X-波段电子自旋成象

报道了自行设计研制的X-波段ESR成象装置并用之对典型样品作了ESR成象测定;用解卷积和分析图象重建中卷积滤波法对自旋样品体系进行了二维的图象重建,获取了能反映真实自旋分布的二维自旋密度图象.     

一种新的成象技术——穆斯堡尔成象

穆斯堡尔成象技术是1987 年由美国国家标准局S.J.Norton首先提出的[1].它与X射线成象(又称为CT断层成象)、核磁共振成象(NMR)一样能给出立体图象,虽然现在还不能在医学中应用,但在材料科学研究方面却已显示出广泛的应用前景. 在介绍穆斯堡尔成象之前,先介绍一下NMR成象.由于穆斯堡尔成象与NMR成象都依赖于原子核共振效应,因此它们具有许多相同的特征.NMR成象的原理是:由于原子核共振频率正比于局域磁场强度,因此,当施加一个外磁场于自旋体系时,不同频率的信号对应于实验样品内不同的空间位置.用这种方法可以将不同频率的信号转变为…     

X－波段电子自旋成象

报道了自行设计研制的Ｘ－波段ＥＳＲ成象装置并用之对典型样品作了ＥＳＲ成象测定；用解卷积和分析图象重建中卷积滤波法对自旋样品体系进行了二维的图象重建，获取了能反映真实自旋分布的二维自旋密度图象．     

硬X射线位相衬度成象

常规X射线成象技术是建立在吸收衬度和几何光学基础上.介绍了“in-line”位相衬度成象 技术和成象理论.以生物样品为例,说明常规X射线吸收衬底成象与位相衬度成象的差别,并 对X射线源尺寸对成象衬度的影响进行了研究.此外,对吸收衬底象和位相衬度象的关键参量 进行了计算模拟和讨论. 关键词： 位相衬度 成象 硬X射线     

激光光热偏转成象法无损检测光学薄膜的激光损伤

介绍了应用激光光热偏转成象法无损检测光学薄膜激光损伤的基本原理，由此建立了实验检测装置，对光学薄膜表面的激光损伤进行了扫描检测，并以直观的灰度象显示. 实验结果证明了激光光热偏转成象法检测光学薄膜激光损伤具有直观、有效、可确定损伤阈值的优点.     

NiFe/Pt薄膜中角度相关的逆自旋霍尔效应

NiFe/Pt双层薄膜样品在铁磁共振时, NiFe磁矩进动所产生的自旋流注入到Pt层中, 由于逆自旋霍尔效应产生直流电压V_ISHE, 此电压会叠加到NiFe薄膜由于自旋整流效应而产生的电压V_SRE 上, 实验测量所得电压为V_ISHE和V_SRE的叠加. 为了区分这两种不同机理对电压的贡献, 本文采取旋转外加静磁场的方法, 通过分析所测电压随磁场角度的变化从而分离出V_ISHE 的大小. 研究结果表明, 相比于单层NiFe(20 nm)薄膜样品, NiFe(20 nm)/Pt(10 nm)双层膜样品中由于NiFe自旋注入到Pt 中导致铁磁共振线宽增加. 与逆自旋霍尔效应产生的电压相比, 自旋整流效应的贡献较小, 但不可忽略. 本文工作有助于认清铁磁/非磁性金属材料中的自旋相关效应, 并提供了一种准确的分析逆自旋霍尔效应的方法.     

生物样品的散射和吸收特性对双光子激发和共焦成象深度的影响

本文研究了生物样品的散射和吸收特性对双光子激发和共焦成象深度的影响.生物组织内30μm的成象结果表明,双光子激发具有比共焦成象更深的成象深度.来自生物组织的模型实验和蒙特卡罗模拟均表明,散射和吸收的影响是导致这一特点的重要原因.     

NdBa2Cu3-xMnxOy体系的结构和声子振动

利用X光衍射、红外光谱、电子顺磁共振等实验手段对多晶样品NdBa2Cu3-xMnxOy(0≤x≤0.3)的结构、声子振动和自旋关联情况进行了研究.结果表明:随着Mn掺杂浓度的增加,样品由四方结构转变为正交结构.红外谱的研究发现:所有样品在580cm-1附近都有一个峰,强度随着掺杂浓度的增加而增强,振动膜逐渐软化这和样品的微结构变化密切有关.ESR研究表明: NdBa2Cu3-xMnxOy体系在不掺杂或低掺杂浓度时只有很弱的自旋共振信号,进一步增加Mn含量,自旋信号增强,线宽降低,显示Mn掺杂浓度增加引起Mn离子的自旋局域化程度增强.本文讨论了掺杂对结构、红外谱和自旋关联的影响.     

壳聚糖水凝胶折射率特性研究

水凝胶是一种具有三维网络结构的新型功能高分子材料。水凝胶因其可注射性、良好的组织相容性、无毒副作用、在生物体内可降解性、环境敏感性广泛用于药物释控、吸附材料、仿生工程、光纤传感、组织工程、智能穿戴等方面。水凝胶的传感主要是随着外界环境因素的改变,引起溶胀度的不同,导致水分子填补凝胶内部孔洞的程度不同,呈现出水凝胶整体折射率变化的过程。为了研究不同的溶胀度对水凝胶折射率的影响,以壳聚糖为原料,以过硫酸铵, N,N-亚甲基双丙烯酰胺分别作为引发剂和交联剂,与丙烯酸接枝反应,在氮气的环境中以化学方式制备壳聚糖水凝胶。通过设计测量结构、搭建实验平台,检测了壳聚糖水凝胶的溶胀特性并对凝胶的溶胀度进行了标定;以卤钨灯作为光源,通过光谱仪检测了壳聚糖水凝胶透射光谱;运用光在介质面传播特性与光波的偏振性原理,对壳聚糖水凝胶透射光谱进行分析,研究了不同溶胀度下壳聚糖水凝胶折射率的变化规律,发现了不同溶胀度下凝胶对不同波长光波的折射能力存在差异性;通过对数据的处理,计算了波长为400 nm时,凝胶折射率随溶胀度变化的范围及灵敏度Q_1。通过对实验数据的拟合,得出了壳聚糖水凝胶折射率对溶胀度、波长的响应规律且拟合度较高,为壳聚糖水凝胶在光学传感方面的应用提供了实验基础。通过实验,说明了壳聚糖水凝胶有着优秀的溶胀特性、较宽的折射率变化范围及较高的灵敏度,在智能穿戴、仿真皮肤、光学传感等领域的应用有一定的优势。     

Sherrington-Kirkpatric自旋玻璃模型的非平衡态性质

通过动力学蒙特卡罗模拟对Sherrington-Kirkpatric （SK）自旋玻璃模型进行研究. 结果表明,弱场下自旋玻璃的磁化率在转变点非常陡峭,而比热容则呈现比较宽的转变. 同时,也成功地模拟了自旋玻璃体的年龄效应和记忆效应. 通过模拟发现,不同的弛豫时间对系统的能量影响很大,这直接导致了年龄效应和记忆效应;各向同性的SK模型不能给出实验中的交换偏移现象. 关键词： 自旋玻璃 记忆效应 年龄效应 磁化率     

Swelling Behavior of Physically Cross-Linked Gelatin Gels in Varied Salt Solutions

A series of physically cross-linked gelatin networks were prepared and the effects of salt concentration and chemical valence of the salt ions on the swelling properties of the gelatin gels were studied in detail. It was found that the swelling behaviors as polyelectrolytic or polyampholytic gels depended on the charge distribution on the gelatin chains. The swelling capacity of polyelectrolytic gels with excess positive charges decreased with an increase in salt concentrations. However, the swelling capacity of polyelectrolytic gels with excess negative charges showed a nonmonotonic change with salt concentration. For polyampholytic gels, the equilibrium swelling ratio increased monotonously with the concentration of NaCl and CaCl₂ solutions_. On the other hand, the swelling capacities of the polymer networks increased first and were then followed by a decrease with an increase in the concentration of AlCl₃ solution. Moreover, the swelling kinetics of the gelatin gels in varied salt solutions with different concentrations was also investigated.     

Lu2Ti2O7和Lu2TiO5陶瓷材料的Kr离子辐照损伤研究

钛酸盐因其优异的物理化学性能,可作为高放射性核废物（HLW）和锕系元素（钚）的重要候选固化材料之一。采用传统的陶瓷烧结工艺制备了多晶的Lu₂Ti₂O₇和Lu₂TiO₅陶瓷材料。在室温下,用800 keVKr2+对两种材料进行辐照,辐照后的样品采用GIXRD进行表征,观察到两种样品都经历了先肿胀、然后再发生非晶相变的过程。不同的是Lu₂Ti₂O₇的晶格肿胀程度大于Lu₂TiO₅。另外,Lu₂TiO₅样品的辐照到2×10₁₄ ions/cm₂时非晶含量达95.54%,而Lu₂Ti₂O₇样品在此剂量下非晶含量只有74.66%。通过第一性原理计算了Lu₂Ti₂O₇晶体的晶格肿胀随反位浓度的变化关系,结果表明,Lu₂Ti₂O₇出现非晶前的晶格肿胀主要由阳离子反位导致,而Lu₂TiO₅是无序的萤石结构,其辐照所导致的晶格肿胀不含阳离子反位的贡献,晶格肿胀程度较低。     

Swelling of cross-linked polyelectrolyte gels

A model of a cross-linked polyelectrolyte gel has been examined using Monte Carlo simulations. The simple model contained a charged defect-free network represented by linked charged beads and explicit counterions. Pressure-density relations for the polyelectrolyte gel, a corresponding non-ionic polymer gel, and several partly or fully degraded gels have been determined. The polyelectrolyte gel displayed a very large swelling capacity, in agreement with experiments. The swelling mechanism and chain properties are discussed and foundations of current theories on gel swelling are examined.     

基于SEM与FTIR研究改性钢渣/橡胶复合材料的热氧老化机理

钢渣是冶金工业中产生的主要固体废弃物,其产量约为每年粗钢产量的15%~20%。由于技术的局限,导致我国钢渣利用率较低,仅为年钢渣产量的10%,同时加之管理制度的不健全,导致钢渣大量露天堆放,对土地资源、地下水源,以及空气质量形成严重影响。面对上述问题,以热闷渣、电炉渣和风淬渣研发改性钢渣微粉,并且将改性钢渣微粉与复合橡胶进行复合制备改性钢渣/橡胶复合材料。依据《硫化橡胶或热塑性橡胶热空气加速老化和耐热试验》（GB/T3512—2014）对改性钢渣/橡胶复合材料进行热氧老化处理,采用平衡溶胀法测定改性钢渣/橡胶复合材料的交联密度,扫描电子显微镜（SEM）、热重分析仪（TGA）和傅里叶转换红外光谱仪（FTIR）分别测试其微观形貌、失重率和结构组成,从微观层面阐述改性钢渣/橡胶复合材料的热氧老化机理。结果表明在热氧老化前期老化作用在改性钢渣/橡胶复合材料表面,其内部以交联键形成反应为主;在热氧老化中期老化作用已经作用改性钢渣/橡胶复合材料内部,造成交联键断裂反应速度高于交联键形成反应速度,形成大量断裂交联键;在热氧老化后期由于改性钢渣/橡胶复合材料内部已经存在大量断裂交联键,导致主链及交联键断裂速度降低,交联键形成反应占优势。改性钢渣微粉以热闷渣（SiO₂含量高）为原材料,有利于形成聚合物大分子链贯穿炭黑网络的结构,提高综合性能,尤其是物理机械性与滞后性;以电炉渣、风淬渣（Fe₂O₃含量高）制备改性钢渣微粉,有利于热传导性能的改善,不仅提高改性钢渣/橡胶复合材料的耐热性,而且提高其硬度与脆性。热氧老化过程中改性钢渣/橡胶复合材料内部在橡胶分子链α-H上发生了不同程度的氧化反应,并在橡胶分子链周围生成了羟基、羧基和醇类化合物,双键烯氢含量降低。     

Solid-state 13C NMR study of poly(vinyl alcohol) gels

Poly(vinyl alcohol) (PVA) with 55% and 61% syndiotacticity, and their related dry and hydrated gels obtained by two different freeze–thawing cycles have been investigated using the solid-state ¹³C CP-MAS NMR technique. From a comparative analysis of the spectra, evidence was obtained that the gelation process largely disrupts the intramolecular hydrogen-bonded network of the PVA. The addition of water to the dry gels favours their swelling, destroying intra-chain hydrogen bonds between hydroxyl groups as a function of the degree of tacticity and the gelation procedure, and promotes the formation of new networks of interchain hydrogen bonds. Information on the dynamics of the polymeric domains in the kilohertz range has been obtained from the analysis of the spin relaxation times T_1ρ(¹H) and T_1ρ(¹³C), indicating that homogeneous arrangements of the amorphous or swollen polymeric chains exist, independent of the preparation method or the tacticity of the PVA chains.     

Pulsed nuclear magnetic resonance of gamma-irradiated lithium hydride

Some of the effects of ⁶⁰Co gamma irradiation on lithium hydride are described. Volume increase and nuclear magnetic resonance data are given for samples irradiated from 40 to 395°C. Maximum swelling occurs between 160 and 200°C; negligible swelling occurs above 300°C. Motionally narrowed proton and ⁷Li nuclear magnetic resonance signals appear on irradiation and increase with increasing swelling. These decomposition products, which are trapped inside the LiH, can amount to more than one-tenth the total sample at doses of 50 Grad. At this point, 25 volume per cent swelling has occurred and the growth rate has subsided. The hydrogen nuclear magnetic resonance signal has been shown to come from H₂ molecules by observation of the ortho-para conversion on cooling. Hydrogen densities derived independently from the longitudinal relaxation time and the swelling data are in reasonable agreement. The corresponding gas pressures range from 750 to 5000 atm. The H₂ is thought to be in bubbles which cause the volume growth, and recent electron microscopy results support this view. The ⁷Li signal has a Knight shift, and the lithium is present as metal particles. Above 200°C, the H₂ and Li back-react rapidly. Above 300°C this reaction takes place as fast as the decomposition, which was caused by the irradiation.     

Studies on mechanical and swelling behavior of polymer networks on the basis of the scaling concept. 6. Gels immersed in polymer solutions

In order to describe the mechanical and swelling behavior of gels immersed in polymer solutions, theoretical considerations based on both classical and scaling theories are discussed and compared with experimental findings. Three situations are studied: (1) the gel is separated from the surrounding solution by a semipermeable membrane; (2) the gel is immersed in the semidilute solution of a chemically identical polymer; (3) the gel is directly immersed in the semidilute solution of a chemically different polymer. An attempt is made to take into account the effect of the penetrating polymer on the elastic modulus and the swelling pressure of the gel. Experimental data referring to chemically cross-linked poly(vinyl alcohol) and poly(vinyl acetate) networks are presented. It was found that the concentration of the free chains inside moderately cross-linked networks may be considerable even for polymers having relatively long chains (27,000 < < M _n < 130,000). Experimental results indicate that the presence of free chains only slightly alters the elastic modulus; however, the swelling pressure is considerably affected by the penetrating polymer. The analysis of mechanical and equilibrium deswelling measurements carried out on several series of gel homologues shows that scaling theory satisfactorily describes the experimental data.     

Characterization of Poly(Vinyl Alcohol) Membranes Cross-Linked by Aldehyde-Substituting Cyclotriphosphazene

A new type of cross-linker, based on cyclotriphosphazene with six aldehyde groups, was used for the cross-linking of poly(vinyl alcohol) membranes. FTIR-ATR analysis indicated that cyclophosphazene reacted with poly(vinyl alcohol) by forming C–O–C bonds. TGA and DTG analysis showed that cross-linking improved the thermal stability. The swelling degree and pervaporation properties of cross-linked PVA membranes were also characterized. With increasing cross-linker concentration, swelling degrees and flux decrease while separation factors increase. Compared with PVA membranes cross-linked by glutaraldehyde, PVA membranes cross-linked by cyclophosphazene exhibited better selectivity and permeation rate.     

STUDY ON PREPARATION OF UV CROSS-LINKING FILMS OF POLYURETHANE-LiClO4 COMPLEXES AND THEIR IONIC CONDUCTIVITY

The complexes of polyurethane containing double bonds with LiClO₄ were formed, and cross-linked films were produced by UV radiation, All of the films were uniform, transparent, flexible and smooth-faced with a considerable mechanical strength. The ionic conductivities of the films of several series of polymers with different molecule weights of PEG segment were measured, of which the highest is 8.09×10^-5S·cm^-1 at 300K under anhydrous atmosphere. Also the conductivity is deeply influenced by the molecule weight of the soft segment PEG of the polyurethane and the content of LiClO₄. The transport number of Li⁺ is about 0.57. Structure characteristic measurement much as DSC, XRD, IR etc., have been done and the conductive mechanism is discussed.     

蓝宝石R面上ZnO薄膜的NH3掺杂研究

以NH₃为掺杂源,利用金属有机化学气相沉积(MOCVD)系统在蓝宝石R面上生长出掺氮ZnO薄膜。通过XRD,SEM测量优化了其生长参数,在610℃和在80sccm的NH₃流量下生长出了〈1120〉单一取向的ZnO薄膜。经Hall电阻率测量,得知该薄膜呈现弱p型或高电阻率,并对其光电子能谱进行了研究。