scholarly journals Destabilization of the hard coal microstructure by a weak electric field

2018 ◽  
Vol 60 ◽  
pp. 00023
Author(s):  
Oleksandr Molchanov ◽  
Dmytro Rudakov ◽  
Valerii Soboliev ◽  
Oleksii Kamchatnyi
Keyword(s):  
Electric Fields ◽  
Chemical Activation ◽  
Practical Significance ◽  
Weak Electric Field ◽  
Hard Coal ◽  
Scanning Calorimetry ◽  
Paramagnetic Resonance ◽  
Destruction Mechanism ◽  
Coal Organic Matter ◽  
Outburst Hazard

This study aims to analyse physical and chemical changes in hard coal samples under the influence of low-intensity electric fields in comparison to the fragments of ejected coal, as well as the coal samples selected from the zones of high and low outburst hazard. We used physical methods including X-raying, electron paramagnetic resonance, thermogravimetric analysis, differential scanning calorimetry, laser diffraction analysis of particle sizes, IR-spectrometry, nuclear magnetic resonance, and Raman spectroscopy. It has been shown that destruction of coal organic matter (COM) can be caused not only by mechanical impacts or thermal influences but also weak electric fields. Scientific novelty consists in the fact that for the first time we established the identity of the COM destruction mechanism of mechanical-chemical activation and weak electric fields influencing on the previously destabilized coal microstructure. The destruction mechanism is based on thermal field regularities in both cases. The results obtained are of practical significance for the technologies of coal conversion to other products. The research results can be useful in the development of methods for reducing outburst hazard in coal mines.

scholarly journals Experimental Analysis of Pore Structure and Fractal Characteristics of Soft and Hard Coals With Same Coalification

2021 ◽  
Author(s):  
Barkat Ullah ◽  
Yuanping Cheng ◽  
Liang Wang ◽  
Weihua Yang ◽  
Izhar Mithal Jiskani ◽  
...  
Keyword(s):  
Pore Structure ◽  
Adsorption Capacity ◽  
Gas Adsorption ◽  
Hysteresis Loops ◽  
Control Measures ◽  
Practical Significance ◽  
Coal Bed ◽  
Hard Coal ◽  
Pore Surface ◽  
Soft Coal

Abstract Accurate and quantitative investigation of the physical structure and fractal geometry of coal has important theoretical and practical significance for coal bed methane and the prevention of dynamic disasters such as coal and gas outbursts. This study investigates the pore structure and fractural characteristics of soft and hard coals using nitrogen and carbon dioxide (N2/CO2) adsorption. Coal samples from Pingdingshan Mine in Henan province of China were collected and pulverized to the required size (0.2-0.25mm). N2/CO2 adsorption tests were performed to evaluate the pore size distribution (PSD), specific surface area (SSA), and pore volume (PV). The pore structure was characterized based on fractural theory. The results unveiled that the strength of coal has a significant influence on pore structure and fracture dimensions. The obvious N2-adsorption isotherms of the coals were verified as Type IV (A) and Type II. The shape of the hysteresis loops indicates the presence of slit-shaped pores. There are significant differences in SSA and PV between both coals. The soft coal showed larger SSA and PV than hard coal that shows consistency with adsorption capacity. The fractal dimensions of soft coal are respectively larger than that of hard coal. The greater the value of D1 (complexity of pore surface) of soft coal is, the larger the pore surface roughness and gas adsorption capacity is. The results enable us to conclude that the characterization of pores and fractures of soft and hard coals is different, tending to different adsorption/desorption characteristics and outburst sensitivity. In this regard, results provide a reference for formulating corresponding coal and gas outburst prevention and control measures.

scholarly journals Origin of the enhanced structural and reorientational relaxation rates in the presence of relatively weak dc electric fields

2004 ◽  
Vol 76 (1) ◽  
pp. 215-221 ◽  
Author(s):  
A. Vegiri
Keyword(s):  
Molecular Dynamics ◽  
Electric Field ◽  
Electric Fields ◽  
Structural Relaxation ◽  
Structural Changes ◽  
Common Mechanism ◽  
Weak Electric Field ◽  
Water Molecules ◽  
Relaxation Rates ◽  
Dynamics Simulations

The origin of the dramatic increase of the reorientational and structural relaxation rates of single water molecules in clusters of size N = 16, 32, and 64 at T = 200 K, under the influence of an external, relatively weak electric field (~0.5 107 V/cm) is examined through molecular dynamics simulations. The observed effect is attributed not to any profound structural changes, but to the increase of the size of the molecular cage. The response of water to an electric field in this range shows many similarities with the dynamics of water under low pressure. By referring to simulations and experiments from the literature, we show that in both cases the observed effects are dictated by a common mechanism.

scholarly journals Understanding the Properties of Starch in Potatoes (Solanum tuberosum var. Agria) after Being Treated with Pulsed Electric Field Processing

Foods ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 159 ◽  
Author(s):  
Setya B.M. Abduh ◽  
Sze Ying Leong ◽  
Dominic Agyei ◽  
Indrawati Oey
Keyword(s):  
Solanum Tuberosum ◽  
Electric Field ◽  
Light Microscopy ◽  
Electric Fields ◽  
Potato Starch ◽  
Potato Tissue ◽  
Scanning Calorimetry ◽  
Starch Properties ◽  
Polarised Light

The purpose of this study was to investigate the properties of starch in potatoes (Solanum tuberosum cv. Agria) after being treated with pulsed electric fields (PEF). Potatoes were treated at 50 and 150 kJ/kg specific energies with various electric field strengths of 0, 0.5, 0.7, 0.9 and 1.1 kV/cm. Distilled water was used as the processing medium. Starches were isolated from potato tissue and from the PEF processing medium. To assess the starch properties, various methods were used, i.e., the birefringence capability using a polarised light microscopy, gelatinisation behaviour using hot-stage light microscopy and differential scanning calorimetry (DSC), thermal stability using thermogravimetry (TGA), enzyme susceptibility towards α-amylase and the extent of starch hydrolysis under in vitro simulated human digestion conditions. The findings showed that PEF did not change the properties of starch inside the potatoes, but it narrowed the temperature range of gelatinisation and reduced the digestibility of starch collected in the processing medium. Therefore, this study confirms that, when used as a processing aid for potato, PEF does not result in detrimental effects on the properties of potato starch.

Studies on the Microstructure and Thermal Properties of Pulsed Electric Fields (PEF)-Treated Maize Starch

2012 ◽  
Vol 8 (1) ◽  
Author(s):  
Zhong Han ◽  
Qian Yu ◽  
Xin An. Zeng ◽  
Dong Hui Luo ◽  
Shu Juan Yu ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Treatment Time ◽  
Dominant Role ◽  
Pulsed Electric Fields ◽  
Maize Starch ◽  
Scanning Calorimetry ◽  
Significant Difference

Maize starch-water suspensions (8.0%) were submitted to the pulsed electric fields (PEF) with different electric field strength and treatment time up to 50 kV/cm and 1272 μs. Samples were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR). GPC analysis showed that molecular weights (Mw and Mn) were decreased with increasing electric field strength and treatment time. DSC studies showed a decrease in gelatinization temperatures (To and Tp) and the enthalpy of gelatinization (ΔHgel) with increasing electric field strength and treatment time. It was explored that electric field strength played a dominant role in the PEF treatments. On the other hand, it was demonstrated from NMR and TGA analysis that no significant difference among the native and PEF-treated maize starches was obtained, which indicated that PEF treatments did not affect the chemical structure of maize starch.

Comparison of Cable Insulation Control in Weak and Strong Electric Fields

2015 ◽  
Vol 756 ◽  
pp. 486-490 ◽  
Author(s):  
Nadezda S. Starikova ◽  
Vitaly V. Redko ◽  
G.V. Vavilova
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Strong Electric Field ◽  
Weak Electric Field ◽  
Cable Insulation ◽  
Modern Methods ◽  
Insulation Thickness ◽  
Defect Dimension ◽  
Cylindrical Capacitor ◽  
Strong Electric Fields

In this paper the modern methods of cable products insulation control are referred. A comparison of efficiency of the cable insulation defects control by changing in cable area capacitance is carried out in the strong and weak electric fields. The electric cable can be represented as a cylindrical capacitor, but to simplify the issue the insulation area is represented as a plate capacitor with anisotropic dielectric. The cable insulation model is created in the software Comsol Multyphysic. The effect of the defect dimension on the cable area electric capacitance in a strong and weak electric field is described. Also, the control sensitivity of both methods was assessed and compared with each other. The control sensitivity in a weak electric field is slightly higher for the defects with small size (less than 70% from insulation thickness). The control sensitivity in a strong electric field is considerably higher for the defects with big size (more than 70% from insulation thickness).

Preparation and characterization of pure and copper-doped PVC films

2017 ◽  
Vol 37 (1) ◽  
pp. 83-92 ◽  
Author(s):  
K. Bhagya Sree ◽  
Y. Madhava Kumar ◽  
N.O. Gopal ◽  
Ch. Ramu
Keyword(s):  
Polymer Film ◽  
Polymer Films ◽  
Dopant Concentration ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Bending Vibrations ◽  
Paramagnetic Resonance ◽  
Solution Cast ◽  
Ft Ir

Abstract Pure and Cu2+-doped polyvinyl chloride (PVC) polymer films were prepared using the solution cast technique. Investigations were conducted using DSC, TGA, XRD, FT-IR, UV–Vis, SEM and EPR. Differential scanning calorimetry studies suggested that the Cu2+ samples have higher values of the glass transition (Tg) temperature, and thermo gravimetric studies show that weight loss of polymer film indicates the improved thermal stability of the polymer film. The features of the complexation of the polymer films were studied by X-ray diffraction. FT-IR spectra exhibits the bands in three regions, which are attributed to C–Cl, C–C and numerous CH groups of stretching and bending vibrations. The absorption spectra have been recorded in the wavelength range 200–900 nm. The absorption edge, direct bandgap, indirect bandgap and urbach energy have been evaluated. Film morphology was examined by scanning electron microscopy. XRD, DSC and SEM reveal the amorphous nature and surface morphology of polymer films, respectively. Electron paramagnetic resonance studies were used to calculate the number of spins and paramagnetic susceptibility as a function of dopant concentration, all the Cu2+-doped PVC samples exhibit signal with g values g⊥=2.176 and g||=2.254. The observed variation in the EPR signal intensity is due to variation in the dopant concentration.

scholarly journals The Composites of PCL and Tetranuclear Titanium(IV)-oxo Complexes as Materials Exhibiting the Photocatalytic and the Antimicrobial Activity

2021 ◽  
Vol 22 (13) ◽  
pp. 7021
Author(s):  
Barbara Kubiak ◽  
Aleksandra Radtke ◽  
Adrian Topolski ◽  
Grzegorz Wrzeszcz ◽  
Patrycja Golińska ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Diffuse Reflectance Spectroscopy ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Antibacterial Properties ◽  
Visible Range ◽  
Resonance Spectroscopy ◽  
Direct Reaction ◽  
Scanning Calorimetry ◽  
Paramagnetic Resonance ◽  
Oxo Complexes

Excessive misuse of antibiotics and antimicrobials has led to a spread of microorganisms resistant to most currently used agents. The resulting global threats has driven the search for new materials with optimal antimicrobial activity and their application in various areas of our lives. In our research, we focused on the formation of composite materials produced by the dispersion of titanium(IV)-oxo complexes (TOCs) in poly(ε-caprolactone) (PCL) matrix, which exhibit optimal antimicrobial activity. TOCs, of the general formula [Ti4O2(OiBu)10(O2CR')2] (R' = PhNH2 (1), C13H9 (2)) were synthesized as a result of the direct reaction of titanium(IV) isobutoxide and 4-aminobenzoic acid or 9-fluorenecarboxylic acid. The microcrystalline powders of (1) and (2), whose structures were confirmed by infrared (IR) and Raman spectroscopy, were dispersed in PCL matrixes. In this way, the composites PCL + nTOCs (n = 5 and 20 wt.%) were produced. The structure and physicochemical properties were determined on the basis of Raman microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), electron paramagnetic resonance spectroscopy (EPR), and UV–Vis diffuse reflectance spectroscopy (DRS). The degree of TOCs distribution in the polymer matrix was monitored by scanning electron microscopy (SEM). The addition of TOCs micro grains into the PCL matrix only slightly changed the thermal and mechanical properties of the composite compared to the pure PCL. Among the investigated PCL + TOCs systems, promising antibacterial properties were confirmed for samples of PCL + n(2) (n = 5, 20 wt.%) composites, which simultaneously revealed the best photocatalytic activity in the visible range.

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