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Abstract  

The aim of the present study was the pore structure characterization of porous glass derived from a leachable precursor. Two independent techniques were applied on this purpose. The interpretation of the results obtained by these techniques, i.e. thermoporometry and nitrogen porosimetry was indicative for their supplementary character in what concerns the calculation of pore size distributions. The experimental work described in this study gives an example for the monitoring of the compositional evolution of phase separating compact-glass precursors of porous glasses.

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N2 adsorption at 77 K was used to follow the change in the pore structure of silica (mesoporous) produced on heating at 300 and 600‡C in the presence of different contents of mechanically mixed ZnO (15–85 mol%).

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Abstract  

Two types of raw materials, original kaolin sand OKS I and OKS II were used for experiment. They were transformed (1 h at 650 °C with 10 °C/min temperature increase) to burnt kaolin sand (BKS I and BKS II) with pozzolanic properties. Contents of decisive mineral—metakaolinite—in BKSs are as follows: BKS I (fraction below 0.06 mm) 20%; BKS II (fraction below 0.06 mm) 36% and BKS II (fraction below 0.1 mm) 31% by mass. Mortars with blends of Portland cement (PC) and BKS were prepared announced as: MK I (0.06) with 5 and 10% cement substitution by metakaolinite; MK II (0.06) with 5 and 10% cement substitution by metakaolinite and MK II (0.1) with 5, 10, 15 and 20% cement substitution by metakaolinite. The reference mortar with 100% of PC was made for comparison. All mortars were adjusted on the constant workability 180 ± 5 mm flow. Besides significant increase in compressive strengths—the refinement of pore structure in mortars with BKS connected with decreases in permeability and Ca(OH)2 content were revealed. The above facts confirm pozzolanic reaction of BKS in contact with hydrated PC and indicate perceptiveness of BKS for the use in cement-based systems as a pozzolanic addition.

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Journal of Thermal Analysis and Calorimetry
Authors: Xue-Gang Chen, Shuang-Shuang Lv, Ping-Ping Zhang, Lu Zhang, and Ying Ye

pore structures of rice hull. In this study, rice hull from Zhejiang Province, China, was ashed at 300–750 °C in air and nitrogen atmosphere, respectively. We systematically investigated the effects of ashing temperature and atmosphere on the

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, depends on the nature of pore size and distribution in a fibrous assembly [ 8 – 10 ]. Therefore, describing the pore structure properties of fibrous assemblies is of great importance. Several researches have discovered the fractal features of porous media

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pattern (not shown) of the parent silica material exhibits reflections typical of the hexagonally arranged pore structure. XRD data of the modified samples in this region confirm the preservation of the hexagonal structure after the modification process

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Abstract  

Physico-chemical properties (adsorption capacity, desorption energy distribution and pore-size distribution functions) of nanomaterial surfaces from selected materials, based on sorptometric and liquid thermodesorption measurements under quasi-equilibrium conditions, are presented. The fractal dimensions of nanotubes using sorptometric and AFM data have been evaluated. Comparison of thermogravimetric and other data provide new information about the adsorption and pore structure of the studied materials. The fractal dimensions of nanomaterial surfaces using sorptometry are in good agreement with those from AFM.

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Abstract  

Evolution of the internal pore structure during the combustion of two different types of coal chars is compared. In this study brown coal char prepared from brown coal (coal-mine Novky) by drying and devolatilization, and commercial black coal char (provided by U.S. Steel Košice) were used. Particles were combusted to different degrees of burnout at an initial temperature of 800C in a low oxygen containing atmosphere (5 vol%). It was shown that the combustion of both types of coal chars proceeds via the same shell progressive mechanism, despite differences in their original internal pore structure. The internal surface area of the brown coal char particles mainly belongs to the region of micropores, while for the black coal char is typical its macropore structure. Inside the brown coal particle cores pore structure evolution was observed. This change of the structure was caused by the reaction between solid carbon and carbon dioxide, due to which the specific surface area in the region of micropores significantly increased.

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