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恒流微弧氧化工艺参数对膜层表面粗糙度的影响 总被引:1,自引:1,他引:0
铝合金微弧氧化膜表面粗糙度的影响因素较多,膜表面的粗糙度对其应用有影响,过去研究甚少,为了找出改善和控制膜层表面粗糙度的方法,在恒流模式下利用双极性脉冲电源对LD10铝合金试件进行了微弧氧化处理,采用TR200粗糙度仪检测了膜层表面粗糙度,分析了加工参数对膜层表面粗糙度的影响.结果表明:在一定范围内单独缩短微弧氧化时间、减小正向或负向电流密度、提高频率、降低占空比,都有利于降低膜层表面粗糙度;但温度过高或过低都不利于降低膜层表面粗糙度,只有在30~40 ℃的工作液中处理获得的膜层表面粗糙度才最佳.在30 ℃、电流密度10 A/dm2、脉冲频率200 Hz、占空比24%时,可获得最佳表面粗糙度(Ra 1.2 μm)的硬质微弧氧化膜层. 相似文献
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处理时间对铝合金微弧氧化陶瓷膜特性的影响 总被引:1,自引:0,他引:1
为了研究恒定电流密度下铝合金微弧氧化陶瓷膜的特性随处理时间的变化规律,在工作电流密度设定为25 A/dm2时制备了处理时间分别为1、3、5、10、20、30 min的样品共6块,并采用光学显微镜、显微硬度计、表粗糙度测量仪和SEM等手段对氧化陶瓷膜的形成机理进行了研究.结果表明,陶瓷膜表面呈圆饼状结构,圆饼的中心存在一个放电通道;膜的厚度、表面粗糙度、圆饼和放电通道的直径随处理时间线性增加;陶瓷膜的显微硬度与处理时间密切相关. 相似文献
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目前有关铝合金微弧氧化膜的膜层结构和精密薄壁件微弧氧化前后的尺寸精度变化研究较少.以航空发动机燃油控制系统附件——6061铝合金衬套(精密薄壁件)为研究对象,在试件表面进行A、B、C、D 4组不同微弧氧化工艺处理,对陶瓷膜层的微观组织形貌、成分、表面硬度进行检测分析,并分别测量其在微弧氧化处理前后内径尺寸、内孔圆柱度、表面粗糙度的变化.试验结果表明:采用特殊辅助工装的C、D组微弧氧化工艺,膜层性能优异,其表面硬度可达900 HV,是6061铝合金基材硬度的6倍,能大幅提高零件的耐磨性和使用寿命,同时满足尺寸精度要求,为后期铝合金微弧氧化工艺的工程化应用奠定了 一定的基础. 相似文献
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钛对FeAl金属间化合物高温氧化行为的影响 总被引:2,自引:0,他引:2
探究了钛元素对FeAl金属间合理化物在1000℃和1100℃大气环境下的循环氧化行为的影响。合金的氧化动力学过程通过增重法测定,氧化产物通过X射线衍射、能谱和扫描电镜等鉴定。实验结果表明,加钛和未加钛Fe-36.5Al合金的氧化动力学曲线均可拟合为抛物线;(△W/S)^2=Kpt+C。加钛FeAl合金在1000℃和1100℃时的Kp值分别为2.4,3.3mg^2cm^-4h^-1。而未加钛Feal 相似文献
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The electrocatalysis of the oxidation of hydrazine, formaldehyde and glucose on a nanoporous Pd-modified TiO2 electrode, prepared by the hydrothermal process, was investigated in 0.1 M NaOH solutions. The electrocatalytic activity of the Pd-modified TiO2 electrode for the electrochemical oxidation of hydrazine, formaldehyde and glucose is characterized by the low onset potentials of −0.80, −0.70 and −0.85 V (vs Ag,AgCl), respectively. Compared to the oxidation of formaldehyde and glucose, the hydrazine oxidation on the Pd-modified TiO2 presents the highest anodic oxidation current densities, showing that the Pd-modified TiO2 electrode is more electro-active for the hydrazine oxidation than for the oxidation of formaldehyde and glucose. Chronoamperograms at different concentrations of hydrazine and formaldehyde showed that the Pd-modified TiO2 electrode is a promising electrochemical sensor for the detection of hydrazine with a sensitivity of 0.554 mA cm−2 mM−1 and a detection limit of 0.023 mM, and for the detection of formaldehyde with a sensitivity of 0.20667 mA cm−2 mM−1 and a detection limit of 0.015 mM. However, it was found from the chronoamperometric responses at various glucose concentrations that a linear plot of the anodic oxidation current density versus glucose concentration developed only in the range of 7-35 mM glucose while an obvious deviation from the linear relationship was observed at both low and large glucose concentrations. Results show that the prepared Pd-modified TiO2 electrode could be applied to the direct liquid (hydrazine, formaldehyde, and glucose) fuel cells as an effective anodic catalyst, in addition to be a promising electrochemical sensor for the detection of hydrazine and formaldehyde. 相似文献
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涡轮叶片工作温度的不断提高,使得制备叶片的镍基单晶高温合金的合金化程度越来越高,而涡轮叶片在高温下的氧化行为影响着叶片的工作寿命.为此,本文以一种新型镍基高温合金为研究对象,利用氧化动力学曲线、X射线衍射分析,扫描电镜和能谱仪研究其在900和1 100 ℃下200 h的高温氧化行,并探究新型合金的氧化机理.研究发现:新型合金在900 ℃氧化时,表面氧化膜未发生剥落,动力学曲线遵循抛物线规律;在1 100 ℃氧化时,合金增重迅速且表面氧化膜剥落严重,新型合金内部出现了多层不连续的Al2O3内氧化层.研究结果表明:900 ℃时,新型合金中Cr含量降低的同时没有增加Re和Ta等活性元素,导致新型合金不能在氧化初期通过选择性氧化迅速形成保护性Cr2O3氧化膜,因此,增重迅速;1 100 ℃时,由于外氧化层的碎裂剥落,合金内部氧通量再次升高,已生成的Al2O3保护性氧化膜被消耗突破,合金进一步氧化,直到氧通量随着氧化的进行再次降低至适合Al2O3保护性氧化膜生成为止. 相似文献
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耐1300℃新型Ni-Fe-Cr-Al基高温合金抗氧化机理研究 总被引:1,自引:0,他引:1
对新型高温合金(3YC52)的抗氧化机理进行了系统研究。结果表明,研制合金(3YC52)具有的优异抗氧化性能在于高温下合金表面能形成致密保护层。扫描电镜(SEM)、电子探针显微分析(EPMA)和X射线衍射分析(XRD)分析表明,1100℃,合金氧化层的内层为Cr2O3,外层为Al2O3;1300℃,合金氧化层为单一的Al2O3。差热分析(DTA)研究表明(Al,Cr)2O3和α-Al2O3的形成分别在1060℃和1356℃达到最大值。当温度大于1150℃时,Cr2O3易剥落,因此随着时间的延长,最终留下致密的α-Al2O3保护层。 相似文献
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用热重法研究了Zr_(58)Cu_(16)Ni_3Al_(10)Nb_3块体非晶合金在玻璃态温度(Tg=657 K)和过冷液相区(Tg=657 KTTx=759 K)不同时间(1.5 h和126 h)的等温氧化过程,同时比较了在玻璃态温度下623 K和过冷液相区673 K下,长时间126 h等温氧化的产物和基体结构。实验结果表明,在短时间1.5 h等温氧化,573K—673 K,氧化产物均为t-Zr O_2,基体为非晶态结构。玻璃态温度下623 K氧化速率变化与时间成线性关系,而过冷液相区氧化速率存在高速增长阶段(0—1 h),速率降低阶段(1 h—6.5 h)和稳定低速阶段(6.5 h—126h)。晶化与过冷液相区长时间氧化机制有密切关系。 相似文献
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镍基单晶合金高温氧化的动力学特征 总被引:3,自引:0,他引:3
通过对镍基单晶合金高温氧化后的组织结构观察和内氧化层深与循环氧化质量变化动力学曲线的测定,研究了合金的高温氧化特性,结果表明:在大气环境条件下,无保护涂层合金发生明显的氧化和内氧化;在近异形大颗粒内氧化物处于现贫Al区,使区内γ′强化相消失,内氧化层的深度随时间的变化服从抛物线规律。外加拉伸应力使内氧化加剧,在循环氧化初期,由于形成以Al为主的氧化膜易剥落,质量变化动力学曲线表现出较快的减重趋势,合金在20-80h的循环变化期间,在1040℃和1070℃分别呈较缓的增,减重趋势。 相似文献
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《Materials at High Temperatures》2013,30(1):133-137
AbstractPreliminary studies have been undertaken on cyclic and isothermal oxidation at 1,300°C of thin (125 μm) samples of commercial ODS alloy PM2000 for up to 350h in two different oxidising environments; dry and moist air. Scanning electron microscopy (SEM) and electron microprobe analysis (EPMA) have been used to study the influence of such environments on alumina scale formation and growth. Initial mass gain observations showed that the alumina scale, which formed on the samples oxidised in air+2.5vol% H2O grew faster in the early stages of oxidation than in the case of dry air. However the SEM analysis revealed that the scale morphologies in both dry air and air+2.5vol% H2O were similar. In both cases the scales consisted of equiaxed grains at the scale–gas interface with Ti-rich particles in the outermost part of the scale. The major factor for the total scale failure, the formation of non-protective iron oxide, is the depletion of Al levels to a critical value, below which no protective alumina scale can form; and this occurred slightly faster in moist air than in dry air 相似文献
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Wet electrolytic oxidation of cationic red X-GRL 总被引:1,自引:0,他引:1
Wet electrolytic oxidation (WEO) under mild condition, a relatively less reported process which coupled the advantages of both wet air oxidation (WAO) and electrochemical oxidation (EO) was investigated for the removal of one azo dye, cationic red X-GRL, in a 2L autoclave reactor. It was found that this novel process showed synergistic effect for TOC removal compared with that by the individual WAO and EO, and presented much higher dye removal efficiency. At similar conditions of temperature of 100-180 degrees C, P(N(2))= 0.50 MPa and P(O(2))= 0.14 MPa, a little introduction of current density of 2 mA cm(-2) led to the apparent reaction constants for WEO two times larger than those of WAO. Possible mechanism for the synergistic effect was discussed based on the analysis of free-radical generation and intermediates detected by GC/MS. 相似文献