Mercury intrusion porosimetry in pulp and paper technology

Mercury intrusion is frequently used for the characterization of porous materials, giving access to parameters such as porosity and pore size distribution as well as density (skeletal and bulk).The present work aims at studying the suitability of the mercury intrusion technique to evaluate the pore structure and related information of different kinds of woods used for pulp production, pulp handsheets and commercial paper sheets. Differences in wood structure, pulp composition and paper composition and structure could be easily detected by changes in the measured parameters, thus enabling a better understanding and/or prediction of the behaviour of these materials.     

Mercury porosimetry and its application to the analysis of coal pore structure

Mercury porosimetry, gas adsorption, helium and mercury densities and small angle X-ray scattering were the methods used for studying porosity characteristics of a number of Czechoslovak coals ranging from lignite to semi-anthracite. Total pore volumes were measured in the pore radii range 0.1 – 7500 nm and then divided into the following groups: micropores (smaller than 1.8 nm), mesopores (1.8 – 30 nm) and macropores (over 30 nm). Coal porosity values ranged from 1.3 up to 43%. With low and medium-rank coals (carbon content under 76%), porosity is mostly due to mesopores. Micropores and mesopores account for a substantial share of the porosity of bituminous coals (carbon content over 80.6%). The distribution of mesopores was determined for an identical pore radii interval on the basis of data obtained independently by means of mercury penetration, gas adsorption and small angle X-ray scattering. High-pressure mercury penetration is an effective method of obtaining the coal porosity spectrum within a broad interval of pore radii, provided that a correction is made for the coal compressibility when evaluating the measured data. The recommended value of the mercury—coal contact angle is 1352 for brown coal and 130° for bituminous coal.     

Mercury porosimetry in pharmaceutical technology

The literature on the use of mercury porosimetry in pharmaceutical technology is reviewed. The relation between the application and the preferable pore size distribution presentation is also discussed. In addition, pore size distributions of lactose tablets are presented and the calculated values for the porosity, pore diameter and specific surface area are compared with results from air permeability and nitrogen adsorption measurements. The agreement is acceptable taking into account the simplifications and the inaccuracy of the methods.     

Microstructural evolution of cemented paste backfill: Mercury intrusion porosimetry test results

The microstructural evolution of different cemented paste backfill (CPB) samples made with ground silica was evaluated using mercury intrusion porosimetry (MIP). The influence of three binders (OPC, OPC with fly ash, and OPC with blast furnace slag) and of three types of water (one deionised and two sulphated) on the microstructure was studied over the curing time. Uniaxial compressive strength (UCS) tests were also performed to relate MIP results to the backfill mechanical strength. Among other findings, the MIP analyses indicate that the slag based binder combined with a mixing water having a high sulphate content (of 7549 ppm) showed the highest percentage of fine pores and the highest strength. This behaviour is related to the potential precipitation of sulphate phases in pores, which may contribute to strength enhancement. Based on MIP pore size distributions and UCS results, the authors propose a general relationship applicable for CPB.     

Characterization of pore structure in cement-based materials using pressurization-depressurization cycling mercury intrusion porosimetry (PDC-MIP)

Numerous mercury intrusion porosimetry (MIP) studies have been carried out to investigate the pore structure in cement-based materials. However, the standard MIP often results in an underestimation of large pores and an overestimation of small pores because of its intrinsic limitation. In this paper, an innovative MIP method is developed in order to provide a more accurate estimation of pore size distribution. The new MIP measurements are conducted following a unique mercury intrusion procedure, in which the applied pressure is increased from the minimum to the maximum by repeating pressurization-depressurization cycles instead of a continuous pressurization followed by a continuous depressurization. Accordingly, this method is called pressurization-depressurization cycling MIP (PDC-MIP). By following the PDC-MIP testing sequence, the volumes of the throat pores and the corresponding ink-bottle pores can be determined at every pore size. These values are used to calculate pore size distribution by using the newly developed analysis method. This paper presents an application of PDC-MIP on the investigation of the pore size distribution in cement-based materials. The experimental results of PDC-MIP are compared with those measured by standard MIP. The PDC-MIP is further validated with the other experimental methods and numerical tool, including nitrogen sorption, backscanning electron (BSE) image analysis, Wood's metal intrusion porosimetry (WMIP) and the numerical simulation by the cement hydration model HYMOSTRUC3D.     

Mercury porosimetry and the interpretation of pore geometry in sedimentary rocks and artificial models

The major objectives of this paper are to investigate how the form and hysteresis of mercury injection, withdrawal and reinjection capillary pressure curves are affected by the geometry of pores and their connections in samples of sedimentary rocks and also in artificial and theoretical pore-network models.In particular, those aspects of pore systems which may influence trapping of mercury during pressure reduction and withdrawal are considered. These are: pore to throat ratio, throat to pore coordination number or connectivity and the types and extent of random and non-random heterogeneities within the system.These aspects of pore systems influence the threshold pressure and the gradient of injection curves as well as the gradients and degree of hysteresis displayed by withdrawal and re-injection curves. Such curves are useful in interpreting pore geometry and give information which is valuable in assessing multiphase fluid behaviour in oil and gas reservoir rocks. In the case of water displacing oil or gas, in a strongly water-wet system, the trapping of oil or gas is controlled mainly by capillary forces and a direct analogy with the air-mercury system is possible.     

Mercury penetration porosimetry in analysis of exhaust catalysts and catalyst supports

The application of mercury penetration porosimetry is reported, in which data of samples from several manufacturers are presented. The technique has been used to investigate the loss of catalyst activity by high-temperature aging as correlated with pore structure alterations. It has been possible to determine the difference between catalyst deterioration due to poisons deposited on the catalyst and deterioration due to loss of surface area resulting from extremely high temperatures. Some data are also presented which indicate that, by choosing the proper conditions in the honeycomb fabrication process, the porosity of the resulting product can be controlled.     

Hydration of cement and pore structure of concrete cured in tropical environment

This paper presents the results of an experimental study on the effect of curing on the degree of cement hydration and capillary porosity of concrete in a tropical environment. It provides basic information for the estimation of w/c of hardened concrete using petrographic methods. Concrete with w/c ratios of 0.30 to 0.70 with an increment of 0.05 was investigated. The concrete was cured at 20 and 35 °C and exposed to various durations of moist curing. The results indicated that the concrete cured at 20 °C water for 28 days had a higher degree of cement hydration and lower capillary porosity than did the concrete cured in water of the same temperature for 7 days followed by exposure to outdoor air for 21 days, but had an opposite trend compared to the concrete cured in 35 °C water for 7 days followed by exposure to outdoor air. However, the differences on the degree of cement hydration and capillary porosity for the concrete cured in these different conditions were not significant.     

Three-dimensional visualization of pore structure in hardened cement paste by the gallium intrusion technique

It is widely known that the pore structure of concrete strongly influences its physical properties. Therefore, we developed a technique for the visualization of the pore structure because of clearing it correctly. However, this visualization is limited to two-dimensional imaging for sections of the specimen. As a result, in this study, we developed a technique for reconstructing the acquired 2D images of the pore structure into 3D form by stacking them. By using this image, the relationship between water permeability and pore connectivity was clarified, and it was shown clearly that the pore connectivity strongly affects the water permeability.     

Synthesis of bamboo-derived porous carbon: exploring structure change,pore formation and supercapacitor application

Biomass porous carbon possessing hierarchical pores and abundant heteroatoms has emerged as a sustainable and cost-effective functional material. Herein, a green cellulose solvent was employed as the activation agent and nitrogen source to obtain this distinctive structure from bamboo cellulose fibers. With the assistance of thermal treatment, the solvent could fully infiltrate into cellulose structure of raw material and result in the cellulosic structure damage, forming ultimately the three-dimensional conductive network, hierarchical pores, as well as high heteroatom doping (8.43 at%). Benefited from the unique structure, the obtained porous carbon as the supercapacitor electrode showed excellent capacitive performance (280 F/g at 0.3 A/g), good rate capability and cyclic stability. Moreover, influences of hydrothermal temperature on cellulose structure, pore formation, and the resultant supercapacitor performance were demonstrated. This green strategy shows potential for producing hierarchical porous carbon with high heteroatoms from biomass resources.

     

超缓凝技术在混凝土中的研究应用

本文探讨了外加剂、矿物掺合料、环境温湿度等因素对超缓凝混凝土性能的影响,试验数据结果：混凝土凝结时间随着超缓凝剂掺量增加而延长;超缓凝剂相同掺量下,高水灰比时,超缓凝剂能有效抑制胶凝材料水化反应进程,增加了混凝土凝结时间;在同一基准下, 固定超缓凝剂掺量,提高矿物掺合料的掺量能延长凝结时间;在低温、高湿条件下有利于延长混凝土凝结时间。通过优化配合比参数,成功配制出凝结时间为72 h的超缓凝混凝土, 28 d抗压强度符合要求,60 d抗压强度无损失,能满足施工要求。     

关键工艺作用辨识方法及其在耐火材料中的运用

分析了工艺作用和作用模型,讨论了相关关系和因果关系、重要关系和关系网络,叙述了利用方差分析、网络分析等技术识别关键工艺作用,提出决定性的问题解决方案,介绍了该方法在开发高纯硅砖中的应用。     

Porosity, pore size distribution and in situ strength of concrete

In this study, in situ strength of concrete was determined through compression test of cores drilled out from laboratory cast beams. The apparent porosity and pore size distribution of the same concrete were determined through mercury intrusion porosimetry, performed on small-drilled cores. The normal-strength concrete mixes used in the experimental investigation were designed to exhibit a wide variation in their strengths. To ensure further variation in porosity, pore size distribution and strength, two modes of compaction, two varieties of coarse aggregates, different levels of age, curing period and exposure condition of concrete were also introduced in experimental scheme. With the data so generated, an appraisal of the most frequently referred relationships involving strength, porosity and pore size of cement-based materials was carried out. Finally, a new empirical model relating the in situ strength of concrete with porosity, pore size characteristics, cement content, aggregate type, exposure conditions, etc., is presented.     

Evaluation of chloride penetration in high performance concrete using neural network algorithm and micro pore structure

Chloride attack is one of the major causes of deterioration of reinforced concrete structures. In order to evaluate the chloride behavior in concrete, a reasonable prediction for the diffusion coefficient of chloride ion, which governs mechanism of chloride diffusion inside concrete, is basically required. However, it is difficult to obtain chloride diffusion coefficients from experiments due to time and cost limitations.In this study, a numerical technique for chloride diffusion in high performance concrete (HPC) using a neural network algorithm is proposed. In order to collect comparative data on diffusion coefficients in concrete with various mineral admixtures such as ground granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF), a series of electrically driven chloride penetration tests was performed. Seven material components in various mix designs and duration time are selected as neurons in a back-propagation algorithm, and associated learning of the neural network is carried out. An evaluation technique for chloride behavior in HPC using the obtained diffusion coefficients from the neural network algorithm is developed based on, so-called, Multi-Component Hydration Heat Model (MCHHM) and Micro Pore Structure Formation Model (MPSFM). The applicability of the developed technique is verified by comparing the analytical simulation results and the experimental results obtained in this study. Furthermore, this proposed technique using the neural network algorithm and micro modeling is applied to available experimental data for verification of its applicability.     

5-甲基糠醛的制备及其应用研究进展

介绍了5-甲基糠醛的性质与特点。重点综述了以5-甲基呋喃、糠醛或其卤代物、5-羟甲基糠醛或其卤代物、生物质基碳水化合物等为原料制备5-甲基糠醛的研究及5-甲基糠醛的应用进展。     

Syntheses and application of silica monolith with bimodal meso/macroscopic pore structure

A route to synthesize porous materials with a bimodal macro/mesoscopic pore system has been investigated in this work. Polystyrene with sub-micrometer size was used as a template in the synthesis. The resulting mesoporous silica wall replicated inversely the morphology of polystyrene template and had highly ordered three-dimensional arrays of macro pores. Large and moldable meso/macro porous silica monoliths could be obtained in centimeter scale by using monodispersed polystyrene beads and PEO-PPO-PEO/SBA-15 sol solutions. These bimodal structured porous silicates have been used as supports for asymmetric kinetic resolution of racemic epoxides to synthesize optically pure epoxide.     

Sorption and diffusion of water,salt water,and concrete pore solution in composite matrices

In recent years, the use of fiber‐reinforced polymer composites in civil infrastructure has been promoted as a solution to the deterioration of bridges, buildings, and other structures composed of traditional materials, such as steel, concrete, and wood. Any application of a polymer composite in an outdoor environment invariably involves exposure to moisture. There is also potential for exposure to saline conditions in waterfront or offshore structures, and alkaline environments, as would be encountered by a reinforcing bar in a cementitious material. This study characterizes the sorption and transport of distilled water, salt solution, and a simulated concrete pore solution in free films of vinyl ester, isophthalic polyester (isopolyester) and epoxy resins, all commercially important materials for use in structural composites. Diffusion of all three liquids in each of the three materials was observed to follow a Fickian process. Mass loss was observed for the isopolyester in salt water and concrete pore solution at 60°C, suggesting hydrolysis that was accelerated by the high temperature exposure. Both the rate of uptake, as well as the equilibrium uptake, were greater at 60°C, compared with ambient conditions. Diffusion coefficients calculated from the mass uptake data revealed that, although the epoxy resin had the highest equilibrium uptake, it had the lowest diffusion coefficient. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 483–492, 1999     

Syntheses and application of silica monolith with bimodal meso/macroscopic pore structure

A route to synthesize porous materials with a bimodal macro/mesoscopic pore system has been investigated in this work. Polystyrene with sub-micrometer size was used as a template in the synthesis. The resulting mesoporous silica wall replicated inversely the morphology of polystyrene template and had highly ordered three-dimensional arrays of macro pores. Large and moldable meso/macro porous silica monoliths could be obtained in centimeter scale by using monodispersed polystyrene beads and PEO-PPO-PEO/SBA-15 sol solutions. These bimodal structured porous silicates have been used as supports for asymmetric kinetic resolution of racemic epoxides to synthesize optically pure epoxide.