简介:将SO4^2-/TiO2-HZSM-5负载镧制备了新型催化剂SO4^2-/La2O3-TiO2-HZSM-5,以对羟基苯甲酸和丙醇的酯化反应为探针,考察了不同制备条件对催化剂性能的影响。结果表明:la^3+浸渍浓度为0.07mol/L,经110℃烘干后于500℃焙烧3h所得催化剂活性最好。对影响酯化反应的因素进行考察,最佳实验条件为n(醇)∶n(酸)=5∶1,反应时间4h,催化剂用量3.0%(总物料),酯化率可达96.0%。且该催化剂具有良好的重复使用和再生能力,适宜合成对羟基苯甲酸酯。
简介:TheZrO2-Al2O3ceramiccompositeswerepreparedbyappropriatetechniqueswithcommercialZrO2andAl2O3powdersasrawmaterialsandY2O3asstabilizer.TheresultsindicatethatwiththeintroductionofAl2O3intotheZrO2matrixwherethequantityofadditiveY2O3is3.5%(molefraction),thegrowthofZrO2grainsisefficientlyinhibited,whichhelpstheZrO2grainsexistinametastabletetragonalmanner;thushigherstrengthandtoughnessareacquired.Whenthecontentofaluminais20%(massfraction),thebendingstrengthandfracturetoughnessofthecompositesare676.7MPaand10MPa·m1/2respectively,themechanicalbehaviorsareclosetothosepreparedwithZrO2andAl2O3powderssynthesizedthroughwetchemicalapproach.Themechanicalbehaviorsofthecompositesarewellimprovedowingtothedispersiontougheningofaluminagrainsandphasetransformationtougheningofzirconiagrains.
简介:采用Nb2O3、Y2O3复合稳定剂,制得了高韧性、高强度的四方相ZrO2陶瓷材料,发现在Y2O3-ZrO2材料中加入0.5~1molNb2O3,可使材料在保持原有抗弯强度的同时,一定程度上改善了断裂韧性和相组成。
简介:Inthispaper,varioustechniquesincludingBET,XRD,SEMandXPSwereusedtostudythesinteringofpureandLa2O3-dopedtitania.Theexperimentalresultsshowthatsinteringoftitaniaproceedsviavolumediffu-sion.Addingoflanthanumoxidedecreasestherateofsinteringandhindersthephasetransitionfromanatasetorutilecrystalbystrongsurfaceinteractionbetweenthemixedcrystals(La4Ti9O24,La0.66TiO2.99)andTiO2.
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简介:ZrO_2-SnO_2-TiO_2(ZST)系统陶艺的微波电介质性质作为Sb_2O_5掺杂物的数量的功能被学习。与0-0的增加。5%Sb_2O_5(臼齿的比率),有Sb~(5+)离子的Ti~(4+)离子的替换减少了sintering温度并且由于氧空缺的减小增加了优秀因素Q。当Sb~(5+)的数量进一步增加了时(超过0.5%)。Q被增加电子浓度减少。当与0.5%Sb_2O_5做的系统是在为6h的1150℃的sintered时,相对的绝缘的经常的ε,Qf_0,和反响的频率(TCF)的温度系数是38.46,44500GHz,20.0x10~(-6)/℃,分别地,在6GHz。
简介:摘要采用溶胶-凝胶法制备了Al2O3-ZrO2复合溶胶膜,研究了化学组成和添加剂对复合溶胶的影响。结果表明,当Al2O3/ZrO2=1,DMF=40vol%时,可得到澄清透明,粘度适中,稳定性好,且凝胶干燥后几乎无开裂的溶胶膜
简介:TiO2@ZrO2@Y2O3:有coremultishell结构的Eu3+合成粒子通过layer-by-layer(LBL)的联合被综合自己组装方法和一个solgel过程。获得的样品与扫描电子被描绘显微镜学(SEM),传播电子显微镜学(TEM),X光检查光电子光谱学(XPS),X光检查衍射(XRD),和荧光spectrophotometry。结果证明合成粒子有coremultishell结构,球形的形态学,和狭窄的尺寸分布。TiO2核心上的ZrO2层的存在能有效地阻止在TiO2核心和Y2O3壳之间的反应;为在在TiO2@ZrO2@Y2O3的TiO2核心和Y2O3壳之间的反应的温度:Eucoremultishell黄磷能被300提高
简介:TheRamanspectraof3%(molefraction)Y2O3-ZrO2(3Y)areobtainedatdifferenttemperaturefrom77Kto853K.Theresultsshowthat260cm-1Egand460cm-1Egmodesonthespectrashifttowardlowerwavenumberwiththeincreaseoftemperature;meanwhile,thecontinuityoftheHalfWidthatHalfMaximum(HWHM)andwavenumber(frequency)ofRamanbandsarebrokenandt-phaseonlypartiallytransformstom-phaseat523K.Basedontheexperimentalresults,thispaperdiscussesthet-phaselatticevibrationof3YandpresentstheimagesofvibrationdisplacementofsixRaman-activemodesfort-phaseofZrO2.TheanalysisindicatesthattherearediversitiesexistinginthedisplacementoftheatomicvibrationofRaman-activemodesbecauseoftheirdifferentsymmetriesatvarioustemperature,whichleadstothedifferentchangetendenciesofRamanbands.Furthermore,theabruptchangesofsomeRaman-activemodesindicatingtheatomicdisplacementareassumedtobethecondensationsofphononmodesinthet→mphasetransition.
简介:AnO'-Sialon-Al2O3compositerefractorywaspreparedbyinsitureactionofSi3N4-ZrSiO4-Al2O3mixturewithfusedaluminaaggregates.Densification,insitureactionprocedureandmicrostructureofthematerialwereinvestigatedbymeansofX-raydiffraction,opticalandscanningelectronicmicroscopesandEDAX.
简介:基于国外定向凝固氧化物/氧化物共晶复合陶瓷的晶体生长动力学行为的研究成果,阐述其动力学机制,分析动力学因素对微观结构形态的影响,探讨晶体生长热力学、动力学行为与微观结构形态之间的关系,同时结合以燃烧合成、快速凝固技术制备的新型高强韧A12O3/ZrO2(Y2O3)共晶复合陶瓷,探讨共晶复合陶瓷在快速凝固条件下的晶体生长动力学行为。结合定向凝固与快速凝固两种晶体生长机制,得知过冷度、凝固界面前沿的温度梯度是影响晶体生长方式的重要因素,且受二者决定的凝固速率(即晶体生长速率)则决定材料的最终微观结构与形态。