scholarly journals Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2973 ◽  
Author(s):  
Dongming Yan ◽  
Lingjun Xie ◽  
Xiaoqian Qian ◽  
Shaoqin Ruan ◽  
Qiang Zeng
Keyword(s):  
Pore Structure ◽  
Pore Volume ◽  
Total Pore Volume ◽  
Strength Loss ◽  
Compression Tests ◽  
Compositional Dependence ◽  
Cold Regions ◽  
Air Voids ◽  
Structure Strength ◽  
Pore Liquid

The understanding of the composition dependent properties and freezing-thawing (F-T) resistance of geopolymer materials is vital to their applications in cold regions. In this study, metakaolin-based geopolymer (MKG) mortars were fabricated by controlling the Si/Al ratio and the Na/Al ratio. The pore structure and strength were measured by mercury intrusion porosimetry and compression tests, respectively, which both showed obvious correlations with the material composition. Mass loss, strength loss, visual rate, and microscopic observation were adopted to assess the changes of the material properties and microstructure caused by F-T loads. The results showed that the strength-porosity relationship roughly followed a linear plot. Increases of the Si/Al ratio increased the capillary pore volume, but decreased the gel pore volume and the F-T resistance. Increases of the Na/Al ratio decreased the gel pore, but roughly enhanced the F-T resistance. The MKG mortar at the Na/Al ratio of 1.26 showed the lowest total pore volume and the best F-T resistance. The mechanisms of our experimental observations were that the abundantly distributed air voids connected by the capillary pores facilitated the relaxation of hydraulic pressures induced by the freezing of the pore liquid. The findings of this work help better clarify the compositional dependence of the pore structure, strength, and freezing-thawing resistance of MKG materials and provide fundamental bases for their engineering applications in cold regions.

scholarly journals Nanometer Pore Structure Characterization of Taiyuan Formation Shale in the Lin-Xing Area Based on Nitrogen Adsorption Experiments

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 298
Author(s):  
Chenlong Ding ◽  
Jinxian He ◽  
Hongchen Wu ◽  
Xiaoli Zhang
Keyword(s):  
Specific Surface ◽  
Pore Structure ◽  
Surface Area ◽  
Specific Surface Area ◽  
Shale Gas ◽  
Pore Volume ◽  
Ordos Basin ◽  
Total Pore Volume ◽  
Nitrogen Adsorption ◽  
Taiyuan Formation

Ordos Basin is an important continental shale gas exploration site in China. The micropore structure of the shale reservoir is of great importance for shale gas evaluation. The Taiyuan Formation of the lower Permian is the main exploration interval for this area. To examine the nanometer pore structures in the Taiyuan Formation shale reservoirs in the Lin-Xing area, Northern Shaanxi, the microscopic pore structure characteristics were analyzed via nitrogen adsorption experiments. The pore structure parameters, such as specific surface area, pore volume, and aperture distribution, of shale were calculated; the significance of the pore structure for shale gas storage was analyzed; and the main controlling factors of pore development were assessed. The results indicated the surface area and hole volume of the shale sample to be 0.141–2.188 m2/g and 0.001398–0.008718 cm3/g, respectively. According to the IUPAC (International Union of Pure and Applied Chemistry) classification, mesopores and macropores were dominant in the pore structure, with the presence of a certain number of micropores. The adsorption curves were similar to the standard IV (a)-type isotherm line, and the hysteresis loop type was mainly similar to H3 and H4 types, indicating that most pores are dominated by open type pores, such as parallel plate-shaped pores and wedge-shaped slit pores. The micropores and mesopores provide the vast majority of the specific surface area, functioning as the main area for the adsorption of gas in the shale. The mesopores and macropores provide the vast majority of the pore volume, functioning as the main storage areas for the gas in the shale. Total organic carbon had no notable linear correlation with the total pore volume and the specific surface area. Vitrinite reflectance (Ro) had no notable correlation with the specific surface area, but did have a low “U” curve correlation with the total pore volume. There was no relationship between the quartz content and specific surface area and total pore volume. In addition, there was no notable correlation between the clay mineral content and total specific surface area and total pore volume.

Experimental Study on Coal Pore Characteristic Based on Cryogenic Liquid Nitrogen Method

2013 ◽  
Vol 341-342 ◽  
pp. 345-350 ◽  
Author(s):  
Wei Min Cheng ◽  
Xiao Qiang Zhang ◽  
Rui Zhang ◽  
Gang Wang
Keyword(s):  
Pore Structure ◽  
Surface Area ◽  
Liquid Nitrogen ◽  
Pore Volume ◽  
Single Point ◽  
Total Pore Volume ◽  
Nitrogen Adsorption ◽  
Cryogenic Liquid ◽  
Adsorption Method ◽  
Point Total

In view of pore distribution in coal, this paper applies BJH method that is based on the cylinder theory and adopts cryogenic liquid nitrogen adsorption method to carry out experimental investigation on pore structure of No.3U coal seam in Sanhekou Coalmine, obtaining the fact that pore structure of No.3U coal is complicated, the cool pores are mostly flask pores, others are the parallel plate pores with one end closed and the cylinder pores with one end closed; According to the distribution of BJH pore volume and pore surface area, ultramicropores with apertures less than 10 nm are among the most; Then obtain the average BET specific surface area, the distribution of BJH pore volume and pore area, average single-point total pore volume and most probable pore .etc, which conducive to a better understanding of the micropores characteristic of coal.

scholarly journals The influence factors for gas adsorption with different ranks of coals

2017 ◽  
Vol 36 (3-4) ◽  
pp. 904-918 ◽  
Author(s):  
Deyong Guo ◽  
Xiaojie Guo
Keyword(s):  
Moisture Content ◽  
Specific Surface ◽  
Pore Structure ◽  
Adsorption Capacity ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Gas Adsorption ◽  
Total Pore Volume ◽  
Factors Influencing

In this paper, scanning electron microscopy, low-temperature N2 adsorption and CH4 isothermal adsorption experiments were performed on 11 coal samples with Ro,max between 0.98 and 3.07%. The pore structure characteristics of coals (specific surface area, total volume distribution) were studied to assess the gas adsorption capacity. The results indicate that there is significant heterogeneity on coal surface, containing numerous channel-like pores, bottle-shaped pores and wedge-shaped pores. Both Langmuir volume (VL) and Langmuir pressure (PL) show a stage change trend with the increase of coalification degree. For different coalification stages, there exist different factors influencing the VL and PL values. For low-rank coals (Ro,max < 1.1%), the increase of VL values and decrease of PL values are mainly due to the abundant primary pore and fracture within coal. For middle-rank coals (1.1% < Ro,max < 2.1%), the moisture content, vitrinite content and total pore volume are all the factors influencing VL, and the reduction of PL is mainly attributed to the decrease of moisture content and inertinite content. Meanwhile, this result is also closely related to the pore shape. For high-rank coals (Ro,max > 2.1%), VL values gradually increase and reach the maximum. When the coal has evolved into anthracite, liquid hydrocarbon within pore begins pyrolysis and gradually disappears, and a large number of macropores are converted into micropores, leading to the increase of specific surface area and total pore volume, corresponding to the increase of VL. In addition, the increase of vitrinite content within coal also contributes to the increase of VL. PL, reaches the minimum, indicating that the adsorption rate reaches the largest at the low pressure stage. The result is mainly controlled by the specific surface area and total pore volume of coal samples. This research results will provide a clearer insight into the relationship between adsorption parameters and coal rank, moisture content, maceral composition and pore structure, and it is of great significance for better assessing the gas adsorption capacity.

Effect of Heat-Treatment in Ar Atmosphere on Pore Structure of Carbonaceous Materials from Polysiloxane

2014 ◽  
Vol 602-603 ◽  
pp. 279-284
Author(s):  
Li Qun Duan ◽  
Chen Chen Zhang ◽  
Qing Song Ma ◽  
Zhao Hui Chen
Keyword(s):  
Heat Treatment ◽  
Pore Structure ◽  
Pore Size ◽  
Pore Volume ◽  
Average Pore Size ◽  
Total Pore Volume ◽  
Treatment Temperature ◽  
Carbonaceous Materials ◽  
Average Pore ◽  
Pore Size Distributions

Nanoporous carbonaceous materials derived from polysiloxane were first prepared by pyrolysis at 1300°C followed with hydrofluoric acid (HF) etching treatment. Their thermal stability of pore structure in inert condition was investigated in this paper by nitrogen adsorption technique in detail. The specific surface area (SSA) and pore volume (total pore volume, micropore volume, mesopore volume) decreased continually in the heat-treatment temperature range of 1000~1400°C. The average pore size almost kept the same with the raw sample. However, when the temperature exceeded 1400°C, the micropore interconnection began transforming to mesopore structure, which led to the decline of SSA and the increase of average pore size. Furthermore, the pore size distributions (PSDs) curves showed that heat-treatment had an advantage on the transition process of pore structure from disorder to regularity to some extent when heat-treated in the range 1000~1400°C for the most possible reason of relief of residue strain in the carbonaceous materials.

Strength Development and Pore Structure of Alkali-Activated Slag Cement in Bittern Environment

2014 ◽  
Vol 584-586 ◽  
pp. 1440-1443
Author(s):  
Qiang Song ◽  
Jian Hui Zhu ◽  
Xiao Yan Zhang
Keyword(s):  
Pore Structure ◽  
Pore Volume ◽  
Total Pore Volume ◽  
Experimental Results ◽  
Strength Development ◽  
Soaking Time ◽  
Alkali Activated Slag ◽  
Chemical Attack ◽  
Activated Slag ◽  
Alkali Activated

The effect of bittern on alkali-activated slag (AAS) cement and OPC was studied by testing on the strength and pore structure of the specimens stored in artificial bittern solution at certain periods. The experimental results show that the (AAS) cement exhibits excellent resistance to chemical attack of bittern. The significant increase of strength of (AAS) mortar stored in bittern solution was observed with the soaking time, and the strength increases very quickly before 27 d. But the strength of OPC decreases fast after17d. The more the contents of NaOH activator in AAS cement, the more the strength gained. And the more the contents of activator, the less porosity is. Curing the AAS cement in bittern environment leads to a reduction in the total pore volume and to a refinement of the pore structures.

Pore Structure Of Hydrated Cement Determined By Mercury Porosimetry And Nitrogen Sorption Techniques.

1988 ◽  
Vol 137 ◽  
Author(s):  
Yahia Abdel-Jawad ◽  
Will Hansen
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Pore Volume ◽  
Mercury Porosimetry ◽  
Total Pore Volume ◽  
Curing Temperature ◽  
Vycor Glass ◽  
Degree Of Hydration

AbstractThe pore structure (i.e. total pore volume, surface area and pore-size distribution curves) was measured using mercury porosimetry and nitrogen sorption. Hydrated portland cement (type I) of water-cement (w/c) ratios 0.3, 0.4 and 0.6 by weight was analyzed at three degrees of hydration (i.e., 30%, 50% and 80%; 70% for the 0.3 w/c system) corresponding to low, intermediate and high levels of hydration. The effect of curing temperature (3°, 23°, and 43°C) on pore structure was also studied. The two techniques were evaluated as well on porous Vycor glass, which has a narrow pore size distribution in the size range accessible to both. Results obtained by both techniques on porous Vycor glass agreed well. However neither technique can be used alone to study the entire pore structure in well-hydrated cement due to the wide range in pore sizes and the presence of micropores. Due to the unstable pore structure in cement a specimen treatment procedure such as methanol replacement, combined with volume-thickness (V-t) analysis, is necessary in order to measure the micropores. At low hydration values the pore structure can be estimated by mercury intrusion porosimetry (MIP). At higher hydration values, however, this technique underestimates total pore volume and surface area due to the presence of micropores which MIP cannot determine. In the pore size range of overlap, higher pore volumes were obtained with MIP. Nitrogen V-t analysis shows that micropores are more pronounced with lower w/c ratios. This finding is consistent with pore size distribution curves obtained by MIP. For a given w/c ratio and degree of hydration the total pore volume measured by MIP was found to be independent of curing temperature in the temperature range studied. At any w/c ratio, capillary porosity is controlled by degree of hydration alone.

scholarly journals Correlations between Air Permeability Coefficients and Pore Structure Indicators of Cementitious Materials

2018 ◽  
Author(s):  
Yuya Sakai
Keyword(s):  
Pore Structure ◽  
Pore Volume ◽  
Percolation Theory ◽  
Permeability Coefficient ◽  
Pore Diameter ◽  
Total Pore Volume ◽  
Cementitious Materials ◽  
Air Permeability ◽  
Permeability Coefficients ◽  
Using Data

Correlations between the air permeability coefficient and various pore structure indicators in cementitious materials were examined to determine the pore structure indicator that best evaluated air permeability using data from previous studies of air permeabilities and pore structures. The determination coefficients of air permeability with total pore volume, critical pore diameter, and ordinary threshold pore diameter were low, although these have often been used as indicators. The median and threshold pore diameters obtained by percolation theory showed high determination coefficients. The equation using the threshold pore diameter better estimated the air permeability coefficient than the Katz&ndash;Thompson equation.

Experimental Study of the Pore Structure Characterization in Shale With Different Particle Size

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Shuwen Zhang ◽  
Xuefu Xian ◽  
Junping Zhou ◽  
Guojun Liu ◽  
Yaowen Guo ◽  
...  
Keyword(s):  
Particle Size ◽  
Specific Surface ◽  
Pore Structure ◽  
Pore Volume ◽  
Gas Adsorption ◽  
Total Pore Volume ◽  
Structure Characterization ◽  
Particle Sizes ◽  
Average Pore ◽  
Longmaxi Shale

In order to study the effects of particle size on the determination of pore structure in shale, the outcrop of Ordovician Wufeng (WF) and Silurian Longmaxi shale (LMX) samples from Sichuan basin were chosen and crushed into various particle sizes. Then, pore structure was analyzed by using low-pressure gas adsorption (LPGA) tests. The results show that the pore of shales is mainly composed of slit-type pores and open pores. The specific surface areas of shale are mainly contributed by micropores, while the largest proportion of the total pore volume in shale is contributed by mesopores. With the decreasing of particle size, the specific surface area of both samples is decreased, while average pore diameter and the total pore volume are increased gradually. The influences of particle size on the pore structure parameters are more significant for micropore and macropore, as the particle sizes decrease from 2.36 mm to 0.075 mm, the volume of micropores in Longmaxi shale increases from 0.283 cm3/100 g to 0.501 cm3/100 g with an increment almost 40%, while the volume of macropores decreases from 0.732 cm3/100 g to 0.260 cm3/100 g with a decrement about 50%. This study identified the fractal dimensions at relative pressures of 0–0.50 and 0.50–0.995 as D1 and D2, respectively. D1 increases with the decrease of particle size of shale, while D2 shows an opposite tendency in both shale samples.

scholarly journals The dynamic change of pore structure for low-rank coal under refined upgrading pretreatment temperatures

2020 ◽  
Author(s):  
Teng Li ◽  
Cai-Fang Wu ◽  
Zi-Wei Wang
Keyword(s):  
Pore Structure ◽  
Pore Volume ◽  
Dynamic Change ◽  
Total Pore Volume ◽  
Nitrogen Adsorption ◽  
Volatile Matter ◽  
Low Rank ◽  
Low Rank Coal ◽  
Pore Collapse ◽  
Pretreatment Temperature

AbstractPore structure characteristics are significant factor in the evaluation of the physical characteristics of low-rank coal. In this study, three low-rank coal samples were collected from the Xishanyao Formation, Santanghu Basin, and low-temperature liquid-nitrogen adsorption (LP-N2A) measurements were taken under various pretreatment temperatures. Owing to the continuous loss of water and volatile matter in low-rank coal, the total pore volume assumes a three-step profile with knee temperatures of 150 °C and 240 °C. However, the ash in the coal can protect the coal skeleton. Pore collapse mainly occurs for mesopores with aperture smaller than 20 nm. Mesopores with apertures smaller than 5 nm exhibit a continuous decrease in pore volume, whereas the pore volume of mesopores with apertures ranging from 5 to 10 nm increases at lower pretreatment temperatures (<150 °C) followed by a faint decrease. As for mesopores with apertures larger than 10 nm, the pore volume increases significantly when the pretreatment temperature reaches 300 °C. The pore structure of low-rank coal features a significant heating effect, the pretreatment temperature should not exceed 150 °C when the LP-N2A is used to evaluate the pore structure of low-rank coal to effectively evaluate the reservoir characteristics of low-rank coal.

Modulated Synthesis of UiO-67 for High Resistance to CH2Cl2

2016 ◽  
Vol 852 ◽  
pp. 609-613
Author(s):  
Long Yang ◽  
Li Xian Sun ◽  
Fen Xu ◽  
Yong Jin Zou ◽  
Hai Liang Chu
Keyword(s):  
Acetic Acid ◽  
Pore Structure ◽  
Surface Area ◽  
High Resistance ◽  
Pore Volume ◽  
Total Pore Volume ◽  
Bet Surface Area ◽  
Heating Method

UiO-67 has been synthesized by using the acetic acid as a template via conventional electric (CE) heating method. With the same adding of acetic acid, different crystallinity and pore structure are obtained through change the order of addition of acetic acid. The BET surface area and total pore volume are 2861 m2 g-1 and 1.14 cm3 g-1 for of CE-0-3, and 1650 m2 g-1 and 0.67 m2 g-1 for CE-1-2, respectively. Although CE-0-3 has a better crystallinity, higher BET surface area and total pore volume than those of CE-1-2, CE-1-2 presents a better resistance to CH2Cl2 than CE-0-3.

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