Rich Vapor Research Articles

Optimizing lean and rich Vapor compression with solar Assistance for post-combustion carbon capture in natural gas-fired power plant

The integration of post-combustion capture (PCC) CO2 technologies with power plants and high-emission industrial processes has become imperative for reducing carbon emissions and mitigating environmental impacts. This study focuses on addressing the significant energy consumption associated with PCC and explores the potential of using solar thermal energy to optimize configurations, thereby enhancing sustainability and reducing dependency on conventional power sources. Simulate various configurations under steady-state conditions using Aspen HYSYS V11 and Aspen Economic Evaluation software. The results indicate a substantial reduction in energy consumption to 2.1 GJ/ton CO2 after the initial optimization steps. The key innovations involve the integration of Lean Vapor Compression (LVC), Solvent Split Flow (SSF), Rich Solvent Recycle (RSR), and Rich Vapor Compression (RVC). Further optimization was conducted by integrating a reboiler with parabolic trough collectors (PTC), to reduce energy penalties. The LVC + RVC + RSR + SSF + PTC configuration results reveal a notable improvement in exergoeconomic factors, ranging from 3.13% to 7.8%, highlighting the economic feasibility of the optimized configurations. Simultaneously, the energy penalty decreased by 11.1%, signifying enhanced sustainability in the proposed PCC system. This study contributes to the gap in research by demonstrating the efficacy of solar thermal energy in optimizing PCC configurations, providing a pathway towards more sustainable and energy-efficient solutions for carbon capture in high-emission industrial sectors. The findings offer insights for researchers, engineers, and policymakers aiming to address the pressing issue of carbon emissions from industrial processes.

Chemical recycling of PVC-containing plastic waste for recycling of critical metals

Chemical recycling of polyvinyl chloride containing plastic waste to recover critical metals is a promising way to solve two important problems (polyvinyl chloride disposal and critical metal recovery) in waste management and is being transferred on a larger scale in the “CHM-Technology” project. Various polyvinyl chloride containing plastic wastes were pyrolyzed to generate a hydrogen chloride rich vapor. This hydrogen chloride rich vapor is used in a second step to chlorinate indium in liquid crystal displays. Indium chloride has a lower boiling point than indium-tin-oxide and evaporates. This is cooled down and generates a metal concentrate together with the decomposed volatile materials from liquid crystal displays. The chlorine content in the polyvinyl chloride containing plastic waste residues is reduced. The products solid, oil, hydrochloric acid and gas can be used for new products. For metal purification the metal concentrate is mixed with water, filtrated, distilled and an electrolysis is carried out to recover metallic indium. Nine waste containing PVC were used with significant differences: when more hydrochloric acid and less volatile organic fraction was produced, more indium was transferred to the metal concentrate. The best recovery of indium (78% purity after electrolysis) was 39 wt-% from LCD panels containing 83 mg In/kg.

Technoeconomic evaluation of combined rich and lean vapour compression configuration for CO2 capture from a cement plant

A combined rich and lean vapour compression configuration was investigated for CO2 capture from a cement plant. This was to assess its performance in energy consumption, actual CO2 emission reduction, and cost reduction potentials compared with the conventional process and the simple rich vapour compression and lean vapour compression configurations. Two electricity supply scenarios were considered: from natural gas combined cycle power plant and a renewable source like hydropower. The three vapour compression configurations outperformed the standard CO2 absorption configuration in energy requirement, actual CO2 emissions reduction and in CO2 avoided cost reduction. The best performance was achieved by the combined rich and lean vapour compression configuration. The reboiler heat, equivalent heat and CO2 avoided cost reduction performance was 24 – 30 %, 16 -18 % and 13 – 16 % respectively. However, the performances in energy, CO2 emissions reduction and CO2 avoided cost are only marginally better than the lean vapour compression configuration. The use of renewable electricity, like hydropower electricity will help CO2 capture processes to achieve higher CO2 emission reduction and lower CO2 avoided cost compared to fossil fuel based electricity.

Interdecadal Pacific Variability dominated the decadal variation of cold season precipitation in arid West Asia

This study examines the interdecadal variation of cold season precipitation in arid West Asia (AWA) from 1960 to 2019 and identifies the underlying physical mechanisms. The results indicate that the precipitation in this region has exhibited significant interdecadal variation over the past 60 years, which is closely related to Interdecadal Pacific Variability (IPV). During the positive IPV phase, which was associated with a warming equatorial Middle East Pacific Ocean, an eastward-propagating Rossby wave induced a negative geopotential height anomaly over AWA, providing the dynamic conditions for precipitation. Additionally, IPV caused the westerly jet to move southward and strengthen, providing rich water vapor. Moreover, a positive geopotential height anomaly over the Indo-West Pacific, caused by cold sea surface temperature, led to the upward transport of water vapor from the Northern Indian Ocean to AWA, further enhancing the water vapor conditions. These factors together resulted in excess precipitation in AWA during the positive IPV phase, with a 17.6 mm increase compared to the negative phase, accounting for approximately 12% of the cold season precipitation. These findings were also confirmed by the piControl simulation of CESM2.

Determining impacts of prenatal cannabis exposure on cannabis vapor self-administration using a novel response-contingent vapor model in pregnant rat dams

Cannabis use during pregnancy is becoming increasingly common despite a lack of knowledge regarding its long-term effects on developing offspring. Determining effects of prenatal cannabis exposure on cannabis use later in life has been especially difficult given the problems inherent to traditional models of cannabinoid self-administration. Thus, we adopted a model of response-contingent cannabis vapor delivery in pregnant rat dams to investigate impacts of maternal cannabis use on reinforcing properties of ∆9-tetrahydrocannabinol (THC)-rich cannabis vapor in offspring. Rat dams were trained to self-administer a vaporized cannabis extract or vehicle vapor in 1-hr sessions twice daily until 24-48 hr prior to parturition, while a third group received no vapor exposure. Cannabis vapor self-administration was assessed in adult offspring using a 22-day escalating reinforcement schedule that culminated in a 3 hr progressive ratio challenge. Dams reliably self-administered cannabis vapor during the gestational period and showed better discrimination for the vapor-paired nosepoke than vehicle self-administering dams. In accordance with human data, cannabis-exposed offspring displayed lower birthweights than vehicle-exposed offspring. Effects of prenatal cannabis exposure on vapor self-administration in adult offspring differed by sex. Male cannabis-exposed offspring made fewer active responses and earned fewer vapor deliveries than vehicle-exposed offspring, regardless of their assigned vapor condition. Conversely, female offspring showed higher rates of responding for cannabis relative to vehicle, but rates of self-administration were unaffected by prenatal cannabis exposure. Altogether, these data demonstrate feasibility of response-contingent cannabis vapor delivery in pregnant rat dams and indicate paradoxical suppressive effects on vapor self-administration in male offspring.

Study of pathways to reduce the energy consumption of the CO2 capture process by absorption-regeneration

Several industrial sectors, such as for example cement manufacturers and lime producers, produce so-called “unavoidable” CO2 emissions because these ones are intrinsically linked to the industrial process itself (decarbonation of calcium carbonate). In order to reduce these emissions, it is necessary to implement a Carbon Capture, Utilization and/or Storage (CCUS) process chain, whose step of capture, although already technologically mature (especially the absorption-regeneration process using amine(s)-based solvents), leads to very high energy consumption. Three pathways to reduce this consumption have been investigated (experimentally and/or through the development of Aspen PlusTM simulations), namely: (i) upstream of the process thanks to the increase of the flue gas CO2 content (by partial oxy-combustion and/or flue gas recirculation), (ii) within the process (using more efficient and innovative mixtures of solvents such as demixing solutions), and (iii) at the configurational level by using advanced configurations in the capture process. It emerged that the use of a demixing process such as the mixture composed of diethylethanolamine (DEEA) and methylamino-propylamine (MAPA), or the implementation of an advanced process configuration (InterCooling Absorber + Rich Vapor Compression + Rich Solvent Splitting and Preheating, with methyldiethanolamine (MDEA) + piperazine (PZ) as a solvent) are the most energy reducing pathways for the absorption-regeneration process, i.e. more than 40% in comparison with a conventional process using monoethanolamine (MEA). Moreover, from an economical point of view, and compared to a basic configuration with MEA, the demixing technology has the advantage of being able to achieve such energy performance with a more limited investment (CAPEX) (+1.6%) than with advanced process configurations (+8.8%).

Techno-economic feasibility and sustainability of an integrated carbon capture and conversion process to synthetic natural gas

Carbon Capture Utilization and Storage (CCUS) technologies are receiving increasing interest and its implementation at world scale appears to be crucial to reduce CO2 emissions. In this context, Power-to-Gas technologies (PtG) are very promising, allowing to store renewable electricity and valorize captured CO2 to produce Synthetic Natural Gas (SNG), among other. The present work simulates an integrated CO2 capture and conversion process to SNG, and investigates its techno-economic and environmental performances. Different scenarios are defined considering the application to a cement plant flue gas and the production of renewable hydrogen. An advanced CO2 capture unit is implemented, considering a configuration (Rich Vapor Compression and Inter Cooling) and a solvent (MDEA + PZ) allowing to minimize its specific energy consumption (35 % regeneration energy savings in comparison with a conventional amine-based CO2 capture system). The excess heat released by the catalytic conversion is recovered for the solvent regeneration maximizing the amount of captured CO2. From the scenarios analyses, it is shown that integrating the CO2 capture and conversion steps is beneficial for reducing both the net CO2 emission to the atmosphere, by 45 %, and the contribution to fossil depletion, by 81 %, in comparison with the non-integrated one, as the production of fossil-based natural gas is replaced by renewable SNG. The proposed process leads to a cost of 2.39 € per kg Raw-SNG, with expected revenues of 0.87 € per kg Raw-SNG. Significant subsidies and incentives would thus be needed to compete with conventional energy prices for natural gas (0.55 € per kg).

Integration of rich and lean vapor recompression configurations for aqueous ammonia-based CO2 capture process

Post-combustion carbon capture (PCC) using a chemical solvent is the most mature and well-proven technology to mitigate carbon dioxide (CO2) emission. However, substantial energy consumption for solvent regeneration is still a critical challenge for widespread deployment of this PCC. In this study, a novel low-energy, combined rich and lean vapor recompression (RLVR) process for the CO2 capture process using dilute aqueous ammonia (NH3) solvent was developed and optimized by integrating of rich vapor recompression (RVR) and lean vapor recompression (LVR) approaches. A parametric study showed that the minimum total equivalent work can be obtained when CO2 loading and NH3 concentration of lean solution are 0.275 mol CO2/mol NH3 and 5.0 wt%, respectively and the pressures of stripper, rich and lean solvent flash drums are maintained at 10.5 bar, 4.62 bar and 6.93 bar, respectively. Under such operation conditions, the total equivalent work required for a CO2 capture plant was remarkably reduced to 0.123 kW h/kg of CO2 captured, which is equivalent to about 10% energy penalty. This amounts to 26–54% reduction from recent literature reports. Furthermore, this combined RLVR process can completely eliminate the need of reboiler, leads to improving the flexibility of the capture plant since it can be separated from power plant steam systems.

Techno-Economic and Environmental Assessment of Carbon Capture at a Cement Plant and CO2 Utilization in Production of Synthetic Natural Gas

The purpose of this study is to evaluate the interest of a Power-to-Gas integrated system converting CO2 from cement plan flue gas. The integrated CO2 capture and CO2 catalytic conversion into Synthetic Natural Gas (SNG) process, using H2 produced by electrolysis, is investigated and simulated in Aspen Plus. More precisely, the process chain implemented is designed to capture almost 1 ton of CO2 per hour coming from a conventional cement plant equipped with the Best Available Techniques (flue gas CO2 content of 20 mol.%). An advanced amines-based CO2 capture process is implemented applying a Rich Vapor Compression configuration including intercooling, and a blend composed of methyldiethanolamine (MDEA) and piperazine (PZ) as solvent, allowing to minimize the specific energy consumption of the process. The captured CO2 is then sent to the exothermal catalytic methanation reactor together with renewable hydrogen to produce SNG. The heat provided by the exothermal methanation reactions is recovered. A fraction of the released heat is used for the regeneration of the CO2 capture solvent, while an excess recovered heat is used to produce steam for other applications, such as capturing more CO2 or producing electricity. An economic assessment is proposed to estimate the investment and operational costs of the process chain. Finally, a Life Cycle Analysis method is performed to identify the main environmental hotspots while comparing two scenarios (cement plant with and without the integrated CO2 capture-conversion process).

Nanosecond laser-induced reshaping of periodic silicon nanostructures

We demonstrated the use of laser-induced reshaping to produce periodic silicon nanostructures (PSNs) with different geometries. Periodically located silicon nanostructures were preformed by dry etching of a silicon wafer covered with a monolayer of self-assembled polystyrene nanospheres. These PSNs were reshaped under ambient conditions by irradiation with two kinds of nanosecond lasers (532 nm and 355 nm). The effects of the irradiation parameters on the reshaped geometry were systematically investigated. Vertical growth of the irradiated PSNs resulted from the epitaxial deposition of rich silicon vapor during laser irradiation. However, the growth was limited even with higher laser fluence because of the nanoscale structure, the size of which is smaller than the melting depth induced by the nanosecond lasers. The reshaped PSNs displayed reflection spectra that are tunable by varying the characteristics of reshaping-laser input. This method offers a promising approach for the site-selective fabrication of optically tunable 3D nanostructures.

Energy Minimization in Piperazine Promoted MDEA-Based CO2 Capture Process

A piperazine (PZ)-promoted methyldiethanolamine (MDEA) solution for a carbon dioxide (CO2) removal process from the flue gas of a large-scale coal power plant has been simulated. An Aspen Plus® was used to perform the simulation process. Initially, the effects of MDEA/PZ concentration ratio and stripper pressure on the regeneration energy of CO2 capture process were investigated. The MDEA/PZ concentration ratio of 35/15 wt.% (35 wt. MDEA and 15 wt.% PZ) was selected as an appropriate concentration. The reboiler duty of 3.235 MJ/kg CO2 was obtained at 35/15 wt.% concentration ratio of MDEA/PZ. It was considered a reference or base case, and process modifications including rich vapor compression (RVC) process, cold solvent split (CSS), and the combination of both processes were investigated to check its effect on the energy requirement. A total equivalent work of 0.7 MJe/kg CO2 in the RVC and a reboiler duty of 2.78 MJ/kg CO2 was achieved in the CSS process. Similarly, the total equivalent work, reboiler duty, and condenser duty of 0.627 MJe/kg CO2, 2.44 MJ/kg CO2, and 0.33 MJ/kg CO2, respectively, were obtained in the combined process. The reboiler duty and the total equivalent work were reduced by about 24.6 and 16.2%, respectively, as compared to the reference case. The total energy cost saving was 1.79 M$/yr. Considering the additional equipment cost in the combined process, the total cost saving was 0.67 M$ per year.

Energy-saving performance of advanced stripper configurations for CO2 capture by ammonia-based solvents

In an ammonia-based post-combustion carbon capture (PCC) process, the regeneration energy of CO2-lean solvent comprises the main fraction of overall energy consumption. The use of a pressurized CO2 stripper to enhance the CO2 purity in the overhead vapor is one option for reducing the regeneration energy. Further energy reductions can be achieved by modifying stripper configurations reported in the literature. In this study, the energy-saving performance of advanced stripper configurations is investigated, including cold split bypass (CSB), lean vapor compression (LVC), and rich vapor compression (RVC). Our results show that the energy reduction by CSB has been underestimated in the literature because the effect of the warm rich feed stage has been neglected. Compared with a standard stripper operated at 10 atm, the CSB modification achieves 34.2% of energy reduction, and the combination of CSB and LVC reaches 34.4%. In other words, LVC only improves the energy saving of CSB by 0.2%.

Analysis of a rich vapor compression method for an ammonia-based CO2 capture process and freshwater production using membrane distillation technology

Post-combustion capturing of CO2 through chemical solvent absorption is a promising technique for reducing the CO2 emissions from fossil fuel power plants. However, the energy penalty associated with the absorbent regeneration continues to be a critical challenge in the chemical solvent absorption process. In this study, the operating parameters of ammonia-based CO2 capture were optimized to reduce the energy penalty. This optimized process was considered a base process to which process modifications were added, with the goal of further reducing the energy consumption. These process modifications included absorber inter-cooling and rich vapor compression (RVC) combined with cold solvent split (CSS) processes. The combined RVC and CSS process was compared with the base process and advanced NH3-based CO2 capture processes, such as the rich split process and the inter-heating process. Compared to the base process, the combined process reduced the energy requirements by 20.2%, which was higher than the 11.6% and 8.26% energy reductions obtained via the rich split and inter-heating processes, respectively. The combined process was also compared with MEA-based process modifications. The energy savings from the combined process were higher than those of the MEA-based process modifications. To estimate the trade-offs between the energy savings resulting from the combined process vs. the capital cost of the additional equipment required, the Aspen Capital Cost Estimator (ACCE) was used. The results showed that the combined process saved $0.707 million per year. Furthermore, a membrane distillation (MD) technology was integrated with the CO2 capture unit to produce freshwater. This additional process produced freshwater at a rate of 719.240 m3/day at a feed stream temperature to the MD unit of 35.66 ℃.

Bandgap tuning of Monolayer MoS2(1-x)Se2x alloys by optimizing parameters

Among the two-dimensional (2D) materials, transition-metal dichalcogenide (TMD) monolayer alloys attract significant attention as they allow for bandgap engineering, which is highly beneficial for their applications in nanoelectronics, optoelectronics, and photonics. In this research, we present a facile and repeatable molybdenum sulphoselenide (MoS2(1-x)-Se2x) monolayer growth through systematic investigation of CVD growth parameters such as gas flow rates, substrate temperature and precursor concentration (S/Se ratio). We have obtained a full control of the x values within the range of 0–1 allowing for bandgap tailoring between 1.82 eV (MoS2) and 1.56 eV (MoSe2) where the size of the grown monolayer flakes has been measured as large as 150 μm on SiO2 (300 nm)/Si substrates. We find that S/Se ratio and the growth temperature are the most critical parameters to control the composition (x value) of the monolayer alloy TMDs. In our study, we find two growth regimes, where S rich alloys are grown by controlling S to Se ratio at 750 °C and Se rich alloys are synthesized at higher growth temperatures (900 °C) by utilizing Se rich vapor conditions. Growth of Se rich alloys at a higher growth temperature is attributed to the chalcogen exchange mechanism (CEM) referring to substitution of S atoms in as grown alloy host lattice site with Se atoms present in the Se rich vapor. CEM is proposed as the basic alloying mechanism for selenium rich monolayer alloys. Regarding the structural properties, FWHM of the photoluminescence (PL) spectral peaks of our flakes range between 19 and 37 nm together with uniform spatial PL emission intensities indicating high crystalline quality. Tuning the bandgap of high-quality and large area TMD monolayers by simply changing the basic CVD parameters is of great benefit for future 2D optoelectronic devices.

Temporal and spatial characteristics of droughts and floods in northern China from 1644 to 1911

This study analyses the temporal and spatial distributions of droughts and floods in northern China during the Qing Dynasty (1636–1912), with data ranging from 1644 to 1911, or nearly the entire dynastic period. Variations in the intensities of droughts and floods are investigated across different timescales and with respect to their spatial variation. The impacts and physical mechanisms of solar activity as well as surface temperatures of the Pacific Ocean on drought and flood intensities in northern China are analysed using a cross-wavelet method. The results reveal periodicities on scales of 10–11, 20–22, 45–50 and 90–100 yrs. Seven rapid changes are found on the 10-yr scale and four are found on the 30-yr scale. Analysing the spatial distribution of drought and flood intensities, we found a trend of decreasing precipitation from east to west. Precipitation over the Shandong region, which is in the eastern part of the study area, is significantly higher than that of the other regions, which may be explained by its coastal location and the resultant rich water vapour content of the atmosphere. Analyses of cross-wavelet power spectra and coherence spectra among the different drought and flood intensities and the Niño3 regional sea surface temperature (SST) index series and sunspot series indicate significant correlations between the drought and flood series and the Niño3 SST index series at scales of 2–4 and 8–12 yrs, and the phase difference differs across the different timescales. Furthermore, the drought and flood series and the sunspot series are closely correlated at a scale of 8–14 yrs.

Ammonia-based CO2 capture parameters optimization and analysis of lean and rich vapor compression processes

Carbon dioxide (CO2) capture through chemical solvent absorption process is the most favourable and well-proven technique to reduce CO2 emission. However, in this technique, the energy penalty correlated with absorbent regeneration is a critical challenge. To reduce energy consumption, the operating parameters in NH3-based CO2 capture process were optimized. Then flowsheet modifications including rich vapor compression (RVC) and lean vapor compression (LVC) were proposed for the first time in the NH3-based CO2 capture process. Both the LVC and RVC schemes were combined with cold solvent split (CSS) process to further reduce the energy requirements. Moreover, the LVC and RVC processes of this study were also compared with the advanced NH3-based and MEA-based LVC and RVC processes with respect to energy reduction. The optimized process was considered as a base process and it was compared with the modified processes. The RVC and LVC combined with CSS process reduced the reboiler duty by 26.7% and 19%, respectively. These energy savings are much higher than that of 11.6% and 8.26% energy savings of the advanced NH3-based rich split and inter-heating processes, respectively. The total equivalent energy savings of LVC, RVC, LVC with CSS, and RVC with CSS processes in this study were about 6.4%, 18.1%, 3.4%, and 15%, respectively, which are higher than 3.4% and 8.5% energy savings of MEA-based LVC with CSS and RVC with CSS processes, respectively. Furthermore, these combined processes can also avoid the use of a condenser.

Non-equilibrium fractal growth of MoS2 for electrocatalytic hydrogen evolution

Non-equilibrium fractal growth of MoS2 was induced by establishing an extremely Mo rich chemical vapor deposition (CVD) environment using a rapid heating rate in a confined reaction space.

Improved process modifications of aqueous ammonia-based CO2 capture system

Extensive research works on CO2 capture process using MEA have been carried out and showed promising results. Nevertheless, it has been acknowledged that the use of MEA is associated with high cost, solvent degradation issues and corrosion. The issues above have motivated researchers to explore and test other potential solvents such as aqueous ammonia (NH3). As result, NH3 based CO2 capture systems have recently attracted much attention as an alternative to MEA based counterparts. Despite their encouraging applications, high volatility of NH3 raise concerns on the energy requirement related to the solvent recovery. Consequently, energy efficient NH3 based CO2 capture systems by modifying the process is desirable. This study, therefore, aims to propose and evaluate three different stand-alone process configurations of absorption-desorption processes in a NH3-based system and compare them with the traditional absorption-desorption system in respect to total energy consumption. These modifications include Rich Solvent Split (RSS), Lean Vapor Compression (LVC), and Rich Vapor Compression (RVC). Results indicate that among these three proposed process modifications, LVC led to the highest reboiler energy savings of 38.3% and total energy savings of 34.5% compared to NH3 based conventional configuration. These findings can serve as essential recommendations for further studies on and large-scale implementations of aqueous NH3 as a better solvent.

Fluid Evolution of Fuzishan Skarn Cu-Mo Deposit from the Edong District in the Middle-Lower Yangtze River Metallogenic Belt of China: Evidence from Petrography, Mineral Assemblages, and Fluid Inclusions

The Fuzishan Cu-Mo deposit is located in the Edong district of the Middle-Lower Yangtze River Metallogenic Belt, China. The orebodies mainly occurred as lenticular and bedded shapes in the skarn zone between the Lower Permian Qixia Formation carbonate rocks and the quartz diorite. Four paragenetic stages have been recognized based on petrographic observations: (1) prograde skarn stage, (2) retrograde skarn stage, (3) quartz-sulfide stage, and (4) carbonate stage. Six fluid inclusion types were recognized: S1(vapor + liquid + halite ± other daughter minerals), S2(vapor + liquid + daughter minerals except halite), LV(rich liquid + vapor), VL(rich vapor + liquid), V (vapor), and L (liquid) types. Fluid inclusion studies show distinct variations in composition, final homogenization temperature, and salinity in four stages. Daughter minerals of the primary fluid inclusions include chalcopyrite, molybdenite, hematite, anhydrite, calcite, and halite in the prograde skarn stage and hematite, calcite, and sulfide (?) in the retrograde skarn stage. No daughter minerals occurred in the quartz-sulfide and carbonate stages. Final homogenization temperatures recorded in these stages are from 405 to >550°C, from 212 to 498°C, from 150 to 485°C, and from 89 to 223°C, respectively, while salinities are from 3.7 to 42.5, from 2.6 to 18.5, from 2.2 to 17.9, and from 0.2 to 11.5 wt.% NaCl equivalent, respectively. The coexisting VLand S1type fluid inclusions show similar homogenization temperature of 550 to about 650°C in the prograde skarn stage, indicating that immiscibility occurred at lithostatic pressure of 700 bars to perhaps 1000 bars, corresponding to a depth of 2.6 km to about 3.7 km. The coeval VLand LVtypes fluid inclusions with homogenization temperature of 350 to 400°C in the late retrograde skarn and quartz-sulfide stages suggest that boiling occurred under hydrostatic pressure of 150 to 280 bars, equivalent to a depth of 1.5 to 2.8 km. Mo mineralization in the retrograde stage predated Cu mineralization which mainly occurred in the quartz-sulfide stage. Fluid compositions indicate that ore-forming fluid has highfO2and rich Cu and Mo concentration in the early stage, while relatively lowerfO2and poor Cu and Mo concentration in the middle to late stages. Microthermometric data show a decreasing trend in temperature and salinity in the fluid evolution process. Decreasing temperature and boiling event may be the main factors that control the ore precipitation.

First principles investigation on mechanical and thermal properties of α‐ and β‐YAlB4 ultra‐high temperature ceramics

AbstractUltra‐high temperature ceramics (UHTCs) exhibit a unique combination of excellent properties that makes them promising candidates for applications in extreme environments. Various UHTCs are needed due to diverse harsh conditions that UHTCs are faced with in different applications. Due to structural similarity to ZrB2, possible high melting point and possible protective oxide scale formed in oxygen rich and water vapor environments, REAlB4 (RE: rare‐earth) is suggested a good candidate for UHTCs. In the present work, temperature‐dependent mechanical and thermal properties of both α‐YAlB4 (YCrB4 type, space group Pbam) and β‐YAlB4 (ThMoB4 type, space group Cmmm) were investigated by first principles calculations in combination with quasi‐harmonic approach. Due to the structural similarity between α‐YAlB4 and β‐YAlB4, their properties are very similar to each other, which are approximately transverse isotropic with properties in (001) plane being almost the same and differing from properties out of (001) plane. The results reveal that resistance to normal strain in (001) plane (~460 GPa) is higher than that along [001] direction (~320 GPa) and thermal expansion in (001) plane (~10 × 10−6 K−1) is lower than that along [001] direction (~17 × 10−6 K−1), which is because the stiff boron networks are parallel to (001) plane. The average thermal expansion coefficient is around 12 × 10−6 K−1, which is fairly high among UHTCs and compatible with metallic frameworks. The combination of high thermal expansion coefficient and protective oxidation scale forming ability suggest that REAlB4 is promising for practical applications not only as high‐temperature structural ceramic but also as oxidation resistant coating for alloys.