The evaluation/application of Hydrus-2D model for simulating macro-pores flow in loess soil

Soil hydraulic properties were mainly governed by soil structures especially when the structures is full of the connected soil macro-pores.Therefore,the good hydrological models need to be well documented for revealing the process of soil water movement affected by soil medium.The Hydrus-2D model with double domain was recommended in simulating water movement in a heterogeneous medium of soil.To evaluate the performance of the double domain Hydrus-2D model in loess soil,the dynamic of soil wetting front movement in differential loess soil columns under the constant water head were observed and the processes was simulated by Hydrus-2D model under conditions of different soil properties.The results indicated that the Hydrus-2D model was quite good in simulation of loess soil water movements,and the relative errors of simulation results are less than 15%,MRE less than 5%,and R^(2)>0.9.The results provided the appropriate infiltration parameters of loess soil.

Ceria modified three-dimensionally ordered macro-porous Pt/TiO_2 catalysts for water-gas shift reaction

Three-dimensionally ordered macro-porous （3DOM） TiO2 and ceria-modified 3DOM TiO2 supported platinum catalysts were prepared with template and impregnation methods, and the resultant samples were characterized by scanning electron microscopy（SEM）, X-ray diffractometer（XRD）, high-resolution transmission electron microscopy（HRTEM） and temperature programmed reducfion（TPR） techniques. The catalytic performances over the platinum-based catalysts were investigated for water-gas shift （WGS） reaction in a wide temperature range （180-360 ℃）. The results showed that 3DOM Pt/TiO2 catalyst exhibited obviously better catalytic performance than the corresponding non macro-porous catalyst, owing to the macro-porous structure favoring mass transfer. Addition of celia into 3DOM Pt/TiO2 led to improvement of catalytic activity. TPR and HRTEM results showed that the interaction existed between ceria and titanium oxide and addition of ceria promoted the reducibility of platinum oxide and TiO2 on the interface of platinum and TiO2 particles, which contributed to high activity of the celia modified catalysts. The results indicated that ceria-modified 3DOM Pt/TiO2 was a promising candidate of fuel cell oriented WGS catalyst.

Fabrication of Macro-porous β-zeolite by Using Colloidal Polystyrene Spheres as a Template

A β-zeolite/polystyrene composite material was synthesized by co-deposition of mono-disperse polystyrene spheres and nano β-zeolite particles in aqueous suspension on a vertical substrate. Macro-porous β-zeolite was obtained after the polystyrene template was removed by calcination. The micro/macro-pore structure of the prepared β-zeolite was highly ordered. In comparison with other assembly methods, the co-deposition method could obtain a highly ordered macro-porous material with relatively large zeolite filling particles, and therefore the co-deposition of particles with different size is a promising method for the fabrication of macro-porous materials.

Three-dimensionally ordered macro-porous Pt/TiO_2 catalyst used for water-gas shift reaction

Three-dimensionally ordered macro-porous （3DOM） Pt/TiO2 catalysts were prepared by template and impregnation methods, and the resultant samples were characterized by using TG-DTA, XRD, SEM, TEM, and TPR techniques. The catalytic performance for water-gas shift （WGS） reaction was tested, and the influences of some conditions, such as reduction temperature of catalysts, the amount of Pt loadings and space velocity on catalytic performance were investigated. It was shown that Pt particles were homogeneously dispersed on 3DOM TiO2. The reduction of TiO2 surface was important for the catalytic performance. The activity test results showed that the 3DOM Pt/TiO2 catalysts exhibited very good catalytic performance for WGS reaction even at high space velocity, which was owing to the better mass transfer of 3DOM porous structure besides the high intrinsic activity of Pt/TiO2.

Influence of Geometric Structure of Immobilized Aluminium Chloride Catalyst on Catalytic Property in Isobutene Polymerization

The catalytic property of AICl(3) catalyst immobilized on gamma -Al2O3 for isobutene polymerization has been studied. It was found that the activity, selectivity and stability of the catalyst are dependent greatly on geometric characteristic pf the pore structure and size of catalyst. Although the activity and selectivity of the catalysts with micro- and meso-pore structure are all high in initial stage, but their stability is low, while those with bimodal meso- and macro-pore structure are excellent. Increasing granularity of the catalyst(particle become fine) brings about an increase in isobutene conversion, but a decrease in selectivity, resulting in lower average molecular weight and iis broader distribution.

The facile method developed for preparing polyvinylidene fluoride plasma separation membrane via macromolecular interaction

The design of membrane pore is critical for membrane preparation. Polyvinylidene fluoride(PVDF) membrane exhibits outstanding properties in the water-treatment field. However, it is a huge challenge to prepare PVDF macro-pore plasma separation membrane by non-solvent induced phase separation(NIPS). Herein, a facile strategy is proposed to prepare PVDF macro-pore plasma separation membrane via macromolecular interaction. ATR-FTIR and ^(1)H NMR showed that the intermolecular interaction existed between polyethylene oxide(PEO) and polyvinylpyrrolidone(PVP). It could significantly affect the PVDF macro-pore membrane structure. The maximum pore of the PVDF membrane could be effectively adjusted from small-pore/medium-pore to macro-pore by changing the molecular weight of PEO. The PVDF macro-pore membrane was obtained successfully when PEO-200 k existed with PVP. It exhibited higher plasma separation properties than the currently used plasma separation membrane.Moreover, it had excellent hemocompatibility due to the similar plasma effect, hemolysis, prothrombin time, blood effect and complement C_(3a) effect with the current utilized plasma separation membrane,implying its great potential application. The proposed facile strategy in this work provides a new method to prepare PVDF macro-pore plasma separation membrane by NIPS.

Nano-silica particles enhanced adsorption and recognition of lysozyme on imprinted polymers gels

Molecular imprinting technology has a great potential to be used in protein separation and purification. In this work, lysozyme imprinted polyacrylamide gel was prepared with silica particles as a sacrificial template to generate macro-porosity for fast adsorption. The adsorption equilibrium time and adsorption capacity were 9 h and 56 mg/g respectively, which was 2 h less and 2.3-fold more than polymers without the sacrificial template. In order to test molecular imprinting polymers （MIPs） ＇ selectivity, bovine serum albumin （BSA） was chosen as interferent for binary adsorption tests. In addition, the adsorption selectivity was further investigated using different molar ratios of lysozyme to BSA with fixed total concentration of proteins, as well as using various total concentra- tions of proteins with an equimolar ratio of lysozyme to BSA. It has been proven that the total con- centration of proteins should be larger than 1.5 × 10^-7 mol/mL, when the molar ratio of BSA to Lyz is 1： 1, in order to effectively separate Lyz from the binary protein mixture. The macro-porous lyso- zyme molecularly imprinted polymers have less adsorption time, larger adsorption capacity, and bet- ter imprinting effect.

Biomimetic porous silicon oxycarbide ceramics with improved specific strength and efficient thermal insulation

Considering the challenge of aerodynamic heating,the development of high-performance insulating ce-ramic materials with lightweight and low thermal conductivity is crucially important for aerospace vehi-cles to achieve flight at high speed for a long time.In this work,macro-porous silicon oxycarbide(SiOC)ceramics with directional pores(DP-SiOC)(mean pore size of 88.1μm)were prepared using polysiloxane precursors via freeze casting and photocrosslinking,followed by pyrolysis.The DP-SiOC samples were lightweight(density∼0.135 g cm^(-3))with a porosity of 90.4%,which showed good shapability through the molding of polysiloxane precursors.The DP-SiOC samples also exhibited an ultra-low thermal con-ductivity of 0.048 W(m K)^(-1)at room temperature,which can also withstand heat treatment at 1200°C for 1 h.In addition,scaffolds with triply periodic minimal surfaces(TPMS)were fabricated using digital light processing(DLP)printing,which was further filled with polysiloxane precursors for increasing the strength of DP-SiOC.The TPMS scaffolds filled with macro-porous SiOC ceramics(TPMS-DP-SiOC)showed good integration between TPMS and macro-pore structures,which had a porosity∼75%and high specific strength of 9.73×10^(3)N m kg^(-1).The thermal conductivity of TPMS-DP-SiOC samples was 0.255 W(m K)^(-1)at room temperature.The biomimetic TPMS-DP-SiOC ceramics developed in this study are likely used for thermal protection systems.

Single-Cu-atoms anchored on 3D macro-porous carbon matrix as efficient catalyst for oxygen reduction and Pt co-catalyst for methanol oxidation

Single metal atoms immobilized on a carbon substrate are of great potential for enhancing the catalytic activities for oxygen reduction and methanol oxidation reactions(ORR/MOR)owing to the maximized atom utilization.Herein,single copper atoms(SCAs)are loaded on macro-porous nitrogen-doped carbon(Cu-NC)derived from zeolitic imidazolate framework-8(ZIF-8),which are used as catalysts for ORR and Pt-supports for MOR.For ORR,the catalyst marked as Cu-NC-3 exhibits a higher peak potential of 0.87 V(vs.Reversible hydrogen electrode)than that of commercial Pt/C(0.83 V),mainly attributing to that the 3D macro-porous structure of Cu-NC-3 provides adequate space for uniform dispersion of SCAs as the main active species,and smooth diffusion pathways for fast transport of substances(O_(2),H_(2)O),therefore reducing the overpotential and the intermediate(H_(2)O_(2))generation to enhance ORR activity.For MOR,Pt-Cu-NC-3 has a higher mass activity of 1217.4 mA/mg Pt than that of Pt/C(752.4 mA/mg Pt),and its activity maintenance(decline of 27.6%)is also better than Pt/C(decline of 44.0%)after 5000 cyclic voltammetry(CV)cycles.The interactions between SCAs and Pt nanoparticles should facilitate the generation of OH−from water molecules,which can fast eliminate the adsorbed CO to recover the Pt active sites to improve MOR performance.This synthesis strategy affords a new inspiration to prepare single metal atoms loaded on ZIFs-derived macro-structure with diverse activities for ORR/MOR.

Distribution threshold values of CaCl_2 onto the 10X-zeolite and macro-pore silica gel

The calcium chloride used for adsorption separation of ammonia is promising for its large adsorptive capacity and lower desorption temperature,but difficult to develop because of the liable expansion,lump and chip in the adsorption/desorption process.Composite adsorbents made by monolayer dis-persion of calcium chloride onto carriers with high surface areas exhibit better adsorptive capacity and stability.Several models were developed to confirm the maximum monolayer dispersion capacity of calcium chloride onto the carriers(the distribution threshold value),and the closely packed monolayer dispersion model was considered the most suitable for this study.The distribution threshold values given by this model were 0.60 g CaCl2/(g 10X-zeolite) and 0.38 g CaCl2/(g SiO2).When the divalent salt was dispersed onto the carriers,however,anions were separated into two types,causing that the en-tropy of the system tended to increase and the system was not stable.To minimize the entropy,a new model was put forward as the modified closely packed monolayer dispersion model.Based on this model,the distribution threshold values are 0.52 g CaCl2/(g 10X-zeolite) and 0.33 g CaCl2/(g SiO2),re-spectively.The distribution threshold values were also gained experimentally by XRD quantitative phase analysis:0.61 g CaCl2/(g 10X-zeolite) and 0.31 g CaCl2/(g SiO2).Comparison between experi-mental values of distribution threshold with theoretical ones based on two different model showed that the closely packed monolayer dispersion model fits the monolayer dispersion of calcium chloride onto micro-pore carrier - 10X-zeolite,and the modified closely packed monolayer dispersion model is more suitable for the bigger aperture carrier - macro-pore silica gel.

Microstructure,mechanical property and corrosion behavior of porous Ti-Ta-Nb-Zr

In this paper,biomedical porous Ti-Nb-Ta-Zr with 40%porosity and 166±21μm macro-pore size was successfully fabricated by space holder method.The microstructure,Vickers hardness,compressive and electrochemistry behavior were studied.It results that a few second phases exist inβmatrix of the porous Ti-Nb-Ta-Zr.Its Young's modulus is 0.8 GPa,close to 0.01-3 GPa for trabecular bone.The total recovery strain ratio and pseudoelastic strain ratio are 8.8%and 2.7%,respectively.It fails mainly by brittle cleavage with the fan-shaped and smooth cleaved facets.Although,local ductile fracture by a few dimples and a small amount of transcrystalline fracture with the cleavage of similarly oriented laths in a colony are observed on the fracture surface.The impedance spectrum of porous Ti-Nb-Ta-Zr has the characteristics of half capacitive arc resistance,showing good corrosion resistance in SBF solution.