Structure and Performance of Fe-N_x-C Catalyst for Oxygen Reduction Reaction Prepared by Vacuum Casting Method and the Second Pyrolysis

Affordable non-precious metal（NPM） catalysts played a vital role in the wide application of polymer electrolyte membrane fuel cells（PEMFC）. In current work, a facile vacuum casting reacting method based on vacuum casting was introduced to prepare Fe-N_x-C oxygen reduction reaction（ORR） catalysts with high efficient in acid medium. The catalysts were prepared with ammonium ferrous sulfate hexahydrate（AFS） and 1,10-phenanthroline monohydrate utilizing homemade mesoporous silica template. The heat treatment and its influence on structure and performance were systematically evaluated to achieve superior ORR performance and some clues were found. And 850 ℃ was found to be the best temperature for the first and second pyrolysis. The linear sweep voltammetry（LSV） results showed that there were only 18 mV slightly negative shifts of half-wave potential（E_（1/2）） of the optimal catalyst（749 mV） compared with the commercial Pt/C（20 μg·Pt·cm^-2）. Besides, I850 R also showed better electrochemical stability and methanol-tolerance than that of Pt/C. All evidences proved that our vacuum casting reacting strategy and heat treatment process were prospective for the future R＆D of high performance Fe-N_x-C ORR catalysts.

Influence of carbon coating prepared by microwave pyrolysis on properties of LiNi_(1/3) Mn_(1/3) Co_(1/3) O_2

A novel synthesis method of carbon-coated LiNil/3Mnl/3COl/302 cathode material for lithium-ion battery was reported. The carbon coating was produced from a precursor, glucose, by microwave-pyrolysis method. The prepared powders were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, X-ray fluorescence （XRF） and charge/discharge tests. XRD results indicate that the carbon coating does not change the phase structure of LiNil/3Mnl/3C01/302 material. SEM results show that the surface of spherical carbon-coated material becomes rough. Electrochemical performance results show that the carbon coating can improve the cycling performance of LiNii/3Mnl/3C01/302. The specific discharge capacity retention of the carbon-coated LiNi1/3Mnt/3Col/30z reached 85.0%-96.0% at the 50th cycle at 0.2C rate, and the specific discharge capacity retention is improved at a high rate.

Type Ⅰ kerogen-rich oil shale from the Democratic Republic of the Congo: mineralogical description and pyrolysis kinetics

The Democratic Republic of the Congo holds important reserves of oil shale which is still under geological status.Herein,the characterization and pyrolysis kinetics of typeⅠkerogen-rich oil shale of the western Central Kongo(CK)were investigated.X-ray diffraction,Fourier-transform infrared spectroscopy and thermal analysis(TG/DTA)showed that CK oil shale exhibits a siliceous mineral matrix with a consistent organic matter rich in aliphatic chains.The pyrolysis behavior of kerogen revealed the presence of a single mass loss between 300 and 550°C,estimated at 12.5%and attributed to the oil production stage.Non-isothermal kinetics was performed by determining the activation energy using the iterative isoconversional model-free methods and exhibits a constant value with E=211.5±4.7 kJ mol.1.The most probable kinetic model describing the kerogen pyrolysis mechanism was obtained using the Coats–Redfern and Arrhenius plot methods.The results showed a unique kinetic triplet confirming the nature of kerogen,predominantly typeⅠand reinforcing the previously reported geochemical characteristics of the CK oil shale.Besides,the calculation of thermodynamic parameters(ΔH~*,ΔS~*andΔG~*)corresponding to the pyrolysis of typeⅠkerogen revealed that the process is non-spontaneous,in agreement with DTA experiments.

Mechanism,Kinetics,and Thermodynamic Characteristics for the Demetallization of Used Lubricating Oil via Pyrolysis

This study analyzed the pyrolysis mechanism,developed a pyrolysis kinetic model,and determined the corresponding thermodynamic parameters for the removal of calcium from used lubricating oil using sulfurized calcium alkyl phenolate(T-115B)as a model compound.The pyrolysis process and products were evaluated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.Visual inspection indicated that the removal of calcium from T-115B depended primarily on the destruction of micelles caused by the pyrolysis of compounds at high temperatures.The pyrolysis characteristics of T-115B at different heating rates were investigated by thermogravimetry and differential thermal analysis,which revealed two distinct pyrolysis phases.Thus,the pyrolysis mechanism can be described by a twostep model.The activation energy and thermodynamic parameters(ΔH,ΔG,andΔS)were determined by applying the Kissinger-Akahira-Sunose,Flynn-Wall-Ozawa,Friedman,and Starink methods;the average activation energies for T-115B pyrolysis obtained using these methods were 115.80,119.84,124.96,and 116.14 kJ/mol,respectively.Further,both stages of the pyrolysis reaction followed Fn mechanisms with n=1.39 in the first stage and n=0.86 in the second stage.This study provides reliable and effective pyrolysis models along with kinetic and thermodynamic parameters to facilitate the largescale industrial application of used lubricating oil.

Effect of preparation methods on the adsorption property of municipal solid waste-based carbon materials

Three different preparation methods including steam physical activation, catalytic carbonation and KOH chemical activation methods were used to prepare municipal solid waste- based carbon materials. The methylene blue （MB） adsorption value was applied to evaluate the adsorption capabilities of the prepared carbon materials. The effects of preparation methods on adsorption capability and yield of products were investigated. The yield of carbon materials with the catalytic carbonation method is the highest, and the KOH activation method is the second level. Considering the adsorption performance, the KOH activation method is much more favorable. Among the different components of municipal solid waste-based carbon materials, the adsorption properties of the single component of paperboard, the double components of tire and paperboard, the triple components of tire, paperboard and polyvinyl chloride （PVC）, and the multi-component mixtures are better than those of other single-, double-, triple- and multi-component mixtures, respectively.

Pyrolysis Empirical Modeling of Polyester Glass Fiber Reinforced Plastics Using Sestak-Berggren Model Method

Polyester Glass Fiber Reinforced Plastic(Polyester GFRP),a thermosetting plastic comprised of glass fiber and polyester polymer compounds,is extensively utilized in high-speed trains.Unraveling its pyrolysis mechanism is crucial as it significantly influences the combustion characteristics and fire safety aspects.Currently,kinetic research on polyester GFRP primarily focuses on employing the Coats-Redfern method to derive a theoretical kinetic model.However,the pyrolysis process of polyester GFRP is complex and the aforementioned theoretical model fails to accurately describe the pyrolysis mechanism.Therefore,this study seeks to utilize the Sestak and Berggren(SB) model as a methodological approach to reveal the complex reaction mechanism during the pyrolysis process.Based on thermogravimetric analysis,the entire pyrolysis process of polyester GFRP is divided into two primary stages.Furthermore,model-free methods are employed to ascertain the activation energy and pre-exponential factor.The results show that the fitted empirical models of the two main pyrolysis stages are f(α)=(1-α)^(1.47)[-ln(1-α)]^(1.50) and f(α)=(1-α)^(1.77)[-ln(1-α)]^(1.72),respectively.The predicted results are in good agreement with experimental data under different heating rates,which indicates that the empirical model can sufficiently describe the pyrolysis process of polyester GFRP.

PREPARATION OF MULTI-WALLED CARBON NANOTUBES USING NiO CATALYST SYNTHESIZED BY HYDROTHERMAL METHOD

The Ni(OH)2/SiO2 binary colloid was prepared using Ni(NO3)2.6H2O and (C2H5O)4SiO4 as starting materials and was used to form NiO/SiO2. composite powder by hydrothermal method and desiccant method in open air respectively. Multi-walled carbon nanotubes (MWCNTs) were synthesized respectively by chemical vapor deposition using the NiO/SiO2 catalyst prepared by different methods. The phase and morphology of the catalysts and the morphology, output yield and purity of MWCNTs were compared by XRD, TEM and SEM. The results show that the catalyst powder prepared by hydrothermal method, compared with that by desiccant method, is smaller, better dispersion and has stronger catalytic activity. Pure MWCNTs with smaller tube diameter and narrow range could be obtained at a high yield using that NiO/SiO2 powder prepared by hydrothermal method as catalyst.

Disposal methods for used passenger car tires: One of the fastest growing solid wastes in China

With the rapid growth in the number of passenger cars(PCs)in China over the past decades,more than ten million tons of used tires have already become solid wastes and subsequently caused serious environmental issues.Due to the presence of synthetic rubber in PC tires,waste PC tires cannot be disposed through rubber reclaiming technology.Thus,waste PC tires have become one of fastest growing solid wastes in China.First,the current disposal capacity of the pyrolysis method,regarded as a promising technology for the disposal of waste PC tires,is surveyed and compared with other disposal methods mentioned in previous papers.Second,this work establishes a model to predict the total number of waste PC tires in the next five years depending on the rate of PC growth and current waste tire disposal capacity.Moreover,pyrolysis is evaluated on 15 collected waste PC tires selected from the most representative tire brands in the Chinese market.The corresponding results imply that~68.5%of S was into oil and~44.3%N and large amount of heavy metals resided in solid carbon which severely limit further applications.Finally,a new pyrolysis technology is introduced that may represent a solution to the limits in the application of tire disposal methods and relief for the coming waste tire crisis.

Verification of an Explicitly Coupled Thermal-Phase Field-Mechanical Electromagnetic (TPME) Framework by the Method of Manufactured Solutions

An explicitly coupled two-dimensional (2D) multiphysics finite element method (FEM) framework comprised of thermal, phase field, mechanical and electromagnetic (TPME) equations was developed to simulate the conversion of solid kerogen in oil shale to liquid oil through in-situ pyrolysis by radio frequency heating. Radio frequency heating as a method of in-situ pyrolysis represents a tenable enhanced oil recovery method, whereby an applied electrical potential difference across a target oil shale formation is converted to thermal energy, heating the oil shale and causing it to liquify to become liquid oil. A number of in-situ pyrolysis methods are reviewed but the focus of this work is on the verification of the TPME numerical framework to model radio frequency heating as a potential dielectric heating process for enhanced oil recovery. Very few studies exist which describe production from oil shale;furthermore, there are none that specifically address the verification of numerical models describing radio frequency heating. As a result, the Method of Manufactured Solutions (MMS) was used as an analytical verification method of the developed numerical code. Results show that the multiphysics finite element framework was adequately modeled enabling the simulation of kerogen conversion to oil as a part of the analysis of a TPME numerical model.

五氧化二钒薄膜材料制备方法研究进展

由于V^(5+)的饱和氧化态,五氧化二钒成为钒体系中最稳定的氧化物。作为功能材料,五氧化二钒薄膜在众多科学领域有着巨大的应用潜力,因而受到越来越多的关注。这主要归功于其特殊的层状结构、高能量密度、良好的化学和热稳定性以及优异的光学和电学性能。五氧化二钒薄膜的制备方法很多,采用不同的实验方法在不同衬底上制备的五氧化二钒薄膜因化学成分和组织结构差异而造成其电学、光学性能也存在显著的差异。本文详细阐述了五氧化二钒薄膜现有的制备技术,并对五氧化二钒薄膜材料应用的发展趋势进行了展望,以期为五氧化二钒薄膜产业的发展提供参考。

有机前驱体法制备氮化硼纤维的研究

氮化硼(BN)纤维是一种耐热和介电性能优异的陶瓷纤维,目前的主要合成方法为有机前驱体转化法。以聚三甲胺基环硼氮烷为前驱体,通过熔融纺丝、不熔化和力热耦合热解处理,制备出直径均匀的BN纤维。利用扫描电镜(SEM)、X射线衍射(XRD)、X光电子能谱(XPS)、BET比表面积等手段对BN纤维的微观结构、结晶性能、元素组成以及孔隙率进行详细表征。结果表明:1600℃热处理得到的BN纤维,表面光滑,织态结构完整,拉伸强度可达640.3MPa,而1000℃热处理得到的BN纤维,孔隙率高,比表面积最大,比表面积可达362.64m^(2)/g。

氮掺杂生物质多孔碳材料的制备及其在超级电容器中的应用

以碳化后的纤维素为基底,KOH为活化剂,尿素作为掺杂剂,采用热解法和活化法相结合成功制备了氮掺杂生物质多孔碳(N-PBCs),并通过一系列的表征手段证明了所制备的N-PBCs电极材料具有良好的孔径结构和大量的缺陷结构。此外,基于N-PBCs的水系对称超级电容器的最高比电容达到了230.1F·g^(-1)(电流密度0.3A·g^(-1)),当电流密度增加到10A·g^(-1)时,其比电容量保持率仍高达84.7%。这为下一代新型储能器件材料的开发提供了新思路。

氟掺杂富锂层状氧化物的电化学性能

富锂锰基正极材料的应用前景广阔,但循环稳定性较差。为增强材料的电化学稳定性,设置F掺杂浓度梯度实验。采用聚合-热解法,通过优化丙烯酸聚合过程中的原料比例,制备Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54) O_(2-x)F_(x)材料,探究F掺杂比例对正极材料微观形貌和电化学稳定性的影响,定量分析首次充放电过程中,不同阶段氧化还原反应的容量释放情况。采用XRD、SEM分析样品的物相组成和微观形貌;采用恒流充放电和电化学阻抗测试分析样品的电化学性能。F掺杂可提升富锂锰基正极材料的电化学稳定性,x=0.03时,样品LMNC-F0.03的层状结构明显,阳离子混排程度低,电化学稳定性最优。以0.5 C在2.0~4.8 V循环100次,放电比容量为186.97 mAh/g,容量保持率为85.76%,放电中值电压保持率为84.93%;2.0 C倍率下的平均放电比容量为147.68 mAh/g。

生态环境视域下基层医院医疗废物处理研究

医疗废物含有大量的病毒、致病微生物以及化学药剂等,若直接排放对生态环境污染性大。因此,文章研究一种生态环境视域下基层医院医疗废物处理方法。该方法采用高温高压蒸汽灭菌与热解气化联合技术,对医疗废物进行前处理和深度处理。通过此法,废物中的病毒、致病微生物及化学药剂得到有效消减。研究结果表明,处理后二噁英含量显著降低,符合国家标准,杀菌率高达90%以上。这不仅验证了联合处理技术的有效性,也显示了对生态环境的保护作用。此方法为基层医院处理医疗废物提供了新的解决方案,有助于减少环境污染,促进生态平衡。

常用电缆热解气体产生规律研究

研究电缆的热解气体产生规律,可以为电缆火灾早期预警提供依据。本文针对常用电缆搭建了高温热解实验平台,分别对75、100、120、150℃下电缆PVC外护套的热解气体产生规律和185℃、225℃下电缆内部材料的热解气体产生规律进行了研究。结果表明:PVC电缆外护套材料在75℃时已经发生热解,热解气体组分为CO和CO_(2);温度低于120℃时,热解气体组分只有CO和CO_(2),所以CO和CO_(2)适合作为常用电缆火灾的早期特征气体组分;当温度为150℃时,热解气体中出现了CH_(4)、C_(2)H_(4)、C_(3)H_(6)和CH_(3)Cl等气体组合,所以CH_(4)、C_(2)H_(4)、C_(3)H_(6)和CH_(3)Cl可以作为常用电缆过热故障加剧的特征气体组分。

液相法合成三聚氰酸体系热力学分析

以二元醇为循环剂液相法合成三聚氰酸是一个由醇解、消去和环加成反应构成的连串反应体系。采用基团贡献法计算了该反应体系中各组分热力学数据以及各步反应的焓变、Gibbs自由能变和平衡常数,依据热力学计算结果并结合已有文献实验数据分析反应路径的可行性及难易程度。结果表明:醇解和消去反应为吸热反应,升温有利于反应,但反应平衡常数小;环加成反应为放热反应且进行较为完全,适当强化条件下三步连串反应可顺利进行。计算及分析结果可为该体系的工业放大工艺过程开发提供理论指导。

基于壳层法的黄陵气煤低温热解数值模拟

针对煤热解过程模拟难以兼顾预测能力和计算量的问题,通过壳层法与Ergun公式分别对网格单元及动量方程进行简化,同时采用水分蒸发模型、煤热解动力学模型、焦油裂解模型与控制方程结合的方法对黄陵气煤低温热解过程进行数值计算,建立了一种计算速度快且能够较好地预测煤样内部温度、气体速度、挥发分产率分布的一维瞬态模型。该模型模拟的各挥发分产率与实验结果基本吻合,误差不超过14%;低温热解模拟过程可在47 min内快速计算完成。利用该模型分析了低温热解过程中煤样内部多物理场的变化规律及其对热解进程、产物分布的影响。研究发现,水分蒸发吸热导致煤样内层升温较慢,从而迟滞热解反应的进行并增加热解反应时间;水蒸气、焦油和热解气生成速率决定气体速度,气体速度对焦油裂解反应影响显著,气体速度越小,焦油裂解越快,即从煤样外部到内部发生焦油裂解反应的概率越高;升温速率是影响热解气和焦油产率的重要因素,升温速率越低,热解越充分,挥发分所代表的热解气与焦油产率越高;煤样粒度对热解气和焦油产率的影响较小。

铁基碳铝催化剂的制备及其催化玉米秸秆热解制氢研究

以生物质玉米秸秆(CS)为原料,将废弃铝灰(WA)活化处理后得到的活化铝灰(AWA)作为载体,Fe为活性组分,采用水热炭化法(HTC)制备铁基碳铝催化剂(Fe/CS-AWA)并用于催化CS热解制氢。在探讨了Fe负载量对催化剂性能影响的基础上,进一步采用响应面(RSM)法优化了水热炭化条件对Fe/CS-AWA结构性质和催化CS热解制氢的影响规律。研究结果表明:与CS热解相比,AWA和CS混合水热炭化作为催化剂使CS热解产氢能力提高了19.11 mL/g;更重要的是Fe提高了CS-AWA的催化活性,且负载量为10%时,气体总产率为160.93 mL/g,氢气占比为39.96%。经RSM优化后的最佳工艺条件为:m AWA∶m_(CS)为2∶1、250℃停留时间60 min、炭化温度500℃。此工况下制备的Fe/CS-AWA催化CS热解的气体总产率为267.43 mL/g,H_(2)占比达37.80%。表征发现,Fe/CS-AWA表面形成了不规则的铁碳化物和Al—O—C中间体,提高了Fe/CS-AWA的催化作用。