短中波红外长线阵拼接集成滤光片技术研究

空间光谱成像技术的发展使得探测器阵列与分光元件的集成成为一种趋势,长线阵拼接集成滤光片是空间多光谱成像仪实现焦平面集成分光的关键器件,在我国空间多光谱成像光学系统中需求明显。设计了4通道短中波红外长线阵拼接集成滤光片,采用离子束辅助轰击的电子枪蒸发方法制备了各通道窄带滤光片,利用专门研制的工装探索了拼接工艺,研制出了短中波红外长线阵拼接集成滤光片。测试结果表明:集成滤光片各通道平均透射率达到90%,最小带宽为230 nm （中心波长为4.95 μm）,光谱性能与设计结果吻合,满足性能指标要求。最小拼缝宽度仅为10 μm,拼缝不平行误差为1 μm,集成滤光片设计结构和拼接强度能够耐受抗振性试验。该集成滤光片已经在空间光学遥感仪器上成功应用。     

Numerical research of a 2D axial symmetry hybrid model for the radio-frequency ion thruster

Since the high efficiency discharge is critical to the radio-frequency ion thruster (RIT),a 2D axial symmetry hybrid model has been developed to study the plasma evolution of RIT.The fluid method and the drift energy correction of the electron energy distribution function (EEDF) are applied to the analysis of the RIT discharge.In the meantime,the PIC-MCC method is used to investigate the ion beam current extraction character for the plasma plume region.The beam current simulation results,with the hybrid model,agree well with the experimental results,and the error is lower than 11％,which shows the validity of the model.The further study shows there is an optimal ratio for the radio-frequency (RF) power and the beam current extraction power under the fixed RIT configuration.And the beam extraction efficiency will decrease when the discharge efficiency beyond a certain threshold (about 87 W).As the input parameters of the hybrid model are all the design values,it can be directly used to the optimum design for other kinds of RITs and radio-frequency ion sources.     

Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

In order to study the influence of three-grid assembly thermal deformation caused by heat accumulation on breakdown times and an ion extraction process,a hot gap test and a breakdown time test are carried out to obtain thermal deformation of the grids when the thruster is in 5 k W operation mode.Meanwhile,the fluid simulation method and particle-in-cell-Monte Carlo collision(PICMCC) method are adopted to simulate the ion extraction process according to the previous test results.The numerical calculation results are verified by the ion thruster performance test.The results show that after about 1.2 h operation,the hot gap between the screen grid and the accelerator grid reduce to 0.25–0.3 mm,while the hot gap between the accelerator grid and the decelerator grid increase from 1 mm to about 1.4 mm when the grids reach thermal equilibrium,and the hot gap is almost unchanged.In addition,the breakdown times experiment shows that 0.26 mm is the minimal safe hot gap for the grid assembly as the breakdown times improves significantly when the gap is smaller than this value.Fluid simulation results show that the plasma density of the screen grid is in the range 6?×10~(17)–6?×?10~(18) m~(13) and displays a parabolic characteristic,while the electron temperature gradually increases along the axial direction.The PIC-MCC results show that the current falling of an ion beam through a single aperture is significant.Meanwhile,the intercepted current of the accelerator grid and the decelerator grid both increase with the change in the hot gap.The ion beam current has optimal perveance status without thermal deformation,and the intercepted current of the accelerator grid and the decelerator grid are 3.65 m A and 6.26 m A,respectively.Furthermore,under the effect of thermal deformation,the ion beam current has over-perveance status,and the intercepted current of the accelerator grid and the decelerator grid are 10.46 m A and 18.24 m A,respectively.Performance test results indicate that the breakdown times increase obviously.The intercepted current of the accelerator grid and the decelerator grid increases to 13 m A and 16.5 m A,respectively,due to the change in the hot gap after 1.5 h operation.The numerical calculation results are well consistent with performance test results,and the error comes mainly from the test uncertainty of the hot gap.     

原子层沉积技术改性CrN硬质涂层性能的第一性原理研究

目的 基于密度泛函理论的第一性原理,对原子层改性氮化铬(CrN)涂层的关键性能进行仿真计算,以充分了解涂层微观组织结构演变和微观界面结构本质,为后续原子层沉积CrN工艺研究提供理论指导.方法 通过建立CrN(011)-CrN(011)复合体系模型,分析计算了涂层的界面性能、弹性性能及热力学性能.结果 模型结构经过优化后,各原子层间间距均发生不同程度的减小,且各层间距趋于一致.态密度分析表明:其优良的结构稳定性主要来自6.4～4.8 eV范围内Cr原子3d轨道和N原子2p轨道间的相互作用;基于应力应变的弹性常数满足波恩准则判定依据,力学性能稳定,计算结果为硬度30.29 GPa,体积模量409.83 GPa,剪切模量270.86 GPa.采用NVT系综模拟,当温度T≤1023 K时,温度波动振荡收敛;当温度T>1023 K时,温度在某个时间点瞬时激增而不收敛,可以得出CrN涂层的极限使用温度为1023 K.结论 原子层沉积改性的CrN硬质涂层具有优良的界面相容性,成键强度高,界面能低,结构性能稳定.     

导电材料缺陷的涡流成像检测技术研究

针对目前涡流无损检测尚存在检测精度低、反演识别难的问题,利用理论仿真分析,设计了励磁均匀性较好的励磁线圈和阵列隧道磁阻(TMR)传感器探头,基于阵列探头提出了等空间间隔插值成像缺陷检测方法,搭建试验系统,并进行缺陷检测试验。结果表明,提出的方法可有效地避免探头速度对成像结果的影响,从而实现不同形状尺寸缺陷的轮廓成像检测,为后续导电材料缺陷的涡流智能检测提供支持。     

The oxidation resistance mechanism of SiC-B4C-xAl2O3 ceramics at 1400 ℃ in air atmosphere

The oxidation property of SiC-B₄C-xAl₂O₃ (x ranges from 0 wt% to 30 wt%) ceramics was studied in air at 1400 ℃. Results show that the porous oxide layer becomes dense and smooth with addition of Al₂O₃. When the content of Al₂O₃ is proper, the DOP (degree of polymerization) of borosilicate network can be improved with increase of Al₂O₃ content, inhibiting the migration of atoms and molecular groups. With that, the crystallization of SiO₂ and volatilization of B₂O₃ can be restrained. When the content of Al₂O₃ is excessive, the DOP of borosilicate network will be decreased, deteriorating the oxide layer morphology. It is believed that the damage of borosilicate network by excess Al₂O₃ should be responsible for this phenomenon. In this research, the SiC-B₄C ceramic with optimal oxidation resistant can be obtained when the content of Al₂O₃ is 15 wt%.     

Effect of low content sintering aids addition on β-SiC sintered by spark plasma sintering

The influence of low content of sintering aids addition on the properties of β-SiC sintered by spark plasma sintering was studied based on X-ray diffraction and SEM observations. Three dopants, respectively Al₂O₃, Al₂O₃-Y₂O₃ and Al₂O₃-AlN were chosen, and the investigation was undertaken in the [0.5–5 wt%] content range. The analyses revealed the possibility to increase the density of sintered pellets close to 100% of theoretical density (T.D.), even with the addition of very low sintering aids contents, as low as 0.5 wt%, for each dopant. The combination with high sintering pressure allowed keeping a fine microstructure and a pristine cubic crystalline structure while avoiding the formation of secondary phases.     

添加稀土Nd改善金刚石/铜复合材料界面

目的添加稀土Nd改善金刚石/铜复合材料界面间的缺陷,抑制金刚石与铜之间的弱润湿性,增强复合材料的界面结合。方法采用放电等离子烧结(SPS)技术制备含有不同质量分数Nd的镀钛金刚石/铜复合材料,采用扫描电子显微镜观察界面处的微观形貌,采用X射线衍射仪和X射线能谱仪分析界面处组织,采用排水法测试复合材料的密度和致密度。结果添加稀土Nd后,金刚石-铜两相界面间促生了Cu_5Nd、NdCu_2、Cu_3Ti等相。界面间的Cu_5Nd、NdCu_2、Cu_3Ti、TiC填补了镀钛金刚石/铜复合材料界面处原有的空隙、孔洞等缺陷。未添加稀土Nd的镀钛金刚石/铜复合材料的密度为4.589 g/cm~3,致密度为81%;添加3wt%的Nd元素后,镀钛金刚石/铜复合材料的密度和致密度分别达到了5.569 g/cm~3和98%,密度较未添加Nd的复合材料提升了21%。随着Nd含量的增加,金刚石-铜界面间的缺陷逐渐减少,界面结合效果逐渐转好。结论稀土Nd极大地改善了镀钛金刚石/铜复合材料两相界面处的缺陷,很好地修饰了原本润湿性较差的金刚石-铜两相界面。添加Nd元素后,复合材料两相界面结合紧密。     

倒圆锥面基底蒸发镀膜均匀性理论分析

通过计算得出了蒸发源位于倒圆锥面正下方外部镀膜时锥面上各点的膜厚方程,并对整个锥面上膜厚均匀性进行了理论分析。结果表明：当圆锥面形状固定时,蒸发源与圆锥底圆圆心距离增大使锥面上膜厚均匀性变好;当蒸发源固定时,增大底圆半径导致锥面上膜厚均匀性变差。在同样的配置下,蒸发源为点源或小平面源时锥面上膜厚均匀性的变化趋势一致,小平面源蒸镀比点源蒸镀时圆锥面上膜厚均匀性差。     

电推力器电磁辐射测试透波副舱性能评价

为了获得电推力器工作时的电磁辐射干扰（EMI）数据,通过试验对电推力器的电磁辐射开展测试,测试时推力器必须工作在具有良好透波性的真空副舱内,根据此需求研制了一种集成于现有不锈钢真空室主舱的玻璃纤维透波副舱,针对研制的透波副舱设计指标,提出了从透波率、工作热特性和系统极限真空等方面开展透波副舱综合性能评价的方法。通过测试获得的透波副舱工作特性以及分析评价结果,为透波副舱用于推力器产品电磁辐射试验提供了可靠依据。