塑料微球表面制备聚乙烯醇涂层研究进展

在聚苯乙烯（PS）-聚乙烯醇（PVA）-碳氢聚合物（CH）三层球的设计中制备PVA涂层的方法主要包括乳液微封装法、炉内成球涂层法、浸(旋)涂法、界面缩聚法及喷涂法等,前三种方法目前最为常用。总结了前三种制备PVA涂层方法的优缺点及目前的研究和制备现状。乳液微封装法适合于500 m以下小尺寸双层球的制备,具有微球成活率高、产品质量较好等优点,但制备过程受人为因素影响较大,且不易制备大直径双层球。炉内成球涂层法也适用于小尺寸双层球的制备,其制备周期短,但液滴发生器的设计苛刻,PVA层的均匀性差,且不易制得较大尺寸的双层球。浸（旋）涂法可制备1000 m以上的大直径双层球,但该方法中影响PVA涂层铺展的因素较多,得到的PVA涂层均匀性较差,且涂层很薄。     

充气温度对PS-PVA-CH塑料微球性能的影响

 主要研究了PS-PVA-CH空心塑料微球充气时，充气平衡温度对微球强度、球形度和表面形貌的影响。对PS，PVA和CH材料的热重分析结果表明，PS和PVA具有较高的分解温度，而PS-PVA双层球和PS-PVA-CH塑料微球升温后的耐外压实验表明，温度升高后双层球耐外压强度降低很快，不能满足充Ar气需要；而3层球在100~120℃仍有很高强度，在该温度下，可以实现充Ar气。微球表面形貌分析结果显示，高温充气后，3层球表面粗糙度升高。     

臭氧改性及搅拌桨结构对大直径双层球制备的影响

随着高功率激光器的飞速发展,ICF物理实验对聚苯乙烯（PS）-聚乙烯醇（PVA）双层空心微球的规格要求逐渐提高,直径要求将达到700～900 m。针对该直径范围的PS-PVA双层空心微球,通过采用PS球臭氧化表面改性技术和搅拌桨叶轮结构优化技术,对传统乳液微封装法制备双层空心微球工艺进行了改进,臭氧化表面改性后PS固体核心发生憎水-亲水转变,提高了PS与PVA之间的作用强度;搅拌桨叶轮结构优化,改善了体系容器内溶液流场均匀性,使得微球在整个体系中的运动相对平稳,从而初步制得了直径范围在700～900 m的双层空心微球。     

载气环境对液态空心玻璃微球运动状态的影响

 研究了载气组份、温度、压力以及微球直径和壁厚对液态空心玻璃微球在炉内运动状态的影响。结果表明：在用干凝胶法制备空心玻璃微球工艺的常用载气组份、温度和压力范围内，载气的组份、温度和压力对相同直径和壁厚的液态玻璃微球在炉内运动速度的影响小于8.3%，但载气组份和压力对液态玻璃微球运动雷诺数和韦伯数的影响很显著。玻璃微球的直径和壁厚是液态玻璃微球运动速度、雷诺数和韦伯数的重要影响因素。提高载气中的氦气含量或降低载气压力可以降低载气对液态玻璃微球的非球形化作用，提高载气温度可以降低其球形化的阻力。     

ICF微球壳层掺溴含量的XRF表征

通过EC法与FP法的混合定量分析方法,建立了用于微球壳层掺杂元素含量测量的校准模型;基于对微球直径、PS、PVA层厚度对分析元素荧光强度影响的理论计算及XRF实验研究,将该模型用于ICF微球壳层掺溴含量的测量,得到微球壳层掺溴含量较为精确的分析结果,实验结果表明:XRF法测最ICF微球壳层掺溴含量具有较高的精度,在微球涂层厚度大于10μm时,其测量相对误筹在5%左右.     

干凝胶粒子物性对空心玻璃微球炉内成球过程的影响

为实现干凝胶法制备惯性约束聚变靶用空心玻璃微球(HGM)炉内成球工艺过程的有效控制,从数值模拟和工艺实验两个方面研究了干凝胶粒子直径、比热容、发泡剂质量分数和辐射吸收系数对干凝胶粒子炉内成球过程及最终HGM性能参数的影响。结果表明,随着干凝胶粒子直径和/或比热容的增大,干凝胶粒子在吸热封装阶段的升温速率显著降低,在炉内成球过程各工艺阶段的停留时间快速下降,尤其是在精炼阶段的停留时间急剧缩短。降低干凝胶粒子的比热容和/或提高干凝胶粒子的发泡剂质量分数,HGM的直径和壁厚均匀性增大,高质量空心球的比例也相应提高。干凝胶粒子的辐射吸收系数变化对炉内成球过程几乎没有影响。     

用于ICF靶的空心玻璃微球的干凝胶法制备

 为用干凝胶法制备用于ICF靶的空心玻璃微球（HGM），研究了载气组份、温度和压力对成球过程和HGM品质的影响，优化了制备工艺参数。结果表明：提高载气中氦气的含量，有利于增加干凝胶粒子的成球率和HGM的纵横比；适当提高载气中氩气的含量，有利于提高HGM的表面质量。降低载气压力可以提高HGM的纵横比；升高载气温度可以提高干凝胶粒子成球率和HGM品质。当载气中氦气的体积分数在50%~80%，载气压力在(0.75~1.00)×10⁵ Pa，载气温度在1 500~1 650 ℃时，干凝胶粒子的成球率较高，HGM的球形度、同心度和表面光洁度较好。制备得到了直径100~500 μm、壁厚0.5~3.0 μm的HGM，其耐压强度、抗大气侵蚀性能和表面粗糙度等指标均满足ICF物理实验要求。     

干凝胶炉法制备聚苯乙烯空心微球

研究了一步乳化法制备初始粒子的过程中相比及搅拌强度对初始粒子直径的影响 ,初步探讨了干凝胶炉内成球过程中 ,炉温、炉内气氛、压力等对聚苯乙烯 (PS)空心微球产率及同心度的影响。以分子量为 2 2万的聚苯乙烯制得了直径在 70～ 550μm的初始粒子 ,经乙醇浸泡后 ,制得了含 2 %质量分数发泡剂的干凝胶粒子 ,并在 Polymer-70 0干凝胶炉上制备出了外直径为 4 0 0～ 90 0 μm、壁厚为 2～1 0 μm、同心度≥ 95%的     

制备大直径无气泡聚苯乙烯空心微球

 高品质聚苯乙烯（PS）空心微球是惯性约束聚变（ICF）实验用多层塑料微球靶的重要芯轴,常由乳液技术制备。针对由乳液技术制备的PS微球壳壁内容易形成气泡而且大直径微球制备困难的问题,实验研究了对壳壁内存在的气泡以及消除方法和制备大直径PS微球的制备技术。     

PA-PVA-CH塑料微球充D2和Ar

ICF塑料靶丸典型结构由3层组成：内层起支撑作用的聚苯乙烯（PS），中间起阻气作用的聚乙烯醇（PVA）和外部的烧蚀层碳氢（CH）。作为靶丸，空心塑料微球内的气体由燃料气体和诊断气体组成。燃料气体目前使用的主要是D2。塑料微球采用热扩散法充气，D2在塑料球壳中扩散很快，而Ar却渗透很慢，因此，塑料靶丸充气的核心工艺是如何充Ar和如何保D2。利用充Ar条件充D2或利用保D2技术保Ar都是很容易实现的。塑料微球充气在自行研制的充气系统中完成，球内气体采用四极质谱或X射线荧光谱仪进行测量。     

基于小波分析的ARIMA与LSSVM组合的高炉煤气预测

高炉煤气发生量的准确预测对钢铁企业能源优化调度具有重要意义。针对钢铁企业中基于机理模型的高炉煤气发生量难以准确预测问题,建立了基于小波分析的最小二乘支持向量机(LSSVM)和自回归差分滑动平均(ARIMA)相结合的高炉煤气预测模型。预测前利用小波去噪对原始数据进行消噪处理,并对处理后的数据进行小波变换得到趋势序列和波动序列,然后对各部分序列分别建模和预测,最后将各部分预测结果叠加;仿真结果表明,组合预测模型减小了预测误差,提高了预测精度。与其他模型相比,组合预测模型更适合高炉煤气预测。     

Prediction of particle sticking efficiency for fly ash deposition at high temperatures

The tendency of ash particles to stick under high temperatures is dictated by the ash chemistry, particle physical properties, deposit surface properties and furnace operation conditions. A model has been developed in order to predict the particle sticking efficiency for fly ash deposition at high temperatures. The model incorporates the particle properties relevant to the ash chemistry, particle kinetic energy and furnace operation conditions and takes into consideration the partial sticking behaviour and the deposit layer. To test the model, the sticking behaviours of synthetic ash in a drop tube furnace are evaluated and the slagging formation from coal combustion in a down-fired furnace is modelled. Compared with the measurements, the proposed model presents reasonable prediction performance on the particle sticking behaviour and the ash deposition formation. Through a sensitivity analysis, furnace operation conditions (velocity and temperature), contact angle and particle size have been found to be the significant factors in controlling the sticking behaviours for the synthetic ash particles. The ash chemistry and furnace temperature dictate the wetting potential of the ash particles and the melting ability of the deposit surface; particle size and density not only control the particle kinetic energy, but also affect the particle temperature. The furnace velocity condition has been identified as being able to influence the selective deposition behaviour, where the maximum deposition efficiency moves to smaller particles when increasing the gas velocity. In addition, the thermophoresis effect on the arrival rate of the particles reduces with increasing the gas velocity. Further, increasing the melting degree of the deposit layer could greatly enhance the predicted deposition formation, in particular for the high furnace velocity condition.     

A simple and effective route for the preparation of poly(vinylalcohol) (PVA) nanofibers containing gold nanoparticles by electrospinning method

Poly(vinylalcohol) (PVA) nanofibers containing gold nanoparticles have been simply obtained by electrospinning a solution containing gold nanoparticles without the additional step of introducing other stabilizing agents. The optical property of gold nanoparticles in PVA aqueous solution was observed by UV-visible absorption spectra. Morphology of the Au/PVA nanofibers and distribution of the gold nanoparticles were characterized by transmission electron microscopy (TEM). The structure transformation was characterized from PVA to PVA/Au composite by Fourier transform infrared spectroscopy (FTIR).     

Thermal calculation for a furnace with three-tiered near-wall burners

The paper considers using a differential method for thermal calculation of a furnace with finding the thermal and aerodynamic parameters within the radiation chamber of a tube furnace. The furnace is equipped with acoustictype burners allocated in three tiers on the lateral walls. The method implies joint numerical solution of 2D radiation transfer equations using the S ₂-approximation of the discrete ordinate method, of energy equations, flow equations, k-ε turbulence model, and single-stage modeling of gas fuel combustion. Typical results of simulation are presented.     

Phase transitions of perfluorocarbon nanoemulsion induced with ultrasound: A mathematical model

While ultrasound has been used in many medical and industrial applications, only recently has research been done on phase transformations induced by ultrasound. This paper presents a numerical model and the predicted results of the phase transformation of a spherical nanosized droplet of perfluorocarbon in water. Such a model has applications in acoustic droplet vaporization, the generation of gas bubbles for medical imaging, therapeutic delivery and other biomedical applications.The formation of a gas phase and the subsequent bubble dynamics were studied as a function of acoustic parameters, such as frequency and amplitude, and of the physical aspects of the perfluorocarbon nanodroplets, such as chemical species, temperature, droplet size and interfacial energy. The model involves simultaneous applications of mass, energy and momentum balances to describe bubble formation and collapse, and was developed and solved numerically. It was found that, all other parameters being constant, the maximum bubble size and collapse velocity increases with increasing ultrasound amplitude, droplet size, vapor pressure and temperature. The bubble size and collapse velocity decreased with increasing surface tension and frequency. These results correlate with experimental observations of acoustic droplet vaporization.     

Structural parameters of synthetic opals: Statistical analysis of electron microscopy images

The paper reports on a comprehensive study of the statistical characteristics of an ensemble of a-SiO₂ particles in synthetic opals. The results of processing of the electron microscopy images obtained in the investigation of the (111) growth layer are presented. To calculate the statistical parameters, an algorithm is developed which permits determination of the diameters of a-SiO₂ particles and coordinates of their centers. The algorithm is based on the pattern recognition procedure of objects with radially symmetric boundaries by means of a transformation of the original image similar to the Hough transformation. Our image processing study yields structural parameters of the (111) growth layer, more specifically, the average particle diameter, ～316 nm, the distribution profile half-width, ～7%, and the average distance between the centers of neighboring particles, ～315 nm. The results of the opal image processing are compared with data of optical experiments.     

改进型 PSO‐SVM算法对井下多组分气体定量分析的研究

对于多组分混合气体定量分析而言，基于特征光谱的定量分析技术具有不可比拟的优势，而定量检测效率与精度取决于其采用的光谱数据处理算法的优劣。优化光谱分析算法参数与改进光谱数据处理方式是提高定量分析速度与精度的重要手段。针对井下多组分气体定量分析建模过程中支持向量机(SVM)参数难以确定，并且随组分数增多而呈指数增长的光谱数据运算量的问题，提出了一种改进型粒子群优化-支持向量机(PSO-SVM)算法。该算法主要针对多组分气体混合光谱数据量大，光谱特征信息存在交叠的问题进行研究。通过粒子变异约束PSO算法的收敛路径，再通过粒子信息共享提高模型优化效率，最后利用设置动态不敏感区提高模型精度。设计了一种井下多组分气体快速定量检测系统。该系统由CPU控制信号调制模块驱动红外光源，信号光经过滤尘除湿后的气室照射在探测器上。在压力与温度传感器补偿的基础上，由信号处理模块将探测得到的光信号量化传入CPU，最终，结合改进型PSO-SVM算法实现各组分气体浓度的定量分析。在完成井下实际样气采集、预处理的基础上，对浓度范围0～10.0%的CH₄和浓度范围0～1.0%的C₂H₆，C₃H₈，SO₂和CO₂共5种组分的混合气体进行了测试，获得了800组红外光谱数据，其中训练集400组，验证集400组。采用SVM建立了多组分气体的定量分析模型，利用改进型PSO对SVM中的参数进行了优化，并将获得的最优参数重建了定量分析模型。对采集的红外光谱数据分别由本算法与传统BP网络算法进行各组分气体浓度反演，实验结果显示，由于变异粒子对其产生的约束，使最优值收敛范围变小，从而提高了收敛速度，该算法建模时间仅为传统方法的1/10；由于通过气体光谱特性给出不敏感区，使特征光谱计算时交叉敏感效率降低，从而提高了模型预测的准确度，平均误差约为传统方法的1/5。由此可见，该算法在全局优化及快速收敛方面得到了显著提升，改进型PSO结合SVM用于井下多组分气体定量分析是可行的。改进型PSO-SVM算法对于多组分气体混合红外光谱数据的分离具有很好的适用性，其有一定的实际应用价值。     

A CFD assisted control system design with applications to NO x control in a FGR furnace

In this paper, a novel technique to design control systems for industrial processes with non-linear distributed parameters is proposed. The technique utilizes computational fluid dynamics (CFD) simulation to extract the most essential characteristics from the non-linear industrial process, and then represent them as a set of linear dynamic models around a specific operating point. Based on the linear dynamic representation, a closed-loop feedback linear control system can be designed to maintain the desired performance for the system around the chosen operating point. To illustrate such a design process, an industrial reheating furnace with flue gas recirculation (FGR) is selected herein. The method involves the numerical solution of the partial differential equations describing the fluid flow, heat transfer and combustion process in the furnace. The resulting dynamic relations between the furnace inputs and outputs can then be represented in terms of a multi-input and multi-output transfer function matrix. The objective of the control system is then to maintain the optimally selected furnace operating conditions and compensate for any deviations caused by disturbances to minimize the nitric oxides (NO _x ) emission through feedback mechanisms. The performance of the closed-loop controlled furnace is evaluated not only in the linear domain, but also with the detailed full-scale non-linear CFD model. The results have shown that the proposed method is viable and the designed control system can indeed minimize the deviation of the furnace from the desired operating conditions and hence to prevent any excessive NO _x formation in the combustion process.     

碳氢烧蚀层的厚度对聚乙烯醇薄膜阻气性能的影响

 以ICF实验塑料靶丸保气的需求为背景，研究了水蒸气在低压等离子体聚合碳氢（CH）膜、聚乙烯醇（PVA）膜、聚苯乙烯（PS）膜中的扩散渗透行为。根据实验数据，算出在40℃ 90%相对湿度下,水蒸气在三种样品膜中的渗透系数分别为1.906×10^-13，5.950×10^-15，.432×10 ^-14mol·m/(m²·s·Pa)，并借助多层复合膜模型的近似算法，算出在40 ℃ 90%相对湿度的外界环境下，类似多层塑料微球结构的三层复合膜中，PVA阻气层所处环境的相对湿度为53.06%，推导出PVA所处环境的相对湿度与外层CH层厚度的关系式。研究表明：CH烧蚀层越厚，PVA所处环境的相对湿度越小，保气性能越好。     

The parameter space for the direct spinning of fibres and films of carbon nanotubes

We have recently introduced a method for the continuous spinning of carbon nanotube fibres and films directly from the gas phase of a chemical vapour deposition furnace [Y. Li, et al., Science 304 (2004) 276]. In this work the effect of the process parameters on the ability to spin continuously is studied, with particular focus on the carrier gas and feedstock flow rates. Catalyst dilution by high carrier gas flow rates led to smaller diameter nanotubes but these conditions are found the hardest to spin.