天然木棉纤维／磁性纳米粒子原位复合反应特性研究

以天然木棉纤维为基材,用原位复合法制备磁性纳米复合纤维.研究预处理及熟化方式对复合效果的影响,用SEM,AFM,X射线衍射,超导量子磁强计(SQUID)对复合纤维的结构与磁性进行表征.研究表明:预处理后木棉纤维是有效的模板材料,磁性粒子不仅在纤维表面还可在纤维空腔内复合,粒径为30～100nm,晶体类型为γ-Fe2O3;静磁场熟化复合的铁含量最高为7.54%.(质量分数).SQUID显示制备的木棉/磁性纳米复合纤维具有超顺磁性.     

微晶纤维素/CdS纳米复合材料的原位复合反应

以微晶纤维素(MCC)为模板,采用原位复合法制备MCC/CdS纳米复合材料。研究了超声波预处理以及镉离子、硫离子物质的量比对复合效果的影响,用扫描电镜(SEM),原子力显微镜(AFM),X射线衍射,荧光光谱(PL)以及激光共聚焦显微镜(CLSM)对复合材料的结构及性能进行表征。研究表明,超声波预处理后的纤维素对镉离子吸附能力更强,粒径为30 nm~100nm的CdS粒子均匀分布于纤维素表面,所得CdS为立方型晶体,复合材料体现出一定强度的光致发光性,较佳Cd2+∶S2-(物质的量比)为3∶1。     

纤维素/CdS纳米复合材料的声化学制备及其光电性能

以无水氯化镉和硫化钠为原料,微晶纤维素MCC为模板,采用声化学法成功制备MCC/CdS纳米复合材料.用原子力显微镜(AFM),X射线衍射(XRD),荧光光谱(PL)以及光电化学实验对复合材料的结构及性能进行表征.研究表明,粒径为30-70nm的CdS粒子均匀分布于微晶纤维素表面,所得CdS粒子为立方型晶体.PL光谱分析...     

纳米纤维素/CdS纳米复合光电材料的制备和性能

以NaClO2为主要氧化剂,使用氧化漂白桉木浆制备C-6位羧基含量为0.8mmol/g的TEMPO氧化纤维素,然后将其剪切为纳米纤维素(NCC)。再以NCC为基材,以无水氯化镉及硫化钠为前驱体,用声化学法制备了NCC/CdS纳米复合光电材料。用X射线衍射(XRD)、场发射扫描电镜(SEM)、傅里叶红外光谱仪(FT-IR)以及光电化学实验对复合材料的结构及性能进行表征。结果表明,大量CdS纳米粒子复合在NCC基材上形成NCC/CdS纳米复合材料,CdS晶粒为立方型晶体,大小为7.3nm。用NCC/CdS纳米复合材料形成的薄膜器件在可见光区域的透光率高达60%。这种复合材料可产生1.35μA的光电流,其光电转换效率为微晶纤维素/CdS复合材料的6倍。     

原位复合制备纤维素基CdS纳米复合材料及其表征

以微晶纤维素(MCC)为模板,氯化镉、硫化钠等为原料,在水的悬浮液中,用原位复合法制备了MCC/CdS纳米复合材料。对复合反应条件进行了初步研究,探讨了Cd2+浓度、Cd2+吸附时间及超声功率对复合反应的影响。研究表明,适当提高Cd2+吸附时间及超声功率有利于提高复合材料中硫化镉颗粒的复合量,Cd2+浓度对复合量的影响是显著的。应用X射线衍射(XRD),扫描电镜(SEM),红外光谱(FT-IR),光致荧光光谱(PL)对MCC/CdS复合材料进行了表征。结果表明,复合在微晶纤维素上的CdS颗粒大小均一,且均匀分布在微晶纤维素模板表面;制备的复合材料具有一定的荧光特性。     

PVP为偶联剂制备核壳型PS/CdS纳米复合粒子及表征

以聚乙烯吡咯烷酮(PVP)为偶联剂,利用超声化学法制备了PS/CdS核壳型复合纳米粒子。为了深入理解核壳型纳米粒子的界面行为和形成机制,详细考察了PVP加入与否及用量、前体加入顺序、Cd2+与S2-摩尔比和反应时间等实验参数对核壳复合材料结构的影响。结果表明,适量PVP可改善CdS纳米粒子与PS聚合物基体间的亲和性,增强壳与核之间的相互作用,成功地将PS与CdS复合成单分散的、壳层完整且厚度可控的三维核壳型PS/CdS纳米复合粒子;且复合物比纯CdS粒子具有更高的可见光响应活性。     

纳米SiO2/PEA复合粒子的制备和表征

在经预处理的SiO2表面上通过乳液聚合反应接枝丙烯酸乙酯,用FT-IR和XPS对制备的纳米SiO2/PEA复合粒子进行了表征,研究了由复合粒子填充的PP/POE/SiO2复合材料的力学性能、结晶性能和结构形态。结果表明:通过乳液聚合反应成功地将EA接枝到纳米SiO2的表面上;由复合粒子填充的PP/POE/SiO2复合材料,纳米SiO2在基体中的分散尺寸约为100 nm,分布较均匀,复合材料的冲击强度和断裂伸长率均得到提高,在SiO2含量4%(质量分数)时,PPβ晶峰的强度最强。     

镍/木棉纤维衍生碳复合材料的制备及吸波性能研究

近年来,生物质碳因成本低廉、易制备、理化性能优异和具有多孔结构被广泛应用于吸波领域。然而,其吸波性能仍然受较高电导率引发的不良阻抗限制。在此,使用镍(Ni)改性木棉纤维,并使用不同的碳化温度获得镍/木棉纤维衍生碳(Ni/C)复合材料。扫描电镜结果表明,随着碳化温度的升高,Ni颗粒的尺寸增加,且木棉纤维表面出现更多的缺陷结构。XRD和XPS结果证明了Ni和木棉纤维衍生碳的成功复合。Raman结果表明碳化温度的升高导致碳组分石墨化程度增加,提高了复合材料的传导损耗能力。最后,我们将复合材料与石蜡以5∶95的超低填充比例混合,Ni/C-800展现出-52.6 dB的反射损耗值和8.32 GHz的有效吸收带宽。复合材料优异的吸波性能取决于衰减能力和阻抗匹配的协同、介电损耗和磁损耗的共同作用以及大比表面积和中空多孔结构造成的多重散射能力的增强。     

利用水溶性聚合物PVP作稳定剂合成CdS、CdSe半导体纳米晶体

以水溶性聚合物聚乙烯基吡咯烷酮(PVP)作分散剂,在水相溶液中制备CdS/PVP纳米粒子.通过控制水溶液体系的pH值或者分散剂含量,实现了纳米粒子从球形到棒状的转变;同时探讨了Cd/S比值变化对纳米粒子结构的影响.利用原子力显微镜(AFM)表征CdS/PVP纳米体系的形貌,并进一步利用透射电镜(TEM)、红外光谱(FT-IR)和粉末X-射线衍射(XRD)等对其结构进行了分析和研究.     

银/聚苯胺纳米复合材料的制备及形成机理

采用反胶束原位复合法制备了银/聚苯胺(Ag/PANI)纳米复合材料,并且探讨了Ag/PANI纳米复合材料的形成机理。通过红外光谱、紫外吸收光谱、X射线衍射、扫描电镜和透射电镜对复合物进行了表征。研究结果表明,Ag/PANI复合材料中Ag为纳米粒子,粒径为50 nm,苯胺自吸附在银纳米粒子表面聚合,形成PANI包覆Ag纳米粒子壳-核结构。Ag纳米粒子在PANI中均匀分散,Ag/PANI复合粒子大部分呈现类球形状的表面形貌,复合粒子粒径较PANI有了明显减小。并提出了Ag/PANI复合材料的形成机制。     

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.     

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...     

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.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

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.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.