含复合(Ti,Mo)C析出相的马氏体钢的氢捕获与解吸附

采用热脱氢分析装置 (TDS) 研究了含复合 (Ti,Mo)C析出相的马氏体钢的氢的捕获与解吸附行为。结果表明,36-60 nm的未溶球形(Ti,Mo)复合析出相在室温电化学充氢过程中不能捕获氢,而回火析出的1-5 nm的复合 (Ti,Mo)C析出相是有效的氢陷阱,尽管其氢陷阱激活能相对较低,为16.4-22.1 kJ/mol,与晶界、位错处的氢陷阱激活能相近,同时远低于纯的共格TiC析出相的氢陷阱激活能,但在大气中放置时,被回火析出的1-5 nm的复合 (Ti,Mo)C析出相捕获的氢无法解吸。     

FCC-to-HCP Phase Transformation in CoCrNix Medium-Entropy Alloys

A hybrid first-principles/Monte Carlo simulation is combined with experiments to study the structure and elastic properties of CoCrNi_x (x = 1-0.5) alloys. The experimental X-ray diffraction patterns show that the structures have changed from the single-phase face-centered cubic (FCC) structure at x = 1-0.8 to the coexistence of FCC and the hexagonal close-packed structures at x = 0.7-0.5, which is further confirmed by calculations on mixing energies. The elastic moduli by calculation are basically in agreement with experiments. Room-temperature tension shows that the six alloys have a certain plasticity, the strength and plasticity of the alloys have a linear decrease with the decrease in Ni contents, and the plasticity of the alloys drops from 84 to 23%. Furthermore, first-principles density function theory calculations were employed to reveal the electronic and magnetic structures of alloys. The electron density of states for all alloys is asymmetrical, which illustrates that the alloys are ferromagnetism. It is found that Cr atoms can suppress the ferromagnetism of alloys, since Cr atoms have both positive and negative magnetic moments in all alloys.     

Effect of Ni-coated MoS2 on microstructure and tribological properties of (Cu−10Sn)-based composites

The (Cu−10Sn)−Ni−MoS₂ composites, prepared by powder metallurgy, were studied for the effects of Ni-coated MoS₂ on the microstructure, mechanical properties and lubricating properties. The mechanism of effects of Ni and MoS₂ on the properties of composites was analyzed through a comparative experiment by adding Ni and MoS₂ separately. The results show that the nickel wrapping around the MoS₂ particles decreases the reaction rate of MoS₂ with the copper matrix, and greatly improves the bonding of the matrix. The composites with 12 wt.% Ni-coated MoS₂ (C12) show the optimum performance including the mechanical properties and tribological behaviors. Under oil lubrication conditions, the friction coefficient is 0.0075 with a pressure of 8 MPa and a linear velocity of 0.25 m/s. The average dry friction coefficient, sliding against 40Cr steel disc, is measured to be 0.1769 when the linear velocity and pressure are 0.25 m/s and 4 MPa, respectively.     

Nanoparticle evolution in flame spray pyrolysis—Process design via experimental and computational analysis

In flame spray pyrolysis (FSP), the evolution of metal oxide nanoparticles relies on quite a number of droplet (liquid) and vapor phase related physical mechanism as for instance precursor evaporation, oxidation, nucleation via gas-to-particle conversion mechanism, and subsequent particle (solid) growth mechanisms based on coagulation, sintering/coalescence, and agglomeration. The liquid precursor and dispersion oxygen feed rates are relevant control parameters of the FSP process for tailoring the nanoparticle size (diameter) and structure as well as the atomizer nozzle configuration. Sophisticated nonintrusive, laser-based in situ and ex situ diagnostics with multiscale spatial resolution (micrometer to meter range) are applied for analyzing droplet formation and size, gas velocity, temperature, species concentration, as well as primary and agglomerate diameters along the flow direction. Computational fluid dynamics (CFD) are coupled with population balance modeling (PBM) to elucidate the nanoparticle dynamics within the reactive spray. It is found that the CFD-PBM approach allows estimations of primary and agglomerate nanoparticle diameters within 80 and 75% accuracy compared to experimental data, suggesting that the methods presented could pave the way for designing next-generations of flame reactors.     

In situ reaction and solid solution induced hardening in (Ti,Zr)B2-(Zr,Ti)C composites

(Ti,Zr)B₂ - (Zr,Ti)C ceramics were synthesized by reactive hot-pressing and solid solution coupling effect using ZrB₂ and TiC powders as starting materials. Effects of sintering temperature on phase relations, microstructure and mechanical properties were reported. The equimolar ZrB₂ and TiC reactants ensured a complete in situ reaction to form (Ti,Zr)B₂ and (Zr,Ti)C solid solutions. The (Ti,Zr)B₂ - (Zr,Ti)C composite sintered at 1750°C was fully densified, and exhibited a high hardness of 29.1 GPa due to fine-grain hardening and solid solution hardening. The optimized comprehensive mechanical properties such as a hardness of 27.9 GPa, a strength of 705 MPa and an indentation fracture toughness of 5.3 MPa m^1/2 were achieved in (Ti,Zr)B₂ - (Zr,Ti)C composites sintered at 1800°C for 1 hour.     

Pure and mixed gas permeation study of silica incorporated polyurethane-urea membrane modified by MOCA chain extender

Polyurethane-urea (PUU) nanocomposite membranes have been prepared using various loadings of silica (SiO₂) nanoparticles. A Novel PU was fabricated by a two-step bulk polymerization technique based on polycaprolactone (PCL), hexamethylene diisocyanate (HDI), and diamine chain extender, 4,4-methylenebis(2-chloroaniline) (MOCA). The FTIR spectra indicated that the extent of phase separation reduces with increasing SiO₂ content. The presence of crystal regions in the soft and hard segments was confirmed by DSC and XRD analyses. The obtained results illustrated a decrement in the gases' permeation in the presence of SiO₂ particles. By increasing the filler content up to 15 wt% and pressure of 8 bar, the gas permeation value of the CO₂, O₂, and N₂ decreased 36%, 54%, and 59%, respectively. However, the permselectivity of the CO₂/N₂ and O₂/N₂ increased considerably, 55% and 13% respectively. On the contrary, by raising the temperature, a dramatic augmentation in the permeability of all gases with a simultaneous reduction in the selectivity values of both gas pairs was revealed. Increasing the pressure led to a decrease in the permeability values of all membranes for O₂ and N₂, whereas the permeability for CO₂ increased with the pressure. Nevertheless, the selectivity values for the pair of gases increased (at a pressure of 10 bar, 1.66 and 1.17 times the neat PU for CO₂/N₂ and O₂/N₂, respectively). Furthermore, the permeability of the CO₂, O₂, and N₂ for the mixed gases was smaller than for pure ones at the same gas upstream pressure. Nonetheless, like the pure gas, the selectivity of both pair gases increased.     

A hybrid system of hydrogel/frog egg-like microspheres accelerates wound healing via sustained delivery of RCSPs

In this article, a hybrid system of hydrogel/frog egg-like microspheres (H-FMS) formed by the combination of coaxial electrostatic spraying and freeze-drying was introduced for enhancing wound healing efficiency through the sustained release of Rana chensinensis skin peptides (RCSPs). The porous PVA/gelatin hydrogel were obtained and frog egg-like microspheres (FMS) of sodium alginate (SA), shaping uniform and smooth, were embedded into hydrogel. Based on PVA/gelatin hydrogel, the FMS addition increased the water absorption of hydrogel to 1,105%. RCSPs were more effectively encapsulated into FMS than solid microspheres (MS). Not only does the H-FMS act as good “depots” for sustained release of RCSPs over 9 days, without exhibiting obvious burst release, but also show good biocompatibility in vitro. In vivo studies on wound healing as well as the histology of fibroblasts, re-epithelialization, inflammation, and hair follicles indicated that the structure of H-FMS released RCSPs continuously and promoted wound healing in rats significantly.     

异烟肼衍生物对聚L-乳酸性能的影响

以异烟肼和均苯三酸为原料合成了新型均苯三酸三异烟肼,考察了其对聚L-乳酸(PLLA)结晶性能和热稳定性的影响。结果表明:均苯三酸三异烟肼起到了异相成核的作用,能有效提升PLLA的结晶速率,其中添加质量分数2.0%的均苯三酸三异烟肼可使PLLA有最大非等温结晶焓,但过量的均苯三酸三异烟肼却不利于PLLA的结晶。均苯三酸三异烟肼的加入不会改变PLLA的热分解行为,但随着均苯三酸三异烟肼含量的增加,其起始分解温度下降。     

带有约束条件的四参数Logistic曲线分析在干扰素生物学活性检定中的应用

目的改进目前干扰素(interferon,IFN)生物学活性检定中的数据处理方法。方法在四参数Logistic曲线回归中加入约束条件,使之成斜度比例或平行曲线。结果用改进的方法对已有的实验数据进行分析,生物学活性计算结果与当前检定方法近似。此方法可对实验的可靠性进行初步估计,并可估计检测结果的置信区间。结论带约束条件的四参数Logistic曲线分析法可用于IFN生物学活性检定,模型在统计学方面较目前的数据处理方法更完整、可靠。     

卡介菌纯蛋白衍生物的稳定性评价

目的评价卡介菌纯蛋白衍生物(purified protein derivative of BCG,BCG-PPD)的稳定性。方法将3批BCGPPD样品置2~8℃存放30个月,分别于第0、3、6、9、12、18、24、30个月进行物理外观检查、pH和效价测定,第0、12、18、24、30个月同时进行鉴别试验、无菌试验、装量差异、异常毒性及苯酚含量检测;于(25±2)℃条件下存放12个月,第0、1、2、3、6、9、12个月进行物理外观检查、pH和效价测定;于(37±2)℃条件下存放12周,在第0、1、2、3、4、8、12个月进行外观检查、pH和效价测定。结果 3批BCG-PPD于2~8℃存放不同时间样品的鉴别试验、物理外观、装量差异、无菌试验及异常毒性检测结果均合格,pH为7. 12~7. 25,苯酚含量为2. 48~2. 72 g/L,效价为0. 92~1. 13,均呈稳定状态。3批BCG-PPD样品于(25±2)和(37±2)℃条件下保存,物理外观检查均合格,pH分别为7. 12~7. 32和7. 11~7. 20,效价分别为0. 93~1. 06和0. 91~1. 02,均符合要求。结论 BCG-PPD具有良好的稳定性,可满足将其有效期延长至24个月的要求。