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1.
Samples in Si–Al-R-O-N (R = Y, Gd, Yb) systems were prepared by solid-state reactions using R2O3, Al2O3, SiO2 and Si3N4 powders as starting materials. X-ray diffraction was done to investigate RAM-J(R) solid solutions [RAM = R4Al2O9, J(R) = R4Si2N2O7] formation and their equilibrium with RSO (R4Si2O10). Phase relations between RAM, J(R) and RSO at 1700 °C were summarized in a phase diagram. It was determined that a limited solid solution of RAM and RSO could be formed along RAM-RSO tie-line, while RAM and J(R) form a continuous solid solution along RAM-J(R) tie-line. In RAM-J(R)-RSO ternary systems, the RAM-J(R) tie-lines were extended towards the RSO corner to form a continuous solid solution area of JRAMss (R = Y, Gd, Yb). The established phase relations in the Si–Al-R-O-N (R = Y, Gd, Yb) systems may facilitate compositional selections for developing JRAMss as monolithic ceramics or for SiC/Si3N4 based composites using the solid-solutions as a second refractory phase.  相似文献   
2.
30CrMnSiA钢沉头螺栓断裂失效分析   总被引:1,自引:0,他引:1       下载免费PDF全文
某飞机用30CrMnSiA钢沉头螺栓在拆卸过程中发生断裂,同炉批未曾使用的螺栓经磁粉检测也存在裂纹。为查找失效分析原因,通过对断裂件和同炉批开裂的螺栓外观检查、断口宏微观分析、能谱分析、硬度检测、金相分析等方法对断裂和开裂的螺栓进行了分析。结果表明:断裂螺栓和开裂螺栓断裂类型为氢脆,螺栓氢脆断裂主要与抗拉强度和热处理工艺有关,通过改善热处理工艺参数,适当降低螺栓的强度,增加酸洗后的除氢时间降低氢含量,从而避免氢脆发生的可能性。  相似文献   
3.
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs.  相似文献   
4.
Traditional self-powered ultraviolet photodetectors, which are usually designed based on p-n junction interfacial effects, exhibit low responsivity and specific detectivity because the photogenerated electrons and holes cannot be separated effectively. Unlike wide band-gap semiconductor materials, ferroelectrics have large remnant polarization and thus high depolarization electric field throughout the whole bulk region, which can cause effective separation of photogenerated electrons and holes. Based on this, in this study, we prepare Pb0.93La0.07(Zr1-xTix)0.9825O3 (PLZT) ferroelectric thin films with large remnant polarization and self-powered ultraviolet photodetectors with Au/PLZT/FTO structure. The results indicate that the photoelectric response performances of the detectors improve as the remnant polarization of the PLZT thin film and positive poling voltage increase. By adjusting the Ti content, due to large remnant polarization of 47.4 μC/cm2 in the PLZT thin films with 80 mol% Ti, the corresponding photodetector exhibits the best self-powered ultraviolet photoelectric response with the high photo/dark current ratio of 2600, responsivity of 2.05 mA/W, specific detectivity of 5.45 × 1010 Jones, and fast response speed (rise time of 18 ms). These values are superior to those of recently reported self-powered ultraviolet photodetectors.  相似文献   
5.
采用硬质合金涂层刀具高速铣削AF1410高强度钢,基于单因素试验法研究了切削参数对切屑形态和毛边形态的影响,分析了切屑锯齿间距、毛边几何参数随切削速度和进给量的变化规律.结果 表明:切削速度较低时,切屑自由表面形成上窄下宽、上深下浅的剪切滑移变形带,带内剪切变形较小,切削速度增加,绝热剪切变形增大,切屑自由表面形成平行的锯齿形态,锯齿间距随切削速度的提高而增大;在高速切削条件下,锯齿间距随进给量的提高而略有增大,切屑由顶部沿锯齿节间沟槽发生纵向撕裂形成毛边,毛边宽度和高度随切削速度先增大后减小,随进给量减小.  相似文献   
6.
针对DZLY180型硬齿面点线啮合齿轮减速器,利用SolidWorks建立其高速级齿轮副三维模型,采用Ansys Workbench对模型进行动态接触应力仿真分析,然后对其进行修形并重新建模、仿真,结果显示修形后点线啮合齿轮接触应力减小,啮入冲击得到明显改善。  相似文献   
7.
In this study, the thickness and wax content of wax deposits were found to be thinner and lower in the polyethylene (PE) pipe than in the stainless steel (SS) pipe using a flow loop apparatus. The diffusivity of wax, radial thermal gradient, and wax precipitation rate in the PE and SS pipes were calculated and compared. It was found the diffusivity of wax in the PE pipe was higher and tended to enhance the wax deposition in the PE pipe, while the radial thermal gradient and wax precipitation rate were lower in the PE pipe and had the opposite effects. These factors are shown to be comparable with each other and the effect of the thermal gradient dominates the mass flux of wax from bulk to the oil-deposit interface and into the deposits finally, thus causing differences in thickness and wax content of deposits between the PE and SS pipes.  相似文献   
8.
GaFeO3-type iron oxide is a promising room-temperature multiferroic material due to its large magnetization and polarization. To expand the scope of its application, it is crucial to control the magnetic properties. Based on introducing the ferromagnetic (FM) Fe3O4 in the antiferromagnetic (AFM) GaFeO3 to build the FM-AFM interface by changing the Ga/Fe ratio, Ga0.69Fe1.31O3 (GFO) was successfully grown by the floating zone method. The resulting sample was characterized by X-ray diffraction (XRD), and its magnetic properties were measured using a superconducting quantum interference device (SQUID). The temperature-dependent AC susceptibility measurement shows that the spin glass-like behavior of GFO at temperatures close to 50 K is a manifestation of the geometrical frustration arising from cation site disorder. In addition, the magnetic property measurement shows that the magnetic transition temperature Tc is at 650 K, which is introduced by Fe3O4 and suppresses the ferromagnetic transition around 320 K of GFO. Interestingly, the observed exchange bias effect, which does not exist in the bulk GaFeO3-type family, is attributed to the formation of an FM/AFM interface due to the existence of FM Fe3O4 in the GFO. This study provides a new perspective on the properties of the GaFeO3-type family for potential applications in spintronic devices.  相似文献   
9.
黄睿  邢艳 《计算机时代》2021,(1):83-85,88
计算机图形学是计算机和多媒体技术等相关专业的一门重要的专业基础课程.由于其涵盖数学、物理、程序设计语言和算法等多方面的知识,导致课程的学习难度较大.同时,由于没有后续课程使用计算机图形学的知识,致使学生无法将图形学理论与实际应用较好的结合,从而影响计算机图形学的教学效果.为了使学生理解图形学相关算法及其应用场景,与游戏开发应用结合,探讨计算机图形学的课程建设.  相似文献   
10.
Succinic acid is an important synthetic monomer but it is difficult to use it as a precursor for synthesizing high molecular weight polyamide, due to its tendency to perform intra-cyclization reaction at high temperature. In order to solve this problem, in this paper, the direct solid-state polymerization (DSSP) method with the initial reactant, nylon salt which was composed of 1, 5-diaminopentane, succinic acid, and terephthalic acid, was applied to synthesize the bio-based copolyamide PA 5T/54. In comparison with the conventional melting polymerization method, the DSSP method can prevent the cyclization reaction of succinic acid effectively due to the lower reacting temperature as well as the restriction effect of the nylon salt. As a result, the product fabricated by DSSP method has higher molecular weight and much lighter color from red to white. Therefore, the DSSP method is advantageous for the synthesis of the polymers or copolymers composed of the succinic acid as the monomer. Furthermore, the polymerization mechanism proposed in this work can serve as a guidance for the design of the molecular structure and control of the polymerization process.  相似文献   
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