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Effects of composite oxide scale on oxidation resistance of superalloy K273 被引量:2
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作者 Wang Haitao Tan Jiwen +1 位作者 Chu Zhong Yu Huashun 《China Foundry》 SCIE CAS 2012年第2期165-170,共6页
A Si-containing K273 superalloy was made using intermediate frequency induction furnace in the study. In the testing of oxidation resistance, the oxidation process of the alloy specimens during the testing at 900℃ fo... A Si-containing K273 superalloy was made using intermediate frequency induction furnace in the study. In the testing of oxidation resistance, the oxidation process of the alloy specimens during the testing at 900℃ for 500 h was examined by oxidation weight gain method. The morphology and composition of the oxide scales were determined using scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The effects of the transferring of ions and electrons on the oxidation resistance were further analyzed microscopically by semiconductor oxide models. The results show that the composite oxide scales consist of Cr203, SiO2 and spinel- type oxide MCr204, with flat and compact structure, and fine grains in uniform distribution. All of these endow the superalloy K273 with strong oxidation resistance. The reason for the powerful oxidation resistance of the composite scale is that the formation process of P+N type semiconductor oxide enables to consume most of the surplus negative and positive ions in the oxide scales, which makes the number of the mobile ions and electrons dropped enormously, and the transfer rate of them falls heavily. So the oxidation rate of the metal phase in the alloy matrix is reduced significantly. 展开更多
关键词 SUPERALLOY SILICON oxide scale oxidation resistance
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Influence of Cr_2O_3-Al_2O_3 Composite Oxide Scale on Oxidation Resistance of ZG40Cr24 被引量:1
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作者 王海涛 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2012年第3期405-410,共6页
Test alloys ZG40Cr24 with alloying of 3 wt% aluminium were cast by intermediate frequency induction furnace. The oxidation resistance of test alloys at 1 000 ℃ for 500 hours was examined according to oxidation weight... Test alloys ZG40Cr24 with alloying of 3 wt% aluminium were cast by intermediate frequency induction furnace. The oxidation resistance of test alloys at 1 000 ℃ for 500 hours was examined according to oxidation weight gain method. The scale morphology and composition were studied using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. By energy dispersive spectroscopy (EDS) studies, a kind of composite oxide scale compounded highly by Cr2O3, Al2O3 and spinel MCr2O4 in molecule scale came into being at high temperature. With flat and compact structure, fine and even grains, such composite scale granted complete oxidation resistance to alloy ZG40Cr24. The oxidation resistance mechanism was studied deeply in electrochemistry corrosion. The P+N semiconductor composite scale composed plenty of inner PN junctions, of which the unilateral conductive and the out-of-order arrangement endowed itself insulating in all directions. The positive and negative charges in scale could not move, and the mobile number and transferring rate of them both dropped enormously, as a result, the oxidation rate of the matrix metal was cut down greatly. So the composite scale presented excellent oxidation resistance. 展开更多
关键词 oxide scale oxidation resistance CR2O3 AL2O3 SEMICONDUCTOR
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Effect of Heating Rates on the Formable Oxide Scale on a C-Steel Surface 被引量:1
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作者 A.A.El-Meligi 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2004年第5期591-594,共4页
Oxide scale formation on a C-steel surface has been investigated using linear heating rates ranging from 0.1℃/min to 10℃/min at high temperatures. The studies on the oxide scale formation at high temperature (650℃)... Oxide scale formation on a C-steel surface has been investigated using linear heating rates ranging from 0.1℃/min to 10℃/min at high temperatures. The studies on the oxide scale formation at high temperature (650℃) at slower heating rate (0.1℃/min) shows that the kinetic regime is linear. X-ray diffraction measurements revealed that the scale constituents are significantly influenced by the heating rate. The adherence of the scale was improved by using slower heating rate (0.1℃/min-≤650℃), while above such degree the scale was susceptible to cracking and flaking out of the alloy surface. In fact, the development of oxide growth stresses can cause considerable scale cracking. As well, variation of the crystallite sizes under the aforementioned conditions might affect the scale stacking to the alloy surface. The secondary electron detector images of the oxide scale shows that the scale was imperfectly smooth and there were a number of voids and defects in the scale skin, especially at fast heating rate. This observation could be attributed to defects of the as-received alloy. In general, slower heating rate reduced the defects of the scale and improved its adherence. 展开更多
关键词 C-steel oxide scale Heating rate Weight gain XRD
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Improvement to anti-rust property of hot rolled rebar by compact oxide scale 被引量:1
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作者 CHEN Qing-an LIU Li-zhong +1 位作者 LIU Xin LIU Xiang-hua 《Journal of Central South University》 SCIE EI CAS CSCD 2017年第12期2813-2818,共6页
A method was proposed to improve the anti-rust property of hot rolled rebar, which uses oil–water emulsion cooling instead of water cooling after hot rolling. The experiments were carried out by two cooling methods, ... A method was proposed to improve the anti-rust property of hot rolled rebar, which uses oil–water emulsion cooling instead of water cooling after hot rolling. The experiments were carried out by two cooling methods, one cooled by water, the other cooled by oil–water emulsion. The results of wet/dry cyclic accelerated corrosion test showed that the anti-rust property of rebar cooled by oil–water emulsion was better than that by water obviously. The results of OM, SEM and EPMA analysis indicated that these two scales contained three layers: an outer Fe_3O_4 layer, an intermediate Fe O layer with island-shaped pro-eutectoid Fe_3O_4, an inner eutectoid Fe_3O_4 layer. For the water cooled rebar, all three layers of oxide scale were relatively thin. Moreover, the scale had plenty of defects such as porosity, and crack. However, for the oil–water emulsion cooled rebar, all three layers of oxide scale were relatively thick and compact, which played an important role in protecting the rebar from atmospheric rust. 展开更多
关键词 hot rolled REBAR anti-rust PROPERTY COMPACT oxide scale oil–water EMULSION cooling
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Thin Film of Perovskite Oxide with Atomic Scale p-n Junctions 被引量:1
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作者 HU Bin HUANG Ke-ke +3 位作者 HOU Chang-min YUAN Hong-ming PANG Guang-sheng FENG Shou-hua 《Chemical Research in Chinese Universities》 SCIE CAS CSCD 2012年第3期379-381,共3页
Thin films of perovskite manganese oxide Lao.66Ca0.29K0.05MnO3(LCKMO) on Au/ITO(ITO=indium tin oxide) substrates were prepared by off-axis radio frequency magnetron sputtering and characterized by X-ray diffrac- t... Thin films of perovskite manganese oxide Lao.66Ca0.29K0.05MnO3(LCKMO) on Au/ITO(ITO=indium tin oxide) substrates were prepared by off-axis radio frequency magnetron sputtering and characterized by X-ray diffrac- tion(XRD), high-resolution transmission electron microscopy(HRTEM), and conductive atomic force microscopy (C-AFM) at room temperature. The thin films with thickness ranged from 100 nm to 300 nm basically show cubic structures with a=0.3886 nm, the same as that of the raw material used, but the structures are highly modulated. C-AFM results revealed that the atomic scale p-n junction feature of the thin films was the same as that of the single crystals. The preparation of the thin films thus further confirms the possibility of their application extending from micrometer-sized single crystals to macroscopic thin film. 展开更多
关键词 Perovskite oxide Thin film Atomic scale p-n junction
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Influence of oxide scales on the corrosion behaviors of B510L hot-rolled steel strips 被引量:3
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作者 Cheng Man Chao-fang Dong +3 位作者 Hui-bin Xue Kui Xiao Xiao-gang Li Hui-bin Qi 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2016年第7期769-778,共10页
The influence of oxide scales on the corrosion behaviors of B510 L hot-rolled steel strips was investigated in this study. Focused ion beams and scanning electron microscopy were used to observe the morphologies of ox... The influence of oxide scales on the corrosion behaviors of B510 L hot-rolled steel strips was investigated in this study. Focused ion beams and scanning electron microscopy were used to observe the morphologies of oxide scales on the surface and cross sections of the hot-rolled steel. Raman spectroscopy and X-ray diffraction were used for the phase analysis of the oxide scales and corrosion products. The corrosion potential and impedance were measured by anodic polarization and electrochemical impedance spectroscopy. According to the results, oxide scales on the hot-rolled strips mainly comprise iron and iron oxides. The correlation between mass gain and test time follows a power exponential rule in the damp-heat test. The corrosion products are found to be mainly composed of γ-Fe OOH, Fe3O4, ?-Fe OOH, and γ-Fe2O3. The contents of the corrosion products are different on the surfaces of the steels with and without oxide scales. The steel with oxide scales is found to show a higher corrosion resistance and lower corrosion rate. 展开更多
关键词 strip steel hot rolling focused ion beams Raman spectroscopy oxide scale corrosion
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DEFLECTION METHOD FROM TWO SIDES OXIDATION TO STUDY EFFECT OF Y ON INTERNAL STRESS OF OXIDE SCALES
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作者 LI Tiefan LI Meishuan Corrosion Science Laboratory,Institute of Corrosion and Protection of Metals,Academia Sinica Shenyang.China 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 1992年第12期447-450,共4页
Au investigation was carried ont of the effect of Y addition upon the internal stress of Al_2O_3 scale formed during oxidation of sputtering coating on Co-30Cr-6Al alloy and the growth stress of oxidized film on Fe-23... Au investigation was carried ont of the effect of Y addition upon the internal stress of Al_2O_3 scale formed during oxidation of sputtering coating on Co-30Cr-6Al alloy and the growth stress of oxidized film on Fe-23Cr-5Al alloy heating up to 900℃ in air,using a specially designed deflection method from thin strip specimen with coat- ings,ion-implanted Y on one side and oxidized onto both sides.Results indicate that Y may decrease the internal stress of oxide scale on 2×10^(17) Y^+/cm^2 implanted Co- 30Cr-6Al coating,and increase one on 2×10^(16) Y^+/cm^2 implanted Fe-23Cr-5Al alloy. This seems due to whether or not Y promotes the plastic deformation of oxide scale.In addition,at initial oxidation stage,the change of growth stress of oxide scale formed on Y-implanted Co-30Cr-6Al coating may be related to the influence of Y on oxidation process of the coating. 展开更多
关键词 growth stress oxide scale ion implantation Y.high temperature oxidation
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Study on direct cold rolling of hot rolled austenitic stainless steel SUS 304 with oxide scale
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作者 He Shen Shen Jicheng 《Baosteel Technical Research》 CAS 2008年第1期18-21,共4页
The austenitic stainless steel SUS 304 with oxide scale was directly cold rolled at different reductions of 10%, 20% and 30% respectively. It was proved that the surface quality (lower surface roughness) of the cold... The austenitic stainless steel SUS 304 with oxide scale was directly cold rolled at different reductions of 10%, 20% and 30% respectively. It was proved that the surface quality (lower surface roughness) of the cold rolled products was achieved after subsequent annealing and pickling possesses, compared to the conventional hot rolled No. 1 product, whereas the grain size, mechanical and corrosion-resistant properties were comparable to those of the No. 1 product. 展开更多
关键词 austenitic stainless steel cold rolling oxide scale
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Effect of Hot-Rolled Oxide Scale on Dry/ Wet Cyclic Corrosion Behavior of Q370qNH Steel in Simulated Industrial Atmosphere Environment
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作者 REN Yuxia GUO Tieming +4 位作者 XU Xiujie LI Guangming TANG Jian NAN Xueli JIA Jiangang 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2022年第6期1216-1227,共12页
The corrosion behavior of Q370qNH steel in the presence and absence of hot-rolled oxide scale in simulated industrial atmospheric environment was studied by dry/wet cycle accelerated corrosion experiments.The experime... The corrosion behavior of Q370qNH steel in the presence and absence of hot-rolled oxide scale in simulated industrial atmospheric environment was studied by dry/wet cycle accelerated corrosion experiments.The experimental results show that the corrosion type of bare steel is uneven overall corrosion and large size pitting corrosion in small areas;that of oxide scale sample is local dissolution corrosion and small size pitting corrosion in large areas,and corrosion rate is much smaller than that of bare steel.The corrosion products of both steels are composed ofα-FeOOH,γ-FeOOH,Fe_(2)O_(3),and Fe_(3)O_(4),but the formation mechanism is different.The bare steel generatesα-FeOOH andγ-FeOOH through“acid regeneration cycle mechanism”;the oxide scale sample generates hydroxides mainly through the gradual dissolution of the oxide film,and then through“the acid regeneration cycle mechanism”.With the extension of corrosion time,the electrochemical stability of the sample with oxide scale increases,but the change of tafel curve of bare steel sample is not obvious.In simulated industrial atmosphere,the existence of hot-rolled oxide scale can facilitate the formation of dense rust layer on the surface of Q370qNH steel,which is more protective than bare steel. 展开更多
关键词 Q370qNH steel oxide scale NAHSO3 corrosion behavior
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Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system 被引量:35
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作者 PENG Yongzhen HOU Hongxun +2 位作者 WANG Shuying CUI Youwei Zhiguo Yuan 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2008年第4期398-403,共6页
To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal (SNDPR), a whole course of SNDPR damage and recovery was... To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal (SNDPR), a whole course of SNDPR damage and recovery was studied in a pilot-scale, anaerobicanoxic oxidation ditch (OD), where the volumes of anaerobic zone, anoxic zone, and ditches zone of the OD system were 7, 21, and 280 L, respectively. The reactor was fed with municipal wastewater with a flow rate of 336 L/d. The concept of simultaneous nitrification and denitrification (SND) rate (rSND) was put forward to quantify SND. The results indicate that: (1) high nitrogen and phosphorus removal efficiencies were achieved during the stable SND phase, total nitrogen (TN) and total phosphate (TP) removal rates were 80% and 85%, respectively; (2) when the system was aerated excessively, the stability of SND was damaged, and rSND dropped from 80% to 20% or less; (3) the natural logarithm of the ratio of NOx to NH4^+ in the effluent had a linear correlation to oxidation-reduction potential (ORP); (4) when NO3^- was less than 6 mg/L, high phosphorus removal efficiency could be achieved; (5) denitrifying phosphorus removal (DNPR) could take place in the anaerobic-anoxic OD system. The major innovation was that the SND rate was devised and quantified. 展开更多
关键词 oxidation ditch biological nitrogen removal biological phosphorus removal simultaneous nitrification and denitrification (SND) pilot scale municipal wastewater
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Effects of composite scale on high temperature oxidation resistance of Fe-Cr-Ni heat resistant alloy 被引量:6
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作者 Wang Haitao Wang Yuqing +2 位作者 Yu Huashun Min Guanghui Wang Zhifu 《China Foundry》 SCIE CAS 2009年第2期109-114,共6页
Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain meth... Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain method, the oxidation resistances of the test alloys were determined at 1,200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted and the functions were regressed by the least squares method. The results show that the oxidation kinetic curves follow the power function of y = ax^b (a〉0, 0〈b〈1). The effects of scale compositions on oxidation resistance were studied further by analyses using X-ray diffraction (XRD) and scanning electron microscope (SEM). It is found that the composite scale compounds of Cr203, a-Al2O3, SiO2 and FeCr2O4, with compact structure and tiny grains, shows complete oxidation resistance at 1,200℃. When the composite scale lacks a-Al2O3 or SiO2, it becomes weak in oxidation resistance with a loose structure. By the criterion of standard Gibbs formation free energy, the model of the nucleation and growth of the composite scale is established. The forming of the composite scale is the result of the competition of being oxidized and reduced between aluminum, silicon and the matrix metal elements of iron, chromium and nickel. The protection of the composite scale is analyzed essentially by electrical conductivity and strength properties. 展开更多
关键词 Fe-based alloy heat resistant alloy oxide scale oxidation resistance
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Scale up and stability test for oxidative coupling of methane over Na_2WO_4-Mn/SiO_2 catalyst in a 200 ml fixed-bed reactor 被引量:3
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作者 Haitao Liu Xiaolai Wang +3 位作者 Dexin Yang Runxiong Gao Zhonglai Wang Jian Yang 《Journal of Natural Gas Chemistry》 EI CAS CSCD 2008年第1期59-63,共5页
The study of scale up for the oxidative coupling of methane (OCM) has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 (W-Mn/SiO2) catalyst. The effects of reaction ... The study of scale up for the oxidative coupling of methane (OCM) has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 (W-Mn/SiO2) catalyst. The effects of reaction conditions were investigated in detail. The results showed that, with increasing reaction temperature, the gas-phase reaction was enhanced and a significant amount of methane was converted into COx; with the CH4/O2 molar ratio of 5, the highest C2 (ethylene and ethane) yield of 25% was achieved; the presence of steam (as diluent) had a positive effect on the C2 selectivity and yield. Under lower methane gaseous hourly space velocity (GHSV), higher selectivity and yield of C2 were obtained as the result of the decrease of released heat energy. In 100 h reaction time, the C2 selectivity of 66%-61% and C2 yield of 24.2%-25.4% were achieved by a single pass without any significant loss in catalytic performance. 展开更多
关键词 scale up oxidative coupling of methane W-Mn/SiO2 200 ml fixed-bed reactor
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Changes of Nitric Oxide and Its Relationship with Clinical Features,Intracranial Pressure and Outcome in Acute Head Injury 被引量:1
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作者 周东 裘明德 +1 位作者 关玉娟 李龄 《Journal of Huazhong University of Science and Technology(Medical Sciences)》 SCIE CAS 2000年第2期148-150,共3页
To investigate the content and dynamics of nitric oxide (NO) in the cerebrospinal fluid (CSF) of patients with acute head injury and to clarify the relationship of NO with clinical features and intracranial pressure (... To investigate the content and dynamics of nitric oxide (NO) in the cerebrospinal fluid (CSF) of patients with acute head injury and to clarify the relationship of NO with clinical features and intracranial pressure (ICP) as well as outcomes, 38 adults with acute head injury were studied. Glasgow Coma Scale (GCS) obtained at admission and Glasgow Outcome Scale (GOS) 3 months after injury was assessed. ICP was surveyed via intraventricular catheter and lumbar puncture and CSF samples were obtained simultaneously. NO was determined with Griess reagents. Results showed that NO peak content in the head injury group was significantly higher than that of the control group. During dynamic research, no peak content of mildly injured cases and severely injured ones appeared in different time windows respectively. The peak value of NO was distinctly higher in the severe group than in the mild group. NO peak value of the raised ICP group was remarkably higher than that of the normal ICP group. The peak value of NO was considerately higher in the poor outcome group than in the good outcome group. When the content of NO was over 6. 5 μmol/L, the rate of poor outcome was increased. There existed a correlation between NO and GCS, ICP and GOS. It is concluded that the content of NO was increased in patients with acute head injury and the changes of NO had different time windows in severely injured patients and mildly injured ones. The more sever the injury, the higher the NO content; and the more serious the secondary brain injury and brain edema, the worse the outcomes. When NO is combined with GCS, GOS and ICP, it increases the accuracy of judgement to the degree of head injury and outcome. 展开更多
关键词 nitric oxide Glasgow coma scale intracranial pressure Glasgow outcome scale head injury
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HIGH TEMPERATURE OXIDATION AND STRUCTURE OF SCALE AND WHISKERS FOR Fe-Ni-Cr SEALING ALLOYS
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作者 DONG Zhili MA Jusheng +1 位作者 TANG Xiangyun YOU Liang Tsinghua University,Beijing,China lecturer Department of Materials Science and Engineering,Tsinghua University,Beijing 100084,China 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 1993年第8期147-150,共4页
The oxidation rate,the growth,morphology and structure of oxide scale and whiskers for Fe-Ni-Cr sealing alloys in H_2-H_2O atmosphere at high temperatures have been studied. The growth rate of scale is controlled by d... The oxidation rate,the growth,morphology and structure of oxide scale and whiskers for Fe-Ni-Cr sealing alloys in H_2-H_2O atmosphere at high temperatures have been studied. The growth rate of scale is controlled by diffusion.The scale is composed of Cr_2O_3 and spinel(Fe,Mn)O·Cr_2O_3 and the oxide whisker,are spinel(Fe,Mn)O·Cr_2O_3. 展开更多
关键词 oxidATION oxide scale oxide whisker Fe-Ni-Cr sealing alloy
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Effects of Scale Composition on Oxidation Kinetics of Fe-based Superalloy
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作者 王海涛 于化顺 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2010年第1期99-103,共5页
By oxidation weight gain method, four groups of Fe-based superalloys with different content of chromium, aluminium and silicon were tested at 1 200 ℃ for 500 hours. According to the oxidation weight gains, the oxidat... By oxidation weight gain method, four groups of Fe-based superalloys with different content of chromium, aluminium and silicon were tested at 1 200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted, and the equations were regressed by least square method and non-linear curve fitting. The effects of different scale compositions on the morphology and oxidation kinetic law were studied further by analysis of X-ray diffraction (XRD) and scanning electron microscope (SEM). It is found that the compounded scale is composed of Cr2O3, Al2O3, SiO2 and FeCr2O4, with compact structure and fine grains, possessing complete oxidation resistance at 1 200 ℃, and the oxidation kinetic curve follows the power function of y=axb (a0, 0b1). When the compounded scale lacks Al2O3 or SiO2, it becomes weak in oxidation resistance, but the oxidation kinetic curve still follows the power function with bigger parameter b. When Cr2O3 is absent, the kinetic curve shows two parts: the slow adding of oxidation weight gains at the beginning and the ascending line in the end. Such scale loses oxidation resistance completely. 展开更多
关键词 SUPERALLOY iron alloy oxide scale oxidation resistance property
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Crystal Growth Kinetics and Size Controls——Ⅰ.for Some Anode Active Oxides 被引量:1
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作者 王欣 唐中帜 唐电 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 2010年第6期972-976,共5页
RuO2,IrO2 and PdO are the most frequently employed active oxides in titanium anode coatings,so studies on the kinetics of their crystal-growth are important for anode material preparations.In this paper,the particle g... RuO2,IrO2 and PdO are the most frequently employed active oxides in titanium anode coatings,so studies on the kinetics of their crystal-growth are important for anode material preparations.In this paper,the particle growths of RuO2,IrO2 and PdO with increased temperature were discussed.The least-squares method was used to fit the kinetic data.As a result,the two-stage phenomena are found in all three noble material systems.The linear regression equations are correct both for the first and second stages.It is suggested that based on the corresponding kinetics equation Ln D =-QL/kT + a,the sizes of oxide particles can be controlled for the three noble oxides. 展开更多
关键词 noble-metal oxides NANO-scale KINETICS
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Cu enrichment behavior at steel-scale interface during high temperature oxidation of Cu containing steel
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作者 Hae-Geon LEE Seong-Woo KIM 《Baosteel Technical Research》 CAS 2010年第S1期17-,共1页
In order to suppress the surface cracking induced by Cu during reheating and hot rolling process,Cu enrichment and its migration at the steel-scale interface was investigated during heating of steel cast at temperatur... In order to suppress the surface cracking induced by Cu during reheating and hot rolling process,Cu enrichment and its migration at the steel-scale interface was investigated during heating of steel cast at temperatures between 1000℃and 1200℃in N_2-O_2 and N_7-H_2O atmospheres.For oxidation of Cu containing steel,Cu enriched phase was formed by the preferential oxidation of Fe and the enrichment and migration behavior of Cu depends on the oxidation temperature,steel chemistry and atmosphere condition.Ni in steel induced the formation of solid Cu and Ni enriched phase at steel/scale interface and in scale layer and the formation of uneven steel/scale interface, which suppresses the Cu enrichment because of extrusion of Cu enriched region before the formation of liquid phase.On the other hand,Sn addition promotes the liquid Cu formation at steel/scale interface and penetration into grain boundary of Cu enriched phase by decreasing solidus temperature and solubility limit.In addition,for oxidation at 1 200℃,the behavior of Cu at and around the steel-scale interface was found dependent to a large extent on morphology of the oxide scale formed during oxidation.At the early stage of oxidation,Cu-rich phase formed and accumulated at the steel scale interface under both O_2-N_2 and H_2O-N_2 atmospheres.As the oxidation proceeded,however,Cu enrichment at and its migration from the steel-scale interface were vastly different for different oxidizing atmospheres.In the case of O_2-N_2 oxidation,an oxide layer formed initially at the steel surface, but soon after a gap was developed at the steel-scale interface and grew in its size,which practically separated the scale from the steel substrate.The scale layer formed under this condition was porous.The Cu-rich phase initially formed at the interface was found migrating to the scale layer,leaving no Cu-rich phase at the interface.In the case of H_2O-N_2 oxidation,however,the scale layer formed was dense and tightly attached to the steel surface,and the Cu rich-phase continued to accumulate at the interface.Regarding the behavior of Cu-rich phase formed at the interface,it is proposed with experimental evidences that,when a gap forms at the steel-scale interface,it is the vaporization of Cu in the Cu-rich phase through the gap that brings Cu to the scale. 展开更多
关键词 STEEL oxidATION COPPER copper enrichment scale steel oxidATION COPPER copper enrichment scale
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Insights into electrochemical CO_2 reduction on tin oxides from first-principles calculations
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作者 Siwen Wang Jiamin Wang Hongliang Xin 《Green Energy & Environment》 SCIE 2017年第2期168-171,共4页
Density functional theory calculations were used to unravel the mechanism of CO_2 electroreduction on SnO_x surfaces. Under highly reducing conditions(<-0.6 V vs. RHE), the SnO(101) surface with oxygen vacancies is... Density functional theory calculations were used to unravel the mechanism of CO_2 electroreduction on SnO_x surfaces. Under highly reducing conditions(<-0.6 V vs. RHE), the SnO(101) surface with oxygen vacancies is likely the active phase for CO_2 reduction. We showed that the proton-electron transfer to adsorbed *CO_2 forming *OCHO, a key intermediate for producing HCOOH, is energetically more favorable than the formation of *COOH, justifying the selectivity trends observed on Sn-based electrocatalysts. With linear scaling relations, we propose the free formation energy of *CO_2 at the oxygen vacancy as the reactivity descriptor. By engineering the strain of the SnO(101) surface, the selectivity towards HCOOH can be further optimized at reduced overpotentials. 展开更多
关键词 CO2 electroreduction Tin oxides Strain effect Scaling relations Density functional theory
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Visualization of atomic scale reaction dynamics of supported nanocatalysts during oxidation and ammonia synthesis using in-situ environmental(scanning) transmission electron microscopy
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作者 Michael R.Ward Robert W.Mitchell +1 位作者 Edward D.Boyes Pratibha L.Gai 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2021年第6期281-290,I0007,共11页
Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as... Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as platinum are of interest in fuel cells and as diesel oxidation catalysts for pollution control,and practical ruthenium nanocatalysts are explored for ammonia synthesis.Graphite and graphitic carbons are of interest as supports for the nanocatalysts.Despite considerable literature on the catalytic processes on graphite and graphitic supports,reaction dynamics of the nanocatalysts on the supports in different reactive gas environments and operating temperatures at the single atom level are not well understood.Here we present real time in-situ observations and analyses of reaction dynamics of Pt in oxidation,and practical Ru nanocatalysts in ammonia synthesis,on graphite and related supports under controlled reaction environments using a novel in-situ environmental(scanning) transmission electron microscope with single atom resolution.By recording snapshots of the reaction dynamics,the behaviour of the catalysts is imaged.The images reveal single metal atoms,clusters of a few atoms on the graphitic supports and the support function.These all play key roles in the mobility,sintering and growth of the catalysts.The experimental findings provide new structural insights into atomic scale reaction dynamics,morphology and stability of the nanocatalysts. 展开更多
关键词 In-situ visualization Atomic scale reaction dynamics In-situ environmental scanning transmission electron microscopy with single atom resolution Supported nanoparticles Ammonia synthesis oxidation reactions
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Mass Synthesis in Polyol of Tailored Zinc Oxide Nanoparticles for Photovoltaic Applications
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作者 Mongia Hosni Ivaylo Hinkov +4 位作者 Christian Ricolleau Thierry Pauporté Samir Farhat Noureddine Jouini 《Journal of Surface Engineered Materials and Advanced Technology》 2016年第1期1-10,共10页
Zinc oxide nanoparticles with different sizes and shapes have been synthesized in polyol using a bottom-up approach. We have studied the scale-up of the process to massively produce high quality nanoparticles of contr... Zinc oxide nanoparticles with different sizes and shapes have been synthesized in polyol using a bottom-up approach. We have studied the scale-up of the process to massively produce high quality nanoparticles of controlled size and shape. The scale-up strategy required the effective mixing of reagents using either axial or radial mixing configurations and was experimentally validated by comparing structural properties of particles obtained in a small and a large size reactor. In addition, the flow patterns in these reactors have been calculated using three-dimensional turbulent computational fluid dynamics (CFD) simulations. Our results indicate a strong connection between the flow patterns, as obtained by CFD simulations, and the size and shape of the particles. Actually, our pilot scale reactor allowed producing sample aliquots of ~50 grams with nanoparticle sizes ranging from 8 nm to 600 nm and aspect ratio varying from 1 (nanospheres) to 20 (nanorods). After their synthesis, these two nanoparticle classes have been tested as building blocks in D149-dye-sensitized solar cell (DSSC). The measured power conversion efficiency (PCE) was 4.66% for nanorods shaped particles and 4.21% for nanospheres. These values were significantly higher than the 3.90% PCE obtained with commercial Degussa VP20 ZnO nanoparticles. 展开更多
关键词 Zinc oxide Polyol Process NANOPARTICLES scale-Up Strategy Dye-Sensitized Solar Cells
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