Copper, iron and cobalt based pre-alloyed powders for diamond tools were prepared by ultrahigh pressure water atomization（UPWA） process. Pre-alloyed powders prepared by different processes including UPWA, convention...Copper, iron and cobalt based pre-alloyed powders for diamond tools were prepared by ultrahigh pressure water atomization（UPWA） process. Pre-alloyed powders prepared by different processes including UPWA, conventional water atomization （CWA） and elemental metal mechanical mixing （EMMM） were sintered to segments and then compared in mechanical properties, holding force between matrix and diamond, fracture morphology of blank and sintering diamond section containing matrix. The results showed that the pre-alloyed powder prepared by UPWA exhibits the best mechanical properties including the relative density, the hardness and the bending strength of matrix sinteredsegment. Sintered segments fractography of UPWA pre-alloyed powder indicatesmechanical mosaic strength and chemical bonding force between the pre-alloyed powder and the diamond, leading to the great increase in the holding force between matrix and diamond. The mechanical performance andthe service life of diamond tools were greatly improved by UPWA pre-alloyed powders.展开更多
To improve the oxidation and graphitization resistances of the polycrystalline diamond(PCD), Ti coating was deposited on the diamond powders via magnetic sputtering method, which achieved a uniform Ti C protection bar...To improve the oxidation and graphitization resistances of the polycrystalline diamond(PCD), Ti coating was deposited on the diamond powders via magnetic sputtering method, which achieved a uniform Ti C protection barrier in PCD during the sintering process. The phase compositions, microstructures and thermal stability of Ti-PCD were characterized by X-ray diffraction(XRD), Auger electron spectroscopy(AES),scanning electron microscopy(SEM) and thermal gravimetric-differential scanning calorimetry(TG-DSC).The results demonstrate that the oxidation and graphitization resistances of PCD are strengthened due to the existence of Ti C phase, which acts as an effective inhibitor. The as-received inhibitor delays the oxidation and graphitization of PCD, elevating their initial temperature by ~50°C and ~100°C, respectively. During the annealing treatment of Ti-PCD, the priory oxidation of Ti C, which produces Ti O2 as an oxygen barrier, postpones the diamond oxide. Moreover, the Ti C barrier also protects diamond grains from direct contact with cobalt, thus a lower cobalt-catalytic graphitization, and yields to an improved graphitization resistance of PCD. The enhanced oxidation and graphitization resistances of PCD are of significant importance for practical applications to elevated temperatures.展开更多
Fine Ni powder is often added to Co and bronze-based metal binder powders for diamond tool segments.Ni is a lower cost substitute for extra-fine Co powder and increases the toughness of Co-Fe diamond binders at the ex...Fine Ni powder is often added to Co and bronze-based metal binder powders for diamond tool segments.Ni is a lower cost substitute for extra-fine Co powder and increases the toughness of Co-Fe diamond binders at the expense of lower hardness and bend strength.In bronze-based diamond binder segments,Ni increases hardness and yield strength.Several grades of Ni powder are used commercially with both Co and bronze-based diamond binders.This paper compares properties of diamond binders containing carbonyl Ni powders including standard Inco(?) T255,T123 PM and T 110 PM.Binder materials were made by ball milling or dry mixing of the fine carbonyl Ni and Fe powders with either XF Co or air atomized bronze(90/10 Cu/Sn) powders.Co-based powder blends were hot pressed at 20～35 MPa and 700℃to 900℃.Bronze-based powder blends were cold pressed and sintered at 840℃.Apparent density,apparent hardness and bend strength(TRS) were compared for different binder compositions and processing conditions.展开更多
Nickel coated diamond composite powders were fabricated via a newly developed direct electrodeposition technique. The effects of activators on the coating of diamond were firstly investigated and diamond grinding whee...Nickel coated diamond composite powders were fabricated via a newly developed direct electrodeposition technique. The effects of activators on the coating of diamond were firstly investigated and diamond grinding wheels were then prepared from Ni-coated diamond composite powders with different activators. The microstructural characterizations of this composite powders were finally conducted by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, and the mechanical and tribological properties of as-prepared diamond grinding wheels were also measured. There are changes in microstructures and properties of the composite powders with activators. The activator concentration also has an influence on the morphologies and phase structures of the Ni coating on diamond particles.The composite powders with more compact coating of nickel can be prepared by adding 1 g dm^（-3） or more AgNO_3 as an activator to electrodeposit nickel on diamond. The mechanical and tribological properties of diamond grinding wheels were significantly improved when the coating phase structure of Ni crystal grew with（111） plane orientation on the surface of diamond particles. The wheels made from nickel coated diamond composite powders possessed the advantages of easy preparation and outstanding tribological properties. Therefore, Ni coated diamond composite powders exhibit a great potential to be extensively applied in diamond cutting and grinding tools.展开更多
In this paper, diamond crystallization from carbonyl nickel powders-C and carbonyl nickel powders + Fe–C systems are investigated in detail at a pressure of 6.0 GPa and temperatures ranging from 1410°C–to 1435&...In this paper, diamond crystallization from carbonyl nickel powders-C and carbonyl nickel powders + Fe–C systems are investigated in detail at a pressure of 6.0 GPa and temperatures ranging from 1410°C–to 1435°C by temperature gradient growth. The effects of Fe additive on the crystal morphology are discussed in the diamond crystallization process.Furthermore, Fourier infrared measurement results indicate that the spectrum of the diamond obtained from Ni + Fe–C system after annealing treatment is nearly consistent with that of natural diamond crystal. We believe that this study is of benefit to a further understanding of the growth mechanism of natural diamond.展开更多
A numerical investigation was carried out to examine the role of micro-sized diamond powder filler on the on-axis tensile stiffness properties of the standard modulus T300 and the high modulus YS90A woven fabric compo...A numerical investigation was carried out to examine the role of micro-sized diamond powder filler on the on-axis tensile stiffness properties of the standard modulus T300 and the high modulus YS90A woven fabric composite plates by progressive damage modeling. Finite element modeling (FEM) results for the T300 composite with and without diamond powder predicted a specific case of fiber failure in all the plies showing the characteristics of brittle failure. Static tensile tests were carried out on the YS90A composite coupons containing no diamond powder (DP) and filled with 6% and 12% volume fractions of DP. A higher content of diamond powder in the coupons led to agglomeration. This induced stress concentrations and subsequently reduced the mechanical properties. FEM was carried out considering specimens with and without an induced stress concentration geometry in the YS90A coupons filled with DP. The results of the on-axis tensile tests indicated a delamination type of failure in both cases with additional fiber fracture in the Open Hole Tensile (OHT) coupons.展开更多
Diamond polycrystal powder has been produced directly from gas phase in an arc discharge plasma jet system.Acetylene diluted in argon was used as hydrocarbon source gas.The product was the mixture of diamond polycryst...Diamond polycrystal powder has been produced directly from gas phase in an arc discharge plasma jet system.Acetylene diluted in argon was used as hydrocarbon source gas.The product was the mixture of diamond polycrystal powders and soot.The 3C cubic phase diamond which is dominant,and the mixture phases of cubic and 6H hexagonal diamond are identified in the produced diamond polycrystal powders by electron diffraction patterns.展开更多
Boron doped diamond(BDD)electrode is a promising electrochemical material for detecting dopamine level in the human’s body.In this work,we developed a new doping source-graphite and solid boron oxide powders to synth...Boron doped diamond(BDD)electrode is a promising electrochemical material for detecting dopamine level in the human’s body.In this work,we developed a new doping source-graphite and solid boron oxide powders to synthesize BDD film with microwave plasma chemical vapor deposition,so as to avoid using toxic or corrosive dopants,such as boroethane and trimethylborate.The synthesized BDD film is pinhole free and with high doping density of 8.44×10^20 cm^-3 calculated from the Raman spectroscopy.Subsequently,Au nanospheres were decorated on the surface of BDD film to improve electrochemical performance of the BDD film.The Au nanoparticles modified BDD electrode demonstrates an excellent electrochemical response,a high sensitivity(in the range of 5μM-1 m M),and a low detection limit(~0.8μM)for detecting dopamine.展开更多
Diamond/Cu-Sn-Ti composites have been successfully prepared by cold-press forming in conjunction with high-temperature vacuum active brazing at 1223 K.Ensuing wetting behaviors between diamond and filler metal,interfa...Diamond/Cu-Sn-Ti composites have been successfully prepared by cold-press forming in conjunction with high-temperature vacuum active brazing at 1223 K.Ensuing wetting behaviors between diamond and filler metal,interfacial characteristics of the reaction layer,and wear resistance of the bulky composite have been fully investigated.It is revealed that all diamond particles can only be fully coated when the TiH_(2)content exceeds 5 wt%,below which sharp edges on diamond can still be observed.The interfacial reaction layer is found to be composed of TiC,the thickness of which is demonstrated to increase as a function of TiH_(2)content,arriving at the peak value of 1.70μm and remaining almost constant afterwards.It is further shown that the maximum wear resistance occurs approaching 5 wt%TiH_(2)content.Potential mechanisms responsible for such interesting phenomena have been postulated.展开更多
Nanocrystalline WC-Co composite powder and coated tungsten diamond by using vacuum vapor deposition were consolidated by the spark plasma sintering （SPS） process to prepare diamond-enhanced WC-Co cemented carbide co...Nanocrystalline WC-Co composite powder and coated tungsten diamond by using vacuum vapor deposition were consolidated by the spark plasma sintering （SPS） process to prepare diamond-enhanced WC-Co cemented carbide composite materials. The interface microstructures between coated tungsten diamond and WC-Co cemented carbide matrix were investigated by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）. The results showed that there is a transitional layer between the diamond and the matrix, in which the carbon content is 62.97wt.%, and the content of cobalt in the transitional zone is 6.19wt.%; the content of cobalt in the WC-Co cemented carbide matrix is 6.07wt.%, in which the carbon content is 15.95wt.%, and the content of cobalt on the surface of diamond is 7.30wt.%, in which the carbon content is 80.38wt.%. The transitional zone prevents the carbon atom of the diamond from spreading to the matrix, in which the carbon content does coincide with the theoretical value of the raw nanocomposite powders, and the carbon content forms a graded distribution among the matrix, transitional zone, and the surface of diamond; after the 1280℃ SPS consolidated process the diamond still maintains a very good crystal shape, the coated tungsten on the surface of the diamond improves thermal stability of the diamond and increases the bonding strength of the interface between the diamond and the matrix.展开更多
The work presents the possibility of substitution of expensive, wear resistant Co-WC powders, that have been traditionally used in the production of sintered diamond tools, with cheap iron-base counterparts manufactur...The work presents the possibility of substitution of expensive, wear resistant Co-WC powders, that have been traditionally used in the production of sintered diamond tools, with cheap iron-base counterparts manufactured by ball milling. It has been shown that ball-milled Fe-Ni-Cu-Sn-C powders can be consolidated to a virtually pore-free condition by hot pressing at 900 ℃. The as-consolidated material has nanocrystalline structure and is characterised by a combination of high hardness, mechanical strength and excellent resistance to abrasion. Its properties can be widely modified by changing the milling conditions.展开更多
We demonstrate an innovative preparation approach of diamond/Cu composites by powder-in-tube technique and rolling. A small copper tube was loaded with Ti- and Cu-coated diamond particles, mad then the diamond particl...We demonstrate an innovative preparation approach of diamond/Cu composites by powder-in-tube technique and rolling. A small copper tube was loaded with Ti- and Cu-coated diamond particles, mad then the diamond particles were combined with Cu matrix by composite rolling. The morphology and element distribution of the interface between diamond and Cu were determined by scanning electron microscopy and energy-dispersive spectrometer. Finite element method （FEM） simulation was used to analyze the rolling process associated with experiment by DEFORM-3D. The final experimental results showed that homogeneous distribution of diamond particles could be observed in the center layer of the composites. According to the contrast experiments, the sample, whose diamond particle size is 0.12-0.15 mm and thickness of pre-rolling is 1.2 mm, showed relatively complete morphologies and homogeneous distribution. Experimental results indicated a poor efficacy of excessive rolling reduction. The thermal conductivity of the composites is about 453 W （m K）-1 by theoretical calculation. For FEM simulation, roiling strain and temperature field of the composites were simulated by DEFORM-3D. Simulation results were interpreted, and numerical results verified the reliability of the model. The simulation predicted that the local area of large strain, indicative of the strain along the thickness direction, could be intensified by adding diamond particles.展开更多
A novel process, which was based on powder injection molding, was investigated for the fabrication of ceramic photonic bandgap structure with three-dimensional diamond lattice. The SiO2-TiO2 ceramic powder was mixed w...A novel process, which was based on powder injection molding, was investigated for the fabrication of ceramic photonic bandgap structure with three-dimensional diamond lattice. The SiO2-TiO2 ceramic powder was mixed with a water-soluble agent to produce slurry. The slurry was then injected into an epoxy mold with inverse diamond lattice, fabricated by the stereolitographic rapid prototyping process. To increase the density of the green compact, cold isostatic pressing was applied on the unit. Using thermal debinding, the water-soluble agent and the epoxy were extracted at 360 and 650 K, respectively. Sintering was immediately done at 950 K for 5 h and the desired three-dimensional ceramic structure was obtained. The calculated band diagram for this structure indicated the existence of an absolute photonic bandgap for all wave vectors. At 14.7-18.5 GHz, a complete band gap was located with a maximum attenuation of 30 dB at 17 GHz, when transmission was measured in the 〈100〉 direction between 10 and 20 GHz.展开更多
By analyzing the abrasive theory of concrete diamond sawblade, the proposal that the diamond should be selected by its function in cutting concrete is presented. The part of the big grit diamonds cut rock, and the par...By analyzing the abrasive theory of concrete diamond sawblade, the proposal that the diamond should be selected by its function in cutting concrete is presented. The part of the big grit diamonds cut rock, and the part of the small grit diamonds improve the wearability of the matrix. The contrast tests are done with different shapes of sawbaldes in split segment, slant "U" slot segment, sandwich segment, turbo segment and three-slot segment. The special shapes of sawblades can improve the effect of cooling and the removing ability of the rock powder. The data of tests show that the efficiency of cutting and the life of sawblades are improved by designing the diamond prescription and using the especial geometry of segment.展开更多
基金Projects(2010SK3172,2015JC3005)supported by the Key Program of Science and Technology Project of Hunan Province,China
文摘Copper, iron and cobalt based pre-alloyed powders for diamond tools were prepared by ultrahigh pressure water atomization（UPWA） process. Pre-alloyed powders prepared by different processes including UPWA, conventional water atomization （CWA） and elemental metal mechanical mixing （EMMM） were sintered to segments and then compared in mechanical properties, holding force between matrix and diamond, fracture morphology of blank and sintering diamond section containing matrix. The results showed that the pre-alloyed powder prepared by UPWA exhibits the best mechanical properties including the relative density, the hardness and the bending strength of matrix sinteredsegment. Sintered segments fractography of UPWA pre-alloyed powder indicatesmechanical mosaic strength and chemical bonding force between the pre-alloyed powder and the diamond, leading to the great increase in the holding force between matrix and diamond. The mechanical performance andthe service life of diamond tools were greatly improved by UPWA pre-alloyed powders.
基金financially supported by the National Natural Science Foundation of China(Nos.51875537,41572359 and 51375466)the Beijing Natural Science Foundation(No.3172026)+2 种基金the Beijing Nova program(No.Z171100001117059)the Fundamental Research Funds for the Central University(No.2652018094)the Natural Science Foundation of Ningxia Province(No.2018AAC03200)。
文摘To improve the oxidation and graphitization resistances of the polycrystalline diamond(PCD), Ti coating was deposited on the diamond powders via magnetic sputtering method, which achieved a uniform Ti C protection barrier in PCD during the sintering process. The phase compositions, microstructures and thermal stability of Ti-PCD were characterized by X-ray diffraction(XRD), Auger electron spectroscopy(AES),scanning electron microscopy(SEM) and thermal gravimetric-differential scanning calorimetry(TG-DSC).The results demonstrate that the oxidation and graphitization resistances of PCD are strengthened due to the existence of Ti C phase, which acts as an effective inhibitor. The as-received inhibitor delays the oxidation and graphitization of PCD, elevating their initial temperature by ~50°C and ~100°C, respectively. During the annealing treatment of Ti-PCD, the priory oxidation of Ti C, which produces Ti O2 as an oxygen barrier, postpones the diamond oxide. Moreover, the Ti C barrier also protects diamond grains from direct contact with cobalt, thus a lower cobalt-catalytic graphitization, and yields to an improved graphitization resistance of PCD. The enhanced oxidation and graphitization resistances of PCD are of significant importance for practical applications to elevated temperatures.
文摘Fine Ni powder is often added to Co and bronze-based metal binder powders for diamond tool segments.Ni is a lower cost substitute for extra-fine Co powder and increases the toughness of Co-Fe diamond binders at the expense of lower hardness and bend strength.In bronze-based diamond binder segments,Ni increases hardness and yield strength.Several grades of Ni powder are used commercially with both Co and bronze-based diamond binders.This paper compares properties of diamond binders containing carbonyl Ni powders including standard Inco(?) T255,T123 PM and T 110 PM.Binder materials were made by ball milling or dry mixing of the fine carbonyl Ni and Fe powders with either XF Co or air atomized bronze(90/10 Cu/Sn) powders.Co-based powder blends were hot pressed at 20～35 MPa and 700℃to 900℃.Bronze-based powder blends were cold pressed and sintered at 840℃.Apparent density,apparent hardness and bend strength(TRS) were compared for different binder compositions and processing conditions.
基金funded by the National Natural Science Foundation of China (Nos. 21476066 and 51271074)
文摘Nickel coated diamond composite powders were fabricated via a newly developed direct electrodeposition technique. The effects of activators on the coating of diamond were firstly investigated and diamond grinding wheels were then prepared from Ni-coated diamond composite powders with different activators. The microstructural characterizations of this composite powders were finally conducted by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, and the mechanical and tribological properties of as-prepared diamond grinding wheels were also measured. There are changes in microstructures and properties of the composite powders with activators. The activator concentration also has an influence on the morphologies and phase structures of the Ni coating on diamond particles.The composite powders with more compact coating of nickel can be prepared by adding 1 g dm^（-3） or more AgNO_3 as an activator to electrodeposit nickel on diamond. The mechanical and tribological properties of diamond grinding wheels were significantly improved when the coating phase structure of Ni crystal grew with（111） plane orientation on the surface of diamond particles. The wheels made from nickel coated diamond composite powders possessed the advantages of easy preparation and outstanding tribological properties. Therefore, Ni coated diamond composite powders exhibit a great potential to be extensively applied in diamond cutting and grinding tools.
基金supported by the National Natural Science Foundation of China(Grant No.51172089)the Natural Science Foundation of Guizhou Provincial Education Department,China(Grant No.KY[2013]183)the Research Fund for the Doctoral Program of Tongren University,China(Grant Nos.DS1302 and trxy S1415)
文摘In this paper, diamond crystallization from carbonyl nickel powders-C and carbonyl nickel powders + Fe–C systems are investigated in detail at a pressure of 6.0 GPa and temperatures ranging from 1410°C–to 1435°C by temperature gradient growth. The effects of Fe additive on the crystal morphology are discussed in the diamond crystallization process.Furthermore, Fourier infrared measurement results indicate that the spectrum of the diamond obtained from Ni + Fe–C system after annealing treatment is nearly consistent with that of natural diamond crystal. We believe that this study is of benefit to a further understanding of the growth mechanism of natural diamond.
文摘A numerical investigation was carried out to examine the role of micro-sized diamond powder filler on the on-axis tensile stiffness properties of the standard modulus T300 and the high modulus YS90A woven fabric composite plates by progressive damage modeling. Finite element modeling (FEM) results for the T300 composite with and without diamond powder predicted a specific case of fiber failure in all the plies showing the characteristics of brittle failure. Static tensile tests were carried out on the YS90A composite coupons containing no diamond powder (DP) and filled with 6% and 12% volume fractions of DP. A higher content of diamond powder in the coupons led to agglomeration. This induced stress concentrations and subsequently reduced the mechanical properties. FEM was carried out considering specimens with and without an induced stress concentration geometry in the YS90A coupons filled with DP. The results of the on-axis tensile tests indicated a delamination type of failure in both cases with additional fiber fracture in the Open Hole Tensile (OHT) coupons.
文摘Diamond polycrystal powder has been produced directly from gas phase in an arc discharge plasma jet system.Acetylene diluted in argon was used as hydrocarbon source gas.The product was the mixture of diamond polycrystal powders and soot.The 3C cubic phase diamond which is dominant,and the mixture phases of cubic and 6H hexagonal diamond are identified in the produced diamond polycrystal powders by electron diffraction patterns.
基金financially supported by the National Science Fund for Distinguished Young Scholars(No.51625201)the National Natural Science Foundation of China No.51,702,066+2 种基金the National Key Research and Development Program of China(No.2016YFE0201600)the Key Laboratory of Micro-systems and Micro-structures Manufacturing,Ministry of Education,Harbin Institute of Technology(No.2016KM001)the Innovative research group of NSFC11421091。
文摘Boron doped diamond(BDD)electrode is a promising electrochemical material for detecting dopamine level in the human’s body.In this work,we developed a new doping source-graphite and solid boron oxide powders to synthesize BDD film with microwave plasma chemical vapor deposition,so as to avoid using toxic or corrosive dopants,such as boroethane and trimethylborate.The synthesized BDD film is pinhole free and with high doping density of 8.44×10^20 cm^-3 calculated from the Raman spectroscopy.Subsequently,Au nanospheres were decorated on the surface of BDD film to improve electrochemical performance of the BDD film.The Au nanoparticles modified BDD electrode demonstrates an excellent electrochemical response,a high sensitivity(in the range of 5μM-1 m M),and a low detection limit(~0.8μM)for detecting dopamine.
基金the support from the National Natural Science Foundation of China(Nos.52104360 and U20A20277)Research Fund for Central Universities(Nos.N2025025 and N2125024)+5 种基金Project funded by China Postdoctoral Science Foundation(Nos.2020TQ0060 and 2020M680965)Postdoctoral research fund of Northeastern University(No.20210202)the State Key Laboratory of Tribology,Tsinghua University(No.SKLTKF20B14)State Key Laboratory of Solid Lubrication,Lanzhou Institute of Chemical Physics,Chinese Academy of Sciences(No.LSL-2003)State Key Laboratory of Advanced Brazing Filler Metals and Technology,Zhengzhou Research Institute of Mechanical Engineering Co.,LTD(No.SKLABFMT202002)supported by the Fund of the State Key Laboratory of Solidification Processing,Northwestern Polytechnic University(Grant No.SKLSP202114)。
文摘Diamond/Cu-Sn-Ti composites have been successfully prepared by cold-press forming in conjunction with high-temperature vacuum active brazing at 1223 K.Ensuing wetting behaviors between diamond and filler metal,interfacial characteristics of the reaction layer,and wear resistance of the bulky composite have been fully investigated.It is revealed that all diamond particles can only be fully coated when the TiH_(2)content exceeds 5 wt%,below which sharp edges on diamond can still be observed.The interfacial reaction layer is found to be composed of TiC,the thickness of which is demonstrated to increase as a function of TiH_(2)content,arriving at the peak value of 1.70μm and remaining almost constant afterwards.It is further shown that the maximum wear resistance occurs approaching 5 wt%TiH_(2)content.Potential mechanisms responsible for such interesting phenomena have been postulated.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50502026), the Chinese 863 Program (No. 2002AA302504), the Science Foundation of Wuhan University of Technology (No. xjj2005166), and the Key Project for Science and Technology Development of Wuhan City (No. 20041003068-04)
文摘Nanocrystalline WC-Co composite powder and coated tungsten diamond by using vacuum vapor deposition were consolidated by the spark plasma sintering （SPS） process to prepare diamond-enhanced WC-Co cemented carbide composite materials. The interface microstructures between coated tungsten diamond and WC-Co cemented carbide matrix were investigated by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）. The results showed that there is a transitional layer between the diamond and the matrix, in which the carbon content is 62.97wt.%, and the content of cobalt in the transitional zone is 6.19wt.%; the content of cobalt in the WC-Co cemented carbide matrix is 6.07wt.%, in which the carbon content is 15.95wt.%, and the content of cobalt on the surface of diamond is 7.30wt.%, in which the carbon content is 80.38wt.%. The transitional zone prevents the carbon atom of the diamond from spreading to the matrix, in which the carbon content does coincide with the theoretical value of the raw nanocomposite powders, and the carbon content forms a graded distribution among the matrix, transitional zone, and the surface of diamond; after the 1280℃ SPS consolidated process the diamond still maintains a very good crystal shape, the coated tungsten on the surface of the diamond improves thermal stability of the diamond and increases the bonding strength of the interface between the diamond and the matrix.
文摘The work presents the possibility of substitution of expensive, wear resistant Co-WC powders, that have been traditionally used in the production of sintered diamond tools, with cheap iron-base counterparts manufactured by ball milling. It has been shown that ball-milled Fe-Ni-Cu-Sn-C powders can be consolidated to a virtually pore-free condition by hot pressing at 900 ℃. The as-consolidated material has nanocrystalline structure and is characterised by a combination of high hardness, mechanical strength and excellent resistance to abrasion. Its properties can be widely modified by changing the milling conditions.
基金supported by the National Nature Science Foundation of China (Nos. 51174028 and 51541406)
文摘We demonstrate an innovative preparation approach of diamond/Cu composites by powder-in-tube technique and rolling. A small copper tube was loaded with Ti- and Cu-coated diamond particles, mad then the diamond particles were combined with Cu matrix by composite rolling. The morphology and element distribution of the interface between diamond and Cu were determined by scanning electron microscopy and energy-dispersive spectrometer. Finite element method （FEM） simulation was used to analyze the rolling process associated with experiment by DEFORM-3D. The final experimental results showed that homogeneous distribution of diamond particles could be observed in the center layer of the composites. According to the contrast experiments, the sample, whose diamond particle size is 0.12-0.15 mm and thickness of pre-rolling is 1.2 mm, showed relatively complete morphologies and homogeneous distribution. Experimental results indicated a poor efficacy of excessive rolling reduction. The thermal conductivity of the composites is about 453 W （m K）-1 by theoretical calculation. For FEM simulation, roiling strain and temperature field of the composites were simulated by DEFORM-3D. Simulation results were interpreted, and numerical results verified the reliability of the model. The simulation predicted that the local area of large strain, indicative of the strain along the thickness direction, could be intensified by adding diamond particles.
基金This work was financially supported by the Major State Basic Research Development Program of China (No.2004CB719802).
文摘A novel process, which was based on powder injection molding, was investigated for the fabrication of ceramic photonic bandgap structure with three-dimensional diamond lattice. The SiO2-TiO2 ceramic powder was mixed with a water-soluble agent to produce slurry. The slurry was then injected into an epoxy mold with inverse diamond lattice, fabricated by the stereolitographic rapid prototyping process. To increase the density of the green compact, cold isostatic pressing was applied on the unit. Using thermal debinding, the water-soluble agent and the epoxy were extracted at 360 and 650 K, respectively. Sintering was immediately done at 950 K for 5 h and the desired three-dimensional ceramic structure was obtained. The calculated band diagram for this structure indicated the existence of an absolute photonic bandgap for all wave vectors. At 14.7-18.5 GHz, a complete band gap was located with a maximum attenuation of 30 dB at 17 GHz, when transmission was measured in the 〈100〉 direction between 10 and 20 GHz.
文摘By analyzing the abrasive theory of concrete diamond sawblade, the proposal that the diamond should be selected by its function in cutting concrete is presented. The part of the big grit diamonds cut rock, and the part of the small grit diamonds improve the wearability of the matrix. The contrast tests are done with different shapes of sawbaldes in split segment, slant "U" slot segment, sandwich segment, turbo segment and three-slot segment. The special shapes of sawblades can improve the effect of cooling and the removing ability of the rock powder. The data of tests show that the efficiency of cutting and the life of sawblades are improved by designing the diamond prescription and using the especial geometry of segment.
