Surface Microscopic Morphology Research Articles

Microstructure and corrosion-resisting properties of CeO2-SiO2-Al2O3 composite coatings prepared by plasma electrolytic oxidation on aluminum matrix composites

CeO2-SiO2-Al2O3 composite coatings were prepared on aluminum matrix composites by plasma electrolytic oxidation in the electrolyte of a silicate system consisting of Na2SiO3 and NaOH. The effects of the content of the soluble salt additive Ce(NO3)3·6 H2O on the microstructure, elemental composition, phase structure, thickness, corrosion resistance, and resistance to high-temperature oxidation of the PEO coatings were systematically investigated. The results showed that the CeO2-SiO2-Al2O3 ternary composite ceramic coatings were prepared with the main components of the physical phases as α-Al2O3, γ-Al2O3, Al, and SiC. And the addition of Ce(NO3)3·6 H2O increased the thickness of the coatings from 14.75 μm to 82.71 μm. Meanwhile, densification showed a tendency to increase and then decrease with the concentration of Ce(NO3)3·6 H2O. The surface microscopic morphology of the PEO coatings was optimized with the increase of the added concentration when the Ce(NO3)3·6 H2O concentration was lower than 1.0 g/L, and the surface quality of the coatings deteriorated when the Ce(NO3)3·6 H2O concentration was higher than 1.0 g/L. The corrosion resistance of the coatings was improved when the concentration of Ce(NO3)3·6 H2O was increased to 82.71 μm by the electrochemical experiments and the cavitation experiments. The corrosion resistance of the coatings was optimized when the concentration of Ce(NO3)3·6 H2O was added at 1.0 g/L, the coating’s corrosion resistance was optimized.

Experimental study on the effect of preinhibition pressure on the inhibition of coal spontaneous combustion

A pressurized inhibition method is proposed based on the pre-inhibition process to study the inhibition law and mechanism of the pre-inhibition pressure on the coal spontaneous combustion, with a purpose of enhancing the inhibiting effect of chloride salt inhibitors. In this work, inhibited coal samples were prepared by immersing raw coal in high-temperature and high-pressure reactor at 1 MPa, 2 MPa, 3 MPa, 4 MPa, and 5 MPa, respectively, using MgCl2 solution with a mass concentration of 20 %. The variation rules of the characteristic parameters, such as the indicator gas concentration, inhibition rate, surface microscopic morphology, and reactive groups, of various coal samples with the elevation of the pre-inhibition pressure were investigated using the programmed temperature-raising oxidation system, infrared spectroscopy, and SEM. It was found that the pre-inhibition pressure was in the range of 1–4 MPa, and with the increase of pre-inhibition pressure, the gas-producing concentration and the content of active groups of coal decreased, and the inhibition rate increased significantly. Increasing the pre-inhibition pressure can significantly improve the inhibition effect, and the optimum pre-inhibition pressure is 4 MPa. Continuing to increase the pre-inhibition pressure will destroy the pore structure of the coal and reduce the inhibition effect.

Study on the picosecond laser surface treatment and tribological properties of 3D woven carbon fiber reinforced carbon matrix (Cf/C) composites

Carbon fiber reinforced carbon matrix (Cf/C) composites have demonstrated great significance in many fields, especially in aircraft and automobiles as brake materials. The surface physical/chemical states of Cf/C composites significantly affect their tribological properties. Although ultrafast laser machining technology has been proven to be an effective method for modifying material surfaces, there are some issues concerning the ultrafast laser surface treatment of Cf/C composites and the adjustment of their tribological properties by laser treatment. Here, the 3D woven Cf/C composites were treated with an infrared picosecond laser. The effects of machining parameters on the surface microscopic morphology, chemical compositions, and graphitization degree were investigated. The experiment results indicated that the ultrafast laser treatment could eliminate surface defects, improve surface quality, and reduce the porosity of the Cf/C composites due to photothermal-mechanical ablation. More importantly, the laser-induced photothermal effects led to a graphitization transformation of Cf/C composites from a disordered turbostratic structure into an ordered graphite structure with an increased graphitization degree. The abundant micro-nano structures and the graphitization transformation on the Cf/C composite surface contributed to forming a complete and dense friction film on the Cf/C composites. Therefore, the laser-treated Cf/C composites showed lower COF, higher wear rate, and more stable tribological properties. This study demonstrated a method to adjust the tribological properties of Cf/C composites by ultrafast laser surface treatment, which showed great significance for the surface treatment and tribological property enhancement of Cf/C composites.

Recycling glass fibers from thermoset epoxy composites by in situ oxonium-type polyionic liquid formation and naphthalene-containing superplasticizer synthesis with the degradation solution of the epoxy resin

Glass fibre-reinforced thermoset (GFRT) epoxy composites with permanent cross-linked polymer networks are difficult to recycle, leading to the production of large amounts of waste. Developing an efficient approach to reuse both the high-value fibre and the resin matrices is thus imperative. In this work, we explored the application of H2SO4 (98%) to react with ether and benzene groups in the epoxy backbone at room temperature. As a result, a new family of poly(ionic liquid)s (PILs) comprising cationic oxonium was produced. The in situ oxonium PIL formation enables clean glass fibres to be released with well-maintained surface microscopic morphology, chemical structure and tensile modulus close to the virgin glass fibres (vGFs). Furthermore, the dissolved matrix solution functions as a synergistic sulfonation agent in the synthesis of naphthalene containing superplasticizer. The obtained additive is superior to the fresh H2SO4 sulfonated naphthalene formaldehyde condensate (SNF) in reducing water content (33% vs 19%) and improving compressive strength of cementitious materials by 29%. Therefore, this novel eco-friendly strategy provides an open-loop solution for GFRT composites recycling at ambient conditions producing no new waste.

Optimization design and performance evaluation of a novel asphalt rejuvenator

The development of a regeneration agent is one of the key technologies for pavement regeneration and one of the methods to reduce carbon emissions in the transportation field, so it is very necessary to develop a regeneration agent. Based on the composition of asphalt and rejuvenator components, the optimal dosing of extraction oil, plasticizer dioctyl phthalate (DOP), and hydrogenated (carbon 9) C9 petroleum resin was determined by the response surface method, and the suitable dosing of the anti-aging agent was also designed to optimize the orthogonal experiment to prepare the ZJ-I (Zenith Yummy-Invent) rejuvenator with good overall performance. On the basis of the ZJ-I rejuvenator, dynamic shear rheology (DSR), bending beam rheometery (BBR), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and contact angle experiments were used to investigate the effects of the ZJ-I rejuvenator dosing on the high- and low-temperature rheology, chemical structure, surface microscopic morphology, and adhesion between asphalt and aggregate of aged asphalt and to explore the regeneration effect and regeneration mechanism of the ZJ-I rejuvenator. The results showed that the ZJ-I rejuvenator formulated with 83.6% extracted oil, 15% plasticizer DOP, 1.4% hydrogenated petroleum resin, 0.6% antioxidant, and 0.4% light stabilizer has the best regeneration effect, and its optimal dosing is 7% aging degree. It can also improve the adhesion performance of asphalt and aggregate.

Laser ablation enhancing the electrochemical sensing performance of copper foam toward glucose

In this work, a copper foam with surface oxidation and micro-nano structure was fabricated via a femtosecond laser ablation technique. The change in surface microscopic morphology and electronic structure was investigated by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Based on its rough surface, unique electronic state and oxygen defects, the laser-treated copper foam exhibited excellent electrochemical sensing performance for glucose. The sensitivity and detection limit was determined to be 27.4517 mA cm −2 mM −1 and 1.5 μM, respectively. Furthermore, the good selectivity of the present laser-treated copper foam was also demonstrated by the anti-interference experiment.

Recycling of carbon fibers from unsaturated polyester composites via a hydrolysis-oxidation synergistic catalytic strategy

Unsaturated polyester resins (UPRs) composites have many industrial applications, such as fan blades in wind energy. However, the stable cross-linked polymer networks of resin matrix lead to large numbers of composite wastes that are difficult to recycle. Developing an efficient approach to explore the recovery of high-value fiber from composites is thus imperative. In this paper, an efficient and mild hydrolysis-oxidation synergistic catalytic strategy was proposed to efficiently recycle carbon fibers from UPRs composites by selectively cleaving chemical bonds of UPRs. Ester bonds in UPRs were cleaved by using hydrolysis of 80% hydrazine hydrate along with NaOH. Afterwards, the cleavage of carbon-carbon bonds was accomplished via the Fenton reaction for the purpose of complete degrading UPRs. The result figured that UPRs could be efficiently degraded at 100 °C below via this hydrolysis-oxidation strategy. Interestingly, applying the strategy, the recovery of carbon fibers from UPRs composites was investigated. The reclaimed carbon fibers kept their original surface microscopic morphology, chemical structure and tensile strength almost close to the virgin carbon fibers. This strategy opens up a new way for efficient and mild degradation of thermosets.

Study on the Wettability of a Composite Solution Based on Surface Structures of Coal.

In order to research the influence of composite surfactant solutions on the wetting ability of coal, the wettability parameters, pore structure parameters, and surface microscopic morphology were determined in this study. The results show that the wettability of the surfactant can be improved by adding NaCl. As the concentration of NaCl increased, the spreading coefficient of the NaCl–SDS composite solution increases; the spreading coefficient increased from −10.838 to −3.7624 mN/m. The surface free energy decreased from −2.031 to 3.670 J/mol × 103, and the adhesion work decreased from 113.802 to 55.058 mJ/m2. In terms of the pore structure and surface morphology of coal, the pore size will affect the wettability of coal. The contact angle reduces with pore size increase (R2 = 0.955). The surface pores of coal treated with the NaCl–SDS composite solution increase and the fracture connectivity is improved, which facilitated the solution to penetrate coal for wetting. The results of this paper have great practical significance for mining at the face to reduce coal dust pollution.

Swelling behaviour and microstructure of biochar bentonite

Biochar bentonite is a potential candidate as a porous layer for nuclear waste repositories. It would provide an ideal niche for bacteria that could feed on sulfate from the host rock and hydrogen from the corroding canisters. In this study, the influence of biochar amendment on the swelling properties of bentonite at different densities has been examined through swelling experiments. Scanning electron microscopy (SEM) images were used to study the surface microscopic morphology of biochar bentonite samples. On the basis of the SEM results, the fractal dimension representing the microstructure of biochar bentonite was determined. The relationship between fractal dimension and the maximum swelling pressure was discussed to reveal the correlation between the microstructure and the variation of mechanical properties for biochar bentonite.

Influence of sodium carbonate addition on weight loss of bagasse alkaline black liquor during pyrolysis

To understand the effects and the mechanism of sodium carbonate (Na2CO3) addition on the bagasse alkaline black liquor (BABL) pyrolysis, the reaction variables such as temperature, heating rate, and amount of Na2CO3 addition into BABL-solids were investigated under N2 atmosphere from 50 °C to 1000 °C by thermogravimetic analysis (TGA). Scanning electron microscopy (SEM) and the Coats–Redfern method (CRM) were employed for surface microscopic morphology observations and kinetic analysis, respectively. The results showed that Na2CO3 plays an inhibiting and promoting role during devolatilization (200 °C to 650 °C) and the reduction stages (650 °C to 1000 °C), respectively. Adding Na2CO3 into BABL-solids tends to increase the thickness of the salt layer covering the BABL-solids surface, which increases the activation energy and reduces the weight loss ratio of BABL-solids pyrolysis within 200 °C to 650 °C. Adding Na2CO3 into the BABL-solids tends to increase the number of alkaline compounds or the active site of the reduction reaction, which reduces the activation energy and increases the weight loss ratio of BABL-solids pyrolysis within 650 °C to 1000 °C. The role of Na2CO3 as an additive could be well understood by studying the influence mechanism of Na2CO3 on BABL-solids pyrolysis.

Study of surface microscopic properties of asphalt based on atomic force microscopy

In this paper, atomic force microscopy (AFM) was utilized to investigate the surface microscopic morphology (SMM) and bee structure (BS) of several asphalts and quantitatively evaluate them via roughness theory. The effects of asphalt properties, aging, moisture and anti-stripping agents on the SMM and BS were studied comprehensively. Five types of asphalts were investigated, and each asphalt was prepared with four different conditions. The results showed that the oil source was the only factor among the asphalt properties that influenced the presence of BS, and the BS changed the SMM. The larger the asphalt grade was, the rougher the asphalt SMM, the larger the BS number and the smaller the BS size. The SMM of SBS-modified asphalt was flatter than that of the original asphalt. After aging, the SMM of matrix asphalt became smooth, while the SMM of SBS-modified asphalt became rough. Compared to the original asphalt, the BS number and size of the aged asphalt increased and decreased, respectively.After immersion in water, the phenomenon of water piercing occurred on the asphalt surface, which further changed the SMM and BS; specifically, the roughness of the SMM increased, the BS size decreased, the BS peak increased, and the BS valley decreased. After being blended with the anti-stripping agent, the SMM of the matrix asphalts became smooth, and the SBS-modified asphalts became rough; the BS number increased, the BS size decreased, and both the BS peak and the maximum valley decreased.

A novel functional disperse dye doped with graphene oxide for improving antistatic properties of polyester fabric using one-bath dyeing method

A novel functional disperse dye doped with graphene oxide for antistatic properties of polyester fabric was achieved, which means that the dyeing and antistatic finishing can be simultaneously obtained by a one-bath method. Functional dyes were used to dye polyester fabric by a high-temperature, high-pressure dyeing method. The surface microscopic morphology of the dyed polyester fabric, and the dispersion properties of the disperse dye, graphene oxide, and the functional disperse dye, were characterized by scanning electron microscopy. The effects of the dyeing temperature on the particle sizes of three dyeing liquors were explored; this revealed that the temperature of the dyeing process had no effect on particle size. The dosage and reduction time of graphene oxide were investigated. The surface electrical resistance of the dyed fabric, 9.8 × 106 Ω, obtained at a condition of 2% (o.m.f) graphene oxide with a reduction time of 30 min, achieved A-grade antistatic standard. Furthermore, the rubbing and washing fastness of the treated fabric were 4- and 4 ∼ 5 grades, respectively. This preparation of the functional disperse dye provides a possibility in one-bath dyeing and antistatic finishing of polyester fabric.

Surface fractal dimension of bentonite affected by long-term corrosion in alkaline solution

To study the change mechanisms of the fractal dimension of bentonite affected by a corrosion process in alkaline solution, sodium bentonite was mixed with 1 mol/L NaOH solution and sealed for reaction for up to 720 d (days). The fractal dimensions of bentonite specimens at different stages of the corrosion process were obtained from N2 adsorption and swelling deformation tests, and the results of both methods suggested that the fractal dimension tends to increase with duration of the corrosion process. From X-ray diffraction (XRD) tests, it was found that montmorillonite, the main component of bentonite, was dissolved gradually in the alkaline solution. However, the decline in montmorillonite content had no relation to the change in fractal dimension, which was validated by swelling deformation tests of bentonite–quartz mixtures, as the swelling characteristics of the bentonite–quartz mixtures could be expressed by a unique curve of the em–ps relation (em is the void ratio of montmorillonite, ps is the vertical stress) with an identical fractal dimension. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images were used to observe the surface microscopic morphology of the original and alkaline-corroded bentonite. It was found that montmorillonite layers in the original bentonite were often aggregated into plate-like particles. However, after corrosion in the alkaline solution, these montmorillonite aggregates were cracked into small stacks and the surface of montmorillonite layers became more uneven, resulting in a more complicated surface and a higher fractal dimension.

Lubrication performance analysis of sealing structures in rodless open cylinders

As the lubrication performance of sealing structures in rodless open cylinders varies with sliding velocity, the concept of a critical velocity is proposed based on the aforementioned characteristics and the lubrication performance of sealing structure is analysed. A finite-element model of sealing structure is established and the oil film load under dynamic lubrication condition is obtained. A two-dimensional theoretical model of lubrication performance in sealing structure is established based on the proposed critical velocity. The influence on critical velocity of parameters including pre-compression, geometry size and microscopic morphology is analysed. Considering surface microscopic morphology, generation of heat by friction, heat flux distribution and other factors, a three-dimensional numerical model of lubrication performance of sealing structure is established to reveal the influence of texture mechanism on lubrication performance. As concluded, with the increase of pre-compression, the lip angle and the temperature of lubrication oil, the critical velocity increases. The three-dimensional microscopic morphology of seal ring is found to pose obvious influence on critical velocity, and the isotropic microscopic morphology tends to form total lubrication under the same conditions.

Fabrication of Tunable, Stable, and Predictable Superhydrophobic Coatings on Foam Ceramic Materials

Superhydrophobic foam ceramic materials can be used as distillation column internals, and surface wettability has a remarkable influence on column trays. There are no existing methods for industrial fabrication of superhydrophobic surfaces on foam ceramic materials. This paper presents a facile method for fabricating stable superhydrophobic or hydrophobic coatings on the outside and inside of foam SiC materials with submicrometer silica particles, for dip-coating, and alkylchlorosilane, for surface reaction. Scanning electron microscopy, atomic force microscopy, dynamic light scattering methods, and Fourier transform infrared spectroscopy were employed to study the physical and chemical details. The contact angle of coatings can be tuned to 155°, 140°, 125°, and 95° by adapting coating times and particle size. Superhydrophobic surfaces presented excellent stability under various conditions. In addition, a theoretical prediction strategy by surface microscopic morphology and surface chemical composition ba...

The effects of humidity on the surface modification of wool fabric through atmospheric pressure plasma jet

Current research was carried out on hydrophilic wool fibers at three different humidity conditions through atmospheric pressure plasma jet (APPJ). Samples were taken to evaluate surface microscopic morphology, surface roughness, directional friction effect (DFE), and surface chemical composition. The scanning electron microscope (SEM) and fiber friction coefficient test (FFT) results show that wetting pretreatment has significant effect on surface etching and DFE, but very limited effect on surface roughness. Allworden reaction and X-ray photoelectron spectroscopy (XPS) results reveal that extra moisture changes C, O, N, S contents and their related characteristic functional groups, therefore increases etching degree on wool fiber surface scales. It was concluded that APPJ treatment is effective in processing wool fiber with high moisture contents.

Influence of Oxidation Temperature on the High-Temperature Oxide Film Forming Behavior of T22 Heat-Exchange Tubes

In this study, without changing the whole manufacturing process of T22 coiled tubes, high-temperature oxide films are formed through atmosphere adjustment by taking advantages of the cooling process after stress elimination heat treatment. The corrosion resistance of T22 heat-exchange tubes is improved, which are used in the steam generators (SG) of high-temperature gas cooled reactors (HTR). The surface microscopic morphology of the oxide films is observed using a scanning electron microscope, and the structure of these films is characterized using an X-ray diffractometer. The stability of the high-temperature oxide film forming process is investigated using TG-DTG, as well as the thermal expansion coefficient of the films. The results prove that: (1) The oxide film generated at 550 °C is uniform and dense; (2) The oxide films formed at various holding temperatures are mainly consisted by Fe2O3 and Fe3O4. When the holding temperature is 550 °C, the content of Fe3O4 is the highest as 70.1%; (3) The films are stable when placed in inert atmosphere (N2) below 900 °C, and there is not any change in the composition and structure of the films even after reacting with steam at 550 °C for 24 h; (4) The expansion coefficient of high-temperature oxide films is very close to that of the matrix of the heat exchange tube, and the difference between these two thermal expansion coefficients is 5.3×10-9 mm/°C.

An experimental study of the wear behavior of dental feldspathic glass-ceramic and lithium disilicate glass-ceramic

To investigate the tribology characteristics of two ceramic materials in vitro:feldspathic glass-ceramic (veneer porcelain) and lithium disilicate glass-ceramic (heat-pressed ceramic), and to evaluate the wear resistance of different ceramic materials from the dynamic chewing perspective. Wear tests were performed in simulated oral environment with stainless steel ball antagonists (r = 3 mm), veneer porcelain (CERAMCO 3) and heat-pressed ceramic (IPS e.max Press HT type) in the chewing simulator. The tribological tests were carried out under artificial saliva lubrication condition in room temperature with a vertical load of 10 N for 1.2×10(6) cycles (f = 1.5 Hz, uniform circular motion, revolving speed = 90 r/min, radius = 0.5 mm). The wear volumes were measured using three-dimensional profiling, and surface microscopic morphology were observed using scanning electron microscopy at time point of 200 000, 400 000, 600 000, 800 000, 1 000 000, and 1 200 000 cycles. In a simulated oral environment, the wear rates of veneer porcelain were (0.001 20 ± 0.00 018) , (0.000 10 ± 0.000 03) , (0.000 50 ± 0.000 05), (0.000 10 ± 0.000 02) , (0.004 10 ± 0.000 38) , and (0.019 00 ± 0.003 53) (×10(-4) mm(3)/cycles) at 200 000, 400 000, 600 000, 800 000, 1 000 000, 1 200 000 cycles. The wear rates of heat-pressed ceramic were (0.139 50 ± 0.030 94), (0.124 40 ± 0.031 20), (0.054 80 ± 0.005 38), (0.038 80 ± 0.006 10), (0.011 10 ± 0.003 75), (0.198 90 ± 0.045 80) (×10(-4) mm(3)/cycles) at 200 000, 400 000, 600 000, 800 000, 1 000 000, 1 200 000 cycles. Three stages were observed in the wear loss process of the two materials: running-in stage, steady wear stage and severe wear stage. In running-in and steady wear stage, the shallow wear tracks of veneer porcelain were produced by the fatigue effect.While in severe wear stage, the wear tracks turned into ploughing. In running-in stage, the surface of heat-pressed ceramic was characterized by dense and shallow ploughing. In steady wear stage, the wear tracks turned into flake peeling produced by fatigue effect. At last, the whole layer was worn off by the effects of ploughing. In a simulated oral environment, the wear rate and wear loss of heat-pressed ceramic are greater than that of veneer porcelain.

Smelting of Al-Li Alloy Containing High Li by Micro-Gravity Electromagnetic Force Simulation Facilities and Texture Study

The electromagnetic micro-gravity simulation smelting is a new preparation technology of Al-Li alloy containing high Li. In the aluminum lithium binary system, based the principle of electromagnetic force applied on the metal alloy melt, the Al-Li alloy was smelt and cast at 0.5T and 800°C with home-made apparatus. Through composition analysis by means of XPS, surface microscopic morphology with SEM and density measurement, the results show that the low density, 10wt% of Li in Al, homogeneous lithium distribution and compact and uniform and compact microstructure Al-Li alloy can prepared by using the technique of electromagnetic simulating micro-gravity method.