Zr、Y元素对Pt-10Rh合金性能的影响研究

在Pt-10Rh合金中添加少量的Zr、Y元素,利用真空充氩电弧熔炼方法制备了Pt-10Rh-0.5Zr合金及Pt-10Rh-0.5Zr-0.2Y合金。研究了合金的相结构、室温与高温力学性能以及高温抗氧化性能,观察分析了合金高温氧化及高温断口的形貌组织结构。结果表明,合金形成了由铂铑固溶体基体相与少量的金属间化合物相构成的组织结构;添加少量的Zr、Y元素大幅提高了Pt-10Rh合金的力学性能,同时Y元素还显著改善了Pt-10Rh-0.5Zr合金的高温塑性和抗氧化性能。     

铑在不同载体材料上的分配比对低含量贵金属催化剂性能的影响

采用浸渍法制备了一系列低Pt、Rh含量的Pt-Rh型汽车尾气净化催化剂.研究了在Pt、Rh含量一定以及其他条件不变的情况下,只改变铑在不同栽体上的分配比对催化剂性能的影响,测定了催化剂对C3H8、CO、NO的起燃温度,并对催化剂样品进行了程序升温还原(H2-TPR)、程序升温脱附(O2-TPD)表征.结果表明:新鲜催化剂对C3H8、CO、NO的起燃温度相差不大,但经过1000℃、5h的水热老化后,催化剂性能发生了显著的变化,C3H8、CO、NO的起燃温度出现较大的差异,说明了铑在不同栽体上的分配比对催化剂性能有一定影响,特别是对催化剂的抗老化性能影响较大.     

Study of the Structure of Oxide Interface in the Pt-Rh Alloy by AP-FIM

This paper reports the study of structure of oxide interface in Pt-Rh alloy by atom probe field ion micro-scope (AP-FIM) which is well suited for the study of atom distribution with atomic scale at the surface and in-terface of alloy. AP depth profiles show that oxide interface exist in the Pt-Rh alloy which consists of PtO,RhO, PrO_2 and RhO_2 . The mechanism of oxidation of the alloy is considered as that first oxygen moleculesadsorbed on-to the surface of alloy then dissociate into oxygen atoms (0_2→2O). Consequently oxygen atomsdiffuse into interior through grain boundary forming oxide (M+O→MO). When the concentration of oxygencontinuously increases the dioxide (MO+O→-MO_2) forms.     

Aging-Induced Metal Redistribution in Bimetallic Catalysts

Alloy particles were detected by XRD in bimetallic catalysts, made from physical mixtures of powders comprising distinct metal-support combinations (e.g., Pd on alumina and Rh on ceria-zirconia), following high-temperature redox aging. The morphology of the catalysts was examined by TEM, and the compositional structure of some of the alloy particles was determined. Two different effects of the redistribution of metals on oxygen-storage capacity were identified, one due to Pd enrichment of the surface of Pd-Rh alloy particles and the other due to loss of contact between metal and ceria-zirconia.     

Electro-oxidation of methanol on Pt-Rh alloys

Methanol adsorption and electro-oxidation on Pt-Rh alloys have been studied in aqueous 0.5 M H₂SO₄ for a broad range of alloy surface composition including the pure Pt and Rh metals. Adsorption results have been compared with equivalent data obtained for CO and CO₂ adsorption on these alloys. Current densities of continuous methanol oxidation on Pt, Rh and a Pt-Rh alloy with optimum surface molar fraction of Rh have been measured.Although on the pure Pt and Rh metals the methanol adsorption products exhibit similar energetic stability, as judged from the peak potential of electro-desorption, on the Pt-Rh alloys, there is a lowering of the stability. Similar behavior is observed for the CO and CO₂ adsorption products, however, the lowering for methanol is much less than for CO and CO₂. In the case of methanol, the maximum lowering is obtained for a surface molar fraction of Rh equal to ca. 0.65 and it is the same alloy surface composition that results in maximum lowering of the stability of the CO₂ adsorption products, but not of the CO adsorption products (optimal fraction of Rh equal ca. 0.10). Structural similarity of the methanol and the CO₂ adsorption products finds support in similar values of the electrons-per-site parameter obtained.Pt-Rh alloys show insufficient electrode potential improvement over Pt in continuous methanol electro-oxidation due to the susceptibility of Rh to strong poisoning by the methanol adsorption products, which switches off the bi-functional mechanism of methanol electro-oxidation on this alloy. The presence of Rh in the alloy with Pt additionally strongly lowers the methanol electro-oxidation turnover rate of the Pt component.     

微型热偶用的特细Pt-Rh合金丝材

研制成功快速测温用φ０．０５ｍｍ－０．０３ｍｍ（ＰｔＡ）Ｒｈ１０－ＰｔＡ（Ｓ型）、（ＰｔＡ）Ｒｈ３０－（ＰｔＡ）Ｒｈ６（Ｂ型）、（ＰｔＡ）Ｒｈ１３－ＰｔＡ（Ｒ型）３种特细热电偶丝其丝构成的热电偶,热电特性和主要物理性能符合相应国际行标和国际ＩＥＣ标准的要求。材料具有良好的热稳定性、抗高温冲击和抗污染。偶丝制成的微型热电偶,经过对１７００℃左右的钢液测温应用试验表明,测量准确、可靠、精度高,足以满足     

氧化物弥散强化Pt/Pt-Rh合金机理研究

运用位错理论,综述氧化物弥散强化Pt／Pt-Rh合金的机理。一方面,基体中的位错被高度弥散分布的第二相颗粒所钉扎,使位错运动受到阻碍：另一方面,分布在晶界的第二相颗粒阻碍晶界迁移和晶粒长大,从而提高基体的再结晶温度。由以上因素共同作用达到强化材料的目的。对氧化物弥散强化机理的深入分析,可为开发更优质的Pt／Pt-Rh合金弥散强化材料提供理论依据。     

硝酸工厂铂合金催化网的铂耗

铂耗和氨耗是硝酸生产的主要技术指标。在流动氧气氛模拟条件下,以及800~950℃的硝酸生产实际氨氧化环境中,Pt-Rh二元和Pt-Pd-Rh三元合金及其催化网的失重和铂耗均遵循相同的模式,即ΔW/S=Kt2/3与ΨΣ=K't2/3。工厂实际测定数据表明,在常压氨氧化法生产硝酸过程中,Pt-12Pd-3.5Rh合金催化网的铂耗为0.044 g Pt/t(HNO3),比Pt-4Pd-3.5Rh合金催化网的铂耗(0.061g Pt/t(HNO3))低28%;在中压氨氧化法生产硝酸过程中,Pt-12Pd-3.5Rh合金催化网的铂耗为0.121g Pt/t(HNO3),比Pt-5Rh和Pt-10Rh合金催化网的铂耗(0.15~0.153 g Pt/t(HNO3))低21%,而其氨耗比后者降低3%~7%。研究结果证明,在Pt-Rh合金中添加钯或在Pt-Pd-Rh合金中增加钯含量明显降低催化合金的铂耗。     

Alloy-oxide equilibria in the system Pt-Rh-O

The composition of Pt-Rh alloys that co-exist with Rh₂O₃ in air have been identified by experiment at 1273 K. The isothermal sections of the phase diagram for the ternary system Pt-Rh-O at 973 K and 1273 K have been computed based on experimentally determined phase relations and recent thermodynamic measurements on Pt_1−X Rh _X alloys and Rh₂O₃. The composition dependence of the oxygen partial pressure for the oxidation of Pt_1−X Rh _X alloys at different temperatures, and temperature for the oxidation of the alloys in air are computed. The diagrams provide quantitative information for optimization of the composition of Pt_1−X Rh _X alloys for high temperature application in oxidizing atmospheres.     

Effect of BaO on Catalytic Activity of Pt-Rh TWC

The effect of BaO doping to the Pt-Rh catalysts on its three-way catalytic activity and water-gas transfer was investigated. The results show that the light-off temperatures of hydrocarbon and carbon monoxide and nitrogen oxides have little difference in the fresh catalysts. But after the hydrothermal-aged 5 h at 1000 ℃, the catalysts containing CeO2-ZrO2-BaO has lower light-off temperature and better catalytic activity than the catalysts containing BaO and CeO2-ZrO2,