退火温度对La0.75Mg0.25Ni3.5Co0.2贮氢电极合金的结构及电化学性能的影响

为了改善La-Mg-Ni系合金电极的循环稳定性,对铸态合金La0.75Mg0.25Ni3.5Co0.2在0.3 MPa压力氩气保护下进行不同温度的退火（1123,1223和1323 K）,保温时间均为10 h。系统研究了退火温度对合金的微观结构及电化学性能的影响。X射线衍射（XRD）和扫描电镜（SEM）研究结果表明,合金具有多相结构,当铸态及1123 K温度退火后合金主要由LaNi5,（La,Mg）2（Ni,Co）7相以及少量的LaNi2相组成。当退火温度为1223和1323 K时,合金中LaNi2相消失,合金主要由LaNi5,（La,Mg）2（Ni,Co）7及（La,Mg）（Ni,Co）3相组成。随退火温度提高,合金最大放电容量单调下降,但合金的循环稳定性得到改善。退火处理改善合金循环稳定性的原因在于退火后合金组织均匀,晶粒增大,在KOH电解质溶液中增强合金电极抗氧化腐蚀能力,抑制合金颗粒粉化。     

Nontrivial Solution for a Kirchhoff Type Problem with Zero Mass

Consider the Kirchhoff type equation \begin{equation}\label{eq0.1}-\left(a+b\int_{\mathbb{R}^{N}}|\nabla u|^{2}\,dx\right) \Delta u=\left(\frac{1}{|x|^\mu}*F(u)\right)f(u)\ \ \mbox{in}\ \mathbb{R}^N, \ \ u\in D^{1,2}(\mathbb{R}^N), ~~~~~~(0.1)\end{equation}where $a>0$, $b\geq0$, $0<\mu<\min\{N, 4\}$ with $N\geq 3$, $f: \mathbb{R}\to\mathbb{R}$ is a continuous function and $F(u)=\int_0^u f(t)\,dt$. Under some general assumptions on $f$, we establish the existence of a nontrivial spherically symmetric solution for problem (0.1). The proof is mainly based on mountain pass approach and a scaling technique introduced by Jeanjean.     

Removal performance and mechanism of Fe3O4/graphene oxide as an efficient and recyclable adsorbent toward aqueous Hg(II)

Decontamination of aqueous heavy metal is a challenging task of environmental remediation. Herein, we demonstrated an adsorptive method for efficient removal of aqueous Hg(II) using a magnetic nanocomposite Fe₃O₄/graphene oxide (Fe₃O₄/GO). Adsorption of Hg(II) onto Fe₃O₄/GO equilibrated in 4 min, with the adsorption percent and quantity of 91.17% and 547.01 mg g^?1, respectively. Fe₃O₄/GO can be easily recovered from solution via magnetic separation for reuse, and retaining 73.5% of its original capacity after five consecutive cycles. The Temkin model and PSO model were most suitable for describing adsorption in equilibrium and non-equilibrium state, respectively. Both GO and Fe₃O₄ adsorbed Hg(II) via donating electrons in oxygen atoms toward Hg(II). Moreover, GO made a major contribution, while Fe₃O₄ made a minor one to adsorption. The facile preparation, high adsorption efficiency, easy recovery, and reusability may enable Fe₃O₄/GO to be a promising adsorbent for aqueous Hg(II).

     

球磨La2Mg17+x％Ni(x=50,100,150,200)复合贮氢合金的电化学性能研究

研究了球磨制备的La2 Mg17+x％Ni(x =50,100,150,200)复合贮氢合金的电化学性能.XRD分析表明:随着Ni含量的增加,复合合金的晶体结构逐渐转变为非晶结构.电化学测试显示:球磨制备的La2Mg17+x％Ni复合贮氢合金在首次循环后即可达最大放电比容量,合金具有较好的活化性能;复合合金的放电比容量也随Ni粉加入量的增加而增大.在经过60h球磨后制得的非晶态的La2 Mg17+ 200％ Ni复合贮氢合金,其303 K下放电比容量为353.1 mAh·g-1.电化学放电比容量的提高应归因于非晶结构的形成以及Ni粉对表面状态的改变.     

Graphene oxide–starch composite as an efficient adsorbent for removing Cu(II): removal performance and adsorption mechanism

Research on Chemical Intermediates - Water pollution caused by heavy metals is a severe environmental issue. In this work, a graphene oxide–starch composite (GO/WS) was facilely prepared via...     

铸态和快淬态Mm(NiCoMnAl)5Bx (x=0～0.4)贮氢合金的微观结构与电化学性能

用铸造及快淬工艺制备了低钴AB5型MmNi3.8Co0.4Mn0.6Al0.2Bx (x=0, 0.1, 0.2, 0.3, 0.4)贮氢合金, 分析测试了铸态及快淬态合金的微观结构与电化学性能, 研究了硼及快淬工艺对合金微观结构及电化学性能的影响. 结果表明, 铸态合金具有双相组织, 主相为CaCu5型相, 还有少量CeCo4B第二相, 第二相的相丰度随硼含量x的增加而增大. 对合金进行了不同淬速的快淬处理, 随淬速的增加, 合金中第二相的量减少. 快淬使合金的晶格参数略有增大. 快淬工艺对合金的电化学性能产生显著影响, 随淬速的增加, 合金的容量下降, 循环稳定性显著提高. 快淬使合金的活化性能降低, 但随着硼含量的增加, 活化性能、高倍率放电能力及放电电压特性均得到不同程度的改善.