Extraordinary mechanical performance in charged carbyne

Carbyne, the linear chain of carbon, promises the strongest and toughest material but possesses a Peierls instability (alternating single-bonds and triple-bonds) that reduces its strength and toughness. Herein, we computationally found that the gravimetric strength, strain-to-failure, and gravimetric toughness can be improved from 74 GPa·g^-1·cm³, 18%, and 9.4 kJ·g^-1 for pristine carbyne to the highest values of 106 GPa·g^-1·cm³, 26%, and 19.0 kJ·g^-1 for carbyne upon hole injection of +0.07 e/atom, indicating the charged carbyne with record-breaking mechanical performance. Based on the analyses of the atomic and electronic structures, the underlying mechanism behind the record-breaking mechanical performance was revealed as the suppressed and even eliminated bond alternation of carbyne upon charge injection.     

Poly (vinyl chloride)/poly (α‐methylstyrene–acrylonitrile)/acrylic resin ternary blends with enhanced toughness and heat resistance

In this study, tough and high heat‐resistant poly (vinyl chloride) (PVC)/poly (α‐methylstyrene–acrylonitrile) (α‐MSAN) blends (70/30) containing acrylic resin (ACR) as a toughening modifier was prepared. With the addition of ACR, heat distortion temperature increased slightly, which corresponded with the increase in glass transition temperature measured by differential scanning calorimetry and dynamic mechanical thermal analysis. Thermogravimetric analysis showed that addition of ACR improved the thermal stability. With regard to mechanical properties, tough behavior was observed combined with the decrease in tensile strength and flexural strength. A brittle‐ductile transition (BDT) in impact strength was found when ACR content increased from 8 to 10 phr. The impact strength was increased by 34.8 times with the addition of 15 phr ACR. The morphology correlated well with BDT in impact strength. It was also suggested from the morphology that microvoids and shear yielding were the major toughening mechanisms for the ternary blends. Our present study offers insight on the modification of PVC, since combination of α‐MSAN and ACR improves the toughness and heat resistance of pure PVC simultaneously. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental study on the Karst area fracture zones of the synthesizing geophysical methods

岩溶地区地形、地质情况相对复杂,各种物探方法的应用都受到一定条件限制,进行岩溶断裂破碎带勘察时,应进行综合物探勘察,为设计和施工提供可靠的原始资料;本文采用综合物探方法对广州地铁九号线工程田美断裂进行探测,详细查明田美断裂的走向、破碎带宽度、构造破碎特征、断裂的性质、规模和产状等;同时辅以少量勘察验证孔施工对断裂做验证,以便有效地揭示断裂特征,通过实验取得较理想的成果,并意外地发现了田美断裂的次一级断裂。     

Flowability and Mechanical and Thermal Properties of Nylon 6/Ethylene bis-Stearamide/Carboxylic Silica Composites

Nylon 6 (PA 6)/ethylene bis-stearamide (EBS)/SiO₂- carboxylic acid-functionalized silica nanoparticles (COOH) composites were prepared by in-situ polymerization of caprolactam. SiO₂-COOH was used to enhance the compatibility between SiO₂ and PA 6 matrix. For comparison, pure PA 6 and PA 6/EBS composites were also prepared via the same method. The PA 6/EBS/SiO₂-COOH composites with low content of EBS and SiO₂-COOH had greater melt-flow index (MFI) (the value of MFI increased by 50%–80%) than the pure PA 6. The results of mechanical properties showed almost no decrease in the tensile strength of PA 6/EBS/SiO₂-COOH composites, with the bending strength decreasing by 17%–21%. However, the Izod impact strength of the PA 6/EBS/SiO₂-COOH composites was greatly improved compared with pure PA 6, which indicated that the toughness of PA 6/EBS/SiO₂-COOH had been greatly improved. The morphology of Izod impacted fractured surfaces of PA 6/EBS/SiO₂-COOH was observed by scanning electron microscopy. The results revealed that the PA 6/EBS/SiO₂-COOH composites presented a typical ductile fracture behavior with large amounts of long and large strip-like cracks. When the content of SiO₂-COOH was 0.2 wt%, the SiO₂-COOH particles were uniformly dispersed over the entire body of the PA 6 matrix. The results from differential scanning calorimetry indicated that the melting point (T_m), degree of crystallinity (X_c), and crystallization temperatures (T_c) of PA 6/EBS/SiO₂-COOH composites were lower than the pure PA 6.     

Morphology of Fractured Polymer‐Polymer Interfaces Bonded at Ambient Temperature as Studied by Atomic Force Microscopy

The amorphous polymer surfaces of polystyrene (PS, M _n=200 kg/mol, M _w/M _n=1.05) and poly(methyl methacrylate) (PMMA, M _n=51.9 kg/mol, M _w/M _n≤1.07) were brought into contact at 21°C to form PS‐PS (for 54 days) and PMMA‐PMMA auto‐adhesive joints (for 11 days). After contact at that temperature corresponding to T _g‐bulk ?81°C for PS and to T _g‐bulk–88°C for PMMA, where T _g‐bulk is the calorimetric glass transition temperature of the bulk sample, the bonded interfaces were fractured and their surfaces were analyzed by atomic force microscopy (AFM). The surface roughness, R _q, of the fractured interfaces was larger by a factor of 3–4 than was that of the free PS and PMMA surfaces aged for the same period of time. A similar increase in R _q was found by comparison of the free PS surface aged at T _g‐bulk+15°C for 1 h and of the surface of the PS‐PS interface fractured after healing at T _g‐bulk+15°C for 1 h. These observations, indicative of the deformation of the fractured interfaces, suggest the occurrence of some mass transfer across the interface even below T _g‐bulk ?80°C.     

μ‐Raman spectroscopy of prehistoric paintings from the Abrigo Remacha rock shelter (Villaseca,Segovia, Spain)

The composition of the materials present in prehistoric paintings discovered on the walls of the Abrigo Remacha rock shelter (Villaseca, Segovia, Spain) has been characterised by micro‐Raman spectroscopy. In addition, scanning electron microscopy and energy dispersive X‐ray microanalysis have been used as auxiliary techniques. The results show that haematite (α‐Fe₂O₃) is the main component of the red pigment. Amorphous carbon and paracoquimbite (Fe₂(SO₄)₃.9H₂O) have been detected in the bluish black pigment used in a significant bi‐colour pictograph. This is the first time that this mineral has been discovered in a prehistoric painting. Accretions of whewellite and weddellite form crusts covering most of the painting panel. Different carbonates are the main components of the rocky substrate. The detection of gypsum on the surface of the panel is associated to the flaking process that is affecting the painting panel. Copyright © 2013 John Wiley & Sons, Ltd.     

Composites of Hydroxyapatite Whiskers/poly(L-lactide-co-glycolide) with High Tensile Plasticity

Hydroxyapatite whiskers (HAW) with a maximum aspect ratio of 20 were employed to improve the toughness of poly(L-lactide-co-glycolide) (PLGA). 3-Aminopropyltriethoxysilane (AMEO) was grafted on the surface of the hydroxyapatite whiskers (g-HAW) to improve its wetting in the PLGA matrix. Composites based on HAW, g-HAW, and PLGA were prepared. The structure and properties of the composites were subsequently investigated by powder X-ray diffraction (XRD), scanning electron microscopy, differential scanning calorimetry, and tensile testing. The g-HAW were distributed homogenously in the PLGA matrix because of improved wetting of g-HAW while the HAW were aggregated. The stronger interfacial bonding also gave rise to improved mechanical properties of the g-HAW/PLGA composites. The HAW/PLGA and g-HAW/PLGA composites failed in a tough manner with intensive plastic deformation. The g-HAW/PLGA composite (5 wt% g-HAW) failed at a maximum elongation of 366%, although the tensile strength dropped slightly. The g-HAW/PLGA composite (1 wt% g-HAW) maintained the initial tensile strength of neat PLGA but failed at an equally high elongation of 347%, whereas PLGA failed at an elongation of 11%.     

Self‐Toughening and Self‐Reinforcing Injection‐Molded Isotactic Polypropylene via Midfrequency Vibration Field

The effect of vibration frequency on the mechanical properties of general grade polypropylene (PP) prepared by two types of vibration injection molding (VIM) was investigated. With the application of vibration injection molding, the mechanical properties of isotactic PP are improved. The yield strength was upgraded with the increment of vibration frequency and a peak occurs at a particular frequency for each VIM. The elongation at break was also raised by increased vibration frequency, and the vibration frequency also improves impact strength. Self‐reinforcing and self‐toughening polypropylene molded parts were found at high vibration frequency. The wide angle X‐ray diffraction (WAXD) curves and scanning electronic micrograph (SEM) micrographs have shown that, in the vibration field, the enhancement of mechanical properties can be attributed to the occurrence of a γ‐phase crystalline structure and a more pronounced elongation in shape than obtained by conventional injection moldings. In addition, smaller crystals of the β‐phase crystal form improve toughness.     

Study on the Morphological and Mechanical Properties of Nylon 6/ABS/Nano-SiO2 Composites

The mechanical properties and morphology of the composites of nylon 6, acrylonitrile-butadiene-styrene (ABS) rubber, and nano-SiO₂ particles were examined as a function of the nano-SiO₂ content. A mixture with separation and encapsulation microstructures existed in the nylon 6/ABS/nano-SiO₂ at lower nano-SiO₂ content, and ABS and nano-SiO₂ improved the toughness synergistically, while obvious agglomeration appeared at higher nano-SiO₂ content and the impact strength decreased. Moreover, the addition of nano-SiO₂ particles also affected the dispersion of the rubber phase, resulting in the appearance of smaller rubber particles. The deformation and toughening mechanisms of the composites were also investigated; they resulted from rubber voiding, crack forking, and plastic deformation of the matrix.     

Studies on the Thermal Properties of Epoxy Resins Modified with Two Kinds of Silanes

Dimethyldiethoxysilane (DMDES) and diphenyldimethoxysilane (DPDMS)-containing epoxy resins were synthesized by dehydration polycondensation. The chemical structures were determined by FT-IR, ¹H NMR, and ¹³C NMR. The cured samples, with 4, 4′-diaminodiphenylmethane (DDM) as curing agent, were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and tensile and impact testing. Results showed that DMDES and DPDMS-modified epoxy resins possess higher glass transition temperatures, better thermal stability, and better fracture toughness than the neat epoxy resin.