Measuring Microscopic Properties of a Single-Crystalline Diamond by Nano-Indentation Technology

2015 ◽  
Vol 1120-1121 ◽  
pp. 378-382 ◽  
Author(s):  
Qi Long Wei ◽  
Xiao Bin Yue ◽  
Xiao Yuan Li ◽  
Bo Liu ◽  
Xiao Feng Zhang ◽  
...  
Keyword(s):  
Great Influence ◽  
Fused Silica ◽  
Diamond Surface ◽  
Measurement Properties ◽  
Indentation Hardness ◽  
Silica Sample ◽  
Single Crystalline ◽  
Nano Indentation ◽  
Indentation Force ◽  
Before And After

Nano-indentation technology was brought to study microscopic mechanical properties of a single-crystalline diamond (SCD). Nano-indentation measurement was conducted on the {100} plane of SCD, and influences of various factors on measured results were analyzed, from which methods were confirmed to improve veracity of measurement. Properties of the indenter were checked with a fused silica sample both before and after indentation on diamond, which provided guarantee to veracity of results on diamond. It was found that tilt of diamond surface had so great influence that it could damage the indenter, and make the indentation curves anomalous. While damage of indenter could be avoided and valid measurement results could be obtained when tilt of diamondsurface was decreased below 0.10º and the maximal indentation force was less than 10 mN. Deformation of the diamond was almost full-elastic during indentation process. Indentation hardness of {100} plane of the SCD was about 70 GPa with standard deviation less than 3 GPa. And there had good reproducibility between two groups of measurements.

Effects of Neutron, Ion and Proton Irradiation on Nano-Indentation Hardness of RPV Steels

2020 ◽  
Vol 999 ◽  
pp. 39-46
Author(s):  
Cheng Liang Li ◽  
Guo Gang Shu ◽  
Jing Li Yan ◽  
Wei Liu ◽  
Yuan Gang Duan
Keyword(s):  
Proton Irradiation ◽  
Indentation Hardness ◽  
Irradiation Embrittlement ◽  
Irradiation Hardening ◽  
Nano Indentation ◽  
Rpv Steel ◽  
Hardness Tests ◽  
Increase Rate ◽  
Before And After ◽  
Reactor Pressure

The irradiation embrittlement damage of reactor pressure vessel (RPV) steel is one of its primary failure mechanisms. In this work, neutron, ion and proton irradiation experiments were carried on the same commercial RPV steels with the same irradiation fluence under the same temperature of 292°C. Then the nano-indentation hardness tests were performed on the RPV steel before and after irradiation. The results show that the irradiation hardening effects are observed by means of nano-indentation technique under the above three irradiations, and the hardening features are basically the same. While the max variation and increase rate are obviously different between those irradiations. It is found that the main reason of the above differences are caused by different energies of irradiation energetic particles, resulting in different types and quantities of defects. The conclusions in this paper are helpful to select and compare different irradiation experiments to the research of RPV steels irradiation embrittlement damage.

scholarly journals Testing Invariance of Measures of Internalizing Symptoms Before and After a Major Life Stressor: The Impact of COVID-19 in an Adolescent and Young Adult Sample

Assessment ◽  
2021 ◽  
pp. 107319112110153
Author(s):  
Thomas M. Olino ◽  
Julia A. C. Case ◽  
Mariah T. Hawes ◽  
Aline Szenczy ◽  
Brady Nelson ◽  
...  
Keyword(s):  
Internalizing Symptoms ◽  
Adolescent And Young Adult ◽  
Measurement Properties ◽  
Major Life ◽  
Longitudinal Measurement Invariance ◽  
Longitudinal Measurement ◽  
Before And After ◽  
Life Stressor ◽  
The Impact ◽  
Consistent Support

There are reports of increases in levels of internalizing psychopathology during the COVID-19 pandemic. However, these studies presume that measurement properties of these constructs remained unchanged from before the pandemic. In this study, we examined longitudinal measurement invariance of assessments of depression, anxiety, and intolerance of uncertainty (IU) in adolescents and young adults from ongoing longitudinal studies. We found consistent support for configural and metric invariance across all constructs, but scalar invariance was unsupported for depression and IU. Thus, it is necessary to interpret pandemic-associated mean-level changes in depression and IU cautiously. In contrast, mean-level comparisons of panic, generalized, and social anxiety symptoms were not compromised. These findings are limited to the specific measures examined and the developmental period of the sample. We acknowledge that there is tremendous distress accompanying disruptions due to the COVID-19 outbreak. However, for some instruments, comparisons of symptom levels before and during the pandemic may be limited.

scholarly journals Dynamic Characteristics and Experimental Research of a Two-Span Rotor-Bearing System with Rub-Impact Fault

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Rui Zhu ◽  
Guang-chao Wang ◽  
Qing-peng Han ◽  
An-lei Zhao ◽  
Jian-xing Ren ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Great Influence ◽  
Experimental Platform ◽  
Rotating Machine ◽  
Rotor Bearing ◽  
Before And After ◽  
Analysis System ◽  
The Stability ◽  
Bearing System

Rotor rub-impact has a great influence on the stability and safety of a rotating machine. This study develops a dynamic model of a two-span rotor-bearing system with rubbing faults, and numerical simulation is carried out. Moreover, frictional screws are used to simulate a rubbing state by establishing a set of experimental devices that can simulate rotor-stator friction in the rotor system. Through the experimental platform and its analysis system, the rubbing experiment was conducted, and the vibration of the rotor-bearing system before and after the critical speed is observed. Rotors running under normal condition, local slight rubbing, and severe rubbing throughout the entire cycle are simulated. Dynamic trajectories, frequency spectrum diagrams, chart of axis track, and Poincare maps are used to analyze the features of the rotor-bearing system with rub-impact faults under various parameters. The vibration characteristics of rub impact are obtained. Results show that the dynamic characteristics of the rotor-bearing system are affected by the change in velocity and degree of impact friction. The findings are helpful in further understanding the dynamic characteristics of the rub-impact fault of the two-span rotor-bearing system and provide reference for fault diagnosis.

Fracture Characteristic of Single Crystalline Silicon Using Nano-Indentation and Finite Element Analysis

2006 ◽  
Vol 306-308 ◽  
pp. 601-606
Author(s):  
Seung Baek ◽  
Jae Mean Koo ◽  
Chang Sung Seok
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Phase Transformation ◽  
Crystalline Silicon ◽  
Indentation Test ◽  
Indentation Load ◽  
Single Crystalline Silicon ◽  
Element Analysis ◽  
Single Crystalline ◽  
Nano Indentation

Nano-indentation test is used widely to determine the fracture toughness of brittle materials and to provide information on important material properties such as the Young’s modulus and hardness. In this study, using nano-indentation testing, atomic force microscope (AFM), and finite element method (FEM), we performed the indentation fracture toughness and fracture strength measurement for a (100) single crystalline silicon at different load states. In addition, the loads of the phase transformation events during unloading were estimated by the load-depth curves. The phase transformation load and micro-crack propagation events at pop-out during the unloading process depended on the maximum applied indentation load.

A Simple Method of Tip Shape Calibration for Nano-Indentation Test of Thin Films

2002 ◽  
Vol 750 ◽  
Author(s):  
Koichiro Hattori ◽  
Junhua Xu ◽  
Hidetoshi Nakano ◽  
Isao Kojima
Keyword(s):  
Thin Films ◽  
Contact Stiffness ◽  
Simple Procedure ◽  
Single Crystal Silicon ◽  
Indentation Test ◽  
Fused Silica ◽  
Shape Effect ◽  
Crystal Silicon ◽  
Simple Method ◽  
Nano Indentation

ABSTRACTWe have evaluated the hardness and elastic properties of thin films by using a simple procedure to calibrate the tip shape effect of the nano-indentation data. For the simplification, a truncated-shape approximation and linear fit are used to estimate the tip-shape and contact stiffness, respectively, substituting for polynomial area-function and power-law fit. The parameters used in the correction were determined by a fused silica and a single crystal silicon (100) surface. Different film/substrate systems are designed in order to assess these fitted parameters used in the correction. The transition behavior observed from the film to the substrate is well coincide with the other film thickness results, where the indentation depth above 50nm.

EFFECT OF TRANSFORMATION VOLUME STRAIN ON THE SPHERICAL INDENTATION OF SHAPE MEMORY ALLOYS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5957-5964 ◽  
Author(s):  
WENYI YAN ◽  
QINGPING SUN ◽  
HONG-YUAN LIU
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Indentation Depth ◽  
Mechanical Response ◽  
Spherical Indentation ◽  
Indentation Hardness ◽  
Volume Strain ◽  
Volume Contraction ◽  
Indentation Force

The mechanical response of spherical indentation of superelastic shape memory alloys (SMAs) was theoretically studied in this paper. Firstly, the friction effect was examined. It was found that the friction influence is negligibly small. Secondly, the influence of the elasticity of the indenter was investigated. Numerical results indicate that this influence can not be neglected as long as the indentation depth is not very small. After that, this paper focused on the effect of transformation volume contraction. Our results show that the transformation volume contraction due to forward martensitic transformation can reduce the maximum indentation force and the spherical indentation hardness. These research results enhance our understanding of the spherical indentation responses, including the hardness of the smart material SMAs.

Annealing Temperature and Substrate Effects on the Raman Spectra of Transferred CVD Graphene

2012 ◽  
Vol 1407 ◽  
Author(s):  
Barbara M. Nichols ◽  
Yasmine R. Doleyres ◽  
Gregory P. Meissner
Keyword(s):  
Raman Spectra ◽  
Intensity Ratio ◽  
Substrate Surface ◽  
Single Layer ◽  
Fused Silica ◽  
Single Layer Graphene ◽  
Hole Doping ◽  
Pmma Layer ◽  
Layer Graphene ◽  
Before And After

ABSTRACTThis work explores the influence of the post-transfer anneal temperature and the substrate on transferred graphene and its Raman properties. Graphene grown by low pressure chemical vapor deposition on copper foils was transferred to SiO2/Si, fused silica, and silicon substrates via a process that involves coating the graphene with PMMA as a protective handling layer during the wet chemical etching of the copper and then placing the PMMA/graphene onto the substrate. The PMMA layer was then removed by heating in a hydrogen/argon atmosphere at temperatures ranging from 350 to 550 °C or by exposing the PMMA to heated acetone vapor/liquid. Raman spectroscopy measurements, taken before and after PMMA removal, reveal differences in the prominent Raman features, the G and G’ peaks, upon annealing. These changes include (1) a shift in the average G and G’ peak positions when comparing Raman spectra before and after PMMA removal and (2) a decrease in the G’:G peak intensity ratio (IG’/IG), which is typically used as a measure of the number of graphene layers. For both the as-transferred graphene and graphene removed by the heated acetone, the IG’/IG peak ratio was approximately 2, indicating single layer graphene. However, when the graphene was annealed at temperatures above 350 °C, the IG’/IG intensity ratio varied from 0.5 to 1.5. These changes in the Raman spectra are similar to those observed in exfoliated single layer graphene supported on SiO2/Si substrates and are indicative of graphene-substrate interaction effects that lead to hole doping of the graphene [1,2]. These trends were observed for graphene transferred to all three substrates, regardless of the substrate surface roughness and/or composition.

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