Absorption Plateau Research Articles

Hydrogen absorption/desorption behavior of Mg50La20Ni30 bulk metallic glass

In this work, Mg50La20Ni30 bulk metallic glass (BMG) was prepared and its hydrogen absorption/desorption behavior was studied. The amorphous structure was found to be retained after gaseous hydrogenation. The Tg and Tx of the hydrogenated Mg50La20Ni30 BMG was 561 K and 619 K respectively, much higher than the corresponding value of 463 K and 504 K of the unhydrogenated sample. Mg50La20Ni30 BMG absorbed 0.73 and 1.85 wt% hydrogen within 1 h at 313 K and 423 K respectively, which was higher than that of ball-milled Mg2Ni alloy. Mg50La20Ni30 BMG exhibited an equilibrium hydrogen absorption plateau with a pressure of 0.07 MPa in pressure–composition isotherm curve at 423 K. It suggested that Mg-based BMGs are promising materials for hydrogen storage applications.

Hydrogen storage properties and thermal stability of amorphous Mg70(RE25Ni75)30 alloys

In this study, amorphous Mg70(RE25Ni75)30 (RE=La, Pr, Nd) alloys were produced by melt spinning, their hydrogen storage properties and the thermal stabilities have been studied by means of PCTPro2000 and Differential Scanning Calorimetry (DSC), respectively. After hydrogenation of Mg70(RE25Ni75)30 samples at 573K under 2MPa hydrogen pressure, XRD results indicate the formation of new phases of MgH2, Mg2NiH4, LaH3.01 (RE=La), PrH2.92 (RE=Pr) and Nd2H5 (RE=Nd). The experimental data of hydrogen desorption kinetics at 523K, 553K, 573K are well fitted through Avrami–Erofeev equation, and the hydrogen desorption kinetics were in the order of Pr>La>Nd. Based on the results of DSC analysis, dehydrogenation activation energies of these samples were determined to be 68.81±2.50kJ/mol (RE=La), 64.79±1.09kJ/mol (RE=Pr) and 73.37±3.23kJ/mol (RE=Nd), which are in accordance with the results of hydrogen desorption kinetics. As shown in the P–C isotherm curves, two hydrogen absorption plateaus at about 0.07MPa and 0.2MPa have been observed for Mg70(RE25Ni75)30 (RE=La, Pr) tested at 573K, while there is only one sloping hydrogen absorption plateau in the range of 0.06–0.3MPa for Mg70(Nd25Ni75)30 alloy. The maximum hydrogen absorption capacity is 4.21wt.% for Mg70(Nd25Ni75)30 and the maximum hydrogen desorption capacity is 2.74wt.% for Mg70(Pr25Ni75)30.

Enhanced mechanical properties and degradability of poly(butylene succinate) and poly(lactic acid) blends

To improve the tensile properties and degradability of poly(butylene succinate) (PBS) for biomedical usage, biodegradable polymer blends have been developed. A series of PBS and poly(lactic acid) (PLA) blends were prepared, and their degradation behaviors in simulated body fluid for 16 months were investigated based on morphology, tensile test, weight analysis, and molecular weight. The results showed that the incorporation of PLA into PBS increased the initial tensile strength to some extent, and the blends lost their tensile properties earlier than their parent polymers with the proceeding of hydrolysis. Both blends and parent polymers went through a plateau and subsequent rise stage in mass loss and water absorption, but the blends hydrolyzed faster than the parent polymers. The molecular weight variations also demonstrated faster hydrolysis of the blends. Moreover, both blends and their parent polymers underwent a slow-to-fast transition in their hydrolysis rates. When the Mn of PBS and PLA reached 4.0 × 104 and 9.0 × 104, the hydrolysis of parent polymers and blends began to accelerate, which is the start of auto-acceleration. The blends hydrolyzed faster in both stages. The interface between the components initiated accelerating hydrolysis in the first stage, and the reciprocal auto-acceleration effect resulted in faster hydrolysis of the blends in the second stage.

A theory of multiple photon absorption by graphene in intense laser fields

A theoretical analysis of multiple photon absorption by Dirac fermions in graphene subjected to intense laser fields is made. An analytic expression for the probability of n‐photon absorption is derived. It shows that the fundamental functional dependence of n photon absorption rate is governed by a Bessel function of order n, , where , is the Fermi‐velocity, F is the peak field strength, ω is the frequency; and θ0 are the polar angles of the fermion momentum and the laser polarization, respectively. The result is used to investigate the rate of n photon absorption in the THz and the near‐infrared domains and both in the weak‐field perturbative, and the strong‐field non‐perturbative intensity regimes. Formation of an n‐photon absorption plateau followed by an exponential cut‐off beyond is also predicted to occur.

Preparation and hydrogen storage properties of ultrafine pure Mg and Mg–Ti particles

The ultrafine pure Mg and Mg–Ti particles were prepared through a direct current (DC) arc plasma method. The X-ray diffraction (XRD), transmission electron microscopy (TEM), pressure-composition-temperature (PCT) method and TG/DTA techniques were used to study the phase components, microstructure and hydrogen sorption properties of the powders before and after hydrogen absorption. It is revealed that most of the ultrafine Mg and Mg–Ti particles are hexagonal in shape with particle size in the range of 50-700 nm. According to the Van't Hoff equation, the hydrogenation enthalpy of Mg–Ti powders is determined to be about −67 kJ/mol H2 based on the PCT curves of hydrogen absorption plateau pressures. This value is much higher than −78.6 kJ/mol H2 for pure Mg powders. TG/DTA analyses show that the onset dehydriding temperature of hydrogenated Mg–Ti powders is 386 °C, which is significantly lower than that of the hydrogenated Mg (423 °C). The results prove that the addition of Ti into Mg through arc evaporation method can improve the thermodynamic properties of Mg for hydrogen storage.

The electronic states of 1,2,4-triazoles: A study of 1H- and 1-methyl-1,2,4-triazole by vacuum ultraviolet photoabsorption and ultraviolet photoelectron spectroscopy and a comparison with ab initio configuration interaction computations

The first vacuum ultraviolet absorption spectrum of a 1,2,4-triazole has been obtained and analyzed in detail, with assistance from both an enhanced UV photoelectron spectroscopic study and ab initio multi-reference multi-root configuration interaction procedures. For both 1H- and 1-methyl-1,2,4-triazoles, the first ionization energy bands show complex vibrational structure on the low-energy edges of otherwise unstructured bands. Detailed analysis of these bands confirms the presence of three ionized states. The 6-7 eV VUV spectral region shows an unusual absorption plateau, which is interpreted in terms of the near degeneracy of the first two ionization energies, leading to a pseudo Jahn-Teller effect. The "fingerprint" of the ionization spectrum yields band origins for several Rydberg states. The configuration interaction study shows that although the equilibrium structure for the first cation is effectively planar, the second cation shows significant twisting of the ring system. Some calculated singlet electronic states also show skeletal twisting in which the ring C-H is substantially out of plane.

Reversible hydrogen-storage at reduced temperatures in the intermetallic compound Mg6(Ni,Pd)

A rapidly-solidified Mg–Ni–Pd alloy is shown to exhibit reversible hydrogen-storage of 5 mass % H at a temperature of 473 K, nearly 100 K below temperatures typically required for Mg-based alloys, with an equilibrium absorption plateau near 1 atm H2 pressure. Additionally, a single plateau is observed in the pressure–composition isotherm where MgH2 and Mg2NiH4 form and decompose simultaneously during the absorption/desorption process. The increase in absorption plateau pressure to 100 kPa suggests a decrease in the free energy by as much as 15 kJ/mol resulting from either a decrease in enthalpy or an increase in entropy of reaction between the hydride and metallic phases. The improved thermodynamics are discussed in terms of the formation of a new equilibrium metallic phase, Mg6(Ni,Pd). The phase alters the thermodynamics of the hydriding reaction, allowing both MgH2 and Mg2NiH4 to form cooperatively in a single reaction. This method for reducing the free energy of the hydriding reaction is promising, and may prove useful in a variety of other metal-hydride hydrogen-storage systems.

Synthesis and Crystal Structure of a Pr5Ni19 Superlattice Alloy and Its Hydrogen Absorption–Desorption Property

The intermetallic compound Pr(5)Ni(19), which is not shown in the Pr-Ni binary phase diagram, was synthesized, and the crystal structure was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Two superlattice reflections with the Sm(5)Co(19)-type structure (002 and 004) and the Pr(5)Co(19)-type structure (003 and 006) were observed in the 2θ region between 2° and 15° in the XRD pattern using Cu Kα radiation. Rietveld refinement provided the goodness-of-fit parameter S = 6.7 for the Pr(5)Co(19)-type (3R) structure model and S = 1.7 for the Sm(5)Co(19)-type (2H) structure model, indicating that the synthesized compound has a Sm(5)Co(19) structure. The refined lattice parameters were a = 0.50010(9) nm and c = 3.2420(4) nm. The high-resolution TEM image also clearly revealed that the crystal structure of Pr(5)Ni(19) is of the Sm(5)Co(19) type, which agrees with the results from Rietveld refinement of the XRD data. The P-C isotherm of Pr(5)Ni(19) in the first absorption was clearly different from that in the first desorption. A single plateau in absorption and three plateaus in desorption were observed. The maximum hydrogen storage capacity of the first cycle reached 1.1 H/M, and that of the second cycle was 0.8 H/M. The 0.3 H/M of hydrogen remained in the metal lattice after the first desorption process.

Structure and hydrogen storage performance of LaNi 4.25Al 0.75 alloy

Hydrogen storage properties of LaN 4.25Al 0.75 alloy were experimentally investigated by XRD, PC isotherm curves, hydrogen absorption kinetics curves, XPS and its particle diameter. The structure of unit cell of LaNi 4.25Al 0.75 alloy was deduced. The relationship between its structure and hydrogen storage performance of LaNi 4.25Al 0.75 alloy was analyzed. The results show that LaNi 4.25Al 0.75 alloy has rapid hydrogen absorption rate and good resistance to combustibility. It is also found that the function of the hydrogen absorption plateau pressure and temperature is ln p eq=-4 820/ T+12.46, and the hydrogen absorption rate of the alloy decreases with increasing the temperature.

Comparing Study of Energy-Absorbing Behavior for Honeycomb Structures

Honeycomb materials，as a type of ultra-light multifunctional material，have been examined extensively in recent years and have been applied in many fields. This study investigated the energy absorption capacity and their mechanisms of honeycomb structures with five different cell geometry (square，triangular，circular, hexagonal，kagome). It has been shown that the honeycomb structure with kagome cells is the best choice under the targets of the energy absorption capacity, peak force and plateau stress, when relative density and cell wall thickness of the five kinds of honeycombs are the same. Besides, honeycomb with hexagonal cells and honeycomb with triangular cells are also ideal structures for energy absorption purpose.

The influence of Co content on LaNi3.2-xMn03Cox (x=0.2∼0.8) Alloy Hydrogen Storage and Electrochemical Properties

The cold crucible levitation melting prepared LaNi3.2-xMn03Cox (x = 0.2 ∼ 0.8) series alloys, the system of Co substitution of Ni on the alloy structure, hydrogen storage performance and electrochemical properties. XRD analysis showed that the cast alloy by the La2Ni7 phase, LaNi5 phase and LaNi3 phase composition; PCT test shows that with the Co substitution increases, the amount of the cast alloy of hydrogen first increased and then decreased, alloy hydrogen absorption and desorption plateau pressure changed little . Electrochemical tests show that as x increases the maximum discharge capacity of alloy electrodes decreases, the maximum discharge capacity Cmax by the x = 0.2 when 320.5mAh / g decreased to x = 0.8 when 286.6mAh / g, but the cycle stability significantly improved after 60 charge-discharge cycles, the alloy electrode capacity retention rate (S60) by the x = 0.2 and gradually increased to 72.9% when x = 0.8 at 84.9%.

Hydrogen storage properties of TiMn 1.5V 0.2-based alloys for application to fuel cell system

To meet the requirements of fuel cell power system for electric bike, the influence of partial substitution of Zr and Cr on hydrogen storage performance of TiMn 1.5V 0.2-based alloys is investigated first, and a hydrogen storage tank is then built using the developed TiMn 1.5V 0.2-based alloy as metal hydride bed and its hydrogen supply ability is further evaluated. It is found that for TiMn 1.5V 0.2-based alloys, the Zr substitution for Ti effectively reduces the plateau pressure but increases the plateau slope, while the partial substitution of Mn by Cr decreases the absorption plateau pressure, leading to a smaller hysteresis factor. After the optimization of components, 6 kg of Ti 0.95Zr 0.05Mn 1.4Cr 0.1V 0.2 alloy powder with 5 wt.% aluminum foam is mixed uniformly to form a metal hydride bed inside the tank. The measurements show that the tank releases up to 82 g of hydrogen to produce a 200 W fuel cell output for 300 min and has a stable cyclic capacity, indicating that hydrogen storage system of TiMn 1.5V 0.2-based alloys for fuel cell power system of electric bike is applicable.

Hydrogen storage properties of spark generated palladium nanoparticles

Palladium nanoparticles of ∼4 nm were synthesized using spark discharge generation, and their hydrogen storage properties were determined using both thermal desorption spectroscopy (TDS) and Sievert’s (PCT) measurements. PCT measurements indicate that the thermodynamic properties of the nanoparticles towards hydrogen storage differ significantly from that of bulk Pd, even after sintering of the crystallites to 24 nm as determined using X-ray diffraction (XRD). Both the enthalpy and entropy of hydrogen absorption and desorption differ from bulk values, resulting in less hysteresis between absorption and desorption equilibrium plateau pressures and a lowering of the critical temperature of hydride formation T c by approximately 100 K. The TDS measurements indicate a transition from diffusion to surface-barrier limited hydrogen desorption when going from Pd foil to Pd nanoparticles. This results in a strong decrease in the hydrogen thermal desorption temperatures by ∼160 K during TDS. These results indicate that spark discharge is an interesting method for metal hydride nanoparticle generation.

Single-dose pharmacokinetics and pharmacodynamics of anacetrapib, a potent cholesteryl ester transfer protein (CETP) inhibitor, in healthy subjects.

Anacetrapib is an orally active and potent inhibitor of CETP in development for the treatment of dyslipidaemia. These studies endeavoured to establish the safety, tolerability, pharmacokinetics and pharmacodynamics of rising single doses of anacetrapib, administered in fasted or fed conditions, and to preliminarily assess the effect of food, age, gender and obesity on the single-dose pharmacokinetics and pharmacodynamics of anacetrapib. Safety, tolerability, anacetrapib concentrations and CETP activity were evaluated. Anacetrapib was rapidly absorbed, with peak concentrations occurring at approximately 4 h post-dose and an apparent terminal half-life ranging from approximately 9 to 62 h in the fasted state and from approximately 42 to approximately 83 h in the fed state. Plasma AUC and C(max) appeared to increase in a less than approximately dose-dependent manner in the fasted state, with an apparent plateau in absorption at higher doses. Single doses of anacetrapib markedly and dose-dependently inhibited serum CETP activity with peak effects of approximately 90% inhibition at t(max) and approximately 58% inhibition at 24 h post-dose. An E(max) model best described the plasma anacetrapib concentration vs CETP activity relationship with an EC(50) of approximately 22 nm. Food increased exposure to anacetrapib; up to approximately two-three-fold with a low-fat meal and by up to approximately six-eight fold with a high-fat meal. Anacetrapib pharmacokinetics and pharmacodynamics were similar in elderly vs young adults, women vs men, and obese vs non-obese young adults. Anacetrapib was well tolerated and was not associated with any meaningful increase in blood pressure. Whereas food increased exposure to anacetrapib significantly, age, gender and obese status did not meaningfully influence anacetrapib pharmacokinetics and pharmacodynamics.

High Conductivity PEDOT Using Humidity Facilitated Vacuum Vapour Phase Polymerisation

AbstractThe synthesis of high conductivity poly(3,4‐ethylenedioxythiophene) (PEDOT) films using vacuum vapour phase polymerisation is reported. Water vapour is introduced into the chamber and results suggest that it acts as a proton scavenger during polymerisation. Process optimisation leads to PEDOT films that have high conductivity and a blue‐black appearance. Poor quality films have lower conductivity and a characteristic greenish colour. UV‐vis‐NIR spectra show that poor PEDOT films are characterised by higher absorption in the UV‐vis region and an absorption plateau in the NIR region, which suggests an increased level of disrupted conjugation along the polymer backbone or higher oligomer content. Conversely, high quality PEDOT is characterised by an extended NIR absorption tail and lower absorption in the UV‐vis region.magnified image

Hydrogen absorption/desorption properties of MmNi4.5Cr0.5−xZrx alloys

Abstract Hydrogen absorption/desorption properties of MmNi 4.5 Cr 0.5− x Zr x alloys ( x = 0, 0.05, 0.1) were investigated in the present work. The Pressure–Composition (PC) isotherms and absorption kinetics were measured in the temperature range of 273 ≤ T ≤ 303 K by the volumetric method. XRD patterns showed that the as-annealed MmNi 4.5 Cr 0.5− x Zr x alloys had CaCu 5 type hexagonal structure and could keep the same single phase after 16 cycles of absorption/desorption. It was found that with the increase of x in MmNi 4.5 Cr 0.5− x Zr x alloys, the dissociation plateau pressure increased, the hysteresis was diminished, the hydrogen uptake capacity was reduced and the absorption kinetics was improved. The absorption plateau pressure increased when x was increased to 0.05, but decreased when x increased to 0.1. It was also found that the dissociation plateau pressure increased linearly with increasing cell volume V and the lattice parameter a , and the hydrogen uptake capacity decreased linearly with increasing Zr content.

Hydrogen absorption properties of the γ-Mg17Al12 phase

In the present work, the Mg-Al system was studied towards hydrogen absorption properties.Several MgxAl100-x compounds from X=47.5 to 70 by incremental step of 2.5 were prepared by ball-milling with post-annealing. Different experimental measurements were performed and are in mutual agreement with properties of existing phases. They show that deviation from the ideal composition of Mg17Al12 (X=58.62) leads to a decrease of the homogeneity. The single γ-phase range is extended at room temperature for initial 55≤X≤62.5 atomic % of Mg.The hydrogenation properties have been investigated for two compounds at the nominal composition X=50 and X=58.6. The hydrogen absorption is presented at 350°C and shows a maximum hydrogen capacity of 3.5 and 3.7 wt% respectively. For these two compounds, the pressure-composition isotherm (PCT) curves show two absorption plateaux, with equilibriums around 10 bars which are higher than that of pure MgH2. The shape discontinuity corresponds to a transformation into a 2-step process as described in this work. After final desorption, the initial compounds are recovered, indicates that the reactions are reversible.

Concentration response to the coenzyme Q10 supplement Q-Gel in human volunteers.

Coenzyme Q10 (CoQ10) is essential for every cell in the body, and deficiency has been implicated in many diseases. Studies to confirm the benefit of supplementation require efficacious supplementation. Previously we found Q-Gel to be highly bioavailable. The objective of the present study was to identify the most efficacious dose of Q-Gel for use in supplementation studies. In a randomized crossover design, 8 young healthy male volunteers received single doses of 60, 150, and 300 mg CoQ10 via Q-Gel 30-mg capsules, and of 300 mg via 100-mg Q-Gel capsules. Doses were given after a 10-hour overnight fast, a week apart. Plasma was analyzed for CoQ10, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triacylglycerols at baseline and at 2, 4, 6, 8, and 10 hours after supplement ingestion. Areas under the curve (AUCs) were calculated for each participant at each dose and compared by 1-way analysis of variance. AUC increased significantly between 60- and 150-mg doses (P < .001), but not between 150- and 300-mg doses (P = .198). A plateau in absorption occurs near 200 mg. AUC for the 300-mg dose via 100-mg capsules was significantly lower than that for 300 mg via 30-mg capsules (P < .001), which may be due to the lower ratio of CoQ10 to oil in the 30-mg capsules or to the higher vitamin E content in the 100-mg capsules. We conclude that the most efficacious single dose of Q-Gel is 200 mg, and higher absorption is obtained using multiple smaller capsules.

Structure, morphology and hydrogen storage properties of composites prepared by ball milling [formula omitted] with La–Mg-based alloy

Hydrogen storage alloy composites Ti 0.9 Zr 0.2 Mn 1.5 Cr 0.3 V 0.3 - x wt % La 0.7 Mg 0.25 Zr 0.05 ( Ni 0.85 Co 0.15 ) 3.5 ( x = 0 , 5 , 10 ) were prepared by ball milling method. Their structures, morphologies and the hydrogen storage characteristics were intensively studied in the present work. It was found that the bulk of composites maintained the hexagonal C14 Laves phase structure after ball milling with additional La–Mg-based alloy for two hours. Scanning electron microscopy (SEM) observations revealed that the average size of Ti 0.9 Zr 0.2 Mn 1.5 Cr 0.3 V 0.3 and La 0.7 Mg 0.25 Zr 0.05 ( Ni 0.85 Co 0.15 ) 3.5 particles were reduced to several hundred nanometers after ball milling process. Energy dispersive X-ray spectrometer (EDS) patterns of the composites showed that the La 0.7 Mg 0.25 Zr 0.05 ( Ni 0.85 Co 0.15 ) 3.5 phase was uniformly distributed on the surface of Ti 0.9 Zr 0.2 Mn 1.5 Cr 0.3 V 0.3 . The hydrogen absorption–desorption characteristics of the composites were improved with increasing dispersivity of the La 0.7 Mg 0.25 Zr 0.05 ( Ni 0.85 Co 0.15 ) 3.5 alloy particles. Pressure–composition–temperature (PCT) measurements revealed that the pressure plateau and the hysteresis decreased with increasing x. Among these composites, the sample of x = 10 exhibited more significant hydrogen storage performances. Its hydrogen absorption and desorption plateau pressure were 0.547 and 0.302 MPa, respectively, which were much lower than those of the Ti 0.9 Zr 0.2 Mn 1.5 Cr 0.3 V 0.3 alloy. Moreover, it took only 200 and 2500 s to reach the constant pressure for the hydrogen absorption and desorption reaction. These improvements can be attributed to the preferable dispersivity of La–Mg-based alloy particles and also the formation of micro-crack after ball milling. Both factors synergetically facilitate the diffusion of hydrogen atoms in the composites and accelerate the dissociation of hydrogen molecules and recombination of hydrogen atoms on the surface of composites during the hydrogen absorption–desorption process.

Some factors influencing the hydrogen storage properties of 30V–Ti–Cr–Fe alloys

In this paper, the effects of Ti/(Cr+Fe) ratio, Cr/Fe ratio, Ti/Cr ratio, lattice parameter and e/a value on hydrogen storage properties of 30V–Ti–Cr–Fe alloys have been researched. Ti/(Cr+Fe) ratio, Cr/Fe ratio and Ti/Cr ratio have great influences on the hydrogen absorption and desorption capacities and plateau pressures in the desorption process, and the influences can be attributed to the effects of lattice parameter and e/a value in a great part. Lattice parameter (a) is the main factor which decides the hydrogen absorption and desorption capacities. When a<3.03Å, hydrogen absorption capacity increases with the increase of a, and it trends stably when a grows further. Hydrogen desorption capacity increases first and then decreases with the increase of a, and it reaches its maximum when a=3.035Å. A critical e/a value of 5.25 was found in 30V–Ti–Cr–Fe system. When e/a<5.25, the alloys have high absorption capacities which decrease rapidly when e/a>5.25. V30Ti32Cr31.91Fe6.09 alloy with high capacity was developed, which absorbs 3.78wt.%H and desorbs 2.26wt.%H at 298K.