碳纤维增强聚醚醚酮复合材料的制备与性能

通过高温模压方法,制备了碳纤维/聚醚醚酮(CF/PEEK)复合材料。采用差示扫描量热、热失重、弯曲测试、拉伸测试、扫描电子显微镜等分析方法对制品热学性能和力学性能进行了分析。分析结果表明,制备CF/PEEK复合材料的最佳工艺参数为:成型温度380℃~390℃,停留时间30 min,保温保压30 min、2 MPa~3 MPa,后期保压压力4 MPa~5MPa,保压时间3 h。复合材料制品弯曲强度达到1783 MPa,分解温度达578℃,表明其具有优良的力学性能和热稳定性。     

防火玄武岩纤维中空织物复合材料的制备及性能

采用手工铺料法制备了水性无机硅树脂/玄武岩纤维中空织物复合材料，在其表面涂覆防火涂料，三次固化制备出防火玄武岩纤维中空织物复合材料。采用电子万能试验机、氧-乙炔烧蚀试验机、热重分析仪表征了复合材料的力学性能、阻燃性能和耐高温性能。详细考察了防火涂料用量和固化工艺对复合材料力学性能和阻燃性能的影响，研究了材料的结构和耐高温性能。结果表明：防火涂料用量为14.5%,第一次固化温度80℃/固化时间5h,第二次固化温度120℃/固化时间4h,第三次固化温度120℃/固化时间1.5h,在上述固化工艺条件下复合材料的力学性能和耐烧蚀性能较好；其拉伸强度、弯曲强度、质量烧蚀率分别为34.97MPa、60.36MPa、61mg/s;复合材料热失重15%的温度为683.9℃;防火涂料的涂覆有助于提升复合材料的耐高温性能。     

PLA/木质纤维复合材料的制备及性能

目的研究PLA/木质纤维复合材料的制备工艺过程,分析PLA纤维含量对复合材料力学性能的影响,确定最优配比,以获得一种可应用于包装中的新型环保复合材料。方法将不同质量配比的PLA纤维及木质纤维按照造纸的工艺进行抄造,获得湿纸胚后再进行热压处理,获得需要的复合材料。对PLA纤维在复合材料中的分散性以及复合材料的力学性能进行表征与测试。结果分散性试验表明,PLA纤维能够与木质纤维均匀混合;当PLA纤维的质量分数为10%时,复合材料的性能较好。力学测试表明,复合材料的拉伸强度最大可达到42.79 MPa,耐折次数可达到1015次。结论 PLA/木质纤维复合材料可采用造纸的方法进行制备,且力学性能较好,能在包装领域内有较为广泛的应用,同时也为可降解纤维的研究应用提供了一种新思路。     

棉秆皮预处理对棉秆皮纤维/PP复合材料力学性能的影响研究

用碱处理、蒸汽闪爆、蒸汽闪爆结合碱处理这3种预处理方法制备的棉秆皮纤维作为增强体,通过热压成型制备了棉秆皮纤维/聚丙烯复合材料。首先优化了制备该复合材料的棉秆皮纤维长度、热压温度、压力以及时间等工艺参数,并以此优化工艺为基础,研究了3种预处理方法制备的棉秆皮纤维对复合材料拉伸、弯曲、冲击性能以及微观形貌的影响。结果表明:在棉秆皮纤维长度为8cm、热压温度170℃、热压压力3MPa、热压时间4min条件下制备的复合材料性能较优;在3种预处理方法中,采用蒸汽闪爆与碱预处理棉秆皮纤维制备的复合材料性能最优,复合材料拉伸强度为36.290MPa、拉伸模量为4557.40MPa、弯曲强度为63.31MPa、弯曲模量为4780.00MPa、冲击强度为485.0J/m。     

纳米二氧化钛含量对秸秆/聚乳酸复合材料性能的影响

目的 为改善纤维增强聚乳酸(PLA)复合材料增强相与基体相之间差的界面结合。方法 以秸秆粉(SP)为填料,纳米二氧化钛(TiO2)作为界面改性剂,构建SP/PLA复合材料相容界面,通过力学性能测试、吸水率测试、扫描电子显微镜(SEM)、X射线衍射(XRD)和热重分析法(TGA)等表征手段,探究不同含量纳米二氧化钛对SP/PLA复合材料力学性能和界面相容性的影响。结果 研究发现,纳米二氧化钛的质量分数为2.0%时,复合材料的拉伸强度和弯曲强度分别达到42.78 MPa和91.25 MPa,其耐水性能、结晶度、耐热性能也达到最好。结论 纳米二氧化钛可有效提高秸秆/聚乳酸复合材料的性能。     

陶瓷基复合相变储热材料的制备和成型工艺

采用混合烧结法工艺,将三元氯盐体系Na Cl-KCl-MgCl_2相变材料与氧化镁陶瓷基体进行复配并制备定型材料,考察成型压力、烧成温度和盐含量对材料成型的影响,对最佳成型条件的材料进行储热性能表征。结果表明:当盐的质量分数为50%、烧成温度为450℃、成型压力为8 MPa时复合材料成型效果较好,相变材料无渗出、体积变化较小且复合材料致密度较高;DSC测试结果表明,所制备的复合相变储热材料的相变温度为399.8℃,相变潜热为129.6 J/g。     

纤维热氧-接枝处理与基体改性对CF/VE复合材料力学性能的影响

针对碳纤维增强乙烯基酯树脂(CF/VE)复合材料界面性能薄弱的问题,通过热氧-接枝的方法对碳纤维表面进行改性,通过添加偶联剂改性树脂,并采用真空辅助成型工艺制备了CF/VE复合材料。通过纤维扫描电镜(SEM)表征和CF/VE复合材料力学性能测试、动态力学测试、界面粘结参数计算以及界面的微观表征验证改性方法的效果。SEM测试表明改性后纤维比表面积和粗糙度提高;TGA测试表明碳纤维氧化温度大于210℃,且氧化温度在600℃时,CF/VE复合材料综合性能最佳;CF/VE复合材料界面性能随隅联剂质量浓度的增大先提高后降低,且在其质量浓度为1%时,层间剪切强度最大,相对于未改性CF/VE复合材料的提高了74.3%;动态力学性能测试(DMA)表明改性CF/VE复合材料的玻璃化转变温度Tg较未改性的提高了约10℃;界面粘结参数A和α的定量计算表明改性CF/VE复合材料界面性能得到较大改善。     

亚麻纤维增强聚乳酸可降解复合材料的制备与性能

将制浆造纸用亚麻短纤维与聚乳酸(PLA)熔融共混,用注塑方法成型亚麻纤维/聚乳酸复合材料试样。通过差示扫描量热实验(DSC)、动态力学性能测试(DMA)、热重分析(TGA)和力学性能测试等方法,研究了聚乳酸和亚麻纤维在不同质量配比下,复合材料热性能、动态力学性能和力学性能的变化规律。随着亚麻纤维的加入,复合材料的结晶度增大,热稳定性增强,储能模量得到提高,力学性能也有了明显变化:纤维含量为20%时,拉伸强度为45.88 MPa,比纯PLA的增加了21%;同时,弯曲模量的增幅达到30%。     

表面改性纳米SiO2增强木质纤维/聚氯乙烯复合材料性能

SiO₂粒子经偶联剂γ-氨丙基三乙氧基硅烷（KH550）表面改性后,与木质纤维、聚氯乙烯（PVC）及其它助剂通过熔融混炼制备改性SiO₂-木质纤维/PVC复合材料,用FTIR、SEM和同步热分析仪（STA）对SiO₂粒子和SiO₂-木质纤维/PVC复合材料的结构与性能进行测试与表征。FTIR分析表明,SiO₂粒子表面接枝了KH550的特征官能团,KH550成功地接枝到SiO₂粒子表面;SEM分析表明,改性纳米SiO₂粒子能在木质纤维/PVC复合材料中均匀分散,其粒径在100 nm左右;添加改性的SiO₂粒子后,木质纤维和PVC结合更加紧密,孔洞间隙减少。纳米SiO₂质量分别占木质纤维质量的10%、8%和10%时,SiO₂-木质纤维/PVC复合材料的弹性模量、拉伸强度、冲击强度分别达到最优值4.66 GPa、31.12 MPa和4.11 kJ/m²,与未添加SiO₂的复合材料相比分别提高了50.29%、28.91%和16.65%。     

连续碳纤维增强杂萘联苯共聚芳醚砜复合材料的制备及力学性能

以含二氮杂萘酮联苯共聚芳醚砜(PPBES)为树脂基体,连续碳纤维T700-12K为增强材料,采用溶液浸渍和模压成型的方法制备出单向复合材料。通过对复合材料样条进行三点弯曲以及短梁剪切力学性能测试,考察了复合材料纤维体积分数、模压成型温度、成型压力及保压时间对复合材料弯曲强度、模量及层间剪切强度的影响。分别测试了复合材料在干态及湿态下的高温力学性能的变化规律。结果表明,当复合材料纤维体积分数为63%,模压成型温度为350℃,成型压力为4 MPa,保压时间为20 min时,复合材料的力学性能最佳。动态热机械性能测试结果表明复合材料在230℃之前,储能模量保持稳定。而水煮48 h后复合材料的吸水率为0.3%。     

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 ...