Medium-low Temperature Research Articles

Genesis of Cu deposits hosted by volcanic rocks in Yunxian-Jinggu Arc, Western Yunnan: Constraints from fluid inclusions and C-O-S isotopes

A series of vein-type Cu deposits have been preserved in the Triassic volcanic rocks of the Yunxian-Jinggu area. The Guanfang, Bazijie, and Minleyichang deposits are typical examples of regional Cu mineralization. The deposits are preserved in the intermediate-basic volcanic rocks, and the ore bodies are controlled by NNE-trending structures with similar alteration features and mineral assemblages. The fluid inclusions are recognized in quartz and calcite at the three deposits, dominated by aqueous inclusions (L) and liquid phase-rich vapor–liquid two-phase inclusions (L-V) with similar temperature (270-140℃) and salinity (14.0–20.2 wt% NaCl eq.). The three deposits have a medium–low temperature, moderate salinity, and higher oxidation rate than the volcanic host rocks, confirmed by the fluid inclusion, alteration, and mineral assemblage. The O isotope values for early quartz associated with sulfides in the three deposits are comparable (δ18OSMOW = 15.23 to 20.01 ‰). Late quartz in the Guanfang and Bazijie deposits shows a deficit in O isotope values compared to early quartz (δ18OSMOW = 9.89 to 13.98 ‰), indicating the incorporation of meteoric water or basin fluid during the late stage of mineralization. The early calcite in the Guanfang and Bazijie deposits have similar C-O isotopic signatures (δ13CV-PDB = −10.51 to −4.75 ‰, δ18OV-SMOW = 11.29 ‰ to 12.63 ‰), and δ18Ofluid (3.84 to 5.18 ‰) calculated from calcite is approximately the same as the δ18Ofluid (2.08 to 3.95 ‰) calculated from early quartz. The early calcite and early quartz in the Guanfang and Bazijie deposits may be connected to the same fluid source based on the similar δ18Ofluid signatures and salinities. The calcite C-O isotopic compositions of the Minleyichang deposit are 13CV-PDB = −23.03 to −17.74 ‰ and δ18OV-SMOW = 19.72 to 28.32 ‰, which exhibit the characteristics of biogenic carbon and indicate that the material originated from sedimentary layers in the Simao Basin. The sulfide δ34SV-CDT ranges from −17.2 to 3.2 ‰ in the three deposits, which is related to the addition of reduced S from the sedimentary strata in the Simao Basin. The fluid characteristics of medium to low temperature, moderate salinity, and the S-C isotope signatures indicate that the ore-forming fluids are the basin brine from the Simao Basin. The Cu mineralization in the Yunxian-Jinggu area is closely related to the thrust-fold structure system formed during the Late Cretaceous to the Cenozoic period. The ore-forming fluids may have come from the brine in the central part of the Simao Basin, which migrated through the thrust fault and assimilated the materials in the regional volcanic rocks and sedimentary rocks, forming Cu deposits in the Triassic volcanic rocks of Yunxian-Jinggu area.

Trimetallic FeNiCu Atomic Clusters Supported on Carbon Matrix: Highly Active Catalysts for C3H6-SCR of NO.

C3H6-SCR denitrification technology faces catalyst deactivation problems and low catalytic performance at medium-low temperatures. This study utilized the intermetallic synergies to prepare atomic cluster catalysts (FeNiCu/NC) by anchoring Fe-Ni-Cu on a carbon matrix to enhance the C3H6-SCR performance at medium-low temperatures. The synergistic effect of the Fe-Ni-Cu is reflected in the differences in the physicochemical properties of the catalysts, which is proved by several characterization techniques. Results showed that the FeNiCu/NC catalyst had a larger surface area (541.4 m2/g) and there were no metal oxides on the surface of the catalyst but abundant defective sites that anchored Fe/Ni/Cu atoms through N atoms to form M-Nx active sites and atomic clusters. The hollow carbon morphology provides sufficient active sites for C3H6-SCR. The coordination environments of active sites were M-Nx-C, Fe2/FeCu2/FeNi2, Ni3/NiFe/NiCu2, and Cu4/CuFe2/CuNi2, where the synergistic action of trimetal leads to the presence of Fe-Ni-Cu-Nx-C. The synergistic action of the Fe-Ni-Cu significantly improved the C3H6-SCR performance at medium-low temperatures. The FeNiCu/NC exhibited an 81% NO conversion at 150 °C under 2% O2, 15% and 20% higher than FeNi/NC and FeCu/NC catalysts, respectively. Even at 4% O2, the FeNiCu/NC catalyst was active to remove 78% NO and achieve a 93% N2 selectivity at 150 °C and maintained a 100% NO conversion at 300-425 °C. The DRIFTS results demonstrated that NO and C3H6 could combine with active O at metal cluster, M-Nx, or defective oxygen sites to produce various intermediate species, wherein acetates and nitrates were the main active intermediates. Based on the DRIFTS results, a reaction pathway for C3H6-SCR over the FeNiCu/NC catalyst was proposed.

Improved volatile fatty acid production in anaerobic digestion via simultaneous temperature regulation and persulfate activation by biochar: Chemical and biological response mechanisms

Increasing volatile fatty acid (VFA) production via persulfate activation (i.e., chemical effect) in anaerobic digestion (AD) is an emerging resource utilization method. However, the reaction mechanisms responsible for improving VFA production in AD via simultaneous temperature regulation and persulfate activation by biochar remain unclear. In this study, three PB15 treatment systems of low temperature (15 °C), medium temperature (35 °C) and high temperature (55 °C) were set to explore the relationship between VFAs production and treatment temperature and the influence of temperature on the reaction mechanism. The results show that the improvement of hydrolysis and acidification efficiency of the system in the medium temperature system is the highest. The VFA yield and acid production rate in the treatment group at 35 °C were 2.49 and 5.22 times higher than those in the control group, respectively. The chemical effect effectively initiated the anaerobic acid production process and maintained the dominant role of the biological effect. The activity of persulfate is too low at low temperature, and its decomposition is too fast at high temperature. Plenty of free radicals lead to enhanced oxidation of the system, which may kill the fermentation bacteria. The NCM model indicates that microbial stability is reduced in high temperature systems. The SEM model showed that temperature change mainly affected substrate degradation by hydrolytic bacteria and indirectly affected acid production by acid-producing bacteria. This study provides a new strategy for realizing pollutant recycling and increasing VFAs production in cold area.

A Review on Linear Fresnel Reflector (LFR) as a Solar Line Concentrator in Polygeneration for Low-Medium Temperature Applications among the Rural Livelihoods

A Review on Linear Fresnel Reflector (LFR) as a Solar Line Concentrator in Polygeneration for Low-Medium Temperature Applications among the Rural Livelihoods

A Machine-Learning Approach to Biosignature Exploration on Early Earth and Mars Using Sulfur Isotope and Trace Element Data in Pyrite.

We propose a novel approach to identify the origin of pyrite grains and distinguish biologically influenced sedimentary pyrite using combined in situ sulfur isotope (δ34S) and trace element (TE) analyses. To classify and predict the origin of individual pyrite grains, we applied multiple machine-learning algorithms to coupled δ34S and TE data from pyrite grains formed from diverse sedimentary, hydrothermal, and metasomatic processes across geologic time. Our unsupervised classification algorithm, K-means++ cluster analysis, yielded six classes based on the formation environment of the pyrite: sedimentary, low temperature hydrothermal, medium temperature, polymetallic hydrothermal, high temperature, and large euhedral. We tested three supervised models (random forest [RF], Naïve Bayes, k-nearest neighbors), and RF outperformed the others in predicting pyrite formation type, achieving a precision (area under the ROC curve) of 0.979 ± 0.005 and an overall average class accuracy of 0.878 ± 0.005. Moreover, we found that coupling TE and δ34S data significantly improved the performance of the RF model compared with using either TE or δ34S data alone. Our data provide a novel framework for exploring sedimentary rocks that have undergone multiple hydrothermal, magmatic, and metamorphic alterations. Most significant, however, is the demonstrated potential for distinguishing between biogenic and abiotic pyrite in samples from early Earth. This approach could also be applied to the search for potential biosignatures in samples returned from Mars.

The Role of Asymmetry of Perfluoro anion in Ionic Liquids: From Basic Physical Properties to the Application in Lithium Batteries

Room-temperature ionic liquids (RTILs) have attracted significant attention as non-volatile, non-flammable electrolytes over the past three decades. While the synthesis of cationic species is relatively well-established through the quaternization reaction of tertiary amines, the synthesis of perfluoro anions is much more difficult, resulting in a more limited variety compared to cations. In this study, we explore the influence of anionic species on both fundamental properties, such as thermal properties and transport properties, and on the performance of lithium-ion batteries, particularly their rate capabilities. Furthermore, we highlight how novel anionic species not only improve the properties of RTILs but also lead to the development of unique electrolyte systems, such as organic ionic plastic crystals and medium-low temperature lithium molten salts. Through our research results, we would like to demonstrate the importance of developing new anionic species from fundamental studies to practical applications in RTILs.

Ore genesis of the Chazangcuo Cu-Pb-Zn deposit in Tibet: evidence from mineralogy, fluid inclusions, S-Pb isotopes, and elemental geochemistry

The Chazangcuo copper-lead-zinc deposit (hereafter referred to as the Chazangcuo deposit) is situated in the northern portion of the western section of the Gangdese polymetallic metallogenic belt in Tibet, with ore bodies strictly governed by Linzizong Group magmatic rocks and EW-trending faults. This study aims to ascertain the mineralization periods, sources of ore-forming materials, metallogenic physicochemical conditions, and genesis of this deposit. Based on comprehensive field geological surveys, sampling, and microscopic examination of petrological and mineralogical characteristics, we perform qualitative and quantitative geochemical analyses of major elements, trace elements, and rare earth elements (REEs), fluid inclusions, and sulfur and lead isotopes. The findings reveal that the mineralization process of the Chazangcuo deposit can be divided into three periods and four stages: the magmatic-hydrothermal, hydrothermal, and supergene mineralization periods sequentially, which consist of the mineralization stages of quartz-pyrite-sphalerite, medium-low-temperature hydrothermal sulfides, chlorite-carbonate minerals, and supergene oxidation in a chronological order. The ore-forming fluids prove to be medium-low-temperature low-density fluids, and the ore-forming materials are characteristic of upper crustal-derived materials. The ore-forming environment is a medium-low mineralization temperature, a shallow and weakly reducing environment. Overall, the Chazangcuo deposit is identified as a medium-low-temperature magmatic-hydrothermal deposit. The metallogenic model has the vertical zoning characteristics of lead-zinc in the upper part and copper in the lower part.

Microstructure evolution and tribological properties over a wide temperature range of Ni-based composite coatings with Ti3AlC2 addition

Ni60A alloy powders doped with varying concentrations (0, 10 wt% and 20 wt%) of Ti3AlC2 MAX phase were coated on S31008 NiCr stainless steel substrate using atmosphere plasma spraying technique in this work. Comparative investigation was conducted to examine the effects of Ti3AlC2 additions on the microstructure evolution, microhardness, and wide temperature range (room temperature to 800 oC) tribological performance of the composite coatings. The findings demonstrated that the composite coatings were composed of γ-Ni, intermetallic hard metal borides, Ti3AlC2 and TiC phases, without any noticeable oxide phases. The 20 wt% Ti3AlC2 additions to the Ni60A alloy coating exhibited minimum imperfections in microstructure with a porosity drop of 65.8 %, and the highest microhardness which was enhanced by 64 % to 924 HV0.515. After introducing of Ti3AlC2, the coefficient of friction decreased and appeared to distinguish itself by remaining minimal and stable at low-medium temperatures compared with an increase of more than 70 % at high temperatures. Ni60A-10 wt% Ti3AlC2 coating resulted in the lowest friction coefficient of approximately 0.45 from room temperature to 400 oC and it peaked to 0.78 at 800 oC, reducing by 19.6 % and 6 % compared to non-composite coating, respectively. The wear resistance of the composite coating was considerably improved with the increment of Ti3AlC2, and the coating with 20 wt% Ti3AlC2 showed the most significant reduction in wear rate: 18.5 % at room temperature, 45.2 % at 200 oC, 37.2 % at 400 oC, 60 % at 600 oC, 90.8 % at 800 oC. The lubricate layered Ti3AlC2 phases and the tribo-oxide film predominate composed of derivative NiO, Cr2O3 Al2O3 and TiO2 played a critical role in antifriction and wear resistance. The wear mechanisms were accordingly conducted as abrasion and adhesion wear at low-medium temperature and transferred into tribo-oxidation wear at elevated temperature.

The effect of Cu-doping to the DLC interlayer on the temperature dependent current-conduction mechanisms and barrier shape of the Schottky devices

The objective of this study is to determine the temperature and voltage-dependent current conduction mechanisms (CCMs) of the Al/Cu-doped DLC/p-Si Schottky device. It is aimed to obtain extensive and detailed data by current-voltage (I–V) measurements taken with 0.3 V voltage steps in the ±4 V voltage range, at 30 K intervals from 80 K to 410 K. Firstly, an examination of the semi-logarithmic I–V curve revealed that the low temperature (LTs, 80 K–170 K), medium temperature (MTs, 200 K–290 K) and high temperature (HTs, 320 K–410 K) regions should be examined separately. The basic parameters of the Schottky device such as the ideality factor (n), reverse saturation current (Io) and zero-biasing potential barrier height (ΦBo) were obtained separately for LTs, MTs and HTs by the Thermionic Emission (TE) theory. The results obtained show that the device deviates from ideality, especially in LTs and HTs, and the n values decrease with increasing temperature, while the ΦBo values increase. The analysis of the presence of other CTMs in the Schottky device revealed that Field Emission (FE) and Thermionic Field Emission (TFE) were effective in LTs and MTs, while FE was effective in HTs. Since it is thought that quantum mechanical CTMs cannot be the cause of such a deviation from ideality due to the interface layer thickness, the existence of Gaussian Distribution originating from lateral barrier inhomogeneity was investigated. As a result, it is concluded that the Multiple Gaussian Distribution (MGD) is dominant in the possible CTMs of the Schottky device.

New insights into improved SO2＆H2O resistance over MoCrCeOx catalyst by CTAB for medium-low temperatures NH3-SCR: Regulation of surface acid and oxygen species

Selective catalytic reduction (NH3-SCR) of NH3 is the most efficient NOx removal technology. Improving the SO2/H2O resistance of SCR catalyst is of great importance for its industrial application. The Mo(0.3)-CrCeOx catalysts synthesized by the citric acid method exhibited excellent high concentration SO2 resistance but poor H2O tolerance. In this work, cetyltrimethylammonium bromide (CTAB) was used to improve SO2＆H2O resistance over Mo(0.3)-CrCeOx catalyst at medium-low temperatures. The mechanism of CTAB modification and the discrepancy to citric acid (CA) method were investigated. The results indicated that the CTAB catalyst had a large specific surface area, and was conducive to forming a specific structural strength. The enhancement of surface acidity of CTAB is the reason for the further enhancement of SCR activity. The regulation of hydroxyl oxygen to promote the activation of Brønsted acid sites is the key factor to SO2＆H2O resistance. In addition, the in-situ DRIFTS results revealed the different mechanisms of the two catalysts. This paper raised the deactivation reason of sol-gel catalyst caused by SO2＆H2O and presented an effective modification strategy.

Genesis of the Jianbeigou Gold Deposit on the Southern Margin of the North China Craton: Insights from Fluid Inclusions, H‐O‐S Isotopes, and Pyrite in situ Trace Element Analyses

AbstractThe Jianbeigou gold deposit is a typical lode gold deposit in the Qinling metallogenic belt, located on the southern margin of the North China Craton. Three stages of the hydrothermal process can be distinguished, including the quartz ± pyrite, quartz‐polymetallic sulfide, and quartz‐carbonate ± pyrite stages. From the early to late stages, the homogenization temperatures of primary fluid inclusions are 281–362°C, 227–331°C, and 149–261°C, respectively. The corresponding salinities estimated for these fluids are 3.9–9.9 wt%, 0.4–9.4 wt%, and 0.7–7.2 wt% NaCl equiv. Combined with laser Raman spectroscopy data, the ore‐forming fluid belongs to a H2O‐CO2‐NaCl ± CH4 system with medium–low temperature and salinity. The δ18Ofluid and δD values for the quartz veins are –1.0‰ to 6.0‰ and –105‰ to –84‰, respectively, which indicates that the ore‐forming fluid is of mixed source, mainly derived from magma, with a contribution from meteoric water. Pyrite has been identified into three generations based on mineral paragenetic sequencing, including Py1, Py2, and Py3. The pyrites have δ34S sulfur isotopic compositions from three stages between 3.7‰ and 8.4‰, indicating that sulfur mainly originated from magma. Te, Bi, Sb, and Cu contents in pyrite were all high and showed a strong correlation with Au concentrations. Native gold and the Au‐Ag‐Bi telluride minerals were formed concurrently, and the As concentration was low and decoupled from the Au content. Therefore, Te, Bi, Sb and other low‐melting point chalcophile elements play an important role for gold mineralization in arsenic‐deficient ore‐forming fluid. Combined with the geological setting, evolution of pyrite, and ore‐fluids geochemistry, we propose that the Jianbeigou deposit can be classified as a magmatic–hydrothermal lode gold deposit. Gold mineralization on the southern margin of the North China Craton is related to Early Cretaceous magmatism and formed in an extensional setting.

Low-cycle fatigue behavior of coated and uncoated single crystal Ni-based superalloy at various temperatures

Within this work, the effect of different oxidation-resistant coatings on the low-cycle fatigue (LCF) behavior and damage mechanisms of third-generation single crystal (SC) Ni-based superalloy was investigated. Stress-controlled LCF tests of bare alloy, MCrAlY-coated and PtAl-coated thin-walled specimens were carried out at 760 °C, 850 °C and 980 °C. A unique clamping system was meticulously designed to overcome the clamping challenge in high-temperature furnaces. The cracking behaviors and failure modes were determined by advanced microstructure characterization. The results show that the coatings are detrimental to the LCF lifetime of thin-walled specimens, especially at low-medium temperatures of 760 °C and 850 °C. For bare alloy, the tip cracks nucleate from the surface oxide layer, whereas cracks in the coating-substrate system nucleate prematurely from the coating surface and propagate to the substrate. The oxygen diffusion and the frontward propagation of cracks are synergistically enhanced in the SC substrate, resulting in oxidation-assisted crack propagation and ultimate failure. Finally, A fatigue life prediction model is proposed by introducing coating-induced crack initiation and oxidation effects, where the predictive results fit well with experimental results. This study provides a comprehensive insight into the damage mechanisms and coating-induced LCF life degradation of the coating-substrate system.

Effect of low vacuum medium temperature drying on reduction of residual stress and correction of warp of Japanese cedar timber

Cryptomeria japonica (Japanese cedar) in Japan plantations are aging, and the main supply of timber in the market is shifting from small- and medium-diameter to large-diameter logs. The effective utilization of these logs has become an important issue in the timber industry. When producing timber-without-pith from large-diameter logs, an unavoidable warp occurs because of the release of residual stress within the logs. Utilizing high-temperature drying with a load on these timbers has achieved significant drying effects, and the residual stress-induced warp was corrected. However, high-temperature drying has drawbacks, such as high energy consumption and the potential for thermal degradation. We applied low-vacuum-medium-temperature drying (LVMT-drying, 10 days, 40 kPa, 80/55 °C (DB/WB)—90/65 °C (DB/WB)) with load (650 kgf/m2) to the stacked timber sawn from large-diameter logs to address these questions. When LVMT-drying was successful, residual stresses in timber-with-pith were reduced to nearly zero, and warps in timber-without-pith were reduced to less than 8 mm, i.e., below the Japan Agriculture Standard "Level 1" for 4000 mm timber, and the acceptance rate for "Level 1" increased from 45% (green timber) to 85% (treated timber) in the most successful sample. LVMT-drying is a practical drying method for timber from large-diameter logs because it is effective in reducing residual stress and correcting warps while shortening the treatment period and avoiding thermal degradation.

Identifying the genetic mechanism of medium-low temperature fluoride-enriched geothermal groundwater by the self-organizing map and evaluating health risk in the Wugongshan area, southeast China.

Fluoride-enriched groundwater is a serious threat for groundwater supply around the world. The medium-low temperature fluoride-enriched geothermal groundwater resource is widely distributed in the circum-Wugongshan area. And the fluoride concentration of all geothermal samples exceeds the WHO permissible limit of 1.5mg/L. The Self-Organizing Map method, hydrochemical and isotopic analysis are used to decipher the driving factors and genetic mechanism of fluoride-enriched geothermal groundwater. A total of 19 samples collected from the circum-Wugongshan geothermal belt are divided into four clusters by the self-organizing map. Cluster I, Cluster II, Cluster III, and Cluster IV represent the geothermal groundwater with the different degree of fluoride concentration pollution, the different hydrochemical type, and the physicochemical characteristic. The high F- concentration geothermal groundwater is characterized by HCO3-Na with alkalinity environment. The δD and δ18O values indicate that the geothermal groundwater origins from the atmospheric precipitation with the recharge elevation of 1000-2100m. The dissolution of fluoride-bearing minerals is the main source of fluoride ions in geothermal water. Moreover, groundwater fluoride enrichment is also facilitated by water-rock interaction, cation exchange and alkaline environment. Additionally, the health risk assessment result reveals that the fluorine-enriched geothermal groundwater in the western part of Wugongshan area poses a more serious threat to human health than that of eastern part. The fluoride health risks of geothermal groundwater for different group show differentiation, 100% for children, 94.74% for adult females, and 68.42% for adult males, respectively. Compared with adult females and adult males, children faced the greatest health risks. The results of this study provide scientific evaluation for the utilization of geothermal groundwater and the protection of human health around the Wugongshan area.

High wide-temperature-range thermoelectric performance in GeTe through hetero-nanostructuring

GeTe is emerging as promising medium-temperature thermoelectric material due to its highly competitive performance and good mechanical properties. Strong Rashba spin splitting was harnessed to markedly improve the Seebeck coefficient and power factor of Bi and Sn codoped GeTe at low-medium temperature. Moreover, it is found that Bi-Sn-Cu doping reduces the phase-transition temperature to extend better electrical transport behavior of cubic phase to low temperature. As a result, the electrical transport properties in low-medium temperature were overall enhanced. In the meanwhile, endotaxial hetero-nanostructures efficiently scatter phonons and play a dominant role on affecting phonon propagation. The lattice thermal conductivity was reduced to 0.2 W m−1K−1 at 673 K. Drive by strengthening Rashba effect and endotaxial hetero-nanostructures, a record-high average ZT (300–823 K) of 1.6 and a high ZT of 2.1 were obtained in lead-free GeTe-based compounds. The vast increase of ZT promotes GeTe as a promising candidate for a wide range of applications in waste heat recovery and power generation.

An efficient approach for the preparation of branched starch through thermophilic glycogen branching enzyme modification

Glycogen branching enzymes (GBEs, EC 2.4.1.18) play a crucial role in modifying the starch structure and enhancing its properties. The common approaches to starch modification by GBEs typically involve either fully gelatinization the starch at high temperatures (above 95 °C) and then cooling it before adding the enzymes or directly modifying the starch granules at medium-low temperatures (below 60 °C). However, both of these methods have their limitations. Therefore, in this study, we utilized thermally stable mutant Pyrococcus horikoshii (Ph) OT3 GBEs (The thermally stable Ph GBEs mutant were named as H415W and T508K, respectively) to directly act on an ungelatinized normal corn starch (NCS) emulsion at 70 °C, enabling simultaneous starch swelling and branching modification. The results showed that after modification at 70 °C, the crystalline structure of the starch almost completely disappeared, the short-branched chains increased, and the amylose content, rapid digestibility, and retrogradation enthalpy (ΔH) of the H415W- and T508K-modified starch were reduced by 8.2%, 20.35%, and 4.38 J/g when compared to the NCS. Furthermore, when compared to wild-type (WT)-modified starch (modification conducted at 60 °C), the amylose content, rapid digestibility, and retrogradation enthalpy (ΔH) of the H415W- and T508K-modified starch were reduced by 4%, 11.71% and 1.52 J/g, respectively. The branching efficiency of the starch was enhanced due to the achievement of simultaneous starch swelling and branching modification at 70 °C, resulting in an improved branching efficiency. These findings offer valuable insights for the industrial development of branched starch through enzymatic modification.

Efficient catalysis and products regulation of methane dry reforming under mild temperature conditions using novel high-entropy catalyst

Dry reforming of methane to syngas (H2/CO) is the most dominant upstream reaction in chemical production line, which also helps capture greenhouse gases. In this work, we report a novel CoxNi0.8-xLa0.2Ca0.5Ce0.5@Al2O3 high-entropy catalyst applied to CH4-CO2 reforming reaction, which can widen the reaction-temperature window and achieve over 40 % methane conversion and 220 mmol·gcat−1·h−1 hydrogen yield at 500 °C. Compared with other studies, the activity of proposed CoxNi0.8-xLa0.2Ca0.5Ce0.5@Al2O3 high-entropy catalyst exhibits absolute advantage in low-medium temperature environments (500–650 °C). Due to the regulation of structure–activity relationship among various active metal elements, the proposed catalysts present synergistic effect within catalytic system, which can also suppress carbon deposition and maintain stable activity during a 12-hour continuous operation. Importantly, this research utilizes the remarkable characteristics of high-entropy alloys to induce the orderly transformation of reactants. The thermodynamic regulation of the reaction process is also improved by regulating the catalyst structure and thermal properties through intermetallic lattice distortion and “Maximum Entropy Theory”. The experimental results show that the product H2/CO ratio can be stably maintained over 0.9 for temperature ranging from 500 to 850 °C. This provides a reference for the application of high-entropy alloys in the field of carbon capture and hydrogen production.

Quantifying the negative effects of dissolved organic carbon of maize straw-derived biochar on its carbon sequestration potential in a paddy soil

Biochar of low-medium temperature may contain abundant dissolved organic carbon (BDOC), affecting its priming effect and carbon sequestration potential in soils. However, the direct and quantitative evidence for such impacts remains lacking. This study conducted incubation experiments on maize straw-derived 300/450 °C biochar, BDOC-extracted biochar residues and BDOC, and applied δ13C analysis to quantify biochar's mineralization and their priming effects on native soil organic carbon in a paddy soil. BDOC contained abundant lipid-, protein-, carbohydrate-like species, serving as nutrients for the metabolism of microorganisms, and thus enhanced native soil organic carbon's mineralization by 15–20%. After BDOC extraction, 300 °C biochar-trigged priming effect shifted from a positive (3.7 mg CO2–C kg−1 soil) to a negative state (−14.4 mg CO2–C kg−1 soil), and 450 °C biochar-induced negative priming effect increased by 31%; biochar's mineralization also decreased by 41–65%. Overall, after BDOC extraction, the net carbon balance in biochar-amended soils reduced by 7–8%. Furthermore, BDOC shifted the dominant priming mechanisms of biochar mainly by enhancing soil macro-aggregates while reducing sorptive protection for native soil organic carbon. Its extraction reduced the amount of soil macro-aggregates by 16–25% but enhanced the sorption affinity of native soil organic carbon by biochar by 68–122%. Additionally, after BDOC extraction, the microbial communities in biochar-amended soils contained more fungi and G+-bacteria. These findings proved that BDOC extraction appears a feasible strategy to enhance the short-period carbon sequestration potential of biochar.

Enhancing efficiency and sustainability: Utilizing high energy density paraffin-based various PCM emulsions for low-medium temperature applications

This research investigated the potential of high-energy-density Paraffin-based four different phase change materials (PCMs) (Paraffin 56/58, n-Eicosane, n-Octadecane, and n-Heptadecane) emulsions as a promising heat transfer fluid for low and medium-temperature applications at different concentrations. The primary focus is on elevating efficiency and sustainability within this domain. The investigation revolves around formulation and characterizations of these PCM emulsions, meticulously assessing their thermal attributes and stability. The results showed that producing these PCM emulsions using a high-energy manufacturing method with surfactant achieved superior dispersion stability and uniform size distribution throughout PCM emulsions. Among the pristine PCMs, n-Eicosane exhibited the highest latent heat of 252.7 kJ/kg during the melting process. In comparison, other PCMs, Paraffin 56/58, n-Octadecane, and n-Heptadecane demonstrated latent heat fusions of 197.7, 244.3, and 221.3 kJ/kg, respectively. Moreover, the energy storage density of PCM emulsions increased with increasing PCM concentration in basefluid. The highest energy storage density was observed in the case of 70 wt% n-Eicosane PCM emulsion, which is 401.1 kJ/kg. By examining the effectiveness of Paraffin-based PCM emulsions, this research aims to contribute to advancing eco-conscious and effective thermal management systems across diverse applications.

Pyrolysis of shenmu coal to prepare blue-coke used as reductant

Blue-coke is a form of granular char prepared by medium-low temperature pyrolysis of low-rank coal. As a reductant, it has been widely used in calcium carbide production, ferroalloy, copper pyro refining, and ferrosilicon production in China due to the abundant reserves of raw coal and its excellent performance. However, there is little research on the pyrolysis process of granular coal to produce blue-coke and its characteristics as a reductant. Thus, the effects of pyrolysis temperature, heating rate, particle size and holding time at the final temperature on blue-coke preparation were investigated in a rotary kiln reactor. The quality index of blue-coke as a reductant and its properties, including the element composition, surface function groups, carbon forms, reactivity and lower heating value under different pyrolysis temperatures, were analyzed in detail. It is demonstrated that the pyrolysis temperature had a more significant impact on the quality of blue-coke compared to other pyrolysis conditions. With the rise of pyrolysis temperature, the blue-coke’s C/O and C/H increased. With the particle size and heating rate increased, the temperature gradients developed within the granular coal during the pyrolysis process led to the volatile release shifting to higher temperature zone and more secondary reaction occurrence. Nevertheless, the secondary reaction was restrained in the rotary kiln with good heat and mass transfer. The indexes of blue-cokes as reductants were met by the chars produced at temperatures from 550 oC to 750 oC with a holding time 60 min at this temperature and a heating rate of 10 oC/min. As the key index of blue-coke, the electrical resistivity decreased with the increase of pyrolysis temperature. It was found to be closely related to the removal of H and O heteroatom at the pyrolysis temperature below 700 °C. While at the higher temperature, the development of graphitized carbon structure took a major role on it. Nonetheless, the crystallite sizes of the blue-coke obtained under this low temperature pyrolysis were small and the carbon forms were turbostratic. These resulted in the blue-coke's high combustion reactivity, which would gradually decline with the rise of pyrolysis temperature.