Zn(BH4)2-LiNH2复合储氢材料的制备及储氢性能

以NaBH4,ZnCl2和LiNH2为原料,机械球磨法制备Zn(BH4)2-LiNH2复合储氢材料.采用X-射线衍射(XRD)、红外光谱(FTIR)、差示扫描量热-热重分析(DSC-TGA)和扫描电镜(SEM)和吸放氢测试装置等方法表征Zn(BH4)2-LiNH2复合储氢材料的物相、键合特征、热稳定性、储氢性能和形貌.结果表明:Zn(BH4)2-LiNH2复合体系在116℃和193℃时分别发生熔化和热分解.随着放氢温度的升高,体系在150℃时放氢气量为0.015 mol/g.而在200℃时,材料的放氢量增加至0.018 mol/g,提高放氢温度对该体系的放氢动力学影响有限.循环吸氢实验发现(BH4)2-LiNH2复合体系在150℃,0.1 MPa H2条件下不能可逆吸氢.     

机械球磨合成LiNH2及LiNH2+LiH的放氢性能

以LiH为初始原料,在室温下用LiH与氨气进行机械球磨原位化学合成LiNH2.将合成产物LiNH2与LiH按摩尔比1∶1球磨混合和改性,通过恒温放氢性能测试和TG及DSC热分析方法分析机械球磨改性后LiNH2 LiH储氢材料体系的放氢规律;用X-射线衍射和Rietveld全谱拟合方法分析合成产物和放氢后固体产物.研究表明,球磨改性后的LiNH2 LiH试样在230℃即开始放氢,在230~340℃放氢迅速,放氢过程属于LiNH2与LiH直接反应放氢;经吸放氢循环的LiNH2 LiH从320℃开始放氢,在340~440℃放氢迅速,放氢时LiNH2首先分解出氨气,氨气与LiH发生反应生成氢气析出.     

金属催化剂对储氢材料(90-x)Mg5C5NCxM(M=Al,Mo或Ni,x=0～10)性能的影响

添加金属催化剂是改善镁基储氢材料储氢性能的有效方式。为研究金属Al,Mo,Ni对镁碳材料的储氢性能的催化作用,用氢气反应球磨法制备了镁碳储氢材料(90-x)Mg5C5NCxM(C=无烟煤基微晶碳,NC=针状焦,M=Al,Mo或Ni,x=0～10),并用排水法放氢测试装置和差示扫描量热分析仪对材料的放氢性能进行了测试。结果表明,添加适量的金属催化剂均能够提高材料的储氢密度,其中添加0.5%的Al可使储氢密度提高11.9%,达4.7%,但Al添加量≥2%时,物料在球磨时容易发生焊接,导致储氢密度降低;Ni具有催化储氢材料放氢的作用,材料89Mg5C5NC1Ni的初始放氢温度仅206.4℃,比不添加Ni时降低了119.2℃。     

低温球磨制备Mg-4%Ni-1%NiO储氢材料及其性能

采用低温球磨技术制备了Mg-4%Ni-1%NiO储氢材料,主要研究低温球磨时间对材料形貌结构以及储氢性能的影响.采用扫描电子显微镜(SEM)和X射线衍射(XRD)分析材料的形貌和相组成,采用压力-组成-温度(P-C-T)设备研究材料的储氢性能.结果表明:分别经过2、4和7 h球磨后,材料的相组成没有发生明显改变,只有极少量的Mg2Ni合金相生成.随着球磨时间的延长,材料的平均粒度逐渐下降,作为催化剂的Ni、NiO相逐渐揉进基体内部.伴随着上述变化,材料的活化性能、吸氢性能逐渐提高,球磨到7 h后材料仅需活化1次即可达到最大吸放氢速率,初始吸氢温度降为60℃,在4.0 MPa初始氢压和200℃下吸氢量为6.4%(质量分数),60s即可完成饱和吸氢量的80%,10min内完成饱和吸氢量的90%;材料的放氢性能则在球磨4 h后已经基本保持不变,0.1MPa下初始放氢温度为310℃,在350℃、0.1MPa下材料可在500s内释放饱和储氢量的80%.     

球磨制备Mg-In-Zn三元固溶体的储氢性能及机理

采用"烧结-球磨"方法制备Mg0.92In0.05Zn0.03三元固溶体合金,减小了Mg的晶格常数.利用粉末X-射线衍射分析合金的相组成、微观结构和吸放氢过程的相转变,通过扫描电镜观察合金的微观形貌及相分布.采用体积法测定合金的等温吸放氢曲线(PCT)和动力学曲线,确定了合金的吸放氢反应焓变、熵变及氢化反应激活能.结果表明:Mg0.92In0.05Zn0.03三元固溶体具有良好的活化性能和动力学性能,脱氢反应焓降低至-68.6 kJ/mol H2.     

固液反应球磨制备Al-Cu-Fe与Al-Si-Fe三元合金

利用固液反应球磨技术,采用Fe球球磨液态Al-Cu和A1-Si三元合金,研究了Al-Cu-Fe和Al-Si-Fe三元合金相形成规律.在923 K球磨液态的Al-33.2%Cu共晶合金,球磨48 h后,得到Al13Cu4Fe3的固相粉末;在943 K球磨Al-54%Cu(Al2Cu)合金熔体,球磨24 h后,Al2Cu的液相消失,得到了固相的Al65Cu20Fe15和Al13Cu4Fe3混合粉末;在963 K球磨Al-7%Si亚共晶合金熔体,球磨48 h后,Al-Si液相消失,得到固态的Al8Fe2Si合金粉末;在963 K球磨Al-12.6%Si共晶合金熔体,球磨48 h后,Al-Si的液相消失,得到固态的Al8Fe2Si粉末;在1133 K球磨Al-30%Si过共晶合金熔体,球磨24 h后,Al-Si的液相消失,得到固态的Al3FeSi合金粉末.在上述球磨中,若加入一定量的Fe粉,将加速反应进程.固液反应球磨产物是在打击剥离的过程中制得的.     

Mg+x% Mm(NiCoMnAl)5复合储氢材料吸放氢性能研究

采用高能球磨法制备了Mg x%Mm(NiCoMnAl)_5(x=10、20、30和40)纳米晶和非晶混合结构的复合储氢材料,并对其结构和吸放氢性能进行了研究．XRD结果表明,Mg与Mm(NiCoMnAl)_5球磨200h后有Mg_2Ni和La_2Mg_(17)相生成．吸氢动力学研究发现,在423K和3．4 MPa下,随着x增大,吸氢速率和最大吸氢量都出现了先增大后减小的趋势．当x=20时,复合材料的吸氢性能达到最佳,其最大吸氢速率达到0．45%/s,50s内即可吸氢3．6%．热重分析结果表明,Mg的氢化物相放氢温度降低到259℃(x=40)．     

非晶态TiB_2@C催化剂对NaAlH_4合成和可逆储氢性能的影响

为了提高NaAlH_4的吸放氢动力学性能,采用球磨烧结两步法制备了非晶态TiB_2和C复合催化剂(简写为TiB_2@C),并系统地研究了TiB_2@C对NaAlH_4合成和储氢性能的影响。研究结果表明,以NaH和Al为原料,添加质量分数为6%的TiB_2@C作为复合催化剂,在室温、5 MPa氢压下进行球磨成功制备出NaAlH_4。相对于球磨后的纯NaAlH_4,复合体系的起始放氢温度、三步放氢过程的峰值温度和前两步放氢过程的表观活化能均大幅降低。吸放氢测试结果显示,TiB_2@C能够有效地改善NaAlH_4的吸放氢动力学性能,且复合体系在10次吸氢循环过程中表现出优异的循环稳定性。这一系列性能的改善主要源于TiB_2@C催化剂中TiB_2和C的协同催化效应。     

高能球磨制备MgxTi100-x合金的微观组织及储氢性能

应用振动高能球磨机械合金化方法制备MgxTi100-x(x=35,50,65,80)系列合金,采用XRD、SEM、TEM以及吸放氢测试等手段分析研究Mg含量与球磨时间对MgxTi100-x球磨产物微观组织演化规律、相结构和吸氢行为的影响.结果表明:在相同球磨时间(20 h)下,球磨合金MgxTi100-x微观组织的相组...     

机械球磨固相化学反应制备AlH_3

以LiAlH4和AlCl3为原料,采用机械球磨固相化学反应方法合成铝氢化合物,通过XRD、TG-DSC和MS等方法对反应产物进行分析和表征,研究不同球磨时间对球磨反应体系合成产物的转变规律和对产物热力学性能的影响.结果表明,随着球磨时间的增加,合成反应按3LiAlH4 AlCl3→4AlH3 3LiCl方向进行并形成了非晶态铝氢化合物(AlH3),球磨20 h时反应基本完全.球磨产物的放氢失重温度主要集中在100～200 ℃,对应的DSC曲线在135 ℃和165 ℃出现2个放热峰,随球磨时间的增加,失重量减少,最大失重质量分数达到3.5%～6.1%.球磨过程中形成的反应产物LiCl*H2O及少量AlH3发生分解是影响球磨反应产物最大失重量的主要因素.     

硫化氢环境下氢扩散的影响因素

采用典型的电化学渗氢装置,对材料的化学成分、焊接和环境中CO2和NH4 的质量浓度、溶液的pH值对硫化氢应力腐蚀开裂中氢扩散行为的影响进行了研究.结果表明:金属中夹杂物数量、焊缝金属中空位和焊接缺陷使得氢扩散系数增加;在硫化氢环境中,氢扩散稳态电流随pH值的增加而降低,随着NH4 的质量浓度的增加而增加,且增加幅度随着pH值的增加而加大;CO2的质量浓度对氢稳态扩散电流的影响是随着pH值的变化而起着不同的作用,在低pH值条件下氢稳态扩散电流随着CO2的质量浓度增加而增加,在较高的pH值中氢稳态扩散电流随着CO2的质量浓度增加而减小.     

Upgradation of bauxite by molecular hydrogen and hydrogen plasma

An approach was developed to upgrade the bauxite ore by molecular hydrogen and hydrogen plasma. A gibbsite-type bauxite sample was obtained from National Aluminium Company (NALCO), Odisha, India. The obtained sample was crushed and sieved (to 100 μm) prior to the chemical analysis and grain-size distribution study. The bauxite sample was calcined in the temperature range from 500 to 700°C for different time intervals to optimize the conditions for maximum moisture removal. This process was followed by the reduction of the calcined ore by molecular hydrogen and hydrogen plasma. Extraction of alumina from the reduced ore was carried out via acid leaching in chloride media for 2 h at 60°C. X-ray diffraction, scanning electron microscopy, thermogravimetry in conjunction with differential scanning calorimetry, and Fourier transform infrared spectroscopy were used to determine the physicochemical characteristics of the material before and after extraction. Alumina extracted from the reduced ore at the optimum calcination temperature of 700°C and the optimum calcination time of 4 h is found to be 90% pure.     

氢爆碎工艺中的吸氢和放氢现象

研究了氢爆碎 (hydrogen decrepitation,HD)过程中不同合金及合金表面状态的吸氢速率和吸氢量 ,并采用 X射线衍射、扫描电镜等手段研究 HD粉加热去氢过程中放氢规律和粉体微观形貌的变化。结果表明氢爆碎的吸氢速度和吸氢量与钕铁硼合金铸锭表面的活性有关 ,表面新鲜、活性大的合金铸锭氢爆碎的时间短、效率高。合金中存在足够的富 Nd相 ,是室温氢爆碎过程得以进行的前提条件。将 HD粉加热处理时 ,随加热温度的升高 ,氢不断释放出来 ,到10 73K时磁粉中氢的质量分数已降低到 1.5× 10 - 5,氢气基本释放。生产中可以将 HD粉经 5 2 3～ 72 3K加热放氢 1h后再进行磁场成型 ,以减少氢气对 HD粉体成型取向度的影响     

氢能供应链中最佳运氢方式的选择

氢的运输在整个氢能供应链的经济、能耗和排放性能中占有很大比重。该文通过设计以运氢规模和运输距离为特征参数的"点对点"运输情景,对比分析了3种运氢方式(气氢拖车、气氢管道和液氢罐车)在不同情景参数下的成本、能耗和CO2排放特性。分析结果表明不同运氢方式适合不同的运输情景:在以经济性为主要评价指标的前提下,气氢拖车方式适合小规模、短距离运输;气氢管道方式适合大规模、中短距离运输;液氢罐车方式适合长距离运输。     

从炼厂酸性气中回收氢气和硫磺的实验研究

利用氧化还原反应和电解反应构成的双反应工艺 ,对炼油厂含硫化氢的酸性气进行处理 ,回收氢气和硫磺。考察了液相流量、液相中Fe3 + 的浓度及气相流量对硫化氢吸收传质速率的影响 ,并对双反应工艺的稳定运转进行了实验验证。实验结果表明 ,该工艺过程可行 ,在适宜的操作条件下 ,硫化氢的吸收率可达 99.9%以上     

从炼厂酸性气体中回收氢气和硫磺的实验研究

利用氧化还原反应和电解反应构成的双反应工艺,对炼油厂含硫化氢的酸性气体进行处理,回收氢气和硫磺,考察了液相流量,液相中Fe^3 的浓度及气相流量对硫化氢吸收传质速率的影响,并对双反应工艺的稳定运转进行了实验验证。实验结果表明,该工艺过程可行,在适宜的操作条件下,硫化氢的吸收率可达99．9％以上。     

Influence of heat exchanger structure on hydrogen absorption-desorption performance of hydrogen storage vessel

The influence of heat exchanger structure on hydrogen absorption-desorption performance of hydrogen storage vessel was studied, in which the AB₅ (La_0.25Ce_0.75Ni_4.4Al_0.1Mn_0.1Co_0.4) hydrogen storage alloy was used as a typical representative. In order to obtain the data on reaction enthalpy, the PCT curve of the alloy was measured with three different temperatures, and the linear fitting was carried out according to the Van't Hoff relation curve. The SMCR (Spiral-mini-channel Reactor) reactor structure was adopted. The heat transfer method and its simplified model were studied by finite element method to explore the effect of size of heat transfer structure, particularly for heat pipe diameter, on the hydrogen absorption-desorption performance of hydrogen storage alloy in the vessel.     

Optical studies of solid hydrogen to 320 GPa and evidence for black hydrogen

The quest for metallic hydrogen at high pressures represents a longstanding problem in condensed matter physics. Recent calculations have predicted that solid hydrogen should become a molecular metal at pressures above 300 GPa, before transforming into an alkali metal; but the strong quantum nature of the problem makes the predictions difficult. Over a decade ago, an optical study of hydrogen was made using a diamond anvil cell to reach 250 GPa. However, despite many subsequent efforts, quantitative studies at higher pressures have proved difficult and their conclusions controversial. Here we report optical measurements of solid hydrogen up to a pressure of 320 GPa at 100 K. The vibron signature of the H2 molecule persists to at least 316 GPa; no structural changes are detected above 160 GPa, and solid hydrogen is observed to turn completely opaque at 320 GPa. We measure the absorption edge of hydrogen above 300 GPa, observing features characteristic of a direct electronic bandgap. This is at odds with the most recent theoretical calculations that predict much larger direct transition energies and the closure of an indirect gap. We predict that metal hydrogen should be observed at about 450 GPa when the direct gap closes.     

Carrier transport characteristics of H-terminated diamond films prepared using molecular hydrogen and atomic hydrogen

The H-terminated diamond films, which exhibit high surface conductivity, have been used in high-frequency and high-power electronic devices. In this paper, the surface conductive channel on specimens from the same diamond film was obtained by hydrogen plasma treatment and by heating under a hydrogen atmosphere, respectively, and the surface carrier transport characteristics of both samples were compared and evaluated. The results show that the carrier mobility and carrier density of the sample treated by hydrogen plasma are 15 cm2·V-1·s-1 and greater than 5×1012 cm-2, respectively, and that the carrier mobilities measured at five different areas are similar. Compared to the hydrogen-plasma-treated specimen, the thermally hydrogenated specimen exhibits a lower surface conductivity, a carrier density one order of magnitude lower, and a carrier mobility that varies from 2 to 33 cm2·V-1·s-1. The activated hydrogen atoms restructure the diamond surface, remove the scratches, and passivate the surface states via the etching effect during the hydrogen plasma treatment process, which maintains a higher carrier density and a more stable carrier mobility.