粉末压片-X-射线荧光光谱法分析砂岩型铀矿制样中粘结剂用量的探讨

由于砂岩型铀矿的成矿特性,样品粉末的内聚力小,采用直接压片法有时难以成型,样片表面常见裂纹,上机测量易碎裂。混合压片法适应性强,制样成功率高,但常见的问题是样品经粘结剂稀释会影响元素的检出限及结果的准确性。本文对粉末压片-X射线荧光光谱法测定砂岩型铀矿地质样品时,前期制样中添加粘结剂的比例进行了研究。试验按照不同比例在铀矿石标准物质GBW04101、GBW04102中添加粘结剂,在扫描电镜下观察到随着粘结剂用量的增加样片表面的光滑度及致密度都呈上升趋势,在X-射线荧光光谱仪上对主量元素进行测定后发现X射线强度在粘结剂添加量大于0.2 g时明显下降,经与GBW04101、GBW04102标准值进行对比后优选出粘结剂与样品的最佳比例为1：20,在此比例下制成的样片光滑平整,不易碎裂,用粉末压片-X射线荧光光谱法进行测定,标准物质测定结果的相对误差为0.56%～6.76 %,相对标准偏差(RSD,n=12)为0.013 %～7.68 %,均达到了《地质矿产实验室测试质量管理规范》DZ/T 0130-2006的要求。本文为粉末压片-X射线荧光光谱法分析砂岩型铀矿地质样品提供了可靠的实验参考依据。     

Effect of binder on the properties of iron oxide sorbent for hot gas desulfurization

The most difficult problem in hot gas desulfurization in Integrated Coal Gasification Combined Cycle (IGCC) is the pulverization of sulfur removal sorbents. Appropriate binders for hot gas sulfur removal sorbents can solve the pulverization problem. In this paper, six sorbents with binders of different argillaceous minerals were prepared by mechanical mixing method. Desulfurization behavior for hot gas desulfurization sorbents was investigated in a fixed-bed reactor. Result showed that sorbent NTKW2 with binder of clay had a better sulfidation performance. NTKW2 had a more stable performance than other sorbents in the continuous sulfidation-regeneration cycles. Sulfur capacity of sorbent remained the same in each cycle. The desulfurization efficiency and mechanical strength of NTKW2 were the best among the tested sorbents. The behavior of NTKW2 at different temperatures showed different performances, and the best reaction temperature was 550 ℃. Higher heat stability, sulfur capacity and desulfurization efficiency were found on NTKW2 in six continuous sulfidation-regeneration cycles.     

高性能锂-硫电池用复合正极的构造与粘结剂

采用球磨混合及热处理方法制备了含有多壁碳纳米管(MCNTs)的硫基复合正极材料,利用X射线衍射(XRD)和扫描电子显微镜(SEM)测定材料的结构和形貌,较系统地研究了MCNTs含量和粘结剂种类对硫基复合正极容量、循环稳定性和自放电行为等的影响.结果表明:MCNTs的合适含量为5%-8%(w,质量分数),以水性粘结剂环糊精制备的硫基复合正极电化学性能最佳.锂-硫电池在常温和半充电状态下放置30天几乎没有自放电;当电流倍率为0.1C时,β-环糊精为粘结剂的正极初始充电容量为687.7mAh.g-1,100次循环以后可逆容量为623.8mAh.g-1,容量保持率达90.7%.     

锂离子电池高比容量负极用粘结剂

随着锂离子电池向高比能量方向发展,传统的石墨负极材料将逐渐被合金、金属氧化物等高比容量负极材料所取代。高比容量负极材料在循环过程中易产生较大的体积变化,从而导致电极循环性能衰退,限制了其实际应用。除从材料本身入手外,变换粘结剂是改善高比容量负极材料电化学性能的有效途径。本文对近十年来锂离子电池高比容量负极用粘结剂的发展进行了总结。对聚偏氟乙烯(PVDF)粘结剂进行改性处理,提高其黏弹性,可以显著改善电极的电化学性能。与PVDF相比,水性羧甲基纤维素(CMC)粘结剂可以明显提高Si基电极的电化学性能。CMC用作高比容量负极材料粘结剂明显优于PVDF的原因包括其利于电极浆料分散、与电解液不反应以及能够与活性物质之间形成化学键(共价键或氢键)等。同时,CMC本身的结构参数(分子量、取代度、阳离子)、CMC加入量、浆料pH值及电极孔隙率均对CMC电极的性能具有重要影响。聚丙烯酸(PAA)及海藻酸钠粘结剂由于含有更多的羧基(—COOH)基团,对高比容量负极材料具有更好的效果。其他新型粘结剂在高比容量负极性能的提升方面也具有较大潜力。     

粘结剂对形貌各异的石墨负极电化学性能的影响

As an important component in electrodes, the choice of an appropriate binder is significant when fabricating lithium-ion batteries (LIBs) with good cycle stability and rate capability, which are used in numerous applications, especially portable electronics and eco-friendly electric vehicles (EVs). Semi-crystalline poly(vinylidene fluoride) (PVDF), which is a traditional and widely used binder, cannot efficiently accommodate the volume changes observed in the anode during the charge-discharge process while binding all the components in the electrode together, which results in increased internal cell resistance, detachment of the electrode components, and capacity fading. Herein, we have investigated a highly polar and elastomeric polyacrylonitrile-butadiene (NBR) rubber for use as a binder in LIBs, which can accommodate graphite particles of different shapes compared to semi-crystalline PVDF. Prior to our electrochemical tests, NBR was analyzed using thermogravimetric analysis (TGA) and X-ray diffraction (XRD), showing good thermal stability and an amorphous morphology. NBR is more conformable to irregular surfaces, which results in the formation of a homogeneous passivation layer on both spherical and flaky graphite particles to effectively suppress any electrolyte side reactions, further allowing more uniform and fast Li ion diffusion at the electrolyte/electrolyte interface. As a result, the electrochemical performance of both spherical and flaky shape graphite electrodes was significantly improved in terms of their first cycle Coulombic efficiency (CE) and cycle stability. With comparative specific capacity, the first cycle CE of the NBR-based spherical and flaky graphite electrodes were 87.0% and 85.5%, compared to 85.3% and 82.6% observed for their corresponding PVDF-based electrodes, respectively. After 1000 discharge-charge cycles at 1C, the capacity retention of the NBR-based graphite electrodes was significantly higher than that of PVDF-based electrodes. This was attributed to the good stability of the solid electrolyte interphase (SEI) formed on the graphite electrodes and the high stretching ability of the elastomeric NBR binder, which help to accommodate the repeated volume fluctuation of graphite observed during long-term charge-discharge cycling. Electrochemical impedance spectroscopy (EIS) and microscopic analysis (SEM and TEM) were carried out to investigate the formation and evolution of the SEI layers formed on the spherical and flaky graphite electrodes. The results show that thin, homogeneous, and stable SEI layers are formed on the surface of both spherical and flaky graphite electrodes prepared using the NBR binder. When compared to the PVDF-based graphite electrodes, the graphite electrodes constructed using NBR showed decreased resistance in the SEI layer and faster charge transfer, thus enhancing the electrode kinetics for Li ion intercalation/deintercalation. Our study shows that the electrochemical performance of spherical and flaky graphite electrodes prepared using the NBR binder is significantly improved, demonstrating that NBR is a promising binder for these electrodes in LIBs.     

无粘结剂ZSM-5沸石催化剂骨架脱铝改性的研究

对比了无粘结剂和有粘结剂ZSM-5沸石催化剂的吸附性质, 证实前者的优良品质. 以27Al固体核磁共振(MAS NMR)考察了盐酸处理、水蒸气处理及水蒸气-盐酸相结合处理后无粘结剂ZSM-5沸石催化剂的骨架脱铝行为以及非骨架铝的状态. 以X射线粉末衍射(XRD), X射线荧光光谱(XRF), 低温氮吸附, NH3-TPD和吡啶吸附原位红外光谱(in situ IR)等详细表征了骨架脱铝对其晶体、元素组成及孔结构、表面强(S)酸与弱(L)酸、Brönsted(B)酸与Lewis(L)酸酸量分布等影响. 揭示了水蒸气处理的深度骨架脱铝强烈地调变沸石的结构和表面酸性的本质, 证明了该处理方式对调变S酸和B酸起主导作用.     

粘结剂型可溶芯用酚醛树脂快干涂料的研制

文中采用可溶性盐作基体材料配制酚醛树脂快干涂料，用用铝合金粘结剂型可溶性型芯的表面质量改善，配制过程及合金砂型与金属型浇铸实验表明，该涂料具有良好的使用性能。     

铑靶康普顿散射校正XRF测定铝用碳素材料中的微量元素

通过对常用粘结剂中杂质元素含量的测定,选择硬脂酸做粘结剂,研磨压片制备样品,用X射线荧光光谱仪(XRF)测定铝用炭素阳极材料中硫、钒、钠、钙、硅、铁、镍、钛、铝、镁、磷、铅、锌、铬、锰含量的元素含量。通过实验确定了最佳的样品和粘结剂比例为12 g炭素试样加入2 g硬脂酸,研磨时间为20 s。测定铅元素时,选择一点法扣除背景,通过谱线强度数据确定使用PbLβ1做分析线。用铝用炭素阳极材料系列标准样品制作校准曲线,用铑靶康普顿散射内标校正铁、镍、铅、锌、铬、锰等元素,其余元素用经验系数法校正。样品精密度试验表明,样品中各元素测定结果的相对标准偏差(RSD,n=11)一般在8%以下,最高的钠元素和钛元素也在10%左右,未知样品的检测结果与标准结果没有显著性差异。     

给、吸电子基团对吡嗪衍生物电子结构影响的DFT研究

采用B3LYP方法在6—31G^#基组水平上优化了对位取代吡嗪衍生物的几何构型，利用TD—DFT方法计算了它们的前线分子轨道能级和电子光谱．结果表明，带有给、吸电子基团对吡嗪衍生物与苯、吡啶相比，也具有很好的共轭性；随着分子共轭链的增长，分子的偶极矩增大，前线分子轨道能级差减小，最大吸收波长发生红移．对于具有相同共轭链的同分异构体，推电子基团与具有给电子性质的共轭链相连，则分子的电荷转移明显，导致偶极矩增大，前线分子轨道能级间的电子跃迁更容易；吸电子基团与具有给电子性质的共轭链相连，情况正好相反，这些结果对分子设计有重要意义。     

Na2Ti3O7纳米片原位制备与钠离子电池负极材料应用

报道了Na₂Ti₃O₇纳米片的原位生长和钠离子电池负极材料的应用。通过简单的腐蚀市售的钛片制备出相互连接的微纳结构的Na₂Ti₃O₇纳米片。此外,腐蚀后的钛片在不用添加导电剂或粘结剂的情况下,可以直接作为电极材料使用。这种电极材料表现出优越的电化学性能,在50 mA·g^–1的电流密度下具有175 mAh·g^–1的可逆容量,在2000 mA·g^–1的电流密度下循环3000周后,其容量仍保持120 mAh·g^–1,容量保持率为96.5%。Na₂Ti₃O₇纳米片电极的优越电化学性能归因于二维结构具有较短的离子/电子扩散路径以及无粘结剂结构能有效的增加电极的电子传导能力。结果表明,这种微纳结构能够有效地克服Na₂Ti₃O₇作为电极材料离子/电子导电性差的缺点。因此,这种无粘结剂结构的Na₂Ti₃O₇纳米片负极材料是一种很有潜力的钠离子负极材料。