Treatment of peat soil foundation in Yunnan surrounding Dianchi and Erhai Lakes poses complex problems for engineering projects.It is insufficient to rely on ordinary cement to reinforce peat soil.In order to make the...Treatment of peat soil foundation in Yunnan surrounding Dianchi and Erhai Lakes poses complex problems for engineering projects.It is insufficient to rely on ordinary cement to reinforce peat soil.In order to make the reinforcement reliable,this experiment mixed(ultrafine cement)UFC into ordinary cement to form a composite solidify agent.This study aimed to analyze the influence of UFC proportion on the strength of cement-soil in the peat soil environment.Unconfined compressive strength(UCS)and scanning electron microscope(SEM)tests were conducted on samples soaked for 28 and 90 days,respectively.The test results show that without considering the effects of Humic Acid(HA)and Fulvic Acid(FA),incorporating UFC can significantly improve the UCS of cement-soil.The rapid hydration of the fine particles generates a large number of cementitious products,improves the cohesion of the soil skeleton,and fills the pores.However,when the proportion of UFC increases,the aggregate structure formed by a larger quantity of fine particles reduces the hydration rate and degree of cement hydration,making the UCS growth rate of cement-soil insignificant.In the peat soil environment,HA significantly weakened the UCS of cement-soil in both physical and chemical aspects.However,UFC can mitigate the adverse effect of HA on cement-soil by its small particle size,high surface energy,and solid binding ability.In addition,FA has a positive effect on the UCS of cement-soil soaked for 28 days and 90 days.The UFC addition could promote the enhancement effect of FA on cement-soil UCS.SEM test results showed that cement hydration products increased significantly with the increase of UFC proportion,and cementation between hydration products and soil particles was enhanced.The size and connectivity of cement-soil pores were significantly reduced,thereby improving cement-soil structural integrity.展开更多
Compared with Cu/Al_(2)O_(3)composites,high-strength Cu/Al_(2)O_(3)composites usually exhibit obviously deteriorated electrical conductivity.A chemical and mechanical alloying-based strategy was adopted to fabricate u...Compared with Cu/Al_(2)O_(3)composites,high-strength Cu/Al_(2)O_(3)composites usually exhibit obviously deteriorated electrical conductivity.A chemical and mechanical alloying-based strategy was adopted to fabricate ultrafine composite powders with lowcontent reinforcement and constructed a combined structure of Cu ultrafine powders covered with in-situ Al_(2)O_(3)nanoparticles.After consolidation at a relatively lower sintering temperature of 550℃,high-volume-fraction ultrafine grains were introduced into the Cu/Al_(2)O_(3)composite,and many in-situ Al_(2)O_(3)nanoparticles with an average size of 11.7±7.5 nm were dispersed homogeneously in the Cu grain.Results show that the composite demonstrates an excellent balance of high tensile strength(654±1 MPa)and high electrical conductivity(84.5±0.1%IACS),which is ascribed to the synergistic strengthening effect of ultrafine grains,dislocations,and in-situ Al_(2)O_(3)nanoparticles.This approach,which utilizes ultrafine composite powder with low-content reinforcement as a precursor and employs low-temperature and high-pressure sintering subsequently,may hold promising potential for large-scale industrial production of high-performance oxide dispersion strengthened alloys.展开更多
The ultrafine copper wire with a diameter of 18μm is prepared via cold drawing process from the single crystal downcast billet(Φ8 mm),taking a drawing strain to 12.19.In this paper,in-depth investigation of the micr...The ultrafine copper wire with a diameter of 18μm is prepared via cold drawing process from the single crystal downcast billet(Φ8 mm),taking a drawing strain to 12.19.In this paper,in-depth investigation of the microstructure feature,texture evolution,mechanical properties,and electrical conductivity of ultrafine wires ranging fromΦ361μm toΦ18μm is performed.Specially,the microstructure feature and texture type covering the whole longitudinal section of ultrafine wires are elaborately characterized.The results show that the average lamella thickness decreases from 1.63μm to 102 nm during the drawing process.Whereas,inhomogeneous texture evolution across different wire sections was observed.The main texture types of copper wires are comprised of<111>,<001>and<112>orientations.Specifically,the peripheral region is primarily dominated by<111>and<112>,while the central region is dominated by<001>and<111>.As the drawing strain increases,the volume fraction of hard orientation<111>with low Schmid factor increases,where notably higher fraction of<111>is resulted from the consumption of<112>and<001>for the wire ofΦ18μm.For drawn copper wire of 18μm,superior properties are obtained with a tensile strength of 729.8 MPa and an electrical conductivity of 86.9%IACS.Furthermore,it is found that grain strengthening,dislocation strengthening,and texture strengthening are three primary strengthening mechanisms of drawn copper wire,while the dislocation density is the main factor on the reducing of conductivity.展开更多
Objective Emerging evidence suggests that exposure to ultrafine particulate matter(UPM,aerodynamic diameter<0.1μm)is associated with adverse cardiovascular events.Previous studies have found that Shenlian(SL)extra...Objective Emerging evidence suggests that exposure to ultrafine particulate matter(UPM,aerodynamic diameter<0.1μm)is associated with adverse cardiovascular events.Previous studies have found that Shenlian(SL)extract possesses anti-inflammatory and antiapoptotic properties and has a promising protective effect at all stages of the atherosclerotic disease process.In this study,we aimed to investigated whether SL improves UPM-aggravated myocardial ischemic injury by inhibiting inflammation and cell apoptosis.Methods We established a mouse model of MI+UPM.Echocardiographic measurement,measurement of myocardialinfarct size,biochemical analysis,enzyme-linked immunosorbent assay(ELISA),histopathological analysis,Transferase dUTP Nick End Labeling(TUNEL),Western blotting(WB),Polymerase Chain Reaction(PCR)and so on were used to explore the anti-inflammatory and antiapoptotic effects of SL in vivo and in vitro.Results SL treatment can attenuate UPM-induced cardiac dysfunction by improving left ventricular ejection fraction,fractional shortening,and decreasing cardiac infarction area.SL significantly reduced the levels of myocardial enzymes and attenuated UPM-induced morphological alterations.Moreover,SL significantly reduced expression levels of the inflammatory cytokines IL-6,TNF-α,and MCP-1.UPM further increased the infiltration of macrophages in myocardial tissue,whereas SL intervention reversed this phenomenon.UPM also triggered myocardial apoptosis,which was markedly attenuated by SL treatment.The results of in vitro experiments revealed that SL prevented cell damage caused by exposure to UPM combined with hypoxia by reducing the expression of the inflammatory factor NF-κB and inhibiting apoptosis in H9c2 cells.Conclusion Overall,both in vivo and in vitro experiments demonstrated that SL attenuated UPMaggravated myocardial ischemic injury by inhibiting inflammation and cell apoptosis.The mechanisms were related to the downregulation of macrophages infiltrating heart tissues.展开更多
The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lam...The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lamellae and ferrite recrystallisation for a range of deformation temperatures(600–700℃),cooling/soaking time(water quenching,air cooling,10 and 30 min of soaking time)and interpass time(0–10 s)was analysed.During deformation,the spheroidisation of pearlite is dynamically accelerated mainly by boundary splitting mechanism together with the rapid dissolution of cementite,while ferrite softening is attributed to dynamic recovery and continuous dynamic recrystallisation.The strong microstructural evolution during cooling/soaking time indicates that deformation energy accumulated is sufficient to activate metallurgical phenomena in both phases also statically.Static spheroidisation is a diffusive process,with rate controlled by the diffusion of vacancies,as suggested by the estimated activation energy.Ferrite refinement is the result of the evolution of continuous recrystallisation and pinning effect exerted by fine,globulised and homogeneously dispersed cementite particles.Increasing temperature causes accelerated kinetics in metallurgical phenomena;therefore,cooling/soaking time becomes key parameters to achieve ultrafine grained and spheroidised microstructures.Interpass time favours spheroidisation and promotes continuous recrystallisation;however,it must be carefully controlled to find a balance between recrystallisation and Ostwald ripening to optimise microstructural development.展开更多
An ultra-strong steel with enhanced ductility and ultrafine lamellar structure was produced by heavy warm rolling(HWR)of metastable austenite and subsequent quenching.The HWR steel exhibited an ultrahigh yield strengt...An ultra-strong steel with enhanced ductility and ultrafine lamellar structure was produced by heavy warm rolling(HWR)of metastable austenite and subsequent quenching.The HWR steel exhibited an ultrahigh yield strength of 1.09 GPa and an ultimate tensile strength of 2.6 GPa,with a total elongation of 6.7%at room temperature.The high yield strength was primarily attributed to the synergistic strengthening of high-density dislocations,nanotwins,and ultrafine martensite grains with an average effective grain size of 1.02μm.The enhanced ductility is attributed to the parallel lamellar structure,which increased the work-hardening capacity and resulted in delamination toughening.Compared to the heavy multistage rolling(HMR)process,which starts rolling at higher temperatures,the HWR method employed in this study demonstrates significant enhancements in both strength and ductility.Following a 150℃ low-temperature tempering for 1 h,the yield strength of HWR steel was further increased to 2.2 GPa,and the total elongation improved to 10.1%.展开更多
BACKGROUND In recent years,the use of ultrafine choledochoscopy has gradually increased in the treatment of cholelithiasis.However,stone incarceration and residual spasm of the sphincter of Oddi may be inevitable when...BACKGROUND In recent years,the use of ultrafine choledochoscopy has gradually increased in the treatment of cholelithiasis.However,stone incarceration and residual spasm of the sphincter of Oddi may be inevitable when an ultrafine choledochoscope is used alone.AIM To investigate the safety and feasibility of ultrafine choledochoscopy combined with low-dose atropine in the treatment of Oddi intersphincter stones.METHODS Seventeen patients with Oddi intersphincter stones were retrospectively analyzed.The perioperative clinical data and follow-up information were collected.RESULTS Among the 17 patients,3 were male and 14 were female.The mean age was 40.6±13.9 years,and the mean diameter of the common bile duct was 7.8±1.3 mm.All patients successfully underwent Oddi intersphincter stone removal using a combination of ultrafine choledochoscopy and low-dose atropine.No serious complications,such as postoperative hemorrhage,pancreatitis or bile leakage occurred in the 17 patients.During the one-year follow-up,none of the patients experienced stone recurrence.CONCLUSION Ultrafine choledochoscopy combined with low-dose atropine is safe and feasible for the treatment of Oddi intersphincter stones.展开更多
Pt-based materials are the benchmarked catalysts in the cathodic hydrogen evolution reaction(HER)of water splitting;the prohibitive cost and scarcity of Pt immensely impede the commercialization of hydrogen energy.Ru ...Pt-based materials are the benchmarked catalysts in the cathodic hydrogen evolution reaction(HER)of water splitting;the prohibitive cost and scarcity of Pt immensely impede the commercialization of hydrogen energy.Ru has aroused significant concern because of its Pt-like activity and much lower price.However,it’s still a top priority to minimize the Ru loading and pursue the most superior cost performance.展开更多
Controlling the adhesion of potentially corrosive substances from flue gas on grate bar is crucial for extending the operational lifespan of the equipment.The adhesive behaviour and mechanism of ultrafine particulate ...Controlling the adhesion of potentially corrosive substances from flue gas on grate bar is crucial for extending the operational lifespan of the equipment.The adhesive behaviour and mechanism of ultrafine particulate matters(UPM)throughout the sintering process were elucidated,and measures to control adhesion on grate bars were developed.Research findings indicated that a small quantity of UPM were found on grate bar during the initial sintering stages(ignition stage and middle stageⅠandⅡ).The main compositions of UPM were FexOy-rich,CaO-rich,and aluminium silicate-rich particles.In contrast,corrosive substances like alkali metal compounds were almost absent.These UPM adhered onto grate bar primarily through inertial impaction.When moving to the final sintering stages(middle stageⅢand temperature rising stage),many UPM rich in corrosive substances like NaCl and KCl adhered to the grate bar.These UPM adhered to grate bar through thermal diffusion and vortex deposition.Solid waste water washing technology can greatly decrease the quantity of UPM(rich in NaCl and KCl)on the grate bar due to vortex deposition and thermal diffusion,and it represents a potentially promising way to control adhesion and corrosion on grate bars.展开更多
Nowadays, ultrafine explosives are widely used in military fields. Ultrafine 2,2',4,4',6,6'-hexanitrostilbene(HNS) has emerged as an optimal primer for explosion foil initiators due to its excellent therma...Nowadays, ultrafine explosives are widely used in military fields. Ultrafine 2,2',4,4',6,6'-hexanitrostilbene(HNS) has emerged as an optimal primer for explosion foil initiators due to its excellent thermal stability and high-voltage short-pulse initiation performance. However, the solid phase ripening of ultrafine HNS leads to a degradation in its impact detonation performance. Previous studies have indicated that residual dimethyl formamide(DMF), which is present in ultrafine HNS prepared using the recrystallization method, affects ultrafine HNS ripening. The mechanism of residual solvent effects on solid phase ripening of ultrafine HNS is unclear. In this work, the specific surface area(SSA) derived from small angle X-ray scattering(SAXS) was utilized for kinetic fitting analysis to explore the mechanism by which residual solvents enhance the solid phase ripening of ultrafine HNS. The results of the SSA measured by insitu SAXS under conditions of 150℃ for 40 h revealed that the sample with 0.2% residual DMF exhibited a 21.51% decrease in SSA, whereas the sample with only 0.04% residual DMF showed a decrease of 15.66%.Furthermore, the higher amounts of residual DMF accelerated the reduction in SSA with time. Kinetic fitting analysis demonstrated that reducing residual DMF would lower both the activation energy and the pre-exponential factor, consequently decreasing the rate constant of solid phase ripening. The mechanism was speculated that it primarily facilitated the Ostwald ripening(OR). Additionally, contrast variation small angle X-ray scattering(CV-SAXS) confirmed that coating of ultrafine HNS particles is an effective method for inhibiting ripening, significantly reducing both the rate and extent of ripening of ultrafine HNS. This study predicts how residual solvents impact the solid phase ripening process of ultrafine HNS and proposes strategies for enhancing the long-term stability of ultrafine explosives.展开更多
[Objectives]To explore the mechanism of action of Tongxieyaofang ultrafine granular powder in treating visceral hypersensitivity in rats with diarrhea-predominant irritable bowel syndrome(IBS-D)based on enteric glial ...[Objectives]To explore the mechanism of action of Tongxieyaofang ultrafine granular powder in treating visceral hypersensitivity in rats with diarrhea-predominant irritable bowel syndrome(IBS-D)based on enteric glial cells(EGCs).[Methods]Eighty-four healthy male Wistar rats of SPF grade were selected and randomly assigned to seven groups,each comprising 12 rats:a normal control group,a model control group,a traditional Tongxieyaofang granular powder group(4.060 g/kg),three Tongxieyaofang ultrafine granular powder groups at low,medium,and high doses(1.015,2.030,and 4.060 g/kg of raw drug,respectively),and a pinaverium bromide group(0.018 g/kg).With the exception of the normal control group,all other groups were subjected to an IBS-D visceral hypersensitivity sensitivity model in rats developed by the chronic water avoidance stress method.Three days post modeling,the rats received continuous oral gavage administration for 8 d.Following the treatment period,serum and colon tissue samples were collected from each group.The BDNF level in the serum was quantified using ELISA.Additionally,the protein expression levels of GFAP,BDNF,and TrkB in colon tissues were assessed via Western blot assay.[Results]Compared to the normal control group,the serum BDNF levels in the model control group were significantly elevated(P<0.01).In contrast,each treatment group exhibited a significant reduction in serum BDNF levels relative to the model control group(P<0.01).Furthermore,the protein expression levels of GFAP,BDNF,and TrkB in colon tissue were significantly higher in the model control group compared to the normal control group(P<0.05,P<0.01).Conversely,these protein expressions were significantly decreased in each treatment group compared to the model control group(P<0.05,P<0.01).[Conclusions]Tongxieyaofang ultrafine granular powder effectively alleviates visceral sensitivity in IBS-D rats and inhibits the activation of EGCs,speculating that its mechanism of action involves the suppression of abnormal EGC activation.展开更多
Effects of stirring speed and time, pH and sodium oleate concentration on the shear hydrophobic flocculation of ultrafine Anshan hematite with sodium oleate as the surfactant were discussed. The results show that thes...Effects of stirring speed and time, pH and sodium oleate concentration on the shear hydrophobic flocculation of ultrafine Anshan hematite with sodium oleate as the surfactant were discussed. The results show that these parameters significantly affect the shear hydrophobic flocculation of ultrafine hematite. The optimum conditions for the flocculation are： stirring speed 1 400 r/min, flocculation time 20 min, pH 9 and sodium oleate concentration 3.94×10-4 mol/L; the flotation recovery of hematite flocs is remarkably high compared with non flocculated ultrafine hematite. According to the extended DLVO theory, the total interaction potential of Anshan ultrafine hematite was determined. The calculation results indicate that the hydrophobic flocculation state of the ultrafine hematite-sodium oleate system is mainly dominated by electric double layer repulsive interaction potential and hydrophobic interaction potential. A mechanical agitation is required to impart particles a kinetic energy to overcome potential barrier between them due to the existence of electric double layer repulsive interaction potential. Those particles further approach to form flocs due to the significant increase of the hydrophobic interaction potential.展开更多
In order to accelerate the sedimentation of super-large-scale argillized ultrafine tailings with bad features such as low settling velocity, muddy overflow water, and large flocculant dosage, a fly-ash-based magnetic ...In order to accelerate the sedimentation of super-large-scale argillized ultrafine tailings with bad features such as low settling velocity, muddy overflow water, and large flocculant dosage, a fly-ash-based magnetic coagulant （FAMC） was used in a dynamic experimental device. To obtain the best possible combination of the impact factors （magnetic intensity, FAMC dosage, flocculant dosage, and feed speed） for minimum overflow turbidity, a response surface methodology test coupled with a four-factor five-level central composite design was conducted. The synergy mechanism of FAMC and flocculant was analyzed based on the potential measurement and scanning electron microscopy. The results show that the flocculant dosage, overflow turbidity, and solid content can be reduced by 50%, 90%, and 80%, while the handling capacity per unit and efficiency of backfill and dry stacking can be promoted by 20%, 17%, and 13%, respectively, with a magnetic intensity of 0.3 T, FAMC dosage of 200 mL/t, flocculant dosage of 30 g/t, and feed speed of 0.6 t/（m^2·h）. Therefore, synergy of FAMC and flocculant has obvious efficiency in saving energy and protecting the environment by allowing 70×10^6 t/a of argillized ultrafine tailings slurry to be disposed safely and efficiently with a cost saving of more than 53×106 Yuan/a, which gives it great promise for use in domestic and foreign mines.展开更多
Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind ...Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported cat-alysts. Here, a N-doped ordered mesoporous carbon with a high N content （9.58 wt%）, high surface area （417 m^2/g）, and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles （NPs）. The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs （about 1.0 ± 0.5 nm） to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger （4.4 ± 1.7 nm） and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity （conversion 100%） and selectivity （〉99%） in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst （conversion 89% and selectivity 90%）. This outstanding catalytic perfor-mance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction ac-tivity and selectivity.展开更多
Ultrafine diamond (UFD) is produced at high pressure and high temperature generated by explosive detonation. We manage to search for a new technology to purify the UFD by using potassium permanganate and concentrated ...Ultrafine diamond (UFD) is produced at high pressure and high temperature generated by explosive detonation. We manage to search for a new technology to purify the UFD by using potassium permanganate and concentrated sulfuric acid as oxidant. The experiment results show that, compared with others, the purifying effect by this technology is satisfactory and is a more efficient, cheaper, and safer purification technology with less pollution and less investment. It can be put into commercial use. The related principle of the technology is discussed. It is believed that the atomic state oxygen produced during the reaction mechanism is an active substances which would react with the graphite——the main impurity existing in the detonation soot, and the reaction temperature is the key factor in the process.展开更多
The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.O...The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.展开更多
Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particle...Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particles (UFP) was obtained by the method of microemulsion, which was used to mix with silicon oil. aam electroinduced stress and apparent viscosity of the ER fluids with three different volume fractions were tested under the conditions of different temperatures, electric fields and shear rates. Results A series of systematic tests show that the new type of ER fluids with volume fraction of 30% possesses obvious ER effect. Conclusion The double layers polarization plays an important role in ER effect.展开更多
The ultrafine pure Mg and Mg-Ti particles were prepared through a direct current （DC） arc plasma method. The X-ray diffraction （XRD）, transmission electron microscopy （TEM）, pressure-composition-temperature （PC...The ultrafine pure Mg and Mg-Ti particles were prepared through a direct current （DC） arc plasma method. The X-ray diffraction （XRD）, transmission electron microscopy （TEM）, pressure-composition-temperature （PCT） method and TG/DTA techniques were used to study the phase components, microstructure and hydrogen sorption properties of the powders before and after hydrogen absorption. It is revealed that most of the ultrafine Mg and Mg-Ti particles are hexagonal in shape with particle size in the range of 50-700 nm. According to the Van’t Hoff equation, the hydrogenation enthalpy of Mg-Ti powders is determined to be about -67 kJ/mol H2 based on the PCT curves of hydrogen absorption plateau pressures. This value is much higher than -78.6 kJ/mol H2 for pure Mg powders. TG/DTA analyses show that the onset dehydriding temperature of hydrogenated Mg-Ti powders is 386 °C, which is significantly lower than that of the hydrogenated Mg （423 °C）. The results prove that the addition of Ti into Mg through arc evaporation method can improve the thermodynamic properties of Mg for hydrogen storage.展开更多
Western Australian magnetite concentrates normally have ultrafine granularity and much higher specific surface areas than Chinese magnetite concentrates owing to the significant pre-grinding and beneficiation for sale...Western Australian magnetite concentrates normally have ultrafine granularity and much higher specific surface areas than Chinese magnetite concentrates owing to the significant pre-grinding and beneficiation for saleable iron grade. Such characteristics will inevitably affect the subsequent pelletization process. However, very few investi- gations have been done before. Thus, the oxidation and induration characteristics of pellet made from a Western Aus- tralian ultrafine magnetite concentrate were revealed by conducting routine preheating-roasting tests in an electric tube furnace and investigating the microstructure of fired pellets under an optical microscope in comparison with that of pellets made from typical Chinese magnetite concentrate. The liquidus regions of CaO-SiO2-Fe2O3 and CaO-SiO2- Al2O3 ternary systems in air at various temperatures were calculated by FactSage software to explain the importance of liquid phase in the consolidation of fired pellets. The results show that pellet made from ultrafine magnetite con- centrate possesses better oxidability and preheating performance than that made from Chinese magnetite concentrate. However, it has inferior roasting performance, usually requiring conditions of roasting at 1280℃ for at least 30 rain to acquire sufficiently high compressive strength, which are attributed to higher temperature sensitivity caused by its smaller particle size and less formation of liquid phase because of low impurities like CaO and Al2O3 in raw materials. Correspondingly, its roasting performanee can be significantly improved by blending with Chinese magnetite concen- trates or increasing the pellet basicity （WCaO/WSiO2）. By comprehensive evaluation, blending with Chinese iron ore concentrates is an appropriate way to utilize Western Australia ultrafine magnetite concentrates.展开更多
An ultrafine-grained（UFG） Mg-13Zn-1.55 Y alloy（ZW132） with a high volume fraction（7.4%） of icosahedral phase（I-phase, Mg;Zn;Y） particles was prepared by applying high-ratio differential speed rolling（HRDSR） ...An ultrafine-grained（UFG） Mg-13Zn-1.55 Y alloy（ZW132） with a high volume fraction（7.4%） of icosahedral phase（I-phase, Mg;Zn;Y） particles was prepared by applying high-ratio differential speed rolling（HRDSR） on the cast microstructure following homogenization. The alloy exhibited excellent superplasticity at low temperatures(tensile elongations of 455% and 1021% 473 K-10;s;and 523 K-10;s;,respectively). Compared with UFG Mg-9.25Zn-1.66 Y alloy（ZW92） with a lower volume fraction of I-phase particles（4.1%）, which was prepared using the same processing routes, the UFG ZW132 alloy exhibited a higher thermal stability of grain size. Rapid grain coarsening, however, occurred at temperatures beyond523 K, leading to a loss of superplasticity. The high-temperature deformation behavior of the HRDSRprocessed ZW132 alloy could be well described assuming that the mechanisms of grain boundary sliding and dislocation climb creep competed with each other and considering that the grain-size was largely increased by accelerated grain growth at the temperatures beyond 523 K.展开更多
基金National Natural Science Foundation of China(No.41967035)。
文摘Treatment of peat soil foundation in Yunnan surrounding Dianchi and Erhai Lakes poses complex problems for engineering projects.It is insufficient to rely on ordinary cement to reinforce peat soil.In order to make the reinforcement reliable,this experiment mixed(ultrafine cement)UFC into ordinary cement to form a composite solidify agent.This study aimed to analyze the influence of UFC proportion on the strength of cement-soil in the peat soil environment.Unconfined compressive strength(UCS)and scanning electron microscope(SEM)tests were conducted on samples soaked for 28 and 90 days,respectively.The test results show that without considering the effects of Humic Acid(HA)and Fulvic Acid(FA),incorporating UFC can significantly improve the UCS of cement-soil.The rapid hydration of the fine particles generates a large number of cementitious products,improves the cohesion of the soil skeleton,and fills the pores.However,when the proportion of UFC increases,the aggregate structure formed by a larger quantity of fine particles reduces the hydration rate and degree of cement hydration,making the UCS growth rate of cement-soil insignificant.In the peat soil environment,HA significantly weakened the UCS of cement-soil in both physical and chemical aspects.However,UFC can mitigate the adverse effect of HA on cement-soil by its small particle size,high surface energy,and solid binding ability.In addition,FA has a positive effect on the UCS of cement-soil soaked for 28 days and 90 days.The UFC addition could promote the enhancement effect of FA on cement-soil UCS.SEM test results showed that cement hydration products increased significantly with the increase of UFC proportion,and cementation between hydration products and soil particles was enhanced.The size and connectivity of cement-soil pores were significantly reduced,thereby improving cement-soil structural integrity.
基金Foundation of Northwest Institute for Non-ferrous Metal Research(YK2020-9,ZZXJ2203)Capital Projects of Financial Department of Shaanxi Province(YK22C-12)+4 种基金National Natural Science Foundation of China(62204207)Innovation Capability Support Plan in Shaanxi Province of China(2022KJXX-82,2023KJXX-083)Natural Science Foundation of Shaanxi Province(2022JQ-332)Shaanxi Innovative Research Team for Key Science and Technology(2023-CX-TD-46)Key Research and Development Projects of Shaanxi Province(2024GX-YBXM-351)。
文摘Compared with Cu/Al_(2)O_(3)composites,high-strength Cu/Al_(2)O_(3)composites usually exhibit obviously deteriorated electrical conductivity.A chemical and mechanical alloying-based strategy was adopted to fabricate ultrafine composite powders with lowcontent reinforcement and constructed a combined structure of Cu ultrafine powders covered with in-situ Al_(2)O_(3)nanoparticles.After consolidation at a relatively lower sintering temperature of 550℃,high-volume-fraction ultrafine grains were introduced into the Cu/Al_(2)O_(3)composite,and many in-situ Al_(2)O_(3)nanoparticles with an average size of 11.7±7.5 nm were dispersed homogeneously in the Cu grain.Results show that the composite demonstrates an excellent balance of high tensile strength(654±1 MPa)and high electrical conductivity(84.5±0.1%IACS),which is ascribed to the synergistic strengthening effect of ultrafine grains,dislocations,and in-situ Al_(2)O_(3)nanoparticles.This approach,which utilizes ultrafine composite powder with low-content reinforcement as a precursor and employs low-temperature and high-pressure sintering subsequently,may hold promising potential for large-scale industrial production of high-performance oxide dispersion strengthened alloys.
基金Project supported by“Unveiled the List of Commanders”Key Core Common Technology Projects of Ji’an,ChinaProject(LJKMZ20220591)supported by the Basic Scientific Research Project of the Education Department of Liaoning Province,ChinaProject(CSTB2023NSCQ-LZX0116)supported by the Natural Science Foundation Joint Fund for Innovation and Development Projects of Chongqing,China。
文摘The ultrafine copper wire with a diameter of 18μm is prepared via cold drawing process from the single crystal downcast billet(Φ8 mm),taking a drawing strain to 12.19.In this paper,in-depth investigation of the microstructure feature,texture evolution,mechanical properties,and electrical conductivity of ultrafine wires ranging fromΦ361μm toΦ18μm is performed.Specially,the microstructure feature and texture type covering the whole longitudinal section of ultrafine wires are elaborately characterized.The results show that the average lamella thickness decreases from 1.63μm to 102 nm during the drawing process.Whereas,inhomogeneous texture evolution across different wire sections was observed.The main texture types of copper wires are comprised of<111>,<001>and<112>orientations.Specifically,the peripheral region is primarily dominated by<111>and<112>,while the central region is dominated by<001>and<111>.As the drawing strain increases,the volume fraction of hard orientation<111>with low Schmid factor increases,where notably higher fraction of<111>is resulted from the consumption of<112>and<001>for the wire ofΦ18μm.For drawn copper wire of 18μm,superior properties are obtained with a tensile strength of 729.8 MPa and an electrical conductivity of 86.9%IACS.Furthermore,it is found that grain strengthening,dislocation strengthening,and texture strengthening are three primary strengthening mechanisms of drawn copper wire,while the dislocation density is the main factor on the reducing of conductivity.
基金supported by CACMS Innovation Fund(No CI2021A04611,CI2021A05106)Scientific and technological innovation project of China Academy of Chinese Medical Sciences(CI2021B015)+1 种基金Scientific and technological innovation project of China Academy of Chinese Medical Sciences(CI2023E001TS01)Fundamental research funds for the central public welfare research institutes(L2022035).
文摘Objective Emerging evidence suggests that exposure to ultrafine particulate matter(UPM,aerodynamic diameter<0.1μm)is associated with adverse cardiovascular events.Previous studies have found that Shenlian(SL)extract possesses anti-inflammatory and antiapoptotic properties and has a promising protective effect at all stages of the atherosclerotic disease process.In this study,we aimed to investigated whether SL improves UPM-aggravated myocardial ischemic injury by inhibiting inflammation and cell apoptosis.Methods We established a mouse model of MI+UPM.Echocardiographic measurement,measurement of myocardialinfarct size,biochemical analysis,enzyme-linked immunosorbent assay(ELISA),histopathological analysis,Transferase dUTP Nick End Labeling(TUNEL),Western blotting(WB),Polymerase Chain Reaction(PCR)and so on were used to explore the anti-inflammatory and antiapoptotic effects of SL in vivo and in vitro.Results SL treatment can attenuate UPM-induced cardiac dysfunction by improving left ventricular ejection fraction,fractional shortening,and decreasing cardiac infarction area.SL significantly reduced the levels of myocardial enzymes and attenuated UPM-induced morphological alterations.Moreover,SL significantly reduced expression levels of the inflammatory cytokines IL-6,TNF-α,and MCP-1.UPM further increased the infiltration of macrophages in myocardial tissue,whereas SL intervention reversed this phenomenon.UPM also triggered myocardial apoptosis,which was markedly attenuated by SL treatment.The results of in vitro experiments revealed that SL prevented cell damage caused by exposure to UPM combined with hypoxia by reducing the expression of the inflammatory factor NF-κB and inhibiting apoptosis in H9c2 cells.Conclusion Overall,both in vivo and in vitro experiments demonstrated that SL attenuated UPMaggravated myocardial ischemic injury by inhibiting inflammation and cell apoptosis.The mechanisms were related to the downregulation of macrophages infiltrating heart tissues.
基金financially supported by the European Coal and Steel Community(RFCS-2015.No.709828).
文摘The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lamellae and ferrite recrystallisation for a range of deformation temperatures(600–700℃),cooling/soaking time(water quenching,air cooling,10 and 30 min of soaking time)and interpass time(0–10 s)was analysed.During deformation,the spheroidisation of pearlite is dynamically accelerated mainly by boundary splitting mechanism together with the rapid dissolution of cementite,while ferrite softening is attributed to dynamic recovery and continuous dynamic recrystallisation.The strong microstructural evolution during cooling/soaking time indicates that deformation energy accumulated is sufficient to activate metallurgical phenomena in both phases also statically.Static spheroidisation is a diffusive process,with rate controlled by the diffusion of vacancies,as suggested by the estimated activation energy.Ferrite refinement is the result of the evolution of continuous recrystallisation and pinning effect exerted by fine,globulised and homogeneously dispersed cementite particles.Increasing temperature causes accelerated kinetics in metallurgical phenomena;therefore,cooling/soaking time becomes key parameters to achieve ultrafine grained and spheroidised microstructures.Interpass time favours spheroidisation and promotes continuous recrystallisation;however,it must be carefully controlled to find a balance between recrystallisation and Ostwald ripening to optimise microstructural development.
基金supported by the National Natural Science Foundation of China(No.52071212).
文摘An ultra-strong steel with enhanced ductility and ultrafine lamellar structure was produced by heavy warm rolling(HWR)of metastable austenite and subsequent quenching.The HWR steel exhibited an ultrahigh yield strength of 1.09 GPa and an ultimate tensile strength of 2.6 GPa,with a total elongation of 6.7%at room temperature.The high yield strength was primarily attributed to the synergistic strengthening of high-density dislocations,nanotwins,and ultrafine martensite grains with an average effective grain size of 1.02μm.The enhanced ductility is attributed to the parallel lamellar structure,which increased the work-hardening capacity and resulted in delamination toughening.Compared to the heavy multistage rolling(HMR)process,which starts rolling at higher temperatures,the HWR method employed in this study demonstrates significant enhancements in both strength and ductility.Following a 150℃ low-temperature tempering for 1 h,the yield strength of HWR steel was further increased to 2.2 GPa,and the total elongation improved to 10.1%.
基金Supported by Health Research Program of Anhui,No.AHWJ2023A30034.
文摘BACKGROUND In recent years,the use of ultrafine choledochoscopy has gradually increased in the treatment of cholelithiasis.However,stone incarceration and residual spasm of the sphincter of Oddi may be inevitable when an ultrafine choledochoscope is used alone.AIM To investigate the safety and feasibility of ultrafine choledochoscopy combined with low-dose atropine in the treatment of Oddi intersphincter stones.METHODS Seventeen patients with Oddi intersphincter stones were retrospectively analyzed.The perioperative clinical data and follow-up information were collected.RESULTS Among the 17 patients,3 were male and 14 were female.The mean age was 40.6±13.9 years,and the mean diameter of the common bile duct was 7.8±1.3 mm.All patients successfully underwent Oddi intersphincter stone removal using a combination of ultrafine choledochoscopy and low-dose atropine.No serious complications,such as postoperative hemorrhage,pancreatitis or bile leakage occurred in the 17 patients.During the one-year follow-up,none of the patients experienced stone recurrence.CONCLUSION Ultrafine choledochoscopy combined with low-dose atropine is safe and feasible for the treatment of Oddi intersphincter stones.
基金supported by the Development Project of Youth Innovation Team in Shandong Colleges and Universities(No.2019KJC031)the Natural Science Foundation of Shandong Province(Nos.ZR2019MB064,ZR2021MB122 and ZR2022MB137)the Doctoral Program of Liaocheng University(No.318051608).
文摘Pt-based materials are the benchmarked catalysts in the cathodic hydrogen evolution reaction(HER)of water splitting;the prohibitive cost and scarcity of Pt immensely impede the commercialization of hydrogen energy.Ru has aroused significant concern because of its Pt-like activity and much lower price.However,it’s still a top priority to minimize the Ru loading and pursue the most superior cost performance.
基金supported by the National Natural Science Foundation of China(No.52274344)the Provincial Natural Science Foundation of Hunan(Nos.2022JJ30723 and 2023JJ20068)the Science and Technology Innovation Program of Hunan Province(2023RC3042).
文摘Controlling the adhesion of potentially corrosive substances from flue gas on grate bar is crucial for extending the operational lifespan of the equipment.The adhesive behaviour and mechanism of ultrafine particulate matters(UPM)throughout the sintering process were elucidated,and measures to control adhesion on grate bars were developed.Research findings indicated that a small quantity of UPM were found on grate bar during the initial sintering stages(ignition stage and middle stageⅠandⅡ).The main compositions of UPM were FexOy-rich,CaO-rich,and aluminium silicate-rich particles.In contrast,corrosive substances like alkali metal compounds were almost absent.These UPM adhered onto grate bar primarily through inertial impaction.When moving to the final sintering stages(middle stageⅢand temperature rising stage),many UPM rich in corrosive substances like NaCl and KCl adhered to the grate bar.These UPM adhered to grate bar through thermal diffusion and vortex deposition.Solid waste water washing technology can greatly decrease the quantity of UPM(rich in NaCl and KCl)on the grate bar due to vortex deposition and thermal diffusion,and it represents a potentially promising way to control adhesion and corrosion on grate bars.
基金the Presidential Foundation of CAEP(Grant No.YZJJZQ2023005)the National Natural Science Foundation of China(Grant No.22375191).
文摘Nowadays, ultrafine explosives are widely used in military fields. Ultrafine 2,2',4,4',6,6'-hexanitrostilbene(HNS) has emerged as an optimal primer for explosion foil initiators due to its excellent thermal stability and high-voltage short-pulse initiation performance. However, the solid phase ripening of ultrafine HNS leads to a degradation in its impact detonation performance. Previous studies have indicated that residual dimethyl formamide(DMF), which is present in ultrafine HNS prepared using the recrystallization method, affects ultrafine HNS ripening. The mechanism of residual solvent effects on solid phase ripening of ultrafine HNS is unclear. In this work, the specific surface area(SSA) derived from small angle X-ray scattering(SAXS) was utilized for kinetic fitting analysis to explore the mechanism by which residual solvents enhance the solid phase ripening of ultrafine HNS. The results of the SSA measured by insitu SAXS under conditions of 150℃ for 40 h revealed that the sample with 0.2% residual DMF exhibited a 21.51% decrease in SSA, whereas the sample with only 0.04% residual DMF showed a decrease of 15.66%.Furthermore, the higher amounts of residual DMF accelerated the reduction in SSA with time. Kinetic fitting analysis demonstrated that reducing residual DMF would lower both the activation energy and the pre-exponential factor, consequently decreasing the rate constant of solid phase ripening. The mechanism was speculated that it primarily facilitated the Ostwald ripening(OR). Additionally, contrast variation small angle X-ray scattering(CV-SAXS) confirmed that coating of ultrafine HNS particles is an effective method for inhibiting ripening, significantly reducing both the rate and extent of ripening of ultrafine HNS. This study predicts how residual solvents impact the solid phase ripening process of ultrafine HNS and proposes strategies for enhancing the long-term stability of ultrafine explosives.
基金Supported by Science and Technology Plan Project of Zhongshan City(2022B1126).
文摘[Objectives]To explore the mechanism of action of Tongxieyaofang ultrafine granular powder in treating visceral hypersensitivity in rats with diarrhea-predominant irritable bowel syndrome(IBS-D)based on enteric glial cells(EGCs).[Methods]Eighty-four healthy male Wistar rats of SPF grade were selected and randomly assigned to seven groups,each comprising 12 rats:a normal control group,a model control group,a traditional Tongxieyaofang granular powder group(4.060 g/kg),three Tongxieyaofang ultrafine granular powder groups at low,medium,and high doses(1.015,2.030,and 4.060 g/kg of raw drug,respectively),and a pinaverium bromide group(0.018 g/kg).With the exception of the normal control group,all other groups were subjected to an IBS-D visceral hypersensitivity sensitivity model in rats developed by the chronic water avoidance stress method.Three days post modeling,the rats received continuous oral gavage administration for 8 d.Following the treatment period,serum and colon tissue samples were collected from each group.The BDNF level in the serum was quantified using ELISA.Additionally,the protein expression levels of GFAP,BDNF,and TrkB in colon tissues were assessed via Western blot assay.[Results]Compared to the normal control group,the serum BDNF levels in the model control group were significantly elevated(P<0.01).In contrast,each treatment group exhibited a significant reduction in serum BDNF levels relative to the model control group(P<0.01).Furthermore,the protein expression levels of GFAP,BDNF,and TrkB in colon tissue were significantly higher in the model control group compared to the normal control group(P<0.05,P<0.01).Conversely,these protein expressions were significantly decreased in each treatment group compared to the model control group(P<0.05,P<0.01).[Conclusions]Tongxieyaofang ultrafine granular powder effectively alleviates visceral sensitivity in IBS-D rats and inhibits the activation of EGCs,speculating that its mechanism of action involves the suppression of abnormal EGC activation.
基金Project (20062026) supported by Natural Science Foundation of Liaoning Province, China
文摘Effects of stirring speed and time, pH and sodium oleate concentration on the shear hydrophobic flocculation of ultrafine Anshan hematite with sodium oleate as the surfactant were discussed. The results show that these parameters significantly affect the shear hydrophobic flocculation of ultrafine hematite. The optimum conditions for the flocculation are： stirring speed 1 400 r/min, flocculation time 20 min, pH 9 and sodium oleate concentration 3.94×10-4 mol/L; the flotation recovery of hematite flocs is remarkably high compared with non flocculated ultrafine hematite. According to the extended DLVO theory, the total interaction potential of Anshan ultrafine hematite was determined. The calculation results indicate that the hydrophobic flocculation state of the ultrafine hematite-sodium oleate system is mainly dominated by electric double layer repulsive interaction potential and hydrophobic interaction potential. A mechanical agitation is required to impart particles a kinetic energy to overcome potential barrier between them due to the existence of electric double layer repulsive interaction potential. Those particles further approach to form flocs due to the significant increase of the hydrophobic interaction potential.
基金Project(2012BAC09B02)supported by the 12th-Five Years Key Programs for Science and Technology Development of ChinaProject(2015zzts078)supported by the Fundamental Research Funds for the Central Universities of Central South University,ChinaProject(2015CX005)supported by Innovation Driven Plan of Central South University,China
文摘In order to accelerate the sedimentation of super-large-scale argillized ultrafine tailings with bad features such as low settling velocity, muddy overflow water, and large flocculant dosage, a fly-ash-based magnetic coagulant （FAMC） was used in a dynamic experimental device. To obtain the best possible combination of the impact factors （magnetic intensity, FAMC dosage, flocculant dosage, and feed speed） for minimum overflow turbidity, a response surface methodology test coupled with a four-factor five-level central composite design was conducted. The synergy mechanism of FAMC and flocculant was analyzed based on the potential measurement and scanning electron microscopy. The results show that the flocculant dosage, overflow turbidity, and solid content can be reduced by 50%, 90%, and 80%, while the handling capacity per unit and efficiency of backfill and dry stacking can be promoted by 20%, 17%, and 13%, respectively, with a magnetic intensity of 0.3 T, FAMC dosage of 200 mL/t, flocculant dosage of 30 g/t, and feed speed of 0.6 t/（m^2·h）. Therefore, synergy of FAMC and flocculant has obvious efficiency in saving energy and protecting the environment by allowing 70×10^6 t/a of argillized ultrafine tailings slurry to be disposed safely and efficiently with a cost saving of more than 53×106 Yuan/a, which gives it great promise for use in domestic and foreign mines.
基金supported by the National Natural Science Foundation of China(201573136,U1510105)the Scientific Research Start-up Funds of Shanxi University(RSC723)~~
文摘Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported cat-alysts. Here, a N-doped ordered mesoporous carbon with a high N content （9.58 wt%）, high surface area （417 m^2/g）, and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles （NPs）. The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs （about 1.0 ± 0.5 nm） to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger （4.4 ± 1.7 nm） and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity （conversion 100%） and selectivity （〉99%） in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst （conversion 89% and selectivity 90%）. This outstanding catalytic perfor-mance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction ac-tivity and selectivity.
文摘Ultrafine diamond (UFD) is produced at high pressure and high temperature generated by explosive detonation. We manage to search for a new technology to purify the UFD by using potassium permanganate and concentrated sulfuric acid as oxidant. The experiment results show that, compared with others, the purifying effect by this technology is satisfactory and is a more efficient, cheaper, and safer purification technology with less pollution and less investment. It can be put into commercial use. The related principle of the technology is discussed. It is believed that the atomic state oxygen produced during the reaction mechanism is an active substances which would react with the graphite——the main impurity existing in the detonation soot, and the reaction temperature is the key factor in the process.
基金Funded by the Technology Innovation Leading Program of Shaanxi(No.2022QFY08-02)。
文摘The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.
文摘Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particles (UFP) was obtained by the method of microemulsion, which was used to mix with silicon oil. aam electroinduced stress and apparent viscosity of the ER fluids with three different volume fractions were tested under the conditions of different temperatures, electric fields and shear rates. Results A series of systematic tests show that the new type of ER fluids with volume fraction of 30% possesses obvious ER effect. Conclusion The double layers polarization plays an important role in ER effect.
基金Project (10JC1407700) supported by the Key Basic Project from Science and Technology Committee of Shanghai, ChinaProject(11ZR1417600) supported by Shanghai Nature Science Foundation from Science and Technology Committee of Shanghai, China+2 种基金Project(11PJ1406000) supported by ‘Pujiang’ project from the Science and Technology Committee of Shanghai, ChinaProject (12ZZ017)supported by Shanghai Education Commission, ChinaProject (20100073120007) supported by China Education Commission
文摘The ultrafine pure Mg and Mg-Ti particles were prepared through a direct current （DC） arc plasma method. The X-ray diffraction （XRD）, transmission electron microscopy （TEM）, pressure-composition-temperature （PCT） method and TG/DTA techniques were used to study the phase components, microstructure and hydrogen sorption properties of the powders before and after hydrogen absorption. It is revealed that most of the ultrafine Mg and Mg-Ti particles are hexagonal in shape with particle size in the range of 50-700 nm. According to the Van’t Hoff equation, the hydrogenation enthalpy of Mg-Ti powders is determined to be about -67 kJ/mol H2 based on the PCT curves of hydrogen absorption plateau pressures. This value is much higher than -78.6 kJ/mol H2 for pure Mg powders. TG/DTA analyses show that the onset dehydriding temperature of hydrogenated Mg-Ti powders is 386 °C, which is significantly lower than that of the hydrogenated Mg （423 °C）. The results prove that the addition of Ti into Mg through arc evaporation method can improve the thermodynamic properties of Mg for hydrogen storage.
基金supported by Hunan Provincial Co-innovation Center for Clean and Efficient Utilization of Strategic Metal Mineral Resources
文摘Western Australian magnetite concentrates normally have ultrafine granularity and much higher specific surface areas than Chinese magnetite concentrates owing to the significant pre-grinding and beneficiation for saleable iron grade. Such characteristics will inevitably affect the subsequent pelletization process. However, very few investi- gations have been done before. Thus, the oxidation and induration characteristics of pellet made from a Western Aus- tralian ultrafine magnetite concentrate were revealed by conducting routine preheating-roasting tests in an electric tube furnace and investigating the microstructure of fired pellets under an optical microscope in comparison with that of pellets made from typical Chinese magnetite concentrate. The liquidus regions of CaO-SiO2-Fe2O3 and CaO-SiO2- Al2O3 ternary systems in air at various temperatures were calculated by FactSage software to explain the importance of liquid phase in the consolidation of fired pellets. The results show that pellet made from ultrafine magnetite con- centrate possesses better oxidability and preheating performance than that made from Chinese magnetite concentrate. However, it has inferior roasting performance, usually requiring conditions of roasting at 1280℃ for at least 30 rain to acquire sufficiently high compressive strength, which are attributed to higher temperature sensitivity caused by its smaller particle size and less formation of liquid phase because of low impurities like CaO and Al2O3 in raw materials. Correspondingly, its roasting performanee can be significantly improved by blending with Chinese magnetite concen- trates or increasing the pellet basicity （WCaO/WSiO2）. By comprehensive evaluation, blending with Chinese iron ore concentrates is an appropriate way to utilize Western Australia ultrafine magnetite concentrates.
基金supported financially by the Mid-Career Researcher Program through the National Research Foundation of Korea(2016) funded by the Ministry of Education, Science and Technology (2016R1A2B4015481)
文摘An ultrafine-grained（UFG） Mg-13Zn-1.55 Y alloy（ZW132） with a high volume fraction（7.4%） of icosahedral phase（I-phase, Mg;Zn;Y） particles was prepared by applying high-ratio differential speed rolling（HRDSR） on the cast microstructure following homogenization. The alloy exhibited excellent superplasticity at low temperatures(tensile elongations of 455% and 1021% 473 K-10;s;and 523 K-10;s;,respectively). Compared with UFG Mg-9.25Zn-1.66 Y alloy（ZW92） with a lower volume fraction of I-phase particles（4.1%）, which was prepared using the same processing routes, the UFG ZW132 alloy exhibited a higher thermal stability of grain size. Rapid grain coarsening, however, occurred at temperatures beyond523 K, leading to a loss of superplasticity. The high-temperature deformation behavior of the HRDSRprocessed ZW132 alloy could be well described assuming that the mechanisms of grain boundary sliding and dislocation climb creep competed with each other and considering that the grain-size was largely increased by accelerated grain growth at the temperatures beyond 523 K.
