家用冰箱储藏室内挥发性有机物检测及分析

为研究家用冰箱储藏室中挥发性有机化合物(VOCs)的释放量及主要来源,采用气相色谱–质谱法对工作状态下冰箱储藏室的VOCs含量进行检测;利用傅里叶变换红外光谱仪对冷藏室的物料进行成分分析,同时用密封舱法探究冷藏室不同物料对VOCs含量贡献。结果表明,冰箱冷藏室物料中发泡聚苯乙烯风道泡沫释放的总挥发性有机化合物(TVOC)、正戊烷及异戊烷最多,是造成异味的关键性物料,而正戊烷、异戊烷是冰箱异味的主要成分。聚氯乙烯门封条对异味的贡献也较大,通用聚苯乙烯抽屉体贡献的VOCs种类最多;在工作状态下,随着密闭时间的增加,冰箱储藏室的VOCs的种类及含量增加,但苯、甲苯、二甲苯、TVOC及戊烷类的含量均未超过国家标准。储藏室异戊烷含量较高,是冰箱的异味的主要来源。     

Infrared heat treatment of Ti-6Al-4V with electroplated Cu

The objective of this study is to investigate an innovative infrared (IR) technique to enhance adhesion of electroplated copper (Cu) on Ti-6Al-4V without dichromate dipping. The ultimate goal is to develop a Cu coating process on Ti-6Al-4V without hazardous hexavalent chromium (Cr) solution treatments. Cu coatings of around 50 μm were electroplated on Ti-6Al-4V specimens at a current density of 0.03 A/cm² in an acidic Cu solution. To improve adhesion of coatings, IR heat treatments were performed on the Cu-coated samples at different temperatures and durations: 860 °C for 600 s and 875 °C for 20–120 s. This process was accomplished in an attempt to replace the use of dichromate dipping before electroplating. For samples heat treated at 860 °C, no bonding existed, even after 600 s. It is believed that solid-state diffusion prevailed at 860 °C and that 600 s was not enough for sufficient diffusion to occur. Adhesion was poor when samples were heat treated at 875 °C for 20 s. Excellent adhesion was observed when the heat treatment holding time was increased to 40 s. For 90 s, the surface appearance of coatings partially changed from Cu-colored to a grayish color. There was no Cu left on the surface after a 120 s heat treatment. From optical microscopic observations on sample cross sections, an interlayer between the Cu and Ti-6Al-4V formed when heat treated at 875 °C for 40 s and longer. The interlayer thickness increased as the holding time increased, until depletion of Cu. The sheet resistivity of coated specimens was on the order of pure Cu for samples heat treated at 875 °C and less than 90 s. During the 875 °C heat treatment, the following occurred: solid-state diffusion of Cu in Ti-6Al-4V, formation of eutectic solutions, dissolution of Cu and Ti-6Al-4V into the liquid phase, and the formation of intermetallic compounds. The lowest eutectic temperature of 875 °C played a key role in this innovative process of Cu coating on Ti-6Al-4V. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana and appears on pp. 403–10 of the Proceedings.     

INFLUENCE OF Al ON DUCTILITY IMPROVEMENT BY B IN Ni_3Al ALLOYS

The “order-disorder” model was adopted to calculate the lattice vacancies related to the com- position change in Ni_3Al alloys.A great deal of vacancies,i.e.,the non-stoichiometric vacan- cies,may exist in the Ni_3Al alloys containing Al over stoichiometry,i.e.25 at.-%.This was confirmed by the positron annihilation technique.Therefore,the influence of Al content on the enhancing behaviour of B towards the ductility of Ni_3Al alloys can be understood by the interaction of non-stoiehiometric vacancies and B atoms.     

The influence of titanium on the electrochemical properties of the AB5-type metal hydrides

AB₅-type intermetallic compounds were prepared by arc-melting in argon atmosphere. The composition of a stoichiometric compound LaNi_3.6Al_0.4Co_0.7Mn_0.3 with a hexagonal CaCu₅ structure was varied by stoichiometric and nonstoichiometric addition of Ti. With the increase of the Ti y0.05 content in LaNi_3.6Al_0.4Co_0.7Mn_0.3Ti_y, the hydrogen storage capacity is enhanced, whereas when y=0.1–0.3, it is decreased. The discharge capacity and cyclability are increased considerably by addition of titanium in the range of 0.02–0.1 with a maximum value at about 0.1%. The highest maximum capacity is achieved for a nonstoichiometric addition of 0.05% Ti. The kinetic properties are also additionally improved by the formation of a titanium-rich second phase. This can explain the improvement of the capacity for alloys with low Ti content. The decrease in capacity for high Ti content was also correlated with the amount of the Ti-rich phase. Therefore, the improvement of kinetics are due to the catalytic effect, grain boundary diffusion effect or more pronounced alloy pulverization upon cycling. This study has been aimed to improve the electrode properties of a series of multicomponent LaNi_3.6Al_0.4Co_0.7Mn_0.3Ti_y (y=0.0, 0.02, 0.05, 0.1, 0.2, 0.3) alloys which have mutual complementary properties. All the prepared alloys have been subjected to analyses by EDS, SEM and XRD. In order to determine the hydrogen storage capacity, the pressure composition isotherms (P–C–T curves) have been used. The metal hydride electrodes were characterized by galvanostatic cycling test.     

XPS spectra of the AFe4Al8 compounds with A=Y, Sc, U and Th

The XPS electronic structures of the AFe₄Al₈ (A=Sc, Y, U, Th) single crystals were measured. The valence band of UFe₄Al₈ exhibits domination of the U 5f states at the Fermi level, while for the other AFe₄Al₈ compounds the valence states are shifted by 0.5 eV toward higher binding energy. The multiplet structure of the U 4f and Th 4f states was analyzed in comparison with the U 4f states of U₃Ge₅ and UNiSb₂.     

Titanium in the rapidly cooled hypereutectic gray iron

The effect of titanium on the structure and properties of a rapidly cooled hypereutectic cast gray iron has been studied on the example of permanent mold (PM) casting. A microstructure study showed that titanium is a relatively strong element in controlling solidification structure by increasing undercooling and thus promoting type D graphite. The effectiveness of titanium additions depends on the base iron carbon equivalent (CE) with more pronounced changes in iron with a lower CE. The undercooling ability of the titanium decreases after exceeding a certain level. Increasing titanium from 0.09–0.12% slightly increases undercooling in iron with lower CE, but this effect was reduced in a more strongly hypereutectic iron. Alloying with titanium generally improves tensile strength, but the effectiveness of titanium additions also depends on the base iron CE range. Scanning electron microscope (SEM) studies revealed that most of the titanium-containing compounds were located in the metallic matrix: titanium carbides have been found in pearlite, while titanium nitrides and carbonitrides were located in ferrite. The presence of large amounts of extremely hard titanium-containing compounds, which often appear with steadite in a relatively high phosphorous content PM gray iron, amplifies the negative effect of titanium on machinability. This study suggests that for optimal combination of tensile strength/microstructure with good machinability, the titanium content in PM gray iron should not exceed 0.075%.     

Nd2Mn17-xAlx(X=1～10)化合物的结构及其稳定性

用电弧炉熔炼制备了Nd2Mn17-xxAlx(x=1-10)样品，对其进行的粉末X－射线衍射研究表明，样品具有菱方相Th2Zn17型结构，随着Ai替代量的增加，Nd2Mn17-xxAlx(x=1-10)化合物样品的晶格常数a,c及单胞体积v都增加，对样品的时效研究表明，Nd2Mn17-xAlx(x=1-10)化合物在自然环境中十分稳定，这表明Al比C更能使富锰的2：17相（Th2Zn17)稳定。     

Effect of bismuth on the growth kinetics of intermetallic compounds in Sn-3.5Ag solder joints: A growth kinetic model

The effect on the growth kinetics of the intermetallic compounds (IMCs) in solder/Cu joints, caused by adding Bi to eutectic Sn-3.5Ag solder alloy, was examined at the aging temperatures of 150°C and 180°C. The Cu₆Sn₅ layer growth was significantly enhanced, but the Cu₃Sn layer growth was slightly retarded by the addition of Bi, resulting in significant growth enhancement of the total (Cu₆Sn₅+Cu₃Sn) IMC layer with increasing Bi addition. The IMC layer growth in the Bi-containing solder joints was accompanied by the accumulation of Bi ahead of the Cu₆Sn₅ layer that resulted in the formation of a liquid layer at the Cu₆Sn₅/solder interface. A kinetic model was developed for the planar growth of the Cu₆Sn₅ and Cu₃Sn layers in the solder joints, accounting for the existence of interfacial reaction barriers. Predictions from the kinetic model showed that the experimental results could be well explained by the hypothesis that the formation of a Bi-rich liquid layer at the Cu₆Sn₅/solder interface reduces the interfacial reaction barrier at the interface.     

稀土元素对NiAl/CrMo(Hf)共晶合金氧化性能影响

研究了稀土元素Ce、Nd对NiAl-28Cr-5．5Mo—0．5Hf合金高温氧化性能的影响。并通过扫描电镜和能谱分析研究了氧化产物的微观组织与成分．结果表明：稀土的加入改变了表层氧化膜中各氧化物的含量。适量稀土元素的加入可消除内氧化和减小氧化增重．