The mineral transition mechanism and physicochemical property of calcium aluminate clinker sintered at 1350 ℃ were systematically studied using analytical reagent α-Al 2O 3,CaCO 3 and SiO 2 when the molar ratio of C...The mineral transition mechanism and physicochemical property of calcium aluminate clinker sintered at 1350 ℃ were systematically studied using analytical reagent α-Al 2O 3,CaCO 3 and SiO 2 when the molar ratio of CaO to Al 2O 3 is 1.0.The results show that the formation of Ca 2SiO 4 accelerates the diffusion of CaO and Al 2O 3,which promotes the formation of CaAl 2O 4 determined by dilatometer,X-ray diffraction,Fourier transform infrared spectroscopy and scanning electron microscopy methods.CaAl 4O 7,Ca 3Al 2O 6,Ca 3SiO 5 and Ca 2Al 2SiO 7 only exist in the initial stage of reactions,the amounts of which decrease with the increase of sintering duration.Ca 3Al 2O 6 and Ca 12Al 14O 33 react with Al 2O 3 and CaAl 4O 7 to form CaAl 2O 4,while Ca 2Al 2SiO 7 reacts with CaO and Ca 12Al 14O 33 to form Ca 2SiO 4 and CaAl 2O 4.The sintered clinker contains CaAl 2O 4 and γ-Ca 2SiO 4 as well as some Ca 12Al 14O 33 when the sintering duration is longer than 1.0 h.The differential scanning calorimetry results reveal that Ca 2SiO 4,Ca 2Al 2SiO 7 and CaAl 2O 4 are formed at985 ℃,1045℃ and 1339 ℃,respectively.Increasing the sintering duration contributes to the transition of β-Ca 2SiO 4 to γ-Ca 2SiO 4,which improves the pulverization and alumina leaching property of the sintered clinker.展开更多
The mineral transition and formation mechanism of calcium aluminate compounds in CaO-Al2O3-Na2O system during the hightemperature sintering process were systematically investigated using DSC-TG,XRD,SEM-EDS,FTIR,and Ra...The mineral transition and formation mechanism of calcium aluminate compounds in CaO-Al2O3-Na2O system during the hightemperature sintering process were systematically investigated using DSC-TG,XRD,SEM-EDS,FTIR,and Raman spectra,and the crystal structure of Na4Ca3(AlO2)10 was also simulated by Material Studio software.The results indicated that the minerals formed during the sintering process included Na4Ca3(AlO2)10,CaO·Al2O3,and 12 CaO·7 Al2O3,and the content of Na4Ca3(AlO2)10 could reach 92 wt%when sintered at 1200°C for 30 min.The main formation stage of Na4Ca3(AlO2)10 occurred at temperatures from 970 to 1100°C,and the content could reach82 wt%when the reaction temperature increased to 1100°C.The crystal system of Na4Ca3(AlO2)10 was tetragonal,and the cells preferred to grow along crystal planes(110)and(210).The formation of Na4Ca3(AlO2)10 was an exothermic reaction that followed a secondary reaction model,and its activation energy was 223.97 kJ/mol.展开更多
The crystal structure,formation kinetics and micro-morphology of CaO·SiO2 during high-temperature sintering process were studied in low-calcium system by XRD,FT-IR,Raman and SEM-EDS methods.When the molar ratio o...The crystal structure,formation kinetics and micro-morphology of CaO·SiO2 during high-temperature sintering process were studied in low-calcium system by XRD,FT-IR,Raman and SEM-EDS methods.When the molar ratio of CaCO3 to SiO2 is 1.0,β-2CaO·SiO2 forms firstly during the heating process,and then CaO·SiO2 is generated by the transformation reaction of pre-formed 2CaO·SiO2 with SiO2.3CaO·SiO2 and 3CaO·2SiO2 do not form either in the heating or sintering process.Rising the sintering temperature and prolonging the holding time promote the phase transition of 2CaO·SiO2 to CaO·SiO2,resulting in the sintered products a small blue shift and broadening in Raman spectra.The content of CS can reach 97.4%when sintered at 1400℃ for 1 h.The formation kinetics of CaO·SiO2 follows the second-order chemical reaction model,and the corresponding apparent activation energy and pre-exponential factor are 505.82 kJ/mol and 2.16×10^14 s^−1 respectively.展开更多
High-entropy oxides(HEOs)have received significant attention because of their tunable mechanical properties and wide range of functional applications.However,the conventional method used for sintering HEOs requires pr...High-entropy oxides(HEOs)have received significant attention because of their tunable mechanical properties and wide range of functional applications.However,the conventional method used for sintering HEOs requires prolonged processing time,which results in excessive grain growth,thereby compromising their performance.Here,an ultrafast high-temperature sintering(UHS)strategy was adopted,and rock-salt composite(Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2))O was selected as model materials.Experimental parameters were tuned to illustrate the influence of applied current and soaking time on the densification process and resulting grain size.Additionally,the electrochemical performance of UHS-synthesized microparticles as anode materials in lithium-ion batteries was investigated.The results show that the ultrafast heating rate results in fine grains with a diameter of~6–8μm and density of 95%,which are much smaller and similar to those obtained using the conventional sintering method(25μm and 96%).Moreover,the high surface area and reactivity of the microparticles,as well as their sluggish diffusion effect and structural stability,contribute to outstanding performance with high capacity(336 mA·h/g at 1 A/g)and ultralong cyclability(1000 cycles).This novel technique offers valuable insights into the densification process of HEOs and other materials and can thus broaden their application range.展开更多
To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretre...To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.展开更多
TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing Ti...TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing TiB_(2)coatings have disadvantages such as high equipment costs,complicated processes,and highly toxic gas emissions.This paper proposes an environmentally friendly method,which requires inexpensive equipment and simple processing,for preparing TiB_(2)coating on molybdenum via electrophoretic deposition within Na3AlF6-based molten salts.The produced TiB_(2)layer had an approximate thickness of 60μm and exhibited high density,outstanding hardness(38.2 GPa)and robust adhesion strength(51 N).Additionally,high-temperature oxidation experiments revealed that,at900℃,the TiB_(2)coating provided effective protection to the molybdenum substrate against oxidation for 3 h.This result indicates that the TiB_(2)coating prepared on molybdenum using molten salt electrophoretic deposition possesses good high-temperature oxidation resistance.展开更多
In this study,the design,analysis,manufacturing,and testing of a 3D-printed conformal microstrip array antenna for high-temperature environments is presented.3D printing technology is used to fabricate a curved cerami...In this study,the design,analysis,manufacturing,and testing of a 3D-printed conformal microstrip array antenna for high-temperature environments is presented.3D printing technology is used to fabricate a curved ceramic substrate,and laser sintering and microdroplet spraying processes are used to add the conductive metal on the curved substrate.The problems of gain loss,bandwidth reduction,and frequency shift caused by high temperatures are addressed by using a proper antenna design,with parasitic patches,slots,and metal resonant cavities.The antenna prototype is characterized by the curved substrates and the conductive metals for the power dividers,the patch,and the ground plane;its performance is examined up to a temperature of 600℃in a muffle furnace and compared with the results from the numerical analysis.The results show that the antenna can effectively function at 600℃and even higher temperatures.展开更多
This study investigated enhancing the wear resistance of Ti6Al4V alloys for medical applications by incorporating Ti C nanoreinforcements using advanced spark plasma sintering(SPS). The addition of up to 2.5wt% Ti C s...This study investigated enhancing the wear resistance of Ti6Al4V alloys for medical applications by incorporating Ti C nanoreinforcements using advanced spark plasma sintering(SPS). The addition of up to 2.5wt% Ti C significantly improved the mechanical properties, including a notable 18.2% increase in hardness(HV 332). Fretting wear tests against 316L stainless steel(SS316L) balls demonstrated a 20wt%–22wt% reduction in wear volume in the Ti6Al4V/Ti C composites compared with the monolithic alloy. Microstructural analysis revealed that Ti C reinforcement controlled the grain orientation and reduced the β-phase content, which contributed to enhanced mechanical properties. The monolithic alloy exhibited a Widmanstätten lamellar microstructure, while increasing the Ti C content modified the wear mechanisms from ploughing and adhesion(0–0.5wt%) to pitting and abrasion(1wt%–2.5wt%). At higher reinforcement levels, the formation of a robust oxide layer through tribo-oxide treatment effectively reduced the wear volume by minimizing the abrasive effects and plastic deformation. This study highlights the potential of SPS-mediated Ti C reinforcement as a transformative approach for improving the performance of Ti6Al4V alloys, paving the way for advanced medical applications.展开更多
Fully dense aluminum nitride(AIN) ceramics were synthesized by self-propagating high-temperature synthesis(SHS) method using AIN powder as raw material with Y2O3additive. The sintering behavior was studied at differen...Fully dense aluminum nitride(AIN) ceramics were synthesized by self-propagating high-temperature synthesis(SHS) method using AIN powder as raw material with Y2O3additive. The sintering behavior was studied at different sintering temperatures and additive contents. The change of phase compositions, secondary phase distributions and grain morphologies during sintering process were investigated. It is shown that fully dense ceramics using AIN powder prepared by SHS method can be obtained when the sintering temperature is above 1830 ℃. Both Y2O3content and sintering temperature have an important influence on the formation of Y-Al-O phase and grain shape. When Y2O3content is identified, the grain morphology converts from polyhedron into sphere-like shape with the rise of sintering temperature. At a certain sintering temperature,the grain size decreases with the increase in Y2O3content. The influencing mechanisms of different YAl-O secondary phases and sintering temperatures on the grain size and morphology were also discussed based on the experimental results.展开更多
The high-temperature performance of iron ore fmes is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other ...The high-temperature performance of iron ore fmes is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other studies always leads to a large deviation from the desired results. In this study, the fuzzy membership functions of the assimilation ability temperature and the liquid fluidity were proposed based on the fuzzy mathematics theory to construct a model for predicting the high-temperature performance of mixed iron ore. Comparisons of the prediction model and experimental results were presented. The results illustrate that the prediction model is more accurate and effective than previously developed models. In addition, fuzzy constraints for the high-temperature performance of iron ore in this research make the results of ore blending more comparable. A solution for the quantitative calculation as well as the programming of fuzzy constraints is also introduced.展开更多
FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property...FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property of the sintered FeAl samples was investigated in this paper.The results showed that 1 wt.% La2O3 addition could refine the microstructure and increase the density of the FeAl intermetallic compound,and correspondingly improved the high-temperature wear resistance.SEM and EDS analyses of the wo...展开更多
We developed a mathematical optimization model coupling chemical compositions and high-temperature characteristics of sintering materials, targeting the best quality and lowest cost. The simplex algorithm was adopted ...We developed a mathematical optimization model coupling chemical compositions and high-temperature characteristics of sintering materials, targeting the best quality and lowest cost. The simplex algorithm was adopted to solve this model. Four kinds of imported iron ores, two kinds of Chinese iron ore concentrates, and two kinds of fluxes were selected to verify both the model and the algorithm. The results confirmed the possibility of considering both chemical compositions and high-temperature characteristics of iron ores in the optimization model. This model provides a technical roadmap to obtain a precise mathematical correlation between the lowest cost and the grade of iron in sinters based on the condition of given raw materials, which can provide a reference to adjust the grade of iron in the sintering process for enterprise.展开更多
A high Nb containing TiA1 alloy was prepared from the pre-alloyed powder of Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y （at%） by spark plasma sintering （SPS）. Its high-temperature mechanical properties and compressive deformati...A high Nb containing TiA1 alloy was prepared from the pre-alloyed powder of Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y （at%） by spark plasma sintering （SPS）. Its high-temperature mechanical properties and compressive deformation behavior were investigated in a temperature range of 700 to 1050℃ and a strain rate range of 0.002 to 0.2 s 1. The results show that the high-temperature mechanical properties of the high Nb containing TiA1 alloy are sensitive to deformation temperature and strain rate, and the sensitivity to strain rate tends to rise with the deformation temperature increasing. The hot workability of the alloy is good at temperatures higher than 900℃, while fracture occurs at lower temperatures. The flow curves of the samples compressed at or above 900℃ exhibit obvious flow softening after the peak stress. Un- der the deformation condition of 900-1050℃ and 0.002-0.2 s 1, the interrelations of peak flow stress, strain rate, and deformation tempera- ture follow the Arrhenius＇ equation modified by a hyperbolic sine function with a stress exponent of 5.99 and an apparent activation energy of 441.2 kJ.mol-1.展开更多
ZrB2 ceramics were prepared by self-propagating high-temperature synthesis（SHS） and were sintered by hot pressing（HP）.The effects of the granularities and doses of raw materials in Zr-B2O3-Mgon SHS process and pro...ZrB2 ceramics were prepared by self-propagating high-temperature synthesis（SHS） and were sintered by hot pressing（HP）.The effects of the granularities and doses of raw materials in Zr-B2O3-Mgon SHS process and product were investigated.XRD and combustion temperature curves prove that the ideal SHS reactants of Zr-B2O3-Mg are 50μm Zr powder,75μm B2O3 powder and 400μm Mg powder with 45% excessive.The particle sizes of SHS product,acid-leached product,sintered product are 2-5μm,0.5-2μm,2-10μm respectively.Chemical analysis indicates that the acid-leached product consists of ZrB2（94.59%）,ZrO2（3.87%）,and H3BO3（1.54%）,The sintered product has a relative density of 95.4%.展开更多
The high-temperature characteristics of iron ores play important roles in optimizing ore proportion of sintering,which are tested by using iron-ore fines and analytical reagent CaO as raw materials.Two calculation met...The high-temperature characteristics of iron ores play important roles in optimizing ore proportion of sintering,which are tested by using iron-ore fines and analytical reagent CaO as raw materials.Two calculation methods of CaO addition amount based on binary basicity(basicity method)and n(Fe2O3)/n(CaO)(mole ratio method),respectively,were employed to evaluate the liquid phase fluidity(LPF)and the capability of calcium ferrite formation(CCFF)of iron ores.The results show that the rule of LPF of iron ores under the mole ratio method is different from that with basicity method.The LPF measured by basicity method has a linear positive correlation with the SiO2 content,and there is no linear relationship between LPF and Al2O3 content or mass loss on ignition,which are inconsistent with the results of the previous study.And the results of CCFF with low SiO2 content(<3 wt.%)or high SiO2 content(>7 wt.%)based on basicity method cannot reflect the true CCFF.The mole ratio method could successfully solve this problem by reducing the effect of CaO addition amount changes caused by SiO2 content of iron ores.展开更多
Layered cathode materials of high-temperature lithium batteries, Li Ni1/3Mn1/3Co1/3O2 are synthesized by a sol-gel method with variation in final sintering temperature for borehole applications. The structure, morphol...Layered cathode materials of high-temperature lithium batteries, Li Ni1/3Mn1/3Co1/3O2 are synthesized by a sol-gel method with variation in final sintering temperature for borehole applications. The structure, morphology and high-temperature discharge performance of these resulting products are investigated by X-Ray Diffraction(XRD), scanning electron microscopy(SEM), laser particle size analysis, galvanostatic and pulse discharge. The results of structural analysis indicate that the sample sintered at 800 ℃ has the characteristics of good crystallinity, narrow size distribution and large specific surface area at the same time. The discharge experiments also indicate that this sample has the best electrochemical properties, with the maximum discharge capacities of 314.57 and 434.14 m Ah·g-1 at 200 and 300 ℃ respectively and the minimum cell internal resistances at both temperatures.展开更多
The behaviors of typical iron ores at high temperature were observed by confocal scanning laser microscopy. Four critical temperature points and liquid flow velocity at high temperatures of iron ores were obtained and...The behaviors of typical iron ores at high temperature were observed by confocal scanning laser microscopy. Four critical temperature points and liquid flow velocity at high temperatures of iron ores were obtained and the temperature points contain temperature at which sample starts to shrink, temperature at which the initial liquid phase forms, temperature at which a lot of liquid forms and temperature at which liquid consolidation ends. Under the same CaO to Fe203 ratio, the liquid phase fluidity of iron ore fines of Carajas （IOC） is good. However, under the same basicity, as the content of SiO2 in IOC is low, the liquid phase fluidity of IOC is much smaller than that of Yandi fine. After analysis of the initial formation and development of the liquid phase and the final consolidation process, the high-temperature process evaluation system （HTPES for short） of iron ore was established. The idea of ＂dense ore matching fusible ore＂ instead of ＂relatively fusible ore＂ was proposed based on the results of HTPES and applied in ore matching of a sinter plant from Shougang Jingtang. The use of IOC （13-18%） instead of standard sintering fines （SSF） improved liquid phase fluidity and ensured the sinter quality. Furthermore, the use of IOC fine （18-23%） with Hainan fine （0-2%） instead of SSF, a mixture of hematite and Marra Mamba ore and concentrates guaranteed the quality of sinter ore through improving fluidity, in the meantime reducing ore matching costs. With the establishment and application of HTPES, the sinter plant has achieved good economic benefits under the premise of ensuring the quality of sinter ore.展开更多
Canadian iron concentrate(CIC)can elevate the ferrous grade and lower the contents of gangue components and harmful elements in the sinter.To understand high-temperature characteristics of CIC and typical iron ore,the...Canadian iron concentrate(CIC)can elevate the ferrous grade and lower the contents of gangue components and harmful elements in the sinter.To understand high-temperature characteristics of CIC and typical iron ore,the formation of the melt was calculated mainly through FactSage 7.2,and melt fluidity(MF)test for iron ore fines and penetration characteristic test of CIC melt into iron ore nuclei were carried out via micro-sintering method.The results show that hematite,calcium ferrites,dicalcium silicate,and magnetite take part in the formation of the melt in N2.The formation temperature of the liquid for CIC is higher than that for hematite/limonite ore.The MF of CIC is lower than that of hematite/limonite ore fines.The MF of hematite/limonite ore fines is dominated by the liquid amount and melt viscosity.The penetration depth(PD)of CIC melt into limonite ore nuclei is smaller than that into hematite ore nuclei.The PD is related to the reaction ability of the nuclei with the melt.Based on above results,sinter pot tests were conducted.The result shows that in the base ore blends including two hematite ores and two limonite ores,adding CIC deteriorates the sintering indexes.Increasing the proportion of high-MF and small-PD hematite ore can significantly improve the sintering indexes.10 mass%is a suit-able proportion for adding CIC in ore blends.展开更多
YBa_(2)Cu_(3)O_(7-x)(YBCO)is a kind of high-temperature superconducting material that has important application in information,energy,medical treatment,etc.,and the superconducting properties of YBCO are closely relat...YBa_(2)Cu_(3)O_(7-x)(YBCO)is a kind of high-temperature superconducting material that has important application in information,energy,medical treatment,etc.,and the superconducting properties of YBCO are closely related to its internal microstructure.In this study,the microwave heating method was adopted to prepare the YBCO materials.The internal 3 D online evolution observation based on the synchrotron radiation computed tomography technology shows that there was directional grain growth phenomenon of YBCO during microwave sintering process.In local regions with special microstructure,these particles grew to the same point.Here,the theoretical models of single and multiple particles in the microwave electromagnetic fields were established.Based on these theoretical models and finite element analysis,it shows that the YBCO particles can modulate the distribution of electromagnetic fields,resulting in the significantly higher electric field intensity at the particle junctions than other regions.Moreover,there were very high electric field intensity and temperature gradients in the directions of particle growth.These factors were crucial in directional sintering.These results will provide theoretical basis and technical guidance for the controllable preparation and performance optimization of the internal microstructure of superconducting materials in the preparation process.展开更多
Sinter is the core raw material for blast furnaces.Flue pressure,which is an important state parameter,affects sinter quality.In this paper,flue pressure prediction and optimization were studied based on the shapley a...Sinter is the core raw material for blast furnaces.Flue pressure,which is an important state parameter,affects sinter quality.In this paper,flue pressure prediction and optimization were studied based on the shapley additive explanation(SHAP)to predict the flue pressure and take targeted adjustment measures.First,the sintering process data were collected and processed.A flue pressure prediction model was then constructed after comparing different feature selection methods and model algorithms using SHAP+extremely random-ized trees(ET).The prediction accuracy of the model within the error range of±0.25 kPa was 92.63%.SHAP analysis was employed to improve the interpretability of the prediction model.The effects of various sintering operation parameters on flue pressure,the relation-ship between the numerical range of key operation parameters and flue pressure,the effect of operation parameter combinations on flue pressure,and the prediction process of the flue pressure prediction model on a single sample were analyzed.A flue pressure optimization module was also constructed and analyzed when the prediction satisfied the judgment conditions.The operating parameter combination was then pushed.The flue pressure was increased by 5.87%during the verification process,achieving a good optimization effect.展开更多
基金financial support of the project from the National Natural Science Foundation of China (Nos.51174054,51104041 and 51374065)the Fundamental Research Funds for the Central Universities (No.N130402010)
文摘The mineral transition mechanism and physicochemical property of calcium aluminate clinker sintered at 1350 ℃ were systematically studied using analytical reagent α-Al 2O 3,CaCO 3 and SiO 2 when the molar ratio of CaO to Al 2O 3 is 1.0.The results show that the formation of Ca 2SiO 4 accelerates the diffusion of CaO and Al 2O 3,which promotes the formation of CaAl 2O 4 determined by dilatometer,X-ray diffraction,Fourier transform infrared spectroscopy and scanning electron microscopy methods.CaAl 4O 7,Ca 3Al 2O 6,Ca 3SiO 5 and Ca 2Al 2SiO 7 only exist in the initial stage of reactions,the amounts of which decrease with the increase of sintering duration.Ca 3Al 2O 6 and Ca 12Al 14O 33 react with Al 2O 3 and CaAl 4O 7 to form CaAl 2O 4,while Ca 2Al 2SiO 7 reacts with CaO and Ca 12Al 14O 33 to form Ca 2SiO 4 and CaAl 2O 4.The sintered clinker contains CaAl 2O 4 and γ-Ca 2SiO 4 as well as some Ca 12Al 14O 33 when the sintering duration is longer than 1.0 h.The differential scanning calorimetry results reveal that Ca 2SiO 4,Ca 2Al 2SiO 7 and CaAl 2O 4 are formed at985 ℃,1045℃ and 1339 ℃,respectively.Increasing the sintering duration contributes to the transition of β-Ca 2SiO 4 to γ-Ca 2SiO 4,which improves the pulverization and alumina leaching property of the sintered clinker.
基金financially supported by the National Key R&D Program of China(No.2018YFC1901903)the National Nature Science Foundation of China(Nos.51674075 and 51774079)the Fundamental Research Funds for the Central Universities,China(No.N182508026)。
文摘The mineral transition and formation mechanism of calcium aluminate compounds in CaO-Al2O3-Na2O system during the hightemperature sintering process were systematically investigated using DSC-TG,XRD,SEM-EDS,FTIR,and Raman spectra,and the crystal structure of Na4Ca3(AlO2)10 was also simulated by Material Studio software.The results indicated that the minerals formed during the sintering process included Na4Ca3(AlO2)10,CaO·Al2O3,and 12 CaO·7 Al2O3,and the content of Na4Ca3(AlO2)10 could reach 92 wt%when sintered at 1200°C for 30 min.The main formation stage of Na4Ca3(AlO2)10 occurred at temperatures from 970 to 1100°C,and the content could reach82 wt%when the reaction temperature increased to 1100°C.The crystal system of Na4Ca3(AlO2)10 was tetragonal,and the cells preferred to grow along crystal planes(110)and(210).The formation of Na4Ca3(AlO2)10 was an exothermic reaction that followed a secondary reaction model,and its activation energy was 223.97 kJ/mol.
基金Projects(51674075,51774079)supported by the National Natural Science Foundation of ChinaProject(2018YFC1901903)supported by the National Key R&D Program of ChinaProject(N182508026)supported by the Fundamental Research Funds for the Central Universities of China。
文摘The crystal structure,formation kinetics and micro-morphology of CaO·SiO2 during high-temperature sintering process were studied in low-calcium system by XRD,FT-IR,Raman and SEM-EDS methods.When the molar ratio of CaCO3 to SiO2 is 1.0,β-2CaO·SiO2 forms firstly during the heating process,and then CaO·SiO2 is generated by the transformation reaction of pre-formed 2CaO·SiO2 with SiO2.3CaO·SiO2 and 3CaO·2SiO2 do not form either in the heating or sintering process.Rising the sintering temperature and prolonging the holding time promote the phase transition of 2CaO·SiO2 to CaO·SiO2,resulting in the sintered products a small blue shift and broadening in Raman spectra.The content of CS can reach 97.4%when sintered at 1400℃ for 1 h.The formation kinetics of CaO·SiO2 follows the second-order chemical reaction model,and the corresponding apparent activation energy and pre-exponential factor are 505.82 kJ/mol and 2.16×10^14 s^−1 respectively.
基金the National Natural Science Foundation of China(Grant Nos.52202069,52102144)the China Postdoctoral Science Foundation(Grant No.2022MD713790)+2 种基金the Natural Science Basic Research Plan in Shaanxi Province of China(Grant Nos.2022JQ-389,2022JQ-354,and 2022JM-255)the Postdoctoral Research Project of Shaanxi Province(Grant No.2023BSHEDZZ315)Research Grants Council of Hong Kong(Grant No.21203123)is gratefully acknowledged.
文摘High-entropy oxides(HEOs)have received significant attention because of their tunable mechanical properties and wide range of functional applications.However,the conventional method used for sintering HEOs requires prolonged processing time,which results in excessive grain growth,thereby compromising their performance.Here,an ultrafast high-temperature sintering(UHS)strategy was adopted,and rock-salt composite(Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2))O was selected as model materials.Experimental parameters were tuned to illustrate the influence of applied current and soaking time on the densification process and resulting grain size.Additionally,the electrochemical performance of UHS-synthesized microparticles as anode materials in lithium-ion batteries was investigated.The results show that the ultrafast heating rate results in fine grains with a diameter of~6–8μm and density of 95%,which are much smaller and similar to those obtained using the conventional sintering method(25μm and 96%).Moreover,the high surface area and reactivity of the microparticles,as well as their sluggish diffusion effect and structural stability,contribute to outstanding performance with high capacity(336 mA·h/g at 1 A/g)and ultralong cyclability(1000 cycles).This novel technique offers valuable insights into the densification process of HEOs and other materials and can thus broaden their application range.
基金National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.
基金supported by the Original Exploratory Program of the National Natural Science Foundation of China(No.52450012)。
文摘TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing TiB_(2)coatings have disadvantages such as high equipment costs,complicated processes,and highly toxic gas emissions.This paper proposes an environmentally friendly method,which requires inexpensive equipment and simple processing,for preparing TiB_(2)coating on molybdenum via electrophoretic deposition within Na3AlF6-based molten salts.The produced TiB_(2)layer had an approximate thickness of 60μm and exhibited high density,outstanding hardness(38.2 GPa)and robust adhesion strength(51 N).Additionally,high-temperature oxidation experiments revealed that,at900℃,the TiB_(2)coating provided effective protection to the molybdenum substrate against oxidation for 3 h.This result indicates that the TiB_(2)coating prepared on molybdenum using molten salt electrophoretic deposition possesses good high-temperature oxidation resistance.
基金National Natural Science Foundation of china(No.U2241205)the Natural Science Basic Research Program of Shaanxi(Nos.2022JC-33,2023-GHZD-35,and 2024JC-ZDXM-25)+1 种基金the Fundamental Research Funds for the Central Universitiesthe National 111 Project to provide fund for conducting experiments。
文摘In this study,the design,analysis,manufacturing,and testing of a 3D-printed conformal microstrip array antenna for high-temperature environments is presented.3D printing technology is used to fabricate a curved ceramic substrate,and laser sintering and microdroplet spraying processes are used to add the conductive metal on the curved substrate.The problems of gain loss,bandwidth reduction,and frequency shift caused by high temperatures are addressed by using a proper antenna design,with parasitic patches,slots,and metal resonant cavities.The antenna prototype is characterized by the curved substrates and the conductive metals for the power dividers,the patch,and the ground plane;its performance is examined up to a temperature of 600℃in a muffle furnace and compared with the results from the numerical analysis.The results show that the antenna can effectively function at 600℃and even higher temperatures.
文摘This study investigated enhancing the wear resistance of Ti6Al4V alloys for medical applications by incorporating Ti C nanoreinforcements using advanced spark plasma sintering(SPS). The addition of up to 2.5wt% Ti C significantly improved the mechanical properties, including a notable 18.2% increase in hardness(HV 332). Fretting wear tests against 316L stainless steel(SS316L) balls demonstrated a 20wt%–22wt% reduction in wear volume in the Ti6Al4V/Ti C composites compared with the monolithic alloy. Microstructural analysis revealed that Ti C reinforcement controlled the grain orientation and reduced the β-phase content, which contributed to enhanced mechanical properties. The monolithic alloy exhibited a Widmanstätten lamellar microstructure, while increasing the Ti C content modified the wear mechanisms from ploughing and adhesion(0–0.5wt%) to pitting and abrasion(1wt%–2.5wt%). At higher reinforcement levels, the formation of a robust oxide layer through tribo-oxide treatment effectively reduced the wear volume by minimizing the abrasive effects and plastic deformation. This study highlights the potential of SPS-mediated Ti C reinforcement as a transformative approach for improving the performance of Ti6Al4V alloys, paving the way for advanced medical applications.
基金financially supported by the International Cooperation Project of Zhejiang Province (No. 2012C24007)
文摘Fully dense aluminum nitride(AIN) ceramics were synthesized by self-propagating high-temperature synthesis(SHS) method using AIN powder as raw material with Y2O3additive. The sintering behavior was studied at different sintering temperatures and additive contents. The change of phase compositions, secondary phase distributions and grain morphologies during sintering process were investigated. It is shown that fully dense ceramics using AIN powder prepared by SHS method can be obtained when the sintering temperature is above 1830 ℃. Both Y2O3content and sintering temperature have an important influence on the formation of Y-Al-O phase and grain shape. When Y2O3content is identified, the grain morphology converts from polyhedron into sphere-like shape with the rise of sintering temperature. At a certain sintering temperature,the grain size decreases with the increase in Y2O3content. The influencing mechanisms of different YAl-O secondary phases and sintering temperatures on the grain size and morphology were also discussed based on the experimental results.
基金financially supported by the National Natural Science Foundation of China (No. 51204013)the National Key Technology R&D Program in the 12th Five Year Plan of China (No. 2011BAC01B02)
文摘The high-temperature performance of iron ore fmes is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other studies always leads to a large deviation from the desired results. In this study, the fuzzy membership functions of the assimilation ability temperature and the liquid fluidity were proposed based on the fuzzy mathematics theory to construct a model for predicting the high-temperature performance of mixed iron ore. Comparisons of the prediction model and experimental results were presented. The results illustrate that the prediction model is more accurate and effective than previously developed models. In addition, fuzzy constraints for the high-temperature performance of iron ore in this research make the results of ore blending more comparable. A solution for the quantitative calculation as well as the programming of fuzzy constraints is also introduced.
基金supported by the National Natural Science Foundation of China (50575034)
文摘FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property of the sintered FeAl samples was investigated in this paper.The results showed that 1 wt.% La2O3 addition could refine the microstructure and increase the density of the FeAl intermetallic compound,and correspondingly improved the high-temperature wear resistance.SEM and EDS analyses of the wo...
基金financially supported by the National Natural Science Foundation of China and Baosteel Group Co., Ltd., of Shanghai (U1260202)the Postdoctoral Science Foundation of China (2012T50045)
文摘We developed a mathematical optimization model coupling chemical compositions and high-temperature characteristics of sintering materials, targeting the best quality and lowest cost. The simplex algorithm was adopted to solve this model. Four kinds of imported iron ores, two kinds of Chinese iron ore concentrates, and two kinds of fluxes were selected to verify both the model and the algorithm. The results confirmed the possibility of considering both chemical compositions and high-temperature characteristics of iron ores in the optimization model. This model provides a technical roadmap to obtain a precise mathematical correlation between the lowest cost and the grade of iron in sinters based on the condition of given raw materials, which can provide a reference to adjust the grade of iron in the sintering process for enterprise.
基金supported by the National Natural Science Foundation of China (No.50974017)Research Fund for the Doctoral Program of Higher Education of China (No.20110006120023)
文摘A high Nb containing TiA1 alloy was prepared from the pre-alloyed powder of Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y （at%） by spark plasma sintering （SPS）. Its high-temperature mechanical properties and compressive deformation behavior were investigated in a temperature range of 700 to 1050℃ and a strain rate range of 0.002 to 0.2 s 1. The results show that the high-temperature mechanical properties of the high Nb containing TiA1 alloy are sensitive to deformation temperature and strain rate, and the sensitivity to strain rate tends to rise with the deformation temperature increasing. The hot workability of the alloy is good at temperatures higher than 900℃, while fracture occurs at lower temperatures. The flow curves of the samples compressed at or above 900℃ exhibit obvious flow softening after the peak stress. Un- der the deformation condition of 900-1050℃ and 0.002-0.2 s 1, the interrelations of peak flow stress, strain rate, and deformation tempera- ture follow the Arrhenius＇ equation modified by a hyperbolic sine function with a stress exponent of 5.99 and an apparent activation energy of 441.2 kJ.mol-1.
文摘ZrB2 ceramics were prepared by self-propagating high-temperature synthesis（SHS） and were sintered by hot pressing（HP）.The effects of the granularities and doses of raw materials in Zr-B2O3-Mgon SHS process and product were investigated.XRD and combustion temperature curves prove that the ideal SHS reactants of Zr-B2O3-Mg are 50μm Zr powder,75μm B2O3 powder and 400μm Mg powder with 45% excessive.The particle sizes of SHS product,acid-leached product,sintered product are 2-5μm,0.5-2μm,2-10μm respectively.Chemical analysis indicates that the acid-leached product consists of ZrB2（94.59%）,ZrO2（3.87%）,and H3BO3（1.54%）,The sintered product has a relative density of 95.4%.
基金the Key Project of National Natural Science Foundation of China(Grant No.U1660206)the Projects of National Natural Science Foundation of China(Grant Nos.51674002 and 51704009).
文摘The high-temperature characteristics of iron ores play important roles in optimizing ore proportion of sintering,which are tested by using iron-ore fines and analytical reagent CaO as raw materials.Two calculation methods of CaO addition amount based on binary basicity(basicity method)and n(Fe2O3)/n(CaO)(mole ratio method),respectively,were employed to evaluate the liquid phase fluidity(LPF)and the capability of calcium ferrite formation(CCFF)of iron ores.The results show that the rule of LPF of iron ores under the mole ratio method is different from that with basicity method.The LPF measured by basicity method has a linear positive correlation with the SiO2 content,and there is no linear relationship between LPF and Al2O3 content or mass loss on ignition,which are inconsistent with the results of the previous study.And the results of CCFF with low SiO2 content(<3 wt.%)or high SiO2 content(>7 wt.%)based on basicity method cannot reflect the true CCFF.The mole ratio method could successfully solve this problem by reducing the effect of CaO addition amount changes caused by SiO2 content of iron ores.
文摘Layered cathode materials of high-temperature lithium batteries, Li Ni1/3Mn1/3Co1/3O2 are synthesized by a sol-gel method with variation in final sintering temperature for borehole applications. The structure, morphology and high-temperature discharge performance of these resulting products are investigated by X-Ray Diffraction(XRD), scanning electron microscopy(SEM), laser particle size analysis, galvanostatic and pulse discharge. The results of structural analysis indicate that the sample sintered at 800 ℃ has the characteristics of good crystallinity, narrow size distribution and large specific surface area at the same time. The discharge experiments also indicate that this sample has the best electrochemical properties, with the maximum discharge capacities of 314.57 and 434.14 m Ah·g-1 at 200 and 300 ℃ respectively and the minimum cell internal resistances at both temperatures.
文摘The behaviors of typical iron ores at high temperature were observed by confocal scanning laser microscopy. Four critical temperature points and liquid flow velocity at high temperatures of iron ores were obtained and the temperature points contain temperature at which sample starts to shrink, temperature at which the initial liquid phase forms, temperature at which a lot of liquid forms and temperature at which liquid consolidation ends. Under the same CaO to Fe203 ratio, the liquid phase fluidity of iron ore fines of Carajas （IOC） is good. However, under the same basicity, as the content of SiO2 in IOC is low, the liquid phase fluidity of IOC is much smaller than that of Yandi fine. After analysis of the initial formation and development of the liquid phase and the final consolidation process, the high-temperature process evaluation system （HTPES for short） of iron ore was established. The idea of ＂dense ore matching fusible ore＂ instead of ＂relatively fusible ore＂ was proposed based on the results of HTPES and applied in ore matching of a sinter plant from Shougang Jingtang. The use of IOC （13-18%） instead of standard sintering fines （SSF） improved liquid phase fluidity and ensured the sinter quality. Furthermore, the use of IOC fine （18-23%） with Hainan fine （0-2%） instead of SSF, a mixture of hematite and Marra Mamba ore and concentrates guaranteed the quality of sinter ore through improving fluidity, in the meantime reducing ore matching costs. With the establishment and application of HTPES, the sinter plant has achieved good economic benefits under the premise of ensuring the quality of sinter ore.
基金The authors are grateful for the financial support of the Fundamental Research Funds for the Central Universities(Grant No.FRF-IC-18-010).
文摘Canadian iron concentrate(CIC)can elevate the ferrous grade and lower the contents of gangue components and harmful elements in the sinter.To understand high-temperature characteristics of CIC and typical iron ore,the formation of the melt was calculated mainly through FactSage 7.2,and melt fluidity(MF)test for iron ore fines and penetration characteristic test of CIC melt into iron ore nuclei were carried out via micro-sintering method.The results show that hematite,calcium ferrites,dicalcium silicate,and magnetite take part in the formation of the melt in N2.The formation temperature of the liquid for CIC is higher than that for hematite/limonite ore.The MF of CIC is lower than that of hematite/limonite ore fines.The MF of hematite/limonite ore fines is dominated by the liquid amount and melt viscosity.The penetration depth(PD)of CIC melt into limonite ore nuclei is smaller than that into hematite ore nuclei.The PD is related to the reaction ability of the nuclei with the melt.Based on above results,sinter pot tests were conducted.The result shows that in the base ore blends including two hematite ores and two limonite ores,adding CIC deteriorates the sintering indexes.Increasing the proportion of high-MF and small-PD hematite ore can significantly improve the sintering indexes.10 mass%is a suit-able proportion for adding CIC in ore blends.
基金financially supported by the National Natural Science Foundation of China(No.U1832216,No.11627901)the Major Program of the National Science Foundation of China(No.11890683)the National Key Research and Development Program of China(No.2017YFA0403803)。
文摘YBa_(2)Cu_(3)O_(7-x)(YBCO)is a kind of high-temperature superconducting material that has important application in information,energy,medical treatment,etc.,and the superconducting properties of YBCO are closely related to its internal microstructure.In this study,the microwave heating method was adopted to prepare the YBCO materials.The internal 3 D online evolution observation based on the synchrotron radiation computed tomography technology shows that there was directional grain growth phenomenon of YBCO during microwave sintering process.In local regions with special microstructure,these particles grew to the same point.Here,the theoretical models of single and multiple particles in the microwave electromagnetic fields were established.Based on these theoretical models and finite element analysis,it shows that the YBCO particles can modulate the distribution of electromagnetic fields,resulting in the significantly higher electric field intensity at the particle junctions than other regions.Moreover,there were very high electric field intensity and temperature gradients in the directions of particle growth.These factors were crucial in directional sintering.These results will provide theoretical basis and technical guidance for the controllable preparation and performance optimization of the internal microstructure of superconducting materials in the preparation process.
基金supported by the General Program of the National Natural Science Foundation of China(No.52274326)the China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202109)the Seventh Batch of Ten Thousand Talents Plan of China(No.ZX20220553).
文摘Sinter is the core raw material for blast furnaces.Flue pressure,which is an important state parameter,affects sinter quality.In this paper,flue pressure prediction and optimization were studied based on the shapley additive explanation(SHAP)to predict the flue pressure and take targeted adjustment measures.First,the sintering process data were collected and processed.A flue pressure prediction model was then constructed after comparing different feature selection methods and model algorithms using SHAP+extremely random-ized trees(ET).The prediction accuracy of the model within the error range of±0.25 kPa was 92.63%.SHAP analysis was employed to improve the interpretability of the prediction model.The effects of various sintering operation parameters on flue pressure,the relation-ship between the numerical range of key operation parameters and flue pressure,the effect of operation parameter combinations on flue pressure,and the prediction process of the flue pressure prediction model on a single sample were analyzed.A flue pressure optimization module was also constructed and analyzed when the prediction satisfied the judgment conditions.The operating parameter combination was then pushed.The flue pressure was increased by 5.87%during the verification process,achieving a good optimization effect.
