Reaction bonded SiC（RBSiC） is attractive for optical application because of its favorable properties and low fabrication cost. However, the difficultness and cost involved in RBSiC grinding limit its application. Th...Reaction bonded SiC（RBSiC） is attractive for optical application because of its favorable properties and low fabrication cost. However, the difficultness and cost involved in RBSiC grinding limit its application. The investigation on high efficient and low-cost machining with good grinding quality is desired. Generally, high efficient machining for RBSiC is realized by using coarse grain size grinding wheels, but serious grinding damage is inevitable. In this paper, monolayer nickel electroplated coarse grain size diamond grinding wheels with grain sizes of 46 μm, 91 μm, and 151 μm were applied to the grinding of RBSiC. An electrolytic in-process dressing（ELID） assisted conditioning technique was first developed by using cup shape copper bonded conditioning wheels with grain sizes of 15 μm and 91 μm to generate the conditioned coarse grain size wheels with minimized wheel run-out error within 2 μm, constant wheel peripheral envelop as well as top-flattened diamond grains. Then, the grinding experiments on RBSiC were carried out to investigate the grinding performance and material removal mechanism. The experimental results indicate that the developed conditioning technique is applicable and feasible to condition the coarse grain size diamond wheels under optimal conditioning parameters, and the material removal mechanism involved in RBSiC grinding is the combination of brittle fracture and ductile deformation to generate smooth ground surface. This research is significant for the high efficient and low-cost precision grinding of RBSiC with good ground surface quality.展开更多
The thermal conductivity of diamond/copper composites with bimodal particle sizes was studied. The composites were prepared through pressure infiltration of liquid copper into diamond preforms with a mixture of 40 and...The thermal conductivity of diamond/copper composites with bimodal particle sizes was studied. The composites were prepared through pressure infiltration of liquid copper into diamond preforms with a mixture of 40 and 100 pm-size diamonds. The permeability of the preforms with different coarse-to-fine volume ratios of diamonds was investigated. The thermal conductivity of the diamond/copper composites with bimodal size distribution was compared to the theoretical value derived from an analytical model developed by Chu. It is predicted that the diamond/copper composites could reach a higher thermal conductivity and their surface roughness could be improved by applying bimodal diamond particle sizes.展开更多
Microcrystalline diamond(MCD)films with different grain sizes ranging from 160 nm to 2200 nm are prepared by using a hot filament chemical vapor deposition(HFCVD)system,and the influences of grain size and structural ...Microcrystalline diamond(MCD)films with different grain sizes ranging from 160 nm to 2200 nm are prepared by using a hot filament chemical vapor deposition(HFCVD)system,and the influences of grain size and structural features on optical properties are investigated.The results show that the film with grain size in a range of 160 nm–310 nm exhibits a higher refractive index in a range of(2.77–2.92).With grain size increasing to 620±300 nm,the refractive index shows a value between 2.39 and 2.47,approaching to that of natural diamond(2.37–2.55),and a lower extinction coefficient value between 0.08 and 0.77.When the grain size increases to 2200 nm,the value of refractive index increases to a value between 2.66 and 2.81,and the extinction coefficient increases to a value in a range of 0.22–1.28.Visible Raman spectroscopy measurements show that all samples have distinct diamond peaks located in a range of 1331 cm-1–1333 cm-1,the content of diamond phase increases gradually as grain size increases,and the amount of trans-polyacetylene(TPA)content decreases.Meanwhile,the sp2 carbon clusters content and its full-width-at-half-maximum(FWHM)value are significantly reduced in MCD film with a grain size of 620 nm,which is beneficial to the improvement of the optical properties of the films.展开更多
The shrimp beam trawl fishery in the northern South China Sea is characterized by high by-catch and poor selectivity problems.Among by-catch species,banded scad(Caranx(Atule)kalla)is economically the most important on...The shrimp beam trawl fishery in the northern South China Sea is characterized by high by-catch and poor selectivity problems.Among by-catch species,banded scad(Caranx(Atule)kalla)is economically the most important one.The aim of this study is to improve the selective properties of codends for banded scad.Size selectivity of 2 traditional diamond mesh codends,with mesh size 25 and 30 mm(defined as D25 and D30,respectively),and 4 new combined square and diamond mesh codends,with25 mm square-mesh and 25 mm diamond-mesh(S25+D25),30 mm square-mesh and 25 mm diamondmesh(S30+D25),35 mm square-mesh and 25 mm diamond-mesh(S35+D25),and 35 mm square-mesh and18 mm diamond-mesh(S35+D18),were tested for banded scad in shrimp beam trawl fishery of the South China Sea.A total of 54 valid hauls were finished using the covered codend method,and 5750 banded scad were caught.Selective parameters were obtained using the logistic equation with the maximum likelihood method,by incorporating the between-haul variation.The results show that the present minimum mesh size for shrimp beam trawl in the South China Sea,25-mm diamond mesh size,is insufficient to release immature banded scad.The S35+D25 codend is proved to be the most eff ective codend to release immature banded scad,and its 50%retention length(L _(50))is larger than the minimum landing size(MLS=63.5 mm)of banded scad.However,the 95%confidence intervals of L _(50) overlap among the three combined mesh codends,the S25+D25,S30+D25 and S35+D25 codend.For a sustainable exploitation of banded scad,larger mesh sizes are suggested to be investigated for the combined mesh codends.展开更多
Ti, Al, graphite and diamond powders were used as raw materials to prepare Ti_2AlC matrixbonded diamond composite using self-propagating high-temperature synthesis(SHS) method. The effect of diamond size and content o...Ti, Al, graphite and diamond powders were used as raw materials to prepare Ti_2AlC matrixbonded diamond composite using self-propagating high-temperature synthesis(SHS) method. The effect of diamond size and content on the fabrication of Ti_2AlC-bonded diamond material was investigated. Results showed that Ti_2AlC matrix-bonded diamond composites could be obtained by SHS. The phase composition and microstructure of the Ti_2AlC-bonded diamond material were influenced by the diamond content and size. When the diamond(93 μm) additive amounts were 10% and 20%, the product phases included Ti_2AlC, TiC and Al_3Ti. However, excess Ti and Al persisted in the sample that contained 30% diamond. Diamond bonded well with the matrix in the sample that contained 10% diamond. Moreover, addition of coarse diamond particles with sizes of 93 and 125 μm produced a mainly Ti_2AlC matrix. However, diamond adequately reacted with Ti to form TiC when finer diamond particles(5 and 10 μm) were used.展开更多
The wear behaviour of composite coatings is related to the nature of embedded particles.The effects of particle size on the wear behaviour of composite coatings are analyzed.Electroless nickel composite coatings conta...The wear behaviour of composite coatings is related to the nature of embedded particles.The effects of particle size on the wear behaviour of composite coatings are analyzed.Electroless nickel composite coatings containing diamond particles with the sizes in the range of 0—0.5,0.5—1,1—2μm are prepared.The surface morphology of diamond particles and composite coatings are observed by scanning electron microscopy(SEM).The wear tests of composite coatings are comparatively evaluated by sliding against a cemented tungsten carbide ball.The 3D morphology of worn scar is evaluated by using a 3Dprofiler.The results show that the hardness and wear resistance of composite coatings can increase with the increase of particle sizes.The mixture mechanism of adhesive wear and abrasive wear turn into single abrasive wear with the increase of particle sizes as well.The transformation of wear behaviour is mainly attributed to particle roles during wear process.展开更多
The dispersion behavior of micro-diamond particles ranging from 0 to 0.5 micron was compared between in DI water and in electroless nickel solution. The effects of the concentration of electroless solution, temperatur...The dispersion behavior of micro-diamond particles ranging from 0 to 0.5 micron was compared between in DI water and in electroless nickel solution. The effects of the concentration of electroless solution, temperature, ultrasonic treatment, stirring speed, and baffles on the size distribution of micro diamond particles in electroless nickel solution were studied. Results show that the dispersion of micro diamond particles in DI water is obviously superior to that in electroless nickel solution. Micro diamond particles agglomerate evidently when the concentration of electroless solution Velect：VDI in dispersion media exceeds 5%0. Diamond particles agglomerate more and more seriously with the increase of the ion concentration. Applying ultrasonic, increasing stirring speed and adding baffles are helpful to improving the dispersion of diamond particles in the electroless nickel solution and its uniform distribution in the Ni-P coating.展开更多
Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literatur...Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literature.The energy difference of C2vand C3vstructures is qualitatively affected by the supercell size,and the 216-atom supercell could be proposed as the minimum to obtain stable configuration of substitutional S in diamond.Using supercells of up to 512 atoms,the donor level of substitutional S with C2vsymmetry is deep.展开更多
基金supported by the Alexander von Humboldt (AvH) Stiftung/Foundation of Germany,National Key Project of China (Grant No. 09ZX04001-151)the "111" Project of China (Grant No. B07018)
文摘Reaction bonded SiC（RBSiC） is attractive for optical application because of its favorable properties and low fabrication cost. However, the difficultness and cost involved in RBSiC grinding limit its application. The investigation on high efficient and low-cost machining with good grinding quality is desired. Generally, high efficient machining for RBSiC is realized by using coarse grain size grinding wheels, but serious grinding damage is inevitable. In this paper, monolayer nickel electroplated coarse grain size diamond grinding wheels with grain sizes of 46 μm, 91 μm, and 151 μm were applied to the grinding of RBSiC. An electrolytic in-process dressing（ELID） assisted conditioning technique was first developed by using cup shape copper bonded conditioning wheels with grain sizes of 15 μm and 91 μm to generate the conditioned coarse grain size wheels with minimized wheel run-out error within 2 μm, constant wheel peripheral envelop as well as top-flattened diamond grains. Then, the grinding experiments on RBSiC were carried out to investigate the grinding performance and material removal mechanism. The experimental results indicate that the developed conditioning technique is applicable and feasible to condition the coarse grain size diamond wheels under optimal conditioning parameters, and the material removal mechanism involved in RBSiC grinding is the combination of brittle fracture and ductile deformation to generate smooth ground surface. This research is significant for the high efficient and low-cost precision grinding of RBSiC with good ground surface quality.
基金supported by the National Natural Science Foundation of China (No. 50971020)the National High-Tech Research and Development Program of China (No. 2008AA03Z505)
文摘The thermal conductivity of diamond/copper composites with bimodal particle sizes was studied. The composites were prepared through pressure infiltration of liquid copper into diamond preforms with a mixture of 40 and 100 pm-size diamonds. The permeability of the preforms with different coarse-to-fine volume ratios of diamonds was investigated. The thermal conductivity of the diamond/copper composites with bimodal size distribution was compared to the theoretical value derived from an analytical model developed by Chu. It is predicted that the diamond/copper composites could reach a higher thermal conductivity and their surface roughness could be improved by applying bimodal diamond particle sizes.
基金Project supported by the Key Project of the National Natural Science Foundation of China(Grant No.U1809210)the National Natural Science Foundation of China(Grant Nos.50972129 and 50602039)+4 种基金the International Science Technology Cooperation Program of China(Grant No.2014DFR51160)the National Key Research and Development Program of China(Grant No.2016YFE0133200)the European Union’s Horizon 2020 Research and Innovation Staff Exchange(RISE)Scheme(Grant No.734578)the Belt and Road International Cooperation Project from Key Research and Development Program of Zhejiang Province,China(Grant No.2018C04021)the Natural Science Foundation of Zhejiang Province,China(Grant Nos.LQ15A040004 and LY18E020013)
文摘Microcrystalline diamond(MCD)films with different grain sizes ranging from 160 nm to 2200 nm are prepared by using a hot filament chemical vapor deposition(HFCVD)system,and the influences of grain size and structural features on optical properties are investigated.The results show that the film with grain size in a range of 160 nm–310 nm exhibits a higher refractive index in a range of(2.77–2.92).With grain size increasing to 620±300 nm,the refractive index shows a value between 2.39 and 2.47,approaching to that of natural diamond(2.37–2.55),and a lower extinction coefficient value between 0.08 and 0.77.When the grain size increases to 2200 nm,the value of refractive index increases to a value between 2.66 and 2.81,and the extinction coefficient increases to a value in a range of 0.22–1.28.Visible Raman spectroscopy measurements show that all samples have distinct diamond peaks located in a range of 1331 cm-1–1333 cm-1,the content of diamond phase increases gradually as grain size increases,and the amount of trans-polyacetylene(TPA)content decreases.Meanwhile,the sp2 carbon clusters content and its full-width-at-half-maximum(FWHM)value are significantly reduced in MCD film with a grain size of 620 nm,which is beneficial to the improvement of the optical properties of the films.
基金Supported by the Special Fund for Agro-scientific Research in the Public Interest(No.201203018)
文摘The shrimp beam trawl fishery in the northern South China Sea is characterized by high by-catch and poor selectivity problems.Among by-catch species,banded scad(Caranx(Atule)kalla)is economically the most important one.The aim of this study is to improve the selective properties of codends for banded scad.Size selectivity of 2 traditional diamond mesh codends,with mesh size 25 and 30 mm(defined as D25 and D30,respectively),and 4 new combined square and diamond mesh codends,with25 mm square-mesh and 25 mm diamond-mesh(S25+D25),30 mm square-mesh and 25 mm diamondmesh(S30+D25),35 mm square-mesh and 25 mm diamond-mesh(S35+D25),and 35 mm square-mesh and18 mm diamond-mesh(S35+D18),were tested for banded scad in shrimp beam trawl fishery of the South China Sea.A total of 54 valid hauls were finished using the covered codend method,and 5750 banded scad were caught.Selective parameters were obtained using the logistic equation with the maximum likelihood method,by incorporating the between-haul variation.The results show that the present minimum mesh size for shrimp beam trawl in the South China Sea,25-mm diamond mesh size,is insufficient to release immature banded scad.The S35+D25 codend is proved to be the most eff ective codend to release immature banded scad,and its 50%retention length(L _(50))is larger than the minimum landing size(MLS=63.5 mm)of banded scad.However,the 95%confidence intervals of L _(50) overlap among the three combined mesh codends,the S25+D25,S30+D25 and S35+D25 codend.For a sustainable exploitation of banded scad,larger mesh sizes are suggested to be investigated for the combined mesh codends.
基金Funded by National Natural Science Foundation of China(Nos.51602356 and 11472316)the University Innovation Team Project in Henan Province(Nos.15IRTSTHN004,16A430049,17A430034,and 18A430035)Henan Innovative Excellent Scientific and Technological Team(No.CXTD2013048)
文摘Ti, Al, graphite and diamond powders were used as raw materials to prepare Ti_2AlC matrixbonded diamond composite using self-propagating high-temperature synthesis(SHS) method. The effect of diamond size and content on the fabrication of Ti_2AlC-bonded diamond material was investigated. Results showed that Ti_2AlC matrix-bonded diamond composites could be obtained by SHS. The phase composition and microstructure of the Ti_2AlC-bonded diamond material were influenced by the diamond content and size. When the diamond(93 μm) additive amounts were 10% and 20%, the product phases included Ti_2AlC, TiC and Al_3Ti. However, excess Ti and Al persisted in the sample that contained 30% diamond. Diamond bonded well with the matrix in the sample that contained 10% diamond. Moreover, addition of coarse diamond particles with sizes of 93 and 125 μm produced a mainly Ti_2AlC matrix. However, diamond adequately reacted with Ti to form TiC when finer diamond particles(5 and 10 μm) were used.
基金Supported by the National Natural Science Foundation of China(51175260)the Fundamental Research Funds for the Central Universities(NP2012506)the Open Fund of Jiangsu Province Key Laboratory for Materials Tribology(kjsmcx0901)
文摘The wear behaviour of composite coatings is related to the nature of embedded particles.The effects of particle size on the wear behaviour of composite coatings are analyzed.Electroless nickel composite coatings containing diamond particles with the sizes in the range of 0—0.5,0.5—1,1—2μm are prepared.The surface morphology of diamond particles and composite coatings are observed by scanning electron microscopy(SEM).The wear tests of composite coatings are comparatively evaluated by sliding against a cemented tungsten carbide ball.The 3D morphology of worn scar is evaluated by using a 3Dprofiler.The results show that the hardness and wear resistance of composite coatings can increase with the increase of particle sizes.The mixture mechanism of adhesive wear and abrasive wear turn into single abrasive wear with the increase of particle sizes as well.The transformation of wear behaviour is mainly attributed to particle roles during wear process.
基金Funded by the Jiangsu Key Laboratory for Materials Tribology(No.kjsmcx0901)
文摘The dispersion behavior of micro-diamond particles ranging from 0 to 0.5 micron was compared between in DI water and in electroless nickel solution. The effects of the concentration of electroless solution, temperature, ultrasonic treatment, stirring speed, and baffles on the size distribution of micro diamond particles in electroless nickel solution were studied. Results show that the dispersion of micro diamond particles in DI water is obviously superior to that in electroless nickel solution. Micro diamond particles agglomerate evidently when the concentration of electroless solution Velect：VDI in dispersion media exceeds 5%0. Diamond particles agglomerate more and more seriously with the increase of the ion concentration. Applying ultrasonic, increasing stirring speed and adding baffles are helpful to improving the dispersion of diamond particles in the electroless nickel solution and its uniform distribution in the Ni-P coating.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11704143,51672102,51632002,and 11604023)the National Key Research and Development Program of China(Grant Nos.2018YFA0305900 and 2016YFB0201204)the Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT-15R23)
文摘Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literature.The energy difference of C2vand C3vstructures is qualitatively affected by the supercell size,and the 216-atom supercell could be proposed as the minimum to obtain stable configuration of substitutional S in diamond.Using supercells of up to 512 atoms,the donor level of substitutional S with C2vsymmetry is deep.
