Copper Phase Research Articles

Complete removal of CO at ambient conditions using copper manganese oxide (CuMnOx) catalysts synthesised via co-precipitation with ultrasonic irradiation

This present work investigates the novel method of synthesising copper manganese oxide (Hopcalite) catalysts with a Cu:Mn ratio of 1:2 by using a facile ultrasound-assisted co-precipitation synthesis technique. The CuMnOx catalysts were synthesised using an ultrasonic bath or an ultrasonic probe with varying ultrasonic powers. The catalysts were further characterised and evaluated for the oxidation of carbon monoxide (CO). Characterisation results revealed that samples prepared using the ultrasonic method exhibited enhanced physical properties, such as highly dispersed particles with a larger surface area and pore size. Besides, the presence of mixed copper and manganese oxide phases was detected, which provided synergistic interactions to facilitate and enhance CO oxidation. The amorphicity and reducibility of the catalysts were also improved, thus indicating the presence of more active sites. Furthermore, the catalyst prepared using the ultrasonic probe at a power of 23.3 W with a 15 min sonication time was found to be the most active, with the capability of oxidising CO to CO2 to completion (100 %) at ambient conditions. It also possessed high catalytic stability, in which catalytic activity was not compromised for as long as 200 min. On the whole, this work has ascertained that by incorporating a simple ultrasonic irradiation step into the synthesis procedure of copper manganese oxide catalysts, the overall performance of the catalyst can be greatly improved compared to those already found in the literature, which demonstrates the potential application of this new method on a wider, commercial scale for carbon monoxide removal.

Effects of four hormones on the mitigation of ovarian damage in tilapia (Oreochromis niloticus) after copper and cadmium exposure

Female tilapia of the Genetic Improvement of Farmed Tilapia (GIFT) strain were selected as an animal model to study the effects of four hormonal drugs in mitigating ovarian damage following exposure to copper and cadmium. After combined exposure to copper and cadmium in aqueous phase for 30 d, tilapia were randomly injected with oestradiol (E2), human chorionic gonadotropin (HCG), luteinizing hormone releasing hormone (LHRH), or coumestrol and raised in clear water for 7 d Ovarian samples were collected after combined exposure to heavy metals for 30 d and after recovery for 7 d Gonadosomatic index (GSI), copper and cadmium levels in the ovary, reproductive hormone levels in serum, and mRNA expression of key reproductive regulatory factors were determined. After 30 d of exposure to the combined copper and cadmium in aqueous phase, the Cd2+ content in tilapia ovarian tissue increased by 1,242.46% (p < 0.05), whereas the Cu2+ content, body weight, and GSI decreased by 68.48%, 34.46%, and 60.00% (p < 0.05), respectively. Additionally, E2 hormone levels in tilapia serum decreased by 17.55% (p < 0.05). After drug injection and recovery for 7 d, compared to the negative control group, the HCG group exhibited an increase of 39.57% (p < 0.05) in serum vitellogenin levels. Increases of 49.31%, 42.39%, and 45.91% (p < 0.05) in serum E2 levels were observed, and mRNA expression of 3β-HSD increased by 100.64%, 113.16%, and 81.53% (p < 0.05) in the HCG, LHRH, and E2 groups, respectively. The mRNA expression of CYP11A1 in tilapia ovaries increased by 282.26% and 255.08% (p < 0.05) and mRNA expression of 17β-HSD increased by 109.35% and 111.63% in the HCG and LHRH groups, respectively (p < 0.05). All four hormonal drugs, particularly HCG and LHRH, promoted the restoration of tilapia ovarian function to varying degrees after injury induced by combined exposure to copper and cadmium. This study presents the first hormonal treatment protocol for the mitigation of ovarian damage in fish exposed to combined aqueous phases of copper and cadmium as a strategy to prevent and treat fish ovarian damage induced by heavy metals.

Chemical and Biological Leaching of Chalcopyrite- Elemental Sulfur Reaction Products

ABSTRACT Chalcopyrite ores are processed mostly by pyrometallurgical techniques due to the refractory nature of the mineral to the current hydrometallurgical techniques. In order to overcome such refractoriness, pretreatment steps such as sulfurization may be applied to produce different copper phases and therefore improve the metal dissolution in the leaching step. The current study investigated the reaction products of the reaction between chalcopyrite and elemental sulfur at different chalcopyrite/sulfur ratios (1/1 and 1/2), reaction time (60 min and 90 min), and temperature (350ºC, 400°C and 450ºC). The sulfurization experiments revealed that covellite, nukundamite, bornite, and pyrite-like compounds were produced according to the experimental conditions applied. Then, the sulfurization products were submitted to chemical leaching tests at temperatures ranging from 32ºC to 70ºC, whereas bioleaching tests were also carried out with Acidithiobacillus ferrooxidans, at 32ºC. In the chemical leaching experiments at 70ºC, only 14% copper was recovered from the original chalcopyrite sample while the maximum copper extraction was 78% from bornite produced at 450ºC (90 min and mass ratio of chalcopyrite/sulfur of 1/2). On the other hand, copper extraction achieved 96% from the same sulfurization product containing synthetic bornite within 20 days of bioleaching. Bioleaching of the original chalcopyrite sample implied in a copper recovery of only 25% in the same period. Summarizing, the current work showed that chalcopyrite sulfurization at 450ºC was able to transform chalcopyrite into a bornite-like phase, which was chemically leached and bioleached by At. ferrooxidans.

A study of the structure, mechanical and corrosion properties of the copper matrix composites with CNTs/Cu foams as 3-dimensional skeleton reinforcements

In this paper, inhomogeneous copper matrix composite with carbon nanotube reinforced copper foam (CNTs/Cuf) as the three-dimensional (3-D) skeleton is designed to overcome the paradox between strength and ductility or conductivity. The open cell composite foams with uniformly embedded CNTs are filled with dense copper phase in the foam pores by spark plasma sintering (SPS) to form the inhomogeneous composites. The inhomogeneous composite reinforced with CNTs/Cuf shows a combination of high electrical conductivity (93.4% IACS), tensile strength (366.7 MPa), and fracture elongation (31.78%) with a quite low CNTs content (0.2414 vol%). In addition, the polarization curves and AC impedance (EIS) tests show that the best corrosion resistance is achieved with the CNTs content of 0.2414 vol%, and the corrosion rate is reduced by 71.9% and 49.1% compared with the Cu and Cuf®Cu samples, respectively.

Application of quantitative mineralogy to determine sources of airborne particles at a European copper smelter

Copper processing operations, such as smelters and refineries, can produce airborne particles that may impact the health of workers. At these operations, worker exposure to chemicals are regularly monitored to ensure that regulatory compliance with occupational exposure limit values (OELVs) are maintained. Determining the type of airborne particles present is important for characterizing the composition of dust exposures and better understanding the relationship between worker exposure and health. Routine methods of analysis (e.g., chemical assay) are unable to differentiate between phases containing the same elements and may result in ambiguity. A novel approach of a combination of Quantitative Evaluation of Materials by Scanning Electron Microscope (QEMSCAN) and chemical characterization was used here to evaluate airborne and settled dust collected at key locations throughout a copper smelter in Europe. The copper (Cu) phases present in the airborne dust are indicative of the activities performed at specific locations. In the batch preparation area where Cu concentrate is received, significant amounts of Cu were carried in sulfidic minerals (chalcocite, chalcopyrite/bornite, >40%), whereas near the anode and electric furnace, the majority of Cu in dust was carried in metallic and oxidic phases (60–70%). Particle size analysis of the settled dust indicates that the sulfidic and oxidic Cu minerals are more likely to become airborne over metallic Cu. Furthermore, overall Cu concentrations decreased with particle size where metallic and oxidic Cu dominate, which suggests that differences in the proportion of Cu forms present in the dust will impact how much Cu ends up in the respirable fraction. These results highlight the need to understand the characterization of Cu in dust in order to set better OELVs.

Phase Transformation during the Selective Dissolution of a Cu85Pd15 Alloy: Nucleation Kinetics and Contribution to Electrocatalytic Activity

This study determined the critical parameters for the morphological development of the electrode surface (the critical potential and the critical charge) during anodic selective dissolution of a Cu-Pd alloy with a volume concentration of 15 at.% palladium. When the critical values were exceeded, a phase transition occurred with the formation of palladium's own phase. Chronoamperometry aided in the determination of the partial rates of copper ionization and phase transformation of palladium under overcritical selective dissolution conditions. The study determined that the formation of a new palladium phase is controlled by a surface diffusion of the ad-atom to the growing three-dimensional nucleus under instantaneous activation of the nucleation centres. We also identified the role of this process in the formation of the electrocatalytic activity of the anodically modified alloy during electro-oxidation of formic acid. This study demonstrated that HCOOH is only oxidated at a relatively high rate on the surface of the Cu85Pd15 alloy, which is subjected to selective dissolution under overcritical conditions. This can be explained by the fact that during selective dissolution of the alloy, a pure palladium phase is formed on its highly developed surface which has prominent catalytic activity towards the electro-oxidation of formic acid. The rate of electro-oxidation of HCOOH on the surface of the anodically modified alloy increased with the growth of the potential and the charge of selective dissolution, which can be used to obtain an electrode palladium electrocatalyst with a set level of electrocatalytic activity towards the anodic oxidation of formic acid.

Plastic deformation behavior of a Cu–10Ta alloy under strong impact loading

In this work, a Cu–10Ta alloy with a copper to tantalum mass ratio of 9:1 is prepared using powder metallurgy technology. Physical properties of the alloy, including density, microstructure, melting point, and constant-volume specific heat, are tested. Via the split Hopkinson pressure bar (SHPB) and flyer-plate impact experiments, the relationship between equivalent stress and equivalent plastic strain of the material is studied at temperatures of 298–823 K and under strain rates of 1 × 10−3–5.2 × 103 s−1, and the Hugoniot relationship at impact pressures of 1.46–17.25 GPa and impact velocities of 108–942 m/s is obtained. Evolution of the Cu–10Ta microstructure that occurs during high-strain-rate impact is analyzed. Results indicate that the Cu–10Ta alloy possesses good thermal stability, and at ambient temperatures of up to 50% its melting point, stress softening of less than 15% of the initial strength is observed. A modified J-C constitutive model is employed to accurately predict the variation of yield strength with strain rate. Under strong impact, the copper phase is identified as the primary source of plastic deformation in the Cu–10Ta alloy, while significant deformation of the high-strength tantalum particles is less pronounced. Furthermore, the longitudinal wave speed D is found to correlate linearly with the particle velocity u upon strong impact. Analysis reveals that the sound speed and spallation strength of the alloy increase with increasing impact pressure.

Investigating the Phase Diagram of SiO&lt;sub&gt;2&lt;/sub&gt;–CaO–CrO&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt; System to Evaluate Distribution of Platinum between Slag and Molten Copper

In the hydrometallurgical process used for recycling platinum group metals (PGMs), a residue containing mainly Cr2O3 and a small amount of PGMs is generated. In the present work, a pyrometallurgical process was applied in which PGMs from the residue generated in the hydrometallurgical process are concentrated in a molten copper phase as a collector-metal, and Cr2O3 is separated into a slag phase with SiO2 and CaO as a flux. To reduce the loss of PGMs to the slag, it is necessary to have a homogenous liquid and a lower dissolution of PGMs into the slag. Therefore, the phase diagram of the SiO2–CaO–CrOx system was investigated at 1773 and 1873 K in an oxygen partial pressure pO2 = 10-10 to obtain knowledge of the homogeneous melts. Based on the determined phase diagram, the distribution ratios of Pt as representative PGMs between the liquid SiO2–CaO–Al2O3–CrOx or the liquid SiO2–CaO–CrOx slag and molten copper were measured at 1773 K in pO2 = 10-10. The experimental results showed that CrOx solubility in the slag increased with decreasing slag basicity, B defined as B = (mass%CaO)/(mass%SiO2). Furthermore, the results showed that the distribution of Pt in the slag increased with increasing CrOx concentration in the slag.

Uniform Si‐Infused UiO‐66 as a Robust Catalyst Host for Efficient CO2 Hydrogenation to Methanol

AbstractDue to the weak nature of organic coordination bonds, metal–organic frameworks (MOFs) can hardly retain their intrinsic physicochemical properties and structural integrity when functioning in harsh heterogeneous reactions. Herein, a post‐synthetic strategy to reinforce the MOF structure by inserting siliceous linkers inside is proposed, according to which a Si‐infused UiO‐66 (s‐UiO‐66) with well‐developed porosity and exceptional thermal/structural stability is fabricated. This monodispersed Si‐infused matrix with enlarged nanopores is then utilized as the catalyst host, and is highly conductive to confining ultrafine CuO nanoparticles with uniform dispersion. Targeting CO2 hydrogenation to methanol reaction, the Cu‐loaded s‐UiO‐66 (CuO/s‐UiO‐66) delivers a remarkable and efficient methanol production rate outperforming other Cu/ZrO2‐based catalysts and the commercial catalyst. Moreover, the robust structure of CuO/s‐UiO‐66 prevents both copper phase and host material from aggregation during the catalyst preparation procedure and the reaction. In addition to material‐oriented studies, in situ characterization techniques are employed to identify the active Cu component and key intermediates formed during the CO2 hydrogenation reaction, separately. It is envisioned that this Si infusion strategy can be applied to construct stable host materials with boundary‐defined structures from the pristine MOFs for broadened applications under extreme circumstances.

Ефективність впливу легування міддю на зношування заевтектоїдних сталей

The intensity of wear of graphitized eutectoid steels with a carbon content in the range of 1.1÷1.7%, by weight was investigated. The effectiveness of the effect of copper doping on the wear of eutectoid steels in the cast state has been determined. It was established that under conditions of dry friction by sliding and taking into account the friction parameters in the sealing units the temperature on the worn surface and in the thin near-surface layer should exceed 1100 0С, at such temperatures and copper content more than 12%, by weight, in the binary system Fe-Cu there is a two-phase region +-phase, and  - phase, exists in the state of liquid and acts as a lubricant, the wear mode goes from dry to limiting. Lines of existence of -phases in the liquid state are constructed. The results of studies of the effect of copper on the intensity of wear of steels with different carbon content, under conditions of dry friction by slipping, indicated that regardless of the amount of carbon, doping of alloys with copper significantly reduces their intensity of wear to copper content at the level of 10-12%, by weight, a further increase in copper doping equalizes the effectiveness of the impact and reduces the intensity of wear. Alloying of steels with copper of 12% or more causes the formation of a copper phase film on the friction surface. Under the condition of alloying steel with copper less than 12%, the steel structure contains -phase, as a product of a three-phase eutectoid reaction and as a decomposition product of supersaturated solid iron solution. As the copper content in steel increases, the amount of copper phase in the steel structure and its amount on the contact surface increases, after reaching the copper content in the steel sufficient to form the primary grains of the copper phase, the formation of a stable layer of copper on the contact surface begins, which is the constant boundary layer of copper -phase in the liquid state. Keywords: steel, copper, carbon, alloying, wear resistance, friction.

Microstructure and hydrogen transport properties of (V90Cr5Al5)90Cu10 alloy membranes

Our newly developed V90Cr5Al5 hydrogen permeable alloy has been extended to enhance malleability by Cu alloying. The resulting (V90Cr5Al5)90Cu10 consists of bcc-(V) and fcc-(Cu) phases and can be cold rolled into a thin membrane with a thickness of 0.1 mm due to the introduction of the ductile copper phase. After rolling and annealing, (V90Cr5Al5)90Cu10 contains finer grains and a higher percentage of special grain boundaries compared to the as-cast case. The rolled/annealed (V90Cr5Al5)90Cu10 exhibits a lower hydrogen diffusivity than the as-cast one, but a significantly improved hydrogen permeation flux due to the reduced membrane thickness and the inverse relationship of flux and thickness. Typically, a pronounced high hydrogen flux of ∼72 cc H2 cm−2min−1 was achieved at a hydrogen pressure difference of 0.6 MPa at 673 K. In comparison with V90Cr5Al5, Cu alloyed membranes exhibit enhanced resistance against hydrogen embrittlement and enhanced long-term hydrogen permeation stability at 673 K.

Equiatomic binary phases of Copper-Rare Earth Elements. An overview of monocuprides from first-principles calculations.

Equiatomic binary phases of copper with rare earth (RE) elements exhibit either primitive cubic ( ) or orthorhombic (Pnma) structures and in some cases both. By using density functional theory (DFT), we calculated the enthalpies of formation along the series of RE elements combined equimolarly with copper. For RE from Sc to Lu, the calculated enthalpies of formation fall in the range -49.8 kJ/mol for LuCu to -9.1 kJ/mol for the least thermodynamically stable CeCu. Except NdCu, all the other cubic or orthorhombic compounds exhibit lattice stability. Either forms of NdCu indicated lattice instability. Along the Sc-group, the hypothetical primitive cubic and orthorhombic forms of LuCu are found thermodynamically and mechanically stable. The overall trend of the formation enthalpies as a function of the Meyer Periodic Number is consistent with the energy trend of the 4 f-orbital filling as moving from Sc to Lu monocuprides. In addition, the calculated Gibbs free energies indicate that the thermodynamic stability is largely due to the entropic contributions. All standard DFT calculations were also repeated with DFT+U to better describe the correlation between the 5d-4f and 3d shells of RECu compounds. It has been found that DFT+U slightly affects the enthalpies of formation of RECu binaries. Moreover, DFT+U shifts up the f-band energies of RECu with light RE elements (such as La, Ce and Pr) and in contrast lowers them in the case of RECu with heavy RE elements from Nd to Lu.

Inhomogeneous copper matrix composites reinforced by RGO/Cu composite foams with high electrical conductivity, tensile strength and fracture elongation

A three-dimensional (3-D) skeleton-reinforced copper composite was designed to overcome the paradox between strength and ductility or conductivity. Open cell copper matrix foams with uniformly embedded reduced graphene oxide (RGO) were prepared via electrodeposition. The foam pores were filled with pure copper phase via spark plasma sintering (SPS). Cu2O nanoparticles were formed at the RGO-Cu interface, resulting in improved interfacial bonding. Three-dimensional skeleton-reinforced composites showing a combination of high electrical conductivity (93.24% IACS), tensile strength (343 MPa), and fracture elongation (39.4%) were fabricated with low levels of RGO (0.024 wt%). The possible strengthening mechanism of the skeleton-reinforced composites is discussed basing on the test results.

Microstructure evolution in steel/copper graded deposition prepared using wire arc additive manufacturing

• 316L stainless steel (SS)/copper gradient materials obtained using cold metal transfer-based WAAM. • No intermetallic and metastable phase found in the deposition. • Microstructure evolution of SS/copper via CMT-WAAM revealed. Fabrication of steel and copper bimetallic material through cold metal transfer-based wire arc additive manufacturing (CMT-WAAM) is a novel exploration. In this experiment, a graded structure was obtained successfully by depositing copper layers on the AISI 316L stainless steel. The iron-rich phases were present in the deposit up to the interface of second and third copper layer, and the iron distribution in the copper matrix was comparably more uniform after the first copper layer. The iron phase is deposited in globular and dendritic morphologies. Supersaturated copper phase precipitates were traced inside the globular iron, but no such precipitation was evident in iron dendrites. No metastable or intermetallic phases were detected by XRD analysis. Hardness measurement results were in good agreement with the grain size and phase precipitation within the copper layers.

Testing a single slope solar still with copper heating coil, external condenser, and phase change material

A worldwide shortage of drinkable water has resulted from the rapid rise of industrialization and population, which has prompted researchers to find an alternative method to meet this requirement. Solar still are systems powered by solar energy that can provide drinkable water, however it has a low production issue. In this study a conventional solar still (CSS) and a modified solar still (MSS) have been tested in this experimental study. Copper water heating coil, an external condenser, and Nano-phase change material (PCM-Ag) have been employed to increase the productivity of the MSS. In three sets of experiments the performance of MSS and CSS were compared under identical meteorological conditions. The findings showed that, the productivity increase/thermal efficiency for MSS with heating coil, MSS with external condenser, and MSS with PCM-Ag layer are 76 %/45.4 %, 120 %/52 % and 111 %/50.7 %, respectively. So, employing PCM or external condenser increased the productivity of MSS with heating coil by about 35 % and 44 %, respectively. Economic analysis was also taken into account, and the costs of the distilled freshwater for the CSS, MSS-PCM, and MSS-EC 0.029, 0.024, and 0.022 $/l, respectively.

Effect of Reducing Agent on Characteristics and Antibacterial Activity of Copper-Containing Particles in Textile Materials.

Textile materials modified with copper-containing particles have antibacterial and antiviral properties that have prospects for use in healthcare. In the study, textile materials were saturated with copper-containing particles in their entire material volume by the absorption/diffusion method. The antibacterial properties of modified textile materials were confirmed by their inhibitory effect on Staphylococcus aureus, a Gram-positive bacterium that spreads predominantly through the respiratory tract. For the modification, ordinary textile materials of various origins and fiber structures were used. Technological conditions and compositions of modifying solutions were established, as well as the most suitable textile materials for modification. To assess the morphological and physical characteristics of copper-containing particles and the textile materials themselves, X-ray diffraction, a scanning electron microscope, and an energy-dispersive X-ray spectrum were used. In modified textile samples, XRD data showed the presence of crystalline phases of copper (Cu) and copper (I) oxide (Cu2O). On the grounds of the SEM/EDS analysis, the saturation of textile materials with copper-containing particles depends on the structure of the textile materials and the origins of the fibers included in their composition, as well as the modification conditions and the copper precursor.

Mineralogical characteristics of copper smelting slag affecting the synchronous flotation enrichment of copper and arsenic

Synchronous enrichment of copper and arsenic has become a newly emerging and significant problem during copper smelting slag (CSS) flotation, which affects environmental safety and CSS utilization. This study on CSS and its flotation products revealed the factors that affect the flotation enrichment of copper and arsenic from a mineralogy perspective. Mineralogical characteristic studies revealed that copper existed primarily in the form of matte with excellent floatability, whereas arsenic was primarily dissolved or wrapped in glassy silicates without floatability. The second occurrence phase of copper and arsenic, copper–arsenic alloy, was closely embedded with gangue minerals, which increased the difficulty of enriching copper and arsenic. Sequential extraction and X-ray photoelectron spectroscopy analysis indicated that the floatability of copper was better than that of arsenic. Flotation tests showed that copper recovery could reach 82.79 %, whereas arsenic recovery was only 40.83 %, which further confirmed that copper and arsenic could not be enriched synchronously. Mineral phase reconstruction was proposed as a potential scheme to enhance arsenic recovery. Arsenic was released from glassy silicates and combined with a copper-bearing phase to form copper–arsenic alloy during mineral phase reconstruction, which significantly increased arsenic recovery by 39.34 % and slightly increased copper recovery. The synchronous enrichment of copper and arsenic effectively reduces the total arsenic emission during copper pyrometallurgy, thereby alleviating the pressure of environmental pollution caused by CSS flotation tailings. This work provides a scientific reference for CSS processing toward recycling and harmlessness.

Laser-Induced Crystallization of Copper Oxide Thin Films: A Comparison between Gaussian and Chevron Beam Profiles.

The use of a laser with a Gaussian-beam profile is frequently adopted in attempts of crystallizing nonsingle-crystal thin films; however, it merely results in the formation of polycrystal thin films. In this paper, selective area crystallization of nonsingle-crystal copper(II) oxide (CuO) is described. The crystallization is induced by laser, laser-induced crystallization, with a beam profile in the shape of a chevron. The crystallization is verified by the exhibition of a transition from a nonsingle-crystal phase consisting of small (∼100 nm × 100 nm) grains of CuO to a single-crystal phase of copper(I) oxide (Cu2O). The transition is identified by electron back scattering diffraction and Raman spectroscopy, which clearly suggests that a single-crystal domain of Cu2O with a size as large as 5 μm × 1 mm develops. The transition may embrace several distinctive scenarios such as a large number of crystallites that densely form grow independently and merge, and simultaneously, solid-state growth that takes place as the merging proceeds reduce the number of grain boundaries and/or a small number of selected crystallites that sparsely form grow laterally, naturally limiting the number of grain boundaries. The volume fraction of the single-crystal domain prepared under the optimized conditions─the ratio of the volume of the single-crystal domain to that of the total volume within which energy carried by the laser is deposited─is estimated to be 32%. Provided these experimental findings, a theoretical assessment based on a cellular automaton model, with the behaviors of localized recrystallization and stochastic nucleation, is developed. The theoretical assessment can qualitatively describe the laser beam geometry-dependence of vital observable features (e.g., size and gross geometry of grains) in the laser-induced crystallization. The theoretical assessment predicts that differences in resulting crystallinity, either single-crystal or polycrystal, primarily depend on a geometrical profile with which melting of nonsingle-crystal regions takes place along the laser scan direction; concave-trailing profiles yield larger grains, which lead to a single crystal, while convex-trailing profiles result in smaller grains, which lead to a polycrystal, casting light on the fundamental question Why does a chevron-beam profile succeed in producing a single crystal while a Gaussian-beam profile fails?

Development of highly active Cu-based CO2 hydrogenation catalysts by solution combustion synthesis (SCS): Effects of synthesis variables

This work investigates the effects of solution combustion synthesis (SCS) variables on the performance of copper-based catalysts for CO2 hydrogenation to methanol. The catalyst with a composition of 30wt%CuO50%ZnO/Al2O3 was prepared at various glycine to nitrates (G/O) ratios in the range between 0.1 and 1.23. A correlation of the effects of calcination and activation temperatures with catalytic activity was also studied. The catalyst synthesized at a G/O ratio of 0.206, calcined in air at 400 °C and activated in a stream of pure hydrogen at a temperature of 350 °C resulted in a significant improvement in the performance of the catalyst for CO2 hydrogenation. The exceptionally high catalytic performance of the catalyst was attributed to the synergic effects between small well-dispersed CuO nanoparticles and high number of induced copper phases. The highest activity of the catalyst was recorded at an operating temperature of 300 °C, a pressure of 85 bar and GHSV of 7000 h−1. The CO2 conversion, CO selectivity and methanol selectivity under these conditions were 30%, 38.60%, and 61.4%, respectively; whereas, methanol and CO yields were 0.52gMeOH/g-cat.h and 0.33gCO/g-cat.h, respectively.

Residual elastic strain evolution due to thermal cycling of a ceramic-metal composite (WC-Cu) via high energy X-ray diffraction and analytical modeling

Residual stress, when superimposed with in-service loading, can significantly reduce the lifetime and performance of a component. Ceramic-metal composites are susceptible to residual stresses due to the thermal expansion mismatch of the ceramic and metallic phases. The WC-Cu composite explored in the present study provides a promising combination of thermal conductivity and strength properties, while exhibiting counterintuitive improvements in strength and ductility after thermal cycling. This work quantifies the evolution of the residual elastic strains as a result of processing and cyclic thermal loading in a co-continuous WC-Cu composite through experimental high energy X-ray diffraction and kinetics-based modeling. Both analyses indicate that processing-induced residual tensile stress in the copper phase is relieved upon subsequent thermal cycling, with kinetics modeling revealing the cyclic-dependent nature of the active power-law creep mechanisms. The results indicate that, through stress relaxation, this material system maintains structural stability during thermal cycling. The illustrated kinetics of relaxation can inform general material processors and designers of ceramic-metal composites to minimize detrimental residual stress and improve performance of these material systems.