Nanofluid minimum quantity lubrication(NMQL)is a green processing technology.Cottonseed oil is suitable as base oil because of excellent lubrication performance,low freezing temperature,and high yield.Al_(2)O_(3)nanop...Nanofluid minimum quantity lubrication(NMQL)is a green processing technology.Cottonseed oil is suitable as base oil because of excellent lubrication performance,low freezing temperature,and high yield.Al_(2)O_(3)nanoparticles improve not only the heat transfer capacity but also the lubrication performance.The physical and chemical proper-ties of nanofluid change when Al_(2)O_(3)nanoparticles are added.However,the effects of the concentration of nanofluid on lubrication performance remain unknown.Furthermore,the mechanisms of interaction between Al_(2)O_(3)nanoparti-cles and cottonseed oil are unclear.In this research,nanofluid is prepared by adding different mass concentrations of Al_(2)O_(3)nanoparticles(0,0.2%,0.5%,1%,1.5%,and 2%wt)to cottonseed oil during minimum quantity lubrication(MQL)milling 45 steel.The tribological properties of nanofluid with different concentrations at the tool/workpiece interface are studied through macro-evaluation parameters(milling force,specific energy)and micro-evaluation parameters(surface roughness,micro morphology,contact angle).The result show that the specific energy is at the minimum(114 J/mm^(3)),and the roughness value is the lowest(1.63μm)when the concentration is 0.5 wt%.The surfaces of the chip and workpiece are the smoothest,and the contact angle is the lowest,indicating that the tribological proper-ties are the best under 0.5 wt%.This research investigates the intercoupling mechanisms of Al_(2)O_(3)nanoparticles and cottonseed base oil,and acquires the optimal Al_(2)O_(3)nanofluid concentration to receive satisfactory tribological properties.展开更多
The implanted ion range, the depth profile and the film sttucture of the implanted layer were studied; the carrier concentration and the mobility were measured; the conductivity mechanism of the film implanted Fe into...The implanted ion range, the depth profile and the film sttucture of the implanted layer were studied; the carrier concentration and the mobility were measured; the conductivity mechanism of the film implanted Fe into Al_2O_3 ceramic was discussed. The conclusion is that the implanted Fe^(2+) ions move into Al_2O_3 lattice and replace Al^(3+) to form subs- titution impurities so that the ion implanted lat- tice, as compared with the original one, presents an effective negative charge which forms a negative charge center. A vacancy is bound arround it, and an acceptor is introduced in the forbidden band.展开更多
Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite's formation greatly limits the applications.In this paper,we systematically investigate the st...Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite's formation greatly limits the applications.In this paper,we systematically investigate the stability,electronic properties,and Li-ion mobility of the LLZO surface by the ifrst-principles calculations.We consider the(110) and(001) slab structures with different terminations in the t-and c-LLZO.Our results indicate that both(110) and(001) surfaces prefer to form Li-rich termination due to their low surface energies for either t-or c-LLZO.Moreover,with the decrease of Li contents the stability of Li-rich surfaces is improved initially and degrades later.Unfortunately,the localized surface states at the Fermi level can induce the formation of metallic Li on the Li-rich surfaces.In comparison,Li/La-termination has a relatively low metallic Li formation tendency due to its rather low diffusion barrier.In fact,Li-ion can spontaneously migrate along path II(Li3→Li2) on the Li/La-T(001) surface.In contrast,it is more difficult for Li-ion diffusion on the Li-T(001) surface,which has a minimum diffusion barrier of 0.50 eV.Interestingly,the minimum diffusion barrier decreases to 0.34 eV when removing four Li-ions from the Li-T(001) surface.Thus,our study suggests that by varying Li contents,the stability and Li-ion diffusion barrier of LLZO surfaces can be altered favorably.These advantages can inhibit the formation of metallic Li on the LLZO surfaces.展开更多
Atomic-layer-deposited（ALD） aluminum oxide（Al2O3） has demonstrated an excellent surface passivation for crystalline silicon（c-Si） surfaces, as well as for highly boron-doped c-Si surfaces. In this paper, water-b...Atomic-layer-deposited（ALD） aluminum oxide（Al2O3） has demonstrated an excellent surface passivation for crystalline silicon（c-Si） surfaces, as well as for highly boron-doped c-Si surfaces. In this paper, water-based thermal atomic layer deposition of Al2O3 films are fabricated for c-Si surface passivation. The influence of deposition conditions on the passivation quality is investigated. The results show that the excellent passivation on n-type c-Si can be achieved at a low thermal budget of 250℃ given a gas pressure of 0.15 Torr. The thickness-dependence of surface passivation indicates that the effective minority carrier lifetime increases drastically when the thickness of Al2O3 is larger than 10 nm. The influence of thermal post annealing treatments is also studied. Comparable carrier lifetime is achieved when Al2O3 sample is annealed for 15 min in forming gas in a temperature range from 400℃ to 450℃. In addition, the passivation quality can be further improved when a thin PECVD-SiNx cap layer is prepared on Al2O3, and an effective minority carrier lifetime of2.8 ms and implied Voc of 721 mV are obtained. In addition, several novel methods are proposed to restrain blistering.展开更多
Interfaces and surfaces of YBa_2Cu_3O_(7-x)(YBCO)-Ag have been studied by SEM-EDX and AES.No effect of Ag on 123 structure in X-ray diffraction pattern was observed for 0.4 mol Ag doped YBCO.AES analysis indicated tha...Interfaces and surfaces of YBa_2Cu_3O_(7-x)(YBCO)-Ag have been studied by SEM-EDX and AES.No effect of Ag on 123 structure in X-ray diffraction pattern was observed for 0.4 mol Ag doped YBCO.AES analysis indicated that Ag segregated on surface of YBCO and resulted in decrease of YBCO-metal lead resistance.In addition,solution and segregation of Ag as elemental state were often appeared on interfaces and surfaces of high temperature annealed YBCO,whether elemental Ag or compound Ag_2O and AgNO_3 adopted as doping material.展开更多
The manganese-cerium complex oxide catalysts were prepared by coprecipitation.The crystal structures,the desorption properties of surface oxygen and reducibility of these catalysts were investigated by means of X-ray ...The manganese-cerium complex oxide catalysts were prepared by coprecipitation.The crystal structures,the desorption properties of surface oxygen and reducibility of these catalysts were investigated by means of X-ray diffraction analysis (XRD),temperature-programmed desopotion-mass spectrography (TPD-MS) and temperature-programmed reduction (TPR).The crystal structure of Mn-O and Mn-Ce-O catalysts are bixbyite-Mn2O3 and γ-Mn2O3 respectively.The presence of CeO2 can not change the position of the feature peaks of Mn2O3 on the TPD or profiles,but can increase evidently the amount of the adsorbed surface oxygen,which are correlated with the catalytic activity for methanol oxidation.The activity of the catalyst is optimum when Mn/Ce atom ratio is 4:1.The presence of CeO2 brings a change of the reducibility,which reveals that there is an interaction between Mn2O3 and CeO2.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51806112,51975305)PhD Research Startup Foundation of Qingdao University of Technology,China(Grant Nos.JC2022-012,20312008).
文摘Nanofluid minimum quantity lubrication(NMQL)is a green processing technology.Cottonseed oil is suitable as base oil because of excellent lubrication performance,low freezing temperature,and high yield.Al_(2)O_(3)nanoparticles improve not only the heat transfer capacity but also the lubrication performance.The physical and chemical proper-ties of nanofluid change when Al_(2)O_(3)nanoparticles are added.However,the effects of the concentration of nanofluid on lubrication performance remain unknown.Furthermore,the mechanisms of interaction between Al_(2)O_(3)nanoparti-cles and cottonseed oil are unclear.In this research,nanofluid is prepared by adding different mass concentrations of Al_(2)O_(3)nanoparticles(0,0.2%,0.5%,1%,1.5%,and 2%wt)to cottonseed oil during minimum quantity lubrication(MQL)milling 45 steel.The tribological properties of nanofluid with different concentrations at the tool/workpiece interface are studied through macro-evaluation parameters(milling force,specific energy)and micro-evaluation parameters(surface roughness,micro morphology,contact angle).The result show that the specific energy is at the minimum(114 J/mm^(3)),and the roughness value is the lowest(1.63μm)when the concentration is 0.5 wt%.The surfaces of the chip and workpiece are the smoothest,and the contact angle is the lowest,indicating that the tribological proper-ties are the best under 0.5 wt%.This research investigates the intercoupling mechanisms of Al_(2)O_(3)nanoparticles and cottonseed base oil,and acquires the optimal Al_(2)O_(3)nanofluid concentration to receive satisfactory tribological properties.
文摘The implanted ion range, the depth profile and the film sttucture of the implanted layer were studied; the carrier concentration and the mobility were measured; the conductivity mechanism of the film implanted Fe into Al_2O_3 ceramic was discussed. The conclusion is that the implanted Fe^(2+) ions move into Al_2O_3 lattice and replace Al^(3+) to form subs- titution impurities so that the ion implanted lat- tice, as compared with the original one, presents an effective negative charge which forms a negative charge center. A vacancy is bound arround it, and an acceptor is introduced in the forbidden band.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12064015 and 12064014)。
文摘Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite's formation greatly limits the applications.In this paper,we systematically investigate the stability,electronic properties,and Li-ion mobility of the LLZO surface by the ifrst-principles calculations.We consider the(110) and(001) slab structures with different terminations in the t-and c-LLZO.Our results indicate that both(110) and(001) surfaces prefer to form Li-rich termination due to their low surface energies for either t-or c-LLZO.Moreover,with the decrease of Li contents the stability of Li-rich surfaces is improved initially and degrades later.Unfortunately,the localized surface states at the Fermi level can induce the formation of metallic Li on the Li-rich surfaces.In comparison,Li/La-termination has a relatively low metallic Li formation tendency due to its rather low diffusion barrier.In fact,Li-ion can spontaneously migrate along path II(Li3→Li2) on the Li/La-T(001) surface.In contrast,it is more difficult for Li-ion diffusion on the Li-T(001) surface,which has a minimum diffusion barrier of 0.50 eV.Interestingly,the minimum diffusion barrier decreases to 0.34 eV when removing four Li-ions from the Li-T(001) surface.Thus,our study suggests that by varying Li contents,the stability and Li-ion diffusion barrier of LLZO surfaces can be altered favorably.These advantages can inhibit the formation of metallic Li on the LLZO surfaces.
基金Project supported by the Beijing Municipal Science and Technology Commission,China(Grant No.Z151100003515003)the National Natural Science Foundation of China(Grant Nos.110751402347,61274134,51402064,61274059,and 51602340)+3 种基金the University of Science and Technology Beijing(USTB)Start-up Program,China(Grant No.06105033)the Beijing Municipal Innovation and Research Base,China(Grant No.Z161100005016095)the Fundamental Research Funds for the Central Universities,China(Grant Nos.FRF-UM-15-032 and 06400071)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2015387)
文摘Atomic-layer-deposited（ALD） aluminum oxide（Al2O3） has demonstrated an excellent surface passivation for crystalline silicon（c-Si） surfaces, as well as for highly boron-doped c-Si surfaces. In this paper, water-based thermal atomic layer deposition of Al2O3 films are fabricated for c-Si surface passivation. The influence of deposition conditions on the passivation quality is investigated. The results show that the excellent passivation on n-type c-Si can be achieved at a low thermal budget of 250℃ given a gas pressure of 0.15 Torr. The thickness-dependence of surface passivation indicates that the effective minority carrier lifetime increases drastically when the thickness of Al2O3 is larger than 10 nm. The influence of thermal post annealing treatments is also studied. Comparable carrier lifetime is achieved when Al2O3 sample is annealed for 15 min in forming gas in a temperature range from 400℃ to 450℃. In addition, the passivation quality can be further improved when a thin PECVD-SiNx cap layer is prepared on Al2O3, and an effective minority carrier lifetime of2.8 ms and implied Voc of 721 mV are obtained. In addition, several novel methods are proposed to restrain blistering.
文摘Interfaces and surfaces of YBa_2Cu_3O_(7-x)(YBCO)-Ag have been studied by SEM-EDX and AES.No effect of Ag on 123 structure in X-ray diffraction pattern was observed for 0.4 mol Ag doped YBCO.AES analysis indicated that Ag segregated on surface of YBCO and resulted in decrease of YBCO-metal lead resistance.In addition,solution and segregation of Ag as elemental state were often appeared on interfaces and surfaces of high temperature annealed YBCO,whether elemental Ag or compound Ag_2O and AgNO_3 adopted as doping material.
文摘The manganese-cerium complex oxide catalysts were prepared by coprecipitation.The crystal structures,the desorption properties of surface oxygen and reducibility of these catalysts were investigated by means of X-ray diffraction analysis (XRD),temperature-programmed desopotion-mass spectrography (TPD-MS) and temperature-programmed reduction (TPR).The crystal structure of Mn-O and Mn-Ce-O catalysts are bixbyite-Mn2O3 and γ-Mn2O3 respectively.The presence of CeO2 can not change the position of the feature peaks of Mn2O3 on the TPD or profiles,but can increase evidently the amount of the adsorbed surface oxygen,which are correlated with the catalytic activity for methanol oxidation.The activity of the catalyst is optimum when Mn/Ce atom ratio is 4:1.The presence of CeO2 brings a change of the reducibility,which reveals that there is an interaction between Mn2O3 and CeO2.
