Residual tensile stress in robust insulating rhombohedral Bi1−xLaxFe1−yTiyO3 multiferroic ceramics and its ability to pin ferroelectric polarization switching

2015 ◽  
Vol 106 (11) ◽  
pp. 112907 ◽  
Author(s):  
Linlin Zhang ◽  
Jian Yu
Keyword(s):  
Tensile Stress ◽  
Polarization Switching ◽  
Ferroelectric Polarization ◽  
Residual Tensile Stress

Stress Development in Low Dielectric Constant Silica Films During Drying and Heating Process

1999 ◽  
Vol 594 ◽  
Author(s):  
Mengcheng Lu ◽  
C. Jeffrey Brinker
Keyword(s):  
Dielectric Constant ◽  
Tensile Stress ◽  
Sol Gel ◽  
Low Dielectric Constant ◽  
Heating Process ◽  
Residual Tensile Stress ◽  
Silica Films ◽  
Stress Development ◽  
Low Dielectric

AbstractLow dielectric constant silica films are made using a surfactant templated sol-gel process (K∼2.5) or an ambient temperature and pressure aerogel process (K∼1.5). This paper will present the in-situ measurement and analysis of stress development during the making of these films, from the onset of drying till the end of heating. The drying stress is measured by a cantilever beam technique; the thermal stress is measured by monitoring the wafer curvature using a laser deflection method. During the course of drying, the surfactant templated films experience a low drying stress due to the influence of the surfactant on surface tension and extent of siloxane condensation. The aerogel films first develop a biaxial tensile stress due to solidification and initial drying. At the final stage of drying where the drying stress vanishes, dilation of the film recreates the porosity of the wet gel state, reducing the residual stress to zero. For the surfactant templated films, very small residual tensile stress remains after the heat treatment is finished (∼30MPa). Aerogel film has almost no measurable stress developed in the calcination process. In situ spectroscopic ellipsometry analysis during drying and heating, and TGA/DTA are all used to help understand the stress development.

The Photoluminescence and TEM Studies of Patterned GaAs films on Si Substrate Grown by Molecular Beam Epitaxy

1988 ◽  
Vol 116 ◽  
Author(s):  
Henry P. Lee ◽  
Yi-He Huang ◽  
Xiaoming Liu ◽  
Hong Lin ◽  
John. S. Smith ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Uniaxial Stress ◽  
Luminescence Spectra ◽  
Residual Tensile Stress ◽  
Photoluminescence Intensity ◽  
Patterned Substrate ◽  
Si Substrates ◽  
Gaas Films ◽  
Patterned Films ◽  
Window Area

AbstractPatterned epitaxial GaAs films have been formed on Si substrates by either growth over patterned substrate (selective -area epitaxy) or chemical etching of patterns after growth. The optical properties of these samples are studied by 77K photoluminescence (PL) and the defect structures are investigated by transmission electron microscope (TEM). The patterned substrate consisted of bare Si stripes with width ranging from 10 µm to 100 µm surrounded by Si3N4 films on both sides and a reference area of bare Si. For 1.5 µmiann d 3 µm thick films, PL intensities from the films inside the 10 µm stripe shows 140% and 75% increase over unpatterned areas while the residual tensile stress in the patterned films is very similar to that of the unpatterned area. The increase in the photoluminescence intensity is ascribed to the reduction of crystalline defects inside the the window area. In the chemically etched sample, the pattern consisted of 4 µm by 4 µm squares and 1 mm long stripes with widths ranging from 100 µm to 4 plm. From the shift of PL peaks, a monotonic decrease in the tensile stress versus stripe width is observed. In particular, when the width of the stripe is less than 7 µm. tensile stress becomes essentially uniaxial in agreement with the results obtained by Yacobi et al [16] on a GaAs on InP sample. The polarization of the luminescence spectra parallel and perpendicular to the uniaxial stress of a 4 µm wide stripe agrees well with theoretical prediction. It is also observed that tensile stress is almost completely relieved in the 4 µm by 4 muentc hed squares.

An approach to reduce stress and defects: a hybrid process of laser cladding deposition and shot peening

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiaoyu Zhang ◽  
Dichen Li ◽  
Jiale Geng
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Laser Cladding ◽  
Shot Peening ◽  
Hybrid Process ◽  
Layer By Layer ◽  
Residual Tensile Stress ◽  
Forming Process ◽  
Content Type ◽  
Thermal Forming

Purpose Laser cladding deposition is limited in industrial application by the micro-defects and residual tensile stress for the thermal forming process, leading to lower fatigue strength compared with that of the forging. The purpose of this paper is to develop an approach to reduce stress and defects. Design/methodology/approach A hybrid process of laser cladding deposition and shot peening is presented to transform surface strengthening technology to the overall strengthening technology through layer-by-layer forming and achieve enhancement. Findings The results show that the surface stress of the sample formed by the hybrid process changed from tensile stress to compressive stress, and the surface compressive stress introduced could reach more than four times the surface tensile stress of the laser cladding sample. At the same time, internal micro-defects such as pores were reduced. The porosity of the sample formed by the hybrid process was reduced by 90.12% than that of the laser cladding sample, and the surface roughness was reduced by 43.16%. Originality/value The authors believe that the hybrid process proposed in this paper can significantly expand the potential application of laser cladding deposition by solving its limitations, promoting its efficiency and applicability in practical cases.

Coupled Thermal-Mechanical Analysis of CO2 Laser Irradiation on Fused Silica

2016 ◽  
Vol 1136 ◽  
pp. 531-536
Author(s):  
Run Qiang Li ◽  
Peng Yao ◽  
Hao Meng ◽  
Jun Wang ◽  
Ke Zhang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Tensile Stress ◽  
Laser Irradiation ◽  
Laser Energy ◽  
Viscoelastic Behavior ◽  
Mechanical Analysis ◽  
Fused Silica ◽  
Depth Of Cut ◽  
Residual Tensile Stress ◽  
Thermally Induced

To grind fused silica in ductile mode, it was proposed to repair surface and subsurface micro cracks of fused silica by CO2 laser irradiation. However, excessive residual stress remains on the surface because the melt fused silica on the surface quenches in air. It causes the critical depth of cut for ductile grinding fused silica to be smaller than 0.2μm. To investigate the distribution of the residual stress and look for an optimal manner of irradiation to control residual tensile stress, a numerical model of was built for simulating the dynamic behavior of fused silica when irradiated by CO2 laser. Laser energy absorption, heat transmission, viscoelastic behavior of fused silica and thermally induced stress were considered in the numerical simulation. The results show how the residual stress is formed and distributed. We found that an appropriate control of the temperature field as a function of time and position in the laser process is the key to reduce the residual stress. Therefore, three kinds of processes were proposed to reduce residual tensile stress on the surface of fused silica introduced by laser irradiation. The residual stress distributions of these three processes were compared by numerical analysis to decide a better method of laser irradiation.

Ferroelectric Polarization Switching in Sodium Nitrite

1963 ◽  
Vol 18 (8) ◽  
pp. 1229-1230 ◽  
Author(s):  
Ichiro Hatta ◽  
Shozo Sawada ◽  
Yohko Asao ◽  
Taketoshi Yanagi
Keyword(s):  
Sodium Nitrite ◽  
Polarization Switching ◽  
Ferroelectric Polarization

Mechanical Properties of Boron Doped Si and Si/SiO 2 Membranes

2002 ◽  
Vol 729 ◽  
Author(s):  
Gabe Kuhn ◽  
Todd Myers ◽  
Susmita Bose ◽  
Amit Bandyopadhyay
Keyword(s):  
Tensile Stress ◽  
Boron Concentration ◽  
Boron Doping ◽  
Residual Tensile Stress ◽  
Flexural Mode ◽  
Si Substrates ◽  
Boron Doped ◽  
Pzt Film ◽  
Processing Variables ◽  
Etch Stop

AbstractIn our research, PZT film actuated micro-machined Si substrates are being developed for numerous applications in which membranes are actuated primarily in flexural mode. Silicon wafers, 3-inches in diameter, underwent boron doping in order to act as an etch stop. Approximately 200-nm of SiO2 was grown on the boron-doped side of the wafers. Photolithography and backside etching using EDP resulted in 2-μm thick membranes. Using reactive ion etching (RIE), beam structures resulted from the membranes. Nano-mechanical testing of the beams indicated that there were substantial residual tensile stresses in these structures. Initial calculations reveal a tensile stress of 57.7 MPa in the Si/SiO2 beams. The residual tensile stress subsequently caused the overall beam stiffness to be two orders of magnitude higher than it would be without stress. After stripping the oxide with a buffered oxide etchant (BOE), a residual stress of 26.5 MPa was measured, which is presumably caused from the remaining boron concentration. The aim of this paper is to understand influences of boron doping and processing variables on residual stresses.

Residual Stress Distribution in Pure Bending Beam Subjected to Tensile Failure on One Side

2006 ◽  
Vol 524-525 ◽  
pp. 253-258
Author(s):  
X.B. Wang
Keyword(s):  
Residual Stress ◽  
Tensile Strength ◽  
Stress Distribution ◽  
Tensile Stress ◽  
Strain Localization ◽  
Tensile Strain ◽  
Residual Stress Distribution ◽  
Neutral Axis ◽  
Residual Tensile Stress ◽  
Pure Bending

The stress distribution on the midsection of a pure bending beam where tensile strain localization band initiates on the tensile side of the beam and propagates within the beam is analyzed. Using the static equilibrium condition on the section of the midspan of the beam and the assumption of plane section as well as the linear softening constitutive relation beyond the tensile strength, the expressions for the length of tensile strain localization band and the distance from the tip of the band to the neutral axis are derived. After superimposing a linear unloading stress distribution over the initial stress distribution, the residual stress distribution on the midsection of the beam is investigated. In the process of strain localization band’s propagation, strain-softening behavior of the band occurs and neutral axis will shift. When the unloading moment is lower, the length of tensile strain localization band remains a constant since the stress on the base side of the beam is tensile stress. While, for larger unloading moment, with an increase of unloading moment, the length of tensile strain localization band decreases and the distance from the initial neutral axis to the unloading neutral axis increases. The neutral axis of midsection of the beam will shift in the unloading process. The present analysis is applicable to some metal materials and many quasi-brittle geomaterials (rocks and concrete, etc) in which tensile strength is lower than compressive strength. The present investigation is limited to the case of no real crack. Moreover, the present investigation is limited to the case that the length of strain localization band before unloading is less than half of depth of the beam. Otherwise, the residual tensile stress above the elastic neutral axis will be greater than the tensile strength, leading to the further development of tensile strain localization band in the unloading process.

Effect of the Mechanical Properties and Geometric Parameters on the Crack Density of a Multi-Layered Thin Film Structure under Residual Tensile Stress

2014 ◽  
Vol 543-547 ◽  
pp. 1533-1536
Author(s):  
Ban Quan Yang ◽  
Xue Jun Chen ◽  
Wei Hai Sun ◽  
Hong Qian Chen ◽  
Jing Wen Pan ◽  
...  
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Tensile Stress ◽  
Fracture Behavior ◽  
Crack Density ◽  
Film Structure ◽  
Geometric Parameters ◽  
Residual Tensile Stress ◽  
Thin Film Structure ◽  
Layered Thin Film

The effect of the mechanical properties and geometric parameters on the crack density of a multi-layered thin film structure under residual tensile stress is investigated theoretically. The numerical results show that the crack density of the thin film decreases with the increase of the thickness of the thin film and (or) the fracture strength of the thin film. These results can help us more deeply understand the fracture behavior of the multi-layered thin film structure under residual tensile stress.

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