低阶煤热解条件对高炉喷吹半焦燃烧性能及动力学特性的影响

采用热重分析法研究了不同热解条件下半焦的燃烧性能和动力学特征，利用Ozawa法求取动力学参数。结果表明，热解温度越低、保温时间越短时，半焦的燃烧性能越好；热解升温速率对半焦燃烧过程的反应程度影响不大；粒度越大，燃烧性能差异性越明显。热解温度对半焦燃烧性能影响较大，550℃是本研究中制备高燃烧反应性半焦的适宜热解温度。两种不同粒度原煤制得的半焦均随转化率增大，活化能减小。1~3 mm原煤在热解温度为550℃时所得半焦在燃烧过程中符合反应级数模型，化学反应为限制性环节，反应最概然机理函数为f(α)=(1–α)2。     

通过RRLC-Q-TOF MS和UPLC-QQQ MS分析原人参三醇型皂苷在人肠道菌群中的代谢产物

通过高分离度快速液相色谱-四极杆飞行时间质谱(RRLC-Q-TOF MS)和超高效液相色谱-三重四极杆质谱(UPLC-QQQ MS)法对原人参三醇型皂苷Re、Rg 1、Rg 2、Rh 1、Rf、F 1、R 1在人肠道菌群中的转化产物进行定性、定量分析,确定原人参三醇型皂苷的代谢产物、转化途径和60 h时的转化率。结果表明,人参皂苷Re的转化产物为人参皂苷Rg 1、Rg 2、Rh 1、F 1和PPT,转化率为91%;人参皂苷Rg 1的转化产物为人参皂苷Rh 1、F 1和PPT,转化率为80%;人参皂苷Rg 2的转化产物为人参皂苷Rh 1和PPT,转化率为73%;人参皂苷Rh 1和F 1主要通过PPT代谢,转化率分别为82%和81%;人参皂苷Rf的转化产物为人参皂苷Rh 1和PPT,转化率为89%;三七皂苷R 1的转化产物为人参皂苷Rg 1、R 2、Rh 1和PPT,转化率为79%。原人参三醇型皂苷类成分可被人肠道菌群代谢,主要通过丢失糖残基形成转化产物,而次级皂苷和苷元是人参在体内发挥药理作用的物质基础。     

涂料行业职业基本知识与基本技能(41)——助剂

乳胶漆用助剂主要有分散剂、润湿剂、消泡剂、增稠剂、pH调节剂、防腐剂、防霉剂、成膜助剂等。这些助剂在乳胶漆中起着各种优化性能的作用,可以使生产过程更顺利,施工更流畅,贮存更稳定。但有些助剂在发挥某一主要作用的同时可能会带来另一方面的负面影响,如用于分散颜填料的分散剂对漆膜的耐水性有负面影响。所以助剂的使用并非越多越好,须平衡好各自利弊。     

基于稳定连接的配电网边缘划分方法及应用研究

随着能源互联网的建设,为了应对配电主站所面临的数据接入和计算压力,文章提出了二级配电网边缘架构,以分布式边缘智能架构缓解主站压力。主要从边缘定义、划分方法、边缘功能描述与交互描述4个方面对所提边缘架构进行介绍。提出电网稳定连接区域概念及其生成方法,并结合南京地区电网实例,说明了以电网稳定连接区域作为边缘划分的合理性。最后,对所提边缘架构在配电网中的实际应用场景进行了设计和展望。     

Ni对铁基合金粉块氩弧堆焊层组织和性能的影响

通过氩弧焊在基体材料Q235钢板上熔敷铁合金混合粉末压块,研究了压块成分及堆焊工艺对堆焊层组织及性能的影响。结果表明:在固定压块粉末总质量为16 g、镍铁含量为0.64 g、堆焊电流为180 A时,堆焊层的硬度最大,达到HRC48.9;耐磨性最高,相对磨损量为0.013 4 g/(cm^2·min)。     

碳含量对激光熔覆CoCrFeMnNiCx高熵合金涂层摩擦磨损和耐蚀性能的影响

采用激光熔覆技术在 45 钢基体上制备了不同碳含量(等摩尔比)的 CoCrFeMnNiC_x( x = 0,0. 03,0. 06,0. 09, 0. 12,0. 15)高熵合金涂层。 通过 X 射线衍射(XRD)、扫描电镜( SEM)、HVS-1000A 型显微硬度计、RST5000 型电化学工作站、UMT-2 型摩擦磨损试验机等表征和测试手段研究了不同碳含量对激光熔覆 CoCrFeMnNiC_x 高熵合金涂层物相结构、显微硬度、摩擦磨损及耐腐蚀性能的影响。 结果表明,当碳含量 x 由 0 逐渐增加至 0. 09 时,高熵合金相结构由 FCC 固溶体转变为 FCC 固溶体和 M23C6 相共存,合金微观组织变得细小;熔覆层硬度由 183. 20 HV_{0. 2} 增加至 223. 48 HV_{0. 2} ; 涂层的摩擦因数降低,耐磨性能变强;腐蚀电位由-469 mV 增大至-348 mV,腐蚀电流密度由 14. 95 μA·cm^-2 减小为 2. 29 μA·cm^-2 ,耐腐蚀性增强。 当碳含量 x 由 0. 09 逐渐增加至 0. 15 时,合金相结构再次转变为 FCC 固溶体,且合金微观组织恢复粗大状态;熔覆层硬度与耐腐蚀性降低,但耐磨性能却先减弱后增强。 合金在碳含量为 0. 09 时,硬度最高且耐腐蚀性能最强;在碳含量为 0. 15 时,耐磨性最强。     

Preparation of near net size porous alumina-calcium aluminate ceramics by gelcasting-pore-forming agent processs

In the processing of porous ceramics, shrinkage from green body to sintered compact during drying and sintering is one of the key concerns which affect microstructure and properties of porous ceramics. Through releasing gases from the burning of the pore forming agents, and volume expansion from the formation of low density resultants during sintering, the sintering shrinkage can be effectively compensated and near net size preparation can be achieved. Herein, near net size porous alumina-calcium aluminate ceramics with controllable shrinkage have been prepared using a combination of gelcasting and pore-forming agent process by adjusting the amount of CaCO₃ and polymethyl methacrylate (PMMA) microspheres added. Al₂O₃ and CaCO₃ were used as raw materials, PMMA microspheres were used as pore-forming agent, isobutylene/maleic anhydride copolymer (Isobam104) was used as gelling agent and dispersing agent. The effects of the addition amounts of CaCO₃ and PMMA in the slurry on the phase composition, shrinkage, porosity, and strength of porous alumina-calcium aluminate ceramics were investigated. The results show that as the CaCO₃ addition amount increases from 0 to 20 wt%, the shrinkage of the samples gradually decreases from 7.3% to −1.4%, and the consequent porosity increases from 58% to 66%, while the compressive strength increases from 5.9 to 15.5 MPa. When PMMA content increases from 10 to 50 wt%, the shrinkage of the samples decreases first and then increases, the porosity increases from 51% to 74%, and the compressive strength decreases from 12.5 to 5.3 MPa. The mechanisms for controlling shrinkages during preparation of porous alumina-calcium aluminate ceramics can be attributed to the following aspects: on one hand, gas release from burning of PMMA and decomposition of CaCO₃ during sintering; on the other hand, volume expansion due to the formation of lower density calcium aluminates which come from the reactions between CaO and Al₂O₃. The near net size preparation technique is of great significance for the manufacture of porous ceramics since the subsequent machining cost can be effectively reduced.     

Controllable layer-by-layer assembly based on brucite and alginates with the assistance of spray drying and flame retardancy influenced by gradients of alginates

With the aim of tailoring and controlling surface assembly, multifunctional flame retardants (FRs) were obtained based on depositing alginates and silane coupling agents on brucite via the spray-drying-assisted layer-by-layer assembly technique. The assembly was controllable in both structure and gradient mass. Two series of FRs were named CuFR1-3 and NiFR1-3 based on the assembly content of metal alginates. With the assistance of spray drying, good compatibility between FRs and ethylene-vinyl acetate (EVA) was obtained, resulting in better mechanical properties. Meanwhile, the FRs improved flame retardancy and smoke suppression when used in EVA composites. With 55 wt % loading, composites with CuFR3 and NiFR1 passed UL 94 V-0 rating, while those with brucite were not rated. The peak of heat release rate decreased by 51.7 and 49.3% while the residue increased by 9.8 and 11.9%, respectively. The FRs also reduced the smoke and CO production rates. For the two series of FRs, the relationship between FR efficiency and alginate contents is different. The CuFRs assembled more copper alginates and exerted better flame retardancy caused by lower catalytic graphitization. NiFRs exerted a higher catalyzing efficiency at low assembly content. However, at high assembly content, the catalytic graphitization effect would decrease by thermally oxidized degradation leading to excess nickel alginates. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47570.     

Transformation of the reabsorption characteristics of lignite treated by low and high temperature drying process

Abstract

The reabsorption characteristics of the lignite treated by low and high temperature drying process were addressed in the paper. The information about the moisture form, functional groups, effective water-filled porosities and equilibrium moisture content of the lignite before and after the drying process was investigated using Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and a self-made reabsorption device, respectively. The results show that the low drying temperature (140, 190, 230?°C, 10?min, N₂) has little impact on the effective water-filled porosities of the resulted samples, whereas it has a great influence on the main oxygen-containing functional groups, which amount firstly decreases and then increases with the drying temperature increasing. In the case of the lignite samples dried under high-temperature (600, 700, 800?°C, 30?s, N₂), the amount of the effective water-filled porosity of the sample decreases and the amount of oxygen-containing functional groups increases as the temperature increasing. The reabsorption capability of the high temperature dried sample is much lower than that of the sample treated under low drying temperature. The reabsorption characteristics of the low-temperature dried samples are affected by the amount of the oxygen-containing functional groups, while the effective water-filled porosity is main factor for the lignite samples derived from high temperature drying process. Moreover, the work gives a good evidence that the high-temperature drying process is an effective choose for lignite upgrading.