采用可编程I/O接口的多路串行通讯模拟器设计

某航天器闭式贮箱增压控制系统的测试中,需要设计具有多路串行通讯接口的模拟器,用于模拟数字式压力传感器的输出信号。对于72路串行发送和10路串行接收功能,若采用传统商用的标准串行通讯接口板,则整个模拟器需要十多套板卡,系统复杂,体积大,且多个通道之间难以实现同步与实时控制。为此提出了一种采用多路可编程I/O接口板实现485通讯功能的方案,借助于LabVIEW软件开发平台,由FPGA编程实现通讯协议;并配置信号调理板以实现信号的隔离传输和驱动。最终仅用一台小型便携式设备和三块板卡就实现了模拟器的所有功能,可以灵活地根据系统设置的工作模式模拟传感器的输出,在增压系统的测试中表现优异。试验结果表明,此种设计方案具有较强的通用性和适应性,可以广泛推广到多种通讯应用场合。     

The influence of SiCp oxidized on the interface layer and thermal conductivity of SiCp/Al composites

In this work, oxidation of silicon carbide particles (SiCp) at elevated temperature and its influence on the interface layer and thermal conductivity of SiCp/ZL101 composites prepared using pressure infiltration process were investigated respectively. It is found that initial temperature for the oxidation of SiCp is about 850?°C, and that the oxidation increment of SiCp and the thickness of SiO₂ layer increase with the increase in pre-oxidation temperature and time, when the oxidized temperature exceeds 1100?°C, or the duration time exceeds 2?h at 1100?°C, a small amount of ablation will take place on the SiCp, as well as the oxidized layer has some loss. The formation of SiO₂ layer can provide certain interface reactions with interface layers (3.1–6.36?μm), and the higher the thickness of SiO₂ layer, the thicker the interface layer in SiCp/Al composites. However, the thickness of SiO₂ layer is more than 5.9?μm, which is not benefit for the formation of interface layer. With the increase in the thickness of interface layer, thermal conductivity declines, but is not linear.     

The effect of magnetic field heat treatment on magnetostriction of Terfenol-D 2-2 composites

Based on the analysis of the magnetostriction for Terfenol-D composites, Terfenol-D 2-2 magnetostrictive composites have been prepared with laminations perpendicular to [1 1 2] axes. Then one of the samples was annealed in the vacuum at 423 K for 15 min at the magnetic field of 240 kA/m, which is along the direction of laminations and vertical to the [1 1 2] axes of the specimen. The static magnetostriction λ and dynamic magnetostrictive coefficient d₃₃ of samples were measured under the compressive stress of 0, 2, 4, 6 and 8 MPa. Effects of the compressive stress and the magnetic field heat treatment on the magnetostriction λ have been investigated. It is found that the magnetostriction of 2-2 composites can be improved under the compressive stress when the magnetic field is larger than 20 kA/m. The magnetostriction of 2-2 composites with the magnetic field heat treatment increases under compressive stress, and it can reach 1390×10⁻⁶ at the magnetic field of 200 kA/m and under the compressive stress of 4 MPa, much larger than the value of 860×10⁻⁶ without the magnetic field heat treatment. The highest magnetostriction of the 2-2 composite with the magnetic field heat treatment can reach 1530×10⁻⁶. The dynamic magnetostrictive coefficient d₃₃ of 2-2 composites with the magnetic field heat treatment have been improved, compared with that without magnetic field heat treatment. The maximum value of d₃₃ of the sample with magnetic field heat treatment is 71% larger than that without magnetic field heat treatment.     

氘等离子体预辐照对W-Y2O3合金耐热冲击性能的影响

应用直线等离子体装置，对W-Y₂O₃合金的垂直于锻造轴(锻造面)和平行于锻造轴(横截面)的两个表面迚行了氘等离子体辐照。利用60kW电子束材料测试平台，研究了等离子体辐照前、后的W-Y2O3合金在功率0.22~0.44GW·m^-2下耐瞬态热冲击性能。结果表明，氘等离子体辐照没有降低钨合金的裂纹阈值，其中锻造面的裂纹阈值范围高于横截面，且超过了0.33GW·m^-2。综合考虑高能率锻造W-Y₂O₃合金的氘离子辐照与热冲击行为，锻造面可能更适合面对等离子体。     

The effect of surface modification on the properties of sisal fiber and improvement of interfacial adhesion in sisal/starch composites induced by starch nanocrystals

A facile approach was utilized to introduce starch nanocrystals (SNCs) onto sisal fiber (SF) to improve the interfacial adhesion between SF and starch. For this, fibers were treated with alkali and then subjected to cold plasma treatment to increase the accessibility with SNCs, which was confirmed through X-ray photoelectron spectroscopy (XPS). It was found that due to the influence of cold plasma treatment, new functional groups were introduced onto SF. The surface characteristics of SF were examined by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The observed results suggested that SNCs were successfully distributed onto SF. Tensile strength and interfacial shear strength of fibers treated under different conditions were calculated and compared through a two-parameter Weibull model. The highest interfacial shear strength of 3.05 MPa was obtained by Alkali-300 W-SNCs, which indicated an increase of 80.6% than untreated SF. It has also been proved that the starch nanocrystals produced hydrogen bonding and physical interlocking between sisal fiber and starch. Notably, the outcome of this investigation indicates that SNCs may be applied for the fabrication of high performance, environmentally friendly sisal/starch composites for a range of technological applications.     

FT-IR与微量吸附量热联用研究BaO/Al_2O_3催化剂表面酸碱性质

运用红外光谱与微量吸附量热联用技术研究了焙烧温度对BaO/γ-Al2O3表面酸碱性的影响。结果表明,γ-Al2O3经1000℃焙烧转化为θ-Al2O3和α-Al2O3,BaOγ-Al2O3经高温焙烧后生成BaO·Al2O3和BaO·6Al2O3等物相。600℃焙烧后,BaO/γ-Al2O3的表面酸性比γ-Al2O3的稍有下降,而碱性却大为增强。经1000℃焙烧后,表面的酸碱性则均大为降低,只有少量较弱的酸碱性位。     

Effect of spraying power on microstructure and bonding strength of MoSi2-based coatings prepared by supersonic plasma spraying

MoSi₂-based oxidation protective coatings for SiC-coated carbon/carbon composites were prepared using a supersonic plasma spraying at the power of 40 kW, 45 kW, 50 kW and 55 kW, respectively. Effect of spraying power on the microstructure and bonding strength of MoSi₂-based coatings was studied. The results show that coatings become more and more compact and the bonding strength increases when the spraying power increases from 40 kW to 50 kW. At the power of 50 kW, the coatings were dense and the bonding strength reached a maximum value of 14.5 MPa. As the spraying power is of sufficient magnitude, many cracks and pores reappaer in coatings and the bonding strength between coating and substrate also decreases.     

The location of excess electrons on H2O/TiO2(110) surface and its role in the surface reactions

Excess electrons play a key role in many of the properties of Titanium dioxide (TiO₂). Understanding their behaviour is important for improving the performance of TiO₂ in energy-related applications. Here, we describe a DFT + U study of the locations of the unpaired electron (UPE) on rutile TiO₂(110) (R-TiO₂(110)) surface and H₂O/R-TiO₂(110) surface. Our results show that the subsurface are preferred with R-TiO₂(110) surface. In contrast to previous studies, we find that the UPE tends to migrate to the surface H₂O-Ti_5c (the five-coordinated titanium (Ti_5c) at surface with H₂O adsorption) with the increasing of H₂O coverage and UPE concentration. In addition, we have shown that the UPE plays an important role in the O-H bond dissociation and other important elementary reactions in photo-catalytic H₂O dissociation on R-TiO₂(110) such as H, OH and H₂ desorption. Specifically, it enhances the O-H bond dissociation, as well as H and H₂ desorption from bridging hydroxyl and Ti_5c-OH (the Ti_5c with OH adsorption), but hinders the OH and H desorption from Ti_5c. We believe our results afford a further understanding of the adsorbent dependent UPE migration, and the role of UPE in the surface reactions.