Free radicals trigger the closure of open pores in lignin-derived hard carbons toward improved sodium-storage capacity

The chemical activation of various precursors is effective for creating additional closed pores in hard carbons for sodium storage.However,the formation mechanism of closed pores under the influence of pore-forming agents is not well understood.Herein,an effective chemical activation followed by a high-temperature self-healing strategy is employed to generate interconnected closed pores in lignin-derived hard carbon(HCs).By systematic experimental design combined with electron paramagnetic res-onance spectroscopy,it can be found that the content of free radicals in the carbon matrix influences the closure of open pores at high temperatures.Excessively high activation temperature(>700 C)leads to a low free radical concentration,making it difficult to achieve self-healing of open pores at high tempera-tures.By activation at 700°C,a balance between pore making and self-healing is achieved in the final hard carbon.A large number of free radicals triggers rapid growth and aggregation of carbon microcrys-tals,blocking pre-formed open micropores and creating additional interconnected closed pores in as-obtained hard carbons.As a result,the optimized carbon anode(LK-700-1300)delivers a high reversible capacity of 330.8 mA h g^(-1) at 0.03 A g^(-1),which is an increase of 86 mA h g^(-1) compared to the pristine lignin-derived carbon anode(L-700-1300),and exhibits a good rate performance(202.1 mA h g^(-1) at 1 A g^(-1)).This work provides a universal and effective guidance for tuning closed pores of hard carbons from otherprecursors.

The Negative Thermal Expansion Property of NdMnO_(3) Based on Pores Effect and Phase Transition

A novel negative thermal expansion(NTE) material NdMnO_(3) was synthesized by solid-state method at 1 523 K. The crystal structure, phase transition, pores effect and negative expansion properties of NdMnO_(3) were investigated by variable temperature X-ray diffraction(XRD), scanning electron microscope(SEM) and variable temperature Raman spectra. The compound exhibits NTE properties in the orderly O' phase crystal structure. When the temperature is from 293 to 759 K, the ceramic NdMnO_(3) shows negative thermal expansion of-4.7×10^(-6)/K. As temperature increases, the ceramic NdMnO_(3) presents NTE property range from 759 to 1 007 K. The average linear expansion coefficient is-18.88×10^(-6)/K. The physical mechanism of NTE is discussed and clarified through experiments.

Maceral evolution of lacustrine shale and its effects on the development of organic pores during low mature to high mature stage:A case study from the Qingshankou Formation in northern Songliao Basin,northeast China

Organic matter(OM)hosted pores are crucial for the storage and migration of petroleum in shale reservoirs.Thermal maturity and macerals type are important factors controlling the development of pores therein.In this study,six lacustrine shale samples with different thermal maturities from the first member of the Qingshankou Formation in the Songliao Basin,of which vitrinite reflectance(R_(o))ranging from 0.58% to 1.43%,were selected for a comparative analysis.Scanning electron microscopy(SEM)and reflected light microscopy were combined to investigate the development of organic pores in different macerals during thermal maturation.The results show that alginite and liptodetrinite are the dominant primary macerals,followed by bituminite.Only a few primary organic pores developed in the alginite at the lowest maturity(R_(o)=0.58%).As a result of petroleum generation,oil-prone macerals began to transform to initial-oil solid bitumen at the early oil window(R_(o)=0.73%)and shrinkage cracks were observed.Initial-oil solid bitumen cracked to oil,gas and post-oil bitumen by primary cracking(R_(o)=0.98%).Moreover,solid bitumen(SB)was found to be the dominant OM when R_(o)>0.98%,which indicates that SB is the product of oil-prone macerals transformation.Many secondary bubble pores were observed on SB,which formed by gas release,while devolatilization cracks developed on migrated SB.Additionally,at the late oil window(Ro?1.16%),migrated SB filled the interparticle pore spaces.With further increase in temperature,the liquid oil underwent secondary cracking into pyrobitumen and gas,and spongy pores developed on the pyrobitumen at higher levels of maturity(Ro=1.43%),which formed when pyrobitumen cracked into gas.Vitrinite and inertinite are stable without any visible pores over the range of maturities,verifying their low petroleum generation potential.In addition,it was concluded that clay minerals could have a catalytic effect on the petroleum generation,which may explain why organicclay mixtures had more abundant pores than single OM particles.However,after R_(o)>0.98%,authigenic minerals occupied the organic pore spaces on the organic-clay mixtures,resulting in fewer pores compared to those observed in samples at the early to peak oil window.

Preparation of Chiral Silica Nanostructures with Radial Pores through Single-templating Approach

A chiral low-molecular-weight gelator(LMWG) L-16Ala5PyPF6 was synthesized from L-alanine, which can cause physical gel in n-propanol, ethyl acetate, butylene oxide, water, benzene, 1,4-dioxane and chloroform. The sol-gel reactions were carried out in a mixture of stronger ammonia water and n-propanol at the volume ratio of 2:8. Single-handed twisted silica nanostructures with pore channels vertical to the wall surfaces were first prepared through a single-templating approach comparing with the reported double template method. The formation mechanism of radial pore structure was studied by transmission electron microscopy at different reaction time intervals, which indicated that the radial pore structure was formed via a structural transition in the sol-gel transcription process.

Organic matter pores in the chang 7 lacustrine shales from the Ordos Basin and its effect on reflectance measurement

To quantify the pore characteristics of various macerals in Chang 7 lacustrine shales,macerals were effectively identified according to their optical and morphological characteristics,and the nanoscale pore structure of macerals was observed by scanning electron microscope.Meanwhile,the reflectances of different positions in the same pieces of vitrinite or solid bitumen with heterogeneous pores development were measured.The results showed that the average contents of sapropelinite,liptinite,vitrinite,inertinite and solid bitumen are 42.7%,8.7%,13.6%,13.8% and 21.2%,respectively,which suggests that the source of the organic matter of the Chang 7 shales is a mixed source input.The organic pores of Chang 7 shales are enriched,and the pore shapes are mostly round or elliptical.The pore size of organic pores has a wide distribution,mainly concentrate in the range of 100-400 nm,and the average plane porosity of organic pores is 10.13%.The size order of the organic pores in various macerals is:solid bitumen<bituminite<alginite<vitrinite<fusinite<liptinite.The abundance order of organic matter pores of each maceral is as follows:alginite>fusinite>bituminite>solid bitumen>vitrinite>liptinite.OM pores are mainly contributed by bituminite,solid bitumen and fusinite.The plane porosity of bituminite increases with maturity.In the process of thermal evolution,the plane porosity of fusinite is distributed in the two ranges of 20%-28% and 1%-7%.The former is mainly the primary pores of the fusinite itself,and the latter is the secondary pores formed in the thermal evolution.As for the organic pores of other macerals,no obvious thermal evolution law was found.Meanwhile,the surface imperfections of vitrinite or solid bitumen is enhanced by the enrichment of organic pores(an increase in pore size or pore number),which may result in the underestimation of their reflectances.

Types and microstructures of pores in shales of the Ordovician Wulalike Formation at the western margin of the Ordos Basin, China

Shale samples from the Ordovician Wulalike Formation at the western margin of the Ordos Basin are studied to define the types, microstructures and connectivity of pores as well as the relationships between the pore structures and gas content of the samples by using experimental techniques such as high-resolution field emission scanning electron microscopy (FESEM), mercury injection capillary pressure (MICP), low-temperature nitrogen adsorption (LTNA), CO_(2) adsorption, and focused ion beam scanning electron microscopy (FIB-SEM). The results show that the shale has 10 different lithofacies, typical mixed sedimentary characteristics, and poorly developed pores. The reservoir space mainly consists of intercrystalline pores, dissolution pores, intergranular pores, and micro-fissures, with organic pores occasionally visible. The pore size is mostly within 0.4–250 nm range but dominated by micropores and mesopores less than 20 nm, with pore numbers peaking at pore sizes of 0.5 nm, 0.6 nm, 0.82 nm, 3 nm, and 10 nm, respectively. The pores are poorly connected and macropores are rarely seen, which may explain the low porosity and low permeability of the samples. Samples with high content of organic matter and felsic minerals are potential reservoirs for oil and gas with their favorable physical properties and high connectivity. The pores less than 5 nm contribute significantly to the specific surface area and serve as important storage space for adsorbed gas.

Size Determination of Ultramicropores and Small Mesopores Using a Calculation Procedure Based on the Tangents of Comparison Plot

Pore size distribution（PSD） curves of synthesized hollow silica spheres with ultrmicropores and small mesopores were obtained from calculations based on the BJH,KJS,SF,MP,NLDFT models and Prof.Zhu＇s method.Comparisons indicate that Zhu＇s method not only gives reasonable small mesopore size but also could be further extended to the ultramicropores region for the PSD evaluation.

Thick and hard anodized aluminum film with large pores for surface composites

Al-base surface self-lubricating composites need thick and hard alumina membranes with large pores to add lubricants easily. This kind of porous alumina layer was fabricated in additive-containing, phosphoric acid-based solution. The effects of additive containing organic carboxylic acid and Ce salt on the properties of the oxide film and mechanism were investigated in detail with SEM and EDAX analyses. The results show that the pore diameter is about 100 nm, the film thickness increases by 4 -5 times, and the Vickers hardness improves by about 50% through adding some amount of organic carboxylic acid and Ce salt. Such an improvement in properties is explained in terms of a lower film dissolving velocity and better film quality in compound solution.

Simulation of methane adsorption in diverse organic pores in shale reservoirs with multi-period geological evolution

In shale reservoirs,the organic pores with various structures formed during the thermal evolution of organic matter are the main storage site for adsorbed methane.However,in the process of thermal evolution,the adsorption characteristics of methane in multi type and multi-scale organic matter pores have not been sufficiently studied.In this study,the molecular simulation method was used to study the adsorption characteristics of methane based on the geological conditions of Longmaxi Formation shale reservoir in Sichuan Basin,China.The results show that the characteristics of pore structure will affect the methane adsorption characteristics.The adsorption capacity of slit-pores for methane is much higher than that of cylindrical pores.The groove space inside the pore will change the density distribution of methane molecules in the pore,greatly improve the adsorption capacity of the pore,and increase the pressure sensitivity of the adsorption process.Although the variation of methane adsorption characteristics of different shapes is not consistent with pore size,all pores have the strongest methane adsorption capacity when the pore size is about 2 nm.In addition,the changes of temperature and pressure during the thermal evolution are also important factors to control the methane adsorption characteristics.The pore adsorption capacity first increases and then decreases with the increase of pressure,and increases with the increase of temperature.In the early stage of thermal evolution,pore adsorption capacity is strong and pressure sensitivity is weak;while in the late stage,it is on the contrary.

Distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression

The distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression have been systematically studied. We investigated sedimentary facies and carried out a comprehensive analy-sis of the vast amount of data from casting thin sections, scanning electron microscope and physical data. Then we analyzed the pore types, pore evolution, distribution and genesis of secondary pores in our study area and discussed the factors controlling the distribution of secondary pores. The results show that pores in the study area are largely composed of intergranular dissolution pores and constituent dissolved pores. Three secondary pore zones were developed in the study area at depths of 2800~3400 m, 3600~4200 m and 4500~4800 m. Secondary pores have been formed mainly because carbonate cement, feldspar, clastic debris and other plastic substances were dissolved by organic acid, released during the evolution of organic matter and acid water formed by CO2. The development and distribution of secondary pores are vertically controlled by the maturity time of source rocks and hori-zontally by the distribution of acid water. As well, this distribution was affected by the sedimentary facies belt and the development of fault zones.

Formation of layer-shaped pores in TiC-Fe cermet by combustion synthesis

To study the formation of layer shaped pores in TiC Fe cermet, two Ti C Fe powder compacts containing Ti powders with two size ranges (< 44μm and 135～ 154μm ) respectively were ignited in a special ignition mode. The combustion temperatures of the reactions were measured, the phase constituents of the combustion synthesized products were inspected by X ray diffractometry (XRD), and the structures of the products were observed with scanning electron microscope (SEM). In the case of the finer Ti powder used, TiC Fe cermet and pore rank in an alternately laminar shape, and the shape of the pore is the same as that of the combustion wavefront, implying that the layer shaped pore results from a gather of the retained gas into the combustion wavefront. While in the case of the coarser Ti powder used, the lower combustion temperature causes the gather of the retained gas to be difficult, the pore being present in an arbitrary shape and distributing randomly.

Efficient Solution of 3D Solids with Large Numbers of Fluid- Filled Pores Using Eigenstrain BIEs with Iteration Procedure

To deal with the problems encountered in the large scale numerical simulation of three dimensional(3D)elastic solids with fluid-filled pores,a novel computational model with the corresponding iterative solution procedure is developed,by introducing Eshelby’s idea of eigenstrain and equivalent inclusion into the boundary integral equations(BIE).Moreover,by partitioning all the fluid-filled pores in the computing domain into the near-and the far-field groups according to the distances to the current pore and constructing the local Eshelby matrix over the near-field group,the convergence of iterative procedure is guaranteed so that the problem can be solved effectively and efficiently in the numerical simulation of solids with large numbers of fluid-filled pores.The feasibility and correctness of the proposed computational model are verified in the numerical examples in comparison with the results of the analytical solution in the case of a single spherical fluid-filled pore under uniform pressure in full space and with the results of the subdomain BIE in a number of other cases.The overall mechanical properties of solids are simulated using a representative volume element(RVE)with a single or multiple fluid-filled pores,up to one thousand in number,with the proposed computational model,showing the feasibility and high efficiency of the model.The effect of random distribution of fluid-filled on overall properties is also discussed.Through some examples,it is observed that the effective elastic properties of solids with a large number of fluid-filled pores in random distributions could be studied to some extent by those of solids with regular distributions.

Formation Mechanism of Micropores on the Surface of Pure Aluminum Induced by High-Current Pulsed Electron Beam Irradiation

The mechanism of micropores formed on the surface of polycrystalline pure aluminum under high-current pulsed electron beam(HCPEB)irradiation is explained.It is discovered that dispersed micropores with sizes of 0.1–1μm on the irradiated surface of pure aluminum can be successfully fabricated after HCPEB irradiation.The dominant formation mechanism of the surface micropores should be attributed to the formation of supersaturation vacancies within the near surface during the HCPEB irradiation and the migration of vacancies along grain boundaries and/or dislocations towards the irradiated surface.It is expected that the HCPEB technique will become a new method for the rapid synthesis of surface porous materials.

Pt-confinement catalyst with dendritic hierarchical pores on excellent sulfur-resistance for hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

Metal confinement catalyst Mo S_(2)/Pt@TD-6%Ti(TD,TS-1/Dendritic mesoporous silica nanoparticles composite) in dendritic hierarchical pore structures was synthesized and showed excellent sulfur-resistance performance and stabilities in catalytic hydrodesulfurization reactions of probe sulfide molecules.The Mo S_(2)/Pt@TD-6%Ti catalyst combines the concepts of Pt-confinement effect and hydrogen spillover of Pt noble metal.The modified micropores of Mo/Pt@TD-6%Ti only allow the migration and dissociation of small H_(2) molecules(0.289 nm),and effectively keep the sulfur-containing compounds(e.g.H_(2)S,0.362 nm) outside.Thus,the Mo S_(2)/Pt@TD-6%Ti catalyst exhibits higher DBT and 4,6-DMDBT HDS activities because of the synergistic effect of the strong H_(2) dissociation ability of Pt and desulfurization ability of Mo S_(2) with a lower catalyst cost.This new concept combining H2dissociation performance of noble metal catalyst with the desulfurization ability of transition metal sulfide Mo S_(2) can protect the noble metal catalyst avoiding deactivation and poison,and finally guarantee the higher activities for DBT and 4,6-DMDBT HDS.

Modeling Tracer Flow Characteristics in Different Types of Pores: Visualization and Mathematical Modeling

Structure of porous media and fluid distribution in rocks can significantly affect the transport characteristics during the process of microscale tracer flow.To clarify the effect of micro heterogeneity on aqueous tracer transport,this paper demonstrates microscopic experiments at pore level and proposes an improved mathematical model for tracer transport.The visualization results show a faster tracer movement into movable water than it into bound water,and quicker occupancy in flowing pores than in storage pores caused by the difference of tracer velocity.Moreover,the proposed mathematical model includes the effects of bound water and flowing porosity by applying interstitial flow velocity expression.The new model also distinguishes flowing and storage pores,accounting for different tracer transport mechanisms(dispersion,diffusion and adsorption)in different types of pores.The resulting analytical solution better matches with tracer production data than the standard model.The residual sum of squares(RSS)from the new model is 0.0005,which is 100 times smaller than the RSS from the standard model.The sensitivity analysis indicates that the dispersion coefficient and flowing porosity shows a negative correlation with the tracer breakthrough time and the increasing slope,whereas the superficial velocity and bound water saturation show a positive correlation.

First report of TSR origin minerals filled in anhydrite dissolved pores in southeastern Ordos Basin

1.Objective Yican 1 well, drilled in Southeastern Ordos Basin by Oil & Gas Survey, China Geological Survey in 2014 produced 3.7×104 m3 natural gas daily, which is the most productive well in the area by far. However, the reservoir quality is poor compared with those of Jingbian gas field in the middle of the Basin, which is mainly caused by the pores filling in karst reservoir.

TiO_2 hierarchical pores/nanorod arrays composite film as photoanode for quantum dot-sensitized solar cells

Power conversion efficiency(PCE) of quantum dot-sensitized solar cells(QDSSCs) was boosted in a TiO_2 composite film(TCSF) with delicate design in structure where TiO_2 hierarchical porous film(THPF) situated on the top of TiO_2 nanorod arrays film(TNAF). In this case, TNAF could supply efficient scattering centers for high light harvesting and direct electrical pathways for fast electron transfer while the THPF could offer porous channels for loading high quantity of previously synthetized quantum dots(QDs) and facilitate the penetration of electrolyte. Meanwhile, in this specific configuration, the presence of anatase–rutile heterojunction at the interface could help the rutile TNAF layer to efficiently collect photo-injected electrons from the anatase THPF layer thus suppressing the recombination of electrons and holes in electrolyte. The results showed that the PCE of QDSSC based on the TNAF photoanode was about 1.4-fold higher(η = 3.05%, J_(sc)= 15.86 m A cm^(-2), V_(oc)= 0.602 V, FF = 0.319) than that of device based on pure THPF(η = 2.20%, J_(sc)= 13.82 m A cm^(-2), V_(oc)= 0.572 V, FF = 0.278).

A Potential Model for Cylindrical Pores

An analytical potential for cylindrical pores has been derived by introducing a variational method into the integration for the calculation of the interaction energy between the wall molecules and a test molecule, all of which are represented by Lennard-Jones potential. The model proposed gives good fit to the results from the cylindrical surface model and the pseudoatom model. To test the potential proposed rigorously, we have carried out grand canonical ensemble Monte Carlo(GCMC) simulation of nitrogen in the MCM-41 pore at 77 K, and compared the simulated adsorption isotherm with the experimental data reported in the literature. The simulated isotherm from our model is in almost qualitative agreement with experiment. Consequently, the model proposed provides an explicit and accurate description of cylindrical pores represented by the Lennard-Jones potential. Moreover, the model can be easily applied to a variety of cylindrical pores, ranging from cylindrical surface to finite thickness walls, in both theoretical studies and computer simulations.

Conductance and DNA Translocation Current Blockage of Solid-State Nanopores

The current blockage during DNA molecule translocation through a solid-state nanopore is very important in DNA analysis techniques based on nanopores.We use Poisson-Nernst-Planck descriptions of electrolyte behavior in a nanopore with and without the presence of DNA molecules to simulate the nanopore conductance and current blockage of DNA molecules. Actual experimental parameters,such as pore size,length of nanopores,DNA drift velocity,and the charge issue of nanopores and DNA,are applied to evaluate the precise current blockage amplitude,which is found to agree very well with the experimental results.

A Novel Titania Membrane with Uniform Macropores

A procedure for fabricating novel TiO_(2) membrane materialwith sub-micrometre pores and large specific surface area from the template has been demonstrated. The morphology and structure of the membrane have been characterized by scanning electron microscopy. The results have indicated that the macroporous membraneconsists of uniform hollow spheres which are interconnected to each other by 'small windows'. Potential unique applications of this macroporous materialin the fields of catalysis, optics, sensors, etc, are suggested.