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Ultra-thin electromagnetic absorption materials promise great application potential in stealth technology and integrated microwave device. However, the large thickness of the current low-density carbon-based composites is still a critical issue to hinder their practical application. Herein, the carbon nanotubes (CNTs) were oxidized by using mixed acid and strong oxidant, and the lightweight resin-based CNTs coatings were fabricated via a facile method. The composite coatings after modification demonstrate an excellent microwave absorption performance at low thickness. With the low filler loading of 2.3 wt%, the maximum absorption is as strong as 20.4 dB and the effective absorption bandwidth (reflection loss ≤ − 10 dB) reaches 4.51 GHz covering 45.1% of the entire measured bandwidth at only 1.2 mm thickness. Compared with the CNTs coatings before modification, the CNTs coatings after modification possess broader effective absorption bandwidth, and the optimal filler loading of the absorbent shifts to a lower concentration. This work provides a feasible approach for the preparation of composite coatings with high-performance absorption.

Low-frequency microwave absorption remains a key issue to plague the attenuation of electromagnetic energy in conventional absorber. In this work, lightweight and flexible composite textiles were fabricated by in situ synthesis method. The microstructure and electromagnetic properties of the composite textiles were studied. The carbonyl iron/reduced graphene oxide/non-woven fabric (NW-RGO-CI) composite textiles possess excellent microwave absorption performance at low frequency range (2.91–5.1 GHz), and the qualified bandwidth of the composites reaches 9.2 GHz, which originates from synergistic effect of electricity and magnetism. The as-fabricated flexible and lightweight composite textiles could serve as potential materials in wearable electromagnetic absorption coatings and devices.

Absorbents with lightweight, low filler loading and broadband absorption are highly desired in electromagnetic wave absorbing field. Herein, the carbon black/reduced graphene oxide (CB/RGO) composite materials were fabricated via a facile synthetic method. The composite absorbents demonstrate an excellent microwave absorption performance. With the low filler loading of 7 wt%, the maximum absorption is as strong as 47.5 dB and the effective absorption bandwidth (reflection loss

Stable broadband microwave absorption is widely interested for their irreplaceable role in stealth technology for multiband microwave communication and detection. In this paper, a flexible broadband microwave absorber with self-recoverability was fabricated by self-assembling graphene sheets into polypropylene 3D framework. The as-fabricated absorber has a full-band absorption (more than 90%) in the working ranges of microwave communication and detection in military radars (2–40 GHz and 75–110 GHz), exhibiting larger bandwidth than the absorbers reported in literature. Furthermore, its bandwidth with more than 97% absorption (Reflection loss ≤ −15 dB) is as large as 62.73 GHz. The impressive absorption ability attributes to the impedance matching to free-space, coupling of multiple resonances and edge scattering of the microwave absorber, which could be manipulated by the pattern design of SA. For both the transverse electric and transverse magnetic polarizations, the broadband absorptions keep stable in a wide range of incidence angle, and they are recoverable after press and folding. The stable broadband absorption and recoverability make the flexible absorber suitable for the stealth of deformable objects like robots or foldable wings.

Sensitivity and reliability are essential factors for the practical implementation of a wearable sensor. This study explores the possibility of using a hybrid high-resolution Bragg grating sensor for achieving a fast response to dynamic, continuous motion and Bragg signal pattern monitoring measurement. The wavelength shift pattern for real-time monitoring in picometer units was derived by using femtosecond laser Bragg grating processing on an optical wave path with long-period grating. The possibility of measuring the demodulation system&rsquo, s Bragg signal pattern on the reflection spectrum of the femtosecond laser precision Bragg process and the long-period grating was confirmed. By demonstrating a practical method of wearing the sensor, the application of wearables was also explored. It is possible to present the applicability of sophisticated micro transformation measurement applications in picometer units.

Our objective was to construct textile braiding manufacturing methods to facilitate high precision and accurate measurements using optical fiber Bragg grating sensors for various structures. We aimed to combine three-dimensional (3D) braiding processing with the optical Bragg grating sensor&rsquo, s accurate metrology. Outside the limits of the sensor&rsquo, s epoxy attachment methods, the textile braiding method can diversify the scope of application. The braiding process can be used to design a 3D fabric module process for multiple objective mechanical fiber arrangements and material characteristics. Optical stress&ndash, strain response conditions were explored through the optimization of design elements between the Bragg grating sensor and the braiding. Here, Bragg grating sensors were located 75% away from the fiber center. The sensor core structure was helical with a 1.54 cm pitch, and a polyurethane synthetic yarn was braided together with the sensor using a weaving machine. From the prototype results, a negative Poisson&rsquo, s ratio resulted in a curled braided Bragg grating sensor. The number of polyurethane strands was studied to determine the role of wrap angle in the braiding. The 12-strands condition showed an increase in double stress&ndash, strain response rate at a Poisson&rsquo, s ratio of 1.3%, and the 16-strands condition was found to have noise affecting the sensor at a Poisson&rsquo, s ratio of 1.5%. The findings suggested the application of braiding fabrication to the Bragg grating sensor could help to develop a new monitoring sensor.

A porous graphene oxide/melamine composite sponge with highly dispersed graphene oxide sheets are prepared for high-sensitivity and self-recovery sensor of ethanol. The combination of graphene oxide and melamine with large surface area leads to sensitive to surface absorption due to avoiding the overlap of the graphene oxide sheets assembled in the sponge scaffold. The sensor exhibits a highly sensitive ethanol detection based on dielectric loss with two orders of magnitude change at 1670 ppm ethanol concentration, which is much higher than other sensors based on resistance or electrical conductivity. The detection limit is 70 ppm, which can be decreased by increasing the electrode area. The remarkable sensor performance is linked with the local conductive networks and relaxation polarization from introduction of polar functional groups in the sponges. Furthermore, the sensor has shape self-recovery capability due to its unique three-dimensional interconnect porous structure, which can be used to fabricate “electronic nose” of human-like robot closer to reality.

Reduced graphene oxide (RGO) has been widely used for improved electrical conductivity, thermal conductivity and mechanical properties, allowing for broad applications in electronics and aerospace industry. In the present work, two-dimensional RGO interfaces were introduced into the one-dimensional carbon fiber (CF) networks for synthesizing a three-dimensional carbon fiber/reduced graphene oxide (CF-RGO) composite textile. Besides, the zero-dimensional nickel nanoparticles were deposited on the surface of CF-RGO to prepare a lightweight and flexible carbon fiber/reduced graphene oxide/nickel (CF-RGO-Ni). Furthermore, the microscopic morphologies, X-ray diffraction (XRD) spectras, saturation magnetization, dielectric parameter and microwave absorption property of the as-prepared samples were characterized. Consequently, The results show that the dielectric parameters and microwave absorption property of the as-prepared composite textiles would substantially influenced by the presence of RGO nanosheets and nickel nanoparticles. Furthermore, both the thickness of the composite textiles and the proportion of the composite in wax-based composites have been studied to explore their effects on the microwave absorption performance. The results present that the qualified bandwidth (

Since dielectric materials are highly attractive in the emerging industry due to their significant applications in energy storage, power electronics, medical devices, etc., the pursuit of novel dielectric materials with fantastic properties is one of the most active areas of research. Based on their porous structures and chemical components, herein, we report three-dimensional (3D) graphene oxide foams (GOFs) as novel lightweight compressible dielectric materials, which are considered as the simplest carbon-air prototypes for variable dielectrics. With the increasing compression, much enhanced dielectric properties along with enlarged densities were found, and the exclusive mechanisms based on the dipole alignment and isolated conductive regions in the 3D GO–air configurations were considered as the major factors contributing to their dielectric properties. For understanding this interesting dielectric variation in 3D GOFs, a general model was proposed to explain the density-dependent dielectric constant; moreover, the percolation theory and Maxwell-Garnett theory were used to explain the variations in the dielectric loss at lower and higher frequency, respectively. According to the experimental and theoretical results, implication of the decoupled dielectric properties suggests that utilization of 3D GOFs highlights an exceptional platform for the fabrication of unique dielectric materials with various properties.

A lithium vanadium oxide cathode material was synthesized via sol-gel processing using citric acid as the chelating agent. The cathode powder was treated with two different processes. The composition, morphology and electrochemical performance of the samples were characterized by X-ray diffraction, scanning electron microscopy, open circuit potential monitoring and galvanostatic discharge testing. Results show that the sample sintered at 450 °C has even micron-sized crystallites and its corresponding mixed electrode exhibits the best electrochemical performance. Although the impurity of the active material was changed by the adsorption, leading to sharp initial voltage spikes, the adsorbed electrodes show more potential as cathodes due to their stable discharge curve and comparable special capacity.

A multi-step reduction process was developed to produce reduced graphene oxide (rGO) paper for electromagnetic interference (EMI) shielding. First step reduction was achieved by hydroiodic acid to remove most of the oxygen-containing functional groups, and sodium borohydride was used in the second step reduction to reduce carbonyl group which is the most difficult functional group to remove. In the last step reduction, hydroiodic acid was used as reducing agent again to remove the remaining oxygen-containing functional groups. The results show that this method can greatly improve the conductivity and EMI shielding performance of rGO paper. The resulting rGO paper with a C/O ratio of 19.38 and a thickness of 9.1[Formula: see text][Formula: see text]m exhibited high conductivity of 1084[Formula: see text]S/cm and excellent average EMI shielding efficiency of 45.84[Formula: see text]dB in the X-band, better than that reduction by other chemical methods.

Carbon nanotube (CNTs) based heterostructures, such as CNT/metal, CNT/polymer, CNT/semiconductor, are attractive for the combined properties and unique applications in cutting-edge electronics and devices. Here in this work, nanostructured beta-silicon carbide (β-SiC)/CNTs heterostructures were synthesized by carbothermal reduction of silica (SiO 2 ) and CNTs with diverse mixing ratios of n C : n Si . Different techniques were carried out for the characterization of the structures and morphologies of the achieved heterostructures, demonstrating dramatic different morphologies which were associated with the different starting ratios of the n C : n Si . The dielectric properties and microwave absorption of wax-based composites were investigated. The parameters for morphologically controllable synthesis and related mechanism for dielectric properties and electromagnetic attenuation were discussed.

Multilayer graphene/polymer composite films with good mechanical flexibility were fabricated into paraffin-based sandwich structures to evaluate electromagnetic interference (EMI) shielding. Experimental results showed the relationship between electrical properties and shielding performance, demonstrating that electrical properties are significant factors in EMI shielding. Calculation based on electrical conductivity of the composite films was carried out to investigate the fundamental mechanisms of absorption, reflection and multiple-reflections for the polymeric graphene composite films. Both experimental and calculated results indicate that reflection is the dominating shielding mechanism for the as-fabricated polymeric graphene films. The optimization of thickness, skin depth and electrical conductivity in the shielding materials could be highly significant in achieving enhanced EMI shielding. Further improvement in absorption shielding has been achieved by increasing the shielding thickness in order to enhance the overall shielding performance. The optimized shielding effectiveness up to 27 dB suggested effective shielding of the composite films. The implication of the mechanisms for optimizing shielding performance demonstrates significant fundamental basis for designing high-performance EMI shielding composites. The results and techniques also promise a simple and effective approach to achieve light-weight graphene-based composite films for application potentials in EMI shielding coatings.

Multi-walled carbon nanotubes (MWCNTs) snipped by the acidification process were fabricated into alumina (Al2O3) matrices via hydrothermal crystallization and hot-pressing techniques for achieving MWCNT/Al2O3 composites. The electrical conductivity and complex permittivity of the as-fabricated composites were investigated in the range of 8.2–12.4 GHz, and the corresponding microwave reflection loss was evaluated. Compared to the pristine MWCNT/Al2O3 composites, the percolation threshold of electrical conductivity was observed to increase from the range of 0.094–2.5 wt% to 3.89 wt%, mainly owing to the decrease of MWCNT aggregations based on the shortened tubes. The resulting shortened MWCNTs/Al2O3 were found to demonstrate strong microwave absorption in the investigated region.

Graphene receives world-wide attention due to its unique two-dimensional structure and exceptional electrical and mechanical properties. The graphene/polypyrrole (Gr/PPy) nanocomposites, have been synthesized via dispersing the graphene into polymers, which can be widely used in microwave absorption, supercapacitors and electronic devices. Molecular dynamics simulations are carried out to investigate the microscopic mechanism of interactions on Gr/PPy nanocomposites interface. The interaction configurations, intermolecular interaction energy and pair correlation functions between graphene and PPy are computed. The curves of temperature, energy evolution and interaction energy analysis indicate that Gr/PPy system reaches equilibrium in a relatively short time, and it is a thermodynamic equilibrium system. The interaction configurations show that there is an attractive interaction between the graphene and PPy. Pair correlation functions reveal that there are van der Waals interactions and hydrogen bond betw...

Carbon nanotubes-alumina (CNTs-Al2O3) composite ceramics with 25vol% CNTs were fabricated by sol-gel method and followed by hot-pressing. The resultant ceramics and powders were characterized for their microstructure and composition by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and infrared spectra (IR). The mechanical properties of the ceramics were measured by micromechanical testing system (MTS). The results show that both ultrasonic calefaction process during the gelation of alumina sol and annealing process during the sintering can remarkably enhance the fracture toughness and flexural strength of CNTs-Al2O3composite ceramics, compared with the composite ceramics without undergoing these processes. It is believed to be due to the relatively uniform dispersion of CNTs and the lower thermal stress in the matrices.

Novel high-performance Ni-rGO coated polymer (NiGP) foams for EMI shielding were developed with a dip-coating and reduction method. The obtained NiGP3 foams with a thickness of 10 mm prepared by 3 rounds of dip-coating, exhibited excellent EMI shieling effectiveness (EMI SE) of 24.03−27.71 dB at 30−1500MHz, which can fully meet the requirement of practical application. Furthermore, the NiGP foams maintain the compressibility of the original polymer foams.

Alumina/carbon nanotubes (Al2O3/CNTs) composite coating was synthesized by plasma spray employing mixtures of Al2O3-coated CNTs and nano-sized α-Al2O3 at atmosphere. This coating was characterized for the microstructure and the composition by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), thermo gravimetric analysis (TG), differential scanning calorimetry analysis (DSC) and scanning electron microscopy (SEM). The results show that the thickness of the coating is about 0.5mm and the constituent elements were changed to α-Al2O3, CNTs and γ-Al2O3 duo to the superhigh temperature during the plasma spray process. The great mass of the mixtures were melted well and the CNTs were dispersed uniformly in the melted ceramic. The oxidation resistance and the microwave absorption properties were discussed simply to describe the functions of the composite coating.

Electrical explosion of wire has a prosperous future in fine powder producing. In the process of electrical explosion of segmented metal wire (EESW),energy deposited in the wire was influenced by process variables such as the initial charging voltage of the capacitors, the length and the diameter of the segmented wire,and the electrode spacing. For understanding their relation completely, a series of experiments of electrical explosion was carried out with variations of the initial charging voltage and the segmented wire lengths and diameter. Results show that, energy deposition efficiency was weakly dependent on the wire length , whereas it has a strong dependence on the wire diameter, the initial charging voltage of the capacitors have an important influence on the energy deposition.

Multi-walled carbon nanotubes (MWCNTs) were coated with a nano-sized α-alumina polycrystalline layer by hydrothermal crystallization under autoclave conditions followed by manipulative calcination. These nanocomposites were characterized for their microstructure and composition by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The results show that the microcrystalline α-alumina layer with the thickness of 1–3 nm was rough and compact, which profited from well adhesion by boehmite sol, the lower temperature for the conversion of the hydroxide to oxide, and the slower speed for the calefaction process. In addition, the α-alumina-coated MWCNTs were dispersed uniformly in alumina particles.

Anastomotic leakage (AL) is a serious complication in laparoscopic rectal cancer surgery, and risk factors for AL are not well defined. Herein, we conducted a systematic review to quantify the clinicopathologic factors predictive for AL in patients who underwent laparoscopic anterior resection (LAR) for rectal cancer.A systematic search of electronic databases (PubMed, Embase, Cochrane CENTRAL, Scopus Database, and Wanfang Database) for studies published until August 2014 was performed. Cohort, case-control studies, and randomized controlled trials that examined clinical risk factors for AL were included.Fourteen studies (seven prospective and seven retrospective studies) involving 4580 patients met final inclusion criteria. From the pooled analyses, five demographic factors were found to be significantly associated with the development of AL, including male gender (OR 2.04, 95% CI 1.50-2.77), BMI ≥25 kg/m(2) (OR 1.46, 95% CI 1.00-2.14), ASA score2 (OR 1.74, 95% CI 1.04-2.93, P = 0.04), tumor size5 cm (OR 1.63, 95% CI 1.01-2.64, P = 0.05), and preoperative chemotherapy (OR 1.67, 95% CI 1.10-2.55, P = 0.02). Four operative factors were significantly associated with increased risk of AL, including longer operative time (95% CI 1.71-5.77, P = 0.0002), number of stapler firings ≥3 (OR 0.17, 95% CI 0.07-0.41, P0.001), intra-operative transfusions/blood loss100 mL (OR 3.79, 95% CI 2.48-5.49, P0.001), and anastomosis level within 5 cm from the anal verge (OR 9.63, 95% CI 3.05-30.43, P = 0.0001), while pelvic drain (OR 0.43, 95% CI 0.19-0.94, P = 0.04) was significantly associated with a lower AL rate.Our analysis identified several clinicopathologic factors associated with AL in patients who underwent LAR. The knowledge of these risk factors may influence treatment- and procedure-related decisions and possibly reduce the leakage rate.

Since manipulating electromagnetic waves with electromagnetic active materials for environmental and electric engineering is a significant task, here a novel prototype is reported by introducing reduced graphene oxide (RGO) interfaces in carbon fiber (CF) networks for a hierarchical carbon fiber/reduced graphene oxide/nickel (CF-RGO-Ni) composite textile. Upon charaterizations of the microscopic morphologies, electrical and magnetic properties, the presence of three-dimensional RGO interfaces and bifunctional nickel nanoparticles substantially influences the related physical properties in the resulting hierarchical composite textiles. Eletromagnetic interference (EMI) shielding performance suggests that the hierarchical composite textiles hold a strong shielding effectiveness greater than 61 dB, showing greater advantages than conventional polymeric and foamy shielding composites. As a polymer-free lightweight structure, flexible CF-RGO-Ni composites of all electromagnetic active components offer unique understanding of the multi-scale and multiple mechanisms in electromagnetic energy consumption. Such a novel prototype of shielding structures along with convenient technology highlight a strategy to achieve high-performance EMI shielding, coupled with a universal approach for preparing advanced lightweight composites with graphene interfaces.

Multi-wall carbon nanotubes (MWCNTs) were oxidized by soaking in mixed acids. Their microstructure and composition were characterized using transmission electron microscopy, atomic force microscopy, Raman spectroscopy and infrared spectroscopy. The influence of soaking time on microstructure and dispersibility of the cut MWCNTs in aqueous solution was investigated. Results show that the MWCNTs were oxidized at defect sites by the mixed acids and converted from highly tangled ropes into short, open-ended nanotubes with lengths of 200–1500 nm. The isoelectric point was reduced from 4.5 to 3.5 due to hydroxyl and carboxyl groups on the surface and the open ends of the cut MWCNTs. The aggregation experiments and UV–vis absorbance spectra revealed that the cut MWCNTs can be best dispersed in an aqueous solution containing 0.1 wt.% of sodium dodecyl-benzenesulfonate when sonicated at a pH value of 2 for 40 min. [New Carbon Materials 2014, 29(2): 109–117]