掺杂钇铋Ce-Zr-Al储氧材料的制备及性能研究

采用共沉淀法制备了掺杂Y3+、Bi3+的CeO2-ZrO2-Al2O3(CZA)储氧材料,并通过XRD、低温N2吸附-脱附、氧脉冲吸附(OSC)及H2-TPR等手段进行了表征.XRD结果表明,600℃和1000℃焙烧后,Y3+、Bi3+的加入没有改变物相结构,所有样品均形成单一立方相萤石结构固溶体.低温N2吸附结果表明,Y3+掺杂的Ce0.6Zr0.3Y0.1O1.95-Al2O3(CZYA)材料,其织构性能及热稳定性都有很大的改善,1000℃老化5h后,比表面积和孔容可分别达80.75m2/g和0.22mL/g.OSC和H2-TPR结果表明,同时掺杂Y3+、Bi3+的Ce0.6Zr0.2Y0.1Bi0.1O1.9-Al2O3(CZYBA)材料,其储氧性能明显增强,经600和1000℃焙烧后分别达到461和242μmol/g;同时掺杂Y3+、Bi3+增强了CZA材料的还原性能,1000℃老化5h后还原峰温度从546℃降低到429℃.     

Ce-Zr-Mn-O固溶体作为甲烷燃烧过渡金属催化剂载体的研究

用溶胶凝胶法制备了不同锰含量的 Ce Zr Mn O固溶体,样品在老化前后均用 XRD、TPR表征,并测定其储氧性能。结果表明锰含量对该储氧材料(OSM)的储氧性能有很大的影响:样品的储氧量(OSC)老化前随着 Mn含量的增加而增加;老化后则先增加而后又降低,以 Mn含量 20%为最佳。以不同比例的OSM(含 20%锰)YSZ Al2O3 为载体制备了一系列Fe、Co、Mn三组分氧化物的整体式催化剂,考察了它们的甲烷催化燃烧活性。结果表明老化前后,Fe Co Mn/OSM YSZ Al2O3 (其中 OSM和 YSZ Al2O3质量比为1∶1)活性明显高于Fe Co Mn/YSZ Al2O3,且具有可与贵金属催化剂相比美的特性———较低的起燃温度、很窄的完全反应温度区间,同时兼有较好的热稳定性,有望成为实用的甲烷燃烧催化剂。     

沉淀剂对稀土储氧材料性能的影响

利用不同的沉淀剂制备了一系列储氧材料,并应用BET、XRD、TPR及其储氧量的测定等方法对储氧材料进行了表征.结果表明,不同沉淀剂对样品的性能有重要的影响.在控制其它条件一致的情况下,用分别以氨水和以碳酸铵做沉淀剂可得到高温老化后仍保持高比表面积,储氧性能稳定的储氧材料;用(NH4)2CO3和NH3·H2O做混合沉淀剂所制得的储氧材料,其抗老化性能较差.3种不同沉淀剂所制备的储氧材料均可形成结构为四方晶相的CeO2-ZrO2固溶体,材料的还原性取决于比表面积,但与储氧性能无直接关系.     

掺杂不同量Nd2O3对CeO2-ZrO2-Al2O3材料性能的影响

采用共沉淀法制备了一系列Nd2O3含量为0～13wt%的CeO2-ZrO2-A12O3(CZA)复合氧化物,并通过X射线衍射(XRD)、低温N2吸附–脱附、氧脉冲吸附(OSC)、H2–程序升温还原(H2-TPR)及扫描电子显微镜(SEM)等方法对所制备的材料进行了表征.研究结果表明,Nd2O3在CZA固溶体中的溶解限约为10wt%,过量Nd的添加会出现分相形成Nd0.5Ce0.5O1.75氧化物.掺杂适量Nd能有效抑制氧化物晶粒的长大,提高材料的热稳定性和氧化还原性能.Nd2O3的掺杂量为10wt%时,样品的织构稳定性最好,1000℃老化5 h后,比表面积和孔容分别达97.14 m2/g和0.44 mL/g.Nd2O3的掺杂量为7wt%时,样品有高的储氧量,经600℃和1000℃焙烧后储氧量分别为938.01μmol/g和821.72μmol/g;体相氧的移动能力最强,还原性能最佳,老化后还原峰温由465℃升高到483℃.SEM结果表明,所制备的材料均为球形颗粒,Nd2O3的添加可以有效阻止高温焙烧过程中粒子的团聚.     

掺杂Sn对低铈型复合氧化物纳米储氧材料性能的影响

采用共沉淀法制备了低铈型Ce-Zr-Sn复合氧化物纳米储氧材料,采用X射线衍射、储氧量、比表面积等研究手段对其进行了分析和表征,结果表明,低铈型Ce（0.35）Zr（0.55-x）SnxLa（0.1）O（1.95）（x=0-0.12）复合氧化物纳米储氧材料具有高的比表面积和储氧量,且物相单一,只含有稳定的立方结构的固溶体晶相。少量Sn的掺入有利于低铈型铈锆固溶体储氧材料热稳定性能和低温储氧性能的提高。当Sn含量（摩尔分数）为0.06时,样品的低温储氧量和比表面积最高,抗老化性能最佳,经1000℃高温老化5h后,储氧量和比表面积仍可达298.1μmo1/g和48.95m~2/g。     

纳米Ce_(0.92)M_(0.08)O_(2)(M=Co,Mn,Fe,La)固溶体的制备及其氧化还原性能EI北大核心

采用水热法制备Ce_(0.92)M_(0.08O_(2))(M=Co,Mn,Fe,La)固溶体,系统分析固溶体的微观结构、光谱特征及氧化还原性能。研究结果表明,Co离子掺杂样品中观察到Co_(3)O_(4)杂相,而另外三种离子均完全溶解在CeO_(2)中形成固溶体。样品为纳米尺寸,晶格常数与掺杂离子半径密切相关,样品的能隙明显降低,而且掺杂离子能够明显提高固溶体的氧空位浓度,氧空位浓度由小到大的顺序依次为:CeO_(2)相似文献   

用于高性能单Pd三效催化剂的复合组分CexZr1-xO2材料的制备

用简单的顺序沉淀法制备了两种具有混合组分的CeO₂-ZrO₂材料。用X射线衍射(XRD), 拉曼光谱(Raman), X射线光电子能谱(XPS), 氮气吸附-脱附, 氢气程序升温还原(H₂-TPR)和储氧量(OSC)研究了不同组合形式对负载的单Pd催化剂性能的影响。结果表明, 两个混和组分的催化剂结构和织构性能都得到了改善。由于贵金属和载体材料之间以及载体材料内部各组分之间的强相互作用, 组合的结构促进了Ce³⁺和晶格缺陷的形成, 提高了氧的移动性, 并且相应的催化剂老化前后对于CO、C₃H₈和NO的转化都具有较宽的窗口范围, 说明这种具有混合组分的载体材料在汽油车尾气净化方面具有良好的应用前景。     

制备方法对铈锆铝复合氧化物还原热处理性能的影响

采用沉淀前驱物混合法制备铈锆铝复合氧化物(CZ+A(pm))和沉淀机械研磨混合法制备铈锆铝复合氧化物(CZ+A(mm))(x(Ce)∶x(Zr)∶x(Al)=1∶1∶2)。将样品分别在空气和10%H_2/Ar气氛下进行热处理,利用X射线粉末衍射(XRD)、N_2吸脱附(BET)、O_2脉冲吸附、H_2程序升温还原(H_2-TPR)等手段研究了复合氧化物的结构及性能。结果表明,CZ+A(pm)、CZ+A(mm)新鲜样品经1 100℃还原热处理后的CZ+A(pm)-H_2-1 100样品的XRD图谱出现较多且尖锐的归属于CeAlO_3的衍射峰,而CZ+A(mm)-H_2-1 100样品没有观察到CeAlO_3晶相;其储氧量分别为157和773μmol/g,均大于CZA-H_2-1 100的23.2μmol/g;H_2-TPR耗氢量分别为960和1 916μmol/g,而CZA-H_2-1 100样品H_2-TPR耗氢量仅为310μmol/g,CZ+A(pm)储氧性能受还原热处理时CeAlO_3形成的影响,与还原性能的变化结果相吻合。研究发现,铈锆铝复合氧化物中CZ+A(pm)样品的铈锆和氧化铝粒子尺度较小,相互之间接触较紧密,使得CeO_2和Al_2O_3较易发生固相化合反应生成CeAlO_3,而CZ+A(mm)样品中铈锆和氧化铝粒子更大,相互之间间隔更远,经还原热处理时能抑制CeAlO_3的形成,从而改善材料在还原气氛下的储氧性能和还原性能。     

焙烧温度对Ce0.65Zr0.35O2储氧材料性能的影响

用共沉淀法制备了Ce0.65Zr0.35O2氧化物,对不同温度处理后的样品进行了XRD、Raman、BET和储氧量(OSC)的表征.并考察了不同温度焙烧后的氧化物对单钯催化剂三效性能的影响.结果表明,焙烧温度的不同,样品具有不同的织构性能,但该样品的晶相结构稳定,老化前后均为立方相的铈锆固溶体,经1000℃焙烧后未出现相分离,说明该氧化物具有良好的热稳定性能;活性测试结果表明,不同焙烧温度的载体对催化活性影响较大,并以700℃焙烧后的氧化物为载体的催化剂具有最好的三效性能.     

不同制备方法对CeO2-ZrO2-Al2O3材料性能的影响

分别采用共沉淀法、胶溶法和胶溶?共沉淀法制备了Ce0.5Zr0.5O2(12wt%)-Al2O3(CZA)储氧材料,并通过XRD、低温N2吸附?脱附、氧脉冲吸附(OSC)、程序升温还原(H2-TPR)和O2-程序升温脱附(O2-TPD)等手段进行了表征.材料经过1000℃焙烧后,XRD结果表明,三种方法制备的样品均存在CeO2-ZrO2立方萤石和γ-Al2O3两种晶型.N2吸附?脱附结果表明,胶溶?共沉淀法制备的样品,具有最大的比表面积和孔容,分别为146.2m2/g和0.5mL/g,且有最佳的孔径分布;氧脉冲吸附(OSC)和H2-TPR结果表明胶溶?共沉淀法制备的材料,具有最佳的储氧性能和还原能力;同时实验还比较了经1100℃焙烧对几种方法制备样品性能的影响.     

Atmospheric pressure solvothermal synthesis of ceria–zirconia solid solutions and their large oxygen storage capacity

Ceria–zirconia solid solution has a function as an oxygen storage material, which keeps air to fuel ratio (A/F) on a stoichiometric composition at the surface of three-way catalyst (TWC) for automotive exhaust. When A/F could be kept stoichiometric, TWC shows good catalytic activity. At first, ceria which dissolves 20 mol% of zirconia was developed by Ozawa et al. in 1987. After that, the ceria–zirconia solid solution was improved to achieve a complete solubility in the solid state at nano-level by surfactant modified homogeneous coprecipitation (J catal 169:490, 1997). Nano-level solid solution of ceria and zirconia could have been made by various methods. Those materials have similar amount of oxygen storage capacity (OSC). The improvement of OSC comes from the larger amount of bulk oxygen that can contributes OSC by the larger amount of zirconia dissolving into ceria (Catal Lett 33(1–2):193–200 1995). Solvothermal synthesis is usually done in a higher temperature than that can be reached under atmospheric pressure. The higher temperature accelerates generation of precipitation; however, a pressure vessel is necessary, and such a hermetically closed system is unsuitable to the material synthesis of the low-value-added product. Atmospheric pressure solvothermal (APS) synthesis was applied to ceria-zirconia solid solutions in this study. The APS ceria-zirconia showed larger amount of OSC. The excellent OSC performance was presumed to come from further uniformity of zirconium ions in the ceria lattice.     

变质和热处理对高强度铸造Al-Cu-Si-Mn合金组织和性能的影响

通过变质处理和热处理实验,研究了不同的Ti变质加入量和固溶时效处理对高强度铸造Al-Cu-Si-Mn合金组织和性能的影响.结果表明,试验材料的铸态组织为粗大的α(Al)固溶体和其晶界分布的θ(Al2Cu)及T(Al12CuMn2)相,加入0.15%～0.2%Ti变质处理可以细化试验材料的铸态组织,变质处理后进行固溶和时效处理,组织由α(Al)固溶体和其晶内弥散分布的二次T相组成,晶界处残留有未完全固溶的T(Al12CuMn2)相,组织中出现α(Al)晶界无析出区.Ti变质处理高强度Al-Cu-Si-Mn合金组织对壁厚效应的敏感性不明显.     

Synthesis of hollow ceria-zirconia solid solution particles by spray pyrolysis with organic ligands and its oxygen storage capacity

CeO₂-based materials have been explored as oxidative catalysts owing to the reversible oxygen absorption and release behavior. The catalytic property is stabilized by addition of ZrO₂ to form the solid solution. Hollow CeO₂-ZrO₂ solid solution particles were prepared by a spray pyrolysis method with organic additives, characterized by SEM, XRD and TEM, and evaluated for oxygen storage capacity (OSC). Spherical hollow particles with a size of about 500 nm formed, which were composed of about 10 nm nanoparticles. CeO₂-rich particles had cubic crystal structure, while tetragonal phase was included in ZrO₂-rich particles. The addition of organic ligands was effective to form uniform solid solution and increase specific surface area. The spray-pyrolysis temperature should be low to keep the specific surface area. At 50 mol% ZrO₂, although the specific surface area was not so high as 20 m²/g, the maximum OSC of 650 μmol-O₂/g was achieved. It was found that the OSC depends on ZrO₂ content and the oxygen release rate increases with specific surface area.     

Shape Memory Effect of As-aged Fe-14Mn-5Si-8Cr-4Ni-0.2C Alloy

1. IntroductionFe-Mn-St-Cr-Ni shape memory alloys exhibit notonly a good shape memory effect (SME), but alsoa good corrosion resistance[1'21, compared with FeMn-St alloys. Furthermore, it can be used in manufacturing pipe couplings because of its high phasetransformation temperature and great thermal hysteresis. But the recovery strain in these alloys is stilllow, which limits their application in pipe couplings.Therefore, to increase the recovery strain is key totheir practical applica,ti…     

基于FTIR和RBF网络的二元脂肪酸/SiO2相变储湿复合材料热湿性能优选预测

采用溶胶-凝胶法制备二元脂肪酸（BFA）/SiO₂相变储湿复合材料,既具有相变调温性能,又具有储湿调湿性能,还能满足无机材料的相容性。研究溶液pH值、超声波功率、去离子水用量、无水酒精用量及BFA用量对BFA/SiO₂相变储湿复合材料结构的影响规律,通过FTIR分析BFA/SiO₂相变储湿复合材料的嵌合机制。通过RBF网络,研究BFA/SiO₂相变储湿复合材料的结构参数与热湿性能优选预测模型。结果表明：BFA/SiO₂相变储湿复合材料中BFA与SiO₂仅仅是物理嵌合。最优热湿性能的BFA/SiO₂相变储湿复合材料制备工艺参数：pH值为3.64、超声波功率为120 W、去离子水用量为1.45 mol、无水乙醇用量为0.78 mol和BFA用量为0.079 mol。预测结果：30%相对湿度（RH）~90% RH湿容量为0.1676 g/g、相变焓为41.89 J/g。测试结果：30% RH~90% RH湿容量为0.1653 g/g、相变焓为41.22 J/g。     

热处理对Ti-6Al-2.5V-1.5Fe-0.15O合金组织及力学性能的影响

以真空非自耗电弧炉制备的低成本Ti-6Al-2.5V-1.5Fe-0.15O合金为对象,研究了不同冷却速率下固溶及时效温度对合金组织及性能的影响,发现固溶温度主要影响初生α相的含量.固溶冷却方式影响α的类型.单相区固溶时,初生α相消失,β晶粒内出现α片层集束,固溶淬火组织主要由残余未转变的β相以及针状的α';随着固溶温度的升高,针状马氏体α'相增多;两相区固溶后,时效组织均有固溶时产生的α相、时效α相以及残留的β相.时效温度较低时,α相形核能较低,元素扩散困难,需借助过饱和β相析出弥散相形核,因而针状α相细小而弥散;时效温度升高,α相形核以及长大驱动力大,时效α相易长大变粗.经固溶时效处理,合金强度随着温度升高先小幅升高后显著降低,塑性先增大后因晶界粗化以及粗片状α集束而降低.     

Oxygen release–absorption properties and structural stability of Ce0.8Fe0.2O2−x

Oxygen release–absorption properties and structural stability of Ce–Fe mixed oxides (Ce_0.8Fe_0.2O_2?x) with different calcination temperatures (600–1000 °C) were investigated and correlated to their oxygen storage capacity. Iron ions could be incorporated into the CeO₂ lattice to form a solid solution after calcination at low temperatures, but such solid solution was unstable under high-temperature thermal treatments. High-temperature (≥800 °C) calcination resulted in the appearance of exposed Fe₂O₃ phases on the surface of the solid solution, and this structural evolution finally affected the reduction behavior. The Fe³⁺ reduction from the Ce–Fe oxide solid solution was easier than the bulk Fe₂O₃ particles, while the small Fe₂O₃ particles in close contact with CeO₂ could enhance the reducibility of cerium oxides. The strong interaction between the exposed small Fe₂O₃ particles and the solid solution made the Ce–Fe mixed oxides possess good reduction stability and high oxygen storage capacity (OSC) even after repeated redox treatments. Such interactions were absent toward the physically mixed sample. An unusual enhancement on the reducibility of Ce–Fe mixed oxides was observed after a successive redox treatment. Large oxygen evolution appeared at around 600 °C for the recycled samples, and the OSC rose to 1.31 mmol-O₂/g after six redox cycles. The XRD, Raman, and TEM analyses revealed that the material structure of the mixed oxides was stabilized to have an inter-region between the Fe₂O₃ particles and the solid solution after the redox treatment. It was concluded that such microstructural evolutions of composite particle from solid solution under redox conditions brought beneficial property to the OSC of the Ce–Fe mixed oxides.     

热处理对SCR成形Al-1.5Mg-0.3Sc合金线材性能的影响

采用单辊搅拌冷却技术（Shearing—Cooling-Rolling，简称SCR）和在线固溶处理方法制备了Al-1．5Mg-0．3Sc（wt％）合金线材，研究了不同在线固溶温度条件下时效处理对合金线材的微观组织和拉伸性能的影响．结果表明：SCR技术对合金线材具有剪切细化功能，在铝基体内产生大量位错，时效析出大量Al3Sc强化相粒子，与位错交互作用．随着在线固溶温度下降，合金线材时效析出沉淀相Al3Sc的弥散度增加，合金线材的抗拉强度和延伸率提高；随着过时效时间的延长，合金线材的抗拉强度下降，线材的延伸率提高，时效8h，延伸率达峰值．     

Elastic, piezoelectric, and dielectric characterization of modified BiScO3-PbTiO3 ceramics

The perovskite solid solution system (1-x)BiScO3-(x)PbTiO3 represents an interesting new family of high-temperature piezoelectric materials. Compositions near the morphotropic phase boundary (x approximately 0.64) have been reported to have high Curie temperatures (Tc > 450 degrees C) and good piezoelectric coefficients (d33 approximately 460 pC/N). In this work, manganese additions were used to improve the high-temperature electrical resistivity and RC time constant of compositions near the morphotropic phase boundary. The addition of manganese was found to shift Tc to slightly lower temperatures (442 degrees C and 456 degrees C for x = 0.64 and x = 0.66, respectively). The piezoelectric activities of the modified materials were found to be reduced slightly due to the hardening effect of manganese; however, the temperature stability and resistivity of the modified materials were significantly enhanced. In this paper we present, for the first time, a complete set of materials constants, including the elastic (sij, cij), piezoelectric (dij, eij, gij, hij), dielectric (epsilonij, betaij), and electromechanical (kij) coefficients and compare them to both unmodified 0.36BiScO3-0.64PbTiO3 and PZT5A ceramics.