单斜与锐钛矿双晶相TiO_2/MWNTs复合材料的制备及其可见光光催化活性

以超强耐酸碱的表面活性剂-丁基封端脂肪醇聚氧乙烯醚作为晶型调节剂,利用钛酸丁酯和氢氧化钠的水热反应制备了单斜相与锐钛矿相双晶相TiO2/多壁碳纳米管(简称MWNTs)复合材料,并考察了复合材料的可见光光催化活性。结果显示:MWNTs的加入可调控TiO2的晶相组成,增强TiO2的光催化活性,其中含5%MWNTs的样品具有较高的催化降解效率;随煅烧温度的升高,样品的光催化活性大幅提升。其机理归因于(1)促进单斜相和锐钛矿相双晶相结构的形成;(2)碳纳米管优良的导电作用及碳纳米管/TiO2间的异质结效应;(3)高温下碳纳米管分解产生的碳元素掺杂作用。

单斜与锐钛矿双晶相TiO_2的水热法制备与机理探讨

以一种具有超强耐酸碱的表面活性剂-丁基封端脂肪醇聚氧乙烯醚作为晶型调节剂,利用钛酸丁酯和氢氧化钠的水热反应制备了双晶相(单斜相与锐钛矿相)TiO2,考察了丁基封端脂肪醇聚氧乙烯醚和钛酸丁酯的物质的量比R、反应时间、反应温度等因素对产物的晶相组成的影响,并对不同条件下的晶相转变机理进行了初步探讨。

水淬电炉渣制备双晶相微晶陶瓷的析晶行为

以中钢滨海公司铁镍冶炼排放出的水淬矿热电炉渣为主要原料,通过复配、研磨、成型和高温烧结,制备成双晶相微晶陶瓷烧结体。通过正交实验和单因素实验验证,研究成核剂的添加量、球磨时间和焙烧温度等因素对双晶相微晶陶瓷强度的影响。并利用X-射线衍射分析（XRD）、热分析（TG、DTA（TG-DTA））和扫描电镜（SEM）等测试手段,研究不同焙烧温度下,形成的双晶相微晶陶瓷的物相组成、晶体结构和结晶度的变化规律,结合热分析曲线,讨论温度对电炉渣微晶陶瓷析晶行为的影响。结果表明：烧结温度是影响双晶相微晶陶瓷强度、晶粒尺寸和比例的关键,成核剂能够提高烧结体的强度,促进透辉石相和橄榄石相晶体的共生。当成核剂Mn O2的加入量为5%,在1200℃烧结2 h时,微晶陶瓷样品的抗弯强度可达59.8 MPa,形成晶粒直径2~4μm的短柱状结构透辉石和斜方晶系橄榄石共存的双晶相微晶材料。

Si/SiGe/Si-SOI异质结构的同步辐射双晶貌相术和高分辨三轴晶X射线衍射

运用同步辐射双晶貌相术结合高分辨三轴晶X射线衍射对经原位低温热处理的Si/SiGe/Si SOI异质结构进行研究,发现Si层(004)衍射峰两侧半高宽(FWHMs)处同步辐射双晶形貌像特征存在明显差异.对同步辐射双晶摇摆曲线中Si层(004)衍射峰的不对称性给予了解释,同时阐明了高分辨三轴晶X射线衍射2θω扫描曲线中Si层(004)衍射双峰与Si层衍射结构的对应关系.

基于LiYF_(4):Ln^(3+)(Ln=Tb,Dy)和ZnAl_(2)O_(4):Cr^(3+)双晶相玻璃陶瓷的荧光强度比温度传感特性

采用熔融急冷法在母体玻璃中原位析出四方LiYF_(4)和立方Zn Al_(2)O_(4)两种纳米晶。结构和光谱表征表明Ln^(3+)(Ln=Eu,Tb,Dy)随玻璃原位晶化进入LiYF_(4)晶相,而Cr^(3+)进入ZnAl_(2)O_(4)晶相中,因此发光中心Ln^(3+)和Cr^(3+)实现空间隔离,有效抑制其能量传递,从而同时得到Ln^(3+)和Cr^(3+)的高效发光。此外,利用Ln^(3+)和Cr^(3+)发光对温度的不同响应,实现Ln^(3+)/Cr^(3+)的荧光强度比温度传感。在377 nm波长激发下,Tb^(3+)和Cr^(3+)同时被有效激发,并且Tb^(3+):^(5)D_(4)→^(7)F_(5)和Cr^(3+):2E→4A2能级跃迁强度比呈现出强烈的温度依赖特性,测温相对灵敏度在570 K时达到最大值0.80%·K^(-1);在364 nm波长激发下,Dy^(3+)的^(4)F_(9/2)→^(6)H_(13/2)和Cr^(3+)离子的^(2)E→4A2能级跃迁强度比随温度变化而剧烈变化,测温相对灵敏度在573 K时达到最大值0.86%·K^(-1)。因此,双晶相玻璃陶瓷可有效隔离Ln^(3+)和Cr^(3+)等不同发光中心,同时实现高效发光,有利于荧光强度比光学测温,同时也拓展了玻璃陶瓷材料的应用。

Er^(3+)/Ni^(2+)共掺双相微晶玻璃的结构与发光性能研究

采用熔融法制备了Er3+/Ni^(2+)共掺含Gd F3与Ga_2O_3双晶化相透明微晶玻璃。X射线粉末衍射(XRD)和透射电子显微(TEM)分析表明,平均粒径为34 nm的六方相Gd F3和9 nm的立方相Ga2O3晶粒在玻璃基体中均匀分布。吸收与荧光光谱结果显示,Er3+位于Gd F3纳米晶,Ni^(2+)选择性地进入Ga2O3纳米晶。受益于此,在976 nm激光激发下,透明微晶玻璃具有覆盖1050~1600 nm波段的宽近红外发射带,由位于1210 nm的Ni^(2+):3T2(F)→3A2(F)跃迁转变和位于1530 nm的Er^(3+):4I13/2→4I15/2跃迁转变组成。

Microstructure evolution of isothermal holding treatment during melt solidification of Ti-6Al-4V alloy

Effect of isothermal holding treatment in the solidification process on the microstructure of Ti-6Al-4V alloy was studied by temperature controlled induced melting apparatus. The result shows that with isothermal holding treatment above the β transus temperature during solidification, the colony structure consisting of parallel lamellae was obtained. While the isothermal holding treatment was set at 960 °C, a unique bi-modal microstructure consisting of coarse primary α and fine secondary lamellar α was obtained. The primary lamellar α tended to break into several pieces, globularize and present equiaxed morphology. The formation mechanism of the equiaxed α can be explained with the atom immigration, high density dislocations, combined action with the interface tension of formed α phase during the isothermal holding treatment. After the isothermal holding, the retained β matrix transformed into fine lamellar α, thus, bi-modal microstructure was acquired. Compared with the lamellar structure, the grain boundary α presented discontinuously and cannot be distinguished from the primary α lamellae easily. The size of colonies α was greatly decreased. The microstructure tended to be much more homogeneous in the whole section of the samples.

Effect of microvoids on microplasticity behavior of dual-phase titanium alloy under high cyclic loading(Ⅰ):Crystal plasticity analysis

A crystal plasticity finite element(CPFE)model was established and 2D simulations were carried out to study the relationship between microvoids and the microplasticity deformation behavior of the dual-phase titanium alloy under high cyclic loading.Results show that geometrically necessary dislocations(GND)tend to accumulate around the microvoids,leading to an increment of average GND density.The influence of curvature in the tip plastic zone(TPZ)on GND density is greater than that of the size of the microvoid.As the curvature in TPZ and the size of the microvoid increase,the cumulative shear strain(CSS)in the primaryα,secondaryα,andβphases increases.Shear deformation in the prismatic slip system is dominant in the primaryαphase.As the distance between the microvoids increases,the interactive influence of the microvoids on the cumulative shear strain decreases.

Insights into effects of ZrO_(2) crystal phase on syngas‐to‐olefin conversion over ZnO/ZrO_(2) and SAPO‐34 composite catalysts

The utilization of metal oxide‐zeolite catalysts in the syngas‐to‐olefin reaction is a promising strategy for producing C_(2)–C_(4) olefins from non‐petroleum resources.However,the effect of the crystal phase of metal oxides on the catalytic activity of these oxides is still ambiguous.Herein,typical metal oxides(ZnO/ZrO_(2))with different crystal phases(monoclinic(m‐ZrO_(2))and tetragonal(t‐ZrO_(2)))were employed for syngas conversion.The(ZnO/m‐ZrO_(2)+SAPO‐34)composite catalyst exhibited 80.5%selectivity for C_(2)–C_(4) olefins at a CO conversion of 27.9%,where the results are superior to those(CO conversion of 16.4%and C_(2)–C_(4) olefin selectivity of 76.1%)obtained over(ZnO/t‐ZrO_(2)+SAPO‐34).The distinct differences are ascribed to the larger number of hydroxyl groups,Lewis acid sites,and oxygen defects in ZnO/m‐ZrO_(2) compared to ZnO/t‐ZrO_(2).These features result in the formation of more formate and methoxy intermediate species on the ZnO/m‐ZrO_(2) oxides during syngas conversion,followed by the formation of more light olefins over SAPO‐34.The present findings provide useful information for the design of highly efficient ZrO_(2)‐based catalysts for syngas conversion.

Study on Solution Crystallization of Musk Ketone and Musk Xylene

The ternary phase diagrams of musk ketone, musk xylene and various solvent were obtained by calcu- lations. Moreover, the double saturated lines were found to be curve for the first time. The methods to separate eutectic mixtures of musks by solution crystallization were suggested on the basis of these phase diagrams. A new process was proposed to get musk ketone and musk xylene from the eutectics by adding acetonitrile and heptane in turn, which was verified by experiments. Musk xylene with purity of 97.50% and musk ketone with purity of 98.10% were obtained.

Theoretical Hypothesis of a Double Barrier Regarding the D-D Interaction in a Pd Lattice： A Possible Explanation of Cold Fusion Experiment Failures

During the past 15 years, disputable experimental evidence has built up for LERN （low energy nuclear reaction） phenomena in specialized heavy hydrogen systems. Actually, it can not be said that a new branch of science is beginning. In spite of experimental contributions, the real problem is that the theoretical statements of LERN are unknown. In this work, the authors analyze the deuteron-deuteron reactions within palladium lattice by means of the coherence theory of nuclear and condensed matter and, using this general theoretical framework accepted from ＂cold fusion scientists＂, it will be shown the low occurrence probability of fusion phenomena. In fact, in the coherence approach, the D-D potential exhibits double barrier features and, in this way, the D-D fusion is hampered.

Deformation study of bicrystalline and nano-polycrystalline structures using phase field crystal method

Deformation behaviors of bicrystalline and nano-polycrystalline structures of various tilt angles and inclination angles in two dimensions are investigated in detail using a two-mode phase field crystal model.The interaction between grain boundary(GB)and dislocation is also examined in bicrystals and nano-polycrystals that both contain asymmetric and symmetric tilt GBs,with energy analysis being carried out to analyze these processes.During deformation simulations,we assume the volume of each simulation cell at every time step is coincident with that of the initial state just before deformation.Our simulation results show that the behaviors of symmetric and asymmetric GBs in bicrystals and nano-polycrystals differ from each other depending on tilt angle and inclination angle.A new dislocation emission mechanism of interest is observed in bicrystals which contain low angle symmetric tilt GBs.Low angle GB has a higher mobility relative to high angle GB in both bicrystalline and nano-polycrystalline structures,as does asymmetric GB to symmetric GB.The generation,motion,pileup and annihilation of dislocations,grain rotation and grain coalescence are observed,which is consistent with the simulation results obtained by molecular dynamics.These simulation results can provide strong guidelines for experimentation.

The polarization-dependent supercontinuum generation in photonic crystal fibers with high birefringence and two-zero dispersion

A polarization-dependent supercontinuum spectrum source of light from the UV to infrared region has been generated in our photonic crystal fiber with birefringence B=2.23×10 3.By tuning the polarization direction of the input pulse,it is found that the width of the supercontinuum spectrum changes dramatically with the input polarization directions.At the same time,we qualitatively explain the blue-shift peak and the red-shift peak in the experimental spectrum using phase matching conditions on dispersive waves,stoke waves and the pump wave.In addition,we also found that supercontinuum spectrum generation,to some extent,is dependent on the pump wavelength and average power of the pump.The spectrum is broadened with the increase of average power,but unchanged after average power reaches a certain value;when the pump wavelength is located in the anomalous dispersion and further away from the zero-dispersion wavelength,the spectrum of the supercontinuum is wider.

Dual solidification mechanisms of liquid ternary Fe-Cu-Sn alloy

Liquid ternary Fe47.5Cu47.5Sn5 alloy displayed dual solidification mechanisms when it was undercooled by up to 329 K （0.19TL）. Below a critical undercooling of about 196 K, it solidified just like a normal peritectic alloy, even though metastable phase separation occurred to a microscopic extent. Once bulk undercooling exceeds 196 K, macroscopic segregation played a domi- nant role in solidification. In both cases, the solidification process was always characterized by two successive peritectic trans- formations： firstly primary yFe dendrites reacted with liquid phase to form （Cu） phase, and subsequently the （Cu） phase reacted with residual liquid phase to yield β-Cu5.6Sn intermetallic compound. The primary yFe dendrites achieved a maximum growth velocity of 400 mm/s and experienced a growth kinetics transition as a result of macrosegregation. Since the （Cu） phase was both the product phase of the first peritectic transformation and also the reactant phase for the second peritectic transformation, it appeared as two layers in solidification microstructures due to the microsegregation of Sn solute. The boundary continuity between the macroscopically separated Fe-rich and Cu-ricb zones was enhanced with the increase of undercooling.