超滤膜污染的成因及模型表征研究进展

文章从超滤膜的理化性质、分离的料液性质和运行操作条件三方面介绍了超滤膜污染的成因,阐述了膜污染的数学模型研究概况,并对膜污染未来的研究方向进行了展望。     

二芳基对苯二胺类防老剂的制备及性能研究

制备二苯基对苯二胺(防老剂BBPD)、苯基甲苯基对苯二胺(防老剂BTPD)和苯基(二甲基)苯基对苯二胺(防老剂BXPD)3种二芳基对苯二胺类防老剂,测试其熔点和研究其应用性能,并与市售防老剂DTPD进行对比。结果表明:3种自制的二芳基对苯二胺类防老剂的熔点高于防老剂DTPD,胶料的加工性能、硫化特性和耐臭氧老化性能与防老剂DTPD胶料相当,物理性能和耐热氧老化性能比防老剂DTPD胶料好,防老剂BTPD和BXPD胶料的耐屈挠疲劳性能优于防老剂DTPD胶料。     

Acoustic damping flexible polyurethane foams: Effect of isocyanate index and water content on the soundproofing

High-efficiency sound absorbing flexible polyurethane foams (FPUFs) are manufactured using nonpolar polyester resin, methylene diphenyl diisocyanate, and other reagents by one-shot bulk polymerization. In this study, the impact of the isocyanate index (90, 100, and 110) and water content (2.5 and 5%) on the microphase separation and soundproofing behavior of FPUFs are examined using atomic force microscopy, Fourier transform infrared spectroscopy, optical microscope, and an impedance tube device. The results reveal that the increase of the isocyanate index and water content leads to the increase of the cell size, cell size distribution, open-cell content, cell wall roughness, and microphase separation. Also, maximum sound absorption coefficient (α) reaches to 0.98 and the average of α in the frequency range of 1500–4000 Hz increases from 0.7 to 0.87 by increasing the water content from 2.5 to 5% and isocyanate index from 90 to 110; therefore, acoustic damping performance enhances up to 26.24% due to the synergic effects of microphase separation on the viscose media formation, open-cell content, cell wall roughness, cell size, and cell size distribution. In conclusion, FPUFs with an optimal amount of microphase separation and drainage flow can be a promising candidate for sound insulating materials. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47363.     

2004年铂市场回顾及2005年预测

2004年影响铂市场的主要因素有基本面、投机活动和美元走势。在这3个因素的综合影响下，铂市场价格冲上24年的高点937美元／盎司，年均价格达到845．31美元／盎司，为历史最高。2004年铂的总需求达到647万盎司，比2003年仅增长1个百分点：总的供应量达到643万盎司，比前一年增长了3．7％；供应缺口维持在4万盎司，为6年来的最低。预计2005年的铂市场将继续维持在美元线上，基金活动仍将主控市场，价格维持宽幅振荡的格局；供应和需求将继续增长；铂的年平均价将下跌到800美元／盎司，在760～920美元／盎司的范围内交易。     

Fe—Ni—Cr封接合金的高温氧化及氧化膜,氧化物晶须的结构

试验表明,Fe-Ni-Cr封接合金在高温湿氢气氛中氧化膜的生长受扩散控制,其主要组成为刚玉型的Cr_2O_3与尖晶石型的(Fe,Mn)O·Cr_2O_3。电子衍射及能谱分析证实,氧化过程中生长的晶须为(Fe,Mn)O·Cr_2O_3。     

Electronic struture of titanium silicides

ＥＬＥＣＴＲＯＮＩＣＳＴＲＵＣＴＵＲＥＯＦＴＩＴＡＮＩＵＭＳＩＬＩＣＩＤＥＳＬｏｎｇ，Ｘｉａｎｇｙｕｎ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙ，Ｃｈａｎｇｓｈａ４１００８３）Ｃ...     

EFFECT OF MICROSTRUCTURE AND ELEMENT DISTRIBUTION ON EROSION－CORROSION BEHAVIOUR OF AN IRON BASE CAST ALLOY

用扫描电镜、Ｘ射线衍射、电子探针等手段测定及分析了Ｆｅ基铸造合金Ｃｒ３０Ｎｉ１７Ｍｏ２Ｃｕ以不同速度凝固后的显微组织和主要合金元素分布，在含固相颗粒的强酸性双相流介质中测定了冲刷腐蚀性能。结果表明，快凝铸态组织耐冲刷腐蚀性能最佳，慢凝铸态次之；时效热处理虽能提高硬度，但抗冲刷腐蚀性能反而下降。     

Investigation on minimum quantity lubricant-MQL grinding of 100Cr6 hardened steel using different abrasive and coolant–lubricant types

Large quantities of coolant–lubricants are still widely used in the metal working industry, generating high consumption and discard costs and impacting the environment. Alternatives to current practices are getting more serious consideration in response to environmental and operational cost pressures. In the grinding process, promising alternatives to conventional dry and fluid coolant applications are minimum quantity lubrication (MQL) or near dry grinding process. Despite several researches, there have been a few investigations about the influence of different types of coolant–lubricants and grinding wheels on the process results. The current study aims to show the effects of the above parameters on grinding performance such as grinding forces and surface quality. The tests have been performed in presence of fluid, air jet and eleven types of coolant–lubricants, as well as, in dry condition. The grinding wheels employed in this study were vitrified bond corundum, resin bond corundum and vitrified bond SG wheels. The results indicate that SG wheels and MQL oils have potential for the development of the MQL process in comparison to vitrified and resin bond corundums and water miscible oils. Also, the lowest thermal damages, material side flow on the ground surface and wheel loading were generated by using the SG grinding wheel in MQL grinding process.     

Study on Hot Ring Compression Test of Nimonic 115 Superalloy Using Experimental Observations and 3D FEM Simulation

In hot forging of Nimonic 115, it is desirable to determine friction coefficients. Changing magnitudes of temperature and type of lubricant at the surface of the workpiece and dies influence friction coefficient. This paper describes an experimental investigation of friction under hot forging conditions using the ring compression test. The 3D FEM simulations were used to derive the friction calibration curves and to evaluate material deformation, geometric changes, and load-displacement results. A series of ring compression tests were carried out to obtain friction coefficients for a number of lubricants including mica plate, glass powder, graphite powder, and dry condition. The experiments show how the variations in temperature at the interface affected frictional behavior. On the basis of these results, mica is recommended for hot forging of Nimonic 115 and its friction coefficient is approximately 0.3.     

Study of crystal structure of (polyvinylidene fluoride/clay) nanocomposite films: Effect of process conditions and clay type

Three Polyvinylidene fluoride (PVDF) different in molecular structure were used to produce nanocomposities films by cast extrusion with a particular emphasis on maximizing the β crystal phase content. The PVDF/clay compounding followed by cast film production was carried out through melt extrusion using a twin screw extruder equipped with a slit die. X‐ray diffraction (XRD) results showed that clay melt intercalation is almost similar for all three PVDFs. The XRD results also revealed that nanocomposite films from PVDF with branched chain structure (PVDFB) generated the greatest amount of β phase. FTIR spectroscopy measurements confirmed the XRD results but also revealed that significant stretching of the melt films at the die or rapid cooling would adversely affect the formation of β phase. The amount of β phase obtained based on nanoclay compounding was compared with that obtained from conventional method: stretching of molded PVDF film with initial α phase. Stretching of PVDF film at 60°C yielded pure β phase that means complete transformation of α to β. From mechanical properties, tensile tests were carried out on PVDF nanocomposite films to evaluate mechanical strength. PVDF with low molecular weight exhibited a very low strain at break while branched PVDF and high molecular weight PVDF could sustain more strain. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers