Ren-Guan Duan - Academia.edu (original) (raw)
Papers by Ren-Guan Duan
Materials Transactions, JIM, 1998
Materials Transactions, JIM, 1998
Materials Science and Engineering: A, 1998
The structures of 20CaO· 17Al2O3· 63SiO2, 20CaO· 17Al2O3· 63SiO2· 4.5 TiO2, and 20CaO· 17Al2O3· 6... more The structures of 20CaO· 17Al2O3· 63SiO2, 20CaO· 17Al2O3· 63SiO2· 4.5 TiO2, and 20CaO· 17Al2O3· 63SiO2· 9TiO2 glasses are investigated by the methods of 29Si-, and 27Al-MAS-NMR spectra, Al2p X-ray photoelectron spectroscopy and Raman spectra. The ...
Materials Research Bulletin, 1998
This paper investigates the CaO-Al 2 O 3-SiO 2 system glass. When the glasses were heat treated a... more This paper investigates the CaO-Al 2 O 3-SiO 2 system glass. When the glasses were heat treated at different temperatures and times, they crystallized from the surface. The main crystals were dendrites of anorthite (CaAl 2 Si 2 O 8). The morphology of crystallization was observed using scanning electron microscopy, and the crystal size was measured by optical microscopy. It was found that the growth of anorthite (CaAl 2 Si 2 O 8) crystals was diffusion controlled. The apparent activation energy for crystal growth was about 581 kJ/mol. The rate of crystal growth was not constant during the growth process; the rate was highest at the beginning of crystallization and gradually decreased with increasing time. The higher the temperature, the less time required to complete crystal growth. The total process of diffusion may be determined by the diffusion rate of Ca 2ϩ .
Materials Chemistry and Physics, 1998
Raman spectra and differential thermal analysis (DTA) were used to investigate structure of 27CaO... more Raman spectra and differential thermal analysis (DTA) were used to investigate structure of 27CaOÁ12Al 2 O 3 Á61SiO 2 glass with and without Na 2 O. A new phenomenon is found: that is, the addition of a low content of Na 2 O to 27CaOÁ12Al 2 O 3 Á61SiO 2 glass resulting in an increase of the aggregation extent of the glass network. Addition of the Na ions to glass leads to the Al 3 ions, existing as network modi®ers, further entering as network formers. This results in the decrease of the amount of nonbridging oxygen ions. Al 3 ions located as network modi®ers enter as network formers, which corresponds to the highest value of the aggregation extent of the glass network. The nonbridging oxygen ions will re-increase continuously with the Na 2 O content, which corresponds to the continuous decrease of the aggregation extent of glass network. The most effective content of the Na 2 O added is about 4.3 mol%.
Journal of the European Ceramic Society, 1998
... The correctness of the new criterion, k D (T), had been verified through being used in theCaO... more ... The correctness of the new criterion, k D (T), had been verified through being used in theCaO-Al 2 O 3 -SiO 2 system glasses and ... PII: S09S5-2219(98)00003-X 0955-2219/98/S19.00 + 0.00 A New Criterion for the Stability of Glasses Ren-Guan Duan,* Kai-Ming Liang and Shou ...
Journal of Materials Processing Technology, 1998
In this work, the composition of glass is decided according to the forming glass field of the CaO... more In this work, the composition of glass is decided according to the forming glass field of the CaO–Al2O3–SiO2 system, glass heat-treated at different temperatures being prepared by the fusion of pure initial materials in alumina crucibles. DTA, XRD and SEM methods are used to investigate these glasses samples, yielding the following results: (i) glass that is heat-treated only at a temperature slightly above the glass transition temperature Tg is in the state of phase separation; (ii) the above glass continuously heat-treated at a temperature near to the glass crystallization peak temperature Tp obtains a structure of uniform and fine crystals in the interior and large dendrites on the surface, which later grow from the surface towards the interior; (iii) another piece of glass heat-treated directly at the temperature Tp crystallizes also on the surface, these crystals growing from the surface to the interior, whilst simultaneously some tiny crystals in the interior distributed amongst the glass base are also formed and grow very slowly; (iv) the above glass heat-treated again at a temperature slightly above Tg for a long time has no great change in the layer of crystals on the surface, whilst in the interior the glass is again in the state of phase separation and tiny crystals disappear.
Journal of Materials Processing Technology, 1999
The differential thermal analysis (DTA) curve of Na2O–CaO–MgO–Al2O3–SiO2–TiOs system glasses has ... more The differential thermal analysis (DTA) curve of Na2O–CaO–MgO–Al2O3–SiO2–TiOs system glasses has two exothermic peaks, which means that at least two kinds of main crystal are produced in the process of heat treatment. Some additives such as typical network modifier (Na2O, CaF2), and network intermediate (Al2O3) are added in the above glasses. After the glasses with additives are heat treated in the different processes, they are investigated by the method of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Some important results are obtained. The main crystal corresponding to the first exothermic peak temperature is fassaite (Ca(Ti,Mg,Al)(Si,Al)2O6), and another main crystal corresponding to the second exothermic peak temperature is anorthite (CaAl2Si2O8). The additives of Na2O and CaF2 play a role in decreasing the nucleation and growth of fassaite. Na2O has no obvious effect on the nucleation and growth of anorthite, but CaF2 suppresses the nucleation and growth of anorthite and itself comes out of the base glasses. B2O3 hinders fluorite’s coming out of the base glasses and improves the nucleation and growth of fassaite and anorthite.
Materials in engineering, 2007
This paper reports a scanning electron microscopy (SEM) investigation of polystyrene artificial o... more This paper reports a scanning electron microscopy (SEM) investigation of polystyrene artificial opal achieved through self-assembly of monodisperse polystyrene nanospheres with a diameter of 250 nm from colloidal suspension after being ambient dried. A detailed analysis of the SEM images verifies that the face-centered cubic (fcc) phase is the most stable one for the polystyrene opal prepared. This finding provides a strong support for, by using polystyrene opal as template, fabricating a photonic crystal with inverse fcc structure of full band gap if the refractive index contrast is higher than 2.8 and the filling fraction of the high index materials is between 0.2 and 0.3.
Journal of the American Chemical Society, Jul 10, 2008
Journal of Non-crystalline Solids, Mar 1, 2001
The stiffness and internal friction (Q− 1) of a CaOAl2O3 SiO2 glass and an Na2OCaOSiO2 glass h... more The stiffness and internal friction (Q− 1) of a CaOAl2O3 SiO2 glass and an Na2OCaOSiO2 glass have been measured from room temperature to their respective glass transition temperatures (Tg) using the impulse excitation technique (IET). Thermomechanical ...
Advanced Materials, Jul 5, 2004
Physics Letters, Feb 1, 2000
This Letter presents a new kinetic description for phase separation of materials. The unstable no... more This Letter presents a new kinetic description for phase separation of materials. The unstable non-uniform regions fluctuate to form the steadily critical non-uniform regions, which diffuse to grow by either nucleation growth or Spinodal decomposition mechanism. The equation describing fluctuation stage is c(r,t)-c0=Pcos(betaWt)cos(beta.r), and the equations describing diffusion stage are lambda2=Ht (nucleation growth) and c(r,t)- c0=PQ2exp[R2(beta)t]cos(beta.r) (early stage of Spinodal decomposition). The process of forming a steadily critical non-uniform region is that the region size fluctuates near the critical one, the amplitude of fluctuation decreases gradually, and the composition of region tends to stable.
Powder Technology, Sep 1, 2012
In the absence of template and thermal stabilizer, novel mesoporous ZrO 2 and Y 2 O 3-stabilized ... more In the absence of template and thermal stabilizer, novel mesoporous ZrO 2 and Y 2 O 3-stabilized ZrO 2 (YSZ) spherical powders were synthesized via the improved spray reaction (SR) technique. The synthesized materials were characterized by thermo-gravimetry/differential thermal analysis (TG/DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Nitrogen adsorption/desorption isotherm techniques. Results reveal that the microstructure of ZrO 2 precursor significantly depends on the aging process, and the particle size, surface area and phase composition of prepared ZrO 2-based materials significantly depend on the calcination temperature. For pure ZrO 2 spherical particles, the size varies from 1.63 μm, 1.58 μm to 1.60 μm in correspondent to the calcined temperature 700°C, 800°C and 1000°C, respectively. And also the major cubic ZrO 2 (c-ZrO 2) is formed when calcined at 700°C whereas the predominant monoclinic ZrO 2 (m-ZrO 2) is synthesized when calcined at 800-1000°C. For YSZ spherical particles, the size changes from 1.65 μm, 1.59 μm, 1.62 μm to 1.45 μm in correspondent to the calcined temperature 500°C, 600°C, 700°C and 1000°C, respectively. The synthesized YSZ spheres exhibit the similar phase constitution of predominant tetragonal ZrO 2 (t-ZrO 2) at all experimental temperatures but show the different surface area and pore diameter,~14.72 m 2 /g surface area and 10.7 nm pore diameter at 500°C as well as~34.39 m 2 /g surface area and 8.3 nm pore diameter at 600°C.
Key Engineering Materials, Dec 1, 2001
Journal of The European Ceramic Society, Nov 1, 1998
This paper studied that the influence of changes in the TiO2 content on the glass structure of Ca... more This paper studied that the influence of changes in the TiO2 content on the glass structure of CaO-Al2O3-SiO3 system and the formation of crystalline phases on reheating. The activation energy (E) for crystal growth and the Avrami parameter (n) have also been evaluated by means of differential thermal analysis (DTA) techniques. The value of the Avrami parameter (n) agrees well
L'invention concerne une composition polymere chargee qui presente une resistance au plasma a... more L'invention concerne une composition polymere chargee qui presente une resistance au plasma amelioree. La composition comprend une charge particulaire dispersee dans une matrice polymere. La charge particulaire peut etre Nb 2 O 5 , YF 3 , AlN, SiC ou Si 3 N 4 et des oxydes de terres rares. Selon un mode de realisation, la composition est utilisee en tant qu'adhesif de liaison pour mandrin electrostatique, en tant qu'adhesif de liaison pour pomme de douche, en tant qu'adhesif de liaison pour revetement interieur, en tant que materiau d'etancheite, en tant que joint torique ou en tant que composant plastique.
Materials Transactions, JIM, 1998
Materials Transactions, JIM, 1998
Materials Science and Engineering: A, 1998
The structures of 20CaO· 17Al2O3· 63SiO2, 20CaO· 17Al2O3· 63SiO2· 4.5 TiO2, and 20CaO· 17Al2O3· 6... more The structures of 20CaO· 17Al2O3· 63SiO2, 20CaO· 17Al2O3· 63SiO2· 4.5 TiO2, and 20CaO· 17Al2O3· 63SiO2· 9TiO2 glasses are investigated by the methods of 29Si-, and 27Al-MAS-NMR spectra, Al2p X-ray photoelectron spectroscopy and Raman spectra. The ...
Materials Research Bulletin, 1998
This paper investigates the CaO-Al 2 O 3-SiO 2 system glass. When the glasses were heat treated a... more This paper investigates the CaO-Al 2 O 3-SiO 2 system glass. When the glasses were heat treated at different temperatures and times, they crystallized from the surface. The main crystals were dendrites of anorthite (CaAl 2 Si 2 O 8). The morphology of crystallization was observed using scanning electron microscopy, and the crystal size was measured by optical microscopy. It was found that the growth of anorthite (CaAl 2 Si 2 O 8) crystals was diffusion controlled. The apparent activation energy for crystal growth was about 581 kJ/mol. The rate of crystal growth was not constant during the growth process; the rate was highest at the beginning of crystallization and gradually decreased with increasing time. The higher the temperature, the less time required to complete crystal growth. The total process of diffusion may be determined by the diffusion rate of Ca 2ϩ .
Materials Chemistry and Physics, 1998
Raman spectra and differential thermal analysis (DTA) were used to investigate structure of 27CaO... more Raman spectra and differential thermal analysis (DTA) were used to investigate structure of 27CaOÁ12Al 2 O 3 Á61SiO 2 glass with and without Na 2 O. A new phenomenon is found: that is, the addition of a low content of Na 2 O to 27CaOÁ12Al 2 O 3 Á61SiO 2 glass resulting in an increase of the aggregation extent of the glass network. Addition of the Na ions to glass leads to the Al 3 ions, existing as network modi®ers, further entering as network formers. This results in the decrease of the amount of nonbridging oxygen ions. Al 3 ions located as network modi®ers enter as network formers, which corresponds to the highest value of the aggregation extent of the glass network. The nonbridging oxygen ions will re-increase continuously with the Na 2 O content, which corresponds to the continuous decrease of the aggregation extent of glass network. The most effective content of the Na 2 O added is about 4.3 mol%.
Journal of the European Ceramic Society, 1998
... The correctness of the new criterion, k D (T), had been verified through being used in theCaO... more ... The correctness of the new criterion, k D (T), had been verified through being used in theCaO-Al 2 O 3 -SiO 2 system glasses and ... PII: S09S5-2219(98)00003-X 0955-2219/98/S19.00 + 0.00 A New Criterion for the Stability of Glasses Ren-Guan Duan,* Kai-Ming Liang and Shou ...
Journal of Materials Processing Technology, 1998
In this work, the composition of glass is decided according to the forming glass field of the CaO... more In this work, the composition of glass is decided according to the forming glass field of the CaO–Al2O3–SiO2 system, glass heat-treated at different temperatures being prepared by the fusion of pure initial materials in alumina crucibles. DTA, XRD and SEM methods are used to investigate these glasses samples, yielding the following results: (i) glass that is heat-treated only at a temperature slightly above the glass transition temperature Tg is in the state of phase separation; (ii) the above glass continuously heat-treated at a temperature near to the glass crystallization peak temperature Tp obtains a structure of uniform and fine crystals in the interior and large dendrites on the surface, which later grow from the surface towards the interior; (iii) another piece of glass heat-treated directly at the temperature Tp crystallizes also on the surface, these crystals growing from the surface to the interior, whilst simultaneously some tiny crystals in the interior distributed amongst the glass base are also formed and grow very slowly; (iv) the above glass heat-treated again at a temperature slightly above Tg for a long time has no great change in the layer of crystals on the surface, whilst in the interior the glass is again in the state of phase separation and tiny crystals disappear.
Journal of Materials Processing Technology, 1999
The differential thermal analysis (DTA) curve of Na2O–CaO–MgO–Al2O3–SiO2–TiOs system glasses has ... more The differential thermal analysis (DTA) curve of Na2O–CaO–MgO–Al2O3–SiO2–TiOs system glasses has two exothermic peaks, which means that at least two kinds of main crystal are produced in the process of heat treatment. Some additives such as typical network modifier (Na2O, CaF2), and network intermediate (Al2O3) are added in the above glasses. After the glasses with additives are heat treated in the different processes, they are investigated by the method of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Some important results are obtained. The main crystal corresponding to the first exothermic peak temperature is fassaite (Ca(Ti,Mg,Al)(Si,Al)2O6), and another main crystal corresponding to the second exothermic peak temperature is anorthite (CaAl2Si2O8). The additives of Na2O and CaF2 play a role in decreasing the nucleation and growth of fassaite. Na2O has no obvious effect on the nucleation and growth of anorthite, but CaF2 suppresses the nucleation and growth of anorthite and itself comes out of the base glasses. B2O3 hinders fluorite’s coming out of the base glasses and improves the nucleation and growth of fassaite and anorthite.
Materials in engineering, 2007
This paper reports a scanning electron microscopy (SEM) investigation of polystyrene artificial o... more This paper reports a scanning electron microscopy (SEM) investigation of polystyrene artificial opal achieved through self-assembly of monodisperse polystyrene nanospheres with a diameter of 250 nm from colloidal suspension after being ambient dried. A detailed analysis of the SEM images verifies that the face-centered cubic (fcc) phase is the most stable one for the polystyrene opal prepared. This finding provides a strong support for, by using polystyrene opal as template, fabricating a photonic crystal with inverse fcc structure of full band gap if the refractive index contrast is higher than 2.8 and the filling fraction of the high index materials is between 0.2 and 0.3.
Journal of the American Chemical Society, Jul 10, 2008
Journal of Non-crystalline Solids, Mar 1, 2001
The stiffness and internal friction (Q− 1) of a CaOAl2O3 SiO2 glass and an Na2OCaOSiO2 glass h... more The stiffness and internal friction (Q− 1) of a CaOAl2O3 SiO2 glass and an Na2OCaOSiO2 glass have been measured from room temperature to their respective glass transition temperatures (Tg) using the impulse excitation technique (IET). Thermomechanical ...
Advanced Materials, Jul 5, 2004
Physics Letters, Feb 1, 2000
This Letter presents a new kinetic description for phase separation of materials. The unstable no... more This Letter presents a new kinetic description for phase separation of materials. The unstable non-uniform regions fluctuate to form the steadily critical non-uniform regions, which diffuse to grow by either nucleation growth or Spinodal decomposition mechanism. The equation describing fluctuation stage is c(r,t)-c0=Pcos(betaWt)cos(beta.r), and the equations describing diffusion stage are lambda2=Ht (nucleation growth) and c(r,t)- c0=PQ2exp[R2(beta)t]cos(beta.r) (early stage of Spinodal decomposition). The process of forming a steadily critical non-uniform region is that the region size fluctuates near the critical one, the amplitude of fluctuation decreases gradually, and the composition of region tends to stable.
Powder Technology, Sep 1, 2012
In the absence of template and thermal stabilizer, novel mesoporous ZrO 2 and Y 2 O 3-stabilized ... more In the absence of template and thermal stabilizer, novel mesoporous ZrO 2 and Y 2 O 3-stabilized ZrO 2 (YSZ) spherical powders were synthesized via the improved spray reaction (SR) technique. The synthesized materials were characterized by thermo-gravimetry/differential thermal analysis (TG/DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Nitrogen adsorption/desorption isotherm techniques. Results reveal that the microstructure of ZrO 2 precursor significantly depends on the aging process, and the particle size, surface area and phase composition of prepared ZrO 2-based materials significantly depend on the calcination temperature. For pure ZrO 2 spherical particles, the size varies from 1.63 μm, 1.58 μm to 1.60 μm in correspondent to the calcined temperature 700°C, 800°C and 1000°C, respectively. And also the major cubic ZrO 2 (c-ZrO 2) is formed when calcined at 700°C whereas the predominant monoclinic ZrO 2 (m-ZrO 2) is synthesized when calcined at 800-1000°C. For YSZ spherical particles, the size changes from 1.65 μm, 1.59 μm, 1.62 μm to 1.45 μm in correspondent to the calcined temperature 500°C, 600°C, 700°C and 1000°C, respectively. The synthesized YSZ spheres exhibit the similar phase constitution of predominant tetragonal ZrO 2 (t-ZrO 2) at all experimental temperatures but show the different surface area and pore diameter,~14.72 m 2 /g surface area and 10.7 nm pore diameter at 500°C as well as~34.39 m 2 /g surface area and 8.3 nm pore diameter at 600°C.
Key Engineering Materials, Dec 1, 2001
Journal of The European Ceramic Society, Nov 1, 1998
This paper studied that the influence of changes in the TiO2 content on the glass structure of Ca... more This paper studied that the influence of changes in the TiO2 content on the glass structure of CaO-Al2O3-SiO3 system and the formation of crystalline phases on reheating. The activation energy (E) for crystal growth and the Avrami parameter (n) have also been evaluated by means of differential thermal analysis (DTA) techniques. The value of the Avrami parameter (n) agrees well
L'invention concerne une composition polymere chargee qui presente une resistance au plasma a... more L'invention concerne une composition polymere chargee qui presente une resistance au plasma amelioree. La composition comprend une charge particulaire dispersee dans une matrice polymere. La charge particulaire peut etre Nb 2 O 5 , YF 3 , AlN, SiC ou Si 3 N 4 et des oxydes de terres rares. Selon un mode de realisation, la composition est utilisee en tant qu'adhesif de liaison pour mandrin electrostatique, en tant qu'adhesif de liaison pour pomme de douche, en tant qu'adhesif de liaison pour revetement interieur, en tant que materiau d'etancheite, en tant que joint torique ou en tant que composant plastique.