Optical properties of carbonized sporinite in vitrinite/sporinite blends

A study is made of the morphological and optical properties of a blend of concentrated sporinite and vitrinite macerals (equal parts) from the same coal carbonized between 400–900 °C at 5 °C/min under nitrogen. Two coals of different rank were used and the results compared with properties of unblended carbonized sporinites. Coke from a blend of low-rank vitrinite and sporinite produced a two-phase optical texture, whereas coke from the medium-rank vitrinite and sporinite mixture produced a three-phase optical texture. A ‘Transitional Zone’ of optical texture was observed at interfaces between carbonized vitrinite and sporinite, this zone being wider for the coal of higher rank. The increase of bireflectance in oil with carbonization temperature of the sporinite in the blends was lower than for the carbonized unblended sporinite, caused by a reduction in fluidity of sporinite with blending. The decrease of refractive index for sporinite carbonized > 600 °C in the blends was lower than that of the unblended sporinite.     

Disclinations in the optical texture of a high-rank vitrinite coke and a petroleum needle-coke

The microstructure of coke formed on carbonization of a low-volatile bituminous rank vitrinite (NCB Classification 204), at a heating rate of 60 °C min^?1, was found to consist largely of coarse-grained mozaic and domain type optical texture. The domain optical texture possessed a variety of optical structures, e.g. $\text{‘X’}$ and $\text{‘Y’-}\text{type}$ crosses and nodes, characteristic of it having passed through a nematic liquid crystal stage (mesophase) during carbonization. These structures are compared with, and found equivalent to, disclination structures found in the domains of a petroleum needle-coke, the surface of which had been gasified to reveal the underlying graphitic structure. The formation of disclination structures in the domains of the coal-coke is strong evidence for the formation and coalescence of mesophase during its carbonization as a result of the very high heating rate used.     

Thermoplastic properties of coal at elevated pressures: 1. Evaluation of a high-pressure microdilatometer

Thermoplastic behaviour of a Pittsburgh seam hvA coal (PSOC1099) was characterized by the use of a high-pressure microdilatometer. Phenomena such as softening, swelling, final resolidification, and the temperatures at which they occur were measured as functions of heating rate (25 ° and 65 °C min^?1), particle size (= 75 μm and 250 × 425 μm), gaseous atmosphere (N₂, H₂, $\text{CO}\text{H}{}_2$) and applied gas pressure (atmospheric to 2.8 M Pa). The results obtained illustrate several important aspects of thermoplastic properties of this coal under the conditions utilized. It is observed that pressure alone can play a major role in determining its overall thermoplastic behaviour. Compared to that at atmospheric pressure, swelling is significantly reduced at 2.8 MPa of pressure for any given heating rate or particle size. In these experiments, the chemical composition of the gaseous atmospheres ($\text{CO}\text{H}{}_2$, H₂ and N₂) does not appear to alter significantly the plastic phenomena at any given pressure. Increasing the heating rate or decreasing the particle size results in increased swelling at all applied pressures and atmospheres.     

Thermoplastic properties of coal at elevated pressures: 2. Low-temperature preoxidation of a Pittsburgh Seam coal

The thermoplastic properties of a preoxidized Pittsburgh Seam HVAb coal (air-treated at 383 K to different levels of weight gain) were examined using a high-pressure microdilatometer over a range (0.1–2.9 MPa) of pressures. The results suggest that the thermoplastic properties of the coal, depending on the extent of preoxidation, can be significantly different at elevated pressures from those at atmospheric pressure. The maximum swelling parameters of this preoxidized coal are always lower than those of untreated coal at pressures < 1.0 MPa. However, > 2.0 MPa, the maximum swelling parameters of the mildly oxidized samples are, in general, greater than those of untreated coal.     

Thermoplastic properties of coals at elevated pressures: 3. Effects of low-temperature preoxidation and subsequent heat-treatment on behaviour in H2 and He

The thermoplastic properties of a mildly preoxidized Lower Kittanning seam low volatile coal have been examined at elevated pressures of H₂ and He utilizing a high-pressure microdilatometer. It was observed that the maximum swelling parameter (V_s, vol%) of the preoxidized coal was significantly restored at elevated pressures of He. The thermoplastic properties of the preoxidized coal were even further restored at high pressures of H₂. The results indicate that carbonization of this coal at elevated H₂ pressures reduces the effect of preoxidation by removing some of the oxygen introduced during preoxidation and replacing it with reactive donatable hydrogen. It was shown that subsequent heat-treatment of the preoxidized coal at a relatively mild condition (in vacuum at 403 K) results in dramatic reductions in the thermoplastic behaviour of coal when subsequently carbonized at elevated pressures of H₂ or He.     

Optical properties of carbonized vitrinites

The optical properties have been examined of three vitrinite-rich coals (carbon, daf: 82.5, 88.0 and 93.1%), carbonized at temperature intervals of 25 °C over the greater part of the range 20–950 °C using a heating rate of 2.45 °C/min. The small temperature interval employed has allowed a satisfactory correlation between alterations in the physical state of the carbonized products and fluctuations in the rates of change of their optical properties during carbonization. In general, as temperature rises the variation of all the optical properties reflects the growth and development of organized polycondensed aromatic systems, but in detail reflectivity does not prove as sensitive an indicator of structural changes as do other optical parameters, particularly refractive index. The behaviour of the refractive-index curves of the carbonized vitrinites is governed by changes in the heights of the crystallites forming the aromatic systems. The shape of these curves closely follows the shape of curves produced in independent X-ray diffraction studies giving the heights of crystallites. While all the refractive-index and all the absorptiveindex curves are similar in shape and trend to one another, each of these curves for carbonized coking-coal vitrinite is displaced from the equivalent curves for low-rank bituminous and anthracitic vitrinites. The displacement can be related to the formation of the highly-plastic stage during carbonization of the coking-coal vitrinite, which ultimately yields weakly cross-linked structures with good crystallite orientation, in contrast to the strongly cross-linked structures with lower ordering developed in carbonization of vitrinites of both lower and higher rank.     

Optical properties of carbonized preoxidized vitrinites

The optical properties at 546 nm of three vitrinites (daf carbon contents 82.5, 88.0 and 93.1%) have been examined after pre-oxidation for 14 days at 105 °C and carbonization at intervals of 50 °C within the temperature range 300–800 °C. In general, pre-oxidation prior to carbonization produces only relatively small changes in the trends of optical parameters with temperature that were observed for the same vitrinites when carbonized fresh; the properties of the anthracitic vitrinite displayed little modification. Reflectivities of carbonized pre-oxidized vitrinites of bituminous rank are higher than those for the equivalent fresh vitrinites up to 500 °C, supporting the suggestion that oxidation raises aromaticity and consequently the reflectivity. The most noticeable optical difference occurs with the bituminous-rank vitrinites, in the variation with carbonization temperature of their refractive-index curves, which parallel the behaviour of the L_c curves of X-ray diffraction studies. In particular, the refractive-index track for the carbonized pre-oxidized vitrinite of coking-coal rank no longer shows the same marked contrast to the refractive-index tracks of vitrinites of higher and lower rank, as it does at temperatures above 600 °C when carbonized fresh. The absorptive indices follow similar trends to the reflectivities for all the chars.     

Coal pyrolysis at high temperatures and pressures

At high temperatures (s> 1100°C), pyrolysis of coal plays an increasingly important role in the overall coal conversion process. This Paper presents experimental data on the extent of pyrolysis of coal at 800–1600°C. In addition, the effects of the following parameters are examined: gaseous environment (N₂, CO₂ and H₂O), pressure (1–20 atm), particle size, moisture content and type of coal. Previous data on some of these parameters are non-existent. A unique TGA apparatus constructed for this work allows high heating rates (10²–10³°Cs^?1) due to the direct radiation heating. In all the gaseous environments, a plateau in per cent pyrolysis is noticed at 1200–1400°C followed by a sharp increase in the amount of pyrolysis as the temperature is raised. This is found consistent with the three-stage mechanism proposed for the evolution of volatiles. In CO₂ and steam environments, there is slightly less pyrolysis than in pure nitrogen, while considerably more pyrolysis is noted for predried coal and for smaller particle sizes. The results suggest a strong influence of secondary volatile reactions on the extent of pyrolysis. Pyrolysis in steam at 800–900°C shows an increase with pressure similar to that reported for pyrolysis in hydrogen. Finally, gasification rates of chars immediately following the pyrolysis are found to be much higher than those of chars prepared separately and then reacted. These results suggest morphological rearrangements and crystallization effects.     

Optical properties of bismuth tellurite based glass

A series of binary tellurite based glasses (Bi(2)O(3))(x) (TeO(2))(100-) (x) was prepared by melt quenching method. The density, molar volume and refractive index increase when bismuth ions Bi(3+) increase, this is due to the increased polarization of the ions Bi(3+) and the enhanced formation of non-bridging oxygen (NBO). The Fourier transform infrared spectroscopy (FTIR) results show the bonding of the glass sample and the optical band gap, E(opt) decreases while the refractive index increases when the ion Bi(3+) content increases.     

Macerals in bituminous coals and the coking process: 2. Coal mass properties and coke mechanical properties

Bituminous coals produced in the Ostrava-Karviná coal basin show considerable variation in their maceral composition, vitrinite reflectance and fluidity. There is a close association of the latter with the $\text{H}\text{O}$ atomic ratio expressing the different chemico-structural properties of vitrinites of lower coalification. These properties of the coal mass all influence the coke mechanical properties; moreover the $\text{H}\text{O}{}_{\mathrm{at}}$ parameter is of principal importance to the course of the coking process. Laboratory, pilot-plant and full-scale experiments show that coals rich in inertinite may give cokes of suitable mechanical properties, providing the $\text{H}\text{O}{}_{\mathrm{at}}$, ratio and the bulk density are high enough. It should be noted, however, that these coals contain finely dispersed inertinite in the vitrinite mass and this may have a positive effect on the coke mechanical properties.     

Optical properties of high-temperature heat-treated vitrinites

Three vitrinites (C = 80.0, 87.9 wt%, daf and 94.2 wt%, dmmf) have been heat-treated over the temperature range 1000–2400 °C in the presence of argon. The variation of morphological and optical properties of the heat-treated samples is studied systematically using reflected-light microscopy. An optically isotropic, highly reflecting material is formed on the surface of anisotropic particles of two of the vitrinites (C, 80 and 94.2 wt%) during semi-graphitization (1000–1400 °C), which decreases in extent with increasing temperature and is absent at the end of this stage. The development and subsequent disappearance of the isotropic material is probably due to the evolution of volatile matter and subsequent deposition of pyrolytic carbon during semi-graphitization. The continuous increase of bireflectance of these two vitrinite residues, with heat-treatment temperature, indicates progressive improvement in the ordering of the molecular structure. The reflectance of the heat-treated anthracitic vitrinite (C, 94.2 wt%), increases continuously whereas the reflectance of the heat-treated low-rank vitrinite (C, 80 wt% decreases slightly from a maximum during semi-graphitization. The third vitrinite (C, 87.9 wt%) does not develop an optically isotropic highly reflecting material on particle surfaces during semi-graphitization. However, this vitrinite softens during carbonization (25–1000 °C) producing a residue with a mosaictype anisotropic microstructure. The condition of polished surfaces prepared from residues of this vitrinite from the semi-graphitization to crystallization stages (1000–2300 °C) deteriorates, values of bireflectance and reflectance decrease continuously with increasing temperature. This appears to result from a reduction in the surface hardness of particles of this vitrinite residue resulting on transformation from two-dimensional ordering to three-dimensional graphitic ordering.     

Optical properties of plasticized polycarbonate

Optical properties of polycarbonate plasticized by pentaerythritol tris(1,1,2,3,3,3‐hexafluoropropyl) ether (HFP), diheptadecyl‐o‐phthalate and pentaerythrityl tetrabenzoate (TBP) have been determined at wavelengths from 300 to 700 nm. X‐ray diffraction analysis, which was used to examine the polymer structure, showed that all the plasticized systems were amorphous. HFP and, especially, TBP impeded crystallization of the polymer. Plasticized polycarbonate films remained transparent over long periods of time even if they were heated at a temperature higher than the polymer glass transition temperature. © 2003 Society of Chemical Industry     

焦炭光学组织在煤质鉴别中的应用

对我国山东、青海等地煤质较特殊的炼焦煤进行了工业分析指标、煤岩指标、焦炭光学组织和性能研究,并与同类型炼焦煤煤质进行比较。研究结果表明,焦炭光学组织能从本质上反映炼焦煤的质量,对一些煤质较特殊的煤,焦炭光学组织与工业分析指标和煤岩指标结合可更好地鉴别煤质。     

Thermoplastic properties of coals carbonized at elevated pressures: effects of waste inorganic materials (GOB)

Thermal behaviour of coal-derived asphaltenes was investigated under atmospheric pressure by thermogravimetry (TG). The weight loss is rapid from 300 to 500°C and is slow above 500°C. The asphaltene comparatively low in molecular weight shows the greater weight loss. The temperature at which the differential thermogravimetry peak appears, T_m, correlates to the asphaltene aromaticity: the asphaltene comparatively high in aromaticity shows higher T_m. Of the residual asphaltene after heating up to 600°C, the obtained crystallite thickness through the c-axis direction (Lc₀₀₂) has a correlation with the molecular weight of the parent asphaltene: the parent asphaltene comparatively low in molecular weight produces residual asphaltene of larger Lc₀₀₂.     

碳纳米管的光学性质及其在光限幅中的应用

碳纳米管是一种新型的碳材料,具有特殊的结构,独特的力学、电磁学和光学性质,已引起人们的极大兴趣。综述了近年来碳纳米管光学性质的研究进展及其在光限幅中的应用,并对今后的研究方向作了展望。     

煤岩显微组分与焦炭显微结构组成之间关系的研究

对煤的显微组分与其焦炭显微结构组成的对应关系进行了定性与定量测定。结果表明：焦炭中的破片、类丝炭来源于煤中的用性组分。焦炭显微结构中光学各向异性单元尺寸取决于煤的变质程度。     

Materials Development of Optical Fiber

Traditionally, new materials are developed in response to the requirements of an emerging device technology. In the optical fiber case, development of glass as a transmission medium came as the culmination of a century-long quest for improved broadband telecommunications, a search that established the superiority of light signals transmitted through glass over electronic signals transmitted by wire.     

刚玉质浇注料加热过程中内部不同位置的蒸汽压力和温度

将纯铝酸钙水泥和SiO2微粉复合结合的刚玉质浇注料振动浇注成100 mm×100 mm×100 mm的试样,并在距试样上表面不同深度(分别为40、50、60 mm)处埋入压力引管和热电偶,养护24 h后脱模,然后以5℃·min-1的加热速度升温,记录炉温从100℃升温至约450℃过程中试样内部不同深度处的蒸汽压力和温度。结果表明:1)当炉温升至约400℃时,试样内部不同深度处的蒸汽压力均达到最大,对应的试样内部温度比较接近,约为260℃;炉温超过400℃后,试样内部的蒸汽压力迅速降低。2)在受热过程中,试样的最大蒸汽压力出现在试样中心位置。