Metal-Free C_(3)N_(4) with plentiful nitrogen vacancy and increased specific surface area for electrocatalytic nitrogen reduction

As a substitute for synthetic ammonia under mild condition, electrocatalytic nitrogen reduction reaction(NRR) provides a hopeful approach for the development of ammonia. Nevertheless, the current development of NRR electrocatalysts is far from enough and a systematic research is needed to gain a better improvement. This article presents that 2 D C_(3)N_(4)-NV with a large specific surface area and abundant nitrogen vacancies is prepared by a simple and feasible method, and used as a metal-free catalyst for electrocatalytic NRR. Experiment result and density functional theory(DFT) calculation reveal that nitrogen vacancies in 2 D C_(3)N_(4)-NV can act as an efficient active site for catalytic NRR, which is conducive to capturing and activating N_(2), lowering Gibbs free energy(DG) in reaction and inhibiting hydrogen evolution reaction(HER) at the same time. In addition, the larger specific surface area also makes more active site exposed, which is good for the contact between the electrolyte and the active site, thus enhancing its NRR activity. The electrocatalyst shows an excellent catalytic activity for NRR in 0.1 M HCl, including Faradaic efficiency of 10.96%, NH_(3) yields of 17.85 lg h^(-1) mg_(cat)^(-1)., and good stability(over 20 h).

Nickel catalysts supported on MgO with different specific surface area for carbon dioxide reforming of methane

In this paper, three kinds of MgO with different specific surface area were prepared, and their effects on the catalytic performance of nickel catalysts for the carbon dioxide reforming of methane were investigated. The results showed that MgO support with the higher specific surface area led to the higher dispersion of the active metal, which resulted in the higher initial activity. On the other hand, the specific surface area of MgO materials might not be the dominant factor for the basicity of support to chemisorb and activate CO2, which was another important factor for the performance of catalysts. Herein, Ni/MgO(CA) catalyst with proper specific surface area and strong ability to activate CO2exhibited stable catalytic property and the carbon species deposited on the Ni/MgO(CA) catalyst after 10 h of reaction at 650 ?C were mainly activated carbon species.

Relationship between the specific surface area of rust and the electrochemical behavior of rusted steel in a wet–dry acid corrosion environment

The relationship between the specific surface area（SSA） of rust and the electrochemical behavior of rusted steel under wet-dry acid corrosion conditions was investigated. The results showed that the corrosion current density first increased and then decreased with increasing SSA of the rust during the corrosion process. The structure of the rust changed from single-layer to double-layer, and the γ-FeOOH content decreased in the inner layer of the rust with increasing corrosion time; by contrast, the γ-FeOOH content in the outer layer was constant. When the SSA of the rust was lower than the critical SSA corresponding to the relative humidity during the drying period, condensed water in the micropores of the rust could evaporate, which prompted the diffusion of O_2 into the rust and the following formation process of γ-FeOOH, leading to an increase of corrosion current density with increasing corrosion time. However, when the SSA of the rust reached or exceeded the critical SSA, condensate water in the micro-pores of the inner layer of the rust could not evaporate which inhibited the diffusion of O_2 and decreased the γ-FeOOH content in the inner rust, leading to a decrease of corrosion current density with increasing corrosion time.

Effects of Specific Surface Area and Impurities of Reactive Alumina on Properties of Corundum Based Castables

Effects of specific surface area and tiny amount of impurities of reactive alumina on the workability, sinte- ring and high temperature mechanical strength of corun- dum based castables were investigated. The results show that the presence of reactive alumina with high specific surface area leads to accelerating of the hydration of calcium aluminate cement, thus shortening the working time and setting time of the castables, which can be as- cribed that the critical energy barrier for stable nuclei of hydration products of cement can be reduced by the high specific surface area of reactive alumina. The sintering of the corundum based castables can be accelerated by the reactive alumina with high specific surface area and high amount of impurities, however, the reactive alumina with too high specific surface area and impurities can al- so lead to noticeable shrinkage of castables. In addition, high temperature mechanical strength of corundum based castables can be decreased by the higher amount of trace impurities of reactive alumina due to formation of low- melting phase at high temperatures.

A statistical reappraisal of the relationship between liquid limit and specific surface area, cation exchange capacity and activity of clays

More than 500 datasets from the literature have been used to evaluate the relationships of specific surface area (SSA),cation exchange capacity (CEC) and activity versus the liquid limit (LL).The correlations gave R^2 values ranging between 0.71 and 0.92.Independent data were also used to validate the correlations.Estimated SSA values slightly overestimate the measured SSA up to 100 m^2/g.Regarding the estimated CEC values,they overestimated the measured CEC values up to 20 meq/(100 g).A probabilistic approach was performed for the correlations of SSA,CEC and activity versus LL.The analysis shows that the relations of SSA,CEC and activity with LL are robust.Using the LL values,it is possible to assess other basic engineering properties of clays.

Effects of specific surface area of metallic nickel particles on carbon deposition kinetics

Carbon deposition on nickel powders in methane involves three stages in different reaction temperature ranges. Temperature programing oxidation test and Raman spectrum results indicated the formation of complex and ordered carbon structures at high deposition temperatures. The values of I（D）/I（G） of the deposited carbon reached 1.86, 1.30, and 1.22 in the first, second, and third stages, respectively. The structure of carbon in the second stage was similar to that in the third stage. Carbon deposited in the first stage rarely contained homogeneous pyrolytic deposit layers. A kinetic model was developed to analyze the carbon deposition behavior in the first stage. The rate-determining step of the first stage is supposed to be interfacial reaction. Based on the investigation of carbon deposition kinetics on nickel powders from different resources, carbon deposition rate is suggested to have a linear relation with the square of specific surface area of nickel particles.

Surface distribution of alkalinity and specific alkalinity and their application to water mass tracing in Kuroshio area of the East China Sea

Surface distribution and seasonal variation of alkalinity and specific alkalinity in Kuroshio area of the East ChinaSea and their application to the water mass tracing are discussed in this paper. Results show a distinct seasonal variation of the alkalinity, which is concerned with the process of vertical mixing. Different specific alkalinity in various water masses has been found. On the basis of the difference of the specific alkalinity and the distribution of alkalinity, two water fronts in summer season, located at 27°-30°N and 124°-1 27°E, (Ⅰ), and at the northern waters about one latitude from the Taiwan Island, (Ⅱ); one in winter season at about one longitude from coast of mainland of China and 26°-30°N were found. In summer season, about 1-2 longitudes eastward shift of front (Ⅰ) is found by comparison of data in May and August. And the high alkalinity of the northern East China Sea in summer season may be caused by the Huanghe River runoff flowing southward along with the Huanghai Sea Coastal Current.

Preparation of High Surface Area, Large Pore Volume Alumina by Using β-Cyclodextrin as a Non-surfactant Template

A series of alumina samples were prepared using β-cyclodextrin as the non-surfactant template. These samples were characterized by XRD, BET and TEM. The results showed that the alumina samples prepared using β-cyclodextrin template had the higher surface areas （124-484 m^2/g）, larger pore volumes （0.7-1.27 mL/g） and more thermal stability than samples prepared without using β-cyclodextrin.

Performance of Adsorbents for NO_(2) in Furnace Flue Gas

To meet the emission standard of nitrogen oxides(NOx)in the flue gas of batch furnaces through dry adsorption,a calcium-silica inorganic adsorbent was prepared with limestone and quartz as raw materials.Sample Cu-BTC 1#was obtained by solvothermal synthesis,drying and purification in vacuum at 120℃using trimesic acid(H3BTC)and copper nitrate trihydrate(Cu(NO_(3))2·3H_(2)O)as raw materials;likewise,sample Cu-BTC 3#was obtained at 200℃.Sample Cu-BTC 2#was obtained by hydrothermal synthesis,drying and purification in air(metal-organic frameworks,1,3,5-benzene tricarboxylic acid copper).The two types of materials were tested in terms of the NO_(2) adsorption,and then the specific surface area,pore volume,NO_(2) adsorption performance,phase composition,microstructure and thermal stability of the adsorbent materials were exploredvia N_(2) physical adsorption-desorption,SEM,XRD and TG characterization.The results show that:(1)the Cu-BTC samples have higher adsorption capacity than the calcium-silica adsorbent,in which sample Cu-BTC 3#has the largest specific surface area and pore volume,thus adsorption capacity for NO_(2);(2)the calcium-silica adsorbent has better thermal stability and lower total mass loss during the entire process than the Cu-BTC samples;sample Cu-BTC 2#has the best thermal stability among the three Cu-BTC samples,and the metal Cu active sites of the Cu-BTC samples can be exposed at least above 150℃.

Oxidation and Electrical Properties of Cu-Mn_(3)O_(4)Composite Coating Obtained by Electrodeposition on SOFC Interconnects

Cu-Mn_(3)O_(4)composite coating was prepared on the SUS 430 ferritic stainless steel by electrodeposition and then exposed in air at 800℃corresponding to the cathode atmosphere of solid oxide fuel cell(SOFC).A dual-layer oxide structure mainly comprising an external layer of CuO followed by(Cu,Mn,Fe)_(3)O_(4)spinel and an internal layer of Cr-rich oxide was thermally developed on the coated steel.The scale area-specific resistances(ASRs)of the coated steels were lower than the scale ASR of the uncoated steel after identical thermal exposure.The external layer of CuO/(Cu,Mn,Fe)_(3)O_(4)spinel not only served as a barrier to reduce the growth rate of Cr-rich oxide internal layer and to suppress the outward diffusion of Cr,but also lowered the surface scale ASRs considerably.

EXPERIMENTAL STUDY ON ULTRAFINE COMMINUTION IN THEORY OF VERTIGINOUS CURRENT OF BULK MATERIAL

Experiment about ultrafine comminution in theory of vertiginous current of bulk material has successfully performed by a lately developed vertical shaft centrifugal autogenous grinder. The results of tested several materials are analyzed, moreover. the comminution mechanism and the affecting factors of ultrafine comminution are analyzed.

RESEARCH ON CLEANUP AND ACTIVATION OF SEPIOLITE

A simple process of purifying and activating sepiolite is introduced. Impure minerals in sepiolite can be removed by fully agitating the sepiolite suspension to which a few amount of disperser has been added. After being purified and activated, fine sepiolite particles present prior properties such as increased specific area,better dispersiveness and increased adsorptivity, moreover, the pulping ratio can be raised from original 4-5m3/2 to 20m3 /t. The process with simple technique and utilizing cheap chemical agents extends the application of low-grade sepiolite.

Adsorption Isotherm of BET Nitrogen of Concretes with Consolidated Soil by Sugar Cane Molasses

Sugar cane molasses is often poured out on roads with soil in the city of Nkayi,Republic of Congo in order to reduce the dust.Nitrogen physical adsorption has allowed us to collect information on the state of the accessible total area according to the quantity of sugar cane molasses.The adsorption isotherms,the specific area,the adsorbed quantity of nitrogen on a Qm mono layer,the number of molecules constituting the adsorbed sugar cane molasses(n′)have been examined.The obtained results show that the quantity of sugar cane molasses in the material does not modify the adsorption isotherm of nitrogen of type IV that remains and a hysteria loop of type H4 in all samples,this justifies the monocoat-multicoat adsorption mechanism with capillary condensation and mesopores presence in the structure of materials.Materials with elaborated raw soil by clayey fine soil used are mesoporous materials.More of 50×1018 molecules constituting sugar cane molasses occupy the extreme area accessible to soil clay,without occupying on accessible sites.

The scaling method of specific catchment area from DEMs

Specific Catchment Area （SCA） is defined as the upstream catchment area of a unit contour. As one of the key terrain parameters, it is widely used in the modeling of hydrology, soil erosion and ecological environment. However, SCA value changes significantly at different DEM resolutions, which inevitably affect terrain analysis results. SCA can be described as the ratio of Catchment Area （CA） and DEM grid length. In this paper, the scale effect of CA is firstly investigated. With Jiuyuangou Gully, a watershed about 70 km2 in northern Shaanxi Province of China, as the test area, it is found that the impacts of DEM scale on CA are different in spatial distribution. CA value in upslope location becomes bigger with the decrease of the DEM resolution. When the location is close to downstream areas the impact of DEM scale on CA is gradually weakening. The scale effect of CA can be concluded as a mathematic trend of exponential decline. Then, a downscaling model of SCA is put forward by introducing the scale factor and the location factor. The scaling model can realize the conversion of SCA value from a coarse DEM resolution to a finer one at pixel level. Experiment results show that the downscaled SCA was well revised, and consistent with SCA at the target resolution with respect to the statistical indexes, histogram and spatial distribution. With the advantages of no empirical parameters, the scaling model could be considered as a simple and objective model for SCA scaling in a rugged drainage area.

Differences in leaf functional traits between red and green leaves of two evergreen shrubs Photinia×fraseri and Osmanthus fragrans

Leaf functional traits are adaptations that enable plants to live under different environmental conditions. This study aims to evaluate the differences in leaf functional traits between red and green leaves of two evergreen shrubs Photinia × fraseri and Osrnanthus fragrans. Specific areas of red leaves are higher than that of green leaves in both species. Thus, the material investment per unit area and per lamina of red leaves is significantly lower than that of green leaves, implying an utmost effort of red leaves to increase light capture and use efficiency because of their low leafchlorophyll concentration. The higher petiole length of green leaves compared with that of red leaves indicates that adult green leaves may have large fractional biomass allocation to support the lamina structures in capturing light with maximum efficiency and obtaining a high growth rate. The high range of the phenotypic plasticity of leaf size, leaf thickness, single-leaf wet and dry weights, and leaf moisture of green leaves may be beneficial in achieving efficient control of water loss and nutrient deprivation. The high range of phenotypic plasticity of leaf chlorophyll concentration of red leaves may be advantageous in increasing resource （especially light） capture anduse efficiency because this leaf type is juvenile in the growth stage and has low leaf-chlorophyll concentration.

Effect of Heat Treatment on Silica Aerogels Prepared via Ambient Drying

Silica aerogels were prepared at ambient drying by using ethanol/trimethylchlorosilane （TMCS）/heptane solution as pore water exchange and surface modification of the wet gel before drying. The obtained silica aerogels exhibit a sponge-like structure with uniform pore size distribution. The effects of heat-treatment on the hydrophobicity, specific surface area and other properties were investigated. The results indicated that the hydrophobicity of silica aerogels could be maintained up to 350℃. With increasing heating temperature, hydrophobicity decreased, and became completely hydrophilic after heat-treatment at 500℃. Brunaueremmitt-teller （BET） surface area results indicated that the specific surface area of silica aerogels increased with increasing heating temperature in the range of 150-500℃. The effects of heat-treatment on the morphology and chemical bonding state of silica aerogels were investigated by scanning electron microscopy （SEM）, differential temperature analysis （DTA） and Fourier-transform infrared spectroscopy （FT-IR）.

Preparation and Characterization of Microporous Nano-Tungsten Trioxide and Its Photocatalytic Activity after Doping Rare Earth

Aqueous sols and gels of tungstic acid were prepared from Na2WO4 with protonated cation-exchange resin. Nano-tungsten oxide of a microporous lamella was synthesized by means of washing of WO3· 2H2O with distilled water under ultrasonic wave agitation and centrifuging repeatedly, and the specific surface area tended to increase gradually with washing and centrifuging. The sample of centrifuged 7 h has more than 2 times highs specific surface area and more high photocatalytic activity . The mechanisms are also discussed.

Physiological responses of Populus euphratica Oliv. to groundwater table variations in the lower reaches of Heihe River, Northwest China

Riparian vegetation in the lower reaches of Heihe River serves important ecological functions. However, the riparian ecosystems have been constantly deteriorating in the past 30 years simply due to water interception for oasis agricultural irrigation in the middle reaches of the river. This study pays a particular attention to Populus eu- phratica Oily. forest because it is a dominant component of the riparian ecosystem in the lower reaches of Heihe River where the depth of groundwater table is the controlling factor in sustaining riparian ecosystems. To reveal leaf-related physiological responses of Populus euphratica Oliv. forest to groundwater table variations, we analyzed the relationships between the depth of groundwater table （DG） and three leaf-related parameters, i.e. leaf stomatal density （SD）, specific leaf area （SLA）, and stable carbon isotopic composition （6~SC）. Our results show that the relationship between DG and leaf SD is a bi-mode one shaped by both salt stress and water stress. That is, salt stress appeared in shallow groundwater conditions and water stress happened in deep groundwater conditions, and the thin layer around 2.7 m of DG is a stress-free layer. Leaf SD fluctuated according to the DG variation, first de- creased with increasing DG, then increased at depths ranging 2.7-3.7 m, and after a relatively stable plateau of SD at depths ranging 3.7-5.2 m, decreased again with increasing DG. Our results also show that SLA decreased ex- ponentially with increasing DG and foliar 6130 values are also strongly dependent on DG, further demonstrating that these two parameters are sensitive indicators of water stress. The exponential curve suggests that SLA is more sensitive to DG when groundwater table is shallow and 3 m seems to be a threshold beyond which SLA becomes less sensitive to DG. Foliar 613C becomes more sensitive when the groundwater table is deep and 7 m seems to be a threshold below which the 6130 signature becomes more sensitive to DG. These findings should be helpful in monitoring the growth and development of Populus euphratica Oliv. forests and also in providing protection measures （i.e. DG related） for Heihe River riparian forests.

Well-dispersed NiCoS_(2) nanoparticles/rGO composite with a large specific surface area as an oxygen evolution reaction electrocatalyst

Developing efficient oxygen evolution reaction(OER) electrocatalysts such as transition metal sulfides(TMSs) is of great importance to advance renewable hydrogen fuel toward further practical applications.Herein,NiCoS_(2) nanoparticles well decorated on double-sided N-doped reduced graphene oxide sheets(NiCoS_(2)/rGO) are prepared from an Al-containing ternary NiCoAl-layered double hydroxide precursor(NiCoAl-LDH) grown on GO support as an OER electrocatalyst.The Al-confinementassisted sulfurization,followed by selective acid treatment,endows the resulting NiCoS_(2)/rGO composite with the advantages:well-dispersed NiCoS_(2) nanoparticles,dualsided rGO support,as well as a large specific surface area of 119.4 m^(2)·g^(-1) and meso-/macroporous size distribution.The NiCoS_(2)/rGO electrocatalyst exhibits an overpotential of 273 mV at 10 mA·cm^(-2) and a good stability of 24 h,which outperform those of the counterparts of NiS_(2)/rGO and CoS_(2)/rGO.The results of electrochemical active surface area and electrochemical impedance spectra experimentally provide convincing rationales of the information of active sites and good conductivity,both underpin the enhanced electrocatalytic performances.

A modified Kozeny-Carman equation for predicting saturated hydraulic conductivity of compacted bentonite in confined condition

Kozeny-Carman(KC) equation is a well-known relation between hydraulic conductivity and pore properties in porous material. The applications of KC equation to predicting saturated hydraulic conductivities of sands and non-expansive soils are well documented. However, KC equation is incapable of predicting saturated hydraulic conductivity of expansive soil(e.g. bentonite) well. Based on a new dualpore system, this study modified KC equation for improving the prediction of saturated hydraulic conductivities of bentonites. In this study, an assumption that inter-layer space(micropore) has limited effect on fluid flow performance of compacted bentonite was adopted. The critical parameters including total porosity and total tortuosity in conventional KC equation were replaced by macroporosity and tortuosity of macropore, respectively. Macroporosity and microporosity were calculated by basal spacing of compacted bentonite, which was estimated by assuming that specific surface area is changeable during saturation process. A comprehensive comparison of bentonite’s saturated hydraulic conductivity predictions, including modified KC equation proposed in this study, conventional KC equation, and prediction method based on diffuse double layer(DDL) theory, was carried out. It was found that the predicted saturated hydraulic conductivity of bentonites calculated using modified KC equation fitted the experimental data better than others to a certain extent.