Waves scattering induced by an interface crack in a coated material

This paper deals with the two-dimensional problem of elastic wave scattering from a finite crack at the interface between a coated material layer and its substrate. By adopting the Fourier transform method and introducing the crack opening displacement function, the boundary value problem is simplified for numerically solving a system of Cauchy-type singular integral equations by means of Jacobi polynomial expansion. The stress intensity factors and the crack opening displacements are defined in terms of the integral equations solutions. The influence of the dimensionless wave number and the ratio of crack length to layer thickness on the stress intensity factors and crack opening displacements are discussed.

Measurements of Formaldehyde and TVOC Emission from Paints and Coating Materials using Small Chamber Method for Building Composites

An optimal test method for paint is proposed; additionally, the Field and Laboratory Emission Cell （FLEC） method used in Europe is applied as a substitute for the 20 L small chamber method. The emission factors of total volatile organic compounds （TVOC） and formaldehyde from oil-based paint, emulsion paint, and water-dispersion paint with a coating weight of 300 g/m2, cured for 24/48 hours, were measured using the 20 L small chamber method. The emission rate of TVOC and formaldehyde from all paints began to stabilize after approximately 7 days after 24/48 hours of curing even though Korean standards stipulate that paint should be measured and analyzed after the third day of application. The emission factor of TVOC and formaldehyde from oil-based, emulsion, and water-dispersion paints were also measured using the FLEC method. There was good correlation between the 20 L small chamber method and the FLEC method for oil-based, emulsion, and water-dispersion paint emissions. With the FLEC method, using paints prepared under identical conditions, the emission rate was stable 24 hours after installation of samples because the air flow rate of FLEC is much higher than that of a 20 L small chamber, and the relative cell volume of FLEC is much smaller than that of a 20 L small chamber.

MORPHOLOGICAL,MECHANICAL,THERMAL AND TRIBOLOGICAL PROPERTIES OF ENVIRONMENTALLY FRIENDLY CONSTRUCTION MATERIALS:RECYCLED LDPE COMPOSITES FILLED BY BLAST FURNACE DUST

This study focused on developing a sustainable composite material using metallic wastes of the iron-steel industry and plastic wastes of the plastic industry in order to reduce resultant waste from the production processes of various industrial products and to sustain waste management of these industries.In this study,different amounts of blast furnace dust(BFD),which is the major iron-steel industry waste and is used as filler for recycled low-density polyethylene(LDPE),was mixed with LDPE to produce the composite material.The morphology,mechanical,vicat softening temperature thermal conductivity,hardness and wear resistance properties of BFD filled LDPE composites were assessed.The increasing of BFD in recycled LDPE improved the heat resistance,increased thermal conductivity and wear resistance of composite materials.In addition,it was found that the composite materials had sufficient mechanical properties,when mechanical tests were evaluated.These results showed that the produced composite material could be used in buildings as a floor coating material and thereby saving raw materials and resources,as well as potentially reducing environmental problems.

Antibacterial activities and corrosion behavior of novel PEO/nanostructured ZrO_2 coating on Mg alloy

Plasma electrolytic oxidation（PEO） was developed as a bond coat for air plasma sprayed（APS） nanostructure ZrO2 as top coat to enhance the corrosion resistance and antibacterial activity of Mg alloy. Corrosion behavior and antibacterial activities of coated and uncoated samples were assessed by electrochemical tests and agar diffusion method toward Escherichia coli（E. coli） bacterial pathogens, respectively. The lowest corrosion current density and the highest charge transfer resistance, phase angle and impedance modulus were observed for PEO/nano-ZrO2 coated sample compared with those of PEO coated and bare Mg alloys. Nano-ZrO2 top coat which has completely sealed PEO bond coat is able to considerably delay aggressive ions transportation towards Mg alloy surface and significantly enhances corrosion resistance of Mg alloy in simulated body fluid（SBF） solution. Moreover, higher antibacterial activity was also observed in PEO/nano-ZrO2 coating against bacterial strains than that of the PEO coated and bare Mg alloys. This observation was attributed to the presence of ZrO2 nanoparticles which decelerate E. coli growth as a result of E. coli membranes.

Preparation of microencapsulatedα-olefin drag reducing polymer used in oil pipeline transportation

Microcapsules containing oil drag-reducing polymer particles were prepared by melting-scattering and condensing of polyethylene wax,in-situ polymerization of urea and formaldehyde,and interfacial polymerization of styrene respectively.The related processes were studied by a molecular dynamics simulation method,and molecular design of microcapsule isolation agent was carried out on the basis of the simulation.The technologies for preparing microencapsulated oil drag-reducing polymer particles were compared and the circulation drag reducing efficiency of the microencapsulated polymer particles was evaluated based on the characterization results and their dissolution properties.Molecular design of a microcapsule isolation agent suggests that a-olefin polymer particles can be stably dispersed in water by using long-chain alkyl sodium salt surfactant which can prevent the agglomeration ofα-olefin polymer particles.The results of simulation of the adsorption process shows that the amount of alkyl sodium salt surfactant can directly affect the stability of microencapsulatedα-olefin polymer particles, and there must be a minimum critical amount of it.After characterization of the morphology by Scanning Electron Microscopy（SEM） and comparison of the static pressure stability,especially the conditions of reaction and technological control of microcapsules with different shell materials,microencapsulation of a-olefin polymer particles with poly-（urea-formaldehyde） as shell material was selected as the optimum scheme,because it can react under mild conditions and its technological process can be controlled in a large range.The relationship of drag reducing rate and dissolving time of microcapsules showed that the formation of microcapsules did not affect the maximum drag reducing rate,and the drag reducing rate of each sample can reach about 35%along with the dissolving time,i.e.microencapsulation did not affect the drag reducing property ofα-olefin polymer.

Glass formation in Fe-Cr-Zr-B-Mo alloys by tuning Nb addition

Fe-based bulk metallic glasses(BMGs)with high boron content have potential application as a coating material used in the framework for storing spent nuclear fuels to support their safe long-term disposal.The high glass forming ability(GFA)and large supercooled liquid region are therefore required for such Fe-based BMGs in either the glassy powder fabrication or the subsequent coating spraying.In order to meet these requirements,the influence of Nb content on the GFA of Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(7-x)Nb_(x)(x=1-5,at.%)alloys was investigated,as Nb has positive roles in GFA and thermal stability of BMGs.The results indicate that a fully amorphous phase in the as-cast samples with 3 mm in diameter is obtained for both the Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(5)Nb_(2) and Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(4)Nb_(3) alloys.The corresponding supercooled liquid regions of the two BMGs are 78 K and 71 K,respectively.The mechanism for improving their GFA was analyzed based on the principle of metal solidification,the parameters for glass formation and thermal properties of the alloys.The compression strength and Vicker’s hardness of the two BMGs are 1,950 MPa and 1,310 HV,2,062 MPa and 1,180 HV,respectively.The developed BMGs with high B content,good GFA,and very high hardness can be used as coating materials to the framework for spent nuclear fuels.

In situ synthesis of Fe-based alloy clad coatings containing TiB_2–TiN –(h-BN)

Fe-based alloy coatings containing TiB2–TiN –（h-BN） were synthesized in situ on Q235 steel substrates by a plasma cladding process using the powders of Fe901 alloy, Ti, and h-BN as raw materials. The effects of Ti/h-BN mass ratio on interfacial bonds between the coating and substrate along with the microstructures and microhardnesses of the coatings were investigated. The results show that the Ti/h-BN mass ratio is a vital factor in the formation of the coatings. Free h-BN can be introduced into the coatings by adding an excess amount of h-BN into the precursor. Decreases in the Ti/h-BN mass ratio improve the microstructural uniformity and compactness and enhance the interfacial bonds of the coatings. At a Ti/h-BN mass ratio of 10/20, the coating is free of cracks and micropores, and mainly consists of Fe-Cr, Fe3B, TiB2, TiN, Ti2N, TiB, FeN, FeB, Fe2B, and h-BN phases. Its average microhardness in the zone between 0.1–2.8 mm from the coating surface is about Hv0.2 551.5.

Water-conducting Characteristics and Micro-dynamic Self-adjusting Behavior of Polyacrylamide/Montinorillonite Coating

A water-conducting polyacrylamide/montmorillonite coating was prepared by solutionblending.The coating was coated on fiber and then composited with polymer to form a composite film material that used for water saving and tree planting in arid and desert regions.The coating＇s water-conducting characteristics and dynamic self-adjusting behavior were investigated by Fourier transform infrared（FTIR）spectroscopy,thermal analysis（TG-DTA）,and environmental scanning electron microscopy（ESEM）.The results showed that the coating＇s water-conducting rate increased but water-retention capacity weakened with increasing montmorillonite content.The water-loss rate was positively related to temperature and negatively related to soil moisture.Water potential greatly influenced the water-conducting rate of the coating during its water conduction process.When the coating was at a low water potential,the montmorillonite particles interconnected and water was conducted quickly via montmorillonite layers,whereas when the coating was at a high potential,the montmorillonite particles disconnected and water was conducted slowly via the swelled polyacrylamide net structure.The rate can be regulated by changing the proportion of polyacrylamide and montmorillonite to guarantee a reasonable water supply for trees and make trees easier to survive.Thus,the survival rate of trees can be increased and the use of water resources can be significantly reduced.

Sputter Deposited Carbon Material based Fabry-Perot Sensor and Downhole Application

To prevent hydrogen-induced loss and achieve long-term effective parameters monitoring in harsh downhole environment,we proposed a Fabry-Perot sensor with vacuum sputter deposited carbon coating film,in which we employed a deposition technology with a higher particle kinetic energy,closer substrate adhesion,and denser films,to deposit the coating film on the surface of the quartz capillary glass tube to protect the sensor from corrosion.The sensitivity and accuracy of the Fabry-Perot sensor with carbon film deposition can reach 369 nm/MPa and 0.02%FS,respectively.Meanwhile,the sensor has less hysteresis error and good pressure linearity of more than 0.99999 for repeatable pressure measurement.The downhole practice monitoring data indicated that this fiber-optic sensor exhibited excellent performance and the sputter deposited carbon coating can effectively decrease hydrogen loss.

Performance of the Cement Matrix Composite Material With Rubber Powder

The effect of the deferent rubber content substituted for fine aggregate on the mortar performance was studied.The effects of the rubber coated with the coating materials on the mortar compressive strength,bending strength and impact work were discussed.The optimum rubber powder content and the suitable coating material were found.Through the electrical probe test-BEI,SEI and calcium ion distribution,and the slight crack and the interface between the rubber and cement matrix are analyzed.The results show that the rubber powder coated with the surface treatment materials A,B and C has the capability of absorbing a large amount of energy under the compressive and flexural load and the slight cracks of R-C were controlled and restrained.

Molecular simulation of interfacial reaction between TiAl alloy melts and different coatings

The effect of coatings(Y_2O_3, Zr O_2 and Al_2O_3) on the interfacial reaction of Ti Al alloys was studied with molecular dynamics. The binding energy of coatings and the diffusion process of oxygen in the melt were simulated, and then the simulation results were compared with the experimental results. The simulation results indicate that for each of the three simulated coatings, inordinate interfacial reactions have occurred between the coating and the melt. The binding energy results show that Y_2O_3 has the best stability and is the most difficult to break down. Zr O_2 has the greatest decomposition energy and is the easiest to break down in the melt. Besides, the molecular dynamics indicate that the diffusion coefficient of the oxygen atom in Al_2O_3 is larger than that in the other two coatings, indicating that oxygen diffusion in Al_2O_3 is the fastest at a given temperature. The experimental results show that the oxygen concentration of the melt with Al_2O_3 coating is the highest, and the oxygen diffusion is of similar magnitude to the simulation values, from which the conclusion can be obtained that the oxygen concentration is significantly influenced by the coating materials.

Fabrication of Fe–TiC–Al_2O_3 composites on the surface of steel using a TiO_2–Al–C–Fe combustion reaction induced by gas tungsten arc cladding

The aim of the present study was to fabricate Fe-TiC-Al2O3 composites on the surface of medium carbon steel.For this purpose,TiO2-3C and 3TiO2-4Al-3C-xFe（0 ≤ x ≤ 4.6 by mole） mixtures were pre-placed on the surface of a medium carbon steel plate.The mixtures and substrate were then melted using a gas tungsten arc cladding process.The results show that the martensite forms in the layer produced by the TiO2-3C mixture.However,ferrite-Fe3C-TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO2-4Al-3C mixture.The addition of Fe to the TiO2-4Al-3C reactants with the content from 0 to 20wt%increases the volume fraction of particles,and a composite containing approximately 9vol%TiC and A12O3 particles forms.This composite substantially improves the substrate hardness.The mechanism by which Fe particles enhance the TiC ＋ A12O3 volume fraction in the composite is determined.

Behavior of Deuterium in Boron Films Covered by Oxygen-Containing Layer

Boron is an attractive candidate of the first wall coating materials in fusion reactors. The behavior of deuterium implanted into boron films has been studied . This paper reports the effect of thin oxygen-containing boron layer on the behavior of deuterium im- planted into boron film by X-ray photoelectron spectroscopy （XPS） and thermal desorption spectroscopy （TDS）.

FePO4-coated Li[Li0.2Ni0.13Co0.13Mn0.54]O2 with improved cycling performance as cathode material for Li-ion batteries

Li[Li0.2Ni0.13Coo.13Mn0.54]O2 cathode materials were synthesized by carbonate-based co-precipitation method, and then, its surface was coated by thin layers of FePO4. The prepared samples were characterized by X-ray diffraction （XRD）, field emission scanning electron micro- scope （FESEM）, energy-dispersive spectroscopy （EDS）, and transmission electron microscopy （TEM）. The XRD and TEM results suggest that both the pristine and the coated materials have a hexagonal layered structure, and the FePO4 coating layer does not make any major change in the crystal structure. The FePO4-coated sample exhibits both improved initial discharge capacity and columbic efficiency compared to the pristine one. More significantly, the FePO4 coating layer has a much positive influence on the cycling perfor- mance. The FePO4-coated sample exhibits capacity reten- tion of 82 % after 100 cycles at 0.5℃ between 2.0 and 4.8 V, while only 28 % for the pristine one at the same charge-discharge condition. The electrochemical impe- dance spectroscopy （EIS） results indicate that this improved cycling performance could be ascribed to the presence of FePO4 on the surface of Li[Li0.2Ni0.13Co0.13Mno.54102 par- ticle, which helps to protect the cathode from chemical attacks by HF and thus suppresses the large increase in charge transfer resistance.

Fabrication of NiO coated SiO_2 and SiO_2 coated NiO for the removal of Pb^(2+) ions

We have prepared silica,SiO2coated NiO and NiO coated SiO2by sol-gel method.The physicochemical properties of the desired materials were investigated by surface charge properties,scanning electron microscopy（SEM）,energy dispersive X-ray（EDX） spectroscopy,surface area measurements and X-ray diffraction（XRD） analyses.The point of zero charge（PZC） of the solid was determined by the salt addition method.In coated materials,two PZC values were noted representing the surface charge of their counterparts.The SEM image of SiO2coated NiO displays a uniform coating of silica on the surface of NiO whereas in case of NiO coated SiO2,a honeycomb like appearance was observed with highly porous structures.In the diffractograms of NiO,the characteristic peaks were suppressed in NiO coated silica however,no diffraction peak could be seen in SiO2coated NiO.Batch adsorption technique was applied for the removal of Pb2＋ions from aqueous solution.The sorption trend for Pb2＋ions was observed in the order of NiO coated SiO2〉 SiO2coated NiO 〉 NiO 〉 SiO2.This trend confirms that the coated materials have more sorption capacities than their parent counterparts.

Preparation and Properties of Smart Thermal Control and Radiation Protection Materials for Multi-functional Structure of Small Spacecraft

Considering the unique properties of small spacecraft, such as light weight, low power-consumption and high heat flux density, a new kind of lightweight boron carbide （B4C） radiation-protection coating material was proposed. New techniques for preparing LSMO thermal control coating and B4C radiation-protection coating were developed. The sample piece of multi-functional structure was manufactured by using the proposed materials, and a series of performance tests, such as thermal control and radiation-protection behaviors were evaluated. Test results show that： the emissivity of the multi-functional structure varies from 0.42 to 0.86 at 240 K to 353 K and the phase transition temperature is about 260 K. The electron radiation-protection ability of the multi-functional structure is 3.3 times better than that of Al material. The performance index of this multi-functional structure can meet the requirements for space application in on-board electronic equipment.

Scaling relationships of elastic-perfectly plastic film/coating materials from small scale sharp indentation

The scaling relationships of elastic-perfectly plastic film/coating materials during sharp indentation have been obtained using dimensional analysis and finite-element modeling. Besides the bulk substrate materials, a wide range of film/coating materials with different ratios in term of the Young’s modulus and yield strength were examined, namely different values of Ef/Esand Yf/Es.Based on these scaling relationships, the substrate effects on indentation response and deformed surface profile of residual imprint are given. Furthermore, the scaling relationship among the work of indentation, reduced elastic modulus and hardness has been found. It is found that the ratio of the indentation hardness to measurement of substrate elastic modulus could be used to characterize the wear resistance of film/coating materials. In addition, a novel method to acquire the intrinsic hardness and elastic modulus of film/coating materials is proposed combined with the well-known 10% critical indentation depth rule, which avoids the error caused by estimating the contact area. This work could be contributed for characterizing the mechanical properties of film/coating materials at micro-and nanoscale.

Preparation,characterization and combustion properties of Zr/ZrH_2 particles coated with α-FeOOH crystal grains

Zr/ZrH2 particles with irregular morphologies and broad size distribution were uniformly coated with acicular α-FeOOH crystal grains via a facile route without using polymers or surfactants. The as-synthesized material was characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray （EDX）, UV-vis diffusion reflection （UV-vis） and Raman spectrometry. Based on these characterizations, the synthesis mechanism was explained in terms of combined heterogeneous nucleation and solid state transformation reaction. The presence of α-FeOOH coating greatly changed the combustion behavior of Zr/ZrH2 particles： the combustion lasting time decreased from 32 s for un-coated Zr/ZrH2 particles to 0.2 s for coated particles while the maximum temperature in the combustion process increased from 1510 ℃ to 2036℃.

High-entropy ferroelastic(10RE_(0.1))TaO_(4) ceramics with oxygen vacancies and improved thermophysical properties

The primary purpose of this work is to optimize the thermophysical properties of rare-earth tan-talate ceramics using the high-entropy effect.Here,the high-entropy rare-earth tantalate ceramic(Y_(0.1)Nd_(0.1)Sm_(0.1)Gd_(0.1)Dy_(0.1)Ho_(0.1)Er_(0.1)Tm_(0.1)Yb_(0.1)Lu_(0.1))TaO_(4)((10RE_(0.1))TaO_(4))is synthesized successfully.The lat-tice distortion and oxygen vacancy concentration are characterized firstly in the rare-earth tantalates.Notably,compared with single rare-earth tantalates,the thermal conductivity of(10RE_(0.1))TaO_(4) is reduced by 16%-45%at 100℃ and 22%-45%at 800℃,and it also presents lower phonon thermal conductivity in the entire temperature range from 100 to 1200℃.The phonon thermal conductivity(1.0-2.2 W m^(-1) K^(-1),100-1200℃)of(10RE_(0.1))TaO_(4) is lower than that of the currently reported high-entropy four-,five-and six-component rare-earth tantalates.This is the result of scattering by the ferroelastic domain,lattice distortion associated with size and mass disorder,and point defects,which target low-,mid-and high-frequency phonons.Furthermore,(10RE_(0.1))TaO_(4),as an improved candidate for thermal barrier coatings materials(TBCs),has a higher thermal expansion coefficient(10.5×10^(-6)K^(-1) at 1400℃),lower Young’s modulus(123 GPa)and better high-temperature phase stability than that of single rare-earth tantalates.