TC4表面激光熔覆TiC和TiC-NiCrBSi涂层的微观组织研究

采用激光熔覆技术在TC4合金表面制备TiC和TiC-NiCrBSi涂层,研究了激光熔覆层的微观组织和硬度。结果表明,在TiC激光熔覆层中,表层(熔覆区)大部分TiC颗粒发生了熔化并以树枝晶形式结晶,底层(稀释区)TiC颗粒向钛合金中溶解并以树枝晶形式沉淀析出。随激光比能的增加,基底钛合金的稀释作用增加,熔覆层的硬度降低。在TiC-NiCrBSi激光熔覆层中,熔覆区中的TiC颗粒向Ni基合金中溶解并以细小的球状颗粒和树枝晶形式沉淀析出,随激光比能的增加,TiC颗粒的溶解程度增加。当TiC颗粒的体积分数超过50%时,TiC颗粒出现偏聚现象。TiC-NiCrBSi激光熔覆层的稀释区是Ni基合金和钛合金的混熔区,呈细小的树枝晶形态。     

高精度高比容独石电容器用瓷料研究及其介电常数的计算

首先利用蒙特卡罗有限元法在分析陶瓷材料内电场分布的基础上 ,对微粒混合陶瓷材料的介电常数与各成分含量及其介电常数之间的关系进行了探讨。研究表明 ,由于介质极化的原因 ,在陶瓷材料内部 ,等势线的分布将主要集中于低介电常数成分所占的区域 ,并且 ,微粒混合陶瓷材料各成分的含量及其介电常数都会对陶瓷材料内电场的分布产生重要影响 ,并使陶瓷材料的宏观介电常数发生变化。当陶瓷材料中含有与其他成分介电常数差别相当大的成分时 ,利用蒙特卡罗有限元法可获得较其他传统方法更为准确的结果系统地研究了钡钛钕系统陶瓷的介电性能。研究结果表明 ,Ba Ti O3中掺入极少量的 Nd2 O3(例如摩尔分数 x为 0 .1% )时 ,材料呈半导性 ,电阻率呈明显的 PTCR效应。Ba Ti O3中掺入少量的 Nd2 O3(x≥ 0 .2 % )时 ,材料呈绝缘性 ,且随着 Nd2 O3掺入量的增加 ,材料的平均晶粒尺寸不断减小 ,居里峰向负温方向移动 ,居里峰不断降低。Ba Ti O3中掺入少量 Nd2 O3· 2 Ti O2时 ,随着掺入量的增加 ,居里峰向负温方向移动 ,晶粒尺寸不断增大 ;Ba Ti O3中掺入较多的 Nd2 O3· 2 Ti O2 时 ,随着掺入量的增加 ,介电常数不断减小 ,介电常数的温度特性曲线的非线性程度不断减小 ,并且 ,当 Ba Ti O3与 Nd2 O3· 2 Ti O2 的摩尔比?     

Humidity‐Triggered Self‐Healing of Microporous Polyelectrolyte Multilayer Coatings for Hydrophobic Drug Delivery

Layer‐by‐layer (LbL) self‐assemblies have inherent potential as dynamic coatings because of the sensitivity of their building blocks to external stimuli. Here, humidity serves as a feasible trigger to activate the self‐healing of a microporous polyethylenimine/poly(acrylic acid) multilayer film. Microporous structures within the polyelectrolyte multilayer (PEM) film are created by acid treatment, followed by freeze‐drying to remove water. The self‐healing of these micropores can be triggered at 100% relative humidity, under which condition the mobility of the polyelectrolytes is activated. Based on this, a facile and versatile method is suggested for directly integrating hydrophobic drugs into PEM films for surface‐mediated drug delivery. The high porosity of microporous film enables the highest loading (≈303.5 μg cm^?2 for a 15‐bilayered film) of triclosan to be a one‐shot process via wicking action and subsequent solvent removal, thus dramatically streamlining the processes and reducing complexities compared to the existing LbL strategies. The self‐healing of a drug‐loaded microporous PEM film significantly reduces the diffusion coefficient of triclosan, which is favorable for the long‐term sustained release of the drug. The dynamic properties of this polymeric coating provide great potential for its use as a delivery platform for hydrophobic drugs in a wide variety of biomedical applications.     

Edible Coatings to Inhibit Lipid Migration in a Confectionery Product

Coatings containing hydrocolloids and sweetners were tested for lipid barrier and sensory properties, adhesion to chocolate, viscosity, and a_w. A coating containing high methoxyl pectin, acacia gum, high fructose corn syrup, dextrose, fructose, and sucrose was most effective. Coatings (0.5 mm thick, a_w 0.5) showed no detectable oil migration after 47 days at 30 ± l°C, compared to 11.5 mg/cm² trilinolein equivalents migration in 1 day at 21 ± 2°C. Coatings (0.5 mm thick) were applied between chocolate and peanut butter and tested for sensory characteristics. Except for the color of the coating, no significant difference occurred in overall preference compared to control (no coating) samples.     

赤泥制作瓷质砖黑色颗粒料的研究

本文探讨了以赤泥为主要原料研制瓷质砖黑色颗粒料的可行性。结果表明 :以赤泥为主要原料可合成出呈色纯正 ,价格低廉的黑色颜料 ,但赤泥用量应适当控制 ,烧成温度、气氛需严格控制。     

混合烧成法制取低温PTCR陶瓷材料的研究

本文提出了用混合烧成制取低温ＰＴＣＲ陶瓷材料的工艺方法，该方法和普通工艺相比，不仅降低ＢａＴｉＯ３陶瓷的工作温区，而且室温电阻率比普通工艺下的要小，即半导化程度比普通工艺要好。     

AZ91D镁合金表面激光熔覆Al+Al2O3涂层研究

为了改善AZ91D镁合金的表面性能,试验利用3kW横流CO2激光器在AZ91D镁合金表面上进行了激光熔覆Al+Al2O3涂层处理。熔覆后使用X射线衍射仪(XRD)和扫描电镜(SEM)对熔覆层进行了微观分析,测试了熔覆层的显微硬度及摩擦磨损性能。试验结果表明:熔覆层由Mg,Mg17Al12,Al2O3等相组成,表层微观结构主要是Mg和Al的亚共晶基体及其上弥散的Al2O3颗粒;熔覆层的平均显微硬度最高达到250HV0.05,明显高于基体AZ91D(70～80HV0.05);其磨损性能与基体相比也有了较大提高。     

电子束熔凝NiCoCrAlY涂层的高温氧化行为分析

在GH140高温合金钢基体表面采用磁控溅射沉积NiCoCrAlY涂层,并用电子束进行熔凝处理。分析结果表明,电子束熔凝使NiCoCrAlY涂层与基体形成组分梯度变化的混合层,提高了涂层与基体的结合程度。涂层经1000℃和1100℃,10h的对比氧化试验,结果表明,在1000℃时,Cr扩散至表面,由于CrO3的挥发而迅速损耗,但Y的存在,在一定程度上减缓了Cr的损失速度。1100℃时起抗氧化作用的主要来自Al、Ti、Si、Mn等,Al的内氧化抑止了Al的外扩散。     

30mm口径半穿甲模拟弹侵彻陶瓷复合靶板SPH数值模拟

30mm口径半穿甲模拟弹侵彻陶瓷/金属复合靶板,采用非线性有限元分析软件ANSYS/LS-DYNA3D进行数值模拟.陶瓷采用SPH算法,其余部分采用有限单元法.模拟结果与试验结果基本吻合,避免了纯Lagrangian算法处理大变形、大应变率和高压作用中的网格消蚀和网格重分.研究表明该算法可行有效.     

Preparation of Ba2YCu3O7-δ Thin Films with Preferred Orientation through an Organometallic Route

Superconducting Ba₂YCu₃O_7-δ thin films were prepared through an organometallic route. Single-phase Ba₂YCu₃O_7-δ thin films with preferred orientation were successfully prepared on SrTiO₃ (100) single-crystal substrates at 800°C by a dip coating method using partially hydrolyzed Ba-Y-Cu organometallic solutions. Preferentially oriented Ba₂YCu₃-O_7-δ thin films were also prepared on MgO (100) substrates. By controlling the partial hydrolysis conditions, a coating solution for precursor thin films was kept accurately at the stoichiometric composition. The use of ozone gas during the pyrolysis of the precursor thin films was found to suppress the formation of BaCO₃. Ba₂YCu₃O_7-δ thin films with c -axis orientation perpendicular to a SrTiO₃ (100) substrate, which were heat-treated at 900°C for 15 min, exhibited a superconductivity transition with an onset of 90 K and an end of 75 K.