Preparation and Characterization of CeO2-ZrO2 Solid Solution Ultrafine Particles Using Reversed Microemulsion

The development of the TWCs (three-way cata-lysts) was dictated bythe need to si multaneously con-vert the three main pollutants inthe exhaust gases ,i .e .,hydrocarbons (HCs) ,COand NOxpresent in theautomotive exhaust to H2O, CO2and N2[1]. Highestconvers…     

Surface and Texture Properties of Tb-Doped Ceria-Zirconia Solid Solution Prepared by Sol-Gel Method

The three-way catalysts （TWCs） promoters Ce0.6Zr0.4- x TbxO2-y were prepared by sol-gel method. BET surface areas analysis indicated that an increase of the dopant Tb content from x = 0.05 to x = 0.15 favors an increase of surface area from 66.8 to 80.4 m^2· g^-1 compared with the undoped sample Ce0 .6oZr0.40O2 65.1 m^2·g^- 1 after calcination at 650℃. Transmission electron microscopy （TEM） observation indicated that the doped samples have a higher thermal stability. The XRD and Raman spectra confirmed that the Ce0.6Zr0.4-xTbxO2-y cubic solid solution is formed. XPS analysis revealed that Ce and Tb mainly existed in the form of Ce^4＋ and Tb^3 ＋ , and Zr existed in the form of Zr^4＋ on the surface of the samples. The doped samples were homogenous in composition ; the introduction of Tb into the CeO2-ZrO2 promoters resuited in the formation of a solid solution, and the concentration of surface lattice oxygen was increased.     

Preparation of High-Surface Area Nano-CeO2 by Template-Assisted Precipitation Method

The high-surface area nano-CeO2 was prepared by Ce（NO3）3 by precipitation method, with surfactant cetyhrimethyl ammonium bromide （CTAB） as templating agent. The effects of the precipitating agents, reaction temperature, ageing time, and calcination temperature on the surface area, as well as the pore structure and the mean crystallite size of nano-CeO2 were studied. It was found that the reaction of Ce（NO3）3 with NaOH in the presence of CTAB at 90℃ for 12 h yieldsed a cerium oxide/surfaetant mixture, which after calcination at 400℃ resulted in high-surface area nano-CeO2. The mean crystallite size of CeO2 was approximately 6 nm, surface area was in excess of 200 m^2· g ^- 1, pore size was approximately 9 nm, and the pore distribution was concentrative. Moreover, the surface area can still reach 147 m^2·g^- 1 after calcination at 700 ℃, which showed the good thermal stability of the CeO2. The number of oxygen vacancies in the structure of CeO2 corresponded with the surface area of CeO2, and the high surface area was propitious to the formalion of oxygen vacancies.     

烧结温度对锂离子电池负极材料Li4Ti5O12性能的影响

采用钛酸四丁酯为钛源、一水合氢氧化锂为锂源，利用水热法制备锂离子电池负极材料Li₄Ti₅O₁₂（LTO），研究了水热后不同烧结温度对LTO相组成、微观形貌及电化学性能的影响。结果表明:当煅烧温度分别为500、550、600、650、700℃时，烧结LTO均为尖晶石型；500、550、600℃烧结LTO的微观形貌为纳米片状结构，当温度升高到650℃时，LTO出现纳米棒状结构，随着温度继续升高，LTO在700℃时生成较厚的纳米片状结构；当烧结温度为650℃时，LTO的比表面积为94.5907 m2·g-1，气孔体积为0.9663 mL·g-1，此时Li₄Ti₅O₁₂的放电比容量达到最大值240 mAh·g-1；电流密度100 mA·g-1、循环260次条件下，LTO容量保持率达96.45%，电流密度为1和2 A·g-1、循环1000次条件下，LTO容量保持率达92.97%和77.21%。     

固相反应条件对磷酸铁锂电化学性能的影响

以碳酸锂(Li₂CO₃)为锂源, 磷酸二氢铵(NH₄H₂PO₄)为磷源, 草酸亚铁(FeC₂O₄·2H₂O)为铁源, 柠檬酸(C₆H₈O₇·H₂O)为碳源, 采用固相反应法制备橄榄石晶型磷酸铁锂。利用X射线衍射仪, 扫描电子显微镜, 能谱仪, 比表面积分析仪和电化学测试等设备和方法对磷酸铁锂材料的物相组成、结构、形貌和电化学性能进行表征, 研究煅烧温度和保温时间对磷酸铁锂电化学性能的影响, 并通过添加碳对试样进行包覆改性。结果表明, 在煅烧温度为700℃, 保温时间为12 h条件下制备的磷酸铁锂正极材料的电化学性能良好, 碳包覆能有效改善电极材料的性能。包覆碳后的磷酸铁锂电极材料在0.2C充电电流密度下首次放电比容量可达319.2 mAh·g-1; 在1C充电电流密度下循环100次后, 放电比容量保持在168.1 mAh·g-1。     

前驱体煅烧法制备CeO2颗粒及其抛光性能的研究

以Ce(OH)₃为前驱体,采用前驱体煅烧法制备CeO₂抛光粉。通过调节煅烧温度、升温速率和保温时间获得的具有不同比表面积的CeO₂颗粒样品,将样品球磨破碎,制备出中位粒径为(1.0±0.1)μm的CeO₂抛光液。通过分析CeO₂抛光液对K9玻璃的抛光切削量和表面粗糙度Ra值来评价其抛光性能,采用比表面仪(BET)、X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)和原子力显微镜(AFM)等表征手段对样品的比表面积、物相组成、微观组织结构和抛光玻璃表面粗糙度进行分析,结果表明:前驱体Ce(OH)₃煅烧可以制备具有立方萤石结构、尺寸均匀的纳米级CeO₂抛光粉,煅烧温度的升高,保温时间的延长和升温速率降低均会使CeO₂颗粒的比表面积减小。CeO₂颗粒的比表面积是其抛光性能的关键,比表面积越小切削能力越强,本实验样品对K9玻璃的切削量最大可达900 nm·min^-1,此外,比表面积对玻璃抛光质量也有重要影响,在比表面积为5 m²·g^-1时,获得的玻璃表面粗糙度小,玻璃表面质量高。     

Preparation of La0.9RE0.1MnO3 Ultra-fine Particles Used for CH4 Oxidation

Ｐｅｒｏｖｓｋｉｔｅ ｔｙｐｅｏｘｉｄｅｓ (ｇｅｎｅｒａｌｆｏｒｍｕｌａＡＢＯ3 )ｈａｖｅｂｅｅｎａｔｔｒａｃｔｉｎｇｍｕｃｈａｔｔｅｎｔｉｏｎｆｏｒｍｏｒｅｔｈａｎｔｗｏｄｅｃａｄｅｓｄｕｅｔｏｔｈｅｉｒｐｏｔｅｎｔｉａｌｃｏｍｍｅｒｃｉａｌａｐｐｌｉｃａｔｉｏｎｓａｓｃａｔａｌｙｓｔｓｆｏｒｖａｒｉｏｕｓｒｅａｃｔｉｏｎｓ :ｏｘｉｄａｔｉｏｎｏｆＣＯ[1～ 3 ] ａｎｄｌｉｇｈｔｈｙ ｄｒｏｃａｒｂｏｎｓ[4～ 7] ,ｃｏｍｂｕｓｔｉｏｎｏｆｎａｔｕｒａｌｇａｓｏｒＣＨ4 [8～ 1 1 ] (ｔｏｃｏｎｔｒｏｌＮ…     

Influence of pH on Morphology and Formation Mechanism of CeO2 Nanocrystalline

Nanoparticles of cerium oxide were prepared by common precipitation method using cerium nitrate solution and ammonia reagent. Cerium oxide particles with different morphologies were synthesized through adjusting pH values of the solution. TEM and BET results showed that spherical crystal was gained in acid solution, with the specific surface of 148. 1944 m2·g^-1. The cerium oxide appeared in the form of spherical and rod-like grains under neutral condition, and the specific surface changed to 114.7975 m^2·g^-1. Moreover, in alkaline solution, cerium oxide powders were exhibited in rod-like form with the specific surface of 106.2465 m^2·g^-1. Precipitation formation mechanism of different morphologies was also discussed, which followed decomposition precipitation mechanism and topology reaction mechanism in acid and alkaline solution, respectively.     

Catalytic Activity of Ceria-Zirconia Nanostructured Materials Prepared via Reversed Microemulsion Method

CeO2-ZrO2mixed oxides have a number of i mpor-tant catalytic applications[1].They are extensively em-ployed in current automotive three-way catalysts(TWCs)as the oxygen storage promoters,i.e.materi-als that regulate the oxygen partial pressure throughtheC…     

石蜡/二氧化硅复合相变材料的制备及其性能

以石蜡为相变芯材,以正硅酸乙酯为硅源,在酸性条件下通过溶胶-凝胶法制备出石蜡/二氧化硅复合相变材料.应用傅里叶红外光谱、X射线衍射、扫描电镜、差示扫描量热法、热重法等手段对所制备复合相变材料的形貌、成分、热性能等进行了表征.实验结果表明,所制备的石蜡/二氧化硅复合相变材料的形貌是直径约为2μm的核/壳结构微球.当核/壳质量比为2∶1时,石蜡包覆率为66.3%,熔点为54.2℃,熔化焓为133.8 J·g-1,凝固点为49.5℃,凝固焓为127.5 J·g-1.与传统的有机高分子壳层材料相比,无机二氧化硅壳层材料具有更好的热导率,提升了复合相变材料的导热性能,且其不易燃烧,无腐蚀性,更加安全环保,有效拓展了相变材料在建筑保温和智能保温纺织物等领域的实际应用.      

高比表面积纳米CeO_2的制备

采用模板法制备高比表面积纳米CeO_2. 详细考察了铈盐和NaOH滴加速度、晶化时间和温度、铈盐种类、表面活性剂用量等对CeO_2比表面、晶粒尺寸的影响. 结果表明, 当CeCl_3加入速度=2.5 ml·min~(-1)、 NaOH加入速度=3 ml·min-1、晶化温度=90 ℃、晶化时间=24 h、 CeCl3∶ C_(12)H_(25)SO_4Na∶ NaOH∶ H2O=1∶ 2.7∶ 7.3∶ 1100(摩尔比)、焙烧温度=200 ℃时, CeO_2的比表面积和晶粒尺寸分别为457 m~2·g~(-1)和2.0 nm. 这种高比表面纳米CeO_2与常规CeO_2相比, 具有独特的物理、化学性质, 有望成为一种应用广泛的新型材料.     

纳米二氧化硅粉体的微乳液制备及表征

以硅酸盐溶液／环已烷／聚乙二醇辛基苯基醚／正戊醇体系的微乳液反应为基础,以浓硫酸为 沉淀剂,采用微乳液法制备了高比表面积纳米SiO2粉体,并通过比表面积(BET),透射电镜 (TEM),红外光谱分析(IR),X射线衍射(XRD),差热一热重分析(DTA-TG)对样品进行了形态表 征和物相分析。研究结果表明:采用微乳液法制备的纳米SiO2粉末均由非晶态物质组成,粉体颗 粒形貌近似呈球形,粒径为15-35nm,比表面积达580-630 m2／g。     

Influence of [La(EDTA)]~- on pore structure of activated alumina carrier at high-temperature

The activated alumina as a catalyst carrier were widely used in automotive exhaust catalysts under high temperature,such as,petroleum refining catalysts,hydrogenation and hydrodesulfurization catalyst carrier in China and abroad.γ-Al2O3 was the catalyst carrier that was the most widely used and the best carrier of improved specific surface area .However,the activation of the coating consisted of γ-Al2O3 were usually transformed into α-Al2O3 at 800 oC,causing increased density,reduced specific surface area,and the collapse result of pore structure.While the temperature reached 1200 oC,activation of coating detached from the carrier,the resistance of flowing gas increased,catalytic activity decreased.Addition of La2O3 stabilized the γ-Al2O3 crystal structure,which would keep the activation stability of coating at a high temperature and inhibit activity loss.The activated alumina carrier treated with the solid-pore-expanding agent containing [La(EDTA)]-that synthesized using solid and solid-hybrid approach with the thermal stabilizer lanthana and EDTA at the high-temperature had a 10-30 μm large pore porous network-like structure,after alumina was calcined at 1200 oC for 1 h.The specific surface area of four specimen were beyond 120 m2/g,while the sample specific surface area of x([La(EDTA )]-)=1% was up to 150.36 m2/g.     

固体超强酸S_2O_8~(2-)/TiO_2-WO_3的制备及其催化性能研究

用溶胶-凝胶法制备了固体超强酸S2O82-/TiO2-WO3,并对其进行了XRD与IR表征,用乙酸乙酯合成模型反应考察了其催化性能,系统研究了WO3的含量、焙烧温度等制备条件对S2O82-/TiO2-WO3性能的影响。实验表明:在(NH4)10W12O41.xH2O质量分数为5.0%、焙烧温度为500℃条件下通过溶胶-凝胶法制备的固体超强酸S2O82-/TiO2-WO3,其载体为微细且晶格不太完整的锐钛矿型TiO2,比表面积较大,具有比浸渍法制备的SO42-/TiO2更高的硫含量和更强酸性,并具有较高的催化酯化活性和稳定性,在反应条件为:醇酸摩尔比1.48∶1、催化剂用量为冰醋酸的6.0%、反应时间2.0h,乙酸转化率可达74.1%(不加分水器)。催化剂在无需任何再生的条件下重复使用,活性下降趋势平缓,显示良好的稳定性。     

Preparation and Characterization of Porous Yttrium Oxide Powders with High Specific Surface Area

Y2O3isoftenusedinthemanufactureofphos phorsandceramics[1～3].However,itisalsousedas selectivecatalysts[1,4,5],suchasforthedehydrationof2alkanols,thedimerizationofmethane,1butene isomerization,hydrogenationof1,3butadieneandac etonealdoladdition,andsupport[6,7]formetalsthat catalyzetheformationofmethanolfromCO2andH2.It iswidelyacceptedthatthecatalysispropertiesofox idesdependstronglyontheirphysicalcharacteristics,especiallyontheirspecificsurfaceareaandporous structure.Agreatdealofattentionhasb…     

喷雾干燥法合成锂离子电池复合正极材料xLiFePO4.yLi3V2(PO4)3及性能研究

采用喷雾干燥和高温固相法合成了一系列xLiFePO4·yLi3 V2( PO4)3复合正极材料.电化学测试结果表明,0.95LiFePO4·0.05Li3 V2( PO4)3复合正极材料具有较高的比容量、优良的循环性能和倍率性能,在电压范围为2.0V～4.3V,0.1C,1C,5C条件下的放电容量分别为162.7,147.7和122.3 mAh·g-1.0.5LiFePO4·0.5Li3 V2(PO4)3和0.3LiFePO4·0.7Li3 V2 (PO4)3复合正极材料则表现出了良好的倍率性能,5C,10C充放电条件下容量保持率分别为:77％,73％,88％,82％.     

包裹型SiO2/Al复合粉体的制备及烧结性能研究

为了克服金属陶瓷两相分布不均、界面不润湿和难以烧结致密等难题,采用球磨技术将增强相均匀包裹在基体材料表面,研究包裹型SiO₂/Al复合粉体的球磨制备工艺及其烧结性能,提高金属陶瓷的综合性能。结果表明,随着球磨时间的延长,SiO₂/Al复合粉体的比表面积先增大后减小,球磨6 h获得的复合粉体比表面积最大,达到8.1 m2·g?1。随着球料比的增大,SiO₂/Al复合粉体的比表面积先增大后减小,说明SiO₂包裹在Al粉表面的量呈现先增多再减少的趋势。随着球磨转速的增大,SiO₂/Al复合粉体比表面积先增大后减小。随着烧结温度的提高,SiO₂/Al金属陶瓷表面硬度先增高后降低,在烧结温度为900 ℃时,SiO₂/Al金属陶瓷的表面硬度达到最高。球磨时间为6 h,球料比为2:1,球磨转速为360 r·min?1,烧结温度900 ℃可以获得性能较佳的SiO₂/Al金属陶瓷。     

Effect of doping elements on catalytic performance of CeO2-ZrO2 solid solutions

CeZr, CeYZr, LaCeZr, LaCePrZr, LaCePrYZr, and LaCePr solid solutions were prepared via the coprecipitation method, and characterized by means of X-Ray Diffraction (XRD) and Brunauer-Emmett-Teller (BET) techniques. The oxygen storage capacity (OSC) of the solid solutions was evaluated by the pulse technique and the catalytic activity was assessed using a 4-channel catalysis device. It was seen that the solid solutions presented cubic structure. The specific surface area and thermal stability could be enhanced by doping Y into the solid solutions. Doping a small amount of La had a positive effect on the thermal durability while doping a large amount of La decreased the specific surface area and the thermal stability. LaCePrZr and LaCePrYZr solid solutions synthesized using Baotou rare earth mineral residue enriched with LaCePr after Nd extraction presented a certain higher value in specific surface area and thermal stability, thereby enabling to be used as economic catalysts for automobile exhaust purification. Coating Al2O3 or SiO2 layer on the surface of ceria-zirconia solid solutions increased the specific surface area and thermal resistance.     

盐酸改性对天然斜发沸石孔道特征、成分、表面电位及阳离子交换性能的影响

采用不同浓度盐酸对天然斜发沸石进行改性,并系统地研究了改性沸石的孔道特征、化学成分、表面电位及阳离子交换性能的变化.盐酸改性后,沸石晶体结构破坏较小,表面变得疏松粗糙,K+、Na+、Ca2+和Mg2+元素含量均小幅下降;表面负电荷增加,阳离子交换容量减小;比表面积和总孔体积均有所提高,最高分别从原沸石的35.97 m2·g-1和0.0761 m3·g-1提高至64.46 m2·g-1和0.1156 m3·g-1.盐酸改性对沸石微孔、介孔和大孔的分布影响明显.从迟滞回线形状判断沸石孔道类型均为不均匀狭缝型孔道,盐酸改性不会改变沸石孔道类型.      

Kaolin/ZrO2复合纳米粉体制备及性能研究

以Zr (NO₃)₄·5H₂O为锆源, 利用水热法分别制备ZrO₂和kaolin/ZrO₂复合纳米粉体, 采用扫描电子显微镜、X射线衍射仪、红外光谱仪分析了样品的微观形貌及特性, 使用紫外-可见分光光度计研究了样品的吸光特性, 利用Brunauer-Emmet-Teller (BET)气体吸附法(氮气吸附)测定并计算了样品的比表面积。结果表明, 经过400℃煅烧后, kaolin/ZrO₂表面微球颗粒较纯ZrO₂更加均匀、单一, 不存在成块团聚体; 两种样品均存在介孔结构, ZrO₂主要以无定形形式存在, 但样品中都存在少量的四方相ZrO₂; 在波长190~800nm范围内, kaolin/ZrO₂纳米粉体吸光率均高于纯ZrO₂, 并且其BET比表面积也比纯ZrO₂高19.05m2·g-1, kaolin/ZrO₂纳米粉体在防紫外光特种材料制备及光催化处理工业废水等方面具有更大的优势与潜力。