Ti对铬钼钒模具钢奥氏体化组织与性能的影响

??The microstructure and properties of die steels with Ti and without Ti at different austenitizing temperatures were studied through the combination of thermodynamic calculation and experiment. The results show that the total solution temperature of Cr23C6, Cr7C3, VC, V2C, V8C7, MoC, Mo2C and TiC is 748. 2, 952. 7, 977. 3, 632. 9, 1116. 0, 1131. 2, 645. 3 and 1044. 1??, respectively. Hardness and impact toughness both increase with the increase in temperature. When the austenitizing temperature is above 1200 ??, it has a greater influence on the hardness. Toughness of die steel with Ti is better than that without Ti. The grain becomes coarse and the amount of martensite increases with the increase of temperature. The average grain size of the die steel with Ti is 21. 4??m smaller than that without Ti, and the size of the undissolved phase of the former is about 0. 2??m smaller than that of the latter.     

Tunable temperature‐ and shear‐responsive hydrogels based on poly(alkyl glycidyl ether)s

We describe the synthesis, characterization and direct‐write 3D printing of triblock copolymer hydrogels that have a tunable response to temperature and shear stress. In aqueous solutions, these polymers utilize the temperature‐dependent self‐association of poly(alkyl glycidyl ether) ‘A’ blocks and a central poly(ethylene oxide) segment to create a physically crosslinked three‐dimensional network. The temperature response of these hydrogels was dependent upon composition, chain length and concentration of the ‘A’ block in the copolymer. Rheological experiments confirmed the existence of sol–gel transitions and the shear‐thinning behavior of the hydrogels. The temperature‐ and shear‐responsive properties enabled direct‐write 3D printing of complex objects with high fidelity. Hydrogel cytocompatibility was also confirmed by incorporating HeLa cells into select hydrogels resulting in high viabilities over 24 h. The tunable temperature response and innate shear‐thinning properties of these hydrogels, coupled with encouraging cell viability results, present an attractive opportunity for additive manufacturing and tissue engineering applications. © 2018 Society of Chemical Industry     

分光光度法和光度滴定法联合测定湿法炼锌流程中钴渣浸出液中锌钴镍

湿法炼锌流程中钴渣浸出液中含有高浓度的Fe²⁺和Mn²⁺,用分光光度法测定Co²⁺和Ni²⁺时,Fe²⁺-EDTA会严重干扰Co²⁺和Ni²⁺的测定;在用光度滴定法测定Zn²⁺和Co²⁺合量时,Ni²⁺对二甲酚橙指示剂具有封闭作用,Mn²⁺亦与EDTA螯合,导致滴定结果偏高。为消除Fe²⁺和Mn²⁺对Zn²⁺、Co²⁺和Ni²⁺测定的干扰,实验进行氧化分离Fe²⁺和Mn²⁺预处理,在NaAc/Hac缓冲体系下,以EDTA作显色剂用分光光度法测定Co²⁺、Ni²⁺。在波长466nm处,Co²⁺的线性范围为50~500mg/L时与吸光度呈线性,相关系数R²为0.9992;在384nm处,Ni²⁺的线性范围为50~500mg/L时与吸光度呈线性,相关系数R²为0.9998。根据分光光度法测出Ni²⁺物质的量,加入1.1倍的丁二酮肟以除去Ni²⁺,用二甲酚橙为指示剂,EDTA鳌合-光度滴定法测定Zn²⁺、Co²⁺合量,扣减Co²⁺含量得出Zn²⁺含量。选取4个锌湿法炼锌流程中钴渣浸出液实际样品,按照实验方法中的分光光度法测定Co²⁺和Ni²⁺,光度滴定法测定Zn²⁺、Co²⁺合量,Zn²⁺、Co²⁺和Ni²⁺测定结果的相对标准偏差(RSD,n=6)均不大于0.70%,加标回收率分别为99.59%~100.41%、99.69%~100.64%、99.92%~100.08%。     

pH-independent dissolution enhancement for multiple poorly water-soluble drugs by nano-sized solid dispersions based on hydrophobic–hydrophilic conjugates

The objective of this study was to achieve an optimal formulation of hydrophilic–hydrophobic conjugates for nano-sized solid dispersions (SDs) with enhanced dissolution of multiple drugs in different gastrointestinal (GI) tract environments. A new conjugate powder with an optimized process was used to fabricate SDs that contained three poorly water-soluble drugs that were also poorly soluble in different dissolution media. The self-assembled nanoparticle formation, drug crystallinity and SD molecular interactions were investigated by measuring the particle size during dissolution testing and physicochemical property analysis (powder X-ray diffraction and Fourier transform infrared spectroscopy). Drug release studies indicated that SD containing conjugated powder significantly improved the dissolution rates of these poorly water-soluble drugs in the GI tract. In addition, particle size analysis showed nano-sized particles in the dissolution media in the early stage with a tendency to reduce smaller particles over time. Physicochemical characterizations demonstrated almost amorphous drug states and hydrogen bonding interactions between the drugs and conjugates in the SD. This study optimized a promising material for SD, and the material was shown to have a promising performance under various pH medium conditions with poorly water-soluble drugs.     

Controllable 1D Patterned Assembly of Colloidal Quantum Dots on PbSO4 Nanoribbons

Control of the 1D self‐assembly pattern of colloidal quantum dots (QDs) on PbSO₄ nanoribbon (NRb) templates is achieved. The internal structure of the NRbs is investigated by X‐ray diffraction, revealing the isotropic packing of the PbSO₄ nanoclusters in the NRbs. Colloidal QDs in a chloroform/hexane mixture are adsorbed onto the region close to the edges of the NRbs and form a 1D assembly of straight single line or double lines by controlling the amount of OAm. This is the first demonstration of a densely packed 1D self‐assembly of colloidal QDs with a straight line pattern without the use of any molecular bridge or adhesive. Atomic force microscopy measurements of the NRbs show depressions in the phase profile along the width of the NRbs, corresponding to the position of the 1D QD chain. The amount of adsorbed QDs on the NRbs in solution decreases as the addition of OAm increases, suggesting that additional OAm prevents interaction between the QDs and NRbs but facilitates the uniform adsorption of the 1D assembly. The low‐dimensional self‐assembly of colloidal QDs in this study opens up the possibility for the creation of anisotropically assembled QD superstructures.     

Catalytic oxidation of CO on mesoporous codoped ceria catalysts:Insights into correlation of physicochemical property and catalytic activity

Codoping approach is an appealing strategy to further improve the catalytic activity of Ce-based catalysts. In the present study,Mn and/or Cu doped ceria solid solutions MnxCuyCe_(1-x-y)O_2,Cu_xCe_(1-x)O_2,Mn_xCe_(1-x)O_2 and pure CeO_2 were prepared by CTAB-assisted hydrothermal method for CO oxidation.XRD, SEM, EDS, BET, Raman, H2-TPR, XPS and in situ DRIFTS techniques were carried out to study the physicochemical properties and to correlate them to the activity. The doped samples maintain the cubic fluorite structure of CeO_2 with high crystallinity and small crystallite size, forming Ce-based solid solutions. The obtained catalysts have large mesoporous structure with average pore size of 10-14 nm. The doped transition metal enhances the oxygen vacancies and improves reducibility of the solids. The synergistic interaction of Mn and Cu codoping induces mo re oxygen vacancies, pro moting the increase of surface adsorbed oxygen and the transfer of bulk oxygen of catalyst, thereby enhancing the catalytic activity for CO oxidation. Besides, the decomposition rate of the carbonate species which is derived from in situ DRIFTS for each catalyst can provide a measure to evaluate its catalytic activity of CO oxidation.     

气瓶内部淬火过程的流动换热特性

 大直径厚壁气瓶内部淬火时的流动换热过程极其复杂，受到多种因素的影响，而研究气瓶内部压强和温度的变化规律对改善流动换热效果、提高产品组织性能具有重要的理论指导意义。以914 mm厚壁气瓶和瓶内流体为研究对象，建立了二维等效流 固耦合模型；采用多喷嘴系统对气瓶内外进行喷水淬火，研究了气瓶总长、喷水流速及淬火时间对瓶内压强及内壁温度的影响，通过间歇淬火试验验证了数学模型的正确性。结果发现，气瓶长度对瓶内压强和瓶壁温度的影响显著，喷水流速次之，当喷水流速大于8 m/s后，水量对瓶壁的冷却效果大大降低；气瓶内壁长度方向的温度梯度分别随气瓶总长的增加和淬火时间的延长而减小，但基本不受喷水量的影响。     

积分中值屈服准则解析厚板轧制椭圆速度场

为解决非线性Mises比塑性功率积分困难以及由此导致的轧制功率解析式难以获得的问题,本文通过建立并利用线性比塑性功率表达式对提出的椭圆速度场进行能量分析,得到了轧制力能参数的解析解.文中通过对变角度屈服函数求积分中值,构建了一个新的屈服准则,它是主应力分量的线性组合,在π平面上的轨迹是逼近Mises圆的等边非等角的十二边形,其基于Lode参数表达式的理论结果也与实验数据吻合较好.同时,根据厚板轧制时金属流动速度从入口到出口逐渐增大的特点,提出了水平速度分量满足椭圆方程的速度场,该速度场满足运动许可条件.通过相应的轧制能量分析,获得了基于线性屈服准则的内部变形功率以及基于应变矢量内积法上的摩擦功率与剪切功率.在此之上,通过泛函的极值变分导出了轧制力矩、轧制力以及应力状态系数的解析解,并与现场实测数据进行了对比,结果表明利用本文提出的屈服准则与速度场所建立的轧制力矩与轧制力模型与实测值吻合较好,其中轧制力误差小于5.3%,轧制力矩误差在6%左右.     

镀液温度实时控制系统的设计与实现

针对镀液温度变化的非线性和滞后性,设计了采用专家规则的镀液温度实时控制系统。该系统在实时监测的基础上,构建了综合评判镀液温度偏差和镀液温度偏差变化率的专家规则,实现了镀液温度的自适应快速调节。仿真分析结果表明,该系统克服了非线性和滞后性的不良影响,能够实现镀液温度的实时控制。