Preparation,mechanical properties and surface morphologies of waterborne fluorinated polyurethane-acrylate

A series of waterborne fluorinated polyurethane-acrylate (WFPUA) materials were prepared from polyester polyol (NJ-330), isophorone diisocyanate (IPDI), dimethylol propionic acid (DMPA) and different content of hexafluorobutyl acrylate (FA). The chemical structure was characterized with FT-IR, ¹H and ¹³C NMR; and the result confirmed that the FA monomer had been introduced into the chain of the WPUA polymer. The physical properties of WFPUA dispersions, mechanical properties and thermal properties of WFPUA films were measured. When the content of FA monomer was 3.0 wt.%, the film exhibited the highest tensile strength, hardness and excellent chemical resistance. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used for characterization of cross and surface sections of the WFPUA films to verify the results. The obtained WFPUA materials have great potential application such as coatings, leather finishing, adhesives, sealants, plastic coatings and wood finishes.     

Effect of target peak power density on the phase formation,microstructure evolution,and mechanical properties of Cr2AlC MAX-phase coatings

The applicability of Cr₂AlC MAX-phases as protective coatings in energy conversion or aerospace applications requires a dense, single-phase structure. Therefore, we study the effect of target power density and substrate bias on phase formation, microstructure evolution, and mechanical properties of Cr₂AlC coatings utilizing direct current (DCMS) and high-power pulsed magnetron sputtering (HPPMS). Generally, HPPMS results in coatings with superior density and hence larger elastic moduli compared to DCMS, indicating that ion bombardment by ionized film-forming species is beneficial. However, decreasing the substrate bias to ?200 V for DCMS and ?100 V for HPPMS favors the ion bombardment induced formation of the disordered (Cr,Al)₂C_x solid solution. It is evident that there is an optimum moderate ion energy for the formation of dense Cr₂AlC coatings. Too low energy results in the formation of under-dense coatings. Too high energy yields the formation of (Cr,Al)₂C_x in addition to Cr₂AlC.     

Effects of in-situ carbon layer and volume fraction of SiC fiber on the mechanical properties and fracture behaviors of SiCf/SiC composites fabricated by a modified PIP method

Unidirectional SiC_f/SiC composites (UD SiC_f/SiC composites) with excellent mechanical properties were successfully fabricated by a modified PIP method which involved the preparation of film-like matrix containing carbon layer with a low concentration PCS solution followed by the rapid densification of composites with a high concentration PCS solution. Carbon layers were in-situ formed and alternating with SiC layers in the as-received matrix. The unique microstructure endows the composites with appropriate interfacial bonding state, good load transfer ability of interphase and matrix and load bearing ability of fiber, and great crack deflection capacity, which ensures the synergy of high strength and toughness of composites. It is also found that the fiber volume fraction in the preform makes a non-negligible effect on the distribution of interphase and matrix, of which the reasonable adjustment can be utilized to optimize the mechanical properties of composites. Compared with the composites only using high concentration PCS solution, the UD SiC_f/SiC composites prepared by the modified PIP method exhibit superior mechanical properties. Ultrahigh flexural strength of 1318.5 ± 158.3 MPa and fracture toughness of 47.6 ± 5.6 MPa·m^1/2 were achieved at the fiber volume fraction of 30%.     

Online monitoring of laser remelting of plasma sprayed coatings to study the effect of cooling rate on residual stress and mechanical properties

This investigation deals with laser remelting of plasma sprayed alumina and chromia coatings. The time-temperature history of the laser remelted zone was recorded using an infrared pyrometer during the remelting operation. Cooling rates, under varying scanning speed, were determined from the time temperature curve. Surface morphology, microstructure, and phases of the laser treated and as-sprayed coatings were characterized using scanning electron microscopy, optical microscopy, X-ray diffraction, respectively. X-ray diffraction was also employed to measure the surface residual stress of the coatings. Inherent features of plasma sprayed coatings like porosity and inter-lamellar boundary were obliterated upon laser remelting. A columnar grain growth perpendicular to the laser scanning direction was observed. The range of roughness of the as-sprayed coatings reduced from 6 to 8?µm to 1–2?µm in the remelted layers. For both coatings, more than 90% reduction in porosity was found upon laser remelting. Surface residual stress of the as-sprayed alumina and chromia coatings was found to be tensile and compressive, respectively. Within the limits of the testing condition the tensile residual stress of the remelted layers increased by up to around 500% in the alumina coatings. In the chromia coating a decrease of compressive stress by up to around 80% was recorded. In the remelted layer the tensile nature of the stress showed a tendency to increase with an increase in the cooling rate. However, the state of stress of the as-sprayed layer, i.e., tensile or compressive, was retained in the remelted layer. The residual stress was found to decrease in the remelted layer with an increase in the degree of overlap of the remelted tracks.     

Improving the mechanical resistance of waterborne wood coatings by adding cellulose nanofibres

In the present study, microfibrillated cellulose (MFC) and nanocrystalline cellulose (NCC) were applied as additives for a waterborne acrylate/polyurethane-based wood coating in order to improve the mechanical resistance of coated wood surfaces. Coating mixtures containing up to 5 wt% nanocellulose were prepared by high-shear mixing and applied to wood substrates. The optical, mechanical and chemical properties of cured coatings were characterized. Surface roughness, gloss, scratch resistance, abrasion resistance and resistance against chemicals were determined according to the relevant European standards. Additionally, nanoindentation (NI) was used to assess the micromechanical properties of modified and unmodified coatings. Owing to a higher surface roughness, cellulose-filled coatings showed significantly lower levels of gloss than the unmodified coating indicating that nanocellulose acts as a matting agent. NI experiments revealed a slightly positive effect of nanocellulose addition on the hardness and modulus of the coatings. While scratch resistance improved consistently with increasing nanocellulose addition, abrasion resistance was found to improve only sporadically. Tensile tests on free-standing coating films revealed a significantly higher tensile strength and modulus for cellulose-filled coatings. Overall, the results suggest that the addition of cellulose nanofibres primarily improves the internal cohesion of the coating layer whereby MFC was more effective than NCC.     

Influence of thickness on mechanical properties and crack-bridging ability of coatings for concrete

Different variables can influence the crack-bridging ability (CBA) of a coating. These parameters can be related to: (i) the substrate, i.e. the way the crack opens and develops in the concrete; (ii) the substrate/coating interface, i.e. the adhesion of the organic coating to the concrete; (iii) the coating, i.e. its thickness and mechanical properties; (iv) the external conditions, i.e. the temperature in field and the mechanical solicitation of the structure. In the present paper, some experiments were performed to analyse the third point, i.e. to find possible relationships between the variation of the CBA (in situ failure of the coating applied to the concrete substrate) and the mechanical properties (free-film failure) of coatings with thickness. Experimental results suggest that the value of strain at break is a key factor in the variation of CBA of a coating with thickness.     

Microstructure and mechanical properties of Si3N4f/Si3N4 composites with different coatings

The Si₃N₄ coating and Si₃N₄ coating with Si₃N₄ whiskers as reinforcement (Si₃N_4w-Si₃N₄) were prepared by chemical vapor deposition (CVD) on two-dimensional silicon nitride fiber reinforced silicon nitride ceramic matrix composites (2D Si₃N_4f/Si₃N₄ composites). The effects of process parameters of as-prepared coating including the preparation temperature and volume fraction of Si₃N_4w on the microstructure and mechanical properties of the composites were investigated. Compared with Si₃N₄ coating, Si₃N_4w-Si₃N₄ coating shows more significant effect on the strength and toughness of the composites, and both strengthening and toughening mechanism were analyzed.     

Ceramic TiC/a:C protective nanocomposite coatings: Structure and composition versus mechanical properties and tribology

The relationship between the structure, elemental composition, mechanical and tribological properties of TiC/amorphous carbon (TiC/a:C) nanocomposite thin films was investigated. TiC/a:C thin film of different compositions were sputtered by DC magnetron sputtering at room temperature. In order to prepare the thin films with various morphology only the sputtering power of Ti source was modified besides constant power of C source. The elemental composition of the deposited films and structural investigations confirmed the inverse changes of the a:C and titanium carbide (TiC) phases. The thickness of the amorphous carbon matrix decreased from 10 nm to 1–2 nm simultaneously with the increasing Ti content from 6 at% to 47 at%. The highest hardness (H) of ~26 GPa and modulus of elasticity (E) of ~220 GPa with friction coefficient of 0.268 was observed in case of the film prepared at ~38 at% Ti content which consisted of 4–10 nm width TiC columns separated by 2–3 nm thin a:C layers. The H3/E2 ratio was ~0.4 GPa that predicts high resistance to plastic deformation of the TiC based nanocomposites beside excellent wear-resistant properties (H/E=0.12).     

铝炭复合材料的机械性能

对影响铝炭复合材料机械性能的诸因素，如气孔率、结合剂种类及用量、焙烧温度、石墨用量等进行了实验研究。     

Exploring the effect of dry premixing of sand and cement on the mechanical properties of mortar

A spout-fluid bed device was developed for dry premixing sand and cement to produce mortar. The goal of the work was to explore the efficacy of a new method for dispersing cement in sand to produce a mortar with better mechanical and physical properties. This strategy was found to work best at high sand/cement ratios, indicating that the dry premixing is more effective as the cement content is reduced and that it may be possible to produce commercially acceptable mortars with a lower cement content. Other properties of the mortar are also positively affected, including a decrease in the shrinkage and an increase in the workability.     

The effect of oxidation on the mechanical properties and dielectric properties of porous Si3N4 ceramics

The effect of oxidation temperature and time on the microstructures, phase compositions, mechanical properties, and dielectric properties of porous Si₃N₄ ceramics was investigated in the temperature range from 900 °C to 1300 °C for 1 h, 5 h, and 24 h. The weight gain measured either at lower temperature (900 °C) for long time (24 h) or at higher temperature (1300 °C) for 1 h demonstrated that the porous Si₃N₄ ceramics were easily oxidized under the current test conditions. Results showed that the amount of open pores, flexural strength, compressive strength, and dielectric constant all decreased with the increase of oxidation temperature independent upon the oxidation time. The oxidation product SiO₂ was low-temperature quartz in mild condition (low temperature, short time) and cristobalite in severe condition (high temperature, long time). The existence of cracks on the oxide scale was due to the phase transformation of SiO₂ and thermal expansion coefficient mismatch between SiO₂ and Si₃N₄.     

Synergistic effect of glass fibre and Al powder on the mechanical properties of glass-ceramics

To explore the synergistic effect of glass fibre and Al powder on the mechanical properties of glass-ceramics, blast furnace slag was chosen as the main material, and glass fibre and Al powder as reinforcement materials. The phase compositions, microstructures, compressive properties, and apparent density of the glass-ceramics with varying quantities of glass fibre and Al powder were investigated. The experimental results indicated that Al powder could exist as a simple substance in glass-ceramics and form a dense net coating on the surface of blast furnace slag to improve the plasticity of the glass-ceramic. The glass fibre had better reinforcement effect than Al powder because of its extremely high mechanical strength. The plasticity of glass-ceramics, however, severely decreased; the glass-ceramics exhibited brittle failure during compression. A slight increase in the content of CaSi₂ and SiO₂ in the glass-ceramics was closely related to the addition of glass fibre. Considering safety and economy, glass-ceramics with 6% Al and 14% glass fibre (S4) have the best mechanical properties. The compressive strength, strain at maximum force, and apparent density were 40?MPa, 19% and 1.974?g/cm³, respectively.     

Preparing the SiC coated C/C composites with excellent mechanical and antioxidative properties using a buffer layer

The preparation of SiC coating on C/C composites via a pack cementation method would cause serious mechanical damage to C/C substrate due to the siliconization corrosion by molten silicon during the ultra-high-temperature preparation process (2173–2373 K). In order to prepare SiC coated C/C composites with excellent mechanical and antioxidative properties, we applied a buffer layer on the surface of C/C to inhibit siliconization corrosion and densify coating. Results showed that the siliconized area ratio of the C/C substrate was decreased from 60.9% to 24.8%, and its bending strength was increased from 36.9 MPa to 60.6 MPa. Moreover, the mass loss of the modified SiC coated C/C sample has reduced by ~4.14 times after oxidation for 144 h in air at 1773 K and decreased from 2.44% to ? 0.15% after suffering 50 thermal cycles between room temperature and 1773 K.     

The influence of latex blend composition on crosslinking and mechanical properties

Model reactive latices were synthesized by semicontinuous emulsion copolymerization of n‐butyl methacrylate and acetoacetoxyethyl methacrylate or dimethylaminoethyl methacrylate. The two functional latices were then blended in various ratios to study the influence of blend composition on crosslinking and mechanical properties of the resulting films. Crosslinking was quantified through swelling measurements. It was found that the crosslink density increased with increasing amounts of acetoacetoxy‐functional polymer. In addition, the crosslink density exhibited two maxima, at 30/70 and 70/30 (acetoacetoxy‐functional latex/amino‐functional latex) blend compositions. The mechanical properties of the films were quantified by dynamic mechanical analysis (DMA). It was shown that optimal mechanical properties occurred when the particles packed most efficiently at the 30/70 and 70/30 blend compositions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3774–3779, 2007     

Combined effect of corona discharge and enzymatic treatment on the mechanical and surface properties of wool

The enzymatic treatment of textile fibers is a nontoxic and environmentally benign process. The objective of the present study is to investigate the improvement of physic-chemical characteristics of wool fabrics by surface modification induced by corona discharge and enzymatic treatment with protease and cellulose. Thus, it was found that, compared with pristine wool fabric, the enzyme-treated fabrics exhibited lower tensile strength, increased elongation, and higher alkali solubility. The surface roughness and the zeta potential of the enzyme-treated wool fabrics decreased with increasing treatment duration.     

Effect of Ti particle size on mechanical and tribological properties of TiCN coatings prepared by reactive plasma spraying

Titanium carbonitride (TiCN) coatings were successfully fabricated by reactive plasma spraying (RPS) from agglomerated Ti-graphite feedstock. The effect of Ti particle size on the microstructure and phase composition of plasma sprayed TiCN coatings was investigated. The Vickers microhardness of coatings was measured by a Microhardness Test and the corresponding Weibull distribution were also analyzed. In addition, a pin-on-disk tribometer was employed to determine the trobological properties of coatings. Results show that all the coatings consist of TiC_xN_1−x (0 ≤ x ≤1) and minor Ti₂O phases, and the amount of Ti₂O increases with the increase of Ti particle size. The Weibull distribution of Vickers microhardness of all the coatings shows apparent scattering, while the coating sprayed with Ti particle size of 28 µm exhibits a relatively even distribution. Compared with the coating sprayed with Ti particle size of 14 µm or 48 µm, the coating sprayed with Ti particle size of 28 µm exhibits improved mechanical and tribological properties, which are attributed to the high microhardness and strong bonding strength.     

水性丙烯酸酯汽车涂料制备及其漆膜性能研究

合成了水性丙烯酸树脂并用其配制了汽车罩光清漆,研究了硬/软单体配比、丙烯酸单体的用量、芳香酯单体的用量、氨基树脂固化剂/丙烯酸树脂的配比及固化条件对漆膜性能的影响。结果发现,硬/软单体配比为39/35,丙烯酸质量分数为6%,甲基丙烯酸苄酯(BNMA)质量分数为12%,固化剂/树脂配比为40/100,固化温度及时间分别为140℃和30 min时,固化漆膜具有优良的综合性能,其光泽度达到98(60°),冲击强度为0.50 kJ/m,硬度为2H,附着力为0级,耐溶剂、耐紫外老化性能良好。FT-IR分析显示氨基树脂/丙烯酸树脂漆膜固化后表征羟基和甲氧基的吸收峰强度显著变弱,表明氨基树脂和丙烯酸树脂发生了交联固化。     

Structure and mechanical properties of plasma sprayed coatings of titania and alumina

The paper concerns the use of traditional and depth-sensing indentation (DSI) for investigation of deposits produced from powders based on conventional and nano-sized particles by plasma spray technology.

Plasma sprayed coatings of titania and alumina were studied. Polished cross-section of each coating was prepared and matrices of nano-indents with Berkovich tip were applied onto both materials to explore local elastic behavior. Applied load was in the range of mN to create indents with the same size scale as the thickness of splats—the main building units of the coating. The hardness value as well as the load/unload curve for each indent was stored. Titania coating was sprayed from a novel type of nanoscale-size powder agglomerated to particles useful for plasma spraying, whereas fused and crushed conventional powder was utilized for alumina spraying and for titania coating used as reference. The effect of annealing on elastic properties of titania was studied as well. The values of elastic parameters as well as the character of the coating inhomogeneity seem to reflect: (i) the composition of material and the fabrication technique and (ii) microstructural differences between coatings that are partly inherited from the feedstock powders. The results of DSI tests are discussed also in comparison with common technique used for the investigation of plasma coatings hardness—Vickers microhardness measurement.     

Effects of Ni content on microstructure,mechanical properties and Inconel 718 cutting performance of AlTiN-Ni nanocomposite coatings

AlTiN-Ni coatings with various Ni contents (0–3?at%) were deposited using cathodic arc evaporation. X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, a nanohardness tester, scratch-adhesion tester, and cutting tester were used to examine the microstructure, mechanical properties, and cutting performance of the coatings. The AlTiN coatings exhibited a columnar structure, while the AlTiN-Ni coatings exhibited a nanocrystal structure due to the formation of nc-AlTiN/Ni nanocomposite coatings. The nanohardness of the AlTiN-Ni coatings decreased from 26.2?GPa to 20.9?GPa as the Ni content increased from 0 to 3?at%. At an Ni content of 1.5?at%, the coating possessed a high toughness and sufficient adhesion strength; however, these dropped drastically for the AlTiN-Ni coating with 3?at% Ni owing to the presence of amorphous Ni. The results for the Inconel 718 turning indicated that the wear mode is adhesion at the rake face, abrasion and adhesion (built-up edge) at the flank face, and chipping at the cutting edge. Compared to AlTiN-Ni₃ and AlTiN-coated tools, the lifetime of the AlTiN-Ni_1.5 coated tool increased to 160% at a cutting speed of 40?m/min. This was attributed to less adhesion at the rake face and chipping at the cutting edge, due to the nanocrystal structure and higher toughness of the AlTiN-Ni_1.5 coating.     

Effects of inclination angle applied to a polyethylene terephalate substrate before the coating of Al-doped ZnO on film quality and mechanical and optical properties

A flat plate in the deposition stage is designed to be tilted flexibly with an angle such that an inclination angle is formed between the ion beam and the direction normal to a polyethylene terephthalate (PET) substrate. Five kinds of PET/aluminum-doped zinc oxide specimen, with 0°, 15°, 30°, 45°, and 60° inclination angles, respectively, were prepared to examine the effect of inclination angle on the mechanical, electrical, and optical properties and morphology of coating films. Using the peaks of the ZnO (002) and ZnO (103) planes in X-ray diffraction analyses, the relative intensity ratios for these two crystallines are defined and used to evaluate the parameters of composite grain size ((g)_Composite) and residual stress ((σ)_Composite). The experimental results indicate that (σ)_Composite increases but (g)_Composite mostly decreases with increasing inclination angle. A nearly linear relationship is found between (g)_Composite and the d-spacing parameter ((d)_Composite). They both decrease with increasing inclination angle. The intensities of ZnO (002) and ZnO (103) planes significantly influence the mean transmittance, absorption, and reflection in the wavelength range of 801–2500 nm (near-infrared). An increase in the relative peak intensity of ZnO (002) increases the mean transmittance and thus lowers the mean absorption and reflectance. The average transmittance decreases and the average reflection increases in the wavelength range of 300–2500 nm with increasing inclination angle. Increasing the composite grain size decreases the average reflection. The ZnO film thickness is proportional to the mean surface roughness of the film.