Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique. The convex domes on the bionic sample were fabricated by compression molding under a compressive stre...Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique. The convex domes on the bionic sample were fabricated by compression molding under a compressive stress of 92.5 MPa. The water contact angles of the as-anodized bionic samples were measured using a contact angle meter （JC2000A） with the 3μL water drop at room temperature. The measurement of the wetting property showed that the water contact angle of the unmodi- fied as-anodized bionic alumina samples increases from 90° to 137° with the anodizing time. The increase in water contract angle with anodizing time arises from the gradual formation of hierarchical structure or composite structure. The structure is composed of the micro-scaled alumina columns and pores. The height of columns and the depth of pores depend on the ano- dizing time. The water contact angle increases significantly from 96° to 152° when the samples were modified with self-assembled monolayer of octadecanethiol （ODT）, showing a change in the wettability from hydrophobicity to su- per-hydrophobicity. This improvement in the wetting property chemical modification. is attributed to the decrease in the surface energy caused by the展开更多
The electronic structures and optical properties of Y-doped ZnO are calculated using first-principles calculations.It is found that the replacement of Zn by the rare-earth element Y presents a shallow donor,and the Fe...The electronic structures and optical properties of Y-doped ZnO are calculated using first-principles calculations.It is found that the replacement of Zn by the rare-earth element Y presents a shallow donor,and the Fermi level moves into the conduction band(CB).The high dispersion and s-type character of CB is expected to result in an increase in conductivity.Moreover,the absorption spectrum of the Y-doped ZnO system exhibits a slight blue shift with an increase of Y concentration,and a higher transparency in visible light is expected.Therefore,the Y-doping in ZnO would enhance the mobility and hence increase the electrical conductivity without sacrificing the optical transparency,which is essential for the improvement of ZnO's behavior and its performance in extension applications.展开更多
Optical and electronic properties of Zn_(1−x)Mg_(x)O ternary alloys of wurtzite structure are calculated by using first-principles based on the framework of generalized gradient approximation to density functional the...Optical and electronic properties of Zn_(1−x)Mg_(x)O ternary alloys of wurtzite structure are calculated by using first-principles based on the framework of generalized gradient approximation to density functional theory with the introduction of the on-site Coulomb interaction.The use of the𝑈parameter on Zn-3d𝑑and O-2p𝑝orbits is obviously crucial,which can improve the GGA to predict the electronic properties and bandgap of the Zn_(1−x)Mg_(x)O(0≤𝑥≤0.25)system reasonably.It is further demonstrated that the bandgap widens with an increasing Mg concentration from 3.217 eV of ZnO to 3.877 eV of Zn0.75Mg0.25O.Therefore,the theoretical results show that Zn_(1−x)Mg_(x)O ternary alloys are potential candidates for optoelectronic materials,especially for UV photon emitters and detectors.展开更多
Thermal fatigue and wear both seriously affect the service life of some working parts. Environmental temperature will modify the surface conditions and influences the result of wear. In this research, to come close to...Thermal fatigue and wear both seriously affect the service life of some working parts. Environmental temperature will modify the surface conditions and influences the result of wear. In this research, to come close to working conditions, specimens were tested by a combination of thermal cycles and wear. Different cycles of thermal fatigue was carried out first on the gray iron specimens and subsequently wear test was performed to evaluate the effect of these thermal fatigue cycles. In this case, bionic laser processing was used to enhance the wear performance. The results indicated that bionic laser processing reduces the negative effects from thermal fatigue, such as grain fragmentation and oxidation. Because the initiation and growth of cracks as well as oxidation are suppressed in bionic processed areas. Bionic specimens exhibit high wear resistance compared with the common one. The process described can be considered as an effective method to improve the performance of gray iron in combined thermal fatigue and wear service conditions.展开更多
基金The authors are grateful to the National Nature Science Foundation of China （Grant No. 50635030） and the development project on industrialization of bionic non-adhesive cooker （Grant No. 2006D90304010） for the support of this work.
文摘Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique. The convex domes on the bionic sample were fabricated by compression molding under a compressive stress of 92.5 MPa. The water contact angles of the as-anodized bionic samples were measured using a contact angle meter （JC2000A） with the 3μL water drop at room temperature. The measurement of the wetting property showed that the water contact angle of the unmodi- fied as-anodized bionic alumina samples increases from 90° to 137° with the anodizing time. The increase in water contract angle with anodizing time arises from the gradual formation of hierarchical structure or composite structure. The structure is composed of the micro-scaled alumina columns and pores. The height of columns and the depth of pores depend on the ano- dizing time. The water contact angle increases significantly from 96° to 152° when the samples were modified with self-assembled monolayer of octadecanethiol （ODT）, showing a change in the wettability from hydrophobicity to su- per-hydrophobicity. This improvement in the wetting property chemical modification. is attributed to the decrease in the surface energy caused by the
基金Supported by the National Nature Science Foundation under Grant No 50871046, the National Basic Research Program of China under Grant No 2010CB631001, and the Program for Changjiang Scholars and Innovative Research Team in University.
基金Supported by the National Basic Research Program of China(No 2010CB631001)the National Natural Science Foundation of China(No 50871046)+1 种基金the Programs of Science and Technology Department of Heilongjiang Province(No QC2011C026)the Program for Changjiang Scholars and Innovative Research Team in University.
文摘The electronic structures and optical properties of Y-doped ZnO are calculated using first-principles calculations.It is found that the replacement of Zn by the rare-earth element Y presents a shallow donor,and the Fermi level moves into the conduction band(CB).The high dispersion and s-type character of CB is expected to result in an increase in conductivity.Moreover,the absorption spectrum of the Y-doped ZnO system exhibits a slight blue shift with an increase of Y concentration,and a higher transparency in visible light is expected.Therefore,the Y-doping in ZnO would enhance the mobility and hence increase the electrical conductivity without sacrificing the optical transparency,which is essential for the improvement of ZnO's behavior and its performance in extension applications.
基金by the National Natural Science Foundation of China under Grant No 50871046the National Basic Research Program of China(No 2010CB631001)the Program for Changjiang Scholars and Innovative Research Team in University.
文摘Optical and electronic properties of Zn_(1−x)Mg_(x)O ternary alloys of wurtzite structure are calculated by using first-principles based on the framework of generalized gradient approximation to density functional theory with the introduction of the on-site Coulomb interaction.The use of the𝑈parameter on Zn-3d𝑑and O-2p𝑝orbits is obviously crucial,which can improve the GGA to predict the electronic properties and bandgap of the Zn_(1−x)Mg_(x)O(0≤𝑥≤0.25)system reasonably.It is further demonstrated that the bandgap widens with an increasing Mg concentration from 3.217 eV of ZnO to 3.877 eV of Zn0.75Mg0.25O.Therefore,the theoretical results show that Zn_(1−x)Mg_(x)O ternary alloys are potential candidates for optoelectronic materials,especially for UV photon emitters and detectors.
基金Acknowledgment This work is supported by the National Natural Science Foundation （No. 51005097 and 51275200）, and the Project 985-High Performance Materials of Jilin University.
文摘Thermal fatigue and wear both seriously affect the service life of some working parts. Environmental temperature will modify the surface conditions and influences the result of wear. In this research, to come close to working conditions, specimens were tested by a combination of thermal cycles and wear. Different cycles of thermal fatigue was carried out first on the gray iron specimens and subsequently wear test was performed to evaluate the effect of these thermal fatigue cycles. In this case, bionic laser processing was used to enhance the wear performance. The results indicated that bionic laser processing reduces the negative effects from thermal fatigue, such as grain fragmentation and oxidation. Because the initiation and growth of cracks as well as oxidation are suppressed in bionic processed areas. Bionic specimens exhibit high wear resistance compared with the common one. The process described can be considered as an effective method to improve the performance of gray iron in combined thermal fatigue and wear service conditions.
