热处理对相变材料纳米胶囊性能的影响

以环己烷和正十八烷为囊心,用原位聚合法合成了三聚氰胺-甲醛树脂为囊壁的相变材料纳米胶囊,在不同温度下对胶囊热处理不同的时间,采用SEM,DSC,TG-DTA和IR等测试手段对胶囊的性能进行了研究.结果表明,热处理对胶囊的表观形貌、相变性能和耐热性能有很大的影响,热处理过程中环己烷扩散出囊壁,在胶囊内形成预留膨胀空间,使胶囊的耐热温度增高.当热处理温度为160～180℃,热处理时间在30～60min时,得到的胶囊破裂较少,胶囊的相变热为150J/g,耐热温度可以达到215℃左右.     

热处理对PMMA@PCM纳米胶囊相变特性的影响及机理

采用界面聚合法制备了以石蜡为芯材、聚甲基丙烯酸甲酯为壳层的纳米胶囊相变材料。胶囊的直径为100~400nm,相变焓可达29J/g,封装比率约为35%。采用差示热扫描量热仪(DSC)对PMMA@PCM经40℃、60℃及100℃热处理后相变特性的变化进行了探讨。结果显示,随着热处理时间的延长,相变温度均有所升高。凝固温度的升高是由于胶囊表面形成了一定量的相变晶种,而熔化温度的升高则是由于纳米胶囊体积的增加而引起的热传导率降低。这一研究结果将有助于分析纳米胶囊相变过程的微结构变化理论。     

磷酸亚铁锂纳米薄膜的制备及其光学性能

将水热法合成的LiFePO4粉体作为原料,通过浸渍-提拉法制备了LiFePO4纳米薄膜。观察了热处理温度对薄膜折射率和透光率等光学性能的影响。结果表明,在120～450℃范围内,随着热处理温度的升高,薄膜折射率和透射率(在可见光区)增大,并膜厚减小。     

Fe-Ni基纳米晶软磁粉芯磁性能研究

采用模压成型成功制备了Fe-Ni基纳米晶磁粉芯。并研究了热处理温度和时间、纳米晶粉体的粒度、成型压力等对其磁性能的影响和其温度稳定性和频率稳定性。结果表明,当100～900℃内退火,随着温度升高,μe和Q值都呈先增后减,600℃时μe达到最大值31.5,其最佳退火时间为2h。成型压力和纳米晶粉体粒度越大,μe越大,Q值越小。在100～1000kHz内,磁粉芯具有较好的频率稳定性。在25～100℃内,随着温度的升高,μe逐渐下降,其中25～40℃内,μe变化敏感,温度系数αμ为-1.95×10-3℃-1,而高于40℃时,其温度系数αμ仅为-2.48×10-4℃-1。     

以非离子型水性聚氨酯为囊壁材料乳液聚合制备相变纳米胶囊

在无外加乳化剂的情况下,用非离子型聚氨酯作为乳化剂和囊壁材料,以石蜡为芯材,制备了一系列稳定分散在水中的相变纳米胶囊(PCMN),经动态光散射(DLS),透射电镜(TEM),差示扫描量热(DSC)和热重分析(TGA)等手段对PCMN的粒径,形态,热稳定性和相变性能进行研究。通过对乳液聚合转化率的跟踪测试,考察了引发体系、引发剂用量和反应温度对乳液聚合的影响。制备的相变纳米胶囊在透射电镜下有核壳型和聚氨酯粒子型两种粒子。调节囊壁材料和芯材的比例可以得到具有不同相变焓的纳米胶囊,其相变焓可以达到89J/g。热失重分析表明相变纳米胶囊的热稳定性随着交联单体含量的增加而增加。     

聚乙烯醇/海藻酸钠/甲基丙烯酸缩水甘油酯复合纳米纤维制备与性能

采用静电纺丝技术制备聚乙烯醇/海藻酸钠/甲基丙烯酸缩水甘油酯复合纳米纤维膜,经过加热处理获得交联的海藻酸钠复合纳米纤维膜。研究复合纳米纤维制备、交联工艺对材料表面形貌、耐水性、热性能等影响。结果表明:纳米纤维直径在200～500nm之间,经过120℃热处理后纤维形态不发生改变。热处理后材料发生交联反应,热稳定性提高。改性后的复合纳米纤维材料耐水性随着甲基丙烯酸缩水甘油酯含量增大而提高,吸液倍率在9.6～14.6之间且随着甲基丙烯酸缩水甘油酯含量增大而先增后减,获得的复合纳米纤维膜具有良好的吸液性,有望作为新型医用创伤敷料使用。     

胶原/TiO2纳米复合红外低发射率材料的制备与表征

用胶原与改性纳米TiO2复合得到新型有机-无机复合材料，研究复合物中胶原的含量随复合温度、pH的变化规律，并考察TiO2晶型、Al2O3包膜改性及戊二醛交联改性对复合材料红外发射率的影响．结果表明;胶原与改性纳米TiO2复合的最佳温度为50℃、pH为8．0，胶原含量最高可达9．45wt％，两者间较强的复合协同作用明显降低了材料的红外发射率，并提高了材料的热稳定性；复合材料经戊二醛交联改性后可形成紧密有序的网络层状结构，热稳定性进一步提高，红外发射率最低可降至0．502．     

Yb3+/Er3+共掺杂BaY2F8纳米颗粒的水热合成与上转换发光

采用水热方法合成了Yb3+/Er3+共掺杂BaY2F8纳米颗粒,并对其进行了不同温度的热处理,热处理温度为200℃-800℃。研究了热处理温度对纳米粒子的晶相、粒径和上转换发光强度的影响。结果发现随着热处理温度的升高,纳米粒子的粒径和上转换发光强度明显增加。讨论了BaY2F8:Yb3+,Er3+纳米粒子的上转换发光机理。     

不同热处理温度下纳米羟基磷灰石/聚酰胺66多孔支架制备及力学性能研究

热处理温度是热致相分离法制备多孔支架材料的关键因素。在不同热处理温度下(60℃、75℃和90℃)制备了纳米羟基磷灰石/聚酰胺66(n-HA/PA66)复合多孔支架材料。对比研究了不同热处理温度下制备的多孔支架孔隙结构、孔隙率及力学性能。结果表明:处理温度对多孔支架的孔隙结构,孔隙率,力学性能有显著的影响,随着温度的升高,多孔支架的孔隙率、平均孔径升高,贯通性改善,但弹性模量和屈服极限降低。多孔支架的热处理温度为75℃时,其孔径、孔隙率和力学性能与天然松质骨相当,是较为理想的骨组织工程支架材料。     

悬浮聚合法制备相变材料微/纳胶囊

采用悬浮聚合法合成了以正十八烷为囊芯、苯乙烯-新戊二醇二丙烯酸酯共聚物为囊壁的相变材料微/纳胶囊,并通过扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)、差示扫描量热仪(DSC)、热重分析仪(TGA)等对其形貌、结构、热性能、热稳定性等进行了分析。结果表明,相变材料微/纳胶囊形貌完整、分散性好;相变材料微胶囊热稳定良好,其失重起始温度较囊芯材料提高了近40℃;相变材料微/纳胶囊在降温过程中有不同程度的过冷结晶现象。     

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.     

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...     

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 ...