The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Qisheng Wu - One of the best experts on this subject based on the ideXlab platform.
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Physical properties and microstructure of Nickel Slag/metakaolin-based geopolymer with different contents of Nickel Slag
Advances in Cement Research, 2020Co-Authors: Changsen Zhang, Qisheng Wu, Yang Li, Zhenzhe Feng, Yu Wang, Zhichao HuAbstract:Geopolymer pastes based on Nickel Slag/metakaolin (NS/MK) were prepared and their physical properties and microstructure as a function of NS content were studied. The results showed that the additi...
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Preparation and characterization of porous ceramics from Nickel smelting Slag and metakaolin
Ceramics International, 2020Co-Authors: Qisheng Wu, Qiujing Chen, Zichen Huang, Bin Gu, Liang TianAbstract:Abstract Porous ceramics with high porosity and low bulk density were prepared by using Nickel Slag and metakaolin as the primary raw materials, glass powder as flux, and SiC as the foaming agent. The content of Nickel Slag and foaming agent had a significant effect on the bulk density, porosity, and flexural strength of the porous ceramics. The porous ceramics with the best properties were obtained at 1100 °C for 30 min with 50 wt% Nickel Slag, 40 wt% metakaolin, 10 wt% waste glass, and 0.8 wt% SiC. It had a low bulk density (as low as 245 kg/m3), high flexural strength and compressive strength (0.6 MPa and 1.17 MPa, respectively), and high porosity (about 89.8%). The Nickel Slag was magnetically separated as well. The density of Nickel Slag powder could be reduced via magnetic separation, and there was no significant change in the crystal structure of the raw material. Compared with porous ceramics prepared using Nickel Slag without magnetic separation, ceramics subjected to magnetic separation had lower bulk density, higher porosity, and the same phase composition. This study can be used as an indicator for the application of Nickel Slag in porous ceramics, which is of great significance in providing a great substitute Nickel Slag towards recovery and utilization.
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Re-examining the suitability of high magnesium Nickel Slag as precursors for alkali-activated materials
Construction and Building Materials, 2019Co-Authors: Tao Yang, Zuhua Zhang, Qisheng WuAbstract:Abstract High-magnesium Nickel Slag (HMNS) has shown the potential as precursor in the production of alkali-activated materials (AAMs). This study re-examines the suitability of HMNS by comparatively investigating the reactivity of four different sourced HMNSs and analyzing impacts of the magnesium sources in HMNS on the reaction products of AAMs. Results show that the cooling way plays a determinant role of their mineral compositions. The air-cooled HMNSs contain only ∼30 wt% glassy phases, while the water-quenched one is dominantly amorphous. The reactivity of HMNS determined by the dissolution tests correlates well with the calculated depolymerization degree of glasses. HMNS indeed exhibits lower reactivity than the precursors commonly used for AAMs production, such as fly ash and blast furnace Slag. In the HMNS samples in the sodium hydroxide solution, M-S-H, C-S-H and hydrotalcite are the main reaction products. The OH− ions in the aqueous system react with Mg2+ to form the brucite, indicating that there is still a volume expansion risk if sodium hydroxide is used as activator. In comparison, only M-S-H and C-S-H gels are coexistent in the samples leached in the sodium silicate solution, because of the kinetic hindrance of soluble silicates for the formation of hydrotalcite and brucite.
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Effect of High-Magnesium Nickel Slag on Hydration Characteristics of Portland Cement
Journal of Materials in Civil Engineering, 2019Co-Authors: Qisheng Wu, Shunxiang Wang, Tao Yang, Shuiping LiAbstract:AbstractThis paper aims to study the effect of high-magnesium Nickel Slag on the hydration characteristics of portland cement paste. High-magnesium Nickel Slag was used as supplementary cementitiou...
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influence of Nickel Slag powders on properties of magnesium potassium phosphate cement paste
Construction and Building Materials, 2019Co-Authors: Qi Wang, Changjuan Yu, Jianming Yang, Linlin Chong, Xuancheng Xu, Qisheng WuAbstract:Abstract This paper aims to study the effect of Nickel Slag powders on the properties of potassium magnesium phosphate cement (MKPC) paste. MKPC pastes containing different contents of Nickel Slag powders were prepared. We then tested their fluidity, setting time, compressive strength, the residual ratio of compressive strength under water curing condition, shrinkage deformation and hydration temperature. The micro morphology and the phase compositions of hardened MKPC pastes were also analyzed. The results indicate that adding some Nickel Slag powders in MKPC can improve the particle gradation of alkali components in MKPC and further improve the fluidity of fresh MKPC paste. The water stability of MKPC paste can be improved obviously by adding 30–40% Nickel Slag powders. The 60-day compressive strength of MKPC paste with 30–40% Nickel Slag powers exceeds 70 MPa and the residual ratio of compressive strength under water curing condition is higher than 100%. This should be attributed to the decrease in the proportion of harmful pores in hardened MKPC paste with some Nickel Slag powers. In addition, adding some Nickel Slag powders can obviously reduce the shrinkage deformation of MKPC paste. The 60-day drying shrinkage rate of hardened MKPC paste with 30% Nickel Slag powders is only 48.2% of that of the reference sample without Nickel Slag powders. This is attributed to the improvement of particle size distribution of alkali components, the micro-aggregate effect of Nickel Slag powders and less water use. These factors result in the decrease in the total porosity of the hardened MKPC paste with Nickel Slag powders and finally smaller shrinkage deformation.
Seongcheol Choi - One of the best experts on this subject based on the ideXlab platform.
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alkali silica reactivity of cementitious materials using ferro Nickel Slag fine aggregates produced in different cooling conditions
Construction and Building Materials, 2015Co-Authors: Young Cheol Choi, Seongcheol ChoiAbstract:Abstract In this study, the alkali–silica reactivity of cementitious materials using ferro-Nickel Slag (FNS) fine aggregates was experimentally evaluated for potential use in concrete. The results revealed that the reactivity of cement mortars using the aggregates varied with the cooling speed and particle size of the FNS. For example, the rapidly (i.e., water-) cooled FNS exhibited higher alkali–silica reactivity than its gradually (air-) cooled counterpart. The particle size of the water-cooled FNS also affected the reactivity of the specimens. Furthermore, the partial replacement of FNS with sea sand, and of cements with fly ash or ground granulated blast furnace Slag was effective in reducing the alkali–silica reactivity of cementitious materials containing FNS as fine aggregates.
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Alkali–silica reactivity of cementitious materials using ferro-Nickel Slag fine aggregates produced in different cooling conditions
Construction and Building Materials, 2015Co-Authors: Young Cheol Choi, Seongcheol ChoiAbstract:Abstract In this study, the alkali–silica reactivity of cementitious materials using ferro-Nickel Slag (FNS) fine aggregates was experimentally evaluated for potential use in concrete. The results revealed that the reactivity of cement mortars using the aggregates varied with the cooling speed and particle size of the FNS. For example, the rapidly (i.e., water-) cooled FNS exhibited higher alkali–silica reactivity than its gradually (air-) cooled counterpart. The particle size of the water-cooled FNS also affected the reactivity of the specimens. Furthermore, the partial replacement of FNS with sea sand, and of cements with fly ash or ground granulated blast furnace Slag was effective in reducing the alkali–silica reactivity of cementitious materials containing FNS as fine aggregates.
Young Cheol Choi - One of the best experts on this subject based on the ideXlab platform.
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alkali silica reactivity of cementitious materials using ferro Nickel Slag fine aggregates produced in different cooling conditions
Construction and Building Materials, 2015Co-Authors: Young Cheol Choi, Seongcheol ChoiAbstract:Abstract In this study, the alkali–silica reactivity of cementitious materials using ferro-Nickel Slag (FNS) fine aggregates was experimentally evaluated for potential use in concrete. The results revealed that the reactivity of cement mortars using the aggregates varied with the cooling speed and particle size of the FNS. For example, the rapidly (i.e., water-) cooled FNS exhibited higher alkali–silica reactivity than its gradually (air-) cooled counterpart. The particle size of the water-cooled FNS also affected the reactivity of the specimens. Furthermore, the partial replacement of FNS with sea sand, and of cements with fly ash or ground granulated blast furnace Slag was effective in reducing the alkali–silica reactivity of cementitious materials containing FNS as fine aggregates.
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Alkali–silica reactivity of cementitious materials using ferro-Nickel Slag fine aggregates produced in different cooling conditions
Construction and Building Materials, 2015Co-Authors: Young Cheol Choi, Seongcheol ChoiAbstract:Abstract In this study, the alkali–silica reactivity of cementitious materials using ferro-Nickel Slag (FNS) fine aggregates was experimentally evaluated for potential use in concrete. The results revealed that the reactivity of cement mortars using the aggregates varied with the cooling speed and particle size of the FNS. For example, the rapidly (i.e., water-) cooled FNS exhibited higher alkali–silica reactivity than its gradually (air-) cooled counterpart. The particle size of the water-cooled FNS also affected the reactivity of the specimens. Furthermore, the partial replacement of FNS with sea sand, and of cements with fly ash or ground granulated blast furnace Slag was effective in reducing the alkali–silica reactivity of cementitious materials containing FNS as fine aggregates.
Zuhua Zhang - One of the best experts on this subject based on the ideXlab platform.
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Alkali-Activated Cement (AAC) From Fly Ash and High-Magnesium Nickel Slag
Handbook of Low Carbon Concrete, 2020Co-Authors: Zuhua Zhang, Tao Yang, Hao WangAbstract:This chapter reports the potential of the alkali-activation method, also known as geopolymer technology, in converting high-volume industrial waste streams into green cements with significant reduction of energy consumption and CO 2 emissions in comparison with the conventional ordinary Portland cement (OPC). A particular case of using fly ash blended with high-magnesium Nickel Slag (HMNS) as solid materials to manufacture alkali-activated cement (AAC) in laboratory conditions is analyzed in this chapter. By optimizing the dose of alkali activator and the blending quantity of HMNS, it is possible to make a high-strength AAC binder with compressive strength up to 60 MPa, which is comparable to OPC and adequate for many construction purposes. The analysis on the carbon emissions and in-body energy indicates that manufacturing the same mass of binder will emit 0.21–0.22 t CO 2 and require 1.20–1.25 GJ for each ton of AAC binder. The slight variation is dependent on the HMNS blending ratio as HMNS has a higher process cost. Alkali-activation method technology is shown to be a highly promising green technology to convert local industrial wastes into useful construction and building materials.
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Re-examining the suitability of high magnesium Nickel Slag as precursors for alkali-activated materials
Construction and Building Materials, 2019Co-Authors: Tao Yang, Zuhua Zhang, Qisheng WuAbstract:Abstract High-magnesium Nickel Slag (HMNS) has shown the potential as precursor in the production of alkali-activated materials (AAMs). This study re-examines the suitability of HMNS by comparatively investigating the reactivity of four different sourced HMNSs and analyzing impacts of the magnesium sources in HMNS on the reaction products of AAMs. Results show that the cooling way plays a determinant role of their mineral compositions. The air-cooled HMNSs contain only ∼30 wt% glassy phases, while the water-quenched one is dominantly amorphous. The reactivity of HMNS determined by the dissolution tests correlates well with the calculated depolymerization degree of glasses. HMNS indeed exhibits lower reactivity than the precursors commonly used for AAMs production, such as fly ash and blast furnace Slag. In the HMNS samples in the sodium hydroxide solution, M-S-H, C-S-H and hydrotalcite are the main reaction products. The OH− ions in the aqueous system react with Mg2+ to form the brucite, indicating that there is still a volume expansion risk if sodium hydroxide is used as activator. In comparison, only M-S-H and C-S-H gels are coexistent in the samples leached in the sodium silicate solution, because of the kinetic hindrance of soluble silicates for the formation of hydrotalcite and brucite.
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geopolymer with improved thermal stability by incorporating high magnesium Nickel Slag
Construction and Building Materials, 2017Co-Authors: Tao Yang, Qisheng Wu, Zuhua ZhangAbstract:Abstract The present study investigates the thermal stability of binary geopolymers prepared with fly ash and high magnesium Nickel Slag (HMNS). TGA, XRD and SEM techniques are adopted to investigate the chemical composition and microstructure of the binder gel phase exposed to high temperatures. The results show that incorporating HMNS mitigates dehydration induced mass loss and volume shrinkage of the geopolymer samples between room temperature and 250 °C, and increases their residual strengths when exposed to high temperatures between 600 °C and 800 °C. The key role that HMNS substitution of improving the thermal stability of geopolymers is associated with the formation of sodium-alumina(magnesia)-silica hydrate (N-A(M)-S-H) gel phase, which turns to be a less porous microstructure after thermal exposure when compared with the N-A-S-H gel phase, which is formed in the pure fly ash sample. The binary geopolymers exhibit higher residual strengths and better maintaining of volume stability in the range from 250 °C to 550 °C compared to Portland cements. However, both the geopolymer and Portland cement show severer volume shrinkage after exposure of 600 °C, because of the viscous sintering of geopolymer gels and the decomposition of cement hydration products, respectively.
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geopolymer prepared with high magnesium Nickel Slag characterization of properties and microstructure
Construction and Building Materials, 2014Co-Authors: Tao Yang, Zuhua ZhangAbstract:High-magnesium Nickel Slag (HMNS) is a hazardous waste that is generated in Nickel pyrometallurgical production. The present work investigates the feasibility of using this Slag in geopolymer manufacturing. The effects of HMNS addition on the reaction, mechanical properties and microstructure of fly ash-based geopolymers are studied through isothermal conduction calorimetry (ICC), compressive strength testing, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), X-ray diffractometry (XRD) and drying shrinkage testing. The results showed that the major phase in fly ash-HMNS geopolymers was a type of sodium magnesium aluminosilicate gel (N–M–A–S) with amorphous features. The Si/Al ratio of the gel phase increased with HMNS content due to the high silica supplied by HMNS. In terms of compressive strength, the maximal strength of fly ash-based geopolymers was achieved by 20% HMNS substitution. At this optimal content, the sample possessed a refiner pore structure and lower linear drying shrinkage compared with the other samples containing 0%, 40% and 60% HMNS contents. This study shows the potential of incorporating HMNS as value source material for geopolymer production.
Xueyan Du - One of the best experts on this subject based on the ideXlab platform.
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Microwave Absorption Properties of Magnetite Particles Extracted from Nickel Slag
Materials, 2020Co-Authors: Yongqian Shen, Xueyan Du, Junkai ChongAbstract:The utilization of Nickel Slag has attracted much attention due to its high-content of valuable elements. As a part of these efforts, this work focuses on whether magnetite crystals, obtained from Nickel Slag via molten oxidation, magnetic separation, and ball-milling can be used as a microwave absorber. The composition, morphology, microstructure, magnetic properties, and microwave absorption performance were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and vector network analysis (VNA). The results reveal that the magnetite crystals exhibit excellent microwave absorption properties because of the synergistic action between dielectric loss and magnetic loss. The minimum reflection loss (RL) of the particles obtained after 6 h ball-milling reaches −34.0 dB at 16.72 GHz with thickness of 5 mm. The effective frequency bandwidth (RL ≤ −10 dB) is 4.8–5.4 GHz and 15.9–17.6 GHz. Interfacial polarization of the particles could play a crucial role in improving absorbing properties because several components contained in the particles can dissipate electromagnetic wave effectively. The current study could show great potential in the preparation of magnetite crystals and utilization of Nickel Slag.
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Phase transformations during the oxidation of fayalite in iron-rich Nickel Slag
International Journal of Materials Research, 2020Co-Authors: Yongbo Ma, Xueyan DuAbstract:Abstract Phase transformations during the oxidation of fayalite (Fe2SiO4) are investigated for the recovery of iron from iron-rich Nickel Slag by oxidation–magnetic separation. The proportions of v...
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Viscosity and Structure of a CaO-SiO2-FeO-MgO System during a Modified Process from Nickel Slag by CaO.
Materials, 2019Co-Authors: Yingying Shen, Junkai Chong, Ziniu Huang, Jianke Tian, Wenjuan Zhang, Xingchang Tang, Wanwu Ding, Xueyan DuAbstract:There is a high iron content in Nickel Slag that mainly exists in the fayalite phase. Basic oxide can destroy the stable structure of fayalite which is beneficial to the treatment and comprehensive utilization of Nickel Slag. The research was based on the composition of the raw Nickel Slag, taking the CaO-SiO2-FeO-MgO system as the object and CaO as a modifier. The effect of basicity on the melting characteristics, viscosity and structure of the CaO-SiO2-FeO-MgO system was studied. The relationship between the viscosity and structure of the CaO-SiO2-FeO-MgO system was also explored. The results show as follows: (1) When the basicity is lower than 0.90, the primary phase of the Slag system is olivine phase. When the basicity is greater than 0.90, the primary phase of the Slag system transforms into monoxide. When the basicity is 0.90, olivine and monoxide precipitate together as the temperature continues to decrease. At the same time, the liquidus temperature, softening temperature, hemispherical temperature, and flow temperature all reach the lowest value. (2) With the increase of basicity, the critical viscosity temperature of the CaO-SiO2-FeO-MgO system decreases first and then increases. Critical viscosity temperature is the lowest at the basicity of 0.90, which is 1295 °C. (3) When the Slag system is heterogeneous, the viscosity of the molten Slag increases rapidly because of the quantity of solid phase precipitated from the CaO-SiO2-FeO-MgO system. (4) When the Slag system is in a homogeneous liquid phase, the molar fraction of O0 decreases with the increase of basicity and the mole fraction of O−, and O2− increases continuously at the basicity of 0.38~1.50. The silicate network structure is gradually depolymerized into simple monomers, resulting in the degree of polymerization, and the viscosity, being reduced. The mole fraction of different kinds of oxygen atoms is converged to a constant value when the basicity is above 1.20.
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Crystallization and Beneficiation of Magnetite for Iron Recycling from Nickel Slags by Oxidation-Magnetic Separation
Metals, 2017Co-Authors: Yongbo Ma, Xueyan Du, Yingying Shen, Guozhou Li, Ming LiAbstract:The iron resources in Nickel Slag were recycled by oxidation and magnetic separation. The effects of holding time, temperature, air flow rate and basicity on the crystallization of magnetite were investigated systematically. Moreover, the influence of particle size and magnetic flux density on the recovery and grade of iron during the magnetic separation was also explored. Results showed that the magnetite particles were significantly influenced by holding time, and the average diameter size reached about 20 μm after holding for 20 min at 1623 K. The holding temperature obviously affected the microstructure of magnetite phases: with the increase in holding temperature, the shapes of the magnetite particles changed from polyhedral form to skeletal particles. As the air flow rate was increased to 170 mL/min, the magnetite developed into tiny spherical particles due to the strong stirring. It was also found that the crystallization of magnetite was slightly effected by basicity. The iron recovery reduced with the decrease of particle size, while the iron grade first increased to a maximal value of 38 μm, and then decreased. As the magnetic flux density increased, the iron recovery initially increased rapidly, reaching a maximal value at 120 mT, while the iron grade remained almost constant. The final iron recovery and grade were 75.99% and 54.08%, respectively, via multi-step magnetic separation instead of single magnetic separation. Iron in concentrate mainly exists in the form of magnetite and magnesium ferrite, and contents of siderophile elements (Ni, Co) in final concentrate were also higher than that of raw Slags.