掺杂纳米硅薄膜中电子自旋共振研究

研究了掺杂纳米硅薄膜(nc∶Si∶H)中的电子自旋共振(ESR)及与之相关的缺陷态.样品是用等离子体增强化学气相沉积方法制成,为两相结构,即纳米晶粒镶嵌于非晶本体之中.对掺磷的nc-Si∶H样品,测量出其ESR信号的g值为1.9990—1.9991,线宽ΔH_pp为(40—42)×10^-4T,ESR密度Nss为10¹⁷cm^-3数量级.对掺硼的nc-Si∶H样品,其ESR信号的g值为2.0076—2.0078,ΔH_{关键词： 纳米硅薄膜 微结构 电子自旋共振}     

TiH2粉末制备钛合金的烧结脱氢规律及工艺

 以TiH₂粉末为原料,通过压制成型和烧结工艺制备粉末钛合金,不同于传统钛粉末冶金方法。通过热分析和热膨胀技术研究不同球磨粒度TiH₂粉末的脱氢和收缩规律,以此入手研究了TiH₂粉末压坯和TiH₂-Al-V粉末压坯的烧结致密特性,以及影响烧结过程的主要工艺因素,包括烧结温度、烧结时间、升温速率、压坯密度、压坯成型方式、合金体系,并对烧结组织进行了分析。结果表明,TiH₂粉末球磨后脱氢温度降低,粉末越细,开始温度越低。TiH₂粉末压坯在烧结过程中脱氢后获得新鲜钛,其易发生黏接并引起α-Ti的强烈收缩,这时烧结体很容易致密,并获得相对密度大于99%坯体;相比之下,TiH₂-Al-V粉末压坯烧结时因为合金元素的溶解,不如纯TiH₂粉末压坯的烧结容易致密。TiH₂-Al-V粉末经过成型、烧结脱氢可获得典型的层片状α+β钛合金组织,合金元素分布均匀。     

多组元Al基体系热力学和动力学数据库及其应用

采用差示扫描量热法(DSC)、光学显微镜、扫描电镜SEM和电子探针EPMA实验技术,系统研究了多组元Al基Al356.1合金定向凝固的显微组织及显微偏析,用所建立的热力学及动力学数据库计算模拟了3个多组元Al合金(Al356.1,Al356.2,Al518.2)的平衡凝固、Scheil-Gulliver非平衡凝固及其在实际凝固条件下的显微组织与显微偏析,并将计算结果与研究实验结果及文献中的实验数据进行了比较.研究结果表明:模拟计算结果同实验结果相吻合,所建立的热力学及动力学数据库精确、可靠.     

3D Bioprinting of Artificial Tissues: Construction of Biomimetic Microstructures

It is promising that artificial tissues/organs for clinical application can be produced via 3D bioprinting of living cells and biomaterials. The construction of microstructures biomimicking native tissues is crucially important to create artificial tissues with biological functions. For instance, the fabrication of vessel‐like networks to supply cells with initial nutrient and oxygen, and the arrangement of multiple types of cells for creating lamellar/complex tissues through 3D bioprinting are widely reported. The current advances in 3D bioprinting of artificial tissues from the view of construction of biomimetic microstructures, especially the fabrication of lamellar, vascular, and complex structures are summarized. In the end, the conclusion and perspective of 3D bioprinting for clinical applications are elaborated.     

钇对Mg-0.8Zr-0.35Zn基合金组织及高温性能的影响

采用XJG-04型金相显微镜、 JCXA-733电子探针、 D/max-rB型X射线衍射仪及WDW-200型电子万能实验机研究了Y对Mg-0.8Zr-0.35Zn基合金铸态、固溶时效组织及高温(250 ℃)性能的影响. 结果表明: Y能细化Mg-0.8Zr-0.35Zn基合金铸态及热处理态组织, 加入Y形成新相Mg24Y5. 在250 ℃时, 随着Y含量增加合金高温抗拉强度增大, 延伸率及断面收缩率降低; 高温拉伸断口SEM图像显示脆性断裂趋势增大, 断裂由延性向解理方式发展.     

Cell Shape Normalization,Dendrite Orientation,and Melanin Production of Normal and Genetically Altered (Haploinsufficient NF1)‐Melanocytes by Microstructured Substrate Interactions

Little is known about how functional regulation failure in genetically altered cells is influenced by topographical confinement of cells, a situation often present in tissues in vivo. We used cultured melanocytes derived from human skin samples as a model system for such investigations. Normal melanocytes have a very well defined shape consisting of a cell body and two dendrites arranged 180° relative to each other. In contrast, neurofibromin 1‐melanocytes (NF1‐melanocytes) have up to a 50 % reduction of neurofibromin 1, which results in an altered morphology that can be easily measured. NF1‐melanocytes deviate from the defined structure of normal melanocytes by forming more than two dendrites per cell. We show that morphology consequences of genetically altered melanocytes can be canceled if cells interact with substrates microstructured by stripes that apply mechanophysical signals in the form of physical topography. The strength of the mechanophysical signal was varied systematically by increasing the height of the microstructures. Melanocytes respond to surface topographical features that are larger than 50 nm and have lateral confinements smaller 4 μm. The response of normal and NF1‐melanocytes to different topographies was analyzed quantitatively by determining density distributions for the number of dendrites per cell, the angles between dendrites, and the orientation imprinted in the substrate. The synthesis of melanin, a pigment produced by melanocytes, differs in the case of genetically altered NF1‐ and normal melanocytes. In both cases, the interaction with microstripes enhanced melanin production significantly. This enhanced melanin production is speculated to be caused by the mechanical stabilization of the dendrites by substrate guidance.     

Influence of electric field on the phase transitions of the hexagonal cylinder phase of diblock copolymers.

We have used the cell dynamic simulations (CDS) method to study the evolution of asymmetric and symmetric diblock copolymers under electric fields. For symmetric diblock copolymers, long-range-ordered lamellar phases form readily under electric fields. For asymmetric diblock copolymers, sphere-to-cylinder phase transitions occur rapidly when strong electric fields are applied, but it takes longer for the system to form hexagonal cylinder structures. The results of these simulations suggest that the sphere phase is stable under weak electric fields, but a threshold electric intensity exists for the sphere-to-cylinder phase transition. In addition, we also studied the kinetic pathways of the transition of the lamellar phase to the hexagonal cylinder phase of the asymmetric diblock copolymers under electric fields. Hexagonal cylinder structures form when the lamellar phase is subjected to a sudden temperature jump. The scattering functions suggest that the hexagonal cylinder structures are very regular and possess very few flaws.     

Self‐(Un)rolling Biopolymer Microstructures: Rings,Tubules, and Helical Tubules from the Same Material

We have demonstrated the facile formation of reversible and fast self‐rolling biopolymer microstructures from sandwiched active–passive, silk‐on‐silk materials. Both experimental and modeling results confirmed that the shape of individual sheets effectively controls biaxial stresses within these sheets, which can self‐roll into distinct 3D structures including microscopic rings, tubules, and helical tubules. This is a unique example of tailoring self‐rolled 3D geometries through shape design without changing the inner morphology of active bimorph biomaterials. In contrast to traditional organic‐soluble synthetic materials, we utilized a biocompatible and biodegradable biopolymer that underwent a facile aqueous layer‐by‐layer (LbL) assembly process for the fabrication of 2D films. The resulting films can undergo reversible pH‐triggered rolling/unrolling, with a variety of 3D structures forming from biopolymer structures that have identical morphology and composition.     

机械活化粉末制备W-Cu合金的微观组织

为了改善制备工艺和提高W-Cu合金的密度与性能,对原料粉末进行了机械活化处理,通过成形和烧结制备了W-Cu合金,考察了活化后粉末的变化,观察了合金的烧结组织并测量了密度.结果表明,机械活化能增大钨铜粉末的表面能和晶格畸变能,有效地促进烧结,改善烧结组织;烧结体中存在大量团絮状组织,团粒内部钨颗粒主要以固相方式烧结在一起,而团粒之间则以液相烧结为主.烧结组织细密、均匀,相对密度达98%以上;烧结组织中钨铜两相在微米尺度下仍然结合良好,部分界面出现了互溶.