PP-EPR-PP增容PP/EPT的研究

采用δ－ＴｉＣｌ３－Ｅｔ２ＡｌＣｌ催化合成了三元乙丙嵌段共聚物ＰＰ－ＥＰＲ－ＰＰ，作为乙丙橡胶（ＥＰＴ）增韧聚丙烯（ＰＰ）的增容剂，以改善ＰＰ的低温冲击性能。实验发现，ＰＰ－ＥＰＲ－ＰＰ中ＥＰＲ段较长，有利于提高其增容效果，ＰＰ－ＥＰＲ－ＰＰ的加入量仅为４％，就可以显著的改善ＰＰ和ＥＰＴ相容性，使ＰＰ／ＥＰＴ／ＰＰ－ＥＰＲ－ＰＰ共混物的无缺口冲击强度比相应的ＰＰ／ＥＰＴ在－２０℃时提高４０％，在－４０℃时提高了１２０％，达到较高的耐冲击等级。形态观察表明，ＰＰ－ＥＰＲ－ＰＰ同时又起到了“乳化剂”的作用，使ＥＰＴ在ＰＰ中均匀分散。还提出了ＰＰ－ＥＰＲ－ＰＰ的增容模型，完满地解释了实验结果。

PP-EPR对PP/EPT增容作用的研究

通过δ-TiCl_3-Et_2AICl催化淤浆聚合合成了不同嵌段长度的聚丙烯-乙丙橡胶嵌段共聚物(PP-EPR),作为乙丙橡胶(EPT)和PP的增容剂,明显改善PP的低温耐冲击性能。实验发现,当PP-EPR中PP段的聚合时间为5min,EPR段的聚合时间为30min时,PP-EPR的增容效果最好;PP-EPR加入量仅为4％,就可以显著地改善PP和EPT的相容性,使共混物PP/EPT/PP-EPR的拉伸强度只比PP降低22％,而-20℃和-40℃下的冲击强度分别为PP的9倍和8倍。

用EPR方法研究人造金刚石中杂质氮

本文用电子顺磁共振(EPR)方法,研究人造金刚石中氮的电子结构。提出用自旋浓度来表征氯含量的方法,并对不同方法制得的金刚石进行测定。

Geochemical anomalies of hydrothermal plume at EPR 13 degrees N

During the DY105-12, 14cruise (RN DAYANG YIHAO, November 2003) on East Pacific Rise (EPR) 12-13 degrees N, the submarine hydrothermal activity was investigated and the CTD hydrocast was carried out at EPR12 degrees 39 ' N - 12 degrees 54 ' N. From the temperature anomalies and the concentrations of magnesium, chlorine, bromine in seawater samples, we discover that magnesium depletes 9.3%-22.4%, chlorine and bromine enrich 10.3%-28.7% and 10.7%-29.0% respectively relative to normal seawater at the stations which have chemistry anomalies, moreover temperature and chemistry anomalies are at the same layer. The depletion of magnesium in the plume may be caused by a fluid lacking of magnesium which rises after the hydrothermal fluid reaches the equilibrium with ambient seawater, the enrichment of chlorine and bromine might be the result of inputting later brine which is generated by phase separation due to hydrothermal activity. In addition, the Br/CI ratio in the abnormal layers at the survey area is identical to that in seawater, which implies that halite dissolution (or precipitation) occurs neither when the fluid is vented nor when hydrothermal fluid entraining ambient seawater rises to form plume. From the abnormal instance at E55 station, it is very possible that there might exist a new hydrothermal vent site.

Evaluation of the Effectiveness of Representative Methods for Determining Young's Modulus and Hardness from Instrumented Indentation Data

The effectiveness of Oliver & Pharr's (O&P's) method, Cheng & Cheng's (C&C's) method, and a new method developed by our group for estimating Young's modulus and hardness based on instrumented indentation was evaluated for the case of yield stress to reduced Young's modulus ratio (sigma(y)/E-r) >= 4.55 x 10(-4) and hardening coefficient (n) <= 0.45. Dimensional theorem and finite element simulations were applied to produce reference results for this purpose. Both O&P's and C&C's methods overestimated the Young's modulus under some conditions, whereas the error can be controlled within +/- 16% if the formulation was modified with appropriate correction functions. Similar modification was not introduced to our method for determining Young's modulus, while the maximum error of results was around +/- 13%. The errors of hardness values obtained from all the three methods could be even larger and were irreducible with any correction scheme. It is therefore suggested that when hardness values of different materials are concerned, relative comparison of the data obtained from a single standard measurement technique would be more practically useful. It is noted that the ranges of error derived from the analysis could be different if different ranges of material parameters sigma(y)/E-r and n are considered.

大偏心率远距离航天器编队飞行设计

为寻求适用于大偏心率远距离航天器编队设计的方法，摒弃了简化航天器相对运动非线性微分方程的传统思路，致力于简化该微分方程的解析解。首先，在同周期假定前提下，由运动学得到了椭圆轨道航天器相对于圆轨道航天器运动的封闭解析解，然后将其展开成傅立叶级数，证明了在特定条件下，单倍频项是最主要的，从而导出了编队飞行设计的新公式。最后以空间圆形编队设计为例，阐明了利用新公式进行编队设计的步骤，并用精确的数值计算验证了设计结果的正确性。与C—W方法和一般轨道参数设计方法相比，推导过程中并未采用小偏心率近距离假定，因此导出的新公式可适用于大偏心率远距离航天器的编队设计。

Microstructure and mechanical properties at TiCp/Ni-alloy interfaces in laser-synthesized coatings

Titanium carbide particle (TiCp) reinforced Ni alloy composite coatings were synthesized by laser cladding using a cw 3 kW CO2 laser. Two kinds of coatings were present in terms of TiCp origins, i.e. undissolved and in situ reacted TiCp, respectively. The former came from the TiCp pre-coated on the sample, whereas the latter from in situ reaction between titanium and graphite in the molten pool during laser irradiation. Conventional and high-resolution transmission electron microscope observations showed the epitaxial growth of TiC, the precipitation of CrB, and the chemical reaction between Ti and B elements around phase interfaces of undissolved TiCp. The hardness, H, and elastic modulus, E, were measured by nanoindentation of the matrix near the TiCp interface. For undissolved TiCp, the loading curve revealed pop-in phenomena caused by the plastic deformation of the crack formation or debounding of TiCp from the matrix. As for in situ generated TiCp, no pop-in mark appears. On the other hand, in situ reacted TiCp led to much higher hardness and modulus than that in the case of undissolved TiCp. The coating reinforced by in situ generated TiCp displayed the highest impact wear resistance at both low and high impact conditions, as compared with coatings with undissolved TiCp and without TiCp. The impact wear resistance of the coating reinforced by undissolved TiCp increases at a low impact work but decreases at a high impact work, as compared with the single Ni alloy coating. The degree of wear for the composite coating depends primarily on the debonding removal of TiCp.

Revelation of a Functional Dependence of the Sum of Two Uniaxial Strengths/Hardness on Elastic Work/Total Work of Indentation

Dimensional and finite element analyses were used to analyze the relationship between the mechanical properties and instrumented indentation response of materials. Results revealed the existence of a functional dependence of (engineering yield strength sigma(E,y) + engineering tensile strength sigma(E,b))/Oliver & Pharr hardness on the ratio of reversible elastic work to total work obtained from an indentation test. The relationship links up the Oliver & Pharr hardness with the material strengths, although the Oliver & Pharr hardness may deviate from the true hardness when sinking in or piling up occurs. The functional relationship can further be used to estimate the SUM sigma(E,y) + sigma(E,b) according to the data of an instrumented indentation test. The sigma(E,y) + sigma(E,b) value better reflects the strength of a material compared to the hardness value alone. The method was shown to be effective when applied to aluminum alloys. The relationship can further be used to estimate the fatigue limits, which are usually obtained from macroscopic fatigue tests in different modes.