High-density amorphous phase of silicon carbide obtained under large plastic shear and high pressure

2012 ◽  
Vol 85 (5) ◽  
Author(s):  
Valery I. Levitas ◽  
Yanzhang Ma ◽  
Emre Selvi ◽  
Jianzhe Wu ◽  
John A. Patten
Keyword(s):  
Silicon Carbide ◽  
High Pressure ◽  
Amorphous Phase ◽  
High Density ◽  
Plastic Shear

Nitroethane at high density: an experimental and computational vibrational study

2021 ◽  
Vol 23 (15) ◽  
pp. 9325-9336
Author(s):  
Akio Yoshinaka ◽  
Serge Desgreniers ◽  
Anguang Hu
Keyword(s):  
High Pressure ◽  
Raman Spectra ◽  
Vibrational Spectra ◽  
Unit Cell ◽  
High Density ◽  
Monoclinic Unit Cell ◽  
Vibrational Study

Raman and IR vibrational spectra confirm two molecular units associated with the monoclinic unit cell of nitroethane under high pressure. Raman spectra are extremely sensitive to predicted effects of unit cell distortion due to changes in H-bonding.

scholarly journals High density of shear bands in the Vitreloy bulk metallic glass subjected to high-pressure torsion

2021 ◽  
Vol 1008 ◽  
pp. 012031
Author(s):  
Vasily Astanin ◽  
Dmitry Gunderov ◽  
Zhi Qiang Ren ◽  
Ruslan Valiev ◽  
Jing Tao Wang
Keyword(s):  
High Pressure ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
High Pressure Torsion ◽  
Shear Bands ◽  
High Density

A Transparent and Tough β-Si3N4 Ceramic with a Whiskery Microstructure

2015 ◽  
Vol 655 ◽  
pp. 1-5
Author(s):  
Peng Xi Li ◽  
Hong Qiang Wang ◽  
Liu Cheng Gui ◽  
Jun Li ◽  
Hai Long Zhang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Amorphous Phase ◽  
Hot Pressing ◽  
High Density ◽  
Indentation Fracture ◽  
Indentation Fracture Toughness ◽  
Resultant Material

The transparent β-Si3N4ceramic with a whisker-like microstructure was prepared by hot-pressing at 2000 °C for 26 h, with MgSiN2as an additive. The resultant material achieves the maximum transmittance of 70 % at the wavelength of about 2.5 μm and the transmittance value keeps higher than 60 % in the range of 700-4500 nm wavelength, which is attributed to the very small amount of the intergranular amorphous phase along with high density. The present transparent β-Si3N4ceramic exhibits an indentation fracture toughness of 7.2±0.3 MPa m1/2.

The Feasibility for Potassium-Based Phosphate Brines To Serve as High-Density Solid-Free Well-Completion Fluids in High-Temperature/High-Pressure Formations

SPE Journal ◽  
2018 ◽  
Vol 24 (05) ◽  
pp. 2033-2046 ◽  
Author(s):  
Hu Jia ◽  
Yao–Xi Hu ◽  
Shan–Jie Zhao ◽  
Jin–Zhou Zhao
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Oil And Gas ◽  
Pressure Coefficient ◽  
High Density ◽  
Well Drilling ◽  
Well Completion ◽  
Oil And Gas Resources ◽  
Completion Fluids ◽  
High Temperature High Pressure

Summary Many oil and gas resources in deep–sea environments worldwide are often located in high–temperature/high–pressure (HT/HP) and low–permeability reservoirs. The reservoir–pressure coefficient usually exceeds 1.6, with formation temperature greater than 180°C. Challenges are faced for well drilling and completion in these HT/HP reservoirs. A solid–free well–completion fluid with safety density greater than 1.8 g/cm3 and excellent thermal endurance is strongly needed in the industry. Because of high cost and/or corrosion and toxicity problems, the application of available solid–free well–completion fluids such as cesium formate brines, bromine brines, and zinc brines is limited in some cases. In this paper, novel potassium–based phosphate well–completion fluids were developed. Results show that the fluid can reach the maximum density of 1.815 g/cm3 at room temperature, which makes a breakthrough on the density limit of normal potassium–based phosphate brine. The corrosion rate of N80 steel after the interaction with the target phosphate brine at a high temperature of 180°C is approximately 0.1853 mm/a, and the regained–permeability recovery of the treated sand core can reach up to 86.51%. Scanning–electron–microscope (SEM) pictures also support the corrosion–evaluation results. The phosphate brine shows favorable compatibility with the formation water. The biological toxicity–determination result reveals that it is only slightly toxic and is environmentally acceptable. In addition, phosphate brine is highly effective in inhibiting the performance of clay minerals. The cost of phosphate brine is approximately 44 to 66% less than that of conventional cesium formate, bromine brine, and zinc brine. This study suggests that the phosphate brine can serve as an alternative high–density solid–free well–completion fluid during well drilling and completion in HT/HP reservoirs.

scholarly journals Effects of temperatures on pressure-induced structural changes in amorphous Si: A molecular-dynamics study

10.29007/6kp3 ◽  
2020 ◽  
Author(s):  
Renji Mukuno ◽  
Manabu Ishimaru
Keyword(s):  
Molecular Dynamics ◽  
Phase Transformation ◽  
Amorphous Phase ◽  
Structural Changes ◽  
Interatomic Potential ◽  
Activation Barrier ◽  
Distribution Functions ◽  
High Density ◽  
Angle Distribution ◽  
Dynamics Simulations

The structural changes of amorphous silicon (a-Si) under compressive pressure were examined by molecular-dynamics simulations using the Tersoff interatomic potential. a-Si prepared by melt-quenching methods was pressurized up to 30 GPa under different temperatures (300K and 500K). The density of a-Si increased from 2.26 to 3.24 g/cm3 with pressure, suggesting the occurrence of the low-density to high-density amorphous phase transformation. This phase transformation occurred at the lower pressure with increasing the temperature because the activation barrier for amorphous-to-amorphous phase transformation could be exceeded by thermal energy. The coordination number increased with pressure and time, and it was saturated at different values depending on the pressure. This suggested the existence of different metastable atomic configurations in a-Si. Atomic pair-distribution functions and bond-angle distribution functions suggested that the short-range ordered structure of high-density a-Si is similar to the structure of the high-pressure phase of crystalline Si (β-tin and Imma structures).

scholarly journals Self-stopping tomatoes - cultural and economic aspects.

1975 ◽  
Vol 23 (3) ◽  
pp. 211-218 ◽  
Author(s):  
A.J. de Visser ◽  
K. Buitelaar
Keyword(s):  
High Pressure ◽  
Fruit Set ◽  
High Density ◽  
Lateral Growth ◽  
Economic Aspects ◽  
Experimental Sequence ◽  
Breeding Programmes

The labour requirements and costs for growing 2 crops of traditionally trained tomatoes per year are contrasted with those estimated for an experimental sequence of 4 self-stopping crops in which specially bred plants are grown at a high density, with little or no lateral growth and once-over harvesting. In preliminary trials with prototype plants, it was necessary to provide support and to remove side-shoots at least twice, and fruit set was enhanced by using a high-pressure sprayer. The need for further developments in cultural techniques and breeding programmes for self-stopping crops is discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Development of New Single and High-Density Heat-Flux Gauges for Unsteady Heat Transfer Measurements for a Rotating Transonic Turbine

2020 ◽  
Author(s):  
Richard Celestina ◽  
Spencer Sperling ◽  
Louis Christensen ◽  
Randall Mathison ◽  
Hakan Aksoy ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Pressure Ratio ◽  
High Density ◽  
Secondary Flows ◽  
Single Stage ◽  
High Pressure Turbine ◽  
Transonic Turbine ◽  
New Generation

Abstract This paper presents the development and implementation of a new generation of double-sided heat-flux gauges at The Ohio State University Gas Turbine Laboratory (GTL) along with heat transfer measurements for film-cooled airfoils in a single-stage high-pressure transonic turbine operating at design corrected conditions. Double-sided heat flux gauges are a critical part of turbine cooling studies, and the new generation improves upon the durability and stability of previous designs while also introducing high-density layouts that provide better spatial resolution. These new customizable high-density double-sided heat flux gauges allow for multiple heat transfer measurements in a small geometric area such as immediately downstream of a row of cooling holes on an airfoil. Two high-density designs are utilized: Type A consists of 9 gauges laid out within a 5 mm by 2.6 mm (0.20 inch by 0.10 inch) area on the pressure surface of an airfoil, and Type B consists of 7 gauges located at points of predicted interest on the suction surface. Both individual and high-density heat flux gauges are installed on the blades of a transonic turbine experiment for the second build of the High-Pressure Turbine Innovative Cooling program (HPTIC2). Run in a short duration facility, the single-stage high-pressure turbine operated at design-corrected conditions (matching corrected speed, flow function, and pressure ratio) with forward and aft purge flow and film-cooled blades. Gauges are placed at repeated locations across different cooling schemes in a rainbow rotor configuration. Airfoil film-cooling schemes include round, fan, and advanced shaped cooling holes in addition to uncooled airfoils. Both the pressure and suction surfaces of the airfoils are instrumented at multiple wetted distance locations and percent spans from roughly 10% to 90%. Results from these tests are presented as both time-average values and time-accurate ensemble averages in order to capture unsteady motion and heat transfer distribution created by strong secondary flows and cooling flows.

High Pressure Sintering of Silicon Carbide with Mg-Cr3C2 Composite Additive

2021 ◽  
Vol 1035 ◽  
pp. 768-772
Author(s):  
Jing Kun Li ◽  
Xue Ping Ren ◽  
Qiang Yan ◽  
Yan Ling Zhang ◽  
Hong Liang Hou
Keyword(s):  
Silicon Carbide ◽  
High Pressure ◽  
Magnesium Alloy ◽  
Chromium Carbide ◽  
Sintered Ceramic ◽  
High Pressure Sintering ◽  
C 30 ◽  
Silicon Carbide Particles ◽  
New Phase ◽  
Carbide Particles

Porous silicon carbide was sintered at 1300 °C/30 MPa for 2 h with 4 wt.% magnesium alloy and 4 wt.% chromium carbide composite additives. The sintered ceramic presented density of around 92% of the theoretical density. No new phase was observed after sintering. Mg segregates around chromium carbide particles in sintered ceramic. The silicon carbide particles were mainly bonded by melt magnesium alloy and chromium carbide diffused in solid state. The voids existed in the sintered ceramic, but much more fracture occurred in silicon carbide particles during bending due to high bonding strength of sintering necks. Some voids existed in the ceramic, which act as crack sources during fracture.

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