To improve the performance of low-carbon magnesia carbon refractories,specimens were prepared using fused magnesia with particle sizes of 3-1,≤1,and≤0.074 mm,flake graphite with a particle size of≤0.15 mm as the ma...To improve the performance of low-carbon magnesia carbon refractories,specimens were prepared using fused magnesia with particle sizes of 3-1,≤1,and≤0.074 mm,flake graphite with a particle size of≤0.15 mm as the main raw materials,phenolic resin as the binder,and adding alumina micropowder with mass percentages of 1%,3%,5%,7%,and 9%,respectively.The obtained green specimens were then cured at 200℃for 24 h and heat-treated at 950℃or 1550℃for 3 h.The effects of the alumina micropowder addition on the properties(including the apparent porosity,bulk density,cold compressive strength,cold modulus of rupture,hot modulus of rupture,and thermal shock resistance)as well as on the phase composition and microstructure of the low-carbon magnesia carbon specimens were investigated.The results show that the physical properties of the specimens are improved as the alumina micropowder addition increases,mainly due to the in-situ reaction between magnesia and alumina to form spinel,which enhances the bonding of the matrix and thus strengthens the overall bonding of the specimens.After the heat treatment at 1550℃,the bulk density,cold compressive strength,and cold modulus of rupture of the specimens first increase and then decrease with the increase of the alumina micropowder addition,reaching the optimal values when the addition is 7%.Both the linear change rate and volume change rate of the specimens increase with the increasing alumina micropowder addition.展开更多
Research on the effects of the amount of fillers in the form of fused alumina,mullite,and tabular alumina,zirconium-containing and silica-containing components of the batches in the form of zircon and silica sand on t...Research on the effects of the amount of fillers in the form of fused alumina,mullite,and tabular alumina,zirconium-containing and silica-containing components of the batches in the form of zircon and silica sand on the properties of alumina-zirconia-silicate(AZS)refractories was conducted.It was found that the introduction of 16%zircon into the composition of samples with fillers such as fused alumina and mullite,as well as tabular alumina,results in an increase in their density,strength,and thermal shock resistance.Petrographic studies have revealed the formation of a multiphase,microcracked structure in these samples,which accounts for the improvement in their properties.The optimal composition of a batch containing a filler of tabular alumina,a finely dispersed matrix ofα-alumina,16%zircon,and 7%silica sand has been determined,which ensures the production of AZS refractories with high bulk density,cold crushing strength,and thermal shock resistance.Research on the plastic strength of the structure of optimal composition AZS mass,depending on its storage time,was conducted.It was found that up to 24 h of storage,the mass is characterized by low plastic strength.It indicates its suitability for use in the vibration casting technology of products.Storage of the mass for more than 24 h leads to an increase in the plastic strength of its structure,which reaches a maximum after 56 h of storage.The developed composition of the batch is recommended for the manufacture of AZS crucibles for induction melting of heat-resistant alloys.展开更多
In order to remove or reduce the negative effect of MgO in calcium aluminate slags, the method of adding Na2O into calcium aluminate slags was studied and its effect on leaching mechanism was also analyzed. The result...In order to remove or reduce the negative effect of MgO in calcium aluminate slags, the method of adding Na2O into calcium aluminate slags was studied and its effect on leaching mechanism was also analyzed. The results show that the alumina leaching efficiency of the calcium aluminate slag increases from 68.73% to 80.86% with Na2O content increasing from 0 to 4% when MgO content is 3%. The XRD results show that the quaternary compound C20A13M3S3 disappears when Na2O content increases to 4%. The addition of Na2O cannot remove the negative effect of MgO on leachability completely. XRD and EDS results indicate that Na2O can come into the lattice of 12CaO·7Al2O3 and promote the formation of 12CaO·7Al2O3展开更多
SiO2 in calcium aluminate slag exists in the form of γ-2CaO·SiO2 which is more stable than β-2CaO·SiO2. However, it is decomposed by sodium carbonate solution during leaching process, leading to the second...SiO2 in calcium aluminate slag exists in the form of γ-2CaO·SiO2 which is more stable than β-2CaO·SiO2. However, it is decomposed by sodium carbonate solution during leaching process, leading to the secondary reaction. The extent of secondary reaction and reaction mechanism of calcium aluminate slag were studied using XRD. The results show that the decomposition rate of γ-2CaO·SiO2 increases with the increase in leaching time and sodium carbonate concentration. The main products of secondary reaction are the mixture of hydrogarnet and sodium hydrate alumina-silicate. SiO2 concentration rises firstly and then drops with the increase of leaching temperature. XRD results indicate that the stable product of secondary reaction at low temperature is hydrogarnet. But hydrogarnet is transformed into sodium hydrate alumina-silicate at high temperature.展开更多
High soda content in fine alumina trihydrate（ATH） limits its application and increases the soda consumption. The variation of soda content in the fine ATH by seeded precipitation was determined by detection of elect...High soda content in fine alumina trihydrate（ATH） limits its application and increases the soda consumption. The variation of soda content in the fine ATH by seeded precipitation was determined by detection of electric conductivity of solution, soda content in ATH, measurement of particle size distribution and microscopic analysis. The results show that high concentration of sodium aluminate solution, ground circulative seed, low temperature or fast initial precipitation rate increases the soda content in ATH. Soda mainly exists in lattice soda and less soda in desilication product （DSP） exists in the fine ATH precipitated from sodium aluminate solution with concentration of Al2O3 （ρAl2O3） more than 160 g/L and mass ratio of alumina to silica （μSiO2） of 400, and lattice soda decreases with increasing initial precipitation temperature, aging seed, and low precipitation rate and precipitation time. Results also imply that -＋ 4）Na Al（OH ion-pair influences lattice soda content in ATH on the basis of electric conductivity variation.展开更多
Al_(2)O_(3)and MgO serve as the primary gangue components in sintered ores,and they are critical for the formation of CaO-Fe_(2)O_(3)-xAl_(2)O_(3)(wt%,C-F-xA)and CaO-Fe_(2)O_(3)-xM gO(wt%,C-F-xM)systems,respectively.I...Al_(2)O_(3)and MgO serve as the primary gangue components in sintered ores,and they are critical for the formation of CaO-Fe_(2)O_(3)-xAl_(2)O_(3)(wt%,C-F-xA)and CaO-Fe_(2)O_(3)-xM gO(wt%,C-F-xM)systems,respectively.In this study,a nonisothermal crystallization thermodynamics behavior of C-F-xA and C-F-xM systems was examined using differential scanning calorimetry,and a phase identification and microstructure analysis for C-F-xA and C-F-xM systems were carried out by X-ray diffraction and scanning electron microscopy.Results showed that in C-F-2A and C-F-2M systems,the increased cooling rates promoted the precipitation of CaFe_(2)O_(4)(CF)but inhibited the formation of Ca_(2)Fe_(2)O_(5)(C2F).In addition,C-F-2A system exhibited a lower theoretical initial crystallization temperature(1566 K)compared to the C-F system(1578 K).This temperature further decreases to 1554 K and 1528 K in the C-F-4A and C-F-8A systems,respectively.However,in C-F-xM system,the increased MgO content raised the crystallization temperature.This is because that the enhanced precipitation of MF(a spinel phase mainly comprised Fe_(3)O_(4)and MgFe_(2)O_(4))and C2F phases suppressed the CF precipitation reaction.In kinetic calculations,the Ozawa method revealed the apparent activation energies of the C-F-2A and C-F-2M systems.Malek's method revealed that the crystallization process in C-F-2A system initially followed a logarithmic law(lnαor lnα2),later transitioning to a reaction order law((1-α)-1or(1-α)^(-1/2),n=2/3)or the lnα2function of the exponential law.In C-F-2M system,it consistently followed the sequencef(α)=(1-α)^(2)(αis the crystallization conversion rate;n is the Avrami constant;?(α)is the differential equations for the model function of C_(2)F and CF crystallization processes).展开更多
Nanotechnology holds immense importance in the biomedical field due to its ability to revolutionize healthcare on a molecular scale.Motivated by the imperative of enhancing patient outcomes,a comprehensive numerical s...Nanotechnology holds immense importance in the biomedical field due to its ability to revolutionize healthcare on a molecular scale.Motivated by the imperative of enhancing patient outcomes,a comprehensive numerical simulation study on the dynamics of blood flow in a stenosed artery,focusing on the effects of copper and alumina nanoparticles,is conducted.The study employs a 2-dimensional Newtonian blood flow model infused with copper and alumina nanoparticles,considering the influence of a magnetic field,thermal radiation,and various flow parameters.The governing differential equations are first non-dimensionalized to facilitate analysis and subsequently solved using the 4th order collocation method,bvp4c module in MATLAB.This approach obtains velocity and temperature profiles,revealing the impact of relevant parameters crucial in the biomedical field.The findings of this study underscore the significance of understanding blood flow dynamics in stenosed arteries and the potential benefits of utilizing copper and alumina nanoparticles in treatment strategies.The incorporation of nanoparticles introduces novel avenues for enhancing therapeutic interventions,particularly in mitigating the effects of stenosis.The elucidation of velocity and temperature profiles provides valuable insights into the behavior of blood flow under different conditions,thereby informing the development of targeted biomedical applications.The arterial curvature flow parameter influences temperature profiles,with increased parameters promoting more efficient heat dissipation.The elevated values of Prandtl number and thermal radiation parameter showcase the diminished temperature profiles,indicating stronger dominance of momentum diffusion over thermal diffusion and radiative heat transfer mechanism.Sensitivity analysis of the pertinent physical parameters reveals that the Prandtl number has the most significant impact on blood flow dynamics.A statistical analysis of the present results and existing literature has also been included in the study.Overall,this research contributes to advancing our understanding of vascular health and lays the groundwork for innovative approaches in stenosis treatment and related biomedical fields.展开更多
High-alumina iron ores(Al_(2)O_(3) content>3.0wt%)are widely utilized in sinter production due to their economic benefits,yet their high alumina content challenges the performance of sinter and the stability of bla...High-alumina iron ores(Al_(2)O_(3) content>3.0wt%)are widely utilized in sinter production due to their economic benefits,yet their high alumina content challenges the performance of sinter and the stability of blast furnaces.This study focuses on the application of high-alumina composite calcium ferrites(SFCA)in the sintering of high-alumina iron ores.By prefabricating calcium ferrites,we aimed to substitute phase adjustment for compositional tuning,particularly examining its effects on enhancing sinter quality at 30wt%,50wt%,and 100wt%replacement ratios of Al_(2)O_(3).Previous work developed two types of high-alumina SFCA(A-type and B-type),with A-type demonstrating superior experimental performance.Our results indicate that increasing the proportion of A-type SFCA in the raw materi-als leads to higher calcium ferrite and composite calcium ferrite contents,while decreasing the proportions of Al_(2)O_(3),CaO,SiO_(2),calcium silicate,and calcium alumino-ferrite(CaAl_(x)Fe_(2-x)O_(4)).Scanning electron microscopy(SEM)and mineralogical analyses reveal that sinter substituted with A-type SFCA primarily consists of SFCA and calcium ferraluminate(CFA),with increasing calcium ferrite content and decreasing porosity and silicate content as the substitution ratio increases.Complete substitution of Al_(2)O_(3) with A-type SFCA enhances the compressive strength of the sinters to 22.57 MPa,a 6.76 MPa improvement over traditional methods.With 100wt%substitution,the redu-cibility reaches 0.85,a 0.33 increase over the baseline(A-type and B-type SFCA are not added).A cost-effective method for SFCA pro-duction using high-alumina ores,hazardous waste,and iron-calcium-based solid waste is proposed to lower production costs and promote the recycling of industrial solid waste.A-type SFCA exhibits significant advantages in mechanical properties,reducibility,and melting characteristics,validating its potential in optimizing sinter performance and reducing carbon emissions,thereby laying a theoretical and practical foundation for the industrial application of high-alumina SFCA.展开更多
Alumina ceramics are crucial for high-performance applications,such as turbine blades,due to their excellent thermal stability and mechanical properties.However,existing fabrication methods often fail to balance stren...Alumina ceramics are crucial for high-performance applications,such as turbine blades,due to their excellent thermal stability and mechanical properties.However,existing fabrication methods often fail to balance strength,porosity,and dimensional precision.This study partially fills this research gap through a systematic investigation of calcium oxide(CaO)doping effects on alumina ceramic cores fabricated via ceramic stereolithography,with controlled doping ratios and sintering parameters.A ceramic paste was prepared using coarse and fine Al_(2)O_(3) particles mixed with CaO as a sintering aid,followed by debinding and sintering to achieve optimal mechanical properties.The results show that CaO doping significantly enhances the fiexural strength of alumina cores while maintaining porosity levels between 20%and 30%and controlling the sintering shrinkage rate to about 5%.Additionally,CaO doping alters the microstructure by inhibiting the transformation of spherical fine particles into fiaky grains,improving sintering activity.However,as the CaO doping content increases,the bending strength increases,while the shrinkage rate of the material also tends to increase,resulting in a reduction in the overall porosity.This has a negative impact on the control of the manufacturing precision of turbine blades.Thus,although CaO doping improves strength and microstructure,achieving necessary dimensional control requires further optimization of doping content and sintering conditions.展开更多
With the gradual reduction in high-quality iron ore resources,the global steel industry faces long-term challenges.For example,the continuous increase in the Al_(2)O_(3) content of iron ore has led to a decrease in th...With the gradual reduction in high-quality iron ore resources,the global steel industry faces long-term challenges.For example,the continuous increase in the Al_(2)O_(3) content of iron ore has led to a decrease in the metallurgical performance of sinter and fluctuations in slag properties.Considering calcium ferrite(CF)and composite CF(silico-ferrite of calcium and aluminum,SFCA)play a crucial role as a binding phase in high-alkalinity sinter and exhibit excellent physical strength and metallurgical performance,we propose incorporating excess Al_(2)O_(3) into SFCA to form a new binding phase with excellent properties for high-quality sinter preparation.In the synthesis of high-Al_(2)O_(3) SFCA,two high-Al_(2)O_(3) phases were identified as types A(Al_(1.2)Ca_(2.8)Fe_(8.7)O_(2)0Si_(0.8))and B(Ca_(4)Al_(4.18)Fe_(1.82)Si_(6)O_(26)).Results show that type A SFCA sample had a higher cell density(4.13 g/cm^(3))and longer Fe-O bond length(2.2193Å)than type B(3.46 g/cm^(3) and 1.9415Å),with a significantly greater lattice oxygen concentration(7.86%vs.1.85%),which demonstrates advantages in strength and reducibility.Type A SFCA sample contained a lower proportion of silicates,was predominantly composed of SFCA,and exhibited minimal porosity.Melting point and viscosity simulation tests indicate that type A SFCA sample formed a liquid phase at 880°C with a viscosity range of 0-0.35 Pa·s,which is notably lower than that of type B SFCA sample(1220°C and 0-20 Pa·s).This finding suggests that type A SFCA sample has a low initial melting temperature and viscosity,which facilitates increasing liquid-phase generation and improving flow properties.Such a condition enhances the adhesion to surrounding ore particles.Compressive strength tests reveal that type A SFCA sample(36.83-42.48 MPa)considerably outperformed type B SFCA sample(5.98-12.79 MPa)and traditional sinter(5.02-13.68 MPa).In addition,at 900°C,type A SFCA sample achieved a final reducibility of 0.89,which surpassed that of type B SFCA sample(0.83).In summary,type A SFCA sample demonstrates superior structural,thermophysical,and metallurgical properties,which highlights its promising potential for industrial applications.展开更多
To enhance the performance,reactive MgO-bonded corundum-spinel castables were prepared using tabular corundum,reactive alumina,reactive MgO,and aluminum lactate as raw materials.The influence of the reactive alumina a...To enhance the performance,reactive MgO-bonded corundum-spinel castables were prepared using tabular corundum,reactive alumina,reactive MgO,and aluminum lactate as raw materials.The influence of the reactive alumina addition(0,8%,13%,and 18%,by mass)on the microstructure,phase composition,physical properties,as well as the resistance to slag corrosion and penetration of the castables was investigated.The results show that:(1)the reactive alumina promotes the sintering of the reactive MgO-bonded corundum-spinel castables,enhancing the bonding between aggregates and matrix,thus densifying the microstructure;(2)with the increase of the reactive alumina,the volume stability of the samples increases,the apparent porosity decreases,the bulk density increases,and the cold modulus of rupture and cold compressive strength as well as the slag resistance are improved;(3)the reactive MgO-bonded corundum-spinel castable with 18%reactive alumina shows optimal comprehensive performance,with the bulk density of 3.05 g·cm^(-3),apparent porosity of 18.5%,permanent linear change rate after heating of 0.31%,cold modulus of rupture of 13.5 MPa and cold compressive strengths of 73.8 MPa,as well as the best slag resistance.However,considering particle size distribution and raw material costs,there is no need to further increase the reactive alumina addition.展开更多
Alumina fibers,with an aspect ratio ranging from 9 to 27,were utilized as the reinforcing materials for silica-sol ceramic shell molds,and the impact of different alumina fiber additions on the green bending strength,...Alumina fibers,with an aspect ratio ranging from 9 to 27,were utilized as the reinforcing materials for silica-sol ceramic shell molds,and the impact of different alumina fiber additions on the green bending strength,room-and high-temperature bending strength,and self-weight deformation of ceramic shell molds was investigated.The green bending strength of shell molds is the maximum at an alumina fiber addition amount of 0.2wt.%,reaching 6.20 MPa.Further increases in alumina fiber content do not significantly affect the green bending strength.As the alumina fiber addition amount increases from 0.2wt.% to 1.0wt.%,the bending strength and the resistance to self-weight deformation of the ceramic shell molds at high-temperatures show a pattern of first increase and then decrease.The shell molds after sintering exhibit the highest room-temperature strength of 17.33 MPa and the highest high-temperature strength(18.97 MPa at 1,100℃;17.78 MPa at 1,200℃;and 15.3 MPa at 1,300℃),and the smallest self-weight deformation of 0.022% at 1,000℃ when the alumina fiber addition is 0.6wt.%.The appropriate amount of fibers in the shell mold matrix consume the energy required for crack growth through mechanisms such as bridging and pulling-out,thereby improving the strength of shell molds.In summary,the comprehensive performance of the shell molds is the best when the fiber addition amount is 0.6wt.%.展开更多
Ceramic materials with intricate structures can be efficiently fabricated using stereolithography(SLA)based 3D printing technology,offering advantages over traditional methods.Sintering temperature has primary effect ...Ceramic materials with intricate structures can be efficiently fabricated using stereolithography(SLA)based 3D printing technology,offering advantages over traditional methods.Sintering temperature has primary effect on properties of ceramics.This study investigated the crucial sintering temperature for 3D printed ceramics to ensure the desired properties.The results indicate that all samples exhibit a consistent layered structure across the experimental sintering temperatures.When the sintering temperature is increased from 1,250℃ to 1,350℃,the grain's morphology changes from spherical to plate-like.Surface morphology analysis reveals a decrease in surface roughness at sintering temperatures above 1,350℃.Mechanical tests show improved flexural strength and stiffness as the sintering temperature rises.Friction and wear experiments demonstrate that as the sintering temperature increases from 1,450℃ to 1,550℃,the wear pattern on ceramic surfaces transitions from deep pits to shallow grooves.The increase in sintering temperature effectively enhances the wear resistance of 3D printed alumina ceramics.This improvement plays a significant role in expanding the application field of these ceramics,prolonging the lifespan of parts,reducing production costs,enhancing performance,and promoting environmental protection.In this study,ceramics achieve the highest strength and best wear resistance when sintered at 1,600℃,resulting in the best overall performance.展开更多
Corn starch was used as a templating agent,and an oxide mixture containing alumina,magnesia,zirconia and yttria was added in the sol-gel state.After slip casting,curing at 85℃,drying and sintering,high-performance po...Corn starch was used as a templating agent,and an oxide mixture containing alumina,magnesia,zirconia and yttria was added in the sol-gel state.After slip casting,curing at 85℃,drying and sintering,high-performance porous alumina ceramics were obtained.The properties of the porous alumina ceramics were analyzed by means of SEM,XRD,flexural strength and porosity.The research findings showed that,when the starch content was 1 wt%,the prepared ceramic mainly consisted of four phases:α-Al_(2)O_(3),MgAl_(2)O_(4),ZrO,and YSZ.The flexural strength reached 157.27 MPa,the flexural strength of the green body was about 3 MPa,and the porosity was around 30%.展开更多
We presented a novel porous alumina ceramics(PACs)with superoleophilicity and superoleo-phobicity when immersed in different oil-water environments.The wettability,separation efficiency,permeation flux and reusability...We presented a novel porous alumina ceramics(PACs)with superoleophilicity and superoleo-phobicity when immersed in different oil-water environments.The wettability,separation efficiency,permeation flux and reusability of the PACs for oil/water separation were investigated and characterized via extensive ex-periments.The PACs material had favourable properties including mechanical strength and chemical durability compared with fabric-based materials and organic sponge-based materials previously reported in literature for oil/water separation.It is believed that the PACs material and methodology presented in this work may provide wastewater remediation industry with a promising alternative for dealing with the catastrophic ocean oil pollu-tion and other oil contamination.展开更多
Three different kinds of corundum aggregates-tabular sintered alumina, dense sintered alumina, and fused dense corundum-were introduced into the silica fume .free or silica fume containing Al2O3 -SiC - C iron runner c...Three different kinds of corundum aggregates-tabular sintered alumina, dense sintered alumina, and fused dense corundum-were introduced into the silica fume .free or silica fume containing Al2O3 -SiC - C iron runner castables to investigate their influences on the flow ability, linear change on heating, bulk density, apparent porosity, cold strength, hot modulus of rupture, therm, al shock resistance, slag resistance, oxidation resistance as well as wear resistance of Al2O3 - SiC - C iron runner castables. The results show that （ 1 ） compared with the specimens with fused dense corundum, the specimens with dense sintered alumina have equivalent installation property, slag resistance and oxidation resistance, equivalent or even higher cold modulus of rupture, cold crushing strength and hot modulus of rupture, exhibiting better thermal shock resistance and cold wear resistance ; （2） adopting bimodal alumina micropowder LISAL22RABL as well as water reducers ZX2 and ZD2 can well reduce the water requirement of silica fume free castables, solving the problem of deteriorated flow ability resulted from the lack of silica fume; since the lack of silica fume avoids the formation of low melting point liquid, the hot modulus of rupture and the thermal shock resistance of the silica fume free castables are both better than those of the silica fume containing castables ; （3） the density of the castable specimens with dense sintered alumina is 4% -6% lower than that of the castable specimens with Jhsed dense corundum so the refractories consumption of one iron runner reduces by 5% by using the tastable with dense sintered alumina, which obviously reduces the cost of refractories.展开更多
The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morpholo...The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to A1203 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 ~C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of A1203/SIO2 up to 2.19：1.展开更多
NH4HSO4 roasting technology was used for preparing Al2O3 from fly ash. First, Al and Fe were extracted from fly ash by NH4HSO4 roasting and deionized water leaching. Then, the Al and Fe in the leached liquid were prec...NH4HSO4 roasting technology was used for preparing Al2O3 from fly ash. First, Al and Fe were extracted from fly ash by NH4HSO4 roasting and deionized water leaching. Then, the Al and Fe in the leached liquid were precipitated by adding NH4HCO3 solution. After the mixed precipitations of Al（OH）3 and Fe（OH）3 were leached by NaOH solution, the NaAl（OH）4 solution was decomposed by carbonation. Finally, the pure Al（OH）3 was calcined to α-Al2O3. The optimal conditions of the whole technology were determined by experiments. The quality ofa-Al2O3 product is up to the technical indicator of YS/T 274-1998 standard.展开更多
To utilize CFBC Al-rich fly ash, a mild hydrochemical extraction process was investigated for recovery of alumina. An alumina extraction efficiency of 92.31%was attained using a 45%NaOH solution, an original caustic r...To utilize CFBC Al-rich fly ash, a mild hydrochemical extraction process was investigated for recovery of alumina. An alumina extraction efficiency of 92.31%was attained using a 45%NaOH solution, an original caustic ratio （molar ratio of Na2O to Al2O3 in the sodium aluminate solution） of 25, a molar ratio of CaO to SiO2 in the fly ash of 1.1, a liquid volume to solid mass ratio of 9, a reaction temperature of 280 ℃, and a residence time of 1 h when treating fly ash with an alumina to silica mass ratio （A/S） of 0.78 and an alumina content of 32.43%. Additionally, the alumina leaching mechanism was explored via structural and chemical analysis, which revealed that after alkaline digestion, the main solid phase containing silica was NaCaHSiO4 with a theoretical A/S of zero.展开更多
Calcium hexaluminate （ CA6 ） was synthesized by mixing light-weight calcium carbonate and Al2O3 mi- cropowder （calcined α-Al2O3, activated α-Al2O3 or α-Al2O3） according to the stoichimetric ratio of CA6, and ...Calcium hexaluminate （ CA6 ） was synthesized by mixing light-weight calcium carbonate and Al2O3 mi- cropowder （calcined α-Al2O3, activated α-Al2O3 or α-Al2O3） according to the stoichimetric ratio of CA6, and reaction sintering at 1 200, 1 300, 1 400 and 1 500 ℃fin 3 h, respectiely. Efcts of the three alu- mina micropowders on the phase composition, micro- structure and properties of CA were investigated. The re- sults show that ： （ 1 ） for the three Al2O3 micropowders, the reaction to generate CA6 in specimens basically com- plete. at about 1 500 ℃ ; CA6 generated in all specimens is planar, bat the array modes are slightly different; （2） the specimel＇s prepared from, calcined α-Al2O3or ρ-Al2O3 shrink almost, while the specimens prepared from activated α-Al2O3 expand ; （ 3 ） the cold crushing strength of the specimen prepared from activated α-Al2O3 is the highest, reaching 42.5 MPa when only CA6 exists （ after firing at 1 500 ℃ ） ; （ 4 ） the specimen prepared from ρ-Al2O3 has the lowest generation temperature of CA6 and the highest apparent porosity, reaching 70. 1% when only CA exists （after firing at 1 500 ℃）; （5） the specimen prepared from calcined α-Al2O3 has the biggest bulk density.展开更多
基金National Natural Science Foundation of China(U24A20101)。
文摘To improve the performance of low-carbon magnesia carbon refractories,specimens were prepared using fused magnesia with particle sizes of 3-1,≤1,and≤0.074 mm,flake graphite with a particle size of≤0.15 mm as the main raw materials,phenolic resin as the binder,and adding alumina micropowder with mass percentages of 1%,3%,5%,7%,and 9%,respectively.The obtained green specimens were then cured at 200℃for 24 h and heat-treated at 950℃or 1550℃for 3 h.The effects of the alumina micropowder addition on the properties(including the apparent porosity,bulk density,cold compressive strength,cold modulus of rupture,hot modulus of rupture,and thermal shock resistance)as well as on the phase composition and microstructure of the low-carbon magnesia carbon specimens were investigated.The results show that the physical properties of the specimens are improved as the alumina micropowder addition increases,mainly due to the in-situ reaction between magnesia and alumina to form spinel,which enhances the bonding of the matrix and thus strengthens the overall bonding of the specimens.After the heat treatment at 1550℃,the bulk density,cold compressive strength,and cold modulus of rupture of the specimens first increase and then decrease with the increase of the alumina micropowder addition,reaching the optimal values when the addition is 7%.Both the linear change rate and volume change rate of the specimens increase with the increasing alumina micropowder addition.
文摘Research on the effects of the amount of fillers in the form of fused alumina,mullite,and tabular alumina,zirconium-containing and silica-containing components of the batches in the form of zircon and silica sand on the properties of alumina-zirconia-silicate(AZS)refractories was conducted.It was found that the introduction of 16%zircon into the composition of samples with fillers such as fused alumina and mullite,as well as tabular alumina,results in an increase in their density,strength,and thermal shock resistance.Petrographic studies have revealed the formation of a multiphase,microcracked structure in these samples,which accounts for the improvement in their properties.The optimal composition of a batch containing a filler of tabular alumina,a finely dispersed matrix ofα-alumina,16%zircon,and 7%silica sand has been determined,which ensures the production of AZS refractories with high bulk density,cold crushing strength,and thermal shock resistance.Research on the plastic strength of the structure of optimal composition AZS mass,depending on its storage time,was conducted.It was found that up to 24 h of storage,the mass is characterized by low plastic strength.It indicates its suitability for use in the vibration casting technology of products.Storage of the mass for more than 24 h leads to an increase in the plastic strength of its structure,which reaches a maximum after 56 h of storage.The developed composition of the batch is recommended for the manufacture of AZS crucibles for induction melting of heat-resistant alloys.
基金Project (51104053) supported by the National Natural Science Foundation of ChinaProject (XL200921) supported by the Foundation Research funds for Hebei University of Science and Technology, China
文摘In order to remove or reduce the negative effect of MgO in calcium aluminate slags, the method of adding Na2O into calcium aluminate slags was studied and its effect on leaching mechanism was also analyzed. The results show that the alumina leaching efficiency of the calcium aluminate slag increases from 68.73% to 80.86% with Na2O content increasing from 0 to 4% when MgO content is 3%. The XRD results show that the quaternary compound C20A13M3S3 disappears when Na2O content increases to 4%. The addition of Na2O cannot remove the negative effect of MgO on leachability completely. XRD and EDS results indicate that Na2O can come into the lattice of 12CaO·7Al2O3 and promote the formation of 12CaO·7Al2O3
基金Project(51104053)supported by the National Natural Science Foundation of ChinaProject(E2012208047)supported by the Natural Science Foundation of Hebei Province,China
文摘SiO2 in calcium aluminate slag exists in the form of γ-2CaO·SiO2 which is more stable than β-2CaO·SiO2. However, it is decomposed by sodium carbonate solution during leaching process, leading to the secondary reaction. The extent of secondary reaction and reaction mechanism of calcium aluminate slag were studied using XRD. The results show that the decomposition rate of γ-2CaO·SiO2 increases with the increase in leaching time and sodium carbonate concentration. The main products of secondary reaction are the mixture of hydrogarnet and sodium hydrate alumina-silicate. SiO2 concentration rises firstly and then drops with the increase of leaching temperature. XRD results indicate that the stable product of secondary reaction at low temperature is hydrogarnet. But hydrogarnet is transformed into sodium hydrate alumina-silicate at high temperature.
基金Project(51274242)supported by the National Natural Science Foundation of China
文摘High soda content in fine alumina trihydrate（ATH） limits its application and increases the soda consumption. The variation of soda content in the fine ATH by seeded precipitation was determined by detection of electric conductivity of solution, soda content in ATH, measurement of particle size distribution and microscopic analysis. The results show that high concentration of sodium aluminate solution, ground circulative seed, low temperature or fast initial precipitation rate increases the soda content in ATH. Soda mainly exists in lattice soda and less soda in desilication product （DSP） exists in the fine ATH precipitated from sodium aluminate solution with concentration of Al2O3 （ρAl2O3） more than 160 g/L and mass ratio of alumina to silica （μSiO2） of 400, and lattice soda decreases with increasing initial precipitation temperature, aging seed, and low precipitation rate and precipitation time. Results also imply that -＋ 4）Na Al（OH ion-pair influences lattice soda content in ATH on the basis of electric conductivity variation.
基金financially supported by the National Natural Science Foundation of China(Nos.52204331 and 52374315)the Major Industrial Innovation Plan of Anhui Provincial Development and the Reform Commission,China(No.AHZDCYCX-LSDT2023-01)。
文摘Al_(2)O_(3)and MgO serve as the primary gangue components in sintered ores,and they are critical for the formation of CaO-Fe_(2)O_(3)-xAl_(2)O_(3)(wt%,C-F-xA)and CaO-Fe_(2)O_(3)-xM gO(wt%,C-F-xM)systems,respectively.In this study,a nonisothermal crystallization thermodynamics behavior of C-F-xA and C-F-xM systems was examined using differential scanning calorimetry,and a phase identification and microstructure analysis for C-F-xA and C-F-xM systems were carried out by X-ray diffraction and scanning electron microscopy.Results showed that in C-F-2A and C-F-2M systems,the increased cooling rates promoted the precipitation of CaFe_(2)O_(4)(CF)but inhibited the formation of Ca_(2)Fe_(2)O_(5)(C2F).In addition,C-F-2A system exhibited a lower theoretical initial crystallization temperature(1566 K)compared to the C-F system(1578 K).This temperature further decreases to 1554 K and 1528 K in the C-F-4A and C-F-8A systems,respectively.However,in C-F-xM system,the increased MgO content raised the crystallization temperature.This is because that the enhanced precipitation of MF(a spinel phase mainly comprised Fe_(3)O_(4)and MgFe_(2)O_(4))and C2F phases suppressed the CF precipitation reaction.In kinetic calculations,the Ozawa method revealed the apparent activation energies of the C-F-2A and C-F-2M systems.Malek's method revealed that the crystallization process in C-F-2A system initially followed a logarithmic law(lnαor lnα2),later transitioning to a reaction order law((1-α)-1or(1-α)^(-1/2),n=2/3)or the lnα2function of the exponential law.In C-F-2M system,it consistently followed the sequencef(α)=(1-α)^(2)(αis the crystallization conversion rate;n is the Avrami constant;?(α)is the differential equations for the model function of C_(2)F and CF crystallization processes).
基金funded by Universiti Teknikal Malaysia Melaka and Ministry of Higher Education(MoHE)Malaysia,grant number FRGS/1/2024/FTKM/F00586.
文摘Nanotechnology holds immense importance in the biomedical field due to its ability to revolutionize healthcare on a molecular scale.Motivated by the imperative of enhancing patient outcomes,a comprehensive numerical simulation study on the dynamics of blood flow in a stenosed artery,focusing on the effects of copper and alumina nanoparticles,is conducted.The study employs a 2-dimensional Newtonian blood flow model infused with copper and alumina nanoparticles,considering the influence of a magnetic field,thermal radiation,and various flow parameters.The governing differential equations are first non-dimensionalized to facilitate analysis and subsequently solved using the 4th order collocation method,bvp4c module in MATLAB.This approach obtains velocity and temperature profiles,revealing the impact of relevant parameters crucial in the biomedical field.The findings of this study underscore the significance of understanding blood flow dynamics in stenosed arteries and the potential benefits of utilizing copper and alumina nanoparticles in treatment strategies.The incorporation of nanoparticles introduces novel avenues for enhancing therapeutic interventions,particularly in mitigating the effects of stenosis.The elucidation of velocity and temperature profiles provides valuable insights into the behavior of blood flow under different conditions,thereby informing the development of targeted biomedical applications.The arterial curvature flow parameter influences temperature profiles,with increased parameters promoting more efficient heat dissipation.The elevated values of Prandtl number and thermal radiation parameter showcase the diminished temperature profiles,indicating stronger dominance of momentum diffusion over thermal diffusion and radiative heat transfer mechanism.Sensitivity analysis of the pertinent physical parameters reveals that the Prandtl number has the most significant impact on blood flow dynamics.A statistical analysis of the present results and existing literature has also been included in the study.Overall,this research contributes to advancing our understanding of vascular health and lays the groundwork for innovative approaches in stenosis treatment and related biomedical fields.
基金supported by the National Natural Science Foundation of China(Nos.52204331 and 52374315)Major Industrial Innovation Plan of Anhui Provincial Development and Reform Commission,China(No.AHZDCYCXLSDT2023-01).
文摘High-alumina iron ores(Al_(2)O_(3) content>3.0wt%)are widely utilized in sinter production due to their economic benefits,yet their high alumina content challenges the performance of sinter and the stability of blast furnaces.This study focuses on the application of high-alumina composite calcium ferrites(SFCA)in the sintering of high-alumina iron ores.By prefabricating calcium ferrites,we aimed to substitute phase adjustment for compositional tuning,particularly examining its effects on enhancing sinter quality at 30wt%,50wt%,and 100wt%replacement ratios of Al_(2)O_(3).Previous work developed two types of high-alumina SFCA(A-type and B-type),with A-type demonstrating superior experimental performance.Our results indicate that increasing the proportion of A-type SFCA in the raw materi-als leads to higher calcium ferrite and composite calcium ferrite contents,while decreasing the proportions of Al_(2)O_(3),CaO,SiO_(2),calcium silicate,and calcium alumino-ferrite(CaAl_(x)Fe_(2-x)O_(4)).Scanning electron microscopy(SEM)and mineralogical analyses reveal that sinter substituted with A-type SFCA primarily consists of SFCA and calcium ferraluminate(CFA),with increasing calcium ferrite content and decreasing porosity and silicate content as the substitution ratio increases.Complete substitution of Al_(2)O_(3) with A-type SFCA enhances the compressive strength of the sinters to 22.57 MPa,a 6.76 MPa improvement over traditional methods.With 100wt%substitution,the redu-cibility reaches 0.85,a 0.33 increase over the baseline(A-type and B-type SFCA are not added).A cost-effective method for SFCA pro-duction using high-alumina ores,hazardous waste,and iron-calcium-based solid waste is proposed to lower production costs and promote the recycling of industrial solid waste.A-type SFCA exhibits significant advantages in mechanical properties,reducibility,and melting characteristics,validating its potential in optimizing sinter performance and reducing carbon emissions,thereby laying a theoretical and practical foundation for the industrial application of high-alumina SFCA.
基金financially supported by the National Key R&D Program of China(No.2023YFB4606101)the National Key R&D Program of China(No.2022YFB4601404)+3 种基金the Innovative and Entrepreneurial PhD Program of Jiangsu Province(No.JSSCBS20210836)the youth program of Jiangnan University(No.JUSRP121038)the Taihu Talent Program of Wuxi Citythe Innovative and Entrepreneurial Talent Program of Jiangsu Province(No.JSSCRC2021531)。
文摘Alumina ceramics are crucial for high-performance applications,such as turbine blades,due to their excellent thermal stability and mechanical properties.However,existing fabrication methods often fail to balance strength,porosity,and dimensional precision.This study partially fills this research gap through a systematic investigation of calcium oxide(CaO)doping effects on alumina ceramic cores fabricated via ceramic stereolithography,with controlled doping ratios and sintering parameters.A ceramic paste was prepared using coarse and fine Al_(2)O_(3) particles mixed with CaO as a sintering aid,followed by debinding and sintering to achieve optimal mechanical properties.The results show that CaO doping significantly enhances the fiexural strength of alumina cores while maintaining porosity levels between 20%and 30%and controlling the sintering shrinkage rate to about 5%.Additionally,CaO doping alters the microstructure by inhibiting the transformation of spherical fine particles into fiaky grains,improving sintering activity.However,as the CaO doping content increases,the bending strength increases,while the shrinkage rate of the material also tends to increase,resulting in a reduction in the overall porosity.This has a negative impact on the control of the manufacturing precision of turbine blades.Thus,although CaO doping improves strength and microstructure,achieving necessary dimensional control requires further optimization of doping content and sintering conditions.
基金financially supported by the National Natural Science Foundation of China(Nos.52204331 and 52374315)the Major Industrial Innovation Plan of the Anhui Provincial Development and Reform Commission,China(No.AHZDCYCX-LSDT2023-01).
文摘With the gradual reduction in high-quality iron ore resources,the global steel industry faces long-term challenges.For example,the continuous increase in the Al_(2)O_(3) content of iron ore has led to a decrease in the metallurgical performance of sinter and fluctuations in slag properties.Considering calcium ferrite(CF)and composite CF(silico-ferrite of calcium and aluminum,SFCA)play a crucial role as a binding phase in high-alkalinity sinter and exhibit excellent physical strength and metallurgical performance,we propose incorporating excess Al_(2)O_(3) into SFCA to form a new binding phase with excellent properties for high-quality sinter preparation.In the synthesis of high-Al_(2)O_(3) SFCA,two high-Al_(2)O_(3) phases were identified as types A(Al_(1.2)Ca_(2.8)Fe_(8.7)O_(2)0Si_(0.8))and B(Ca_(4)Al_(4.18)Fe_(1.82)Si_(6)O_(26)).Results show that type A SFCA sample had a higher cell density(4.13 g/cm^(3))and longer Fe-O bond length(2.2193Å)than type B(3.46 g/cm^(3) and 1.9415Å),with a significantly greater lattice oxygen concentration(7.86%vs.1.85%),which demonstrates advantages in strength and reducibility.Type A SFCA sample contained a lower proportion of silicates,was predominantly composed of SFCA,and exhibited minimal porosity.Melting point and viscosity simulation tests indicate that type A SFCA sample formed a liquid phase at 880°C with a viscosity range of 0-0.35 Pa·s,which is notably lower than that of type B SFCA sample(1220°C and 0-20 Pa·s).This finding suggests that type A SFCA sample has a low initial melting temperature and viscosity,which facilitates increasing liquid-phase generation and improving flow properties.Such a condition enhances the adhesion to surrounding ore particles.Compressive strength tests reveal that type A SFCA sample(36.83-42.48 MPa)considerably outperformed type B SFCA sample(5.98-12.79 MPa)and traditional sinter(5.02-13.68 MPa).In addition,at 900°C,type A SFCA sample achieved a final reducibility of 0.89,which surpassed that of type B SFCA sample(0.83).In summary,type A SFCA sample demonstrates superior structural,thermophysical,and metallurgical properties,which highlights its promising potential for industrial applications.
基金Joint Founds of R&D Program of Henan Province(222301420034)Collaborative Innovation Major Special Project of Zhengzhou(No.20XTZX2025)for the financial support.
文摘To enhance the performance,reactive MgO-bonded corundum-spinel castables were prepared using tabular corundum,reactive alumina,reactive MgO,and aluminum lactate as raw materials.The influence of the reactive alumina addition(0,8%,13%,and 18%,by mass)on the microstructure,phase composition,physical properties,as well as the resistance to slag corrosion and penetration of the castables was investigated.The results show that:(1)the reactive alumina promotes the sintering of the reactive MgO-bonded corundum-spinel castables,enhancing the bonding between aggregates and matrix,thus densifying the microstructure;(2)with the increase of the reactive alumina,the volume stability of the samples increases,the apparent porosity decreases,the bulk density increases,and the cold modulus of rupture and cold compressive strength as well as the slag resistance are improved;(3)the reactive MgO-bonded corundum-spinel castable with 18%reactive alumina shows optimal comprehensive performance,with the bulk density of 3.05 g·cm^(-3),apparent porosity of 18.5%,permanent linear change rate after heating of 0.31%,cold modulus of rupture of 13.5 MPa and cold compressive strengths of 73.8 MPa,as well as the best slag resistance.However,considering particle size distribution and raw material costs,there is no need to further increase the reactive alumina addition.
文摘Alumina fibers,with an aspect ratio ranging from 9 to 27,were utilized as the reinforcing materials for silica-sol ceramic shell molds,and the impact of different alumina fiber additions on the green bending strength,room-and high-temperature bending strength,and self-weight deformation of ceramic shell molds was investigated.The green bending strength of shell molds is the maximum at an alumina fiber addition amount of 0.2wt.%,reaching 6.20 MPa.Further increases in alumina fiber content do not significantly affect the green bending strength.As the alumina fiber addition amount increases from 0.2wt.% to 1.0wt.%,the bending strength and the resistance to self-weight deformation of the ceramic shell molds at high-temperatures show a pattern of first increase and then decrease.The shell molds after sintering exhibit the highest room-temperature strength of 17.33 MPa and the highest high-temperature strength(18.97 MPa at 1,100℃;17.78 MPa at 1,200℃;and 15.3 MPa at 1,300℃),and the smallest self-weight deformation of 0.022% at 1,000℃ when the alumina fiber addition is 0.6wt.%.The appropriate amount of fibers in the shell mold matrix consume the energy required for crack growth through mechanisms such as bridging and pulling-out,thereby improving the strength of shell molds.In summary,the comprehensive performance of the shell molds is the best when the fiber addition amount is 0.6wt.%.
基金supported by the Xinjiang Tianchi Talent Introduction Plan (51052300585)the Fundamental Research Funds for Autonomous Region Universities (XJEDU2022P002)+1 种基金the Natural science foundation project of Xinjiang Uygur Autonomous Region (2023D01C192,2023D01C33)the Tianshan Innovation Team Program of Xinjiang Uygur Autonomous Region (2023D14001)。
文摘Ceramic materials with intricate structures can be efficiently fabricated using stereolithography(SLA)based 3D printing technology,offering advantages over traditional methods.Sintering temperature has primary effect on properties of ceramics.This study investigated the crucial sintering temperature for 3D printed ceramics to ensure the desired properties.The results indicate that all samples exhibit a consistent layered structure across the experimental sintering temperatures.When the sintering temperature is increased from 1,250℃ to 1,350℃,the grain's morphology changes from spherical to plate-like.Surface morphology analysis reveals a decrease in surface roughness at sintering temperatures above 1,350℃.Mechanical tests show improved flexural strength and stiffness as the sintering temperature rises.Friction and wear experiments demonstrate that as the sintering temperature increases from 1,450℃ to 1,550℃,the wear pattern on ceramic surfaces transitions from deep pits to shallow grooves.The increase in sintering temperature effectively enhances the wear resistance of 3D printed alumina ceramics.This improvement plays a significant role in expanding the application field of these ceramics,prolonging the lifespan of parts,reducing production costs,enhancing performance,and promoting environmental protection.In this study,ceramics achieve the highest strength and best wear resistance when sintered at 1,600℃,resulting in the best overall performance.
文摘Corn starch was used as a templating agent,and an oxide mixture containing alumina,magnesia,zirconia and yttria was added in the sol-gel state.After slip casting,curing at 85℃,drying and sintering,high-performance porous alumina ceramics were obtained.The properties of the porous alumina ceramics were analyzed by means of SEM,XRD,flexural strength and porosity.The research findings showed that,when the starch content was 1 wt%,the prepared ceramic mainly consisted of four phases:α-Al_(2)O_(3),MgAl_(2)O_(4),ZrO,and YSZ.The flexural strength reached 157.27 MPa,the flexural strength of the green body was about 3 MPa,and the porosity was around 30%.
基金Fund by the Science and Technology Programme Project of Bengbu City(No.2023gx01)the Key Technologies R&D Program of CNBM(No.2021HX0809)。
文摘We presented a novel porous alumina ceramics(PACs)with superoleophilicity and superoleo-phobicity when immersed in different oil-water environments.The wettability,separation efficiency,permeation flux and reusability of the PACs for oil/water separation were investigated and characterized via extensive ex-periments.The PACs material had favourable properties including mechanical strength and chemical durability compared with fabric-based materials and organic sponge-based materials previously reported in literature for oil/water separation.It is believed that the PACs material and methodology presented in this work may provide wastewater remediation industry with a promising alternative for dealing with the catastrophic ocean oil pollu-tion and other oil contamination.
文摘Three different kinds of corundum aggregates-tabular sintered alumina, dense sintered alumina, and fused dense corundum-were introduced into the silica fume .free or silica fume containing Al2O3 -SiC - C iron runner castables to investigate their influences on the flow ability, linear change on heating, bulk density, apparent porosity, cold strength, hot modulus of rupture, therm, al shock resistance, slag resistance, oxidation resistance as well as wear resistance of Al2O3 - SiC - C iron runner castables. The results show that （ 1 ） compared with the specimens with fused dense corundum, the specimens with dense sintered alumina have equivalent installation property, slag resistance and oxidation resistance, equivalent or even higher cold modulus of rupture, cold crushing strength and hot modulus of rupture, exhibiting better thermal shock resistance and cold wear resistance ; （2） adopting bimodal alumina micropowder LISAL22RABL as well as water reducers ZX2 and ZD2 can well reduce the water requirement of silica fume free castables, solving the problem of deteriorated flow ability resulted from the lack of silica fume; since the lack of silica fume avoids the formation of low melting point liquid, the hot modulus of rupture and the thermal shock resistance of the silica fume free castables are both better than those of the silica fume containing castables ; （3） the density of the castable specimens with dense sintered alumina is 4% -6% lower than that of the castable specimens with Jhsed dense corundum so the refractories consumption of one iron runner reduces by 5% by using the tastable with dense sintered alumina, which obviously reduces the cost of refractories.
基金Project(2652014017) supported by the Fundamental Research Funds for the Central Universities,China
文摘The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to A1203 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 ~C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of A1203/SIO2 up to 2.19：1.
基金Project(2007CB613603)supported by the National Basic Research Program of ChinaProject(2013M530934)supported by the China Postdoctoral Science Foundation
文摘NH4HSO4 roasting technology was used for preparing Al2O3 from fly ash. First, Al and Fe were extracted from fly ash by NH4HSO4 roasting and deionized water leaching. Then, the Al and Fe in the leached liquid were precipitated by adding NH4HCO3 solution. After the mixed precipitations of Al（OH）3 and Fe（OH）3 were leached by NaOH solution, the NaAl（OH）4 solution was decomposed by carbonation. Finally, the pure Al（OH）3 was calcined to α-Al2O3. The optimal conditions of the whole technology were determined by experiments. The quality ofa-Al2O3 product is up to the technical indicator of YS/T 274-1998 standard.
基金Project (2012BAF03B01) supported by the National Science and Technology Support Program of ChinaProject (2011AA060701) supported by the Hi-tech Research and Development Program of China
文摘To utilize CFBC Al-rich fly ash, a mild hydrochemical extraction process was investigated for recovery of alumina. An alumina extraction efficiency of 92.31%was attained using a 45%NaOH solution, an original caustic ratio （molar ratio of Na2O to Al2O3 in the sodium aluminate solution） of 25, a molar ratio of CaO to SiO2 in the fly ash of 1.1, a liquid volume to solid mass ratio of 9, a reaction temperature of 280 ℃, and a residence time of 1 h when treating fly ash with an alumina to silica mass ratio （A/S） of 0.78 and an alumina content of 32.43%. Additionally, the alumina leaching mechanism was explored via structural and chemical analysis, which revealed that after alkaline digestion, the main solid phase containing silica was NaCaHSiO4 with a theoretical A/S of zero.
文摘Calcium hexaluminate （ CA6 ） was synthesized by mixing light-weight calcium carbonate and Al2O3 mi- cropowder （calcined α-Al2O3, activated α-Al2O3 or α-Al2O3） according to the stoichimetric ratio of CA6, and reaction sintering at 1 200, 1 300, 1 400 and 1 500 ℃fin 3 h, respectiely. Efcts of the three alu- mina micropowders on the phase composition, micro- structure and properties of CA were investigated. The re- sults show that ： （ 1 ） for the three Al2O3 micropowders, the reaction to generate CA6 in specimens basically com- plete. at about 1 500 ℃ ; CA6 generated in all specimens is planar, bat the array modes are slightly different; （2） the specimel＇s prepared from, calcined α-Al2O3or ρ-Al2O3 shrink almost, while the specimens prepared from activated α-Al2O3 expand ; （ 3 ） the cold crushing strength of the specimen prepared from activated α-Al2O3 is the highest, reaching 42.5 MPa when only CA6 exists （ after firing at 1 500 ℃ ） ; （ 4 ） the specimen prepared from ρ-Al2O3 has the lowest generation temperature of CA6 and the highest apparent porosity, reaching 70. 1% when only CA exists （after firing at 1 500 ℃）; （5） the specimen prepared from calcined α-Al2O3 has the biggest bulk density.
