scholarly journals The Effects of Precrack Angle on the Strength and Failure Characteristics of Sandstone under Uniaxial Compression

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Shuai Zhang ◽  
Jinhai Xu ◽  
Liang Chen ◽  
Hideki Shimada ◽  
Mingwei Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Axial Strain ◽  
Propagation Path ◽  
Growth Trend ◽  
Long Term Stability ◽  
Engineering Environment ◽  
One Step ◽  
Crack Angle

Characterization of the mechanical properties of cracked rock masses is essential for ensuring the long-term stability of the engineering environment. This paper is aimed at studying the relationship between the strength characteristics of specimen and the angle of precrack, as well as the interaction of cracks under uniaxial compression. To this end, two sandstone specimens, distinguished with a single and three precracks, were built using the PFC software. For the former case, both the peak strength and elastic modulus increase to a peak value as the crack angle α gets closer to the forcing (loading) direction. For the latter case, the strength experiences a trend of increasing-maintaining trend as the crack angle α gets closer to the forcing direction, and the elastic moduli are barely affected. For the specimens containing a single precrack, their crack numbers increased approximately in a one-step or two-step stair pattern with increasing axial strain; whereas for the specimens containing three cracks, their crack numbers all showed a multistep growth trend. Furthermore, the failure mode of the specimen is closely related to the precrack angle. However, if the precrack distribution does not affect the original crack propagation path, it will hardly affect the mechanical properties of the specimen.

scholarly journals One-step synthesis of carbon-supported electrocatalysts

2020 ◽  
Vol 11 ◽  
pp. 1419-1431
Author(s):  
Sebastian Tigges ◽  
Nicolas Wöhrl ◽  
Ivan Radev ◽  
Ulrich Hagemann ◽  
Markus Heidelmann ◽  
...  
Keyword(s):  
Hybrid Material ◽  
Chemical Vapor ◽  
Narrow Particle Size Distribution ◽  
Long Term Stability ◽  
Operational Lifetime ◽  
Metal Acetylacetonate ◽  
One Step ◽  
Supported Electrocatalysts ◽  
Platinum Loading

Cost-efficiency, durability, and reliability of catalysts, as well as their operational lifetime, are the main challenges in chemical energy conversion. Here, we present a novel, one-step approach for the synthesis of Pt/C hybrid material by plasma-enhanced chemical vapor deposition (PE-CVD). The platinum loading, degree of oxidation, and the very narrow particle size distribution are precisely adjusted in the Pt/C hybrid material due to the simultaneous deposition of platinum and carbon during the process. The as-synthesized Pt/C hybrid materials are promising electrocatalysts for use in fuel cell applications as they show significantly improved electrochemical long-term stability compared to the industrial standard HiSPEC 4000. The PE-CVD process is furthermore expected to be extendable to the general deposition of metal-containing carbon materials from other commercially available metal acetylacetonate precursors.

Synthesis of Nanosized Polymer Particles in Nonaqueous Emulsion

2013 ◽  
Vol 1546 ◽  
Author(s):  
Robert Dorresteijn ◽  
Robert Haschick ◽  
Kevin Müller ◽  
Markus Klapper ◽  
Klaus Müllen
Keyword(s):  
Ring Opening ◽  
Continuous Phase ◽  
Size Distributions ◽  
Aqueous Emulsion ◽  
Long Term Stability ◽  
Dispersed Particles ◽  
One Step ◽  
Moisture Sensitive ◽  
The One

ABSTRACTIn nonaqueous emulsion, moisture-sensitive polymerizations are performed in order to generate nanoparticles, which are not accessible by common aqueous emulsion polymerization. A nonaqueous emulsion, consisting of two immiscible aprotic organic solvents, is stabilized by amphiphilic block copolymers, such as PIb-PEO or PIb-PMMA copolymer, and lead to formation of nanosized dispersed droplets. They act as dispersed “nanoreactors” for the one-step synthesis of poly(urethane) nanoparticles in a polyadditon reaction as well as poly(L-lactide) nanoparticles through ring-opening polymerization, catalyzed by a moisture-sensitive catalyst. The well-dispersed particles possess average diameters below 100 nm and have narrow size distributions owing to the long-term stability of the dispersed droplets in the continuous phase.

scholarly journals Rice Husk Shredding as a Means of Increasing the Long-Term Mechanical Properties of Earthen Mixtures for 3D Printing

2022 ◽  
Author(s):  
Elena Ferretti ◽  
Massimo Moretti ◽  
Alberto Chiusoli ◽  
Lapo Naldoni ◽  
Francesco De Fabritiis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Uniaxial Compression ◽  
Rice Husk ◽  
Brittle Material ◽  
Strict Sense ◽  
Compression Tests ◽  
Vegetable Fiber ◽  
Natural Way

This paper is part of a study of earthen mixtures for 3D printing of buildings. To meet the ever-growing environmental needs, the focus of the paper is on a particular type of biocomposite for the stabilization of earthen mixtures—the rice husk-lime biocomposite—and on how to enhance its effect on the long-term mechanical properties of the hardened product. Having assumed that the shredding of the vegetable fiber is precisely one of the possible ways to improve the mechanical properties, we compared the results of uniaxial compression tests performed on cubic specimens made with both shredded and unaltered vegetable fiber, for three curing periods. The results showed that the hardened earthen mixture is not a brittle material in the strict sense, because it exhibits some peculiar behaviors, anomalous for a brittle material. However, being a “designable” material, its properties can be varied with a certain flexibility to get as close as possible to the desired ones. One of the peculiar properties of the hardened earthen mixture deserves further investigation, rather than corrections. This is the vulcanization that occurs (in a completely natural way) in the long term, thanks to the mineralization of the vegetable fiber by carbonation of the lime.

scholarly journals Physical and Mechanical Properties Evolution of Coal Subjected to Salty Solution and a Damage Constitutive Model under Uniaxial Compression

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3264
Author(s):  
Min Wang ◽  
Qifeng Guo ◽  
Yakun Tian ◽  
Bing Dai
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Immersion Time ◽  
Physical And Mechanical Properties ◽  
Relative Mass ◽  
Stress Strain ◽  
Damage Constitutive Model ◽  
Underground Reservoirs

Many underground reservoirs for storing water have been constructed in China’s western coal mines to protect water resources. Coal pillars which work as dams are subjected to a long-term soaking environment of concentrated salty water. Deterioration of the coal dam under the attack of the salty solution poses challenges for the long-term stability and serviceability of underground reservoirs. The evolution of the physical and mechanical properties of coal subjected to salty solutions are investigated in this paper. Coal from a western China mine is made to standard cylinder samples. The salty solution is prepared according to chemical tests of water in the mine. The coal samples soaked in the salty solution for different periods are tested by scanning electron microscope, nuclear magnetic resonance, and ultrasonic detector techniques. Further, uniaxial compression tests are carried out on the coal specimens. The evolutions of porosity, mass, microstructures of coal, solution pH values, and stress–strain curves are obtained for different soaking times. Moreover, a damage constitutive model for the coal samples is developed by introducing a chemical-stress coupling damage variable. The result shows that the corrosion effect of salty solution on coal samples becomes stronger with increasing immersion time. The degree of deterioration of the longitudinal wave velocity (vp) is positively correlated with the immersion time. With the increase in soaking times, the porosity of coal gradually increases. The relative mass firstly displays an increasing trend and then decreases with time. The peak strength and elastic modulus of coal decreases exponentially with soaking times. The developed damage constitutive model can well describe the stress–strain behavior of coal subjected to salty solution under the uniaxial compression.

Optimized Active Layer Morphology via Side-Chain Atomic Substituents to Achieve Efficient and Stable All-Polymer Solar Cells

2021 ◽  
Author(s):  
Shuting Pang ◽  
baoqi wu ◽  
Bao Zhang ◽  
Ruiwen Zhang ◽  
Claas Reckmeier ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solar Cells ◽  
Conjugated Polymers ◽  
Polymer Solar Cells ◽  
Side Chain ◽  
Long Term Stability ◽  
Donor And Acceptor ◽  
Superior Mechanical Properties ◽  
Electron Donor And Acceptor

All-polymer solar cells (all-PSCs), consisting of conjugated polymers for both electron donor and acceptor, are a promising photovoltaic technology owing to their superior mechanical properties and long-term stability in addition...

Bread-inspired foaming strategy to fabricate a wine lees-based porous carbon framework for high specific energy supercapacitors

2021 ◽  
Vol 5 (19) ◽  
pp. 4965-4972
Author(s):  
Hui Peng ◽  
Yipu Xu ◽  
Yaping Jiang ◽  
Xin Wang ◽  
Rui Zhao ◽  
...  
Keyword(s):  
Energy Density ◽  
Porous Carbon ◽  
Fermentation Process ◽  
High Energy ◽  
High Energy Density ◽  
Long Term Stability ◽  
Carbon Framework ◽  
One Step ◽  
High Specific Energy

Inspired by the fermentation process of bread, a novel wine lees-based porous carbon framework (WLCF) having high energy density and excellent long-term stability is prepared via one-step sodium bicarbonate foaming and activation strategy.

A Simplified Method to Assess the Risk of Geotechnical Engineering under Hydro-Chemical Corrosion

2011 ◽  
Vol 243-249 ◽  
pp. 2952-2957
Author(s):  
Peng Li ◽  
Guo He Li ◽  
Jian Liu
Keyword(s):  
Mechanical Properties ◽  
Chemical Kinetics ◽  
Geotechnical Engineering ◽  
Damage Index ◽  
Chemical Thermodynamic ◽  
Chemical Corrosion ◽  
Long Term Stability ◽  
Physical And Chemical ◽  
Reaction Direction

Rock mass are subject to continuous changes induced by physical and chemical processes of natural and anthropic origin. Such changes affect their mechanical properties. To quantitatively evaluate the hydro-chemical corrosion, the theories of chemical thermodynamic and chemical kinetics are introduced. An index was proposed, which provides a criterion to judge whether the corrosion would be happened and indicated the reaction direction. Then based on theoretical and testing results, a hydro-chemical damage index was proposed. And a series of damage degrees of sandstone under different circumstances, which consider the variations of pH values, temperatures, ions species and ions concentrations, were calculated by chemical kinetics method. Based on the results, the sensitivity of influencing factors was discussed. According to the calculation and the theory of poromechanics or testing results, the mechanical properties of geotechnical materials under hydro-chemical corrosion process can be predicted, so can assess the risk of geotechnical engineering long-term stability.

One-step solid-phase boronation to fabricate self-supported porous FeNiB/FeNi foam for efficient electrocatalytic oxygen evolution and overall water splitting

2019 ◽  
Vol 7 (33) ◽  
pp. 19554-19564 ◽  
Author(s):  
Hefeng Yuan ◽  
Shumin Wang ◽  
Xundi Gu ◽  
Bin Tang ◽  
Jinping Li ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Water Splitting ◽  
Oxygen Evolution ◽  
Alkaline Medium ◽  
Solid Phase ◽  
Core Shell ◽  
Environment Friendly ◽  
Long Term Stability ◽  
One Step

A 3D core–shell-type FeNi@FeNiB electrocatalyst fabricated by environment-friendly solid-phase boronation exhibits remarkable catalytic activity and long-term stability for the OER in alkaline medium.

Mechanical properties of the parenchyma of potato (Solanum tuberosum cv. Russet Burbank)

1996 ◽  
Vol 74 (6) ◽  
pp. 859-869 ◽  
Author(s):  
C. H. Pang ◽  
M. G. Scanlon
Keyword(s):  
Mechanical Properties ◽  
Energy Absorption ◽  
Uniaxial Compression ◽  
Compressive Loading ◽  
Shear Stiffness ◽  
Small Strain ◽  
Oscillatory Shear ◽  
Plant Materials ◽  
Short And Long Term

The mechanical properties of plant materials and plant structures influence the form, function, distribution, and utilization of plants. The shear and compressive stiffnesses of different regions of potato parenchyma were measured to more fully characterize the mechanical properties of this important storage organ. Measurements were performed on tubers that had been stored for 1 and 10 months. Slices and cylinders of parenchyma were excised from the centre of the tubers in three directions (and slices from the outer portion in two directions). Slices were subjected to small-strain oscillatory shear at frequencies of 0.02, 0.2, and 2 Hz. Cylinders were subjected to three cycles of uniaxial compression at 2 and 20 cm∙min−1. The coefficient of variation of measured parameters ranged on average from 16 to 44% for both crops and both tests. At small strains, potato parenchyma behaved essentially as an elastic material. The results from both small-strain oscillatory shear and uniaxial compression suggested that potato parenchyma is anisotropic in nature. Slices from the outer and inner regions of the tuber had different shear stiffness values. The shear stiffness of tubers stored for 1 month was approximately 70% greater than those stored for 10 months. Repeated compressive loading of potato parenchyma cylinders ameliorated the differences in stiffness and energy absorption between short- and long-term stored tubers, attributable to movement of fluids from the cells during compression. The observations emphasize the complexity of potato tissue and how its mechanical properties change during storage. Keywords: shear, compression, energy absorption, stiffness, turgor, storage, anisotropicity.

Nitrogen-doped graphene/carbon nanotube/Co3O4 hybrids: one-step synthesis and superior electrocatalytic activity for the oxygen reduction reaction

RSC Advances ◽  
2015 ◽  
Vol 5 (115) ◽  
pp. 94615-94622 ◽  
Author(s):  
Hengyi Lu ◽  
Yunpeng Huang ◽  
Jiajie Yan ◽  
Wei Fan ◽  
Tianxi Liu
Keyword(s):  
Carbon Nanotube ◽  
Reduction Reaction ◽  
Nitrogen Doped ◽  
Long Term Stability ◽  
Crossover Effects ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene ◽  
One Step ◽  
Orr Activity

N-rGO/CNTs/Co3O4 hybrids were prepared through a simple one-step hydrothermal method, and exhibited comparable electrocatalytic ORR activity to Pt/C catalysts, excellent tolerance to methanol crossover effects, and even better long-term stability.

Sign in / Sign up

Export Citation Format

Share Document