Graphene-loaded nickel−vanadium bimetal oxides as hydrogen pumps to boost solid-state hydrogen storage kinetic performance of magnesium hydride

To modify the thermodynamics and kinetic performance of magnesium hydride(MgH_(2))for solid-state hydrogen storage,Ni_(3)V_(2)O_(8)-rGO(rGO represents reduced graphene oxide)and Ni_(3)V_(2)O_(8)nanocomposites were prepared by hydrothermal and subsequent heat treatment.The beginning hydrogen desorption temperature of 7 wt.%Ni_(3)V_(2)O_(8)-rGO modified MgH_(2)was reduced to 208℃,while the additive-free MgH_(2)and 7 wt.%Ni_(3)V_(2)O_(8)doped MgH_(2)appeared to discharge hydrogen at 340 and 226℃,respectively.A charging capacity of about 4.7 wt.%H_(2)for MgH_(2)+7 wt.%Ni_(3)V_(2)O_(8)-rGO was achieved at 125℃ in 10 min,while the dehydrogenated MgH_(2)took 60 min to absorb only 4.6 wt.%H_(2)at 215℃.The microstructure analysis confirmed that the in-situ generated Mg_(2)Ni/Mg_(2)N_(i)H_(4) and metallic V contributed significantly to the enhanced performance of MgH_(2).In addition,the presence of rGO in the MgH_(2)+7 wt.%Ni_(3)V_(2)O_(8)-rGO composite reduced particle aggregation tendency of Mg/MgH_(2),leading to improving the cyclic stability of MgH_(2)during 20 cycles.

Preparation of ZrMn_2 hydrogen storage alloy by electro-deoxidation in molten calcium chloride

ZrMn2 alloy was electro-synthesized directly from cathode pellets compacted with powdered mixture of MnO2 and ZrO2 in molten calcium chloride. Sintering temperature, cell voltage and electrolysis time were the dominant factors that affected the characteristics of the final product. The results confirmed the formation of pure ZrMn2 alloy through the electro-deoxidation of the mixed oxide pellets at 3.1 V for 12 h in 900 °C CaCl2 melt. The X-ray diffraction（XRD） and cyclic voltammetry analysis suggested that the electro-deoxidation proceeded from the reduction of manganese oxides to Mn, followed by ZrO2 or CaZrO3 reduction on the pre-formed Mn to ZrMn2 alloy. The cyclic voltammetry measurements using powder microelectrode showed that the prepared ZrMn2 alloy has a good electrochemical hydrogen storage property.

Effect of Ni,Fe and Fe-Ni alloy catalysts on the synthesis of metal contained carbon nano-onions and studies of their electrochemical hydrogen storage properties

Three types of carbon nano-onions（CNOs） including Ni@CNOs.Fe3C@CNOs and Fe0.64Ni0.36@CNOs nanoparticles have been synthesized by catalytic decomposition of methane at 850 ℃ using nickel,iron and iron-nickel alloy catalysts.Comparative and systematic studies have been carried out on the morphology,structural characteristics and graphitic crystallinity of these CNOs products.Furthermore,the electrochemical hydrogen storage properties of three types of CNOs have been investigated.Measurements show that the Ni@CNOs have the highest discharge capacity of 387.2 mAh/g,coiTesponding to a hydrogen storage of 1.42%.This comparison study shows the advantages of each catalyst in the growth of CNOs.enabling the controllable synthesis and tuning the properties of CNOs by mediating different metals and their alloy for using in the fuel cell system.

Hydrogen Storage Properties of Ti_(1.2)Fe+xCa Hydrogen Storage Alloys

The hydrogen storage properties of Ti1.2Fe+xCa (x=1%, 3% and 5% in mass fraction) alloys was investigated. Results stow that the modified alloys can be activated without any thermal treatment at room temperature due to the addition of Ca and excess Ti in (lie alloys. Hydrogen storage properties of these modified alloys vary with Ca amount and reaction temperature. In addition, the influence mechanism of the addition of Ca and excessive Ti on the activation behavior and hydrogen storage capacity of the alloys was discussed.

Characteristics of Hydrogen Storage Alloy Mg_2Ni Produced by Hydriding Combustion Synthesis

A high activity and large capacity of hydrogen storage alloy Mg2Ni by hydriding combustion synthesis was investigated by means of pressure composition isotherms, X-ray diffraction and scanning electron microscopy. The results showed that the maximum hydrogen absorption capacity of Mg2Ni is 3.25 mass fraction at 523 K, just after synthesis without any activation. The relationships between the equilibrium plateau pressure and the temperature for Mg2Ni were lgp (0.1 MPa)=-3026/T+5.814 (523 K≤T≤623 K) for hydriding and Igp (0.1 MPa)=-3613/T+6.715 (523 K≤T ≤623 K) for dehydriding. The kinetic equation is [-ln(1-a)]3/2 = kt and the apparent activation energy for the nucleation and growth-controlled hydrogen absorption and desorption were determined to be 64.3±2.31kJ/(mol.H2) and 59.9±2.99kJ/(mol.H2)respectively.

HYDROGEN STORAGE PROPERTIES OF Mg MODIFIED WITH TETRAHYDROFURAN

The hydriding and dehydriding behaviors of tetrahydrofuran modified Mg,its electronic struc- ture,crystal structure,micro-morphology as well as its stability have been investigated.The modifield Mg absorbs 3.5 wt-％ hydrogen at 643 K in 3.5 MPa H_2,its hydride gives off 3.2 wt-％ hydrogen at 643 K in a vaccum of 1.3 Pa after 20 cycles of hydriding and dehydriding. Tetrahydrofuran alters the electronic structure of Mg but keeps its crystal strueture unchanged.In hydriding products,a new hydride phase is found in addition to the known MgH_2 phase.The hydride formed from Mg is polv-erystalline.The wide-spreading slip bands and twins within crystals indicate that the transformation during absorption of hydrogen causes serious lattice distortions.

Effect of Ti substitution on hydrogen storage properties of Zr_(1-x)Ti_xCo (x = 0, 0.1, 0.2, 0.3) alloys

Zr1-xTixCo(x = 0, 0.1, 0.2, 0.3) alloys were prepared by arc-melting method and the effect of Ti substitution on hydrogen storage properties was studied systematically. Hydrogen desorption pressure-composition-temperature(PCT) measurements were carried out using Sievert’s type volumetric apparatus for ZrCo(at 473 K, 573 K and 673 K) and Zr1-xTixCo alloys(at 673 K), respectively. Products after dehydrogenation were characterized by X-ray diffraction(XRD). In addition, the kinetics of Zr1-xTixCo hydride was investigated at 473 K and 673 K,respectively, under hydrogen pressure of 5 MPa. Results showed that Ti substitution for Zr did not change the crystal structure of ZrCo phase.With the increase of temperature from 473 K to 673 K, the extent of disproportionation for ZrCo alloy increased. With Ti content increasing at 673 K, the desorption equilibrium pressure of Zr1-xTixCo-H2 systems elevated and the disproportionation reaction of Zr1-xTixCo alloys was inhibited effectively. Ti substitution decreased the kinetics rate and the effective hydrogen storage capacity of Zr1-xTixCo alloys slightly.Generally speaking, it was found that Zr0.8Ti0.2Co alloy had better anti-disproportionation property with less decrease of effective hydrogen storage capacity which was beneficial to tritium application in the International Thermonuclear Experimental Reactor(ITER).

Hydrogen storage properties of magnesium hydride catalyzed by Ni-based solid solutions

The Ni−25%X(X=Fe,Co,Cu,molar fraction)solid solutions were prepared and then doped into MgH_(2) through high-energy ball milling.The initial dehydrogenation temperatures of MgH_(2)/Ni−25%X composites are all decreased by about 90℃relative to the as-milled pristine MgH_(2).The Ni−25%Co solid solution exhibits the most excellent catalytic effect,and the milled MgH_(2)/Ni−25%Co composite can release 5.19 wt.%hydrogen within 10 min at 300℃,while the as-milled pristine MgH_(2) can only release 1.78 wt.%hydrogen.More importantly,the dehydrogenated MgH_(2)/Ni−25%Co composite can absorb 5.39 wt.%hydrogen at 275℃within 3 min.The superior hydrogen sorption kinetics of MgH_(2)/Ni−25%Co can be ascribed to the actual catalytic effect of in-situ formed Mg_(2)Ni(Co)compounds.First-principles calculations show that the hydrogen absorption/desorption energy barriers of Mg/MgH_(2) systems decrease significantly after doping with transition metal atoms,which interprets well the improved hydrogen sorption properties of MgH_(2) catalyzed by Ni-based solid solutions.

Phase structure and hydrogen storage properties of LaMg_(3.70)Ni_(1.18) alloy

The phase structure and hydrogen storage properties of LaMg 3.70 Ni 1.18 alloy were investigated. The LaMg 3.70 Ni 1.18 alloy consists of main LaMg 2 Ni phase, minor La 2 Mg 17 and LaMg 3 phases. The alloy can be activated in the first hydriding/dehydriding process, and initial LaMg 2 Ni, La 2 Mg 17 , and LaMg 3 phases transfer to LaH 2.34 , Mg, and Mg 2 Ni phases after activation. The reversible hydrogen storage capacity of the LaMg 3.70 Ni 1.18 alloy is 2.47 wt.% at 558 K, which is higher than that of the LaMg 2 Ni alloy. The pressure-composition-temperature （PCT） curves display two hydriding plateaus, corresponding to the formation of MgH 2 and Mg 2 NiH 4 . However, only one dehydriding plateau is observed, owing to the synergetic effect of hydrogen desorption between MgH 2 and Mg 2 NiH 4 . The uptake time for hydrogen content to reach 99% of saturated state is less than 250 s, and 90% hydrogen can be released in 1200 s in the experimental conditions, showing fast kinetics in hydriding and dehydriding. The activation energies of the LaMg 3.70 Ni 1.18 alloy are –51.5 ± 1.1 kJ/mol and –57.0 ± 0.6 kJ/mol for hydriding and dehydriding, respectively. The hydriding/dehydriding kinetics of the LaMg 3.70 Ni 1.18 alloy is better than that of the Mg 2 Ni alloy, owing to the lower activation energy values.

Hydrogen storage properties of Mg(Al)solid solution alloy doped with LaF_(3) by ball milling

LaF_(3) was doped to the Mg(Al)solid solution alloy for enhancing the hydrogen absorption and desorption by ball milling.XRD was used to analyze the phases of the samples and the phase transition induced by hydrogenation and dehydrogenation.The microstructure and phase distribution were investigated by SEM and STEM.The hydrogen storage properties were measured by Sieverts method.For Mg_(0.93)Al_(0.07)−5wt.%LaF_(3) nanocomposite,the hydrogen storage kinetic properties were significantly improved by reducing the hydriding and dehydriding activation energies to 65 and 78 kJ/mol,respectively,and the dehydriding enthalpy was calculated to be 69.7 kJ/mol.The improved hydrogen storage properties were mainly attributed to the catalytic effects of the in situ formed nanostructure Al_(11)La_(3) and MgF_(2) together with the dissolving of Al in Mg lattice.

Hydrogen storage behaviors and microstructure of MF_3(M=Ti,Fe)-doped magnesium hydride

MgH2+10%MF3(M=Ti,Fe)(mass fraction) composites were prepared by ball-milling in hydrogen atmosphere,and their hydrogen storage behaviors and microstructure were investigated systematically.The results show that the hydriding and dehydriding kinetics of MgH2 are markedly improved by doping TiF3 and FeF3 fluorides.At 573 K,the two composites can absorb 5.67%-6.07%(mass fraction) hydrogen within 5 min under an initial hydrogen pressure of 3.5 MPa,and desorb 5.34%-6.02% hydrogen within 6 min.Furthermore,the composites can absorb hydrogen rapidly in moderate temperature range of 313-473 K.In comparison,TiF3-doped sample has a better hydriding-dehydriding kinetics than FeF3-doped sample.The microstructure analysis shows that some active particles including MgF2,TiH2 and Fe could be formed in the hydriding-dehydriding processes of the MF3-doped composites.From the Kissinger's plot,the apparent activation energies for the hydrogen desorption of the composites are estimated to be 74.1 kJ/mol for TiF3-doped composite and 77.6 kJ/mol for FeF3-doped composite,indicating MgH2 is significantly activated due to the catalytic effect of the doping of MF3.

A High-Temperature β-Phase NaMnO2 Stabilized by Cu Doping and Its Na Storage Properties

The high-temperature β-phase NaMnO2 is a promising material for Na-ion batteries（NIBs） due to its high capacity and abundant resources. However, the synthesis of phase-pure -NaMnO2 is burdensome and costineffective because it needs to be sintered under oxygen atmosphere at high temperature and followed by a quenching procedure. Here we first report that the pure β phase can be stabilized by Cu-doping and easily synthesized by replacing a proportion of Mn with Cu via a simplified process including sintering in air and cooling to room temperature naturally. Based on the first-principle calculations, the band gap decreases from 0.7 eV to 0.3 eV, which indicates that the electronic conductivity can be improved by Cu-doping. The designed -NaCu（0.1）Mn（0.9）O2 is applied as cathode in NIBs, exhibiting an energy density of 419 Wh/kg and better performance in terms of rate capability and cycling stability than those in the undoped case.

Growth and Holographic Storage Properties of Sc, Fe Co-Doped Lithium Niobate Crystals

The holographic storage properties of Fe （0.03% （mass fraction） Fe2O3）：LiNbO3 doped with Sc at different levels （0, 1%, 2%, 3%） were investigated. The Sc threshold concentration in Fe：LiNbO3 was implied to be about 3% （mole fraction） because O-H vibration absorption peak of Sc （3%）：Fe：LiNbO3 was at 3508 cm^-1, compared with 3484 cm^-1 of crystals with lower Sc doping level. Sc（3%）：Fe：LiNbO3 exhibited higher optical damage resistance ability. The threshold intensity （wavelength 488 nm） of Sc （3%）：Fe：LiNbO3 was 2.2 ×10^2 W ·cm^-2, two orders of masnitude higher than that of Fe：LiNbO3. Holographic storage properties of the crystals were determined in an extraordinary polarized laser of wavelength 632.8 nm by a two-wave coupling method. It was found that in terms of holographic storage properties, the optimal doping concentration of Sc was 2% （mole fraction） among this crystal series.

Microencapsulation of stearic acid with polymethylmethacrylate using iron(Ⅲ) chloride as photo-initiator for thermal energy storage

Aiming to identify the validity of fabricating microencapsulated phase change material(PCM) with polymethylmethacrylate(PMMA) by ultraviolet curing emulsion polymerization method using iron(III) chloride as photoinitiator,SA/PMMA microcapsules were prepared and various techniques were employed to determine the ignition mechanism,structural characteristics and thermal properties of the composite.The results shown that the microcapsules containing SA with maximum percentage of 52.20 wt% formed by radical mechanism and only physical interactions existed in the components both in the prepared process and subsequent use.The phase change temperatures and latent heats of the microencapsulated SA were measured as 55.3 °C and 102.1 J·g^(-1) for melting,and 48.8 °C and 102.8 J·g^(-1) for freezing,respectively.Thermal gravimetric analysis revealed that SA/PMMA has good thermal durability in working temperature range.The results of accelerated thermal cycling test are all shown that the SA/PMMA have excellent thermal reliability and chemical stability although they were subjected 1000 melting/freezing cycles.In summary,the comparable thermal storage ability and good thermal reliability facilitated SA/PMMA to be considered as a viable candidate for thermal energy storage.The successful fabrication of SA/PMMA capsules indicates that ferric chloride is a prominent candidate for synthesizing PMMA containing PCM composite.

Improved Breakdown Strength in(Ba_(0.6)Sr_(0.4))_(0.85)Bi_(0.1)TiO_3 Ceramics with Addition of CaZrO_3 for Energy Storage Application

（Ba（0.6） Sr（0.4））（0.85） Bi（0.1） TiO3 ceramics doped with x wt%CaZrO3（x= 0-10） were synthesized by solid-state reaction method. The effects of CaZrO3 amount on the dielectric properties and structure of（Ba（0.6）Sr（0.4））（0.85） Bi（0.1） TiO3 ceramics were investigated. X-ray diffraction results indicated a pure cubic perovskite structure for all samples and that the lattice parameter increased till x=5 and then slightly decreased. A homogenous microstructure was observed with the addition of CaZrO3. Dielectric measurements revealed a relaxor-like characteristic for all samples and that the diffusivity γ reached the maximum value of 1.78 at x=5. With the addition of CaZrO3, the dielectric constant dependence on electric field was weakened, insulation resistivity enhanced and dielectric breakdown strength improved obviously and reached 19.9 k V/mm at x=7.5. In virtue of low dielectric loss（tan d〈0.001 5）, moderate dielectric constant（er 〉1 500） and high breakdown strength（Eb 〉17.5 k V/mm）, the CaZrO3 doped（Ba（0.6）Sr（0.4））0.85 Bi（0.1） TiO3 ceramic is a potential candidate material for high power electric applications.

Enhanced dehydrogenation kinetic properties and hydrogen storage reversibility of LiBH_4 confined in activated charcoal

LiBH4 was confined into activated charcoal（AC） by melt infiltration method（MI）, and its effects on the hydrogen sorption properties were investigated. The N2 adsorption results reveal that melt infiltration method can effectively incorporated LiBH4 into AC. It can maintain the structural integrity of the scaffold and ensure the confinement effect. The nano-confined LiBH4/AC starts to release hydrogen at around 190 °C, which is 160 °C lower than that of pure LiBH4, and reaches a hydrogen desorption capacity of 13.6% at 400 °C. When rehydrogenated under the condition of 6 MPa H2 and 350 °C, it has a reversible hydrogen storage capacity of 6%, while pure LiBH4 shows almost no reversible hydrogen storage capacity under the same condition. Mass spectrometry analysis（MS） results suggest that no diborane or other impurity gases are released in the decomposition process. The apparent activation energy of dehydrogenation of LiBH4 after confinement into AC decreases from 156.0 to 121.1 k J/mol, which leads to the eminent enhancement of dehydrogenation kinetics of LiBH4.

Holographic Storage Properties of In:Fe:Mn:LiNbO_3 Crystals

In：Fe：Mn：LiNbO3（LN） crystals were grown in air atmosphere by Czochralski method with different concentration of In （0, 1, 2, 3 mol%） in the melts, while the contents of Fe2O3 and MnO were 0.1 and 0.5 mol%, respectively. The location of doping ions was analyzed by Ultravioletvisible absorption spectra and differential thermal analysis. The diffraction efficiency （η）, writing time （τw） and erasure time （τe） of the crystals were measured by two-beam coupling experiment. The dynamic range and photorefractive sensitivity have also been calculated. The results showed that with the increase of In ions in the melt, the absorption edge of In：Fe：Mn：LN crystal shifts to the violet firstly and then makes the Einstein shift, the Curie temperature of crystal increases firstly and then decreases, the storage ratio speeds up, diffraction efficiency decreases, and dynamic range and photorefractive sensitivity increase. The mechanism of holographic storage properties of In：Fe： Mn：LN crystal with different doping concentration of In^3＋ was investigated, suggesting the In： Fe：Mn：LN crystals are excellent holographic storage materiel with better synthetical properties than Fe：Mn：LN crystals.

Effect of Glutathione and Storage Time on Rheological Properties of Per-proofed Frozen Dough

The effect of reduced glutathione (GSH) on fresh and pre-proofed frozen dough rheological properties were investigated using dynamic stress rheometry and small scale extensibility with the addition of three levels (80×10-6, 160× 10-6 and 240×10-6 GSH) and six storage times (0 and 1 day, 2, 4, 6 and 8 weeks). Three relaxation times (1, 13 and 26min) after loading the dough in the rheometer were used to determine storage (G’) and loss (G”) moduli. Correlations for G’ (r=0.678 and 0.622 at 0.05, and 10Hz, respectively) and G” (r=0.699, and 0.690 at 0.05, and 10Hz, respectively) were observed with the area under the extension curve at 26 min relaxation time. The addition of GSH to fresh dough reduced G’ (16.4% to 55.9%) and G” (13.7% to 52.2%). Freezing and frozen storage caused increase in G’ and G”. The addition of GSH reduced dough strength indicated by the reduction in maximum resistance to extension (Rmax) and the ratio of maximum resistance to extensibility (Rmax/E). The reduction in Rmax across all relaxation times ranged from 16.2% to 59.4%. An increase in dough extension (E) was observed with 240×10-6 GSH at all frozen storage and rest period times. Addition of GSH caused an increase of liquid phase (30.6% to 35.3%) in fresh dough and frozen dough (10.3% to 20.7%) after one day frozen storage. Negative correlations of water content in the solid phase with dough extensibility and area under the extensibility curve were found (r=-0.594 and-0.563, respectively, p<0.001). This suggests a loss of dough extensibility and strength as the water holding capacity of the dough components changes during frozen storage.

Evaluation of myocardial viability during cold storage by measurement of myocardual dielectric properties tanδm in radio frequency

Objective To study the mechanism of myocardial dielectric property changes in radio frequency during hypothermic preservation and explore myocardial viability evaluative method. Methods Hybrid young pigs ( 20 - 30 kg) were used in the experiment. Heart arrest was in-

A_(2)B_(7)-type La-Mg-Ni alloys prepared by Mg thermal diffusion for improved hydrogen storage performance

A novel approach based on thermal diffusion was used to achieve controllable Mg content in A_(2)B_(7)-type La-Mg-Ni-based alloys.The formation mechanism of the A_(2)B_(7)-type phase as a result of the thermal diffusion process and the effect of Mg content on hydrogen storage performance were investigated.X-ray diffraction(XRD)patterns and Rietveld refinement results showed that increased Mg transformed the LaNi_(5)phase in the La_(0.74)Sm_(0.03)Y_(0.23)Ni_(4.32)Al_(0.04)precursor alloy into a superlattice structure.Scanning electron microscopy(SEM)images showed that Mg was evenly distributed in the alloy bulk.Mg in the superlattice significantly inhibited the phase decomposition of the superlattice structure during the hydrogen absorption/desorption cycles.An A_(2)B_(7)-type La_(0.57)Sm_(0.02)Y_(0.18)Mg_(0.23)Ni_(3.38)Al_(0.03)alloy composed of Gd_(2)Co_(7)and Ce_(2)Ni_(7)phases was successfully synthesized.The pressure-composition isotherm profiles showed that the alloy had a hydrogen storage capacity as high as 1.73 wt%,with good cycling stability.After 50 cycles of hydrogen absorption/desorption,the alloy retained a hydrogen storage capacity of 1.45 wt%,with a capacity retention rate of up to 84.28%.The Mg thermal diffusion process thus provides a new approach for the controlled preparation of La-Mg-Ni-based alloys.