scholarly journals Bound Water Content and Pore Size Distribution of Thermally Modified Wood Studied by NMR

Forests ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1279
Author(s):  
Chenyang Cai ◽  
Fanding Zhou ◽  
Jiabin Cai
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Water Content ◽  
Size Distribution ◽  
Bound Water ◽  
Fiber Saturation Point ◽  
Saturation Point ◽  
Thermally Modified Wood ◽  
Bound Water Content ◽  
Modified Wood

The physical and mechanical properties of thermally modified wood (TMW) have been comprehensively studied; however, the quantitative analysis of water states and cell wall pores of TMW is limited. In this work, Douglas fir and Norway spruce were thermally modified at 180, 200 and 220 °C, and then studied by NMR cryoporometry method. The results show that thermally modified samples had lower fiber saturation point and the bound water content than the reference samples at all the experimental temperatures, indicating the reduced hygroscopicity due to thermal modification (TM). In addition, TM decreased number of hygroscopic groups, which can be implied by the decreased proportion of bound water sites, and TM also increased the proportion of small voids for bound water clusters. An increase in TM intensity resulted in lower bound water content and a smaller number of hygroscopic groups. In summary, the NMR method detected the water states and pore size distribution and confirmed that TM decreased the fiber saturation point and hygroscopicity of wood by reducing the bound water content and proportion of bound water sites in wood cell walls.

scholarly journals Effect of natural weathering on water absorption and pore size distribution in thermally modified wood determined by nuclear magnetic resonance

Cellulose ◽  
2020 ◽  
Vol 27 (8) ◽  
pp. 4235-4247 ◽  
Author(s):  
Chenyang Cai ◽  
Muhammad Asadullah Javed ◽  
Sanna Komulainen ◽  
Ville-Veikko Telkki ◽  
Antti Haapala ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Pore Size Distribution ◽  
Water Absorption ◽  
Pore Size ◽  
Size Distribution ◽  
Natural Weathering ◽  
Thermally Modified Wood ◽  
Modified Wood ◽  
Nuclear Magnetic

scholarly journals Study on the Mechanical Criterion of Ice Lens Formation Based on Pore Size Distribution

2020 ◽  
Vol 10 (24) ◽  
pp. 8981
Author(s):  
Yuhang Liu ◽  
Dongqing Li ◽  
Lei Chen ◽  
Feng Ming
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Water Content ◽  
Size Distribution ◽  
Initial Water Content ◽  
Mean Stress ◽  
Initial Water ◽  
Unfrozen Water Content ◽  
The Mean ◽  
Lens Formation

Ice lens is the key factor which determines the frost heave in engineering construction in cold regions. At present, several theories have been proposed to describe the formation of ice lens. However, most of these theories analyzed the ice lens formation from a macroscopic view and ignored the influence of microscopic pore sizes and structures. Meanwhile, these theories lacked the support of measured data. To solve this problem, the microscopic crystallization stress was converted into the macro mean stress through the principle of statistics with the consideration of pore size distribution. The mean stress was treated as the driving force of the formation of ice lens and induced into the criterion of ice lens formation. The influence of pore structure and unfrozen water content on the mean stress was analyzed. The results indicate that the microcosmic crystallization pressure can be converted into the macro mean stress through the principle of statistics. Larger mean stress means the ice lens will be formed easier in the soil. The mean stress is positively correlated with initial water content. At the same temperature, an increase to both the initial water content and the number of pores can result in a larger mean stress. Under the same initial water content, mean stress increases with decreasing temperature. The result provides a theoretical basis for studying ice lens formation from the crystallization theory.

Determination of T2 cut-off for shale reservoirs: a case study from the Carynginia formation, Perth Basin, Western Australia

2017 ◽  
Vol 57 (2) ◽  
pp. 664 ◽  
Author(s):  
M. Nadia Testamanti ◽  
Reza Rezaee ◽  
Yujie Yuan ◽  
Dawei Pan
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Petroleum Industry ◽  
Bound Water ◽  
Invasive Technique ◽  
Sources Of Information ◽  
Vacuum Oven ◽  
Low Field ◽  
Wide Range

Over recent decades, the low-field Nuclear Magnetic Resonance (NMR) method has been consistently used in the petroleum industry for the petrophysical characterisation of conventional reservoirs. Through this non-invasive technique, the porosity, pore size distribution and fluid properties can be determined from the signal emitted by fluids present in the porous media. Transverse relaxation (T2) data, in particular, are one of the most valuable sources of information in an NMR measurement, as the resulting signal decay can be inverted to obtain the T2 distribution of the rock, which can in turn be correlated with porosity and pore size distribution. The complex pore network of shales, which can have a large portion of pore sizes in the nanopore and mesopore range, restricts the techniques that can be used to investigate their pore structure and porosity. The ability of the NMR technique to detect signals from a wide range of pores has therefore prompted the quest for more standardised interpretation methods suitable for shales. Using low-field NMR, T2 experiments were performed on shale samples from the Carynginia formation, Perth Basin, at different saturation levels. The shale samples were initially saturated with brine and the T2 spectrum for each sample was obtained. Then, they were placed in a vacuum oven and their weight monitored until a constant value was reached. T2 curves were subsequently obtained for each of the oven-dried samples and a cut-off value for clay-bound water was calculated.

Compaction behaviour of lime-treated metakaolin

2020 ◽  
Author(s):  
Mozhen Hu ◽  
Yu-Jun Cui ◽  
Yunzhi Tan
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Water Content ◽  
Size Distribution ◽  
Uniform Structure ◽  
Dry Density ◽  
Soil Stiffness ◽  
Effect Of Water ◽  
Compaction Curve ◽  
Lime Addition

Metakaolin has been widely used as pozzolanic additive to improve the pozzolanic activity of lime-based products. In this study, normal standard Proctor compaction test was performed on metakaolin with (5% lime) and without (0% lime) lime addition. The changes in stiffness, suction and microstructure with remoulding water content were investigated on statically compacted samples. Results show that lime-treated metakaolin exhibits one and half-peak compaction curve, while untreated metakaolin exhibits common one-peak compaction curve. The uncommon shape of the compaction curve of the treated metakaolin can be explained by the non-fully developed soil suction when water is not continuous. Treated and untreated samples compacted at both dry and wet of optimum show uni-modal pore size distribution characteristics, indicating the absence of aggregates. This is related to the specific thermal treatment, forming separate metakaolin platelets and leading to a modified uniform structure with diffuse platelets. The soil stiffness is rather dominated by the number of particle contacts or soil dry density, the effect of suction being insignificant. For the suction changes, on the dry side, the effect of pore size distribution prevails facing the effect of water content, while on wet side it is the effect of water content that becomes prevailing.

Analysis of Water Forms in Lignite and Pore Size Distribution Measurement Utilizing Bound Water as a Molecular Probe

2017 ◽  
Vol 31 (11) ◽  
pp. 11884-11891 ◽  
Author(s):  
Keji Wan ◽  
Pengchao Ji ◽  
Zhenyong Miao ◽  
Zishan Chen ◽  
Yongjiang Wan ◽  
...  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Bound Water ◽  
Molecular Probe ◽  
Distribution Measurement

scholarly journals The impacts of freeze–thaw cycles on saturated hydraulic conductivity and microstructure of saline–alkali soils

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenshuo Xu ◽  
Kesheng Li ◽  
Longxiao Chen ◽  
Weihang Kong ◽  
Chuanxiao Liu
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Water Content ◽  
Size Distribution ◽  
Saturated Hydraulic Conductivity ◽  
High Water Content ◽  
Soil Permeability ◽  
Freeze Thaw ◽  
Alkali Soil

AbstractStudy on the microscopic structure of saline–alkali soil can reveal the change of its permeability more deeply. In this paper, the relationship between permeability and microstructure of saline–alkali soil with different dry densities and water content in the floodplain of southwestern Shandong Province was studied through freeze–thaw cycles. A comprehensive analysis of soil samples was conducted using particle-size distribution, X-ray diffraction, freeze–thaw cycles test, saturated hydraulic conductivity test and mercury intrusion porosimetry. The poor microstructure of soil is the main factor that leads to the category of micro-permeable soil. The porosity of the local soil was only 6.19–11.51%, and ultra-micropores (< 0.05 μm) and micropores (0.05–2 μm) dominated the pore size distribution. Soil saturated water conductivity was closely related to its microscopic pore size distribution. As the F–T cycles progressed, soil permeability became stronger, with the reason the pore size distribution curve began to shift to the small pores (2–10 μm) and mesopores (10–20 μm), and this effect was the most severe when the freeze–thaw cycle was 15 times. High water content could promote the effects of freeze–thaw cycles on soil permeability and pore size distribution, while the increase of dry density could inhibit these effects. The results of this study provide a theoretical basis for the remediation of saline–alkali soil in the flooded area of Southwest Shandong.

scholarly journals The Study of Bound Water Status and Pore Size Distribution of Chinese Fir and Poplar Cell Wall by Low-Field NMR

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Huimin Cao ◽  
Jianxiong Lyu ◽  
Yongdong Zhou ◽  
Xin Gao
Keyword(s):  
Cell Wall ◽  
Low Temperature ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Adsorption Isotherms ◽  
Bound Water ◽  
Chinese Fir ◽  
Fast Growing ◽  
Pore Size Distributions

With the increasing shortage of timber resources and the advancement of environmental protection projects, many artificial fast-growing forests are planted and used as raw materials in China. There are significant differences in the properties of natural forest wood and artificial fast-growing forest wood, and the properties of wood mainly depend on the change in the status of bound water in the cell wall. In this study, the fiber saturation point (FSP) and pore size distributions within the cell wall of six species of fast-growing forest wood were studied by low-temperature nuclear magnetic resonance (NMR) technology. The effects of species, growth rings, and extractives on the FSP and pore structure were analyzed. The water vapor sorption experiments were performed, and the adsorption isotherms of the samples were fitted through the Guggenheim-Anderson-de Boer (GAB) equation. According to the least-square regression of the adsorption isotherms and combined with the low-temperature NMR experiments, the content and proportion of the different types of bound water were analyzed. The results showed that the average FSP of each Chinese fir was about 40% and that of each poplar was about 35%. There is about a 10% difference between the FSP measured by NMR technology and the adsorption bound water content obtained by adsorption isothermal. The pore size distribution results show that in all samples, the proportion of pores larger than 10.5 nm is very low, about 10%; the proportion of 1.92-10.5 nm pores is about 30%; and the proportion of pores smaller than 1.92nm is more than 50%. This work will be helpful to the study of the wood moisture status and provide reference data for wood modification.

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