炭/炭复合材料硼硅酸盐玻璃涂层制备及性能研究

系统研究了SiO2与B2O3之比、高熔点添加剂种类(包括MoSi2,Y2O3,SiC)及含量对硼硅酸盐(SAB)玻璃涂层高温稳定性、高温流动性的影响规律和最佳工艺参数组合,采用涂刷法在带有疏松结构的SiC内涂层炭/炭(C/C)复合材料表面制备了高温稳定性和流动性良好的硼硅酸盐玻璃外涂层,并测试了带有不同SiC/硼硅酸盐玻璃复合涂层C/C复合材料试样在1500℃静态空气中的抗氧化性能.结果表明:采用SiO2,B2O3摩尔比为4∶1时所得硼硅酸盐玻璃具有相对较高的高温流动性和高温稳定性;与添加Y2O3,SiC相比,在上述硼硅酸盐玻璃中添加MoSi2可以较大幅度提高所得玻璃涂层对C/C基体的氧化保护性能,并且当硼硅酸盐玻璃外涂层中硼硅酸盐与MoSi2的质量比为4∶1时,所得硼硅酸盐玻璃外涂层对SiC-C/C表现出较好的氧化保护能力,氧化17h后涂层C/C试样的失重仅为4.31%.     

炭/炭复合材料高温抗氧化MoSi2/SiC复合涂层及其抗氧化特性

采用两段式包埋法和封闭处理的复合新工艺制得抗氧化性优良的MoSi₂/SiC复合梯度C/C复合材料高温抗氧化涂层。涂层由内至外结构为:SiC过渡层→SiC致密层→MoSi₂/SiC双相层→以MoSi₂为主的外层。对未封闭处理的涂层,制备过程中高温保温时间长的氧化失重少,1200℃、1300℃空气中氧化失重比1400℃、1500℃氧化失重大。用正硅酸四乙酯对涂层表面进行封闭处理,凝胶形成的SiO₂可充填涂层表面裂纹并覆盖在涂层表面。在1500℃空气中氧化一定时间后,未封闭处理的涂层试样表现为氧化失重;封闭处理后的试样为氧化增重,氧化52h仍然只有1.28%的增重,封闭处理使涂层的抗氧化性能明显改善。      

SiC/MoSi_2复合材料1300℃氧化行为研究

采用扫描电镜和X射线衍射研究了不同SiC体积分数(30%～50%)的SiC/MoSi2复合材料的高温(1300℃)氧化性能,建立了SiC/MoSi2复合材料的高温氧化动力学模型,对SiC/MoSi2复合材料的高温氧化行为进行了动力学分析,研究了其高温氧化机理。结果表明,SiC/MoSi2复合材料在高温时具有优异的抗氧化性能,SiC/MoSi2复合材料的高温抗氧化能力好于纯MoSi2的;复合材料的高温抗氧化性随SiC体积分数的增加而降低。     

炭/炭复合材料表面C/SiC/Si-Mo-Cr多层复合防氧化涂层研究(英文)

为提高炭/炭(C/C)复合材料的高温抗氧化性能,采用料浆涂刷法首先在C/C复合材料表面制备了预炭层,然后以Si粉及石墨粉(Si粉与石墨粉的质量配比为:60～80:10～25)为原材料采用包埋法经高温热处理获得C/SiC内涂层,最后在涂有C/SiC内涂层的C/C复合材料表面采用包埋法制备Si-Mo-Cr外涂层。借助扫描电镜、X射线衍射、电子能谱等分析测试手段对涂层试样的微观结构进行了分析,研究了涂层C/C复合材料在1 873 K和1 973 K下的氧化行为。结果表明:由于涂层氧化过程中表面生成了SiO2和Cr2O3复合玻璃层,其在1 873 K温度下表现出优异的防氧化性能,可以有效保护C/C复合材料达135 h。当氧化温度提高至1 973 K并氧化30 h后,该复合涂层氧化过程玻璃层完整性被破坏,涂层失效。     

多涂层炭/炭复合材料抗1500℃燃气冲刷性能的研究

为提高炭/炭(C/C)复合材料的抗高温燃气冲刷性能,分别采用包埋法、化学气相沉积法和料浆法在其表面制备了三层涂层.借助扫描电镜、电子能谱等测试手段对涂层试样的微观结构进行了分析,同时研究了涂层C/C复合材料在高温风洞环境中的抗冲刷性能,并分析了涂层在燃气冲刷环境下的失效原因.结果表明:三层涂层由MoSi2-SiC-Si多相内涂层、SiC中间层和玻璃外涂层构成,其厚度分别为80μm, 20μm和80μm.该复合涂层可在1500℃风洞环境下对C/C复合材料有效保护53h.涂层在高温风洞中防氧化失效是由于涂层在热冲击以及承受气流冲击的恶劣环境下开裂引起的.     

等离子喷涂法制备炭/炭复合材料硅酸钇涂层研究

采用等离子喷涂(Atmospheric plasma spraying,APS)法在炭/炭复合材料碳化硅(SiC)内涂层表面制备了硅酸钇涂层。分别采用XRD和SEM分析了所得涂层的微观结构,并测试了带有SiC/硅酸钇复合涂层的炭/炭复合材料试样在1500℃静态空气中的抗氧化性能。结果表明:通过调节喷涂粉料中的SiO2和Y2O3的摩尔比,可制得Y2SiO5、Y2Si2O7、Y2Si2O7/Y2SiO5和Y4Si3O12/Y2Si2O7/Y2SiO5四种不同结构的硅酸钇涂层;1500℃氧化73h后,SiC/Y4Si3O12/Y2Si2O7/Y2SiO5涂层试样的氧化失重速率相对较低,仅为1.01×10-4g.cm-.2h-1。     

高温氧化及热震对SiC/ZrB2-SiC/SiC涂层炭/炭复合材料力学行为的影响

为提高炭/炭(C/C)复合材料的高温抗氧化性能,同时分析涂层制备及高温氧化对涂层材料力学行为的影响,在C/C复合材料表面采用反应熔渗、料浆涂刷结合化学气相沉积工艺制备了SiC/ZrB2-SiC/SiC三层高温抗氧化涂层。利用SEM和XRD分析复合涂层的微观结构和相组成,考察涂层复合材料1500℃高温抗氧化和1500℃-室温的抗热震性能,研究高温氧化及热震对涂层C/C复合材料力学行为的影响。结果表明,复合涂层试样1500℃静态空气环境下具有优异的抗氧化及抗热震性能:1500℃氧化20 h后试样保持增重,1500℃至室温热震50次后增重为0.69%。因涂层制备过程中粉料的渗入反应,复合材料弯曲强度增长了7.08%。在经历1500℃氧化20 h和1500℃至室温50次热震后,涂层复合材料弯曲强度有所下降,且因材料界面结合力的减弱使得纤维拔出特征明显,材料塑性断裂特征增强。     

炭/炭复合材料用SiC-Glass涂层的高温氧化机理

采用包埋法和预涂-烧结法相结合的组合工艺在炭/炭(C/C)复合材料表面制得SiC-Glass复合涂层, 并借助X射线衍射仪(XRD)和扫描电镜(SEM)对该复合涂层进行了表征, 研究了涂层C/C试样在不同温度下的氧化动力学规律。结果表明: 复合涂层具有双层结构, 包埋SiC内层由β-SiC相和少量游离硅相组成, 外层由MoSi₂颗粒掺杂的硼硅酸盐玻璃构成; 内外层之间结合紧密; 在1300~1600℃的空气气氛中, SiC-Glass涂层表现出良好的抗氧化性能, 其氧化激活能为118.1kJ/mol, 氧化主要受控于氧在Glass层中的体扩散速率; 在1600℃空气气氛中氧化65h后, SiC-Glass涂层C/C试样的氧化失重率仅为1.02%。      

反应熔渗SiC/MoSi_2和SiC/Mo(Si,Al)_2复相材料抗氧化行为

研究了低成本制备技术反应熔渗方法制备的SiC/MoSi2和SiC/Mo(Si,Al)2复合材料高温氧化行为。表面氧化物的形态和氧化增重的研究结果表明,所制备复合材料高温氧化3 h后即发生钝化现象,继续在500℃再进行低温氧化试验,发现限制该材料使用的"Pest"现象消失。其中渗铝复合材料SiC/Mo(Si,Al)2高温增重较渗硅SiC/MoSi2严重。当后者中形成的SiC增强相全部为原位反应生成时,由于界面结合力提高,抗氧化能力更强。     

炭/炭复合材料SiC/Mo(Si_x、Al_(1-x))_2抗氧化涂层(英文)

为了提高炭/炭(C/C)复合材料的高温抗氧化性能,应用多相反应技术在C/C复合材料表面制备SiC/Mo(Six、Al1-x)2复合涂层。利用扫描电镜、电子能谱、X射线衍射仪等测试手段对涂层材料的微观结构和物相组成进行分析,同时研究涂层C/C复合材料在超音速气流中的抗氧化性能。结果表明,C/C复合材料表面形成的抗氧化涂层显示出明显的双层结构,从外向内分别为Mo(Six、Al1-x)2与SiC的复合层和纯SiC层,同时有少量的Mo4.8Si3C0.6存在于涂层中。在温度为1800K、气体速率1500m/s的超音速气流中氧化冲刷96 s,以及在2550 K和室温下热循环24次的测试条件下,制备的SiC/Mo(Six、Al1-x)2涂层材料均未发生破坏现象。涂层材料优良的抗氧化性能和抗热震性能主要归因于基体C/C复合材料的高强度以及在氧化过程中材料表面形成的连续稳定的SiO2和Al2O3玻璃相。     

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.……     

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.     

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.     

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 ...