Evolution of wood cell wall nanopore size distribution in the hygroscopic range

Abstract Owing to technical difficulties, experimental assessment of wood cell wall pore size distribution (PSD) in the hygroscopic range still remains challenging. Here, a “trial-and-error” approach was proposed to calculate such distribution through bridging experimental and simulated sorption isotherms presented by the authors in the past. Two main assumptions were made in the calculations, namely, the generation of new and the swelling of existing cell wall pores during water sorption. The nanopore size distribution of dried cell wall derived from the experimental CO2 gas sorption isotherms was used as the initial boundary condition. Predicted pore size distributions were assessed to be fairly reasonable by comparing them at 95% relative humidity with the PSD of fully saturated cell walls derived from the solute exclusion method. The predicted distribution was relatively wide with several major peaks evolving in the hygroscopic range. The present work also showed that confounded by a wide PSD that includes mostly micropores, the shape of the experimental sorption isotherms was not reliable in assessing the sorption mechanism. The simulations suggested an alternative water sorption mechanism for wood, i.e. micropore filling of cell wall nanopores.

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

International Journal of Polymer Science ◽

10.1155/2021/4954837 ◽

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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Experimental investigation on pore size distribution and drying kinetics during lyophilization of sugar solutions

Proceedings of 21th International Drying Symposium ◽

10.4995/ids2018.2018.7310 ◽

2018 ◽

Cited By ~ 1

Author(s):

Petra Foerst ◽

M. Lechner ◽

N. Vorhauer ◽

H. Schuchmann ◽

E. Tsotsas

Keyword(s):

Pore Structure ◽

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Freeze Drying ◽

Three Dimensional ◽

Drying Kinetics ◽

Process Efficiency ◽

Freeze Dried ◽

Pore Size Distributions

The pore structure is a decisive factor for the process efficiency and product quality of freeze dried products. In this work the two-dimensional ice crystal structure was investigated for maltodextrin solutions with different concentrations by a freeze drying microscope. The resulting drying kinetics was investigated for different pore structures. Additionally the three-dimensional pore structure of the freeze dried samples was measured by µ-computed tomography and the pore size distribution was quantified by image analysis techniques. The two- and three-dimensional pore size distributions were compared and linked to the drying kinetics.Keywords: pore size distribution; freeze drying; maltodextrin solution; freeze drying microscope

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Comparison of Nitrogen Adsorption and Mercury Penetration Results: II. Pore size Distributions Calculated from Type IV Isotherm Data

Adsorption Science & Technology ◽

10.1177/026361748800500301 ◽

1988 ◽

Vol 5 (3) ◽

pp. 168-190 ◽

Cited By ~ 6

Author(s):

Bruce D. Adkins ◽

Burtron H. Davis

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Nitrogen Adsorption ◽

Type Iv ◽

Pore Size Distributions ◽

Nitrogen Desorption ◽

The Difference ◽

Penetration Data ◽

Packed Sphere

The pore distributions calculated from nitrogen desorption and from mercury penetration data are similar for the four materials utilized in this study. While there are small differences in the distributions calculated using different models (Cohan. Foster or Broekhoff-deBoer) with nitrogen adsorption or desorption isotherm data, all three show reasonable agreement with distributions calculated from mercury penetration data. Frequently practical catalysts have such a broad pore size distribution that neither method alone is adequate to measure the total pore size range. The present results suggest a direct comparison, without recourse to a scaling factor, is appropriate when comparing results from the two methods even though the pore size distribution maximum may vary by at least 50% depending upon the model chosen for the calculation. Better agreement may be obtained between the two experimental techniques by adjusting either the nitrogen adsorption data using a packed sphere model or the mercury penetration data by an earlier reported correction ratio. The difference between the two methods becomes less than 20% when a correction procedure is used; however, further studies are needed to define the range of material shaped that these procedures are applicable to.

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Synthesis And Water Sorption Properties Of Aluminophosphate (AlPO4) And Silicoaluminophosphate (Sapo) Molecular Sieves

MRS Proceedings ◽

10.1557/proc-233-237 ◽

1991 ◽

Vol 233 ◽

Cited By ~ 2

Author(s):

P. B. Malla ◽

S. Komarneni

Keyword(s):

Molecular Sieves ◽

Water Sorption ◽

Hysteresis Loops ◽

Sorption Isotherms ◽

Cooperative Interaction ◽

Type I ◽

Relative Pressure ◽

Micropore Filling ◽

General Expectation ◽

Initial Adsorption

ABSTRACTAluminophosphate (AlPO4–5, AlPO4–11, AlPO4–17, AlPO4–20) and silicoaluminophosphate (SAPO-5, SAPO- 11, SAPO-17, SAPO-20) molecular sieves of varying pore sizes (3–8 Å) were synthesized and their water adsorption and desorption properties were studied. Water sorption isotherms of AlPO4 molecular sieves were characterized by unusual isotherm shapes, that is, little or no initial adsorption followed by extreme adsorption leading to volume filling by hydrogen bonding and cooperative interaction in micropores, apparently due to the nonpolar nature of pore surfaces coupled with weak (reversible upon evacuation) chemisorption of water, and hysteresis loops extending to very low pressures. Although micropore filling in AlPO2's and isostructural SAPO's was completed almost at the same relative pressure (p/po), SAPO's exhibited less extreme adsorption isotherms as a result of their slightly more polar nature of pore surfaces compared to AlPO4's. Neither AlPO4apos;s nor SAPO's exhibited Brunauer Type I isotherms with water, contrary to a general expectation of the hydrophilic microporous solids.

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Ink-bottle Effect and Pore Size Distribution of Cementitious Materials Identified by Pressurization–Depressurization Cycling Mercury Intrusion Porosimetry

Materials ◽

10.3390/ma12091454 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1454 ◽

Cited By ~ 5

Author(s):

Yong Zhang ◽

Bin Yang ◽

Zhengxian Yang ◽

Guang Ye

Keyword(s):

Pore Structure ◽

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Mercury Intrusion Porosimetry ◽

Cementitious Materials ◽

Limestone Powder ◽

Accurate Estimation ◽

Mercury Intrusion ◽

Pore Size Distributions

Capturing the long-term performance of concrete must be underpinned by a detailed understanding of the pore structure. Mercury intrusion porosimetry (MIP) is a widely used technique for pore structure characterization. However, it has been proven inappropriate to measure the pore size distribution of cementitious materials due to the ink-bottle effect. MIP with cyclic pressurization–depressurization can overcome the ink-bottle effect and enables a distinction between large (ink-bottle) pores and small (throat) pores. In this paper, pressurization–depressurization cycling mercury intrusion porosimetry (PDC-MIP) is adopted to characterize the pore structure in a range of cementitious pastes cured from 28 to 370 days. The results indicate that PDC-MIP provides a more accurate estimation of the pore size distribution in cementitious pastes than the standard MIP. Bimodal pore size distributions can be obtained by performing PDC-MIP measurements on cementitious pastes, regardless of the age. Water–binder ratio, fly ash and limestone powder have considerable influences on the formation of capillary pores ranging from 0.01 to 0.5 µm.

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Prediction of soil water retention properties using pore-size distribution and porosity

Canadian Geotechnical Journal ◽

10.1139/cgj-2012-0320 ◽

2013 ◽

Vol 50 (4) ◽

pp. 435-450 ◽

Cited By ~ 25

Author(s):

Christopher T.S. Beckett ◽

Charles E. Augarde

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Soil Water ◽

Water Retention ◽

Adsorbed Water ◽

Retention Data ◽

Soil Water Retention ◽

Pore Size Distributions ◽

Water Retention Properties

Several models have been suggested to link a soil's pore-size distribution to its retention properties. This paper presents a method that builds on previous techniques by incorporating porosity and particles of different sizes, shapes, and separation distances to predict soil water retention properties. Mechanisms are suggested for the determination of both the main drying and wetting paths, which incorporate an adsorbed water phase and retention hysteresis. Predicted results are then compared with measured retention data to validate the model and to provide a foundation for discussing the validity and limitations of using pore-size distributions to predict retention properties.

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Two sides of the same inverse problem, in identifying the pore size distribution based on experiments with non-Newtonian fluids

10.5194/egusphere-egu21-14586 ◽

2021 ◽

Author(s):

Martin Lanzendörfer

Keyword(s):

Inverse Problem ◽

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Forward Problem ◽

Size Distributions ◽

Pore Sizes ◽

Pore Size Distributions ◽

Flow Through ◽

Effective Pore Size

Following the capillary bundle concept, i.e. idealizing the flow in a saturated porous media in a given direction as the Hagen-Poiseuille flow through a number of tubular capillaries, one can very easily solve what we would call the forward problem: Given the number and geometry of the capillaries (in particular, given the pore size distribution), the rheology of the fluid and the hydraulic gradient, to determine the resulting flux. With a Newtonian fluid, the flux would follow the linear Darcy law and the porous media would then be represented by one constant only (the permeability), while materials with very different pore size distributions can have identical permeability. With a non-Newtonian fluid, however, the flux resulting from the forward problem (while still easy to solve) depends in a more complicated nonlinear way upon the pore sizes. This has allowed researchers to try to solve the much more complicated inverse problem: Given the fluxes corresponding to a set of non-Newtonian rheologies and/or hydraulic gradients, to identify the geometry of the capillaries (say, the effective pore size distribution).The potential applications are many. However, the inverse problem is, as they usually are, much more complicated. We will try to comment on some of the challenges that hinder our way forward. Some sets of experimental data may not reveal any information about the pore sizes. Some data may lead to numerically ill-posed problems. Different effective pore size distributions correspond to the same data set. Some resulting pore sizes may be misleading. We do not know how the measurement error affects the inverse problem results. How to plan an optimal set of experiments? Not speaking about the important question, how are the observed effective pore sizes related to other notions of pore size distribution.All of the above issues can be addressed (at least initially) with artificial data, obtained e.g. by solving the forward problem numerically or by computing the flow through other idealized pore geometries. Apart from illustrating the above issues, we focus on two distinct aspects of the inverse problem, that should be regarded separately. First: given the forward problem with N distinct pore sizes, how do different algorithms and/or different sets of experiments perform in identifying them? Second: given the forward problem with a smooth continuous pore size distribution (or, with the number of pore sizes greater than N), how should an optimal representation by N effective pore sizes be defined, regardless of the method necessary to find them?

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Yield Stress Fluid Method to Measure the Pore Size Distribution of a Porous Medium

ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels: Parts A and B ◽

10.1115/fedsm-icnmm2010-30509 ◽

2010 ◽

Cited By ~ 1

Author(s):

Aimad Oukhlef ◽

Abdlehak Ambari ◽

Ste´phane Champmartin ◽

Antoine Despeyroux

Keyword(s):

Porous Media ◽

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Size Distributions ◽

First Approximation ◽

Pore Size Distributions ◽

Plastic Fluid ◽

Present Technique ◽

Mathematical Processing

In this paper a new method is presented in order to determine the pore size distribution in a porous media. This original technique uses the non Newtonian yield-pseudo-plastic rheological properties of some fluid flowing through the porous sample. In a first approximation, the very well-known and simple Carman-Kozeny model for porous media is considered. However, despite the use of such a huge simplification, the analysis of the geometry still remains an interesting problem. Then, the pore size distribution can be obtained from the measurement of the total flow rate as a function of the imposed pressure gradient. Using some yield-pseudo-plastic fluid, the mathematical processing of experimental data should give an insight of the pore-size distribution of the studied porous material. The present technique was successfully tested analytically and numerically for classical pore size distributions such as the Gaussian and the bimodal distributions using Bingham or Casson fluids (the technique was also successfully extended to Herschel-Bulkley fluids but the results are not presented in this paper). The simplicity and the cheapness of this method are also its assets.

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Fractal Characteristics of Micro- and Mesopores in the Longmaxi Shale

Energies ◽

10.3390/en13061349 ◽

2020 ◽

Vol 13 (6) ◽

pp. 1349

Author(s):

Xiaoqi Wang ◽

Yanming Zhu ◽

Yang Wang

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Co2 Adsorption ◽

Controlling Factors ◽

Size Distributions ◽

Pore Size Distributions ◽

Longmaxi Shale ◽

Fractal Characteristics ◽

Multifractal Behavior

To better understand the variability and heterogeneity of pore size distributions (PSDs) in the Longmaxi Shale, twelve shale samples were collected from the Xiaoxi and Fendong section, Sichuan Province, South China. Multifractal analysis was employed to study PSDs of mesopores (2–50 nm) and micropores (<2 nm) based on low-pressure N2/CO2 adsorption (LP-N2/CO2GA). The results show that the PSDs of mesopores and micropores exhibit a multifractal behavior. The multifractal parameters can be divided into the parameters of heterogeneity (D−10–D10, D0–D10 and D−10–D0) and the parameters of singularity (D1 and H). For both the mesopores and micropores, decreasing the singularity of the pore size distribution contributes to larger heterogeneous parameters. However, micropores and mesopores also vary widely in terms of the pore heterogeneity and its controlling factors. Shale with a higher total organic carbon (TOC) content may have a larger volume of micropores and more heterogeneous mesopores. Rough surface and less concentrated pore size distribution hinder the transport of adsorbent in mesopores. The transport properties of micropores are not affected by the pore fractal dimension.

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