Low Partial Pressure Research Articles

Experimental analysis of thermal behavior in cryogenic propellant tank with different pressurants

The thermal behavior of cryogenic propellant tanks is crucial issue in the operation of cryogenic propulsion systems. Herein, ground experiments were conducted in a 600-mm-diameter cryogenic tank filled with liquid nitrogen. As pre-pressurants, gaseous helium and gaseous nitrogen (of the same species as the liquid), were used to investigate its effect in accordance with actual propulsion systems. The tank was sealed after pre-pressurization to observe the self-pressurization. The evaporation rate and heat flow in the tank were estimated based on pressure and temperature measurements. In addition, the axial liquid temperature distribution was obtained through the liquid draining from the tank bottom, and a thermal stratification model was developed. These results demonstrated that the type of pre-pressurant significantly affected the thermal behavior in the tank. A higher evaporation rate and higher liquid internal energy rise rate with a thicker thermal layer were observed in the helium pre-pressurization case. The lower nitrogen partial pressure in the helium case enhanced the vaporization and growth of the thermal layer. Estimation of the power balance in the tank demonstrated that not only the ullage but also the heat mass of the tank provided heat for the evaporation and thermal layer. The evaporation occurs mainly at the contact point between the tank skin and liquid surface. The nitrogen vapor rises in a thin layer along the tank skin because of buoyancy under nitrogen pre-pressurization; however, buoyancy is lower under helium pre-pressurization, and a radial vapor flow is probably produced from the contact point instead, leading to a higher heat flux to the liquid.

Transport and Interfacial Properties of Mixed Molten Carbonate/Hydroxide Electrolytes by Molecular Dynamics Simulations

We use molecular dynamics simulations based on a recently developed force field to obtain the viscosity, ionic conductivity, and liquid–vapor surface tension of molten alkali-metal carbonate–hydroxide mixtures over a range of cation and hydroxide compositions. Recent experimental and simulation studies have suggested that molten carbonates contain non-negligible amounts of hydroxide ions in the presence of water at low partial pressures of CO2. However, due to the high temperatures (≃600 °C or higher) required to melt pure alkali carbonates and their mixtures, there is a lack of experimental thermodynamic and transport data for these molten phases. Here, we deploy a recently parametrized force field for molten alkali carbonates and hydroxides [ J. Chem. Theory Comput. 2020, 16, 5736−5746, DOI: 10.1021/acs.jctc.0c00285] to simulate some physical properties using atomistic molecular dynamics. Our predictions show a consistent decrease in viscosity and an increase in ionic conductivity with increasing hydroxide fractions, whereas a higher Li+ mole fraction leads to an increase in both viscosity and ionic conductivity. The computed surface tension values exhibit an upward trend with higher asymmetry in cation and anion sizes. Structural analysis suggests that in the carbonate–hydroxide melts the smaller/harder ions, OH– and Li+, are more favored at the interface than the larger/softer ions, CO32– and K+/Na+. The current approach provides a systematic route to obtaining physicochemical properties of molten alkali carbonate and hydroxide mixtures over a large domain of chemical compositions and thus can steer future experimental research for molten carbonates and their applications.

Nitrogen Assimilation and Transport by Ex Planta Nitrogen-Fixing Bradyrhizobium diazoefficiens Bacteroids Is Modulated by Oxygen, Bacteroid Density and l-Malate.

Symbiotic nitrogen fixation requires the transfer of fixed organic nitrogen compounds from the symbiotic bacteria to a host plant, yet the chemical nature of the compounds is in question. Bradyrhizobium diazoefficiens bacteroids were isolated anaerobically from soybean nodules and assayed at varying densities, varying partial pressures of oxygen, and varying levels of l-malate. Ammonium was released at low bacteroid densities and high partial pressures of oxygen, but was apparently taken up at high bacteroid densities and low partial pressures of oxygen in the presence of l-malate; these later conditions were optimal for amino acid excretion. The ratio of partial pressure of oxygen/bacteroid density of apparent ammonium uptake and of alanine excretion displayed an inverse relationship. Ammonium uptake, alanine and branch chain amino acid release were all dependent on the concentration of l-malate displaying similar K0.5 values of 0.5 mM demonstrating concerted regulation. The hyperbolic kinetics of ammonium uptake and amino acid excretion suggests transport via a membrane carrier and also suggested that transport was rate limiting. Glutamate uptake displayed exponential kinetics implying transport via a channel. The chemical nature of the compounds released were dependent upon bacteroid density, partial pressure of oxygen and concentration of l-malate demonstrating an integrated metabolism.

Volatilization Behavior of Manganese from Molten Steel with Different Alloying Methods in Vacuum

The volatilization loss of manganese during the vacuum smelting process is one of the key factors that determines the manufacturing cost and quality of manganese steel. In this study, the laboratory experiments and thermodynamic calculations were performed to investigate volatilization behavior of manganese from molten steels with different alloying methods in vacuum process. Based on the thermodynamic analysis, with the increase of manganese content, the partial vapor pressure of the manganese component increased, resulting in manganese being easily volatilized from molten steel. The carbon content in the steel shows an evident influence on partial vapor pressure of manganese component, and a higher carbon content in steel leads to a lower partial vapor pressure of manganese, but it not influenced by the silicon content. Compared with the alloying method of high carbon ferromanganese, the volatilization loss of manganese in the alloying method of silicon manganese presents faster decay, agreeing well with the thermodynamic analysis. Besides, the volatile fraction generated in the alloying method of high-carbon ferromanganese is composed of a large amount of MnO nanorods with a lateral length approximately 500 nm and a small number of Mn3O4/Mn nanoparticles with a diameter less than 500 nm. Additionally, the volatile fraction generated in the alloying method of silicon manganese shows Mn3O4 nanoparticles as the main phase. It can be inferred that the existence of the manganese oxide phase is attributed to the high chemical activity of nanoscale particles within air.

A new concept for pore-scale precipitation-dissolution modelling in a lattice Boltzmann framework – Application to portlandite carbonation

Modelling of combined dissolution-precipitation at the pore scale requires the conceptualization of mineral precipitation and crystal growth, the formation of a protective diffusive layer by precipitants and slow reaction kinetics that are all coupled with alterations of the microstructure. In this work, we propose an improved approach for handling these challenges in a pore-scale coupled reactive transport model and apply it to portlandite carbonation. The model combines mineral geometry update as a consequence of dissolution-precipitation reactions during diffusive transport through a saturated porous medium, thermodynamic equilibrium chemistry and dissolution kinetics. Transport of ions is calculated by the lattice Boltzmann transport solver YANTRA. Transport and reaction processes are incorporated at different spatial length scales with the multilevel approach, i.e. mixed liquid-solid nodes in a pore-scale model, which accounts for processes at scales below the model spatial resolution. Instead of defining arbitrary values such as threshold or residual porosities to initiate or halt precipitation, information on crystal shapes, packing and solubility in nano-pores based on interfacial surface energy is used to control precipitation. Additionally, the sensitivity study has been performed on model parameters such as portlandite dissolution kinetics, interfacial surface energy, calcite crystal size, CO2 partial pressure on the rate of carbonation and on the calcite layer properties such as residual porosity and thickness. From the comparison between the modelled calcite growth and the experimental data it has been found that low diffusivity of calcite layer decreases the effect of portlandite dissolution kinetics rate in case of carbonation and diminishes the effect of CO2 partial pressure. Also differences in the structure of the calcite layer were observed for carbonation of portlandite at low and high CO2 partial pressures.

A high efficient absorbent for the separation of H2S from low partial pressure coke oven gas.

To high efficiently remove H2S from low partial pressure coke oven gas (COG), a novel activator (tetramethylammonium arginine, [N1111][Arg]) was used to blend with N-methyldiethanolamine (MDEA) for the absorption of H2S. High concentrated [N1111][Arg]-MDEA aqueous solution was used as absorbent. Thermodynamic properties including absorption amount and H2S loading values were measured, then the kinetic apparent absorption rate was calculated based on the change of absorption amount with time. The removal efficiency of H2S in simulated COG was verified in tray towers. Compared with monoethanolamine (MEA)-MDEA and tetramethylammonium glycinate ([N1111][Gly])-MDEA aqueous solutions, [N1111][Arg]-MDEA aqueous solution takes advantages of higher absorption capacity, absorption rate and removal efficiency. Our results showed that the proposed absorbent has good industrial application prospect in coke oven gas desulfurization, because it achieved 100% removal of H2S in the tray tower containing only 4 sieve plates under high concentrated condition (water content < 45%), which may significantly decrease the energy consumption.

Mill scale and flue dust briquettes as alternative burden to low height blast furnaces

The present work evaluated the behavior of self-reducing briquettes produced from mill scale and blast furnace flue dust at high-temperature and reducing atmosphere conditions, aiming to recycle these wastes through low height blast furnaces. Briquettes prepared in three different carbon/oxygen mass ratios were submitted to interrupted high-temperature tests in CO-reducing atmospheres and evaluated in terms of reduction and mechanical strength behavior. Metallic iron was identified in the samples obtained even at low temperature and moderate CO partial pressure, which revealed the high reducibility of these briquettes comparatively to lump iron ores. It was observed that self-reducing reactions play an important role at low temperatures (up to 900 °C), while at high temperatures the external atmosphere had a greater influence. The mechanical strength of the briquettes was strongly affected by self-reducing reactions and the proportions of wastes. At 900 °C the briquettes swelled, which was more pronounced when blast furnace flue dust increased in the briquettes. Briquettes with the lowest carbon/oxygen mass ratio (0.25) presented the best performance to use in blast furnaces reactors. A mass balance considering this briquette for recycling mill scale and blast furnace flue dust from integrated steel mills through low height charcoal blast furnace showed to be an attractive route to improve the sustainability of iron and steelmaking industry.

An Ultra-Microporous Metal-Organic Framework with Exceptional Xe Capacity.

Molecular confinement plays a significant effect on trapped gas and solvent molecules. A fundamental understanding of gas adsorption within the porous confinement provides information necessary to design a material with improved selectivity. In this regard, metal-organic framework (MOF) adsorbents are ideal candidate materials to study confinement effects for weakly interacting gas molecules, such as noble gases. Among the noble gases, xenon (Xe) has practical applications in the medical, automotive and aerospace industries. In this Communication, we report an ultra-microporous nickel-isonicotinate MOF with exceptional Xe uptake and selectivity compared to all benchmark MOF and porous organic cage materials. The selectivity arises because of the near perfect fit of the atomic Xe inside the porous confinement. Notably, at low partial pressure, the Ni-MOF interacts very strongly with Xe compared to the closely related Krypton gas (Kr) and more polarizable CO2 . Further 129 Xe NMR suggests a broad isotropic chemical shift due to the reduced motion as a result of confinement.

Respiratory nursing care with Angong Niuhuang pill for patients with chronic obstructive pulmonary disease following cardiac surgery.

Angong Niuhuang pill (ANP) is a traditional Chinese medicine (TCM) drug widely used for treating stroke. This study aimed to investigate the effect of ANP on respiratory nursing outcomes in chronic obstructive pulmonary disease (COPD) patients following cardiac surgery. A total of 80 COPD patients following cardiac surgery were enrolled and randomized into the control group receiving routine postoperative nursing and ANP group additionally receiving ANP treatment for 3 days (n = 40 for both group). The frequency of back percussion, time of back percussion, amount of expectoration, arterial blood gas levels were compared between groups. Compared to the control group, the ANP group had a significantly shorter daily mean time of back percussion at day 3 (p = .036) and day 7 (p = .014). The daily mean amount of expectoration was higher at day3 (p = .018) but lower at day 7 (p = .043) in the ANP group than in the control group. In addition, the ANP group had significantly higher hemoglobin saturation (SpO2 ) and partial pressure of oxygen (PaO2 ) but lower partial pressure of carbon dioxide (PaCO2 ) at both day 3 and day 7 than the control group (all p < .05). Furthermore, the time of postoperative aerosol inhalations (p = .041), pulmonary infection rate (p = .025) and postoperative hospital stay (p = .036) were significantly reduced in the ANP group. The ANP group had significantly lower TCM symptom scores at day 3 and day 7 after surgery. These results suggested that ANP treatment can effectively promote the postoperative recovery and respiratory nursing outcomes in COPD patients following cardiac surgery.

Hypoxia-mediated regulation of mitochondrial transcription factors in renal epithelial cells: implications for hypertensive renal physiology.

Kidneys have a high resting metabolic rate and low partial pressure of oxygen due to enhanced mitochondrial oxygen consumption and ATP production needed for active solute transport. Heightened mitochondrial activity leads to progressively increasing hypoxia from the renal cortex to the renal medulla. Renal hypoxia is prominent in hypertensive rats due to increased sodium reabsorption within the nephrons, which demands higher energy production by oxidative phosphorylation (OXPHOS). Consequently, spontaneously hypertensive rats (SHR) display greater oxygen deficiency (hypoxia) than normotensive Wistar Kyoto rats (WKY). Here, we sought to investigate the expression of key proteins for mitochondrial biogenesis in SHR and WKY, and study the regulation of mitochondrial transcription factors (mtTFs) under in vitro hypoxic conditions in renal epithelial cells. We report that renal expressions of hypoxia-inducible factor-1-alpha (HIF-1α), peroxisome proliferator-activated receptor-gamma coactivator-1-alpha (PGC-1α), mtTFs, and OXPHOS proteins are elevated in SHR compared to WKY. In addition, our experiments in cultured kidney cells demonstrate that acute hypoxia augments the expression of these genes. Furthermore, we show that the transcripts of HIF-1α and mtTFs are positively correlated in various human tissues. We reveal, for the first time to our knowledge, that HIF-1α transactivates mtTF genes by direct interaction with their promoters in rat kidney epithelial cells (NRK-52E) under acute hypoxia. Concomitant increases in the mitochondrial DNA and RNA, and OXPHOS proteins are observed. Taken together, this study suggests that hypoxia within the renal epithelial cells may enhance mitochondrial function to meet the energy demand in proximal tubular cells during prehypertensive stages in kidneys of young SHR.

EUV-induced carbon growth at contaminant pressures between 10-10 mbar and 10-6 mbar: Experiment and model.

Carbon contamination induced by ultraviolet (UV) radiation affects precision optics in applications as diverse as semiconductor lithography and satellite observations of the Sun. Our previous experiments have shown that low-intensity UV-induced surface contamination depends quasi-logarithmically on the partial pressure of the organic contaminant due to the poly-dispersive nature of the surface-adsorbate system. This complex dependence presents difficulties because, without a physically motivated model, it cannot be extrapolated to low pressures. We present measurements and a model of carbon growth induced by UV exposure in the presence of tetradecane vapor. The model, which includes a coverage-dependent adsorption energy, describes the measurements over four orders of magnitude in pressure, and we expect that it can be extrapolated to the lower pressures of interest to the extreme ultraviolet (EUV) lithography and solar astronomy communities. Our experience with other contaminants leads us to expect that other organic contaminants will behave similar to tetradecane. The results also provide insights into the kinetics governing coverage isotherms at extremely low partial pressures.

Reaction of hydrogen peroxide vapor on platinum on alumina spheres

An experimental and numerical study of the rates of decomposition of hydrogen peroxide vapor on catalytic surfaces was conducted. Hydrogen peroxide vapor and helium carrier gas flowed over a catalyst (platinum on alumina spheres of varying diameter) at a total pressure of <3 Torr, simulating the conditions of a flash evaporation propulsion system for space applications. After reacting on the catalyst, the product gas composition was measured using near-infrared laser absorption on a known hydrogen peroxide line in a multi-pass flow cell. Global reaction rate constants were inferred for varying catalyst surface areas, residence times, and temperatures. The combination of these experimental data with numerical simulations led to the conclusion that under the conditions employed in this study, namely low peroxide partial pressures and low Reynolds numbers, decomposition rates are transport-limited rather than reaction-limited. These results may be applicable to the development of catalyst bed designs for small satellite propulsion systems.

Kinetic study of Mn vacuum evaporation from Mn steel melts

Considering the interference of Mn volatilization on the composition control during the vacuum treatment of medium/high Mn steel melt. The kinetic analysis of Mn volatilization from steel melt in various initial Mn contents, holding times, temperature and pressure regimes were investigated in lab scale experiments. The results show that Mn evaporation is accelerated significantly with the increase of temperature and initial Mn content in steel melt or with the decrease of chamber pressure. Furthermore, the logarithm of Mn content in steel melt has a linear function relationship with the holding time, indicating the first-order kinetic reaction of Mn evaporation. In addition, the overall mass transfer coefficient of Mn significantly decreases from 2.176E−05 to 5.932E−06 m s−1 with the increase of the initial Mn content from 2% to 30%. Moreover, high temperature and low partial pressure can obviously improve the overall mass transfer coefficient of Mn. Simultaneously, the apparent activation energy for Mn evaporation from steel melt is calculated to be 324.55 kJ mol−1. The theoretical kinetics model is established to fully analyze the evaporation mechanics of Mn, which is consistent with experimental results. In particular, with the increase of initial Mn content, the rate-limiting step transforms from mass transfer in the steel melt boundary layer to gas phase mass transfer, and mass transfer resistance in the gaseous phase is reached 91.22% with initial Mn content of 30%. Besides, the Mn evaporation process at high temperature and high partial pressure is determined by the mass transfer in the steel melt boundary layer and gas phase, respectively. This work systematically clarifies the factors influencing Mn loss in vacuum refining on high quality Mn steel manufacture.

K-doping effect in the kinetics of CO2 capture at high temperature over lithium silicates obtained from rice husks: In situ/operando techniques

K-doped lithium silicates were synthesized as CO2 sorbents using rice husks as silica source. Two different doping methods were used to prepare the solids, incipient wetness impregnation and co-impregnation. Noticeable differences were observed between the sorbents obtained by each route. Unlike the co-impregnated sample, a KLi3SiO4 phase was detected by XRD in the doped-samples prepared by incipient wetness impregnation. This phase was associated with a porous layer deposition over the sorbent particle surface, which was observed by SEM. The effect of CO2 partial pressure and sorption temperature was evaluated for the solids. A remarkable improvement of the capture efficiency was observed in the doped-samples, especially at low temperature and CO2 partial pressure. The kinetics of the samples was studied using the double exponential model and operando Raman and DRIFT spectroscopies. Different reactivity properties were found depending on the synthesis method employed. The complete analysis of the results allowed us to propose a transformation mechanism for the solids during the sorption step, highlighting the improvement of surface reaction and volumetric diffusion processes in the CO2 capture step.

Effect of Sub-Stoichiometric Fe(III) Amounts on LCFA Degradation by Methanogenic Communities.

Long-chain fatty acids (LCFA) are common contaminants in municipal and industrial wastewater that can be converted anaerobically to methane. A low hydrogen partial pressure is required for LCFA degradation by anaerobic bacteria, requiring the establishment of syntrophic relationships with hydrogenotrophic methanogens. However, high LCFA loads can inhibit methanogens, hindering biodegradation. Because it has been suggested that anaerobic degradation of these compounds may be enhanced by the presence of alternative electron acceptors, such as iron, we investigated the effect of sub-stoichiometric amounts of Fe(III) on oleate (C18:1 LCFA) degradation by suspended and granular methanogenic sludge. Fe(III) accelerated oleate biodegradation and hydrogenotrophic methanogenesis in the assays with suspended sludge, with H2-consuming methanogens coexisting with iron-reducing bacteria. On the other hand, acetoclastic methanogenesis was delayed by Fe(III). These effects were less evident with granular sludge, possibly due to its higher initial methanogenic activity relative to suspended sludge. Enrichments with close-to-stoichiometric amounts of Fe(III) resulted in a microbial community mainly composed of Geobacter, Syntrophomonas, and Methanobacterium genera, with relative abundances of 83–89%, 3–6%, and 0.2–10%, respectively. In these enrichments, oleate was biodegraded to acetate and coupled to iron-reduction and methane production, revealing novel microbial interactions between syntrophic LCFA-degrading bacteria, iron-reducing bacteria, and methanogens.

Risk factors for disease-related deterioration following diagnostic bronchoalveolar lavage procedures in diffuse lung disease: a case-control study.

BackgroundAlthough the risk factors for diagnostic bronchoalveolar lavage (BAL)-induced acute exacerbations in patients with idiopathic pulmonary fibrosis (IPF) have been previously reported, no study has assessed these in patients with non-IPF. We aimed to identify the risk factors for BAL-induced disease deterioration (BAL-DD) in all types of diffuse lung disease.MethodsPatients with diffuse lung disease who underwent BAL at our hospital from April 2012 to November 2017 were retrospectively analyzed. The patient information, laboratory data, radiological findings, and BAL fluid analysis results in patients who developed BAL-DDs were compared with those in patients who did not.ResultsBAL-DDs occurred in 14 (3.3%) of the 429 patients included the study. The BAL-DD group had a significantly poorer performance status, higher C-reactive protein level, lower partial pressure of oxygen in the arterial blood at rest, greater proportion of desaturation on exertion and cases having followed a progressive clinical course before BAL, and more extensive consolidation and ground-glass opacity on chest high-resolution computed tomography (HRCT) than the non-BAL-DD group. A high total cell concentration and an increased number of eosinophils in the BAL fluid were more frequently found in patients with BAL-DD than in those without.ConclusionsPatients with decreased physical activity level, increased level of inflammatory markers, low oxygenation status, and extensive lung involvements on chest HRCT and following a progressive clinical course before BAL may be warned of the BAL-DD risk. Elevated eosinophil counts in the BAL fluid could be associated with the triggering of BAL-DDs.

Phase transitions involving Ca – The most abundant ash forming element – In thermal treatment of lignocellulosic biomass

Torrefaction, pyrolysis and gasification are of interest to convert lignocellulosic biomass into fuels and chemicals. These techniques involve thermal treatment at low partial pressures of oxygen. However, little is known about the transformation of ash elements during these processes. The phase transition of the major ash element calcium (Ca) was therefore studied with powder from pine as biomass model treated at temperatures 300–800 °C under atmospheres of 100% N2, 3% O2 and 6% O2 and thermodynamic equilibrium modelling. For evaluation, X-ray powder diffraction and synchrotron Ca K-edge X-ray absorption near edge structure (XANES) spectroscopy in combination with linear combination fitting and reference compounds was used.The results indicated that the most abundant Ca-containing species in the untreated material was thermally unstable Ca oxalate (CaC2O4) primarily decomposing into Ca phases dominated by carbonates at temperatures up to 600 °C. Double carbonates of calcium and potassium were observed in the form of fairchildiite/butscheliite (K2Ca(CO3)2), and these phases were stable over the low temperature range studied. Hydroxyapatite (Ca5(PO4)3OH) was expected to be present and thermally stable over the entire temperature interval and was found in untreated material. At temperatures above 600 °C calcium oxide (CaO) was formed. The amount of oxygen had little effect on the phase transitions. The results of thermodynamic modeling were in agreement with XANES showing that this is a versatile technique that can be applied to systems as complex as Ca phase transitions in thermally treated lignocellulosic biomass at low partial pressures of oxygen.

Extremely low-oxygen storage: aerobic, anaerobic metabolism and overall quality of apples at two temperatures

ABSTRACT The objective of this work was to evaluate the effect of extremely low-oxygen storage on the aerobic, anaerobic metabolism and overall quality maintenance of ‘Royal Gala’ and ‘Galaxy’ apples stored at two temperatures. For ‘Royal Gala’ apples, four treatments were evaluated in a two-factor scheme (2 × 2), with two storage conditions: [1] 1.2 kPa O2 + 2 kPa CO2; [2] 0.8 kPa O2 + 1.6 kPa CO2; and two temperatures (1.0 and 1.5 °C). For ‘Galaxy’ apples, the experiment was conducted in a two-factor (3 × 2) scheme with three storage conditions: [1] 1.2 kPa O2 + 2 kPa CO2; [2] 0.8 kPa O2 + 1.6 kPa CO2; [3] 0.4 kPa O2 + 1.2 kPa CO2, and two temperatures (1.0 and 1.5 °C). The ‘Royal Gala’ apples stored under 0.8 kPa O2 + 1.6 kPa CO2 at 1.5 °C had higher flesh firmness, healthy fruit and soluble solids along with lower incidence of flesh breakdown and mealiness. The ‘Galaxy’ apples stored under 0.4 kPa O2 + 1.2 kPa CO2, at temperature of 1.5 °C had lower 1-carboxylic acid-1-aminocyclopropane (ACC) oxidase enzyme activity, ethylene production, occurrence of mealiness, when compared to 1.0 °C. The storage of these two cultivars at 1.5 °C with extremely low O2 partial pressures is possible. The possibility to increase the storage temperature from 1 °C, which is traditionally used for these mutants, to 1.5 °C allows to keep better quality with the advantage of energy saving.

Preface

The 2020 International Conference on Energy Saving and Environmental Protection and Civil Engineering (ESEPCE2020) was held on August 7-9, 2020 in Shanghai, China. Although the impact of covid-19, most participants were still highly enthusiastic about participating in this conference. In order to comply with the control and prevention of the pandemic covid-19, ESEPCE2020 was adjusted to be held online conference to avoid crowd gathering and physical contact. ESEPCE2020 will focus on green architecture, intelligent architecture, design of practicality and artistic. The conference aims to provide opportunities for the delegates to exchange new ideas and application experiences face to face, to establish business or research relations and to find global partners for future collaboration.During the conference, the conference model was divided into three sessions, including keynote speeches, oral presentations and online Q&A discussion. In the keynote speeches session, keynote speakers were each allocated 30-40 minutes to hold their speeches. More than fifty scholars from different renowned universities attended this conference. We are honored to invite Prof. Nazri bin Ali from Faculty of Civil Engineering, Universiti Teknologi Malaysia to serve as our Conference Chair and made amazing keynote speeches on Hydrological Effect On Slope Stability Analysis. This keynote discusses some of the previous failures, the type of failures, the causes of failures, and summaries some suggestions to lessen future occurrence. And we are glad to invite Prof. Shijian Lu from Sinopec Petroleum Engineering Corporation and China University of Petroleum(East China) as keynote speakers to made amazing speeches about Key technology and application of low partial pressure CO2 capture, transportation and oil displacement storage surface engineering. His projects have implemented CO2 emission reduction effectively, promoted the development of national green economy and protected the environment. In the oral presentations session, some scholars were given about 5-10 minutes to perform their oral presentations one by one. In the Q&A session, all participants were invited to join in academic groups to discuss and explore the academic issues after the presentations. The discussion session will last 40 minutes.The proceedings collected the latest research and results in the field of Energy Saving, Environmental Protection and Civil Engineering. The topic of this collection is related to energy saving and environmental protection technology, Internet+Environmental protection, architecture and urban planning, civil and structural engineering and so on. All manuscripts published in the proceeding have been through rigorous review and process to meet the requirements of International publication standard.We would like to express our sincere gratitude to the Chairman, the distinguished keynote speakers, as well as all the participants. We also want to thank the publisher for publishing the proceedings. We are grateful to all those who have contributed to the success of ESEPCE2020. We hope that all participants and other interested readers benefit scientifically from the proceedings.Committee member, Conference Chair, Organizing Committees, Technical Committees are available in the pdf.

Synthesis of graphitic carbon nitride under low ammonia partial pressure

Graphitic carbon nitride (g-C3N4) is a very attractive potential solar-light-activated photocatalyst for hydrogen evolution. Substantial effort has been devoted to improving the photoactivity of g-C3N4, but to date most g-C3N4 prepared by the thermal polymerization of melamine are the linear polymer carbon nitride “melon”. We thus explored a new way of synthesizing g-C3N4 under low ammonia partial pressure using an approach similar to train sublimation. The obtained product (p-CN) is reddish-orange in color and has a different chemical composition and different optical properties from those of melon and melon-based materials. These differences were characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction measurements and X-ray photoemission spectroscopy. Our findings show that p-CN is nano-scale g-C3N4. In addition, theoretical calculations using density functional theory, as well as direct observation of the characteristic electronic structure around the energy gap of p-CN using ultraviolet photoemission spectroscopy combined with inverse photoemission spectroscopy, provide evidence that p-CN has the g-C3N4 structure. These findings shed light on the synthesis of g-C3N4 composed of stacked two-dimensional layers of heptazine networks. Furthermore, the fundamental insights into the electronic structures of melem, melon and p-CN are particularly significant for research in the field of visible light-responsive photocatalysts.