scholarly journals Structural and Textural Characteristics of Selected Copper-Bearing Rocks as One of the Elements Aiding in the Assessment of Gasogeodynamic Hazard

2017 ◽  
Vol 39 (2) ◽  
pp. 51-59 ◽  
Author(s):  
Anna Pajdak ◽  
Mateusz Kudasik
Keyword(s):  
Structural Properties ◽  
Gas Adsorption ◽  
Mercury Porosimetry ◽  
High Porosity ◽  
Copper Mine ◽  
Rock Samples ◽  
Computed Microtomography ◽  
Structural And Textural Parameters ◽  
Textural Parameters ◽  
The Mean

Abstract The characteristics of copper-bearing rocks that include the structural and textural parameters are an important factor determining a possible gas accumulation in those rocks. In September 2009, in the Rudna copper mine in Poland, an outburst of gases and dolomite occurred. The analysis of the outburst mass showed that one of the main causes of the outburst was the different structural properties such as high porosity and presence of gas in the pores. This paper presents data from the structural analysis of dolomite from the Polkowice-Sieroszowice copper mine and the Rudna copper mine. Seven rock samples from various areas of the mines were tested by the following methods: mercury porosimetry (MIP), low pressure gas adsorption (LPNA), scanning electron microscopy (SEM), computed microtomography (micro-CT). The SEM analyses of the rock samples allowed pores of various sizes and shapes to the observed. The porosity (MIP) of the dolomite changed in the range of 3-15%. The total micro and mesopore volume (LPNA) was from 0.002 cm3/g to 0.005 cm3/g. The macropore volume (MIP) was from 0.01 cm3/g to 0.06 cm3/g and the mean macropore diameter was from 0.09 μm to 0.18 μm. The dolomite samples varied in the surface area (LPNA) (0.7-1.5 m2/g) and the pore distribution. The structure of dolomite determines the possibility of the occurrence of gasogeodynamic phenomena and hence it is urgent that research be conducted into its changeability. To better understand the gasogeodynamic processes in copper-bearing rocks, it is necessary to constantly monitor and analyse in detail those areas that have different structural properties.

Covalent Organic Frameworks for Electrochemical Sensors: Recent Research and Future Prospects

2021 ◽  
Vol 17 ◽  
Author(s):  
Linyu Wang ◽  
Shasha Hong ◽  
Yuxi Yang ◽  
Yonghai Song ◽  
Li Wang
Keyword(s):  
Specific Surface ◽  
Electrochemical Sensors ◽  
Gas Adsorption ◽  
Low Cost ◽  
High Sensitivity ◽  
Crystalline Polymer ◽  
Synthesis Methods ◽  
High Porosity ◽  
Covalent Organic Frameworks ◽  
Covalent Bonds

Background: In recent years, electrochemical sensors are widely preferred because of their high sensitivity, rapid response, low cost and easy miniaturization. Covalent organic frameworks (COFs), a porous crystalline polymer formed by organic units connected by covalent bonds, have been widely used in gas adsorption and separation, drug transportation, energy storage, photoelectric catalysis, electrochemistry and other aspects due to their large specific surface, excellent stability, high inherent porosity, good crystallinity as well as structural and functional controllability. The topological structure of COFs can be designed in advance, the structural units and linkage are diversified, and the structure is easy to be functionalized, which are all beneficial to their application in electrochemical sensors. Methods: The types, synthesis methods, properties of covalent organic frameworks and some examples of using covalent organic frameworks in electrochemical sensors are reviewed. Results: Due to their characteristics of a large specific surface, high porosity, orderly channel and periodically arranged π electron cloud, COFs are often used to immobilize metal nanoparticles, aptamers or other materials to achieve the purpose of building electrochemical sensors with high sensitivity and good stability. Since the structure of COFs can be predicted, different organic units can build COFs with different structures and properties. Therefore, organic units with certain functional groups can be selected to build COFs with certain properties and used directly for electrochemical sensors. Conclusion: COFs have a good application prospect in electrochemical sensors.

Microstructure characterization of mullite foam by image analysis, mercury porosimetry and X-ray computed microtomography

2018 ◽  
Vol 44 (11) ◽  
pp. 12315-12328 ◽  
Author(s):  
Eva Gregorová ◽  
Tereza Uhlířová ◽  
Willi Pabst ◽  
Petra Diblíková ◽  
Ivona Sedlářová
Keyword(s):  
Image Analysis ◽  
Mercury Porosimetry ◽  
Microstructure Characterization ◽  
X Ray ◽  
Computed Microtomography ◽  
X Ray Computed

INVESTIGATION OF CARBON BLACK AND SILICA SURFACE STRUCTURE BY STATIC GAS ADSORPTION WITH VARIOUS GASES

2018 ◽  
Vol 91 (2) ◽  
pp. 509-519 ◽  
Author(s):  
J. Plagge ◽  
M. Klüppel
Keyword(s):  
Carbon Black ◽  
Surface Area ◽  
Adsorption Energy ◽  
Gas Adsorption ◽  
Expectation Maximization Algorithm ◽  
Quadrupole Moments ◽  
Characteristic Energy ◽  
The Mean ◽  
Adsorption Of Co2 ◽  
Pressure Regime

ABSTRACT The surface of various carbon black and silica grades is characterized via static gas adsorption using different gases. From decomposition of the adsorption isotherm into distinct energetic contributions, the adsorption energy distribution as well as the surface area are obtained. The decomposition is done by an iterative expectation maximization algorithm specifically designed for this problem. It is found that the adsorption isotherms of the various gases differ significantly in the low-pressure regime, leading to characteristic energy distributions with distinct maxima. As expected, the mean adsorption energy generally increases with the cross section of the gases, and systematic deviations are found reflecting the polar and dispersive interaction characteristics of silica and carbon black, respectively. The surface fractal dimension of two different carbon black grades is estimated using the yardstick method. The obtained values 2.6 and 2.7 agree with previous findings that the carbon black surface morphology is very rough. The adsorption of CO2 on both carbon blacks delivers unexpectedly low values of the monolayer coverage or specific surface area, indicating that mainly high energetic sites of the surface are covered. In consequence, compared with N2, a relatively high value of the mean adsorption energy is found. For both investigated silicas, the mean adsorption energy scales with the quadrupole moments of CO2 and N2, which is indicative of a large polar contribution to interaction energy.

scholarly journals Quantification of Random Pore Structures of Porous Adsorbents

1991 ◽  
Vol 8 (4) ◽  
pp. 196-216 ◽  
Author(s):  
R. Mann ◽  
H.N.S. Yousef
Keyword(s):  
Image Analysis ◽  
Gas Adsorption ◽  
Mercury Porosimetry ◽  
Stochastic Networks ◽  
Random Pattern ◽  
Sem Images ◽  
Pore Networks ◽  
Fractal Surfaces ◽  
Pore Structures ◽  
Particulate Form

The structure of pore spaces in typical catalyst particles could often be described as being “not so much fabricated as thrown together”. Thus whilst for certain materials, such as zeolites, the microstructures are well defined and have a precise geometry, most materials when used in typical particulate form are at least partly composed of chaotically configured pore spaces. These random pore structures can be important in determining an adsorbent's performance, so it is necessary to define them quantitatively. A heirarchy of approaches based upon developments from simple stochastic pore networks is described. A stochastic pore network is one in which simple pore segments form interconnecting networks within which pores can be either randomly or partly randomly distributed. Such stochastic networks can be characterised by mercury porosimetry and low-temperature gas adsorption. Interconnectivity and randomness affect the degree of hysteresis for both these techniques. For 3-D random pattern stochastic networks, it is possible to interpret sectioned SEM images using ‘random’ slices of particles subject to low melting point alloy visual porosimetry in order to arrive at measures of random pore structure. This ‘image analysis’ approach is being extended to 3-D image reconstruction of SEM sections using fractal surfaces in conjunction with randomly tortuous pores.

Hydromechanical effects: (I) on the Na-smectite microtexture

Clay Minerals ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 525-536 ◽  
Author(s):  
J . -F. Alcover ◽  
Y. Qi ◽  
M. Al-mukhtar ◽  
S. Bonnamy ◽  
F. Bergaya
Keyword(s):  
Mechanical Stress ◽  
Pore Volume ◽  
Gas Adsorption ◽  
Mercury Porosimetry ◽  
Considerable Effect ◽  
Particle Sizes ◽  
Structural Formulae

AbstractChanges in particle organization and pore-spaces with applied mechanical and hydraulic stresses were followed using TEM, SAXS mercury porosimetry and gas adsorption for two Na-smectites, Laponite and hectorite, with similar structural formulae but different particle sizes. The TEM images show that hectorite has particles larger and more anisotropic than those of Laponite. The particles order perpendicularly to the direction of axial mechanical stress and become disoriented under hydraulic stress. According to the SAXS results, Laponite is composed of 1 – 3 small layers and hectorite of more compact (10 – 80 layers) particles. In Laponite, mechanical stress strongly reduces the amount of macropores but does not affect micropores and mesopores; hydraulic stress increases the macropores. In hectorite, the pore-volume is lower than in Laponite. The different techniques used yield complementary results and show the considerable effect of layer dimension on the behaviour and microtexture parameters of smectite submitted to hydromechanical stresses.

scholarly journals The Suitability of Granite and Granite-Gneiss of part of Minna Sheet 164 SW North-Central Nigeria as Construction Aggregates

2021 ◽  
pp. 47-58
Author(s):  
A.A Sidi ◽  
N.M Waziri ◽  
A. Musa ◽  
A. Hamidu ◽  
H.M Liman ◽  
...  
Keyword(s):  
Specific Gravity ◽  
Granite Gneiss ◽  
Absorption Capacity ◽  
Normal Weight ◽  
High Porosity ◽  
Rock Samples ◽  
Maximum Value ◽  
Average Impact ◽  
Geotechnical Tests ◽  
Geotechnical Testing

Geotechnical tests were performed on granite and granite-gneiss rock samples of parts of Minna to know their suitability as construction aggregates. Eight rock samples were selected for porosity test, impact value, specific gravity and absorption capacity. The average porosity of the samples is 0.21, 0.12, 0.30, 0.10, 0.25, 0.25, 0.24 and 0.11 respectively for L1, L14, L15, L19, L21, L23, L25 and L29 which shows they are normal except L15 with a high porosity. Average impact value of the samples show they are suitable for wearing surface course in road and bridge construction, except samples L14 and L19 with average impact value of 32.8 and 34.9 respectively making them suitable only as bituminous macadam (maximum value = 35%). Sample L1 is not suitable as construction aggregates because it exceeds the maximum value specified for that purpose. The average specific gravity of the rocks are L1=2.68, L14=2.65, L15=2.65, L19=2.67, L21= 2.63, L23= 2.71, L25=2.65, and L29=2.69 respectively and which make them suitable as normal weight materials for construction. The average absorption capacity values of the rock samples are 0.20%, 0.20%, 0.50%, 0.10%, 0.25%, 0.10%, 0.50% and 0.20% respectively for samples L1, L14, L15, L19, L21, L23, L25, and L29. All testing followed the respective ASTM standards. Keywords: Geotechnical testing, construction aggregates, granite, granite-gneiss, Minna, Nigeria.

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