Although the strengthening and grain refinement effects of TiB_(2) particles on aluminum alloys have been extensively studied,their influence on casting behavior remains relatively underexplored.In this study,the infl...Although the strengthening and grain refinement effects of TiB_(2) particles on aluminum alloys have been extensively studied,their influence on casting behavior remains relatively underexplored.In this study,the influence of different addition amounts of submicron TiB_(2) particles on the microstructure,casting performance,and mechanical properties of an Al-Cu(ZL205A)alloy was systematically investigated.The introduction of TiB_(2) particles leads to significant grain refinement,transforming the microstructure from coarse grains to fine equiaxed grains by providing additional nucleation sites and inhibiting grain growth.SEM and TEM analyses reveal that the added submicron TiB_(2) particles exhibit minimal effect on the distribution of intermetallic phases or precipitates.Casting performance,as evaluated by spiral fluidity and hot tearing tests,shows notable improvements with TiB_(2) additions.At a TiB_(2) content of 3wt.%,the fluidity length increases by 20%,and the hot tearing susceptibility coefficient decreases by 29%.These enhancements are mainly due to the refined grain structure and the formation of interdendritic bridging in TiB_(2)-reinforced alloys.However,the overall enahncement in casting properties shows little variation across the TiB_(2) additions from 0.2wt.% to 3wt.%.Mechanical testing shows that the highest hardness and strength are achieved with a 1wt.%addition of TiB_(2) particles,primarily attributed to refined grain size and reinforcement of the aluminum matrix.Based on these findings,a TiB_(2) particle content of 1wt.%is recommended for optimizing both the casting performance and mechanical properties of the ZL205A alloy.展开更多
Background:Diabetes,a metabolic disease marked by endocrine dysfunctions,significantly impacts oxidative stress pathways.This study explores the protective effects of lemongrass extract(LE),citral,and lemongrass extra...Background:Diabetes,a metabolic disease marked by endocrine dysfunctions,significantly impacts oxidative stress pathways.This study explores the protective effects of lemongrass extract(LE),citral,and lemongrass extract-synthesized silver nanoparticles(LE-AgNP)against hyperglycemia-induced oxidative stress by modulating the Nrf2 pathway,which is crucial for antioxidant responses.Methods:Various techniques characterized the nanoparticles,including ultraviolet–visible spectroscopy,dynamic light scattering,zeta potential analysis,Fouriertransform infrared spectroscopy,scanning electron microscopy and transmission electron microscopy.Seventy rats,divided into seven groups,were used for in vivo experiments.Type 2 diabetes was induced using streptozotocin(65 mg/kg)and nicotinamide(90 mg/kg).After six weeks,biochemical parameters such as total antioxidant capacity,malondialdehyde,Nrf2,and Nrf2 miRNA were evaluated in pancreas tissue and blood serum,along with serum blood glucose levels.Results:LE-AgNP significantly improved weight gain,reduced food and water intake,and lowered blood glucose levels in diabetic rats.LE and citral did not significantly alter these parameters but prevented the decline in Nrf2 gene expression.LE-AgNP showed a significant increase in Nrf2 gene expression compared to the diabetic control group.Conclusions:This study highlights the potential of LE,citral,and especially LE-AgNP in mitigating oxidative stress induced by diabetes.LE-AgNP demonstrated superior therapeutic benefits,including improved oxidative stress conditions and hypoglycemic effects.展开更多
Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interfac...Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interface anchoring,and inorganic particles have gained extensive attention recently owing to their large interfacial desorption energy,while their low affinity to bulk components is a drawback.In this study,an interfacial atom transfer radical polymerization(ATRP)technique was employed to grow polystyrene(PS)and poly(2-hydroxyethyl methacrylate)(PHEMA)simultaneously on different hemispheres of Br-functionalized SiO_(2) nanoparticles to stabilize a Pickering emulsion,whereby a brush-type Janus nanoparticle(SiO_(2)@JNP)was developed.The polymer brushes were well-characterized,and the Janus feature was validated by transmission electron microscope(TEM)observation of the sole hemisphere grafting of SiO_(2)-PS as a control sample.SiO_(2)@JNP was demonstrated to be an efficient compatibilizer for a PS/poly(methyl methacrylate)(PMMA)immiscible blend,and the droplet-matrix morphology was significantly refined.The mechanical strength and toughness of the blend were synchronously enhanced at a low content SiO_(2)@JNP optimized~0.9 wt%,with the tensile strength,elongation at break and impact strength increased by 17.7%,26.6%and 19.6%,respectively.This enhancement may be attributed to the entanglements between the grafted polymer brushes and individual components that improve the particle-bulk phase affinity and enforce interfacial adhesion.展开更多
In this study,a NbB_(2)/AZ91 composite exhibiting desirable mechanical properties was fabricated using a sample casting technique,followed by hard-plate rolling and short-term annealing.The effect of NbB_(2)particles ...In this study,a NbB_(2)/AZ91 composite exhibiting desirable mechanical properties was fabricated using a sample casting technique,followed by hard-plate rolling and short-term annealing.The effect of NbB_(2)particles on the microstructural evolution of the AZ91 alloy was investigated.The presence of NbB_(2)was shown to have a grain-refining effect on the AZ91 alloy and promoted dynamic recrystallization(DRX)and precipitation of fine Mg_(17)Al_(12)phases via particle-stimulated nucleation(PSN).Tensile testing revealed substantial enhancements in the ultimate tensile strength(UTS),yield strength(YS),and elongation(EL)of the as-rolled AZ91 alloy,with values of 379 MPa,292 MPa,and 14.7%,respectively,owing to the incorporation of NbB_(2)particles.Annealing led to further enhancements in EL with slight reductions in UTS and YS(360 MPa,252 MPa,and 16.8%,respectively).Owing to grain refinement and the PSN effect of the NbB_(2)particles,a significant number of geometrically necessary dislocations(GNDs)were induced in the matrix during the rolling process,which reduces the nucleation barrier and increases the number of nucleation sites for the recrystallized grains and Mg_(17)Al_(12)precipitates.Meanwhile,many residual dislocations and fine Mg_(17)Al_(12)precipitates in the as-rolled alloys were annihilated during annealing,resulting in slight grain growth and coarsening.The strengthening mechanism of the NbB_(2)/AZ91 composite are mainly associated with grain-refinement strengthening,particle-induced dislocation strengthening,strengthening resulting from mismatching coefficients of thermal expansion(CTE),and heterodeformation-induced(HDI)strengthening.Textural weakening,increased activation of non-basal slip systems,more-uniform strain patterns resulting from NbB_(2)particles,and precipitation are mainly responsible for enhancing ductility.展开更多
Ethanol steam reforming(ESR)represents a promising route for sustainable hydrogen production,leveraging the high hydrogen content,renewability,and logistical advantages of ethanol.Although Ni-based catalysts are leadi...Ethanol steam reforming(ESR)represents a promising route for sustainable hydrogen production,leveraging the high hydrogen content,renewability,and logistical advantages of ethanol.Although Ni-based catalysts are leading non-noble candidates for ESR,their practical deployment is hindered by compromised H_(2) production efficiency and rapid deactivation.In this work,we combined catalyst synthesis,kinetic analysis,and mechanistic investigation to elucidate the effectsof Ni particle size(3-9 nm)on ESR performance of Ni/CeO_(2) catalysts.These Ni/CeO_(2) catalysts were prepared via a citric acid-assisted coprecipitation method,and systematically characterized using complementary techniques,including high-resolution transmission electron microscopy(HRTEM),in situ X-ray photoelectron spectroscopy(XPS),hydrogen temperature-programmed reduction(H_(2)-TPR),Raman spectroscopy,O_(2)/CO chemisorption,and temperature-programmed surface reaction(TPSR)analyses.Mechanistic study revealed that ethanol dehydrogenation to acetaldehyde is the rate-determining step,defining the intrinsic activity of Ni sites,whereas C-C bond cleavage governs H_(2) selectivity in ESR.At smaller Ni sizes(e.g.,3.1 nm),larger CeO_(2) surface was exposed,which promoted acetaldehyde condensation to acetone,and consequently reduced H_(2) production efficiency.The Ni/CeO_(2) catalyst with~5 nm of Ni particles afforded the highest H_(2) yield(66.3%)and outstanding stability by balancing dehydrogenation activity,H_(2) selectivity,and coking resistance.Conversely,larger Ni particles(>6 nm)facilitated methanation reaction and catalyst deactivation.This work reconciles prior inconsistencies in the Ni size effects on ESR and provides guidance for the design of efficient and durable Ni-based catalysts for H_(2) production.展开更多
The instantaneous desulfurization of CaO-Al_(2)O_(3)-SiO_(2)slag particles in the molten steel was in situ observed using a high-temperature confocal scanning laser microscope.The desulfurization effect of CaO-Al_(2)O...The instantaneous desulfurization of CaO-Al_(2)O_(3)-SiO_(2)slag particles in the molten steel was in situ observed using a high-temperature confocal scanning laser microscope.The desulfurization effect of CaO-Al_(2)O_(3)-SiO_(2)slags with different compositions was discussed.The influence of CaO/Al_(2)O_(3)and CaO/SiO_(2)on the desulfurization effect was analyzed.It was shown that in the liquid phase range,the higher CaO/SiO_(2)and CaO/Al_(2)O_(3)can significantly improve the desulfurization effect of the slag.A dimensionless desulfurization index Sindex was introduced to evaluate the desulfurization ability of CaO-Al_(2)O_(3)-SiO_(2)slags quantitatively.The Sindex values of CaO-Al_(2)O_(3)-SiO_(2)with different compositions at 1550°C were calculated.It was suggested to use(65%-75%)CaO-(0-20%)SiO_(2)-(20%-40%)Al_(2)O_(3)slags to improve the molten steel desulfurization.展开更多
We employed Monte Carlo simulations via Geant4 to model the interactions of^(60)Co gamma rays(1.25 MeV),electrons(0.1-10 MeV),and protons(0.5-10 MeV)with Ta_(2)O_(5)optical coatings.By analyzing secondary electron gen...We employed Monte Carlo simulations via Geant4 to model the interactions of^(60)Co gamma rays(1.25 MeV),electrons(0.1-10 MeV),and protons(0.5-10 MeV)with Ta_(2)O_(5)optical coatings.By analyzing secondary electron generation and energy deposition,we found that 1.0 MeV electrons and protons produce 67.5 and 67 secondary electrons per particle,respectively,compared to 116 from 1.25 MeV gamma rays in thick targets.Boltzmann-function fitting revealed depth-dependent ionization equivalence:0.582 gamma photons match the secondary electron yield of a 1.0 MeV electron,and 0.577 gamma photons match a 1.0 MeV proton.These results establish a framework to convert ground-based gamma-ray test data to space environment scenarios,accounting for critical differences in penetration depth-protons deposit energy within 10μm(coating layers),while gamma rays penetrate>100 mm into substrates.This provides a theoretical basis for evaluating radiation effects using existing^(60)Co facilities,enabling reliable predictions of optical component durability in complex space environments.展开更多
Silicon(Si)is an inevitable impurity element in the AZ31 alloy.In this study,the Si impurity was detected mainly as fine Mg_(2)Si particles dispersed widely within the central region of the Mg_(17)Al_(12) phase.During...Silicon(Si)is an inevitable impurity element in the AZ31 alloy.In this study,the Si impurity was detected mainly as fine Mg_(2)Si particles dispersed widely within the central region of the Mg_(17)Al_(12) phase.During the solidification process,the Mg_(2)Si particle precipitates at about 565℃,before the Mg_(17)Al_(12) phase of 186℃,potentially acting as the heterogeneous nucleation core for the Mg_(17)Al_(12) phase.The orientation relationship between Mg_(2)Si and Mg_(17)Al_(12) was investigated using the Edge-to-Edge matching model(E2EM)calculations,which showed a misfit of only 0.1%.This low misfit suggests that Mg_(2)Si can serve as a heterogeneous nucleation site for Mg_(17)Al_(12).The surface and interface structures of Mg_(2)Si(220)and Mg_(17)Al_(12)(332)were constructed,and then investigated through the first-principles calculation.The theoretical results indicate that Mg and Al are easily adsorbed on the surface of Mg_(2)Si,with Al showing higher adsorption energy than Mg.Furthermore,the interface between Mg_(2)Si and Mg_(17)Al_(12) exhibits favorable thermodynamic stability.Combined with experiments and theoretical calculations,it is confirmed that the Mg_(2)Si particles,formed due to the Si impurity,provide effective heterogeneous nucleation sites for the Mg_(17)Al_(12) phase.展开更多
The chemistry of sulfur cycle contributes significantly to the atmospheric nucleation process,which is the first step of new particle formation(NPF).In the present study,cycloaddition reaction mechanism of sulfur trio...The chemistry of sulfur cycle contributes significantly to the atmospheric nucleation process,which is the first step of new particle formation(NPF).In the present study,cycloaddition reaction mechanism of sulfur trioxide(SO_(3))to hydrogen sulfide(H_(2)S)which is a typical air pollutant and toxic gas detrimental to the environment were comprehensively investigate through theoretical calculations and Atmospheric Cluster Dynamic Code simulations.Gas-phase stability and nucleation potential of the product thiosulfuric acid(H_(2)S_(2)O_(3),TSA)were further analyzed to evaluate its atmospheric impact.Without any catalysts,the H_(2)S+SO_(3)reaction is infeasible with a barrier of 24.2 kcal/mol.Atmospheric nucleation precursors formic acid(FA),sulfuric acid(SA),and water(H_(2)O)could effectively lower the reaction barriers as catalysts,even to a barrierless reaction with the efficiency of cis-SA>trans-FA>trans-SA>H_(2)O.Subsequently,the gas-phase stability of TSA was investigated.A hydrolysis reaction barrier of up to 61.4 kcal/mol alone with an endothermic isomerization reaction barrier of 5.1 kcal/mol under the catalytic effect of SA demonstrates the sufficient stability of TSA.Furthermore,topological and kinetic analysis were conducted to determine the nucleation potential of TSA.Atmospheric clusters formed by TSA and atmospheric nucleation precursors(SA,ammonia NH_(3),and dimethylamine DMA)were thermodynamically stable.Moreover,the gradually decreasing evaporation coefficients for TSA-base clusters,particularly for TSA-DMA,suggests that TSA may participate in NPF where the concentration of base molecules are relatively higher.The present new reaction mechanismmay contributes to a better understanding of atmospheric sulfur cycle and NPF.展开更多
Nano-sized titanium dioxide （nano-TiO2） has wide industrial applications and therefore considerable chances of exposure are created for human beings and ecosystems. To better understand the interactions between nano...Nano-sized titanium dioxide （nano-TiO2） has wide industrial applications and therefore considerable chances of exposure are created for human beings and ecosystems. To better understand the interactions between nano-TiO2 and aquatic organisms, we first studied TiO2 uptake by algae exemplified by Pseudokirchneriella subcapitata. P. subcapitata were exposed to nano-TiO2 in a series of concentrations and at various pH. TiO2 uptake was quantified using a sedimentation curve analysis technique. After exposure of algae to TiO2, the variation of zeta potential was measured and the morphology of algae-TiO2 aggregate was observed with scanning electron microscopy and the optical microscopy. The steady-state TiO2 uptake was found to be pH-dependent and the isotherms can be described well by Freundlich model. TiO2 deposited on algal surfaces causes the shift of pHzpc of TiO2-covered algae from that of algae toward that of TiO2. The attraction between TiO2-covered algal cells induces the agglomeration of algae and TiO2 and thus the formation of algae-TiO2 aggregates in the size of 12 to 50 μm. The 2-D fractal dimension of the aggregates is pH- dependent and ranges from 1.31 to 1.67. The theoretical analysis of the Gibbs energy of interaction indicates that both TiO2 uptake by algae and the formation of algae-TiO2 aggregate are influenced by the interaction between TiO2 particles.展开更多
To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag?4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallur...To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag?4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallurgy. The microstructure of Ag?4%SnO2 contact materials was characterized, and the relative density, hardness and electrical conductivity were measured. The arc erosion of Ag?4%SnO2 contact materials was tested, the arc duration and mass loss before and after arc erosion were determined, the surface morphologies and compositions of Ag?4%SnO2 contact materials after arc erosion were characterized, and the arc erosion mechanism of AgSnO2 contact materials was discussed. The results show that fine SnO2 particle is beneficial for the improvement of the relative density and hardness, but decreases the electrical conductivity. With the decrease of SnO2 particle size, Ag?4%SnO2contact material presents shorter arc duration, less mass loss, larger erosion area and shallower arc erosion pits.展开更多
The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and trib...The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and tribological properties of the composite coatings were researched. The results show that the composite coatings mainly consist of γ-Ni, α-Al2O3, γ-Al2O3 and rutile-TiO2 etc, and exhibit lower friction coefficients and wear losses than the Ni-based alloy coatings at different loads and speeds. The composite coating bears low contact stress at 3 N and its wear mechanism is micro-cutting wear. As loads increase to 6-12 N, the contact stress is higher than the elastic limit stress of worn surface, and the wear mechanisms change into multi-plastic deformation wear, micro-brittle fracture wear and abrasive wear. With the increase of speeds, the contact temperature of worn surface increases. The composite coating experiences multi-plastic deformation wear, fatigue wear and adhesive wear.展开更多
The surface of Titanium Hydride (TiH 2) is coated by Nano Titanium Dioxide (TiO 2) particles prepared in both of methods of hydrolysis reaction of Ti(OC 4H 9) 4 and base precipitation reaction of Ti(SO 4) 2. ...The surface of Titanium Hydride (TiH 2) is coated by Nano Titanium Dioxide (TiO 2) particles prepared in both of methods of hydrolysis reaction of Ti(OC 4H 9) 4 and base precipitation reaction of Ti(SO 4) 2. TiH 2 coated with nano TiO 2 particles, in which there is an oxidation film on its surface, shown in the experiments, will obviously achieve good effects on releasing hydrogen slowly in high temperature. There are different structures and properties of TiH 2 coated by nano TiO 2 particles prepared in different ways in high temperature, which can influence on releasing hydrogen.展开更多
SnO2 nano particles with various Pd-doping concentrations were prepared using a template-free hydrothermal method.The effects of Pd doping on the crystal structure,morphology,microstructure,thermal stability and surfa...SnO2 nano particles with various Pd-doping concentrations were prepared using a template-free hydrothermal method.The effects of Pd doping on the crystal structure,morphology,microstructure,thermal stability and surface chemistry of these nano particles were characterized by transmission electron microscope,X-ray diffractometer and X-ray photoelectron spectroscope respectively.It was observed that Pd-doping had little effect on the grain sizes of the obtained SnO2 nano particles during the hydrothermal route.During thermal annealing,Pd-doping could restrain the growth of grain sizes below 500℃ while the grain growth was promoted when the temperature increased to above 700℃.XPS results revealed that Pd existed in three chemical states in the as-synthesized sample as Pd^0,Pd^2＋ and Pd^4＋,respectively.Pd^4＋ was the main state which was responsible for improving the gas-sensing property.The optimal Pd-doping concentration for better gas-sensing property and thermal stability was 2.0%-2.5% （mole fraction）.展开更多
Al2O3p-Al composites were synthesized using an in-situ reaction in the 80%Al-20%CuO （mass fraction） system. The effects of the CuO particle size on the synthesis temperature and microstructure of the composites were...Al2O3p-Al composites were synthesized using an in-situ reaction in the 80%Al-20%CuO （mass fraction） system. The effects of the CuO particle size on the synthesis temperature and microstructure of the composites were investigated by various methods. The results indicate that the CuO particle size has a significant effect on the temperature at which the complete reaction in the Al-CuO system occurs：the temperature is 200 ℃ lower in the Al-CuO system containing CuO particles with sizes less than 6μm than that containing CuO particles with sizes less than 100μm. The interfacial bonding between Al2O3 particles and Al is not complete when the temperature is below a critical value. The morphology of the Al2O3 particles varies from ribbon-like shape to near spherical shape when the temperature is above a critical value. These two critical temperatures are affected by the particle size of CuO, and the critical temperature of the sample containing CuO particles with sizes less than 6μm is 100 ℃ lower than that of the sample containing CuO particles with sizes less than 100μm.展开更多
Wedge-shaped copper casting experiment was conducted to study the engulfment behavior of TiB2 particle and the interaction between particle or cluster and the solid/liquid front in commercial pure aluminum matrix. The...Wedge-shaped copper casting experiment was conducted to study the engulfment behavior of TiB2 particle and the interaction between particle or cluster and the solid/liquid front in commercial pure aluminum matrix. The experimental results show that the particle size distribution obeys two separate systems in the whole wedge-cast sample. Furthermore, it is found that the big clusters are pushed to the center of the wedge shaped sample and the single particle or small clusters consisting of few particles are engulfed into the α-Al in the area of the sample edge. The cluster degree of particles varies in different areas, and its value is 0.2 and 0.6 for the cluster fraction in the edge and in the center of the wedge sample, respectively. The cluster diameter does not obey the normal distribution but approximately obeys lognormal distribution in the present work. More importantly, in the whole sample, the particle size obeys two separate log-normal distributions.展开更多
The hot forming behavior,failure mechanism,and microstructure evolution of in-situ TiB_(2)particle-reinforced 7075 aluminum matrix composite were investigated by isothermal compression test under different deformation...The hot forming behavior,failure mechanism,and microstructure evolution of in-situ TiB_(2)particle-reinforced 7075 aluminum matrix composite were investigated by isothermal compression test under different deformation conditions of deformation temperatures of 300−450℃ and strain rates of 0.001^(−1)s^(−1).The results demonstrate that the failure behavior of the composite exhibits both particle fracture and interface debonding at low temperature and high strain rate,and dimple rupture of the matrix at high temperature and low strain rate.Full dynamic recrystallization,which improves the composite formability,occurs under conditions of high temperature(450℃)and low strain rate(0.001 s^(−1));the grain size of the matrix after hot compression was significantly smaller than that of traditional 7075Al and ex-situ particle reinforced 7075Al matrix composite.Based on the flow stress curves,a constitutive model describing the relationship of the flow stress,true strain,strain rate and temperature was proposed.Furthermore,the processing maps based on both the dynamic material modeling(DMM)and modified DMM(MDMM)were established to analyze flow instability domain of the composite and optimize hot forming processing parameters.The optimum processing domain was determined at temperatures of 425−450℃ and strain rates of 0.001−0.01 s^(−1),in which the fine grain microstructure can be gained and particle crack and interface debonding can be avoided.展开更多
Two kinds of Al based functionally gradient composite tubes reinforced by primary Si particles alone and primary Si/in situ Mg2Si particles jointly were successfully prepared by centrifugal casting,and their structura...Two kinds of Al based functionally gradient composite tubes reinforced by primary Si particles alone and primary Si/in situ Mg2Si particles jointly were successfully prepared by centrifugal casting,and their structural and mechanical characters were compared.It is found that the composite reinforced with primary Si particles takes a characteristic of particles distribution both in the inner and outer layers.However,composite reinforced with primary Si/Mg2Si particles jointly takes a characteristic of particles distribution only in the inner layer and shows a sudden change of particles distribution across the section of inner and outer layers.The hardness and wear resistance of Al-19Si-5Mg tube in the inner layer are greatly higher than that in the other layers of Al-19Si-5Mg tube and Al-19Si tube.Theoretical analysis reveals that the existence of Mg2Si particles is the key factor to form this sudden change of gradient distribution of two kinds of particles.Because Mg2Si particles with a lower density have a higher centripetal moving velocity than primary Si particles,in a field of centrifugal force,they would collide with primary Si particles and then impel the later to move together forward to the inner layer of the tube.展开更多
The coarsening behavior of(Ni,Co)2Si particles in Cu-Ni-Co-Si alloy was investigated by experimental observations and coarsening kinetics calculations when aged at 450,500,550 and 600℃ for different durations.The res...The coarsening behavior of(Ni,Co)2Si particles in Cu-Ni-Co-Si alloy was investigated by experimental observations and coarsening kinetics calculations when aged at 450,500,550 and 600℃ for different durations.The results show that the critical particle radius for coherence mismatch is found to be 10.3 nm,and particles larger than 25 nm are generally semi-coherent.The relationship of(Ni,Co)2Si particles size and aging time follows Lifshitz,Slyosov and Wagner(LSW) theory.The particle size distributions fit well to the LSW theoretical distribution.The activation energy for(Ni,Co)2Si coarsening is accurately determined to be(216.21 ± 5.18)kJ mol-1 when considering the effect of temperature on the solution concentrations in matrix.The coarsening of(Ni,Co)2Si particles in Cu-Ni-Co-Si alloy is controlled by diffusion of Ni,Co and Si in Cu matrix.The growth of particles for long durations suggests that vacancies can be trapped within the structure for long time despite their mobility.展开更多
文摘Although the strengthening and grain refinement effects of TiB_(2) particles on aluminum alloys have been extensively studied,their influence on casting behavior remains relatively underexplored.In this study,the influence of different addition amounts of submicron TiB_(2) particles on the microstructure,casting performance,and mechanical properties of an Al-Cu(ZL205A)alloy was systematically investigated.The introduction of TiB_(2) particles leads to significant grain refinement,transforming the microstructure from coarse grains to fine equiaxed grains by providing additional nucleation sites and inhibiting grain growth.SEM and TEM analyses reveal that the added submicron TiB_(2) particles exhibit minimal effect on the distribution of intermetallic phases or precipitates.Casting performance,as evaluated by spiral fluidity and hot tearing tests,shows notable improvements with TiB_(2) additions.At a TiB_(2) content of 3wt.%,the fluidity length increases by 20%,and the hot tearing susceptibility coefficient decreases by 29%.These enhancements are mainly due to the refined grain structure and the formation of interdendritic bridging in TiB_(2)-reinforced alloys.However,the overall enahncement in casting properties shows little variation across the TiB_(2) additions from 0.2wt.% to 3wt.%.Mechanical testing shows that the highest hardness and strength are achieved with a 1wt.%addition of TiB_(2) particles,primarily attributed to refined grain size and reinforcement of the aluminum matrix.Based on these findings,a TiB_(2) particle content of 1wt.%is recommended for optimizing both the casting performance and mechanical properties of the ZL205A alloy.
文摘Background:Diabetes,a metabolic disease marked by endocrine dysfunctions,significantly impacts oxidative stress pathways.This study explores the protective effects of lemongrass extract(LE),citral,and lemongrass extract-synthesized silver nanoparticles(LE-AgNP)against hyperglycemia-induced oxidative stress by modulating the Nrf2 pathway,which is crucial for antioxidant responses.Methods:Various techniques characterized the nanoparticles,including ultraviolet–visible spectroscopy,dynamic light scattering,zeta potential analysis,Fouriertransform infrared spectroscopy,scanning electron microscopy and transmission electron microscopy.Seventy rats,divided into seven groups,were used for in vivo experiments.Type 2 diabetes was induced using streptozotocin(65 mg/kg)and nicotinamide(90 mg/kg).After six weeks,biochemical parameters such as total antioxidant capacity,malondialdehyde,Nrf2,and Nrf2 miRNA were evaluated in pancreas tissue and blood serum,along with serum blood glucose levels.Results:LE-AgNP significantly improved weight gain,reduced food and water intake,and lowered blood glucose levels in diabetic rats.LE and citral did not significantly alter these parameters but prevented the decline in Nrf2 gene expression.LE-AgNP showed a significant increase in Nrf2 gene expression compared to the diabetic control group.Conclusions:This study highlights the potential of LE,citral,and especially LE-AgNP in mitigating oxidative stress induced by diabetes.LE-AgNP demonstrated superior therapeutic benefits,including improved oxidative stress conditions and hypoglycemic effects.
基金financially supported by the National Natural Science Foundation of China(Nos.22172028,21903015,and 22403017)Natural Science Foundation of Fujian Province of China(No.2022J05041)。
文摘Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interface anchoring,and inorganic particles have gained extensive attention recently owing to their large interfacial desorption energy,while their low affinity to bulk components is a drawback.In this study,an interfacial atom transfer radical polymerization(ATRP)technique was employed to grow polystyrene(PS)and poly(2-hydroxyethyl methacrylate)(PHEMA)simultaneously on different hemispheres of Br-functionalized SiO_(2) nanoparticles to stabilize a Pickering emulsion,whereby a brush-type Janus nanoparticle(SiO_(2)@JNP)was developed.The polymer brushes were well-characterized,and the Janus feature was validated by transmission electron microscope(TEM)observation of the sole hemisphere grafting of SiO_(2)-PS as a control sample.SiO_(2)@JNP was demonstrated to be an efficient compatibilizer for a PS/poly(methyl methacrylate)(PMMA)immiscible blend,and the droplet-matrix morphology was significantly refined.The mechanical strength and toughness of the blend were synchronously enhanced at a low content SiO_(2)@JNP optimized~0.9 wt%,with the tensile strength,elongation at break and impact strength increased by 17.7%,26.6%and 19.6%,respectively.This enhancement may be attributed to the entanglements between the grafted polymer brushes and individual components that improve the particle-bulk phase affinity and enforce interfacial adhesion.
基金supported by the National Natural Science Foundation of China[52171030]the National Key Research and Development Program of China[2018YFA0702903]。
文摘In this study,a NbB_(2)/AZ91 composite exhibiting desirable mechanical properties was fabricated using a sample casting technique,followed by hard-plate rolling and short-term annealing.The effect of NbB_(2)particles on the microstructural evolution of the AZ91 alloy was investigated.The presence of NbB_(2)was shown to have a grain-refining effect on the AZ91 alloy and promoted dynamic recrystallization(DRX)and precipitation of fine Mg_(17)Al_(12)phases via particle-stimulated nucleation(PSN).Tensile testing revealed substantial enhancements in the ultimate tensile strength(UTS),yield strength(YS),and elongation(EL)of the as-rolled AZ91 alloy,with values of 379 MPa,292 MPa,and 14.7%,respectively,owing to the incorporation of NbB_(2)particles.Annealing led to further enhancements in EL with slight reductions in UTS and YS(360 MPa,252 MPa,and 16.8%,respectively).Owing to grain refinement and the PSN effect of the NbB_(2)particles,a significant number of geometrically necessary dislocations(GNDs)were induced in the matrix during the rolling process,which reduces the nucleation barrier and increases the number of nucleation sites for the recrystallized grains and Mg_(17)Al_(12)precipitates.Meanwhile,many residual dislocations and fine Mg_(17)Al_(12)precipitates in the as-rolled alloys were annihilated during annealing,resulting in slight grain growth and coarsening.The strengthening mechanism of the NbB_(2)/AZ91 composite are mainly associated with grain-refinement strengthening,particle-induced dislocation strengthening,strengthening resulting from mismatching coefficients of thermal expansion(CTE),and heterodeformation-induced(HDI)strengthening.Textural weakening,increased activation of non-basal slip systems,more-uniform strain patterns resulting from NbB_(2)particles,and precipitation are mainly responsible for enhancing ductility.
基金supported by the National Key Research and Develop-ment Pr0gram of China(Nos.2021YFA1501104 and 2023YFA1506802)the National Natural Science Foundation of China(No.22032001).
文摘Ethanol steam reforming(ESR)represents a promising route for sustainable hydrogen production,leveraging the high hydrogen content,renewability,and logistical advantages of ethanol.Although Ni-based catalysts are leading non-noble candidates for ESR,their practical deployment is hindered by compromised H_(2) production efficiency and rapid deactivation.In this work,we combined catalyst synthesis,kinetic analysis,and mechanistic investigation to elucidate the effectsof Ni particle size(3-9 nm)on ESR performance of Ni/CeO_(2) catalysts.These Ni/CeO_(2) catalysts were prepared via a citric acid-assisted coprecipitation method,and systematically characterized using complementary techniques,including high-resolution transmission electron microscopy(HRTEM),in situ X-ray photoelectron spectroscopy(XPS),hydrogen temperature-programmed reduction(H_(2)-TPR),Raman spectroscopy,O_(2)/CO chemisorption,and temperature-programmed surface reaction(TPSR)analyses.Mechanistic study revealed that ethanol dehydrogenation to acetaldehyde is the rate-determining step,defining the intrinsic activity of Ni sites,whereas C-C bond cleavage governs H_(2) selectivity in ESR.At smaller Ni sizes(e.g.,3.1 nm),larger CeO_(2) surface was exposed,which promoted acetaldehyde condensation to acetone,and consequently reduced H_(2) production efficiency.The Ni/CeO_(2) catalyst with~5 nm of Ni particles afforded the highest H_(2) yield(66.3%)and outstanding stability by balancing dehydrogenation activity,H_(2) selectivity,and coking resistance.Conversely,larger Ni particles(>6 nm)facilitated methanation reaction and catalyst deactivation.This work reconciles prior inconsistencies in the Ni size effects on ESR and provides guidance for the design of efficient and durable Ni-based catalysts for H_(2) production.
基金support from the National Key R&D Program(No.2023YFB3709901)the National Natural Science Foundation of China(Grant No.U22A20171)China Baowu Low Carbon Metallurgy Innovation Foundation(BWLCF202315).
文摘The instantaneous desulfurization of CaO-Al_(2)O_(3)-SiO_(2)slag particles in the molten steel was in situ observed using a high-temperature confocal scanning laser microscope.The desulfurization effect of CaO-Al_(2)O_(3)-SiO_(2)slags with different compositions was discussed.The influence of CaO/Al_(2)O_(3)and CaO/SiO_(2)on the desulfurization effect was analyzed.It was shown that in the liquid phase range,the higher CaO/SiO_(2)and CaO/Al_(2)O_(3)can significantly improve the desulfurization effect of the slag.A dimensionless desulfurization index Sindex was introduced to evaluate the desulfurization ability of CaO-Al_(2)O_(3)-SiO_(2)slags quantitatively.The Sindex values of CaO-Al_(2)O_(3)-SiO_(2)with different compositions at 1550°C were calculated.It was suggested to use(65%-75%)CaO-(0-20%)SiO_(2)-(20%-40%)Al_(2)O_(3)slags to improve the molten steel desulfurization.
基金Funded by the Zibo Key Research and Development Project(No.2020XCCG0106)the Zibo Key Research and Development Project(No.2021SNPT0004)the Opening Project of Glass-based Functional Material Technology Innovation Center(No.GFMTIC2025C01)。
文摘We employed Monte Carlo simulations via Geant4 to model the interactions of^(60)Co gamma rays(1.25 MeV),electrons(0.1-10 MeV),and protons(0.5-10 MeV)with Ta_(2)O_(5)optical coatings.By analyzing secondary electron generation and energy deposition,we found that 1.0 MeV electrons and protons produce 67.5 and 67 secondary electrons per particle,respectively,compared to 116 from 1.25 MeV gamma rays in thick targets.Boltzmann-function fitting revealed depth-dependent ionization equivalence:0.582 gamma photons match the secondary electron yield of a 1.0 MeV electron,and 0.577 gamma photons match a 1.0 MeV proton.These results establish a framework to convert ground-based gamma-ray test data to space environment scenarios,accounting for critical differences in penetration depth-protons deposit energy within 10μm(coating layers),while gamma rays penetrate>100 mm into substrates.This provides a theoretical basis for evaluating radiation effects using existing^(60)Co facilities,enabling reliable predictions of optical component durability in complex space environments.
基金supported by the National Natural Science Foundation of China(Nos.51871100 and 12074126).
文摘Silicon(Si)is an inevitable impurity element in the AZ31 alloy.In this study,the Si impurity was detected mainly as fine Mg_(2)Si particles dispersed widely within the central region of the Mg_(17)Al_(12) phase.During the solidification process,the Mg_(2)Si particle precipitates at about 565℃,before the Mg_(17)Al_(12) phase of 186℃,potentially acting as the heterogeneous nucleation core for the Mg_(17)Al_(12) phase.The orientation relationship between Mg_(2)Si and Mg_(17)Al_(12) was investigated using the Edge-to-Edge matching model(E2EM)calculations,which showed a misfit of only 0.1%.This low misfit suggests that Mg_(2)Si can serve as a heterogeneous nucleation site for Mg_(17)Al_(12).The surface and interface structures of Mg_(2)Si(220)and Mg_(17)Al_(12)(332)were constructed,and then investigated through the first-principles calculation.The theoretical results indicate that Mg and Al are easily adsorbed on the surface of Mg_(2)Si,with Al showing higher adsorption energy than Mg.Furthermore,the interface between Mg_(2)Si and Mg_(17)Al_(12) exhibits favorable thermodynamic stability.Combined with experiments and theoretical calculations,it is confirmed that the Mg_(2)Si particles,formed due to the Si impurity,provide effective heterogeneous nucleation sites for the Mg_(17)Al_(12) phase.
基金supported by the Budget Surplus of Central Financial Science and Technology Plan (No.2021-JY-14)the Project funded by China Postdoctoral Science Foundation (No.2020M680636)+3 种基金the Fundamental Research Funds for Central Public Welfare Scientific Research Institutes of China,Chinese Research Academy of Environmental Sciences (Nos.2022YSKY-21 and 2022YSKY-27)the National Natural Science Foundation of China (No.41375133)the Science Foundation of Chinese Research Academy of Environmental Sciences (No.JY-41375133)Tian He Qingsuo Project-special fund project.
文摘The chemistry of sulfur cycle contributes significantly to the atmospheric nucleation process,which is the first step of new particle formation(NPF).In the present study,cycloaddition reaction mechanism of sulfur trioxide(SO_(3))to hydrogen sulfide(H_(2)S)which is a typical air pollutant and toxic gas detrimental to the environment were comprehensively investigate through theoretical calculations and Atmospheric Cluster Dynamic Code simulations.Gas-phase stability and nucleation potential of the product thiosulfuric acid(H_(2)S_(2)O_(3),TSA)were further analyzed to evaluate its atmospheric impact.Without any catalysts,the H_(2)S+SO_(3)reaction is infeasible with a barrier of 24.2 kcal/mol.Atmospheric nucleation precursors formic acid(FA),sulfuric acid(SA),and water(H_(2)O)could effectively lower the reaction barriers as catalysts,even to a barrierless reaction with the efficiency of cis-SA>trans-FA>trans-SA>H_(2)O.Subsequently,the gas-phase stability of TSA was investigated.A hydrolysis reaction barrier of up to 61.4 kcal/mol alone with an endothermic isomerization reaction barrier of 5.1 kcal/mol under the catalytic effect of SA demonstrates the sufficient stability of TSA.Furthermore,topological and kinetic analysis were conducted to determine the nucleation potential of TSA.Atmospheric clusters formed by TSA and atmospheric nucleation precursors(SA,ammonia NH_(3),and dimethylamine DMA)were thermodynamically stable.Moreover,the gradually decreasing evaporation coefficients for TSA-base clusters,particularly for TSA-DMA,suggests that TSA may participate in NPF where the concentration of base molecules are relatively higher.The present new reaction mechanismmay contributes to a better understanding of atmospheric sulfur cycle and NPF.
文摘Nano-sized titanium dioxide （nano-TiO2） has wide industrial applications and therefore considerable chances of exposure are created for human beings and ecosystems. To better understand the interactions between nano-TiO2 and aquatic organisms, we first studied TiO2 uptake by algae exemplified by Pseudokirchneriella subcapitata. P. subcapitata were exposed to nano-TiO2 in a series of concentrations and at various pH. TiO2 uptake was quantified using a sedimentation curve analysis technique. After exposure of algae to TiO2, the variation of zeta potential was measured and the morphology of algae-TiO2 aggregate was observed with scanning electron microscopy and the optical microscopy. The steady-state TiO2 uptake was found to be pH-dependent and the isotherms can be described well by Freundlich model. TiO2 deposited on algal surfaces causes the shift of pHzpc of TiO2-covered algae from that of algae toward that of TiO2. The attraction between TiO2-covered algal cells induces the agglomeration of algae and TiO2 and thus the formation of algae-TiO2 aggregates in the size of 12 to 50 μm. The 2-D fractal dimension of the aggregates is pH- dependent and ranges from 1.31 to 1.67. The theoretical analysis of the Gibbs energy of interaction indicates that both TiO2 uptake by algae and the formation of algae-TiO2 aggregate are influenced by the interaction between TiO2 particles.
基金Project(51274163)supported by the National Natural Science Foundation of ChinaProject(13JS076)supported by the Key Laboratory Research Program of Shaanxi Province,China+1 种基金Project(2012KCT-25)supported by the Pivot Innovation Team of Shaanxi Electrical Materials and Infiltration Technique,ChinaProject(2011HBSZS009)supported by the Special Foundation of Key Disciplines,China
文摘To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag?4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallurgy. The microstructure of Ag?4%SnO2 contact materials was characterized, and the relative density, hardness and electrical conductivity were measured. The arc erosion of Ag?4%SnO2 contact materials was tested, the arc duration and mass loss before and after arc erosion were determined, the surface morphologies and compositions of Ag?4%SnO2 contact materials after arc erosion were characterized, and the arc erosion mechanism of AgSnO2 contact materials was discussed. The results show that fine SnO2 particle is beneficial for the improvement of the relative density and hardness, but decreases the electrical conductivity. With the decrease of SnO2 particle size, Ag?4%SnO2contact material presents shorter arc duration, less mass loss, larger erosion area and shallower arc erosion pits.
文摘The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and tribological properties of the composite coatings were researched. The results show that the composite coatings mainly consist of γ-Ni, α-Al2O3, γ-Al2O3 and rutile-TiO2 etc, and exhibit lower friction coefficients and wear losses than the Ni-based alloy coatings at different loads and speeds. The composite coating bears low contact stress at 3 N and its wear mechanism is micro-cutting wear. As loads increase to 6-12 N, the contact stress is higher than the elastic limit stress of worn surface, and the wear mechanisms change into multi-plastic deformation wear, micro-brittle fracture wear and abrasive wear. With the increase of speeds, the contact temperature of worn surface increases. The composite coating experiences multi-plastic deformation wear, fatigue wear and adhesive wear.
文摘The surface of Titanium Hydride (TiH 2) is coated by Nano Titanium Dioxide (TiO 2) particles prepared in both of methods of hydrolysis reaction of Ti(OC 4H 9) 4 and base precipitation reaction of Ti(SO 4) 2. TiH 2 coated with nano TiO 2 particles, in which there is an oxidation film on its surface, shown in the experiments, will obviously achieve good effects on releasing hydrogen slowly in high temperature. There are different structures and properties of TiH 2 coated by nano TiO 2 particles prepared in different ways in high temperature, which can influence on releasing hydrogen.
基金Projects(60806032,20975107) supported by the National Natural Science Foundation of ChinaProject(2009R10064) supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars of Education Ministry,China+2 种基金 Project(2009R10064) supported by "Qianjiang Talent Program"Projects(2009A610058,2009A610030) supported by the Ningbo Natural Science Foundation,ChinaProject supported by K.C.WONG Magna Fund in Ningbo University,China
文摘SnO2 nano particles with various Pd-doping concentrations were prepared using a template-free hydrothermal method.The effects of Pd doping on the crystal structure,morphology,microstructure,thermal stability and surface chemistry of these nano particles were characterized by transmission electron microscope,X-ray diffractometer and X-ray photoelectron spectroscope respectively.It was observed that Pd-doping had little effect on the grain sizes of the obtained SnO2 nano particles during the hydrothermal route.During thermal annealing,Pd-doping could restrain the growth of grain sizes below 500℃ while the grain growth was promoted when the temperature increased to above 700℃.XPS results revealed that Pd existed in three chemical states in the as-synthesized sample as Pd^0,Pd^2＋ and Pd^4＋,respectively.Pd^4＋ was the main state which was responsible for improving the gas-sensing property.The optimal Pd-doping concentration for better gas-sensing property and thermal stability was 2.0%-2.5% （mole fraction）.
基金Project(2012MS0801)supported by the Natural Science Foundation of Inner Mongolia,China
文摘Al2O3p-Al composites were synthesized using an in-situ reaction in the 80%Al-20%CuO （mass fraction） system. The effects of the CuO particle size on the synthesis temperature and microstructure of the composites were investigated by various methods. The results indicate that the CuO particle size has a significant effect on the temperature at which the complete reaction in the Al-CuO system occurs：the temperature is 200 ℃ lower in the Al-CuO system containing CuO particles with sizes less than 6μm than that containing CuO particles with sizes less than 100μm. The interfacial bonding between Al2O3 particles and Al is not complete when the temperature is below a critical value. The morphology of the Al2O3 particles varies from ribbon-like shape to near spherical shape when the temperature is above a critical value. These two critical temperatures are affected by the particle size of CuO, and the critical temperature of the sample containing CuO particles with sizes less than 6μm is 100 ℃ lower than that of the sample containing CuO particles with sizes less than 100μm.
文摘Wedge-shaped copper casting experiment was conducted to study the engulfment behavior of TiB2 particle and the interaction between particle or cluster and the solid/liquid front in commercial pure aluminum matrix. The experimental results show that the particle size distribution obeys two separate systems in the whole wedge-cast sample. Furthermore, it is found that the big clusters are pushed to the center of the wedge shaped sample and the single particle or small clusters consisting of few particles are engulfed into the α-Al in the area of the sample edge. The cluster degree of particles varies in different areas, and its value is 0.2 and 0.6 for the cluster fraction in the edge and in the center of the wedge sample, respectively. The cluster diameter does not obey the normal distribution but approximately obeys lognormal distribution in the present work. More importantly, in the whole sample, the particle size obeys two separate log-normal distributions.
基金the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2018-ZX04044001-008)the National Natural Science Foundation of China(No.52075328).
文摘The hot forming behavior,failure mechanism,and microstructure evolution of in-situ TiB_(2)particle-reinforced 7075 aluminum matrix composite were investigated by isothermal compression test under different deformation conditions of deformation temperatures of 300−450℃ and strain rates of 0.001^(−1)s^(−1).The results demonstrate that the failure behavior of the composite exhibits both particle fracture and interface debonding at low temperature and high strain rate,and dimple rupture of the matrix at high temperature and low strain rate.Full dynamic recrystallization,which improves the composite formability,occurs under conditions of high temperature(450℃)and low strain rate(0.001 s^(−1));the grain size of the matrix after hot compression was significantly smaller than that of traditional 7075Al and ex-situ particle reinforced 7075Al matrix composite.Based on the flow stress curves,a constitutive model describing the relationship of the flow stress,true strain,strain rate and temperature was proposed.Furthermore,the processing maps based on both the dynamic material modeling(DMM)and modified DMM(MDMM)were established to analyze flow instability domain of the composite and optimize hot forming processing parameters.The optimum processing domain was determined at temperatures of 425−450℃ and strain rates of 0.001−0.01 s^(−1),in which the fine grain microstructure can be gained and particle crack and interface debonding can be avoided.
基金Project(2008BB4177) supported by the Natural Science Foundation of Chongqing,China
文摘Two kinds of Al based functionally gradient composite tubes reinforced by primary Si particles alone and primary Si/in situ Mg2Si particles jointly were successfully prepared by centrifugal casting,and their structural and mechanical characters were compared.It is found that the composite reinforced with primary Si particles takes a characteristic of particles distribution both in the inner and outer layers.However,composite reinforced with primary Si/Mg2Si particles jointly takes a characteristic of particles distribution only in the inner layer and shows a sudden change of particles distribution across the section of inner and outer layers.The hardness and wear resistance of Al-19Si-5Mg tube in the inner layer are greatly higher than that in the other layers of Al-19Si-5Mg tube and Al-19Si tube.Theoretical analysis reveals that the existence of Mg2Si particles is the key factor to form this sudden change of gradient distribution of two kinds of particles.Because Mg2Si particles with a lower density have a higher centripetal moving velocity than primary Si particles,in a field of centrifugal force,they would collide with primary Si particles and then impel the later to move together forward to the inner layer of the tube.
基金financially supported by the National Natural Science Foundation of China(Nos.51561008 and 51461017)Jiangxi Yorth Major Natural Science Foundation(Nos.20171ACB21044 and 20161BBE50030)
文摘The coarsening behavior of(Ni,Co)2Si particles in Cu-Ni-Co-Si alloy was investigated by experimental observations and coarsening kinetics calculations when aged at 450,500,550 and 600℃ for different durations.The results show that the critical particle radius for coherence mismatch is found to be 10.3 nm,and particles larger than 25 nm are generally semi-coherent.The relationship of(Ni,Co)2Si particles size and aging time follows Lifshitz,Slyosov and Wagner(LSW) theory.The particle size distributions fit well to the LSW theoretical distribution.The activation energy for(Ni,Co)2Si coarsening is accurately determined to be(216.21 ± 5.18)kJ mol-1 when considering the effect of temperature on the solution concentrations in matrix.The coarsening of(Ni,Co)2Si particles in Cu-Ni-Co-Si alloy is controlled by diffusion of Ni,Co and Si in Cu matrix.The growth of particles for long durations suggests that vacancies can be trapped within the structure for long time despite their mobility.
