Effect of surface treatment on the structure and high-rate dischargeability properties of ABs-type hydrogen storage alloy

Surface-treated MmNi_3.55Co_0.75Mn_0.4Al_0.3 alloy as negative electrode material of nickel-metal hydride battery was employed to improve the high-rate dischargeability. Surface treatment was realized by dipping and stirring the alloy into a HCl aqueous solution with various concentrations at room temperature. The microstructure of the alloy before and after surface treatment was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties before and after surface treatment were comparedand the alloy treated in 0.025 mol/L HCl solution showed the optimal high-rate dischargeability.     

高倍率AB5型稀土贮氢合金的研究进展

综述了AB5型稀土贮氢合金高倍率放电性能的影响因素。从合金成分、制备工艺、粒度控制以及表面改性等几个方面进行总结，并对贮氢合金高倍率放电机制等问题进行了讨论。开发低钴无钴系列合金、非化学计量比、形成双相合金、控制粒度分布以及表面改性处理是目前改善AB5型稀土贮氢合金高倍率放电性能的有效途径。     

Study on High Rate Discharge Performance and Mechanism of AB5 Type Hydrogen Storage Alloys

The effects of surface treatment, particle size distribution, rare earth composition and B additive on the high rate discharge performance of hydrogen storage alloys were investigated. It is found that the activity, discharge capacity and high rate dischargeability of the alloys are improved after physical and chemical modification as a result of the increase of the surface area and formation of the electrocatalysis layers, which increase both the electrochemical reaction rate on the alloy surface and H diffusion rate in the alloy bulk. It is also found that both the over-coarse and over-fine particle size increase the contact resistance of the electrode, resulting in a decrease of discharge capacity, deterioration of high rate dischargeability and lower discharge plateau. In another word, a suitable particle size distribution can enhance the alloy activity, discharge capacity and high rate dischargeability. In addition, the high rate dischargeability is enhanced by in-creasing La content and decreasing Ce content of the alloy composition because of enlargement of the unit cell volume and the improvement of the surface activity. Moreover, B additive resultes in the formation of the second phase, and makes the alloys easier pulverization, which greatly improves the activity, discharge capacity and high rate dischargeability.     

Effect of carbon coating on electrochemical properties of AB3.5-type La-Y-Ni-based hydrogen storage alloys

The superlattice La-Y-Ni-based hydrogen storage alloys have high discharge capacity and are easy to prepare.However,there is still a gap in commercial applications because of the severe corrosion of the alloys in electrolyte and poor high-rate dischargeability(HRD).Therefore,(LaSmY)(NiMnAl)_3.5 alloy was prepared by magnetic levitation induction melting,and then the alloy was coated with different contents(0.1 wt%-1.0 wt%) of nano-carbons by low-temperature sintering with sucrose as th...     

RE-Mg-Ni系储氢合金高倍率放电性能研究现状

RE-Mg-Ni系储氢合金具有超晶格结构,其主相晶格单元是由一定比率的AB5单元和AB2单元沿c轴交替层叠排列而成。该类型合金自问世以来便以其高容量、易活化的优势受到人们的广泛关注,然而其循环稳定性及高倍率放电性能不尽人意。人们通过大量研究有效提高了其循环稳定性,使其基本满足了商业化要求。但是要将基于该负极材料的镍氢电池应用在混合动力汽车上,仍需改进其高倍率放电性能。系统分析了元素替代、多元合金化、制备工艺、化合物复合、表面处理等手段对RE-Mg-Ni系储氢合金晶体结构及高倍率放电性能的影响。其中元素替代是一种重要且有效的手段,文中分析了不同稀土元素及B侧元素的作用机制,结果表明,B侧组分采用Ni,Co,Mn,Al的储氢合金具有较好的性能。多元合金化是一种复杂的过程,不同元素间可能存在一定的协同作用,研究其作用机制也是下一步的工作重点。通过优化实验方案,综合使用多种改性手段,可以得到高倍率放电性能良好的RE-Mg-Ni系储氢合金,使其基本满足电动工具用镍氢电池的要求,并可望在以后的研究中进一步提高其高倍率放电性能,使其满足混合动力汽车用镍氢电池的要求,实现良好的经济和社会效益。     

Microstructure and electrochemical characteristics of La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x（V0.81Fe0.19）x hydrogen storage alloys

Microstructure and electrochemical characteristics of La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x(V0.81Fe0.19)x hydrogen storage alloys were investigated. XRD indicated that La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-x(V0.81Fe0.19)x alloys consisted of a single phase with CaCu5-type structure, and the lattice parameter a and cell volume V increased with increasing x value. The maximum discharge capacity first increased from 319.0 (x=0) to 324.0 mAh/g (x=0.05), and then decreased to 307.0 mAh/g (x=0.20). The high-rate dischargeability at the discharge current density of 1200 mA/g first increased from 52.1% (x=0) to 59.1% (x=0.15), and then decreased to 55.4% (x=0.20). The hydrogen diffusion in the bulky alloy was responsible for the high-rate dischargeability. Cycling stability first increased with increasing x from 0 to 0.10 and then decreased when x increased to 0.20, which was resulted from the synthesized effect of the improvement of the pulverization resistance and the decrease of corrosion resistance.     

Effect of the partial substitution of samarium for lanthanum on the structure and electrochemical properties of La_(15)Fe_(77)B_8-type hydrogen storage alloys

La15Fe77B8 hydrogen storage alloys were prepared using a vacuum induction-quenching furnace. The results of X-ray diffraction(XRD) and scanning electron microscopy(SEM) suggested that La15–xSmxFe2Ni76Mn5B2(x=0, 2, 4, 6) alloys had multiphase structure including the main LaNi5 phase, La3Ni13B2 phase and(Fe, Ni) phase. With the increasing substitution of Sm for La, the main phase structure of alloys did not change, while the unit cell volumes decreased, the cycle stability was improved and the maximum discharge capacity decreased, but the low temperature maximum discharge capacity of the same substitution alloy was gradually approaching the maximum discharge capacity at room temperature, which showed that La15Fe77B8 hydrogen storage alloys of the partial substitution of Sm for La had better low-temperature dischargeability(LTD). For the same substitution alloys, self-discharge characteristics and cycle stability at low temperature were better than that at room temperature. Furthermore, the high-rate dischargeability(HRD) and the exchange current density I0 first increased and then decreased with the increasing of Sm content, whereas the hydrogen diffusion coefficient D in alloy bulk decreased gradually, which indicated that appropriate substitution of Sm for La improved the electrochemical kinetics properties of the alloys. The HRD was mainly dominated by the charge-transfer rate on the alloy surface.     

Optimization of surface roughness and hardness for CoCrMo alloy dental crown manufactured by selective laser melting

To ameliorate the surface roughness and hardness of CoCrMo alloy dental crown fabricated by selective laser melting (SLM) for enhancing the matching suitability between SLM parts and natural teeth, electrolytic polishing and solution treatment were carried out respectively. The surface roughness of the dental crown polished by different electrolytes and electrolytic parameters, and the hardness of the dental crown solution- treated by various parameters were measured. The surface morphology of the dental crown before and after the polishing was observed by three- dimension profiler. Meanwhile, the microstructure was observed by optical microscope and scanning electron microscope. The results show that the polishing effect of the dental crown polished by HNO3 and H3PO4 solution system reaches the maximum, where the roughness decreases by 70% compared to original state. When the dental crown is solution- treated at 1503K for 10h, the hardness decreases from 470HV for no solution treatment state to 350HV, which is equivalent to the value of human natural teeth. Overall performance of CoCrMo alloy dental crown improves a lot.     

Effect of Cerium on Microstructure and Electrochemical Performance of Ti-V-Cr-Ni Electrode Alloy

Effect of cerium on the microstructure and electrochemical performance of the Ti0.25V0.35-xCexCr0.1Ni0.3（x=0,0.005）electrode alloy was investigated by X-ray diffraction（XRD）,field emission scanning electron microscopy/energy dispersive X-ray spectrometry（FESEM-EDS）,and electrochemical impedance spectroscopy（EIS）measurements.On the basis of XRD and FESEM-EDS analysis,the alloy was mainly composed of V-based solid solution with body-centered-cubic structure and TiNi-based secondary phase.Ce did not exist in two phases,instead,it existed as Ce-rich small white particles,with irregular edges,distributed near the grain boundaries of the V-based solid solution phase.Discharge capacity,cycle stability,and high-rate discharge ability of the alloy electrode were effectively improved with the addition of Ce at 293 K.It was very surprising that the charge retention was abnormal with larger discharge capacity after standing at the open circuit for 24 h.EIS indicated that addition of Ce improved the dynamic performance,which caused the charge transfer resistance（RT）to decrease and exchange current density（I0）to increase markedly.The exchange current density of the electrochemical reaction on the alloy surface with Ce addition was about 2.07 and 3.10 times larger than that of the alloy without Ce at 303 and 343 K,respectively.The diffusion coefficient of hydrogen（D）in the bulk alloy electrode decreased with addition of Ce,but it did not decrease so much,and the apparent activation energy（△rH）was far higher than that of the AB5 type alloy.     

MMNi_5基贮氢合金的电极特性

测定了ＭＭＮｉ５基贮氢合金的电极特性。用快淬法制成的ＭＭ（０．９）Ｔｉ（０．１）Ｎｉ（３．９）Ｍｎ（０．４）Ｃｏ（０．４）Ａｌ（０．３）贮氢合金电极的循环寿命和快速放电能力显著提高，其３００次充放电循环后电容量仅下降１８％，这与合金中微晶组织的形成有关，而感应熔炼制成的ＭＭ（０．９）Ｔｉ（０．１）Ｎｉ（３．９）Ｍｎ（０．４）Ｃｏ（０．４）Ａｌ（０．３）贮氢合金电极２００次循环后电容量下降３９％，经１０００℃３ｈ退火后，其３００次循环后电容量下降为２７％。     

TiFe储氢合金的电化学性能研究

研究了机械合金化（MA）、真空电弧熔炼、熔炼后短时间球磨、退火和辐射照对TiFe合金电化学性能的影响。短时间球磨可提高TiFe合金放电容量和倍率放电性能,高能辐照可以激活电极表面活性,促进活化;机械合金化可以降低电极极化,增加循环寿命;退火对TiFe合金的电化学性能不利,同时,对真空电弧熔炼TiFe合金在高温时的电化学性能作了初步研究。     

热处理对La_(0.53)Ce_(0.47)Ni_(3.4)Co_(0.6)Mn_(0.3)Cu_(0.1)合金相结构和储氢性能的影响

采用感应熔炼法制备La_(0.53)Ce_(0.47)Ni_(3.4)Co_(0.6)Mn_(0.3)Cu_(0.1)储氢合金,并在不同温度下进行热处理,通过XRD对其相组成及结构进行表征,并采用双电极模拟电池测试系统对其储氢性能进行测试与分析。结果表明,随着退火温度的升高,合金的相组成未发生变化,但其晶化程度逐渐增高,晶体缺陷和晶格应力逐渐减少。热处理改善了合金的循环稳定性,提高了合金的电化学容量,但恶化了高倍率放电能力。     

Effect of praseodymium substitution for lanthanum on structure and properties of La0.65-xPrxNd0.12Mg0.23Ni3.4Al0.1（X=0.00-0.20） hydrogen storage alloys

In order to investigate the effect of substituting La with Pr on structural and hydrogen storage properties of La-Mg-Ni system (AB3.5-type) hydrogen storage alloys, a series of La0.65-xPrxNd0.12Mg0.23Ni3.4Al0.1(x=0, 0.10, 0.15, 0.2) hydrogen storage alloys were prepared. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) analyses revealed that two alloys (x=0.0 and 0.10) were composed of (La, Mg)2(Ni,Al)7 phase, La(Ni,Al)5 phase and (La,Mg)Ni2 phase, while other alloys (x=0.15 and 0.20) consisted of (La,Mg)2(Ni,Al)7 phase, La(Ni,Al)5 phase, (La,Mg)Ni2 phase and (La, Mg)(Ni,Al)3 phase. All alloys showed, however, only one pressure plateau in P-C isotherms. The Pr/La ratio in alloy composition influenced hydrogen storage capacity and kinetics properties. Elec-trochemical studies showed that the discharge capacity decreased from 360 mAh/g (x=0.00) to 335 mAh/g (x=0.20) as x increased. But the high-rate dischargeability (HRD) of alloy electrodes increased from 26% (x=0.00) to 56% (x=0.20) at a discharge current density of Id=1800 mA/g. Anode polarization measurements were done to further understand the electrochemical kinetics properties after Pr substitution.     

T10钢表面FeMoCoNiCrTix高熵合金熔覆层组织及性能

采用激光熔覆技术在T10A钢表面制备了FeMoCoNiCrTi_x（x分别为0.25,0.50,0.75,1.00）高熵合金熔覆层,分析了试样熔覆层及基体界面处的相结构及组织,并利用显微硬度计测试了试样处理前后的截面硬度变化。研究表明,经过激光熔覆在T10A钢表面得到的高熵合金层主要由NiCrFe、NiCrCoMo 2种固溶体为主,其结构分别为BCC结构和FCC结构,熔覆层的组织以柱状枝晶为主,界面处出现等轴晶;随着Ti含量增多,熔覆层由固溶强化变为固溶体与硬质相混合强化,熔覆层的HV硬度达到了792,热影响区的HV硬度达到了620,均高于基体硬度。同时耐磨损性能有了明显提高,磨损方式由粘着磨损逐渐变为磨粒磨损。      

Mg-5Gd-3Y-0.8Zr合金的微观组织及耐NaCl溶液腐蚀性能研究

系统研究了Mg-5Gd-3Y-0.8Zr合金的微观组织和耐蚀性能,通过静态失重法测定了其在NaCl溶液中的腐蚀速率。结果表明:铸态合金主要由基体α-Mg和方块状β相(Mg_5Gd、Mg_(24)Y_5)组成,时效处理后分布在晶界处的共晶β相数量明显增加;在NaCl溶液中腐蚀12 h以后镁合金的腐蚀速率明显增加,在3.5%Na Cl(质量分数)溶液中腐蚀24 h后,镁合金已被严重腐蚀,表面布满腐蚀坑和未脱落的白色腐蚀产物;镁合金易产生沿晶腐蚀,方块状共晶β相颗粒可有效阻止表面腐蚀沿晶界向镁合金内部扩展,从而提高镁合金的耐蚀性。     

高能球磨稀土高硅铝合金粉末性能表征

对快速凝固法制备得到的Al-20Si-0.35RE合金进行不同时间的高能球磨, 然后对球磨后的粉末进行多次热压变形, 采用XRD, ESEM以及TEM等表征变形前后合金粉末的显微组织, 并对变形后合金的导电性能进行了研究. 研究发现快速凝固Al-20Si-0.35RE合金粉末的显微组织主要由细小的Al-Si固溶体(0.3～0.5 μm)、初晶硅、稀土铝硅化合物(0.16～0.3 μm)组成; 随着球磨时间延长, 颗粒粒径显著减小; 经过多次热压变形后合金晶粒显著细化, 晶格畸变减小, 位错钉扎稀土化合物, 形成类似表面渗流效应, 合金导电率提高至70%IACS.     

医用近β型TLM合金的超亲水表面改性

医用近β型钛合金TLM(Ti - 25Nb - 3Zr - 2Sn - 3Mo)具有优良的力学和生物学性能.TLM合金经过NaOH溶液处理后表面形成了钛(铌)酸钠凝胶层,再经过稀HCl浸泡后转化为氧化钛(铌)凝胶层.经过2.5 mol/L NaOH(12 h)-HCl处理的TLM合金表面形成了纳米多孔凝胶层,15 mi...     

In vitro effects of anthelmintics on the histochemistry of Haemonchus contortus and Trichuris globulosa

In vitro incubation of Haemonchus contortus (RUD., 1803) and Trichuris globulosa (v. LINSTOW, 1901) were proformed for 10-12 h in Tyrode's solution and 10 and 50 micrograms/ml concentrations each of albendazole (ABZ), fenbendazole (FBZ), thiophenate (TP), dl-tetramisole and oxyclozanide (TO), dl-tetramisole HCI (TMS) and levamisole HCI (LMS) to study morphological and histochemical alterations. The major structural changes observed after treatment with all the drugs were vacuolation in the intestine of H. contortus except with TP treatment and disruption of the epithelium in T. globulosa except with TMS treatment. The other major alteration in T. globulosa was the loss of muscle striations after TP, TO, TMS and LMS treatments. All the six anthelmintics reduced the quantity of neutral mucopolysaccharides in the intestine of H. contortus and T. globulosa except with TMS and LMS treatments in the latter. Acidic mucopolysaccharides detected in the microvilli of the intestine of H. contortus were lost after TO and ABZ treatments. The loss of lipids from the intestine was evident after TO, ABZ, FBZ and TP treatments in H. contortus and by all the drugs in T. globulosa. LMS treatment caused accumulation of very large lipid droplets in the intestine of H. contortus.     

宽温型AB5储氢合金结构及其电化学性能研究

用高频感应熔炼法制备了Mm(NiCoAlMn)5储氢合金,采用模拟电池法测试了合金在238～323 K温度范围内的活化、放电容量和高倍率放电性能.结果表明:制备合金为典型AB5型储氢合金,303K温度条件下吸氢量达到1.38％(质量分数),氢化物生成焓为32.36 kJ ·mol-1H2.合金电极的活化性能、放电容量和高倍率性能受温度影响显著.室温预活化可有效改善电极的低温性能,经室温预活化后合金电极在238 K最大放电容量达到336 mAh·g -1,明显高于未经室温预活化的最大放电容量25 mAh·g-1.Mm(NiCoMn)5贮氢合金电极的高倍率性能随着温度的升高先升高后降低,273和303 K温度条件下合金保持高倍率性能良好,3C放电电流密度条件下容量保持率均高于80％;238 K温度条件下合金的大电流放电性能急剧降低,1C放电电流密度条件下容量保持率仅为10％; 273 K下合金电极的综合性能最佳,最大放电容量达到340 mAh·g-1,300 mA·g-1放电电流密度下的高倍率放电比率为86％.循环伏安法测试证实,在238～323 K范围内,电极的氧化峰峰值电流(Ip)与扫描速度的平方根(v1/2)之间均存在良好的线性关系,整个电极反应受氢原子扩散控制;随着温度的降低氢扩散系数急剧下降,从而导致该合金电极的低温高倍率放电性能变差.由Arrhenius公式计算出合金中的氢扩散活化能为10.56 kJ·mol -1.     

酸再生排放废气粉尘含量超标问题探讨及对策

采用焙烧法处理富含氯化亚铁的盐酸,其排向大气的烟气中的Fe2O3含量一直难以控制,宝钢乃至国内诸多酸再生处理均存在粉尘含量超标的问题,文章对酸再生系统进行分析,详细介绍部分废气处理的关键设备,找出一些解决的办法.