In order to study the effect of scanning speed on the electrochemical corrosion resistance of laser cladding TC4 alloy in artificial seawater, the x-ray diffraction analysis, microstructure of cross-section, microhard...In order to study the effect of scanning speed on the electrochemical corrosion resistance of laser cladding TC4 alloy in artificial seawater, the x-ray diffraction analysis, microstructure of cross-section, microhardness variation, and impedance spectrum have been studied in comparison with the TC4 titanium alloy. The results show that the main phase of cladding coating is α-Ti, and the change of scanning speed has no obvious effect on it; therefore, the supersaturated α-Ti solid solution is formed, and the acicular α martensite is obtained. As the scanning speed increases, the microstructure of cladding coating is orthogonal basket-weave, the crystal surface spacing decreases, and the average microhardness of laser cladding TC4 alloy slightly increases. When the scanning speed increases to 10 mm/s, the microhardness is about 14.71%higher than that of the substrate, and the electrochemical corrosion resistance of laser cladding TC4 alloy is also improved,which is about 2.48 times more than the substrate. Grain refinement has a great effect on enhancing the anti-electrochemical corrosion.展开更多
In resonance with the Fukushima Daiichi Nuclear Power Plant accident lesson, a novel fuel design to enhance safety regarding severe accident scenarios has become increasingly appreciated in the nuclear power industry....In resonance with the Fukushima Daiichi Nuclear Power Plant accident lesson, a novel fuel design to enhance safety regarding severe accident scenarios has become increasingly appreciated in the nuclear power industry. This research focuses on analysis of the neutronic properties of a silicon carbide(SiC) cladding fuel assembly, which provides a greater safety margin as a type of accident-tolerant fuel for pressurized water reactors. The general physical performance of SiC cladding is explored to ascertain its neutronic performance. The neutron spectrum, accumulation of ^(239)Pu, physical characteristics,temperature reactivity coefficient, and power distribution are analyzed. Furthermore, the influences of a burnable poison rod and enrichment are explored. SiC cladding assemblies show a softer neutron spectrum and flatter power distribution than conventional Zr alloy cladding fuel assemblies. Lower enrichment fuel is required when SiC cladding is adopted. However, the positive reactivity coefficient associated with the SiC material remains to be offset. The results reveal that SiC cladding assemblies show broad agreement with the neutronic performance of conventional Zr alloy cladding fuel. In the meantime, its unique physical characteristics can lead to improved safety and economy.展开更多
Accident-tolerant fuel(ATF)has attracted considerable research attention since the 2011 Fukushima nuclear disaster.To improve the accident tolerance of the fuel-cladding systems in the current light-water reactors,it ...Accident-tolerant fuel(ATF)has attracted considerable research attention since the 2011 Fukushima nuclear disaster.To improve the accident tolerance of the fuel-cladding systems in the current light-water reactors,it is proposed to develop and deploy(1)an enhanced Zrbased alloy or coated zircaloy for the fuel cladding,(2)alternative cladding materials with better accident tolerance,and(3)alternative fuels with enhanced accident tolerance and/or a higher U density.This review presents the features of the current UO2-zircaloy system.Different techniques and characters to develop coating materials and enhanced Zr-based alloys are summarized.The features of several selected alternative fuels and cladding materials are reviewed and discussed.The neutronic evaluations of alternative fuel-cladding systems are analyzed.It is expected that one or more types of ATF-cladding systems discussed in the present review will be implemented in commercial reactors.展开更多
High-speed laser cladding technology, a kind of surface technology to improve the wear-resistance and corrosion-resistance of mechanical parts, has the characterizations of fast scan speed, high powder utilization rat...High-speed laser cladding technology, a kind of surface technology to improve the wear-resistance and corrosion-resistance of mechanical parts, has the characterizations of fast scan speed, high powder utilization rate, and high cladding efficiency. However, its thermal-stress evolution process is very complex, which has a great influence on the residual stress and deformation. In the paper, the numerical models for the high-speed laser cladding coatings with overlap ratios of 10%,30%, and 50% are developed to investigate the influence rules of overlap ratio on the thermal-stress evolution, as well as the residual stresses and deformations. Results show that the heat accumulation can reheat and preheat the adjacent track coating and substrate, resulting in stress release of the previous track coating and decreased longitudinal stress peak of the next track coating. With the overlap ratio increasing, the heat accumulation and the corresponding maximum residual stress position tend to locate in the center of the cladding coating, where the coating has a high crack susceptibility. For a small overlap ratio of 10%, there are abrupt stress changes from tensile stress to compressive stress at the lap joint, due to insufficient input energy in the position. Increasing the overlap ratio can alleviate the abrupt stress change and reduce the residual deformation but increase the average residual stress and enlarge the hardening depth. This study reveals the mechanism of thermal-stress evolution, and provides a theoretical basis for improving the coating quality.展开更多
We report on the fabrication of circular cladding waveguides with cross-section diameters of 60−120μm in Pr:YAG crystal by applying femtosecond laser inscription.The fabricated waveguides present 2D guidance on the c...We report on the fabrication of circular cladding waveguides with cross-section diameters of 60−120μm in Pr:YAG crystal by applying femtosecond laser inscription.The fabricated waveguides present 2D guidance on the cross-section and fairly low propagation losses.Multiple high-order guiding modes are observed in waveguides with different diameters.Corresponding simulation results reveal the origin of a specific kind of guiding modes.Confocal micro-Raman(μ-Raman)experiments demonstrate the modification effects in femtosecond laser affected areas and ascertain the refractive index induced guiding mechanism.In addition,luminescence emission properties of Pr3+ions at waveguide volume are well preserved during the femtosecond laser inscription process,which may result in a potential high-power visible waveguide laser.展开更多
A novel Yb3+-doped double-clad silica fibre with rectangular inner cladding was designed and developed by using the modified chemical vapour deposition process, solution-doping and optical machining all together. The ...A novel Yb3+-doped double-clad silica fibre with rectangular inner cladding was designed and developed by using the modified chemical vapour deposition process, solution-doping and optical machining all together. The dimensions of the inner cladding are 100 × 70 μm, and Yb^(3+)-doped concentration in the core is about 0.24 wt. %. The operation of the fibre laser pumped by inner cladding is reported. The threshold of the laser is 34mW.When the pump power launched is 141mW, the laser output is 84mW at the wavelength 1075.6nm, and the slope efficiency is 77%.展开更多
A refractive index(RI)sensor based on a cladding-etched thin-core single-mode fiber(TCSMF)sandwiched between two single-mode fibers is demonstrated.The experimental results show that the sensitivity,within the RI rang...A refractive index(RI)sensor based on a cladding-etched thin-core single-mode fiber(TCSMF)sandwiched between two single-mode fibers is demonstrated.The experimental results show that the sensitivity,within the RI range of 1.333–1.340,is enhanced at least 6 times by etching.It increases with the surrounding RI and reaches 857.5 nm/RIU at RI of 1.3684,and it can be expected to be higher with the decrease of the cladding diameter of the TCSMF.展开更多
Process and mechanism of high frequency were studied in this paper by means of cold attachment for the preparation of GNi WC25 coating . The results show its special distribution law of eddy current while the magnetic...Process and mechanism of high frequency were studied in this paper by means of cold attachment for the preparation of GNi WC25 coating . The results show its special distribution law of eddy current while the magnetic transition temperature and electric resistivity of the coating have been measured .Wear resistance of the high frequency induction coating has an advantage over those of laser cladding coating and oxygen acetylene spraying fusing coating . Moreover , the GNi WC25 coating by high frequency induction cladding has smooth surface and even microstructure.展开更多
This study attempts to analyze the microstructure and interface behavior of aluminum 6061(Al 6061)-Vgrooved stainless steel(SS304)explosive cladding by numerical and experimental methods.Numerical simulation was perfo...This study attempts to analyze the microstructure and interface behavior of aluminum 6061(Al 6061)-Vgrooved stainless steel(SS304)explosive cladding by numerical and experimental methods.Numerical simulation was performed by Smoothed Particle Hydrodynamics(SPH)technique,in ANSYS AUTODYN,and the results are correlated with experimental outcome.The machining of V-grooves on the base plate transform the melted layer formed in conventional cladding(without grooves on the base plate)into a smooth undulating interface,for a similar experimental condition.The flyer plate and collision velocities,observed in numerical simulation,are in good agreement to the analytical expectations.The pressure developed in the flyer plate is higher than the base plate and the maximum pressure is witnessed at the collision point irrespective of grooved base plate or otherwise.The temperature developed in the collision point of conventional explosive cladding exceeds the melting point of both the participant metals,whereas,it exceeds the melting point of aluminum alone,in case of V-grooved base plate cladding.The shear and impact strengths of the V-grooved base plate clads are higher than the conventional clads and the fracture surfaces exhibit mixed modes of fracture.展开更多
The transient multiphysics models were updated in CAMPUS to evaluate the accident-tolerant fuel performance under accident conditions.CAMPUS is a fuel performance code developed based on COMSOL.The simulated results o...The transient multiphysics models were updated in CAMPUS to evaluate the accident-tolerant fuel performance under accident conditions.CAMPUS is a fuel performance code developed based on COMSOL.The simulated results of the UO_(2)–Zircaloy fuel performance under accident conditions were compared with those of the FRAPTRAN code and the experimental data to verify the correctness of the updated CAMPUS.Subsequently,multiphysics models of the UO_(2)–BeO fuel and composite SiC coated with Cr(SiC_(f)/SiC-Cr)cladding were implemented in CAMPUS.Finally,the fuel performance of the three types of fuel cladding systems under Loss of Coolant Accident(LOCA)and Reactivity Insertion Accident(RIA)conditions was evaluated and compared,including the temperature distribution,stress distribution,pressure evolution,and cladding failure time.The results showed that the fuel temperature of the UO_(2) fuel under accident conditions without pre-irradiation was lower after being combined with SiC_(f)/SiC-Cr cladding.Moreover,the centerline and outer surface temperatures of the UO_(2)–BeO fuel combined with SiC_(f)/SiC-Cr cladding reduced further under accident conditions.The cladding temperature increased after the combination with the SiC_(f)/SiC-Cr cladding under accident conditions with pre-irradiation.In addition,the use of SiC_(f)/SiC-Cr cladding significantly reduced the cladding hoop strain and plenum pressure.展开更多
Fiber cladding surface plasmon resonance(SPR)sensors have few structures,and a clad SPR sensor based on S-type fiber is proposed in this paper.This new type of fiber cladding SPR sensor was formed by electrofusing an ...Fiber cladding surface plasmon resonance(SPR)sensors have few structures,and a clad SPR sensor based on S-type fiber is proposed in this paper.This new type of fiber cladding SPR sensor was formed by electrofusing an S-shaped structure on the fiber to couple the light in the fiber core to the cladding.In this paper,the effects of fiber parameters on the performance of the sensor were studied by simulation and experiment.Based on the conclusion that the smaller the core diameter is,the closer the working band of the SPR resonance is to long wavelengths,and that the geometric characteristics mean that a multimode fiber can receive the fiber cladding light from a small core diameter few-mode fiber,a dual channel SPR sensor with a double S-type fiber cascade was proposed.In the refractive index detection range of 1.333–1.385refractive index units(RIU),the resonant working band of channel I is 627.66 nm–759.78 nm,with an average sensitivity of 2540.77 nm/RIU,and the resonant working band of channel II is 518.24 nm–658.2 nm,with an average sensitivity of2691.54 nm/RIU.The processing method for the S-type fiber cladding SPR sensor is simple,effectively solving the problem of this type of SPR sensor structure and the difficult realization of a dual channel.The sensor is expected to be used in the fields of medical treatment and biological analysis.展开更多
Severe production conditions in coal mines cause damage and failure problems with the oriented sliding boots of the mechanical shearer. Wear has been an especially vexing problem. Plasma cladding methods were used to ...Severe production conditions in coal mines cause damage and failure problems with the oriented sliding boots of the mechanical shearer. Wear has been an especially vexing problem. Plasma cladding methods were used to study optimized sliding boot design. By cladding the substrate steel the surface may be made of a material more resistant to wear. The iron based alloy Cr4MnTi was coated onto a modified 45 steel matrix material in these tests. The results show that the alloy cladding layer is high strength, has high hardness, and is highly resistant to wear. After hardening and tempering, 45 steel substrate has great tenacity so the combined structure meets the performance requirements for the construction of shearer sliding boots.展开更多
NieAl alloy coatings with different Y additions are prepared on 45#medium steel by laser cladding. The influence of Y contents on the microstructure and properties of NieAl alloy coatings is investigated using X-ray d...NieAl alloy coatings with different Y additions are prepared on 45#medium steel by laser cladding. The influence of Y contents on the microstructure and properties of NieAl alloy coatings is investigated using X-ray diffraction, scanning electron microscopy, electron probe microanalyzer, Vickers hardness tester, friction wear testing machine, and thermal analyzer. The results show that the cladding layers are mainly composed of NiAl dendrites, and the dendrites are gradually refined with the increase in Y additions. The purification effect of Y can effectively prevent Al2O3oxide from forming. However, when the atomic percent of Y addition exceeds 1.5%, the extra Y addition will react with O to form Y2O3oxide, even to form Al5Y3O12oxide, depending on the amount of Y added. The Y addition in a range of 1.5e3.5 at.% reduces the hardness and anti-attrition of cladding layer, but improves obviously its wear and oxidation resistances.展开更多
To improve the performance of double clad high power fibre lasers, inner cladding design plays a significant role. A triangular inner cladding and silica structure second cladding with large air holes go acquire high ...To improve the performance of double clad high power fibre lasers, inner cladding design plays a significant role. A triangular inner cladding and silica structure second cladding with large air holes go acquire high inner cladding numerical aperture are designed. Single mode and high power output of the fibre lasers need the double clad Yb doped fibre with large core. A fibre with annular refractive index distribution core and low numerical aperture to acquire a large mode area fibre core is designed and fabricated. Furthermore co-doping with aluminium （A1） has been used to improve the solubility of ytterbium （Yb） into silicate network, and the core absorption coefficients of two Yb doped fibres are compared with different A1 concentration experimentally.展开更多
We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide （SMCW） and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding la...We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide （SMCW） and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding layer. The light matter interaction in the ferrofluid film leads to the formation of a regular nanoparticle pattern, which changes the phase match condition of the ultrahigh order modes in return. When two lasers are incident on the same spot of the waveguide chip, experiments illustrate all-optical modulation of one laser beam by adjusting the intensity of the other laser. A possible theoretical explanation may be due to the optical trapping and Soret effect since the phenomenon is considerable only when the control laser is effectively coupled into the waveguide.展开更多
An effective top cladding for silicon-on-insulator grating coupler is designed and the validity of the design is confirmed experimentally.The proposed double-layer silicon oxide/silicon nitride(SiO_(2)/Si_(3)N_(4))cla...An effective top cladding for silicon-on-insulator grating coupler is designed and the validity of the design is confirmed experimentally.The proposed double-layer silicon oxide/silicon nitride(SiO_(2)/Si_(3)N_(4))cladding demonstrates antireflection properties and affects a coupling strength of the grating structure.A coupling efficiency of 65%is obtained after cladding layer deposition.展开更多
We report a high-average-power noise-like pulse(NLP) and dissipative soliton(DS) pulse fiber laser. Average power as high as 4.8 W could be obtained at the fundamental mode-locked repetition rate. The NLP can also be ...We report a high-average-power noise-like pulse(NLP) and dissipative soliton(DS) pulse fiber laser. Average power as high as 4.8 W could be obtained at the fundamental mode-locked repetition rate. The NLP can also be transformed into a more powerful DS mode-locking state by optimizing the polarization and losses of intra-cavity pulses in the nonlinear polarization evolution regime. The operation mode between the NLP and DS can be switched, and the laser output performance in both modes has been studied. The main advantage of this work is switchable high-power operation between the NLP and DS. In comparison with conventional single-mode NLP fiber lasers, the multi-function high-power optical source will greatly push its application in supercontinuum generation, coherence tomography, and industrial processing.展开更多
A refractive index(RI)sensor based on the surface plasmon resonance effect is proposed using a truncated cladding negative curvature fiber(TC-NCF).The influences of the TC-NCF structure parameters on the sensing perfo...A refractive index(RI)sensor based on the surface plasmon resonance effect is proposed using a truncated cladding negative curvature fiber(TC-NCF).The influences of the TC-NCF structure parameters on the sensing performances are investigated and compared with the traditional NCF.The simulation results show that the proposed TC-NCF RI sensor has an ultra-wide detection range from 1.16 to 1.43.The maximum wavelength sensitivity reaches 12400 nm/RIU,and the corresponding R^(2)of the polynomial fitting equation is 0.9999.The maximum and minimum resolutions are 2.56×10^(-5)and 8.06×10^(-6),respectively.In addition,the maximum amplitude sensitivity can reach-379.1 RIU^(-1)when the RI is chosen as 1.43.The proposed TC-NCF RI sensor could be useful in biochemical medicine,environmental monitoring,and food safety.展开更多
We propose a design of terahertz refractive index sensing based on the multi-metal-wire（MMW） hybrid-cladding hollow waveguide. The proposed terahertz hybrid-cladding hollow waveguide comprises one air core in the ce...We propose a design of terahertz refractive index sensing based on the multi-metal-wire（MMW） hybrid-cladding hollow waveguide. The proposed terahertz hybrid-cladding hollow waveguide comprises one air core in the center surrounding MMW surrounded dielectric. The central air core is used for filling lossless measurands and transmitting terahertz light. In particular, the refractive index sensing is realized by measuring the mode field area（MFA） variation of radially polarized mode. The modal effective refractive index, mode field intensity distribution, and mode field area properties responding to the measurand refractive indexes for different operating frequencies and structure dimensions are investigated, respectively.Simulations show that the proposed terahertz refractive index sensor can realize easily the measurement of the measurand refractive index. Meanwhile, the effects of operating frequency and structure parameters on sensitivity and measurement accuracy are also studied. In view of the trade-off between sensitivity and measurement accuracy, the reasonable choice of the operating frequency and structure parameters can optimize appropriately the sensitivity and measurement accuracy, and the sensitivity can reach approximately 0.585 mm^2/RIU（RIU is short for refraction index units） with the proper frequency and structure parameter.展开更多
Metal matrix composite coating Ni-Fe/SiC was prepared on an iron-based substrate bythermal spraying combined with laser cladding,using SiC particulates as the reinforcing agent.The micro-structures of the coatings for...Metal matrix composite coating Ni-Fe/SiC was prepared on an iron-based substrate bythermal spraying combined with laser cladding,using SiC particulates as the reinforcing agent.The micro-structures of the coatings formed at different thermal spraying and laser cladding conditions were character-ized by means of X-ray diffraction and electron probe microanalysis.The thermal oxidation properties of themixed powders composed of different content of SiC particulates and relevant Ni-based alloy as the balancewere examined using differential scanning calorimetry.The hardness profile of the thermal sprayed and lasercladding coatings was investigated as well.It was found that SiO2particulates were generated and dissolvedand dispersed during the melting and solidification of the laser cladding process,which was ascribed to theoxidation of the dispersed SiC particulates.The micro-hardness depth profile of the target laser claddingcomposite coating was characterized by gradient distribution,which could be related to the gradient distribu-tion of the hard SiC and SiO2particulates in the dendrites and interdendrites of the cladding layer.Both SiCand SiO2particulates contributed to greatly increasing the microhardness and mechanical properties of the ti-tled laser cladding composite coatings.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61475117 and 51471084)the National Key Research and Development Program of China(Grant No.2017YFB1103604)the Tianjin Municipal Special Program of Talents Development for Excellent Youth Scholars,China(Grant No.TJTZJHQNBJRC-2-15)
文摘In order to study the effect of scanning speed on the electrochemical corrosion resistance of laser cladding TC4 alloy in artificial seawater, the x-ray diffraction analysis, microstructure of cross-section, microhardness variation, and impedance spectrum have been studied in comparison with the TC4 titanium alloy. The results show that the main phase of cladding coating is α-Ti, and the change of scanning speed has no obvious effect on it; therefore, the supersaturated α-Ti solid solution is formed, and the acicular α martensite is obtained. As the scanning speed increases, the microstructure of cladding coating is orthogonal basket-weave, the crystal surface spacing decreases, and the average microhardness of laser cladding TC4 alloy slightly increases. When the scanning speed increases to 10 mm/s, the microhardness is about 14.71%higher than that of the substrate, and the electrochemical corrosion resistance of laser cladding TC4 alloy is also improved,which is about 2.48 times more than the substrate. Grain refinement has a great effect on enhancing the anti-electrochemical corrosion.
基金supported by the National Natural Science Foundation of China(No.11675057)the Fundamental Research Funds for the Central Universities(No.2017ZD100)
文摘In resonance with the Fukushima Daiichi Nuclear Power Plant accident lesson, a novel fuel design to enhance safety regarding severe accident scenarios has become increasingly appreciated in the nuclear power industry. This research focuses on analysis of the neutronic properties of a silicon carbide(SiC) cladding fuel assembly, which provides a greater safety margin as a type of accident-tolerant fuel for pressurized water reactors. The general physical performance of SiC cladding is explored to ascertain its neutronic performance. The neutron spectrum, accumulation of ^(239)Pu, physical characteristics,temperature reactivity coefficient, and power distribution are analyzed. Furthermore, the influences of a burnable poison rod and enrichment are explored. SiC cladding assemblies show a softer neutron spectrum and flatter power distribution than conventional Zr alloy cladding fuel assemblies. Lower enrichment fuel is required when SiC cladding is adopted. However, the positive reactivity coefficient associated with the SiC material remains to be offset. The results reveal that SiC cladding assemblies show broad agreement with the neutronic performance of conventional Zr alloy cladding fuel. In the meantime, its unique physical characteristics can lead to improved safety and economy.
基金supported by the National Key Research and Development Program of China(No.2018YFB1900405)the National Natural Science Foundation of China(No.11775316)+3 种基金the Tip-top Scientific and Technical Innovative Youth Talents of Guangdong Special Support Program(No.2016TQ03N575)the Fundamental Research Funds for the Central Universities(No.19lgpy299)the Science and Technology Planning Project of Guangdong Province,China(No.2019A050510022)the Nuclear Power Institute of China(No.HT-ATF-14-2018001)
文摘Accident-tolerant fuel(ATF)has attracted considerable research attention since the 2011 Fukushima nuclear disaster.To improve the accident tolerance of the fuel-cladding systems in the current light-water reactors,it is proposed to develop and deploy(1)an enhanced Zrbased alloy or coated zircaloy for the fuel cladding,(2)alternative cladding materials with better accident tolerance,and(3)alternative fuels with enhanced accident tolerance and/or a higher U density.This review presents the features of the current UO2-zircaloy system.Different techniques and characters to develop coating materials and enhanced Zr-based alloys are summarized.The features of several selected alternative fuels and cladding materials are reviewed and discussed.The neutronic evaluations of alternative fuel-cladding systems are analyzed.It is expected that one or more types of ATF-cladding systems discussed in the present review will be implemented in commercial reactors.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFC0810500)the National Natural Science Foundation of China(Grant No.51975042)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-19-004A3)。
文摘High-speed laser cladding technology, a kind of surface technology to improve the wear-resistance and corrosion-resistance of mechanical parts, has the characterizations of fast scan speed, high powder utilization rate, and high cladding efficiency. However, its thermal-stress evolution process is very complex, which has a great influence on the residual stress and deformation. In the paper, the numerical models for the high-speed laser cladding coatings with overlap ratios of 10%,30%, and 50% are developed to investigate the influence rules of overlap ratio on the thermal-stress evolution, as well as the residual stresses and deformations. Results show that the heat accumulation can reheat and preheat the adjacent track coating and substrate, resulting in stress release of the previous track coating and decreased longitudinal stress peak of the next track coating. With the overlap ratio increasing, the heat accumulation and the corresponding maximum residual stress position tend to locate in the center of the cladding coating, where the coating has a high crack susceptibility. For a small overlap ratio of 10%, there are abrupt stress changes from tensile stress to compressive stress at the lap joint, due to insufficient input energy in the position. Increasing the overlap ratio can alleviate the abrupt stress change and reduce the residual deformation but increase the average residual stress and enlarge the hardening depth. This study reveals the mechanism of thermal-stress evolution, and provides a theoretical basis for improving the coating quality.
基金We are grateful for financial supports from National Natural Science Foundation of China(NSFC)(Grants No.61575097 and 11704201)National Natural Science Foundation of Tianjin City(NSFTJ)(17JCQNJC01600 and 19JCZDJC32700)the Fundamental Research Funds for the Central Universities.
文摘We report on the fabrication of circular cladding waveguides with cross-section diameters of 60−120μm in Pr:YAG crystal by applying femtosecond laser inscription.The fabricated waveguides present 2D guidance on the cross-section and fairly low propagation losses.Multiple high-order guiding modes are observed in waveguides with different diameters.Corresponding simulation results reveal the origin of a specific kind of guiding modes.Confocal micro-Raman(μ-Raman)experiments demonstrate the modification effects in femtosecond laser affected areas and ascertain the refractive index induced guiding mechanism.In addition,luminescence emission properties of Pr3+ions at waveguide volume are well preserved during the femtosecond laser inscription process,which may result in a potential high-power visible waveguide laser.
基金Supported by the National Natural Science Foundation of China under Grant No.69877006Tianjin Natural Science Foundation(003600911)。
文摘A novel Yb3+-doped double-clad silica fibre with rectangular inner cladding was designed and developed by using the modified chemical vapour deposition process, solution-doping and optical machining all together. The dimensions of the inner cladding are 100 × 70 μm, and Yb^(3+)-doped concentration in the core is about 0.24 wt. %. The operation of the fibre laser pumped by inner cladding is reported. The threshold of the laser is 34mW.When the pump power launched is 141mW, the laser output is 84mW at the wavelength 1075.6nm, and the slope efficiency is 77%.
基金Supported by Zhejiang Provincial Natural Science Foundation of China under Grant Nos Y5090150 and Y6100244the National Natural Science Foundation of China under Grant No 61007051.
文摘A refractive index(RI)sensor based on a cladding-etched thin-core single-mode fiber(TCSMF)sandwiched between two single-mode fibers is demonstrated.The experimental results show that the sensitivity,within the RI range of 1.333–1.340,is enhanced at least 6 times by etching.It increases with the surrounding RI and reaches 857.5 nm/RIU at RI of 1.3684,and it can be expected to be higher with the decrease of the cladding diameter of the TCSMF.
文摘Process and mechanism of high frequency were studied in this paper by means of cold attachment for the preparation of GNi WC25 coating . The results show its special distribution law of eddy current while the magnetic transition temperature and electric resistivity of the coating have been measured .Wear resistance of the high frequency induction coating has an advantage over those of laser cladding coating and oxygen acetylene spraying fusing coating . Moreover , the GNi WC25 coating by high frequency induction cladding has smooth surface and even microstructure.
文摘This study attempts to analyze the microstructure and interface behavior of aluminum 6061(Al 6061)-Vgrooved stainless steel(SS304)explosive cladding by numerical and experimental methods.Numerical simulation was performed by Smoothed Particle Hydrodynamics(SPH)technique,in ANSYS AUTODYN,and the results are correlated with experimental outcome.The machining of V-grooves on the base plate transform the melted layer formed in conventional cladding(without grooves on the base plate)into a smooth undulating interface,for a similar experimental condition.The flyer plate and collision velocities,observed in numerical simulation,are in good agreement to the analytical expectations.The pressure developed in the flyer plate is higher than the base plate and the maximum pressure is witnessed at the collision point irrespective of grooved base plate or otherwise.The temperature developed in the collision point of conventional explosive cladding exceeds the melting point of both the participant metals,whereas,it exceeds the melting point of aluminum alone,in case of V-grooved base plate cladding.The shear and impact strengths of the V-grooved base plate clads are higher than the conventional clads and the fracture surfaces exhibit mixed modes of fracture.
基金support from the General Universities Characteristic Innovation Project of Guangdong Province(No.2022KTSCX006)Sichuan Science and Technology Program(No.2019ZDZX0001)。
文摘The transient multiphysics models were updated in CAMPUS to evaluate the accident-tolerant fuel performance under accident conditions.CAMPUS is a fuel performance code developed based on COMSOL.The simulated results of the UO_(2)–Zircaloy fuel performance under accident conditions were compared with those of the FRAPTRAN code and the experimental data to verify the correctness of the updated CAMPUS.Subsequently,multiphysics models of the UO_(2)–BeO fuel and composite SiC coated with Cr(SiC_(f)/SiC-Cr)cladding were implemented in CAMPUS.Finally,the fuel performance of the three types of fuel cladding systems under Loss of Coolant Accident(LOCA)and Reactivity Insertion Accident(RIA)conditions was evaluated and compared,including the temperature distribution,stress distribution,pressure evolution,and cladding failure time.The results showed that the fuel temperature of the UO_(2) fuel under accident conditions without pre-irradiation was lower after being combined with SiC_(f)/SiC-Cr cladding.Moreover,the centerline and outer surface temperatures of the UO_(2)–BeO fuel combined with SiC_(f)/SiC-Cr cladding reduced further under accident conditions.The cladding temperature increased after the combination with the SiC_(f)/SiC-Cr cladding under accident conditions with pre-irradiation.In addition,the use of SiC_(f)/SiC-Cr cladding significantly reduced the cladding hoop strain and plenum pressure.
基金the National Natural Science Foundation of China(Grant No.61705025)Chongqing Natural Science Foundation(Grant Nos.cstc2019jcyjmsxmX0431 and cstc2018jcyjAX0817)+2 种基金the Science and Technology Project Affiliated to the Education Department of Chongqing Municipality(Grant Nos.KJQN201801217,KJQN201901226,KJQN202001214,and KJ1710247)Chongqing Key Laboratory of Geological Environment Monitoring and Disaster Early-Warning in Three Gorges Reservoir Area(Grant Nos.ZD2020A0103 and ZD2020A0102)Fundamental Research Funds for Chongqing Three Gorges University of China(Grant No.19ZDPY08).
文摘Fiber cladding surface plasmon resonance(SPR)sensors have few structures,and a clad SPR sensor based on S-type fiber is proposed in this paper.This new type of fiber cladding SPR sensor was formed by electrofusing an S-shaped structure on the fiber to couple the light in the fiber core to the cladding.In this paper,the effects of fiber parameters on the performance of the sensor were studied by simulation and experiment.Based on the conclusion that the smaller the core diameter is,the closer the working band of the SPR resonance is to long wavelengths,and that the geometric characteristics mean that a multimode fiber can receive the fiber cladding light from a small core diameter few-mode fiber,a dual channel SPR sensor with a double S-type fiber cascade was proposed.In the refractive index detection range of 1.333–1.385refractive index units(RIU),the resonant working band of channel I is 627.66 nm–759.78 nm,with an average sensitivity of 2540.77 nm/RIU,and the resonant working band of channel II is 518.24 nm–658.2 nm,with an average sensitivity of2691.54 nm/RIU.The processing method for the S-type fiber cladding SPR sensor is simple,effectively solving the problem of this type of SPR sensor structure and the difficult realization of a dual channel.The sensor is expected to be used in the fields of medical treatment and biological analysis.
基金Financial support for this work, provided by the fundingsupport: the National Natural Science Foundation General Projects(No. 51075387)the National "Eleventh Five-Year" Plan Major Projects supported by the National Science and Technology (No.2008BAB36B02)
文摘Severe production conditions in coal mines cause damage and failure problems with the oriented sliding boots of the mechanical shearer. Wear has been an especially vexing problem. Plasma cladding methods were used to study optimized sliding boot design. By cladding the substrate steel the surface may be made of a material more resistant to wear. The iron based alloy Cr4MnTi was coated onto a modified 45 steel matrix material in these tests. The results show that the alloy cladding layer is high strength, has high hardness, and is highly resistant to wear. After hardening and tempering, 45 steel substrate has great tenacity so the combined structure meets the performance requirements for the construction of shearer sliding boots.
文摘NieAl alloy coatings with different Y additions are prepared on 45#medium steel by laser cladding. The influence of Y contents on the microstructure and properties of NieAl alloy coatings is investigated using X-ray diffraction, scanning electron microscopy, electron probe microanalyzer, Vickers hardness tester, friction wear testing machine, and thermal analyzer. The results show that the cladding layers are mainly composed of NiAl dendrites, and the dendrites are gradually refined with the increase in Y additions. The purification effect of Y can effectively prevent Al2O3oxide from forming. However, when the atomic percent of Y addition exceeds 1.5%, the extra Y addition will react with O to form Y2O3oxide, even to form Al5Y3O12oxide, depending on the amount of Y added. The Y addition in a range of 1.5e3.5 at.% reduces the hardness and anti-attrition of cladding layer, but improves obviously its wear and oxidation resistances.
文摘To improve the performance of double clad high power fibre lasers, inner cladding design plays a significant role. A triangular inner cladding and silica structure second cladding with large air holes go acquire high inner cladding numerical aperture are designed. Single mode and high power output of the fibre lasers need the double clad Yb doped fibre with large core. A fibre with annular refractive index distribution core and low numerical aperture to acquire a large mode area fibre core is designed and fabricated. Furthermore co-doping with aluminium （A1） has been used to improve the solubility of ytterbium （Yb） into silicate network, and the core absorption coefficients of two Yb doped fibres are compared with different A1 concentration experimentally.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11274091 and 11274092)the Fundamental Research Funds for the Central Universities of Hohai University, China (Grant No. 2011B11014)
文摘We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide （SMCW） and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding layer. The light matter interaction in the ferrofluid film leads to the formation of a regular nanoparticle pattern, which changes the phase match condition of the ultrahigh order modes in return. When two lasers are incident on the same spot of the waveguide chip, experiments illustrate all-optical modulation of one laser beam by adjusting the intensity of the other laser. A possible theoretical explanation may be due to the optical trapping and Soret effect since the phenomenon is considerable only when the control laser is effectively coupled into the waveguide.
基金Supported by the National Basic Research Program of China under Grant No 2011CB301701the National Natural Science Foundation of China under Grant Nos 60877036,61107048+1 种基金Chinese Academy of Sciences for a fellowship for young international scientists(No 2011Y1GB07)China Postdoctoral Science Foundation(No 2011M500372).
文摘An effective top cladding for silicon-on-insulator grating coupler is designed and the validity of the design is confirmed experimentally.The proposed double-layer silicon oxide/silicon nitride(SiO_(2)/Si_(3)N_(4))cladding demonstrates antireflection properties and affects a coupling strength of the grating structure.A coupling efficiency of 65%is obtained after cladding layer deposition.
基金supported by the National Natural Science Foundation of China (Grant No. 12164030)the Major Program of the National Natural Science Foundation of China (Grant No. 12034020)+1 种基金Young Science and Technology Talents of Inner Mongolia, China (Grant No. NJYT22101)the Talent Development Fund of Inner Mongolia, China。
文摘We report a high-average-power noise-like pulse(NLP) and dissipative soliton(DS) pulse fiber laser. Average power as high as 4.8 W could be obtained at the fundamental mode-locked repetition rate. The NLP can also be transformed into a more powerful DS mode-locking state by optimizing the polarization and losses of intra-cavity pulses in the nonlinear polarization evolution regime. The operation mode between the NLP and DS can be switched, and the laser output performance in both modes has been studied. The main advantage of this work is switchable high-power operation between the NLP and DS. In comparison with conventional single-mode NLP fiber lasers, the multi-function high-power optical source will greatly push its application in supercontinuum generation, coherence tomography, and industrial processing.
基金the National Natural Science Foundation of China(Grant No.61935007).
文摘A refractive index(RI)sensor based on the surface plasmon resonance effect is proposed using a truncated cladding negative curvature fiber(TC-NCF).The influences of the TC-NCF structure parameters on the sensing performances are investigated and compared with the traditional NCF.The simulation results show that the proposed TC-NCF RI sensor has an ultra-wide detection range from 1.16 to 1.43.The maximum wavelength sensitivity reaches 12400 nm/RIU,and the corresponding R^(2)of the polynomial fitting equation is 0.9999.The maximum and minimum resolutions are 2.56×10^(-5)and 8.06×10^(-6),respectively.In addition,the maximum amplitude sensitivity can reach-379.1 RIU^(-1)when the RI is chosen as 1.43.The proposed TC-NCF RI sensor could be useful in biochemical medicine,environmental monitoring,and food safety.
基金Project supported by the National Natural Science Foundation of China(Grant No.51309059)
文摘We propose a design of terahertz refractive index sensing based on the multi-metal-wire（MMW） hybrid-cladding hollow waveguide. The proposed terahertz hybrid-cladding hollow waveguide comprises one air core in the center surrounding MMW surrounded dielectric. The central air core is used for filling lossless measurands and transmitting terahertz light. In particular, the refractive index sensing is realized by measuring the mode field area（MFA） variation of radially polarized mode. The modal effective refractive index, mode field intensity distribution, and mode field area properties responding to the measurand refractive indexes for different operating frequencies and structure dimensions are investigated, respectively.Simulations show that the proposed terahertz refractive index sensor can realize easily the measurement of the measurand refractive index. Meanwhile, the effects of operating frequency and structure parameters on sensitivity and measurement accuracy are also studied. In view of the trade-off between sensitivity and measurement accuracy, the reasonable choice of the operating frequency and structure parameters can optimize appropriately the sensitivity and measurement accuracy, and the sensitivity can reach approximately 0.585 mm^2/RIU（RIU is short for refraction index units） with the proper frequency and structure parameter.
文摘Metal matrix composite coating Ni-Fe/SiC was prepared on an iron-based substrate bythermal spraying combined with laser cladding,using SiC particulates as the reinforcing agent.The micro-structures of the coatings formed at different thermal spraying and laser cladding conditions were character-ized by means of X-ray diffraction and electron probe microanalysis.The thermal oxidation properties of themixed powders composed of different content of SiC particulates and relevant Ni-based alloy as the balancewere examined using differential scanning calorimetry.The hardness profile of the thermal sprayed and lasercladding coatings was investigated as well.It was found that SiO2particulates were generated and dissolvedand dispersed during the melting and solidification of the laser cladding process,which was ascribed to theoxidation of the dispersed SiC particulates.The micro-hardness depth profile of the target laser claddingcomposite coating was characterized by gradient distribution,which could be related to the gradient distribu-tion of the hard SiC and SiO2particulates in the dendrites and interdendrites of the cladding layer.Both SiCand SiO2particulates contributed to greatly increasing the microhardness and mechanical properties of the ti-tled laser cladding composite coatings.
