Evolution Of Chemical Composition Research Articles

Development of a-C:H coatings doped with trimethylsilyl acetate prepared using plasma enhanced chemical vapor deposition

The main aim of the present study was to develop hard a-C:H:SiOx coatings prepared from the unique gaseous mixture of trimethylsilyl acetate (TMSAc) with methane using plasma of RF capacitively coupled glow discharge. Studied coatings were prepared using different methane ratios in TMSAc/CH4 gaseous mixtures ranging from 7.1 % to 85.7 %. Simultaneously, the influence of the power supplied to the discharge (25–100 W) on the properties of resulting coatings was investigated. The presented research work discusses in detail the evolution of chemical composition, mechanical characteristics, and optical properties of resulting coatings depending on variable CH4 ratio and discharge power. Within this study, various materials with the smooth surface structure were achieved. Applying low CH4 ratio and 25 W power led to the formation of soft SiOxCyHz coatings with high content of Si–O and –CH3 groups exhibiting hardness of approx. 0.95 GPa. Gradually increasing the CH4 ratio and discharge power up to the specified limit values (85 % and 100 W, respectively) induced structural changes, resulting in a-C:H:SiOx coatings with a remarkable hardness of 11 GPa and excellent fracture resistance. These attributes are of utmost importance in numerous industrial applications, including anticorrosive coatings, low-friction wear-resistant coatings to prolong the lifetime of car engines, biocompatible coatings, components for plastic molds, as well as parts for optical disc molds and textile machinery.

Exploring the potential of decade-air exposed perovskite membranes through sustainable recycling approaches

The stability of perovskite-based oxygen permeable membranes under long-term storage conditions, especially in the presence of water and carbon dioxide, presents a significant challenge. In this study, we examined the impact of extended storage (more than 10 years) on Nb2O5-doped SrCo0.8Fe0.2O3-δ (10Yr-SCFN) membranes. To unlock their industrial application potential, various approaches involving a combination of physical and chemical treatments to restore membrane properties in aged membranes are proposed and validated, while systematically investigating the evolution in chemical composition, microstructure, mechanical strength, and oxygen permeability. The 10Yr-SCFN membranes can be effectively restored through the secondary sintering method, wherein the membrane is first powdered and then calcinated in static air to maximize the removal of impurities. The mechanical strength and oxygen permeability reach levels of 30 MPa and 1.2 ml cm−2 min−1 (900 °C), respectively, comparable to the performance of freshly prepared membranes. These findings shed some light on the potentiality of sustainable recycling of perovskite membranes and provide theoretical and technical support for the practical application and industrialization of oxygen permeable membranes.

Field evidence of brown carbon absorption enhancement linked to organic nitrogen formation in Indo-Gangetic Plain

Atmospheric brown carbon (BrC), a short-lived climate forcer, absorbs solar radiation and is a substantial contributor to the warming of the Earth's atmosphere. BrC composition, its absorption properties, and their evolution are poorly represented in climate models, especially during atmospheric aqueous events such as fog and clouds. These aqueous events, especially fog, are quite prevalent during wintertime in Indo-Gangetic Plain (IGP) and involve several stages (e.g., activation, formation, and dissipation, etc.), resulting in a large variation of relative humidity (RH) in the atmosphere. The huge RH variability allowed us to examine the evolution of water-soluble brown carbon (WS-BrC) diurnally and as a function of aerosol liquid water content (ALWC) and RH in this study. We explored links between the evolution of WS-BrC mass absorption efficiency at 365 nm (MAEWS-BrC-365) and chemical characteristics, viz., low-volatility organics and water-soluble organic nitrogen (WSON) to water-soluble organic carbon (WSOC) ratio (org-N/C), in the field (at Kanpur in central IGP) for the first time worldwide. We observed that WSON formation governed enhancement in MAEWS-BrC-365 diurnally (except during the afternoon) in the IGP. During the afternoon, the WS-BrC photochemical bleaching dwarfed the absorption enhancement caused by WSON formation. Further, both MAEWS-BrC-365 and org-N/C ratio increased with a decrease in ALWC and RH in this study, signifying that evaporation of fog droplets or bulk aerosol particles accelerated the formation of nitrogen-containing organic chromophores, resulting in the enhancement of WS-BrC absorptivity. The direct radiative forcing of WS-BrC relative to that of elemental carbon (EC) was ∼19 % during wintertime in Kanpur, and ∼ 40 % of this contribution was in the UV-region. These findings highlight the importance of further examining the links between the evolution of BrC absorption behavior and chemical composition in the field and incorporating it in the BrC framework of climate models to constrain the predictions.

High temperature fracture behavior of 316L stainless steel-Inconel 718 functionally graded materials manufactured by directed energy deposition: Role of interface orientation and heat treatment

Investigation of functionally graded component consisting of stainless steel 316L (SS316L) and Inconel 718 superalloy (IN718) deposited by laser directed energy deposition (LDED) is presented here. Ambient as well as high temperature mechanical behavior is observed for as-deposited (AD) and for heat-treated (HT) states. The gradient sample was manufactured with the interface orientation parallel and perpendicular to the loading direction to understand the impact of this factor on the materials properties. The evolution of chemical composition, grain structure, phase transformations, and tensile properties at room and elevated temperatures, as well as creep behavior before and after heat treatment was determined. With use of digital image correlation (DIC) analysis, the effects of interface orientation and heat treatment on deformation and fracture mechanism was revealed. Results show that heat treatment smooths the chemical composition and mechanical deformation process, as characterized by the formation of an enhanced gradient diffusion zone in the IN718-rich region near the interface. Heat treatment impacts mechanical properties based on the orientation of the interface. Specimens with interfaces parallel to the load direction combine the strengths of both materials effectively. After HT, they exhibit enhanced mechanical performance, achieving an ultimate tensile strength of 973 MPa and 14% elongation at room temperature. Additionally, at elevated temperatures, the specimen demonstrates exceptional creep resistance, sustaining structural integrity for over 1700 h at 650 °C and 225 MPa. Sample orientation is shown a decisive effect on deformation and fracture mechanism, with the interface not consistently being the weakest point across various gradient samples.

Synthesis of PtNi Nanoparticles to Accelerate the Oxygen Reduction Reaction.

We report the synthesis of core-shell Ni-Pt nanoparticles (NPs) with varying degrees of crystallographic facets and surface layers rich in Pt via a seed-mediated thermolytic approach. Mixtures of different surfactants used during synthesis resulted in preferential surface passivation, which in turn dictated the size, chemical composition, and geometric evolution of these PtNi NPs. Electrochemical investigations of these pristine core-shell Ni-Pt structures in the oxygen reduction reaction (ORR) show that their catalytic functionalities outperform the commercial Pt/C reference catalyst. The enhanced electrocatalytic ORR performances of these Pt-based PtNi NPs are correlated with the weakened oxygen binding strength or surface-adsorbed hydroxyl (OH) species on active Pt surface sites induced by the downshift of the d-band center as a result of compressive strain effects. Our studies offer a robust synthetic approach for the development of core-shell nanostructures for enhanced ORR catalysis.

The dynamic surface evolution of halide perovskites induced by external energy stimulation.

Tracking the dynamic surface evolution of metal halide perovskite is crucial for understanding the corresponding fundamental principles of photoelectric properties and intrinsic instability. However, due to the volatility elements and soft lattice nature of perovskites, several important dynamic behaviors remain unclear. Here, an ultra-high vacuum (UHV) interconnection system integrated by surface-sensitive probing techniques has been developed to investigate the freshly cleaved surface of CH3NH3PbBr3 in situ under given energy stimulation. On this basis, the detailed three-step chemical decomposition pathway of perovskites has been clarified. Meanwhile, the evolution of crystal structure from cubic phase to tetragonal phase on the perovskite surface has been revealed under energy stimulation. Accompanied by chemical composition and crystal structure evolution, electronic structure changes including energy level position, hole effective mass, and Rashba splitting have also been accurately determined. These findings provide a clear perspective on the physical origin of optoelectronic properties and the decomposition mechanism of perovskites.

Evaluation of metallurgical risk factors in post-test, advanced 9% Cr creep strength enhanced ferritic (CSEF) steel

ABSTRACT About 9 wt.% Cr steels are widely used in the design and fabrication of thick section components in combined cycle or coal-fired applications for working temperatures of 600 ~ 650°C. This family of materials possesses a martensitic microstructure stabilised by precipitates. The presence of nitrides, inclusions or evolution of second-phase particles may increase the metallurgical risk to creep. The chemical composition and microstructural evolution of 9 wt.% Cr steels contribute to thermal stability and long-term performance. In some specialist alloys, Ta is added to the composition which causes the formation of fine MX precipitates which are only present at the nanometre scale in tempered martensite, which hinders the recovery of dislocations and the migration of laths to extend creep life. However, the presence of large Ta-containing particles or inclusions in the 9 wt.% Cr steels may have a detrimental effect on its creep performance, as they may act as preferred sites for cavity nucleation. To fully appreciate the development of damage in these steels, it is necessary to link the pre- and post-test conditions, evaluate damage in the parent metal, develop procedures that provide consistency of results, and obtain statistically relevant data. The evolution of the Ta-containing phase has been tracked and quantified using a variety of correlative characterisation approaches. Utilising focused ion beam microscopy and two-dimensional electron-based microscopic characterisation, three-dimensional tomography has identified a strong relationship between creep cavities and Ta-containing phases from the early stages of creep.

Decomposition behavior and evolution mechanism of MC primary carbonitride at 1473K and 1523K in die steel

Evolution of morphology and chemical composition and decomposition behavior of MC-type primary carbonitride held at 1473K and 1523K in H13 die steel are studied through electron probe microanalyzer (EPMA) and optical microscope (OM). Result shows that the decomposition of MC-type carbonitride has a relationship with constituent, holding temperature and time and carbonitride structure. It is found that Fe would diffuse to carbonitride from steel matrix accompanied by the decomposition of carbonitride at elevated temperature. The metastable (Vx,Mo1–x)(Cy,N1–y) is transformed into fine Fe-rich (Vx,Moz,Fe1–x–z)6(Cy,N1–y) when held at 1473K, and completely disappeared when held at 1523K. During isothermal holding, the mean size of carbonitride is gradually decreased to 6.5 μm, but there are still a small quantity of (Tix,V1–x)(Cy,N1–y) when held at 1253K for 15 h. Theoretical calculation indicates that Ti content in carbonitride is directly proportional to the thermal stability of carbonitride. As a result, the (Tix,V1–x)(Cy,N1–y) is transformed into (Tix,Vz,Fe1–x–z)(Cy,N1–y) with Fe content larger than 13 wt.% and becomes jagged at the edge. The compact (Tix,V1–x)(Cy,N1–y) is then evolved into the porous fishnet structure and finally dissolved as Fe larger than 32 wt.% in carbonitride. High temperature seems more beneficial for carbonitride decomposition than extension of holding time.

Exploring the interplay between thermo-oxidative degradation and asphalt aging in thermoplastic polyurethane-modified asphalt: Mechanisms, properties, and performance evolution

The aging behavior of thermoplastic polyurethane-modified asphalt (TPUMA) is intricate and the mechanisms of its thermal degradation are not well understood. This study examines the viscoelastic, chemical and morphological characteristics of thermoplastic polyurethane modified asphalt (TPUMA) under different aging conditions (RTFOT/PAV). The rheological master curve model of the S parameter was used to analyze the fitting effect on TPUMA, with SBS (styrene–butadiene–styrene) modified asphalt serving as the control group. The relationship between the phase angle plateau area and polymer aging degradation was elucidated. This study investigates the impact of polymer degradation on the high-temperature rheological behavior and medium-temperature fatigue properties of asphalt through temperature sweep, multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) tests. Fourier transform infrared spectrometer (FTIR) and confocal laser scanning microscopy (CLSM) are used to qualitatively and quantitatively analyze the chemical composition and morphological evolution of TPUMA during thermal-oxidative degradation. The findings suggest that TPUMA's performance changes in the aging environment is result from the dual coupling effect of polymer degradation and asphalt oxidative hardening. The closely arranged isocyanate (-NCO) and polar component molecular chains in asphalt slow down its oxidation speed, which enhances the aging and deformation resistance of TPUMA. The successful blending of TPU and asphalt was confirmed, and the degradation degree of the polymer was quantitatively characterized by the percentage of the degraded area. The results provide insights to better understand the interplay between TPU degradation and asphalt oxidation.

Sedimentary porewaters record regional tectonic and climate events that perturbed a deep-sea brine pool in the Gulf of Aqaba, Red Sea

Brine pools in deep-sea environments provide unique perspectives into planetary and geological processes, extremophile microbial communities, and sedimentary records. The NEOM Brine Pool Complex was the first deep-sea brine pool system found in the Gulf of Aqaba, representing a significant extension of the geographical range and depositional setting of Red Sea brine pools. Here, we use a combination of brine pool samples collected via cast using a conductivity, temperature, depth instrument (CTD), as well as interstitial porewaters extracted from a sediment core collected in the NEOM Brine Pool to characterize the chemical composition and subsurface evolution of the brine. New results indicate that the NEOM brines and the subsurface porewaters may originate from different sources. Elemental concentrations suggest the brines in the NEOM pool are likely derived from dissolution of sub-seabed evaporites. In contrast, the sedimentary porewaters appear to have been influenced by periodic turbidite flows, generated either by earthquakes, submarine landslides, or flash floods, in which normal marine waters from the overlying Red Sea became entrained, periodically disturbing the chemistry of the brine pool. Thus, sediment porewaters beneath brine pools may record transient and dynamic changes in these deep marine depositional environments, reflecting the interplay between climate, tectonics, and sedimentation patterns along a rapidly urbanizing coastline. In concert, new results from NEOM extend the range and chemical constraints on Red Sea Brine Pools and highlight the dynamic interplay between Red Sea Deep water, dissolving evaporites, turbidites, and subsurface fluids that produce these unique depositional environments which host microbial life at the edge of habitability. In concert with sedimentological indicators, the chemistry of porewaters beneath deep-sea brine pools may present detailed records of natural hazards arising from interactions between the atmosphere, lithosphere, hydrosphere, and anthroposphere.

Effect of laser preparation strategy on surface wettability and tribological properties under starved lubrication

The preparation strategy determines the microstructure of surface textures, influencing the lubrication properties of surface. This paper proposes three laser scanning strategies aimed at achieving a sinusoidal textured surface, and discussed the evolution of surface structure and chemical composition. The subsequent investigation focuses on the impact of the transition in surface wettability on friction performance. The findings reveal that the ridge structures enhance surface anti-wear properties but concurrently elevates the friction coefficient. However, the oil cover preparation method prevents the formation of ridges and increases the water contact angle to 138°. The shift in wettability is determined by the combined effects of structure and the adsorption of organic compounds. Furthermore, the hydrophobic surface exhibits superior tribological properties in friction tests.

Intra-event evolution of elemental and ionic concentrations in wet deposition in an urban environment

Abstract. A measurement campaign was conducted in the Paris region, focusing on the evolution of chemical composition of wet deposition during rainfall events from sequential sampling. A total of eight rain events were documented and characterized by varying meteorological conditions, atmospheric dynamics, and aerosol particle concentrations representative of urban conditions and influenced by long-range mineral dust transport. The intra-event evolution of the chemical composition of wet deposition revealed the predominant role of meteorological parameters and local sources in the observed mass concentration variability. From selected case studies, the washout ratios (WRs) and scavenging coefficients were quantified by conducting simultaneous measurements of aerosol particle composition and wet deposition. The results highlighted a variability of the WR and scavenging coefficients depending on the rainfall rate and on the chemical species. Scavenging coefficients estimated from WR ranged from 5.4×10-8 to 1.1×10-5 s−1 for chemical elements, and they are within the range of values reported in the literature for 0.2–2 µm particle diameters. Our results pointed out that the scavenging coefficient increases with rainfall rate according to a power law, as previously shown in the literature, indicating a stronger removal of particles from the atmosphere with greater precipitation intensity. Quantitative analysis of the data allowed us to estimate the relative contributions of in-cloud scavenging (ICS) for selected rain events. The ICS relative contributions ranged on average from 23 % to 62 % depending on the rain events, and they varied according to the chemical species within the same rain event. This highlights the variability and complexity of the wet deposition process and the influence of specific factors on the contribution of ICS, such as aerosol particle size and hygroscopicity. Overall, this study highlights the variability of wet deposition and its chemical composition and the need to consider the specificities of each event to fully understand the underlying mechanisms.

Synergetic improvements in surface hydrophobicity and wear resistance of TC4 materials via the combination of rapid heating and EtOH quenching methods

Ti-6Al-4V (TC4) materials with high hydrophobicity and wear resistance improve anticorrosion performance when utilized in offshore conditions. In this work, a novel strategy for simultaneously enhancing the surface hydrophobicity and wear resistance of surface textured TC4 (selected laser melting, SLM-TC4) materials was proposed. An in-situ deposition of ultrathin carbon film is realized via rapid induction heating followed by the EtOH quenching (IHQ-TC4) process. After the IHQ process, the surface chemical composition evolves from Ti (SLM-TC4) to the mixture of carbon film and TiO2 nanoparticles (IHQ-TC4), and the corresponding surface roughness decreases, which results in a surface wettability transition from hydrophilicity (SLM-TC4) to hydrophobicity (IHQ-TC4, 125°). Molecular dynamics simulations were utilized to explore the wettability transition mechanism, and found that the surface chemical composition evolution is the dominant factor, and the carbon film is responsible for the hydrophobicity of IHQ-TC4. Moreover, the surface hardness and wear resistance of IHQ-TC4 are greatly enhanced compared to those of SLM-TC4. The collective enhancements to the hydrophobicity and wear resistance of TC4 materials via the IHQ process provide a novel and facile strategy for enhancing the anticorrosion performance of TC4 materials utilized in offshore conditions.

Enhancing the Longevity and Functionality of Ti-Ag Dry Electrodes for Remote Biomedical Applications: A Comprehensive Study.

This study aims to evaluate the lifespan of Ti-Ag dry electrodes prepared using flexible polytetrafluoroethylene (PTFE) substrates. Following previous studies, the electrodes were designed to be integrated into wearables for remote electromyography (EMG) monitoring and electrical stimulation (FES) therapy. Four types of Ti-Ag electrodes were prepared by DC magnetron sputtering, using a pure-Ti target doped with a growing number of Ag pellets. After extensive characterization of their chemical composition and (micro)structural evolution, the Ti-Ag electrodes were immersed in an artificial sweat solution (standard ISO-3160-2) at 37 °C with constant stirring. Results revealed that all the Ti-Ag electrodes maintained their integrity and functionality for 24 h. Although there was a notable increase in electrical resistivity beyond this timeframe, the acquisition and transmission of (bio)signals remained viable for electrodes with Ag/Ti ratios below 0.23. However, electrodes with higher Ag content (Ag/Ti = 0.31) became insulators after 7 days of immersion due to excessive Ag release into the sweat solution. This study concludes that higher Ag/Ti atomic ratios result in heightened corrosion processes on the electrode's surface, consequently diminishing their lifespan despite the advantages of incorporating Ag into their composition. This research highlights the critical importance of evaluating electrode longevity, especially in remote biomedical applications like smart wearables, where electrode performance over time is crucial for reliable and sustained monitoring and stimulation.

Sulfate resistance and degradation mechanism of basalt fiber modified graphite tailings cement-based materials

This paper delves into the modification mechanism and deterioration mechanism of basalt fiber (BF) on the sulfate resistance of graphite tailings (GT) cement-based materials. Initially, the comprehensive properties of basalt fiber modified graphite tailings cement mortar (BFM-GTCM) under different sulfate cycles, such as apparent morphology, water absorption and mechanical characteristics were investigated. Subsequently, the relationship between the evolution of microstructure, interface stability, pore structure, chemical composition and functional groups of BFM-GTCM and its resistance to sulfate erosion under different cycles was revealed by various microscopic characterization and analysis methods (SEM/XRD/MIP/FTIR/DSI). Simultaneously, a corrosion coefficient-pore structure relationship model was also put forth based on multivariate regression theory, and the mechanism enhancing BFM-GTCM resistance to sulfate attack was investigated. The results demonstrated that a suitable blend of BF and GT can prevent sulfate ion penetration, significantly slow down the generation of corrosion products (AFt and gypsum) in cement mortar during sulfate attack, postpone the occurrence of new cracks and the growth of existing ones, improve pore structure, and significantly lessen the degree of durability degradation of BF-GTCM. Among them, 0.3% BF addition and 20% GT replacement was the ideal ratio.

The Evolutionary Ecology of Plant Chemical Defenses: From Molecules to Communities

Classic theory relates herbivore pressure to the ecology and evolution of plant defenses. Here, we summarize current trends in the study of plant–herbivore interactions and how they shape the evolution of plant chemical defenses, host choice, and community composition and diversity. Inter- and intraspecific variation in defense investment is driven by resource availability. The evolution of defenses at deeper nodes of plant phylogeny is conserved, yet defenses are highly labile at the tips. On an ecological timescale, while greater specialization of tropical herbivores enhances local diversity by reducing the performance of plants with similar defenses, in temperate ecosystems with more generalist herbivores, rare defense profiles are at a disadvantage. On an evolutionary timescale, host choice by herbivores is largely determined by plant defenses rather than host phylogeny, leading to evolutionary tracking by herbivores rather than cocladogenesis. The interplay between plants and herbivores shapes both the origin and maintenance of diversity.

Effect of Fe addition on phase evolution, microstructure and properties of Ti50Ni50-X Fe X alloy

The work aims to study the effect of the Fe content on the properties of Ti50 Ni(50−X) Fe X alloy (where X = 0, 2, 4, 6, 8, and 10 at.-%) sintered at 1050°C and 1150°C using the conventional sintering technique. The microstructure, chemical composition and phase evolution of the sample were analysed by SEM, EDS, and XRD, respectively, along with various properties. It was observed that the sintered sample microstructure consists of (Ni, Fe)-rich, and Ti-rich phases. Here, the porosity decreases, whereas density, hardness, and wear resistance increase with the increasing temperature. The 8at.-%Fe sample shows lower porosity and higher wear resistance, relative density and hardness value than other Fe content samples. The 2at.-%Fe sample sintered at 1050°C shows a higher shape recovery value compared to other compositions sintered at various temperatures.

Recycled carbonates elevate the electrical conductivity of deeply subducting eclogite in the Earth’s interior

The elevated pressure and temperature conditions encountered by a subducted slab entering the deep Earth can substantially alter the chemical composition and physical properties of recycled carbonates. Carbonate-silicate reactions are believed to have a pivotal role in this process. Here we conduct high temperature and high pressure experiments on carbonated eclogite and measure the electrical conductivity in order to constrain the evolution of geophysical properties and chemical composition in the carbonate-bearing eclogitic slab. We find that the carbonate-silicate reaction elevates the conductivity of carbonated eclogite by cations (e.g., Ca, Mg, Fe) exchange between carbonates and silicate. We propose that carbonate-silicate cations exchange can alter the chemical composition of recycled carbonates, potentially impacting their stability and reducing the solidus temperature of carbonate-bearing systems. Combining thermodynamic calculations with the elevated conductivity in our experiments, we re-evaluate the contribution of recycled carbonates to the Earth mantle geophysical anomalies and obtain the potential carbonate capacity in the subducting slab.

On the O2 "Surfactant" Effect during Ag/SiO2 Magnetron Sputtering Deposition: The Point of View of In Situ and Real-Time Measurements.

The use of gaseous species has been proposed in the literature to counteract the three-dimensional growth tendency of noble metals on dielectric substrates and favor an earlier percolation without compromising electrical properties. This "surfactant" effect is rationalized herein in the case of O2 presence during magnetron sputtering deposition of Ag films on SiO2. In situ and real-time techniques (X-ray photoemission, film resistivity, UV-visible optical spectroscopy) and ex situ characterizations (X-ray diffraction and transmission electron microscopy) were combined to scrutinize the impact of O2 addition in the gas flow (%O2), revealing three regimes of evolution of film resistivity, morphology, structure, and chemical composition. At low oxygen flow conditions (%O2 < 4), the observed drastic decrease of the percolation threshold is assigned to a combination of (i) a change in nanoparticle density, wetting, and crystallographic texture and (ii) a delayed coalescence effect. The driving force is ascribed to the presence of specific adsorbed oxygen moieties, the nature of which starts evolving at intermediate oxygen flow conditions (10 ≤ %O2 < 20). At high oxygen flow (20 ≤ %O2 < 40), the found detrimental impact on film resistivity is assigned to an actual oxidation in the form of a Ag2O-like poorly crystallized compound. For all %O2, a composition gradient is observed across the film thickness, with a more metallic Ag at the substrate interface. A correlation between percolation and the nature of the detected O moieties is observed. In parallel to an oxygen spillover mechanism, this gradient can be explained by the competition between different surface processes occurring before percolation, namely, aggregation, metal oxidation, and substrate reactivity. Such findings pave the way to a rational use of O2 as a modifier for Ag growth.

Study on the structural evolution and heat transfer performance of Cu supported on regular morphology CeO2 in CO catalytic combustion and chemical looping combustion

Chemical looping combustion (CLC) and catalytic combustion (CC), which are potential technologies to promote CO→CO2 efficient conversion and energy conservation for the steelmaking off-gas, are investigated in reaction activity, structure evolution catalysts/oxygen carriers (OCs) and energy recovery using Cu/CeO2 materials. Activity results suggest that the rod-shaped samples with well-defined (100) crystal faces exhibit higher activity than the sphere-shaped samples with (111) crystal faces, obtaining the optimized copper content of 3 wt%. IR spectra confirmed the proposed reaction pathway that the CO adsorbed on copper sites (Cu+–CO) at the Cu–Ce interface reacts with adjacent surface lattice oxygen. The gaseous oxygen continuously migrates to the external surface of materials, thus resulting in strongly exothermic CO self-sustained combustion during CC. Such a violent reaction does not cause obvious evolution of chemical composition, crystalline phase and structure. Since the active lattice oxygen is gradually consumed but not replenished by external gaseous O2 in time, CO combustion is not self-sustained during CLC. Therefore, the reduction cycle is no longer confined to the surface of the material but penetrates deep into its body, which accelerates Cu+ enrichment at the surface and leads to irreversible sintering and agglomeration of the material.