Mechanoluminescent(ML)materials,which have the ability to convert mechanical energy to optical energy,have found huge promising applications such as in stress imaging and anti-counterfeiting.However,the main reported ...Mechanoluminescent(ML)materials,which have the ability to convert mechanical energy to optical energy,have found huge promising applications such as in stress imaging and anti-counterfeiting.However,the main reported ML phosphors are based on trap-related ones,thus hindering the practical applications due to the requirement of complex light pre-irradiation process.Here,a self-recoverable near infrared(NIR)ML material of Lali-xO:xCr^(3+)(x=0.2%,0.4%,0.6%,0.8%,1.0%,and 1.2%)has been developed.Based on the preheating method and corresponding ML performance analysis,the influences of residual carriers are eliminated and the detailed dynamic luminescence process analysis is realized.Systematic experiments are conducted to reveal the origin of the ML emissions,demonstrating that ML is dictated more by the non-centrosymmetric piezoelectric crystal characteristic.In general,this work has provided significant references for exploring more efficient NIR ML materials,which may provide potential applications in anti-counterfeiting and bio-stress sensing.展开更多
Cr^(3+)-activated near-infrared(NIR)phosphors are key for NIR phosphor-converted light emitting diodes(NIR pc-LED).While,the site occupancy of Cr^(3+)is one of the debates that have plagued researchers.Herein,Y2Mg2Al2...Cr^(3+)-activated near-infrared(NIR)phosphors are key for NIR phosphor-converted light emitting diodes(NIR pc-LED).While,the site occupancy of Cr^(3+)is one of the debates that have plagued researchers.Herein,Y2Mg2Al2-Si_(2)O1_(2)(YMAS)with multiple cationic sites is chosen as host of Cr^(3+)to synthesize YMAS:xCr^(3+)phosphors.In YMAS,Cr^(3+)ions occupy simultaneously Al/SiO4 tetrahedral,Mg/AlO6 octahedral,and Y/MgO8 dodecahedral sites which form three luminescent centers named as Cr1,Cr2,and Cr3,respectively.Cr1 and Cr2 relate to an intermediate crystal field,with transitions of^(2)E→^(4)A_(2)and^(4)T_(2)→^(4)A_(2)occurring simultaneously.As Cr^(3+)concentration increases,the^(4)T_(2)→^(4)A_(2)transition becomes more pronounced in Cr1 and Cr2,resulting in a red-shift and broadband emission.Cr3 consistently behaves a weak crystal field and exhibits the broad and long-wavelength emission.Wide-range NIR emission centering at 745 nm is realized in YMAS:0.03Cr^(3+)phosphor.This phosphor has high internal quantum efficiency(IQE?86%)and satisfying luminescence thermal stability(I423 K?70.2%).Using this phosphor,NIR pc-LEDs with 56.6 mW@320 mA optical output power is packaged and applied.Present study not only demonstrates the Cr^(3+)multi-site occupancy in a certain oxide but also provides a reliable approach via choosing a host with diverse cationic sites and local environments for Cr^(3+)to achieve broadband NIR phosphors.展开更多
The effects of extreme stray current on the anodic dissolution and passivation of X80 steel in NaHCO3 solution were investigated using measurements of polarization curves and EIS,AFM and SEM techniques.Under the inter...The effects of extreme stray current on the anodic dissolution and passivation of X80 steel in NaHCO3 solution were investigated using measurements of polarization curves and EIS,AFM and SEM techniques.Under the interference of anodic current(i=0~200 A/m2),main constituents of corrosion products of X80 steel were FeO(OH)and Fe3 O4.A double-layer film formed at i=00 A/m2,in which FeOOH was in outer and Fe3 O4 lied in inner.The formation mechanism of Fe3 O4 was confirmed and described by the electrochemical reaction in various regions on anodic potentiodynamic polarization curve.展开更多
In this paper, Al2O3 ultrathin film used as the surface passivation layer for A1GaN/GaN high electron mobility transistor （HEMT） is deposited by thermal atomic layer deposition （ALD）, thereby avoiding plasma-induc...In this paper, Al2O3 ultrathin film used as the surface passivation layer for A1GaN/GaN high electron mobility transistor （HEMT） is deposited by thermal atomic layer deposition （ALD）, thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor deposition （PECVD） SiN passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency （RF） performance are achieved after applying Al2O3＋BCB passivation. For the Al2O3＋BCB passivated device with a 0.7μm gate, the value of fmax reaches up to 100 GHz, but it decreases to 40 GHz for SiN HEMT. The fmax/ft ratio （〉 4） is also improved after Al2O3＋BCB passivation. The capacitancevoltage （C-V） measurement demonstrates that Al2O3＋BCB HEMT shows quite less density of trap states （on the order of magnitude of 1010 cm-2） than that obtained at commonly studied SiN HEMT.展开更多
基金We gratefully acknowledge the financial support from the National Natural Science Foundation of China(No.52202003)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515011893)+1 种基金State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China(No.Sklpm-KF-27)Guangzhou Basic and Applied Basic Research Foundation(No.SL2022A04J00746)。
文摘Mechanoluminescent(ML)materials,which have the ability to convert mechanical energy to optical energy,have found huge promising applications such as in stress imaging and anti-counterfeiting.However,the main reported ML phosphors are based on trap-related ones,thus hindering the practical applications due to the requirement of complex light pre-irradiation process.Here,a self-recoverable near infrared(NIR)ML material of Lali-xO:xCr^(3+)(x=0.2%,0.4%,0.6%,0.8%,1.0%,and 1.2%)has been developed.Based on the preheating method and corresponding ML performance analysis,the influences of residual carriers are eliminated and the detailed dynamic luminescence process analysis is realized.Systematic experiments are conducted to reveal the origin of the ML emissions,demonstrating that ML is dictated more by the non-centrosymmetric piezoelectric crystal characteristic.In general,this work has provided significant references for exploring more efficient NIR ML materials,which may provide potential applications in anti-counterfeiting and bio-stress sensing.
基金supported by the National Natural Science Foundation of China(No.51772330)the Fundamental Research Funds for the Central Universities of Central South University(No.506021713)the National MCF Energy R&D Program of China(No.2018YFE0306100).
文摘Cr^(3+)-activated near-infrared(NIR)phosphors are key for NIR phosphor-converted light emitting diodes(NIR pc-LED).While,the site occupancy of Cr^(3+)is one of the debates that have plagued researchers.Herein,Y2Mg2Al2-Si_(2)O1_(2)(YMAS)with multiple cationic sites is chosen as host of Cr^(3+)to synthesize YMAS:xCr^(3+)phosphors.In YMAS,Cr^(3+)ions occupy simultaneously Al/SiO4 tetrahedral,Mg/AlO6 octahedral,and Y/MgO8 dodecahedral sites which form three luminescent centers named as Cr1,Cr2,and Cr3,respectively.Cr1 and Cr2 relate to an intermediate crystal field,with transitions of^(2)E→^(4)A_(2)and^(4)T_(2)→^(4)A_(2)occurring simultaneously.As Cr^(3+)concentration increases,the^(4)T_(2)→^(4)A_(2)transition becomes more pronounced in Cr1 and Cr2,resulting in a red-shift and broadband emission.Cr3 consistently behaves a weak crystal field and exhibits the broad and long-wavelength emission.Wide-range NIR emission centering at 745 nm is realized in YMAS:0.03Cr^(3+)phosphor.This phosphor has high internal quantum efficiency(IQE?86%)and satisfying luminescence thermal stability(I423 K?70.2%).Using this phosphor,NIR pc-LEDs with 56.6 mW@320 mA optical output power is packaged and applied.Present study not only demonstrates the Cr^(3+)multi-site occupancy in a certain oxide but also provides a reliable approach via choosing a host with diverse cationic sites and local environments for Cr^(3+)to achieve broadband NIR phosphors.
文摘The effects of extreme stray current on the anodic dissolution and passivation of X80 steel in NaHCO3 solution were investigated using measurements of polarization curves and EIS,AFM and SEM techniques.Under the interference of anodic current(i=0~200 A/m2),main constituents of corrosion products of X80 steel were FeO(OH)and Fe3 O4.A double-layer film formed at i=00 A/m2,in which FeOOH was in outer and Fe3 O4 lied in inner.The formation mechanism of Fe3 O4 was confirmed and described by the electrochemical reaction in various regions on anodic potentiodynamic polarization curve.
文摘In this paper, Al2O3 ultrathin film used as the surface passivation layer for A1GaN/GaN high electron mobility transistor （HEMT） is deposited by thermal atomic layer deposition （ALD）, thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor deposition （PECVD） SiN passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency （RF） performance are achieved after applying Al2O3＋BCB passivation. For the Al2O3＋BCB passivated device with a 0.7μm gate, the value of fmax reaches up to 100 GHz, but it decreases to 40 GHz for SiN HEMT. The fmax/ft ratio （〉 4） is also improved after Al2O3＋BCB passivation. The capacitancevoltage （C-V） measurement demonstrates that Al2O3＋BCB HEMT shows quite less density of trap states （on the order of magnitude of 1010 cm-2） than that obtained at commonly studied SiN HEMT.
