Gd_2O_2S∶Pr~(3+)荧光粉的合成与发光性能研究

采用Gd(NO_3)_3、Pr_6O_(11)、HNO_3、(NH_4)_2SO_4和NH_3·H_2O为实验原料,通过共沉淀还原法合成了Gd_2O_2S∶Pr~(3+)荧光粉。利用傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)和光致发光(PL)等手段对合成产物进行了表征。结果表明前驱体具有非晶态结构,在空气气氛中800℃煅烧2 h能转化为单相的Gd_2O_2SO_4粉体,该粉体在氩氢混合气氛下800℃煅烧1 h能转化为单相的Gd_2O_2S粉体。Gd_2O_2S粉体呈准球形,粒径大约1μm左右,团聚严重。PL光谱分析表明在303 nm的紫外光激发下,Gd_2O_2S∶Pr~(3+)荧光粉呈绿光发射,主发射峰位于514nm,归属于Pr~(3+)离子的~3P_0-~3H_4跃迁,Pr~(3+)离子的猝灭浓度为1mol%。     

溶液燃烧法合成Co3O4纳米粉体及热处理研究

分别以氨基乙酸、柠檬酸、葡萄糖为燃料,Co(NO_3)_2·6H_2O为氧化剂,采用溶液燃烧法合成Co_3O_4粉体,并对氨基乙酸为燃料合成的Co_3O_4粉体在500℃、600℃和700℃热处理,研究其结构、微观形貌和磁学性能。研究表明各燃料配制的前驱体溶液在300℃均可发生燃烧反应合成Co_3O_4粉体,以氨基乙酸为燃料时,合成粉体的颗粒较大,中间有气孔,分散性好,残留少量的氨基乙酸。n(氨基乙酸)∶n(硝酸钴)=1.11∶1时合成的Co_3O_4粉体600℃热处理后得到了高纯度、分散性好、平均径向尺寸80nm的Co_3O_4纳米粉体。以氨基乙酸为燃料合成的Co_3O_4产物在600℃和700℃热处理后,其矫顽力和剩磁值都比500℃热处理后的要小。     

PS45/CuAl8伪合金复合涂层高温循环氧化行为

采用超音速活性电弧喷涂技术在Q235钢基体表面制备PS45/CuAl8伪合金复合涂层,将该涂层在600℃和800℃进行循环氧化,采用XRD、SEM和精密天不等手段对涂层的显微结构进行表征,研究了涂层的循环氧化性能。结果表明:PS45/CuAl8伪合金复合涂层主要由Al_2O_3、Cr_2O_3、α-Cu和γ-Ni固溶体组成,组织致密,颗粒成扁平状且扁平化程度高、分布均匀。经高温循环氧化后在涂层表面形成了一层致密的Al_2O_3+Cr_2O_3+Ni(Al,Cr)_2O_4薄膜,避免了Al_2O_3薄膜的剥落,从而降低了涂层氧化速率,提高了基体的抗高温循环氧化性能。     

9Cr-1Mo钢在含水蒸汽气氛中的氧化行为

研究了9Cr-1Mo(ASME T91)钢在(Ar 10%H_2O)气氛中600℃、650℃和700℃下的高温氧化行为.在恒温氧化10 h过程中,在600℃氧化遵从抛物线规律;而在650℃和700℃氧化则遵从分阶段抛物线规律,且后一阶段的速度常数高于前一阶段的;随着温度的升高,氧化速度明显增大;氧化激活能为157.2 kJ/mol.T91钢氧化时表面形成了多层结构的氧化膜,从外到内依次为Fe_2O_3、Fe_3O_4和(Fe,Cr)_3O_4;钢基体也发生了内氧化,内氧化物为FeO和Cr_2O_3.只有在700℃氧化时没有外层Fe_2O_3形成和内氧化发生.9Cr-1Mo钢氧化后冷却至室温后,氧化膜发生开裂或局部剥落.最外层Fe_2O_3与次外层Fe_3O_4间出现很大的裂隙,Fe_2O_3层容易剥落.同时探讨了9Cr-1Mo钢在含水蒸汽气氛中的氧化机制.     

Cr~（3＋）离子掺杂对Al_2O_3粉末结构及发光性能影响

采用球磨法制备了不同浓度Cr_2O_3掺杂的Al_2O_3粉体,并在700℃、1200℃空气中退火2 h。1200℃退火后样品,除掺杂浓度为1.6%的样品中出现少量γ-Al_2O_3相外,其余样品相均为纯α-Al_2O_3。样品晶格常数随着Cr~（3＋）离子浓度的增加而增加。采用波长为579 nm的激发光源对佯品进行荧...     

水蒸气温度对700℃先进超超临界锅炉候选合金GH2984氧化行为的影响

采用X射线衍射仪、扫描电子显微镜对比研究GH2984合金在750℃和850℃纯水蒸气中的氧化行为。结果表明:GH2984合金的氧化动力学遵循抛物线规律;温度升高,Cr挥发加速,外氧化和内氧化的速率急剧增加,氧化膜的组成结构发生明显的变化。750℃时,合金表面形成单层致密的(Cr,Mn)_2O_3膜;温度升至850℃,氧化膜中空洞的数量大幅增加,氧化膜转变为由薄的外层Fe_2TiO_5和厚的次外层(Cr,Mn)_2O_3及薄的内层(Nb,Mo)_2O_5组成的三层结构。Ti,Al优先于晶界处发生内氧化,分别形成TiO_2和Al_2O_3;两种内氧化产物的尺寸和数量均随温度升高而增加。     

溶胶-凝胶法制备高锆含量PLZST反铁电陶瓷粉体

以三水合乙酸铅(Pb(CH_3COO)_2·3H_2O)、乙酸镧(La(CH_3COO)_3)、乙酸锡(Sn(CH_3COO)_4)、乙酸锆(Zr(CH_3COO)_4)、钛酸丁酯(C_(16)H_(36)O_4Ti)为原料,采用改进的溶胶-凝胶(sol-gel)工艺制备(Pb_(0.97)La_(0.02))(Zr_(0.95)Sn_(0.01)Ti_(0.04))O_3(简称PLZST)反铁电陶瓷粉。采用DSC-TGA差热分析研究PLZST干凝胶的分解性能,用XRD和SEM对不同温度煅烧的PLZST陶瓷粉进行表征,分析煅烧温度对产物的影响。实验结果表明,PLZST干凝胶在550℃以上达到完全分解;干凝胶粉体在850℃煅烧2h,可生成较纯钙钛矿相的高锆含量PLZST陶瓷粉体,粉体颗粒呈球形,平均晶粒约为200nm。     

NdBO_3和 Nd(BO_2)_3的标准生成自由能

用 CaF_2单晶和 ZrO_2(+MgO)为固体电解质分别构成原电池:■和 Pt,B_((s)),NdBO_(3(s)),Nd(BO_2)_(3(s))|ZrO_2|Cr_2O_(3(s)),Cr_((s)),Pt联合测了 NdBO_3和 Nd(BO_2)_3的标准生成自由能:ΔG~0_(NdBO_3)=-1757+3.8×10~(-1)TΔG~0_(Nd)(BO_2)_3=-3435+8.8×10~(-1)T由此求出由氧化物生成 NdBO_3及 Nd((BO_2)_3)的反应的标准生成自由能变化:1/2Nd_2O_(3(s))+1/2B_2O_(3■)=NdBO_(3(s))ΔG~0_(NdBO_3)=-242+1.4×10~(-1)T和 1/2Nd_2O_(3(s))+3/2B_2O_(3(s))=Nd(BO_2)_(3■)ΔG~0′_(NdBO_2)3=-693+4.6×10~(-1)T     

MIL-101前驱体制备MnO_x-Cr_2O_3催化剂及其对苯的催化氧化性能

以硝酸铬、对苯二甲酸、氢氟酸为原料,水热法制备MIL-101(Cr);经KMnO_4预浸渍、H_2O_2还原对其进行MnO_x负载,再经热解制备MnO_x-Cr_2O_3复合催化剂;借助BET、XRD、SEM、TEM、XPS等测试手段,研究不同MnO_x负载量的MnO_x-Cr_2O_3复合催化剂对苯的催化氧化活性。结果表明:氢氟酸的添加量对MIL-101(Cr)孔结构影响显著,添加125μL的氢氟酸制备的MIL-101(Cr)具有最佳的多孔性,经甲醇多次活化后,其比表面积达到3 447 m~2/g;MnO_x-Cr_2O_3复合催化剂,比表面积为89.30 m~2/g,远大于市售的Cr_2O_3载体的,对苯催化氧化的活性T_(90%)为280℃;MnO_x负载量质量分数为5%时,催化苯的T_(90%)为266℃,但增加MnO_x负载量对复合催化剂的催化活性影响不大;MnO_x-Cr_2O_3复合催化剂的高催化氧化活性归因于Mn与Cr之间的电子迁移与表面晶格氧含量高;其良好催化活性和无毒MnO_x包覆可抑制毒性Cr元素析出。     

形貌可控的Cr_2O_3纳米颗粒的制备与表征

室温下,将三氧化铬(CrO_3)和聚乙烯醇(PVA)在水溶液中反应合成聚合物前驱体,退火处理得到不同形貌的Cr_2O_3纳米颗粒。采用热重-差热分析仪(TG-DTA)、傅里叶红外光谱仪(FT-IR)、粉末X射线衍射仪(XRD)和扫描电镜(SEM)对所得样品进行了分析。结果表明,750℃退火后获得纯的单相Cr_2O_2纳米颗粒;通过控制PVA和CrO_3的初始反应比例,得到了球形和片状的Cr_2O_3纳米颗粒。     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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 ...