Kinetics of C2(a3Πu) radical reactions with NO, N2O, O2, H2 and NH3

Pulsed laser photolysis/laser-induced fluorescence (LP-LIF) is utilized to measure rate constants for C₂(a³Π_u) reactions with NO, N₂O, O₂, H₂ and NH₃. Multiphoton dissociation of C₂Cl₄ at 266 nm is employed for the generation of C₂(a³Π_u) radicals. The C₂(a³Π_u) concentration is monitored by the fluorescence of the (0, 0) band of the (d³Π_g&#8596;a³Π_u) transition at 516.5 nm. C₂(a³Π_u) removal rate constants for the reactions are determined as k_NO = (5.46 ± 0.10) × 10^-11 cm³ molecule^-1 s^-1 , k_N2O = (1.63 ± 0.20) × 10^-13 cm³ molecule^-1 s^-1 , k_N2O = (1.58 ± 0.16) × 10^-11 cm³ molecule^-1 s^-1, k_O2 = (5.92 ± 1.00) × 10^-14 cm³ molecule^-1 s^-1, k_H2< 1.0× 10^-14 cm³ molecule^-1 s^-1. Based on the data analysis and theoretical calculation, we suggest that the C₂(a³Π_u) reactions with H₂ and NH₃ proceed via the hydrogen abstraction mechanism, barriers exist at the entrance channel of the reactions of C₂(a³Π_u) with H₂ and NH₃.     

Tm~(3+)掺杂3CdO·Al_2O_3·3SiO_2玻璃的合成及光谱特性

合成了Tm3+掺杂的3CdO·Al2O3·3SiO2玻璃，对其吸收光谱、激发和发射光谱进行了测试与分析，并根据Judd－Ofelt理论计算了该玻璃中Tm3+离子的辐射跃迁几率、荧光分支比和积分发射截面等光谱参数．     

CO2/DME/CH3OH和CO2/DME/C2H5OH体系的汽液相平衡研究

文中基于对CO₂/DME,DME/CH₃OH,CO₂/CH₃OH和DME/C₂H₅OH体系汽液相平衡研究的文献调查,采用Gibbs-Duhems方程对实验数据做热力学一致性检验和热力学模型评价。研究表明,PR-NRTL模型组合对四个体系都有良好的表现。进而基于通过检验的二元体系数据拟合了5个组合的NRTL模型的交互作用参数,并以此模型研究了CO₂ /DME/CH₃OH和CO₂/DME/C₂H₅OH两个三元体系。计算给出的CH₃OH/DME/CO₂体系的VLE数据与文献值偏差很小,表明此PR NRTL模型组合能较好地描述其高压下的VLE行为,在此基础上对C₂ H₅OH/DME/CO₂体系的VLE行为进行了预测,给出了VLE相图。     

Ni(puH)2(ClO4)2·3H2O的空间结构与磁矩分析

针对Nikulski等人合成的Ni(puH)2(ClO4)2·3H2O配合物,我们利用配位场的方法进行了理论计算,确定了该配合物的空间构型为C2v,得出了各吸收谱的理论归属与相应的晶体场参数,在C2v对称下,求得了该络合物的磁矩(μeff=3.04)与实验测定一致(误差为3.4%),从而说明了,我们确定的该配合物的空间对称是正确的.     

Fe_2(SO_4)_3·xH_2O催化合成乙酸正丁酯

以Fe_2(SO_4)_3·xH_2O为固体催化剂,由乙酸和正丁醇合成乙酸正丁酯。讨论了催化酯化的各种影响因素,确立了合成乙酸正丁酯的最佳工艺条件。本工艺特点:催化剂用量少,反应时间短,反应条件温和,酯收率高。     

XPS研究BF_3·OEt_2对HZSM—5沸石的脱铝作用

用XPS技术以及 X 射线微区分析法研究BF_3·OEt_2改性HZSM—5的表面组成特征,结果表明:BF_3·OEt_2对 HZSM—5沸石浅表面有明显的脱铝作用,而且可去除阻塞沸石孔道中的无机硅、铝杂质,但对骨架中的硅无作用;改性催化剂表面硅铝比明显提高,甲苯歧化反应活性和对二甲苯选择性均优于改性前 HZSM—5。     

Characteristic parameters and operational curves of γ-Al2O3 nanofiltration membranes

The γ-Al2O3 nanofiltration membranes were manufactured by the sol-gel technique. The result of N2 adsorption and desorption test indicates that the characteristic parameters of the membranes: BJH desorption average pore diameter, BJH desorption cumulative volume of pores and BET surface area are about 3.9 nm, 0.33 cm^3/g and 245 m^3/g respectively, and the pore size distribution is very narrow.The operational curves of γ-Al2O3 nanofiltration membranes of the Ca^2 retention rate vs the trans-membrane pressure,feed concentration of solution treated and pH of solution treated were studied for the first time. It is found that the retention rate for Ca2~ increases with the transmembrane pressure increasing and decreases with the feed concentration of CaCl2 solution increasing. The retention of Ca^2 is very rmuch dependent on the pH of the solution. Minima Ca^2 retention rate is found at the isoelectric point (pH=7.5).     

助剂及载体对MoO3,MxOy/SiO2催化剂性质及甲烷部分氧化性能的影响

在常压下 ,以氧气为氧化剂 ,用两种不同制法的载体分别制备催化剂 (MoO3 ·MxOy/SiO2 ) ,用于甲烷部分氧化反应 ,对比结果表明用醇盐法所制SiO2 (ZSiO2 )做成的催化剂比用市售SiO2 (QSiO2 )做成的催化剂反应活性和选择性好 ,助剂V2 O5加入提高了CH4 转化率和CO2 ,CO选择性 ,降低了HCHO产率和选择性 ,B2 O3 加入提高了CH4 转化率 ,HCHO产率和其选择性 ,降低了CO2 ,CO选择性 ,TPR结果表明载体ZSiO3 的应用减少了载体表面弱酸性位 ,但助剂V2 O5和B2 O3 的加入使MoO3 与ZSiO2 发生了不同的相互作用 ,从而影响了催化剂表面的活性氧物种 ;NH3 TPD结果表明载体ZSiO3 的应用及助剂B2 O3 的加入增加了催化剂表面弱酸性位     

Ni(puH)_2(ClO_4)_2·3H_2O中Ni~(2+)的晶位对称与谱分析

针对Mikulski等人合成的Ni（puH）2（ClO4）2·3H2O配合物，利用配位场的方法进行了理论计算，确定了该配合物的空间构型为C2v，得出了各吸收谱的理论归属与相应的晶场参数，在C2v对称下，求得了该配合物的磁矩（μcef＝3．04）与实验测定一致（误差为3．4％），从而说明了确定的该配合物的空间对称是正确的。     

Density functional theory study of the reaction paths of reactions of CH3C(O)O2 radicals with HO2 in the gas phase

A DFT study on the reactions between CH₃C(O)O₂ and HO₂ radicals has been carried out. It is suggested that both the triplet and singlet potential surfaces involve a complex mechanism with the formation of loosely bound intermediate complexes of reactants and products. The reaction prefers to occur on the triplet surface to produce peracetic acid (CH₃C(O)O₂H) and triplet O₂ molecule. The CH₃C(O)O₂H can further convert into CH₃C(O)O and HO radicals.     

Density functional theory study of the reaction paths of reactions of CH3C(O)O2 radicals with HO2 in the gas phase

A DFT study on the reactions between CH₃C(O)O₂ and HO₂ radicals has been carried out. It is suggested that both the triplet and singlet potential surfaces involve a complex mechanism with the formation of loosely bound intermediate complexes of reactants and products. The reaction prefers to occur on the triplet surface to produce peracetic acid (CH₃C(O)O₂H) and triplet O₂ molecule. The CH₃C(O)O₂H can further convert into CH₃C(O)O and HO radicals.     

Kinetics of C_2(a~3Π_u)radical reactions with NO,N_2O,O_2,H_2 and NH_3

Pulsed laser photolysis/laser-induced fluorescence (LP-LIF) is utilized to measure rate constants for C_2(a~3(multiply from)_u) reactions with NO, N_2O, O_2, H_2 and NH_3. Multiphoton dissociation of C_2CI_4 at 266 nm is employed for the generation of C_2(a~3(multiply from)_u) radicals. The C_2(a~3(multiply from)_u) concentration is monitored by the fluorescence of the (0, 0) band of the (d~3(multiply from)_g←→a~3(multiply from)_u) transition at 516.5 nm. C_2(a~3(multiply from)_u) removal rate constants for the reactions are determined as k_(NO)=(5.46±0.10)×10~(-11)cm~3molecule~(-1)s~(-1), k_(N_2O)=(1.63±0.20)×10~(-13)cm~3molecule~(-1)s~(-1), k_(N_2O)=(1.58±0.16)×10~(-11)cm~3molecule~(-1)s~(-1), k_(O_2)=(5.92±1.00)×10~(-14)cm~3molecule~(-1)s~(-1), k_(H_2)<1.0×10~(-14)cm~3molecule~(-1)s~(-1). Based on the data analysis and theoretical calculation, we suggest that the C_2(a~3(multiply from)_u) reactions with H_2 and NH_3 proceed via the hydrogen abstraction mechanism, barriers exist at the entr     

Preparation and luminescence properties of YeO3：Er^3＋/TiO2 with high specific surface area

The three composites Y2O3 :Er3+ , Y2O3 :Er3+ /Yb 3+ andY2O3 :Er3+ /TiO2 were prepared using coprecipitation and sol-gel techniques. Their morphology, specific surface area, porosity, UV-vis. absorption spectra and fluorescence spectra were measured using SEM, TEM, surface analysis, UV-vis. absorption and photoluminescence spectrophotometry. SEM and TEM showed that samples prepared using coprecipitation were dispersed, while Y2O3 :Er3+ /TiO2 particles possessed a mesoporous surface and average diameter of ab...     

Microstructure and wear resistance of PTA clad Cr7C3/γ-Fe ceramal composite coating

A wear resistant Cr₇C₃/γ-Fe ceramal composite coating was fabricated on substrate of the hardening and tempering C degree steel by PTA (plasma transferred arc) cladding with (wt%) Fe-25Cr-7C elemental powder blends. Microstructure of the coating was characterized by OM, SEM, XRD and EDS. Wear resistance of the coating was tested under dry sliding wear condition at room temperature. The results indicate that the PTA clad ceramal composite coating has a rapidly solidified fine microstructure consisting of Cr₇C₃ primary particles uniformly distributed in the γ-Fe matrix and is metallurgically bonded to the C degree steel substrate. The PTA clad Cr₇C₃/γ-Fe ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test conditions. The excellent wear resistance of the Cr₇C₃/γ-Fe ceramal composite coating is attributed to the coating’s high hardness, strong covalent atomic bonding and refined microstructure.     

Microstructure and wear resistance of PTA clad Cr7C3/γ-Fe ceramal composite coating

A wear resistant Cr₇C₃/γ-Fe ceramal composite coating was fabricated on substrate of the hardening and tempering C degree steel by PTA (plasma transferred arc) cladding with (wt%) Fe-25Cr-7C elemental powder blends. Microstructure of the coating was characterized by OM, SEM, XRD and EDS. Wear resistance of the coating was tested under dry sliding wear condition at room temperature. The results indicate that the PTA clad ceramal composite coating has a rapidly solidified fine microstructure consisting of Cr₇C₃ primary particles uniformly distributed in the γ-Fe matrix and is metallurgically bonded to the C degree steel substrate. The PTA clad Cr₇C₃/γ-Fe ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test conditions. The excellent wear resistance of the Cr₇C₃/γ-Fe ceramal composite coating is attributed to the coating’s high hardness, strong covalent atomic bonding and refined microstructure.     

Activity coefficient of NiO in SiO2-saturated MnO–SiO2slag and Al2O3-saturated MnO–SiO2–Al2O3slag at 1623 K

As a part of the fundamental study related to the reduction smelting of spent lithium-ion batteries and ocean polymetallic nodules based on MnO–SiO₂slags,this work investigated the activity coefficient of NiO in SiO₂-saturated Mn O–Si O₂slag and Al₂O₃-saturated Mn O–SiO₂–Al₂O₃slag at 1623 K with controlled oxygen partial pressure levels of 10^-7,10^-6,and 10^-5Pa.Results showed that the solubility of nickel oxide in the slags increased with increasing oxygen partial pressure.The nickel in the Mn O–Si O₂slag and Mn O–Si O₂–Al₂O₃slag existed as Ni O under experimental conditions.The addition of Al₂O₃in the Mn O–Si O₂slag decreased the dissolution of nickel in the slag and increased the activity coefficient of Ni O.Furthermore,the activity coefficient of Ni O(γN_(i O)),which is solid Ni O,in the Si O₂saturated Mn O–Si O₂slag and Al₂O₃saturated Mn O–Si O₂–Al₂O₃slag at 1623 K can be respectively calculated asγN_(i O)=8.58w(Ni O)+3.18 andγN_(i O)=11.06w(Ni O)+4.07,respectively,where w(Ni O)is the Ni O mass fraction in the slag.     

Microstructure and properties of Ag–Ti3SiC2 contact materials prepared by pressureless sintering

Ti₃SiC₂-reinforced Ag-matrix composites are expected to serve as electrical contacts. In this study, the wettability of Ag on a Ti₃SiC₂ substrate was measured by the sessile drop method. The Ag–Ti₃SiC₂ composites were prepared from Ag and Ti₃SiC₂ powder mixtures by pressureless sintering. The effects of compacting pressure (100–800 MPa), sintering temperature (850–950℃), and soaking time (0.5–2 h) on the microstructure and properties of the Ag–Ti₃SiC₂ composites were investigated. The experimental results indicated that Ti₃SiC₂ particulates were uniformly distributed in the Ag matrix, without reactions at the interfaces between the two phases. The prepared Ag–10wt%Ti₃SiC₂ had a relative density of 95% and an electrical resistivity of 2.76×10-3 mΩ·cm when compacted at 800 MPa and sintered at 950℃ for 1 h. The incorporation of Ti₃SiC₂ into Ag was found to improve its hardness without substantially compromising its electrical conductivity; this behavior was attributed to the combination of ceramic and metallic properties of the Ti₃SiC₂ reinforcement, suggesting its potential application in electrical contacts.     

Effects of baria on propane oxidation activity of Pd/Al2O3 catalyst: Pd–BaO interactio n and reaction routes

The BaO-modified Pd/Al2O3exhibits much better catalytic activity than Pd/Al2O3for C3H8 oxidation both before and after the hydrothermal aging treatment. Further studies ascribe its good activity to the influence of BaO species on the physicochemical characteristics of the catalyst and the reaction routes. Firstly, the BaO species inhibits the phase transformation of alumina, resulting in higher surface area of the catalysts and hereby a better dispersion of Pd. Secondly, the basic nature and electron-withdrawing effect of barium oxide maintain palladium at high oxidation state, which leads to a higher PdO content on surface of the BaO-modified catalyst. Finally, the formation/decomposition of carbonate/bicarbonate species can be promoted by the addition of BaO, which provide extra reaction routes and are important for the deep oxidation of C3H8.