The pretreatment of low rank coal with nitric acid oxidation can promote its bio-liquefaction. However, the detailed mechanism of which remains an unresolved problem. In the present work, the characteristics of Fushun...The pretreatment of low rank coal with nitric acid oxidation can promote its bio-liquefaction. However, the detailed mechanism of which remains an unresolved problem. In the present work, the characteristics of Fushun coal before and after oxidation by nitric acid were investigated combined with elemental composition, pore volume and pore size, Zeta potential, FT-IR, and 13C solid NMR spectrum analysis. The results show that the inorganic substance inlaid in coal are dissolved by ni- tric acid, which results in the decrease of coal ash content and increase of pore volume and pore size. Furthermore, there exist obvious chemical reactions between nitric acid and the functional groups of coal including aromatic ring carboxylation, side chain alkyl of aromatic ring oxidation and aromatic ring nitration. Among these reactions, some led to the increase in content of carboxyl, aliphatic carbon connected with O and humic acid carbon, while others caused the reduction of aromaticity, methyl carbon, substituted aryl carbon and side chain.展开更多
The advantages and disadvantages of organic antioxidant and inorganic salt on suppressing coal oxidation were analyzed on the basis of the theory that coal oxidation mechanisms can be attributed to the free radical ch...The advantages and disadvantages of organic antioxidant and inorganic salt on suppressing coal oxidation were analyzed on the basis of the theory that coal oxidation mechanisms can be attributed to the free radical chain-type reaction mechanism. The inhibition curves on suppressing coal oxidation of the different type and different concentration of organic antioxidant and inorganic salt were given through experimental study and data processing. Then some conclusions can be gained from the experimental study combining with theoretical analysis. First the inhibition mechanism of the organic antioxidant and inorganic salt is different. The former is that the chemical action is the dominant position. It can be called as the chain termination theory because the free radical is captured during coal oxidation. And the later is that the physical effect is the dominant position. It can be called as the decreasing-temperature theory because the liquid membrane which was formed by the inorganic salt can make coal body be the state of wetness and prevent oxygen from coal surface. Second the inhibition effect of the organic antioxidant is higher than the inorganic salt in the later period. But it is lower in the early period.展开更多
Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes rang...Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.展开更多
基金Supported by the National Natural Science Foundation of China （50874107） the Guizhou Science and Technology Fund （Qiankehe J zi [2012]2306）+1 种基金 the Guizhou High-level Talent Special Assistant Fund （TZJF-2011-04） the Guizhou Research Laboratory Platform of Clean and Efficient Use of Coal Resources （Qianke Platform [2011] 4003）
文摘The pretreatment of low rank coal with nitric acid oxidation can promote its bio-liquefaction. However, the detailed mechanism of which remains an unresolved problem. In the present work, the characteristics of Fushun coal before and after oxidation by nitric acid were investigated combined with elemental composition, pore volume and pore size, Zeta potential, FT-IR, and 13C solid NMR spectrum analysis. The results show that the inorganic substance inlaid in coal are dissolved by ni- tric acid, which results in the decrease of coal ash content and increase of pore volume and pore size. Furthermore, there exist obvious chemical reactions between nitric acid and the functional groups of coal including aromatic ring carboxylation, side chain alkyl of aromatic ring oxidation and aromatic ring nitration. Among these reactions, some led to the increase in content of carboxyl, aliphatic carbon connected with O and humic acid carbon, while others caused the reduction of aromaticity, methyl carbon, substituted aryl carbon and side chain.
文摘The advantages and disadvantages of organic antioxidant and inorganic salt on suppressing coal oxidation were analyzed on the basis of the theory that coal oxidation mechanisms can be attributed to the free radical chain-type reaction mechanism. The inhibition curves on suppressing coal oxidation of the different type and different concentration of organic antioxidant and inorganic salt were given through experimental study and data processing. Then some conclusions can be gained from the experimental study combining with theoretical analysis. First the inhibition mechanism of the organic antioxidant and inorganic salt is different. The former is that the chemical action is the dominant position. It can be called as the chain termination theory because the free radical is captured during coal oxidation. And the later is that the physical effect is the dominant position. It can be called as the decreasing-temperature theory because the liquid membrane which was formed by the inorganic salt can make coal body be the state of wetness and prevent oxygen from coal surface. Second the inhibition effect of the organic antioxidant is higher than the inorganic salt in the later period. But it is lower in the early period.
基金supported by the National Natural Science Foundation of China (No 50875252)the Program for New Century Excellent Talents in Universities (NoNCET-06-0479)the Natural Science Foundation of Jiangsu Province (NoBK2008005)
文摘Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.
