Average Pore Area Research Articles

Niobium oxide‐activated yttrium barium titanate nanorod structured ceramics for energy storage applications

AbstractStructure, morphology, and electrical properties of 10 mol% of Nb2O5‐activated yttrium barium titanate (BT) Ba(60‐z)Ti(40‐x)NbzYxO3 (BTY10Nb10), barium titanate (BT), and 10 mol% of Y2O3‐activated BT were explored with calcination and sintering temperatures of 1000°C at 8 h and 1200°C at 6 h, respectively. The thermogravimetric and differential scanning calorimetry (TG–DSC) analysis reported that the total weight loss and residual mass of BT at 1300°C were 16.8 and 83.2%, respectively. The X‐ray diffraction (XRD) pattern confirmed that BTY10Nb10 ceramics containing the BaNbO3 phase were developed. A Raman band of BT at 307 cm–1 unveiled a blue shift slightly for BTY10 to 298 cm–1 and for BTY10Nb10 to 306 cm–1. Average pore area of the ferroelectric BTY10Nb10 was found to be 6.96 nm for the total scanning electron microscopy (SEM) image area of 20.31 nm. Formation of BT nanorods analyzed from transmission electron microscopy (TEM) has been reported in three samples that regulate surface roughness. Moreover, Nyquist diagram of BTY10Nb10 shows two overlapping semicircles as a function of frequency. Nanorod structures led to change the morphology and surface roughness. Recoverable energy storage density and energy storage efficiency were estimated as 2.63 µJ/cm3 and 57%, and BTY10Nb10 ferroelectric showed potential for energy storage applications due to changes in surface morphology and porosity.

Silica Nanoparticles as a Probable Anti-Oomycete Compound Against Downy Mildew, and Yield and Quality Enhancer in Grapevines: Field Evaluation, Molecular, Physiological, Ultrastructural, and Toxicity Investigations.

Downy mildew is the most destructive disease of grapevines in the regions of relatively warm and humid climate causing up to 50% yield losses. Application of silicon- (Si-) based products have been extensively studied against various oomycete, fungal, bacterial, and viral plant diseases, but studies on Si application in their nanosize are limited. In this study, the field application of silica nanoparticles (SiNPs) on Thompson Seedless grapevines (H4 strain) infected with downy mildew was evaluated. In addition, molecular, physiological, ultrastructural, and toxicity investigations were also conducted. The obtained results revealed that spraying of grapevines with SiNPs at 150 ppm significantly overexpressed the transcription factor jasmonate and ethylene-responsive factor 3 recording 8.7-fold, and the defense-related genes β-1,3-glucanase (11-fold), peroxidase (10.7-fold) pathogenesis-related-protein 1 (10.6-fold), and chitinase (6.5-fold). Moreover, a reduction up to 81.5% in the disease severity was achieved in response to this treatment. Shoot length and yield per grapevine were considerably enhanced recording up to 26.3 and 23.7% increase, respectively. The berries quality was also improved. Furthermore, this treatment led to an enhancement in the photosynthetic pigments, induction of phenolic and ascorbic acid contents, an increase in the activity of peroxidase and polyphenol oxidase enzymes, and a reduction in the cellular electrolyte leakage, lipid peroxidation, and H2O2 content. Scanning electron microscopy observations showed an increase up to 86.6% in the number of closed stomata and a reduction up to 55% in the average stomatal pore area in response to this treatment. Observations of the transmission electron microscopy showed ultrastructural alterations in the cells of a grapevine leaf due to the infection with downy mildew, including plasmolysis and disruption of the cellular components, abnormal chloroplasts, and thickening of the cell wall and cell membrane. These abnormal alterations were reduced in response to SiNPs spray. In contrast, this study also showed that this treatment had considerable cytotoxic and genotoxic effects at this direct dose/concentration. So, additional investigations to determine the SiNPs residue in the produced edible plant parts are urgently needed. In addition, the pre-harvest interval, toxicity index, and risk assessment should be evaluated before any recommendation for use.

Biophysical properties of electrospun chitosan-grafted poly(lactic acid) nanofibrous scaffolds loaded with chondroitin sulfate and silver nanoparticles

The aim of this work was to study the biophysical properties of the chitosan-grafted poly(lactic acid) (CH-g-PLA) nanofibers loaded with silver nanoparticles (AgNPs) and chondroitin-4-sulfate (C4S). The electrospun CH-g-PLA:AgNP:C4S nanofibers were manufactured using the electrospinning technique. The microstructure of the CH-g-PLA:AgNP:C4S nanofibers was investigated by proton nuclear magnetic resonance (1H-NMR), scanning electron microscopy (SEM), UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), and Fourier transform infrared (ATR-FTIR) spectroscopy. ATR-FTIR and 1H-NMR confirm the CH grafting successfully by PLA with a substitution degree of 33.4%. The SEM measurement results indicated apparently smooth nanofibers having a diameter range of 340 ± 18nm with porosity of 89 ± 3.08% and an average pore area of 0.27μm2. UV-Vis and XRD suggest that silver nanoparticles with the size distribution of 30nm were successfully incorporated into the electrospun nanofibers. The water contact angle of 12.8 ± 2.7° reveals the hydrophilic nature of the CH-g-PLA:AgNP:C4S nanofibers has been improved by C4S. The electrospun CH-g-PLA:AgNP:C4S nanofibers are found to release ions Ag+ at a concentration level capable of rendering an antimicrobial efficacy. Gram-positive bacteria (S.aureus) were more sensitive to CH-g-PLA:AgNP:C4S than Gram-negative bacteria (E. coli). The electrospun CH-g-PLA:AgNP:C4S nanofibers exhibited no cytotoxicity to the L-929 fibroblast cells, suggesting cytocompatibility. Fluorescence microscopy demonstrated that C4S promotes the adhesion and proliferation of fibroblast cells onto electrospun CH-g-PLA:AgNP:C4S nanofibers.

ANALYSIS OF LEAD WASTE ABSORPTION (Pb) WITH ACTIVATED CHARCOAL ADSORBENT FROM PALM SHELL

Some industries, especially the textile industry in general, use textile dyes containing lead heavy metals (Pb). Lead is a metal that is neurotoxin (toxic to the nervous system) and is accumulative because of its stable nature and has a long half-life, and it can be harmful to the environment and needs to be filtered using adsorbent. This study aims to find out the absorption of activated charcoal palm shell as adsorbent to eliminate lead waste. The method used by varying the concentration of and KOH activator solutions with concentrations of 20%, 30% and 40% respectively. Batch method is done to mix activated charcoal into Pb solution with variation of contact time of 30 minutes, 60 minutes, 90 minutes. SEM (Scanning Electron Microscope) and AAS ((Atomic Absorption Spectrophotometer) tests are conducted to find out the pore area and absorption. SEM test results showed that the best activator is KOH with a concentration of 40% compared to activators with the largest average pore area of 31.755 micrometer. AAS test results obtained the most absorption of 98.59% by activated charcoal KOH 30% at a contact time of 60 minutes.Keywords: adsorption, activators, palm shells, Pb acetate

Pore Structure Characteristics and Its Effect on Mechanical Performance of Cemented Paste Backfill

The development of cemented paste backfilling (CPB) technology has made an important contribution to the mining economy. As a kind of porous material, the pore structure characteristic of cemented paste backfill (CPB) is strongly correlated to its mechanical properties. In this study, CPB specimens were prepared with tailings/cement ratios (T/C ratio) of 4, 6, 10 and curing durations of 3, 7, 14, and 28 days, respectively. Pore structures characteristics of CPB specimens were investigated using nuclear magnetic resonance (NMR) and scanning electronic microscopy (SEM). The uniaxial compressive strength (UCS) was adopted to illustrate the mechanical property of CPB specimens. The coupling effects of T/C ratio and curing time on the pore characteristics of CPB as well as the effect of pore size on the UCS were analyzed. The results indicated that: 1) the microstructural integrity of CPB was highly related to the development status of the pore structure, which can be represented by micro-parameters like porosity, average pore area, etc. 2) a similar normal distribution curve was observed from the four kinds of pore structure in CPB. As the curing time increased, the peak of the pore size curve shifted left, and the peak value decreased, which means that the pore size in CPB decreased and became much concentrated; 3) the extension of the most probable pore size led to the cross-connection of pores and resulted in the fracture of CPB, which was shown as a crack on the main section.

Ultra-Thin Porous PDLLA Films Promote Generation, Maintenance, and Viability of Stem Cell Spheroids.

Three-dimensional (3D) culture bridges and minimizes the gap between in vitro and in vivo states of cells and various 3D culture systems have been developed according to different approaches. However, most of these approaches are either complicated to operate, or costive to scale up. Therefore, a simple method for stem cell spheroid formation and preservation was proposed using poly(D,L-lactic acid) porous thin film (porous nanosheet), which were fabricated by a roll-to-roll gravure coating method combining a solvent etching process. The obtained porous nanosheet was less than 200 nm in thickness and had an average pore area of 6.6 μm2 with a porosity of 0.887. It offered a semi-adhesive surface for stem cells to form spheroids and maintained the average spheroid diameter below 100 μm for 5 days. In comparison to the spheroids formed in suspension culture, the porous nanosheets improved cell viability and cell division rate, suggesting the better feasibility to be applied as 3D culture scaffolds.

Regulating the mechanical properties and microporous structures of hydroxypropyl methylcellulose based microporous photophobic films by adjusting the l-ethyl-3-methylimidazolium acetate content

X-ray diffraction, small angel X-ray scattering, scanning electron microscopy, moisture determination, dynamic mechanical analysis, whiteness assay and mechanical testing were used to study the effects of different doses of [EMIM]Ac on the microstructures and physical properties of HPMC/MSP film. By adjusting the 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) content (0 %–8 %), the mechanical properties and microstructures could be regulated. The elongation of the film increased from 5.91 % to 12.83 % with the increasing [EMIM]Ac content from 0% to 8% without affecting the tensile strength and modulus significantly. The average pore area decreased from 0.82 μm2 to 0.05 μm2 and the pore number increased with the increasing [EMIM]Ac content from 0% to 8%. Moreover, with the increasing [EMIM]Ac content, Tg decreased. 6% and 8% [EMIM]Ac decreased the compactness and smoothness of the fractal structure of the film greatly. [EMIM]Ac improved the ductility of HPMC/MSP film, which was mainly due to the decreased pore size and Tg. The improved photophobic films are both flexible and with easily changeable porous structure, which can be used as controllable packaging to carry and control-release different functional agents for different light sensitive foods.

Influence of iron content on SDAS factor, Al5FeSi intermetallic phases and porosity of the secondary aluminum alloy AlSi7Mg0.6 used in the automotive industry

This paper is focused on evaluating the influence of iron content on SDAS factor, Al5FeSi phase size, and porosity of secondary aluminum alloy AlSi7Mg0.6 used in the automotive industry. These characteristics were evaluated by quantitative analysis on sand-casted experimental alloys with various iron contents (0.128; 0.202; 0.429; 0.75; 1.264 %). Results have shown a decrease of SDAS factor with increasing of iron content. Al5FeSi phase average length and thickness values increased with the rising iron content. These dependencies began to reveal themselves when the iron content reached values around the critical value of the iron content - Fecrit. (0.475 % Fe). The average area of pores (2.05 - 3.8 %) and pore size (39 597 - 70 332 µm2) increased with increasing of iron content (0.128; 0.75; 1.264 %) too.

Morphological analysis of fibrous webs electrospun from Polycaprolactone, polylactic acid and their blends in chloroform based solvent systems

In this study, polycaprolactone (PCL), polylactic acid (PLA), and PLA/PCL blend electrospun fibrous webs are prepared using chloroform based solvent systems at different concentrations. The solvents to be used with chloroform are selected in accordance with the morphological and rheological structures of the polymers. While the morphology of the produced networks is observed under a scanning electron microscope, fiber diameter measurements and pore analysis are performed with Image J Software System. Although bead-free webs could not be achieved for neat PCL samples, neat PLA samples and PCL/PLA blends result in smooth fiber surfaces with homogeneous fiber diameter distributions. The results show that the increase in PLA concentration does not cause much change in fiber diameter but induces an increase in the area of pores. Furthermore, in the PLA/PCL blend, it is determined that as the ratio of PCL in the mixture increases, the fiber diameter decreases even if there is an acceptable reduction in the average pore area.

High-speed synchrotron X-ray imaging of directed energy deposition of titanium: effects of processing parameters on the formation of entrapped-gas pores

Laser based directed energy deposition (DED) is a competitive method for repairing and remanufacturing metallic parts used in numerous industries including aerospace and biomedical. However, the numerous dynamic phenomena associated with the DED process often result in defects such as entrapped-gas pores, lack of fusion, and undesirable anisotropic properties. The entrapped-gas pore, being one of the most common issues, not only influences melt-pool dynamics but also reduces the fabrication quality and mechanical properties of parts fabricated by the DED process. To reduce and further understand this issue, the real-time observation of the pore formation process needs to be studied first. To directly observe the phenomena in the melt pool, high-speed techniques are needed because rapid solidification leads to rapid pore formation and movement. In-situ high-speed X-ray has been proven to be an effective method in investigating the melt pool dynamics and pore formation mechanisms in the laser powder bed fusion process, in which the fabrication process is quite different from that in DED. Here, the high-speed X-ray method is extended to study the formation of entrapped-gas pores. The real-time formation and quantitative analysis of pores under each set of processing parameters (particle velocity, laser power, and spot welding dwelling time of stationary laser) in the DED process are investigated. We found that the DED with a higher particle velocity (3.19 m/s) produced a smaller average pore size of 27.8 µm and a lower pore area fraction of 0.52%. The DED under lower laser power (156 W) generated a smaller average pore size of 20.3 µm and a lower pore area fraction of 1.94%. The shorter dwelling time (10 ms) benefited the decrease of both average pore size and pore area fraction.

Developing “Off the Shelf” Pancreases for Diabetic Patients Using Bacterial and Kombucha Tea Waste

The advent of tissue and organ engineering provides long-term treatment for conditions previously considered chronic and untreatable. Through advances in the field of tissue engineering, patients have the potential to receive synthetic replacements of damaged tissues and cellular grafts. Scaffolds, based in either synthetic or natural polymers, are fundamental to tissue engineering approaches because they provide a structure that mimics the native environment which facilitates cellular differentiation, organization, and functionality. However, current protocols for creating scaffolds remain complex and difficult to translate to the clinic. Our investigation aimed to provide potential solutions to fundamental issues associated with islet cell transplantation, a possible cure for type 1 diabetes. In this study, we used bacterial cellulose as the polymer to create scaffolds. We modulated the structural characteristics of the bacterial cellulose to aid cellular infiltration. After processing, scanning electron micrographs of the scaffolds showed that a favorable blood vessel morphology was maintained and an open pore geometry was obtained. We effectively manipulated the porosity of the scaffold by altering agarose concentrations. The 0.5% agarose-cellulose composite group had an average pore area of 20,000 µm2, which permitted the establishment of regionalized cells islands. Notably, the popular fermented tea drink, kombucha, produces bacterial cellulose as a waste product. Kombucha is made using a symbiotic culture of bacteria and yeast (SCOBY). Normally, SCOBYs are simply discarded after the fermentation process is complete, but could have untapped potential as a platform for tissue engineering and transplantation procedures. To verify that bacterial cellulose can be used as a biomimetic platform, INS-1 cells (an insulin-secreting beta cell-derived line) were seeded in the bacterial cellulose scaffold. We observed morphological changes, such as cytoplasmic extensions and clustering, suggesting reestablishment of functional cell islands. Hence, the results of our experiments suggested that bacterial cellulose is a cost-effective scaffolding platform that can be used to house islet cells as a promising tool in islet cell transplantation, a possible cure for diabetes.

Frost Resistance of Thermoinsulating Recycled-Aggregate Concretes Containing Glazed Hollow Beads

Glazed hollow bead (GHB) is an innovative material that gives concrete very good thermal-insulation properties and improves concrete frost resistance, when used as a partial replacement of ordinary fine aggregate. The improvement in frost resistance under freeze-thaw cycles and the deterioration mechanisms of recycled aggregate thermoinsulating concretes (RATICs) is the objective of this study, after adding GHBs to the mix. Fifteen cubes and ninety prisms made of five RATIC mixes (GHB content = 0, 40, 65, 90 and 130 kg/m3) were tested in compression, to identify the optimum content of GHB. The degradation mechanisms of RATIC were identified based on mass loss, dynamic elastic modulus and uniaxial compressive strength. In addition, RATIC mesostructure was investigated by means of Computed Tomography Scanning, and the deterioration mechanisms by analyzing pore amount, average and maximum pore area and porosity. The experimental results demonstrate that adding glazed hollow beads to recycled aggregate concrete (RAC) moderately changes the mesostructure of the concrete, to the advantage of frost resistance, and that the optimum content of GHB is around 90 kg/m3.

Effect of Barley Antifreeze Protein on Dough and Bread during Freezing and Freeze-Thaw Cycles

In order to verify the cryoprotective effect of an antifreeze protein (BaAFP-1) obtained from barley on bread dough, the effect of BaAFP-1 on the rheological properties, microstructure, fermentation, and baking performance including the proofing time and the specific volume of bread dough and bread crumb properties during freezing treatment and freeze-thaw cycles were analysed. BaAFP-1 reduced the rate of decrease in storage modulus and loss modulus values during freezing treatment and freeze-thaw cycles. It influenced the formation and the shape of ice formed during freezing and inhibited ice recrystallization during freeze-thaw. BaAFP-1 maintained gas production ability and gas retention properties, protected gluten network and the yeast cells from deterioration caused by ice formation and ice crystals recrystallisation in dough samples during freezing treatment and freeze-thaw treatment. It slow down the increase rate of hardness of bread crumb. The average area of pores in bread crumbs decreased significantly (p < 0.05) as the total number of pores increased (p < 0.05), and the addition of BaAFP-1 inhibited this deterioration. These results confirmed the cryoprotective activity of BaAFP-1 in bread dough during freezing treatment and freeze-thaw cycles.

Microstructural response of the fuel phase in U-7Mo dispersion fuel irradiated at different powers

Irradiation conditions such as fission power, fission rates, and temperature are important parameters for nuclear fuels because they influence the microstructural behavior and ultimate irradiation performance. Two U-7Mo/Al-3.5 wt.% Si dispersion fuel plates were irradiated in the Advanced Test Reactor edge-on to the core in the RERTR-9B experiment at different powers to study the effects of power on fuel phase swelling behavior. The results of non-destructive measurements have been reported in a previous paper [1], and the destructive examination results are being reported here. In particular, the microstructural evolution of the U-Mo fuel phase in irradiated fuel plates has been investigated by cutting transverse cross-sections, using generated scanning electron microscopy micrographs, and image processing methods to assess the changes in microstructural features, such as fission gas pore growth and non-recrystallized grain fraction. In this study, the focus was to examine the evolution of fission gas pores from both the constrained and unconstrained regions of U-Mo fuels irradiated at different powers. Based on an estimated linear gradient, the rate of change of fission gas pore size with locally calculated fission densities is more prominent in the higher power specimen. As such, the average porosity and pore area is approximately 11% and 2 × larger in the fuel irradiated at higher power than that of the lower power specimen. The growth of fission gas pores can accelerate the pore interconnectivity and thus fission gas outside the fuel kernel (FGO), which are two precursors for swelling in U-Mo fuels. The influence of increased power, internal plate stresses, and fission-induced creep on fuel kernel deformation and lateral mass transfer is also highlighted.

Computed tomography evaluation of the porosity and fiber orientation in a short carbon fiber material extrusion filament and part

The computed tomography (CT) evaluation of the material extrusion (MEX) of a short carbon fiber (SCF) Nylon-12 filament and part is presented. CT, a non-destructive testing method, was used to quantify the internal structure of specimens into three phases: pore, Nylon, and SCF. The intensity histograms from the CT data were fit using a mixed skew-Gaussian distribution (MSGD) algorithm to segment the CT image into phases. Thresholded images were used to isolate pores in the CT image to determine pore volume and distribution within both the MEX SCF filament and part. The phase volume percentages of the MEX SCF filament were found to be 1.6% pore, 62.2% Nylon, and 36.2% SCF. The volume of most pores within the filament were found to be under 100 μm3. The highest frequency of pores was located near the outside of the filament, but the large pores were located near the center of the filament. This result indicates that the thermoplastic filament extrusion process likely entraps large bubbles in the center of filament or causes large thermal gradients and residual stresses that induce voids during post-extrusion cooling. MSGD analysis of sections of the MEX SCF part estimated phase volume percentages to be 9.8% pore, 59.6% Nylon, and 30.9% SCF. This analysis showed a more than 8% increase in porosity from the MEX SCF filament to the part. For the MEX SCF part, the average pore area was found to be highest (>250 μm2) at the bottom of the layer and smallest (<100 μm2) at the top of the layer, which could be explained by a large temperature gradient between and contractile thermal stresses inside the layer that cause the thermoplastic to shrink into a smaller volume allowing the voids to grow during deposition. A qualitative analysis of fiber orientation conducted on the SCF filament indicated that the SCFs maintain their orientation from filament to part except in the intersection zone of rasters.

Quantitative investigation on micro-parameters of cemented paste backfill and its sensitivity analysis

The mechanical properties of cemented paste backfill (CPB) depend heavily on its pore structural characteristics and micro-structural changes. In order to explore the variation mechanisms of macro-mechanical characteristics and micro-structure of CPB. CPB specimens with different mass concentrations prepared from the full tailings of Xianglushan Tungsten Ore were micro-tests. Moreover, acquired pore digital images were processed by using the pores (particles) and cracks analysis system (PCAS), and a sensitivity analysis was performed. The results show that as the mass concentration of CPB increases from 70% to 78%, the porosity, the average pore area and the number of pores drop overall, leading to a decline in the pores opening degree and enhancing the mechanical characteristics. As the mass concentration of CPB increases, the trend of fractal dimension, probability entropy and roundness is reduced, constant and increased, which can result in an enhancement of the uniformity, an unchanged directionality and more round pores. According to the definition of sensitivity, the sensitivities of various micro-parameters were calculated and can be ranked as porosity > average pore area > number of pores > roundness > fractal dimension > probability entropy.

Thermal conductivities of MgO–Al2O3 hollow fibers formed by biomimetic synthesis

abstract MgO–Al2O3 hollow fibers were effectively prepared by bionics using cogon as a low-cost natural template. Through orthogonal experimental design, the preparation parameters were optimized as follows: Al2O3: MgO ratio of 0.60, mass ratio of 25% solute in the mixture, drying temperature of 80 °C, and sintering temperature of 1100 °C. Overall, with inner pore sizes ranging from 5 μm to 10 μm, the MgO–Al2O3 hollow fibers are a novel low-cost lightweight refractory material. Their stack density is approximately 0.120 g cm−3 and thermal conductivity is 0.2050 W m−1 K−1 at 1273 K. In addition, the porosity and average pore area of the hollow fibers are 80.9% and 0.96 m2 g−1, respectively. Here, the effects of pore size, average pore area, and phase composition on the thermal conductivity of the MgO–Al2O3 hollow fibers are discussed synthetically.

Effect of the Cement–Tailing Ratio on the Hydration Products and Microstructure Characteristics of Cemented Paste Backfill

Cemented paste backfill (CPB) has been widely incorporated into mining practice as an ideal way to protect the environment and eliminate hidden dangers in mines. In this study, the feasibility of CPB was validated using full tailings from the Xianglushan Tungsten Mine. Through a microexperiment of CPB with different C/Ts, digital images of pores were obtained, and the hydration products were identified for processing with the particle and pore identification and analysis system. The evolution of hydrated products under different cement–tailing ratios (C/Ts) was analyzed. Then, microquantitative indices, such as the porosity and fractal dimensions, were used to analyze the evolution of the pore structures under different C/Ts. The results showed that CPB slump of different proportions ranged between 196 and 232 mm, and its flowability met the basic principle of pumping. When the C/T of the CPB mixture was increased from 1:12 to 1:4, the backfill changed from a nonuniform structure with sparse pores to a dense network structure with a few holes and pores. The C/T had a significant effect on the quantitative characteristics. With an increased C/T, the porosity and average pore area generally decreased, resulting in a decrease in the porosity and enhanced mechanical characteristics. The C/T of the CPB also influenced the fractal dimension and roundness. When the C/T increased from 1:12 to 1:4, there was a decreasing trend in the fractal dimension and roundness. Additionally, the size difference between the pores decreased, and the pores were round, resulting in increased uniaxial compressive strength of the CPB. The probability entropy values of the backfill with different C/Ts were all greater than 0.93, and the pore distribution had no obvious orientation.

RESEARCH ON PORE MICROSCOPIC CHARACTERISTICS OF LIGNINMODIFIED LOESS

In order to further research the microscopic mechanism of the lignin-modified loess, the pore microscopic characteristics of the lignin-modified loesswithdifferent lignin contents is analyzed based on SEM.Moreover, the variation of microscopic parameters of the lignin-modified loess with different lignin contents is studied based on PCAS.Combined with the unconfined compressive strength test to evaluate the effect of lignin-modified loess. The results show that lignin can effectively fill the pores of loess and enhance the cementation between particles. The content of lignin has a great influence on the microscopic characteristics. Under the curing age of 28 days, the facial porosity, average pore area, pore porosity fractal dimension and average form factor first rapidly decrease and then slowly increase with the increase of lignin content, while the fractal dimension is completely opposite, and the probability entropy of modified loess with the lignin content of 2% and 4% is low. The modified loess with the lignin content of 2%has the highest compressive strength, while too much lignin content will reduce the compressive strength.

Effects of Soil Properties on the Performance of TRD Cut‐Off Wall

The trench cutting remixing deep wall (TRD) method is a new cement soil cut‐off wall construction technique, which has been widely used in cofferdam, embankment dam, and underground waterproof curtain structures. The chain cutter of TRD moves horizontally to cut and stir different soil layers by up and down to form a cement‐mixed soil diaphragm wall with continuous and uniform thickness, the mechanics and permeability of which are obviously different from those of cement soil with a horizontally mixed single soil layer in traditional deep mixing pile (DMP). In this paper, five sets of onsite walling tests with different cement ratios were carried out to analyse the unconfined compression and permeability of undisturbed cement‐mixed soil in TRD. The difference of both unconfined compressive and permeability coefficients in between TRD and DMP was analysed to discuss the stirring performance of TRD. Then, the microscopic mechanism of soil properties affecting the performance of cement‐mixed soil has been studied by scanning electron microscopy (SEM) in the unconfined compression strength test and permeability coefficient test of cement soil with different mixed soil properties. The test results show that the unconfined compressive strength of cement‐mixed soil is closely correlated to its gradation. As the mixed soil gradation curve approaches to the Fuller curve, the unconfined compressive strength would gradually increase. In mesoscopic, cement fine sand has a large pore structure, and the average pore area is 2.46 times as cement clay. The permeability coefficient of cement‐mixed soil is controlled by the proportion of fine sand content with high permeability.