Well-sintered polycrystalline cubic boron nitride(PCBN)composites with different contents of cubic boron nitride(CBN) were obtained using Al and TiN as additives under pressure of 5.5 GPa and temperature of 1450 ℃.Th...Well-sintered polycrystalline cubic boron nitride(PCBN)composites with different contents of cubic boron nitride(CBN) were obtained using Al and TiN as additives under pressure of 5.5 GPa and temperature of 1450 ℃.The network structure of CBN grains and bonding materials was observed using scanning electron microscope(SEM).With the help of X-ray diffraction(XRD) analysis,TiB2 and AlN could be determined as main products and Al3 Ti also was detected in the Al-rich samples after sintering process.Furthermore,it was shown that Vickers hardness of composites was improved with the increase of CBN contents.However,the lifetime of PCBN composites was in negative correlation with the amount of CBN in turning GCr15 hardened steels,and the surface roughness of workpieces machined by these PCBN composites also showed the same trend.A series of cutting data confirmed that the low CBN content in PCBN composites could enhance the working durability and improve the surface quality in turning hardened steels.The present experiments also indicated that the lowest value of flank wear was not constant for different PCBN composites when they were used to machine several workpieces with different hardness.展开更多
为进一步提高现有实时幸运成像系统的实时性,针对第二代通用串行总线(Universal Serial Bus 2.0,USB2.0)接口的电子倍增电荷耦合(Electron Multiplying Charge-Coupled Devices,EMCCD)相机进行幸运成像观测的情况,提出了一个基于USB2.0...为进一步提高现有实时幸运成像系统的实时性,针对第二代通用串行总线(Universal Serial Bus 2.0,USB2.0)接口的电子倍增电荷耦合(Electron Multiplying Charge-Coupled Devices,EMCCD)相机进行幸运成像观测的情况,提出了一个基于USB2.0总线数据侦听的实时幸运成像技术方案,进行了侦听电路的硬件设计和数字逻辑设计,搭建了一个具有实时侦听、传输、处理、动态更新和显示的幸运成像系统。当相机拍摄天文图像并与个人计算机(Personal Computer,PC)进行数据交互时,系统的USB2.0总线数据侦听子系统就会对交互的USB2.0总线实现无侵入式侦听,并且加以分析处理后,只将有效的天文图像数据发送给底层现场可编程门阵列(Field Programmable Gate Array,FPGA)开发板中的幸运成像子系统,然后幸运成像子系统对接收的数据进行预处理、动态选图、实时配准和叠加处理,最后采用9个实时分割阈值水平切割高分辨率图像并对二值图像进行动态更新和显示。实验结果表明,所实现的系统能够对在USB2.0总线上连续传输的10000帧512×512像素的图像进行实时侦听、幸运成像和动态更新显示,实现了幸运成像技术的实时化。展开更多
Structural, anisotropic, and thermodynamic properties of Imm2-BCN were studied based on density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation（GGA）. T...Structural, anisotropic, and thermodynamic properties of Imm2-BCN were studied based on density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation（GGA）. The elastic constants were confirmed that the predicted Imm2-BCN is mechanically stable. The anisotropy of elastic properties were also studied systematically. The anisotropy studies of Young＇s modulus, shear modulus, linear compressibility, and Poisson＇s ratio show that the Imm2-BCN exhibits a large anisotropy. Through the quasi-harmonic Debye model, the relations between the equilibrium volume V, thermal expansion α, the heat capacity C_V and CP, the Grüneisen parameter γ, and the Debye temperature Θ_D with pressure P and temperature T were also studied systematically.展开更多
文摘Well-sintered polycrystalline cubic boron nitride(PCBN)composites with different contents of cubic boron nitride(CBN) were obtained using Al and TiN as additives under pressure of 5.5 GPa and temperature of 1450 ℃.The network structure of CBN grains and bonding materials was observed using scanning electron microscope(SEM).With the help of X-ray diffraction(XRD) analysis,TiB2 and AlN could be determined as main products and Al3 Ti also was detected in the Al-rich samples after sintering process.Furthermore,it was shown that Vickers hardness of composites was improved with the increase of CBN contents.However,the lifetime of PCBN composites was in negative correlation with the amount of CBN in turning GCr15 hardened steels,and the surface roughness of workpieces machined by these PCBN composites also showed the same trend.A series of cutting data confirmed that the low CBN content in PCBN composites could enhance the working durability and improve the surface quality in turning hardened steels.The present experiments also indicated that the lowest value of flank wear was not constant for different PCBN composites when they were used to machine several workpieces with different hardness.
基金Funded by the Fund for Talents of Yunnan Province,China(No.KKSY201403006)the National Natural Science Foundation of China(No.61564005)
文摘Structural, anisotropic, and thermodynamic properties of Imm2-BCN were studied based on density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation（GGA）. The elastic constants were confirmed that the predicted Imm2-BCN is mechanically stable. The anisotropy of elastic properties were also studied systematically. The anisotropy studies of Young＇s modulus, shear modulus, linear compressibility, and Poisson＇s ratio show that the Imm2-BCN exhibits a large anisotropy. Through the quasi-harmonic Debye model, the relations between the equilibrium volume V, thermal expansion α, the heat capacity C_V and CP, the Grüneisen parameter γ, and the Debye temperature Θ_D with pressure P and temperature T were also studied systematically.
