Co-Sn单相合金深过冷凝固时Co3Sn2 相生长形貌的演变机制

开展了(Co₆₀Sn₄₀)_100-xNb_x (x=0,0.4,0.6,0.8,at%)单相合金的深过冷凝固实验,研究了Co₃Sn₂相生长形貌的演变机制。结果表明,在小过冷度下,Co₃Sn₂相在x=0,0.4以海藻状的模式进行生长,随着添加的Nb含量增加至0.6at%,其生长形貌转变为树枝晶,并在x=0.8进一步转变为分形海藻晶,这主要是由于界面能各向异性和动力学各向异性的变化。随着过冷度的增加,(Co₆₀Sn₄₀)_99.4Nb_0.6合金中Co₃Sn₂相生长形貌在过冷度大于28 K时从树枝晶转变为分形海藻,当过冷度高于143 K时转变为密集海藻。少量的Nb添加在小过冷度和中间过冷度时能提高Co₃Sn₂相的生长速度,但是在大过冷度下会显著降低生长速度。Co₃Sn₂相生长速度随过冷度变化规律的转变对应其生长形貌从分形海藻向密集海藻的转变。     

含吡啶配位聚合物结构对合成温度的不敏感性

采用有机碱吡啶(pyridine)代替常见的强碱(如氢氧化钾或氢氧化钠等)调节反应混合物的pH值,探究水热温度对配位聚合物结构的影响。分别以2,5-二甲基对苯二甲酸和间苯二甲酸(以下简称H2dmbdc和H2ip)为配体和硝酸锌通过水热合成配位聚合物[Zn3(dmbdc)3(py)2]n,1和[Zn4(H2O)(ip)4(py)6]n,2。研究发现,在较大的合成温度范围内(120℃~210℃),得到的配位聚合物结构也都不会随水热合成温度的改变而改变。由此表明当有吡啶参与反应时,配位聚合物的结构对水热温度具有一定的不敏感性。     

胆甾相液晶与向列相液晶共聚物的制备及液晶性能的研究

合成了向列相液晶单体4-乙氧基苯甲酸-4’-烯丙氧基联苯酯(M1)和胆甾相液晶分子4-(4-烯丙氧基苯丙酰氧基)-苯基苯氧羰基戊酸胆甾醇酯(M2),把液晶分子根据不同的浓度配比分别和聚甲基含氢硅氧烷接枝共聚,合成了具有不同化学结构和性能的侧链型液晶聚合物。并利用红外光谱(FT-IR)、热失重分析(TGA)、差示量热扫描分析(DSC)、偏光显微法(POM)和旋光仪等测试手段对其迚行了表征。结果表明:随着单体M2含量的增加,聚合物的比旋光度随之增加;熔融温度和清亮点随M2含量的增加而降低;偏光照片显示P1为典型的向列相液晶;M2液晶分子引入后,P2-P7为典型的胆甾型液晶。     

超细碳酸钙粉体的制备

以CaCl2和(NH4)2CO3为原料,采用气相扩散法合成碳酸钙晶体。通过添加合适的晶形控制剂,选择适当的用量,合成了花生状碳酸钙晶体。用发射扫描电子显微镜(FESEM)和X射线衍射仪(XRD)进行了表征,结果表明,当控制剂柠檬酸钠用量在10 mmol/L时,生成的花生状碳酸钙粒子粒度分布均匀,在700 nm左右,且粒子分散性良好。并对花生状碳酸钙粒子的形成机理进行了探讨。     

硫酸四氨合铜结晶过程的粒度控制技术

氨水和硫酸铜溶液反应形成铜氨溶液,之后与乙醇混合使硫酸四氨合铜以晶体形式析出,过滤、干燥制备硫酸四氨合铜晶体。考察不同操作条件对硫酸四氨合铜晶体粒度分布的影响。结果表明,析出过程中加入合适的表面活性剂对粒度分布有一定影响,混料时以铜氨溶液分散加入到乙醇中效果较好,适当增加乙醇用量和提高搅拌强度有利于得到小粒度产品。     

Binding Mode and Structure–Activity Relationships around Direct Inhibitors of the Nrf2–Keap1 Complex

An X‐ray crystal structure of Kelch‐like ECH‐associated protein (Keap1) co‐crystallised with (1S,2R)‐2‐[(1S)‐1‐[(1,3‐dioxo‐2,3‐dihydro‐1H‐isoindol‐2‐yl)methyl]‐1,2,3,4‐tetrahydroisoquinolin‐2‐carbonyl]cyclohexane‐1‐carboxylic acid (compound (S,R,S)‐ 1 a ) was obtained. This X‐ray crystal structure provides breakthrough experimental evidence for the true binding mode of the hit compound (S,R,S)‐ 1 a , as the ligand orientation was found to differ from that of the initial docking model, which was available at the start of the project. Crystallographic elucidation of this binding mode helped to focus and drive the drug design process more effectively and efficiently.     

Monitoring of degradation of porous silicon photonic crystals using digital photography

We report the monitoring of porous silicon (pSi) degradation in aqueous solutions using a consumer-grade digital camera. To facilitate optical monitoring, the pSi samples were prepared as one-dimensional photonic crystals (rugate filters) by electrochemical etching of highly doped p-type Si wafers using a periodic etch waveform. Two pSi formulations, representing chemistries relevant for self-reporting drug delivery applications, were tested: freshly etched pSi (fpSi) and fpSi coated with the biodegradable polymer chitosan (pSi-ch). Accelerated degradation of the samples in an ethanol-containing pH 10 aqueous basic buffer was monitored in situ by digital imaging with a consumer-grade digital camera with simultaneous optical reflectance spectrophotometric point measurements. As the nanostructured porous silicon matrix dissolved, a hypsochromic shift in the wavelength of the rugate reflectance peak resulted in visible color changes from red to green. While the H coordinate in the hue, saturation, and value (HSV) color space calculated using the as-acquired photographs was a good monitor of degradation at short times (t < 100 min), it was not a useful monitor of sample degradation at longer times since it was influenced by reflections of the broad spectral output of the lamp as well as from the narrow rugate reflectance band. A monotonic relationship was observed between the wavelength of the rugate reflectance peak and an H parameter value calculated from the average red-green-blue (RGB) values of each image by first independently normalizing each channel (R, G, and B) using their maximum and minimum value over the time course of the degradation process. Spectrophotometric measurements and digital image analysis using this H parameter gave consistent relative stabilities of the samples as fpSi > pSi-ch.     

飞秒激光加工单晶金刚石制备正前角磨削工具

目的制造一种磨粒有序排布、具有正前角的无结合剂端面金刚石磨削工具。方法采用波长为1030 nm、脉宽为250 fs的钛蓝宝石飞秒激光对单晶金刚石(SCD)进行烧蚀加工,首先研究加工工艺参数(特别是烧蚀轨迹间距)对金刚石加工效率及表面质量的影响。采用预先设计的激光扫描路径,基于优化后的工艺参数在SCD表面加工出微磨粒阵列结构,各磨粒呈方锥台形结构,其顶部倾斜角约为100°。在此基础上,对微磨粒阵列进行烧蚀加工,将所有微磨粒顶部的倾斜角减小至小于90°。结果当激光烧蚀轨迹间距为10.0μm时,烧蚀加工表面RMS粗糙度最小。确定了一种微磨粒边缘倾斜角小于90°且磨粒有序排布的新型无结合剂金刚石端面磨削工具的激光制备方法和工艺,采用该工艺加工的磨削工具表面质量好,轮廓精度高,磨粒平均正前角约为9.80°。结论采用飞秒激光可以高质量、高效率地制备出磨粒有序排布的新型正前角无结合剂金刚石端面磨削工具,该工具有望在硬脆材料磨削中减小磨削力,提高材料表面完整性。