微通道反应-共沉淀法制备YAG纳米粉体

以碳酸氢铵为沉淀剂,采用微通道反应与共沉淀法相结合的方法制备出了钇铝石榴石纳米粉体。实验考查了溶液浓度、pH值、Nd3+掺杂等因素对合成纯相YAG纳米粉体的影响。结果表明增大沉淀剂浓度不利于纯相YAG粉体的制备,当沉淀剂浓度为0.4mol/L,Al 3+浓度范围为0.1～0.4mol/L的条件下均得到纯相YAG纳米粉体;采用优化的实验条件,体系pH值维持在8左右,以2%(原子分数)的Nd3+取代YAG中的Y3+,900℃保温4h得到纯相Nd∶YAG粉体,粉体平均粒径在40nm左右,分布均匀,呈近球形。     

微波均相沉淀法制备Nd:YAG纳米粉体及其表征

以Al(NO3)3,Y(NO3)3为母盐,尿素为沉淀剂,添加占母盐质量为8%的(NH4)2SO4,以不同浓度的Nd3+取代Y3+,采用微波均相沉淀法制备了具有良好分散性和可烧结性、平均粒径为71nm的Nd:YAG纳米粉体。利用IR、DTA-TG、XRD、TEM、LD等技术对YAG前驱物及其煅烧粉体进行表征。结果表明:采用微波均相法,前驱体在1100℃下煅烧,可得到分散良好的纯YAG相,无YAP、YAM中间相出现,且YAG的单相程度不随Nd3+掺杂浓度的增加而变化。     

微流体快速沉淀法制备Nd∶YAG纳米粉体

采用一种基于微流体快速均匀混合的沉淀方法,以碳酸氢铵(NH4HCO3)为沉淀剂制备前驱体。红外光谱(FT-IR)、X射线衍射(XRD)、透射电镜(TEM)和热分析(TG-DTA)等测试结果显示,该方法获得的前驱体经煅烧后可得到分散性好、形状规则、平均粒径为50nm的纯相Nd∶YAG纳米粉体。     

共沉淀法YAG、Nd∶YAG纳米粉体的制备、结构与光谱性能研究

采用共沉淀方法,以氨水为沉淀剂,与硝酸盐的混合溶液反应得到YAG、Nd∶YAG前驱体,并在不同的温度下对前驱体进行锻烧。利用红外光谱(FT IR)、热重/差热分析(TG/DTA)、X射线衍射(XRD)、透射电镜(TEM)等技术对YAG前驱物及煅烧粉体进行表征,对Nd∶YAG粉体的发光性能进行了测试。结果表明,在800℃下煅烧YAG前驱体,得到纯YAG晶相,无YAP、YAM中间相的出现;XRD、TEM和比表面分析表明在800～1000℃煅烧所得粉体晶粒直径为40～100nm,具有较好的分散性。同时荧光测试表明Nd∶YAG粉体具有良好的发光性能。     

撞击流共沉淀法制备YAG:Ce荧光粉过程的研究

采用Al(NO3)3、Y(NO3)3和Ce(NO3)3为母盐,碳酸氢铵为沉淀剂,利用撞击流共沉淀法制备YAG:Ce(Y3Al5O12:Ce)球形纳米粉体。利用XRD、FT-IR、SEM和荧光分光光度计对YAG前驱体及煅烧纳米粉体进行了表征,并分析了母盐溶液的浓度、溶液的滴加速度以及煅烧方法和温度对制备YAG纳米粉体的影响。结果表明母盐溶液的浓度、滴加速度及煅烧方法和温度对煅烧粉体的组成、分散性、形貌及发光性能有显著的影响。当初始原料浓度较低(c0=0.055mol/L)时,900℃可以获得纯YAG晶相,不形成任何中间相;初始浓度c0在1.0mol/L以上时,1000℃得到的YAG荧光粉中有YAM、YAP和CeO2杂质相存在;适当的提高加料速度,可以增加粉体的结晶度;采用Na2CO3-S-K2CO3助熔剂辅助煅烧,700℃时已完全转变为YAG相,与直接煅烧法相比,YAG相的完全转变温度降低了约300℃,荧光粉的发光强度比不加熔盐明显提高了。     

光学基质粉体YAG及荧光粉体Ce:YAG的制备与表征

采用共沉淀法制备出尺寸分布均匀、分散性良好的立方相钇铝石榴石(YAG)与Ce:YAG纳米粉体.考察了煅烧温度和时间对粉体物相和颗粒大小的影响及Ce~(3+)的掺杂量对Ce:YAG粉体的荧光光谱的影响.借助IR、XRD、BET、SEM和荧光分析仪等测试手段对前驱体、YAG及Ce:YAG纳米粉体进行了表征与分析.结果表明:共沉淀前驱体经900℃煅烧2h后可得到纯立方相的YAG(Ce:YAG)纳米粉体;所得Ce:YAG粉体具有较好的荧光特性且Ce~(3+)的掺杂量增加会造成其荧光光谱红移.     

沉淀剂对共沉淀法制备Lu2O3发光粉体形貌的影响

研究了共沉淀法制备Eu3 掺杂氧化镥(Lu2O3)发光粉体过程中三种不同的沉淀剂(氨水、碳酸氢铵以及NH3·H2O NH4HCO3两者的混合溶液)对所得粉体形貌的影响.通过差热热重质谱联用(DTA-TG-MS)和红外光谱研究了不同沉淀剂所得沉淀前驱体的热分解行为,结合显微结构观察、粒度分布和比表而积测试,对i种沉淀剂影响Lu2O3晶粒尺寸和团聚状态的规律进行了探讨.研究发现:采用NH3·H2O NH4HCO3混合沉淀剂得到的Lu2O3粉体具有最佳的显微结构和粒径分布状态,沉淀前驱体经1000°C煅烧2h,粉体的平均晶粒尺寸为35nm,中位粒径(D50)为0.48μm.     

共沉淀法YAG、Nd:YAG纳米粉体的制备、结构与光谱性能研究

采用共沉淀方法,以氨水为沉淀荆,与硝酸盐的混合溶液反应得到YAG、Nd：YAG前驱体,并在不同的温度下对前驱体进行锻烧。利用红外光谱(FT-IR)、热重／差热分析(TG／DTA)、X射线衍射(XRD)、透射电镜(TEM)等技术对YAG前驱物及煅烧粉体进行表征,对Nd：YAG粉体的发光性能进行了测试。结果表明,在800℃下煅烧YAG前驱体,得到纯YAG晶相,无YAP、YAM中间相的出现;XRD、TEM和比表面分析表明在800～1000℃煅烧所得粉体晶粒直径为40～100nm,具有较好的分散性。同时荧光测试表明Nd：YAG粉体具有良好的发光性能。     

陈化时间对Nd:YAG纳米粉体制备及性能的影响

以NH4Al(SO4)2·12H2O,Y(NO3)3·5H2O,Nd(NO3)3·5H2O为原料,碳酸氢铵为沉淀剂,研究了共沉淀法制备Nd:YAG纳米粉体过程中陈化时间对粉体性能的影响.采用pH计,FT-IR,XRD和TEM测试手段对其进行表征.陈化过程中PH值先减小后增大,XRD曲线显示共沉淀法中不同陈化时间都能得到纯相粉体,而24h所得粉体最好,粉体TEM图谱表明陈化24h所得到的粉体粒径更小,分散性较其他粉体更好.结果表明:共沉淀法制备Nd:YAG纳米粉体过程中陈化时间不影响纯相粉体的制得,但对粉体粒径大小及分布和团聚程度有直接的影响.陈化24h的粉体颗粒最小并且均匀,团聚很少.     

混合沉淀剂对YAG:Ce荧光粉性能的影响

采用沉淀法,以不同配比的NH4HCO3+NH3.H2O作为混合沉淀剂制备了YAG:Ce荧光粉。利用激发光谱、发射光谱、XRD和TEM对其光学特性和形貌进行了研究。结果表明,使用混合沉淀剂可提高YAG:Ce荧光粉的发光强度,当混合沉淀剂为1mol/L碳酸氢铵+4mol/L氨水时,荧光粉的发光强度最大,样品的生成物为纯YAG相粉体,其粒径分布均匀,分散性良好,呈球形,颗粒大小为1μm左右。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from