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The changes in crystal structure and pore size of wheat straw fiber after repeated recycling were studied by means of X-ray diffraction, Fourier transform infrared spectrophotometry, and transmission electron microscopy. The results showed that in unbleached wheat straw cellulose crystallinity increased and the water retention value decreased with increasing rounds of recycling. After five rounds, the crystallinity increased by 14.6% compared with fiber never used for papermaking. The width of the crystallite in a 002 lattice plane (L 002 ) increased after each round of recycling, which indicated co-crystallization during the recycling process. The pore-size distribution of wheat straw fiber consisted of numerous micropores and mesopores but few macropores. The pore volumes of pulp micropores and mesopores decreased after two rounds of recycling, but subsequent rounds scarcely affected the pore-volume distribution. The average pore size and specific surface area of the fiber decreased after recycling. In addition, after recycling and rewetting, the fiber lumen became irreversibly collapsed and distorted, with numerous pleats that changed the shapes and size of the pores.

The full pore size distribution represents the integrated characteristics of micro‐nano pore‐throat systems in tight reservoirs. And it involves experiments of different scales to fully analyze the microscope properties. In this paper, we established a new approach for full pore size characterization through conducting the high‐pressure mercury intrusion (HPMI) experiments and low‐temperature nitrogen gas adsorption (LTN2GA) experiments. Meanwhile, we studied the petrology feature of the tight sandstones through X‐ray diffraction (X‐rD) and TESCAN Integrated Mineral Analyzer (TIMA). Then, we investigated the HPMI capillary pressure curves and pore size distribution characteristics, as well as the adsorption‐desorption isotherms features and BET‐specific surface area. Finally, the BJH, non‐local density functional theory (NLDFT) and the quenched solid density functional theory (QSDFT) are contrasted for analyzing the adsorption and pore size distribution characteristics. The HPMI method characterizes the macropores distribution accurately, and the micro/mesopores take up of 14.47% of the total pore spaces. The physisorption isotherms take on the combining shape of type II and IV(a), and the hysteresis loops are like type H3 combined with H4. The BET‐specific surface area is inversely proportional to permeability, and the constant of adsorption heat shows consistence with the analysis results of mineral content. QSDFT can characterize the pore size distribution of micro/mesopores more accurately than the BJH, HPMI, and NLDFT method. By combining the pores narrower than 34 nm calculated from QSDFT method and pores larger than 34 nm calculated from HPMI data with mercury intrusion pressure lower than 42.65 MPa, the full pore size distribution features of tight sandstones are accurately characterized. The micro/mesopores from the new combination method are 3.72% more than that calculated from the HPMI data, and it is of great significance for the accurate pore distribution evaluation and development of tight reservoirs. We performed low‐temperature nitrogen gas adsorption (LTN2GA), high‐pressure mercury intrusion (HPMI), and X‐ray diffraction (X‐rD) experiments on different ultra‐low permeability/tight sandstones to accurately characterize the full pore size distribution of this kind of reservoir rocks. By combining the micropore and mesopore distribution calculated by QSDFT with the mesopore and macropore distribution calculated by HPMI, the accurate characterization of full pore size distribution for the ultra‐low permeability/ tight sandstones is achieved.

Functional graded materials are gaining increasing attention in tissue engineering (TE) due to their superior mechanical properties and high biocompatibility. Triply periodic minimal surface (TPMS) has the capability to produce smooth surfaces and interconnectivity, which are very essential for bone scaffolds. To further enhance the versatility of TPMS, a parametric design method for functionally graded scaffold (FGS) with programmable pore size distribution is proposed in this study. Combining the relative density and unit cell size, the effect of design parameters on the pore size was also considered to effectively govern the distribution of pores in generating FGS. We made use of Gyroid to generate different types of FGS, which were then fabricated using selective laser melting (SLM), followed by investigation and comparison of their structural characteristics and mechanical properties. Their morphological features could be effectively controlled, indicating that TPMS was an effective way to achieve functional gradients which had bone-mimicking architectures. In terms of mechanical performance, the proposed FGS could achieve similar mechanical response under compression tests compared to the reference FGS with the same range of density gradient. The proposed method with control over pore size allows for effectively generating porous scaffolds with tailored properties which are potentially adopted in various fields.

The main purpose of comprehensive reservoir characterization is to reliably calculate, characterize and identify petrophysical parameters including porosity, permeability, rock fabrics, pore size distribution, pore network system, saturation and capillary pressure. These essential petrophysical properties could be achieved by a combination of Nuclear Magnetic Resonance (NMR), conventional and special core analysis (CCAL/SCAL) in core laboratories. In this study, six core plug samples from the Asmari carbonate Formation in Gachsaran oilfield have been examined by the core measurements and NMR technique to evaluate and compare the petrophysical properties. Initially, the plug samples are prepared by core plugging, trimming, solvent cleaning and oven drying methods. Comparison between well Gamma ray log and core gamma ray adjust the depth to the real position of reservoir target. Basic SCAL measurements are then conducted on the prepared plugs in steps to calculate porosity, permeability, capillary pressure and fluid movements. Then the dry samples are completely saturated with brine and the basic properties are re-measured by the NMR method. The relationship between rock quality values (porosity and permeability) determined from NMR technique and core results demonstrate that by applying some adjustments on NMR modeled values, the precise results are achievable. Pore size distribution curves displayed in this paper confirm the NMR modeled pore throat curves and shows NMR could be applied as useful technique for estimating pore size distribution when they are in agreement with Mercury Injection Capillary Pressure (MICP) pore size distribution. The NMR pseudo capillary pressure curves show consistency with capillary pressure and saturation behavior of MICP tests. In addition, the lithology, rock fabric and pore shapes are checked by petrographic images of thin sections as representative of microscopic reservoir characteristics in the reservoir. In present study, applying of NMR technique to the plugs and comparison the obtained results with SCAL results demonstrate how the NMR technique can objectively and quantitatively provide petrophysical analysis for a carbonate reservoir and combination of core analysis and NMR technique could optimize reservoir quality investigation.

The mechanical properties of rocks are significantly affected by chemical corrosion. To explore the influence of chemical corrosion on the weakening laws of sandstone mechanical properties, the porosity and pore size distribution (PSD) of sandstone samples immersed in different chemical solutions was measured by the nuclear magnetic resonance (NMR) technique. The damage variable based on the change of porosity was proposed to analyse the chemical damage to the sandstone samples. Moreover, both compressive and Brazilian tensile tests under static and dynamic conditions were carried out using a conventional servo-controlled testing machine and a split Hopkinson pressure bar (SHPB) system. The results showed that the porosity and proportion of macropores of the sandstone increase after chemical corrosion. The weakening laws of compressive and tensile strength of the sandstone under static and dynamic states are similar, and the relations among them and the damage variable are exponential. The dynamic tensile strength is most sensitive to the effects of chemical corrosion. The order of the degree of damage of chemical solutions on mechanical properties of sandstone is: DH2SO4 > DNaOH > DDistilledwater. Based on the experimental data, the relationships between the mechanical properties and chemical damage variable can be described as exponential equations. Additionally, the variations of dynamic increase factors versus chemical damage variable, the relationship between PSD and the strength of the chemically corroded sandstone, and the corrosion mechanism are also investigated.

The pore structure of biochar determines many biochar-induced environmental serves. In order to predict quantitatively, the environmental serves of biochar, it is very important to characterize the porosity and pore size distribution of biochar and to understand how biochar pore structure relates to the environmental serves. In this study, pore characteristics of biochars derived from different feedstocks were determined using nitrogen adsorption and the mercury intrusion porosimetry (MIP) methods. A great variation of pore characteristics in biochar was found, depending on feedstock material. The specific surface area (SSA) of biochars varied greatly, ranging from 1.06 to 70.22 m 2 /g. Total pore volume and porosity of biochars determined by the MIP method ranged from 1.28 to 3.68 cm 3 /g and from 57.8 to 79.7%, respectively. The pore size distribution of biochars had bimodal peaks in the range of 5–15 and 1.5–5 μm for the herbaceous plant and broad-leaf forest biochars, while coniferous forest biochar had two peaks at the pore sizes of 6–25 and 1.5–3 μm, respectively. Biochars had substantial storage pores (0.5–50 μm), accounting for about 85% of total pore volume, and small transmission and residual pores. The herbaceous plant biochars had larger volume of transmission pores (> 50 μm) than broad-leaf and coniferous forest biochar. Effects of pyrolysis conditions (temperature and residence time) on pore characteristics largely depended on feedstocks types. The difference in feedstocks would greatly affect pore characteristics of biochar, while the effect of pyrolysis conditions on biochar pore characteristics varied with biomass type. The detailed characterization of pore structure in biochars could effectively predict the potential impacts of biochars as soil amendment and pollutant sorbent.

The pore structure of loess greatly influences its collapse potential and other engineering properties. In this study, the pore structures of Malan loess from Lanzhou (LZ), Qingyang (QY) and Jingyang (JY) and their changes during collapse were characterized and compared through microcomputed tomography (µ-CT) scanning and mercury intrusion porosimetry (MIP) test. The correlation between pore structure and collapse potential was addressed, and a pore classification was ultimately suggested. The results indicate that the LZ loess has a more homogeneous pore structure with inter-skeleton particle pores and spaced pores than the QY and JY loesses with primary inter and intra-aggregate pores and constricted pores. During collapse, pores larger than 35 μm changed into smaller pores, accompanied by a decrease of entrance pores larger than 8 μm in the three loess samples. The pores change in size through two major ways, one is that skeleton particles slide and rearrange, causing the collapse of inter-skeleton and spaced pores and a decrease or closing of pore channels (i.e., for LZ loess). The other is that clay buttresses swell and disperse in the inter-aggregate pores, separating large pores into smaller ones, and forming a more homogeneous pore structure and more pore channels (i.e., for QY loess and JY loess). The dominant inter-skeleton particle pores and the large mean pore size in the LZ loess contribute to its greatest collapse potential. Based on the discrete pore size distributions and their changes, 10, 35 and 80 μm were selected as boundaries for pore classification in terms of collapsibility.

Soil microstructure affects the physical and mechanical properties of a loess; current methods used for measuring pore size distribution (POSD) inside loess samples, however, have certain limitations. To investigate the intrinsic connection between soil–water characteristic curve (SWCC) and pore size distribution curves, water potential, moisture content, and nuclear magnetic resonance (NMR) tests on compacted loess with different dry densities were undertaken to obtain a SWCC and an NMR T2 curve. The Van Genuchten (VG) model was used to satisfactorily fit SWCC and POSD curves of samples with different dry densities. Results indicated that the shape and changing trend of SWCC and cumulative POSD curves were very similar. The evolution mechanism of SWCC was investigated by comparing POSD and SWCC of different dry density specimens. Thus, the modified VG model can fit the cumulative POSD very well. As SWCC and cumulative POSD curve fitting parameters were found to have a linear relationship, indicating that SWCC strongly depends on soil POSD, the SWCC curve can, therefore, be used to predict the POSD curve. The matric suction corresponding to the inflection point of the SWCC curve has a one-to-one correspondence with the relaxation time corresponding to the peak of the T2 curve. Based on the results, an equation for solving the transverse surface relaxation strength (ρ2) is proposed, which provides a new idea for the application of NMR in the soil field.

Loess is widely distributed in China and it is commonly considered as the problematic soil due to its collapsibility subjected to the water invasion. The microstructure plays an important role in the mechanical properties of the loess soil. In this note, the microstructures of intact loess samples and the inundated loess sample were investigated by using both mercury intrusion porosimetry (MIP) and nuclear magnetic resonance cryoporometry (NMRC). It is observed from the results of both MIP and NMRC tests that the intact loess has a multi-model pore size distribution function while the inundated loess has a unimodal pore size distribution function. As the coefficient of collapsibility ( δ s ) is a key parameter commonly used for the evaluation of the engineering properties of the loess, the δ s of the specimens tested under different conditions was measured. Subsequently, a new multi-variable linear model was proposed for the estimation of δ s from the index properties based on the results of factor analyses. The estimated results of δ s from the proposed model show good agreements with the measured data.

Geopolymers offer a potential alternative to ordinary Portland cement owing to their performance in mechanical and thermal properties, as well as environmental benefits stemming from a reduced carbon footprint. This paper endeavors to build upon prior atomistic computational work delving deeper into the intricate relationship between pH levels and the resulting material’s properties, including pore size distribution, geopolymer nucleate cluster dimensions, total system energy, and monomer poly-condensation behavior. Coarse-grained Monte Carlo (CGMC) simulation inputs include tetrahedral geometry and binding energy parameters derived from DFT simulations for aluminate and silicate monomers. Elevated pH values may can alter reactivity and phase stability, or, in the structural concrete application, may passivate the embedded steel reinforcement. Thus, we examine the effects of pH values set at 11, 12, and 13 (based on silicate speciation chemistry), investigating their respective contributions to the nucleation of geopolymers. To simulate a larger system to obtain representative results, we propose the numerical implementation of an Octree cell. Finally, we further digitize the resulting expanded structure to ascertain pore size distribution, facilitating a comparative analysis. The novelty of this study is underscored by its expansion in both system size, more accurate monomer representation, and pH range when compared to previous CGMC simulation approaches. The results unveil a discernible correlation between the number of clusters and pores under specific pH levels. This links geopolymerization mechanisms under varying pH conditions to the resulting chemical properties and final structural state.