Quantitative Analysis of Azodicarbonamide in Insulation Layers of Extruded Cables by HPLC–UV Detection

Azodicarbonamide(ADC),which has been abundantly used in the creation offoamed plastics as a blowing and foaming agent,has attracted more and more attention in recent years due to the health risks associated with its consumption.ADC is actually on the REACH(Registration,Evaluation,Authorization and Restriction of Chemicals)regulation Candidate List of Substances of Very High Concern,and the residual content in products needs to be confirmed by the end users according to regulations.Therefore,the determination and monitoring of ADC in plastic products is necessary and crucial not only for the growth of ADC global market but also for the health of the public.In this work,a quantitative method for ADC in insulation layers of cables was developed by using optimized total dissolution methodology(TDM)for sample preparation followed by HPLC under HILIC conditions with UV absorbance detection.The linear range of this method was 6–600μg·g^(-1) ,and the limit of detection(LOD)and limit of quantitation(LOQ)were 0.94 and 3.1μg·g^(-1) in solution,respectively.The method has good recovery and precision,and is easy to operate.It meets the needs of the industry and is conducive to the growth of ADC global market.This method is expected to be applicable to ADC quantitation in other polyolefin products.

Influence of thermal insulation layer schemes on the frost heaving force in tunnels

In extreme cold regions,a thermal insulation layer(TIL)is commonly employed to mitigate the detrimental effects of frost heaving forces in tunnels.Optimizing the laying scheme of TIL,specifically minimizing frost heaving forces,holds considerable importance in the prevention of frost damage.This research developed a two-dimensional unsteady temperature field of circular tunnels by using the difference method(taking the off-wall laying method as an example)based on the law of conservation of energy.Then,the frozen circle and water migration coefficient were introduced to establish the relationship between the temperature field and frost heaving forces,and a reliable methodology for calculating these forces under the specific conditions of TIL installation was developed.Then(i)the influence of the air layer thickness of the off-wall laying method,(ii)different laying methods of TIL,(iii)the TIL thickness,(iv)the thermal conductivity of the TIL,and(v)the freeze-thaw cycles on the frost heaving force were investigated.The results showed that the frost heaving force served as a reliable and effective metric for evaluating the insulation effect in tunnels.In order to avoid frost damage in compliance with the design requirements,the insulation effects from various laying methods were established,in descending efficacy order as follows:off-wall laying,double layer laying,surface laying,and sandwich laying.Our findings revealed that the optimal thickness for the air layer in the offwall laying method was 0.10 m.The insulation effect of materials with a thermal conductivity below 0.047 W/(m·℃)was furthermore found to be good.Under freeze-thaw cycle conditions,it is concluded that to prevent frost damage,the TIL thickness should be the sum of the thickness r1 of the first freeze-thaw cycle without frost heaving forces and an additional reserve value 0.06r1 of the TIL thickness.

Experimental study on the penetration characteristics of leaking molten salt in the thermal insulation layer of aluminum silicate fiber

The molten salt leakage accident is an important issue in the nuclear safety analysis of molten salt reactors.While the molten salt leaks from the pipeline or storage tank,it will contact the insulation layer outside;hence,the processes of penetration and spreading play an important role in the development of leakage accidents.In this study,the penetration and diffusion of leaking molten salt(LMS)in an aluminum silicate fiber(ASF)thermal insulation layer were studied experimentally.A molten salt tank with an adjustable outlet was designed to simulate the leakage of molten salt,and the subsequent behavior in the thermal insulation layer was evaluated by measuring the penetra-tion time and penetration mass of the LMS.The results show that when the molten salt discharges from the outlet and reaches the thermal insulation layer,the LMS will penetrate and seep out from the ASF,and a higher flow rate of LMS requires less penetration time and leaked mass of LMS.As the temperature of the LMS and thickness of the ASF increased,the penetration time became longer and the leaked mass became greater at a lower LMS flow rate;when the LMS flow rate increased,the penetration time and leaked mass decreased rapidly and tended to flatten.

Experimental study on axial compressive behaviors of prefabricated composite thermal insulation walls after single-side fire exposure

The axial bearing capacity of prefabricated composite walls composed of inner and outer concrete wythes,expandable polystyrene(EPS)boards and steel sleeve connectors is investigated.An experimental study on the axial bearing capacity of four prefabricated composite walls after fire treatment is carried out.Two of the prefabricated composite walls are normal-temperature specimens,and the others are treated with fire.The damage modes and crack development are observed,and the axial bearing capacity,lateral deformation of the specimens,and the concrete and reinforcing bar strain are tested.The results show that the ultimate bearing capacity of specimens after a fire is less than that of normal-temperature specimens;when the insulation board thicknesses are 40 mm and 60 mm,the decrease amplitudes are 20.8%and 16.8%,respectively.The maximum lateral deformation of specimens after a fire is greater than that of normal-temperature specimens,and under the same level of load,the lateral deformation increases as the insulation board thickness increases.Moreover,the strain values of the concrete and reinforcing bars of specimens after a fire are greater than those of normal-temperature specimens,and the strain values increase as the thickness of insulation board increases.

Feature,genetic model and distribution of calcareous insulating layers in marine strata of western Pearl River Mouth basin in north of South China Sea

We have systematically investigated the feature, genetic model and distribution of calcareous insulating layers in marine strata of the Ⅰ oil group in member 2 of Zhujiang formation(ZJ2I oil formation), western Pearl River Mouth basin(PRMB) in the north of the South China Sea by using data such as cores, thin sections, X-ray diffraction of whole-rock, and calcite cement carbon and oxygen isotopes. The lithology of the calcareous insulating layers in the study area is mainly composed of the terrigenous clastic bioclastic limestone and a small amount of fine-grained calcareous sandstone. On this basis, two genetic models of calcareous insulating layers are established, including the evaporation seawater genetic model and shallow burial meteoric water genetic model. The calcareous insulating layers of the evaporation seawater genetic model developed in the foreshore subfacies, mainly at the top of the 1-1 strata and 1-3 strata. The calcareous insulating layers of the shallow burial meteoric water genetic model developed in the backshore subfacies, primarily in the 1-2 strata.

Numerical simulation of vibrational response characteristics of railway subgrades with insulation boards

This study presents a numerical method based on the surface temperature data and the ground temperature increase in Daqing for predicting temperature field distribution in the Binzhou Railway subgrade and analyzing the temporal and spatial distribution of freeze−thaw status of railway subgrade.The calibrated numerical method is applied to simulate the temperature field distribution and roadbed vibrational response of the railway subgrade with a thermal insulation layer at different seasons.The results show the following:(1)The thermal insulation layer can remarkably increase the soil temperature below it and maximum frost depth in the subgrade.(2)Thermal insulation can effectively reduce the subgrade vibration and protect it from frost damage.(3)Given that the strength requirements are met,the insulation layer should be buried as shallow as possible to effectively reduce the subgrade vibration response.The research findings provide theoretical support for the frost damage prevention of railway subgrades in seasonally frozen regions.

Modification of the Hybridization Gap by Twisted Stacking of Quintuple Layers in a Three-Dimensional Topological Insulator Thin Film

Twisting the stacking of layered materials leads to rich new physics. A three-dimensional topological insulator film hosts two-dimensional gapless Dirac electrons on top and bottom surfaces, which, when the film is below some critical thickness, will hybridize and open a gap in the surface state structure. The hybridization gap can be tuned by various parameters such as film thickness and inversion symmetry, according to the literature. The three-dimensional strong topological insulator Bi(Sb)Se(Te) family has layered structures composed of quintuple layers(QLs) stacked together by van der Waals interaction. Here we successfully grow twistedly stacked Sb_2Te_3 QLs and investigate the effect of twist angels on the hybridization gaps below the thickness limit. It is found that the hybridization gap can be tuned for films of three QLs, which may lead to quantum spin Hall states.Signatures of gap-closing are found in 3-QL films. The successful in situ application of this approach opens a new route to search for exotic physics in topological insulators.

Preparation and characterization of carbonyl iron soft magnetic composites with magnesioferrite insulating coating layer

Spherical carbonyl iron(Fe)powders were coated with magnesioferrite(MgFe2O4)insulating coating layer and then mixed with epoxy-modified silicone resin(ESR).Soft magnetic composites(SMCs)were fabricated by compaction of the coated powders and annealing treatment.Transmission electron microscopy(TEM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and X-ray photoelectron spectroscopy(XPS)revealed that the MgFe2O4 layer was coated on the surface of the iron powders.The magnetic properties of SMCs were determined using a vibrating sample magnetometer and an auto testing system for magnetic materials.The results showed that the SMCs prepared at 800 MPa and 550℃ exhibited a significant core loss of 167.5 W/kg at 100 kHz and 50 mT.

Research on the Novel Honeycomb-Like Cabin Based on Computer Simulation

The antiknock capability and thermal protection performance of rescue capsules mainly depend on the structural design of the cabin.By designing a new type of cabin structure,it can resist the impact of explosion shock waves and thermal shocks.In this paper,a new honeycomb-like cabin is proposed;the model has a novel thermal insulation layer design.Then,the antiknock capabilities and thermal protection analysis are carried out by using computer software.The“Autodyn”analysis module in ANSYS Workbench 17.0 has been used to simulate the explosion of TNT with a certain quality in a single room.The pressure map over time and the pressure variation curve at different locations for a single room are obtained.Through the analysis module“Transient Structural,”the stress and deformation of the honeycomb-like cabin under the blast load are simulated.The“Transient Thermal”analysis module in the finite element software is used to conduct a transient thermal analysis on the cabin structure.The temperature map and the temperature rise curve of each layer of the cabin cases are obtained.The analysis results indicate that the honeycomb-like cabin design has a good antiknock capability and thermal protection performance,and it can meet the usage requirements of the rescue capsule under dangerous conditions.

Transforming a Two-Dimensional Layered Insulator into a Semiconductor or a Highly Conductive Metal through Transition Metal Ion Intercalation

Atomically thin two-dimensional(2D) materials are the building bricks for next-generation electronics and optoelectronics, which demand plentiful functional properties in mechanics, transport, magnetism and photoresponse.For electronic devices, not only metals and high-performance semiconductors but also insulators and dielectric materials are highly desirable. Layered structures composed of 2D materials of different properties can be delicately designed as various useful heterojunction or homojunction devices, in which the designs on the same material(namely homojunction) are of special interest because preparation techniques can be greatly simplified and atomically seamless interfaces can be achieved. We demonstrate that the insulating pristine ZnPS_3, a ternary transition-metal phosphorus trichalcogenide, can be transformed into a highly conductive metal and an n-type semiconductor by intercalating Co and Cu atoms, respectively. The field-effect-transistor(FET) devices are prepared via an ultraviolet exposure lithography technique. The Co-ZnPS_3 device exhibits an electrical conductivity of 8 × 10^(4) S/m, which is comparable to the conductivity of graphene. The Cu-ZnPS_3 FET reveals a current ON/OFF ratio of 1-05 and a mobility of 3 × 10^(-2 )cm^(2)·V^(-1)·s^(-1). The realization of an insulator, a typical semiconductor and a metallic state in the same 2D material provides an opportunity to fabricate n-metal homojunctions and other in-plane electronic functional devices.

IGZO/ZTO TFTs with Modulated Double Channel of Thickness Structures

The device characteristics of IGZO/ZTO(indium-gallium-zinc oxide/zinc-tin oxide)TFTs(thin film transistors)with modulated channels were investigated.The field effect mobility was enhanced to 20.4 cm2/Vs in the channel-modulated TFT.The electrical performance of the TFT device was improved by the insertion of a high carrier concentration layer at the channel/gate insulator interfaces.It was due to the enhancement of carrier accumulation and the reduction of parasitic resistance via channel modulation.The threshold voltage was controlled at appropriate value.These results indicate that the device characteristic of TFTs can be enhanced by the modulated channel structure.

Influence of traffic on the temperature field of tunnel in cold region:A case study on the world’s longest highway spiral tunnel

The impact of the piston wind caused by vehicle traffic on the temperature field distribution of the tunnel cannot be ignored,especially in spiral tunnels,where the temperature field distribution is more complicated than that in straight tunnels.Based on the world’s longest highway spiral tunnel,this study explores the influence of traffic on the temperature fields of spiral and straight tunnels,and proposes a new design method for laying length of insulation layer.The results show that traffic has a significant effect on the temperature field dis-tribution in the tunnel.The influence degree of different traffic elements decreases in the following order:average vehicle speed>daily traffic>morning rush hour>evening rush hour.The temperature field distribution of spiral tunnels is asymmetry on the left and right compared with straight tunnels,while the influence degree of traffic on the outside of spiral tunnels is similar to that of straight tunnels.Due to the difference of wind direction and traffic direction at different tunnel openings,an asymmetric insulation layer laying method is proposed.It is suggested that the lengths of the insulation layers of the Jinjiazhuang Tunnel should be 1200 m for the right tunnel inlet,700 m for the right tunnel outlet,700 m for the left tunnel inlet,and 1400 m for the left tunnel outlet.

Flexible mica films coated by magnetron sputtered insulating layers for high-temperature capacitive energy storage

High-temperature energy storage performance of dielectric capacitors is cru-cial for the next generation of power electronic devices.However,conduction losses rise sharply at elevated temperature,limiting the application of energy storage capacitors.Here,the mica films magnetron sputtered by different insulating layers are specifically investigated,which exhibit the excellent high-temperature energy storage performance.The experimental results revealed that the PbZrO3/Al2O3/PbZrO3(PZO/AO/PZO)interface insulating layers can effec-tively reduce the high-temperature leakage current and conduction loss of the composite films.Consequently,the ultrahigh energy storage density(Wrec)and charge‒discharge efficiency(η)can be achieved simultaneously in the flexi-ble mica-based composite films.Especially,PZO/AO/PZO/mica/PZO/AO/PZO(PAPMPAP)films possess excellent Wrec of 27.5 J/cm3 andηof 87.8%at 200◦C,which are significantly better than currently reported high-temperature capaci-tive energy storage dielectric materials.Together with outstanding power density and electrical cycling stability,the flexible films in this work have great appli-cation potential in high-temperature energy storage capacitors.Moreover,the magnetron sputtering technology can deposit large-area nanoscale insulating layers on the surface of capacitor films,which can provide technical support for the industrial production of capacitors.

Strain-modulation and service behavior of Au-MgO-ZnO ultraviolet photodetector by piezo-phototronic effect

Au-MgO-ZnO （AMZ） ultraviolet （UV） photodetectors were fabricated to enhance their sensitivities by an inserting ultrathin insulating MgO layer. With the insulating layer, the sensitivities of the UV photodetectors were improved via the reduction of the dark current. Furthermore, strain modulation was used to enhance the sensitivities of the AMZ UV photodetectors. The sensitivities of the photodetectors were enhanced by the piezo-phototronic effect. However, there was a limiting value of the applied strains to enhance the sensitivity of the photodetector. When the external strains exceeded the limiting value, the sensitivity decreased because of the tunneling dark current. The external strains loaded on the photodetectors result in the degradation of the photodetectors, and an applied bias can accelerate the process. This work presents a prospective approach to engineer the performance of a UV photodetector. In addition, the study on the service behavior of the photodetectors may offer a strain range and theoretical support for safely using and studying metal-insulator-semiconductor （MIS） UV photodetectors.

Interface control for pure ultraviolet electroluminescence from nano-ZnO-based heterojunction devices

Realization of pure and stable ultraviolet electroluminescence(UV EL) of ZnO light-emitting diode(LED)is still a challenging issue, due to complicated defects of intrinsic ZnO and the corresponding device interfaces. In this paper, we demonstrated a simple & feasible method to fabricate n-ZnO/AlN/p-GaN heterojunctions light-emitting devices. First, the vertically aligned ZnO nanorods(NRs) have been prepared as high quality active layer, and the nanostructured heterojunction LED arrays were constructed by directly bonding ZnO NRs onto AlN-coated p-GaN wafer. By optimizing the AlN layer thickness to be 20 nm, a strong and pure ultraviolet emission located at 387 nm can be observed. The energy band alignment of n-ZnO/AlN(20 nm)/p-Ga N heterojunction LED has been studied by using X-ray photoelectron spectroscopy(XPS), the valence band offset between AlN and GaN was calculated to be 0.34 eV. On the other side, the conduction band offset(as large as 3.28 eV) between Al N and ZnO can block the flow of electrons from ZnO top-GaN. Thus, electron-hole recombination takes place in the ZnO layer, and a pure UV EL could be observed. Our results provide a significant approach toward future of pure ultraviolet optoelectronic LEDs.

Improved performance of GaAs-based micro-solar cell with novel polyimide/SiO_2/TiAu/SiO_2 structure

A novel interconnected structure consisting of a conventional polyimide layer(PM) and an additional SiO2/TiAu/SiO2 sandwich multilayer has been firstly proposed for improving the performance of GaAs micro-solar cell array.The specific experimental investigations on the array with 108 unit cells have demonstrated that the novel structure of PM/SiO2/TiAu/SiO2 can effectively enhance the open-circuit voltage from 75 to 84 V and the fill factor from 35% to 57%.The performance improvement of our devices can be attributed to two aspects.Firstly,the TiAu shielding film can prevent the incident light from penetrating into the GaAs substrate so as to induce the serious substrate leakage current.Secondly,the compact texture of SiO2 in the novel structure can reduce the perimere recombination due to the crackle or shrinkage of PM.It is indicated that the novel structure can distinctly reduce the leakage current and improve output characteristic of micro-solar cells.

Organic thin film transistors with a SiO_2/SiN_x/SiO_2 composite insulator layer

We have investigated a SiO2/SiNx/SiO2composite insulation layer structured gate dielectric for an organic thin film transistor(OTFT) with the purpose of improving the performance of the SiO2gate insulator. The SiO2/SiNx/SiO2composite insulation layer was prepared by magnetron sputtering.Compared with the same thickness of a SiO2insulation layer device,the SiO2/SiNx/SiO2composite insulation layer is an effective method of fabricating OTFT with improved electric characteristics and decreased leakage current.Electrical parameters such as carrier mobility by field effect measurement have been calculated.The performances of different insulating layer devices have been studied,and the results demonstrate that when the insulation layer thickness increases,the off-state current decreases.