Influence of [La(EDTA)]− on pore structure of activated alumina carrier at high-temperature

The activated alumina as a catalyst carrier were widely used in automotive exhaust catalysts under high temperature, such as, petroleum refining catalysts, hydrogenation and hydrodesulfurization catalyst carrier in China and abroad. γ-Al₂O₃ was the catalyst carrier that was the most widely used and the best carrier of improved specific surface area . However, the activation of the coating consisted of γ-Al₂O₃ were usually transformed into α-Al₂O₃ at 800 °C, causing increased density, reduced specific surface area, and the collapse result of pore structure. While the temperature reached 1200 °C, activation of coating detached from the carrier, the resistance of flowing gas increased, catalytic activity decreased. Addition of La₂O₃ stabilized the γ-Al₂O₃ crystal structure, which would keep the activation stability of coating at a high temperature and inhibit activity loss. The activated alumina carrier treated with the solid-pore-expanding agent containing [La(EDTA)]^? that synthesized using solid and solid-hybrid approach with the thermal stabilizer lanthana and EDTA at the high-temperature had a 10-30 μm large pore porous network-like structure, after alumina was calcined at 1200 °C for 1 h. The specific surface area of four specimen were beyond 120 m²/g, while the sample specific surface area of x([La(EDTA)]^?)=1% was up to 150.36 m²/g.     

Thermally stable lanthanum-doped mesoporous alumina as a stable support for palladium in catalytic oxidation of C3H8

High thermally stable mesoporous alumina doped with lanthanum was synthesized using inorganic nitrates as precursors and employing pluronic P123 （P123, （EO20PO70EO20, EO=ethylene oxide, PO=propylene oxide）） as a structure-directing agent. After calcination at 400 oC, the resultant lanthanum doped alumina exhibited aγ-Al2O3 phase, which was the same as pure alumina. After the thermal treatment up to 1200 oC, La-doped Al2O3 generated only one phase ofθ-Al2O3 rather than two mixed phase ofθ-Al2O3 andα-Al2O3 and the surface area could still maintain 101 m2/g with a keeping pore volume of 0.66 cm3/g. The excellent thermal sta-bility was explained by the titration of strong Lewis acid sites ofγ-Al2O3 with the assistance of highly dispersed lanthanum species covering on alumina. Furthermore, the lanthanum modified mesoporous alumina was preliminarily employed as a stable support for Pd in the catalytic oxidation of C3H8.     

Influence of cooling rate and addition of lanthanum and cerium on formation of nanoporous copper by chemical dealloying of CUlsAIss alloy

The influence of cooling rate and addition of La and Ce on the formation of nanoporous copper by chemical dealloying of Cu15Al85 alloy was studied. The components and microstructures of nanoporous copper were characterized by utilizing X-ray diffrac-tion, field emission scanning electron microscopy and energy dispersive X-ray analysis. N2 adsorption/desorption experiments were used to evaluate specific surface areas of samples. The results showed that, with the increase of cooling rate, phase composition of precursor alloy almost had no change, the ligament size of nanoporous copper had a decrease trend, and specific surface area in-creased gradually. And it was found that the specific surface area of the nanoporous copper obtained by Cu15Al85 alloy containing La and Ce was 63.258 m2/g, which was more than 11.739 m2/g compared with the nanoporous copper dealloying by Cu15Al85 alloy without La and Ce under the same conditions.     

Influence of zirconium addition on microstructure, magnetic properties and thermal stability of nanocrystalline Nd12.3Fe81.7B6.0 alloy

Effect of Zr addition on microstructure, magnetic properties and thermal stability of Nd12.3Fe81.7B6.0 (x=0-3.0) ribbons melt-spun and annealed was investigated. Magnetic measurement using vibrating sample magnetometer (VSM) revealed that Zr addition was significantly effective in improving the magnetic properties at room temperature. The intrinsic coercivity Hci of the optimally processed rib-boris increased monotonically with increasing Zr content, from 751.7 kA/m for x=0 to 1005.3 kA/m for x=3.0. Unlike the coercivity, the re-manence polarization Jr increased first with Zr addition, from 0.898 T up to 1.041 T at x=1.5, and then decreased with further Zr addition.The maximum energy product (BH)max behaved similarly, increasing from 103.1 KJ/m3 to a maximum of 175.2 kJ/m3 at x=1.5. Microstruc-ture studies using atomic force microscopy (AFM) and transmission electron microscopy (TEM) had shown a significant microstructttre re-finement with Zr addition. The absolute values of temperature coefficients of induction and coercivity were significantly increased with in-creasing Zr content, indicating that Zr was detrimental to thermal stability of the melt-spun Nd2Fe14B-type material.     

Influence of Pr on Magnetic Properties and Microstructure of Melt-Spun （ Nd1-x Prx ） 10.5 （FeCoZr） 83.5 B6 Alloy

Inrareearthsores ,praseodymiumoftencoexistswithneodymiumandtheabundanceofPrisaboutonethirdofNd .Becauseofextremeexcellentpermanentmagneticpropertiesoftherareearth transitionmetalin termetalliccompoundNd2 Fe14 B ,Ndhasbeenwidelyutilizedsincethe 1980s .Withtheexploitationofrareearthsores ,Prisexcessiveinmarketandcheapinpricebecauseofitsnarrowapplication .ItisfoundthatPr2 Fe14 BhasasimilarmagneticpropertieswithNd2 Fe14 B[1] andcancertainlybeusedaspermanentmagneticmateri al[2～ 4 ] .Therefor…     

Thermal Decomposition Mechanism and Non Isothermal Kinetics of Complex of [La_2(P-MBA)_6(PHEN)_2]2H_2O

Ｏｗｉｎｇｔｏｔｈｅｖａｒｉａｔｉｏｎｏｆｃｏｏｒｄｉｎａｔｅｄｍｏｄｅｓｆｏｒｃａｒｂｏｘｙｌａｔｅａｎｉｏｎｓ ,ｍａｎｙｄｉｆｆｅｒｅｎｔｔｙｐｅｓｏｆｃｒｙｓｔａｌｓｔｒｕｃｔｕｒｅｓｆｏｒｔｈｅｒａｒｅｅａｒｔｈｃｏｍｐｌｅｘｅｓｗｉｔｈａｒｏｍａｔｉｃａｃｉｄａｎｄｎｉｔｒｏｇｅｎ ｃｏｎｔａｉｎｉｎｇｌｉｇａｎｄｓｗｅｒｅｏｂｔａｉｎｅｄ[1～ 4 ] .Ｔｈｅｉｒｔｈｅｒｍａｌｄｅｃｏｍｐｏｓｉｔｉｏｎｂｅｈａｖｉｏｒｈａｄｂｅｅｎｒｅ ｐｏｒｔｅｄｉｎｐｒｅｖｉｏｕｓｐａｐｅｒｓ[5～ 8] .…     

Influence of rapid quenching on cyclic stability of La-Mg-Ni system （AB3-type） electrode alloys

Aiming at the improvement of the cyclic stability of La-Mg-Ni system （PuNi3-type） hydrogen storage alloy, Ni in the alloy was partly substituted by Fe. The electrode alloys of La0.7Mg0.3Co0.45Ni255-xFex （x=0, 0.1, 0.2, 0.3, 0.4） were prepared by casting and rapid quenching. The influence of the quenching on cyclic stability as well as structure of the alloys was investigated in detail. The results of electrochemical measurement indicated that rapid quenching significantly improved cyclic stability. When the quenching rate rose from 0 （As-cast was defined as a quenching rate of 0 m/s） to 30 m/s, the cyclic life of Fe-free alloy （x=-0） increased from 81 to 105 cycles, and for alloy containing Fe（x=0.4）, it grew from 106 to 166 cycles at a current density of 600 mA/g. The results obtained by XRD, TEM and SEM revealed that the as-cast and quenched alloys had multiphase structures, including two major phases （La, Mg）Ni3 and LaNi5 as well as an imptLrity phase LaNi2. Rapid quenching helped the formation of an amorphous-like structure in Fe containing alloys.     

Effects of La(NO_3)_3 Treatment on Photocattalytic Activity of TiO_2 Films Prepared by Micro-Arc Oxidation

Effects of La(NO_3)_3 Treatment on Photocattalytic Activity of TiO_2 Films Prepared by Micro-Arc Oxidation     

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.