22 resultados para 500.2 Scienze fisiche

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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表征硫化橡胶弹性体网络的主要结构参数是有效网链密度橡胶弹性体的许多重要力学性能,例如:300%定伸强度、抗张强度、伸长率、抗撕裂、弹性、硬度、静态压缩模量和动态模量等都是和有效网链密度紧密相关的。Flory用平衡溶胀法测定有效网链密度的方程是:Ve = -1/(V_s)·(l_n(1-υ_r) + υ_r + μυ_r~2)/(υ_r~(1/3)-2υ_r/f)式中的Ve是有效网链密度(用单位体积橡胶的有效网链克分子数来表示),υ_r是溶胀网络中橡胶的体积分数,υ_s是溶剂的克分子体积,f是交联点的官能度(f = 4),μ是高聚物溶剂相互作用参数。首先要确定μ才能够用上式来测定硫化胶的有效网链密度以表征硫化程度。实验事实和Flory等人的理论工作表明:μ不是常数,是υ_r的函数。高顺式聚丁二烯橡胶已生产多年,但迄今未有关于高顺式聚丁二烯橡胶在不同溶剂中的μ和υ_r间的函数关系的报导。在实际应用中,人们常常用υ_r值的大小来近似表征硫化程度。但由上式可知:μ和υ_r不成正比关系。因此,必须求得μ值,才能得到Ve值,以正确表征硫化程度,对实际生产起指导作用。本工作采用溶胀-拉伸方法不渗透压,光散射等方法测定顺丁橡胶和溶剂甲苯、苯、正-庚烷的相互作用参数μ,得到了μ和υ_r的线性函数(见附表),μ = μ_o + βυ_r。μ_o是当υ_r趋向于零时的μ值,β是一个常数。溶胀拉伸法外推得到的μ_o值和用渗透压及光散射法得到的μ_o值么接近,为实验的可靠性提供了依据。力学方法和物理化学方法同时测得相近的结果,有文献报导的不多。用溶胀-拉伸法求橡胶-溶剂的相互作用参数μ,由于样品的制作和实验技术上的困难内尚未见报导。国外Kraus和V. Zanboni等人用天然、丁苯、乙丙、丁腈等纯胶硫化胶(未加碳黑的硫化胶)进行溶胀-拉伸实验,测定μ和U_r的函数关系。然后用来计算碳黑硫化胶的μ和Ve。本工作表明:对于同一橡胶-溶剂体系来说,纯胶硫化胶和碳黑硫化胶的μ和υ_r的函数关系并不一样,在相同υ_r时,二者Ve相差2.5-5%,υ_r值越大,Ve相差越大。因此用纯胶硫化胶的μ和υ_r的函数来计算碳黑硫化胶的有效网链密度是不适当的。本工作还用渗透压法测定了1,2-聚丁二烯(1,2-含量分别为90%和60%)及合成异戊橡胶和溶剂甲苯的相互作用参数μ_o。结果表明:合成异戊橡胶和天然橡胶有相同的μ_o值。这说明μ_o值只和化学结构有关,与样品的来源无关。两种1,2-聚丁二烯橡胶和顺丁橡胶也有相接近的μ_o值。其原因是因为三者有基本相同的内聚能密度,则它们在同一种溶剂中所受到的作用力应当相等的缘故。最后,本工作还研究了顺丁橡胶的有效网链密度对300%定伸强度、抗张强度、抗撕裂、伸长率、弹性、硬度、静态压缩模量和动态模量等力学性能的影响。结果表明:有效网链密度Ve和300%定伸强度成直线函数关系:M_(300%) = 17 + 3.61 * 10~5 * Ve(公斤/厘米)。这就为测定硫化胶的有效网链密度提供了另一条途径,因为300%定伸强度是表征硫化胶的一个重要参数,实验简单易行,知道了M_(300%)就可以利用上式估算Ve。本工作发现有效网链密度在2.00~3.10 * 10~(-4)摩尔/厘米~3的范围内,则可望达到优秀的抗张强度和抗撕裂性能,对实际生产的工艺控制有一定现实意义。本工作以稀土催化体系合成的顺丁橡胶(顺1,4-97%、反1,4-2.5%、1.2-0.5%)作为研究对象,订定了顺丁橡胶在溶剂四氢呋喃、甲苯、甲基环乙烷、正-庚烷和丁酮与正-庚烷混合溶剂(体积比为2:1)等中的特性粘数分子量关系式:用Kurata-Stockmayer(KS)方程、Stockmayer-Fixman(SF)方程和Tnagaki-Ptitsyn(IP)方程估算了顺丁橡胶的无扰分子尺寸。顺丁橡胶在溶剂四氢呋喃中的特性粘数-分子量关系式为[η]_(THF)~30 ℃= 0.0246 * M~(0.732)该关系式的获得为采用自记GPC测定和计算顺丁橡胶样品的(M-bar)_w、(M-bar)_n、(M-bar)_w/(M-bar)_x和[η]等重要分子参数提供了方便。因顺丁橡胶在四氢呋喃中的特性粘数-分子量关系式文献至今未见报导。顺丁橡胶在甲苯、甲基环乙烷、正-庚烷和丁酮与正-庚烷混合溶剂中的特性粘数-分子量关系式如下:[η]_(甲苯)~(30 ℃) = 0.0264 * M~(0.719) [η]_(甲基/环已烷)~(30 ℃) = 0.0293 * M~(0.698) [η]_(正-庚烷)~(30 ℃) = 0.1181 * M~(0.547) [η]_(丁酮+正-庚烷)~(30 ℃) = 0.1800 * M~(0.500)发现酮与正-庚烷的混合溶剂(体积比为2:1)在30 ℃时是顺丁橡胶的Θ溶剂。高聚物的无扰分子尺寸,是反映大分子近程相互作用的重要参数,由此可得到有关链结构的重要情报。本工作通过测定已知分子量的样品在四氢呋喃、甲苯、甲基环已烷等良溶剂中的特性粘数,采用KS、SF和IP方程去估算顺丁橡胶的无扰分子尺寸,同时测定了顺丁橡胶在其Θ条件下(丁酮与正-庚烷混合溶剂,体积比2:1,温度30 ℃)的无扰分子尺寸,以此进行对比。用KS方程估算的K_θ = 0.183(ml/g), <γ_o~2>~(1/2)/M~(1/2) = 0.0901(nm)用SF方程估算的K_θ = 0.183和0.200(ml/g), <γ_o~2>~(1/2)/M~(1/2) = 0.0901和0.0928(nm)用IP方程估算的K_θ = 0.192(ml/g), <γ_o~2>~(1/2)/M~(1/2) = 0.0915(nm)用Θ溶剂测定的K_θ= 0.180(ml/g), <γ_o~2>~(1/2)/M~(1/2) = 0.0896(nm)由此可见,用不同方法得到的结果均较接近。

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鉴于在较低温区(<600 ℃)金属中氦泡形核生长的实验数据尚缺乏,我们安排了在400 ℃、500 ℃ 下用2.5MeV He~+离子注入316L 不锈钢(固溶样和冷轧样)的实验,剂量2.5 * 10~(21)ions·m~(-2),剂量率3.4-3.6 * 10~(16)ions·m~(-2)·s~(-1)。由于在透射电镜(TEM)观测中采用横断面制样技术,得到了各样品中He泡深度分布的信息。分析表明实验结果与He泡的双原子形核模型的预言一致;He泡的迁移合并机制不显著,这与实验测得He泡中存在极高的原子密度相对应。固溶样品的离位损伤峰区发生了大量空位向He泡的凝聚从而加速了He泡生长。位错的存在显著增强了He泡的形核并抑制了空位的凝聚,并且这种作用在较低温度下更加显著

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一种小晶粒FeZSM5沸石分子筛的制备方法,以含硅物质、无机铁盐、无机钠盐、有机胺类、无机酸和无离子水为原料,各组分的组成(摩尔比)为Fe3+:SiO2:Na2O:Na+:R:H2O=1:(90-1600):(8.3-13):(13-25):(25-40):(2500-4000)采用水热合成法,在搅拌速度400-500转/分钟、以2℃/分钟的速率由室温升至100-140℃,恒温130小时,完成结晶,然后降温、过滤、洗涤、烘干、焙烧得到晶粒小于1μm分子筛,不需要重复交换一次完成,制备简单。

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Test strip detectors of 125 mu m, 500 mu m, and 1 mm pitches with about 1 cm(2) areas have been made on medium-resistivity silicon wafers (1.3 and 2.7 k Ohm cm). Detectors of 500 mu m pitch have been tested for charge collection and position precision before and after neutron irradiation (up to 2 x 10(14) n/cm(2)) using 820 and 1030 nm laser lights with different beam-spot sizes. It has been found that for a bias of 250 V a strip detector made of 1.3 k Ohm cm (300 mu m thick) can be fully depleted before and after an irradiation of 2 x 10(14) n/cm(2). For a 500 mu m pitch strip detector made of 2.7 k Ohm cm tested with an 1030 nm laser light with 200 mu m spot size, the position reconstruction error is about 14 mu m before irradiation, and 17 mu m after about 1.7 x 10(13) n/cm(2) irradiation. We demonstrated in this work that medium resistivity silicon strip detectors can work just as well as the traditional high-resistivity ones, but with higher radiation tolerance. We also tested charge sharing and position reconstruction using a 1030 nm wavelength (300 mu m absorption length in Si at RT) laser, which provides a simulation of MIP particles in high-physics experiments in terms of charge collection and position reconstruction, (C) 1999 Elsevier Science B.V. All rights reserved.

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Test strip detectors of 125 mu m, 500 mu m, and 1 mm pitches with about 1 cm(2) areas have been made on medium-resistivity silicon wafers (1.3 and 2.7 k Ohm cm). Detectors of 500 mu m pitch have been tested for charge collection and position precision before and after neutron irradiation (up to 2 x 10(14) n/cm(2)) using 820 and 1030 nm laser lights with different beam-spot sizes. It has been found that for a bias of 250 V a strip detector made of 1.3 k Ohm cm (300 mu m thick) can be fully depleted before and after an irradiation of 2 x 10(14) n/cm(2). For a 500 mu m pitch strip detector made of 2.7 k Ohm cm tested with an 1030 nm laser light with 200 mu m spot size, the position reconstruction error is about 14 mu m before irradiation, and 17 mu m after about 1.7 x 10(13) n/cm(2) irradiation. We demonstrated in this work that medium resistivity silicon strip detectors can work just as well as the traditional high-resistivity ones, but with higher radiation tolerance. We also tested charge sharing and position reconstruction using a 1030 nm wavelength (300 mu m absorption length in Si at RT) laser, which provides a simulation of MIP particles in high-physics experiments in terms of charge collection and position reconstruction, (C) 1999 Elsevier Science B.V. All rights reserved.

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Charge transfer due to collisions of ground state O3+ (2s(2)2p P-2) ions with molecular hydrogen is investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method, and electronic and vibrational state-selective cross sections along with the corresponding differential cross sections are calculated for projectile energies of 100, 500, 1000 and 5000 eV/u at the orientation angles of 25 degrees,45 degrees and 89 degrees. The adiabatic potentials and radial coupling matrix elements utilized in the QMOCC calculations were obtained with the spin-coupled valence-bond approach. The infinite order sudden approximation (IOSA) and the vibrational sudden approximation (VSA) are utilized to deal with the rotation of H-2 and the coupling between the electron and the vibration of H-2. It is found that the distribution of vibrationally resolved cross sections with the vibrational quantum number upsilon' of H-2(+) (upsilon') varies with the increment of the projectile energy; and the electronic and vibrational stateselective differential cross sections show similar behaviors: there is a highest platform within a very small scattering angle, beyond which the differential cross sections decrease as the scattering angle increases and lots of oscillating structures appear, where the scattering angle of the first structure decreases as E-P(-1/2) with the increment of the projectile energy E-P; and the structure and amplitude of the differential cross sections are sensitive to the orientation of molecule H-2, which provides a possibility to identify the orientations of molecule H-2 by the vibrational state-selective differential scattering processes.

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利用反应显微成像谱仪对70和100keV He2+与He原子碰撞转移电离(TI)过程中不同出射角度的电子能谱进行了测量,观测到出射电子能谱具有如下分布特征:出射电子速度分布介于0和入射离子速度vp之间;在不同出射角度电子能谱分布均有一极大值存在,随着出射角度的增大,能谱分布极大值逐渐减小;当电子出射角度等于45°时,多数电子集中在0eV附近。上述特征可由低能离子-原子碰撞"准分子"模型进行定性解释。在100keV He2+-He转移电离出射电子能谱中有靶电子被俘获至散射离子连续态(electron capture to continuum,简称ECC)电子的贡献,这可看做是动力学两步过程的作用。

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Low temperature heat capacities of N-(p-methylphenyl)-N'-(2-pyridyl)urea were determined by adiabatic calorimetry method in the temperature range from 80 to 370 K. It was found that there was not any heat anomaly in this temperature region. Based on the experimental data, some thermodynamic function results were obtained. Thermal stability and decomposition characteristics analysis of N-(p-methylphenyl)-N'-(2-pyridyl)urea were carried out by DSC and TG. The results indicated that N-(p-methylphenyl)-N'-(2-pyridyl)urea started to melt at ca. 426 K (153degreesC) and the melting peak located at 447.01 K (173.86degreesC). The melting enthalpy was 204.445 kJ mol(-1) (899.6 J g(-1)). The decomposition peak of N-(p-methylphenyl)-N'-(2-pyridyl)urea was found at 499.26 K (226.11degreesC) from DSC curve. This result was similar with that from TG and DTG experiment, in which the mass loss peak was determined as 500.4 K (227.2degreesC).

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在实验室模拟条件下研究了石油烃、Cu2+单一与复合污染对沙蚕的毒性效应.试验的结果表明,沙蚕的死亡率与石油烃、Cu2+的浓度呈显著相关关系.其半数致死浓度LC50分别为:30.2~116.26μg/L(石油烃);449.52~1130.34μg/L(Cu2+).沙蚕体内Cu2+的积累量随着暴露溶液中Cu2+浓度的上升而增加,当Cu2+的浓度>500μg/L时,这一变化十分显著;而沙蚕体内石油烃的含量随着暴露溶液中石油烃浓度的升高无显著变化.而Cu2+和石油烃复合污染对沙蚕的毒性作用较为复杂,在不同的处理中,表现出了协同和拮抗两种作用方式.同时,在Cu2+与石油烃复合污染条件下,沙蚕体内Cu2+的积累量也有显著变化.在复合处理组中,当Cu2+的浓度达到500μg/L时,Cu2+在沙蚕体内的积累量与Cu2+单一污染相比,Cu2+在沙蚕体内积累量相比显著降低.

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掺杂的CeO2基固体电解质因其在中低温条件下(500 ̄700℃)具有高氧离子电导率而成为有希望的IT-SOFCs(intermediate temperature-solid oxide fuel

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Monodisperse hexagonal Ln(OH)(3) (Ln = Eu, Sm) submicrospindles with uniform morphology and size have been Successfully synthesized in a large scale via a Facile aqueous solution route from the mixture of aqueous solutions or LnCl(3) and NaOH at 5 degrees C without using any surfactant or template. The as-synthesized products are characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The SEM and TEM images show that the as-formed Ln(OH)(3) samples have a spindlelike shape with an equatorial diameter of 80-200 nm and a length of 500-900 nm, which are aggregates of even smaller nanoparticles.

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By using inorganic salts as raw materials and citric acid as complexing agent, alpha-Zn-3(PO4)(2) and Eu3+ doped alpha-Zn-3(PO4)(2) phosphor powders were prepared by a citrate-gel process. X-ray diffraction, (XRD), TG - DTA, FT - IR and luminescence excitation and emission spectra were used to characterize the resulting products. The results of XRD reveal that the powders begin to crystallize at 500 degreesC and pure alpha-Zn-3(PO4)(2) phase is obtained at 800 degreesC. And the results of XRD reveal that Eu3+ exists Lis EoPO(4) ill the powder. In the phosphor powders, the Eu3+ shows its characteristic red-orange (592 nm, D-5(0) - F-7(1)) emission and has no quenching concentration.

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Nanocrystalline Y2O3:Eu3+ phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained, which mainly consisted of grains with an average size of 70 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped Eu3+ showed its characteristic emission in crystalline Y2O3 phosphor films due to an efficient energy transfer from Y2O3 host to them. Both the lifetimes and PL intensity of the Eu3+ increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+ were determined to be 5 mol%.

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The reaction of [Cp*IrCl2](2) with dilithium 1,2-orthocarborane-1,2-diselenolate 3 leads to the green 16-electron diselenolene complex [Cp*Ir{Se2C2(B10H10)}] (4) which takes up two-electron ligands such as trimethylphosphane to give the 18-electron diselenolate derivative [Cp*Ir(PMe3)-{Se2C2(B10H10)}] (5). The molecular structures of 4 and 5 were determined by X-ray crystal structure analysis. The Se-77-nuclear shielding in 4 is lower by almost 500 ppm relative to that in 5.