A New Reactor for Combined Conventional and Microwave Heating

A reactor system was developed to investigate the influence of microwaves on adsorption and desorption processes during heterogeneously catalyzed reactions. The reactor is free of temperature gradients and allows combined conventional and microwave heating. The hydroxylation of benzene with N₂O as an oxidant was used to test the reactor.     

可随机成型的透波性胶凝材料的微波加热特性

研究了硬化铝酸钙材料在不同煅烧温度（700,800,900,1000,1100,1200,1300,1400和1500℃）下的吸波能力、抗压强度、体积收缩率和质量损失率,采用XRF和XRD对不同煅烧温度（800,1000,1300和1500℃）下的试样进行表征,利用铝酸钙材料制备一种简易杯状容器并对其进行微波冲击特性测试。结果表明：硬化铝酸钙材料的吸波能力随煅烧温度的升高而降低,超过1000℃后,吸波能力趋于稳定;材料抗压强度随煅烧温度的升高先升高,在800℃左右达到最高,然后逐渐降低,并在1300℃达到最低,再经过小幅地升高后趋于稳定;同时,材料煅烧后体积收缩率和质量损失率都随着温度的升高而增加;微波冲击特性测试表明硬化铝酸钙材料在长时间微波辐照下强度基本不发生变化,微波-金属放电试验证明该胶凝材料硬化后的高温稳定性好,具有优异的抗高温冲击能力。综上所述,1000℃煅烧后的硬化铝酸钙材料具有透波性能好、力学性能优异、高温稳定性好的特点,非常适用于微波加热领域。     

硼对炭材料氧化行为的综合效应

综述了硼在炭材料中的抗氧化机理,并阐述了炭材料在氧化过程中的行为。硼对炭材料的氧化反应具有催化作用和保护作用的双重特征。     

碳纳米管/聚合物复合材料研究进展

综述了碳纳米管的预处理方法,重点介绍了有关碳纳米管复合材料的制备方法,结构表征,特殊性能及应用等.     

A comparison of surface morphology and chemistry of pyrolytic carbon blacks with commercial carbon blacks

The surface morphology and chemistry of CBp obtained by pyrolysis of waste tyres at 500 and 700 °C, respectively was studied compared with a commercial tyre carbon blacks by laser particle size analyzer, X-ray diffractogram (XRD) and electron spectroscopy for chemical analysis (ESCA). The distribution of CBp aggregates was the mixed particle distribution of commercial carbon blacks added to tyres in fabrication. The concentration of inorganic compounds and carbonaceous deposits (the organic compounds deposited on the surface of the CBp) depends on the pyrolysis temperature. The chemical nature of the CBp from pyrolysis at 700 °C was found to be closer to the commercial tyre carbon blacks than the CBp from pyrolysis at 500 °C.     

高温炭黑反应炉炉衬选材分析

从抵抗高温气流冲蚀、抗炭黑粒子化学侵蚀和抵抗炉气杂质化学侵蚀等三个方面对高纯刚玉砖、刚玉莫来石砖、铬刚玉砖、高铬砖和氧化锆砖作了分析比较。分析认为,在燃烧室和喉管采用高纯刚玉砖和铬刚玉砖,反应段和急冷段采用高纯刚玉砖较好;而氧化锆砖在整个反应炉各段使用都是可行的。高铬砖因抗炭黑粒子化学侵蚀性差,不适合使用于高温炭黑反应炉     

Synthesis of SiC nanowires via catalyst-free pyrolysis of silicon-containing carbon materials derived from a hybrid precursor

SiC nanowires were successfully synthesized without catalyst by pyrolysis of silicon-containing pitch-derived carbon materials in a closed graphite crucible. These silicon-containing carbon materials were obtained by homogenization and co-carbonization of a hybrid precursor consisting of the toluene soluble fraction of coal tar pitch with polycarbosilane (PCS). The composition, morphology and structure of the nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The influence of pyrolysis temperature on the growth of the nanowires was investigated by Fourier transform infrared spectroscopy (FTIR) and thermo-gravimetry coupled with mass spectroscopy (TG-MS) analysis. The results indicate that the growth of the SiC nanowires starts at around 1200 °C. As the pyrolysis temperature increases to 1300–1500 °C, a large quantity of nanowires are formed on the top surface of the pitch-derived carbon substrate. In addition, increasing the pyrolysis temperature leads to an increase in the average diameter and a change in the typical morphology produced. The synthesized SiC nanowires have single-crystalline structure and are grown along the [111] direction with numerous stacking faults and twins. The vapor-solid (VS) mechanism may be responsible for the growth process of the SiC nanowires.     

Chemical vapor deposition and infiltration processes of carbon materials

The chemical vapor deposition (CVD) and the chemical vapor infiltration (CVI) processes of carbon materials are reviewed starting from the historical aspects and including the latest developments in the preparation of C/C composites. Our presentation is based on an analysis of the different types of reactors, of the composite materials with different types of pyrocarbon as matrices and a comparison between the different processes. In particular, the classical isothermal-isobaric technique and temperature or pressure gradient reactors, which lead to a higher deposition efficiency, are compared. A complementary aspect is the structural and physical analysis of the deposited pyrocarbons: they are considered as reproducible metastable phases which are obtained under non-equilibrium thermodynamic conditions. The final relevant point concerns the relationship between the process parameters and the type of pyrocarbon. In particular, the so-called rough laminar microstructure, useful for most composite applications, is described.     

Microwave power absorption profile of detergent surfactant agglomerates during microwave heating

The microwave energy absorption behavior of the linear alkylbenzene sulfonate (LAS) surfactant detergent agglomerates was studied while considering changes in the physical properties of the samples. Microwave heating was used to change the internal structure of the agglomerates to make a reduced density (fluffy) product. The absorption of energy within LAS samples indicated fluctuating trends as microwave heating progressed. This was associated with the dielectric properties of the material which are strongly dependent upon the nature (“free” or “bound”) and quantity of water present in them at any instant which changes during heating. Therefore, complete profiles of the energy absorbed by the samples have been recorded to determine their actual power absorption behavior/total energy consumption over time. The bulk density of the agglomerates decreased significantly when exposed to microwave fields. Hot air drying can be combined with microwave heating to reduce the total heating time. It has been observed that the pre-heating of the samples reduces the total heating time and microwave energy requirement. This is due to the temperature-dependent decomposition of hydrates releasing more “free” water.     

Selective synthesis of carbon nanotubes and nanocapsules using naphthalene pyrolysis assisted with ferrocene

Selective synthesis of well aligned multi-walled carbon nanotubes (MW-CNT) and multi-shelled carbon nanocapsule (MS-CNC) using pyrolysis of naphthalene with the presence of ferrocene was experimentally examined. With higher mole fraction of naphthalene to ferrocene, more MW-CNTs could be synthesized due to higher concentration of carbonaceous precursors emerging from the decomposed naphthalene. Based on kinetic analysis, at lower temperature, MW-CNTs could preferably be synthesized due to the controlled supply of carbonaceous clusters to get onto the surface of Fe clusters. On the other hand, at temperature higher than 900 °C the Fe clusters become more active to catalyze carbonaceous precursors to undergo self assembling process of MS-CNCs. With cheaper cost of naphthalene compared with other high-value hydrocarbons, usage of naphthalene would provide an advantage of reasonably economical synthesis of MW-CNT or MS-CNC.     

4种炭素材料的抗氧化性能研究

在熔炼炉中对电极石墨、模压石墨、挤压石墨、等静压石墨4种炭素材料从室温逐渐加热至700℃,并在一定温度下保温1h,测其质量,绘制材料质量变化曲线图,以质量变化表征其抗氧化性的强弱.通过SEM、XRD等手段分析这几种炭素材料抗氧化性差异的本质原因.研究表明,这4种炭素材料的抗氧化性强弱顺序为等静压石墨、电极石墨、挤压石墨、模压石墨,影响石墨材料的抗氧化性能主要因素有石墨材料的石墨化程度、晶体结构缺陷、体积密度及杂质含量等.     

Pyrolytic carbon: factors controlling in-rubber performance

Abstract

Pyrolysis of waste tyres not only tackles the environmental issues associated with disposal, but also enables the recovery of valuable products such as oils and carbon fillers for elastomeric materials. This study was instigated to benchmark the in-rubber properties of pyrolytic carbon (often referred to as pyrolysis carbon black, pCB) and to understand the compositional parameters that dictate performance. Colloidal properties suggest the pCB materials to have a reinforcing potential between that of N330 and N550 carbon blacks, whereas physical property data suggest that they are more akin to the N700 series. Fundamentally, this disparity in performance appears to be the result of carbonaceous residues on the pCB surface, which both reduce surface activity and dispersability of the recyclate. Both thermogravimetric and dynamic mechanical analyses confirmed a number of pCB samples to have the same specific surface activity, regardless of the pyrolysis process or feedstock utilised.     

Examination of catalytic roles of inherent metallic species in steam reforming of nascent volatiles from the rapid pyrolysis of a brown coal

In-situ steam reforming of tar from the rapid pyrolysis of a Victorian brown coal was studied, employing a single-stage drop-tube reactor and a particular type of two-stage reactor, in which the nascent tar underwent steam reforming and thermal cracking in the presence and absence of nascent char particles, respectively. Na was the most abundant inherent metallic species contained in the coal, and a significant proportion of Na (60–80%) was volatilized during the pyrolysis. However, the Na dispersed in the vapor phase seemed to have no significant catalytic effect on the steam reforming. Na, and/or Ca remaining on the surface of char particles were responsible for rapid and extensive steam reforming of the nascent tar into gases, resulting in tar yield decrease by nearly 90%. The presence of steam alone was effective for suppressing soot formation from the tar vapor by approx. 80%, but in the absence of char particles containing metallic species, the addition of steam led to an increase in the yield of poly-nuclear aromatics.     

Direct synthesis of carbon and nitrogen–carbon nanospheres from aromatic hydrocarbons

In the present work, a controlled production of carbon nanospheres (CNS) via pyrolysis of benzene, aniline and nitrobenzene at 950 °C has been examined. The nature of the carbonaceous product has been characterized by transmission electron microscopy (TEM), N₂ adsorption/desorption, X-ray diffraction (XRD), elemental analysis (CHN), temperature-programmed oxidation (TPO) and X-ray photoelectron spectroscopy (XPS). Time-on-stream served to enhance the spherical morphology of the product, as well as its crystalline character. Nitrogen inclusion resulted in an enhanced curvature of the graphene layers, as well as the incorporation of lattice defects, resulting in a less crystalline material. The reactive nature of the feed influenced the amount of nitrogen incorporated into the carbon matrix, as well as the kind and distribution of nitrogen functionalities.     

Hydrogenation of carbon monoxide under mechanical activation conditions

The work focuses on the hydrogenation of carbon monoxide over solid catalysts undergoing mechanical activation by ball milling. The rate of carbon monoxide conversion at individual ball impacts was estimated by measuring the impact frequency, the mass of powders involved in individual impacts and their duration. The rate of the mechanochemical hydrogenation process was compared with the one of the corresponding thermal process. An enhancement of the catalyst activity under mechanical activation conditions is observed.     

炭发热材料在供暖领域的应用

本文叙述了碳的热电学性质,论述了利用炭作为发热元件供暖的产品结构及发热原理,介绍了炭发热元件的制作工艺流程及特性,指出炭发热材料作为一种新兴的、科学的采暖产品,具有高效、节能、环保、经济、发热迅速、不易老化、使用寿命长等优点,炭作为发热材料在供暖领域的应用前景十分广泛.