A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,micros...A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,microstructures,and microwave dielectric properties were investigated.The results of x-ray diffraction(XRD)and scanning electron microscopy(SEM)showed that a single phase of MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with a spinel structure was obtained at x≤0.12,whereas the second phase of MgTi_(2)O_(5)appeared when x>0.12.The cell parameters were obtained by XRD refinement.As the x values increased,the unit cell volume kept expanding.This phenomenon could be attributed to the partial substitution of(Li_(1/3)Ti_(2/3))^(3+)for Al^(3+).Results showed that(Li_(1/3)Ti_(2/3))^(3+)doping into MgAl_(2)O_(4)spinel ceramics effectively reduced the sintering temperature and improved the quality factor(Q_f)values.Good microwave dielectric properties were achieved for a sample at x=0.20 sintering at 1500℃in air for 4 h:dielectric constantε_(r)=8.78,temperature coefficient of resonant frequencyτ_(f)=-85 ppm/℃,and Q_(f)=62300 GHz.The Q_(f)value of the x=0.20 sample was about 2 times higher than that of pure MgAl_(2)O_(4)ceramics(31600 GHz).Thus,MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with excellent microwave dielectric properties can be applied to 5G communications.展开更多
SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature ...SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature and the mass ratio of SiC to MgAl_(2)O_(4) on the formation of SiAlON polytypoids as well as on the properties of samples were studied.The formation mechanism of SiAlON polytypoids was discussed.The results show that firing at 1650℃in the nitrogen atmosphere,SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids can be obtained.With the gradual increase of the mass ratio of SiC to MgAl_(2)O_(4) in the raw materials,12H forms first,and then coexists with 21H,finally,all 12H converts into 21R in samples.Both phases are plate crystals with flat and smooth edges.Compared with 21R,12H is conducive to improving the density and the cold mechanical properties of materials.After firing at 1650℃in the nitrogen atmosphere,with the mass ratio of SiC to MgAl_(2)O_(4) of 6:4,the sample has the cold modulus of rupture of 27 MPa,showing the optimal performance.展开更多
电控离子交换(Electrochemically switched ion exchange,ESIX)系统内对电极具有保持溶液电中性、增强提锂效果且使系统形成闭合回路的关键作用。在ESIX技术盐湖提锂过程中人们主要关注锂离子捕获电极,关于对电极的研究较少。而本文研...电控离子交换(Electrochemically switched ion exchange,ESIX)系统内对电极具有保持溶液电中性、增强提锂效果且使系统形成闭合回路的关键作用。在ESIX技术盐湖提锂过程中人们主要关注锂离子捕获电极,关于对电极的研究较少。而本文研究了不同类型对电极对ESIX系统提锂性能的影响。分别采用聚吡咯/导电炭黑/聚偏二氟乙烯(PPy/C/PVDF)、活性炭/导电炭黑/聚偏二氟乙烯(AC/C/PVDF)和石墨板电极作为ESIX系统中锰酸锂/导电炭黑/聚偏二氟乙烯(LiMn_(2)O_(4)/C/PVDF)提锂膜电极的对电极,考察了这3种ESIX系统在氯化物型高镁锂比模拟卤水(Mg/Li~50)中的提锂性能。结果表明,当PPy/C/PVDF作为对电极时可有效吸附卤水中Cl^(-),且ESIX系统提锂性能最优,Li^(+)吸附量为13.9 mg/g;当PPy/C/PVDF电极湿膜厚度增加至1 mm时,ESIX系统对Li^(+)的提取率可达44.2%,Li^(+)/Mg^(2+)分离因子可达56.82。因此,针对不同的阴离子型盐湖卤水设计匹配的对电极对ESIX技术在盐湖提锂领域的发展具有重要的理论指导意义。展开更多
基金Project(SKL-SPM-202021) supported by the State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals,ChinaProject(2023YFQ0082) supported by Sichuan Science and Technology Program,ChinaProject(EFMD2022005Z) supported by Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices,China。
基金the Chengdu University of Technology(Grant No.KYQD201907728)。
文摘A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,microstructures,and microwave dielectric properties were investigated.The results of x-ray diffraction(XRD)and scanning electron microscopy(SEM)showed that a single phase of MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with a spinel structure was obtained at x≤0.12,whereas the second phase of MgTi_(2)O_(5)appeared when x>0.12.The cell parameters were obtained by XRD refinement.As the x values increased,the unit cell volume kept expanding.This phenomenon could be attributed to the partial substitution of(Li_(1/3)Ti_(2/3))^(3+)for Al^(3+).Results showed that(Li_(1/3)Ti_(2/3))^(3+)doping into MgAl_(2)O_(4)spinel ceramics effectively reduced the sintering temperature and improved the quality factor(Q_f)values.Good microwave dielectric properties were achieved for a sample at x=0.20 sintering at 1500℃in air for 4 h:dielectric constantε_(r)=8.78,temperature coefficient of resonant frequencyτ_(f)=-85 ppm/℃,and Q_(f)=62300 GHz.The Q_(f)value of the x=0.20 sample was about 2 times higher than that of pure MgAl_(2)O_(4)ceramics(31600 GHz).Thus,MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with excellent microwave dielectric properties can be applied to 5G communications.
文摘SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature and the mass ratio of SiC to MgAl_(2)O_(4) on the formation of SiAlON polytypoids as well as on the properties of samples were studied.The formation mechanism of SiAlON polytypoids was discussed.The results show that firing at 1650℃in the nitrogen atmosphere,SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids can be obtained.With the gradual increase of the mass ratio of SiC to MgAl_(2)O_(4) in the raw materials,12H forms first,and then coexists with 21H,finally,all 12H converts into 21R in samples.Both phases are plate crystals with flat and smooth edges.Compared with 21R,12H is conducive to improving the density and the cold mechanical properties of materials.After firing at 1650℃in the nitrogen atmosphere,with the mass ratio of SiC to MgAl_(2)O_(4) of 6:4,the sample has the cold modulus of rupture of 27 MPa,showing the optimal performance.