Influence of La2O3 addition on microstructure and wear resistance of Fe-Cr-C cladding formed by arc surface welding

The Fe-Cr-C claddings formed by arc surface welding with different La2O3 additions were investigated. The microstructures were observed by optical microscopy (OM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The phase structures were measured by X-ray diffraction (XRD). The wear resistances of the claddings were tested by friction and wear experiment. On this basis, the carbide refinement mechanism by inclusion enriched with La was discussed theoretically. The results showed that, the microstructure of the Fe-Cr-C cladding consisted of primary (Cr,Fe)7C3 carbides and eutectic (γ-Fe+(Cr,Fe)7C3 ) structure. With La2O3 addition increasing, the primary carbides were refined, and the mass loss of the cladding decreased gradually. The Fe-Cr-C cladding with 4wt.% La2O3 addition had a best wear resistance behaviour. The RE inclusion LaAlO3 as heterogeneous nuclei of the primary M7C3 was medium effective, and could refine the M7C3 carbides. Besides, the wear resistance could be improved by adding La2O3 in the claddings.     

Effect of sintering temperature on morphology and arc erosion properties of La-Ni-O ceramic and its composites

Ceramic LaNiO3 samples were prepared by solid state reaction method at different sintering temperatures. It was found that the resultant was not ABO3 perovskite single phase but dual phase La2NiO4 and NiO, and the percentage of the two phases varied with sintering temperature. Ceramics sintered at 1400 ℃ were well crystallized and the phase ratio of La2NiO4 was the maximum. The surface morphology observed by scanning electron microscopy (SEM) indicated that the grains of the ceramics sintered at 1400 ℃ were uniform and compact, which were in agreement with the properties of high density and low electrical resistivity of the samples. X-ray diffraction (XRD) patterns of ceramics before and after arc erosion indicated their high structural stability, which resulted in the good arc erosion resistance properties for silver-based electrical contact materials. The contact materials prepared with the ceramic sintered at 1400 ℃ exhibited better mass transition and arc erosion resisting properties.     

Influence of lanthanum doping on performance of LiFePO4 cathode materials for lithium-ion batteries

Using solid-state synthesis method,a series of samples of lanthanum doped Li1-xLaxFePO4(x=0.0025,0.005,0.0075,0.01) were prepared.Each cathode structural and electrochemical properties were investigated using X-ray diffractometry(XRD),scanning electron microscopy(SEM),electrochemical impedance spectroscopy(EIS) and charge/discharge cycling.Nanopowders material with single-phase could be obtained.The reversible capacity could be drastically improved by the introduction of La.The optimum cells with Li0.99La0....     

稀土La掺杂对层状富锂锰基氧化物正极材料结构及电化学性能的影响

采用碳酸盐共沉淀-高温烧结法制备了La掺杂层状富锂锰基氧化物正极材料Li_1.2Mn_0.54-xNi_0.13Co_0.13La_xO₂（x=0, 0.01, 0.03, 0.05），考察了La掺杂量对正极材料的结构及电化学性能的影响.采用X射线衍射（XRD）和扫描电镜（SEM）分析研究了正极材料的结构和形貌特征，材料的电化学性能采用交流阻抗和充放电测试仪进行测试分析.研究结果表明:所有样品均保持层状α-NaFeO₂结构，随着La掺杂量的增加，样品形貌未发生明显变化，样品放电容量呈现先增大后降低的趋势，当La掺杂量为0.03时，具有最高的放电比容量285.3 mAh/g（0.1 C），经过50次循环后的放电比容量为260.5 mAh/g，容量保持率为91.3 %.      

Effects of annealing on microstructures and electrochemical properties of La0.8Mg0.2Ni2.4Mn0.10Co0.55Al0.10 alloy

The La0.8Mg0.2Ni2.4Mn0.10Co0.55Al0.10 alloy was prepared by induction melting. The structural and morphological characterizations were performed by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical measurements were performed using LAND and CHI 660b electrochemical workstation. The main phases of the alloy were LaNi5 and (La,Mg)Ni3. After annealing, the maximum discharge capacity, cycle stability and high rate dischargeability (HRD) were improved obviously. The maximum discharge capacity reached 373.80 mAh/g (T=1173 K), the C100/Cmax(%) was 72.63% (T=1173 K), and the value of HRD reached 51.8% at a discharge current density of 1150 mA/g (T=1173 K). The cyclic voltammetry (CV) and potentiodynamic polarization were also studied.     

NiO-La2O3/γ-Al2O3催化剂中各组分间的相互作用

本文采用差热分析、X射线衍射、透射电镜和选区电子衍射对催化剂的物种情况及形貌加以研究 ,结合催化剂焙烧过程的相变情况 ,从而获得催化剂焙烧过程的化学反应情况。发现稀土助剂的加入使载体的晶体结构发生变化 ,从而使载体表面改性 ,抑制了 Ni Al2 O4的生成 ,提高了 Ni O的分散度。而且发现有 L a2 O2 CO3晶体存在于载体表面 ,L a2 O3以高度分散的状态存在     

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.     

Effects of lanthanum addition on microstructure and mechanical properties of as-cast pure copper

As-cast Cu-La alloys with La contents in the range of 0–0.32 wt.% were fabricated by vacuum melting method. The effects of La on microstructure and mechanical properties of as-cast pure copper were investigated using optical microscopy(OM), scanning electronic microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and tensile test. The results showed that La had obvious effects on the solidification microstructure and the grain refinement of as-cast pure copper. With the increase of La content, the ultimate tensile strength, the yield strength and the microhardness increased gradually, but the elongation increased first and then decreased while La content exceeded 0.089 wt.%. The improvement of mechanical properties was attributed to the effect of grain refinement strengthening, solid solution strengthening, second phase strengthening and purifying. However, excessive adding La would deteriorate the elongation owing to the excessive Cu6 La phases.     

Hydriding and dehydriding characteristics of nanocrystalline and amorphous Mg20-xLaxNi10（X=0-6） alloys prepared by melt-spinning

In order to improve the hydrogenation and dehydrogenation performances of the Mg2Ni-type alloys, Mg was partially substituted by La in the alloy, and melt spinning technology was used for the preparation of the Mg20-xLaxNi10 (x=0, 2, 4, 6) hydrogen storage alloys. The structures of the alloys were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). It was found that no amorphous phase formed in the as-spun La-free alloy, but the as-spun alloys containing La held a major amorphous phase. When La content x≤2, the major phase in the as-cast alloys was Mg2Ni phase, but with further increase of La content, the major phase of the as-cast alloys changed into LaNi5+LaMg3 phase. Thermal stability of the as-spun alloys was studied by differential scanning calorimetry (DSC), showing that spinning rate was a negligible factor on the crystallization temperature of the amor-phous phase. The hydrogen absorption and desorption kinetics of the as-cast and as-spun alloys were measured using an automatically con-trolled Sieverts apparatus, confirming that the hydrogen absorption and desorption capacities and kinetics of the as-cast alloys clearly in-creased with rising La content. For La content x=2, the as-spun alloy displayed optimal hydrogen desorption kinetics at 200 ℃.     

Study on the preparation and electrochemical performance of rare earth doped nano-Ni（OH）2

Multiphase nano-Ni(OH)2 doped with Y or La was prepared by supersonic co-precipitation method. The crystal morphology, structure and particle size were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and particle size distribution (PSD). The electrochemical performance of samples was investigated by electrochemical workstation and battery tested system. The results indicated that micro-morphology and grain size were changed with the changing of supersonic power, pH values and doping elements. The morphology of Y doped sample was from the flake-like to the needle-like with the increase of supersonic power; Particles were from quasi-spherical particles into needle-like with the increase of pH values; As the supersonic power increased, the proportion of α-Ni(OH)2 increased initially and then decreased. pH value was very important to the formation of crystalline phase. Lower pH value was beneficial to the formation of α-Ni(OH)2. However, the pH values had a slight effect on the reaction reversibility. Complex electrodes were prepared by mixing 8 wt.% nickel hydroxides with commercial micro-size spherical nickel. The discharge capacity of electrodes increased initially and then decreased with the increase of supersonic power. When the supersonic power was 60 W and the pH value was 9, the sample had the largest dis-charge capacity (358 mAh/g) at 0.5 C rate, which was 122.7 and 76 mAh/g higher than the spherical nickel electrode and La doped sample electrode, respectively.     

Age-related differences in movement patterns used by toddlers to rise from a supine position to erect stance

Lanthanum (La) is an extracellular tracer, which stains the interstitial space and the cell surface. This study investigates to what extent the distribution of lanthanum in the myocardium of cardioplegically arrested non-ischaemic hearts was influenced by (a) different incubation times in La containing fixative, (b) different kinds of buffer for rinsing and postfixation dilution and (c) different degree of cellular oedema. Myocytes exhibiting La surface staining, with and without intracellular La, were quantified and the volume density of myofibrils (VVMf) as a parameter for the degree of cellular oedema was determined morphometrically. Samples were taken immediately after cardiac arrest induced by coronary perfusion with a cardioplegic solution. Tissue blocks 1 mm3 in size were fixed by immersion for different time periods in a fixation solution containing 1.1% La(NO3)3. Fixation was followed by rinsing in cacodylate or phosphate buffer. The postfixation solution also contained either cacodylate or phosphate buffer. For La detection electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS), was used. Our results show: (i) the volume densities do not differ significantly in specimens rinsed and postfixed in cacodylate or phosphate buffers; (ii) the percentage of myocytes with La surface staining depends on the incubation time in La containing fixative, independent of the rinsing buffer; (iii) the percentage of myocytes with intracellular La correlates significantly with the VVMf; (iv) the incubation time with La containing fixative does not significantly affect the intracellular La staining of slightly swollen cells; and (v) intracellular La distribution patterns differ in cacodylate- and phosphate-buffered specimens. Thus, La tracer methods in conjunction with microanalysis are valuable tools to detect alterations in membrane permeability not visible by conventional transmission electron microscopy (cTEM) in non-ischaemic hearts exhibiting a well preserved ultrastructure.     

Effects of SrO/Li2O/La2O3/Ta2O5/TiO2-coating on electrochemical performance of LiCoO2

Commercial cathode material (LiCoO2) was modified by coating with a thin layer of SrO/Li2O/La2O3/Ta2O5/TiO2 for improving its performance in lithium ion battery. The morphology and structure of the modified cathode material were characterized by scanning elec-tron microscopy (SEM) and X-ray diffraction (XRD). The performance including cycling stability, diffusion coefficient under different volt-age, C-rate discharge of the batteries with this modified cathode material was examined. The results showed that the battery with the coated cathode material could discharge at a large current density, and it possessed a stable cycle performance in the range from 3.0 V to 4.2 V. It was explained that the rate of Li ion diffusion increased in the batteries using SrO/Li2O/La2O3/Ta2O5/TiO2-coated LiCoO2 as the cathode and the coated layer could act as a fast ion conductor (Sr0.5La0.05Li0.35Ti0.5Ta0.5O3) and as a protecting shell to prevent LiCoO2 particles from be-ing attacked by the acidic electrolyte.     

Behaviors of Lanthanum and Cerium on Grain Boundaries in Carbon Manganese Clean Steel

The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope （HRTEM）, scanning elecetron microscopy（SEM ）, energy dispersive spectrometer （EDS） and X-ray diffraction（XRD） analysis. The existing forms of rare earths （RE） in clean steel were as follows： dissolved in sohd solution, forming inclusion or second phase containing RE （RE-Fe-P, La-P, Fe-La eutectic and Fe-Ce phase）. The dissolved La or Ce segregated at grain boundaries. The segregation of both S and P at gram boundaries was reduced with suitable RE content. The impact toughness of the steel was improved obviously. La and Ce had effecets on purifying molten steel and modifying inclusions in clean steel, whereas with excessive La or Ce, La-Fe-P, La-P and Fe-La eutecetic phase or Ce-Fe-P and Fe-Ce intermetallic compound would form along grain boundaries, causing the impact energy to decrease significantly.     

Analysis of inclusions and precipitates in tough weld metal of X80 steel

Submerged arc welding(SAW)and gas metal arc welding(GMAW)experiments of Nb-bearing X80 steel were conducted with high-toughness wires.The inclusions in weld metals were analyzed in terms of their types and sizes.In GMAW,the inclusions are primarily Ti,Ca,Si,Al,and Mg compounds with no Nb and are generally less than 0.8 pm in size,whereas,in SAW weld,the inclusions are larger,mostly approximately 2-5 μm in size,and are cored with Ca and Ti,exhibiting obvious oxidation metallurgical features.The SAW joint was hot-deformed,and Nb-bearing nano precipitates were newly found in the weld metal through transmission electron microscopy,and Nb-free core-shell inclusion was found through scanning electron microscopy.The inclusions and precipitates were dispersed in or on the boundaries of acicular ferrite,contributing to acicular ferrite nucleation and grain refinement.     

含镧高纯钢中的块状相变组织

 采用金相法和JEM 2010电镜研究了含镧高纯钢的相变。结果表明：固溶镧对γ→α相变影响显著，镧可细化铁素体晶粒。在冰盐水中淬火后，含镧高纯钢中γ→α多型性转变按块状相变方式进行，铁素体晶界不规则，呈块状，有时呈条片状或针状。     

La和Y对细化后A356铝合金显微组织的影响

利用金相显微镜和扫描电子显微镜等设备研究了稀土金属La和Y对经AlTiB和AlSr细化后的A356铝合金α-Al枝晶和共晶Si相显微组织的影响及作用机理。研究表明,金属La和Y加入A356铝合金后以AlSiLa或AlSiY的形式存在于α-Al相晶界中。La和Y不仅对A356铝合金共晶硅相具有明显的变质效果,而且对α-Al晶粒有细化作用。其中Y变质共晶硅和细化α-Al晶粒的效果均优于La。     

Mechanical properties of the A356 aluminum alloy modified with La/Ce

The research of rare earths for the synthesis of materials with improved mechanical performance is of great interest when they are considered for potential applications in the automotive industry. In this regard, the effect on the mechanical properties and microstructure of the automotive A356 aluminum alloy reinforced with 0.2 (wt.%) Al-6Ce-3La (ACL) was investigated. The ACL was added to the melted A356 alloy in the as-received condition and processed by mechanical milling. In the second route, the effect of the ACL processed by mechanical milling and powder metallurgy techniques was investigated, and compared with the results obtained from the A356 alloy strengthened with ACL in the as-received condition. Microstructural properties were evaluated by means of X-ray diffraction in order to observe the solubility of Ce/La in the Al matrix. In addition, electron microscopy was employed in order to investigate the effect of milling time on the size and morphology of La/Ce phase under milling process. Mechanical properties of the A356 alloy modified with ACL were measured by hardness and tensile test. For comparison unmodified specimens of the A356 were characterized according to the previous procedure. The microstructural and mechanical characterization was carried out in specimens after solution and artificial aging. Observations in scanning electron microscopy indicated a homogeneous dispersion of La/Ce phases by using both routes; however, mechanical results, in the modified A356 alloy with the ACL in the as-received condition, showed an improvement in the mechanical performance of the A356 alloy over that reinforced with the ACL mechanically milled.     

Influence of rare earth elements on corrosion behavior of Al-brass in marine water

The corrosion behaviors of Al-brass in stagnant and flowing marine water as a function of combinative rare earths (Ce and La) ad-dition were investigated by electrochemical techniques, X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was demon-strated that RE elements could make the corrosion product layer more protective and strengthen the cohesion between the film and matrix in stagnant seawater. The electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) anal...     

Influence of lanthanum on enhancement of mechanical and electrical properties of Cu-Al_2O_3 composites

Two kinds of Cu-Al_2O_3 composites(with and without La) were prepared via mechanical alloying-spark plasma sintering(MA-SPS) method. Microstructure, mechanical properties and electrical resistivity were investigated systematically using metallography, scanning electron microscopy, transmission electron microscopy, mechanical and electrical properties testing. The results indicate that an appropriate amount of La can homogenize the distribution of Al_2O_3. As such, yield strength, ultimate tensile strength and elongation of Cu-Al_2O_3-La are greatly increased. Some semi-coherent interface between Cu and Al_2O_3 is found, which means a low interface energy. The grain shape of Cu changes to irregular band with the addition of La. This change results in a density decrease of grain boundary and reduces electrical resistance. Lanthanum may exist in the form of La_2O_3.     

聚苯胺/Co0.5Zn0.5La0.1Fe1.9O4复合材料的表征及电磁损耗

采用原位聚合法制备聚苯胺（Pani）/复合材料,使用X射线衍射仪（XRD）、扫描电子显微镜（TEM）和紫外可见吸收光谱（UV-vis）对复合材料进行了表征。XRD结果表明样品为纯Pani和Pani/Co0.5Zn0.5La0.1Fe1.9O4复合材料,SEM照片可知,纯Pani和Pani/Co0.5Zn0.5La0.1Fe1.9O4粒子的平均粒径分别约为150 nm和500 nm,UV-vis光谱表明Pani/Co0.5Zn0.5La0.1Fe1.9O4苯环上的π-π＊和n-π＊分别红移了13 nm和10 nm.在8.2-12.4GHz测试频率范围内,Pani/Co0.5Zn0.5La0.1Fe1.9O4复合材料的介电损耗角正切（tgε）在0.22-0.34之间,磁损耗正切（tgμ）在0.27-0.35之间.