Preparation of nanometer δ- and β-bismuth trioxide by vacuum vapor-phase oxidation

A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, and geometric standard deviation(GSD) was from 1.42 to 1.64. The results show that δ-Bi2O3 is formed when quenching rates is rapid and β-Bi2O3 is formed when it is slow. The size of grains increases with rising reaction temperature, flow rate of carrier gas, residual pressure of system and longer growing time of grains.

Effects of vacuum pre-oxidation process on thermally-grown oxides layer of CoCrAlY high temperature corrosion resistance coating

The influence of the certain specific vacuum pre-oxidation process on the phase transformation of thermally-grown oxides（TGO） was studied.The CoCrAlY high temperature corrosion resistance coatings were produced onto the nickel-based superalloy substrate by high velocity oxygen fuel（HVOF）.It suggests that the TGO usually consists of a great number of chromium oxides,cobalt oxides and spinel oxides besides alumina during the initial period of the high temperature oxidation if the specimens are not subjected to the appropriate vacuum pre-oxidation process.Furthermore,the amount of alumina is strongly dependent on the partial pressure of oxygen;while the CoCr2O4 spinel oxides are usually formed under the conditions of higher partial pressure of oxygen during the initial period and the lower partial pressure of oxygen during the subsequent period of the isothermal oxidation.After the appropriate vacuum pre-oxidation process,the TGO is mainly composed of alumina that contains lower Y element,while alumina that contains higher Y element sporadically distributes,and the spinel oxides cannot be found.After a longer period of the isothermal oxidation,a small amount of porous CoCr2O4 and the chrome oxide sporadically distribute near the continuous alumina.Additionally,after the appropriate vacuum pre-oxidation process,the TGO growth rate is relatively slow.

EFFECT OF VACUUM HEAT TREATMENT ON OXIDATION BEHAVIOR OF SPUTTERED NiCrAlY COATING

A bond coat for thermal barrier coating (TBC), NiCrAlY coating, is subjected to vac-uum heat treatment in order to remove internal stress before ceramic top coat is de-posited. The effect of vacuum heat treatment on the oxidation behavior of the sputtered NiCrAlY coating has been investigated. The as-sputtered NiCrAlY coating consists of γ-Ni and b-NiAl phases. After vacuum heat treatment, the sputtered NiCrAlY coating mainly consists of γ'-Ni3Al, β-NiAl, γ-Ni, and trace of α-Al2O3 phases. The isothermal oxidation of sputtered NiCrAlY coating with and without vacuum heat treatment has been performed at 1000℃. It is shown that a-Al2O3 formed during vacuum heat treatment acts as nuclei for the formation of a-Al2O3, and the protective a-Al2O3 scale is formed more rapidly on the vacuum heat treated NiCrAlY coating than that formed on the untreated coating. Also the a-Al2O3 scale has a better adherence to the vacuum heat treated NiCrAlY coating. Therefore the vacuum heat treatment improves the oxidation resistance of sputtered NiCrAlY coating.

Exploring the Low-Temperature Oxidation Chemistry of Cyclohexane in a Jet-Stirred Reactor:an Experimental and Kinetic Modeling Study

We report the investigation on the low-temperature oxidation of cyclohexane in a jet-stirred reactor over 500-742 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry （SVUV-PIMS） was used for identifying and quantifying the oxidation species. Major products, cyclic olefins, and oxygenated products including reactive hydroperoxides and high oxygen compounds were detected. Compared with n-alkanes, a narrow low-temperature window （-80 K） was observed in the low-temperature oxidation of cyclohexane. Besides, a kinetic model for cyclohexane oxidation was developed based on the CNRS model [Combust. Flame 160, 2319 （2013）], which can better capture the experimental results than previous models. Based on the modeling analysis, the 1,5-H shift dominates the crucial isomerization steps of the first and second O2 addition products in the low-temperature chain branching process of cyclohexane. The negative temperature coefficient behavior of cyclohexane oxidation results from the reduced chain branching due to the competition from chain inhibition and propagation reactions, i.e. the reaction between cyclohexyl radical and O2 and the de- composition of cyclohexylperoxy radical, both producing cyclohexene and HO2 radical, as well as the decomposition of cyclohexylhydroperoxy radical producing hex-5-en-l-al and OH radical.

Effect of depressurizing speed on mold filling behavior and entrainment of oxide film in vacuum suction casting of A356 alloy

The effect of depressurizing speed on mold filling behavior and entrainment of oxide film of A356 alloy was studied. Themold filling behavior and velocity fields were recorded by water simulation with particle image velocimetry. The results show thatthe gate velocity first increased dramatically, then changed with the depressurizing speed: the gate velocity increased slowly atrelatively high depressurizing speed; at reasonable depressurizing speed, the gate velocity kept unchanged; while at lowerdepressurizing speed, the gate velocity decreased firstly and then kept unchanged. High gate velocity results in melt falling backunder gravity at higher speed. The falling velocity is the main factor of oxide film entrainment in vacuum suction casting. The designcriterion of depressurizing rate was deduced, and the A356 alloy castings were poured to test the formula. The four-point bend testand Weibull probability plots were applied to assessing the fracture mechanisms of the as-cast A356 alloy. The results illuminate amethod on designing suitable depressurizing speed for mold filling in vacuum suction casting.

Effect of Y_2O_3 on microstructure and oxidation of γ-Ni+γ′-Ni_3Al coatings transformed from electrodeposited Ni-Al films at 1000℃

The electrodeposited Y2O3-dispersedγ-Ni+γ′-Ni3Al coatings on Ni substrates were developed by the conversion of electrodeposited Ni-Al-Y2O3 films with dispersed Al microparticles in Ni matrix into Ni3Al by vacuum annealing at 800℃for 3 h. For comparison,Y2O3-freeγ-Ni+γ′-Ni3Al coatings with a similar Al content were also prepared by vacuum annealing the electrodeposited microparticle-dispersed composite coatings of Ni-Al under the same condition.SEM and TEM characterizations show that the electrodeposited Y2O3-dispersedγ+γ′coatings exhibit finer grains,a more homogeneous distribution ofγ′,and a narrowedγ′phase spacing compared with the electrodeposited Y 2 O3-freeγ+γ′coatings.The oxidation at 1 000℃shows that the addition of Y2O3 significantly improves the oxidation resistance of the electrodepositedγ+γ′coatings.The effect of Y2O3 particles on the microstructure and oxidation behavior of the electrodepositedγ+γ′coatings was discussed in detail.

Use of various MgO resources for high-purity Mg metal production through molten salt electrolysis and vacuum distillation

A green and effective electrolytic process was developed to produce high-purity Mg metal using primary and secondary resources containing Mg O as a feedstock. The electrolysis of various Mg O resources was conducted using a Cu cathode in MgF2– LiF – KCl molten salt at 1043 K by applying an average current of 1.44 A for 12.5 h. The electrolysis of calcined North Korean magnesite and seawater Mg O clinker yielded Mg alloys of MgCu2and(Cu) phases with current efficiencies of 89.6–92.4%. The electrolysis of oxidized Mg O-C refractory brick, aged ferronickel slag, and ferronickel slag yielded Mg alloys of MgCu2and(Cu) phases with current efficiencies of 59.3–92.3%. The vacuum distillation of Mg alloys obtained was conducted at 1300 K for 10 h to produce high-purity Mg metal. After vacuum distillation, Mg metal with a purity of above 99.994% was obtained. Therefore, this study demonstrates the feasibility of the production of high-purity Mg metal from various Mg O resources using a novel electrolytic process with a Cu cathode, followed by vacuum distillation.

High Temperature Sintering and Oxidation Behavior in Plasma Sprayed TBCs [Single Splat Studies] Paper 1—Role of Heat Treatment Variations

The TBC system is examined with regards to its response to thermal exposure at high temperature. It has been established before that the thermally grown oxide (TGO) layer that forms upon bond coat oxidation is the key factor determining the performance of the TBC system and/or its failure. However, characteristics of TGO growth, bond coat rumpling, principles governing failure of TBC systems and the various failure mechanisms have been studied extensively in case of just super alloy with bond coat or with thick top coating. In this study super alloy/bond coat system with single splats of YSZ instead of thick topcoat is analyzed in order to scrutinize the effect on the first layer of splats during thermal exposure. The splats with microcracks are the building blocks of the top coat. The most important aspect of this layer is the inherent inter-splat and intra-splat porosity which undergoes sintering during thermal exposure. The interactions between the YSZ splats and the evolving TGO is directly linked to the presence or absence of bond coat oxidation. Therefore the high temperature behavior of this system is analyzed with variations in heat treatment involving, temperature, duration and environment of thermal exposure.

High Temperature Sintering and Oxidation Behavior in Plasma Sprayed TBCs [Single Splat Studies] Paper 2—Relevance of Variation in Materials Systems of TBC Components

The TBC system’s response to thermal exposure at high temperature is discussed here. The relevance of the microstructural aspects of each component of the TBC system is emphasized. The top coat is a YSZ ceramic coating consisting of a collection of splats on top of one another. The most important aspect of this layer is the inherent inter-splat and intra-splat porosity which undergoes sintering during thermal exposure. This study investigates the effect of thermal exposure on the microstructure and sintering behavior in single splats produced using different starting powders since this has been shown to influence the basic microstructure of YSZ topcoat. The bond coat is an MCrAlY metallic coating which serves as an Al reservoir and allows the formation of a protective alumina, Thermally Grown Oxide (TGO) layer between the bond coat (BC) and the top coat (TC) layers. This oxide scale formed upon thermal exposure prevents further oxidation of the underlying component (substrate) and thus provides protection. As such, the content of free Al in the bond coat layer is of significance and makes it crucial to understand the influence of bond coat microstructure evolution and oxidation involved during its formation. The interaction between the bond coat, the TGO and the top coat layers is examined in this study to understand the high temperature behavior of the TBC system with regards to variations in the top coat and bond coat material systems used.

Production of high-purity Mg metal from dolomite through novel molten salt electrolysis and vacuum distillation

In this study,a novel Mg production process for producing high-purity Mg metal from dolomite was developed.When the electrolysis of calcined dolomite was conducted using Cu cathode and C anode in MgF_(2)–LiF molten salt at 1083–1173 K by applying an average current of 1.42–1.46 A for 9.50–21.0 h,the current efficiency of 66.4–88.6%was obtained.The produced Mg alloys consisted of MgCu_(2)and Cu(Mg)or MgCu_(2)and CuMg_(2)phases,depending on the Mg concentration in the Mg alloy.When the electrolysis of calcined dolomite was conducted in MgF_(2)–LiF–CaF_(2)molten salt at 1083 K,the current efficiency was 40.9–71.4%,owing to undesired reactions such as electroreduction of Ca^(2+)or/and CO_(3)^(2−)ions.Meanwhile,the current efficiency increased from 40.9%to 63.2%by utilizing a Pt anode,because the occurrence of CO_(3)^(2−)ions in the molten salt was prevented.After vacuum distillation of the obtained Mg alloys at 1300 K for 10 h,Mg metal with a purity of 99.9996–99.9998%was produced.Therefore,the feasibility of this novel process for the production of high-purity Mg metal from dolomite was demonstrated.

不同包装核桃仁氧化机制分析

目的:探究核桃仁氧化机制。方法:将核桃仁进行真空和非真空包装,在60℃条件下加速氧化,定期取样,采用透射电镜和扫描电镜观察核桃仁细胞平面超微结构和立体形貌结构,并测定过氧化值、羰基价及细胞膜透率等氧化指标,分析比较真空与非真空包装核桃仁氧化过程中细胞组织超微结构的变化规律,多维度评价氧化进程,探究氧化机制。结果:加速氧化第14天,非真空组核桃仁氧化油脂开始变黏稠,并逐渐加剧。随时间延长,细胞内蛋白体依次出现表面变粗糙、聚集、向细胞边缘移动、分解再组合的变化;油体膜出现破裂、细胞内网状结构破坏,油脂外溢至细胞间隙,细胞体积变小。真空组核桃仁细胞结构变化远小于非真空组,第28天油脂才开始变黏稠,同时其氧化指标数值也极显著低于非真空组(P<0.01);3个氧化指标变化趋势与细胞超微结构变化趋势吻合。结论:透射电镜与扫描电镜多维度观察结合氧化指标评价能更清晰地呈现核桃仁氧化细胞组织超微结构变化规律。真空与非真空包装核桃仁氧化机制相同,但氧化程度不同,真空包装能显著降低核桃仁的氧化。

真空紫外在水处理中的作用机理及其研究进展

介绍了真空紫外线(VUV,254+185 nm)高级氧化技术辐射水产生活性氧化物质降解水中污染物的作用机理以及在水处理行业中的应用,同时包括VUV辐射氧气或者空气产生臭氧。概述了VUV工艺的优点和局限性以及影响脱色的主要因素,并对其在水处理中的可能应用及未来发展方向进行展望,为真空紫外在有机染料废水后续研究提供参考,提出研究建议。

氧化硅水平隧穿结电子源及其应用

电子源是真空电子设备的核心部件,片上微型电子源是实现微型化、片上化真空电子器件的关键和基础。氧化硅水平隧穿结电子源是本课题组近几年发展的一种新型片上微型电子源,其具有发射效率高、发射电流密度大、工作电压低、能耐受粗真空和时间响应快等优点,展现出较大的应用潜力。文章将从电子发射微观过程及理论模型、阵列化集成以及在真空电子器件中的应用三个方面系统介绍氧化硅水平隧穿结电子源,并对本课题组在该方向上所做的工作进行梳理与总结。

铺层方式对VIHPS制备的GO-CF混杂增强复合材料弯曲性能的影响

本文首先采用真空浸渗热压工艺(VIHPS)制备了不同铺层方式的氧化石墨烯-碳纤维(GO-CF)混杂增强复合材料,并对该材料进行三点弯曲试验,再通过扫描电子显微镜(SEM)表征其微观断口形貌。然后使用Digmat软件的FE模块建立微-纳跨尺度的代表性体积单元(RVE)模型,将该模型导入ANSYS Workbench软件中进行三点弯曲仿真模拟。复合材料三点弯曲试验结果表明,随着沿试样宽度方向(Y向)纤维铺层的增加,复合材料的弯曲强度从433.2 MPa降低至12.7 MPa,弯曲模量从13.8 GPa降低至0.2 GPa,它们分别降低了97.07%和98.55%。最后通过对比试验与仿真结果发现,两种结果的变化趋势基本一致,且仿真结果与试验结果接近。复合材料在弯曲变形过程中,受到拉伸和压缩的共同作用,其中导致复合材料失效的方式主要包括基体开裂、界面脱粘和纤维断裂。

真空冷冻干燥肉苁蓉工艺的研究

为了研究肉苁蓉产地趁鲜切制干燥的可行性,采用真空冷冻干燥法,通过单因素试验比较了肉苁蓉冻干过程中片状、粒状、粉状等不同切制方式对其干燥率及质量的影响,为肉苁蓉的干燥保存提供有效可行的加工方法;使用HPLC-UV方法,对粉状肉苁蓉药材中的松果菊苷和毛蕊花糖苷进行测定。结果表明,通过粉状切制的肉苁蓉产品干燥率及质量最好;粉状的切制方式所得的肉苁蓉放置1年后,松果菊苷和毛蕊花糖苷含量较高;小块状的处理方式最为简易,产品的干燥率也较为优秀,氧化程度在3种制备方式中最低。

超声分散时间对GO-CF增强SMPC形状记忆性能的影响

为了研究超声分散时间对形状记忆聚合物复合材料(SMPC)微观组织和形状记忆性能的影响,采用真空浸渗热压工艺制备6组不同超声分散时间的GO-CF混杂增强SMPC,通过扫描电子显微镜表征SMPC的微观组织形貌,开展形状记忆性能的测试.结果表明,适当的超声分散时间可以将GO剥离成片状结构并均匀分散在SMPC中,形成机械联锁和化学键合.随着超声分散时间的增加,SMPC的形状固定率和形状回复率呈现先增大后减小的趋势,除30 min外,其他SMPC的平均回复速率呈现先减小后增大的趋势,当超声分散60 min时,SMPC具有最佳的形状记忆性能,形状固定率和形状回复率分别达到97.85%和97.30%,最大回复力为10.47 N,平均形状回复速率为1.04°/s,机械联锁和化学键合这种复合结构的增加有利于增强SMPC的形状记忆性能,但需要更多的能量来实现SMPC的形状回复.

Copper nanowires decorated with TiO_(2−x) from MXene for enhanced electrocatalytic nitrogen oxidation into nitrate under vacuum assistance

The green synthesis of nitrate(NO_(3)^(−))via electrocatalytic nitrogen oxidation reaction(NOR)is a promising strategy for artificial nitrogen fixation,which shows great advantages than traditional nitrate synthesis based on Haber–Bosch and Ostwald processes.But the poor N_(2)absorption,high bond energy of N≡N(941 kJ·mol^(−1)),and competing multi-electron-transfer oxygen evolution reaction(OER)limit the activity and selectivity.Herein,we fabricated MXene-derived irregular TiO_(2)−x nanoparticles anchored Cu nanowires(Cu-NWs)electrode for efficient electrocatalytic nitrogen oxidation,which exhibits a NO_(3)−yield of 62.50μg·h^(−1)·mgcat^(−1)and a Faradaic efficiency(FE)of 22.04%,and a significantly enhanced NO_(3)−yield of 92.63μg·h^(−1)·mgcat^(−1),and a FE of 40.58%under vacuum assistance.The TiO_(2)−x/Cu-NWs electrode also shows excellent reproducibility and stability under optimal experimental conditions.Moreover,a Zn-N_(2)reaction device was assembled with TiO_(2−x)/Cu-NWs as an anode and Zn plate as a cathode,obtaining an extremely high NO_(3)−yield of 156.25μg·h^(−1)·mgcat^(−1).The Zn-nitrate battery shows an open circuit voltage(OCV)of 1.35 V.This work provides novel strategies for enhancing the performance of ambient N_(2)oxidation to obtain higher NO_(3)^(−)yield.

双碱法脱硫工艺提标改造与实践

介绍了淄博铁鹰球团制造有限公司双减法脱硫工艺技术改造过程和应用实践。通过对脱硫工艺的石灰浆液制备及输送系统、SO_(2)吸收系统、石膏脱水系统、工艺水系统、电气及自动控制系统等关键环节技术创新与改造,有效解决了脱硫能力不足、压滤效果差、塔体及喷淋管路结晶严重、工艺水平衡困难等运行难题,并实现了由双减法向石灰-石膏法脱硫工艺过渡,满足了生产需要,降低了脱硫运行成本。

Synthesis of a new ordered mesoporous NiMoO_4 complex oxide and its efficient catalytic performance for oxidative dehydrogenation of propane

Highly ordered mesoporous NiMoO4 material was successfully synthesized using mesoporous silica KIT-6 as hard template via vacuum nanocasting method. The structure was characterized by means of XRD, TEM, N2 adsorption-desorption, Raman and FT-IR. The mesoporous NiMoO4 with the coexistence of a-NiMoO4 and fl-NiMoO4 showed well-ordered mesoporous structure, a bimodal pore size distribution and crystalline framework. The catalytic performance of NiMoOa was investigated for oxidative dehydrogenation of propane. It is demonstrated that the mesoporous NiMoO4 catalyst with more surface active oxygen species showed better catalytic performance in oxidative dehydrogena- tion of propane in comparison with bulk NiMoO4.

Preparation of Nano-composites Membranes with Graphic Oxides and Polylactic Acid

Organic polymer materials were used as a layer of adhesive into the graphene sheet between the layers to enhance the interaction force between the nano-structure to achieve excellent mechanical properties and barrier properties. PLA with good flowability and easy processing was selected. The mechanical properties and barrier properties of the graphene-based composites were improved by the use of PLA for good flowability, making it easy to enter the GO layer as a binder. Three methods of preparation of GO/PLA homogeneous composite membranes were designed by vacuum filtration. The experimental results show that the injection of PLA as a molecular binder into the GO layer can effectively mimic the nano-structure, and enhance the intergranular force of the graphene molecules and the compatibility with the polymer matrix.