Effect of CexZryLazOδ Mixed Oxides on the Structural and Catalytic Behavior of Monometallic Catalytic Converters Under Simulated Exhaust Conditions

The effect of CeO₂, La₂O₃ and ZrO₂ structural stabilizers/promoters, in the form of Ce_xZr_yLa_zO_δ mixed oxides, on the catalytic performance and thermal stability of monometallic (Pt), monolithic-type, Al₂O₃-washcoated three-way catalytic converters (TWCs) was investigated under simulated exhaust conditions. The evolution of textural, structural and surface behavior of Ce_xZr_yLa_zO_δ modified TWCs were identified by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and diffuse reflectance infrared spectroscopy (DRIFTS) and appropriately correlated with the catalytic behavior and thermal stability of TWCs.     

Co掺杂对（CeO2）0.92（Y2O3）0.06（La2O3）0.02电解质材料性能的影响

采用固相合成法合成CeO2基粉料(1-x)(CeO2)0.92(Y2O3)0.06(La2O3)0.02+xCoO1.5(x=0,0.5 mol%,1mol%和2mol%),并在不同温度下烧成。采用X射线衍射(X-ray diffraction,XRD)、Archimedes法、交流阻抗谱和热膨胀仪分别测试电解质材料的晶体结构、体积密度、离子电导率和热膨胀。结果表明:掺杂Co的试样经1500℃烧成后均为单一的立方萤石结构相,Co可以有效提高试样的烧结性能,降低烧结温度100℃;试样的晶界电导随着Co含量的增加而提高,当Co掺杂量为2mol%时,试样在700℃时表现出最高的离子电导率0.051s.cm-1。同时发现Co的掺杂对试样的热膨胀影响不大。     

Effect of La2O3 on Ru/CeO2-La2O3 Catalyst for Ammonia Synthesis

A series of CeO₂-La₂O₃ supported ruthenium catalysts were prepared by co-precipitation method and the as-obtained samples were characterized by N₂ physisorption, X-ray diffraction, CO chemisorption, H₂-TPR, H₂-TPD and XPS. The activity test shows that ammonia concentration of the catalyst with 10% La is 13.9% at 10 MPa, 10,000 h^?1, 450 °C, which is 17% higher than that of Ru/CeO₂. La doping can improve the activity of Ru-ceria catalyst for ammonia synthesis by facilitating the reduction of oxygen which subsists in the cerium oxide surface. In addition, it can be realized that the test of catalyst stability proves the stability performance of Ru/CeO₂-La₂O₃ catalyst within the reaction time of 55 h.     

The Effect of Modifiers on the Performance of Ni/CeO2 and Ni/La2O3 Catalysts in the Oxy–Steam Reforming of LNG

This work interrogates for the first time the catalytic properties of various monometallic Ni catalysts in the oxy-steam reforming of LNG. Various research techniques, including X-ray diffraction (XRD), specific surface area and porosity analysis (BET method), scanning electron microscopy with X-ray microanalysis (SEM-EDS), temperature-programmed desorption of ammonia (TPD-NH₃), temperature-programmed reduction (TPR-H₂) and the FTIR method, were used to study their physicochemical properties. The mechanism of the oxy-steam reforming of LNG is also discussed in this paper. The high activity of monometallic catalysts supported on 5% La₂O₃–CeO₂ and 5% ZrO₂–CeO₂ oxides in the studied process have been proven and explained on the basis of their acidity, specific surface area, sorption properties in relation to the reaction products, the crystallite size of the metallic nickel and their phase composition.     

Excellent energy-storage performances in La2O3 doped (Na,K)NbO3-based lead-free relaxor ferroelectrics

Relaxor ferroelectric (FE) materials have received increasing attention owing to their great potentials for energy-storage applications, especially for the ones with high energy-storage density, efficiency and thermal stability simultaneously. A novel lead-free [(Na_0.5K_0.5)_0.97-xLi_0.03](Nb_0.94-xSb_0.06)O₃-xBi(Zn_1/2Zr_1/2)O₃ (NKLNS-xBZZ) ceramics was developed by a solid-state reaction method. The addition of BZZ has induced obvious dielectric relaxation behavior, as well as improved thermal stability of dielectric response. Furthermore, 0.4 wt.% La₂O₃ was added into the NKLNS-0.06BZZ ceramic, leading to an increased breakdown strength as a result of the reduction of grain size, improvement of bulk resistivity and decrease of dielectric loss. A large recoverable energy-storage density (∼4.85 J/cm³) and a high efficiency (∼88.2 %) as well as an excellent thermal stability (±12 %, 25–140 °C) were simultaneously obtained, together with a fast discharge rate (t_0.9∼112 ns). These results suggest that La₂O₃ doped NKLNS-0.06BZZ ceramic could become an attractive dielectric material for temperature-stable energy-storage capacitors.     

稀土La2O3添加对氧化铝多孔陶瓷性能的影响

以煅烧α-Al2O3为原料,稀土氧化镧(La2O3)为添加剂,羧甲基纤维素为成型粘结剂,通过混料、困料、研磨、模压成型、高温烧结等工序制备了氧化铝多孔陶瓷,研究了烧结温度及La2O3添加量对氧化铝多孔陶瓷的线收缩率、体积密度、孔隙率、抗折强度和微观形貌的影响。结果表明:在相同烧结温度下,随稀土添加量的增加,多孔陶瓷的体积密度、线收缩率与抗折强度均降低,而孔隙率则逐渐增加。微观形貌与X衍射分析表明,稀土La2O3的加入,抑制了氧化铝颗粒间的烧结,并在高温下与氧化铝反应生成了片状晶体LaAl11O18,片状晶LaAl11O18阻碍了氧化铝晶粒的长大,进而抑制了坯体的收缩,最终使得氧化铝多孔陶瓷具有较高的孔隙率。     

组分对(K,Na)2O-CaO-Al2O3-B2O3-SiO2系分相乳浊釉性能的影响

采用正交试验法探究组分对(K,Na)2 O-CaO-Al2 O3-B2 O3-SiO2系分相乳浊釉性能的影响,结果表明,(K,Na)2 O/CaO、Al2 O3的变化致使釉的熔融温度和表面张力发生改变,对釉面光泽度影响较大,而Al2 O3、SiO2含量的变化主要改变Al、Si在釉中的配位多面体状态以及Si对游离氧的争夺,因此对釉面乳浊白度有较大影响.(K,Na)2 O/CaO值的变化影响了釉中网络改性剂的含量,B2 O3摩尔含量的变化影响了釉中[BO3]、[BO4]的相对含量,因此两者改变了釉玻璃的结构致密程度进而影响釉面硬度.最优条件下制得釉样白度高于正交试验所有试样,釉式为0.5mol(K,Na)2 O-0.5molCaO-0.4molAl2 O3-0.4molB2 O3-6molSiO2,全熔块制备工艺条件下,釉样白度为58.2％,光泽度为89.3％,维式硬度为669.33 HV,釉面针孔缺陷得到显著改善.     

CeO2、La2O3、Y2O3和V2O5对Co-Cu-Sn-Fe超硬工具胎体力学性能的影响

选用Co55Cu29Sn10Fe6作为基础配方,以稀土氧化物(CeO2、La2O3、Y2O3)和V2O5作为添加物,研究它们对Co-Cu-Sn-Fe体系的胎体性能影响.研究发现,稀土氧化物对胎体的硬度改善不大,甚至会使硬度大幅降低,但是对胎体的抗折强度影响显著.CeO2含量在0.5％～0.8％、La2O3含量在0.6％、Y2O3含量在0.2％～0.5％时,抗折强度均较未加稀土氧化物的基础配方(451.9MPa)提高很多.V2O5对胎体的影响与稀土氧化物明显不同.V2O5含量低于1.0％时,胎体的抗折强度会有一定提高,在456.4～551.4MPa之间.     

Flash Sintering of (La,Sr)(Co,Fe)O3–Gd‐Doped CeO2 Composite

Sintering of composites constituted by two nonstoichiometric phases (La_0.6Sr_0.4)(Co_0.2Fe_0.8)O₃ (LSCF) and Gd_0.1Ce_0.9O₂ (GDC) under constant electric field in constant heating rate experiment is studied in this work. The requirements of field and temperature for composite systematically increase with GDC amounts this indicating the importance of material conductivity. Sintering/grain growth rate is higher in the composite compared to pure LSCF phase. Flash‐sintering phenomenon in the composite is explained on the basis of three factors: (1) large and continuous increase in conductivity of LSCF acts as source of defects, (2) maintenance of sufficient local temperature because of GDC during continuous conductivity increase facilitates the cationic diffusion, and (3) reduction reactions of LSCF, during polaron hopping conduction, and of GDC phase at higher temperature activate the sintering process.     

In situ DRIFTS study of the effect of structure (CeO2–La2O3) and surface (Na) modifiers on the catalytic and surface behaviour of Pt/γ-Al2O3 catalyst under simulated exhaust conditions

The nature and relative populations of adsorbed species formed on the surface of un-promoted and sodium-promoted Pt catalysts supported either on bare Al₂O₃ or CeO₂/La₂O₃-modified Al₂O₃, were investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) under simulated automobile exhaust conditions (CO + NO + C₃H₆ + O₂) at the stoichiometric point. The DRIFT spectra indicate that interaction of the reaction mixture with the Pt/Al₂O₃ catalyst leads mainly to formation of formates and acetates on the support and carbonyl species on partially positively charged Pt atoms (Pt^δ+). Although enrichment of Al₂O₃ with lanthanide elements (CeO₂ and La₂O₃) does not significantly modify the carboxylate species formed on the support, it causes significant modification of the oxidation state of Pt, as indicated by the appearance of a substantial population of carbonyl species on reduced Pt sites (Pt⁰–CO). This modification of the Pt component is enhanced when Na-promotion is used, leading to formation of carbonyl species only on electron enriched Pt (i.e., fully reduced Pt⁰ sites) and to the formation of NCO on these Pt entities (2180 cm⁻¹). The latter are thought to result from enhanced NO dissociation at Na-modified Pt sites. These results correlate well with observed differences in the catalytic performance of the three different systems.     

加工条件对聚L-乳酸热性能的影响

为了更好地掌握聚L-乳酸(PLLA)的加工工艺,系统考察了PLLA熔融温度和时间对其热性能的影响。结果表明:增加熔融时间会使PLLA非等温结晶峰变得尖锐,熔融40 min后PLLA的非等温结晶峰最为显著,而熔融时间的增加会使等温结晶后的熔融过程呈现出熔融双峰现象;熔融温度的增加则会使PLLA非等温结晶峰变得更加尖锐。     

(Na2O+K2O)对Ca-Ba-Mg-Al-B-Si-O玻璃/Al2O3材料性能的影响

实验以Ca-Ba-Mg-Al-B-Si-O玻璃和Al_2O_3粉料为原料,设计玻璃中(Na_2O+K_2O)含量分别为0、2%、4%、8%的优化玻璃组成,800～950℃低温烧结得到LTCC材料。研究结果表明:随着(Na_2O+K_2O)含量升高,Ca-Ba-Mg-Al-B-Si-O系玻璃/Al_2O_3烧结体的体积密度与介电常数逐渐增加,烧结体气孔率随之减小,介电损耗出现先减小后增加的趋势。添加2%(Na_2O+K_2O)的Ca-Ba-Mg-Al-B-Si-O玻璃/Al_2O_3材料,在875℃烧结试样显示出优异性能。     

Thermal Conductivity of Molten B2O3, B2O3–SiO2, Na2O–B2O3, and Na2O–SiO2 Systems

With the aid of the transient hot‐wire method, the thermal conductivity of molten B₂O₃, B₂O₃–SiO₂, Na₂O–SiO₂, and Na₂O–B₂O₃ systems was measured along with their temperature and composition. It was observed that the thermal conductivity of pure B₂O₃ increased with temperature, until about 1400 K, and then decreased subsequently. Using the MAS‐NMR, 3Q‐MAS, and Raman spectroscopy, the structure of B₂O₃ and SiO₂ in the B₂O₃–SiO₂ system was confirmed. Findings show that an addition of B₂O₃ into the pure SiO₂ system causes a significant decrease in thermal conductivity, due to the formation of boroxol rings. The thermal conductivity of the Na₂O–SiO₂ system was measured and its phonon mean free path was calculated. In addition, a positive linear relation between viscosity and thermal conductivity was observed. In the Na₂O–B₂O₃ system, it was found that a change in the relative fraction of 4‐coordinated boron has an influence on the thermal conductivity when the concentration of Na₂O is between 10 and 30 mol%, in which case the tetraborate unit is dominant.     

Thermal and optical properties of La2O3–Ga2O3– (Nb2O5 or Ta2O5) ternary glasses

La₂O₃–Ga₂O₃–M₂O₅ (M = Nb or Ta) ternary glasses were fabricated using an aerodynamic levitation technique, and their glass‐forming regions and thermal and optical properties were investigated. Incorporation of adequate amounts of Nb₂O₅ and Ta₂O₅ drastically improved the thermal stabilities of the glasses against crystallization. Optical transmittance measurements revealed that all the glasses were transparent over a wide wavelength range from the ultraviolet to the mid‐infrared. The refractive indices of the glasses increased and the Abbe number decreased upon substituting Ga₂O₃ with Nb₂O₅, and the decrease in the Abbe number was significantly suppressed when Ta₂O₅ was incorporated into the glass. As a result, excellent compatibility between high refractive index and lower wavelength dispersion was realized in La₂O₃–Ga₂O₃–Ta₂O₅ glasses. Analysis based on the single‐oscillator Drude–Voigt model provided more systematical information and revealed that this compatibility was due to an increase in the electron density of the glass.     

Effect of Na2O on the High‐Temperature Thermal Conductivity and Structure of Na2O–B2O3 Melts

The effect of Na₂O and temperature on the thermal conductivity of the Na₂O–B₂O₃ binary system has been measured using the hot‐wire method to examine the relationship between the thermal conductivity and structure in high‐temperature melts. The thermal conductivity of the binary melt is measured from 1173 to 1473 K in the fully liquid state. The thermal conductivity slightly increases with Na₂O content up to 20 wt%. Above 20 wt% Na₂O, the thermal conductivity decreases with increasing Na₂O. The network structure of molten glass was analyzed using Fourier transform infrared (FTIR), Raman spectroscopy, and XPS. The FTIR analysis shows that 3‐D complex borate structures, such as tri‐, tetra‐, and pentaborate are made by [BO₄] tetrahedral units interconnected with 2‐D structure boroxol rings in the low Na₂O region. Above 20 wt% Na₂O content, nonbridged oxygen in [BO₂O^?] units and diborate groups increase with increase in Na₂O. The same tendency is shown by the Raman spectroscopy and XPS analyses. The Raman analysis shows that boroxol rings disappeared with large [BO₄] groups, such as tri‐, tetra‐, and pentaborate structures, which increase at low Na₂O content. Isolated diborate groups and nonbridged oxygen in [BO₂O^?] units increase at high Na₂O content. It can be inferred that single structure units, such as isolated diborate groups, interfere with conduction. The XPS analysis results show that free oxygen produced by the interconnection of Na₂O in the borate structure does not cause significant changes to O^2? in the low Na₂O region, but increases the O^o and decreases the O^?. Above 20 wt% Na₂O, O^? slightly increases and O^o shows a decreasing trend.     

(Na2O-Al2O3)/B2O3对高硼硅酸盐玻璃粘度和热学性能的影响

采用熔融冷却法制备了不同R’系数的高硼硅酸盐玻璃,其中R’=(Na2O-Al2O3)/B2O3.利用红外光谱、高温旋转粘度计和热膨胀仪等对玻璃的结构和性能进行表征.结果表明:高温段粘度-温度关系符合阿伦尼乌斯定律;R’值的增大导致非桥氧的增加,高温粘度和熔制温度呈显著降低.当R’＞0.5时,热膨胀系数近似线性增大,玻璃化转变温度增大至590℃基本维持不变.R’值影响结构中的[BO3]与[BO4]的比例及硅氧网络的完整程度,从而决定高硼硅酸盐玻璃的性能.     

Application of sonochemical processing to LSC(La0.6Sr0.4CoO3)/SDC(Sm2O3-doped CeO2) composite cathodes for solid oxide fuel cells involving CeO2-based electrolytes

Nanocrystalline Sm₂O₃-Doped CeO₂ (SDC) powders were synthesized in a single- and two-phase material system by using sonochemical processing with high-frequency agitation. The synthesized SDC nanocrystalline powders were used to coat the mixed-conducting La_0.6Sr_0.4CoO₃ (LSC) cathode materials. The combined synthesis processing allows the artificial coating of the LSC materials with the ionic-conducting SDC electrolyte. The electrochemical polarizations of the SDC/LSC composites are characterized using a geometrically constricted contact between the ionic probe and the SDC/LSC composites. The lowest cathode polarization was obtained for the LSC (85 wt%)/SDC (15 wt%). The lowest electrode polarization is believed to result from the high density of the triple-phase boundaries when the constituent phases are interconnected in a 3-dimensional manner.     

混合碱效应对Li2O-Al2O3-SiO2系玻璃结构和热膨胀性能的影响

本文用传统高温熔融法熔制Li₂O-Al₂O₃-SiO₂系高铝玻璃,改变碱金属氧化物n(Li₂O)/n(Na₂O)的摩尔比,运用阿基米德排水法、热膨胀仪、DSC、傅里叶变换红外光谱和拉曼光谱等测试手段和仪器,探究了混合碱金属效应对Li₂O-Al₂O₃-SiO₂系玻璃结构和热膨胀性能的影响。结果显示:随着n(Li₂O)/n(Na₂O)比例增大,混合碱金属效应对Li₂O-Al₂O₃-SiO₂系玻璃的密度和热膨胀系数的影响一致,表现为先增大后减小,当R=0.25(R=n(Li₂O)/[n(Li₂O)+n(Na₂O)],摩尔比)时,出现极值,此时密度达到最大2.447 4 g/cm³,热膨胀系数达到最大7.811 7×10^-6/℃;对玻璃特征温度的影响随着温度的升高而逐渐减弱至消失;对玻璃的析晶能力有一定的提升作用;对玻璃三维骨架结构中的硅氧四面体Qⁿ的影响也各不相同。     

The Effect of Sulphur on the Activity of Pd/Al2O3, Pd/CeO2 and Pd/ZrO2 Diesel Exhaust Gas Catalysts

Pd/Al₂O₃, Pd/CeO₂ and Pd/ZrO₂ diesel oxidation catalysts and their washcoat materials were studied after sulphur treatment. The catalytic activities were analysed in simplified diesel exhaust gas composition by FT-IR technique. ICP-OES or XRF, physisorption and CO chemisorption was used to catalyst characterisation. The result shows that the sulphur treatment clearly deactivates the studied catalysts.     

TAP Investigation of NO Adsorption on Pd/Al2O3: Effect of Thermal Aging

This paper deals with the aging effect on the kinetics of the NO decomposition on a commercial Pd/Al₂O₃ catalyst. Temporal analysis of products experiments are discussed in the light of a selected mechanism involving the recombination of two NO_ads species to form N₂O, which is an intermediate in N₂ formation. Experiments over the fresh catalyst indicate a strong metal/support interface, with a spill-over effect, which is difficult to model. Thermal aging had a detrimental effect over this interface, the kinetic features depending mainly on the metallic Pd sites. The different heats of adsorption and activation energies are proven consistent with other theoretical studies. The mechanism led to a high surface coverage for O ad-atoms.