Etching Mechanism of Ti_(3)C_(2)Cl_(2) MXene Phases by CuCl_(2)-Lewis Molten Salt Method

We described a method for obtaining fluorine-free Ti_(3)C_(2)Cl_(2)MXene phases by melting copper in CuCl_(2)instead of aluminum in Ti_(3)AlC_(2).XRD results show that when molten salt CuCl_(2)etches Ti_(3)AlC_(2),it forms an intermediate product Ti_(3)CuC_(2),and then reacts with Ti_(3)CuC_(2)to obtain Ti_(3)C_(2)Cl_(2).The reaction of Ti_(3)AlC_(2)and CuCl_(2)at a temperature of 800℃for 2 h to obtain Ti_(3)C_(2)Cl_(2)with an optimal lamellar structure is shown in SEM results.The pseudopotential plane-wave(PP-PW)method is used to calculate on the electronic structure.The etching mechanism is investigated by the total energies of each substance.The chemical reaction of Ti_(3)AlC_(2)and CuCl_(2)will first become Ti_(3)CuC_(2)and Cu,and then become Ti_(3)C_(2)Cl_(2)during the Lewis acid etching process,which are consistent with the experimental results.

Simulation of incompressible multiphase flows with complex geometry using etching multiblock method

The incompressible two-phase flows are simulated using combination of an etching multiblock method and a diffuse interface （DI） model, particularly in the com- plex domain that can be decomposed into multiple rectangular subdomains. The etching multiblock method allows natural communications between the connected subdomains and the efficient parallel computation. The DI model can consider two-phase flows with a large density ratio, and simulate the flows with the moving contact line （MCL） when a geometric formulation of the MCL model is included. Therefore, combination of the etch- ing method and the DI model has potential to deal with a variety of two-phase flows in industrial applications. The performance is examined through a series of numerical exper- iments. The convergence of the etching method is firstly tested by simulating single-phase flows past a square cylinder, and the method for the multiphase flow simulation is vali- dated by investing drops dripping from a pore. The numerical results are compared with either those from other researchers or experimental data. Good agreement is achieved. The method is also used to investigate the impact of a droplet on a grooved substrate and droplet generation in flow focusing devices.

FIB Secondary Etching Method for Fabrication of Fine CNT Forest Metamaterials

Anisotropic materials, like carbon nanotubes(CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is still very challenging. In this study, a new method utilizing a focused ion beam(FIB) with additional secondary etching is presented, which can obtain uniform and fine patterning of CNT forest nanostructures for metamaterials and ranging in sizes from hundreds of nanometers to several micrometers. The influence of the FIB processing parameters on the morphology of the catalyst surface and the growth of the CNT forest was investigated, including the removal of redeposited material,decreasing the average surface roughness(from 0.45 to 0.15 nm), and a decrease in the thickness of the Fe catalyst.The results showed that the combination of FIB patterning and secondary etching enabled the growth of highly aligned, highdensity CNT forest metamaterials. The improvement in the quality of single-walled CNTs(SWNTs), defined by the very high G/D peak ratio intensity of 10.47, demonstrated successful fine patterning of CNT forest for the first time. With a FIB patterning depth of 10 nm and a secondary etching of 0.5 nm, a minimum size of 150 nm of CNT forest metamaterials was achieved. The development of the FIB secondary etching method enabled for the first time, the fabrication of SWNT forest metamaterials for the optical and infrared regime, for future applications, e.g., in superlenses, antennas,or thermal metamaterials.

In-situ Characterization of Non-aqueous Nano-dispersion Systems by Freeze-etching TEM and Comparative Study with Laser Scattering Method

In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was reported.To improve just-for-once successive rate of specimen preparation and get good characterization results,an improving specimen preparation method of freezing etching was developed.Size,distribution and morphology of NANDS were directly visualized.Some information of particle dispersion feature and particle density can also be obtained.Reproductivity of the FETEM characterization is excellent.Comparing with laser scattering method,which is liable to give positive error especially for small size particle anchoring disperser,FETEM characterization can give more accurate measurement of particle size.Moreover,FETEM can give dispersion feature of nanoparticle in non-aqueous medium.

Temperature-dependent photoluminescence on organic inorganic metal halide perovskite CH3NH3Pb I3-xClx prepared on ZnO/FTO substrates using a two-step method

Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was-140 K. The films＇ exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH3NH3Pb I（3-x）Clx films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.

Adsorption of CO_(2) on MgAl layered double hydroxides: Effect of intercalated anion and alkaline etching time

The adsorption of CO_(2) on MgAl layered double hydroxides(MgAl-LDHs) based adsorbents has been an effective way to capture CO_(2),however the adsorption capacity was hampered due to the pore structure and the dispersibility of adsorption active sites.To address the problem,we investigate the effect of intercalated anion and alkaline etching time on the structure,morphology and CO_(2) uptake performances of MgAl-LDHs.MgAl-LDHs are synthesized by the onepot hydrothermal method,followed by alkaline etching of NaOH,and characterized by x-ray diffraction,N_(2) adsorption,scanning electron microscopy and Fourier transform infrared spectroscopy.The CO_(2) adsorption tests of the samples are performed on a thermogravimetric analyzer,and the adsorption data are fitted by the first-order,pseudo-second-order and Elovich models,respectively.The results demonstrate that among the three intercalated samples,MgAl(Cl) using chloride salts as precursors possesses the highest adsorption capacity of CO_(2),owing to high crystallinity and porous structure,while MgAl(Ac) employing acetate salts as precursors displays the lowest CO_(2) uptake because of poor crystallinity,disorderly stacked structure and unsatisfactory pore structure.With regard to alkaline etching,the surface of the treated MgAl(Cl) is partly corroded,thus the specific surface area and pore volume increase,which is conducive to the exposure of adsorption active sites.Correspondingly,the adsorption performance of the alkaline-etched adsorbents is significantly improved,and MgAl(Cl)-6 has the highest CO_(2) uptake.With the alkaline etching time further increasing,the CO_(2) adsorption capacity of MgAl(Cl)-9 sharply decreases,mainly due to the collapse of pore structure and the fragmentized sheet-structure.Hence,the CO_(2) adsorption performance is greatly influenced by alkaline etching time,and appropriate alkaline etching time can facilitate the contact between CO_(2) molecules and the adsorbent.

Applying the Dynamic Two-Step Method to Forecast Remaining Oil Distribution of Lower Series ,Xiaermen Oilfield

The distribution of remaining oil is often described qualitatively. The remaining oil distributed in the whole reservoir is calculated according to the characteristics of the space distribution of the saturation of remaining oil. Logging data are required to accomplish this. However, many such projects cannot be completed. Since the old study of remaining oil distribution could not be quantified efficiently, the ＂dynamic two-step method＂ is presented. Firstly, the water cut of every flow unit in one well at one time is calculated according to the comprehensive water cut of a single well at one time. Secondly, the remaining oil saturation of the flow unit of the well at one time is calculated based on the water cut of the flow unit at a given time. The results show that ＂dynamic two-step method＂ has characteristics of simplicity and convenience, and is especially suitable for the study of remaining oil distribution at high water-cut stage. The distribution of remaining oil presented banding and potato form, remaining oil was relatively concentrated in faultage neighborhood and imperfect well netting position, and the net thickness of the place was great. This proposal can provide an effective way to forecast remaining oil distribution and enhance oil recovery, especially applied at the high water-cut stage.

Preparation of Electrode Array by Electrochemical Etching Based on FEM

Process technology of multiple cylindrical micro-pins by wire-electrical discharge machining （wire-EDM） and electrochemical etching was presented. A row of rectangular micro-columns were machined by wire-EDM and then machined into cylindrical shape by electrochemical etching. However, the shape of the multiple electrodes and the consistent sizes of the electrodes row are not easy to be controlled. In the electrochemical process, the shape of the cathode electrode determines the current density distribution on the anode and so the forming of multiple electrodes. This paper proposes a finite element method （FEM） to accurately optimize the electrode profile. The microelectrodes row with uniformity diameters with size from hundreds micrometers to several decades could be fabricated, and mathematical model controlling the shape and diameter of multiple microelectrodes was provided. Furthermore, a good agreement between experimental and theoretical results was confirmed.

Angular Effects on F＋ Etching SiC： MD Study

Molecular dynamics （MD） simulations were performed to investigate F＋ continuously bombarding SiC surfaces with energies of 100 eV at different incident angles at 300 K. The simulated results show that the steady-state uptake of F atoms increases with increasing incident angle. With the steady-state etching established, a Si-C-F reactive layer is formed. It is found that the etching yield of Si is greater than that of C. In the F-containing reaction layer, the SiF species is dominant with incident angles less than 30°. For all incident angles, the CF species is dominant over CF2 and CF3.

The Implementation of the Surface Charging Effects in Three-Dimensional Simulations of SiO_(2) Etching Profile Evolution

Refined control of etched profile in microelectronic devices during plasma etching process is one of the most important tasks of front-end and back-end microelectronic devices manufacturing technologies. A comprehensive simulation of etching profile evolution requires knowledge of the etching rates at all the points of the profile surface during the etching process. Electrons do not contribute directly to the material removal, but they are the source, together with positive ions, of the profile charging that has many negative consequences on the final outcome of the process especially in the case of insulating material etching. The ability to simulate feature charging was added to the 3D level set profile evolution simulator described earlier. The ion and electron fluxes were computed along the feature using Monte Carlo method. The surface potential profiles and electric field for the entire feature were generated by solving Laplace equation using finite elements method. Calculations were performed in the case of simplified model of Ar+/CF4 non-equilibrium plasma etching of SiO2.

The convergence ball and error analysis of the two-step Secant method

Under the assumption that the nonlinear operator has Lipschitz continuous divided differences for the first order,we obtain an estimate of the radius of the convergence ball for the two-step secant method.Moreover,we also provide an error estimate that matches the convergence order of the two-step secant method.At last,we give an application of the proposed theorem.

Solution of Nonlinear Integro Differential Equations by Two-Step Adomian Decomposition Method (TSAM)

The Adomian decomposition method (ADM) can be used to solve a wide range of problems and usually gets the solution in a series form. In this paper, we propose two-step Adomian Decomposition Method (TSAM) for nonlinear integro-differential equations that will facilitate the calculations. In this modification, compared to the standard Adomian decomposition method, the size of calculations was reduced. This modification also avoids computing Adomian polynomials. Numerical results are given to show the efficiency and performance of this method.

氨热法GaN单晶生长的位错密度演变研究

氮化镓单晶具有高击穿电压、直接带隙、高饱和电子漂移速率、良好的化学稳定性等特性,在光电子器件和大功率电子器件中有广泛的应用。然而异质外延氮化镓会产生高位错密度,限制了氮化镓基器件的性能发挥。本研究以HVPE-GaN为籽晶,采用氨热法生长了氮化镓单晶,利用扫描电子显微镜(SEM),光学显微镜和湿法腐蚀研究了氨热法氮化镓单晶籽晶区至侧向生长区的位错演变。研究结果表明,侧向生长区的氮化镓单晶位错密度明显低于籽晶区,侧向生长超过25μm后,位错密度降低2个数量级。

不同酸蚀模式与不同粘结剂在恒牙治疗中的应用比较

利用显微镜与万能拉伸试验机等设备,分析全酸蚀方法、自酸蚀方法、Gluma磷酸酸蚀法的粘接系统,在年轻恒牙治疗中的粘接残余系数、粘接强度与封闭剂脱落率。结果证明,全酸蚀方法的粘接系统在年轻恒牙治疗时的封闭剂脱落率最小;自酸蚀方法的粘接系统封闭效果最差。酸蚀时间对全酸蚀方法影响较大,缩短酸蚀时间,可提升年轻恒牙粘接强度。酸蚀时间对Gluma磷酸酸蚀法影响较小;酸蚀时间一致时,全酸蚀方法的粘接强度明显高于Gluma磷酸酸蚀法,说明全酸蚀方法的粘接系统在年轻恒牙治疗中的效果优于Gluma磷酸酸蚀法的粘接系统。酸蚀浓度对不同酸蚀方法的粘接系统在年轻恒压中治疗效果影响均较小;不同酸蚀浓度时,全酸蚀方法的粘接残余系数最高,粘接强度最强。

基于电化学液膜法腐蚀制备STM钨探针的研究

高质量的探针是保证扫描隧道显微镜(Scanning Tunneling Microscope,STM)4K分辨率的关键。为得到原子级别的探针,实验基于电化学腐蚀原理,使用垂直液膜法制备钨探针。在制备过程中通过控制变量法,研究了腐蚀电压、液膜下钨丝长度等参数对探针质量的影响,实验发现,当使用2 mol/L的NaOH溶液作为液膜时,最佳腐蚀电压为5 V、最佳液膜下钨丝长度为4 mm。该研究为电化学液膜法腐蚀制备钨探针提供了参考依据。

MXene基电磁屏蔽复合材料的应用进展

随着电子设备的快速发展和无线通信需求的急剧增加,电磁污染问题愈发严重。电磁屏蔽材料的研制可以很好地解决这类严峻的问题。MXene独特的层状结构、良好的导电性和优异的机械强度,使其在电磁屏蔽和生物医用领域均展现了极高的应用价值。本文概述了MXene及复合材料的制备,以及在电磁屏蔽、乳腺癌治疗领域的应用进展。

氟离子选择电极法测定含铜蚀刻废液中氟含量方法探讨

准确测定含铜蚀刻废液中氟含量是含铜蚀刻废液中铜盐回收的关键,本文就含铜蚀刻废液中氟含量离子选择电极测定方法[1~3]进行探讨与验证。通过样品前处理与试验,离子选择电极一次标准加入法测定下限为0.9mg·L^(-1),离子选择电极标准曲线法测定下限为1.2 mg·L^(-1);两种方法的相对标准偏差在1.2%~1.7%,两种方法的加标回收率在77%~102%,满足工程应用要求。

Na_(2)O-CaO-SiO_(2)平板玻璃减反射功能化研究

随着光伏产业的高速发展,与之配套使用的减反射玻璃重新进入了研究者们的视野。本文采用湿化学二步刻蚀法制备了具有减反射性能的Na_(2)O-CaO-SiO_(2)平板玻璃,采用分光光度计、扫描电子显微镜、原子力显微镜和X射线能谱仪等测试样品的透过率、表面形貌和断面膜层厚度、表面化学成分、耐酸性和硬度,研究了反应温度和反应时间、玻璃膜层结构与透过率的关系。通过使用弱碱性的混合盐溶液对Na_(2)O-CaO-SiO_(2)玻璃表面进行化学刻蚀,使玻璃表面Si—O键断裂,在玻璃表面形成纳米膜层结构,当膜层厚度达到一定厚度时,一定波长的光在玻璃表面发生相消干涉,透过率最高可达到97.8%,刻蚀前后玻璃成分基本无变化,铅笔硬度达到3H。

红外抗反射微纳结构刻蚀制备研究进展

“蛾眼效应”指光波折射率因蛾眼表面微纳结构在深度方向呈连续性变化,使大部分光被吸收,只有极少被反射的现象。受“蛾眼效应”启发,在材料表面制备微纳结构使其具有独特抗反射性能受到广泛关注,在太阳能电池、光电探测器、光电二极管和军事隐身等领域有广阔应用前景。本文梳理不同微纳结构抗反射原理,并对红外抗反射结构的不同刻蚀制备方法及其应用进行综述,总结了化学刻蚀、反应离子刻蚀、超快激光刻蚀等红外抗反射结构制备方法的特点以及对抗反射性能的影响,阐述红外抗反射结构在红外探测、红外热成像和隐身等方面的应用,并对抗反射结构制备方法研究方向与未来前景进行展望。

中空TiO_(2)微球的可控制备及在隔热涂料中的应用

为满足隔热涂料拥有高近红外反射率的同时还具备较低的导热性能的需求,研发了一种优秀的隔热填料:中空TiO_(2)微球。中空TiO_(2)微球空腔结构可储存大量空气,使得导热系数较低,同时壳层结构对红外线具有较强反射能力,是理想材料之一。以自制粒径约340 nm单分散SiO_(2)微球为硬模板,采用牺牲模板法在最优条件下成功制备粒径约510 nm,壳厚120 nm,空腔尺寸260 nm左右,分散较均匀的中空TiO_(2)微球。探究氨水浓度、反应时间对SiO_(2)微球粒径影响,得出适宜反应时间为2 h,且氨水浓度在一定范围内增大,SiO_(2)粒径随之增大。研究了水热时间、温度、蚀刻液种类对中空TiO_(2)微球形貌的影响,其中50~60℃NaOH溶液蚀刻1 h最适宜。测试了中空TiO_(2)微球在300~2500 nm的反射率,400~1350 nm内反射率维持在90%。用中空TiO_(2)微球制备隔热涂料,隔热性能比用钛白粉、空心玻璃微珠制得的隔热涂料好,隔热温差达10℃左右。