Hardness of bulk single-crystal GaN and AlN

2002 ◽  
Vol 7 ◽  
Author(s):  
Ichiro Yonenaga
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Mechanical Stability ◽  
Indentation Hardness ◽  
Bulk Single Crystal ◽  
Vickers Indentation ◽  
Indentation Method ◽  
Nano Indentation ◽  
High Mechanical Stability

The hardness of single-crystal GaN and AlN of 0.5-mm-thickness was measured by the Vickers indentation method in the temperature range 20 - 1400°C. The hardness of GaN and AlN is 10.2 and 17.7 GPa, respectively, at room temperature. The nano-indentation hardness of single-crystal AlN was measured at room temperature as 18 GPa, harder than GaN and InN. Up to about 1100°C, GaN and AlN maintain its hardness similar to that of SiC and thus, a high mechanical stability for GaN and AlN at elevated temperatures is deduced. Yield strength of nitrides is discussed.

scholarly journals High Temperature Hardness of Bulk Single Crystal GaN

2000 ◽  
Vol 5 (S1) ◽  
pp. 343-348
Author(s):  
I. Yonenaga ◽  
T. Hoshi ◽  
A. Usui
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Room Temperature ◽  
Applied Load ◽  
Elevated Temperatures ◽  
Mechanical Stability ◽  
Bulk Single Crystal ◽  
Indentation Method ◽  
First Time ◽  
High Mechanical Stability

The hardness of single crystal GaN (gallium nitride) at elevated temperature is measured for the first time and compared with other materials. A Vickers indentation method was used to determine the hardness of crack-free GaN samples under an applied load of 0.5N in the temperature range 20 - 1200°C. The hardness is 10.8 GPa at room temperature, which is comparable to that of Si. At elevated temperatures GaN shows higher hardness than Si and GaAs. A high mechanical stability for GaN at high temperature is deduced.

High Temperature Hardness of Bulk Single Crystal GaN

1999 ◽  
Vol 595 ◽  
Author(s):  
I. Yonenaga ◽  
T. Hoshi ◽  
A. Usui
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Room Temperature ◽  
Applied Load ◽  
Elevated Temperatures ◽  
Mechanical Stability ◽  
Bulk Single Crystal ◽  
Indentation Method ◽  
First Time ◽  
High Mechanical Stability

AbstractThe hardness of single crystal GaN (gallium nitride) at elevated temperature is measured for the first time and compared with other materials. A Vickers indentation method was used to determine the hardness of crack-free GaN samples under an applied load of 0.5N in the temperature range 20 - 1200°C. The hardness is 10.8 GPa at room temperature, which is comparable to that of Si. At elevated temperatures GaN shows higher hardness than Si and GaAs. A high mechanical stability for GaN at high temperature is deduced.

High-Temperature Hardness of Bulk Single-Crystal AlN

2001 ◽  
Vol 693 ◽  
Author(s):  
Ichiro Yonenaga ◽  
Andrey Nikolaev ◽  
Yuriy Melnik ◽  
Vladimir Dmitriev
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Applied Load ◽  
Elevated Temperatures ◽  
Mechanical Stability ◽  
Bulk Single Crystal ◽  
Indentation Method ◽  
Temperature Range ◽  
Average Hardness ◽  
High Mechanical Stability

AbstractThe hardness of single-crystal aluminum nitride (AlN) 0.5-mm-thick wafers was measured at elevated temperatures and compared with that of other semiconductors. A Vickers indentation method was used to determine the hardness under an applied load of 0.5 – 5 N in the temperature range 20 - 1400°C. The average hardness was measured as 17.7 GPa at room temperature, harder than GaN and InN. The fracture toughness is 0.5 MPa•m1/2. AlN exhibits the hardness higher than that of GaN in the entire temperature range investigated. Up to about 1100°C, AlN maintains its hardness and thus, a high mechanical stability for AlN at elevated temperatures is deduced.

Nano-Indentation Hardness and Elastic Moduli of Bulk Single-Crystal AlN

2002 ◽  
Vol 41 (Part 1, No. 7A) ◽  
pp. 4620-4621 ◽  
Author(s):  
Ichiro Yonenaga ◽  
Toshiyuki Shima ◽  
Marcel H. F. Sluiter
Keyword(s):  
Single Crystal ◽  
Elastic Moduli ◽  
Indentation Hardness ◽  
Bulk Single Crystal ◽  
Nano Indentation

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Elastic Constants of Single Crystal Hastelloy X at Elevated Temperatures

1998 ◽  
Vol 120 (3) ◽  
pp. 242-247 ◽  
Author(s):  
Howard A. Canistraro ◽  
Eric H. Jordan ◽  
Shi Shixiang ◽  
Leroy H. Favrow ◽  
Francis A. Reed
Keyword(s):  
Single Crystal ◽  
Elastic Constants ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Mechanical Response ◽  
Aerospace Materials ◽  
Hastelloy X ◽  
Percent Change ◽  
Nickel Based Alloy ◽  
Individual Grains

An acoustic time of flight technique is described in detail for measuring the elastic constants of cubic single crystals that allows for the constants to be determined at elevated temperature. Although the overall technique is not new, various aspects of the present work may prove extremely useful to othersinterested in finding these values, especially for aerospace materials applications. Elastic constants were determined for the nickel based alloy, Hastelloy X from room temperature to 1000°C. Accurate elastic constants were needed as part of an effort to predict both polycrystal mechanical properties and the nature of grain induced heterogeneous mechanical response. The increased accuracy of the acoustically determined constants resulted in up to a 15 percent change in the predicted stresses in individual grains. These results indicate that the use of elastic single crystal constants of pure nickel as an approximation for the constants of gas turbine single crystal alloys, which is often done today, is inaccurate.

Constitutive Relations for Modeling Single Crystal GaN at Elevated Temperatures

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Antoinette Maniatty ◽  
Payman Karvani
Keyword(s):  
Single Crystal ◽  
Basal Slip ◽  
Elevated Temperatures ◽  
Constitutive Relations ◽  
Prismatic Slip ◽  
Model Parameters ◽  
Bulk Single Crystal ◽  
Crystal Plasticity Model ◽  
Dislocation Densities ◽  
Strain Data

Thermal–mechanical constitutive relations for bulk, single-crystal, wurtzite gallium nitride (GaN) at elevated temperatures, suitable for modeling crystal growth processes, are presented. A crystal plasticity model that considers slip and the evolution of mobile and immobile dislocation densities on the prismatic and basal slip systems is developed. The experimental stress–strain data from Yonenaga and Motoki (2001, “Yield Strength and Dislocation Mobility in Plastically Deformed Bulk Single-Crystal GaN,” J. Appl. Phys., 90(12), pp. 6539–6541) for GaN is analyzed in detail and used to define model parameters for prismatic slip. The sensitivity to the model parameters is discussed and ranges for parameters are given. Estimates for basal slip are also provided.

scholarly journals Matrix design of a novel ductile cast iron modified by W and Al: A comparison between thermodynamic modeling and experimental data

10.30544/449 ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 15-29
Author(s):  
Gülşah Aktaş Çelik ◽  
Maria-Ioanna T. Tzini ◽  
Şeyda Polat ◽  
Şaban Hakan Atapek ◽  
Gregory N. Haidemenopoulos
Keyword(s):  
Cast Iron ◽  
High Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Mechanical Stability ◽  
Low Cost ◽  
Equilibrium Temperature ◽  
Ductile Cast Iron ◽  
Thermal Expansivity ◽  
Thermodynamic Calculations

In high-temperature applications of ferrous materials, as in the case of exhaust manifolds, high thermal and mechanical stability are required. Stainless steels and Ni-resist alloys having austenitic matrices are good candidates to meet these requirements at elevated temperatures; however, they are expensive materials and present difficulties in casting. Ferritic ductile cast irons, like the commercial SiMo alloy, are comparatively cheaper materials with better castability but they cannot be used above approximately 800 °C. Thus, to meet the requirements with low-cost materials having improved high-temperature properties, new alloys must be developed by ferrite forming elements having the potential to increase equilibrium temperature. In this study, initially, a novel ductile cast iron matrix was designed using 1 W and 0-4 Al wt.-% and their phases stable at room temperature, transformation temperatures, solidification sequences and thermal expansivity values were determined using thermodynamic calculations with Thermo-Calc software. Computational studies revealed that (i) designed alloy matrices had graphite and M6C type carbides embedded in a ferritic matrix at room temperature as expected, (ii) A1 temperature increased as aluminum content increased. The obtained values were all above that of commercial SiMo alloy, (iii) the detrimental effect of increased aluminum addition on graphite content, and thermal expansivity was observed. Secondly, microstructural and thermal characterizations of cast alloys were performed for validation – the obtained data were in good agreement with the thermodynamic calculations.

Amorphization of nanocrystalline 3C-SiC irradiated with Si+ ions

2010 ◽  
Vol 25 (12) ◽  
pp. 2341-2348 ◽  
Author(s):  
W. Jiang ◽  
H. Wang ◽  
I. Kim ◽  
Y. Zhang ◽  
W.J. Weber
Keyword(s):  
Grain Size ◽  
Single Crystal ◽  
Room Temperature ◽  
Ex Situ ◽  
Bulk Single Crystal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ion Channeling

Irradiation-induced amorphization in nanocrystalline and single-crystal 3C-SiC has been studied using 1 MeV Si+ ions under identical irradiation conditions at room temperature and 400 K. The disordering behavior has been characterized using in situ ion channeling and ex situ x-ray diffraction methods. The results show that, compared with single-crystal 3C-SiC, full amorphization of small 3C-SiC grains (˜3.8 nm in size) at room temperature occurs at a slightly lower dose. Grain size decreases with increasing dose until a fully amorphized state is attained. The amorphization dose increases at 400 K relative to room temperature. However, at 400 K, the amorphization dose for 2.0 nm grains is about a factor of 4 and 8 smaller than for 3.0 nm grains and bulk single-crystal 3C-SiC, respectively. The behavior is attributed to the preferential amorphization at the interface.

An ab initio study of the ideal tensile and shear strength of single-crystal β–Si3N4

2003 ◽  
Vol 18 (5) ◽  
pp. 1168-1172 ◽  
Author(s):  
Shigenobu Ogata ◽  
Naoto Hirosaki ◽  
Cenk Kocer ◽  
Yoji Shibutani
Keyword(s):  
Shear Strength ◽  
Single Crystal ◽  
Ab Initio ◽  
Density Functional ◽  
Strain Curve ◽  
High Strength ◽  
Indentation Hardness ◽  
Ideal Strength ◽  
Vickers Indentation ◽  
The Ideal

In this study, the ideal tensile and shear strength of single-crystal β–Si3N4 was calculated using an ab initio density functional technique. The stress-strain curve of the silicon nitride polymorph was calculated from simulations of uniaxial strain deformation. In particular, the ideal strength calculated for an applied ∈11 tensile strain was estimated to be approximately 57 GPa. Recently, a good correlation was reported between the shear modulus of high-strength materials and the experimentally determined Vickers indentation hardness value. Using the reported correlation an estimate was made of the Vickers indentation hardness of single-crystal β–Si3N4: approximately 20.4 GPa.

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