Multi-walled carbon nanotubes coated by multi-layer silica for improving thermal conductivity of polymer composites

Silica has been non-covalently coated on multi-walled carbon nanotubes (MWCNTs) using the sol–gel chemistry, where tetraethoxy silane (TEOS) was used to form an inorganic silica layer immediately next to surface of MWCNTs and octyl triethoxy silane was coated over the TEOS. Transmission electron microscopy (TEM) measurements show that the diameter of MWCNTs increases with increasing the number of coating layer, indicating that the silica has been coated on MWCNTs. Quantitative analysis from thermogravimetric analysis (TG) also indicates that the inorganic and organic silica has been successfully coated on MWCNTs. Further, quantitative analysis found that the amount of silica measured by TG agrees well with the increase of thickness of coated MWCNTs obtained from TEM, indicating that little or no free silica exists in the system. The thermal conductivity of epoxy/MWCNTs composite was studied and the results show that the thermal conductivity of the composite is improved by coating MWCNTs in this manner and increases with increasing the number of coatings.     

Characterization of a hybrid dielectrophoresis and immunocapture microfluidic system for cancer cell capture

The capture of circulating tumor cells (CTCs) from cancer patient blood enables early clinical assessment as well as genetic and pharmacological evaluation of cancer and metastasis. Although there have been many microfluidic immunocapture and electrokinetic techniques developed for isolating rare cancer cells, these techniques are often limited by a capture performance tradeoff between high efficiency and high purity. We present the characterization of shear‐dependent cancer cell capture in a novel hybrid DEP–immunocapture system consisting of interdigitated electrodes fabricated in a Hele‐Shaw flow cell that was functionalized with a monoclonal antibody, J591, which is highly specific to prostate‐specific membrane antigen expressing prostate cancer cells. We measured the positive and negative DEP response of a prostate cancer cell line, LNCaP, as a function of applied electric field frequency, and showed that DEP can control capture performance by promoting or preventing cell interactions with immunocapture surfaces, depending on the sign and magnitude of the applied DEP force, as well as on the local shear stress experienced by cells flowing in the device. This work demonstrates that DEP and immunocapture techniques can work synergistically to improve cell capture performance, and it will aid in the design of future hybrid DEP–immunocapture systems for high‐efficiency CTC capture with enhanced purity.     

Orientational and electro-optical properties of liquid crystal aligned with a directly spinnable carbon nanotube web

We investigated the orientational and electro-optical properties of a nematic liquid crystal (LC) aligned with a directly spinnable carbon nanotube (CNT) web functioning both as an electrode and as an alignment layer. The LC molecules were uniformly oriented along the drawing direction of the CNT web and the spatially averaged birefringence was comparable to a rubbed polyimide sample. The CNT web sample also showed smaller residual DC and hysteresis compared to the polyimide sample.     

Wavelength dispersive X-ray fluorescence imaging using a high-sensitivity imaging sensor

A new wavelength-dispersive X-ray fluorescence (WD-XRF) imaging spectrometer equipped with a high-sensitivity imaging sensor was developed in our laboratory. In this instrument, a straight polycapillary optic was applied instead of a Soller slit as well as a 2D imaging X-ray detector instead of X-ray counters, which are used in conventional WD-XRF spectrometers. Therefore, images of elemental distribution were available after a short exposure time. Ni Kα images and Cu Kα images were clearly obtained at corresponding diffraction angles for a short exposure time of 10 s. By optimizing the spectrometer, the time required for imaging is reduced, leading to XRF image movies. It is difficult to distinguish two peaks (Ti Kα (4.508 keV) and Ba Lα (4.465 keV)) due to the poor energy resolution of EDXRS. However, Ti and Ba images could be successfully observed by the WD-XRF imaging spectrometer. The energy resolution of the developed spectrometer was 25 eV at the Ti Kα peak.     

Compression testing of continuous fiber reinforced polymer composites with out-of-plane fiber waviness and circular notches

We investigated the face-stabilized Open-Hole Compression (OHC) test method for evaluating the effects of fiber waviness on the compression strength of continuous carbon fiber reinforced polymer composites. Temporal evaluations of the load-deformation response, acoustic emissions and optical microscopy are used to understand the failure modes and damage progression in the OHC specimen. The failure modes observed are structurally correlated to matrix failure and kink zone formation leading to fiber fracture. The results show how the resin pocket plays a more critical role than the layup in influencing the initiation of damage in the composite specimens.     

Evaluation of defect induced surface heterogeneity in Metal-Organic Framework materials with alkali dopants employing adsorption isotherm modelling

In this article, an assessment of surface structural heterogeneity in porous metal organic framework (MOF) structure has been demonstrated by employing the methane and carbon-dioxide adsorption isotherms data. The virgin MIL-101-(Cr) MOF was synthesized by the hydrothermal method and defects were induced in the MOF structure by doping with various alkali (K, Na, Li) cations. The synthesized MOFs were characterized by XRD, SEM, EDX and BET measurement techniques. In order to understand the defect induced surface heterogeneity by alkali cation dopants, the surface energy distributions for CH₄ and CO₂ adsorptions on MOFs were measured by Dubinin – Astakhov model equation. The surface heterogeneity is mainly controlled by the limiting uptakes of adsorbates, the polarizability of adsorbates and the adsorbate-adsorbent interaction energy.     

Combustion synthesis of mesoporous CoAl2O4 for peroxymonosulfate activation to degrade organic pollutants

A mesoporous cobalt aluminate (CoAl₂O₄) spinel is synthesized through a combustion method and adopted for the activation of peroxymonosulfate (PMS) to degrade organic pollutants. Multiple characterization procedures are conducted to investigate the morphology and physicochemical properties of the CoAl₂O₄ spinel. Due to its mesoporous structure, large surface area, and high electrical conductivity, the obtained CoAl₂O₄ exhibits remarkable catalytic activity for Rhodamine B (RhB) degradation. Its RhB degradation rate is 89.0 and 10.5 times greater than those of Co₃O₄ and CoAl₂O₄ spinel prepared by a precipitation method, respectively. Moreover, the mesoporous CoAl₂O₄ spinel demonstrates a broad operating pH range and excellent recyclability. The influence of several parameters (catalyst amount, PMS concentration, initial pH, and coexisting inorganic anions) on the oxidation of RhB is evaluated. Through quenching tests and electron paramagnetic resonance experiments, sulfate radicals are identified as the predominant reactive species in RhB degradation. This paper provides new insights for the development of efficient, stable, and reusable cobalt-based heterogeneous catalysts and promotes the application of persulfate activation technology for the treatment of refractory organic wastewater.     

A simulation method of aircraft plumes for real-time imaging

Real-time infrared simulation technology can provide a large number of infrared images under different conditions to support the design, test and evaluation of a system having infrared imaging equipment with very low costs. By synthesizing heat transfer, infrared physics, fluid mechanics and computer graphics, a real-time infrared simulation method is proposed based on the method of characteristics to predict the infrared feature of aircraft plumes, which tries to obtain a good balance between simulation precision and computation efficiency. The temperature and pressure distribution in the under-expansion status can be rapidly solved with dynamically changing flight statuses and engine working states. And a modified C–G (Curtis–Godson) spectral band model that combines the plume streamlines with the conventional C–G spectral band model was implemented to calculate the non-uniformly distributed radiation parameters inside a plume field. The simulation result was analyzed and compared with the CFD++, which validates the credibility and efficiency of the proposed simulation method.     

An improved model for the cantilever NEMS actuator including the surface energy,fringing field and Casimir effects

The influence of the surface energy on the instability of nano-structures under the electrostatic force has been investigated in recent years by different researchers. It appears that in all prior research, the response of all structures becomes softer due to the surface effects. In the present study, the pull-in instability of a NEMS device incorporating the electrostatic force and Casimir intermolecular attraction for different values of the surface parameter is investigated by the Duan–Rach method of determined coefficients (MDC) in order to identify the remarkable effect of the surface energy. Although the obtained results verify the behavior of such structures in presence of the fringing field and the Casimir attraction same as the previous investigations, however the incremental effects of the surface energy cause the aforementioned structures to behave more stiffly in contrast.     

Three-dimensional constitutive equations for Ni–Mn–Ga single crystals

This paper presents a formulation of isothermal three-dimensional (3D) quasi-static magneto-mechanical constitutive equations and 3D magnetisation constitutive equations for tetragonal martensite Ni–Mn–Ga FSMA single crystals (c/a<1)$(c/a<1)$ with both ends restrained from twin-boundary motion. The formulated 3D constitutive equations model the 3D quasi-static magnetic fields as well as the coupling between uniaxial strains and stresses, and shear strains and stresses. The constitutive equations are compared with experimental results available in the literature and are found to correlate well with the experimental results, including magnetic field reversals. Both sets of 3D constitutive equations require only macroscopic parameters that are readily obtainable from magnetisation and mechanical stress–strain curves.