High temperature bending creep behavior of a multi-cation doped α/β-SiAlON composite

SiAlON ceramics with high hardness and high toughness can be made through designing α/β-SiAlON composites. An important advantage of α-SiAlON phase is that the amount of intergranular phase is reduced by the transient liquid phase being absorbed into the matrix of α-SiAlON phase during sintering. But, the thermal stability of the α-SiAlON phase is an important concern for α/β-SiAlON composites especially at high temperatures. The use of different types of single or multiple cations during fabrication directly affects resultant microstructures and mechanical behavior of α/β-SiAlON composites. In this study, the creep behavior of a multi-cation (Y, Sm and Ca) doped α/β-SiAlON composite, in which aluminum-containing nitrogen melilite solid solution phase was designed as intergranular phase, was investigated by four-point bending creep tests under stresses from 50 to 150 MPa and at temperatures from 1300 °C to 1400 °C in air. The stress exponent was determined to be 1.6 ± 0.13 at 1400 °C and the creep activation energy was calculated to be 692 ± 37 kJ/mol⁻¹. Grain boundary sliding coupled with diffusion was identified as the rate-controlling creep mechanism for the α/β-SiAlON composite.     

涤纶织物表面改性及其对水中Cu~(2+)的吸附研究

以柠檬酸作为交联剂,次亚磷酸钠作为催化剂,将β-环糊精整理到涤纶织物上。通过单因素分析发现,织物增重率与β-环糊精浓度、柠檬酸浓度、催化剂浓度、焙烘时间及焙烘温度有关。确定最佳整理工艺为:β-环糊精90 g/L,柠檬酸100 g/L,催化剂30 g/L,焙烘温度180℃,焙烘时间20 min。经过整理后的织物对Cu2+有较好的吸附能力。     

去除全合成β-胡萝卜素中二氯甲烷残留的工艺研究

以正庚烷为溶剂,对全合成β-胡萝卜素中二氯甲烷的去除方法进行了初步研究。以二氯甲烷的溶剂残留量、β-胡萝卜素的含量及收率为主要指标,采用单因素分析法对正庚烷的使用量、搅拌时间、搅拌温度、乙醇含水量、乙醇投料量、精制温度等6个条件进行优化。实验结果表明：30倍（v／w）正庚烷溶解β-胡萝卜素,在70℃下搅拌回流2h,再经真空回收溶剂脱溶,加入无水乙醇在78℃下保温精制2h,冷却结晶并过滤真空干燥,这一方案对β-胡萝卜素中的二氯甲烷的去除具有很好的效果、并获得较高的含量和较好的收率。     

β-环糊精/氯菊酯包合物制备工艺优化

文章采用超声波法制备了β-环糊精/氯菊酯超分子包合物。采用正交设计研究氯菊酯与β-环糊精的主客体摩尔比、包合温度和包合时间等对包合作用的影响,优选出超声波法制备了β-环糊精/氯菊酯超分子包合物的最佳工艺条件。借助紫外光谱、红外光谱、差热分析证明了超分子包合物的形成。     

Formation of β-cylindrites under supercooled extrusion of isotactic polypropylene at low shear stress

Formation of β-cylindrites of isotactic polypropylene under various wall shear stress (σ_w), supercooled temperature of melt (T_e) and crystallization temperature (T_c) has been investigated by polarized light microscopy (PLM), wide angle X-ray diffraction (WAXD), and differential scanning calorimeter (DSC). To have better control over the thermomechanical history, instead of a reciprocating screw, the samples were prepared by extruding supercooled melt through capillary die. β-cylindrites can be observed by PLM in the extruded specimen even at a lower σ_w (0.020 MPa), and the number of β-cylindrites nuclei increases rapidly with the lowering of T_e. The nucleation density of β-cylindrites increases with the raising of wall shear stress under a given T_e of 160 °C. Furthermore, at lower supercooled temperature of melt (145 °C), the radius of β-cylindrites decreases with the increasing of σ_w, and the number of β-cylindrites nuclei almost remain invariant. At relatively higher σ_w (0.090 MPa), a saturation of β-cylindrites nuclei is observed with decreasing T_c. A modified model based on above results has been proposed to explain the effect of the original structure of quiescent supercooled melt on the formation of β-cylindrites under low shear stress.     

Thermo-Mechanical Properties of Semi-Degradable Poly(β-amino ester)-co-Methyl Methacrylate Networks under Simulated Physiological Conditions

Poly(β-amino ester) networks are being explored for biomedical applications, but they may lack the mechanical properties necessary for long term implantation. The objective of this study is to evaluate the effect of adding methyl methacrylate on networks’ mechanical properties under simulated physiological conditions. The networks were synthesized in two parts: (1) a biodegradable crosslinker was formed from a diacrylate and amine, (2) and then varying concentrations of methyl methacrylate were added prior to photopolymerizing the network. Degradation rate, mechanical properties, and glass transition temperature were studied as a function of methyl methacrylate composition. The crosslinking density played a limited role on mechanical properties for these networks, but increasing methyl methacrylate concentration improved the toughness by several orders of magnitude. Under simulated physiological conditions, networks showed increasing toughness or sustained toughness as degradation occurred. This work establishes a method of creating degradable networks with tailorable toughness while undergoing partial degradation.     

A single-step polymerization method for poly(β-amino ester) biodegradable hydrogels

A novel one-step method for the preparation of poly(β-amino ester) hydrogels has been developed. The one-step method utilizes a Michael type addition reaction between a difunctional diacrylate and a tetrafunctional primary diamine to create a crosslinked biodegradable hydrogel. It was shown that the molar ratio of the reactive acrylate to amine controlled the extent of polymerization and crosslinking density of the hydrogel system, which enabled for the end properties of the network (e.g., swelling, degradation, and mechanical) to be tuned.     

绿色高效Ga（DS）_3在溶剂水中催化加成吲哚酮类化合物

采用三价镓十二烷基硫酸盐作催化剂,在溶剂水中,以Michael加成反应制备吲哚酮类化合物,并对其进行了FT-IR、1H NMR等表征。取吲哚1 mmol、不饱和酮1.2 mmol、催化剂Ga（DS）3（10%）、80℃,水溶剂中反应,在较佳反应条件下,得到一系列吲哚酮类化合物,产率均达到80.2%以上。     

尿素催化合成乙酸-β-萘酯

以尿素为催化剂,采用乙酸酐和β-萘酚合成乙酸-β-萘酯.乙酸-β-萘酯合成的最佳工艺条件为:n(乙酸酐)∶n(β-萘酚)为1.2∶1,催化剂尿素用量占β-萘酚物质的量的10％,反应温度80℃,反应时间40 min,此条件下,收率达95.7％,催化剂可重复使用4次以上.     

β晶型聚丙烯微孔纤维的研制

研究了降温速率、纺丝速度、卢晶成核剂等对β晶聚丙烯初生纤维中β晶含量的影响;比较了两种β晶含量测试方法.结果表明:降温速率越快,线密度越低,纺丝速度越大,纤维中β晶含量越少;不同的β晶成核剂受纺丝速度的影响不同,其中稀土配合物成核剂B比酰胺类化合物成核剂A受纺丝速度的影响较大;在纺丝速度91 m/min,线密度55.6...