热活化铅锌尾矿基碱激发胶凝材料的制备及性能

以铅锌尾矿为主要原料,添加由矿渣、钢渣、氟石膏混合而成的辅助胶凝材料,以水玻璃和氢氧化钠为碱激发剂制备铅锌尾矿基碱激发胶凝材料。通过正交试验,探讨了水玻璃模数、水玻璃掺量及尾矿与辅助胶凝材料质量比对胶凝材料抗压强度的影响,并得出最佳原料配比。通过800 ℃、1 000 ℃、1 200 ℃的热处理,制备热活化铅锌尾矿基碱激发胶凝材料,并测试其性能。采用X射线衍射谱、傅里叶红外光谱和扫描电子显微镜对热活化前后尾矿和胶凝材料进行分析表征。结果表明,当水玻璃模数为1.8,水玻璃质量掺比为0.15,尾矿与辅助胶凝材料质量比为7 ∶3时,胶凝材料28 d抗压强度可达到20.68 MPa。胶凝材料内部形成大量水化硅酸钙(C-S-H)与硅铝多聚物构成三维网状结构,覆盖在尾矿晶体表面形成致密整体。当热活化温度为1 000 ℃时,胶凝材料28 d抗压强度达到28.05 MPa。热活化后的尾矿内部结构疏松,利于硅铝质在碱性条件下解聚,同时使得反应体系中生成了更多硅铝多聚体,取代了二聚体为主的C-S-H凝胶,为胶凝材料提供了更优良的抗压强度和早硬特性。此外胶凝材料对Pb、Zn重金属的固定作用极好,大幅降低了尾矿重金属Pb、Zn的毒性浸出浓度,有效解决了尾矿中重金属对周围环境的危害问题。     

锂铝硅透明微晶玻璃析晶动力学研究

本文利用经典方程(Johnson-Mehl-Avrami)分析了非化学计量的锂铝硅Li₂O-Al₂O₃-SiO₂-ZrO₂-P₂O₅透明微晶玻璃的析晶动力学,采用DSC、XRD和SEM研究了晶化温度对玻璃析晶行为的影响。结果表明:在较低的起始析晶温度下Li₂Si₂O₅和Li₂SiO₃析出,随晶化温度的升高,主晶相转变为LiAlSi₄O₁₀,Li₂SiO₃晶相消失,晶体尺寸变小,在550 nm处微晶玻璃透过率由89.3%升高到90.6%;利用Kissinger方法计算出的Li₂Si₂O₅和LiAlSi₄O₁₀的析晶活化能分别为349.5 kJ/mol和184.2 kJ/mol,平均晶体生长指数分别为3.05和1.42。     

磷石膏基矿井充填材料制备及其性能研究

为实现磷石膏的资源化利用,制备了以原状磷石膏为主要原料、赤泥为碱性激发剂的矿井充填材料,并分析了高效减水剂掺量、水泥掺量、赤泥掺量对其性能的影响。实验结果表明,水灰质量比为0.2,聚羧酸盐减水剂掺量为0.5%（质量分数）时,浆料的初始流动度约为230 mm,满足充填材料性能要求;水泥掺量从0增加到10%时,28 d抗压强度从2.03 MPa提升至10.75 MPa,初始流动度从180 mm增加到235 mm,强度保持率从0.39提升至1,表明水泥掺量直接影响充填材料的强度、流动性及耐水性能;赤泥掺量从0增加到5%时,28 d抗压强度提升了50%,强度保持率从0.82提升至1,激发作用明显,对材料的流动性有相反的影响。     

基于阴离子交换反应的NiMn-LDH电极电容性能提升研究

采用一步水热法在泡沫镍网上原位生长镍锰基层状双氢氧化物（NiMn-LDH）纳米片阵列电极,并通过氢氧化钾溶液中浸泡的方式提升电极的容量。采用SEM、XRD、TEM和XPS等手段对浸泡前后的电极材料进行表征。结果表明,在浸泡前后NiMn-LDH电极的形貌没有变化,但在电极材料内部发生了明显的CO₃^2-和OH^-的交换反应,降低体积较大的CO₃^2-在LDH层间的分布数量,使层内空间成为OH^-的“蓄水池”,缩短了电荷存储过程中OH^-的迁移距离,因此电容性能有了明显提升。电化学测试结果表明,在5 mA/cm²电流密度下,电极的比电容从18.0 F/g增加至766.6 F/g（1.69 F/cm²）。将该电极与活性炭组装的全固态不对称超级电容器在功率密度为900 W/kg时,可呈现的能量密度为35.9 W·h/kg,并且器件的循环稳定性良好。     

伊利石合成磷酸硅铝分子筛及其表征

采用碱熔活化方法对伊利石进行活化,系统地考察了煅烧温度、煅烧时间、矿物粒度、矿碱质量比等条件对伊利石活化的影响;以活化伊利石为主要硅、铝源,采用水热法合成磷酸硅铝分子筛（SAPO-11）,系统地考察模板剂种类、模板剂用量、投料硅铝物质的量比、晶化温度等合成条件对产物结构和性质的影响。利用X射线衍射（XRD）、N₂吸附-脱附、扫描电镜（SEM）和透射电镜（TEM）等分析手段对活化产物和合成的分子筛进行了分析表征,结果表明,伊利石的最佳碱熔活化条件为煅烧温度为800 ℃、煅烧时间为90 min、伊利石矿粒径为75 μm、矿碱质量比为1∶0.8,经活化后伊利石的晶型结构基本完全被破坏,活化产物主要是高活性的低聚合态硅铝酸盐,化学反应活性较高;在原料配比为n（三氧化二铝）∶n（五氧化二磷）∶n（模板剂）∶n（二氧化硅）∶n（水）=1∶1∶1∶0.5∶50、水热晶化温度为190 ℃、晶化时间为24 h时成功合成结晶度较高的纯相SAPO-11分子筛,合成的SAPO-11分子筛具有较大的比表面积,样品主要由粒径为1~3 μm的椭球状颗粒组成,该合成方法丰富了磷酸硅铝（SAPO）分子筛的原料来源,拓展了中国伊利石的高附加值利用途径。     

机械活化条件下超细铁矿粉一氧化碳还原特性及机理

采用热重法研究了不同机械活化程度的超细铁矿粉一氧化碳还原特性,并对其还原反应机理进行了分析和讨论。研究结果表明,机械活化有利于一氧化碳还原铁矿粉,机械活化时间越长,反应特征温度越低,活化480 min的铁矿粉的反应峰值温度比未活化的矿粉低217 K。机械活化时间越长,反应活化能越低,但反应机理未发生变化,界面反应一直是限制性环节,活化480 min后的铁矿粉的反应活化能比未活化时低31.23 kJ/mol。机械活化对于一氧化碳的还原铁矿粉的逐级反应进程有明显影响,对于未活化的铁矿粉而言,逐级反应层次不分明,而对于活化后铁矿粉的逐级反应层次分明,而且活化时间越长,层次越分明。     

玉米秸秆热解特性及动力学分析

以玉米秸秆为原料, 利用热重分析法研究其热解的特性及动力学。根据TG和DTG曲线, 研究玉米秸秆的热解特性, 采用Flynn-Wall-Ozawa(FWO)和Kissinger-Akahira-Sunose(KAS)两种等转化率法计算玉米秸秆热解的活化能, 并结合主曲线法和Coats-Redfern(C-R)法探讨了玉米秸秆热解遵循的机理方程。研究结果表明: 玉米秸秆热解过程可分为干燥脱水、过渡、主热解和炭化4个阶段, 随着热解升温速率增大, TG和DTG曲线向高温侧偏移; 利用FWO和KAS法计算得到的表观活化能分别为181.7和181.5 kJ/mol; 利用主曲线法和C-R法求解出玉米秸秆热解的机理方程遵循Avrami-Erofeev方程, 当α=0.1~0.5时, n=3, f(α)=1/3(1-α)[-ln(1-α)]^-2; 当α=0.5~0.7时, n=2, f(α)=1/2(1-α)[-ln(1-α)]^-1。     

A density functional theory study of methane activation on MgO supported Ni9M1 cluster: role of M on C–H activation

Methane activation is a pivotal step in the application of natural gas converting into high-value added chemicals via methane steam/dry reforming reactions. Ni element was found to be the most widely used catalyst. In present work, methane activation on MgO supported Ni–M (M = Fe, Co, Cu, Pd, Pt) cluster was explored through detailed density functional theory calculations, compared to pure Ni cluster. CH₄ adsorption on Cu promoted Ni cluster requires overcoming an energy of 0.07 eV, indicating that it is slightly endothermic and unfavored to occur, while the adsorption energies of other promoters M (M = Fe, Co, Pd and Pt) are all higher than that of pure Ni cluster. The role of M on the first C–H bond cleavage of CH₄ was investigated. Doping elements of the same period in Ni cluster, such as Fe, Co and Cu, for C–H bond activation follows the trend of the decrease of metal atom radius. As a result, Ni–Fe shows the best ability for C–H bond cleavage. In addition, doping the elements of the same family, like Pd and Pt, for CH₄ activation is according to the increase of metal atom radius. Consequently, C–H bond activation demands a lower energy barrier on Ni–Pt cluster. To illustrate the adsorptive dissociation behaviors of CH₄ at different Ni–M clusters, the Mulliken atomic charge was analyzed. In general, the electron gain of CH₄ binding at different Ni–M clusters follows the sequence of Ni–Cu (–0.02 e) < Ni (–0.04 e) < Ni–Pd (–0.08 e) < Ni–Pt (–0.09 e) < Ni–Co (–0.10 e) < Ni–Fe (–0.12 e), and the binding strength between catalysts and CH ₄ raises with the CH₄ electron gain increasing. This work provides insights into understanding the role of promoter metal M on thermal-catalytic activation of CH₄ over Ni/MgO catalysts, and is useful to interpret the reaction at an atomic scale.     

氧化银电极对锌银贮备电池激活时间的影响

采用几种化成制度制备了氧化银电极和锌电极,以恒流极化、单体手动激活放电和组合电池自动激活放电实验考察了电极的电性能;采用扫描电子显微镜(SEM)和化学分析对氧化银电极的表面形态和组分进行了表征。结果表明,氧化银电极放电初期极化大是影响电池组激活时间的主要因素,也是造成电池放电初期电压上升缓慢的主要原因,9 m A/cm2转6、3 m A/cm2的阶梯充电模式有利于提高电池激活速度。     

Precipitation kinetics of GP zones,metastable η′ phase and equilibrium η phase in Al−5.46wt.%Zn−1.67wt.%Mg alloy

Thermal analysis is one of the most used techniques for analyzing the behavior of aluminum alloys in order to analyze the precipitation of Guinier?Preston (GP) zones and different phases formed. In the present work, the behavior of the Al?5.46wt.%Zn? 1.67wt.%Mg alloy was studied. The mechanism and kinetics of precipitation of the GP, the metastable phase η′ and the equilibrium phase η were investigated using DSC carried out between room temperature and 480 °C at heating rates of 5, 10, 15 and 20 °C/min. The apparent activation energies, calculated by DSC from isothermal calculation method using JMAK model, for GP, η′ and η were 56, 79 and 96 kJ/mol, respectively, and those calculated by non-isothermal calculation method using Kissinger methods were 57, 82 and 99 kJ/mol, respectively. The values of Avrami parameter, n, from isothermal calculation, during the precipitation of the GP, η′ and η were 1.103, 1.9075 and 1.92, respectively, and those calculated by non-isothermal were 0.86, 2.30 and 2.24, respectively. The results show that GP zones formation is governed by the migration of Zn and Mg atoms while the precipitation of the η′ metastable phase and the η stable phase is governed by both the migration and the diffusion of the solute atoms.