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991.
研究了Na2O-CaO-Al2O3-B2O3-SiO2-TiO2体系分相过程中两相组成的变化。采用扫描电镜测试、能谱分析和X射线衍射等手段对在不同温度下热处理的试样进行测试。实验结果表明,试样发生相分离后,分离成富碱硼相和富硅相,两相的化学组成随分相温度呈现一定的变化。当热处理温度从700℃升高至850℃时,富碱硼相量增加,玻璃分相程度增大。分相温度较低时,富碱硼相中的网调整氧化物只有氧化钙,而网调整氧化物氧化钠集结在富硅相中。随分相温度的升高,氧化钙仍保持在富碱硼相中,而氧化钠则由在富硅相中集聚逐步转移至在富碱硼相中。在分相过程中二氧化钛在分相界面处集聚并析出。 相似文献
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994.
Lu Zhang Jixing Liu Deqi Huang Wenfeng Zhang Linjie Lu Mingqing Hua Hui Liu Huifang Cheng Huaming Li Wenshuai Zhu 《Frontiers of Chemical Science and Engineering》2023,17(3):276
Particle size governs the electronic and geometric structure of metal nanoparticles (NPs), shaping their catalytic performances in heterogeneous catalysis. However, precisely controlling the size of active metal NPs and thereafter their catalytic activities remain an affordable challenge in ultra-deep oxidative desulfurization (ODS) field. Herein, a series of highly-efficient VOx/boron nitride nanosheets (BNNS)@TiO2 heterostructures, therein, cetyltrimethylammonium bromide cationic surfactants serving as intercalation agent, BNNS and MXene as precursors, with various VOx NP sizes were designed and controllably constructed by a facile intercalation confinement strategy. The properties and structures of the prepared catalysts were systematically characterized by different technical methods, and their catalytic activities were investigated for aerobic ODS of dibenzothiophene (DBT). The results show that the size of VOx NPs and V5+/V4+ play decisive roles in the catalytic aerobic ODS of VOx/BNNS@TiO2 catalysts and that VOx/BNNS@TiO2-2 exhibits the highest ODS activity with 93.7% DBT conversion within 60 min under the reaction temperature of 130 °C and oxygen flow rate of 200 mL·min–1, which is due to its optimal VOx dispersion, excellent reducibility and abundant active species. Therefore, the finding here may contribute to the fundamental understanding of structure-activity in ultra-deep ODS and inspire the advancement of highly-efficient catalyst. 相似文献
995.
Nina Wolfsgruber Andreas Tanda Vasiliki-Maria Archodoulaki Christoph Burgstaller 《Polymer Engineering and Science》2023,63(4):1094-1105
Combining thermal conductivity with electrical isolation is a very interesting topic for electronic applications in order to transfer the generated heat. Typical approaches combine thermally conductive fillers with a thermoplastic matrix. The aim of this work was to investigate the influence of different fillers and matrices on the thermal conductivity of the polymer matrix composites. In this study, various inorganic fillers, including aluminum oxide (Al2O3), zinc oxide (ZnO), and boron nitride (BN) with different shapes and sizes, were used in matrix polymers, such as polyamide 6 (PA6), polypropylene (PP), polycarbonate (PC), thermoplastic polyurethane (TPU), and polysulfone (PSU), to produce thermally conductive polymer matrix composites by compounding and injection molding. Using simple mathematical models (e.g., Agari model, Lewis–Nielson model), a first attempt was made to predict thermal conductivity from constituent properties. The materials were characterized by tensile testing, density measurement, and thermal conductivity measurement. Contact angle measurements and the calculated surface energy can be used to evaluate the wetting behavior, which correlates directly with the elastic modulus. Based on the aforementioned evaluations, we found that besides the volume fraction, the particle shape in combination with the intrinsic thermal conductivity of the filler has the greatest influence on the thermal conductivity of the composite. 相似文献
996.
《Ceramics International》2023,49(1):635-658
Nickel-based superalloy is a critical material for turbine engine components in the aerospace application, but the poor machinability and low machining efficiency have further hampered it to be used widely. Cubic boron nitride (cBN), having extreme hardness and chemical inertness, is the potential candidate to process superalloys. In this paper, we systematically investigated the tool wear characteristic of cBN at different cutting speeds in dry turning of Inconel 718 by experiments and FEM simulations. The FEM model with initial flank wear land (VB) was established and validated. Effects of cutting speeds (200–400 m/min) on cBN tool life and wear mechanisms were systematically investigated. Effects of tool flank wear on cBN tool cutting edge temperature field and Inconel 718 machined surface layer stress distribution were analyzed by FEM simulations. 相似文献
997.
John R. Stockdale Shelbie A. Legett Xavier M. Torres Adam Pacheco Santosh Adhikari Lindsey Bezek Andrea Labouriau 《应用聚合物科学杂志》2024,141(16):e55236
Boron (specifically 10B) is the element of choice to shield thermal neutrons due to its large (n, α) cross-section; however, very few polymer composites containing high boron concentrations are available. This study aimed to determine the maximum possible amount of boron that could be introduced into a polymer matrix. Diverse manufacturing techniques, ranging from additive manufacturing to compression molding, were employed to fabricate inks and filaments for 3D printing, foams, and flexible pads. Composites using siloxanes, poly(lactic acid), and acrylonitrile butadiene styrene containing up to 80 wt% boron were sucessufully fabricated. The addition of known plasticizers (polyethylene glycol) and reinforcing agents (carbon nanofibers and fumed silica) helped to overcome fabrication problems such as clogging of the printing nozzle or crumbling of compression molded parts. In addition, the thermal-mechanical properties of these novel boron composites were determined and shown to vary according to boron concentration, presence of additives, and fabrication techniques utilized. 相似文献
998.
最近发现的全硼富勒烯(硼球烯,D2d B-/040),开启了硼球烯化学研究的新篇章。类似于富勒烯,金属掺杂也是硼球烯修饰和功能化重要途径。本工作采用密度泛函理论预测了一系列锕系金属掺杂硼球烯[An@B39]n+(An=U,n=3;An=Cm,n=2)。理论计算表明,这些硼球烯均为稳定的金属内嵌硼球烯,其中[U@B39]3+的能量最低,结构具有C3对称性,而[Cm@B39]2+为C1结构。成键性质分析表明,[U@B39]3+和[Cm@B39]2+均存在σ和π离域键。另外[An@B39]n+中U-B键的共价相互作用强于Cm-B键,且[U@B39]3+较[Cm@B39]2+更稳定。因此,An-B键的共价特征对于这些锕系金属内嵌硼球烯的形成是必不可少的。本工作扩展了硼球烯体系,并为新型稳定金属内嵌硼球烯的设计提供了理论线索。 相似文献
999.
金属 有机骨架(MOFs)材料作为吸附剂具有吸附硼同位素的潜力,为系统研究硼同位素效应,本文建立测定硼酸溶液中硼浓度的自动电位滴定法,以三种MOFs为例测定其对硼同位素的分离效果。采用弱酸强化法,甘露醇用量为理论用量的4倍,硼酸标准物质的测量值与参考值之差最小(-0.000 13 g),方法的测量不确定度为0.000 2~0.000 8,测量精度为0.10%~0.40%,方法有效、可靠。应用建立的自动电位滴定法测定吸附前、后硼酸溶液的硼浓度,用MC-ICP-MS测定吸附前、后硼酸溶液的硼同位素丰度比10B/11B,以Cu-MOF-OCH3、UiO-66-NH2、MIL-101(Cr)-2,3-OH三种MOFs材料为例,测定其对硼同位素的静态分离效果。结果表明,Cu-MOF-OCH3、UiO-66-NH2和MIL-101(Cr)-2,3-OH对硼同位素的分离因子(S)分别为1.066、1.037和1.079,均大于商用树脂Amberlite IR743的S(1.027),其中,Cu-MOF-OCH3对10B的10/11S>1,UiO-66-NH2、MIL-101(Cr)-2,3-OH对11B的11/10S>1。本结果可为系统研究MOFs材料对硼同位素的分离效果提供参考。 相似文献
1000.
Although the high impermeability of graphene makes it an excellent barrier to inhibit metal oxidation and corrosion, graphene can form a galvanic cell with the underlying metal that promotes corrosion of the metal in the long term. Boron nitride (BN) nanosheets which have a similar impermeability could be a better choice as protective barrier, because they are more thermally and chemically stable than graphene and, more importantly, do not cause galvanic corrosion due to their electrical insulation. In this study, the performance of commercially available BN nanosheets grown by chemical vapor deposition as a protective coating on metal has been investigated. The heating of the copper foil covered with the BN nanosheet at 250 °C in air over 100 h results in dramatically less oxidation than the bare copper foil heated for 2 h under the same conditions. The electrochemical analyses reveal that the BN nanosheet coating can increase open circuit potential and possibly reduce oxidation of the underlying copper foil in sodium chloride solution. These results indicate that BN nanosheets are a good candidate for oxidation and corrosion protection, although conductive atomic force microscopy analyses show that the effectiveness of the protection relies on the quality of BN nanosheets. 相似文献