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采用新颖的气泡液膜法,将Zn2+、Ni2+和Fe3+与OH-的共沉淀反应在气泡液膜中完成,制备了Ni0.7Zn0.3Fe2O4铁氧体前驱体纳米粒子,经元素分析、FT-IR、XRD和SEM等表征。实验结果表明,前驱体较精确地保持了原料溶液中Zn2+、Ni2+和Fe3+的配料摩尔比。前驱体分别经300、400、500、600、700或800℃烧结,制得Ni0.7Zn0.3Fe2O4铁氧体,用XRD和VSM表征。结果表明,在700℃烧结制得的Ni0.7Zn0.3Fe2O4铁氧体的粒径为26.92nm,磁饱和磁化强度sσ=64.22A.m2/kg,剩余磁化强度rσ=14.25A.m2/kg,内秉矫顽力jHc=16kA/m。将这种Ni-Zn铁氧体分散到合成油中,制成耐高温磁性液体。 相似文献
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以SDS(十二烷基硫酸钠)为表面活性剂,乙酸锌为前驱体,水-乙醇混合溶剂为反应介质,通过溶液化学方法制得Zn O纳米粒子。实验过程中考察了反应温度、表面活性剂与前驱体物质的量比等因素对Zn O纳米粒子制备过程的影响。通过紫外-可见吸收光谱(UV-Vis)、透射电子显微镜(TEM)、X-射线衍射(XRD)等对Zn O纳米粒子的结构和性质进行了表征。结果表明,控制合适的反应条件,可以得到量子尺寸效应较为明显的Zn O纳米粒子,Zn O纳米粒子具有球状形貌,尺寸在5~10 nm之间,且具有典型的纤锌矿晶体结构。抗菌实验结果表明,所合成的Zn O纳米粒子具有较好的抗菌性能。 相似文献
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纳米Co3O4在催化和陶瓷.以及防火材料等许多领域都有广泛的应用。本文以四水醋酸钴和1.2-丙二醇为原料,首先制备出前驱体,然后对前躯体进行煅烧,制得空心纳米Co3O4。以XRD,SEM等手段对反应的过程进行了研究,结果表明:实验所制备的前驱体为非晶态的粉末,通过调控分散剂聚乙烯呲咯烷酮(PVP)与Co^2+浓度之比,可以合成尺寸均匀,分散性良好的空心Co3O4纳米颗粒。 相似文献
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将BaCl2.2H2O和H2O2溶液在NH3.H2O中反应制备出前驱体BaO2.H2O2,再用H2TiO3和前驱体BaO2.H2O2作反应物、KNO3和KOH作溶剂,用熔盐法合成了钛酸钡纳米粒子,用XRD、SEM、TEM、EDS和FT-IR对产品的结构、形貌和成份进行了表征。结果表明,在500~600℃煅烧24h可获得粒径约为25~50nm的立方相钛酸钡纳米粒子,粒子大小分布均匀,形状近似为球形。随着反应温度升高,BaTiO3纳米粒子的晶胞参数减少、粒径增大。另外,还讨论了BaTiO3纳米粒子的形成机理。 相似文献
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利用共沉淀法,以Fe3 、Zn2 、Mn2 金属离子溶液为原料制备出锰锌铁氧体前驱体,通过不同的工艺对前驱体进行热处理.研究结果表明:热处理温度和气氛是影响锰锌铁氧体性能的关键因素.在950℃,空气中升温、氮气保护下降温的热处理工艺所制得的锰锌铁氧体具有最高的比饱和磁化强度、最低矫顽力. 相似文献
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采用溶胶-凝胶法以正硅酸乙酯和金属硝酸盐分别作为SiO2和铁氧体的前驱体成功制得Co0.5Zn0.5-Fe2O4/SiO2磁性纳米复合粒子.利用XRD、DSC-TG、Raman和SEM研究了热处理温度和酸添加量对样品晶体结构和晶粒尺寸的影响,并用谢乐公式估算平均晶粒尺寸.最后用振动样品磁场计(VSM)对样品的磁性能进行检测.结果表明,随热处理温度的升高,样品由非晶态转变成SiO2基体中结晶较完整的尖晶石结构的单相铁氧体纳米晶,晶粒尺寸为12.65nm.晶粒尺寸随热处理温度的升高和酸添加量的增加不断变大.对材料的磁性能的研究结果表明,合成的纳米Co0.5Zn0.5Fe2O4/SiO2,其比饱和磁化强度为9.17emu/g,矫顽力为67Oe. 相似文献
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气泡液膜法制备Mn-Zn铁氧体前体纳米粒子 总被引:1,自引:0,他引:1
用气泡液膜法连续式工艺,将MnC12·4H2O、ZnCl2和FeCl3·6H2O的混合水溶液与NaOH水溶液进行反应,制得了Mn0.25Zn0.23Fe1.04O2.04前体纳米粒子。这种前体经240℃、300℃、400℃、500℃、600℃、700℃和800℃烧结后,制得Mn0.25Zn0.23Fe1.04O2.04铁氧体纳米粒子。进行了XRD、VSM、SEM、TEM、FTIR和元素分析等测定,结果表明,全部烧结产品晶粒的粒径均在25nm以下;在240℃-700℃烧结产物的仃。在40.69-46.02emu/g;400℃及其以下温度烧结产品的Hc≈0;600℃烧结产品的Tc为458.1℃。测定了600℃烧结产品的SEM,以及240℃烧结产品的TEM。 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
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. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
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... 相似文献
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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. 相似文献
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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.…… 相似文献
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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. 相似文献
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Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe 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. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
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. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
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 ... 相似文献