为制备具有电容和压敏特性的 Sr Ti O3双功能器件 ,以 Sr(NO3) 2 ,Ti(OC4 H9) 4为原料 ,用溶胶 -凝胶方法制备 Sr Ti O3材料 ,研究了水和醋酸等对 Sr Ti O3材料的影响机理 ,并对其进行 X-射线衍射、红外光谱和 TEM分析 ,证明该薄膜为纳...为制备具有电容和压敏特性的 Sr Ti O3双功能器件 ,以 Sr(NO3) 2 ,Ti(OC4 H9) 4为原料 ,用溶胶 -凝胶方法制备 Sr Ti O3材料 ,研究了水和醋酸等对 Sr Ti O3材料的影响机理 ,并对其进行 X-射线衍射、红外光谱和 TEM分析 ,证明该薄膜为纳米晶体结构 ,晶粒尺寸为 1 2~ 2 5nm。展开更多
Ce-TiO_(2)-RGO composite photocatalyst was prepared by sol-gel method and ultrasonic treatment.The effect of Ce doping mass fraction on the degradation of textile printing and dyeing wastewater was studied.The catalys...Ce-TiO_(2)-RGO composite photocatalyst was prepared by sol-gel method and ultrasonic treatment.The effect of Ce doping mass fraction on the degradation of textile printing and dyeing wastewater was studied.The catalysts were characterized by XRD,SEM,TEM,UV-vis and PL.The results showed that,Ce-TiO_(2)particles uniformly adsorbed on the GO surface,and the particle diameter of Ce-TiO_(2)was approximately 25-110 nm.After Ce doping,the absorption band edge of TiO_(2)-RGO composite photocatalyst was redshifted and the band gap was reduced.With the increase of Ce doping mass fraction,the PL intensity of Ce-TiO_(2)-RGO composite photocatalyst first decreased and then slightly increased,and the emission peak intensity of 6%Ce-TiO_(2)-RGO composite photocatalyst was the lowest at 410 nm and 470 nm.Taking textile printing and dyeing wastewater as the research object of degradation,the COD removal rate of 6%Ce-TiO_(2)-RGO reached the maximum of 82.21%at 180 min,and the COD value after degradation was 88.95 mg/L which was in line with the wastewater discharge standard.On the other hand,at 180 min,the degradation rate for textile printing and dyeing wastewater by 6%Ce-TiO_(2)-RGO also reached the maximum(99.21%).Therefore,the Ce-TiO_(2)-RGO composite photocatalyst showed great application potential in the treatment of textile dyeing wastewater.展开更多
采用 Sol- gel法在玻璃板表面制得均匀的 Ti O2 薄膜 ,并利用光催化还原法镀银得到掺银Ti O2 薄膜。用掺银的 Ti O2 薄膜和未掺银的 Ti O2 薄膜在高压汞灯和太阳光的照射下 ,对有机物苯酚水溶液进行催化光解研究。结果表明掺银 Ti O2 ...采用 Sol- gel法在玻璃板表面制得均匀的 Ti O2 薄膜 ,并利用光催化还原法镀银得到掺银Ti O2 薄膜。用掺银的 Ti O2 薄膜和未掺银的 Ti O2 薄膜在高压汞灯和太阳光的照射下 ,对有机物苯酚水溶液进行催化光解研究。结果表明掺银 Ti O2 薄膜的光催化活性明显大于未掺银 Ti O2 薄膜 ,这是提高 Ti O2展开更多
The Nd-doped TiO2 thin films with higher hydrophilic and photocatalytic activities were prepared on glass slides by an acid-catalyzed sol?gel method. The effects of Nd doping on crystalline phase, surface composition...The Nd-doped TiO2 thin films with higher hydrophilic and photocatalytic activities were prepared on glass slides by an acid-catalyzed sol?gel method. The effects of Nd doping on crystalline phase, surface composition and optical property were investigated by means of techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), optical contact angle tester and UV-Vis spectroscopy. The results show that Nd doping obviously influences the hydrophilic and photocatalytic activities of TiO2thin films. Nd doping could cause the TiO2 lattice distortion, inhibit phase transition from anatase to rutile, cause red shift of the absorption spectrum edge, produce hydroxyl radicals (·OH), and accelerate surface hydroxylation, which result in a significant improvement in the hydrophilicity and photoreactivity of Nd-doped TiO2 thin films. When the content of Nd is 0.1% (mass fraction), TiO2 thin films achieve the smallest grain size (about 15 nm), and the hydrophilic and photocatalytic activities of TiO2 thin film reach the maximum, the contact angle is only 8.1°, and 92% of methylene blue is finally degraded. Moreover, the modification mechanism of Nd doping was also discussed.展开更多
Titania films with nano-sized pores were prepared on the NaOH?HCl pretreated NiTi alloy substrate by sol?gel method.A crack-free film is obtained for the sample with a dense inner layer and a porous outside layer(s...Titania films with nano-sized pores were prepared on the NaOH?HCl pretreated NiTi alloy substrate by sol?gel method.A crack-free film is obtained for the sample with a dense inner layer and a porous outside layer(sample TC1+1).The X-ray diffraction shows that the titania films are composed of anatase,and a little Ni4Ti3 phase in the heat treated substrate is also detected.The X-ray photoelectron spectroscopy results indicate that the titania film completely covered the NiTi substrate for sample TC1+1.The sample TC1+1 is hydrophilic with a contact angle about 20°,and UV illumination treatment for 15 min further decreases the contact angle to(9.2±3.2)°.The potentiodynamic polarization test in 0.9% NaCl solution reveals a better corrosion resistance of sample TC1+1 than the polished NiTi sample.展开更多
The precursor sol of alumina was prepared by sol-gel method with aluminum nitrate and malic acid as raw materials.The effects of content of malic acid and polyvinylpyrrolidone (PVP) on sol spinnability were explored...The precursor sol of alumina was prepared by sol-gel method with aluminum nitrate and malic acid as raw materials.The effects of content of malic acid and polyvinylpyrrolidone (PVP) on sol spinnability were explored.The gel fibers with above 80 cm in length were obtained by mixing aluminum nitrate,malic acid and PVP on mass ratio of 10 3 1.5.Thermogravimetry-differential scanning calorimetry (TG-DSC),Fourier transform infrared (FTIR) spectrum,X-ray diffractometry (XRD),and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibers.The alumina fibers with a smooth surface and about 20μm in diameter were obtained by sintering at 1 200℃,and their main phase was indentified to be α-Al2O3.展开更多
The Li3V2(PO4)3/C composite cathode material was synthesized via sol-gel method using three different chelating agents (citric acid, salicylic acid and polyacrylic acid) at pH value of 3 or 7. The crystal structur...The Li3V2(PO4)3/C composite cathode material was synthesized via sol-gel method using three different chelating agents (citric acid, salicylic acid and polyacrylic acid) at pH value of 3 or 7. The crystal structure, morphology, specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge test. The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents. With salicylic acid or polyacrylic acid as the chelating reagent, the structure, morphology and electrochemical performance of the samples are greatly influenced by the pH values. However, the structure of the materials with citric acid as the chelating agent does not change as pH value changes, and the materials own uniform particle size distribution and good electrochemical performance. It delivers an initial discharge capacity of 113.58 mA·h/g at 10C, remaining as high as 108.48 mA·h/g after 900 cycles, with a capacity retention of 95.51%.展开更多
A sol-gel method using lauric acid as surfactant was used to synthesize Li4Ti5O12 nanocrystals with an ultra-fine particle size distribution between 120 and 250 nm.In order to obtain the electrode materials with the b...A sol-gel method using lauric acid as surfactant was used to synthesize Li4Ti5O12 nanocrystals with an ultra-fine particle size distribution between 120 and 250 nm.In order to obtain the electrode materials with the best electrochemical performance,the content of lauric acid during Li4Ti5O12 synthesis was systematically studied.The physical and electrochemical properties of the synthesized samples were characterized by X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),laser particle size analysis,alternating current impedance(AC) and galvanostatic charge-discharge experiments.The highly dispersed Li4Ti5O12 nanocrystals obtained at 800 ℃ for 10 h can deliver a specific capacity of 163.3 mA-h/g at 1C rate without obvious capacity fade up to 50 cycles.The results suggest that well dispersed Li4Ti5O12 nanocrystals shorten the Li-ion diffusion length and enhance the electrochemical kinetics of the samples,which are very crucial to high rate capability.展开更多
Li3V2-2/3xMnx(PO4)3(0≤x≤0.12) powders were synthesized by sol-gel method. The effect of Mn2+-doping on the structure and electrochemical performances of Li3V2(PO4)3/C was characterized by XRD, SEM, XPS, galva...Li3V2-2/3xMnx(PO4)3(0≤x≤0.12) powders were synthesized by sol-gel method. The effect of Mn2+-doping on the structure and electrochemical performances of Li3V2(PO4)3/C was characterized by XRD, SEM, XPS, galvanostatic charge /discharge and electrochemical impedance spectroscopy(EIS). The XRD study shows that a small amount of Mn2+-doped does not alter the structure of Li3V2(PO4)3/C materials, and all Mn2+-doped samples are of pure single phase with a monoclinic structure (space group P21/n). The XPS analysis indicates that valences state of V and Mn are +3 and +2 in Li3V1.94Mn0.09(PO4)3/C, respectively, and the citric acid in raw materials was decomposed into carbon during calcination, and residual carbon exists in Li3V1.94Mn0.09(PO4)/C. The results of electrochemical measurements show that Mn2+-doping can improve the cyclic stability and rate performance of these cathode materials. The Li3V1.94Mn0.09(PO4)3/C cathode material shows the best cyclic stability and rate performance. For example, at the discharge current density of 40 mA/g, after 100 cycles, the discharge capacity of Li3V1.94Mn0.09(PO4)3/C declines from initial 158.8 mA·h/g to 120.5 mA·h/g with a capacity retention of 75.9%; however, that of the Mn-undoed sample declines from 164.2 mA·h/g to 72.6 mA·h/g with a capacity retention of 44.2%. When the discharge current is increased up to 1C, the intial discharge capacity of Li3V1.94Mn0.09(PO4)3/C still reaches 146.4 mA·h/g, and the discharge capacity maintains at 107.5 mA·h/g after 100 cycles. The EIS measurement indicates that Mn2+-doping with a appropriate amount of Mn2+ decreases the charge transfer resistance, which is favorable for the insertion/extraction of Li+.展开更多
Li3V2(PO4)3 precursor was obtained with V2Os.nH2O , LiOH'H2O, NH4H2PO4 and sucrose as starting materials by grinding-sol-gel method, and then the monoclinic-typed Li3Vz(PO4)3 cathode material was prepared by sint...Li3V2(PO4)3 precursor was obtained with V2Os.nH2O , LiOH'H2O, NH4H2PO4 and sucrose as starting materials by grinding-sol-gel method, and then the monoclinic-typed Li3Vz(PO4)3 cathode material was prepared by sintering the amorphous Li3V2(PO4)3. The as-sintered samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption and electrochemical measurement. It is found that Li3Vz(PO4)3 sintered at 700 ℃ possesses good wormhole-like mesoporous structure with the largest specific surface area of 188 cmZ/g, and the smallest pore size of 9.3 nm. Electrochemical test reveals that the initial discharge capacity of the 700 ℃ sintered sample is 155.9 mA.h/g at the rate of 0.2C, and the capacity retains 154 mA.h/g after 50 cycles, exhibiting a stable discharge capacity at room temperature.展开更多
The LiMnPO4/C composite material was synthesized via a sol-gel method based on the citric acid. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance tests were adopted to...The LiMnPO4/C composite material was synthesized via a sol-gel method based on the citric acid. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance tests were adopted to characterize the properties of LiMnPO4/C. The XRD studies show that the pure olivine phase LiMnPO4 can be obtained at a low temperature of 500 °C. The SEM analyses illustrate that the citric acid used as the chelating reagent and carbon source can restrain the particle size of LiMnPO4/C well. The LiMnPO4/C sample synthesized at 500 °C for 10 h performs the highest initial discharge capacity of 122.6 mA-h/g, retaining 112.4 mA-h/g over 30 cycles at 0.05C rate. The citric acid based sol-gel method is favor to obtain the high electrochemical performance of LiMnPO4/C.展开更多
文摘为制备具有电容和压敏特性的 Sr Ti O3双功能器件 ,以 Sr(NO3) 2 ,Ti(OC4 H9) 4为原料 ,用溶胶 -凝胶方法制备 Sr Ti O3材料 ,研究了水和醋酸等对 Sr Ti O3材料的影响机理 ,并对其进行 X-射线衍射、红外光谱和 TEM分析 ,证明该薄膜为纳米晶体结构 ,晶粒尺寸为 1 2~ 2 5nm。
文摘Ce-TiO_(2)-RGO composite photocatalyst was prepared by sol-gel method and ultrasonic treatment.The effect of Ce doping mass fraction on the degradation of textile printing and dyeing wastewater was studied.The catalysts were characterized by XRD,SEM,TEM,UV-vis and PL.The results showed that,Ce-TiO_(2)particles uniformly adsorbed on the GO surface,and the particle diameter of Ce-TiO_(2)was approximately 25-110 nm.After Ce doping,the absorption band edge of TiO_(2)-RGO composite photocatalyst was redshifted and the band gap was reduced.With the increase of Ce doping mass fraction,the PL intensity of Ce-TiO_(2)-RGO composite photocatalyst first decreased and then slightly increased,and the emission peak intensity of 6%Ce-TiO_(2)-RGO composite photocatalyst was the lowest at 410 nm and 470 nm.Taking textile printing and dyeing wastewater as the research object of degradation,the COD removal rate of 6%Ce-TiO_(2)-RGO reached the maximum of 82.21%at 180 min,and the COD value after degradation was 88.95 mg/L which was in line with the wastewater discharge standard.On the other hand,at 180 min,the degradation rate for textile printing and dyeing wastewater by 6%Ce-TiO_(2)-RGO also reached the maximum(99.21%).Therefore,the Ce-TiO_(2)-RGO composite photocatalyst showed great application potential in the treatment of textile dyeing wastewater.
文摘采用 Sol- gel法在玻璃板表面制得均匀的 Ti O2 薄膜 ,并利用光催化还原法镀银得到掺银Ti O2 薄膜。用掺银的 Ti O2 薄膜和未掺银的 Ti O2 薄膜在高压汞灯和太阳光的照射下 ,对有机物苯酚水溶液进行催化光解研究。结果表明掺银 Ti O2 薄膜的光催化活性明显大于未掺银 Ti O2 薄膜 ,这是提高 Ti O2
基金Projects(51162022,21201098)supported by the National Natural Science Foundation of ChinaProject(GJJ14126)supported by Jiangxi Provincial Education Department,ChinaProject(2012019)supported by the Test Foundation of Nanchang University,China
文摘The Nd-doped TiO2 thin films with higher hydrophilic and photocatalytic activities were prepared on glass slides by an acid-catalyzed sol?gel method. The effects of Nd doping on crystalline phase, surface composition and optical property were investigated by means of techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), optical contact angle tester and UV-Vis spectroscopy. The results show that Nd doping obviously influences the hydrophilic and photocatalytic activities of TiO2thin films. Nd doping could cause the TiO2 lattice distortion, inhibit phase transition from anatase to rutile, cause red shift of the absorption spectrum edge, produce hydroxyl radicals (·OH), and accelerate surface hydroxylation, which result in a significant improvement in the hydrophilicity and photoreactivity of Nd-doped TiO2 thin films. When the content of Nd is 0.1% (mass fraction), TiO2 thin films achieve the smallest grain size (about 15 nm), and the hydrophilic and photocatalytic activities of TiO2 thin film reach the maximum, the contact angle is only 8.1°, and 92% of methylene blue is finally degraded. Moreover, the modification mechanism of Nd doping was also discussed.
基金Project(xjj2011096)supported by the Fundamental Research Fund for the Central Universities,ChinaProject(201107)supported by the Open Project Program of State Key Laboratory of Metastable Materials Science and Technology,ChinaProject(50901058)supported by the National Natural Science Foundation of China
文摘Titania films with nano-sized pores were prepared on the NaOH?HCl pretreated NiTi alloy substrate by sol?gel method.A crack-free film is obtained for the sample with a dense inner layer and a porous outside layer(sample TC1+1).The X-ray diffraction shows that the titania films are composed of anatase,and a little Ni4Ti3 phase in the heat treated substrate is also detected.The X-ray photoelectron spectroscopy results indicate that the titania film completely covered the NiTi substrate for sample TC1+1.The sample TC1+1 is hydrophilic with a contact angle about 20°,and UV illumination treatment for 15 min further decreases the contact angle to(9.2±3.2)°.The potentiodynamic polarization test in 0.9% NaCl solution reveals a better corrosion resistance of sample TC1+1 than the polished NiTi sample.
基金Project(2010K10-21) supported by the Natural Science Foundation of Shaanxi Province,China
文摘The precursor sol of alumina was prepared by sol-gel method with aluminum nitrate and malic acid as raw materials.The effects of content of malic acid and polyvinylpyrrolidone (PVP) on sol spinnability were explored.The gel fibers with above 80 cm in length were obtained by mixing aluminum nitrate,malic acid and PVP on mass ratio of 10 3 1.5.Thermogravimetry-differential scanning calorimetry (TG-DSC),Fourier transform infrared (FTIR) spectrum,X-ray diffractometry (XRD),and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibers.The alumina fibers with a smooth surface and about 20μm in diameter were obtained by sintering at 1 200℃,and their main phase was indentified to be α-Al2O3.
基金Project(2007BAQ01055)supported by the National Key Technology R&D Program of ChinaProject(2011SCU11081)supported by the Sichuan University Funds for Young Scientists,ChinaProject(20120181120103)supported by Ph.D.Programs Foundation of the Ministry of Education of China
文摘The Li3V2(PO4)3/C composite cathode material was synthesized via sol-gel method using three different chelating agents (citric acid, salicylic acid and polyacrylic acid) at pH value of 3 or 7. The crystal structure, morphology, specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge test. The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents. With salicylic acid or polyacrylic acid as the chelating reagent, the structure, morphology and electrochemical performance of the samples are greatly influenced by the pH values. However, the structure of the materials with citric acid as the chelating agent does not change as pH value changes, and the materials own uniform particle size distribution and good electrochemical performance. It delivers an initial discharge capacity of 113.58 mA·h/g at 10C, remaining as high as 108.48 mA·h/g after 900 cycles, with a capacity retention of 95.51%.
基金Project(2007CB2097050)supported by the National Basic Research Program of ChinaProject(20803035)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China
文摘A sol-gel method using lauric acid as surfactant was used to synthesize Li4Ti5O12 nanocrystals with an ultra-fine particle size distribution between 120 and 250 nm.In order to obtain the electrode materials with the best electrochemical performance,the content of lauric acid during Li4Ti5O12 synthesis was systematically studied.The physical and electrochemical properties of the synthesized samples were characterized by X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),laser particle size analysis,alternating current impedance(AC) and galvanostatic charge-discharge experiments.The highly dispersed Li4Ti5O12 nanocrystals obtained at 800 ℃ for 10 h can deliver a specific capacity of 163.3 mA-h/g at 1C rate without obvious capacity fade up to 50 cycles.The results suggest that well dispersed Li4Ti5O12 nanocrystals shorten the Li-ion diffusion length and enhance the electrochemical kinetics of the samples,which are very crucial to high rate capability.
基金Project (20771100) supported by the National Natural Science Foundation of China
文摘Li3V2-2/3xMnx(PO4)3(0≤x≤0.12) powders were synthesized by sol-gel method. The effect of Mn2+-doping on the structure and electrochemical performances of Li3V2(PO4)3/C was characterized by XRD, SEM, XPS, galvanostatic charge /discharge and electrochemical impedance spectroscopy(EIS). The XRD study shows that a small amount of Mn2+-doped does not alter the structure of Li3V2(PO4)3/C materials, and all Mn2+-doped samples are of pure single phase with a monoclinic structure (space group P21/n). The XPS analysis indicates that valences state of V and Mn are +3 and +2 in Li3V1.94Mn0.09(PO4)3/C, respectively, and the citric acid in raw materials was decomposed into carbon during calcination, and residual carbon exists in Li3V1.94Mn0.09(PO4)/C. The results of electrochemical measurements show that Mn2+-doping can improve the cyclic stability and rate performance of these cathode materials. The Li3V1.94Mn0.09(PO4)3/C cathode material shows the best cyclic stability and rate performance. For example, at the discharge current density of 40 mA/g, after 100 cycles, the discharge capacity of Li3V1.94Mn0.09(PO4)3/C declines from initial 158.8 mA·h/g to 120.5 mA·h/g with a capacity retention of 75.9%; however, that of the Mn-undoed sample declines from 164.2 mA·h/g to 72.6 mA·h/g with a capacity retention of 44.2%. When the discharge current is increased up to 1C, the intial discharge capacity of Li3V1.94Mn0.09(PO4)3/C still reaches 146.4 mA·h/g, and the discharge capacity maintains at 107.5 mA·h/g after 100 cycles. The EIS measurement indicates that Mn2+-doping with a appropriate amount of Mn2+ decreases the charge transfer resistance, which is favorable for the insertion/extraction of Li+.
基金Project (51162026) supported by the National Natural Science Foundation of ChinaProjects (20100480949, 201104509) supported by China Postdoctoral Science FoundationProject (133274341015501) supported by Postdoctoral Science Foundation of Central South University, China
文摘Li3V2(PO4)3 precursor was obtained with V2Os.nH2O , LiOH'H2O, NH4H2PO4 and sucrose as starting materials by grinding-sol-gel method, and then the monoclinic-typed Li3Vz(PO4)3 cathode material was prepared by sintering the amorphous Li3V2(PO4)3. The as-sintered samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption and electrochemical measurement. It is found that Li3Vz(PO4)3 sintered at 700 ℃ possesses good wormhole-like mesoporous structure with the largest specific surface area of 188 cmZ/g, and the smallest pore size of 9.3 nm. Electrochemical test reveals that the initial discharge capacity of the 700 ℃ sintered sample is 155.9 mA.h/g at the rate of 0.2C, and the capacity retains 154 mA.h/g after 50 cycles, exhibiting a stable discharge capacity at room temperature.
基金Project (0991025) supported by Natural Science Foundation of Guangxi, ChinaProject (51164007) supported by the National Natural Science Foundation of ChinaProject (201101ZD008) supported by Educational Commission of Guangxi, China
文摘The LiMnPO4/C composite material was synthesized via a sol-gel method based on the citric acid. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance tests were adopted to characterize the properties of LiMnPO4/C. The XRD studies show that the pure olivine phase LiMnPO4 can be obtained at a low temperature of 500 °C. The SEM analyses illustrate that the citric acid used as the chelating reagent and carbon source can restrain the particle size of LiMnPO4/C well. The LiMnPO4/C sample synthesized at 500 °C for 10 h performs the highest initial discharge capacity of 122.6 mA-h/g, retaining 112.4 mA-h/g over 30 cycles at 0.05C rate. The citric acid based sol-gel method is favor to obtain the high electrochemical performance of LiMnPO4/C.