Performance of the Aluminide Coating of SomeLow Alloy Steels

Two low alloy steels 0.5Cr-0.5Mo-0.25V and H85 were pack-aluminized at 900°for 4 h by using Fe-Al powder mixture containing 48% Fe, 20.6% Al- 29.4% Al2O3 and 2% NH4Cl by weight. The microhardness and oxidation resistance at 900℃ of the aluminide coatings were studied. It was found that pack-aluminizing improves the microhardness of the 0.5Cro.5Mo-0.25V steel while it reduces the microhardness of the H85 steel. Pack aluminizing highly improves the oxidation resistance after 20h exposure at 900℃ in air for the investigated steels.

Different Kinds of Microfibrillated Cellulose as Coating Layers Providing Fiber-based Barrier Properties

In this study,we investigated the barrier properties of different kinds of microfibrillated cellulose(MFC)coating layers.The air,oxygen,and water vapor permeability,as well as the water contact angles(WCA),were measured to quantify the barrier efficacy of the applied coatings.The WCA data showed that the surfaces of MFC-coated cardboards are more hydrophilic than those of uncoated cardboards.However,different MFC coatings realize different oxygen transmission rates(OTRs)and water vapor transmission rates(WVTRs).The MFC coating derived from bleached bamboo pulp subjected to carboxyethylation pretreatment(MFCCBP)gave the best oxygen and water vapor barrier performances.The OTR of the virgin cardboard(>16500 cm^(3)/(m^(2)·24 h))decreased to 4638 cm^(3)/(m^(2)·24 h)after coating with the MFCCBP.The WVTR similarly decreased from 1016.7 g/(m^(2)·24 h)to 603.2 g/(m^(2)·24 h).

Preparation of Ultrafine Starch Particle and its Application in Paper Coating

Despite its biodegradability, adequate cohesive strength and comparatively low cost, the use of cooked starch as a paper coating binder is limited due to its high viscosity and serious negative impact on the gloss. Starch-based bio-latex with size in the nanometer or sub-micrometer range has been developed recently to overcome these shortcomings. In this study, ultrafine starch particle(UFSP) was prepared by mechanical milling using a DYNO mill in combination with light chemical pretreatment. Model coating colors containing different dosages of UFSP were applied to base paper and the properties of the coated papers were evaluated. The results showed that the UFSP was disc-shaped with a median particle diameter of 167 nm. Water retention capacity of the coating colors was improved considerably with the addition of UFSP, i.e., the water retention value decreased by nearly 40% when styrene-butadiene latex was replaced by UFSP at a dosage of 3 pph(per hundred parts of pigment). The high shear rate viscosities of the coating colors containing no more than 2 pph of USFP were similar to that of the control coating color at shear strain rate higher than 2000 s^(-1). The properties and performances of the coated papers were comparable to the control coated paper with single synthesized latex binder. The gloss and the print gloss of paper samples with or without USFP were 59.7% and 58.2%, 79.0% and 78.8%, respectively. Surface strength of paper samples with or without USFP were 0.96 and 0.90 m/s, respectively, while the ink absorptivity values were 34% and 33%. This study demonstrates a promising approach to obtain submicrometer sized starch for paper coating.

COATED CARBIDE TOOL'S CUTTING PERFORMANCE AND ITS DATA BASE

The development and application of coated cemented carbide made in China are pres-ented. Three aspects of the coated carbide tool's performance: cutting forces, surface finish and toollife are studied. Furthermore speed-correcting coefficients of the tool are given. On the basis of thework, a data base for coated carbide tools has been built on a microcomputer. It consists of fivemodules. essential data base, tools' comparison and inquiry, recommending cutting regimes, exper.imental curve base and an expert system for tool selection.

Optimization of the spectral performance of an antireflection coating on a micro-spherical substrate

To improve the optical performance of an antireflection（AR） coating on a micro-spherical substrate, the ray angle of the incidence distribution and the thickness profile are taken into consideration during the optical coating design. For a convex spherical substrate with a radius of curvature of 10 mm and a clear aperture of 10 mm,three strategies are used for the optimization of the spectral performance of a broadband AR coating in the spectral region from 480 to 720 nm. By comparing the calculated residual reflectance and spectral uniformity,the developed method demonstrates its superiority in spectral performance optimization of an AR coating on a micro-spherical substrate.

On acoustic performance for viscoelastic coating containing axisymmetric cavities using the multiple scattering method

A semi-analytical/numerical model based on the multiple scattering （MS） method has been established for analyzing the effect of acoustic performance on main energy attenua- tion mechanism in viscoelastic coating containing axisymmetric cavities. The basic functions of stress and displacement of the axisymmetric cavity surface are derived in the system of spheri- cal coordinates. The transition matrix between the incident wave and the scattering wave are obtained by the numerical integral of the basic functions of the cavity surface. The reflection, transmission and absorption performance of viscoelastic materials containing periodic cavities are calculated using the MS method and the wave propagating theory of the multi-layered medium. The results indicate that low frequency energy is mainly attenuated through cavity resonance. The resonant properties are found to be very sensitive to the boundary conditions. The coupling of the double-cavity is capable of extending the absorption to even lower fre- quencies. The absorption performance of the viscoelastic coating in the high frequency range is independent of the backing material. Its energy attenuation depends mainly on acoustic properties of cavity scattering and mode conversion.

Organosilicon leather coating technology based on carbon peak strategy

Based on the demand of carbon peak and carbon emission reduction strategy, divinyl-terminated polydimethyl-siloxane (ViPDMSVi), poly(methylhydrosiloxane) (PMHS), divinyl-terminated polymethylvinylsiloxane (ViPMVSVi), and fumed silica were used as primary raw materials, polydimethylsiloxane (PDMS) synthetic leather coating was in situ constructed by thermally induced hydrosilylation polymerization on the synthetic leather substrate. The effect of the viscosity of ViPDMSVi, the active hydrogen content of PMHS, the molar ratio of vinyl groups to active hydrogen, the dosage of ViPMVSVi and fumed silica on the performance of PDMS polymer coating, including mechanical properties, cold resistance, flexural resistance, abrasion resistance, hydrophobic and anti-fouling properties were investigated. The results show that ViPDMSVi with high vinyl content and PMHS with low active hydrogen content is more conducive to obtaining organosilicon coating with better mechanical properties, the optimized dosage of ViPMVSVi and fumed silica was 7 wt% and 40 wt%, respectively. In this case, the tensile strength and the broken elongation of the PDMS polymer coating reached 5.96 MPa and 481%, showing reasonable mechanical properties for leather coating. Compared with polyurethane based or polyvinyl chloride based synthetic leather, the silicon based synthetic leather prepared by this method exhibits excellent cold resistance, abrasion resistance, super hydrophobicity, and anti-fouling characteristics.

Effect of Monolithic LaB_6 on the Ablation Resistance of ZrC/SiC Coating Prepared by Supersonic Plasma Spraying for C/C Composites

Ablation resistance of monolithic LaB-doped ZrC coating for SiC-coated carbon/carbon composites by supersonic atmospheric plasma spray was investigated under an oxyacetylene torch with a heat flux of 4.18 MW/m~2. Result shows that ZrC coating with 10 vol.% LaBhas a good ablation resistance compared with pure ZrC, ZrC with 20 vol.% LaBand SiC-doped ZrC coating. After ablation for 15 s, the weight is increased by 1.12 mg/s. The good ablation resistance is ascribed to the formation of a stabilized scale which consists of protective LaZrO-containing molten phase and ZrOparticles keeping the integrity of the coating.