Extending the solid solution range of sodium ferric pyrophosphate:Off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)as a novel cathode for sodium‐ion batteries

Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and only a limited candidates have been reported so far.In this work,we found for the first time that a continuous solid solution,Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2)(0≤α≤1,could be obtained by mutual substitution of cations at center‐symmetric Na3 and Na4 sites while keeping the crystal building blocks of anionic P2O7 unchanged.In particular,a novel off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)is thus proposed,and its structure,energy storage mechanism,and electrochemical performance are extensively investigated to unveil the structure–function relationship.The as‐prepared off‐stoichiometric electrode delivers appealing performance with a reversible discharge capacity of 83 mAh g^(−1),a working voltage of 2.9 V(vs.Na^(+)/Na),the retention of 89.2%of the initial capacity after 500 cycles,and enhanced rate capability of 51 mAh g^(−1)at a current density of 1600 mA g^(−1).This research shows that sodium ferric pyrophosphate could form extended solid solution composition and promising phase is concealed in the range of Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2),offering more chances for exploration of new cathode materials for the construction of high‐performance SIBs.

Effects of drought on non-structural carbohydrates and C,N,and P stoichiometric characteristics of Pinus yunnanensis seedlings

To study non-structural carbohydrate character-istics and nutrient utilization strategies of Pinus yunnanen-sis under continuous drought conditions,2-year-old seed-lings were planted in pots with appropriate water,light and moderate and severe drought treatments[(80±5),(65±5),(50±5),and(35±5)%of field water-holding capacity].Non-structural carbohydrates,carbon(C),nitrogen(N),and phosphorus(P)concentrations were measured in each plant component.The results show that:(1)With increasing drought,non-structural carbohydrates gradually increased in leaves,stems,and coarse roots,while gradually decreased in fine roots;(2)C concentrations of all were relatively stable under different stress levels.Phosphorous utilization of each component increased under light and moderate drought conditions,while N and P utilization efficiency of each plant component decreased under severe drought.Growth was mainly restricted by N,first decreasing and then increasing with increased drought;(3)There was a correlation between the levels of non-structural carbohydrates and C,N,and P in each component.Changes in N concentration affected the interconversion between soluble sugar and starch,which play a regulatory role in the fluctuation of the concentration of non-structural carbohydrates;and,(4)Plasticity analysis showed that P.yunnanensis seedlings responded to drought mainly by altering starch concentration,the ratio of soluble sugar to starch in leaves and stems,and further by alter-ing N and P utilization efficiencies.Overall,these results suggest that the physiological activities of all organs of P.yunnanensis seedlings are restricted under drought and that trade-offs exist between different physiological indicators and organs.Our findings are helpful in understanding non-structural carbohydrate and nutrient adaptation mechanisms under drought in P.yunnanensis seedlings.

STOICHIOMETRIC AND OFF STOICHIOMETRIC ALLOYING IN Ti 5Si 3 BY Nb OR Cr ADDITION

Titanium silicide Ti 5Si 3 whose melting temperature is 2 130 ℃ bears the potential for very high temperature application. Results on Nb or Cr addition to this compound with emphasis on its alloying behaviour were reported. Previous theoretical calculation shows that substitution of Ti by Nb or Cr atoms in Ti 5Si 3 crystal will enhance the bonding between atoms. By experiment, two means of alloying were considered: stoichiometric and off stoichiometric alloying. Stoichiometric alloying in Ti 5Si 3 results in compounds consisting of single Ti 5Si 3 phase while off stoichiometric alloying yields hypereutectic microstructure with Ti 5Si 3 being the primary phase. The Ti 5Si 3 phase in both cases dissolves certain amount of Nb or Cr alloying element and its composition agrees with the stoichiometric composition of (Ti,Nb) 5Si 3 or (Ti,Cr) 5Si 3. The moduli of the stoichiometric alloys increase with alloying element addition, indicating an enhancement in Ti 5Si 3 crystal.

Comparative study of the stoichiometric characteristics of karst and non-karst forests in Guizhou, China

Carbon (C), nitrogen (N), and phosphorous (P) levels and their stoichiometry in plant components (leaves, branch trunks, roots) of trees in a karst forest and non-karst forest are compared. The results show that the C contents, C:N and C:P ratios of dominant species in the karst forest were lower than those in the non-karst forest, but the N and P and the N:P ratio were higher;C:N:P ratios in plant organs of trees in the karst forest were in the order of trunks>roots>branches>leaves. However, C:N:P ratio in the non-karst forest trees were trunks>branches>roots>leaves. Moreover, ratio of C:N:P in trunks was highest and lowest in leaves in both forests. In non-karst forest trees, N:P was in the order of leaves> roots>branches>trunks. There were no significant differences in the ratio of N:P in different plant components of trees in the karst forest. However, in karst and non-karst forest trees, the ratio of N:P in leaves was highest;positive correlations between N and P contents, and N and N:P ratios were observed in both karst and non-karst forests (p<0.001). Negative correlations between P and N:P ratios (p<0.05) were observed in karst forest trees, while positive correlations were observed in non-karst forest trees.

The two photorefractive centres in iron doped nearly stoichiometric lithium niobate crystals

This paper investigates the photorefractive properties of iron doped lithium niobate with different [Li]/[Nb] ratios The experimental results show two photorefractive centres for iron doped near-stoichiometric lithium niobate crystal Besides Fe^2＋ and Fe^3＋ ions, small polarons and bipolarons are considered as another photoactive centre.

A new equivalent method to obtain the stoichiometric fuel-air cloud from the inhomogeneous cloud based on FLACS-dispersion

The fuel-air cloud resulting from an accidental discharge event is normally irregular in shape and varying in concentration. Performance of dispersion simulations using the computational fluid dynamics （CFD）-based tool FLACS can get an uneven and irregular cloud. For the performance of gas explosion study with FLACS, the equivalent stoichiometric fuel-air cloud concept is widely applied to get a representative distribution of explosion loads. The Q9 cloud model that is employed in FLACS is an equivalent fuel-air cloud representation, in which the laminar burning velocity with first order SL and volume expansion ratio are taken into consideration. However, during an explosion in congested areas, the main part of the combustion involves turbulent flame propagation. Hence, to give a more reasonable equivalent fuel-air size, the turbulent burning velocity must be taken into consideration. The paper presents a new equivalent cloud method using the turbulent burning velocity, which is described as a function of SL, deduced from the TNO multi- energy method.

C,N,and P Ecological Stoichiometric Characteristics of Two Dominant Mosses in Baotianman Nature Reserve

In order to investigate ecological adaptation mechanism of bryophyte,two dominant mosses Thuidium cymbifolium and Mnium immarginatum in Baotianman Nature Reserve were measured the content of C,N,P and their ratio in bryophyte and soil,and analyzed the relationships of plant and soil ecological stoichiometric characteristics along altitudinal gradients.Results indicate that the content of C,N and P in green tissues of T.cymbifolium and M.immarginatum in Baotianman Nature Reserve was 46.81%-49.09%,0.21%-0.25%,and0.02%-0.08%.Among the different altitudinal gradients,C,N and P displayed significant differences: the significantly different content of C and N were showed in T.cymbifolium,and the content of N and P differed significantly in M.immarginatum.However,only N declined obviously as increasing altitude.In soil,the C,N,N/P and C/P showed an increasing trend with increasing elevation,while the P and C/N along altitudinal gradients exhibited no unified trend.With the increasing in the content C,N of soil,the content C and N of T.cymbifolium raised,while the content C and N of M.immarginatum declined.With the rise in P element of soil,N/P showed different trends between two bryophyte species,the N/P in T.cymbifolium significantly decreased,while N/P in M.immarginatum significantly increased.In addition,mean value of leaf N/P was 8.51,ranking 14-16.These results suggested that the growth of the bryophyte plants in Baotianman Nature Reserve were restricted by N element,and different utilization strategies in soil P element in different bryophyte plants led to differences in ecological stoichiometric characteristics.

Influences of stoichiometric ratio B/A on structures and electrochemical behaviors of La_(0.75)Mg_(0.25)Ni_(3.5)M_x (M=Ni,Co;x=0-0.6) hydrogen storage alloys

In order to investigate the influences of the stoichiometric ratio of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structures and electrochemical performances of the AB3.5-4.1-type electrode alloys, the La-Mg-Ni-Co system La0.75Mg0.25Ni3.5Mx (M=Ni, Co; x= 0, 0.2, 0.4, 0.6) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The results show that the structures and electrochemical performances of the alloys are closely relevant to the B/A ratio. All the alloys exhibit a multiphase structure, including two major phases, (La, Mg)2Ni7 and LaNi5, and a residual phase LaNi2, and with rising ratio B/A, the (La,Mg)2Ni7 phase decreases and the LaNi5 phase increases significantly. When ratio B/A=3.7, the alloys obtain the maximum discharge capacities. The high rate discharge(HRD) capability of the alloy (M=Ni) monotonously rises with growing B/A ratio, but that of the alloy (M=Co) first mounts up then declines. The cycle stability of the alloy (M=Co) monotonously increases with rising B/A ratio, but it first decreases slightly then increases for the alloy (M=Ni). The discharge potential of the alloy (M=Ni) declines with increasing B/A ratio (x>0.2), but for the alloy (M=Co), the result is contrary. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed ratio B/A=3.7, the Co substitution enhances the discharge capacity from 365.7 to 401.8 mA·h/g, the capacity retention ratio (S100) after 100 charging-discharging cycles from 50.32% to 53.26% and the HRD from 88.65% to 90.69%.

EFFECTS OF STOICHIOMETRIC RATIO ON STRUCTURE AND ELECTRODE PERFORMANCE OF HYDROGEN STORAGE ALLOYS

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Structure of Sn Doped AB_5 Non-Stoichiometric Hydrogen-Absorbing Alloys-Ⅰ

Five non stoichiometric alloys, i.e., LaNi 5.15 , La(NiSn) 5.14 , La(NiSnCo) 5.12 , La(NiSnMn) 5.12 , and La(NiSnCoMnAl) 5.10 were studied. It is shown that the second minor phase does not exist in the major phase through the X ray diffraction analysis. By the measurements of the crystal lattice constant, the volume of crystal lattice decreases with the increasing of the amount of atom B in AB 5. It is more obvious when the element nickel in B is partially subsituted by other elements. For non stoichiometric alloys, the lattice volume greatly increases when Ni is partially substituted by Sn. The lattice constant is also effected by the addition of Mn, Co, and Al. By means of electrochemical measurements, the plateau pressure of hydrogen absorption/desorption is measured with the results that Sn, Co, Mn and Al decrease the plateau pressure.

Stoichiometric deduction of activated sludge process for organic carbon and nitrogen removal

The activated sludge process （ASP） is the most generally applied biological wastewater treatment method. The ASP for the removal of organic carbon and nitrogen can be looked as the combination of eight processes. In order to set up an ASP model, the stoichiometric coefficients should be deduced so that the stoichiometric matrix can be presented. The important assumptions and simplifications behind the model for ASP are enumerated. Using the matrix, mass balance equation and consistent units, the stoichiometric coefficients in the eight processes are exclusively deduced one by one.

Hydrogen Diffusivity in Single Crystal Stoichiometric NiAl

The hydrogen diffusion behavior of single crystal stoichiometric NiAl was investigated. The results show that the hydrogen diffusivity and permeabilty of single crystal stoichiometric NiAl obey Arrhenius relationship in the experimental temperature range. The activation energy of hydrogen diffusion in single crystal stoichiometric NiAl is about 45 kJ/mol.

Stoichiometric flexibility regulates the co-metabolism effect during organic carbon mineralization in eutrophic lacustrine sediments

Several studies have suggested the pivotal roles of eutrophic lakes in carbon(C)cycling at regional and global scales.However,how the co-metabolism effect on lake sediment organic carbon(OC)mineralization changes in response to integrated inputs of labile OC and nutrients is poorly understood.This knowledge gap hinders our ability to predict the carbon sequestration potential in eutrophic lakes.Therefore,a 45-day microcosm experiment was conducted to examine the dominant mechanisms that underpin the co-metabolism response to the inputs of labile C and nutrients in lacustrine sediments.Results indicate that the labile C addition caused a rapid increase in the positive co-metabolism effect during the initial stage of incubation,and the co-metabolism effect was positively correlated with the C input level.The positive co-metabolism effect was consistently higher under high C input,which was 152%higher than that under low C input.The higherβ-glucosidase activity after nutrient addition,which,in turn,promoted the OC mineralization in sediments.In addition different impacts of nutrients on the co-metabolism effect under different C inputs were observed.Compared with the low nutrient treatments,the largest co-metabolism effect under high C with high nutrient treatment was observed by the end of the incubation.In the high C treatment,the intensity of the co-metabolism effect(CE)under high nitrogen treatment was 1.88 times higher than that under low nitrogen condition.However,in the low C treatment,the amount of nitrogen had limited impact on co-metabolism effect.Our study thus proved that the microorganisms obviously regulate sediment OC turnover via stoichiometric flexibility to maintain a balance between resources and microbial requirements,which is meaningful for evaluating the OC budget and lake eutrophication management in lacustrine sediments.

Stoichiometric NbTiAl_3 (γ1 Phase) Alloy in Ti-Al-Nb Ternary System

The microstructure and phase constitution in stoichiometric NbTiAl3 (γ1 phase) alloy treated at 1000℃ were examined by metallography and X-ray diffraction. The alloy microstructure is mainly γ1 phase containing η second phase [(Ti,Nb)Al3] less than 1%. DTA analysis shows no phase transformation from room temperature to 1200℃. In the diffusion couple of NbTiAl3 with 7-TiAl compound, clear phase boundary and composition jump exist between γ1 and γ phase.These results further confirm the existence of γ1 single phase at 1000℃ in Ti-Al-Nb ternary system.

The dielectric behaviour of doped near-stoichiometric lithium niobate in the terahertz range

The dielectric properties of near-stoichiometric LiNbO3：Fe and LiNbO3：Ce single crystals have been investigated using terahertz time domain spectroscopy in a frequency range of 0.71.6 THz at room temperature. When coupled with an applied external optical field, obvious photorefractive effects were observed, resulting in a modulation of the complex dielectric constant for the crystals. The variation in refractive index, ｜△n｜, had a linear relationship with the applied light intensity, accompanied by a step-like decrease at high intensity. The findings were attributed to the internal space charge field of the photorefraction and the light-induced domain reversal in the crystals.

Structure of Non-stoichiometric Sr_6Gd_(0.61)Sc_(1.39)(BO_3)_6 Crystal

The crystal of the title compound Sr6Gd0.61Sc1.39(BO3)6 (Mr = 1037.00) was grown by Czochralski method. It crystallizes in trigonal, space group 3Rwith a = 12.415(2), c = 9.274(2) ? Z = 3, V = 1238.0(4) 3, Dc = 4.173 g/cm3, l(MoKa) = 0.71073 ? m = 22.278 mm-1, F(000) = 1411, S = 1.213, the final R = 0.0577 and wR = 0.1414 for 401 observed reflections with I>2s(I). In the structure Gd(1)O6 (Gd(1) = Gd0.46 + Sc0.54) and Gd(2)O6 (Gd(2)= Gd0.15 + Sc0.85) are alternately stacked between the planar triangular BO3 groups to form chains extending along the trigonal axis. These chains are connected through the 9-coordinate Sr atoms.

The effect of an optical pump on the absorption coefficient of magnesium-doped near-stoichiometric lithium niobate in terahertz range

The absorption coefficient of magnesium-doped near-stoichiometric lithium niobate crystal is measured by terahertz time-domain spectroscopy in a frequency range of 0.2 THz^0.9 THz at room temperature. The absorption coefficient is modulated by external optical pump fields. Experimental results show that the absorption coefficient of near-SLN：Mg crystal is approximately in a range of 22 cm- 1_35 cm- 1 in a frequency range of 0.2 THz-0.9 THz and tunable up to nearly 15%. Further theoretical analysis reveals that the variation of absorption coefficient is related to the number of light-induced carriers, domain reversal process, and OH- absorption in this crystal.

Effect of slope position on leaf and fine root C,N and P stoichiometry and rhizosphere soil properties in Tectona grandis plantations

Little is known about C-N-P stoichiometries and content in teak(Tectona grandis)plantations in South China,which are mostly sited on hilly areas with lateritic soil,and the effect of slope position on the accumulation of these elements in trees and rhizosphere soils.Here we analyzed the C,N,P content and stoichiometry in leaves,fine roots and rhizosphere soils of trees on the upper and lower slopes of a 12-year-old teak plantation.The Kraft classification system of tree status was used to sample dominant,subdominant and mean trees at each slope position.The results showed that the C,N and P contents in leaves were higher than in fine roots and rhizosphere soils.The lowest C/N,C/P and N/P ratios were found in rhizosphere soils,and the C/N and C/P ratios in fine roots were higher than in leaves.Nutrient accumulation in leaves,fine roots and rhizosphere soils were significantly influenced by slope position and tree class with their interaction mainly showing a greater effect on rhizosphere soils.Leaf C content and C/N ratio,fine root C and P contents,and C/N and C/P ratios all increased distinctly with declining slope position.The contents of organic matter(SOM),ammonium(NH4+-N),nitrate-nitrogen(NO3--N)and available potassium(AK)in rhizosphere soils were mainly enriched on upper slopes,but exchange calcium(ECa),available phosphorus(AP),and pH were relatively lower.Variations in the C,N and P stoichiometries in trees were mainly attributed to the differences in rhizosphere soil properties.N and P contents showed significant positive linear relationships between leaf and rhizosphere soil,and C content negative linear correlation among leaves,fine roots and rhizosphere soils.Chemical properties of rhizosphere soils,particularly C/N and NH4+-N,had significant effects on the leaf nutrients in trees on the upper slope.Correspondingly,rhizosphere soil properties mainly influenced fine root nutrients on the lower slope,and soil AK was the major influencing factor.Overall,these results offer new insights for the sustainability and management of teak plantations in hilly areas.

Anomalous microstructure and magnetocaloric properties in off-stoichiometric La–Fe–Si and its hydride

In the present work we reported the phase formation, microstructure, magnetocaloric effect and hydrogenation behavior of La-rich La1.7Fe11.6Si1.4alloy. In this off-stoichiometric La（Fe,Si）13alloy, the Na Zn13-type La（Fe,Si）13matrix phase shows faceted grains, with the Cr5B3-type La5Si3 used as the secondary phase distributed intergranularly. Such a peculiar morphology quickly forms upon one day annealing. In La1.7Fe11.6Si1.4alloy, we have observed a significant field dependence of magnetostructural transition temperature（～ 6.3 K/T）, resulting in a large and table-like entropy change（△S～ 18 J/kg·K in 2 T） over a broad temperature range（～ 10 K）. Upon hydrogenation, the maximum value of △S keeps almost unchanged, while the Curie temperature increases up to 350 K. These results indicate that the investigated offstoichiometric La（Fe,Si）13alloy is a promising magnetic material for magnetic refrigerators.