Electrical Conductivity of Pure and Doped Nanocrystalline Cerium Oxide

1996 ◽  
Vol 457 ◽  
Author(s):  
E. B. Lavik ◽  
Y.-M. Chiang
Keyword(s):  
Heat Treatment ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Interfacial Area ◽  
Low Energy ◽  
Direct Proportion ◽  
Treatment Conditions ◽  
Defect Sites ◽  
Interface Reduction ◽  
The Relationship

ABSTRACTWe have previously shown that dense nanocrystalline CeO2−x of approximately 10 nm grain size exhibits enhanced electrical conductivity and an enthalpy of reduction that is more than 2.4 eV lower than that for conventional ceria [1, 2]. These effects were attributed to preferential interface reduction. In this work, we investigated the relationship between interfacial area, heat treatment conditions, and conductivity by varying the grain size of dense samples through annealing at various temperatures. It is shown that the conductivity does not scale in direct proportion to interfacial area. Moderate temperature (700 °C) anneals which change the grain size by only a few nanometers reduce the conductivity by three orders of magnitude. It is suggested that atomistic relaxation occurs at the interfaces, and eliminates many low energy defect sites.

Enhanced Electrical Conductivity and Nonstoichiometry in Nanocrystalline CeO2-x

1995 ◽  
Vol 400 ◽  
Author(s):  
E.B. Lavik ◽  
Y.-M. Chiang ◽  
I. Kosacki ◽  
H.L. Tuller
Keyword(s):  
Electrical Conductivity ◽  
Grain Size ◽  
Oxygen Vacancy ◽  
Electronic Conductivity ◽  
Boundary Resistance ◽  
Low Energy ◽  
Coarse Grained ◽  
Size Dependent ◽  
Nanocrystalline Ceria ◽  
Defect Sites

AbstractDense nanocrystalline CeO2-x. of ∼10 nm grain size exhibits enhanced, PO2-dependent electronic conductivity indicative of intrinsic nonstoichiometric behavior under conditions where coarse-grained counterparts are extrinsic. The enthalpy of reduction is lowered by over 2.4 eV per oxygen vacancy. The nanocrystals also exhibit greatly reduced grain boundary resistance, attributed to grain-size-dependent segregation. We propose that interface doping by selected low energy defect sites dominates the defect and transport properties of nanocrystalline ceria, and possibly other nanocrystalline compounds.

LiNiO2 Thin Films Fabricated by Diffusion of Li on Ni Tapes

2007 ◽  
Vol 336-338 ◽  
pp. 505-508
Author(s):  
Cheol Jin Kim ◽  
In Sup Ahn ◽  
Kwon Koo Cho ◽  
Sung Gap Lee ◽  
Jun Ki Chung
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Grain Size ◽  
Sol Gel ◽  
Surface Oxidation ◽  
Cold Isostatic Pressing ◽  
Tube Furnace ◽  
Treatment Conditions ◽  
Average Grain Size ◽  
Cold Rolling And Annealing

LiNiO2 thin films for the application of cathode of the rechargeable battery were fabricated by Li ion diffusion on the surface oxidized NiO layer. Bi-axially textured Ni-tapes with 50 ~ 80 μm thickness were fabricated using cold rolling and annealing of Ni-rod prepared by cold isostatic pressing of Ni powder. Surface oxidation of Ni-tapes were conducted using tube furnace or line-focused infrared heater at 700 °C for 150 sec in flowing oxygen atmosphere, resulted in NiO layer with thickness of 400 and 800 μm, respectively. After Li was deposited on the NiO layer by thermal evaporation, LiNiO2 was formed by Li diffusion through the NiO layer during subsequent heat treatment using IR heater with various heat treatment conditions. IR-heating resulted in the smoother surface and finer grain size of NiO and LiNiO2 layer compared to the tube-furnace heating. The average grain size of LiNiO2 layer was 0.5~1 μm, which is much smaller than that of sol-gel processed LiNiO2. The reacted LiNiO2 region showed homogeneous composition throughout the thickness and did not show any noticeable defects frequently found in the solid state reacted LiNiO2, but crack and delamination between the reacted LiNiO2 and Ni occurred as the reaction time increased above 4hrs.

Effect of Thermal Treatment on Thermoelectric Properties of Extruded TiO2 Ceramics

2014 ◽  
Vol 604 ◽  
pp. 249-253 ◽  
Author(s):  
Agnese Pura ◽  
Janis Locs ◽  
Liga Berzina-Cimdina
Keyword(s):  
Heat Treatment ◽  
Electrical Conductivity ◽  
Thermal Treatment ◽  
Seebeck Coefficient ◽  
Heating Rate ◽  
Thermoelectric Properties ◽  
Sintering Temperature ◽  
Extrusion Process ◽  
Vacuum Heat Treatment ◽  
Treatment Conditions

TiO2samples were obtained by extrusion process, sintered in air at 1000 °C, 1100 °C, 1200°C and 1300 °C and, afterwards, thermally treated under vacuum conditions at 1250 °C for 1 hour applying two different heating/cooling rates (2 °C/min and 5 °C/min). It was found that thermal treatment conditions substantially affected thermoelectric properties of the samples. Increasing sintering temperature, during the sample thermal treatment in air, the electrical conductivity of the specimens increased, while Seebeck coefficient decreased. With an increase in the heating rate during the vacuum heat treatment of the samples, the electrical conductivity of the samples decreased, while Seebeck coefficient increased.

scholarly journals The Effect of Cooling Rate on Mechanical Properties of Carbon Steel (St 35)

2014 ◽  
Vol 7 (1) ◽  
pp. 109-118
Author(s):  
Jenan Mohammed Nagie
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Carbon Steel ◽  
Cooling Rate ◽  
Experimental Results ◽  
Heat Treated ◽  
Before And After ◽  
Water Media ◽  
The Relationship

This paper is aimed to study the effect of cooling rate on mechanical properties of Steel 35. Specimens prepared to apply tensile, torsion, impact and hardness tests.Many prepared specimens heat treated at (850ºC) for one hour and subsequently were cooled by three different media [Water-Air-furnace] to show the effect of Medias cooling rate on mechanical properties. Microstructures of all specimens examined before and after heat treatment by an optical microscopy.To figure the phases obtained after heat treatment and its effect on the mechanical properties Experimental results have shown that the microstructure of steel can be changed and significantly improved by varying line cooling rate thus, improving one property will effect on the others because of the relationship between all properties.In water media tensile, torsion and hardness improved while impact results reduced. Air media contributed in improving most of the mechanical properties because of grain size homogeneity. At furnace media ductility and impact improved

scholarly journals Hardness and Conductivity of Die Forged ZYK530 Magnesium Alloy

2021 ◽  
Author(s):  
Fenghong CAO ◽  
Yaohui XU ◽  
Chang CHEN ◽  
Zhaohui QIN ◽  
Chi DENG
Keyword(s):  
Heat Treatment ◽  
Electrical Conductivity ◽  
Treatment Process ◽  
Mg Alloy ◽  
Heat Treatment Process ◽  
Optimum Heat ◽  
The Relationship ◽  
Optimum Heat Treatment ◽  
Good Agreement ◽  
Peak Value

The relationship among the microstructure, hardness and electrical conductivity of the as-forged ZYK530 Mg alloy after heat treatment was analyzed and studied using a microscope, X-Ray Diffractometer, eddy current conductivity meter, and Vickers microhardness tester, to explore optimum heat treatment process of ZYK530 Mg alloy. The results show that: with the prolongation of holding time, the electrical conductivity and microhardness show the same change trend, both of which show an oscillatory upward trend, and then decrease in an oscillatory downward trend after reaching the  peak value. There is a linear positive correlation between the conductivity and the hardness, and the fitting results of the conductivity and hardness are in good agreement with the measured results; combined with the actual production, when the heat-treatment is 480 ℃ × 8 h + 220 ℃ × 3 h, the highest hardness is 79.2 HV, the electroconductivity is 36.2%IACS, and the comprehensive performance is the best, which is the best heat treatment process.

Effect of Heat Treatment Conditions on Microstructures and Mechanical Properties of Cu-9Ni-6Sn-0.22Nb Alloy

2021 ◽  
Vol 904 ◽  
pp. 124-130
Author(s):  
Si Yang Xu ◽  
Ying Long Li ◽  
Mu Xin Zhang ◽  
Yi Fu Jiang ◽  
Hua Ding
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Electrical Conductivity ◽  
Grain Boundaries ◽  
Spinodal Decomposition ◽  
Ageing Time ◽  
High Strength ◽  
Ageing Temperature ◽  
Treatment Conditions ◽  
The Matrix

Due to its high strength, excellent electrical conductivity and high resistance to stress corrosion, Cu-Ni-Sn alloy has been selected as a kind of advanced metal material which can be used as the manufacture of springs, connectors, bearings and so on. In addition, the addition of Nb can efficiently improve the comprehensive properties of the alloy. In the present work, the effect of heat treatment conditions on microstructure and mechanical properties were studied in a Cu-9Ni-6Sn-0.22Nb alloy by means of optical microscopy (OM), transmission electron microscopy (TEM), tensile test and microhardness tests. The results show that before ageing, a large number of fine γ precipitates with DO22 type structure are distributed on the matrix. With the prolongation of ageing time, the ultimate tensile strength (UTS), yield strength (YS) and Vickers hardness increased firstly, and then decline. The reason can be attributed to the occurrence of spinodal decomposition and the formation of discontinuous precipitation (DP). At first, spinodal decomposition induced the enhanced interaction between dislocations and internal stress field, resulting in an increase of mechanical properties. Then the increased DP at grain boundaries leads to the decline of strength in the material. Finally, the relationship between the microstructure and the electrical conductivity was also analyzed, and the results show that the electrical conductivity increased with ageing time/ageing temperature increasing for the present alloy. Through the analysis of Matthiessen’ s rule, the variation of electrical resistivity depends on precipitates, solute atoms, dislocations, vacancies and grain boundaries, and the precipitates play an important role among them. Besides, more precipitates improve electrical conductivity. Therefore, the increase of ageing time/ageing temperature induced the increase of DP, resulting in an increase of electrical conductivity.

scholarly journals Microstructure, Texture, Electrical and Mechanical Properties of AA-6063 Processed by Multi Directional Forging

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2419 ◽  
Author(s):  
Alireza Dashti ◽  
Mohammad Shaeri ◽  
Reza Taghiabadi ◽  
Faramarz Djavanroodi ◽  
Farzaneh Vali Ghazvini ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Electrical Conductivity ◽  
Ambient Temperature ◽  
Solution Treated ◽  
Treatment Conditions ◽  
Heat Treated ◽  
Treated Sample ◽  
Average Grain Size ◽  
Shear Yield

In current research, the effect of the multi-directional forging (MDF) process on the microstructure, texture, mechanical and electrical properties of AA-6063 under different heat treatment conditions at various MDF temperatures was studied. The annealed AA-6063 alloy was processed up to three passes of MDF at ambient temperature. Three passes of this process were also applied to the solution-treated AA-6063 at ambient temperature and 177 °C. Microstructural investigations demonstrated that the MDF process led to a significant reduction in the average grain size as well as a considerable increase in the fraction of low angle grain boundaries. Texture analysis revealed that copper and Goss textures were mainly developed within the annealed and solution-treated samples of AA-6063, respectively. The hardness and shear strength values of all processed samples also showed a sizeable improvement compared to the initial heat-treated samples. For example, the hardness and shear yield strength value of the solution-treated sample MDFed for three passes showed more than 100 and 70% increase, respectively. The effect of the MDF process on the electrical conductivity of AA-6063 under different heat treatment conditions at various temperatures was negligible. So, it can be concluded that the MDF process increased the mechanical properties without an appreciable decrease in electrical conductivity.

Effect of Prior Strain on Damping Capacity and Mechanical Property during Heat Treatment

2016 ◽  
Vol 879 ◽  
pp. 1053-1056
Author(s):  
Juho Kwak ◽  
Chang Yong Kang ◽  
Han Sang Kwon ◽  
Kwon Hoo Kim
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Crystal Orientation ◽  
Room Temperature ◽  
Dislocation Motion ◽  
Treatment Temperature ◽  
Damping Capacity ◽  
Treatment Conditions ◽  
Deformation And Heat Treatment ◽  
Temperature Factors

In previous study, it was investigated damping capacity on various deformation and heat treatment conditions in order to study damping capacity that was influenced by grain size and dislocation motion in detail. Magnesium alloy AZ31 was rolled at 673K with different rolling reduction, respectively. Specimens were machined out parallel to the rolled direction and annealed on various temperature and time. Then, damping capacity, microstructure and hardness was measured at room temperature. Factors affected on damping capacity are grain size, crystal orientation, dislocation motion, and so on. It was found that damping capacity has been affected by grain size and crystal orientation. Grain size and hardness is not examined obvious difference after annealing. In large prior strain, however, low damping capacity is appeared and damping capacity increases with increasing of heat treatment temperature. The reason is that resolved shear stress factor is influenced by damping capacity.

Synthesis and Properties of an Ultrafine Grained Ti-45Al-2Cr-2Nb-1B-0.5Ta Alloy Prepared by Double Mechanical Milling and Spark Plasma Sintering

2009 ◽  
Vol 614 ◽  
pp. 49-54
Author(s):  
Yu Yong Chen ◽  
Fan Tao Kong ◽  
Hong Bao Yu ◽  
De Liang Zhang
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Spark Plasma Sintering ◽  
Mechanical Milling ◽  
Composite Powders ◽  
Plasma Sintering ◽  
Ultrafine Grained ◽  
Spark Plasma ◽  
The Relationship ◽  
Bulk Alloys

Ti-45Al-2Cr-2Nb-1B-0.5Ta (at.%) bulk alloys with dense and ultrafine grains were fabricated by Double Mechanical Milling (mechanical milling + heat treatment + mechanical milling) and spark plasma sintering method. The phase composition and microstructure of the milled powder and bulk alloy sintered by SPS at different temperature (900oC, 1000oC and 1100oC), and the relationship between microstructure and properties of bulk alloys were investigated. The results demonstrate that high-quality composite powders (low contaminant, size uniform distribution and elements homogeneous dispersion) can be obtained by double mechanical milling. The composite powders prepared by primary mechanical milling were uniform and partially solid solution. Ti3Al、Ti、Al3Ti and TiAl phases were found after heat treatment while Al phase disappeared. The fined grain size and particle size were achieved by subsequent mechanical milling. The whole mechanical milling leads to alloying and the refined grain and particle, which also cause lattice distortion and powders system energy increased. SPS results showed that the densified and ultrafine grained Ti-45Al-2Cr-2Nb-1B-0.5Ta alloy is mainly consisted of TiAl, Ti3Al phase and a small quantity of TiB2 phase. With the increasing of sintering temperature, grain size of TiAl based alloy increase. The mechanical properties depend on microstructure and grain size. The relationship between compression properties, bending properties and microstructure was discussed.

Effects of Crystal Grain Size and Particle Size on Core Loss for Fe-Si Compressed Cores

2007 ◽  
Vol 534-536 ◽  
pp. 1313-1316 ◽  
Author(s):  
Satoshi Takemoto ◽  
Takanobu Saito
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Grain Size ◽  
High Efficiency ◽  
Core Loss ◽  
Eddy Current Loss ◽  
Power Supplies ◽  
Magnetic Powder ◽  
Soft Magnetic ◽  
Treatment Conditions

Core loss of soft magnetic powder cores have been focused on to achieve high efficiency of power supplies. In this study the effects of crystal grain size on core loss were investigated by changing heat treatment conditions. It was found that core loss is influenced by crystal grain size because eddy current loss decreased and hysteresis loss increased by making crystal grain size smaller, and it is also influenced by the frequency and particle size.

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