TATB/氟聚物PBX沿不同晶面力学性能的分子动力学模拟

用分子动力学(MD)方法, 模拟计算了著名钝感炸药TATB(1, 3, 5-三氨基-2, 4, 6-三硝基苯)与四种氟聚合物[聚偏二氟乙烯(PVDF)、聚三氟氯乙烯(PCTFE)、氟橡胶(F₂₃₁₁)、氟树脂(F₂₃₁₄)]构成的高聚物粘结炸药(PBX)的力学性能. 结果表明, 在TATB中添加少量氟聚物能有效改善其力学性能; 沿TATB不同晶面与氟聚物“粘结”, 构成PBX的力学性能有所不同, 改善力学性能的整体效应为(010)≈(100)>(001).     

浸渍液对MgO表面性质的影响

浸渍液对ＭｇＯ表面性质的影响蔡炳新（湖南大学化学化工学院，长沙４１００１２）毛建新郑小明（杭州大学催化研究所，杭州３１００２８）关键词浸渍液，氧化镁，表面性质，乙烷，氧化脱氢分类号Ｏ６４３近年来，甲烷氧化偶联催化剂一直是热门的研究课题．普遍认为Ｍｇ...     

甲烷氧化偶联催化剂Li/MgO的结构及表面性质的研究

本文用XRD、TEM、XPS和荧光光谱等方法研究了一组不同Li~+含量的Li/MgO催化剂的结构及表面性质,并与它们的氧化偶联甲烷的催化性能相关联。结果表明,低配位O~(2-)(O_(3c)~(2-))是使甲烷活化的活性中心。O_(1s)结合能为531.9eV的氧物种是对甲烷氧化偶联反应的C_2选择性起作用的活性氧物种。     

TATB基PBX结合能和力学性能的理论研究

以SCF-MO-AM1方法和MM-COMPASS力场, 对TATB (1,3,5-三氨基-2,4,6-三硝基苯)与系列高聚物组成的PBX(高聚物粘结炸药)尺寸匹配原子簇, 分别进行全优化几何构型计算, 发现两种方法求得的结合能存在良好的线性关系. 对TATB (3×3×4)超晶胞及其与系列氟聚物组成的双组分PBX, 实施COMPASS力场下的分子动力学(MD)周期性模拟计算, 首次求得其弹性系数、模量和泊松比, 发现添加少量高聚物即能有效改善炸药的力学性能.     

溶胶处理对硅灰石表面性质的影响

本工作用锡和锌两种溶胶对硅灰石进行表面处理。用酸碱测定、X-射线光电子能谱(XPS)、傅里叶变换红外光谱(FT-IR)、粒度分析、比表面测定和扫描电子显微分析(SEM)等方法研究了溶胶处理对硅灰石表面化学性质和物理性质的影响情况。结果表明经过溶胶处理,锡或锌是以氧化物的形式包覆在硅灰石的表面,使得硅灰石的表面组成、形貌和酸碱性都发生了变化。     

分子动力学模拟浓度和温度对TATB/PCTFE PBX力学性能的影响

为探讨高聚物粘结炸药(Polymer Bonded Explosive, PBX)的力学性能随温度和高聚物浓度而变化的规律, 用分子动力学(MD)方法和compass力场, 对著名高能炸药1,3,5-三氨基-2,4,6-三硝基苯(TATB)与常用高聚物粘结剂聚三氟氯乙烯(PCTFE)所构成的TATB/PCTFE PBX进行模拟计算. 结果表明, 在一定范围内, 随高聚物浓度的增加, PBX的弹性系数和模量减小, 表明其刚性减小、弹性增加; 而随温度的升高, PBX的刚性减小、弹性增强. 还发现PBX的结合能随浓度增高而增大, 随温度升高而减小.     

光照对含氟表面活性剂表面性质的影响

以对三氟甲基苯胺为起始原料,制备了一种部分氟化的表面活性剂CF-S,测定其紫外吸收光谱,研究其光异构化。测定CF-S溶液的表面张力,计算相应的物化参数,并与不含氟的表面活性剂CH-S的性能进行比较,结果发现,CF-S的表面活性明显强于CH-S的表面活性。在紫外光激发后,CF-S的cmc和γ_(cmc)增大,Г_(max)减小,A_(min)变大。CF-S对石英的润湿性能测试显示,含氟的表面活性剂能提高石英表面的疏水性。紫外光的照射使CF-S在石英表面的接触角降低,CF-S润湿性能增强。测定了石英在CF-S溶液中的动电位,加入CF-S后,石英表面的动电位增加。在紫外光照射后,石英的动电位降低,部分CF-S从石英表面脱附。     

表面活性剂对共轭聚合物荧光性质及电荷转移的影响

探讨了表面活性剂存在下, 水溶性阴离子共轭聚合物聚[5-甲氧基-2-(3-磺酰化丙氧基)-1,4-苯撑乙烯](简写为MPS-PPV)的微环境变化对荧光性质及电荷转移的影响. 结果表明, 阳离子表面活性剂及非离子表面活性剂使MPS-PPV荧光增强, 阴离子表面活性剂使其荧光先增强后减弱; 在MPS-PPV/表面活性剂体系中加入电子接受体Pd^2＋, 发现非离子表面活性剂体系的荧光猝灭效率提高, 阴离子及阳离子表面活性剂体系荧光猝灭效率下降. 此研究对研制基于阴离子共聚物的新型生物化学传感器具有一定的指导意义.     

表面活性剂对共轭聚合物荧光性质及电荷转移的影响

探讨了表面活性剂存在下, 水溶性阴离子共轭聚合物聚[5-甲氧基-2-(3-磺酰化丙氧基)-1,4-苯撑乙烯](简写为MPS-PPV)的微环境变化对荧光性质及电荷转移的影响. 结果表明, 阳离子表面活性剂及非离子表面活性剂使MPS-PPV荧光增强, 阴离子表面活性剂使其荧光先增强后减弱; 在MPS-PPV/表面活性剂体系中加入电子接受体Pd^2＋, 发现非离子表面活性剂体系的荧光猝灭效率提高, 阴离子及阳离子表面活性剂体系荧光猝灭效率下降. 此研究对研制基于阴离子共聚物的新型生物化学传感器具有一定的指导意义.     

稻壳基二氧化硅/碳复合材料的表面改性及对天然橡胶的影响

以稻壳基二氧化硅/碳复合材料(SiCB)作为天然橡胶(NR)的补强填料, 采用表面化学改性的方法将天然乳胶(NRL)接枝到SiCB表面, 改善其与NR基体的相容性. 研究了不同处理方法对接枝NRL效率的影响, 以及填料填入NR后对硫化橡胶力学性能的影响. 结果表明, 经过硝酸和γ-(甲基丙烯酰氧)丙基三甲氧基硅烷(γ-MPTMS)预处理, NRL能高效接枝在SiCB表面, 得到的样品SiCB_MR10比未处理的SiCB_P有更强的补强能力. 硫化胶NR/SiCB_MR10的拉伸强度、 300%定伸和撕裂强度较NR/SiCB_P分别提高了61.06%, 27.15%和15.90%, 与传统炭黑产品N774填充的硫化胶NR/N774的力学性能相近. 经过NRL接枝改性的SiCB_MR10具有替代商业炭黑的应用前景.     

Molecular dynamics simulation of mechanical properties of TATB/fluorine-polymer PBXs along different surfaces

TATB (1,3,5-triamino-2,4,6-trinitrobenzene) is the well-known high insensitive explosive. With TATB as the main body (90% and above) the polymer bonded explosives ( PBXs) contain a small amount of poly-mers (5%―10%). The composite materials with good saf…     

HDPE-Coconut Flour Composites: Effect of Coupling Agents and Surface Modification

This research work studies the mechanical, thermal and morphological behavior of coconut flour/polyethylene composites, with special emphasis on the influence of the surface modification of coconut flour and the presence of different coupling agents on the interfacial bonding. The different treatments of the composites with an EAA copolymer, with 5 and 18 wt% of NaOH and acetylation, confirm the better tensile behavior of these composites.     

TATB固体与表面吸附水的相互作用研究

TATB（1，3，5-三氨基-2，4，6-三硝基苯）是最著名的耐热钝感炸药；水在 TATB表面的吸附作用研究具有理论和实用双重意义。在B3LYP/6-31G~（**）水平上 ，在对TATB晶体（001）表面作周期性计算的基础上经基组叠加误差（BSSE）校正 ，求得TATB的表面能为-19.90 kJ·mol~(-1)，与实验值良好相符；首次求得水在 TATB（001）面的吸附能为-10.25kJ·mol~(-1)；重点讨论了吸附前后能带和电子 结构的变化。     

表面改性对片状锌粉分散稳定性的影响

采用物理化学法,将实验室自制锌粉分别添加钛酸酯偶联剂、硅烷偶联剂和十二烷基苯磺酸钠进行表面改性,利用沉降法测试高度研究改性前后锌粉的分散稳定性。 结果表明,不同种类、不同浓度的表面改性剂对锌粉的分散稳定性有较大的影响;其中,经1.0%钛酸酯偶联剂改性后锌粉的分散稳定性有了明显的改善,与进口粉的分散稳定性接近。     

Silane Coupling Agent Modifies the Mechanical Properties of a Chitosan Microfiber

Chitosan microfibers are widely used in medical applications because they have favorable inherent properties. However, their mechanical properties require further improvement. In the present study, a trimethoxysilane aldehyde (TMSA) crosslinking agent was added to chitosan microfibers to improve their tensile strength. The chitosan microfibers were prepared using a coagulation method. The tensile strength of the chitosan microfibers was improved by crosslinking them with TMSA, even when only a small amount was used (less than 1%). TMSA did not change the orientation of the chitosan molecules. Furthermore, aldehyde derived from TMSA did not remain, and siloxane units were formed in the microfibers.     

聚丙烯/PMMA/CaCO3纳米复合材料的制备、结构与力学性能

分别将经不同表面处理的纳米碳酸钙粒子与聚合物PP共混,制备PP／CaCO3和PP／PMMA／CaCO3纳米复合材料。用TEM观察了表面处理后纳米粒子的粒径与分散情况,发现复合粒子分散较均匀。用DSC与WAXD研究了复合材料的结晶行为,发现原位聚合制备的PMMA／CaCO3纳米复合粒子与PP共混后,PP有异相成核作用,出现了不稳定的PPβ晶型。PP／PMMA／CaCO3纳米复合材料力学性能有大幅度的提高。     

环四甲撑四硝胺/1,3,5-三氨基-2,4,6-三硝基苯共晶炸药的分子模拟研究

构建环四甲撑四硝胺 (HMX) /1,3,5-三氨基-2,4,6三硝基苯 (TATB)不同的共晶结构模型,用分子动力学(MD)模拟得到其平衡结构。基于平衡结构进行X射线粉末衍射（XRD）图谱模拟和能量计算。结果表明,与纯组分相比,HMX/TATB共晶结构的X射线粉末衍射图与主成分HMX相似,并均有新峰出现;TATB在HMX表面自由能最高、生长速率最慢的 (0 1 1) 晶面上发生取代后的能量最低,结构最稳定,据此推测在制备HMX/TATB共晶炸药过程中,TATB分子更容易进入HMX自由能高的晶面,得到结构稳定的共晶而使HMX变得更为钝感。     

Influence of Proteins on the Mechanical Properties of Agro-Based Materials

Summary : A new biodegradable thermoplastic material based on a wheat flour by-product has been developed. The influence of protein content in wheat flour on the mechanical properties of the material has been investigated. For protein content between 4% and 10%, no influence of the protein content was evidenced, whereas beyond 10% w/w of proteins in the wheat flour, the mechanical properties of agro-based materials decrease, thus confirming the advantage of using a wheat flour by-product (i.e. with protein content below 8% w/w).     

Exciton Coupling of Surface Complexes on a Nanocrystal Surface

Exciton coupling may arise when chromophores are brought into close spatial proximity. Herein the intra‐nanocrystal exciton coupling of the surface complexes formed by coordination of 8‐hydroxyquinoline to ZnS nanocrystals (NCs) is reported. It is studied by absorption, photoluminescence (PL), PL excitation (PLE), and PL lifetime measurements. The exciton coupling of the surface complexes tunes the PL color and broadens the absorption and PLE windows of the NCs, and thus is a potential strategy for improving the light‐harvesting efficiency of NC solar cells and photocatalysts.     

Mechanical Properties of Gel-Derived Materials

The mechanical behaviour of xerogels and aerogels is generally described in terms of brittle and elastic materials, like glasses or ceramics. The main difference compared to silica glass is the order of magnitude of the elastic and rupture moduli which are 10⁴ times lower. However, if this analogy is pertinent when gels are under a tension stress (bending test) they exhibit a more complicated response when the structure is submitted to a compressive stress. The network is linearly elastic under small strains, then exhibits yield followed by densification and plastic hardening. As a consequence of the plastic shrinkage it is possible to densify and stiffen the gel at room temperature. These opposite behaviours (elastic and plastic) are surprisingly related to the same two kinds of gel features: the silanol content and the pore volume. Both elastic modulus and plastic shrinkage depend strongly on the volume fraction of pores and on the condensation reaction between silanols. On the mechanical point of view (rupture modulus and toughness), it is shown that pores and silanols play also an important role. Pores can be considered as flaws in the terms of fracture mechanics and the flaw size, calculated from rupture strength and toughness is related to the pore size distribution. Different kinds of gels structure (fractal or not fractal) have been synthesized by a control of the different steps of transformation such as sintering and plastic compaction. The relationships between structural and the elastic properties are discussed in terms of the percolation theory and fractal structure.