玻璃形核与析晶的研究进展

研究玻璃的形核和析晶具有十分重要的科学意义，综述了近二十年来国内外采用热分析法研究玻璃形核与析晶的最新进展，重点分析了玻璃在非等温过程中的析晶动力学，同时也评述了研究玻璃形核与晶体长大速率比较科学的理论方法。     

基于形核结晶调控的钙钛矿太阳电池印刷制造的研究进展

目的 有机–无机杂化钙钛矿太阳电池以其优异的光电转换性能和低成本溶液加工等优势受到了科研工作者和产业界人士的广泛关注,文中着眼于解决把实验室的旋涂研发工艺转换为可大规模重复生产的工艺这一直接挑战。方法 印刷制造技术具有低成本、大规模、高产率、适用于柔性基底等优点,是应对该挑战的有效手段。深入梳理和总结印刷制造中钙钛矿薄膜的形核与结晶过程,对于印刷高质量钙钛矿薄膜和实现大面积高效钙钛矿太阳电池制造至关重要。结论 分析了钙钛矿形核结晶的热力学与动力学基本理论,从钙钛矿形核结晶调控这一角度出发,对各类印刷工艺制造大面积钙钛矿薄膜及光伏器件的研究现状做出相应评价,认为“升级制备技术、创新材料体系、改善稳定性能”三步走将掀起钙钛矿产业化的新浪潮。     

一种提高金刚石薄膜形核密度的新方法

报导了一种提高火焰法合成高质量金刚石薄膜形核密度的新方法-化学腐蚀法;研究了在化学腐蚀试样表面上金刚石的形核与生长行为、晶粒度与形核密度之间的关系。试验表明:经腐蚀后的样品,金刚石形核均匀致密,2min内便能形成连续的膜。金刚石形核密度随晶粒度的增加而增大。初步分析了化学腐蚀法提高形核密度的原因,认为晶界对金刚石的形核起重要作用。     

The Digital Revolution: A New Paradigm for Microfluidics

The digital revolution has come to microfluidics. In digital microfluidics (DMF), discrete droplets are manipulated by applying electrical fields to an array of electrodes. In contrast to microchannels, in DMF each sample and reagent is individually addressable, which facilitates exquisite control over chemical reactions. Here, we review the state‐of‐the‐art in DMF, with a discussion of device formats, actuation physics, and biological and nonbiological applications. Along the way, we identify the key players in the field, and speculate on the advances and challenges that lie ahead. As with other fronts in the digital revolution, there have been and will be unexpected developments as DMF matures, but we posit that the future is bright for this promising technology.     

A Novel Acoustomicrofluidic Nebulization Technique Yielding New Crystallization Morphologies

A novel acoustic microfluidic nebulization platform is demonstrated, which, due to its unique ability to access intermediate evaporation rate regimes—significantly faster than that in slow solvent evaporation but considerably below that achieved in spray drying, is capable of producing novel crystal morphologies that have yet to be reported in both model inorganic and organic systems. In addition, the potential for simultaneously encapsulating single crystals within a biodegradable polymeric coating in a single simultaneous step together with the crystallization process as the solvent evaporates during nebulization is briefly shown. The platform not only has the potential to be highly scalable by employing a large number of these low‐cost miniature devices in parallel to achieve industrially relevant particle production rates, but could also be advantageous over conventional spray drying in terms of energy utilization, given the tremendous efficiency associated with the high‐frequency ultrasonic microdevice as well as its ambient temperature operation.     

晶核剂及热处理对锂铝硅系微晶玻璃晶化和性能的影响

采用差热分析法研究了LAS玻璃的析晶动力学,讨论了4.5wt%TiO2和2wt%TiO2 2.5 wt% ZrO2两种晶核剂对该系统玻璃晶化过程的影响.通过正交实验确定了玻璃晶化的最优热处理制度,并研究了热处理对微晶玻璃的晶相、显微结构及热膨胀性能的影响.结果表明:与采用TiO2单一晶核剂相比,采用TiO2 ZrO2复合晶核剂的玻璃析晶活化能E降低,晶化指数n加大,体积析晶趋势增大.热处理制度能控制晶相的析出,析晶初始温度下首先析出的晶体为β石英固溶体,晶化温度升高转变为β锂辉石固溶体,可以使样品的热膨胀性能符合要求,最优的热处理制度(使热膨胀系数最小)为:核化温度720℃,核化时间1.5小时,晶化温度810℃,晶化时间2.5小时.     

惰性固体粒子对液固两相循环流化结晶的影响及成核速率模型的建立

以KCl系统为例 ,研究了惰性固体粒子对液 -固两相循环流化结晶特性的影响。实验结果表明 ,惰性固体粒子的加入对循环流化结晶的成核速率B0 和生产速率G有明显的影响 ,并得出结晶成核速率模型 ,模型计算结果与实验数据吻合较好     

A New Paradigm for a New Field: Communicating Representations of Engineering Education Research

Based on a three‐year experience of developing, facilitating, and assessing NSF‐funded workshops on Rigorous Research in Engineering Education (RREE), the authors present four representations of engineering education scholarly work in the United States, specifically teaching and research. Many of the representations describe the relationships between engineering research, education research, teaching, and assessment. For each of the representations, assessment data are presented to evaluate which aspects resonated with workshop participants and which needed to be changed for wide acceptance by a U.S. engineering education audience. It was found that participants preferred continua to dichotomy and were more receptive to models that were introduced inductively through active learning exercises. Lessons learned, implications for the field, and future plans for further development of the paradigm are also included.     

n-SiO2对PA12涂层非等温结晶速率及成核活度系数的影响

利用火焰喷涂技术制备了聚酰胺12(PA12)及PA12/纳米SiO2(n-SiO2)复合涂层,采用差示扫描量热法(DSC)对涂层的非等温结晶性能进行了分析,探讨了n-SiO2对PA12涂层的结晶速率常数及成核活度系数的影响.结果表明,当n-SiO2的添加量在0.5%～2.5%(质量分数,下同)时,RA12/n-SiO2...     

A Series-Solution Method for Free-Boundary Problems Arising from Flow Over Topography

An analytical series method is presented for steady, two-dimensional, irrotational flow of a single layer of constant-density fluid over topography. This problem is formulated as a Laplacian free-boundary problem with fully nonlinear boundary conditions. The method is an iterative scheme that allows the calculation of analytical series solutions for supercritical, transcritical and subcritical flow regimes over arbitrary topography. By an appropriate choice of the free-boundary representation, exponential convergence of the series solution is achieved. With this accuracy, the issue of apparent dual transcritical/subcritical solutions previously obtained by boundary-integral-equation methods (BIEM) is resolved. Results are compared with solutions previously obtained using BIEM, and solutions are presented for flow over asymmetric and arbitrarily shaped obstacles.     

Nucleation and crystallization of solids from solution

Over the past couple of years, important insights into the problem of nucleation from solution on the theoretical as well as on the modeling side have been achieved. Experimentally, in situ techniques applied during the nucleation and the crystallization reaction are being developed, which will help to analyze the elementary processes during these reactions. A particularly active field was that of zeolite formation.     

Staggered Spin-Orbit Order: A New Paradigm of Broken Symmetry Phase of Matter

We propose a novel spin-orbit density wave order, which can arise in a variety of materials classes. In systems where the noninteracting wavefunctions are defined by an exotic quantum number such as total angular momentum, pseudospin, or helical quantum number owing to spin-orbit coupling of various natures, interaction can induce an emergent spin-orbit density wave even when time-reversal symmetry is intact. This density wave order is different from standard time-reversal breaking spin or orbital density wave. We apply this idea to explain the enigmatic “hidden order” phase in heavy fermion URu₂Si₂ as well as an unknown gapped quasiparticle state observed in two-dimensional electron gases, such as the surface state of BiAg₂.     

数字文化新范式与人文创新研究

目的 针对传统文化产业存在的人工成本相对高昂、物资损耗相对较大等问题,利用科技赋能企业服务,从而节省人力资源、降低设计门槛、提高设计效率、灵活对接生产、服务更广人群。方法 将人工智能应用于文化产业,从智能设计和智能制造两方面,拆分文化产业服务环节。一方面,将智能设计具体化为平面设计和结构设计,再进一步将平面设计划分为智能配色和智能排版两个部分。另一方面,智能制造主要基于大数据来调整工厂产能,提高订单处理效率,减少不必要的人力、物力损耗。结果 浙江省北大信息技术高等研究院和大胜达人工智能包装设计联合实验室研发了人工智能设计师小方,并开发出包含AI设计、配材推荐、印前检测、智能供应链、订单管理、产能分配等环节在内的一体化文化设计服务模式,为非专业用户提供了从设计到生产的全流程新智造服务。结论 人工智能在文化产业领域实现了需求分析理解、一键生成设计方案、智能印前检测、灵活对接工厂、随时查询订单状态等功能创新,获得了高效迅捷、所见即所得的竞争优势。同时,人工智能技术尚未触达人类的情感层面,无法捕捉服务对象的人性温度,在人文关怀领域仍有进步空间。     

形核剂对Li2O-Al2O3-SiO2系微晶玻璃晶化过程的影响

采用差热分析(DTA),X射线衍射分析(XRD),扫描电镜(SEM)等分析手段研究了 TiO₂和TiO₂+ZrO₂两种形核剂对Li₂O-Al₂O₃-SiO₂(LAS)系微晶玻璃的形核和晶化的影响. 结果发现,样品经过不同温度的预形核处理后,采用TiO₂单一形核剂,晶化峰值温度和晶化峰 高度的变化较大,而采用TiO₂+ZrO₂复合形核剂,晶化峰值温度和晶化峰高度的变化较小. 当形核时间为2h,两种形核剂样品的最佳形核温度分别为745和760℃.晶化后均可得到纳米 结构的β-石英石固溶体晶相,其中采用TiO₂+ZrO₂复合形核剂样品的晶粒更细小.研究表 明采用复合形核剂的LAS微晶玻璃的形核过程对温度的敏感性小,有利于对形核过程进行控 制,同时形核效率高.     

New Results of the Crystallization Behaviour of Hexagonal Barium Ferrites from a Glassy Matrix

Starting from thermoanalytic measurements of amorphous material with a composition of 40 BaO – 33 B₂O₃ – 27 Fe₂O₃ (mole ‐ %) the onset temperatures of four exothermic reaction peaks have been obtained. On the basis of this results the amorphous material was tempered under different conditions (heating rate and tempering time). The resulting reaction products were analyzed by X – ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), chemical analyses and by a vibrating sample magnetometer (VSM) to obtain information about their chemical composition, their structure and their magnetic properties. In contrast to former studies [2,3,4] it was found, that first an iron – rich phase forms at temperatures about 520 °C – 560 °C [5] followed by the crystallization of BaB₂O₄.     

不同晶核剂对硼硅酸盐钙钛锆石固化体析晶行为及化学稳定性的影响

通过“一步法”热处理制备含24%(质量分数)模拟核废物的硼硅酸盐钙钛锆石固化体,从析晶动力学角度出发,利用Kinssinger法研究不同晶核剂(Fe₂O₃、Cr₂O₃、P₂O₅、CaF₂)作用下固化体的析晶行为及其对化学稳定性的影响。实验结果表明,Cr₂O₃的引入促进了板状CaZrTi₂O₇晶体的析出,析晶活化能E由218 kJ/mol降至128 kJ/mol,并使残留在玻璃基体中的模拟核素进入所析出的晶相,而其他晶核剂对析晶无明显影响。MCC-1标准测试法结果显示,Cr₂O₃作为晶核剂时,模拟核素Ce元素抗浸出性能最为优异,化学稳定性最佳,7 d后归一化元素浸出率小于10-7 g·m-2·d-1。     

Mechanism of Metal Droplet Nucleation from Supersaturated Vapor

An analysis of the full nonlinear mechanism of condensation nucleation from a supersaturated vapor suggests that the classical Markovian growth mechanism may not apply to systems, such as metals, that exhibit pronounced magic-numbered clusters. Packing of atoms in concentric layers and/or quantum confinement of valence electrons lead to particular sized metal clusters that are anomalously stable. They are called magic-numbered clusters. Magic-numbered clusters are not explicitly addressed in the Markovian mechanism that assumes that clusters change size by accommodation or evaporation of one monomer at a time. This is a justifiable approximation only if the frequency of all cluster-cluster collisions is negligible compared with the frequency of the succession of monomer-cluster collisions required to produce an equivalent sized cluster to the cluster-cluster collision. Since the stability of magic-numbered clusters increases the likelihood of collisions between clusters, magic-numbered clusters can affect the nucleation mechanism and may have a significant influence on the nucleation rate from supersaturated metal vapors.     

Nucleation mechanism of stress corrosion cracking from notches

Crack nucleation mechanism of hydrogen assisted cracking at notched cracks in aqueous solutions is investigated, using the compact type specimens with various notch radius in low-tempered 4340 steel. A detached crack initiates at some distance ahead of the notch root. The crack nucleation at the notched root is determined by the electrical potential method. When the crack initiates, the voltage difference starts to increase. The crack nucleation site is examined by SEM. The time for crack nucleation increases with the notch root radius, ρ, and decreases with the apparent stress intensity factor K_ρ. A linear relationship between the crack nucleation time, t_n, and the parameter ${}^2\text{K}{}_{\mathrm{\rho }}\text{/(πρ)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-(2K}{}_{\mathrm{\rho }}\text{/(πρ)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{th}}\text{}}$ is seen in semi-log diagram, where $\text{(2K}{}_{\mathrm{\rho }}\text{/(πρ)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{th}}$ is almost equal to the yield shear strength.In order to explain these experimental results, a new model of micromechanics is proposed on the basis of stress induced diffusion of hydrogen in the high stress region ahead of the notch root. This model suggests that the detached crack initiates at the elasto-plastic boundary where the hydrogen concentration is from 2 to 5 times higher than that of the notch root surface. The theory agrees with experiments with respect to $\text{{2K}{}_{\mathrm{\rho }}\text{/(πρ)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-(2K}{}_{\mathrm{\rho }}\text{/(πρ)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{th}}\text{}}$ vs t_n and t_n vs ρ.The empirical equation holds under constant t_n, K_ρ = K_o(ρ/ρ_eff)^m where K₀ is the stress intensity factor with ρ ≈ 0 under the present environment, ρeff is the effective notch radius and m is constant. The value of m is 0.25 for the crack nucleation time (t_n)_th corresponding to the threshold stress intensity factor (K_ρ)_th, 0.5 for t_n < (t_n)_th and 0 for ρ ≦ ρ_eff. The above equation agrees with the theoretical equation proposed by Tanaka and Mura for any t_n and ρ_eff.