Ultrasonic degradation of the gel phase in impact polystyrenes

The rupture of the crosslinked rubber membranes in the gel particles of impact polystyrene by ultrasonic energy has been discovered to be a novel route for the semiquantitative analysis of the grafted and occluded polystyrene of the composite. Applying this new technique, the weight-average molecular weight of the matrix, grafted, and occluded polystyrene of a bulk-polymerized impact polystyrene was found to be approximately the same.     

超声波在线监测环氧树脂中温固化过程实验研究

采用超声波透射法成功实现了实时在线监测环氧树脂在不同条件下的固化反应过程,研究了超声波振幅衰减随固化反应时间的变化关系,探讨了中温条件下模具厚度和玻璃纤维对环氧树脂固化反应过程的影响。结果表明:振幅衰减呈现出先增加后减小并趋于稳定的规律;随着固化反应的进行,振幅衰减能够准确地反映出环氧树脂体系出现凝胶点的时间和黏稠态—凝胶态—玻璃态各相态的变化过程。提高温度能缩短固化时间,增加厚度和玻璃纤维能在一定程度上延缓凝胶点出现的时间,并对其机理进行了讨论。超声波在线监测为环氧树脂基复合材料的加工成型和制作工艺提供了理论依据和重要的技术手段。     

多层碳纤维布复合材料超声检测的有限元模拟

结合飞机复合材料无损检测需求,介绍了多层碳纤维布的材料工艺,分析了超声反射法的基本原理及其特点,并利用有限元方法对超声检测过程进行了数值模拟。通过实验波形和数值模拟的波形进行对比,可以看出有限元分析法对复合材料的超声检测提供了有力的理论依据,在一定程度和范围内可以对实验进行结果预测和评估。同时实验结果表明,超声波检测复合材料检测精度较高,检测效果较明显,可以准确的识别出是否存在缺陷以及判断出缺陷的位置。     

UHMWPE/CNTs冻胶体系的流变行为研究

研究了碳纳米管(CNTs)的加入对超高分子质量聚乙烯(UHMWPE)稳态表观粘度、粘流活化能、非牛顿指数和结构粘度指数的影响。结果表明:碳纳米管添加量小于或等于3ω时,UHMWPE/CNTs冻胶体系的粘流括化能降低,表观粘度都低于空白UHMWPE冻胶体系。CNTs的加入对UHMWPE冻胶体系的非牛顿指数和结构粘度指数影响不大。     

Separation of ultrasonic contributions and energy utilization characteristics of ultrasonic regeneration

The method of applying ultrasound to silica gel regeneration process has been proved to be able to improve regeneration efficiency and reduce regeneration temperature. The average regeneration rate can be increased by 10% and the benefits should owe to the special “vibration effect” and “heating effect” induced by ultrasound. In this article, a dynamic one‐dimensional mathematical model, validated by experiments, has been developed. It is then used to investigate energy utilization efficiency of the ultrasonic regeneration and respective contribution ratio of the two ultrasonic effects. The results show that the contribution ratio of vibration effect dominates and the energy utilization efficiency of silica gel regeneration with ultrasound can be 1% higher. The ultrasonic regeneration is more energy‐saving when the contribution ratio of vibration effect is greater. The results also show that the enhancement of regeneration brought by ultrasound is not a simple sum of their respective contribution. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1843–1853, 2014     

Decrosslinking of crosslinked high‐density polyethylene via ultrasonically aided single‐screw extrusion

A novel environmentally friendly process for decrosslinking of the peroxide crosslinked HDPE (XHDPE) via ultrasonic assisted single (SSE) is developed and its process characteristics are established. The specific ultrasonic energy decreases with the flow rate and increases with the ultrasonic amplitude, while die pressure increases with the flow rate and decreases with the ultrasonic amplitude. Application of ultrasonic treatment during extrusion enables an increase of productivity. Gel fraction, crosslink density, dynamic and mechanical properties, and thermal behavior of the virgin HDPE, XHDPE, and decrosslinked XHDPE are measured. Gel fraction and crosslink density of the decrosslinked XHDPE are decreased with increasing flow rate and ultrasonic amplitude. A unique linear relation between the normalized gel fraction and the normalized crosslink density is found, regardless of the type of extruders and processing conditions. SEM images reveals that the decrosslinked XHDPE is a composite of submicron size gel particles embedded in its sol matrix. The sol extracted from the decrosslinked XHDPE exhibits a higher complex viscosity and higher level of branching than the virgin HDPE. An increase of the ultrasonic amplitude leads to a decrease of the complex viscosity, storage and loss moduli, and an increase of the loss tangent of the decrosslinked XHDPE. The thermal behavior and mechanical properties of the decrosslinked XHDPE show a weak dependency on processing conditions. At some processing conditions, mechanical properties of the decrosslinked XHDPE are close or higher to those of XHDPE. POLYM. ENG. SCI., 54:2715–2730, 2014. © 2013 Society of Plastics Engineers     

Mass production of multi-layer piezoelectric composite and their energy harvesting properties

We propose a multilayer piezoelectric composite and its mass production technique to solve the problems in applying flexible piezoelectric energy harvesters in industry. A roll-to-roll process is used to fabricate a large-area composite sheet with a high mechanical strength. The sheet is used to fabricate a multilayer composite, which shows considerably higher ferroelectric and piezoelectric properties compared to single-layer composites, and these properties improve as the number of layers increases. A multilayer-composite-based flexible energy harvester with a high output short-circuit current is developed. Therefore, the proposed multilayer composite and fabrication technique are suitable for flexible piezoelectric energy harvester applications.     

平纹编织碳纤维增强碳化硅复合材料低速冲击特性及冲击后的压缩强度

采用落锤冲击试验系统对平纹编织碳纤维增强碳化硅复合材料平板试样进行低速冲击,冲击能量为1.5～9J。冲击试验后,采用超声C扫描得到冲击损伤的大小。对含冲击损伤的试样进行压缩试验,通过与未冲击试样的压缩强度比较,得到冲击试样的剩余压缩强度。并对比了编织陶瓷基复合材料和树脂基复合材料的损伤阻抗和损伤容限。结果显示:随着冲击能量的增加,冲击力峰值、复合材料损伤面积和凹坑深度明显增加,到达峰值冲击力的时间减小。冲击能量的增加会导致冲击损伤面积的增加,而损伤面积的增加会导致剩余压缩强度的明显降低。相对于编织纤维增强树脂基复合材料,编织纤维增强陶瓷基复合材料的损伤阻抗较低,但损伤容限较高。     

复合聚电解质凝胶的制备与性能研究 Ⅰ.表面性能对凝胶的影响

采用柱状灯芯技术(Column Wicking Technique)研究了三种不同阳离子的木质素磺酸盐(木质素磺酸钠、钙和镁)的表面性能,同时应用电导率测试法对聚丙烯酰胺(PAAM)/木质素磺酸盐聚电解质凝胶的形成过程进行了研究。结果表明:木质素磺酸钙具有最高的表面能,而木质素磺酸钠的表面能最低。结合对凝胶过程的研究进一步发现,相对于聚丙烯酰胺凝胶来说,加入木质素磺酸盐对聚电解质凝胶的体系的影响是非常明显的,即木质素磺酸盐表面能大,则所形成的凝胶的电导率就小。上述结论也在实验过程得到了验证,根据手感可发现,在三种木质素磺酸盐中,加入木质素磺酸钙所形成的聚电解质凝胶具有较好的致密性和较高的强度。     

Energy—size reduction laws for ultrasonic fragmentation

The energy requirement is a key criterion for the selection and use of a grinding process. Ultrasonic dispersion is extensively used to disperse submicron agglomerated powders in liquid suspensions. Suspensions of silica agglomerates were ground with solids concentration up to 50% by weight. The fragmentation or grinding rate is inversely proportional to suspension volume. Starting from a semiempirical expression that relates fragmentation rate to particle size, suspension volume and ultrasonic power, energy consumption laws for both eroding and non-eroding powders are developed. Experimental results supporting the energy consumption laws are given. Lower power input for ultrasonication favors efficient energy use. For eroding powders (e.g. silica, zirconia) the energy expenditure per unit powder mass (specific energy) by ultrasonic grinding is lower than that of conventional grinding techniques. In contrast, it is slightly higher than ball milling for non-eroding powders (e.g. titania).     

Single‐step ultrasonic synthesis of biodiesel from crude Jatropha curcas oil

A novel single‐step process with chlorosulfonic acid catalyst for ultrasonic biodiesel synthesis using feedstock with high free fatty acid content is investigated.Jatropha curcas oil has been used as the model feedstock with methanol as alcohol. The distinct merit of chlorosulfonic acid is that it catalyzes both esterification and transesterification reactions. Moreover, chlorosulfonic acid also counteracts inhibition caused by water formed during esterification, which is the cause for very slow kinetics of acid catalyzed transesterification. In addition, sonication of the reaction mixture also causes strong micromixing and emulsification that enhances the transesterification kinetics. Statistical optimization of the process shows 93% yield for 8.5 wt % catalyst, 20:1 alcohol to oil molar ratio and temperature of 333 K. Peculiar feature of this process is that high yield is seen at moderate temperature and molar ratio, which are much smaller than that for conventional sulfuric acid catalyzed processes. The activation energy for the process (57 kJ/mol) is at least 3× lower than the energy for sulfuric acid catalyzed transesterification. The thermodynamic analysis reveals that the net Gibbs energy change for the single‐step process is almost same as that for sulfuric acid catalyzed process. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1572–1581, 2014     

Intensification of biopolymeric microparticles production by ultrasonic assisted atomization

In this work ultrasonic atomization process is applied to produce biopolymer microparticles with potential applications in pharmaceutical and nutraceutical fields. Natural polymer (alginate)/water solution is atomized by ultrasonic assisted process and the droplets spray is reticulated using a solution of copper sulfate, where the Cu²⁺ ions cause the formation of a network structure (hard porous gel). Several operating parameters (solution concentration, flow rate, atomization power) are changed to study their effects on the produced microparticles. Literature correlations able to predict the features of the droplets as functions of process parameters are optimized using a statistical approach. Furthermore, the energy requirement for the drops production is compared with the energy required by traditional techniques to evaluate the intensification effect of the ultrasonic on the atomization process.     

Ultrasonic Evaluation of Initiation and Development of Oxidation Damage in Ceramic-Matrix Composites

In this paper we report on the development of a method for ultrasonic nondestructive characterization of oxidation damage in ceramic-matrix composites. The method is based on ultrasonic measurement of elastic moduli of the composite, which are then used to determine the elastic moduli of the fiber-matrix interphase. Thus the interphasial damage may be estimated quantitatively. As a model system we used, to demonstrate applicability of the method, a unidirectional SiC-fiber-reinforced reaction-bonded silicon nitride matrix composite (SiC/RBSN). The composite samples were oxidized in flowing oxygen for 0.1, 1, 10, and 100 h at 600°, 900°, 1200°, and 1400°C. The ultrasonic phase velocity in the composite was measured at room temperature before and after oxidation; the data were then used to find the composite moduli, which quantify the induced damage. Significant changes in ultrasonic velocities and composite moduli were found as a result of oxidation. Fiber-matrix interphasial moduli were determined by multiphase micromechanical analysis. We found that oxidation of the carbon interphasial layer is the dominant mechanism in decreasing the elastic moduli of the composite. The critical exposure time for transition from the nondamaged to the damaged state at different oxidation temperatures has been determined.     

复合粘结剂炭素材料性能研究

用自制凝胶一沥青作复合粘结剂制备了炭素材料。通过测定不同配方、焙烧温度下试样的物理性能,认为9~#配方试样具有较好的导电性能和较高的抗压强度,沥青用量只有20%,明显低于传统炭素材料沥青用量。结果表明,凝胶一沥青复合粘结剂与石油焦粘结性能好,改变了传统的热压成型工艺。     

节能型三塔N,N-二甲基甲酰胺回收工艺的用能分析及优化

目前精馏方法回收制革废水中N,N-二甲基甲酰胺（DMF）的主要问题是工艺相对落后、能耗大。针对回收高能耗的问题,本文在对节能型三塔DMF回收工艺进行仿真模拟的基础上,结合精馏原理和夹点分析技术,采用塔总组合曲线（CGCC）的方法描述了各精馏塔内能流的分布状况,进而提出节能降耗的改进方案。提出的新流程与现有流程相比节约能耗6%。     

高固含量聚硅酸钾基防火凝胶及其在复合防火玻璃中的应用

通过蒸发浓缩的方法制备了高固含量硅溶胶分散液,采用纳米粒度及Zeta电位分析仪研究了蒸发浓缩前后分散液中无机粒子粒径和Zeta电位的变化。进而,以高固含量硅溶胶分散液为原料,氢氧化钾溶液为固化剂,制备了高固含量聚硅酸钾基防火凝胶和复合防火玻璃,采用小型耐火试验炉、热重分析、扫描电子显微镜、红外光谱等测试手段,研究了复合防火玻璃的耐火性能及防火凝胶的热稳定性和耐火机理。结果表明:蒸发浓缩的方法对纳米粒子的粒径和分散稳定性几乎没有影响;分散液固含量的提高能够极大地提升复合防火玻璃的耐火隔热性,并一定程度上提升防火凝胶的热稳定性。     

Real‐time monitoring of injection molding for microfluidic devices using ultrasound

Real‐time process monitoring of the fabrication process of microfluidic devices using a polymer injection molding machine was carried out using miniature ultrasonic probes. A thick piezoelectric lead‐zirconate‐titanate film as an ultrasonic transducer (UT) was fabricated onto one end of a 4‐mm diameter and 12‐mm long steel buffer rods using a sol gel spray technique. The center frequency and 6 dB bandwidth of this UT were 17 MHz and 14 MHz, respectively. A signal‐to‐noise ratio of more than 30 dB for ultrasonic signals reflected at the probing end was achieved. The probe can operate continuously at 200°C without ultrasonic couplant and cooling. Clear ultrasonic signals were obtained during injection molding of a 1‐mm‐thick part having test patterns on its surface. Shrinkage of the molded part and part detachment from the mold were successfully monitored. Surface imperfections of the molded parts due to a lack of the sufficient holding pressure is discussed with regard to the ultrasonic velocity obtained. The presented ultrasonic probes and technique enable on‐line quality control of the molded part by optimizing the holding pressure and improvement of process efficiency by reducing the cycle time. POLYM. ENG. SCI., 45:606–612, 2005. © 2005 Society of Plastics Engineers     

Capacitive deionization of NaCl solution with carbon aerogel-silicagel composite electrodes

Carbon aerogel-silica gel composite materials with different kinds of ratios were used as the electrode-activematerials for a capacitive deionization (CDI) process, which were prepared by a paste rolling method. The electrochemical parameters such as current values, coulombs, specific coulombs and coulombic efficiencies were investigated using a unit cell. The composite electrodes showed good wettability and high mechanical strengths with adequate durability under 1,000 ppm NaCl solution. Also, the composite electrodes showed an effective cycle ability without destroying active materials from the composite electrode, which decreased the manufacturing time by 50%. Additions of silica gel obviously improved coulombic results and led to effective performance of the CDI process.     

超声波清洗RDX的数值模拟和安全性分析

建立了超声波清洗RDX过程中空泡溃灭过程的数值模型,并从微观角度进行了理论分析,研究了空泡溃灭产生的高温、冲击波和瞬间能量释放等潜在的引爆风险。结果表明,空泡存在空间小,存在时间极短(10-9s量级),空泡溃灭过程中脉冲温度虽高,但并不满足RDX的起爆条件;脉冲压力虽高,但冲击波在水中迅速衰减,热量会迅速被水吸收;理论计算获得的空泡溃灭能量比RDX的最小引燃能量小几个数量级。超声清洗技术用于RDX颗粒的清洗是安全的。     

超声波-复合絮凝剂对石化厂剩余污泥脱水的研究

以污泥含水率为考察指标,研究了超声波-复合絮凝剂对石化厂剩余污泥脱水效果的影响.实验结果表明,复合絮凝剂的脱水效果优于单一絮凝剂;污泥采用复合絮凝剂PAM-PAFC进行絮凝脱水,在投加质量浓度190 mg/L、m(PAM)∶m(PAFC)=1∶1条件下,再经20 kHz、400 W/m2超声处理2.5 min后,污泥含水率从97%降至79%,污泥体积缩小86%左右,比仅投加PAM处理时污泥含水率降低5%左右.可见,超声波-复合絮凝剂可以强化污泥脱水,在提高污泥脱水效果的同时,减少了有机絮凝剂PAM的用量,降低了污泥处理成本.