Recrystallization of Oxygen Contaminated Al Films

1986 ◽  
Vol 71 ◽  
Author(s):  
G.J. Van Der Kolk ◽  
M.J. Verkerk
Keyword(s):  
Grain Size ◽  
Silicon Nitride ◽  
Substrate Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Relative Increase ◽  
Partial Pressures ◽  
Average Grain Size

AbstractAl was evaporated at oxygen partial pressures, PO2, varying between 10−7 and 10−4 Pa on substrates of silicon nitride. The substrate temperature was varied between 20 °C and 250°C. The films were annealed at temperatures up to 500°C.For Al films deposited at 20°C, it was found that the average grain size decreases with increasing oxygen partial pressure. After annealing recrystallization was observed. The relative increase of grain size was less for higher values of pO2. Annealing gave rise to a broad grain size distribution.For Al films deposited at 250°C, the presence of oxygen caused the growth of rough inhomogeneous films. This inhomogeneous structure remained during annealing.

Novel Microstructures in Microwave Sintered Silicon Nitride

1996 ◽  
Vol 430 ◽  
Author(s):  
M. E. Brito ◽  
K. Hirao ◽  
M. Toriyama ◽  
M. Hirota
Keyword(s):  
Grain Size ◽  
Silicon Nitride ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mechanical Performance ◽  
Microwave Sintering ◽  
Preliminary Results ◽  
Nitride Ceramics ◽  
Positive Effect ◽  
Sintered Silicon

AbstractPreliminary results on microwave sintering of seeded silicon nitride show that a well defined bi-modal grain size distribution is attainable in Si3N4-Y2O3-Al2O 3-MgO sintered bodies by microwave sintering at 28 GHz of materials seeded with ß-Si3N4 particles (2 vol. %). A positive effect on the mechanical performance is anticipated for these microstructurally controlled silicon nitride ceramics

scholarly journals Process-Parameter-Dependent Structural, Electrical, and Optical Properties of Reactive Magnetron Sputtered Ag-Cu-O Films

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
P. Narayana Reddy ◽  
A. Sreedhar ◽  
M. Hari Prasad Reddy ◽  
S. Uthanna ◽  
J. F. Pierson
Keyword(s):  
Optical Properties ◽  
Substrate Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Rf Magnetron Sputtering ◽  
Low Oxygen ◽  
Electrical And Optical Properties ◽  
Partial Pressures ◽  
Effect Of Oxygen ◽  
Parameter Dependent

Silver-copper-oxide thin films were formed by RF magnetron sputtering technique using Ag80Cu20target at various oxygen partial pressures in the range 5 × 10−3–8 ×10−2 Pa and substrate temperatures in the range 303–523 K. The effect of oxygen partial pressure and substrate temperature on the structure and surface morphology and electrical and optical properties of the films were studied. The Ag-Cu-O films formed at room temperature (303 K) and at low oxygen partial pressure of 5 × 10−3 Pa were mixed phase of Ag2Cu2O3and Ag, while those deposited at 2 × 10−2 Pa were composed of Ag2Cu2O4and Ag2Cu2O3phases. The crystallinity of the films formed at oxygen partial pressure of 2 × 10−2Pa increased with the increase of substrate temperature from 303 to 423 K. Further increase of substrate temperature to 523 K, the films were decomposed in to Ag2O and Ag phases. The electrical resistivity of the films decreased from 0.8 Ωcm with the increase of substrate temperature from 303 to 473 K due to improvement in the crystallinity of the phase. The optical band gap of the Ag-Cu-O films increased from 1.47 to 1.83 eV with the increase of substrate temperature from 303 to 473 K.

The Inverse Hall-Petch Effect—Fact or Artifact?

2000 ◽  
Vol 634 ◽  
Author(s):  
Carl C. Koch ◽  
J. Narayan
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Computer Simulations ◽  
Nanocrystalline Materials ◽  
Grain Sizes ◽  
Average Grain Size

ABSTRACTThis paper critically reviews the data in the literature which gives softening—the inverse Hall-Petch effect—at the finest nanoscale grain sizes. The difficulties with obtaining artifactfree samples of nanocrystalline materials will be discussed along with the problems of measurement of the average grain size distribution. Computer simulations which predict the inverse Hall-Petch effect are also noted as well as the models which have been proposed for the effect. It is concluded that while only a few of the experiments which have reported the inverse Hall-Petch effect are free from obvious or possible artifacts, these few along with the predictions of computer simulations suggest it is real. However, it seems that it should only be observed for grain sizes less than about 10 nm.

Variable Elastic-Plastic Properties of the Grain Boundaries and Their Effect on the Macroscopic Flow Stress of Nano-Crystalline Metals

2009 ◽  
Vol 1224 ◽  
Author(s):  
Malgorzata Lewandowska ◽  
Romuald Dobosz ◽  
Krzysztof J Kurzydlowski
Keyword(s):  
Grain Size ◽  
Flow Stress ◽  
Grain Boundaries ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Distribution Functions ◽  
Boundary Misorientation ◽  
Plastic Properties ◽  
Nano Crystalline ◽  
Average Grain Size

AbstractThe paper reports new experimental results describing properties and microstructure of nanocrystalline metals. Nano- and sub-micron aluminium has been produced by hydrostatic extrusion at ambient tempearture. The structures have been quantified in terms of size of grains and misorientation of the grain boundaries. Different average size of grains, variable normalized width of grain size distribution and changing grain boundary misorientation distribution functions have been revealed depending on processing parameters. The results of the tensile tests showed that the average grain size, grain size distribution and the distribution function of misorientation angles influence the flow stress of obtained nano-metals. In order to explain the observed difference in the properties of nano- and micro-sized aluminium alloys, a Finite Element Method models have been developed, which assumes that both grain boundaries and grain interiors may accommodated elastic and non-linear plastic deformation. These models assumed true geometry of grains (which differed in size and shape). Also, variable mechanical properties of grain boundaries have been taken into account (elastic modulus, yield strength and work hardening rate). The results of modelling explain in a semi-quantitative way macroscopic deformation of nano-crystalline aggregates. In particular, they illustrate the importance of the interplay between properties of grain boundaries and grain interiors in elastic and plastic regime.

Statistical analysis of the parameters and grain size distribution functions of single-phase polycrystalline materials

2020 ◽  
Vol 86 (4) ◽  
pp. 39-45
Author(s):  
S. I. Arkhangelskiy ◽  
D. M. Levin
Keyword(s):  
Grain Size ◽  
Distribution Function ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Single Phase ◽  
Distribution Functions ◽  
Grain Structure ◽  
Polycrystalline Materials ◽  
Grain Sizes ◽  
Average Grain Size

A statistical analysis of the grain size distribution is important both for developing theories of the grain growth and microstructure formation, and for describing the size dependences of various characteristics of the physical and mechanical properties of polycrystalline materials. The grain size distribution is also an important characteristic of the structure uniformity and, therefore, stability of the properties of the products during operation. Statistical Monte Carlo modeling of single-phase and equiaxed polycrystalline microstructures was carried out to determine the type of statistically valid distribution function and reliable estimates of the average grain size. Statistical parameters (mean values, variances, variation coefficient) and distribution functions of the characteristics of the grain microstructure were obtained. It is shown that the distribution function of the effective grain sizes for the studied polycrystal model is most adequately described by γ-distribution, which is recommended to be used in analysis of the experimental distribution functions of grain sizes of single-phase polycrystalline materials with equiaxed grains. The general average (mathematical expectation) of the effective grain size (projection diameter) with γ-distribution function (parameters of the distribution function are to be previously determined in analysis of the grain structure of polycrystalline materials) should be taken as a statistically valid and reliable estimate of the average grain size. The results of statistical modeling are proved by the experimental data of metallographic study of the microstructures of single-phase model and industrial materials with different degree of the grain structure heterogeneity.

The Effect of Grain Size Distribution on the Mechanical Properties of Nanometals

2008 ◽  
Vol 140 ◽  
pp. 185-190 ◽  
Author(s):  
T.B. Tengen ◽  
Tomasz Wejrzanowski ◽  
R. Iwankiewicz ◽  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Flow Stress ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Deformation Mechanisms ◽  
Average Grain Size ◽  
Significant Interest ◽  
Size Dispersion ◽  
The Relationship

Predicting the properties of a material from knowledge of the internal microstructures is attracting significant interest in the fields of materials design and engineering. The most commonly used expression, known as Hall-Petch Relationship (HPR), reports on the relationship between the flow stress and the average grain size. However, there is much evidence that other statistical information that the grain size distribution in materials may have significant impact on the mechanical properties. These could even be more pronounced in the case of grains of the nanometer size, where the HPR is no longer valid and the Reverse-HPR is more applicable. This paper proposes a statistical model for the relationship between flow stress and grain size distribution. The model considered different deformation mechanisms and was used to predict mechanical properties of aluminium and copper. The results obtained with the model shows that the dispersion of grain size distribution plays an important role in the design of desirable mechanical properties. In particular, it was found that that the dependence of a material’s mechanical properties on grain size dispersion also follows the HPR to Inverse-HPR type of behaviour. The results also show that copper is more sensitive to changes in grain size distribution than aluminium.

Impedance spectroscopy of grain boundaries in nanophase ZnO

1995 ◽  
Vol 10 (9) ◽  
pp. 2295-2300 ◽  
Author(s):  
J. Lee ◽  
J.-H. Hwang ◽  
J.J. Mashek ◽  
T.O. Mason ◽  
A.E. Miller ◽  
...  
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Electrical Properties ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Grain Boundaries ◽  
Defect Characterization ◽  
Impedance Spectra ◽  
Gas Condensation ◽  
Average Grain Size

Sintered compacts of nanophase ZnO (∼60 nm average grain size, presintered at 600 °C) were made from powders (∼13 nm) prepared by the gas-condensation technique. Impedance spectra were taken as a function of temperature over the range 450–600 °C and as a function of oxygen partial pressure over the range 10−3−1 atm (550 and 600 °C only). The activation energy was determined to be 55 kJ/mole (0.57 eV) and was independent of oxygen partial pressure. The oxygen partial pressure exponent was −1/6. Impedance spectra exhibited nonlinear I-V behavior, with a threshold of approximately 6 V. These results indicate that grain boundaries are governing the electrical properties of the compact. Ramifications for oxygen sensing and for grain boundary defect characterization are discussed.

The Issue of Grain Size Distribution Using Mean Field Models for Dynamic and Post-Dynamic Recrystallization

2016 ◽  
Vol 879 ◽  
pp. 1794-1799 ◽  
Author(s):  
Guillaume Smagghe ◽  
David Piot ◽  
Frank Montheillet ◽  
G. Perrin ◽  
A. Montouchet ◽  
...  
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mean Field ◽  
304L Stainless Steel ◽  
Mean Field Model ◽  
Average Grain Size ◽  
Fundamental Equations ◽  
Good Agreement

A mean field model for discontinuous dynamic recrystallization (DDRX) has been developed and chained with a post-dynamic recrystallization (PDRX) model to predict transient and steady-state flow stresses and average grain sizes. Numerical results are compared with experimental data obtained on a 304L stainless steel yielding to a good agreement in terms of average grain size. However an unrealistic grain-size distribution is observed using DDRX, which affects results of the PDRX model. This result is discussed with respect to the fundamental equations of DDRX.

scholarly journals Acoustic emission study of microcracking in 123-type ceramic superconductors

1990 ◽  
Vol 5 (10) ◽  
pp. 2066-2074 ◽  
Author(s):  
T. J. Richardson ◽  
L. C. De Jonghe
Keyword(s):  
Grain Size ◽  
Acoustic Emission ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Ybco Superconductor ◽  
Sintered Ceramic ◽  
Average Grain Size ◽  
Superconducting Compounds ◽  
Emission Study ◽  
Acoustic Emission Study

Acoustic emission from sintered ceramic YBa2Cu3O7−x (YBCO) superconductor pellets provides a direct measure of microcracking behavior during processing. By detection and statistical analysis of acoustic events, the effects of cooling rates, processing atmosphere, average grain size, additives, and grain alignment on microcracking in YBCO have been studied. The onset temperature and duration of acoustic emission during cooling correlate well with the oxygen partial pressure in the furnace. Rapid changes in oxygen partial pressure at constant temperature produce acoustic emission that is characteristic of microcracking. A reported critical grain size for microcracking in sintered polycrystalline YBCO of about 1 μm has been confirmed. Two superconducting compounds, YSrBaCu3O7−x and LaBaCaCu3O7−x with the 123 structure but with smaller crystallographic anisotropy were also examined. Recommendations are made for minimizing microcracking during processing of superconducting ceramics.

Effect of Grain Size Distribution on Tensile Properties of Electrodeposited Nanocrystalline Nickel

2000 ◽  
Vol 634 ◽  
Author(s):  
Fereshteh Ebrahimi ◽  
Zunayed Ahmed ◽  
Kristin L. Morgan
Keyword(s):  
Grain Size ◽  
Strain Hardening ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Tensile Elongation ◽  
Dislocation Motion ◽  
Nanocrystalline Nickel ◽  
Strain Behavior ◽  
Average Grain Size ◽  
Strain Hardening Rate

ABSTRACTWe have produced dense and ductile nanocrystalline nickel with various grain size distributions using electrodeposition techniques. The strength of the nickel deposits fell within the scatter band of the general Hall-Petch curve for nickel. However, large variations in yield strength, strain hardening rate and tensile elongation were associated with a relatively small change in the average grain size. The scatter in the elongation data has been attributed to the formation of nodules and the presence of voids. The variations in strength and strain hardening rate have been shown to be associated with the changes in the grain size distribution. A model based on confined dislocation motion and composite behavior has been developed for predicting the stress-strain behavior of the nanocrystalline nickel.

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