Direct Ink-Jet Printing of Vertical Walls

Direct jet printing can assemble ceramic powder into a three dimensional shape by firing droplets of ink through a nozzle to build a multiple layered structure. As with stereolithography and selective laser sintering, the surface texture is expected to witness the layered assembly. The ability to create vertical walls by direct ink-jet printing was explored using a test piece based on a maze. The structure and topography are discussed in terms of droplet spreading and drying.     

Mechanically robust and thermally enhanced sand-polyacrylamide-2D nanofiller composite hydrogels for water shutoff applications

Herein, we report a facile preparation method for mechanically robust and thermally enhanced sand-polyacrylamide (PAM)-2D-nanofillers composite hydrogels and their application in water shutoff. To prepare the sample, 4 wt% of aqueous PAM solution is mixed with organic cross-linkers of hydroquinone (HQ) and hexamethylenetetramine (HMT) in a 1:1 weight ratio and aqueous potassium chloride (KCl) solution and with a specific amount of 2D-nanofillers such as commercial graphene (CG) nanosheets or boron nitride nanoparticles (BN NPs). A specific amount of the above solution is added to sand, well mixed, and subsequently cured at 150°C for 8 h. The prepared composite hydrogels were characterized by Fourier-transform infrared spectroscopy (FT-IR) for chemical composition and X-ray diffraction (XRD) for successful hydrogel coating onto the sand particles. Thermal stabilities of the samples have been evaluated by differential scanning calorimetry (DSC). Mechanical properties (storage modulus [G′]; loss modulus [G″]; gel strength (G′/G″); and damping factor [G″/G′]) of the samples were determined using dynamic mechanical analyses. The thermal stability of the samples has reached as high as 193.4°C, while the gel strength is found to be a maximum of 16.2. The water swelling ratio for the composite hydrogel has reached a maximum of 1100% within 1 h.     

CFD modeling of multiphase flow distribution in catalytic packed bed reactors: scale down issues

Flow maldistribution in either a bench-scale or commercial scale packed bed is often responsible for the failure of the scale down unit to mimic the performance of the large reactor. The modeling of multiphase flow in a bench-scale unit is needed for proper interpretation of reaction rate data obtained in such units. Understanding the mechanism of flow maldistribution is the first step to avoiding it. In order to achieve this objective, computational fluid dynamic (CFD) simulations of multiphase flow under steady state and unsteady state conditions in bench-scale cylindrical and rectangular packed beds are presented for the first time. The porosity distribution in packed beds is implemented into CFD simulation by pseudo-randomly assigned cell porosity values within certain constraints. The flow simulation results provide valuable information on velocity, pressure, and phase holdup distribution.     

The role of synthetic and natural fillers on three‐body abrasive wear behaviour of glass fabric–epoxy hybrid composites

Polymer matrix composites are a promising candidate in tribological applications due to possibility of tailoring their properties with special fillers. The comparative performance of Glass–Epoxy (G‐E) composites with influence of synthetic fillers such as graphite (Gr) and silicon carbide (SiC) and biobased natural filler jatropha oil cake (JOC) was experimentally investigated. All the composites were fabricated using vacuum‐assisted resin infusion (VARI) technique. The mechanical properties were studied in accordance with ASTM standards. The three‐body abrasive wear studies were carried out with rubber wheel abrasion tester as per ASTM‐G65 standard. Two different loads namely 22 N and 32 N with different abrading distances viz, 135, 270, 405, and 540 m are test parameters. The results reveal that addition of JOC in G‐E composites has significant influence on wear under varied abrading distance/load. Further, it was found that SiC filled G‐E composites exhibited better wear resistance compared to Gr/JOC filled G‐E composites. The operating wear mechanisms have been studied by using scanning electron microscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical,electrical and thermal performance of hybrid polyethylene-graphene nanoplatelets-polypyrrole composites: a comparative analysis of 3D printed and compression molded samples

ABSTRACT

The paper focuses on the investigation of the 3D printing of multi-functional composites using graphene nanoplatelets (GNP), polypyrrole (PPY) and linear low-density polyethylene (LLDPE). A holistic approach was performed and characterization methods to assess the properties of 3D printed composites and compared with those of compression molded composites and neat LLDPE to understand the factors affecting their performance. It has been noted that the 3D printed composites have superior mechanical and electrical properties than neat LLDPE, but slightly lower compared to those of compression molded composites having high packing density of fillers. The nominal increases were 13.2% (tensile strength), 31.9% (flexural strength), 29.4% (flexural modulus) and 24.7% (storage modulus).     

V2O5/RGO/Pt nanocomposite on oxytetracycline degradation and pharmaceutical effluent detoxification

The cover image is based on the Research Article V₂O₅/RGO/Pt nanocomposite on oxytetracycline degradation and pharmaceutical effluent detoxification by Mohan, H et al., DOI: 10.1002/jctb.6238 .

     

Simultaneous accommodation of Dy3+ at the lattice site of β-Ca3(PO4)2 and t-ZrO2 mixtures: Structural stability,mechanical, optical,and magnetic features

Structurally stable β-Ca₃(PO₄)₂/t-ZrO₂ composite mixtures with the aid of Dy³⁺ stabilizer were accomplished at 1500°C. The precursors comprising Ca²⁺, P⁵⁺, Zr⁴⁺, and Dy³⁺ have been varied to obtain five different combinations. The results revealed the fact that complete phase transformation of calcium-deficient apatite to β-Ca₃(PO₄)₂ occurred only at 1300°C, whereas the evidence of t-ZrO₂ crystallization is obvious at 900°C. The dual occupancy of Dy³⁺ at β-Ca₃(PO₄)₂ and t-ZrO₂ structures was evident; however, Dy³⁺ initially prefers to occupy β-Ca₃(PO₄)₂ lattice until its saturation limit and thereafter accommodates at the lattice site of ZrO₂. The typical absorption and emission behavior of Dy³⁺ were noticed in all the systems and, moreover, the surrounding symmetry of Dy³⁺ domains has been determined from the luminescence study. All the systems ensured paramagnetic response that is generally contributed by the presence of Dy³⁺. A gradual increment in the phase content of t-ZrO₂ in the composite mixtures ensured a significant improvement in the hardness and Young's modulus of the investigated compositions.     

Design,Synthesis, and Self-Assembly Studies of a Suite of Monodisperse,Facially Amphiphilic,Protein–Dendron Conjugates

The custom design of protein–dendron amphiphilic macromolecules is at the forefront of macromolecular engineering. Macromolecules with this architecture are very interesting because of their ability to self-assemble into various biomimetic nanoscopic structures. However, to date, there are no reports on this concept due to technical challenges associated with the chemical synthesis. Towards that end, herein, a new chemical methodology for the modular synthesis of a suite of monodisperse, facially amphiphilic, protein–dendron bioconjugates is reported. Benzyl ether dendrons of different generations (G1–G4) are coupled to monodisperse cetyl ethylene glycol to form macromolecular amphiphilic activity-based probes (AABPs) with a single protein reactive functionality. Micelle-assisted protein labeling technology is utilized for site-specific conjugation of macromolecular AABPs to globular proteins to make monodisperse, facially amphiphilic, protein–dendron bioconjugates. These biohybrid conjugates have the ability to self-assemble into supramolecular protein nanoassemblies. Self-assembly is primarily mediated by strong hydrophobic interactions of the benzyl ether dendron domain. The size, surface charge, and oligomeric state of protein nanoassemblies could be systematically tuned by choosing an appropriate dendron or protein of interest. This chemical method discloses a new way to custom-make monodisperse, facially amphiphilic, protein–dendron bioconjugates.     

不锈钢表面阻氢涂层研究进展

不锈钢是高压氢系统的常用材料,在氢能储输技术中发挥重要作用,但高压氢环境引起的塑性降低、疲劳裂纹扩展速率加快等不锈钢氢脆问题,严重阻碍了氢能的产业化发展,在不锈钢材料表面制备阻氢涂层是解决不锈钢氢损伤问题的重要手段之一。本文首先综合介绍了典型涂层材料的应用特点及阻氢性能,探讨了制备工艺对涂层阻氢性能的影响、不同涂层材料的阻氢机理,并分析了涂层阻氢性能影响因素,之后总结了涂层阻氢性能评价方法及各种评价方法的优势与不足,并根据各种评价方法的技术特点,指出每种方法的适用范围。最后,基于阻氢涂层研究进展,文章提出以开发新型涂层结构为研究重点,同时加快新型涂层材料的探索,并重点关注涂层氢环境原位性能评价方法的研究。     

Dyeing studies with hydroxyanthraquinones extracted from Indian madder. Part 2: Dyeing of nylon and polyester with nordamncanthal†

Nordamncanthal is an important constituent of the colouring matter extracted from Indian madder roots. Its dyeing properties have never been studied even though the structural characteristics closely resemble those of disperse dyes. In this study, nylon and polyester have been dyed with this colorant. Linear isotherms have been obtained, confirming that the mechanism is similar to that of disperse dyes. The dye has good affinity for both the fibres. Kinetic and thermodynamic parameters have been calculated.