Stereocomplex Crystallization Induced Significant Improvement in Transparency and Stiffness–Toughness Performance of Core-Shell Rubber Nanoparticles Toughened Poly(l-lactide) Blends

Toughening modification of poly(l -lactide) (PLLA) with rubber particles is often realized at the cost of transparency, mechanical strength, and modulus because high rubber loadings are generally required for toughening. In this work, a promising strategy to simultaneously improve the transparency and stiffness–toughness performance of poly(butyl acrylate)-poly(methyl methacrylate) (BAMMA) core-shell rubber nanoparticles toughened PLLA blends by utilizing the stereocomplex (SC) crystallization between PLLA and poly(d -lactide) (PDLA) is devised. The results reveal that the construction of SC crystallites in PLLA matrix via melt-mixing PLLA/BAMMA blends with PDLA can prevent BAMMA nanoparticles from aggregation and promote them to form network-like structure at lower contents. As a result, not only higher toughening efficiency with less rubber contents but also superior transparency is achieved in the PLLA/PDLA/BAMMA blends as compared with the PLLA/BAMMA ones where large aggregated BAMMA clusters are formed. Moreover, the outstanding reinforcement of SC crystallites network for PLLA can impart an enhanced tensile strength and modulus to PLLA/PDLA/BAMMA blends, thus improving the stiffness–toughness performance of PLLA/PDLA/BAMMA blends to a higher degree. This work demonstrates that SC crystallization is a promising solution to solve the contradiction between transparency and mechanical properties and then obtain superior comprehensive performances in rubber toughened PLLA blends.     

Micron-Scale Soft Actuators Fabricated from Multi-Shell Polystyrene Particle-Gold Nanoparticle Nanohybrids

Actuators made of soft matter are needed for a variety of fields ranging from biomedical devices to soft robotics to microelectromechanical systems. While there are a variety of excellent methods of soft actuation known, the field is still an area of intense research activity as new niches and needs emerge with new technology development. Here, a soft actuation system is described, based on a core-multi-shell particle, which moves via photothermal expansion. The system consists of a novel polystyrene-based thermally expandable microsphere, with a secondary shell of a silicate-silane graft copolymer, to which gold nanoparticles are covalently linked. The gold nanoparticles act as photothermal nano-transducers, converting light energy into the thermal energy necessary for microsphere expansion, which in turn results in material movement. Actuation is shown in isolated particles in thermal and photothermal regimes using metal ceramic heaters or 520 nm laser illumination, respectively. Macroscale actuation is demonstrated by making a composite material of particles suspended in the transparent elastomer polydimethylsiloxane. The sample demonstrates an inchworm-like movement by starting from an arched geometry. Overall, this work describes a new particle-based actuation method for soft materials, and demonstrates its utility in driving the movement of a composite elastomer.     

Facile Deposition of Silver Nanoparticles on Photonic Cellulose Nanocrystals Films: A Study on Solvent Stability and Post Antibacterial Activity

Cellulose nanocrystals (CNCs) incorporated with silver nanoparticles (AgNPs) photonic films have drawn considerable attention due to their plasmonic chiroptical activity. However, the exploitation of some fundamental properties for practical use such as the affinity analysis of metal nanoparticles attached to the surface of photonic films according to the solvent compatibility and antibacterial activity under physical conditions has yet not been studied. Hence, a facile process of in situ deposition of AgNPs into the chiral structure of CNC films is proposed. CNC photonic films, cross-linked by glutaraldehyde are prepared. This interaction generated the solvents-stable photonic film with a considerable amount of unreacted aldehyde functional groups that facilitates the reduction of Ag salt to AgNPs. The formed AgNPs in the photonic films show excellent stability over immersion in various polar and non-polar solvents. The post-solvent treated photonic films display excellent contact-based antibacterial behavior against gram-negative Escherichia coli.     

Red-Blood-Cell-Membrane-Coated Metal-Drug Nanoparticles for Enhanced Chemotherapy

To overcome high toxicity, low bioavailability and poor water solubility of chemotherapeutics, a variety of drug carriers have been designed. However, most carriers are severely limited by low drug loading capacity and adverse side effects. Here, a new type of metal-drug nanoparticles (MDNs) was designed and synthesized. The MDNs self-assembled with Fe(III) ions and drug molecules through coordination, resulting in nanoparticles with high drug loading. To assist systemic delivery and prolong circulation time, the obtained MDNs were camouflaged with red blood cell (RBCs) membranes (RBCs@Fe-DOX MDNs) to improve their stability and dispersity. The RBCs@Fe-DOX MDNs presented pH-responsive release functionalities, resulting in drug release accelerated in acidic tumor microenvironments. The outstanding in vitro and in vivo antitumor therapeutic outcome was realized by RBCs@Fe-DOX MDNs. This study provides an innovative design guideline for chemotherapy and demonstrates the great capacity of nanomaterials in anticancer treatments.     

In-situ generation of platinum nanoparticles on LaCoO3 matrix for soot oxidation

The LaCo_0.94Pt_0.06O₃ catalyst is reduced under 5% H₂/Ar at different temperatures to get Pt/LaCoO₃ with high catalytic activity for soot oxidation. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), X-ray photoelectron spectroscopy (XPS), H₂-temperature programmed reduction (H₂-TPR), O₂-temperature programmed desorption (O₂-TPD) and thermogravimetric analysis (TGA) were used to study the physicochemical properties of the catalyst. SEM and TEM results indicate that Pt nanoparticles (<10 nm) are grown homogeneously on the surface of the LaCoO₃ matrix after in-situ reduction. XRD shows that the reduced catalyst has a high symmetrical structure. TGA results indicate that all reduced catalysts exhibit an excellent activity, especially the catalyst reduced at 350 °C (T₁₀ = 338 °C, T₅₀ = 393 °C, T₉₀ = 427 °C). And perovskite is the primary active component. According to XPS study, the high symmetrical structure benefits the mobility of oxygen vacancy, and Pt nanoparticles induce the oxygen vacancy to move to its adjacent situation, resulting in more adsorbed oxygen on the surface of the reduced catalyst and increasing the activity. The possible reaction principle is also proposed.     

快速凝固铝硅合金粉末加热过程中硅颗粒的粗化行为

利用差示扫描量热仪(DSC)、电子显微镜等设备对Al-12.8%Si合金粉末的原始状态及热处理后的状态进行了分析。发现其显微组织有两个连续的变化过程:在156℃时,固溶在基体Al中的过饱和Si开始析出,并在340℃发生粗化,随着加热温度的升高,粗化现象仍然存在。另外,对Si颗粒的粗化机理进行了研究,发现其粗化符合经典的LSW理论。     

铝合金板材时效组织的高分辨分析

本文通过X射线衍射、扫描电镜、高分辨透射电镜,分析了6009铝合金时效组织,球形Mg2Si是其主要强化相。在电解低钛铝合金中,球形Mg2Si分布更为弥散、均匀。对高分辨像通过傅立叶变换和反傅立叶变换,得到了调幅分解组织的晶格像。结果表明:电解低钛铝合金其力学性能和组织优于熔配加钛铝合金;电解低钛铝合金中Mg和Si原子在铝基体的(200)面上偏聚,形成明显的调幅分解组织。     

高炉铁水含硅量的混沌局部线性预测

对莱钢1号高炉(750 m3)、临钢6号高炉(380 m3)铁水含硅量([Si])进行了混沌局部线性预测.结果表明,两 座高炉[Si]的一步预测的命中率在[Si]±0.1％的范围内均达到80.0％以上,对莱钢1号高炉(b)类样本甚至达89.1％,且预 测精度在10-2数量级,对实际生产具有很好的指导作用.     

Understanding the Influence of Copper Nanoparticles on Thermal Characteristics and Microstructural Development of a Tin-Silver Solder

This paper presents and discusses issues relevant to solidification of a chosen lead-free solder, the eutectic Sn-3.5%Ag, and its composite counterparts. Direct temperature recordings for the no-clean solder paste during the simulated reflow process revealed a significant amount of undercooling to occur prior to the initiation of solidification of the eutectic Sn-3.5%Ag solder, which is 6.5 °C, and for the composite counterparts, it is dependent on the percentage of copper nanopowder. Temperature recordings revealed the same temperature level of 221 °C for both melting (from solid to liquid) and final solidification (after recalescence) of the Sn-3.5%Ag solder. Addition of copper nanoparticles was observed to have no appreciable influence on melting temperature of the composite solder. However, it does influence solidification of the composite solder. The addition of 0.5 wt.% copper nanoparticles lowered the solidification temperature to 219.5 °C, while addition of 1.0 wt.% copper nanoparticles lowered the solidification temperature to 217.5 °C, which is close to the melting point of the ternary eutectic Sn-Ag-Cu solder alloy, Sn-3.7Ag-0.9Cu. This indicates the copper nanoparticles are completely dissolved in the eutectic Sn-3.5%Ag solder and precipitate as the Cu₆Sn₅, which reinforces the eutectic solder. Optical microscopy observations revealed the addition of 1.0 wt.% of copper nanoparticles to the Sn-3.5%Ag solder results in the formation and presence of the intermetallic compound Cu₆Sn_5. These particles are polygonal in morphology and dispersed randomly through the solder matrix. Addition of microsized copper particles cannot completely dissolve in the eutectic solder and projects a sunflower morphology with the solid copper particle surrounded by the Cu₆Sn₅ intermetallic compound coupled with residual porosity present in the solder sample. Microhardness measurements revealed the addition of copper nanopowder to the eutectic Sn-3.5%Ag solder resulted in higher hardness.