第二相粒子（La2O3）尺度对钼镧线切割丝使用性能的影响

采用SEM、TEM和能谱仪等研究掺杂镧钼丝中的La₂O₃粒子在线切割过程中的行为和作用机制。结果表明,在钼丝中掺杂少量La,钼丝使用寿命、切割面积显著提高;La₂O₃是阴极热电子的主要发射源,在切割过程中La₂O₃粒子的活化、蒸发使La在镧钼丝的表面分布均匀。     

铬、钼对耐候钢熔敷金属耐蚀性能和力学性能的影响

通过周浸加速腐蚀试验、锈层微观分析、电化学等方法,研究了铬和钼对耐候钢熔敷金属耐蚀性能和力学性能的影响.结果表明,熔敷金属中铬、钼含量增加,其耐蚀性能提高.钼对耐蚀性的提升优于铬.铬、钼分别以Cr₂O₃,Fe_xCr_3-xO₄,MnFe_xCr_2-xO₄,Mn_1-xFe_xCr₂O₄,NiFe_xCr_2-xO₄和MoO₃形式富集于锈层中,提高锈层致密性,抑制阳极溶解,增强锈层对基体的保护作用,从而提高熔敷金属的耐蚀性能.铬、钼含量增加,熔敷金属强度上升,冲击韧性明显下降.同时,熔敷金属中M-A组元和粒状贝氏体含量增加,针状铁素体含量降低.组织差异是造成熔敷金属强度升高、韧性降低的主要原因.     

一步法合成La0.4Sr0.6Co0.2Fe0.7Nb0.1O3-δ-Ce0.8Gd0.2O2-δ对称电极应用于SOFC性能研究

一步法合成La_0.4Sr_0.6Co_0.2Fe_0.7Nb_0.1O_3-δ-Ce_0.8Gd_0.2O_2-δ(LSCFN-CGO)混合电导对称电极,并采用La_0.8Sr_0.2Ga_0.83Mg_0.17O_3-δ(LSGM)作为电解质制备了结构为LSCFN-CGO‖_LSGM‖LSCFN-CGO的对称电池。分别使用X射线衍射(XRD)仪和扫描电子显微镜(SEM)对LSCFN-CGO粉体物相及电极微观结构进行分析。一步法制得的LSCFN-CGO电极粉体为纯相,LSCFN钙钛矿相与CGO萤石相具备极好的化学相容性,且烧结得到了良好微观结构的对称电极。采用H₂(3%H₂O)、C₃H₈(3%H₂O)为燃料气测试电池性能,850℃电池最大功率密度可分别达980和869mW/cm²。稳定性测试在C₃H₈(3%H₂O)气氛中0.3 A/cm²的恒流放电条件下进行,全程共420 h,衰减较小,期间进行8次电极氧化还原循环,对称电极具有理想的碳基燃料下氧化还原再生能力。结果表明,采用一步法合成混合电导电极是一种简便、优化的电极制备方法,具有广阔的应用前景。     

三层共烧制备LaCrO3基连接体/复合阳极/YsZ电解质的研究

将La_0.7Ca_0.3Cr_0.97O_3-δ（LCC）连接材料引入到NiO/YSZ阳极中,制备NiO/YSZ/LCC三相复合阳极,并进行烧结特性、微观结构、电导率、热嘭胀系数等性能对比测试.结果表明,NiO/YSZ/LCC新型复合阳极具有优良的综合性能.采用浆料浸渍法在NiO/YSZ/LCC阳极戈撑体两个表面上分别制备LCC和YSZ湿膜,1400℃空气条件下三层共烧4 h后,获得致密LCC连接体和YSZ电解质薄膜.     

TC4钛合金表面氧化镧催渗渗硼工艺优化

以渗层厚度和表面硬度为评定依据,采用正交试验对TC4钛合金表面氧化镧催渗渗硼工艺进行优化。结果表明,渗硼温度对渗硼层影响最大,其次为渗硼时间、B₄C含量和La₂O₃含量。最优的催渗渗硼工艺为：渗硼温度1050 ℃,渗硼时间20 h,渗硼剂配比20wt%B₄C+4wt%La₂O₃+76wt%SiC。渗层表面由TiB、Ti₂B₅、TiC和Ti组成;与未添加氧化镧渗硼层相比,添加氧化镧渗硼层厚度与表面硬度明显提高,耐磨性也得到显著改善。     

Y2O3对铁基金刚石工具性能的影响

采用正交试验方法研究热压压力、烧结温度和Y₂O₃含量等3个因素对铁基胎体硬度、致密度、抗弯强度和断口微观形貌等的影响,并获得较优的烧结工艺参数。在此基础上,制备含Y₂O₃的铁基金刚石工具,并对其断口形貌、耐磨性和锋利度等进行检测及分析。结果表明:含Y₂O₃的铁基结合剂胎体,其相对密度和硬度的影响因素次序为Y₂O₃含量＞烧结温度＞热压压力,抗弯强度的影响因素次序为烧结温度＞Y₂O₃含量＞热压压力;且Y₂O₃能促进铁基金刚石胎体组织的致密化,降低其烧结温度。在烧结温度为780 ℃、热压压力为51 kN的较优烧结工艺下,适量的Y₂O₃能使金刚石工具的孔隙率减小、黏结状况改善,并增强黏结剂对金刚石磨粒的把持能力。      

Hf含量对湿化学法制备超细W-Y2O3复合材料显微组织与性能的影响

本文在现有W-Y₂O₃材料基础上,引入微量Hf⁴⁺掺杂入Y₂O₃,调节Y₂O₃与W晶粒之间的界面关系,从而改善W基材料的综合性能。通过改变Y与Hf元素的掺杂比例,获得纳米级W基复合粉体,在氢气气氛下常规烧结制备W-Y₂(Hf)O₃复合材料。采用SEM、TEM等表征手段对W-Y₂(Hf)O₃复合材料的性能进行表征分析,研究Y与Hf元素在材料中的作用规律。结果表明：掺杂Hf元素有利于后续氢气还原,在第二相掺杂量不变条件下,当Hf含量增加时,所获得的粉体粒径减小,W-3Y-7Hf的粒径约为100 nm,明显小于传统制备的W-Y₂O₃粉体。烧结后的块体晶粒尺寸细化,显微硬度和相对密度随之增大,成分为W-3Y-7Hf烧结块体显微硬度最高,为513.7HV_0.2,致密度为97.6%。在钨基材料中...     

Y2O3 对DZ125合金表面Cr-Al-Y渗层的组织结构及抗氧化性能影响

为进一步提高DZ125合金高温服役性能,通过扩散渗方法在其表面制备了稀土元素Y改性的Cr-Al共渗层,研究了Y₂O₃含量对渗层组织结构及抗高温氧化性能的影响。结果表明：不同条件下制备的Cr-Al-Y渗层均具有三层结构,由外向内依次为：Cr+Ni₃Cr₂外层,Ni₃Cr₂+Al₁₃Co₄中间层,以及Ni₃Al内层。当渗剂中Y₂O₃含量为0%～2%(质量分数,下同)时,渗层的厚度与密度显著增加;当稀土Y₂O₃的添加量过高时(5%),渗层的密度及厚度反而下降。1100℃高温氧化实验表明,Cr-Al-Y渗层显著提高了DZ125合金的抗高温氧化性能。     

多孔Ni-Cu-Ti-La2O3复合电极的制备及其析氢性能

采用粉末冶金方法烧结制备了多孔Ni-Cu-Ti-La₂O₃复合电极,讨论不同La₂O₃的掺杂量对电极析氢性能的影响。利用X射线衍射(XRD)、扫描电镜(SEM)、能谱仪(EDS)等测试手段对电极的微观结构和物相组成进行表征。结果表明：Ni-Cu-Ti合金体系中La₂O₃的掺杂可有效提高电极材料的电荷传输速率,多孔Ni-Cu-Ti-La₂O₃复合电极在6 mol/L KOH溶液中表现出良好的析氢催化活性,其整体析氢催化活性明显优于多孔Ni-Cu-Ti、Ni-Cu-W、Ni-Cu-Co、Ni-Cu-Zr和Ni-Cu电极;当烧结温度为1000℃时,成分为Ni-CuTi-9La的多孔复合电极具有最佳的析氢催化性能,其Tafel斜率为63.18 mV/dec,电流密度在10 mA/cm²时过电位为1077 mV(vs Hg/HgO),多孔Ni-Cu-Ti-La₂O₃     

氧化镧添加剂和盐浴共渗温度对TC4钛合金硼氧共渗组织与性能的影响

采用OM、SEM、XRD、EDS、维氏硬度计以及摩擦试验机等分析手段研究了氧化镧添加剂和共渗温度对盐浴硼氧共渗试样组织与性能的影响。结果表明,共渗层厚度随着La₂O₃添加量的增加先增大后减小,当La₂O₃添加量为3%时,共渗层厚度达最大值(32.74 μm);与低温(950 ℃)相比,高温(1000 ℃)时盐浴共渗层具有较好的表面,较高的共渗层厚度(34.19 μm),较高表面硬度(1211 HV0.2),较大界面结合力(87.36 N)和更低的摩擦因数(0.28)。通过将温度对共渗过程的影响和试验结果分析得出:高温1000 ℃盐浴硼氧共渗试验更有研究价值。     

Synthesis and characterization of doped LaCrO3 perovskite prepared by EDTA–citrate complexing method

The La_0.85Sr_0.15Cr_0.95Ni_0.02Co_0.02O₃ (LSC) interconnect materials for solid oxide fuel cells (SOFCs) were synthesized by EDTA–citrate complexing method. Thermal decomposition behavior of the gel, phase formation and morphology of LSC powders were characterized by thermogravimetry/differential thermal (DSC/TG) analysis, X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. It appeared that lower pH value (pH 4.9) of the precursor solution resulted in a transient liquid phase, SrCrO₄, in the calcined LSC powder. The sintering characteristics, electrical conductivity and thermal expansion properties of sintered bars were investigated. La_0.85Sr_0.15Cr_0.95Ni_0.02Co_0.02O₃ prepared in the condition of pH 4.9 showed an electrical conductivity of 15.6 S cm⁻¹ at 800 °C and a thermal expansion coefficient (TEC) of 10.8 × 10⁻⁶ K⁻¹ (20–900 °C), which is suitable for use as interconnect materials for SOFCs.     

Self-propagating high-temperature synthesis of La(Sr)Ga(Mg)O3−δ for electrolyte of solid oxide fuel cells

This paper describes self-propagating high-temperature synthesis (SHS) of an electrolyte for solid oxide fuel (SOFC), in comparison to a conventional solid-state reaction method (SRM). Doped-lanthanum gallate: La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM9182) and LSGM9173 as the SOFC electrolyte, was prepared by the SHS and sintered at different temperatures, for measuring the electrical conductivity of the sintered LSGM and the power generating performance at 1073 K, in comparison to the SRM. In the SHS, the LSGM powders with smaller size were obtained and easily sintered at the 100 K-lower temperature, 1673 K, than in the SRM. Most significantly, the electrical conductivity of the sintered LSGM9182 was as high as 0.11 S cm⁻¹ and its maximum power density was a value of 245 mW cm⁻² in the cell configuration of Ni/LSGM9182 (0.501 mm in thickness)/Sm_0.5Sr_0.5CoO₃. The conclusion was that the proposed SHS-sintering method with many benefits of minimizing the energy requirement and the processing time in the production, easing temperature restriction for the sintering, and improving the electrolyte performance up to a conventional level is practicable for producing the LSGM-electrolyte of SOFC at an intermediate-temperature application.     

Sm0.5Sr0.5CoO3 cathode material from glycine-nitrate process: Formation, characterization, and application in LaGaO3-based solid oxide fuel cells

Cathode material Sm_0.5Sr_0.5CoO₃ (SSC) with perovskite structure for intermediate temperature solid oxide fuel cell was synthesized using glycine-nitrate process (GNP). The phase evolution and the properties of Sm_0.5Sr_0.5CoO₃ were investigated. The single cell performance was also tested using La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM) as electrolyte and SSC as cathode. The results show that the formation of perovskite phase from synthesized precursor obtained by GNP begins at a calcining temperature of 600 °C. The single perovskite phase is formed completely after sintering at a temperature of 1000 °C. The phase formation temperature for SSC with complete single perovskite phase is from 1000 to 1100 °C. The SrSm₂O₄ phase appeared in the sample sintered at 1200 °C. It is also found that the sample sintered at 1200 °C has a higher conductivity. The electrical conductivity of sample is higher than 1000 S/cm at all temperature examined from 250 to 850 °C, and the highest conductivity reaches 2514 S/cm at 250 °C. The thermal expansion coefficient of sample SSC is 22.8 × 10⁻⁶ K⁻¹ from 30 to 1000 °C in air. The maximum output power density of LSGM electrolyte single cell attains 222 and 293 mW/cm² at 800 and 850 °C, respectively.     

Thermal cycle behavior of plasma sprayed La2O3, Y2O3 stabilized ZrO2 coatings

The effects of La₂O₃ addition on thermal conductivity, phase stability and thermal cycle life of Y₂O₃ stabilized ZrO₂ plasma sprayed coatings were investigated. Although low thermal conductivity as well as high resistance to sintering was achieved by La₂O₃ addition, it tended to also result in lower phase stability and thermal cycle life of the coatings. Optimization of the composition and structure of the coatings improved these properties, and the optimized coatings showed prolonged thermal cycle life.     

La0.9Sr0.1Ga0.8Mg0.2O3−δ sintered by spark plasma sintering (SPS) for intermediate temperature SOFC electrolyte

The La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM) powders for intermediate temperature SOFC electrolyte have been synthesized by glycine-nitrate combustion process. The as-synthesized powders show almost pure perovskite phase. And then, the as-synthesized powders were sintered by SPS at 1300 °C to prepare electrolyte. The SEM, XRD and AC impedance were employed to characterize the microstructure, phase and electrical conductivities. Results show that the grain size is very fine, less than 1 μm, and the relative density of the pellet after sintering by SPS is about 94.7%. There is very little amount of secondary phases after SPS and the grain boundary and secondary phase resistance is very small. The electrolyte sintered by SPS shows higher conductivities than that sintered by conventional method at the same temperature. The activation energy at lower temperatures (400–700 °C) and higher temperatures (700–800 °C) is about 0.94 and 0.49 eV, respectively. Spark plasma sintering is a promising and effective method to sinter the LSGM electrolyte.     

Enhanced Thermochemical H_2 Production on Ca-Doped Lanthanum Manganite Perovskites Through Optimizing the Dopant Level and Re-oxidation Temperature

Perovskite material is one of the promising classes of redox catalysts for hydrogen production through two-step thermochemical H20 splitting. Herein, an analogue of La_(1-x)Ca_xMnO_3 perovskite was systematically investigated as a catalyst for thermochemical H2 evolution. The Ca doping level(x = 0.2, 0.4, 0.6, 0.8) and re-oxidation temperature were comprehensively optimized for the improvement of catalytic performance. According to our experimental results, La_(0.6)-Ca_(0.4)MnO_3 perovskite displayed the highest yield of H2 at the re-oxidation temperature of 900℃ and the obtained H2 production was-10 times higher than that of the benchmark ceria catalyst under the same experimental condition. More importantly, La_(0.6)Ca_(0.4)MnO_3 perovskite catalyst exhibited impressive cyclic stability in repetitive O_2 and H_2 test.     

Structure and hydrogen storage properties of MgH2 catalysed with La2O3

The catalytic effect of the addition of lanthanum oxide (La₂O₃), in the range 0.5–2.0 mol%, on the hydrogen storage properties of MgH₂ prepared by ball milling has been studied. The addition of La₂O₃ reduces the formation during milling of the metastable orthorhombic γ-MgH₂ phase. The desorption rate of samples with 1 and 2 mol% La₂O₃ comes out to be about 0.010 wt% per second at 573 K under an hydrogen pressure of 0.3 bar, better than for sample with 0.5 mol% La₂O₃. The presence of LaH₃ after hydrogenation/dehydrogenation cycles has been observed in all samples. The sample with 1 mol% of La₂O₃ gives a lower hysteresis factor compared with sample with 2 mol%.     

Corrosion Behavior of MgZnCa Bulk Amorphous Alloys Fabricated by Spark Plasma Sintering

Centimeter-sized Mg_(65)Zn_(30)Ca_5 bulk amorphous alloys were fabricated by the spark plasma sintering process from the amorphous powders with a size smaller than 5 l m prepared by ball-milling.The sintered Mg_(65)Zn_(30)Ca_5samples were in an amorphous state when the spark plasma sintering was performed at a temperature of 383 K under a pressure of 600 MPa.The data of polarization curves presented that the sintered Mg_(65)Zn_(30)Ca_5bulk amorphous alloys exhibited higher corrosion resistance than pure Mg and AZ31B alloy owing to high content of Zn and homogeneous structure.A calcium phosphate compound layer was formed on the sintered Mg_(65)Zn_(30)Ca_5bulk amorphous sample after immersion in Hanks’solution,which is effective in improving corrosion resistance and bioactivity.The sintered Mg Zn Ca bulk amorphous alloys with large dimensions broaden the potential application of bulk amorphous alloys in the biomedical fields.