分光光度法测定K2FeO4在浓KOH溶液中的稳定性

采用分光光度法研究了K2FeO4在浓KOH溶液中的稳定性.研究发现,在室温25℃下,K2FeO4在浓碱中的稳定性主要受KOH溶液的碱度和其浓度两方面影响.OH-浓度的增大将阻碍FeOOH的生成,而FeOOH对K2FeO4的分解具有催化作用.     

BaFeO4在干燥环境中的分解机理

为深入了解BaFeO4在干燥环境中的稳定性及分解机理,采用恒流放电、X射线光电子能谱(XPS)、X射线衍射(XRD)、红外吸收光谱(IR)等测试手段研究了BaFeO4在不同处理方法后的放电性能和结构性质.恒流放电结果显示,BaFeO4的放电性能随着其放置时间的延长而不断降低;XPS结果证实BaFeO4样品在干燥环境中放置时会逐渐分解为低价态铁盐,并讨论了其可能分解机理.     

K2FeO4扣式电池中电解液的含量对其放电性能的影响

为了解K2FeO4扣式电池的放电性能和电解液含量对其放电性能的影响,本文自制并采用恒流放电手段测试了含有不同含量饱和KOH电解液的K2FeO4扣式电池的放电性能.恒流放电结果显示,K2FeO4扣式电池中饱和KOH电解液的含量越多,其放电容量越高.     

CoOOH的含量对K2FeO4电极放电性能的影响

本文合成并分析了导电剂CoOOH的结构性质、形貌和电性能,着重研究了CoOOH的含量对K2FeO4电极放电性能的影响.研究结果表明,K2FeO4电极的放电性能随着CoOOH含量的增大而逐渐增强.     

毛泡桐花黄酮类化合物的稳定性研究

研究了毛泡桐花黄酮类化合物在不同条件下的稳定性,结果表明:自然光对毛泡桐花黄酮有一定的降解作用;温度对其稳定性影响不明显;碳水化合物对该黄酮类化合物的稳定性有一定的影响;产品在pH=5—6的弱酸性条件下比较稳定,在强酸强碱溶液中不稳定;金属离子K+、Na+、Mg2+、Zn2+、Ca2+对化合物有稳定作用,Al3+、Fe3+影响明显;质量分数为2%的氧化剂H2O2和还原剂Na2SO3对产品稳定性的影响不明显,还原剂Vc的影响较大。     

钛乙烯储氢材料的热力学和动力学性质研究

之前的工作中已经预测了钛乙烯(C_2H_4Ti)储氢的几何结构,本文将继续利用密度泛函理论(DFT)和B_3LYP杂化密度泛函方法来计算之前预测出的C_2H_4Ti(H_2)_n结构中的C_2H_4Ti和H_2反应的焓变和自由能变.通过焓变和自由能变的计算结果,可以看出:钛乙烯在298 K、250 K、200 K下可以稳定的吸附5个氢分子,同时放出大量的热量,生成的C_2H_4Ti(H_2)_n化合物在常温下也具有热力学稳定性.此外,本文通过Gaussian03中的伯恩近似分子动力学(BOMD)方法计算了C_2H_4Ti(H_2)_5化合物在298 K、250 K、200 K三个温度下的动力学性质.通过动力学研究的结果,可以发现钛乙烯分子在常温298 K下储氢时间不长;同时得到钛乙烯分子在200 K下能长时间稳定吸附五个氢分子,这进一步表明降低温度对钛乙烯分子稳定储氢是有利的.     

黄酮化合物的微分脉冲伏安法测定

本文采用微分脉冲伏安法研究了几种黄酮化合物沙苑子甙、水飞蓟宾、葛根素、黄芩甙及芦丁等的电化学性质，结果表明，这几种化合物均有良好的电化学还原活性，但它们的还原行为具有一定的差异，各种化合物的主要还原电流的峰高与浓度均呈良好的线性关系，从而可采用该方法对这几种化合物进行定量测定，并且可在混合体系中测定个别组分的含量。     

复合高铁酸盐在水溶液中稳定性的研究

用分光光度法和循环伏安法研究了复合高铁酸盐在水溶液中的稳定性,考察了静置时间、环境温度和助剂A对复合高铁酸盐稳定性的影响。实验结果表明,通过在复合高铁酸盐溶液中添加稳定助剂A,或降低高铁的储存温度,均可有效抑制复合高铁酸盐在水溶液中的分解速率,延长其储存周期,不同程度的改善其稳定性能;高铁在水溶液中的分解速率随着放置时间的增加而增加,随着助剂A加入量的增加而降低;高铁在水溶液中的循环伏安行为呈现一个单向的不可逆还原过程,其还原电流随着高铁放置时间的增加、溶液中FeO_4~(2-)有效浓度的降低而递减。     

钛乙烯储氢材料的热力学和动力学性质研究

之前的工作中已经预测了钛乙烯（C2H4Ti）储氢的几何结构,本文将继续利用密度泛函理论（DFT）和B3LYP杂化密度泛函方法来计算之前预测出的C2H4Ti(H2)n结构中的C2H4Ti和H2反应的焓变和自由能变。通过焓变和自由能变的计算结果,可以看出：钛乙烯在298K、250K、200K下可以稳定的吸附5个氢分子,同时放出大量的热量,生成的C2H4Ti(H2)n化合物在常温下也具有热力学稳定性。此外,本文通过Gaussian03中的伯恩近似分子动力学（BOMD）方法计算了C2H4Ti(H2)5化合物在298K、250K、200K三个温度下的动力学性质。通过动力学研究的结果,可以发现钛乙烯分子在常温298K下储氢时间不长;同时得到钛乙烯分子在200K下能长时间稳定吸附五个氢分子,这进一步表明降低温度对钛乙烯分子稳定储氢是有利的。     

分光光度法测定K2FeO4 对水中Mn(Ⅱ)的去除效能

采用分光光度法研究投药量、搅拌时间、pH等对K2FeO4去除水中Mn(Ⅱ)效能的影响规律。研究发现,在pH=6和弱碱性条件下,Mn(Ⅱ)的去除率相对较高;K2FeO4与Mn(Ⅱ)的浓度比越大、搅拌时间越长,Mn(Ⅱ)的去除率越高。     

Mössbauer Study of Hexavalent Iron Compounds

Hyperfine Interactions - Six crystalline ferrates(VI): K3Na(FeO4)2, K2FeO4, Rb2FeO4, Cs2FeO4, K2Sr(FeO4)2 and BaFeO4, were studied by Mössbauer spectroscopy. Room-temperature spectra of...     

Quadrupole interactions in tetraoxoferrates (VI)

An applicability of the point charge approach for calculations of quadrupole splittings in Mössbauer spectra of ferrates(VI) was studied. The reasonable correlation between calculated and experimental splittings was observed for the majority of ferrates excepting K₃Na(FeO₄)₂. The comparison of ferrates and chromates was made using calculated nucleus independent coefficient.     

第一性原理计算：锰酸锂掺杂Fe和Co的性质研究

文章基于密度泛函理论的第一性原理计算,研究了LiMn2O4电池材料在掺杂Fe和Co离子时的电子结构和电化学性能。发现Fe\Co取代Mn3+在热力学上是会更加稳定,提升电化学性能。掺杂Fe后,LiMn2O4电池材料晶格参数减小(约0.3%);掺杂Co后,LiMn2O4电池材料晶格参数减小(约0.5%)。这两种掺杂方式让与之相邻的Mn3+被氧化成Mn4+,从而降低了Jahn-Teller畸变情况产生可能性。对于掺Fe尖晶石型锰酸锂(Li8Mn15FeO32),Mn环境中的Li离子会更容易被提取,第一次放电电压从原来的3.7V增加至4.623V;对于掺Co尖晶石型锰酸锂(Li8Mn15CoO32),第一次放电电压从原来的3.7V增加至4.101V。研究为锂电池电容量研究提供理论数据的参考。     

The Fe/ZnO(0 0 0 1) interface: Formation and thermal stability

The room temperature growth mode and the interface reaction of Fe films on single crystalline ZnO(0 0 0 1) substrates prepared in ultra high vacuum (UHV) has been investigated by means of X-ray photoelectron and Auger electron spectroscopy (XPS, AES), low energy electron diffraction (LEED) and low energy ion scattering spectroscopy (LEIS). The results show that Fe grows in the pseudo layer-by-layer mode. At ambient temperature the deposited Fe film reduces the underlying ZnO single crystal resulting in FeO at the interface and metallic Zn, which partially diffuses into the remaining Fe overlayer. Annealing leads to a stepwise oxidation of the Fe to FeO (670 K) and Fe₂O₃ (820 K). The Fe₂O₃ mixes with the substrate resulting in two (1 1 1) oriented textures of a spinel phase found by electron backscatter diffraction analysis (EBSD). Fe-based spin-injection may play a vital role for ZnO-based spintronic devices.     

Adsorption of ethylenediamine on clean and oxygen covered Fe/Ni(100) surfaces studied by XPS

The interaction of ethylenediamine with Fe/Ni(100) surfaces oxidized to various extents has been studied in the temperature range 260–450 K by means of X-ray photoelectron Spectroscopy. The use of ~ 1 monolayer of Fe enables us to characterize the oxidation states of the topmost layer atoms unambiguously, based on the XPS spectra using a conventional spectrometer. On clean and c(2 × 2)-O surfaces the ethylenediamine can dissociate the N-H bond at 260 K. On heating the adlayer to 340 K the dissociation was further developed. On the surfaces whose Fe atoms were oxidized to FeO/Ni(100) and further, only molecularly adsorbed species were present at 260 K and desorbed partly without dissociation of the N-H bond after heating to 340 K.     

Berichtigung

The Fe compounds (Et₄N)₂{[((TSP) (TSPH)Fe]₂suc}³) and K[Fe(TSP) (TSPH)prop] · 3H₂O³) were characterized by means of ⁵⁷Fe Moessbauer spectroscopy and magnetic measurements. In the temperature region from 300 to 390 K the Fe(III) of both compounds undergoes a discontinuous transition from low spin state to high spin state, returning only slowly into low spin state after cooling to room temperature. This process causes a hysteresis behaviour of the magnetic values. The spin crossover is connected with a complex isomerization. Moessbauer spectra of the compounds show a significant asymmetry, which can be explained by relaxation effects according to Blume's theory.     

Structure of iron phosphate glasses modified by alkali and alkaline earth additions: neutron and x-ray diffraction studies

The structure of iron phosphate glasses modified by additions of K(2)O and BaO, with nominal molar compositions [(1 - x)(0.6P(2)O(5)-0.4Fe(2)O(3))]xMe(y)O, where x = 0-0.4 in increments of 0.1; Me=K or Ba; and y = 1 or 2, has been investigated using neutron diffraction and x-ray diffraction techniques. Fitted coordination numbers for P-O and Fe-O showed a notable change in the P-O(NBO) and P-O(BO) contributions at greater than 20 mol% modifier addition, with barium producing a markedly larger increase in P-O(NBO) contribution than potassium. Fitting of T(N)(r) and T(X)(r) provided average n(BaO) = 9 and n(KO) = 6. Iron occurs in a range of coordination sites in these glasses: ([6])Fe(2+), ([4])Fe(3+), ([5])Fe(3+) and ([6])Fe(3+). The partitioning between these sites gives average n(FeO) = 5.2-5.8, with barium-doped glasses exhibiting higher average n(FeO) than potassium-doped glasses. The stronger depolymerizing effect of Ba(2+) than K(+) on the phosphate network, coupled with its greater ionic charge and higher Me-O, Fe-O and O···O coordination numbers, explain previously observed divergences in physical properties between the barium-doped and the potassium-doped glasses.     

Mössbauer effect studies on alkali tris (malonato) ferrates(III)

Mössbauer spectra of alkali tris(malonato) ferrates(III) i.e. M₃[Fe(C₃H₂O₄)₃].4H₂O(M=Li, Na, K, NH₄) at 298±2K display a single broad absorption band due to spin lattice relaxation effect. The isomer shift values indicate these complexes to be high spin with octahedral symmetry. The isomer shift shows a decreasing trend with the increase in electronegativity/polarizing power of the substituent cation (Li⁺, Na⁺, K⁺, NH₄ ⁺). A linear correlation between isomer shift values and the (Fe-O) stretching freguencies has also been observed.     

X-ray and Mössbauer study of structural changes in K3Na(FeO4)2

Mixed potassium–sodium ferrate(VI), K₃Na(FeO₄)₂, has been synthesized by precipitation from alkaline solution. At room temperature it decomposes spontaneously giving Fe(III) compounds and ferrate(VI) with a structure similar to that of K₂FeO₄, which is confirmed by X-ray diffraction and Mössbauer spectroscopy.