甲醛阻聚剂作用原理及其应用

本文对甲醛的物理化学性质做了简单的介绍,并详细地介绍了甲醛聚合的原理,阐述了甲醛阻聚剂的阻聚原理、发展趋势、应用现状和使用过程中注意的问题,并对使用新型高效阻聚剂的经济效益做了分析,指出新型高效阻聚剂具有良好的应用前景和经济效益。     

黑茶水提取物的碳谱分析

通过文献查找和标准样测定,将茶叶的九种化学成分的碳谱特征峰进行整理归属,以此为标准,将十六种黑茶水提取物的碳谱进行对照分析,可将黑茶中的各类成分做出定性确认,但其中仍有许多未知成分,需要使用其他方法分离分析。     

玻璃微珠填充PP结构与性能研究

用一步法和二步法两种混合工艺,研究了经过表面预处理的玻璃微珠填充PP的力学性能。结果表明,经过适当表面处理的玻璃微珠可以通过熔融共混均匀分散在PP中,粒子与基体界面结合良好。填充体系随着玻璃微珠含量的增加,拉伸强度增大,冲击强度下降。流动性随着玻璃微珠含量的增加而增大,然后随之下降。     

聚烯烃热塑性弹性体官能化的方法及其应用

介绍了聚烯烃热塑性弹性体(POE)官能化-熔融接枝的几种方法:在有机过氧化物引发剂存在下的熔融接枝法,裂解引发接枝,机械力引发接枝,复合引发接枝等,POE官能化接枝能改善其与极性的聚物间的界面亲和性,提高共混物的相容性、冲击强度和韧性等,从而拓宽POE的应用领域。     

SEBS的臭氧处理及增韧PA6的研究

研究了臭氧处理对氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)分子结构及其极性的影响,并对臭氧处理SEBS增韧PA6进行了研究。结果表明,通过臭氧处理可在SEBS分子链上引入羰基含氧基团,臭氧处理的SEBS相对分子质量下降,相对分子质量分布变宽,表面能提高,极性增大。与PA6／SEBS体系相比,PA6／臭氧处理SEBS体系的相容性得到明显改善,其冲击强度和断裂伸长率大幅度提高。     

斜顶偏心旋风筒的数值模拟研究

使用Fluent软件，通过RSM湍流模型和离散相模型对斜顶偏心旋风筒进行了数值模拟研究，结论是：斜顶偏心旋风简与普通型旋风筒的流场基本相同，但选择合理的顶板倾斜角度和内简的偏心距离更有利于提高旋风筒的分离效率和降低压力损失。     

锆-4合金低周疲劳断口裂纹扩展能量及分形特征研究

对锆-4合金低周疲劳裂纹扩展过程进行了探索性的研究。通过分析锆-4合金低周疲劳断口在裂纹扩展方向上能量及分形维数变化趋势，发现锆-4合金动态裂纹扩展中扩展期由3个阶段组成，每一阶段的能量和分形维数都不同。A-B段的能量最小，归一化值为0-0．0156，A-B段的分形维数居中，在工工方向均值为2．2796，标准差为0．0277，在LH方向均值为2．4516，标准差为0．0592。D-E段能量远大于A-B段，归一化值为0．8754～0．9652，但分形维数最小，LL方向均值为2．2214，标准差为0．0131，LH方向均值为2．3477，标准差为0．0550。F-H（或G-H）段能量最大，归一化值达到1，同时分形维数也达到最大，LL方向均值为2．3414，标准差为0．0704，LH方向均值为2．5398，标准差为0．0263。虽后，根据二次电子成像原理以及锆-4合金低周疲劳断口的形貌特征对此现象进行了初步分析。     

Refrigerated cooling air cutting of difficult-to-cut materials

One approach to enhance machining performance is to apply cutting fluids during cutting process. However, the use of cutting fluids in machining process has caused some problems such as high cost, pollution, and hazards to operator's health. All the problems related to the use of cutting fluids have urged researchers to search for some alternatives to minimize or even avoid the use of cutting fluids in machining operations. Cooling gas cutting is one of these alternatives. This paper investigates the effect of cooling air cutting on tool wear, surface finish and chip shape in finish turning of Inconel 718 nickel-base super alloy and high-speed milling of AISI D2 cold work tool steel. Comparative experiments were conducted under different cooling/lubrication conditions, i.e. dry cutting, minimal quantity lubrication (MQL), cooling air, and cooling air and minimal quantity lubrication (CAMQL). For this research, composite refrigeration method was adopted to develop a new cooling gas equipment which was used to lower the temperature of compressed gas. The significant experimental results were: (i) application of cooing air and CAMQL resulted in drastic reduction in tool wear and surface roughness, and significant improvement in chip shape in finish turning of Inconel 718, (ii) in the high-speed milling of AISI D2, cooling air cutting presented longer tool life and slightly higher surface roughness than dry cutting and MQL. Therefore, it appears that cooling air cutting can provide not only environment friendliness but also great improvement in machinability of difficult-to-cut materials.     

铝合金搅拌摩擦焊接头服役孔洞裂纹扩展规律研究

以不同尺寸孔洞缺陷的2024铝合金搅拌摩擦焊接头为研究对象,在对接头进行分区建模基础之上,通过试验和有限元数值模拟研究了接头孔洞大小对接头服役裂纹扩展的影响规律。研究表明,接头在准静态服役条件下,力学性能随孔洞减小而不断提高;孔洞直径减小至0.1 mm时,接头力学性能与无缺陷接头相同,断裂于热影响区;而当孔洞直径大于0.1 mm时,接头均断裂于含有孔洞缺陷的焊核区。在交变载荷服役条件下,接头疲劳力学性能随孔洞减小而不断提高,随孔洞增大对载荷的敏感性逐渐降低;断裂的瞬间断口会有温升现象且均断裂于有孔洞缺陷的焊核区。     

Corrosion resistance of Mg(OH)_2/Mg-Al-layered double hydroxide coatings on magnesium alloy AZ31:influence of hydrolysis degree of silane

Mg(OH)_2/Mg-Al-layered double hydroxide(LDH)coatings were modified with methyltrimethoxysilane(MTMS)on magnesium alloys.Effect of hydrolysis degree of silane solution on coating formation was investigated.Chemical compositions and surface morphologies of the coatings were examined using X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and field-emission scanning electronic microscopy(FESEM).Results indicated that the composite coatings consisted of polymethyltrimethoxysilane(PMTMS),LDH and Mg(OH)_2.Electrochemical and hydrogen evolution measurements revealed that the composite coatings possessed good corrosion resistance,especially the ones prepared in a high hydrolysis degree of silane.The optimum corrosion resistance of the composite coating was LDH/PMTMS-3 coating,which had the lowest value of corrosion current density(5.537 × 10~(-9) A·cm~(-2))and a dense surface.Plausible mechanism for coating formation and corrosion process of MTMS-modified Mg(OH)_2/Mg-Al-LDH coatings were discussed.