金属氢化物复合式高压储氢器的研究

为提高高压储氢容器的体积储氢密度,采用具有高体积储氢密度的储氢合金与轻质高压容器复合组成高压金属氢化物复合式储氢器.为获得高压氢源,研究了Mm-Ml-Ni-Al(Mm为富铈混合稀土,Ml为富镧混合稀土)的储氢特性,并试制了化学热压缩器.采用研制的高压氢源,对具有高吸放氢平台压力的Ce-Ni系合金的高压储氢特性进行了研究.实验结果表明:以Ml或Ca部分取代Mm以及Al对Ni的部分置换后合金活化性能和吸放氢压力滞后明显改善,(Mm-Ml)0.8Ca0.2(Ni-Al)多元合金具有较好的储氢性能,适合于作为化学热压缩合金.CeNi5基多元合金在40MPa氢压条件下,合金具有较好的活化性能和吸放氢动力学性能,合金最大储氢容量分别达到1.6wt%.将优化的储氢合金与自制的轻质高压储氢容器复合组成的金属氢化物复合式高压储氢器,当储氢合金的填充量达到0.2(体积分数)时,其体积储氢密度提高50%.     

Li-Al-B-H复合体系的储氢性能研究

以LiAlH4和LiBH4为原料,采用球磨方法制备了Li-Al-B-H复合储氢体系,通过XRD、TG、DSC和SEM等研究手段对复合物的微观结构和性能进行表征.研究结果表明:LiAlH4/2LiBH4复合物加热至500℃时的放氢量达到9.7wt％,在450C和8Mpa H2条件下的最大吸氢量达到6.8wt％.还计算了(LiAlH4/2LiBH4)复合物放氢反应的表观活化能,并对( LiAlH4/2LiBH4)复合物吸放氢反应的机理进行了讨论.     

非晶纳米晶PrMg_(12)型合金微观结构及吸放氢热力学与动力学性能北大核心CSCD

采用机械球磨法制备了非晶纳米晶PrMg_(12)+x%Ni(x=0、10、20、30)合金,系统地研究了镍含量对该合金储氢热力学与动力学的影响。利用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)两种方法分析了合金的相组成及微观组织结构。结果表明:PrMg_(12)+x%Ni(x=0、10、20、30)合金的微观结构主要为非晶纳米晶;加入镍前,吸氢前后的主相分别为PrMg_(12)相、MgH_(2)相以及PrH_(2.92)相;加入镍后,吸氢前后的主相分别为Ni相、PrMg_(12)相、MgH_(2)相以及Mg_(2)NiH_(4)相。采用Sieverts装置测定了合金的P-C-T曲线与吸放氢动力学曲线,并结合Van't Hoff方程、JMAK模型和Arrhenius法计算了热力学与动力学参数。结果表明:随着镍含量由0%增加至30%,合金氢化物的放氢焓值由89.881 kJ/mol降低至82.764 kJ/mol,放氢活化能由126 kJ/mol降低至90 kJ/mol,这进一步证明添加镍可以显著改善球磨PrMg_(12)型合金氢化物的释氢热力学和动力学。     

富镍镧镍合金催化二苄基甲苯加氢性能研究

采用感应熔炼和球磨方法制备镧镍储氢合金,进一步通过酸处理法原位制备富镍镧镍储氢合金。研究不同条件下制备的镧镍储氢合金催化二苄基甲苯（DBT）加氢性能。在反应温度为280 ℃时,经过4 h后,富镍镧镍储氢合金催化二苄基甲苯的加氢量达到5.34%（质量分数）,20 h后,其加氢量达到理论最大值。富镍镧镍储氢合金具备的高效催化二苄基甲苯加氢活性主要归因于镍的高效催化和镧镍储氢合金可逆吸放氢之间的相互促进作用。     

石英负载TiO2催化材料的制备及降解性能研究

选用石英作为载体，采用溶胶-凝胶法负载TiO2制备石英负载TiO2光催化材料。光电子能谱分析结果表明，石英表面成功负载了TiO2。石英负载TiO2光催化材料对偶氮染料废水处理4h后，脱色率达到了96．28％。     

复合Ce、Ag/TiO2粒子环保涂料制备及其光催化活性研究

用全氟树脂与Ce、Ag／TiO2粒子复合制备有净化大气功能的环保涂料，比较油酸和聚甲基丙烯酸甲酯在改性的Ce、Ag／TiO2表面包覆及在涂料中添加2％、5％、8％、11％（质量％）包覆的改性粒子对光催化活性的影响，表明甲基丙烯酸甲酯包覆比油酸好，包覆的Ce、Ag／TiO2添加量为8％比较合理。     

氩气、氢气和空气中球磨改性的多壁碳纳米管的吸氢性能

研究了氩气、氢气和空气不同气氛下球磨改性对多壁碳纳米管储氢性能的影响。发现球磨促使碳管变短和开口，从而更有利于储氢。空气中球磨24h的碳管吸氢量从未球磨时的0．29wt％提高到1.81Wt％。空气中氧化球磨融合了机械力与高温氧化的双重作用，处理后碳管石墨化程度降低、管端开口增加，处理效果最好。     

二氧化锰@纳米多孔金/泡沫镍电极材料的制备及其超级电容性能CSCD

通过结合电化学沉积法与化学去合金法制备纳米多孔金(NPG)/泡沫镍(Ni foam)电极,采用电化学沉积法把二氧化锰(MnO2)沉积在NPG/Nifoam基底表面,获得MnO2@NPG/Ni foam复合电极材料.采用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线光电子能谱(XPS)等分析了MnO2@NPG/Nifoam复合电极材料的微观形貌和成分.将该复合电极材料作为超级电容器的电极材料,对其充放电特性和循环稳定性等电化学性能进行测试.结果表明,与直接在Ni foam表面电化学沉积生长MnO2材料(MnO2@Ni foam)相比,MnO2@NPG/Ni foam复合电极材料拥有更高的比电容、更优的倍率性能及循环性能.在1 A/g的电流密度下,MnO2@NPG/Ni foam复合电极材料的比电容值为377.9 F/g.经过在50 mV/s的扫描速度下循环2500次后,该电极材料的比容量保持在99％左右.     

纳米TiO2协同Fenton试剂光催化降解甲基橙

采用纳米TiO2协同Fenton试剂光催化降解甲基橙,研究了纳米TiO2与Fenton试剂的协同效应,考察了H2O2用量、甲基橙溶液的初始浓度及初始pH值对降解效率的影响,并对其降解动力学规律作了初步探讨。结果表明:纳米TiO2强化了Fenton试剂对甲基橙的降解效率,它们之间产生了较强烈的协同效应。在实验过程中,纳米TiO2协同Fenton试剂光催化降解初始浓度30mg/L、pH=3.0的甲基橙120min,其降解率达到99.4%,分别是同等实验条件下单独纳米TiO2降解率的2.63倍,单独Fenton试剂降解率的2.32倍,是两者算术和的1.2倍。在实验浓度范围内,甲基橙的降解反应符合准一级动力学过程;与Fenton反应相比,在0.2、0.4、0.6g/L纳米TiO2的协同作用下,甲基橙的降解表现反应常数分别提高了1.71、2.51和3.36倍,半衰期相应缩短。另外,H2O2用量、甲基橙溶液初始浓度及初始pH对降解率有一定影响。     

太阳光-TiO2催化氧化法处理棉浆粕黑液

先用酸地对棉浆粕黑液进行预处理，然后用太阳光－TiO2法进行催化氧化。文章研究了催化剂的投加量，pH值，光照时间，光强及搅拌速度对光解作用的影响。结果表明，在适宜的条件下，废水的COD和色度去除率分别可达92．4％和99％，制得的负载型TiO2具有较高的机械强度和化学稳定性，可重复使用，出水用石灰乳中和后可直接排放。     

Improvement in the hydrogenation-dehydrogenation performance of a Mg–Al alloy by graphene supported Ni

Mg-based materials are very promising candidates for hydrogen storage. In this paper, the graphene supported Ni was introduced to the Mg₉₀Al₁₀ system by hydrogenation synthesis (HS) and mechanical milling (MM). The 80 wt%Ni@Gn catalyst was synthesized by a facile chemical reduction method. The microstructures of the catalyst and composite show that Ni nanoparticles are well supported on the surface of graphene and they are dispersed uniformly on the surface of MgH₂ particles. After heating to 450 °C and holding at 340 °C for 2 h subsequently under 2.0 MPa hydrogen pressure, all the samples are almost completely hydrogenated. According to the temperature programmed desorption test, the Mg₉₀Al₁₀-8(80 wt%Ni@Gn) composite could desorb 5.85 wt% H₂ which comes up to 96% of the theoretical hydrogen storage capacity. Moreover, it shows the optimal hydriding/dehydriding performance, absorbing 5.11 wt% hydrogen within 400 s at 523 K, and desorbing 5.81 wt% hydrogen within 1800 s at 573 K.     

Hydrogenation and degradation of Mg–10 wt% Ni alloy after cyclic hydriding–dehydriding

Hydrogenation and degradation properties of Mg–10 wt% Ni hydrogen storage alloys were investigated by cyclic hydriding–dehydriding tests. Mg–10 wt% Ni alloy was synthesized by rotation-cylinder method (RCM) under 0.3% HFC-134a/air atmosphere and their hydrogenation and degradation properties were evaluated by pressure-composition-isotherm (PCI) measurement. Hydrogen storage capacities gradually increased following 160 hydriding–dehydriding cycles and thereafter started to decrease. Measured maximum hydrogen capacity of Mg–10 wt% Ni alloy is 6.97 wt% at 623 K. Hydriding and dehydriding plateau pressure were kept constant for whole cycles. Reversible hydrogen capacity started to descend after 280 hydriding–dehydriding cycles. The lamellar eutectic structure of Mg–Ni alloy consists of Mg-rich α$\alpha$-phase and β$\beta$-_Mg2Ni${\mathrm{Mg}}_2\mathrm{Ni}$. It is assumed that the lamellar eutectic structure enhances hydrogenation properties.     

Enhancement of the hydrogen storage characteristics of Mg by reactive mechanical grinding with Ni,Fe and Ti

Mg-10wt%Ni-5wt%Fe-5wt%Ti powder was prepared by reactive mechanical grinding using a planetary ball mill. The Mg-10wt%Ni-5wt%Fe-5wt%Ti powder exhibited high hydriding and dehydriding rates even at the first cycle, and its activation was completed after two hydriding–dehydriding cycles. After the reactive mechanical grinding, the particle size of the powder was reduced, as compared with those of the starting materials. The hydrogen storage properties were measured at temperatures of 473 K, 573 K and 623 K. The activated Mg-10wt%Ni-5wt%Fe-5wt%Ti powder absorbed 5.31 wt% and 5.51 wt% of hydrogen for 5 min and 1 h, respectively, at 573 K under 12 bar H₂. It desorbed 5.18 wt% of hydrogen at 573 K under 1.0 bar H₂ for 1 h. The initial hydrogen absorption rate increased when passing from 473 K to 573 K, but decreased at 623 K. The hydrogen desorption rate increased rapidly with increasing temperature from 473 K to 623 K. The hydrogen storage capacity was about 6.72 wt% at 573 K.     

Hydrogen storage properties of Mg-23.5Ni-xCu prepared by rapid solidification process and crystallization heat treatment

A Mg-23.5wt%Ni-5wt%Cu alloy was synthesized by the gravity casting method in a large quantity (7.5 kg). From this alloy, Mg-23.5wt%Ni-xwt%Cu (x = 2.5, 5 and 7.5) samples for hydrogen storage were prepared by melt spinning and crystallization heat treatment. The samples were ground under H₂ in order to obtain a fine powder. These alloys contained crystalline Mg and Mg₂Ni phases. The Mg-23.5Ni-2.5Cu alloy had the highest hydriding and dehydriding rates after activation among these alloys. The dehydriding curve under 1.0 bar H₂ at 573 K exhibits two stages; the dehydriding rate is high for about 2.5 min (the decomposition of Mg₂Ni hydride and Mg hydride in small particles), and then it becomes lower (the decomposition of Mg hydride).     

Characterization of Mg–20 wt% Ni–Y hydrogen storage composite prepared by reactive mechanical alloying

Mg–20 wt% Ni–Y composite was successfully prepared by reactive mechanical alloying (RMA). X-ray diffraction (XRD) measurement showed that both MgH₂ and Mg₂NiH₄ co-exist in the milled composite. The composite exhibits excellent hydrogen sorption kinetics and does not need activation on the first hydrogen storage process. It can absorb 3.92 and 5.59 wt% hydrogen under 3.0 MPa hydrogen pressure at 293 and 473 K in 10 min, respectively, and desorb 4.67wt% hydrogen at 523 K in 30 min under 0.02 MPa hydrogen pressure. The equilibrium desorption pressure of the composite are 0.142, 0.051 and 0.025 MPa at 573, 543 and 523 K, respectively. The differential scanning calorimetry (DSC) measurement showed that dehydrogenation of Mg–20 wt% Ni–Y composite was depressed about 100 K comparing to that of milled pure MgH₂. It is deduced that both the catalysis effect of Mg₂Ni and YH₃ distributed in Mg substrate and the crystal defects formed by RMA are the main reason for improving hydrogen sorption kinetics of the Mg–20 wt% Ni–Y composite.     

Microstructure and activation characteristics of Mg–Ni alloy modified by multi-walled carbon nanotubes

An Mg–6 wt% Ni alloy was fabricated by a casting technique and the drilled chips ball-milled by high energy ball milling to be examined for their hydrogenation modified with multi-walled carbon nanotubes (MWCNTs). The activation characteristics of ball-milled alloy are compared with those of the materials obtained by ball milling with 5 wt% MWCNTs for 0.5, 1, 2, 5 and 10 h. MWCNTs enhanced the absorption kinetics considerably in all cases. The hydrogen content of the modified powder with MWCNTs reached maximum hydrogen capacity within 2 min of exposure to hydrogen at 370 °C and 2 MPa pressure. X-ray diffraction analysis provided evidence that no carbon-containing phase was formed during milling. However, milling with MWCNTs reduced the crystallite size, even if the milling was carried out for only an hour. The rate-controlling steps of the hydriding reactions at different milling times were determined by fitting the respective kinetic equations. Evidence is provided that nucleation and growth of hydrides are accelerated drastically by a homogenous distribution of MWCNTs on the surface of the ball-milled powders. We show that MWCNTs are very effective at promoting the hydriding/dehydriding kinetics, as well as in increasing the hydrogen capacity of the magnesium alloy.     

Hydriding behavior of Mg-50 wt% ZrCrFe composite Prepared by high energy ball milling

Magnesium hydride has a high theoretically storage capacity, which amounts to 7.6 wt%. It is therefore a promising candidate for hydrogen storage applications. However, its major drawback is its high desorption temperature of well over 300 °C, which is related to the high stability of the Mg–H bonds and expressed in the high enthalpy of hydride formation (77 kJ/mol). The preparation of Mg composites with other hydrogen storage compounds is an effective method to improve the hydrogen storage properties of Mg. Thus we prepared Mg-50 wt% ZrCrFe alloy composite by high energy ball milling under argon atmosphere. X-ray diffraction (XRD) studies on the composite before and after hydriding cycles suggest no intermetalic phase is formed between Mg and the elements of the alloy. The morphological studies carried on by Scanning Electron Microscope (SEM) technique suggest that the alloy particles are homogeneously distributed throughout the Mg surface. A particle reduction after hydrogenation is also visible. Hydriding/dehydriding properties of the composites are investigated by PCT measurements using a dynamic system. The maximum hydrogen capacity for this composite is found to be 4.5 wt%. The reaction kinetics have also been recorded in a temperature range from RT to 300 °C and the thermodynamic parameters calculated from Van’t Hoff plot. From the results it is found that the alloy reacts with hydrogen also when cooled to room temperature while at higher temperature it works as catalyst.     

Preparation and characterization of NbF5-added Mg hydrogen storage alloy

A sample with a composition of 95 wt% Mg-5 wt% NbF₅ (named Mg-5NbF₅) was prepared by reactive mechanical grinding using Mg instead of MgH₂ as a starting material. Its hydriding and dehydriding rates were then measured under nearly constant hydrogen pressures. The activation of Mg-5NbF₅ was not required, and Mg-5NbF₅ had an effective hydrogen storage capacity, which was defined as the quantity of hydrogen absorbed for 60 min, of 5.50 wt%. At the first cycle (n = 1) at 593 K, the sample absorbed 4.37 wt% H for 5 min and 5.50 wt% H for 30 min under 12 bar H₂, and desorbed 1.03 wt% H for 5 min, 4.66 wt% H for 30 min, and 5.43 wt% H for 60 min under 1.0 bar H₂. Reactive mechanical grinding of Mg with NbF₅, which formed MgH₂, MgF₂, NbH₂, and NbF₃ by the reaction of 11 Mg + 7NbF₅ + 3H₂ → MgH₂ + 10MgF₂ + 2NbH₂ + 5NbF₃, is considered to create defects, to produce reactive clean surfaces, and to reduce the particle size of Mg. The XRD pattern of Mg-5NbF₅ dehydrided at n = 3 revealed Mg, small amounts of β-MgH₂ and MgO, and very small amounts of MgF₂ and NbH₂. An increase in the dehydriding rate of Mg-5NbF₅ was attempted by adding Ni to Mg-5NbF₅. Mg-5NbF₅ had higher initial hydriding and dehydriding (after the incubation period) rates and a larger effective hydrogen storage capacity than Mg-10NbF₅, Mg-10MnO, and Mg-10Fe₂O₃, which were reported to have quite high hydriding rate and/or dehydriding rate.     

Mechanisms of hydrides’ nucleation and the effect of hydrogen pressure induced driving force on de-/hydrogenation kinetics of Mg-based nanocrystalline alloys

Aiming to gain insight on the hydrogen storage properties of Mg-based alloys, partial hydrogenation and hydrogen pressure related de-/hydrogenation kinetics of Mg–Ni–La alloys have been investigated. The results indicate that the phase boundaries, such as Mg/Mg₂Ni and Mg/Mg₁₇La₂, distributed within the eutectics can act as preferential nucleation sites for β-MgH₂ and apparently promote the hydrogenation process. For bulk alloy, it is observed that the hydrogenation region gradually grows from the fine Mg–Ni–La eutectic to primary Mg region with the extension of reaction time. After high-energy ball milling, the nanocrystalline powders with crystallite size of 12～20 nm exhibit ameliorated hydrogen absorption/desorption performance, which can absorb 2.58 wt% H₂ at 368 K within 50 min and begin to desorb hydrogen from ～508 K. On the other side, variation of hydrogen pressure induced driving force significantly affects the reaction kinetics. As the hydrogenation/dehydrogenation driving forces increase, the hydrogen absorption/desorption kinetics is markedly accelerated. The dehydrogenation mechanisms have also been revealed by fitting different theoretical kinetics models, which demonstrate that the rate-limiting steps change obviously with the variation of driving forces.     

Composition dependent microstructure evolution,activation and de-/hydrogenation properties of Mg–Ni–La alloys

In this work, in order to elucidate the effect of different alloying elements on the microstructure, activation and the de-/hydrogenation kinetics performance, the Mg–20La, Mg–20Ni and Mg–10Ni–10La (wt.%) alloys have been prepared by near equilibrium solidification combined with high-energy ball milling treatment to realize the internal optimization as well as particle refinement. The results show that the microstructures of the prepared alloys are significantly refined by forming different types and sizes of intermetallic compounds. Meanwhile, the effects of LaH₃ and Mg₂Ni within the activated samples on de-/hydrogenation kinetics are also discussed. It is observed that the alloy containing LaH₃ preserves stable hydrogenation behavior between 573 and 623 K, while the hydrogenation properties of the alloy containing Mg₂Ni is susceptible to temperature. A preferable hydrogenation performance is observed in Mg–10Ni–10La alloy, which can absorb as high as 5.86 wt% hydrogen within 15 min at 623 K and 3.0 MPa hydrogen pressure. Moreover, the desorption kinetics and the desorption activation energies are evaluated to illustrate the mechanism based on improved dehydrogenation performance. The addition of proper alloying elements Ni and La in combination with reasonable processing is an effective strategy to improve the de-/hydrogenation performance of Mg-based alloys.