Search

To avoid the influence of fluorine on the extraction of beryllium, separating fluorine from high-fluorine beryllium ore was discussed in this study. The factors affecting on fluorine removal, such as roasting temperature, roasting time, dosage of the additive in roasting process, and the variety and concentration of acid in the leaching process, were separately investigated. The intermediates and final products were identified by XRD. Under the following roasting and leaching conditions: heating temperature 800 °C, treatment time 120 min, additive dosage of Na 2 CO 3 by 60% weight, leaching by distilled water at 50 °C for 30 min and acid (1.7 mol/L HNO 3 ) at 60 °C for 60 min, the percentage of fluorine and beryllium oxide was 1.6%; heating temperature 800 °C, treatment time 180 min, additive dosage of Na 3 PO 4 by 50% weight, leaching by distilled water at 50 °C for 30 min and acid (1.7 mol/L HNO 3 ) at 60 °C for 60 min, the percentage of fluorine and beryllium oxide was 7.12%. Both of the results with additive Na 2 CO 3 and Na 3 PO 4 can meet the requirement of the industrial production of beryllium after the pretreatment, while Na 2 CO 3 is more efficient. Results also indicated that nitric acid was more reactive than sulfuric acid. [ABSTRACT FROM AUTHOR]

The conventional pyrometallurgical method for separating lead–antimony alloy produced from jamesonite has a lot of imperfections such as long-term process, tremendous energy cost and harm to the environment. Therefore, a new method to separate lead and antimony from lead–antimony alloy by fractional crystallization is investigated. The experimental results demonstrate that the lead content decreases with the increase of length to the metal column’s bottom. Lead content of the bottom can reach larger than 80% by weight after lifting. In the experimental speed range, the lifting speed has very small impact on the separation effect. After 4 times’ lifting, crude lead bullion (larger than 83% by weight) whose lead content is close to the eutectic point of lead–antimony binary system is gained in the bottom and the antimony can be used for further refining process without converting into Sb 2 O 3 . The separating efficiency of lead in the bottom has reached the theoretical level of fractional crystallization for lead–antimony alloy containing about 40% by weight antimony. [ABSTRACT FROM AUTHOR]

Vacuum co-pyrolysis of Chinese fir sawdust (CFS) and waste printed circuit boards (WPCBs) at different heating conditions were examined in this paper. The composition of the pyrolysis oils was analyzed by gas chromatography–mass spectrometry (GC–MS). It was found that the content of most of the compounds with relatively long molecular chain had a higher value at relatively low temperature (400–600 °C) and short holding time (10 min), and decreased at relatively high temperature (800 °C) and long holding time (30–90 min); while the content of most of the compounds with relatively short molecular chain presented an adverse trend. The co-pyrolysis process was also analyzed by thermogravimetric (TG) analysis with evolved product analysis by Fourier transform infrared (FTIR) spectroscopy. The results showed that the volatiles were mainly generated between 300 and 500 °C, and after 500 °C, noncondensable gases (CO 2 , CO and CH 4 ) were the main components in the pyrolysis process. [ABSTRACT FROM AUTHOR]

Highlights: [•] Co-pyrolysis process presents antagonistic effect in the yields of the volatiles. [•] Co-pyrolysis process is good for the formation of brominated aromatic compounds. [•] The volatiles were mainly formed between 300 and 450°C in the pyrolysis process. [•] Noncondensable gases (CO2, CO, CH4, etc.) were the main components after 450°C. [•] Co-pyrolysis oils show better synthetic properties than the separate ones. [ABSTRACT FROM AUTHOR]

Abstract: Activated carbons with high surface area, large pore volume, and high mesoporosity were prepared from herb residues. The raw material was treated by 0.5M NaOH solution and activated under vacuum using ZnCl2 as the activation agent. Four activated carbons obtained under different preparation conditions were compared in detail. It was found that both the vacuum condition and base-leaching process have positive effects on the specific surface area and mesopore structure characteristics. The Brunauer–Emmett–Teller (BET) surface area and total pore volume of the activated carbon obtained by combining vacuum condition and base-leaching method have increased by 125.3% and 64.9% respectively comparing with those of activated carbon prepared under atmosphere without base-leaching. With an activation temperature of 450°C and an impregnation ratio of 2.5, activated carbon with a BET surface area of 1952m2/g, a total pore volume of 1.479cm3/g, and a mesoporosity of 98.0% was obtained. The thermal decomposition properties of raw materials and activated carbons were studied. Furthermore, the effects of preparation parameters such as activation temperature and impregnation ratio on the properties of activated carbons were investigated. The scanning electron microscopy images of the activated carbon showed a porous structure. [Copyright &y& Elsevier]

Abstract: Activated carbons were prepared from walnut shells by vacuum chemical activation with zinc chloride as the activation agent. To optimize the preparation method, the effects of the main process parameters (such as system pressure, activation temperature, and impregnation ratio) on the properties (expressed in terms of specific surface area and pore volume) of the obtained activated carbons were studied. It was found that the optimum activated carbon obtained with system pressure of 30kPa, activation temperature of 450°C, and impregnation ratio of 2.0 has a BET surface area of 1800m2/g and total pore volume of 1.176cm3/g. The prepared activated carbons were characterized by SEM, TEM, and FTIR. Then they were used as an adsorbent for the removal of methylene blue from aqueous solutions. The results showed that the methylene blue adsorption capacity was positively correlated to the BET surface area. The highest methylene blue adsorption capacity was 315mg/g for the optimum activated carbon. The effect of the dose of the activated carbon was evaluated and the adsorption isotherm of methylene blue was determined. Redlich–Peterson and Langmuir–Freundlich models were found to best represent the equilibrium data, suggesting heterogeneous surface adsorption of methylene blue on the activated carbon. [Copyright &y& Elsevier]

Post-bond heat treatment (PBHT) is an effective way to improve the bonding quality of a brazed joint. Herein, brazing of a nickel-based single crystal superalloy is carried out using a Ni-Cr-Co-B-Si-Al-Ti-W-Mo filler alloy, and the microstructure and creep property of the brazed joint are systematically investigated using scanning electron microscopy (SEM), Thermo-Calc software, an electron probe micro-analyzer (EPMA), X-ray diffractometer, confocal scanning laser microscope (CSLM), and transmission electron microscopy (TEM). The results reveal that the as-prepared joint only consists of an isothermally solidified zone (ISZ) and an athermally solidified zone (ASZ), where the cubic γ′ phase is observed in the ISZ, and skeleton-like M3B2, γ + γ′ eutectic and reticular G phases are observed in the ASZ. Furthermore, the γ + γ′ eutectic and G phases disappear and the M3B2 alters from a skeleton-like to block-like shape in the ASZ after PBHT. Meanwhile, some lath-like M3B2 phases are precipitated at the edge of the ISZ and several M3B2 phases are precipitated in the base metal, forming a new zone in the brazed joint, namely at the diffusion affected zone (DAZ). Owing to the removal of low melting point eutectics from the as-prepared joint, the creep life also increases from 188 h to 243 h after PBHT. The current work provides a method for the optimization of brazed joints based on the Ni-based single crystal superalloy. [ABSTRACT FROM AUTHOR]

The effect of doping ceramic reinforcing particles during the fabrication of amorphous alloy coatings by laser cladding technology has rarely been investigated. A crack-free Fe-based amorphous/crystalline composite coating with good tribological properties was prepared on the surface of 40Cr steel by changing the content of WC–14Co addition during laser cladding. As the content of WC–14Co particles increases, cracks in the coating are first suppressed until gradually disappearing and then re-forming, reaching a crack-free state at 5 wt% addition. SEM, TEM and EBSD results showed that the incorporation of WC–14Co successfully introduced fine WC particles into the coating structure and refined the microstructure of the coating. The Vickers hardness of the coating is 937.7 Hv, and the wear loss of the coating was 1.1 × 10–2 mm3 at a load of 30 N, a friction counterpart of Al2O3, and a sliding speed of 9 mm/s for 1.5 h. The crack-free and good tribological properties of the coating were mainly attribute to the uniform and diffuse distribution of WC, which inhibits the directional growth of columnar crystals at the coating–substrate interface and promotes the refinement of the crystal structure. [ABSTRACT FROM AUTHOR]

In order to gain insight into how the addition of Cu element affects the crystallization mechanism of amorphous nanocrystalline alloys and soft magnetic properties, the crystallization behavior of (Fe 0.83 B 0.11 Si 0.02 P 0.03 C 0.01) 100-x Cu x (x = 0 and 0.5) amorphous ribbons was investigated based on kinetic and thermodynamic behavior under non-isothermal and isothermal annealing conditions. The results show that under non-isothermal annealing conditions, the Cu0.5 amorphous ribbon not only favors the formation of the amorphous structure, but also enlarges the temperature window for annealing and improves the thermal stability of the α-Fe(Si) phase. At the same time, the Cu0.5 amorphous ribbon shows slow kinetic and is insensitive to heating rate change during annealing treatment. Under isothermal conditions, the addition of Cu decreases the nucleation activation energy (E n) and increases the growth activation energy (E g). This further indicates that the nucleation of α-Fe(Si) grains is easier than the growth process, which is conducive to the formation of a homogeneous nanostructure and improves the soft magnetic properties of the alloy. Compared to Cu0 amorphous ribbon, it is also shown that the Cu0.5 amorphous ribbon changes the crystallization mechanism from diffusion-controlled one-dimensional to two-dimensional growth when the crystallization volume fraction x is 10–30 vol%. While three-dimensional growth become dominated when x is reaches 60 vol% for both ribbons. Therefore, the kinetics of crystallization as well as microstructure supports that the Cu0.5 ribbon is able to exhibit uniformly fine nanocrystalline structures. Further, the Cu0.5 nanocrystalline ribbon shows a higher B s of 1.85 T and a lower H c of 2.55 A/m, respectively, and the favorable (100) orientation of α-Fe(Si) grains formed after annealing is another factor to increase B s. • The Cu-containing alloy show kinetic insensitivity and is suitable for a high heating rate. • The addition of Cu changes the crystallization mechanism when x is between 10% and 30%. • When the applied magnetic field is ND, precipitation of (100) orientation α-Fe grains favors enhancing B s. • The Cu0.5 alloy show B s of 1.85 T, H c of 2.55 A/m. [ABSTRACT FROM AUTHOR]

Sn60Pb40 alloy powders were fabricated using the planar flow casting (PFC) atomization process. By using OM, SEM and EPMA, the characteristics of the morphologies and microstructures of the powders have been investigated. It is observed that the environment of ambient gas in the atomization box has great effects on the morphology of the alloy powders. The microstructures of Sn60Pb40 alloy powders produced by the PFC atomization process are completely composed of eutectic, which is made up of both oversaturated α solid solution and β solid solution. The microstructures of small size powders are extraordinarily undeveloped dendritic eutectic, in which the large majority of the α phase appears nearly spherical, evidently since the cooling rate is higher and the under-cooling is larger. As for the large size powders, since the cooling rate and undercooling are relatively low, lamellar α phase apparently increases in the eutectic microstructures of these powders, and there is even typical lamellar eutectic structure clearly observed in some micro-areas. After remelting tests by DTA, the microstructures of small size powders are transformed, which become composed of large crumby α phase and eutectic (α+β), while those of large size powders change into classical tin-lead structures of primary α phase plus lamellar eutectic (α+β). By studying the microstructures of tin-lead alloy powders, a model has been proposed to predict the microstructure formation of Sn60Pb40 alloy powders. [ABSTRACT FROM AUTHOR]

The effects of Ni content on the phase constituent, mechanical properties and damping capacity of the AlCrFe 2 Ni x (x = 1.0, 1.5, 1.7, 2.1, 2.2 and 2.3) medium entropy alloys (MEAs) were studied. When x = 2.1, the microstructure of the MEA consists of BCC phase as the matrix and FCC phase as the second phase with the corresponding volume fractions of 87.7, 12.3 vol%, respectively. The combination of hard BCC matrix and soft FCC secondary phase, especially, the BCC phase is isolated by the circular FCC phase, results in a very high damping capacity up to 0.06936 for the AlCrFe 2 Ni 2.1 MEA at the corresponding strain amplitude of 2.55 × 10−4. Both the BCC matrix and the peculiar microstructure play a key role in increasing the damping capacity of the AlCrFe 2 Ni 2.1 MEA. Excellent damping performance and comprehensive tensile properties of AlCrFe 2 Ni 2.1 MEA indicate that it has potential applications as the candidate of damping materials. • The increase of Ni molar ratio of AlCrFe 2 Ni x medium entropy alloys (MEAs) promotes the phase transition tendency from BCC to FCC. • AlCrFe 2 Ni 2.1 MEAs consisted of BCC phase as matrix and FCC phase as secondary phase have outstanding damping capacity. • A circular FCC phase, similar to the grain boundary, is distributed on the BCC matrix of AlCrFe 2 Ni 2.1 medium entropy alloy. • AlCrFe 2 Ni 2.1 MEAs exhibit excellent strength and suitable plastic strain when BCC phase is dominated as the matrix. [ABSTRACT FROM AUTHOR]

The effect of 1 at. % Cu addition and annealing temperatures on the soft magnetic properties of Fe81B13P3Si2C1 amorphous ribbons was investigated in this paper. The results show that both Fe81B13P3Si2C1 and (Fe81B13P3Si2C1)0.99Cu1 amorphous/nanocrystalline alloys possess excellent soft magnetic properties. Minor Cu addition can enlarge the temperature interval between first and second crystalline temperatures from 48 K to 112 K, enlarging the processing window and increasing the thermal stability of the amorphous alloy. The annealed Fe81B13P3Si2C1 amorphous/nanocrystalline alloy exhibits saturation flux densities (Bs) on the order of 1.69 T and coercivities (Hc) of 14.6 A/m, and the annealed (Fe81B13P3Si2C1)0.99Cu1 alloy shows a high Bs value of up to 1.92 T and Hc of 11.6 A/m. The soft magnetic properties were discussed in terms of microstructure and magnetic domain observation. [ABSTRACT FROM AUTHOR]

By using Zr41.2Ti13.8Ni10Cu12.5Be22.5 (Vit1) bulk metallic glass with a defined cooling history, the heat capacity (Cp) of liquid and glass, and the calorimetric glass transition in differential scanning calorimetry experiments were investigated. Then, a thermal equilibrium model related to the melting and solidifying process was established to extrapolate the solidification glass transition (SGT) temperature range during liquid to glassy solid phase transformation. By using the extrapolated SGT temperature range, the thermodynamic parameters, including the Cp and thermal conductivity (λ), were adjusted, which can make the simulated cooling temperature curves accurately reflect the recorded ones. The coincidence of experimental and simulation results indicates the rationality of the thermal equilibrium model established in the present work. Furthermore, it is proposed that the SGT is resulted from the falling out-of-equilibrium of the undercooled liquid metal that acts as an endothermic trap to suppress the occurrence of recalescence. [ABSTRACT FROM AUTHOR]

A fabrication method comprising near‐field holography (NFH) with an electron beam lithography (EBL)‐written phase mask was developed to fabricate soft X‐ray varied‐line‐spacing gratings (VLSGs). An EBL‐written phase mask with an area of 52 mm × 30 mm and a central line density greater than 3000 lines mm−1 was used. The introduction of the EBL‐written phase mask substantially simplified the NFH optics for pattern transfer. The characterization of the groove density distribution and diffraction efficiency of the fabricated VLSGs indicates that the EBL–NFH method is feasible and promising for achieving high‐accuracy groove density distributions with corresponding image properties. Vertical stray light is suppressed in the soft X‐ray spectral range. [ABSTRACT FROM AUTHOR]

The effect of P on the glass forming ability, soft magnetic properties and oxidation behavior of Fe 78 B 13 Si 9- x P x ( x = 0–7) amorphous alloys were investigated. It is found that the proper introduction of P, can effectively improve the glass forming ability and stability of supercooled liquid region. Fe 78 Si 4 B 13 P 5 BMG, which exhibits high saturation flux density of 1.56 T, was readily made into rod sample with a diameter of 1.5 mm under air casting atmosphere. P bearing alloys also exhibit excellent soft magnetic properties containing low coercivity of 1.7–2.7 A/m, and high effective permeability of 8200–12,200. Slight oxidation can further improve the coercivity to a lower value of 1.1 A/m and the higher effective permeability to 11,900 for the alloys with P content no more than 3 at. %. Excessive addition of P may deteriorate the glass forming ability, soft magnetic properties and oxidation behavior. Magnetic domain revealing the magnetization process of the amorphous ribbons were characterized to explain the effect of P on magnetic properties and oxidation behavior. [ABSTRACT FROM AUTHOR]

Effects of Fe content on magnetic properties and bending ductility of FeSiBPC amorphous alloy ribbons before and after annealing were systematically investigated. It was found that all alloys had high amorphous forming ability and good soft magnetic properties after annealing. The transition temperature of bending ductility-brittleness decreases much faster than that of soft magnetic properties with the increase of Fe content. It is interesting that alloys with Fe content higher than 80 at.% exhibit good ductility before and after annealing at the optimal condition. The alloy with Fe content of 71 at.% is brittle even at as-spun state. The saturation flux density ( B s ) and coercivity ( H c ) decrease with decrease of the Fe content and deviate from a linear fitting tendency. The temperature asynchronism between magnetic properties and bending ductility of amorphous alloy ribbons was discussed. This work will bring a new perspective to study the annealing induced brittleness and a guidance for the future development of the amorphous alloys. [ABSTRACT FROM AUTHOR]

In the present investigation, the glass forming ability (GFA), thermal stability, and soft magnetic properties of Fe 85 Si 6- x B 8 Cu 1 C x alloys are investigated by the substitution of C for Si. It was found that the GFA of C-containing alloys is remarkably enhanced when a certain amount of Si is replaced by C in a C-free alloy. The temperature interval between the first and second crystallization temperatures is also improved by C addition and reaches a maximum value of 169 °C for the as-spun Fe 85 Si 2 B 8 Cu 1 C 4 amorphous alloy. The Fe 85 Si 4 B 8 Cu 1 C 2 nanocrystalline alloy exhibits the best soft magnetic properties with the highest saturation magnetic flux density (B s) of 1.95 T and the lowest coercivity (H c) of 4.1 A/m, which corresponds to the highest grain number density (N d). The high GFA, large annealing window, low cost, and excellent soft magnetic properties enable the Fe 85 Si 2 B 8 Cu 1 C 4 nanocrystalline alloy as a material with wide applicability. Moreover, this work is highly beneficial in balancing the relationship between a high B s and sufficient GFA in the production of Fe-rich nanocrystalline alloys. • Adding C to Fe-Si-B-C-Cu alloys can improve both the GFA and thermal stability of the as-spun amorphous alloy ribbons. • Addition of appropriate amount of C to Fe-Si-B-C-Cu amorphous alloys can enhance their soft magnetic properties. • As-annealed Fe 85 Si 4 B 8 Cu 1 C 2 alloy exhibits a high B s of 1.95 T and low H c of 4.1 A/m. [ABSTRACT FROM AUTHOR]

Compared with the conventional casting process, digital pattern-less casting technology has many advantages such as good machining accuracy, a short processing cycle, and low production cost. It is a new rapid manufacturing technology for castings, integrated with CAD/CAM, casting, CNC machining and many other advanced technologies. With this digital casting technology, no pattern is needed for making molds; it is precise, flexible, and green. Usually, art castings have complex structures and are made in small batches or even made in a single-piece, especially for large-sized art castings. So it has the shortcomings of high cost, low efficiency and long time for making a pattern to produce art castings with the conventional casting processes. However, the digital pattern-less casting technology can be applied to fabricate art castings, since it can greatly shorten the manufacturing cycle and lower the production cost, thus having a very good prospect. In this study, based on the digital pattern-less casting technology, a plaque casting with artistic Chinese characters (a Chinese poem) was designed and manufactured, and the production process was demonstrated in detail. [ABSTRACT FROM AUTHOR]

The influences of minor amounts of scandium on the microstructure and mechanical properties of as-cast ZA27 alloy have been experimentally investigated. The experimental results show that as far as the Sc addition is individually concerned, the refinement result of the as-cast ZA27 alloy with 0.5wt.%Sc addition is comparatively better. After alloying with minor amounts of Sc, the coarse dendrites of the ZA27 alloy are refined and transformed into the uniform and small equiaxed grain microstructure; also the eutectics among the grain boundaries become finer. The test results of mechanical properties show that the tensile strength and hardness of the as-cast ZA27 alloy containing 0.5wt.%Sc approach 495 MPa and 120.2 HB, increase by 28.5% and 33.1%, respectively, compared with those of the ZA27 alloy with no addition of Sc element, while the elongation of the alloy is improved to 7.6% from 2.7%. The SEM, EDAX and XRD analyses show that in the ZA27 alloy, the trace element Sc combines with Al to form the square AI3Sc phase particles, which serve as heterogeneous nuclei, facilitating the refinement of the microstructure and the improvement of the mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]

• The phase constituents of Al x CrFeNi MEAs can be significantly adjusted by tuning x within narrow region between 0.3 and 0.4. • A novel microstructure consisted of FCC distributed on the grain boundaries of BCC phase was found for the Al 0.37 CrFeNi MEA. • The Al 0.37 CrFeNi MEA shows higher damping capacity of 0.07093 and comprehensive compression properties. In this paper, the phase constituent, damping and compressive properties of as-cast Al x CrFeNi (x = 0.3, 0.35, 0.37, 0.4, 0.5) medium entropy alloys (MEAs) were studied. The results show that the phase constituent changes gradually from a face-centered cubic (FCC) dominated structure to a single body-centered cubic (BCC) structure when x increases from 0.3 to 0.5. A novel mesh microstructure consisted of 88.3 vol% BCC phase as the hard matrix and 11.7 vol% FCC structure as the secondary soft phase was screened out by pinpointing x of 0.37. The combination of hard matrix and soft secondary phase results in a very high damping capacity up to 0.07093 for such Al 0.37 CrFeNi MEA at the corresponding strain amplitude of 1.5 × 10−4. Both the grain size of the BCC phase and the grain boundaries where the FCC phase is distributed are important to increase the damping capacity of the MEA. The excellent damping performance and comprehensive mechanical properties indicate that the Al 0.37 CrFeNi MEA has potential application as a damping material. [ABSTRACT FROM AUTHOR]