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First-principles calculations are performed on the influence of transition metal(TM=Cr, Mn, Fe, Co) as codopants on the electronic structure and visible-light absorption of Zn-doped Sr TiO_3. The calculated results show that(Zn,Mn)-codoped Sr TiO_3 requires the smallest formation energy in four codoping systems. The structures of the codoped systems display obvious lattice distortion, inducing a phase transition from cubic to rhombohedral after codoping. Some impurity Cr, Mn and Co 3d states appear below the bottom of conduction band and some Fe 3d states are located above the top of valence band, which leads to a significant narrowing of band gap after transition metal codoping. The enhancement of visible-light absorption are observed in transition metals(TM=Cr, Mn, Fe, Co) and Zn codoped Sr TiO_3 systems. The prediction calculations suggested that the(Zn,Mn)-and(Zn,Co)-codoped SrTiO_3 could be the desirable visible-light photocatalysts.  相似文献   
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煤结构是煤化学的重要研究内容,优质肥煤在我国属于稀缺炼焦煤种。碳是煤结构的基本骨架,是构成煤中有机质及形成焦炭的主要元素。研究高硫肥煤中的碳结构对认知肥煤结构与性质,提高低品质炼焦煤利用效率具有重要意义。采集并制备山东东滩(DT)和山西水峪(SY)、霍州(HZ)、高阳(GY)四个矿区的肥煤样品,利用X-射线衍射(XRD)、傅里叶变换红外光谱(FTIR)以及 X-射线光电子能谱(XPS)对煤中碳结构进行谱学表征和联合解析,结合煤质分析结果,计算不同肥煤样品的碳结构参数。研究结果表明:SY,HZ,GY和DT四种肥煤的芳香度fa-XRD依次增大,芳香层片的延展度Lc和堆垛高度La依次减小,山西煤的芳香碳结构层片在排列规整度和芳香环缩合程度上强于东滩煤。DT和GY煤中芳香烃结构主要以苯环五取代、苯环四取代和苯环三取代形式存在,SY与HZ煤中芳香结构以苯环二取代和苯环四取代为主。DT和GY煤含有较多的支链和较高的芳环缩合度。四种肥煤中脂肪结构均是以亚甲基为主,DT,SY,HZ和GY煤的亚甲基占脂肪结构的比例分别为46.27%,48.89%,44.21%和41.85%,煤中含有较多的烷基侧链。GY与DT煤中甲基含量略高于次甲基,SY和HZ煤则相反,这主要与不同煤样在成烃期间长脂肪族结构发生断裂的程度有关。SY,HZ,GY和DT煤的芳碳率分别为0.83,0.81,0.74和0.68,芳氢率分别为0.51,0.43,0.34和0.29,煤中芳构化程度依次减小,芳香环缩合度依次升高。DT和HZ煤的氧化程度较高,DT煤含有较多的C-O结构,判断DT煤中存在较多不易被热分解或不易起化学反应的非活性氧。  相似文献   
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将超声辐射无皂乳液聚合作用于含有2-丙烯酰胺基-2-甲基丙磺酸(AMPS)和甲基丙烯酸甲酯(MMA)的水溶液中,在不加任何引发剂和乳化剂的条件下合成AMPS/MMA二元共聚高分子微球,考察了超声反应时间对单体转化率的影响,用FTIR、TGA-DSC、TEM和粒度分析仪等技术进行了表征,并初步探讨了聚合反应机理。结果表明,合成得到的高分子微球粒径在0.77μm左右,分散均匀,且具有较好的热稳定性  相似文献   
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为了探究煤中噻吩类有机硫化合物降解规律,采用密度泛函理论搜索过渡态提出了两条反应路径。通过对反应路径中各物种的原子电荷、热力学、动力学参数和噻吩降解的势能剖面图分析得出:各路径发生的难易程度是不同的,噻吩降解的最有利的反应路径为Path1,即首先是H9转移到S5上,接着H8从C3转移到C4上伴随着C4-S5键的断裂,然后H6转移到S5上,最后随着H7从C2转移到C1上,H2S离开原来的结构,丁二炔形成。利用密度泛函理论对煤中噻吩类含硫模型化合物在不同降解路径中的变化规律进行研究,可以有助于理解煤中噻吩硫的脱除机理,为煤中噻吩类有机硫的脱除实验及工业处理过程提供理论指导。  相似文献   
5.
利用XPS分析方法表征煤中有机硫组分,选择与煤中有机硫结构相关的模型化合物,通过同轴传输反射法测试模型化合物介电性质,为微波脱除煤中有机硫的应用提供理论依据。研究表明,山西高硫炼焦煤中有机硫主要以三种形态赋存:硫醇(醚)类、噻吩类和(亚)砜类。三类有机硫模型化合物对微波能吸收最强频段基本在9-12GHz范围内,在理论上,该频段是在微波作用下脱除煤中有机硫的最佳频率条件。当模型化合物中具有不同有机含硫基团时,在低频段对微波的响应值得深入研究。  相似文献   
6.
The enhanced magnetic and photocatalytic properties of(Fe, Ni)-codoped SrTiO_3 with and without oxygen vacancies are investigated using the first-principles calculations based on the density functional theory plus U calculations. It is revealed that the structure phase transition associated with O vacancy imposes significant influence on magnetic and optical properties. The results show that the Ni oxidation state in(Fe, Ni)-codoped SrTiO_3 is about 2~+, which is different from that of 4~+ in Ni monodoped SrTiO_3 in previous experimental investigations. The presence of O vacancy leads to a semiconductor-half-metal transition in codoped SrTiO_3. The(Fe, Ni)-codoped SrTiO_3 without O vacancy produces an enhanced magnetization and induces a giant magnetic moment of 3 μB, while a relatively small magnetic moment of 0.36 μB is generated in(Fe, Ni)-codoped SrTiO_3 with O vacancy. The origin of the large enhancement of magnetic moment in(Fe, Ni)-codoped SrTiO_3 without O vacancy was ascribed to the reduced hybridization in Fe–O bonds and the enhanced hybridization in Ni–O bonds, which modulated antiferromagnetic spin structure. The dispersion of the conduction bands and valence bands of codoped SrTiO_3 is enhanced after codoping, which benefits the photocatalytic performance. Furthermore, the(Fe, Ni)-codoped SrTiO_3 shows a remarkable red-shift of absorption spectra edge and induces a strong optical absorption in the visible light region, indicating that it could be taken as a potential candidate for photocatalytic materials.  相似文献   
7.
超声无皂乳液聚合制备AMPS/MMA二元共聚微球   总被引:2,自引:0,他引:2  
在不加任何引发剂和乳化剂的条件下,用超声辐射无皂乳液聚合合成了AMPS/MMA二元共聚微球,用FTIR、TGA-DSC、TEM和粒度分析仪等测试技术对产物结构和热性能分别进行了表征和测试,并初步探讨了聚合反应机理. 结果表明,超声波功率为200 W,在45 ℃反应75 min后转化率达83%,合成得到的高分子微球分散均匀,粒径在0.77 μm左右,Tg为120 ℃.  相似文献   
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