Glasses with chemical formula of {[(TeO2)0.7(B2O3)0.3]0.8[SiO2]0.2}1-x{MnO2}x where x = 0.00 ≤ x ≤ 0.05 molar fraction were fabricated using melt quenching technique. The temperature used in the heat treatment proce...Glasses with chemical formula of {[(TeO2)0.7(B2O3)0.3]0.8[SiO2]0.2}1-x{MnO2}x where x = 0.00 ≤ x ≤ 0.05 molar fraction were fabricated using melt quenching technique. The temperature used in the heat treatment process of the glass sample is 600?C. Calorimetric measurement had been carried out to study the thermal properties of the fabricated glass. The crystallization kinetics of the glass system we reexamined under non-isothermal conditions via differential scanning calorimetric (DSC). The glass transition (Tg), onset glass transition (To), maximum crystallization temperature (Tc) and melting temperature (Tm) were determined. Results from DSC proved that the studied glasses have good thermal stability (Ts) in which indicates its high resistance to devitrification. Strong indicator for the glass forming ability of a glass material, Hurby parameter (Kgl) was also calculated in this research.展开更多
Five new heat treatment processes were designed,which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal expo...Five new heat treatment processes were designed,which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal exposure at 500,550 ℃ for 100 h were tested. The results indicate that a little differences exist in the performance of mechanical properties at room-temperature after the five heat treatments,and the thermal stability is the key factor for determining heat treatment process. Among the three groups of heat treatment processes,the best thermal stability is achieved after the first group of heat treatment. After annealing treatment at intermediate temperature,some defects and uneven grain boundaries are remained,which leads to the reduction fractions of precipitations on unit grain boundary and the harmful effect of precipitations on grain boundary is weakened. The process of annealing at 650 ℃ for 4 h is recommended the best heat treatment process for Ti40 alloy.展开更多
To investigate the thermal stability of ceramic-matrix composites,three kinds of C/C−ZrC−SiC composites with different Zr/Si molar ratios were synthesized by reactive melt infiltration.Employing region labeling method...To investigate the thermal stability of ceramic-matrix composites,three kinds of C/C−ZrC−SiC composites with different Zr/Si molar ratios were synthesized by reactive melt infiltration.Employing region labeling method,the high-temperature thermal stability of the composites was systematically studied by changing the temperature and holding time of thermal treatment.Results show that the mass loss rate of low Si composites has a growth trend with increasing temperature,and a crystal transformation from β-SiC toα-SiC occurs in the composites.In the calibrated area,SiC phase experiences Ostwald ripening and volume change with location migration,while ZrC phase experiences a re-sintering process with diffusion.Moreover,it is found that increasing temperature has a more obvious effect on the thermal stability than extending holding time,which is mainly attributed to the faster diffusion rate of atoms.展开更多
The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differe...The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differential scanning calorimeter, creep tester and isothermal treatment method. The results indicated that the CHSS composed of Mg2(Al,Ca) and Al2 Ca intermetallics was formed into a typical eutectic structure and no obvious change occurred when the samples were isothermally treated at 250 °C for 96 h and 350 °C for 72 h, respectively. It became a chained structure when isothermally treated at 450 °C for 48 h. The dissolution and reconstruction processes, however, were observed for the CHSS when the processing temperature was up to 550 °C. The creep life at the stress-temperature condition of 50MPa/200°C for the alloy treated at 450 °C for 48 h was as high as 510 h, and the strain at creep time of 100 h was as low as 0.03%, which indicated that the present alloy has not only a good thermal stability, but also a better heat resistance.展开更多
A nanocrystalline layer （NL） was fabricated on the surface of AZ31 magnesium （Mg） alloy sheet by surface mechanical attrition treatment （SMAT）. The microstructure of the Mg alloy was characterized by optical mic...A nanocrystalline layer （NL） was fabricated on the surface of AZ31 magnesium （Mg） alloy sheet by surface mechanical attrition treatment （SMAT）. The microstructure of the Mg alloy was characterized by optical microscopy, X-ray diffraction and microhardness test. The results showed that both the microstructure and microhardness of AZ31 Mg alloy sheet after SMAT revealed a gradient distribution along depth from surface to center. The thermal stability of the NL was investigated through characterizing the microstructure evolution during the post-isothermal annealing treatment within the temperature range from 150 to 250℃. The NL exhibits a certain degree of thermal stability below 150 ℃, while it disappears quickly when annealing at the temperature range of 200-250 ℃. The grain growth kinetics of the nanocrystalline of AZ31 Mg alloy induced by SMAT was investigated. The activation energy of nanocrystalline AZ31 Mg alloy was obtained with a value of 92.8 kJ/mol.展开更多
Two new alkali metal germanophosphates,namely,Na_(3)[Ge(OH)(PO_(4))_(2)]·2 H2 O and Li_(2)Na[GeO(HPO_(4))(PO_(4))],have been prepared by solvothermal method,and their crystal structures were determined by single-...Two new alkali metal germanophosphates,namely,Na_(3)[Ge(OH)(PO_(4))_(2)]·2 H2 O and Li_(2)Na[GeO(HPO_(4))(PO_(4))],have been prepared by solvothermal method,and their crystal structures were determined by single-crystal X-ray diffraction.The title two compounds crystalize in the same orthorhombic space group Pbcm(No.57)and feature similar chain-like structure which is built from zig-zag GeO_(6) octahedral thread loop branched by PO_(4) tetrahedra.For Na_(3)[Ge(OH)(PO_(4))_(2)]·2 H_(2)O,a=10.1650(9),b=13.1975(12),c=6.9751(7)Å,V=935.73(15)Å^(3),Z=4,R=0.0356 and wR=0.1109;and for Li_(2)Na[GeO(HPO_(4))(PO_(4))],a=6.9855(5),b=14.5809(18),c=6.6620(5)Å,V=678.56(11)Å^(3),Z=4,R=0.0286,and w R=0.0762.The partial substitution of Na ions by Li ions not only significantly influences the total structural features and the water molecule contents,but also impacts on their thermal stabilities.Li_(2)Na[GeO(HPO_(4))(PO_(4))]is thermally stable up to 400℃,whereas only 150℃ for Na_(3)[Ge(OH)(PO_(4))_(2)]·2 H2 O.展开更多
We study the influence of alkali oxides on the near-infrared（NIR）-emitting thermal stability of Bi-doped R2O–Si O2–B2O3–Al2O3（R = Li, Na, K） glasses below Tg. Results show that undergoing heat treatment, remark...We study the influence of alkali oxides on the near-infrared（NIR）-emitting thermal stability of Bi-doped R2O–Si O2–B2O3–Al2O3（R = Li, Na, K） glasses below Tg. Results show that undergoing heat treatment, remarkable luminescence quenching occurs for the glasses containing Na2 O and K2 O due to the formation of Bi metallic colloids, whereas the glass with Li2 O shows much better thermal stability. These changes can be understood by the tendency of modifier cations with lower mobility and higher tightness network to restrain the transport of Bi-related NIR-emitting centers. The results provide a scientific reference for composition design of Bi-doped optical fiber.展开更多
Mild thermal treatment is an important partial upgrading technique to enable bitumen pipeline transportation,but no attention has been paid to the impact of mild thermal treatment on the emulsification behavior of eme...Mild thermal treatment is an important partial upgrading technique to enable bitumen pipeline transportation,but no attention has been paid to the impact of mild thermal treatment on the emulsification behavior of emerging partially upgraded bitumen.Asphaltene compounds are active emulsion stabilizers in bitumen oil.The emulsion stabilizing capacity of bitumen asphaltenes was investigated,before and after a mild thermal treatment at 400℃.The structural morphology and mechanical property of the asphaltene interfacial films were analyzed by using a combination of cryo-SEM,Langmuir trough,and Brewster angle microscopy.The thermal treatment significantly enhanced the emulsion stabilizing capacity of bitumen asphaltenes;the interfacial films formed by the thermally treated asphaltene samples appeared to be rougher and thicker with more abundant micron-scale wrinkle structures.The interfacial corrugation may intensify the mechanical stability/flexibility of the asphaltene films and consequently strengthen the stability of emulsion droplet.展开更多
HZSM-5 zeolites with the micro-mesopore hierarchical porosity have been prepared by the post-synthesis of alkali-treatment, and their thermal and hydrothermal stabilities were studied using DTA, XRD, and NH3-TPD chara...HZSM-5 zeolites with the micro-mesopore hierarchical porosity have been prepared by the post-synthesis of alkali-treatment, and their thermal and hydrothermal stabilities were studied using DTA, XRD, and NH3-TPD characterization techniques. Compared to the unmodified zeolite, the thermal and hydrothermal stabilities of the alkali-treated ZSM-5 zeolites were slightly deteriorated because of the introduction of mesopores caused by the desilication. Nevertheless, the alkali-treated zeolite framework could be maintained until the temperature increased to 1175 ℃.展开更多
As-cast CC slabs of microalloyed steels are prone to surface and sub-surface cracking. Precipitation phenomena initiated during solidification reduce ductility at high temperature. The unidirectional solidification un...As-cast CC slabs of microalloyed steels are prone to surface and sub-surface cracking. Precipitation phenomena initiated during solidification reduce ductility at high temperature. The unidirectional solidification unit is employed to simulate the solidification process during continuous casting. Precipitation behavior and thermal stability are systematically investigated. Samples of adding titanium and niobium to steels have been examined using field emission scanning electron microscope （FE-SEM）, electron probe X-ray microanalyzer （EPMA）, and transmission electron microscope （TEM）. It has been found that the addition of titanium and niobium to high-strength low-alloyed （HSLA） steel resulted in undesirable large precipitation in the steels, i. e. , precipitation of large precipitates with various morphologies. The composition of the large precipitates has been determined, The effect of cooling rate on （Ti, Nb）（C, N） precipitate formation is investigated. With increasing the cooling rate, titanium-rich （Ti,Nb）（C,N） precipitates are transformed to niobium-rich （Ti,Nb）（C,N） precipitates. The thermal stability of these large precipitates and oxides have been assessed by carrying out various heat treatments such as holding and quenching from temperature at 800 and 1 200℃. It has been found that titanium-rich （Ti,Nb）（C,N） precipitate is stable at about 1 200 ℃ and niobium-rich （Ti,Nb）（C,N） precipitate is stable at about 800 ℃. After reheating at 1 200℃ for 1 h, （Ca,Mn）S and TiN are precipitated from Ca-Al oxide. However, during reheating at 800 ℃ for l h, Ca-Al-Ti oxide in specimens was stable. The thermodynamic calculation of simulating the thermal process is employed. The calculation results are in good agreement with the experimental results.展开更多
Cordierite honeycomb ceramics was treated with 1.5 M HNO3 , followed with 1.5 M NaOH at 93 ℃. The combination of acid treatment with alkali treatment significantly diminished the rebounding of coefficient of thermal ...Cordierite honeycomb ceramics was treated with 1.5 M HNO3 , followed with 1.5 M NaOH at 93 ℃. The combination of acid treatment with alkali treatment significantly diminished the rebounding of coefficient of thermal expansion （CTE） caused by heat treatment, a phenomenon observed in samples treated solely with acid. Inductively coupled plasma （ICP） analysis results reveal that the alkali treatment preferentially dissolved ＂free＂ SiO2 left in the acid-treated samples, which is considered to be a key factor responsible for the CTE rebounding.展开更多
To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post milling.Annealing above the crystallization temperature（T...To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post milling.Annealing above the crystallization temperature（Tx） not only induced nanoscale intermetallics to precipitate in the amorphous powder,but also increased Cu atomic percentage within the residual amorphous phase.Post milling induced the amorphization of the nanocrystal intermetallics and the formation of Cu9Al4 from the residual amorphous phase.Thus,a mixed structure consisting of amorphous phase and Cu9Al4 was obtained in the powder after annealing and post milling（the APMed powder）.The phase constituent in the APMed powder did not change during the post annealing,which exhibited significantly improved thermal stability in comparison with the as-milled amorphous powder.展开更多
The two kinds of rigid polyurethane （PU） foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in...The two kinds of rigid polyurethane （PU） foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in weight. The indexes of mechanical performance, apparent density, thermal stability and aging resistance were separately tested for the prepared PU foams. The results show that the mechanical property, thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples. The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently. Additionally, the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples. The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.展开更多
The two kinds of rigid polyurethane(PU) foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in we...The two kinds of rigid polyurethane(PU) foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in weight.The indexes of mechanical performance, apparent density, thermal stability and aging resistance were separately tested for the prepared PU foams.The results show that the mechanical property, thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples.The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently.Additionally, the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples.The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.展开更多
文摘Glasses with chemical formula of {[(TeO2)0.7(B2O3)0.3]0.8[SiO2]0.2}1-x{MnO2}x where x = 0.00 ≤ x ≤ 0.05 molar fraction were fabricated using melt quenching technique. The temperature used in the heat treatment process of the glass sample is 600?C. Calorimetric measurement had been carried out to study the thermal properties of the fabricated glass. The crystallization kinetics of the glass system we reexamined under non-isothermal conditions via differential scanning calorimetric (DSC). The glass transition (Tg), onset glass transition (To), maximum crystallization temperature (Tc) and melting temperature (Tm) were determined. Results from DSC proved that the studied glasses have good thermal stability (Ts) in which indicates its high resistance to devitrification. Strong indicator for the glass forming ability of a glass material, Hurby parameter (Kgl) was also calculated in this research.
基金Project(MKPT-01-101ZD) supported by the National Key Project of ChinaProject(2007CB613807) supported by the National Basic Research Program of China
文摘Five new heat treatment processes were designed,which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal exposure at 500,550 ℃ for 100 h were tested. The results indicate that a little differences exist in the performance of mechanical properties at room-temperature after the five heat treatments,and the thermal stability is the key factor for determining heat treatment process. Among the three groups of heat treatment processes,the best thermal stability is achieved after the first group of heat treatment. After annealing treatment at intermediate temperature,some defects and uneven grain boundaries are remained,which leads to the reduction fractions of precipitations on unit grain boundary and the harmful effect of precipitations on grain boundary is weakened. The process of annealing at 650 ℃ for 4 h is recommended the best heat treatment process for Ti40 alloy.
基金supported by the National Natural Science Foundation of China(No.U19A2099)the CAS Key Laboratory of Carbon Materials,China(No.KLCMKFJJ2005)the Fund of Aerospace Research Institute of Material and Processing Technology,China(No.6142906200108).
文摘To investigate the thermal stability of ceramic-matrix composites,three kinds of C/C−ZrC−SiC composites with different Zr/Si molar ratios were synthesized by reactive melt infiltration.Employing region labeling method,the high-temperature thermal stability of the composites was systematically studied by changing the temperature and holding time of thermal treatment.Results show that the mass loss rate of low Si composites has a growth trend with increasing temperature,and a crystal transformation from β-SiC toα-SiC occurs in the composites.In the calibrated area,SiC phase experiences Ostwald ripening and volume change with location migration,while ZrC phase experiences a re-sintering process with diffusion.Moreover,it is found that increasing temperature has a more obvious effect on the thermal stability than extending holding time,which is mainly attributed to the faster diffusion rate of atoms.
文摘The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differential scanning calorimeter, creep tester and isothermal treatment method. The results indicated that the CHSS composed of Mg2(Al,Ca) and Al2 Ca intermetallics was formed into a typical eutectic structure and no obvious change occurred when the samples were isothermally treated at 250 °C for 96 h and 350 °C for 72 h, respectively. It became a chained structure when isothermally treated at 450 °C for 48 h. The dissolution and reconstruction processes, however, were observed for the CHSS when the processing temperature was up to 550 °C. The creep life at the stress-temperature condition of 50MPa/200°C for the alloy treated at 450 °C for 48 h was as high as 510 h, and the strain at creep time of 100 h was as low as 0.03%, which indicated that the present alloy has not only a good thermal stability, but also a better heat resistance.
基金provided by the Grant 2012CB932203 of the National Key Basic Research Program of the Chinese Ministry of Science and Technology and Technologythe Croucher Foundation (No. 9500006)+4 种基金Hong Kong Collaborative Research Fund (CRF) Scheme (No. C402814G)the National Natural Science Foundation of China (No. 51464034)the Hong Kong Scholars Program (No. XJ2012025)the China Postdoctoral Science Foundation funded project (Nos. 2012T50594, 2014M551866)the Jiangxi Postdoctoral Science Foundation (No. 2014KY11)
文摘A nanocrystalline layer （NL） was fabricated on the surface of AZ31 magnesium （Mg） alloy sheet by surface mechanical attrition treatment （SMAT）. The microstructure of the Mg alloy was characterized by optical microscopy, X-ray diffraction and microhardness test. The results showed that both the microstructure and microhardness of AZ31 Mg alloy sheet after SMAT revealed a gradient distribution along depth from surface to center. The thermal stability of the NL was investigated through characterizing the microstructure evolution during the post-isothermal annealing treatment within the temperature range from 150 to 250℃. The NL exhibits a certain degree of thermal stability below 150 ℃, while it disappears quickly when annealing at the temperature range of 200-250 ℃. The grain growth kinetics of the nanocrystalline of AZ31 Mg alloy induced by SMAT was investigated. The activation energy of nanocrystalline AZ31 Mg alloy was obtained with a value of 92.8 kJ/mol.
基金supported by the National Natural Science Foundation of China(No.21201144)。
文摘Two new alkali metal germanophosphates,namely,Na_(3)[Ge(OH)(PO_(4))_(2)]·2 H2 O and Li_(2)Na[GeO(HPO_(4))(PO_(4))],have been prepared by solvothermal method,and their crystal structures were determined by single-crystal X-ray diffraction.The title two compounds crystalize in the same orthorhombic space group Pbcm(No.57)and feature similar chain-like structure which is built from zig-zag GeO_(6) octahedral thread loop branched by PO_(4) tetrahedra.For Na_(3)[Ge(OH)(PO_(4))_(2)]·2 H_(2)O,a=10.1650(9),b=13.1975(12),c=6.9751(7)Å,V=935.73(15)Å^(3),Z=4,R=0.0356 and wR=0.1109;and for Li_(2)Na[GeO(HPO_(4))(PO_(4))],a=6.9855(5),b=14.5809(18),c=6.6620(5)Å,V=678.56(11)Å^(3),Z=4,R=0.0286,and w R=0.0762.The partial substitution of Na ions by Li ions not only significantly influences the total structural features and the water molecule contents,but also impacts on their thermal stabilities.Li_(2)Na[GeO(HPO_(4))(PO_(4))]is thermally stable up to 400℃,whereas only 150℃ for Na_(3)[Ge(OH)(PO_(4))_(2)]·2 H2 O.
基金supported by the National Natural Science Foundation of China under Grant Nos.61265007,61265004,and 51272097
文摘We study the influence of alkali oxides on the near-infrared（NIR）-emitting thermal stability of Bi-doped R2O–Si O2–B2O3–Al2O3（R = Li, Na, K） glasses below Tg. Results show that undergoing heat treatment, remarkable luminescence quenching occurs for the glasses containing Na2 O and K2 O due to the formation of Bi metallic colloids, whereas the glass with Li2 O shows much better thermal stability. These changes can be understood by the tendency of modifier cations with lower mobility and higher tightness network to restrain the transport of Bi-related NIR-emitting centers. The results provide a scientific reference for composition design of Bi-doped optical fiber.
基金supported by National Natural Science Foundation of China(52004266)the Opening Fund of State Key Laboratory of Heavy Oil Processing(SKLOP202001001)+1 种基金the Key R&D Program of Shandong,China(2019JZZY020502)independent innovation project of China University of Petroleum(21CX06008A)
文摘Mild thermal treatment is an important partial upgrading technique to enable bitumen pipeline transportation,but no attention has been paid to the impact of mild thermal treatment on the emulsification behavior of emerging partially upgraded bitumen.Asphaltene compounds are active emulsion stabilizers in bitumen oil.The emulsion stabilizing capacity of bitumen asphaltenes was investigated,before and after a mild thermal treatment at 400℃.The structural morphology and mechanical property of the asphaltene interfacial films were analyzed by using a combination of cryo-SEM,Langmuir trough,and Brewster angle microscopy.The thermal treatment significantly enhanced the emulsion stabilizing capacity of bitumen asphaltenes;the interfacial films formed by the thermally treated asphaltene samples appeared to be rougher and thicker with more abundant micron-scale wrinkle structures.The interfacial corrugation may intensify the mechanical stability/flexibility of the asphaltene films and consequently strengthen the stability of emulsion droplet.
基金the National Key Project for Basic Research of China(973 Project)(No.2005CB221403)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant:DICP K2007D3)
文摘HZSM-5 zeolites with the micro-mesopore hierarchical porosity have been prepared by the post-synthesis of alkali-treatment, and their thermal and hydrothermal stabilities were studied using DTA, XRD, and NH3-TPD characterization techniques. Compared to the unmodified zeolite, the thermal and hydrothermal stabilities of the alkali-treated ZSM-5 zeolites were slightly deteriorated because of the introduction of mesopores caused by the desilication. Nevertheless, the alkali-treated zeolite framework could be maintained until the temperature increased to 1175 ℃.
文摘As-cast CC slabs of microalloyed steels are prone to surface and sub-surface cracking. Precipitation phenomena initiated during solidification reduce ductility at high temperature. The unidirectional solidification unit is employed to simulate the solidification process during continuous casting. Precipitation behavior and thermal stability are systematically investigated. Samples of adding titanium and niobium to steels have been examined using field emission scanning electron microscope （FE-SEM）, electron probe X-ray microanalyzer （EPMA）, and transmission electron microscope （TEM）. It has been found that the addition of titanium and niobium to high-strength low-alloyed （HSLA） steel resulted in undesirable large precipitation in the steels, i. e. , precipitation of large precipitates with various morphologies. The composition of the large precipitates has been determined, The effect of cooling rate on （Ti, Nb）（C, N） precipitate formation is investigated. With increasing the cooling rate, titanium-rich （Ti,Nb）（C,N） precipitates are transformed to niobium-rich （Ti,Nb）（C,N） precipitates. The thermal stability of these large precipitates and oxides have been assessed by carrying out various heat treatments such as holding and quenching from temperature at 800 and 1 200℃. It has been found that titanium-rich （Ti,Nb）（C,N） precipitate is stable at about 1 200 ℃ and niobium-rich （Ti,Nb）（C,N） precipitate is stable at about 800 ℃. After reheating at 1 200℃ for 1 h, （Ca,Mn）S and TiN are precipitated from Ca-Al oxide. However, during reheating at 800 ℃ for l h, Ca-Al-Ti oxide in specimens was stable. The thermodynamic calculation of simulating the thermal process is employed. The calculation results are in good agreement with the experimental results.
基金Funded bythe International Cooperation Project of Jiangsu Prov-ince(No.BZ2001043)
文摘Cordierite honeycomb ceramics was treated with 1.5 M HNO3 , followed with 1.5 M NaOH at 93 ℃. The combination of acid treatment with alkali treatment significantly diminished the rebounding of coefficient of thermal expansion （CTE） caused by heat treatment, a phenomenon observed in samples treated solely with acid. Inductively coupled plasma （ICP） analysis results reveal that the alkali treatment preferentially dissolved ＂free＂ SiO2 left in the acid-treated samples, which is considered to be a key factor responsible for the CTE rebounding.
基金supported by the National Natural Science Foundation of China(Grant Nos.51271036 and 51471035)
文摘To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post milling.Annealing above the crystallization temperature（Tx） not only induced nanoscale intermetallics to precipitate in the amorphous powder,but also increased Cu atomic percentage within the residual amorphous phase.Post milling induced the amorphization of the nanocrystal intermetallics and the formation of Cu9Al4 from the residual amorphous phase.Thus,a mixed structure consisting of amorphous phase and Cu9Al4 was obtained in the powder after annealing and post milling（the APMed powder）.The phase constituent in the APMed powder did not change during the post annealing,which exhibited significantly improved thermal stability in comparison with the as-milled amorphous powder.
文摘The two kinds of rigid polyurethane （PU） foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in weight. The indexes of mechanical performance, apparent density, thermal stability and aging resistance were separately tested for the prepared PU foams. The results show that the mechanical property, thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples. The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently. Additionally, the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples. The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.
基金The key project of "11th Five-Year Plan" in Heilongjiang Province (No. GB06B501-3)
文摘The two kinds of rigid polyurethane(PU) foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in weight.The indexes of mechanical performance, apparent density, thermal stability and aging resistance were separately tested for the prepared PU foams.The results show that the mechanical property, thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples.The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently.Additionally, the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples.The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.
