-Al systems by mechanical milling. The effect of solubility of In and Al on the reversible formation of solid solution structure and hydrogen storage properties were investigated. It is found that although the solute atoms unavoidably are rejected upon hydriding, the hydrogenated products of MgH 2 and intermediate MgIn compound could fully transform back to solid solution after dehydrogenation. In the hydriding of Mg(In, Al) ternary solid solution, Al would get dissolved into MgIn compound rather than forming free Al like the Mg(Al) binary solid solution. Therefore, the presence of In improves the dehydriding reversibility of Mg(Al) solid solution, and the reversible Al concentration could be increased up to the 8 at. %, which is just the solubility limit of Al in Mg by mechanical milling. The reversible phase transformation is responsible for the reduction in the desorption enthalpy of MgH2, being 12 kJ/(mol·H2) reduction for the alloy Mg 0.9In0.1 relative to the desorption enthalpy of pure MgH2. Further, the hydrogen sorption kinetics of Mg(In) solid solutions are enhanced. Comparatively, both the thermodynamic destabilizing effect and the kinetic enhancing effect due to the Al dissolving are inferior to those due to the In dissolving. This work demonstrates a feasible way to improve the thermodynamics and kinetics of Mg base hydrogen storage alloys through traditional metallurgical method. © 2014 American Chemical Society.


Cai W.,South China University of Technology | Cai W.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Wang H.,South China University of Technology | Wang H.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | And 3 more authors.
Journal of Physical Chemistry C | Year: 2013

A reversible reaction, 4LiBH4 + NdH2NdB4 + 4LiH + 7H2, which destabilizes the dehydrogenation thermodynamics of LiBH4, has been found in the present work. Significantly, we prove that the reversibility only exists when NdH2+x is in size of less than about 10 nm. With this reaction, the estimated dehydrogenation enthalpy change is reduced from 74 kJ mol-1 H2 for pristine LiBH4 to 64 kJ mol-1 H2; the theoretical hydrogen capacity is 6.0 wt %, and there is no emission of deleterious BH 3 and B2H6. Moreover, the dehydrogenation kinetics of this reaction are fast - 6.0 wt % hydrogen was released within 1.5 h at 370 C. When the NdH2+x becomes stable owing to its significant growth, the thermodynamic destabilization effect does not occur after several hydrogenation/dehydrogenation cycles. However, the presence of NdH2+x also has a positive effect upon the dehydrogenation kinetics of LiBH 4. This novel finding is beneficial for modifying the reversibility of the reactive hydride composite systems through nanosize controlling. © 2013 American Chemical Society.


Cai W.,South China University of Technology | Cai W.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Wang H.,South China University of Technology | Wang H.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | And 5 more authors.
RSC Advances | Year: 2014

Destabilization by the alkali metal hydroxides LiOH, NaOH, and KOH in the solid-state dehydrogenation of LiBH4 is reported. 6.5 wt% of hydrogen was liberated within 10 minutes at 250 °C. Destabilization originated from the interaction between H+ in [OH]- and H- in [BH4]-. A larger Pauling's electronegativity of the alkali metal (Li > Na > K) led to a greater acidity of the proton donor [OH]- site, and thus enhanced destabilization. The temperature of the predominant dehydrogenation was reduced to 207, 221, and 230 °C, for ball milled LiBH4-LiOH, 2LiBH4-NaOH, and 2LiBH4-KOH, respectively. The LiBH4: LiOH stoichiometry greatly affected the destabilization, by providing differing reaction pathways in LiBH 4-xLiOH (x = 1, 1.36, 4). The incremental increase in the LiOH content of LiBH4-xLiOH increased the dehydrogenation rate, but the temperature increased from 207 °C (x = 1) to 250 °C (x = 4). 4.1 and 6.5 wt% of hydrogen was liberated within 10 minutes by LiBH4-LiOH and LiBH4-4LiOH, respectively. The incremental increase in dehydrogenation temperature was attributed to differing [BH4] -⋯[OH]- interactions, formed by the differing stoichiometric ratios. © 2014 The Royal Society of Chemistry.


Liao J.-H.,South China University of Technology | Zhao Y.-J.,South China University of Technology | Zhao Y.-J.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Tang J.-J.,Kansas State University | And 3 more authors.
Physical Chemistry Chemical Physics | Year: 2016

Alkali-metal intercalated graphite and graphene have been intensively studied for decades, where alkali-metal atoms are found to form ordered structures at the hollow sites of hexagonal carbon rings. Using first-principles calculations, we have predicted various stable structures of high-coverage 3d transition metal (TM) intercalated bilayer graphene (BLG) stabilized by the strain. Specifically, with reference to the bulk metal, Sc and Ti can form stable TM-intercalated BLG without strain, while the stabilization of Fe, Co, and Ni intercalated BLG requires the biaxial strain of over 7%. Under the biaxial strain ranging from 0% to 10%, there are four ordered sandwich structures for Sc with the coverage of 0.25, 0.571, 0.684, and 0.75, in which the Sc atoms are all distributed homogenously instead of locating at the hollow sites. According to the phase diagram, a homogenous configuration of C8Ti3C8 with the coverage of 0.75 and another inhomogeneous structure with the coverage of 0.692 were found. The electronic and magnetic properties as a function of strain were also analyzed to indicate that the strain was important for the stabilities of the high-coverage TM-intercalated BLG. © 2016 the Owner Societies.


Liao J.-H.,South China University of Technology | Zhao Y.-J.,South China University of Technology | Zhao Y.-J.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Yang X.-B.,South China University of Technology | Yang X.-B.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province
International Journal of Hydrogen Energy | Year: 2015

Hydrogen storage with Ti decorated nano-materials is attributed to the d levels of Ti with unsaturated bonding, whose configuration significantly affects the system's stability and activity. Using first-principles calculations, we have investigated hydrogen adsorption and desorption on the Ti decorated defective graphene under various strains (from 0% to 15%), in which Ti atoms' dispersing are energetically stable. According to the phase diagram, we showed that hydrogen uptake can be modulated as a function of chemical potential and strain, since the strain modifies the configuration of d levels, and consequently affects the binding between H2 and Ti atom. Remarkably, Ti decorated defective graphene under 15% strain could be considered as an ideal media of hydrogen storage, in which the desorption temperature of H2 is expected to be ∼300 K at 0.5 atm. The control of strain is found to be dominant to the H2 uptake, besides the temperature and pressure. © 2015 Hydrogen Energy Publications, LLC.


Fan Q.H.,South China University of Technology | Zhao Y.M.,South China University of Technology | Zhao Y.M.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Li D.D.,South China University of Technology
Ceramics International | Year: 2013

Lanthanum hexaboride (LaB6) nanowires have been successfully fabricated by the facile catalytic reaction of lanthanum (La) powders, and gas mixture of boron trichloride (BCl3), hydrogen and argon, where Au was used as the catalyst. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED) were used to characterize the composition, morphology and structure of the samples. Single crystal column-shape LaB6 nanowires were obtained. It is expected that LaB6 nanowires can provide thermionic emission, field-induced emission, and thermal field-induced emission of electrons for TEM, SEM, flat panel displays, as well as many electronic devices that require high-performance electron source. © 2013 Elsevier Ltd and Techna Group S.r.l.


Yuan B.,South China University of Technology | Yuan B.,Northwestern University | Yuan B.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Zheng P.,Northwestern University | And 5 more authors.
Materials and Design | Year: 2015

Strain incompatibilities between grains in polycrystalline Cu-Al-Ni shape-memory alloys undergoing stress-induced reversible transformation reduce their ductility and their recoverable superelastic strains on unloading. These strain incompatibilities can be mitigated by creation of large, textured grains through directional solidification or large, bamboo grains intersecting the free surfaces of pores. To study these two approaches to improve superelasticity in Cu-Al-Ni alloys, polycrystalline Cu-13.5Al-4Ni (wt.%) samples were cast in porous and dense form, with and without directional solidification. When tested in compression, directionally-solidified, oligocrystalline bulk (non-porous) Cu-Al-Ni exhibits recoverable unloading strains as high as 6.6% at 210. °C, as compared to 3.1% for their conventionally-solidified counterparts. Similarly, when comparing conventionally-solidified Cu-Al-Ni SMA with 58% open porosity shows 1.4% recoverable unloading strain at 260. °C, whereas a value of 2.6% is achieved in directionally-solidified porous samples with bamboo grains straddling pores. This improvement in superelasticity remains present after 30 mechanical load-unload cycles at 260. °C. Thus, both directional solidification and addition of porosity can reduce strain incompatibilities between neighboring grains in polycrystalline Cu-Al-Ni alloys, allowing them to approach the intrinsic high superelasticity of single crystals. © 2015 Elsevier Ltd.


Wang Y.,South China University of Technology | Wang Y.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Yang L.,South China University of Technology | Yang L.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | And 6 more authors.
Electrochimica Acta | Year: 2014

Fe2O3-graphite (Fe2O3-G) composites have been facilely and effectively synthesized via ball milling. Structural features and electrochemical properties of the Fe2O 3-G composites as anodes for lithium-ion batteries are investigated. The Fe2O3-G composites benefit from the close contact of nanocrystalline Fe2O3 with the graphite matrix, which improves the electronic conductivity and restrains the volume variation during cycling. The composite with 20% graphite shows the highest reversible capacity up to 491.1 mAh g-1 after 55 cycles with good rate capability. Due to the superior electrochemical performance, the Fe2O3-G composites prepared via ball milling could be promising as anode materials with high capacity, low-cost for lithium-ion batteries. © 2014 Elsevier Ltd.


Wang H.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Zhang J.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Liu J.W.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Ouyang L.Z.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Zhu M.,South China University of Technology
Journal of Alloys and Compounds | Year: 2013

The addition of NaH by ball milling is shown to greatly improve the hydrogen storage properties and the hydrolysis properties of MgH2, which is related to the formation of ternary hydride NaMgH3 with specific perovskite structure. The MgH2-10%NaH mixture exhibits better hydriding and dehydriding kinetics than the MgH2-10%LiH mixture, in which the LiMgH3 with perovskite structure could not be formed. The catalytic role of NaMgH3 is attributed to fast hydrogen mobility in the perovskite structure, which provides fast hydrogen diffusion pathways for the hydriding and dehydriding of MgH2. The NaMgH 3 also shows fast hydrolysis reaction kinetics without any passivation. Our work shows that such perovskite-type hydride demonstrates great potential as efficient catalysts for the high-capacity hydrides for whether reversible or irreversible hydrogen storage. © 2013 Elsevier B.V. All rights reserved.


Lai M.,South China University of Technology | Lai M.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | Gao Y.,South China University of Technology | Gao Y.,Key Laboratory of Advanced Energy Storage Materials of Guangdong Province | And 4 more authors.
Materials and Design | Year: 2015

Nickel-free Ti-Nb alloys were fabricated by conventional powder metallurgy sintering method. The oxygen content of sintered Ti-Nb alloys were successfully decreased to around 0.8wt.% by putting TiH2 powders aside the samples during the sintering process. For the first time, the phase transformation behaviors of these sintered Ti-Nb alloys were observed by differential scanning calorimetry (DSC) measurement. The relationship between martensitic transformation start temperature (Ms) and mechanical properties, including elastic modulus and recoverable strain, was established by compression tests carried out at room temperature. While Ms was close to test temperature, an obvious drop of elastic modulus was observed, which was related to the "β-α" transformation. In the meantime, a remarkable recoverable strain as high as 5% was obtained at room temperature, which is the highest value reported in sintered Ti-Nb alloys until now. The results of this study reveal that the recoverable strain can be further improved by adjusting Ms close to the service temperature, which was neglected in the reported studies before and will provide some guidance for the future design and fabrication of porous Ni-free Ti-based shape memory alloys for biomedical application. © 2015 Elsevier Ltd.

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