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In this paper, three CrNiV series low-alloy steel with different C contents were fabricated by laser melting deposition (LMD) technique. Subsequently, the formability, microstructure and properties of LMD CxCrNiV low-alloy steel were evaluated. The results are as follows: with the increase in C content, the formability of low-alloy steel has decreased. All the samples were mainly composed of α-Fe (martensite) phase, and carbides were found to be dispersively distributed in the microstructure. As the C content increased, the martensite lath was remarkably refined, and the average grain size decreased from 2.76 to 2.33 μm. The tensile strength of the deposited samples increased by 21.58%, and the yield strength increased by 44.68%. As the formability of the deposited sample decreased, the elongation decreased by 35.93%. The average microhardness of deposited samples increased by 26.76%. When the content of C is higher, abrasion-resistant framework can be formed between carbides, and the peeling phenomenon during wear will be greatly reduced, the wear resistance is improved by 86.78%.

Two typical coatings (nickel-based and iron-based) were successfully fabricated on AISI 304 stainless steel via cold metal transfer process as alternative materials with superior wear and cavitation erosion resistance, respectively. Scanning electron microscopy, X-ray diffraction and electron backscattering diffraction were performed to characterize the morphologies, phase composition and crystallographic textures. Subsequently, tribology, cavitation erosion as well as corrosion tests were carried out to analyze the applicability of the coatings in various environments. Experimental results showed that the coatings exhibited few defects and an excellent metallurgical bonding with the substrate, and possessed the strong textural features. The microhardness of the coatings was ∼ 3 times higher than that of the substrate, and the microhardness of nickel-based coating was more stable than that of the iron-based one. Combining with the cumulative volume/weight loss and morphologies, the wear and cavitation erosion resistance of the coatings and substrate were compared, and failure mechanisms were proposed. It was found that the cumulative volume/weight loss of the coatings are one order of magnitude lower than that of the substrate. The combination of toughness and fine dispersed carbides had guaranteed the higher wear resistance of iron-based coating, while the formed massive phases of nickel-based coating played a significant role in the cavitation erosion and corrosion resistance.

The effect of tempering (673 K for 30 min) on the microstructure and tensile properties of laser melt-deposited (LMD) 12CrNi2 low-alloy steel is studied. The results show that LMD 12CrNi2 mainly consists of the ferrite and some Cr23C6 carbides. Characterization of the Schmid factor near the fracture surface shows that after tempering, the slip system with the largest Schmid factor is still {123} , but the Schmid factor of {100} and {112} slip systems increases. Tempering increases the elongation from 6.97 to 11.49% and the tensile strength from 849 to 951 MPa. Tempering increases the average distribution of misorientation between crystals after tensile test, which improves the average dislocation density and promotes strengthening.

The study investigated novel wear and corrosion resistance of stainless steel and 316 stainless steel samples which were successfully prepared by laser melting deposition. Phase composition, microstructure, microhardness, wear resistance, and electrochemical corrosion resistance were studied. The experimental results showed that novel stainless steel was mainly composed of a-Fe and a few carbide phase (Cr, Fe)7C3. The microhardness of novel stainless steel was about 2.7 times greater than 316 stainless steel. Meanwhile, the specific wear rate of novel stainless steel and 316 stainless steel was 2.63 × 10-5 mm3/N m and 1.63 × 10-4 mm3/N m, respectively. The wear volume of 316 stainless steel was 6.19 times greater than novel stainless steel. The corrosion current and the corrosion potential of novel stainless steel and 316 stainless steel were 1.02 × 10-7 A/cm2 and 1.5 × 10-7 A/cm2, and -138.8 mV, -135.9 mV, respectively, in 3.5 wt% NaCl solution. Therefore, both microhardness and wear resistance of novel stainless steel were greatly improved, with high corrosion resistance.

Large-scale NaA zeolite membranes in a length of 1000 mm were successfully synthesized for the first time on macroporous tubular stainless steel (MTSS) supports in this work. The influencing factors for membrane synthesis, such as pre-treatment, synthesis time, synthesis temperature, Na2O/SiO2 ratio, synthesis reproducibility, membrane stability and support reusability, were investigated systematically. The experimental results revealed that the high-flux NaA membranes prepared on the reusable MTSS supports exhibits a high total flux of 8.28 kg m−2 h−1 and a separation factor of 11,000 for the dehydration of a 90 wt% ethanol solution through pervaporation. The MTSS tubes can be used for at least 8 synthesis-rinse-synthesis circles, and the as-synthesized membranes still maintain high competitive pervaporation performance. Additionally, 93 pieces of membrane samples were assembled in an industrial plant that can produce approximate 99.8 wt% ethanol from 93 wt% ethanol mixtures with a product flow rate of about 60 kg h−1. Importantly, the membrane showed a high stability for running over a whole month, demonstrating that the MTSS-supported membranes have reliable stability for industrial applications.

Three various 12CrNi2 alloy steels were successfully fabricated on 35CrMo alloy steel by laser melting deposition with the aim of investigating the effect of powder oxygen content on formability of...

In this study, microstructural features of 24CrNiMo low alloy steel fabricated by selective laser melting (SLM) and laser melting deposition (LMD) were characterized and compared using advanced electron microscopy and electron backscatter diffraction techniques. The results showed that the microstructures with different microstructure types, crystallographic orientations, grain boundaries, grain sizes, dislocations distributions and slip capabilities were observed due to rather different thermal histories between SLM and LMD processes. Such differences in the microstructure can definitely lead to different mechanical properties. This work can provide a reference for the process choice based on practical industrial applications.

Grid harmonics generated additional loss in the transformer, which would lead the transformer winding to overheat. The influence of harmonics on the temperature field of transformer was observed by considering harmonic loss in the transformer flow-heat coupling calculation. This paper took the hysteresis loss, eddy current loss and winding harmonic loss under the influence of harmonics into consideration. The transformer loss calculation formula was derived. Therefore, the temperature distribution of transformer under harmonic condition was obtained through flow-thermal coupling calculation. The hot spot temperature was 73.4°C, which was within safe range. The calculation results of the fluid field showed that the asymmetric structure of the transformer lead to the asymmetry of the heat dissipation path of the oil flow, which brought about the asymmetry of the final temperature distribution result. This paper improved the flow-thermal coupling calculation method because of considering harmonic loss, which provided a reference for improving the calculation accuracy in running transformer.

In this work, a quasi-continuous ratio gradient alloy steel with a 24CrNiMo matrix for high-speed railway brake discs is prepared by selective laser melting (SLM). The composition of sample is x% 24CrNiMo + (1-x)% wear-resistant stainless steel (x is 100, 65, 35 and 0). The relationship between the microstructure and wear resistance of the samples is thoroughly investigated by electron back-scatter diffraction (EBSD) and friction-wear tester. The results show that the grains of samples prepared by SLM can be roughly divided into three types, which correspond to different wear mechanisms according to their growth characteristics. When x is 0, the sample has the finest grains, the smallest Schmidt factor value, the maximum content of low-angle grain boundaries and strengthening phase, corresponding to the optimum wear rate and coefficient of friction (COF) of 7.46 × 10−5 mm3/N m and 0.31, respectively and the wear rate is about 34.8% of the matrix. A micro-wear mechanism analysis model is established to display the micro wear process of SLM samples.

24CrNiMo low alloy steels were fabricated by selective laser melting (SLM), aiming at investigating the effect of volumetric energy density (η) on the densification behavior and microstructural evolution, and then establishing a rational densification-microstructure-microhardness relationship of as-built samples. The results showed that the densification level of the as-built samples was significantly improved with increasing the η, due to the inhibition of balling effects and internal pores. As-built samples mainly exhibited α-Fe (M) and Fe3C, and the diffraction angles of the main phase α-Fe (M) peaks slightly shifted to the left in comparison with their standard locations due to the lattice distortion. The microstructure of the as-built samples mainly composed of high-containing martensite (M) and low-containing lower bainite (LB), resulting from the rapid solidification and the heat accumulation. As the η increased, the size and number of LB gradually increased owing to the relatively decrease of cooling rate. EBSD maps depicted that the grain size of the as-built samples increased with the increase of η. The microhardness of the as-built samples exhibited an upward trend with the η increasing, implying that compared to the grain size, the internal defects played a dominant role in determining the hardness. The solid solution strengthening, dislocation strengthening and precipitate strengthening resulting from M/LB duplex microstructure resulted in the achieved high hardness, under the premise of ensuring relative density.

In this study, the impact of stress-relief heat treatment on the microstructure and fatigue property of a laser melting deposited (LMD) 12CrNi2 low alloy steel was analyzed. Microstructural evolution of processed LMD 12CrNi2 steel by heat treatment was studied using electron backscatter diffraction (EBSD) and X-ray diffraction (XRD), aiming to establish a rational microstructure-fatigue property relationship. The results showed that the main phase of the samples before and after heat treatment was α-Fe phase, whereas the lattice parameter slightly decreased after annealing, as a result of stress relief and carbide formation in the heat-treated samples. Meanwhile, the increase of the hard and diffusely distributed carbides inside the matrix was the main contributor for the higher material strength. Based on the EBSD analysis, the heat treatment decreased grain boundary misorientation leading to a corresponding reduction in the dislocation density, and increased the content of high-angle grain boundaries (HAGBs) promoting the toughness of the material. Furthermore, Schmid factor results revealed that the heat-treated samples exhibited a relatively high ductility resulting from the activation for more slip systems during the cyclic deformation. The stress-relief heat treatment significantly improved the fatigue performance of samples, which was attributed to the enhanced strength and ductility owing to the related microstructure change and the relief of residual stresses.

Laser additive manufactured (LAM) components usually have non-equilibrium microstructures which leads to their high discreteness. The specimens were deposited in argon atmosphere and subsequent heat treatment are recommended for LAM components to achieve homogenous microstructures. In this paper, four different heat treatment procedures were designed, the microstructures evolution and mechanical properties of 12CrNi2V low alloy steel prepared by laser melting deposition (LMD) after different heat treatment were thoroughly studied. According to the EBSD analysis, the types and quantities of high-angle grain boundaries (HAGBs) in the tempered specimens were significantly higher than deposited specimen. The residual austenite (RA) content in the tempered specimen was about 280% higher than deposited specimen. The composition segregation and orientation gradient in the tempered specimens were significantly reduced, and the Schmidt factor value increased. The results of the experiment showed that when the tempering temperature was 620 °C, the specimens had the highest micro-hardness (383 HV) and tensile properties (966 MPa, 14.37%), and its elongation was about 150% higher than deposited specimen. This study provided an experimental and theoretical basis for the development of the subsequent heat treatment process for low alloy steel laser additive manufacturing.

In this paper, 24CrNiMo alloy steel samples under different process parameters were fabricated by selective laser melting technology with an orthogonal experiment in argon atmosphere. The results under the present experimental conditions showed that the formability of 24CrNiMo alloy steel samples was improved significantly as the laser energy density increased in a proper range. The most dense sample was selected for further observation. It was found that the sample was composed of quenched martensite laths, tempered martensite laths and lower bainite with upper bainite ferrite along the building direction. Through further transmission electron microscopy observation, different types of precipitated phases were also found. Electron backscatter diffraction analysis showed that the crystals in the manufacturing process were isotropic with no preferred crystallographic orientation, and the grain size were smaller than 0.5 μm. The distribution of grain boundaries indicated that large proportion of low-grain boundaries occupied the sample, which elevated the grain boundary strengthening effect.

In this research, 12CrNi2 low alloy steel was successfully prepared by laser melting deposition (LMD). The mechanisms driving high cycle fatigue fracture of the as-built LMD 12CrNi2 low alloy steel were investigated and a concurrent process-microstructure-property relationship was established through microstructural analysis. The results showed that the crystal structures of the as-built LMD 12CrNi2 steel mainly consisted of the ferrite and a small amount of Cr23C6 carbides. No preferred texture was observed as a result of the complicated heat flux direction during fabrication. Based on the examination of the fracture surface, fatigue cracks of the as-built LMD 12CrNi2 steel initiated from subsurface defects for all the cases. Crack propagation zones showed a mixed mode of transgranular and intergranular fracture in a brittle manner, whereas the final fracture zones displayed dimples typical of ductile fracture. The kernel average misorientation (KAM) map indicated that the strain localization predominantly occurred at the grain boundaries and slightly appeared at the interior of the ferrite grains. Schmid factor distribution results implied that fatigue cracks originated from grains with {123} slip system due to the prior activation of {123} slip system.

The chemical oxygen demand was over standard seriously due to residual organic additives in sulfonated drilling wastewater, especially sulfonated phenolic resin with hardly degradable chemical structure. The novel solar-assisted catalytic oxidation process was developed to remove the organic pollutants in sulfonated drilling wastewater. The factors including irradiation light source, oxidant, Fe2+, were investigated. The results showed that, solar has more catalytic effects than UV on H2O2-K2S2O8/Fe2+system, H2O2- K2S2O8/Fe2+system was more effective in degrading organic pollutants than H2O2/Fe2+and K2S2O8/Fe2+, in which the synergies occurred between H2O2and K2S2O8in the solar-assisted catalytic oxidation process. The removal amount of organic pollutants was increased with the dosage of Fe2+additon. With the catalytic oxidation process developed, the COD was reduced to 114.4 mg·L-1. Meanwhile, the sulfonated phenolic resin was completely destroyed, and heavy metal was decreased significantly.

This study confirms the existence of several-nanometer ordered structures in amorphous geopolymers by HRTEM and SAED. To obtain low-ratio Si/Al geopolymers and to overcome the disadvantages posed by the use of impure raw materials, an amorphous Al2O3–SiO2 powder is first prepared using a sol–gel method in accordance with specific chemical compositions. The composition of the Al2O3–2SiO2–Na2O geopolymer is designed according to the NaA zeolite composition (Si/Al/Na atom ratio is 1:1:1), and the expected NaA zeolites are obtained from the Al2O3–2SiO2–Na2O geopolymer using a hydrothermal reaction. This process can be used to transform geopolymers into zeolites and provides a new preparation method for the self-supporting NaA zeolite membrane. The preliminary separation resulted in alcohol dehydration and shows that ethanol solutions can be powerfully dehydrated by pervaporation. A feed containing 90 wt.% ethanol at 20 °C and achieving a water flux of 2.67 kg m−2 h−1 with a separation factor H2O/EtOH ≈ 200 is found.

We report a porous geopolymer synthesized from metakaolin, α-Al 2 O 3, Al powder and phosphoric acid at 80 °C for 5 h. The Al powder served as a foaming agent to control porosity, pore size and pore distribution producing a porosity ranging from 40% to 83% and a pore size of approximately 1 mm .The compressive strength was > 6 MPa. The phases of the geopolymers were determined by X-ray diffraction and their thermal properties investigated by TG-DTA and thermal shrinkage analysis. The porous geopolymer consisted of an amorphous phase and minor amounts of quartz, and showed an excellent thermal stability at a high temperature, with a linear shrinkage of only 5.3% at 1450 °C.

The combined de-inking technology of ultrasonic, UV irradiation and enzymatic methods was introduced into the de-inking process of HP laser printed paper. The purpose was to reduce the consumption of alkali or even preprocess without alkali absolutely for the purpose of environment protection. The de-inking effects of cellulase, amylase, lipase and their mixture were compared and the experiment results showed that combined enzymes of cellulase and amylase have the best de-inking efficiency which has a 12% increment of brightness. The de-inking efficiencies of several different de-inking technologies were compared, which can provide basis to establish combined de-inking technologies.

A commercial styrene-acrylic latex binder has been investigated as a good binder for aqueous Al2O3 suspensions tape-casting process. This paper focuses on the forming film mechanism of latex binder, the rheological behaviors of the suspensions, physical properties of green tapes and drying process of aqueous slurries with latex binder system. The drying process of the alumina suspensions is shown to follow a two-stage mechanism (the first stage: evoporation controlled process; and the second stage: diffusion controlled process). During the drying stage of the suspensions, the compressive force presses the latex particles and makes them be distorted, which results in cross-linking structure in contacted latex particles of the solidified tapes. A smooth-surface and high-strength green tape was fabricated by aqueous tape casting with latex binder system. The results from the SEM images of the crossing section microstructure of green tapes show that the latex is a very suitable binder for aqueous tape casting.

This study confirms the existence of several nanometer-ordered structures in amorphous AI2O3-2SiO2-Na2O-7H2O geopolymers by high-resolution transmission electron microscopy and selected area electron diffraction. The composition ratio of the geopolymers was designed according to the NaA zeolite composition (Si/AI/Na atom ratio of 1:1:1), and the expected NaA molecular sieve was achieved by the Al2O3-2Si02-Na20-7H20 geopolymers through a hydrothermal reaction. This design concept was used to convert geopolymers into zeolite molecular sieves and provides a new preparation method for zeolite membranes or zeolite bulk materials.

In this paper, we describe the behavior of impurity transport in the HL-2A electron cyclotron resonance heating (ECRH) L-mode plasma. The neon as a trace impurity is injected by the supersonic molecular beam injection (SMBI) technique, which is used for the first time to study the impurity transport in HL-2A. The progression of neon ions is monitored by the soft X-ray camera and bolometer arrays with good temporal and spatial resolutions. The convection and diffusion process of the neon ions are investigated with the one-dimensional impurity transport code STRAHL. The results show that the diffusion coefficient D of neon ions is a factor of four larger than the neoclassical value in the central region. The value of D is larger in the outer region of the plasma (ρ > 0.6) than in the central region of the plasma (ρ < 0.6). The convective velocity directs inwards with a value of ~ −1.0 m/s in the Ohmic discharge, but it reverses to direct outwards with a value of ~ 8.0 m/s in the outer region of the plasma when ECRH is applied. The result indicates that the impurity transport is strongly enhanced with ECRH.

A conceptual design study of the HL-2M facility has shown that one can create not only a standard single-null divertor configuration on it, but also a second-order null (snowflake (SF)) configuration. For the SF divertor, the magnetic flux expansion closes to the separatrix and exceeds that of the standard configuration by more than a factor of 4 at the outer divertor. The heat load at the divertor targets of this innovative configuration has been investigated by using B2.5-Eirene. It is shown that the heat load it targets is different from that of the standard configuration. As a result of the magnetic flux expansion, the peak heat load reduces and does not concentrate on a small area near the separatrix. The heat load profile becomes flat as compared to the standard divertor. When the upstream density is 2.0 × 1019/m3 with 10 MW heating power flowing into the SOL/divertor regions, the peak load at the outer divertor is 1.64 MW/m2 for the SF divertor, but it is 3.2 MW/m2 for the standard divertor, so the SF divertor can mitigate the heat load at the divertor targets when HL-2M operates at low plasma density and high heating power.