HL—1装置碳化和采用抽气孔栏时的可见辐射观测

本文描述了HL-1装置器壁碳化和采用抽气孔栏时,氢及杂质通量的变化情况;利用多道可见辐射的时空分布测量,得到了MARFE放电,在产生MARFE时,辐射热也相应增强。     

Evaluation of synthesized green carbon catalyst from waste date pits for tertiary butylation of phenol

The present study is intended to adopt a facile method for preparing a sulphonated green carbon catalyst from date pits biomass. Catalyst synthesis involves in situ carbonization and sulphonation and it has been characterized by following techniques such as XRD, SEM, EDX, TEM, FTIR, TGA, and BET. Surface and internal morphology results exhibited that the synthesized sulphonated carbon material possesses a mesoporous structure, while activated carbon possesses a microporous structure. Furthermore, the Fourier transform infrared (FTIR) spectra confirmed the presence of acidic groups (OH, COOH, and SO₃H) in synthesized sulphonated carbon material. Sulphonated carbon material exhibited high acidity (4.7 mmol/g) and good thermal stability. The application of this catalyst for the tertiary butylation of phenol without using any solvent has been investigated. The phenol alkylation reaction showed maximum conversion at reaction condition: temperature (140 °C) with 2 bar (nitrogen gas) pressure with maximum phenol conversion 79.27 wt%, with 68.01% selectivity towards 4TBP+2,4TBP, which is used as an intermediate in antioxidants. The catalyst exhibits comparable catalytic performance up to five reaction cycles. Thus it can be concluded that waste date pits can be successfully employed for green catalyst synthesis and used for reactions involving large molecules.     

基于有机磷酸类MOFs前驱体制备Ni2P/C复合材料

以镍为金属中心、 对二甲苯二磷酸为有机配体, 构筑了一种有机磷酸类Ni-MOF前驱体, 再经过一步碳化, 原位制备出多孔碳包覆Ni₂P纳米颗粒的复合材料. 该复合材料保留了前驱体的片状形貌, 比表面积可达202 m²/g, 复合材料中的Ni₂P纳米颗粒具有良好的结晶度, 颗粒均匀且无团聚现象. 在锂离子电池性能测试中, 该Ni₂P/C复合结构在缓解材料体积膨胀的同时提高了材料的电子和离子电导率, 进而提高了材料的电化学性能. 在0.2 C的电流密度下, 材料首次充、 放电比容量分别为247和226 mA·h·g^-1, 库仑效率可达91.7%, 循环200圈后, 库仑效率接近100%.     

A review of heat treatment on polyacrylonitrile fiber

Developing carbon fiber from polyacrylonitrile (PAN) based fiber is generally subjected to three processes namely stabilization, carbonization, and graphitization under controlled conditions. The PAN fiber is first stretched and simultaneously oxidized in a temperature range of 200-300 °C. This treatment converts thermoplastic PAN to a non-plastic cyclic or a ladder compound. After oxidation, the fibers are carbonized at about 1000 °C in inert atmosphere which is usually nitrogen. Then, in order to improve the ordering and orientation of the crystallites in the direction of the fiber axis, the fiber must be heated at about 1500-3000 °C until the polymer contains 92-100%. High temperature process generally leads to higher modulus fibers which expel impurities in the chain as volatile by-products. During heating treatment, the fiber shrinks in diameter, builds the structure into a large structure and upgrades the strength by removing the initial nitrogen content of PAN precursor and the timing of nitrogen. With better-controlled condition, the strength of the fiber can achieve up to 400 GPa after this pyrolysis process.     

基于前体聚合状态对碳材料进行分类以发展结构-性质关系(英文)

Modern carbon science lacks an efficient structure-related classification of materials. We present an approach based on dividing carbon materials by the aggregate state of the precursor. The common features in the structure of carbon particles that allow putting them into a group are discussed, with particular attention to the potential energy stored in the carbon structure from different rates of relaxation during the synthesis and prearrangement of structural motifs due to the effect of the precursor structure.     

Strong white light emission from a processed porous silicon and its photoluminescence mechanism

We have prepared various porous silicon (PS) structures with different surface conditions (any combination of oxidation, carbonization as well as thermal annealing) to increase the intensity of photoluminescence (PL) spectrum in the visible range. Strong white light (similar to day-light) emission was achieved by carrying out thermal annealing at 1100 °C after surface modification with 1-decene of anodic oxidized PS structures. Temperature-dependent PL measurements were first performed by gradually increasing the sample temperature from 10 to 300 K inside a cryostat. Then, we analyzed the measured spectrum of all prepared samples. After the analysis, we note that throughout entire measured spectrum, only two main peaks corresponding to blue and green-orange emission lines (which can be interpreted by quantum size effect and/or configuration coordinate model) were seem to be predominant for all temperature range. To further reveal and analysis these peaks, finally, measured data were inputted into the formula of activation energy of thermal excitation. We found that activation energies of blue and green-orange lines were approximately 49.3 and 44.6 meV, respectively.     

Thermogravimetric analysis and kinetics modeling of isothermal carbonization of olive wood in inert atmosphere

The kinetics of olive wood carbonization is investigated by means of isothermal thermogravimetric analysis method. Measurements were carried out in a thermobalance for different fixed temperatures between 498 and 648 K. A two-stage semi-global kinetic model consisting of four sequential steps was proposed to derive kinetic parameters. The olive wood is classified in three pseudo-components. For the first two, similar thermal degradation mechanisms take place in a single reaction step. For the third, the thermal degradation takes place in two consecutive steps. The isothermal conditions allow the kinetic constants (activation energy and pre-exponential factors) to be estimated by means of the analytical solution of the mass conservation equations. An overall good agreement was obtained with activation energy values available in the literature.     

传统糯米灰浆碳化过程中Liesegang环的形成机理研究

采用FTIR,XRD,SEM等技术,对传统糯米灰浆碳化过程中出现的Liesegang环现象进行了初步研究。结果表明,使用陈化石灰和糯米浆制备的糯米灰浆在碳化过程中能形成较明显的Liesegang环;陈化石灰-糯米灰浆固化后的极小孔隙,是传统糯米灰浆中Liesegang环形成的本质原因,其形成机理符合延迟成核理论。     

HL—1装置交流放电碳化实验

一种交流放电原位碳化技术首次在HL-1装置环形真空室内壁进行了试验。碳沉积膜样品作了扫描电镜,俄歇电子能谱和二次离子能谱深度轮廓和成分分析。壁碳化前后托卡马克放电杂质可见光谱和真空紫外光谱强度对照分折表明,碳化壁状态下,孔烂和金属壁材料Mo和Cr等在等离子体中含量下降80％左右,而C,O等轻杂质量有所上升;氢粒子约束时间τ_p和再循环率系数R较裸金属壁状态大致增加20％。碳化壁经惰性气体He或Kr放电锻炼后,在托卡马克放电中壁表面显示出明显的抽吸作用。     

Auger electron spectroscopy and electron energy loss spectroscopy studies on carbonization of Si(100) and (111) surfaces with ethylene

The reactions of Si(100) and Si(111) surfaces at 700 °C (973 K) with ethylene (C₂H₄) at a pressure of 1.3×10⁻⁴ Pa for various periods of time were studied by using Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS). For a C₂H₄ exposure level, the amount of C on the (111) surface was larger than that on the (100) surface. The formation of β-SiC grain was deduced by comparing the C_KLL spectra from the sample subjected to various C₂H₄ exposure levels, and from β-SiC crystal.