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1.
In this paper, chemical mechanical planarization (CMP) of amorphous Ge2Sb2Te5 (a-GST) in acidic H2O2 slurry is investigated. It was found that the removal rate of a-GST is strongly dependent on H2O2 concentration and gradually increases with the increase in H2O2 concentration, but the static etch rate first increases and then slowly decreases with the increase in H2O2 concentration. To understand the chemical reaction behavior of H2O2 on the a-GST surface, the potentiodynamic polarization curve, surface morphology and cross-section of a-GST immersed in acidic slurry are measured and the results reveal that a-GST exhibits a from active to passive behavior for from low to high concentration of H2O2 . Finally, a possible removal mechanism of a-GST in different concentrations of H2O2 in the acidic slurry is described.  相似文献   

2.
ABSTRACT

Effects of (H2O)n (n?=?1–3) on the H2O2?+?HO?→?HO2?+?H2O reaction have been investigated by the reactions of H2O2L(H2O)n (n?=?1–3)?+?HO and H2O2?+?HOL(H2O)n (n?=?1–3) at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory, coupled with rate constant calculations by using canonical variational transition state theory. Interestingly, for the former reactions, one-step process and stepwise mechanism are involved, where one-step processes occurring though cage-like hydrogen bonding network complexes and the transition states are favourable. Due to larger effective rate constants, these favourable processes are also favourable than the corresponding latter reactions. Meanwhile, the catalytic effect of (H2O)n (n?=?1–3) is mainly taken from water monomer, because the effective rate constant (k'(R_WM2)) of H2O2···H2O?+?HO reaction is, respectively, larger by 3, 6–10 orders of magnitude than that of H2O2···(H2O)2?+?HO (k'(R_WD1)) and H2O2···(H2O)3?+?HO (k'(R_WT1)) reactions. Furthermore, the enhancement factor of water molecular (k'(R_WM2)/ktot) is only 0.28% at 240?K, while at high temperature (such as at 425?K), the positive water vapour effect enhances up to 27.13%. This shows that at high temperatures the positive water effect is obvious under atmospheric conditions.  相似文献   

3.
A detailed chemical kinetic model for oxidation of C2H4 in the intermediate temperature range and high pressure has been developed and validated experimentally. New ab initio calculations and RRKM analysis of the important C2H3 + O2 reaction was used to obtain rate coefficients over a wide range of conditions (0.003-100 bar, 200-3000 K). The results indicate that at 60 bar and medium temperatures vinyl peroxide, rather than CH2O and HCO, is the dominant product. The experiments, involving C2H4/O2 mixtures diluted in N2, were carried out in a high pressure flow reactor at 600-900 K and 60 bar, varying the reaction stoichiometry from very lean to fuel-rich conditions. Model predictions are generally satisfactory. The governing reaction mechanisms are outlined based on calculations with the kinetic model. Under the investigated conditions the oxidation pathways for C2H4 are more complex than those prevailing at higher temperatures and lower pressures. The major differences are the importance of the hydroxyethyl (CH2CH2OH) and 2-hydroperoxyethyl (CH2CH2OOH) radicals, formed from addition of OH and HO2 to C2H4, and vinyl peroxide, formed from C2H3 + O2. Hydroxyethyl is oxidized through the peroxide HOCH2CH2OO (lean conditions) or through ethenol (low O2 concentration), while 2-hydroperoxyethyl is converted through oxirane.  相似文献   

4.
A γ-Fe2O3/SiO2/chitosan composite was prepared by water-in-oil emulsification, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Effects of various factors, including adsorbent dosage, initial dye concentration, solution pH, and competing anions, on the adsorption of methyl orange from aqueous solutions by the resulting composite were studied by batch adsorption experiments. The adsorption kinetics was found to follow the pseudo-second-order kinetic model, and intraparticle diffusion was related to the adsorption, but not as a sole rate-controlling step. The equilibrium adsorption data were well described by the Freundlich isotherm model. Evaluation of the thermodynamic parameters ΔG°, ΔH°, and ΔS° revealed that the adsorption process was naturally feasible, spontaneous, and exothermic. The composite was proven to be efficient, suitable and promising for the removal of methyl orange from aqueous solutions since it has a relatively higher adsorption capacity than other low-cost adsorbents.  相似文献   

5.
In this article, the isomerisation mechanisms of HN(NO2)2 to O2NNN(O)OH without and with catalyst X (X = H2O, (H2O)2, (H2O)3, HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X (X = H2O, (H2O)2, (H2O)3, HCOOH, H2SO4 and CH3CH2COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X (X = H2O, (H2O)2 and (H2O)3)-assisted transition states, as well as different values of pKa for H2SO4, HCOOH and CH3CH2COOH. Very interesting is also the fact that H2SO4-assisted reaction is the most favourable for the hydrogen transfer from HN(NO2)2 to O2NNN(O)OH, due to the smallest pKa (?3.0) value of H2SO4 than H2O, HCOOH, H2SO4 and CH3CH2COOH, and also because of the largest ∠X???H???Y (the angle between the hydrogen bond donor and acceptor) involved in H2SO4-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO2)2 to O2NNN(O)OH, the apparent activation energy of H2SO4-assisted channel also reduces by 9.6 kcal?mol?1, indicating that H2SO4 can affect the isomerisation of HN(NO2)2 to O2NNN(O)OH, most obvious among all the catalysts H2O, (H2O)2, (H2O)3, HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2.  相似文献   

6.
Surface chemistry of a commercial activated carbon (AC) and of products oxidized in liquid phase using aqueous solutions of a series of oxidizing agents (H2SO4, HNO3, HClO4, H2O2, O3, ClO2, KlO4 and KMnO4) has been studied by FT-IR. Oxidation led to surface groups and structures which, and also the extend of formation, depended on the oxidizing agent and the pH and concentration of the solution used. Most oxidizing agents proved to be effective for the formation of surface C[dbnd]O groups. Variations in pH of solutions of H2O2, KlO4 and KMnO4 unequally affected the oxidation of AC. This was unfavourable with the increase in concentration of the solutions of HNO3 and KMnO4. The reverse was noted with KlO4.  相似文献   

7.
Abstract

A systematic investigation of the brazing of Al2O3 to Kovar® (Fe–29Ni–17Co wt.%) using the active braze alloy (ABA) Ag–35.25Cu–1.75Ti wt.% has been undertaken to study the chemical reactions at the interfaces of the joints. The extent to which silica-based secondary phases in the Al2O3 participate in the reactions at the ABA/Al2O3 interface has been clarified. Another aspect of this work has been to determine the influence of various brazing parameters, such as the peak temperature, Tp, and time at Tp, τ, on the resultant microstructure. As a consequence, the microstructural evolution of the joints as a function of Tp and τ is discussed in some detail. The formation of a Fe2Ti layer on the Kovar® and its growth, along with adjacent Ni3Ti particles in the ABA, dominate the microstructural developments at the ABA/Kovar® interface. The presence of Kovar® next to the ABA does not change the intrinsic chemical reactions occurring at the ABA/Al2O3 interface. However, the extent of these reactions is limited if the purity of the Al2O3 is high, and so it is necessary to have some silica-rich secondary phase in the Al2O3 to facilitate the formation of a Ti3Cu3O layer on the Al2O3. Breakdown of the Ti3Cu3O layer, together with fracture of the Fe2Ti layer and separation of this layer from the Kovar®, has been avoided by brazing at temperatures close to the liquidus temperature of the ABA for short periods of time, e.g., for Tp between 820 and 830 °C and τ between 2 and 8 min.  相似文献   

8.
The partial discharge in SF6-insulated equipment produces characteristic decomposition products: SO2 and H2S. The characteristic decomposition products vastly speed up the process of discharge faults. Based on density functional theory (DFT) calculation, single layer Pd-doped MoS2 (Pd-MoS2) is adopted as the adsorbent to adsorb SO2 and H2S to ensure the operational stability of SF6-insulated equipment. The adsorption energy, charge transfer and structure parameters of SF6, H2S, and SO2 adsorption on the Pd-MoS2 monolayer are analysed to find the most stable adsorption structure. The molecular orbital theory, total density of states and partial density of states are studied to analyse the adsorption mechanism. The results show that Pd-MoS2 adsorbent possesses high catalytic activity and excellent adsorption performance to H2S and SO2 by strong chemical adsorption. This study is of great significance to ensure the operational stability of SF6-insulated equipment by removing these characteristic decomposition products.  相似文献   

9.
In this study, the NiFe2O4 nanoparticles have been prepared by co-precipitation and calcination process. Using a vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometer of X-ray (EDX), and X-ray photoelectron spectroscopy (XPS), the samples obtained by co-precipitation and then by further calcination have been analyzed. The experimental results show that the precursor synthesized by co-precipitation is the composite of both amorphous FeOOH and Ni(OH)2, but has no amorphous NiFe2O4. The results of both EDX and XPS revealed that the FeOOH species is wrapped up by Ni(OH)2 species. In the calcination process, the amorphous composite is dehydrated and transformed gradually into crystalline NiFe2O4 nanoparticles, with the metal ions diffusing. The reaction is different from the one used to prepare other ferrite (e.g., CoFe2O4, MnFe2O4, Fe3O4, etc.) nanoparticles directly by co-precipitation. With increasing calcination temperature, the NiFe2O4 grains grow and the magnetization is enhanced.  相似文献   

10.
Structures of several premixed ethylene-oxygen-argon rich flat flames burning at 50 mbar have been established by using molecular beam mass spectrometry in order to investigate the effect of CO2, or NH3, or H2O addition on species concentration profiles. The aim of this study is to examine the eventual changes of profiles of detected hydrocarbon intermediates which could be considered as soot precursors (C2H2, C4H2, C5H4, C5H6, C6H2, C6H4, C6H6, C7H8, C6H6O, C8H6, C8H8, C9H8 and C10H8). The comparative study has been achieved on four flames with an equivalence ratio (f) of 2.50: one without any additive (F2.50), one with 15% of CO2 replacing the same quantity of argon (F2.50C), one with 3.3% of NH3 in partial replacement of argon (F2.50N) and one with 13% of H2O in replacement of the same quantity of argon (F2.50H). The four flat flames have similar final flame temperatures (1800 K).CO2, or NH3, or H2O addition to the fresh gas inlet causes a shift downstream of the flame front and thus flame inhibition. Endothermic processes CO2 + H = CO + OH and H2O + H = H2 + OH are responsible of the reduction of the hydrocarbon intermediates in the CO2 and H2O added flames through the supplementary formation of hydroxyl radicals. It has been demonstrated that such processes begin to play at the end of the flame front and becomes more efficient in the burnt gases region.The replacement of some Ar by NH3 is responsible only for a slight decrease of the maximum mole fraction of C2H2, but NH3 becomes much more efficient for C4H2 and C5 to C10 species. Moreover, the efficiency of NH3 as a reducing agent of C5 to C10 intermediates is larger than that of CO2 and H2O for equal quantities added.  相似文献   

11.
The reactivity of the (0 0 0 1)-Cr–Cr2O3 surface towards water was studied by means of periodic DFT + U. Several water coverages were studied, from 1.2H2O/nm2 to 14.1H2O/nm2, corresponding to ¼, 1, 2 and 3 water/Cr at the (0 0 0 1)-Cr2O3 surface, respectively. With increasing coverage, water gradually completes the coordination sphere of the surface Cr atoms from 3 (dry surface) to 4 (1.2 and 4.7H2O/nm2), 5 (9.4H2O/nm2) and 6 (14.1H2O/nm2). For all studied coverages, water replaces an O atom from the missing above plane. At coverages 1.2 and 4.7H2O/nm2, the Cr–Os (surface oxygen) acid–base character and bond directionality govern the water adsorption. The adsorption is molecular at the lowest coverage. At 4.7H2O/nm2, molecular and dissociative states are isoenergetic. The activation energy barrier between the two states being as low as 12 kJ/mol, allowing protons exchanges between the OH groups, as evidenced by ab inito molecular dynamics at room temperature. At coverages of 9.4 and 14.1H2O/nm2, 1D- (respectively, 2D-) water networks are formed. The resulting surface terminations are –Cr(OH)2 and –Cr(OH)3– like, respectively. The increased stability of those terminations as compared to the previous ones are due to the stabilization of the adsorbed phase through a H-bond network and to the increase in the Cr coordination number, stabilizing the Cr (t2g) orbitals in the valence band. An atomistic thermodynamic approach allows us to specify the temperature and water pressure domains of prevalence for each surface termination. It is found that the –Cr(OH)3-like, –Cr(OH)2 and anhydrous surfaces may be stabilized depending on (TP) conditions. Calculated energies of adsorption and OH frequencies are in good agreement with published experimental data and support the full hydroxylation model, where the Cr achieves a 6-fold coordination, at saturation.  相似文献   

12.
The nature of antimony-enriched surface layer of Fe-Sb mixed oxides   总被引:1,自引:0,他引:1  
Antimony segregation is a common feature in Fe-Sb mixed oxides, which have been widely applied as catalysts in selective oxidation and ammoxidation reactions. This paper attempts to shed a light on the cause of such a common feature and on the nature of the antimony-enriched surface layer over FeSbO4 by means of XPS surface analysis. Single-phase FeSbO4 samples prepared by different methods were studied, and the antimony in their surface layer is a mixture of both Sb5+ and Sb3+ rather than single Sb5+. Their surface composition is close to FeSb2O6, which could be described as (FeSbO4)(Sb2O4)δ, δ = 0.5, and it is not “Fe(II)Sb(V)2O6” as suggested in literature. Fe-Sb mixed oxides with Sb/Fe > 1 (mol/mol) are mixtures of FeSbO4 and Sb2O4, and the surface of FeSbO4 grains would be a layer of (FeSbO4)(Sb2O4)δ, δ ≥ 0.5. Fe-Sb mixed oxides with Sb/Fe < 1 are mixtures of FeSbO4 and Fe2O3, and the surface of FeSbO4 grains would be a layer of (FeSbO4)(Sb2O4)δ, δ ≤ 0.5, but the remaining Fe2O3 would be encapsulated by a layer of FeSbO4.  相似文献   

13.
In order to elucidate how oxygen content changes in Nd2 − xSrxNiO4 + δ (x = 0, 0.2, 0.4), defect chemical and statistical thermodynamic analyses were carried out. The relationship among δ, P(O2), and T were analyzed by a defect equilibrium model. Since Nd2 − xSrxNiO4 + δ shows metal like band conduction at high temperatures, chemical potential of hole is expressed by the integration of the Fermi-Dirac distribution function and the density of state. The nonstoichiometric variation of oxygen content in Nd2 − xSrxNiO4 + δ can be explained by the defect equilibrium model with a regular solution approximation. Partial molar entropy and partial molar enthalpy of oxygen are calculated from the nonstoichiometric data and Gibbs–Helmholtz equation. The relationship among defect structure, defect equilibrium, and thermodynamic quantities is elucidated by the statistical thermodynamic model. Thermodynamic quantities are calculated by the statistical thermodynamic model with the results of defect chemical analysis and compared with those obtained from experimental results. Thermodynamic quantities calculated by the statistical thermodynamic model can explain rough tendency of those obtained from the δTP(O2) relationship.  相似文献   

14.
The reduction process of Bi3+, HTeO2+ and their mixtures on Au electrode surface was studied by cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy and chronoamperometry. XRD and EDS methods were also used to measure the reductive products prepared under different potentials and provide the evidences of the reactions. The results indicate that the reduction of HTeO2+ occurs at more positive potential than that of Bi3+, but its reduction rate is slower and adsorption phenomenon exists during its reduction process. Bi2Te3 compound can be obtained potentiostatically at a proper potential in all the mixed solutions with concentration ratio CHTe+O2/CBi3+ in our research range (0.1-10). But pure Bi2Te3 compound can only be obtained at 42 mV in the solution with concentration ratio CHTe+O2/CBi3+ equaling to 1. And the formation of Bi2Te3 compound is an inductive co-depositing process: (1) HTeO2+ + 4e + 3H+ → Te0 + 2H2O, (2) 3Te0 + 2Bi3+ + 6e → Bi2Te3.  相似文献   

15.
常温常压下BiMnO_3纳米粉末的制备与物性分析   总被引:1,自引:0,他引:1       下载免费PDF全文
钙钛矿型BiMnO3是同时具有铁磁性和铁电性的多铁性材料,在传感器,信息存储等方面具有潜在的应用前景.但是它的制备条件非常苛刻,需要高温、高压、密封等,这极大地限制了它的应用与发展.本文采用共沉淀法,以MnCl2·4H2O,Bi2O3,NaOH,HNO3和聚乙二醇为材料,在100℃的水溶液中成功地制备出了BiMnO3材料,此方法大大降低了制备的温度和压强,从而节约了能源,降低了成本.同时利用X射线衍射仪(XRD),透射电子显微镜(TEM),振动样品磁强计(VSM)等对其结构、相貌及磁性等进行了检测,并讨论了制备条件及煅烧温度对BiMnO3物性的影响.  相似文献   

16.
HfO2 films are deposited by atomic layer deposition (ALD) using tetrakis ethylmethylamino hafnium (TEMAH) as the hafnium precursor, while O3 or H2O is used as the oxygen precursor. After annealing at 500℃ in nitrogen, the thickness of Ge oxide's interfacial layer decreases, and the presence of GeO is observed at the H2O-based HfO2 interface due to GeO volatilization, while it is not observed for the O3-based HfO2. The difference is attributed to the residue hydroxyl groups or H2O molecules in H2O-based HfO2 hydrolyzing GeO2 and forming GeO, whereas GeO is only formed by the typical reaction mechanism between GeO2 and the Ge substrate for O3-based HfO2 after annealing. The volatilization of GeO deteriorates the characteristics of the high-κ films after annealing, which has effects on the variation of valence band offset and the C–V characteristics of HfO2/Ge after annealing. The results are confirmed by X-ray photoelectron spectroscopy (XPS) and electrical measurements.  相似文献   

17.
High roughness and a greater number of defects were created by lithium niobate (LN; LiNbO3) processes such as traditional grinding and mechanical polishing (MP), should be decreased for manufacturing LN device. Therefore, an alternative process for gaining defect-free and smooth surface is needed. Chemical mechanical planarization (CMP) is suitable method in the LN process because it uses a combination approach consisting of chemical and mechanical effects. First of all, we investigated the LN CMP process using commercial slurry by changing various process conditions such as down pressure and relative velocity. However, the LN CMP process time using commercial slurry was long to gain a smooth surface because of lower material removal rate (MRR). So, to improve the material removal rate (MRR), the effects of additives such as oxidizer (hydrogen peroxide; H2O2) and complexing agent (citric acid; C6H8O7) in a potassium hydroxide (KOH) based slurry, were investigated. The manufactured slurry consisting of H2O2-citric acid in the KOH based slurry shows that the MRR of the H2O2 at 2 wt% and the citric acid at 0.06 M was higher than the MRR for other conditions.  相似文献   

18.
A novel flower-shaped Bi2O3 superstructure has been successfully synthesized by calcination of the precursor, which was prepared via a citric acid assisted hydrothermal process. The precursor and Bi2O3 were characterized with respect to morphology, crystal structure and elemental chemical state by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was shown that both the precursor and Bi2O3 flower-shaped superstructure were constructed of numerous nanosheets while the nanosheets consisted of a great deal of nanoparticles. Furthermore, key factors for the formation of the superstructures have been proposed; a mechanism for the growth of the superstructure has been presented based on the FESEM investigation of different growth stages.  相似文献   

19.
The mechanism and kinetics of the reaction of hydrogen sulphide (H2S(1A1)) with hydroperoxyl radical (HO2(2A″)) on the lowest doublet potential energy surface have been theoretically studied. The potential energy surface for possible pathways has been investigated by employing Complete Basis Set (CBS), DFT, and CCSD(T) methods. Three possible pathways are suggested for the title reaction. The most probable entrance channel consists of formation of a hydrogen-bonded pre-reaction complex (vdw1) and two energised intermediates. Multichannel RRKM-Steady State Approximation and CVT calculations have been carried out to compute the rate constants over a broad range of temperature from 200?K to 3000?K to cover the atmospheric and combustion conditions and pressure from 0.1 to 2000?Torr. No sign of pressure dependence was observed for the title reaction over the stated range of pressure. We have shown that the major products of the title reaction are H2O2 and SH while at higher temperatures, formation of the other products such as H2O, HOS, HSOH and OH are feasible, too. Our calculated overall rate constant is in agreement with the reported experimental data in the literature.  相似文献   

20.
谢伟  王银海  全军  邹长伟  梁枫  邵乐喜 《物理学报》2014,63(1):16101-016101
采用高温固相法制备了发光样品Y1.98O3:Eu3+0.01,Dy3+0.01.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、荧光光谱仪、单光子计数器测试了不同含量的H3BO3对Y1.98O3:Eu3+0.01,Dy3+0.01物相结构、颗粒形貌、发光性能、余辉性能的影响.结果表明当H3BO3含量低于8%(mol)时,样品可保持Y2O3晶格结构,且样品颗粒随H3BO3的含量增加逐渐增大.样品光致发光由Eu3+离子电子的5D0→7FJ跃迁所致,主峰位于612 nm,且发光强度随H3BO3含量的增加呈线性增强.随着H3BO3含量的增加,样品余辉衰减时间逐渐增加,热释光谱分析表明H3BO3的加入增加了基质陷阱能级的深度与浓度,故而导致样品长余辉性能的变化.  相似文献   

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