CeO2掺杂KNN-LiNbO3无铅压电陶瓷的压电与介电性能研究

采用传统固相烧结法制备了0.98K0.5Na0.5NbO3-0.02LiNbO3-xCeO2(0.98KNN-0.02LN+xCeO2)无铅压电陶瓷.研究了不同CeO2掺杂含量(x=0、0.01、0.02、0.03、0.04)对0.98KNN-0.02LN陶瓷显微结构和电学性能的影响.研究结果表明:当CeO2掺杂含量从x=0.00到x=0.01和从x=0.02到x=0.03时,样品出现了正交-四方相转变.当x=0.00和x=0.02时,样品都处于正交与四方两相共存状态.CeO2少量掺杂时Ce4+完全进入晶格,表现为"受主"掺杂的特性;而大量CeO2掺杂时,有杂相的生成,主要起到烧结助剂的作用.样品在1080℃下烧结,当掺杂含量为x=0.02时取得最佳的综合性能:d33=104pC/N,Qm=2201,kp=0.24423,εr=804.2,tanδ=8.748;.     

Ni2+含量对纳米Ni-Zn铁氧体电磁损耗特性的影响

以聚乙二醇为表面活性剂辅助水热法制备了纳米NixZn1-xFe2O4(x=0.4、0.5、0.6、0.7)铁氧体,通过XRD、FESEM、TEM和PNA分析,研究了不同的Ni2+含量对Ni-Zn铁氧体的粒度、形貌及其电磁损耗特性的影响.结果表明,水热法制备的晶体具有良好的结晶度,Ni2+含量不会影响样品的形态和结构,样品颗粒呈类球形,粒径在20～30 nm,在1～ 18 GHz的测试条件下具有介电损耗与磁损耗.Ni-Zn铁氧体电磁损耗随Ni2+含量的增加先增大后减小,当Ni2+含量x=0.6时,晶体晶化更加完整,粒度更加细化,对小于14 GHz中低频微波电磁损耗能力更强,在3GHz处,磁滞损耗正切tanδm达到最大值为1.03,介电损耗正切tanδe在3 GHz、9.5 GHz分别达到0.052、0.057,具有一定的微波吸收能力.     

微波诱导燃烧法合成MgO-Y2O3纳米粉体

以硝酸钇、硝酸镁、乙酸镁为原料,采用微波诱导燃烧法合成了体积比50:50的MgO-Y2O3纳米粉体,并研究了粉体的烧结性能.采用DSC-TGA、XRD、SEM、BET、IR等手段对粉体进行了分析表征.研究表明,在500 W微波功率下合成的粉体,经过600℃煅烧2h,结晶性良好,呈现均匀球状,粒度尺寸在30 ～50nm之间,比表面积为35.6m2/g.粉体经过200 MPa压力下等静压成型后,在1300℃温度下保温2h,样品相对密度可达95;.     

鹿角形状钛酸钡制备及其介电共振现象研究

不同形貌钛酸钡通过将氧化钛前驱体球和钡盐在碱性条件下进行水热和高温烧结制备出来,其与石蜡混合物(75 wt;)在12 GHz微波频率附近发生了介电共振现象.由于钛酸钡是晶格常数降低的顺电立方相/四方相,发生原因是电致伸缩/逆压电效应产生的弹性纵波在晶粒内部的共振吸收.不同条件制备钛酸钡晶粒尺寸(219 nm)趋于一致,共振频率相近,经过110℃水热和1100℃烧结制备的鹿角形状钛酸钡晶粒较大(657 nm)并且相互联接使得共振加强.本工作证明了通过改变钛酸钡晶粒尺寸和形貌从而改变微波介电性能.     

B2O3对6ST-4LA微波介质陶瓷结构与性能的影响

为降低0.6SrTiO3-0.4LaAlO3(简称6ST-4LA)微波介质陶瓷的烧结温度,采用固相反应法,研究了B2O3对其结构与性能的影响.结果表明:添加B2O3可有效地降低6ST-4LA陶瓷的烧结温度,由1550℃降至1450℃;主晶相仍为赝立方钙钛矿结构固溶体,但有第二相的出现,其含量随着B2O3添加量的增加先降低后升高.当B2O3添加量为0.50wt;在1450℃下烧结时,6ST-4LA陶瓷获得最佳微波介电性能:εr=44.46,Q·f=51127 GHz,τf=-2.3×106/℃.     

用陶瓷坩埚在微波炉中熔化金属的研究

借助碳化硅、氧化锆和增韧莫来石陶瓷坩埚,采用不同微波功率和处理时间,对金属(铝、铜和不锈钢)的熔化行为进行了研究。结果表明:微波熔化金属的升温规律和熔化效果与坩埚种类、微波处理条件、金属种类都具有密切关系。通过比较不同工艺条件下金属熔化特点,对相关试验结果进行了分析。微波熔化金属具有快捷、节能和环保等特点,对金属样品分析、精密铸造和废金属回收等具有实用意义。     

Microwave‐promoted Synthesis of Novel Fused Osthole Analogues

Osthole is a natural coumarin derivative and has a broad scope of biological activities. Two series of novel fused osthole analogues were designed, and synthesized through a highly efficient microwave‐promoted synthetic protocol via the reaction of 4‐hydroxycoumarins and β‐ketoesters. The reaction conditions including solvent, catalyst, microwave power and irradiation time were also optimized. The pyrano[3,2‐c]chromene‐2,5‐diones and furo[3,2‐c]coumarins were obtained through two distinct intramolecular cyclization processes, and the proposed mechanism was also discussed.     

Microwave‐assistant route to hybrid semiconductor nanocrystals with quasi solution‐solid‐solid mechanism

A facile microwave‐assistant route was developed for the synthesis of hybrid nanocrystals. Colloidal hybrid nanocrystals, Ag₂S‐CdS, were prepared by using Ag₂S nanocrystals and cadmium diethyldithiocarbamate as raw materials under microwave irradiation. The fast ion conductor, Ag₂S nanocrystal, catalyzes the growth of CdS nano‐building blocks through a quasi solution‐solid‐solid mechanism. The ultraviolet‐visible absorption and photoluminescence spectra of the Ag₂S‐CdS hybrid nanocrystals were investigated. One of the main advantages for this synthesis is the efficiency of dramatically reducing overall processing time. This report provides a new route for the growth of semiconductor hybrid nanocrystals based on Ag₂S and may be extended to the preparation of other hybrid colloidal nanostructures.     

A Novel Method for One‐pot Synthesis of Furo[3,2‐c]coumarin Derivatives from 4‐Hydroxycoumarin and Arylglyoxal under Microwave Irradiation

A novel one‐pot synthesis of furo[3,2‐c]coumarins has been developed from readily available starting materials 4‐hydroxycoumarin and arylglyoxal. This method is simple, rapid and good yielding.