Search2019 Vol. 26, No. 6
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2019, vol. 26, no. 6, pp.
665-672.
https://doi.org/10.1007/s12613-019-1793-x
Abstract:
The micromorphology and physicochemical properties of hydrophobic blasting dust (HBD) from an iron mine were comprehensively analyzed by laser particle size analysis (LPSA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that the HBD particles can be classified into three types based on their particle size (PS):larger particles (PS > 10 μm), medium particles (1 μm ≤ PS ≤ 10 μm), and nanoparticles (PS < 1 μm). The cumulative volume of respirable dust (PS ≤ 10 μm) was 84.45%. In addition, three shapes of HBD were observed by SEM:prism, flake, and bulk. In particular, the small particles were mostly flaky, with a greater possibility of being inhaled. Furthermore, the body and surface chemical compounds of HBD were determined by XRD and XPS, respectively. Ammonium adipate (C6H16N2O4) was the only organic compound in the body of HBD, but its mass fraction was only 13.4%. However, the content of organic C on the surface of HBD was 85.35%. This study demonstrated that the small-particle size and large amount of organic matter on the surface of HBD are the main reasons for its hydrophobicity, which can provide important guidance for controlling respirable dust in iron mines.
The micromorphology and physicochemical properties of hydrophobic blasting dust (HBD) from an iron mine were comprehensively analyzed by laser particle size analysis (LPSA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that the HBD particles can be classified into three types based on their particle size (PS):larger particles (PS > 10 μm), medium particles (1 μm ≤ PS ≤ 10 μm), and nanoparticles (PS < 1 μm). The cumulative volume of respirable dust (PS ≤ 10 μm) was 84.45%. In addition, three shapes of HBD were observed by SEM:prism, flake, and bulk. In particular, the small particles were mostly flaky, with a greater possibility of being inhaled. Furthermore, the body and surface chemical compounds of HBD were determined by XRD and XPS, respectively. Ammonium adipate (C6H16N2O4) was the only organic compound in the body of HBD, but its mass fraction was only 13.4%. However, the content of organic C on the surface of HBD was 85.35%. This study demonstrated that the small-particle size and large amount of organic matter on the surface of HBD are the main reasons for its hydrophobicity, which can provide important guidance for controlling respirable dust in iron mines.
2019, vol. 26, no. 6, pp.
673-680.
https://doi.org/10.1007/s12613-019-1777-x
Abstract:
The aim of this work is to investigate the ability of an adsorbent of a clay mineral composite to remove and recover gold and silver ions from wastewater. The composite was prepared by mixing phosphogypsum (PG), obtained from an industrial waste, and a natural clay mineral. The materials were characterized before and after use in adsorption by several techniques. Batch adsorption experiments were carried out, and the effects of the contact time and the pH and temperature of solution on the removal processes were investigated. The optimum pH for the adsorption was found to be 4. The adsorption of these metal ions reached equilibrium after 2 h of contact. The pseudo-first- and the pseudo-second-order kinetic models, as well as the Freundlich and the Langmuir isotherm equations, were considered to describe the adsorption results. The maximum adsorbed amount of 85 mg·g-1 Ag(I) and 108.3 mg·g-1 Au(Ⅲ) was found. The recovery of the adsorbed gold and silver ions from the adsorbent was also analyzed. Strong acids appeared to be the best desorption agents to recover gold and silver ions. The use of aqua regia gave regeneration rates close to 95.3% and 94.3% for Ag(I) and Au(Ⅲ), respectively. Finally, the removal of gold and silver ions from an industrial wastewater was tested in batch experiments, and percentage recoveries of 76.5% and 79.9% for Ag(I) and Au(Ⅲ), respectively, were obtained. To carry out the industrial application of the proposed methodology, an economic viability study is required.
The aim of this work is to investigate the ability of an adsorbent of a clay mineral composite to remove and recover gold and silver ions from wastewater. The composite was prepared by mixing phosphogypsum (PG), obtained from an industrial waste, and a natural clay mineral. The materials were characterized before and after use in adsorption by several techniques. Batch adsorption experiments were carried out, and the effects of the contact time and the pH and temperature of solution on the removal processes were investigated. The optimum pH for the adsorption was found to be 4. The adsorption of these metal ions reached equilibrium after 2 h of contact. The pseudo-first- and the pseudo-second-order kinetic models, as well as the Freundlich and the Langmuir isotherm equations, were considered to describe the adsorption results. The maximum adsorbed amount of 85 mg·g-1 Ag(I) and 108.3 mg·g-1 Au(Ⅲ) was found. The recovery of the adsorbed gold and silver ions from the adsorbent was also analyzed. Strong acids appeared to be the best desorption agents to recover gold and silver ions. The use of aqua regia gave regeneration rates close to 95.3% and 94.3% for Ag(I) and Au(Ⅲ), respectively. Finally, the removal of gold and silver ions from an industrial wastewater was tested in batch experiments, and percentage recoveries of 76.5% and 79.9% for Ag(I) and Au(Ⅲ), respectively, were obtained. To carry out the industrial application of the proposed methodology, an economic viability study is required.
2019, vol. 26, no. 6, pp.
681-688.
https://doi.org/10.1007/s12613-019-1782-0
Abstract:
For ultra-low-carbon (ULC) steel production, the higher oxygen content before Ruhrstahl-Heraeus (RH) decarburization (de-C) treatment could shorten the de-C time in the RH degasser. However, this would lead to oxidation rates being exceeded by molten steel production, affecting ULC steel surface quality. In this work, a carbon powder addition (CPA) process was proposed to reduce the dissolved oxygen content at the end of RH de-C through addition of carbon powder to molten steel in the vacuum vessel. Carbon and oxygen behavior during the CPA and conventional process was then studied. The results demonstrated that the de-C rate with CPA was lower compared to the conventional process, but the carbon content at the end of de-C presented no difference. The de-C reaction for CPA process took place in the four reaction sites:(1) within the bulk steel where the spontaneous CO bubbles form; (2) splashing area on the liquid steel surface; (3) Ar bubble surface; (4) molten steel surface. The CPA process could significantly reduce the dissolved oxygen content at the end of de-C, the sum content of FeO and MnO in the slag, the aluminum consumption, and the defect rate of rolled products. This was beneficial in improving ULC steel cleanliness.
For ultra-low-carbon (ULC) steel production, the higher oxygen content before Ruhrstahl-Heraeus (RH) decarburization (de-C) treatment could shorten the de-C time in the RH degasser. However, this would lead to oxidation rates being exceeded by molten steel production, affecting ULC steel surface quality. In this work, a carbon powder addition (CPA) process was proposed to reduce the dissolved oxygen content at the end of RH de-C through addition of carbon powder to molten steel in the vacuum vessel. Carbon and oxygen behavior during the CPA and conventional process was then studied. The results demonstrated that the de-C rate with CPA was lower compared to the conventional process, but the carbon content at the end of de-C presented no difference. The de-C reaction for CPA process took place in the four reaction sites:(1) within the bulk steel where the spontaneous CO bubbles form; (2) splashing area on the liquid steel surface; (3) Ar bubble surface; (4) molten steel surface. The CPA process could significantly reduce the dissolved oxygen content at the end of de-C, the sum content of FeO and MnO in the slag, the aluminum consumption, and the defect rate of rolled products. This was beneficial in improving ULC steel cleanliness.
2019, vol. 26, no. 6, pp.
689-700.
https://doi.org/10.1007/s12613-019-1776-y
Abstract:
A new alkaline pressure oxidative leaching process (with NaNO3 as the oxidant and NaOH as the alkaline reagent) is proposed herein to remove arsenic, antimony, and lead from bismuth-rich and arsenic-rich lead anode slime for bismuth, gold, and silver enrichment. The effects of the temperature, liquid-to-solid ratio, leaching time, and reagent concentration on the leaching ratios of arsenic, antimony, and lead were investigated to identify the optimum leaching conditions. The experimental results under optimized conditions indicate that the average leaching ratios of arsenic, antimony and lead are 95.36%, 79.98%, 63.08%, respectively. X-ray diffraction analysis indicated that the leaching residue is composed of Bi, Bi2O3, Pb2Sb2O7, and trace amounts of NaSb(OH)6. Arsenic, antimony, and lead are thus separated from lead anode slime as Na3AsO4·10H2O and Pb2Sb2O7. Scanning electron microscopy and energy-dispersive spectrometry imaging revealed that the samples undergo appreciable changes in their surface morphology during leaching and that the majority of arsenic, lead, and antimony is removed. X-ray photoelectron spectroscopy was used to demonstrate the variation in the valence states of the arsenic, lead, and antimony. The Pb(IV) and Sb(V) content was found to increase substantially with the addition of NaNO3.
A new alkaline pressure oxidative leaching process (with NaNO3 as the oxidant and NaOH as the alkaline reagent) is proposed herein to remove arsenic, antimony, and lead from bismuth-rich and arsenic-rich lead anode slime for bismuth, gold, and silver enrichment. The effects of the temperature, liquid-to-solid ratio, leaching time, and reagent concentration on the leaching ratios of arsenic, antimony, and lead were investigated to identify the optimum leaching conditions. The experimental results under optimized conditions indicate that the average leaching ratios of arsenic, antimony and lead are 95.36%, 79.98%, 63.08%, respectively. X-ray diffraction analysis indicated that the leaching residue is composed of Bi, Bi2O3, Pb2Sb2O7, and trace amounts of NaSb(OH)6. Arsenic, antimony, and lead are thus separated from lead anode slime as Na3AsO4·10H2O and Pb2Sb2O7. Scanning electron microscopy and energy-dispersive spectrometry imaging revealed that the samples undergo appreciable changes in their surface morphology during leaching and that the majority of arsenic, lead, and antimony is removed. X-ray photoelectron spectroscopy was used to demonstrate the variation in the valence states of the arsenic, lead, and antimony. The Pb(IV) and Sb(V) content was found to increase substantially with the addition of NaNO3.
Electrical conductivity of molten LiF-DyF3-Dy2O3-Cu2O system for Dy-Cu intermediate alloy production
2019, vol. 26, no. 6, pp.
701-709.
https://doi.org/10.1007/s12613-019-1775-z
Abstract:
Dy-Cu intermediate alloys have shown substantial potential in the field of magnetostrictive and magnetic refrigerant materials. Therefore, this study focused on investigating the electrical conductivity of molten-salt systems for the preparation of Dy-Cu alloys and on optimizing the corresponding operating parameters. The electrical conductivity of molten LiF-DyF3-Dy2O3-Cu2O systems was measured from 910 to 1030℃ using the continuously varying cell constant method. The dependencies of the LiF-DyF3-Dy2O3-Cu2O system conductivity on the melt composition and temperature were examined herein. The optimal operating conditions for Dy-Cu alloy production were determined via analyses of the electrical conductivity and activation energies for conductance, which were calculated using the Arrhenius equation. The conductivity of the molten system regularly increases with increasing temperature and decreases with increasing concentration of Dy2O3 or Cu2O or both. The activation energy Eκ of the LiF-DyF3-Dy2O3 and LiF-DyF3-Cu2O molten-salt systems increases with increasing Dy2O3 or Cu2O content. The regression functions of conductance as a function of temperature (t) and the addition of Dy2O3 (W(Dy2O3)) and Cu2O (W(Cu2O)) can be expressed as κ=-2.08435 + 0.0068t-0.18929W(Dy2O3)-0.07918W(Cu2O). The optimal electrolysis conditions for preparing the Dy-Cu alloy in LiF-DyF3-Dy2O3-Cu2O molten salt are determined to be 2.0wt% ≤ W(Dy2O3) + W(Cu2O) ≤ 3.0wt% and W(Dy2O3):W(Cu2O)=1:2 at 970 to 1000℃.
Dy-Cu intermediate alloys have shown substantial potential in the field of magnetostrictive and magnetic refrigerant materials. Therefore, this study focused on investigating the electrical conductivity of molten-salt systems for the preparation of Dy-Cu alloys and on optimizing the corresponding operating parameters. The electrical conductivity of molten LiF-DyF3-Dy2O3-Cu2O systems was measured from 910 to 1030℃ using the continuously varying cell constant method. The dependencies of the LiF-DyF3-Dy2O3-Cu2O system conductivity on the melt composition and temperature were examined herein. The optimal operating conditions for Dy-Cu alloy production were determined via analyses of the electrical conductivity and activation energies for conductance, which were calculated using the Arrhenius equation. The conductivity of the molten system regularly increases with increasing temperature and decreases with increasing concentration of Dy2O3 or Cu2O or both. The activation energy Eκ of the LiF-DyF3-Dy2O3 and LiF-DyF3-Cu2O molten-salt systems increases with increasing Dy2O3 or Cu2O content. The regression functions of conductance as a function of temperature (t) and the addition of Dy2O3 (W(Dy2O3)) and Cu2O (W(Cu2O)) can be expressed as κ=-2.08435 + 0.0068t-0.18929W(Dy2O3)-0.07918W(Cu2O). The optimal electrolysis conditions for preparing the Dy-Cu alloy in LiF-DyF3-Dy2O3-Cu2O molten salt are determined to be 2.0wt% ≤ W(Dy2O3) + W(Cu2O) ≤ 3.0wt% and W(Dy2O3):W(Cu2O)=1:2 at 970 to 1000℃.
2019, vol. 26, no. 6, pp.
710-721.
https://doi.org/10.1007/s12613-019-1790-0
Abstract:
The conditions used for friction stir welding of duplex stainless steels determine the resulting mechanical and corrosion performance of the material. This study investigates the corrosion resistance of UNS S32750 and S32760 superduplex stainless steels (SDSSs) joined by friction stir welding, employing cyclic polarization, Mott-Schottky, and microscopy techniques for analysis. The microscopy images indicated the presence of a deleterious intermetallic phase after electrolytic etching of S32760, as well as decreased corrosion resistance. The presence of molybdenum in the steels promoted better passive behavior at low pH. The Mott-Schottky curves revealed p-n heterojunction behavior of the passive oxide. Images acquired after the polarization test by scanning electron microscopy showed higher passivation propensity with increases of temperature and pH.
The conditions used for friction stir welding of duplex stainless steels determine the resulting mechanical and corrosion performance of the material. This study investigates the corrosion resistance of UNS S32750 and S32760 superduplex stainless steels (SDSSs) joined by friction stir welding, employing cyclic polarization, Mott-Schottky, and microscopy techniques for analysis. The microscopy images indicated the presence of a deleterious intermetallic phase after electrolytic etching of S32760, as well as decreased corrosion resistance. The presence of molybdenum in the steels promoted better passive behavior at low pH. The Mott-Schottky curves revealed p-n heterojunction behavior of the passive oxide. Images acquired after the polarization test by scanning electron microscopy showed higher passivation propensity with increases of temperature and pH.
2019, vol. 26, no. 6, pp.
722-731.
https://doi.org/10.1007/s12613-019-1783-z
Abstract:
AA 6061 alloy and interstitial-free (IF) steel plates were joined by the friction stir welding (FSW) method, and the microstructure, mechanical properties, and biaxial stretch formability of the friction stir welded (FSWed) parts were investigated. The results indicate that the FSWed parts showed optimum tensile strength during FSW with the 0.4-mm offset position of the tool. The Fe4Al13 intermetallic compound formed in the defect-free intersection of AA 6061 and IF-steel plates during FSW. The hardness of the IF-steel part of the FSWed region increased almost 90% relative to its initial hardness of HV0.2 105. The tensile and yield strengths of FSWed regions were approximately 170 MPa and 145 MPa, respectively. According to the formability tests, the Erichsen Index (EI) of the IF-steel, AA 6061, and the FSWed samples were determined to be 2.9 mm, 1.9 mm, and 2.1 mm, respectively. The EI of the FSWed sample was almost the same as that of the AA 6061 alloy. However, it decreased compared with that of the IF-steel. The force at EI (FEI) was approximately 1180 N for the FSWed condition. This value is approximately 70% higher than that of AA 6061 alloy.
AA 6061 alloy and interstitial-free (IF) steel plates were joined by the friction stir welding (FSW) method, and the microstructure, mechanical properties, and biaxial stretch formability of the friction stir welded (FSWed) parts were investigated. The results indicate that the FSWed parts showed optimum tensile strength during FSW with the 0.4-mm offset position of the tool. The Fe4Al13 intermetallic compound formed in the defect-free intersection of AA 6061 and IF-steel plates during FSW. The hardness of the IF-steel part of the FSWed region increased almost 90% relative to its initial hardness of HV0.2 105. The tensile and yield strengths of FSWed regions were approximately 170 MPa and 145 MPa, respectively. According to the formability tests, the Erichsen Index (EI) of the IF-steel, AA 6061, and the FSWed samples were determined to be 2.9 mm, 1.9 mm, and 2.1 mm, respectively. The EI of the FSWed sample was almost the same as that of the AA 6061 alloy. However, it decreased compared with that of the IF-steel. The force at EI (FEI) was approximately 1180 N for the FSWed condition. This value is approximately 70% higher than that of AA 6061 alloy.
2019, vol. 26, no. 6, pp.
732-739.
https://doi.org/10.1007/s12613-019-1803-z
Abstract:
The well-known anti-corrosive property of stainless steels is largely attributed to the addition of Cr, which can assist in forming an inert film on the corroding surface. To maximize the corrosion-resistant ability of Cr, a thorough study dealing with the passivation behaviors of this metal, including the structure and composition of the passive film as well as related reaction mechanisms, is required. Here, continuous electrochemical adsorptions of OH-groups of water molecules onto Cr terraces in acid solutions are investigated using DFT methods. Different models with various surface conditions are applied. Passivation is found to begin in the active region, and a fully coated surface mainly with oxide is likely to be the starting point of the passive region. The calculated limiting potentials are in reasonable agreement with passivation potentials observed via experiment.
The well-known anti-corrosive property of stainless steels is largely attributed to the addition of Cr, which can assist in forming an inert film on the corroding surface. To maximize the corrosion-resistant ability of Cr, a thorough study dealing with the passivation behaviors of this metal, including the structure and composition of the passive film as well as related reaction mechanisms, is required. Here, continuous electrochemical adsorptions of OH-groups of water molecules onto Cr terraces in acid solutions are investigated using DFT methods. Different models with various surface conditions are applied. Passivation is found to begin in the active region, and a fully coated surface mainly with oxide is likely to be the starting point of the passive region. The calculated limiting potentials are in reasonable agreement with passivation potentials observed via experiment.
2019, vol. 26, no. 6, pp.
740-751.
https://doi.org/10.1007/s12613-019-1778-9
Abstract:
The effect of adding 0.03wt% Ni on the microstructure and mechanical properties of Al-Mg-Si-Cu-Zn alloys was systematically studied. The results reveal that the number density of spherical Fe-rich phases within grains increases with the addition of Ni, accompanied by the formation of Q (Al3Mg9Si7Cu2) precipitates around the spherical Fe-rich phases. Additionally, Ni addition is beneficial to reducing the grain size in the as-cast state. During the homogenization process, Q phases could be completely dissolved and the grain size could remain basically unchanged. However, compared with the Ni-free alloy, the Fe-rich phase in the Ni-containing alloy is more likely to undergo the phase transformation and further form more spherical particles during homogenization treatment. After thermomechanical processing, the distribution of Fe-rich phases in the Ni-containing alloy was further greatly improved and directly resulted in a greater formability than that of the Ni-free alloy. Accordingly, a reasonable Ni addition positively affected the microstructure and formability of the alloys.
The effect of adding 0.03wt% Ni on the microstructure and mechanical properties of Al-Mg-Si-Cu-Zn alloys was systematically studied. The results reveal that the number density of spherical Fe-rich phases within grains increases with the addition of Ni, accompanied by the formation of Q (Al3Mg9Si7Cu2) precipitates around the spherical Fe-rich phases. Additionally, Ni addition is beneficial to reducing the grain size in the as-cast state. During the homogenization process, Q phases could be completely dissolved and the grain size could remain basically unchanged. However, compared with the Ni-free alloy, the Fe-rich phase in the Ni-containing alloy is more likely to undergo the phase transformation and further form more spherical particles during homogenization treatment. After thermomechanical processing, the distribution of Fe-rich phases in the Ni-containing alloy was further greatly improved and directly resulted in a greater formability than that of the Ni-free alloy. Accordingly, a reasonable Ni addition positively affected the microstructure and formability of the alloys.
2019, vol. 26, no. 6, pp.
752-759.
https://doi.org/10.1007/s12613-019-1780-2
Abstract:
To study the influence of rolling on the interfaces and mechanical performance of graphene-reinforced Al-matrix composites, a rolling method was used to process them. Using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and tensile testing, this study analyzed the micromorphology, interfaces, and mechanical performance of the composites before and after rolling. The experimental results demonstrates that the composites after hot rolling has uniform structures with strong interfacial bonding. With an increase in rolling temperature, the tensile strength and elastic modulus of the composites gradually increase. However, when the rolling temperature is higher than 500℃, granular and rod-like Al4C3 phases are observed at the interfaces and the mechanical performance of the composites is degraded. When the rolling temperature is 480℃, the composites show the optimal comprehensive mechanical performance, with a tensile strength and elastic modulus of 403.3 MPa and 77.6 GPa, respectively, which represent increases of 31.6% and 36.9%, respectively, compared with the corresponding values prior to rolling.
To study the influence of rolling on the interfaces and mechanical performance of graphene-reinforced Al-matrix composites, a rolling method was used to process them. Using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and tensile testing, this study analyzed the micromorphology, interfaces, and mechanical performance of the composites before and after rolling. The experimental results demonstrates that the composites after hot rolling has uniform structures with strong interfacial bonding. With an increase in rolling temperature, the tensile strength and elastic modulus of the composites gradually increase. However, when the rolling temperature is higher than 500℃, granular and rod-like Al4C3 phases are observed at the interfaces and the mechanical performance of the composites is degraded. When the rolling temperature is 480℃, the composites show the optimal comprehensive mechanical performance, with a tensile strength and elastic modulus of 403.3 MPa and 77.6 GPa, respectively, which represent increases of 31.6% and 36.9%, respectively, compared with the corresponding values prior to rolling.
2019, vol. 26, no. 6, pp.
760-765.
https://doi.org/10.1007/s12613-019-1789-6
Abstract:
Alloying is a good approach to increasing its strength but leads to a reduction of damping to pure magnesium. Classifying the alloying characteristics of various alloying elements in magnesium alloys and their combined effects on the damping and mechanical properties of magnesium alloys is important. In this paper, the properties of the Mg-0.6wt%X binary alloys were analyzed through strength measurements and dynamic mechanical analysis. The effects of foreign atoms on solid-solution strengthening and dislocation damping were studied comprehensively. The effect of solid solubility on damping capacity can be considered from two perspectives:the effect of single solid-solution atoms on the damping capacities of the alloy, and the effect of solubility on the damping capacities of the alloy. The results provide significant information that is useful in developing high-strength, high-damping magnesium alloys. This study will provide scientific guidance regarding the development of new types of damping magnesium alloys.
Alloying is a good approach to increasing its strength but leads to a reduction of damping to pure magnesium. Classifying the alloying characteristics of various alloying elements in magnesium alloys and their combined effects on the damping and mechanical properties of magnesium alloys is important. In this paper, the properties of the Mg-0.6wt%X binary alloys were analyzed through strength measurements and dynamic mechanical analysis. The effects of foreign atoms on solid-solution strengthening and dislocation damping were studied comprehensively. The effect of solid solubility on damping capacity can be considered from two perspectives:the effect of single solid-solution atoms on the damping capacities of the alloy, and the effect of solubility on the damping capacities of the alloy. The results provide significant information that is useful in developing high-strength, high-damping magnesium alloys. This study will provide scientific guidance regarding the development of new types of damping magnesium alloys.
2019, vol. 26, no. 6, pp.
766-774.
https://doi.org/10.1007/s12613-019-1784-y
Abstract:
A hybrid joint with a satisfactory mixture of pure magnesium and polypropylene (PP) was achieved via friction stir joining (FSW) in a lap-joint configuration. The tool rotational and travel speeds used in this work were 500-700 r/min and 50-100 mm/min, respectively. The mechanical properties and microstructural analysis of the resultant hybrid Mg/PP joint were examined. The results show that the maximum tensile shear strength (22.5 MPa) of the joint was attained at 700 r/min and 75 mm/min due to the optimum percentage fraction of mechanical interlocking (48%) and the presence of magnesium oxide. The interfacial joint center exhibits the maximum microhardness values because of the presence of refined and intertwined Mg fragments and density dislocations in the matrix of the PP. The joint failed via two different modes:interfacial line and weld zone fractures, respectively.
A hybrid joint with a satisfactory mixture of pure magnesium and polypropylene (PP) was achieved via friction stir joining (FSW) in a lap-joint configuration. The tool rotational and travel speeds used in this work were 500-700 r/min and 50-100 mm/min, respectively. The mechanical properties and microstructural analysis of the resultant hybrid Mg/PP joint were examined. The results show that the maximum tensile shear strength (22.5 MPa) of the joint was attained at 700 r/min and 75 mm/min due to the optimum percentage fraction of mechanical interlocking (48%) and the presence of magnesium oxide. The interfacial joint center exhibits the maximum microhardness values because of the presence of refined and intertwined Mg fragments and density dislocations in the matrix of the PP. The joint failed via two different modes:interfacial line and weld zone fractures, respectively.
2019, vol. 26, no. 6, pp.
775-786.
https://doi.org/10.1007/s12613-019-1779-8
Abstract:
Self-propagating high-temperature synthesis (SHS) was used to fabricate a Fe(Cr)-Al2O3 nanocomposite. The composite was fabricated by the reactions between the powders of Fe, Fe2O3, Cr2O3, and Al. The effect of blending ratio and mechanical activation of the initial powders and the precursor compressing pressure on the microstructure of the final product was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The significance of the effect of each of the aforementioned parameters on the quality of the composite (assessed by measuring the compressive strength and wear resistance) was determined using a full-factorial design of experiments method. The results showed that the best molar powder ratio that produced the most homogeneous product through a sustainable SHS reaction was Fe:Fe2O3:Cr2O3:Al=10:1:1:4. A lower Fe content caused the Fe(Cr) phase to melt and separate from the rest of the materials.
Self-propagating high-temperature synthesis (SHS) was used to fabricate a Fe(Cr)-Al2O3 nanocomposite. The composite was fabricated by the reactions between the powders of Fe, Fe2O3, Cr2O3, and Al. The effect of blending ratio and mechanical activation of the initial powders and the precursor compressing pressure on the microstructure of the final product was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The significance of the effect of each of the aforementioned parameters on the quality of the composite (assessed by measuring the compressive strength and wear resistance) was determined using a full-factorial design of experiments method. The results showed that the best molar powder ratio that produced the most homogeneous product through a sustainable SHS reaction was Fe:Fe2O3:Cr2O3:Al=10:1:1:4. A lower Fe content caused the Fe(Cr) phase to melt and separate from the rest of the materials.
2019, vol. 26, no. 6, pp.
787-795.
https://doi.org/10.1007/s12613-019-1781-1
Abstract:
The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet (UV) resistance of zinc oxide-functionalized halloysite nanotubes (HNT-ZnO). The HNT-ZnO was synthesized using a facile solvent-free route. The properties of the HNT-ZnO nanofillers were characterized using zeta-potential measurement, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The immobilization of ZnO nanoparticles onto HNT is feasible even at the lowest mass ratio of HNT/ZnO. The TGA results indicate that the thermal stability of the HNT-ZnO nanofillers is higher than that of the HNT. Furthermore, UV-Vis diffuse reflectance spectroscopy (UV-DRS) results show that the HNT-ZnO achieve a total reflectance as high as approximately 87.5% in the UV region, as compare with 66.9% for the HNT. In summary, the immobilization of ZnO onto HNT is a viable approach for increasing the thermal stability and improving the UV shielding of HNT.
The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet (UV) resistance of zinc oxide-functionalized halloysite nanotubes (HNT-ZnO). The HNT-ZnO was synthesized using a facile solvent-free route. The properties of the HNT-ZnO nanofillers were characterized using zeta-potential measurement, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The immobilization of ZnO nanoparticles onto HNT is feasible even at the lowest mass ratio of HNT/ZnO. The TGA results indicate that the thermal stability of the HNT-ZnO nanofillers is higher than that of the HNT. Furthermore, UV-Vis diffuse reflectance spectroscopy (UV-DRS) results show that the HNT-ZnO achieve a total reflectance as high as approximately 87.5% in the UV region, as compare with 66.9% for the HNT. In summary, the immobilization of ZnO onto HNT is a viable approach for increasing the thermal stability and improving the UV shielding of HNT.
2019, vol. 26, no. 6, pp.
796-802.
https://doi.org/10.1007/s12613-019-1785-x
Abstract:
In this work, we synthesized monodispersed hexagonal Ag nanoprisms in high yields in a system of poly(vinylpyrrolidone) (PVP) in N-methylpyrrolidone (NMP). A blue shift occurred and was strongly dependent on the thickness of the uniform Ag nanoprisms, which had almost the same radial area. When the Ag nanoprisms grew thicker, their in-plane dipole resonance peaks markedly shifted toward shorter wavelengths (i.e., blue shift). PVP played a critical role of favoring vertical growth of the Ag nanoplates, preventing aggregation, and inducing the formation of Ag hexagonal nanoprisms (HNPs) through the transformation from thin Ag triangular nanoprisms (TNPs). Compared with similar previous research, the present study provides quite uniform Ag hexagonal nanoplates, which makes the blue shift related more solely and distinctly to the thickness of the Ag nanoprisms. The findings of this work provide a new perspective toward understanding the unique optical characteristics of Ag HNPs with different aspect ratios.
In this work, we synthesized monodispersed hexagonal Ag nanoprisms in high yields in a system of poly(vinylpyrrolidone) (PVP) in N-methylpyrrolidone (NMP). A blue shift occurred and was strongly dependent on the thickness of the uniform Ag nanoprisms, which had almost the same radial area. When the Ag nanoprisms grew thicker, their in-plane dipole resonance peaks markedly shifted toward shorter wavelengths (i.e., blue shift). PVP played a critical role of favoring vertical growth of the Ag nanoplates, preventing aggregation, and inducing the formation of Ag hexagonal nanoprisms (HNPs) through the transformation from thin Ag triangular nanoprisms (TNPs). Compared with similar previous research, the present study provides quite uniform Ag hexagonal nanoplates, which makes the blue shift related more solely and distinctly to the thickness of the Ag nanoprisms. The findings of this work provide a new perspective toward understanding the unique optical characteristics of Ag HNPs with different aspect ratios.
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