Y2Cu2O5光催化剂的制备及模拟太阳光催化产氢

分别用固相法和液相法制备Y2Cu2O5光催化剂,利用热重差热分析(TG-DTA)、X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见光漫反射光谱(UV-Vis DRS)等技术对光催化剂进行表征。在模拟太阳光照射条件下,以草酸(H2C2O4)为牺牲剂对所制得的光催化剂制氢性能进行评价,考察制备方法和牺牲剂类型等因素对其产氢性能的影响以及光催化剂的稳定性能。结果表明:溶胶凝胶法所得样品中含有Y2O3杂质,为Y2Cu2O5与Y2O3的混合物;固相法所得样品为纯净的Y2Cu2O5,具备较高的光催化产氢活性。用固相法制备的光催化剂Y2Cu2O5,当其用量为0.8 g/L、草酸为牺牲剂且初始浓度为0.05 mol/L时,表现出最佳光催化产氢活性,其产氢量为3.78mmol/(h.g)。但Y2Cu2O5在草酸溶液中不稳定,会与草酸反应生成Y2(C2O4)3.2H2O,导致产氢活性降低。     

K2La2Ti3O10的制备和光催化产氢性能

通过聚合-配合方法和溶胶-凝胶方法,制备了具有层状钙钛矿结构复合氧化物K2La2Ti3O10光催化剂,采用X射线衍射(XRD)、紫外-可见漫反射光谱(DRS)、扫描电镜(SEM)等手段进行表征;以I-为电子给体,比较了制备方法对K2La2Ti3O10分解水产氢活性的影响.研究结果表明,溶胶-凝胶法制备的K2La2Ti3O10比聚合-配合法制备的K2La2Ti3O10光催化产氢活性要高出1倍左右,且制备条件友好,所得K2La2Ti3O10具有较好的单相性;获得了以I-为电子给体,溶胶-凝胶法制备的K2La2Ti3O10分解水的最佳实验条件:产氢的最佳pH值为11.5,RuO2的负载量为0.2%～0.3%.     

La2(Zr0.7Ce0.3)2O7固相合成行为及热物理性能

采用固相合成制备了热障涂层陶瓷材料La2(Zr0.7Ce0.3)2O7(LZ7C3)。通过差热分析、X射线衍射等分析方法对固相合成行为影响因素进行研究,并用激光脉冲法和高温膨胀仪测试了LZ7C3粉末的热扩散系数和热膨胀系数。结果表明:完全合成LZ7C3的温度至少1400℃,煅烧时间至少5 h,反应粉末的粒度为0.82μm时,合成的LZ7C3粉末X射线衍射图谱没有La2 O3残留峰,其La∶Zr∶Ce为50.09∶35.12∶14.79,非常接近理论原子比例10∶7∶3;LZ7C3的热导率在1200℃时为0.79 W.m-1.K-1,热膨胀系数在1200℃时为11.6×10-6K-1,从室温到1200℃的加热过程中没有失重和相变发生,具有较高的相稳定性。     

以Li_2TiO_3为原料合成Li_4Ti_5O_(12)的机理和电化学性能

以偏钛酸锂(Li2TiO3)和二氧化钛(TiO2)为原料,采用固相法合成钛酸锂(Li4Ti5O12),通过XRD、SEM和电化学测试等方法对合成的钛酸锂材料的结构、形貌和电化学性能进行表征,同时研究一次颗粒长大规律和反应机理。结果表明:Li2TiO3是传统固相法合成Li4Ti5O12的中间产物,用Li2TiO3为原料在720、750℃保温10 h可合成纯的Li4Ti5O12,制备的一次颗粒粒径分别为270、278 nm,较用Li2CO3和TiO2为原料合成纯相的温度更低,一次颗粒粒径更小。反应期间,一次颗粒粒径随着反应分数的增大呈快速增长势头;反应结束后,一次颗粒粒径增长缓慢。750℃合成的Li4Ti5O12在充放电倍率为0.1C、1C、5C、9C时,比容量分别为170、164、149、126 m A·h/g,在0.1C时循环200次容量保持率大于97%,显示制备的Li4Ti5O12具有良好的电化学性能。     

微波法制备LaF3超细粉

以La2O3、HCl为原料制备了LaCl3,并直接用双柱法,以LaCl3溶液同NH4HCO3溶液作用合成了粒度较小的La2(CO3)3粉体;以粉体La2(CO3)3为镧源与NH4F混合,在微波作用下经过固相化学反应,合成了LaF3超细粉;研究了不同分散剂等反应条件对合成LaF3超细粉的粒度和纯度的影响;通过X射线衍射(XRD)检测了不同途径合成的LaF3超细粉体的纯度,通过扫描电镜(SEM)、透射电镜(TEM)测试了不同途径合成的LaF3超细粉体颗粒的粒度和形貌.结果表明:用乙醇作为分散剂经微波加热固相合成得到了纯度较高,平均粒度约为50 nm的LaF3超细粉.     

掺镧方式对La-TZM合金性能的影响

采用粉末冶金法在TZM合金的基础上,分别进行固-固掺杂稀土La2O3,固-液掺杂La(NO3)3,经烧结、热轧、温轧、冷轧后得到不同掺杂方式的La-TZM合金板材。用SEM观察粉末形貌、烧结坯组织及板材断口形貌,用粒度分布、EDS分别对合金粉末粒度及合金成分进行分析。结果表明:固-液掺杂La(NO3)3比固-固掺杂稀土La2O3的La-TZM合金板材第二相分布更为均匀、细小;晶粒尺寸较小;且固-液掺杂La(NO3)3合金的抗拉强度比固-固掺杂稀土La2O3也有显著提高,使其提高了10.9%。     

La对氟盐法制备Al-Ti-B-La反应机理及其细化效果的影响

利用氟盐法制备Al-5Ti-1B和Al-5Ti-1B-1La中间合金,对比分析稀土La添加对合成反应速率、第二相粒子的形态及物相组成的影响,并对比研究中间合金对纯铝和Al-8Si合金的细化效果。结果表明:添加稀土La元素会加速氟盐反应的进行,有利于Ti、B元素的吸收;稀土La可以有效地细化Al_3Ti相,并与其反应生成细小弥散分布的Al_(20)Ti_2La相,同时减弱TiB2相聚集成团的倾向,在细化纯铝过程中表现出更优异的细化长效性;在细化Al-8Si合金过程中,Al-5Ti-1B-La中间合金中所存在的大量细小弥散的第二相形核粒子可以有效地细化铝基体,同时Al_(20)Ti_2La相熔解所释放的稀土La原子还可以对硅相产生变质细化作用,表现出较强的细化效果。     

KzLa2Ti3O10的制备和光催化产氢性能

通过聚合-配合方法和溶胶-凝胶方法，制备了具有层状钙钛矿结构复合氧化物K2La2Ti3O10光催化剂，采用X射线衍射（XRD）、紫外-可见漫反射光谱（DRS）、扫描电镜（SEM）等手段进行表征：以I-为电子给体，比较了制备方法对K2L。2Ti3O10分解水产氢活性的影响。研究结果表明，溶-凝胶法制备的KELaETi3O10比聚合-配合法制备的K2LaETi3O10光催化产氢活性要高出1倍左右，且制备条件友好，所得K2La2Ti3O10具有较好的单相性：获得了以I-为电子给体，溶胶-凝胶法制备的K2La2Ti3O10分解水的最佳实验条件：产氢的最佳pH值为11,5，RuO2的负载量为0.2％～0.3％。     

La2O3改性Mg-Ni纳米复合粒子的结构及电化学性能

采用直流电弧等离子体法制备出Mg-Ni和Mg-Ni/La2O3两种镁基合金纳米粒子,研究了稀土氧化物La2O3对Mg-Ni纳米粒子进行表面改性后对其相结构及电化学性能的影响。结果表明:稀土氧化物La2O3对Mg-Ni纳米粒子进行表面掺杂改性后,有效地抑制了MgO和Mg(OH)2相生成。掺杂La2O3以后,Mg-Ni纳米粒子的电化学性能得到了明显的改善,提高了它在强碱性介质中的耐蚀性能和放电性能。     

磁场辅助烧结法制备La0.67Mg0.33Ni3储氢合金

采用磁场辅助烧结合成法（MASS）制备了化学计量比为La0.67Mg0.33Ni3的储氢合金,通过X射线衍射（XRD）、等温定容法（PCT）和差示扫描量热法（DSC）分析了合金的相结构和吸放氢性能。XRD结果显示：合金主相为PuNi3型结构的(La, Mg)Ni3,氢化后分解为以La2Ni7、MgNi2和LaNi3结构为主的复相产物,合金因吸氢发生晶格膨胀。PCT测试表明：1 T磁场下合成的合金在室温下具有最小的滞后系数（0.480）、最大的放氢量1.307（质量分数,%）,综合性能最优。该合金放氢DSC曲线上有2个交叠的吸热峰,分别对应于(La, Mg)Ni3和LaNi5氢化后的放氢过程。     

Ethanol-assistant solution combustion method to prepare La2O2S:Yb,Pr nanometer phosphor

La₂O₂S:Yb,Pr nanometer phosphor have been prepared by a novel ethanol-assistant solution combustion (EASC) method in ethanol–water solution medium via a relatively mild and slow combustion process, using ethanol as preigniting fuel and inexpensive thioacetamide as sulfur-containing organic fuel. Investigation results show: ethanol preigniting serves the role of ignition combustion decomposition reaction between rare earth nitrate and organic fuel and promotes the formation of uniform and less agglomerative rare earth oxysulfide nanocrystals. Single phase Ln₂O₂S:Yb,Pr nanocrystals are obtained with appropriate ethanol/water ratio and further annealing at 1000 °C for 2 h in reduced atmosphere. The La₂O₂S:Yb,Pr nanocrystals exhibit an intense green emission assigned to the Pr³⁺ ions ³P₀ → ³H₄ transition and a broad near infrared (NIR) emission under 980 nm pump. The defects residing in La₂O₂S:Yb,Pr nanocrystals is the probable origins for the NIR emission. The annealing process makes the green emission improve and the NIR emission weaken. After annealing treatment at 1000 °C, the upconversion luminescence intensity is close to that of the bulk sample prepared by a solid-state reaction method.     

纳米级和微米级稀土氧化物掺杂W-La2O3-Y2O3-ZrO2 阴极尖端的组织和性能

使用粉末冶金法将纳米级(70–80 nm)和微米级(500–600 nm)稀土氧化物(La₂O₃,Y₂O₃)与钨粉混合,随后通过冷等静压、中频感应烧结、旋锻、拉拔等一系列工艺制备了W-1.5La₂O₃-0.1Y₂O₃-0.1ZrO₂(质量分数,%)材料。对含有纳米和微米尺寸稀土氧化物的阴极样品使用相同的焊接电流,分别进行了0.5、1、2 h的氩弧焊。结果表明,具有纳米级稀土氧化物的样品在焊接过程中表现出更高的工作稳定性,烧损同比降低了近85.4%。此外,随着工作时间的延长,阴极尖端不同区域的稀土氧化物聚集度显著增加。结合COMSOL Multiphysics温度模拟发现,第二相的扩散活化能降低了近34%。这是因为更为细小的第二相有效地控制了钨基体组织的演变,保留了大量晶界作为通道,促进了活性物质在电子发射过程中的扩散。     

Synthesis and characterization of La2Ti2O7 employed for photocatalytic degradation of reactive red 22 dyestuff in aqueous solution

Perovskite structured La₂Ti₂O₇ catalyst prepared by polymerized complex method was characterized and examined the photocatalytic activity by decomposing an azo dyestuff, Reactive Red 22, in aqueous solutions under UV irradiation. La₂Ti₂O₇ powders prepared by polymerized complex method exhibit higher surface areas, better homogeneity and are more sensitive to solution than those prepared by solid-state method. The first derivatives of UV–vis DRS patterns confirmed the complete crystallization of La₂Ti₂O₇ sintered at temperatures higher than 900 °C. The effects of sintering temperature of catalyst and solution pH of photocatalytic reaction were studied. The photocatalytic decomposition of Reactive Red 22 per unit surface area was found to be higher for experiments using La₂Ti₂O₇ than using TiO₂. However, the electron–hole recombination was found to be more obvious for La₂Ti₂O₇ than for TiO₂ because the network of metal cations constructed within La₂Ti₂O₇ enhances the mobility of photogenerated electrons and holes.     

Effect of Al on high-temperature corrosion of Co-15a/oNb alloys in H2-H2O-H2S environments

Co–15 at.% Nb alloys containing up to 15 at.% Al were corroded in gaseous H₂–H₂O–H₂S mixtures over the temperature range of 600–900°C. The corrosion kinetics followed the parabolic rate law at all temperatures. Corrosion resistance improved with increasing Al content except at 900°C. Duplex scales formed on alloys consisting of an outer layer of cobalt sulfide and a heterophasic inner layer. A small amount of Al₂O₃ was found only on Co–15Nb–15Al. Contrary to what formed in Co–Nb binary alloys, neither NbS₂ nor NbO₂ were found in the inner layer of all alloys, but Nb₃S₄ did form. The absence of NbS₂ and NbO₂ is due to the formation of stable Al₂O₃ and Al₂S₃ that effectively blocked the inward diffusion of oxygen and sulfur, respectively, and to the reduction of activity of Nb by Al additions in the alloys. Intercalation of ions in the empty hexagonal channels of Nb₃S₄ is associated with the blockage of the transport of cobalt. An unknown phase (possibly Al_0.5NbS₂) was detected. Alloys corroded at 900°C were abnormally fast and formed a scale containing CoNb₃S₆ and Co. Pt markers were found at the interface between the inner and outer layers.     

Effect of MoSi2/rare earth composite particles on microstructure and mechanical properties of molybdenum

MoSi₂/La₂O₃ and MoSi₂/Y₂O₃ composite particles were prepared by mechanical milling and doped into molybdenum by solid-solid method, respectively. Rods with a diameter of 17 mm were made by pressing and sintering. The effects of different composite particles on microstructures and strength of the as-sintered molybdenum were investigated. Results show that the MoSi₂/La₂O₃ and MoSi₂/Y₂O₃ composite particles transformed to La₂O₃/Mo₅Si₃ and Y₂O₃/Mo₅Si₃ composite particles due to the in situ reaction between Mo and MoSi₂ during sintering process. Mo₅Si₃/La₂O₃ and Mo₅Si₃/Y₂O₃ composite particles can reduce the grain size and improve both strength and toughness of sintered molybdenum significantly. Mo₅Si₃/Y₂O₃ composite particles contribute more to the strength, while the effect of Mo₅Si₃/La₂O₃ on toughness is greater than that of Mo₅Si₃/Y₂O₃.     

La2O3包埋渗硼TB2钛合金的腐蚀与磨损性能

为了改善TB2合金的表面性能,采用4％La2O3(质量分数)包埋渗硼法对TB2合金进行1100℃,20 h渗硼处理,研究TB2钛合金的渗硼层组成与厚度以及腐蚀与磨损性能.结果表明,La2O3在渗硼过程中促进硼化物层的生长,提高其连续性和致密性,TiB晶须长度从16.80增至21.84μm.这是因为La2O3能与B反应生...     

Synthesis of LiNi1/3CO1/3Mn1/3O2 cathode material via oxalate precursor

Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation method. And then the LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion battery were prepared from the precursor and LiOH-H2O by solid-state reaction. The precursor and LiNi1/3Co1/3Mn1/3O2 were characterized by chemical analysis, XRD, EDX, SEM and TG-DTA. The results show that the composition of precursor is Ni1/3Co1/3Mn1/3C2O4·2H2O. The product LiNi1/3Co1/3Mn1/3O2, in which nickel, cobalt and manganese are uniformly distributed, is well crystallized with a-NaFeO2 layered structure. Sintering temperature has a remarkable influence on the electrochemical performance of obtained samples. LiNi1/3Co1/3Mn1/3O2 synthesized at 900 ℃ has the best electrochemical properties. At 0.1C rate, its first specific discharge capacity is 159.7 mA·h/g in the voltage range of 2.75-4.30 V and 196.9 mA·h/g in the voltage range of 2.75-4.50 V; at 2C rate, its specific discharge capacity is 121.8 mA·h/g and still 119.7 mA·h/g after 40 cycles. The capacity retention ratio is 98.27%.     

The corrosion of copper by atmospheric sulphurous gases

The sulfurization of copper by atmospheric gases is widely recognized, but the importance of the potential causative agents of sulfurization and the mechanisms involved have remained unresolved. In this work, polycrystalline copper has been exposed to the atmospheric gases hydrogen sulfide (H₂S), carbonyl sulfide (OCS), carbon disulfide (CS₂), and sulfur dioxide (SO₂) in humidified air under carefully controlled laboratory conditions. At room temperature, the rates of sulfurization by H₂S and OCS are comparable, and are some two orders of magnitude greater than those by CS₂ and SO₂. Given the atmospheric concentrations of these gases, it is clear that OCS is the principal cause of atmospheric sulfurization of copper except near sources of the gases where high concentrations may render H₂S (and possibly SO₂) important. At constant absolute humidity, the sulfurization rate of copper by OCS is found to be inversely proportional to temperature over the range 21–80°C, a property attributed to reduced quantities of surface water at high temperatures and the subsequent decrease in the rate of hydrolytic transformation of OCS into a reactive form. In a final series of experiments, the initial sulfurization of copper by 2.2 ± 0.2 ppm H₂S in humidified air at 22°C has been studied in detail. The first stages of sulfurization involve rapid attack by H₂S at surface defect sites. As these corrosive mounds spread and merge, diffusion of copper to the surface is impeded and the fraction of H₂S molecules striking the surface that become incorporated into the corrosion film drops sharply from ～ 5 × 10^?5 (at t = 5 s) to ～ 8 × 10^?7 (at t = 72 h).     

Influence of La and Dy on the properties of the long afterglow phosphor CaAl2O4: Eu, Nd

The long afterglow phosphor CaAl₂O₄:Eu²⁺,Nd³⁺ was prepared by the high temperature solid-state reaction method, and the influence of La³⁺ and Dy³⁺ on the properties of the long afterglow phosphor was studied by X-ray diffraction (XRD), photoluminescence (PL), and thermoluminescence (TL). The XRD pattern shows the host phase of CaAl₂O₄ is produced and no impurity phase appears. The peak wavelength of the phosphor does not vary with La³⁺ and Dy³⁺ doping. It implies that the crystal field, which affects the 5d electron states of Eu²⁺, is not changed dramatically after doping of La³⁺ and Dy³⁺. The TL spectra indicate that the phosphor doped with La³⁺ or Dy³⁺ produces different depths of trap energy level. In the mechanism of long afterglow luminescence, it is considered that La³⁺ or Dy³⁺ works as trap energy level. The decay time lies on the number of electrons in the trap energy level and the rate of the electrons returning to the excitation level.     

Synthesis and Properties of La2O3-Doped 8 mol% Yttria-Stabilized Cubic Zirconia

In this study, 8 mol% yttria-stabilized cubic zirconia (8YSZ) powder as a matrix material and 0-15 wt.% La₂O₃ powder as an additive were used to determine the effect of La₂O₃ addition and its amount on the phase stability, microstructure, sintering, and mechanical properties of 8YSZ. Colloidal processing was used to mix the powders uniformly and to obtain a homogenous microstructure. XRD results showed the existence of only a cubic crystal structure for 1 and 5 wt.% La₂O₃ addition amounts. However, La₂Zr₂O₇ with a hexagonal and cubic crystal structure was observed in 8YSZ specimens doped with 10 and 15 wt.% La₂O₃. Further, up to 5 wt.% La₂O₃ was completely dissolved in the crystal structure of the specimens; however, above 5 wt.%, La₂O₃ reacted with 8YSZ at high temperatures and formed pyrochloric La₂Zr₂O₇. Grain size measurements revealed that the grain size of 8YSZ increased up to 1 wt.% La₂O₃ addition, and then decreased beyond this amount. The hardness and fracture toughness of 8YSZ decreased and increased, respectively, with the increasing La₂O₃ amount.