Research

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14 pages, 2520 KiB

Open AccessArticle

The Strain Rate Sensitivity and Creep Behavior for the Tripler Plane of Potassium Dihydrogen Phosphate Crystal by Nanoindentation

by Jianhui Mao, Wenjun Liu, Dongfang Li, Chenkai Zhang and Yi Ma

Micromachines 2021, 12(4), 369; https://doi.org/10.3390/mi12040369 - 30 Mar 2021

Cited by 4 | Viewed by 1876

Abstract

As an excellent multifunctional single crystal, potassium dihydrogen phosphate (KDP) is a well-known, difficult-to-process material for its soft-brittle and deliquescent nature. The surface mechanical properties are critical to the machining process; however, the characteristics of deformation behavior for KDP crystals have not been [...] Read more.

As an excellent multifunctional single crystal, potassium dihydrogen phosphate (KDP) is a well-known, difficult-to-process material for its soft-brittle and deliquescent nature. The surface mechanical properties are critical to the machining process; however, the characteristics of deformation behavior for KDP crystals have not been well studied. In this work, the strain rate effect on hardness was investigated on the mechanically polished tripler plane of a KDP crystal relying on nanoindentation technology. By increasing the strain rate from 0.001 to 0.1 s⁻¹, hardness increased from 1.67 to 2.07 GPa. Hence, the strain rate sensitivity was determined as 0.053, and the activation volume of dislocation nucleation was 169 Å³. Based on the constant load-holding method, creep deformation was studied at various holding depths at room temperature. Under the spherical tip, creep deformation could be greatly enhanced with increasing holding depth, which was mainly due to the enlarged holding strain. Under the self-similar Berkovich indenter, creep strain could be reduced at a deeper location. Such an indentation size effect on creep deformation was firstly reported for KDP crystals. The strain rate sensitivity of the steady-state creep flow was estimated, and the creep mechanism was qualitatively discussed. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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12 pages, 3734 KiB

Open AccessArticle

Shape Effect of Surface Defects on Nanohardness by Quasicontinuum Method

by Zhongli Zhang, Can Wang, Xiaowen Hu and Yushan Ni

Micromachines 2020, 11(10), 909; https://doi.org/10.3390/mi11100909 - 30 Sep 2020

Viewed by 1373

Abstract

Nanoindentation on a platinum thin film with surface defects in a rectangular shape and triangular shape was simulated using the quasicontinuum method to study the shape effect of surface defects on nanohardness. The results show that the nanohardness of thin film with triangular [...] Read more.

Nanoindentation on a platinum thin film with surface defects in a rectangular shape and triangular shape was simulated using the quasicontinuum method to study the shape effect of surface defects on nanohardness. The results show that the nanohardness of thin film with triangular defects is basically larger than those with rectangular defects, which is closely related to the height of the surface defects at the boundary near to the indenter. Moreover, the triangular defect might have an enhancement effect on nanohardness by a certain size of the defects and the boundary orientation of the defect, where such an enhancement effect increases as the defect grows. Furthermore, the nanohardness decreases when the defect is folded from wide to narrow in the same atom cavity, and particularly expresses a more obvious drop when the height of the defects increases. In addition, larger sizes of the rectangular defect induce more reduction in nanohardness, while the nanohardness of the triangular surface defect is sensitive to the periodic arrangement of atoms changed by the boundary orientation of the defect, which is well explained and demonstrated by the calculation formula theory of necessary load for dislocation emission. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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11 pages, 3299 KiB

Open AccessArticle

Revealing the Plastic Mode of Time-Dependent Deformation of a LiTaO₃ Single Crystal by Nanoindentation

by Shengyun Zhou, Xianwei Huang, Congda Lu, Yunfeng Liu, Taihua Zhang and Yi Ma

Micromachines 2020, 11(9), 878; https://doi.org/10.3390/mi11090878 - 21 Sep 2020

Cited by 2 | Viewed by 1973

Abstract

Recently, instrumental nanoindentation has been widely applied to detect time-dependent plastic deformation or creep behavior in numerous materials, particularly thin films and heterogeneous materials. However, deformation mechanism at nanoindentation holding stage has not been well revealed hitherto. In the current work, nanoindentation holding [...] Read more.

Recently, instrumental nanoindentation has been widely applied to detect time-dependent plastic deformation or creep behavior in numerous materials, particularly thin films and heterogeneous materials. However, deformation mechanism at nanoindentation holding stage has not been well revealed hitherto. In the current work, nanoindentation holding tests with high loads were performed on a brittle LiTaO₃ single crystal. The surface morphologies of residual impressions with various holding times were investigated. It was indicated that generation of secondary cracks and propagation of both main and secondary cracks were the dominating mechanism for time-dependent plastic deformation at the initial holding stage, and the density and length of cracks were invariable at the steady-state holding stage, which suggested a nonlocalized plastic deformation beneath the indenter. It could be concluded that time-dependent plastic deformation of brittle ceramic under nanoindentation is composed of instant cracking as the continuation of loading sequence and homogeneous creep flow by high shear-compression stress at room temperature. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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13 pages, 3102 KiB

Open AccessArticle

Effect of AFM Nanoindentation Loading Rate on the Characterization of Mechanical Properties of Vascular Endothelial Cell

by Lei Wang, Liguo Tian, Wenxiao Zhang, Zuobin Wang and Xianping Liu

Micromachines 2020, 11(6), 562; https://doi.org/10.3390/mi11060562 - 31 May 2020

Cited by 11 | Viewed by 2661

Abstract

Vascular endothelial cells form a barrier that blocks the delivery of drugs entering into brain tissue for central nervous system disease treatment. The mechanical responses of vascular endothelial cells play a key role in the progress of drugs passing through the blood–brain barrier. [...] Read more.

Vascular endothelial cells form a barrier that blocks the delivery of drugs entering into brain tissue for central nervous system disease treatment. The mechanical responses of vascular endothelial cells play a key role in the progress of drugs passing through the blood–brain barrier. Although nanoindentation experiment by using AFM (Atomic Force Microscopy) has been widely used to investigate the mechanical properties of cells, the particular mechanism that determines the mechanical response of vascular endothelial cells is still poorly understood. In order to overcome this limitation, nanoindentation experiments were performed at different loading rates during the ramp stage to investigate the loading rate effect on the characterization of the mechanical properties of bEnd.3 cells (mouse brain endothelial cell line). Inverse finite element analysis was implemented to determine the mechanical properties of bEnd.3 cells. The loading rate effect appears to be more significant in short-term peak force than that in long-term force. A higher loading rate results in a larger value of elastic modulus of bEnd.3 cells, while some mechanical parameters show ambiguous regulation to the variation of indentation rate. This study provides new insights into the mechanical responses of vascular endothelial cells, which is important for a deeper understanding of the cell mechanobiological mechanism in the blood–brain barrier. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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14 pages, 5635 KiB

Open AccessArticle

Elucidating the Effect of Accelerated Carbonation on Porosity and Mechanical Properties of Hydrated Portland Cement Paste Using X-Ray Tomography and Advanced Micromechanical Testing

by Hongzhi Zhang, Claudia Romero Rodriguez, Hua Dong, Yidong Gan, Erik Schlangen and Branko Šavija

Micromachines 2020, 11(5), 471; https://doi.org/10.3390/mi11050471 - 29 Apr 2020

Cited by 18 | Viewed by 3266

Abstract

Carbonation of hydrated cement paste (HCP) causes numerous chemo–mechanical changes in the microstructure, e.g., porosity, strength, elastic modulus, and permeability, which have a significant influence on the durability of concrete structures. Due to its complexity, much is still not understood about the process [...] Read more.

Carbonation of hydrated cement paste (HCP) causes numerous chemo–mechanical changes in the microstructure, e.g., porosity, strength, elastic modulus, and permeability, which have a significant influence on the durability of concrete structures. Due to its complexity, much is still not understood about the process of carbonation of HCP. The current study aims to reveal the changes in porosity and micromechanical properties caused by carbonation using micro-beam specimens with a cross-section of 500 μm × 500 μm. X-ray computed tomography and micro-beam bending tests were performed on both noncarbonated and carbonated HCP micro-beams for porosity characterization and micromechanical property measurements, respectively. The experimental results show that the carbonation decreases the total porosity and increases micromechanical properties of the HCP micro-beams under the accelerated carbonation. The correlation study revealed that both the flexural strength and elastic modulus increase linearly with decreasing porosity. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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9 pages, 826 KiB

Open AccessArticle

Influence of Post-Annealing on the Structural and Nanomechanical Properties of Co Thin Films

by Yeong-Maw Hwang, Cheng-Tang Pan, Ying-Xu Lu, Sheng-Rui Jian, Huang-Wei Chang and Jenh-Yih Juang

Micromachines 2020, 11(2), 180; https://doi.org/10.3390/mi11020180 - 10 Feb 2020

Cited by 5 | Viewed by 2283

Abstract

The correlations between the microstructure and nanomechanical properties of a series of thermal annealed Co thin films were investigated. The Co thin films were deposited on glass substrates using a magnetron sputtering system at ambient conditions followed by subsequent annealing conducted at various [...] Read more.

The correlations between the microstructure and nanomechanical properties of a series of thermal annealed Co thin films were investigated. The Co thin films were deposited on glass substrates using a magnetron sputtering system at ambient conditions followed by subsequent annealing conducted at various temperatures ranging from 300 °C to 800 °C. The XRD results indicated that for annealing temperature in the ranged from 300 °C to 500 °C, the Co thin films were of single hexagonal close-packed (hcp) phase. Nevertheless, the coexistence of hcp-Co (002) and face-centered cubic (fcc-Co (111)) phases was evidently observed for films annealed at 600 °C. Further increasing the annealing temperature to 700 °C and 800 °C, the films evidently turned into fcc-Co (111). Moreover, significant variations in the hardness and Young’s modulus are observed by continuous stiffness nanoindentation measurement for films annealed at different temperatures. The correlations between structures and properties are discussed. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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10 pages, 1782 KiB

Open AccessArticle

The Indentation-Induced Pop-in Phenomenon and Fracture Behaviors of GaP(100) Single-Crystal

by Yi-Jui Chiu, Sheng-Rui Jian, Jyh-Wei Lee and Jenh-Yih Juang

Micromachines 2019, 10(11), 752; https://doi.org/10.3390/mi10110752 - 02 Nov 2019

Cited by 5 | Viewed by 2273

Abstract

The deformation behaviors and fracture features of GaP(100) single-crystal are investigated by using nano- and micro-scale indentation techniques. The hardness and Young’s modulus were measured by nanoindentation using a Berkovich diamond indenter with continuous contact stiffness measurements (CSM) mode and the values obtained [...] Read more.

The deformation behaviors and fracture features of GaP(100) single-crystal are investigated by using nano- and micro-scale indentation techniques. The hardness and Young’s modulus were measured by nanoindentation using a Berkovich diamond indenter with continuous contact stiffness measurements (CSM) mode and the values obtained were 12.5 ± 1.2 GPa and 152.6 ± 12.8 GPa, respectively. In addition, the characteristic “pop-in” was observed in the loading portion of load-displacement curve, which was caused by the nucleation and/or propagation of dislocations. An energetic estimation methodology on the associated nanoindentation-induced dislocation numbers resulting from the pop-in events was discussed. Furthermore, the Vickers indentation induced fracture patterns of GaP(100) single-crystal were observed and analyzed using optical microscopy. The obtained fracture toughness K_C of GaP(100) single-crystal was ~1.7 ± 0.1 MPa·m^1/2, which is substantially higher than the K_IC values of 0.8 MPa·m^1/2 and 1.0 MPa·m^1/2 previously reported for of single-crystal and polycrystalline GaP, respectively. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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Review

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21 pages, 11273 KiB

Open AccessReview

Extended Applications of the Depth-Sensing Indentation Method

by Dániel Olasz, János Lendvai, Attila Szállás, Gábor Gulyás and Nguyen Q. Chinh

Micromachines 2020, 11(11), 1023; https://doi.org/10.3390/mi11111023 - 23 Nov 2020

Cited by 7 | Viewed by 3770

Abstract

The depth-sensing indentation method has been applied for almost 30 years. In this review, a survey of several extended applications developed during the last three decades is provided. In depth-sensing indentation measurements, the load and penetration depth data are detected as a function [...] Read more.

The depth-sensing indentation method has been applied for almost 30 years. In this review, a survey of several extended applications developed during the last three decades is provided. In depth-sensing indentation measurements, the load and penetration depth data are detected as a function of time, in most cases at controlled loading rates. Therefore, beside the determination of hardness and Young’s modulus, different deformation mechanisms and many other dynamic characteristics and phenomena, such as the dynamic elastic modulus, load-induced phase transition, strain rate sensitivity, etc. can be studied. These extended applications of depth-sensing indentation measurements are briefly described and reviewed. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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25 pages, 7003 KiB

Open AccessReview

Low Temperature Nanoindentation: Development and Applications

by Shunbo Wang and Hongwei Zhao

Micromachines 2020, 11(4), 407; https://doi.org/10.3390/mi11040407 - 13 Apr 2020

Cited by 12 | Viewed by 4304

Abstract

Nanoindentation technique at low temperatures have developed from initial micro-hardness driving method at a single temperature to modern depth-sensing indentation (DSI) method with variable temperatures over the last three decades. The technique and implementation of representative cooling systems adopted on the indentation apparatuses [...] Read more.

Nanoindentation technique at low temperatures have developed from initial micro-hardness driving method at a single temperature to modern depth-sensing indentation (DSI) method with variable temperatures over the last three decades. The technique and implementation of representative cooling systems adopted on the indentation apparatuses are discussed in detail here, with particular emphasis on pros and cons of combination with indentation technique. To obtain accurate nanoindentation curves and calculated results of material properties, several influence factors have been carefully considered and eliminated, including thermal drift and temperature induced influence on indenter and specimen. Finally, we further show some applications on typical materials and discuss the perspectives related to low temperature nanoindentation technique. Full article

(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques, Volume II)

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