High Pressure Temperature Research Articles

Strategies for hardening purity metallic materials by high pressure and high temperature quenching method

Purity metallic materials are increasingly demanded in modern manufacturing industries, but their applications are limited owing to their poor wear resistance and mechanical properties. Therefore, exploring an efficient hardening method to significantly enhance the hardness of pure metals is emergent in materials science. In this work, a series of high pressure and high temperature (HPHT) quenching experiments were carried out on several pure metals, with a maximum hardening factor exceeding 10. The results indicated that pressure has an unusual effect on refining grains and increasing the Hall–Petch coefficient ky. The ky value of pure Fe is 49.5 GPa*μm1/2 with a quenching pressure of 5 GPa, which is two orders higher than that of the untreated polycrystalline sample (0.2 GPa*μm1/2). In addition, we report an extreme hardness of 8.34 GPa in pure Ti induced by HPHT quenching, and the unprecedented hardening comes from the formation of the twin and lath martensitic substructures. The hardening mechanism of the HPHT quenching method is a combination of Hall–Petch hardening and work-hardening. Our results provide a practical route to achieve attractive mechanical properties in pure metals and shine a light on the hardening mechanism of metallic materials.

Pore-scale flow simulation of CO2 sequestration in deep shale based on thermal-hydro-mechanical coupled model

The technology of sequestering CO2 in deep shale has shown great potential due to the low permeability of shale and the high adsorption of CO2 by organic-rich characteristics. Deep shale is characterized by high temperature and high pressure with a significant hydro-mechanical coupling effect. The Darcy–Brinkman–Stokes method was integrated with heat transfer equations to simulate thermal-hydro-mechanical coupled single-phase steady-state flow, combined with multiphase flow equations to simulate hydro-mechanical coupled transient flow under high-temperature conditions. This study aims to reveal the effect of temperature difference between CO2 and reservoir, Reynolds number, and formation pressure on the flow process of CO2 geological storage in deep shale based on the constructed real core structure consisting of organic pore, organic matter, and inorganic matter. The results indicate that low-temperature CO2 is conducive to giving full play to the role of convection heat transfer, improving the CO2 saturation and the swept volume of organic pores. The Reynolds number has a negligible impact on the transition of convective and conduction heat transfer. At higher Reynolds numbers, CO2 flows extensively and deeply, and CO2 clusters occupy a higher proportion in organic pores. At higher confining pressures, the Nusselt number is higher and convective heat transfer is more dominant. Shallower reservoirs are favorable conditions for adsorption trapping, as their cores are subjected to slightly lower confining pressure, resulting in higher CO2 saturation in the organic matter and higher sweep efficiency of organic pores. Our main finding is that low-temperature CO2, a higher Reynolds number, and shallower buried depth favor carbon sequestration.

Surface morphology change in DLC: H coatings with gradient Cr under high temperature and high pressure

The pressure influence of the surface morphology of DLC: H Coatings with gradient Cr (DCr) was studied by annealing in argon (HT effect) and HIPping (HT/HP effect). The results show that the voids formed on the HIPping annealed surface are rose-shaped with multi-layered edges but the edge of the voids formed on the argon annealed surface looks single-layered, and the composition of the coating surface is the same after HIPping and argon annealing. The Cr content at the bottom of the voids is higher in the HIPped surface than the argon annealed surface, and the voids formed in the HIPping annealed are relatively smaller but deeper than those in the argon. It is reasonable to deduce that the hydrogen release could have been restricted by the applied high compressive pressure on the surface.

Apparatus to measure density and viscosity of high-pressure carbon dioxide-alcohol mixtures.

Thermophysical properties of (single phase) binary CO2-alcohol mixtures under high pressure and moderate temperature conditions are important in supercritical fluid processes. An apparatus to measure mixture density as a function of temperature (up to 80 °C) and pressure (up to 15.9 MPa) over the full range of CO2 mass fractions was designed and commissioned. The fluid delivery system enables precise control and rapid variation of the CO2 mass fraction to within 0.2% of the desired value. Our apparatus advances the state-of-the-art by assuring a uniform mixture and assuring accuracy through redundant measurements, i.e., a variable-volume method with an uncertainty of 1% of reading and a Coriolis density meter with an uncertainty of 7 kg/m3. The results for a representative CO2-ethanol mixture are provided. Moreover, a third independent "bomb" experiment was used to measure density under selected conditions to further verify our measurements and, when present, discrepancies between them and the published data for the representative system. It is shown that, when the discrepancies were present, it was due to insufficient mixing in the other apparatus. Our apparatus also measures the viscosities of the mixtures using a viscometer accurate to 0.02 cP.

High pressure and high temperature synthesized boron-doped diamond electrodes for effective waste water treatment

The development of efficient and sustainable wastewater treatment technologies is vital to resolve environmental concerns. Finding an effective catalyst for the degradation of organic pollutants in wastewater is challenging. In this study, boron-doped diamond (BDD) particles were synthesized using a high-pressure high-temperature (HPHT) industrial diamond synthesis technology. BDD was investigated as an efficient electrode catalyst to convert organic pollutants into biodegradable substances. BDD self-supporting electrodes exhibited excellent properties with a relative density of 93.07%, an electrical resistivity of 2.71 × 10−4 Ω·m. Furthermore, BDD particles showed superior electrochemical characteristics such as a rapid electron transfer coefficient of about 0.5, good reversibility and redox properties. The BDD self-supporting electrode achieved a methylene blue degradation rate of 98.72% within 60 min. Our research provides valuable insights into using BDD as an effective electrochemical catalyst for wastewater treatment, which can help promote the development of environmentally friendly and economically viable technologies.

Stress corrosion cracking of leaded brass used in oil temperature sensor of vehicle

In today’s modern age, many kinds of sensors are used in cars. Sensors used in automobiles monitor the performance of the entire vehicle. They are used to control and process oil, temperature, emission level, coolant level, etc. In vehicle engine, oil is pumped under high-pressure throughout the engine system to lubricate the engine parts that are in constant friction. By doing so, it also transfers away heat from these engine parts. As the oil travels around the motor, large amount of heat keeps being absorbed and transferred. It eventually reaches engine sump where it is cooled using a coolant, and then again recirculated through the engine. In this process, overheating of this oil can greatly affect its viscosity and reduce its efficiency, eventually causing performance issue of the engine. To prevent overheating, temperature oil sensors are used, that continuously send data to the Electronic Control Unit (ECU) then subsequently ECU adjusts and regulates the fuel quantity and ignition timing. Oil Temperature Sensors (OTS) usually consists of three parts: brass body, thermistor unit and a coupler unit. For continuous temperature monitoring, the brass body is continuously in contact with the engine oil that are based on sulphates and ammoniate, under high pressure and elevated temperature. In present study, we observed leakage failure in the brass body of OTS and conducted root cause failure analysis. The basic objective of failure analysis is to identify the overall damage mode like: mechanical overload, environmental degradation / corrosion, fatigue etc. and its type and root-cause leading to the failure and its understanding help to mitigate similar failures in near future. In the present work, the failed / cracked brass body material was analyzed by using Scanning Electron Microscopy attached with Energy Dispersive Spectroscopy for identifying mechanisms of corrosion failures in OTS brass body components is highlighted. Failure analysis of cracked brass body showed the Stress Corrosion Cracking (SCC) failure which is further confirmed by multiple crack branching and Intergranular (IG) fracture.

Preparation and physical properties of CeO2 doped and modified epoxy resin composites

AbstractEpoxy resin is a widely used polymer material, while its low mechanical properties and thermal stability limit its use in extreme environments such as high temperature and high pressure. In order to improve the performance of EP, this study assessed the enhancement of mechanical properties and thermal stability of EP by stearic acid‐modified n‐CeO2 and its mechanism. Laser particle size analyzers, transmission electron microscopes, and other instruments were used to characterize n‐CeO2. Universal testing machines, thermogravimetric analyzers, and other instruments were used to test n‐CeO2/EP nanocomposites. The results show that fatty acids effectively coated the surface of n‐CeO2, reducing its central particle size from 0.248 μm to 0.193 μm and improving its dispersion and compatibility. The tensile, flexural, impact strength, maximum decomposition temperature, and glass transition temperature (Tg) increased by 382%, 554%, 698%, 5%, and 10%, respectively with 2 wt% filler content. The scanning electron microscopy (SEM) images showed that the addition of n‐CeO2 induced plastic deformation and crack formation in the EP matrix, which enhanced the toughness of the composite material. This study provided the effective methods and basis for the preparation of high‐performance n‐CeO2/EP nanocomposites.Highlights Nano cerium dioxide was modified to improve its dispersion by using stearic acid. High‐performance nanocomposites were prepared by using modified nanoparticles. The stiffness and toughness of the epoxy resin were enhanced by adding n‐CeO2. Thermal stability and heat resistance of the epoxy resin were improved by doping n‐CeO2. SEM images of the impact section showed that n‐CeO2 can prevent crack propagation.

Densification and Surface Carbon Transformation of Diamond Powders under High Pressure and High Temperature.

A new type of poly-diamond plate without a catalyst was produced via the high-pressure high-temperature (HPHT) compression of diamond powders. The densification of diamond powders and sp3 to sp2 carbon on the surface under HPHT compression was investigated through the characterization of the microstructure, Raman spectroscopy analysis and electrical resistance measurement. The densification and sp3-sp2 transformation on the surface are mainly affected by the pressure, temperature and particle size. The quantitative analysis of the diamond sp3 and sp2 carbon amount was performed through the peak fitting of Raman spectra. It was found that finer diamond particles under a higher temperature and a lower pressure tend to produce more sp2 carbon; otherwise, they produce less. In addition, it is interesting to note that the local residual stresses measured using Raman spectra increase with the diamond particle size. The suspected reason is that the increased particle size reduces the number of contact points, resulting in a higher localized pressure at each contact point. The hypothesis was supported by finite element calculation. This study provides detailed and quantitative data about the densification of diamond powders and sp3 to sp2 transformation on the surface under HPHT treatment, which is valuable for the sintering of polycrystalline diamonds (PCDs) and the HPHT treatment of diamonds.

Catalyst Coatings for Ammonia Decomposition in Microchannels at High Temperature and Elevated Pressure for Use in Decentralized and Mobile Hydrogen Generation

We report an investigation of catalyst performance for the decomposition of ammonia under industrially relevant conditions (high temperatures of up to 800 °C and an elevated pressure of 5 bar) with further emphasis on their stability at high reaction temperatures. The catalysts were applied and tested as coatings in 500 µm wide channels of microreactors. Nickel-based catalysts were studied and compared to a ruthenium-based catalyst supported on SiO2. The effect of the support on the catalytic performance was investigated, and CeO2-supported nickel catalysts were found to exhibit the highest activity. Promoters were applied to increase the NH3 decomposition activity of the Ni/CeO2 catalysts. The addition of cesium led to a slight reduction in activity, while lanthanum, calcium, and barium doping resulted in increased activity. In particular, the barium-doped Ni/CeO2 catalyst showed very high ammonia conversion and closed the activity gap with respect to ruthenium catalysts at reactor temperatures of 650 °C and higher. The hydrogen production rates achieved in this work were compared to values in the literature and were shown to exceed values found earlier for both nickel- and ruthenium-based catalysts. Furthermore, the ruthenium-based catalysts under investigation were rapidly deactivated at 700 °C, while the nickel-based catalysts did not show deactivation after 220 h on time on stream at 700 °C.

A Large-Range and High-Sensitivity Fiber-Optic Fabry-Perot Pressure Sensor Based on a Membrane-Hole-Base Structure.

In the field of in situ measurement of high-temperature pressure, fiber-optic Fabry-Perot pressure sensors have been extensively studied and applied in recent years thanks to their compact size and excellent anti-interference and anti-shock capabilities. However, such sensors have high technological difficulty, limited pressure measurement range, and low sensitivity. This paper proposes a fiber-optic Fabry-Perot pressure sensor based on a membrane-hole-base structure. The sensitive core was fabricated by laser cutting technology and direct bonding technology of three-layer sapphire and develops a supporting large-cavity-length demodulation algorithm for the sensor's Fabry-Perot cavity. The sensor exhibits enhanced sensitivity, a simplified structure, convenient preparation procedures, as well as improved pressure resistance and anti-harsh environment capabilities, and has large-range pressure sensing capability of 0-10 MPa in the temperature range of 20-370 °C. The sensor sensitivity is 918.9 nm/MPa, the temperature coefficient is 0.0695 nm/(MPa∙°C), and the error over the full temperature range is better than 2.312%.

High-Pressure Synthesis of Corundum-Type Ga2O3:Cr3+ and Application of Its Fluorescence to the Pressure Scale.

Cr3+-doped Ga2O3 crystals with a corundum structure were synthesized at high temperature and high pressure, and their excitation as well as fluorescence properties were evaluated. The crystals were green under white light illumination but deep red when exposed to ultraviolet light. This can mainly be attributed to R1 and R2 fluorescence spectra caused by the Cr3+ transition. The pressure-dependence of their fluorescence spectra is comparable with ruby (Al2O3:Cr3+), which is currently often used as a pressure scale. The excitation spectrum was shifted to the long-wavelength side compared with ruby, which enabled excitation with long-wavelength lasers, even if the pressure effect is considered. In addition, the R1 and R2 peaks were well-separated with increasing pressure, which might have advantages over the ruby scale.

Liquid to solid phase transition detection by using a vibrating tube densimeter along with densities up to 137 MPa of beef tallow fatty acid alkyl esters

Phase behavior and thermophysical properties of biodiesel at high pressure and high temperature are limited in the literature. These are useful to develop models and to understand their behavior having in mind the use of biodiesel in engines. Liquid to solid phase transitions, by using a vibrating tube densimeter, along with densities of three beef tallow fatty acid alkyl esters were studied in this work. Measurements of the oscillating period for each biofuel were carried out in a modular array constituted by two vibrating tube densimeters coupled in series and connected to a single loading cell. The oscillating period was converted to density by the forced path mechanical calibration (FPMC) method. Experimental liquid density sets for three beef tallow biodiesel samples based on fatty acid alkyl esters (FAAEs) are reported for the first time for pressures up to 137 MPa. These biofuels, named fatty acid methyl esters (FAMEs), fatty acid ethyl esters (FAEEs) and fatty acid butyl esters (FABEs), were measured in the temperature range of 286–393 K. The detection procedure for the beginning of the high-pressure solidification was focused on the beef tallow FABEs sample based upon its lower cloud point (CPFABEs = 281.15 K) in comparison with the reported property for the other esters (CPFAEEs = 289.15 K, CPFAMEs = 291 K) with the same feedstock; therefore, the conditions for the metastable liquid to solid phase transition associated to the effect of high pressure was detailed for waste beef tallow butyl ester biodiesel by performing step-by-step compressions in the interval of 286.20–298.13 K and with the help of the vibrating tube densimeters. FABEs had the lower density in contrast with FAEEs and FAMEs, this one being the denser biofuel. Modeling of liquid density data was performed by the perturbed-chain statistical associating fluid theory (PC-SAFT) Equation of State and the Tammann-Tait equation with maximum absolute average deviations of 0.15 % and 0.05 %, respectively. Both models were applied for correlating the thermodynamic derived properties of the fluid phase: isobaric thermal expansivity and isothermal compressibility.

Structural Design and Analysis of Large-Diameter D30 Conical Polycrystal Diamond Compact (PDC) Teeth under Engineering Rotary Mining Conditions.

In the realm of engineering rotary excavation, the rigid and brittle nature of the Polycrystal Diamond Compact (PDC) layer poses challenges to the impact resistance of conical teeth. This hinders their widespread adoption and utilization. In this paper, the Abaqus simulation is used. By optimizing the parameters of the radius of the cone top arc, we analyzed the changing law of the parameters of large-diameter D30 series conical PDC teeth, such as the equivalent force, impact force, and energy absorption of the conical teeth during the impact process, and optimized the best structure of the conical PDC teeth. After being subjected to a high temperature and high pressure, we synthesized the specimen for impact testing and analyzed the PDC layer crack extension and fracture failure. The findings reveal the emergence of a stress ring below the compacted area of the conical tooth. As the radius of the cone top arc increases, so does the area of the stress ring. When R ≥ 10 mm, the maximum stress change is minimal, and at R = 10 mm, the stress change in its top unit is relatively smooth. Optimal impact resistance is achieved, withstanding a total impact work value of 7500 J. Extrusion cracks appear in the combined layer part of PDC layers I and II, but the crack source is easy to produce in the combined layer of PDC layer II and the alloy matrix and extends to both sides, and the right side extends to the surface of the conical tooth in a "dragon-claw". The failure morphology of the conical teeth includes ring shedding at the top of the PDC layer, the lateral spalling of the PDC layer, and the overall cracking of the conical teeth. Through this study, we aim to promote the popularization and application of large-diameter conical PDC teeth in the field of engineering rotary excavation.

An equation of state based on the scaling properties of vibrational spectra at high pressure

Inter-atomic forces control vibrational properties and elastic moduli of a solid material. Based on first-principle calculations, it has been reported that, for elemental solids, the Debye frequency scales linearly with density to high accuracy. Combining this with other scaling properties of vibrational frequencies at high pressure, a new equation of state is presented. The proposed equation of state is tested against available experimental data for various kinds of solids at high pressure and room temperature. The quality of description of the compressional behavior of solids by our proposed equation of state is, for many cases, comparable to or better than that with the Vinet EOS.

Spatial Confinement of Pt Nanoparticles in Carbon Nanotubes for Efficient and Selective H2 Evolution from Methanol.

H2 generation from methanol-water mixtures often requires high pressure and high temperature (200-300°C). However, CO can be easily generated and poison the catalytic system under such high temperature. Therefore, it is highly desirable to develop the efficient catalytic systems for H2 production from methanol at room temperature, even at sub-zero temperatures. Herein, carbon nanotube-supported Pt nanocomposites are designed and synthesized as high-performance nano-catalysts, via stabilization of Pt nanoparticles onto carbon nanotube (CNT), for H2 production upon methanol dehydrogenation at sub-zero temperatures. Therein, the optimal Pt/CNT nanocomposite presents the superior catalytic performance in H2 production upon methanol dehydrogenation at the expense of B2(OH)4, with the TOF of 299.51min-130 oC. Compared with other common carriers, Pt/CNT exhibited the highest catalytic performance in H2 production, emphasizing the critical role of CNT in methanol dehydrogenation. The confinement of Pt nanoparticles by CNTs is conducive to inhibiting the aggregation of Pt nanoparticles, thereby significantly increasing its catalytic performance and stability. The kinetic study, detailed mechanistic insights, and density functional theory (DFT) calculation confirm that the breaking of O─H bond of CH3OH is the rate-controlling step for methanol dehydrogenation, and both H atoms of H2 are supplied by methanol. Interestingly, H2 is also successfully produced from methanol dehydrogenation at -10°C, which absolutely solves the freezing problem in the H2 evolution upon water-splitting reaction.

Cushy and Cheap Smart Health Monitoring System Incorporating a Ventilator

The handiness of mercantile mechanical ventilators is highly limited in low-income countries due to high rate in the price of its affordability. This factor affects the treatment of so many patients suffering from chronic respiratory syndrome. In this research, a low- cost and easy to use pressure ventilator coupled with a remote health monitoring system to assist the doctors check up on the patients is developed. There is need to maximize the availability of the ventilators in low-income countries at an affordable price tag. This system was developed with the aid of an Arduino nano, ESP8266 based NodeMcu microcontroller, high pressure blower, pressure transducers, humidity and temperature sensor. The developed system was evaluated and compared with existing one, using an actively breathing patient simulator as it mimics through a range of respiratory diseases. In the end, we were able to design a low-cost smart health monitoring system that incorporates ventilator and health vitals monitor. Our Design was implemented and verified to be working and equally satisfying all the specified requirements.

Metamorphic evolution of a metabasite dyke from Ogbagi Akoko area, Southwestern Nigeria

Petrography, mineral chemistry and whole rock analyses were conducted on a metabasite dyke hosted by pelitic gneiss (metapelite) in Ogbagi Akoko area with the aim of determining its metamorphic evolution. The dyke is about 40 cm wide and traceable for some meters along strike. It has a discordant contact relationship that is pencil sharp with the host pelitic gneiss and lack any internal fabric. The mineral assemblage includes: garnet +biotite + plagioclase + quartz + orthopyroxene + K-feldspar + ilmenite, with apatite occurring as an accessory mineral. Plagioclase has anorthite content of about 76 (An76) suggesting bytownite (An76 Ab24 Or0) while garnets are poikiloblastic almandine-pyrope rich with XFe of 0.73-0.75. Orthopyroxene has a composition of Wo0 En50 Fs50 suggesting hypersthene that is depleted in Ca. The mineral assemblage, presence of bytownite, absence of amphibole and lack of internal fabric indicate that the rock has undergone metamorphism at a high temperature and moderate pressure without deformation at granulite facies metamorphism. The absence of deformation structure in the dyke is an indication that the intrusion occurred after the cessation of the regional metamorphism but prevalent high temperature that recrystallized the rock. The whole rock composition and some elemental ratios of the dyke indicate that the metamorphism had little or no effect on the bulk chemistry of the rock.

Research on key technology of packer rubber barrel for integrated fracturing and completion of gas well

The staged and layered fracturing technology plays an important role in unconventional tight reservoirs. And the gas well fracturing and completion integration is the core component to realize the fracturing and completion integration process, which can realize the integration of acid fracturing and later drainage production so as to reduce the secondary pollution to the reservoir. The packer rubber barrel’s performance directly affects the long-term effective sealing reliability itself in high temperature and high pressure environment. In this paper, the constitutive model of rubber tested from high temperature and high pressure curing kettle to simulate the high-temperature and highly corrosive environment of the formation. On this basis, the structure of the packer’s shoulder and the protective ring of the rubber barrels are optimized through Abaqus to reduce its stress failure under high pressure, and its corrosion resistance is improved by improving the rubber material. The sealing performance of the packer rubber cylinder under the field underground requirements is tested through laboratory evaluation test and field test. The results show that the protective ring and rubber tube shoulder at 30° angle are a reasonable result of optimization, and the optimized packer can meet the requirements of 154 °C temperature resistance, 79 MPa pressure bearing and long-term effective sealing. The successful development of packer rubber and the integrated analysis process can lay a solid foundation for the realization of integrated fracturing and completion process for exploration and development of deep volcanic or carbonate reservoirs.

Contrasting graphitization differences between vitrinite and inertinite based on high-temperature and high-pressure experiments

It has been recognized that vitrinite and inertinite exhibit different evolutionary characteristics during coalification processs, but the study of their evolutionary differences after entering the graphitization process is limited. To investigate the graphitization differences, this study conducted high-temperature high-pressure (HT-HP) experiments under different temperature and pressure conditions. The precursor used in the HT-HP experiments was concentrated inertinite-rich samples and vitrinite-rich samples obtained through manual selection, and the parent coal is low volatile bituminous coal (Rmax (%) = 1.7). X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM) were employed to compare and analyze the graphite lattice evolution of the maceral. The experimental results indicated the following: (1) During the construction of the three-dimensional graphite lattice, vitrinite and inertinite exhibited differences in response to temperature and pressure conditions. Inertinite had a higher graphitization threshold compared to vitrinite, and once reached or exceeded, inertinite underwent rapid graphitization seen by the significant decrease of the interlayer spacing d002; (2) In terms of defect healing, under the same stress conditions, vitrinite was more sensitive to temperature compared to inertinite as observed by the Raman parameters R2 and R3; (3) By comparing the development of graphite structure under different temperature and pressure conditions, we found that both efficient graphitization process and development of the graphite structure require a synergistic combination of temperature and pressure, where an excessive or insufficient pressure can inhibit graphitization and even dismantle and damage the formed graphite structure.

Design and implementation of a kind of high precision temperature compensating system for silicon-on-sapphire pressure sensor

In order to reduce the temperature effects on the testing accuracy of the silicon-on-sapphire high-temperature large-range pressure sensor, a miniaturized portable silicon-on-sapphire pressure sensor temperature compensation system is designed and implemented after solving the following three issues: temperature compensation structure design, temperature compensation circuit fabrication, and temperature compensation algorithm implementation. The simulation results indicated that the temperature of the test circuit part of the package structure is close to 30 °C at an ambient temperature of 30 °C, with the sensor sensitive element at 250 °C working temperature and 28 MPa ultimate pressure. Regarding to the problem of large sensor drift in high-temperature environments, a temperature compensation algorithm combining least squares and Lagrange interpolation is designed based on the input and output characteristics of the sensor. The algorithm improves the computational efficiency while also increasing the hysteresis error and nonlinear deviation of the sensor to 0.028%. The test results of the NIM (National Institute of Metrology, China) show that the measurement accuracy of the sensor is higher than 1‰ FS within −20 °C to 140 °C and higher than 3‰ FS within 140 °C to 250 °C.