Properties and application of polyimide-based composites by blending surface functionalized boron nitride nanoplates

Properties and application of polyimide-based composites by blending surface functionalized boron nitride nanoplate

Effects of surface-functionalized aluminum nitride on thermal, electrical, and mechanical behaviors of polyarylene ether nitrile-based composites

Aluminum nitride (AlN) with high thermal conductivity was blended in polyarylene ether nitrile (PEN) to obtain a composite system. A ball milling process could provide AlN particles of smaller size with higher surface silylation for homogeneous particle distribution in polymeric matrix. Thermal, electrical, and mechanical behaviors of the produced composites were characterized to investigate the effects of particles on the performance of PEN-based composites with functionalized AlN. The composite exhibited thermal conductivity of 0.779 W m−1 K−1, a dielectric constant of 7.7, dielectric loss of 0.032, electrical resistivity of 1.39 GΩ.cm, and break strength of 36 N when the fraction of functionalized AlN increased to 42.3 vol%. A fitted equation based on the improved Russell's model could effectively predict a trend for thermal conductivity of the composite systems with consideration of interfacial resistance between AlN and surrounding PEN

Coffee-Ground-Derived Quantum Dots for Aqueous Processable Nanoporous Graphene Membranes

Carbon-based quantum dots (QDs) with ultralow dimensions and controllable surface chemistry have unique properties appealing to diverse applications. Here, we disclose a high-throughput transformation of spent coffee grounds into uniform QDs assembled by few-layer graphene oxide nanosheets, employing a microwave-assisted strategy under aqueous reaction conditions. Given the low dimensions (30 nm) and high structural integrity, the highly oxygenated QDs exhibited excellent dispersibility in water with tunable fluorescence. The structural attributes of QDs conferred excellent affinity to graphene nanosheets, permitting aqueous processing of nanoporous graphene membranes applicable to removing a broad spectrum of water pollutants ranging from organic compounds to heavy metals while sustaining a high flux rate. The proposed “trash-to-treasure” strategy opens up new possibilities for aqueous processing of nanoporous graphene membranes with great potential in the environmental field

Beyond a Model of Polymer Processing-Triggered Shear: Reconciling Shish-Kebab Formation and Control of Chain Degradation in Sheared Poly(l‑lactic acid)

Here we disclose an unprecedented methodology toward high-performance poly­(l-lactic acid) (PLLA) through generation of dense shish-kebabs, while the normal shear stress-induced chain degradation is controlled. The key elements involve the application of a pulse of strong shear and controlled crystallization. Specifically, the shear featuring a short duration of 1 s and a shear rate high to 100 s^–1 was employed to create shish precursors, which was followed by high-temperature crystallization (at 130, 135, and 140 °C) to render the prevailing development of shish-kebabs rather than spherulites. The direct observation of the overgrown shish afforded the demonstration of its origin from shear-aligned bundles of fibrillar chains, implying the crucial importance of chain entanglements in driving the alignment of neighboring chains along the transient shear. For the first time, the shear-aligned shish was revealed to present much higher conformational order, compared to the neighboring kebabs or spherulites. It is of great interest that the application of transient shear flow prevented PLLA from shear-induced degradation, although the PLLA chains are inherently sensitive to external shear stress. The proposed pathway, thus, creates PLLA rich in shish-kebabs with well-preserved high-molecular-weight chains. This signifies a new scenario with respect to previous studies where strong and long-acting shear was required for the formation of oriented structures in PLLA and the property enhancement was to large part hampered by simultaneous chain scissions. Of immense significance is the possibility to utilize these findings during common processing such as extrusion, spinning, and blowing, in which a transient and intensive shear flow is normally generated

Presentation_1_Multimodal ultrasonography findings of extramammary granular cell tumors: Two case reports.ppt

Extramammary masses are infrequently encountered in breast examinations. They may occur in the chest wall and axilla as neighbors of the breast. It is important to determine the nature of the lesion. However, some benign tumors, such as granular cell tumors (GCTs), also show malignant characteristics, which leads to misdiagnosis. To the best of our knowledge, multimodal ultrasound features of GCT have not been elucidated. We report two cases of women with GCTs encountered upon breast cancer screening; the tumor was not located in breast tissue. The first patient was a 37-year-old woman who presented with a slow-growing mass in the right breast and the GCT was located in the pectoralis major muscle. The second patient was a 52-year-old woman who presented with a palpable left axillary mass and the GCT was located in the axilla. Mammography failed to detect the masses in the two patients upon breast cancer screening. However, two-dimensional ultrasonography revealed a solid heterogeneous hypoechoic mass. Shear wave elastography showed that the masses had an increased hardness compared with the surrounding tissue. Further contrast-enhanced ultrasonography showed that the contrast patterns of the two masses were different. In case one, contrast-enhanced ultrasonography showed an inhomogeneous annular high enhancement, and the dynamic curve showed rapid enhancement and regression. In case two, contrast enhanced ultrasound showed slight enhancement around the lesion but no enhancement inside. Postoperative pathology confirmed that the GCT was benign in both cases. The patients showed no signs of recurrence at the 2-year follow-up. Here, we report two cases and present the multimodal ultrasonography findings of this tumor for the first time. Radiologists and surgeons should be aware of these imaging manifestations and include them in their differential diagnoses.</p

Simple Non-Equilibrium Atmospheric Plasma Post-Treatment Strategy for Surface Coating of Digital Light Processed 3D-Printed Vanillin-Based Schiff-Base Thermosets

A simple non-equilibrium atmospheric plasma post-treatment strategy was developed for the surface coating of three-dimensional (3D) structures produced by digital light processing 3D printing. The influence of non-equilibrium atmospheric plasma on the chemical and physical properties of vanillin-derived Schiff-base thermosets and the dip-coating process was investigated and compared to the influence of traditional post-treatment with UV-light. As a comparison, thermosets without post-treatment were also subjected to the coating procedure. The results document that UV post-treatment can induce the completion of the curing of the printed thermosets if complete curing is not reached during printing. Conversely, the plasma post-treatment does not contribute to the curing of the thermoset but causes some opening of the imine bonds and the regeneration of aldehyde functions. As a consequence, no great differences are observed between the not post-treated and plasma post-treated samples in terms of mechanical, thermal, and solvent-resistant properties. In contrast to the UV post-treatment, the plasma post-treatment of the thermosets induces a noticeable increase of the thermoset hydrophilicity ascribed to the reformation of amines on the thermoset surface. The successful coating process and the greatest uniformity of the lignosulfonate coating on the surface of plasma post-treated samples are considered to be due to the presence of these amines and aldehydes. The investigation of the UV shielding properties and antioxidant activities documents the increase of both properties with the increasing amount and uniformity of the formed coating. Interestingly, evident antioxidant properties are also shown by the noncoated thermosets, which are deduced to their chemical structures

Sedimentary response to the intracontinental orogenic process: insight from the anatomy of a small Mesozoic basin in western Yanshan, northern North China

<p>The intra-continental orogeny and tectonic evolution of the Mesozoic Yanshan fold-thrust belt (YFTB) in the northern North China Craton (NCC) have been strongly debated. Here, we focus on the Shangyi basin, located in the centre of the YFTB. An integrated analysis of sedimentary facies, palaeocurrents, clast compositions, and detrital zircon dating of sediments was adopted to determine the palaeogeography, provenance, basin evolution, and intra-continental orogenic process. The Shangyi basin comprises the well-exposed Early–early Middle Jurassic Xiahuayuan Formation and the Longmen Formation, and the Late Jurassic–Early Cretaceous Tuchengzi Formation. Based on the 18 measured sections, five facies associations – including alluvial fan, fluvial, delta, lacustrine, and eolian facies – have been identified and described in detail. The onset of the Shangyi basin was filled with fluvial, deltaic, and lacustrine deposits controlled by the normal fault bounding the northern basin, corresponding to the pre-orogeny. In the Middle Jurassic, the cobble–boulder conglomerates of alluvial fan, as molasse deposits, were compatible with the syn-orogeny of the Yanshan movement, which played a critical role in northern North China and even East Asia. After the depositional break in the Middle–Late Jurassic, the Shangyi basin, controlled by the normal fault present in the north of the basin, re-subsided and quickly expanded southward with thick sedimentation, which is correlative with the post-orogeny. Combined with A-type granites, metamorphic core complexes, mafic dikes, and rift basins of the Late Jurassic–early Early Cretaceous present in the northern NCC and Mongolia, significant extension was widespread in the northern NCC and even in northeast Asia. Moreover, vertical changes of provenance indicate that the Taihang Mountain and the Inner Mongolia palaeo-uplift (IMPU) present at the west and north of the basin, respectively, experienced uplift twice in the Middle–Late Jurassic and Early Cretaceous, resulting in a regional depositional break.</p

Coffee Grounds to Multifunctional Quantum Dots: Extreme Nanoenhancers of Polymer Biocomposites

Central to the design and execution of nanocomposite strategies is the invention of polymer-affinitive and multifunctional nanoreinforcements amenable to economically viable processing. Here, a microwave-assisted approach enabled gram-scale fabrication of polymer-affinitive luminescent quantum dots (QDs) from spent coffee grounds. The ultrasmall dimensions (approaching 20 nm), coupled with richness of diverse oxygen functional groups, conferred the zero-dimensional QDs with proper exfoliation and uniform dispersion in poly­(l-lactic acid) (PLLA) matrix. The unique optical properties of QDs were inherited by PLLA nanocomposites, giving intensive luminescence and high visible transparency, as well as nearly 100% UV-blocking ratio in the full-UV region at only 0.5 wt % QDs. The strong anchoring of PLLA chains at the nanoscale surfaces of QDs facilitated PLLA crystallization, which was accompanied by substantial improvements in thermomechanical and tensile properties. With 1 wt % QDs, for example, the storage modulus at 100 °C and tensile strength increased over 2500 and 69% compared to those of pure PLLA (4 and 57.3 MPa), respectively. The QD-enabled energy-dissipating and flexibility-imparting mechanisms upon tensile deformation, including the generation of numerous shear bands, crazing, and nanofibrillation, gave an unusual combination of elasticity and extensibility for PLLA nanocomposites. This paves the way to biowaste-derived nanodots with high affinity to polymer for elegant implementation of distinct light management and extreme nanoreinforcements in an ecofriendly manner

Graphene Oxide-Driven Design of Strong and Flexible Biopolymer Barrier Films: From Smart Crystallization Control to Affordable Engineering

Development of multifunctional, versatile biobased polymers can greatly benefit from the discovery and application of 2D sheet-like materials. For instance, the hybrid system integrating graphene oxide (GO) nanosheets with enantiomeric poly­(lactic acid) (PLA) showcases several key properties that can address emerging multifunction needs such as good gas barrier and high thermal resistance. Here we revealed that large specific surface area and homogeneous dispersion of GO conferred the construction of interconnected networks in PLA even with relatively low GO contents (0.1 and 0.5 wt %). These well-extended GO nanosheets were ready to provide enormous and active platforms to nucleate preferentially the neighboring stereocomplex chains, prompting the prevailing development of stereocomplex crystals (SCs). The notable scenario associated with the GO distribution was imaged by 2D Fourier transform infrared spectroscopy, and was further elucidated by dynamic crystallization. More importantly, the nanosheets decorated with ordered PLA lamellae, in turn, contributed to the impressive enhancement in barrier and mechanical properties and chemical resistance. For example, a distinct decrease of 98.5% in oxygen permeability coefficient was observed for the composite films containing 0.5 wt % GO (6.264 × 10^–17 cm³ cm cm^–2 s^–1 Pa^–1) compared to the control sample crystallized at 150 °C (4.214 × 10^–15 cm³ cm cm^–2 s^–1 Pa^–1). The performance distinction was accompanied by the unusual combination of high tensile strength (73.5 MPa) and high elongation (13.6%), displaying an increase of 31.7% and 183.3% compared to the counterpart, respectively. This may provide a broader context for exploiting 2D nanosheets as robust cells to advance the function and property of PLA, which helps to outline the roadmap for fashioning high-performance, affordable bioplastics

Immobilized Graphene Oxide Nanosheets as Thin but Strong Nanointerfaces in Biocomposites

Graphene oxide (GO) nanosheets featuring high surface activity and large planar dimension may function as robust nanointerfaces in biocomposites, contributing to simultaneous promotion of mechanical and gas barrier properties. Here, a solution-processed, additive-free approach to immobilize few-layer GO nanosheets on starch granule surfaces (GO@starch) by hydrogen bonding is demonstrated. This approach enabled a straightforward pathway to remove the intersheet van der Waals forces (π–π stacking) that generally cause reaggregation and poor dispersion of GO in polymer matrices. Incorporation of GO@starch into poly­(lactic acid) (PLA) allowed an interesting structure with few-layer nanosheets firmly immobilized at the PLA–starch interfaces. Inheriting the high aspect ratio and surface energy of GO, GO@starch distinctly strengthened the interfacial interactions with PLA, albeit present at ultralow GO concentrations (up to 0.03 wt %), facilitating the dispersion of GO@starch and nucleation of PLA. The morphological regulation rendered composite films with an impressive combination of high thermal stability, mechanical strength and oxygen resistance. A substantial increase of 280% in tensile strength (58.2 MPa) and a prominent decline of 82% in oxygen permeation coefficient (4.0 cm³ mm cm^–2 day^–1 atm^–1) were achieved in the composites loaded with 30 wt % GO@starch in comparison with the counterpart. The cost–performance ratio for the nanostructured biocomposites was excellent even compared to the established packaging materials. The multiscale morphological regulation of sheet-like nanofillers by controlled exfoliation and immobilization of GO on microsized starch particle surfaces, the simplicity of manufacturing, together with the versatility of the engineered composites should make our strategy broadly applicable to other material combinations