Influence of Grain Size and Grain Boundary State on Work Function of Nickel

2006 ◽  
Author(s):  
R. V. Khasfatov ◽  
R.Kh. Khisamov ◽  
L.R. Zubairov ◽  
R.R. Mulyukov
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Work Function ◽  
Boundary State

EFFECT OF GRAIN SIZE ON THE ELECTRON WORK FUNCTION OF Cu AND Al

2004 ◽  
Vol 11 (02) ◽  
pp. 173-178 ◽  
Author(s):  
WEN LI ◽  
D. Y. LI
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Grain Boundary ◽  
Work Function ◽  
Electron Work Function ◽  
Deformation Texture ◽  
Kelvin Probe ◽  
Surface Conditions ◽  
The Mean ◽  
Sophisticated Instrument

The Kelvin probe is a sophisticated instrument which is very sensitive to changes in surface conditions, such as deformation, texture, phase transformation and contamination. Efforts have been made to use this technique to diagnose wear. In this study, the effect of the grain boundary (GB) on the electron work function (EWF) was examined with the aim of investigating the contribution of changes in grain size to total changes in the EWF during wear. Copper and aluminum were studied as examples. It was demonstrated that the EWF dropped in the vicinity of GB's and the mean EWF decreased as the grain size decreased. The mechanism responsible for the changes in the EWF with respect to the GB is discussed.

Influence of Annealing on the Microstructure and Mechanical Properties of Electrodeposited Nanocrystalline Nickel

2011 ◽  
Vol 683 ◽  
pp. 103-112 ◽  
Author(s):  
B. Yang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Grain Boundary ◽  
Boundary Structure ◽  
Boundary State ◽  
Microstructure And Mechanical Properties ◽  
Grain Boundary Structure ◽  
Average Grain Size ◽  
Different Grain Size

The evolution of the microstructure and mechanical properties of electrodeposited nanocrystalline Ni with different annealing procedures was studied systematically. For the annealed specimens hardness decreases with increasing average grain size but the dependence changes at different grain size ranges. The specimens annealed at a low temperature show higher hardness compared to the as-deposited nanocrystalline Ni, despite an increased measured average grain size. In association with this hardening an increase in elastic modulus and a decrease in microstrain was observed after annealing. With increasing annealing temperature both the tensile strength and the fracture strain were observed to decrease, this is companied with a transition from ductile to brittle in the fracture surfaces. These results indicated that the mechanical behaviour of nanocrystalline Ni depends not only on the average grain size but also on the grain boundary structure. A change in the grain boundary state arising from annealing may be responsible for the observed increase in hardness and elastic modulus as well as the deterioration of tensile properties.

Light Effects on Grain Boundary Properties in Silicon

1981 ◽  
Vol 5 ◽  
Author(s):  
L. J. Cheng ◽  
C. M. Shyu
Keyword(s):  
Experimental Data ◽  
Grain Boundary ◽  
Minority Carrier ◽  
State Density ◽  
Boundary State ◽  
Carrier Recombination ◽  
Boundary Properties ◽  
Light Effects ◽  
Recombination Velocity ◽  
P Type

ABSTRACTWe have studied the photoconductivity of grain boundaries in p–type silicon. The result demonstrates the applicability of the technique for the measurement of minority carrier recombination velocity at the grain boundary. The experimental data are consistent with the thought that the recombination velocity increases with the boundary state density and light intensity.

The Effect of Grain Boundary State on Deformation Process Development in Nanostructured Metals Produced by the Methods of Severe Plastic Deformation

2011 ◽  
Vol 683 ◽  
pp. 69-79 ◽  
Author(s):  
Evgeny V. Naydenkin ◽  
Galina P. Grabovetskaya ◽  
Konstantin Ivanov
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Deformation Process ◽  
Process Development ◽  
Grain Boundary Sliding ◽  
Total Deformation ◽  
Nanostructured Metals ◽  
Boundary State ◽  
Boundary Sliding

In this review the investigations of deformation process development are discussed which were carried out by tension and creep in the temperature range Т<0.4Tm (here Тm is the absolute melting point of material) for nanostructured metals produced by the methods of severe plastic deformation. The contribution of grain boundary sliding to the total deformation in the above temperature interval is also considered. An analysis is made of the effect of grain size and grain boundary state on the evolution of grain boundary sliding and cooperative grain boundary sliding in nanostructured metals.

Improvement of Strength of Mg-12Gd-3Y-0.5Zr Alloys Processed by Combination of ECAP and Extrusion

2011 ◽  
Vol 682 ◽  
pp. 211-216
Author(s):  
Rong Zhu ◽  
Jin Qiang Liu ◽  
Jing Tao Wang ◽  
Ping Huang ◽  
Yan Jun Wu ◽  
...  
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Grain Boundary ◽  
Low Temperatures ◽  
Basal Slip ◽  
Extrusion Direction ◽  
Strengthening Mechanisms ◽  
Step Process ◽  
Angular Pressing ◽  
Peak Intensity

Equal channel angular pressing (ECAP) has been used to refine the grain size of Mg-12Gd-3Y-0.5Zr billet at about 400°C because it lacks sufficient ductility at low temperatures. However, <0001> peak intensity is oriented about 50º from the extrusion direction, which facilitates the basal slip, and decreases the yield strength. We have employed conventional extrusion at 300°C following ECAP to modify the texture in hard orientation. This two-step process makes use of two strengthening mechanisms a) grain boundary strengthening due to small grain size, and (b) texture strengthening due to grains in hard orientation. The samples processed by the two-step show the yield and ultimate strength to 283 and 308 MPa, respectively. Moreover, the activation of <c+a> slip and fine grains resulted from the ECAP helped to maintain a good ductility even after significant straining from conventional extrusion.

Structural and thermodynamic properties of nanocrystalline fcc metals prepared by mechanical attrition

1992 ◽  
Vol 7 (7) ◽  
pp. 1751-1761 ◽  
Author(s):  
J. Eckert ◽  
J.C. Holzer ◽  
C.E. Krill ◽  
W.L. Johnson
Keyword(s):  
Thermal Analysis ◽  
Grain Size ◽  
Melting Point ◽  
Grain Boundary ◽  
Bulk Modulus ◽  
Atomic Level ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fcc Metals ◽  
Mechanical Attrition

Nanocrystalline fcc metals have been synthesized by mechanical attrition. The crystal refinement and the development of the microstructure have been investigated in detail by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The deformation process causes a decrease of the grain size of the fcc metals to 6–22 nm for the different elements. The final grain size scales with the melting point and the bulk modulus of the respective metal: the higher the melting point and the bulk modulus, the smaller the final grain size of the powder. Thus, the ultimate grain size achievable by this technique is determined by the competition between the heavy mechanical deformation introduced during milling and the recovery behavior of the metal. X-ray diffraction and thermal analysis of the nanocrystalline powders reveal that the crystal size refinement is accompanied by an increase in atomic-level strain and in the mechanically stored enthalpy in comparison to the undeformed state. The excess stored enthalpies of 10–40% of the heat of fusion exceed by far the values known for conventional deformation processes. The contributions of the atomic-level strain and the excess enthalpy of the grain boundaries to the stored enthalpies are critically assessed. The kinetics of grain growth in the nanocrystalline fcc metals are investigated by thermal analysis. The activation energy for grain boundary migration is derived from a modified Kissinger analysis, and estimates of the grain boundary enthalpy are given.

Solid-phase crystallization of ultra-thin amorphous Ge layers on insulators

2021 ◽  
Author(s):  
Ryo Oishi ◽  
Koji ASAKA ◽  
Bolotov Leonid ◽  
Noriyuki Uchida ◽  
Masashi Kurosawa ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Barrier Height ◽  
Carrier Mobility ◽  
Solid Phase ◽  
Hole Mobility ◽  
Solid Phase Crystallization ◽  
Simple Method ◽  
20 Nm ◽  
Grain Boundary Barrier

Abstract A simple method to form ultra-thin (< 20 nm) semiconductor layers with a higher mobility on a 3D-structured insulating surface is required for next-generation nanoelectronics. We have investigated the solid-phase crystallization of amorphous Ge layers with thicknesses of 10−80 nm on insulators of SiO2 and Si3N4. We found that decreasing the Ge thickness reduces the grain size and increases the grain boundary barrier height, causing the carrier mobility degradation. We examined two methods, known effective to enhance the grain size in the thicker Ge (>100 nm). As a result, a relatively high Hall hole mobility (59 cm2/Vs) has been achieved with a 20-nm-thick polycrystalline Ge layer on Si3N4, which is the highest value among the previously reported works.

Creep Deformation / Oxidation Behavior of Re-Cr-Ni Diffusion Barrier Coated Hastelloy-X at 970°C in Air

2008 ◽  
Vol 595-598 ◽  
pp. 107-116 ◽  
Author(s):  
Shigenari Hayashi ◽  
Mikihiro Sakata ◽  
Shigeharu Ukai ◽  
Toshio Narita
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Barrier Layer ◽  
Creep Deformation ◽  
Diffusion Barrier ◽  
Hastelloy X ◽  
Alloy Substrate ◽  
Barrier Coating ◽  
Diffusion Barrier Layer ◽  
Coated Alloy

High temperature oxidation / creep deformation behavior of a diffusion barrier coated Hastelloy-X alloy, with large grain size ~500μm, was investigated at 970°C in air with external tensile stress of 22.5, 27.5, 32, and 40MPa. The diffusion barrier coating formed on Hastelloy-X consisted of a duplex structure with an inner diffusion barrier layer of Re-Cr-Ni alloy, and an outer oxidation resistant layer of β-NiAl. Un coated bare Hastelloy-X alloy with same grain size was also examined under the same conditions for comparison. The composition of the as-coated diffusion barrier coating was (15~21)Ni, (33~37)Cr, (30~33)Re, (11~15)Mo, and (9~14)Fe. This composition corresponds to σ-phase in the Ni-Cr-Re ternary system, which is known as a topologically close packed, TCP phase. The composition of this diffusion barrier layer did not change during the experiment. The oxide scales formed after creep testing on the coated and un-coated alloy surfaces were needle-like θ-Al2O3, and Cr2O3 with small amount of FeCr2O4, respectively. Grain boundary oxidation was also found in the subsurface region of the un-coated alloy. The Al2O3 scale exhibited severe spallation, and many cracks were formed perpendicular to the stress direction. However, no spallation or cracks were observed in the Cr2O3. The creep rupture times for the diffusion barrier coated alloy were about 1.5 times longer than those for bare alloy at all creep stress conditions. The fracture surface after rupture indicates that fracture occurred along alloy grain boundaries in both the coated and un-coated alloy substrate. Many cavities and cracks were observed within the diffusion barrier coated alloy substrate. These cavities and cracks tended to propagate from the substrate toward the diffusion barrier layer, and then stopped at the Re-Cr-Ni / β-NiAl interface. Cracks formed in the un-coated alloy initiated at the tip of grain boundary oxides, and propagated into alloy substrate. However no major cavities were observed inside the alloy substrate. The stress index, n, for both specimens was about 6, and this indicates that the deformation mechanism of both samples was dislocation creep. These results suggest that the Re-Cr-Ni diffusion barrier layer acts as a barrier against the movement of dislocations at the interface with the alloy surface.

Effect of Post Weld Heat Treatment on Fusion and Heat Affected Zone Microstructure and Mechanical Properties of Inconel X-750 Welds

2011 ◽  
Vol 214 ◽  
pp. 108-112 ◽  
Author(s):  
Prachya Peasura ◽  
Bovornchok Poopat
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Grain Boundary ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
Aging Temperature ◽  
Post Weld Heat Treatment ◽  
High Aging Temperature ◽  
Zone Microstructure

The Inconel X-750 indicates good hot corrosion resistance, high stability and strength at high temperatures and for this reason the alloy is used in manufacturing of gas turbine hot components. The objective of this research was study the effect of post weld heat treatment (PWHT) on fusion zone and heat affected zone microstructure and mechanical properties of Inconel X-750 weld. After welding, samples were solutionized at 1500 0C. Various aging temperature and times were studied. The results show that aging temperature and time during PWHT can greatly affect microstructure and hardness in fusion zone and heat affected zone. As high aging temperature was used, the grain size also increased and M23C6 at the grain boundary decreased. This can result in decreased of hardness. Moreover excessive aging temperature can result in increasing MC carbide intensity in parent phase (austenite). It can also be observed that M23C6 at the grain boundary decreased due to high aging temperature. This resulted in decreasing of hardness of weld metal and heat affected zone. Experimental results showed that the aging temperature 705 0C aging time of 24 hours provided smaller grain size, suitable size and intensity of MC carbide resulting in higher hardness both in weld metal and HAZ.

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