以硅氧烷醇锂为催化剂的氟硅生胶的合成

介绍了单体三氟丙基甲基环三硅氧烷通过硅氧烷醇锂催化剂聚合成氟硅生胶,讨论了不同催化剂及其用量,原料中水分含量、不同乙烯基含量对氟硅生胶分子量的影响.     

双端乙烯基氟硅油的研制

以1,3,5-三甲基-1,3,5-三(3,3,3-三氟丙基)环三硅氧烷为原料、四甲基二乙烯基二硅氧烷为封端剂、硫酸为催化剂制得双端乙烯基氟硅油,研究了反应时间、催化剂用量、反应温度对产物黏度和挥发分质量分数的影响;采用红外光谱和核磁共振波谱表征了产物结构.结果表明,产物为双端乙烯基氟硅油.较佳的制备条件为反应时间1 h...     

有机氟硅改性聚丙烯酸树脂和乳液的研究

以八甲基环四硅氧烷 (D4)、三氟丙基环硅氧烷 (DF3 )、乙烯基环四硅氧烷 (DVi4)为原料 ,四甲基氢氧化铵为催化剂 ,在 90～ 10 0℃、真空度 4 6 6 7～ 6 6 6 6kPa条件下 ,进行三元共聚合反应 ,制取了含三氟丙基、乙烯基的活性有机硅中间体 (简称氟硅中间体 )。然后分别以过氧化苯甲酰、过硫酸铵为引发剂 ,与甲基丙烯酸甲酯、甲基丙烯酸丁酯溶液或乳液接枝共聚 ,制得有机氟硅改性聚丙烯酸树脂和乳液。D4、DF3 与DVi4进行开环共聚的适宜条件为反应温度 90～ 10 0℃ ,真空度为 4 6.6 7～ 6 6.6 6kPa ;合成有机氟硅改性聚丙烯酸树脂的较佳反应条件为反应温度 80～ 90℃ ,反应时间 5～ 7h ,有机氟硅改性聚丙烯酸树脂的收率大于 80 % ;乳液聚合反应的适宜条件为反应温度 6 0℃ ,pH值 6. 5～ 7.1。     

低黏度自交联氟氢乙烯基硅油的合成及应用

采用阳离子交换树脂催化八甲基环四硅氧烷(D4)、四甲基四氢环四硅氧烷(D4H)和三氟丙基三甲基环三硅氧烷(D3F)开环共聚,以四甲基二乙烯基二硅氧烷(D2Vi)为封端剂,制备了低黏度自交联氟氢乙烯基硅油(F-PMHS).探讨了聚合温度、聚合时间、催化剂用量、催化剂循环等因素对聚合反应的影响.通过FTIR、1HNMR、TGA对共聚物进行分析.结果表明,当聚合温度为60℃、反应时间为6 h、催化剂用量为总单体质量5％时,得到的F-PMHS产率为88.69％,黏度为32.7 mPa·s.将硅油进行涂膜测试,所得涂膜固化性好,剥离力低至7 g/25 mm,水滴静态接触角达114.9°.     

膜用高乙烯基含量硅橡胶

大连理工大学的赵婵等人以八甲基环四硅氧烷（D4）和四甲基四乙烯基环四硅氧烷（D4^Vi）为原料、四甲基二乙烯基二硅氧烷（MM^Vi）为封端剂、氢氧化钾为催化剂,合成了乙烯基摩尔分数为5％的硅橡胶PVDMS。研究了反应时间、反应温度及MM^Vi加入量对产物黏度的影响,最佳合成条件是：反应温度140℃,反应时间180～210min、MM^Vi质量分数0．9％-1．8％。将PVDMS应用到气体分离膜上有较高的透气性和分离性。     

低粘度自交联氟氢乙烯基硅油的合成及应用

采用高活性强酸性阳离子交换树脂（HND-580）催化八甲基环四硅氧烷（D4）、四甲基四氢环四硅氧烷（D4H）和三氟丙基甲基环三硅氧烷（D3F）开环共聚,以四甲基二乙烯基二硅氧烷（D2Vi）为封端剂,制备了低粘度含氟含氢乙烯基硅油。探讨了聚合温度、聚合时间、催化剂用量、催化剂循环等因素对开环共聚反应的影响。通过核磁、红外测试分析共聚物的分子结构;通过热分析法测试共聚物热分解温度;研究结果表明,当聚合温度为60℃、反应时间为4h、催化剂用量为3%~5%时,得到的含氟含氢端乙烯基硅油产率为88.69%,粘度为31mpa?s。将硅油进行涂膜测试,所得水滴静态接触角可达115.2?。     

高相对分子质量氟硅生胶的制备与热性能研究

以γ-三氟丙基甲基环三硅氧烷(D3F)、三甲基三乙烯基环四硅氧烷(D3Vi)为原料,碱为催化剂制得了乙烯基质量分数为0.25%、不同相对分子质量的氟硅橡胶。采用D3Vi作为共聚单体可以将乙烯基引入到共聚物中,实验中D3F的聚合速率非常高,10 min后的转化率均为90%以上。优化了聚合反应条件,通过FTIR、1H-NMR、GPC表征了氟硅生胶的结构组成和相对分子质量,通过DSC和TG研究了其热性能。结果表明,氟硅生胶的玻璃化转变温度为-69℃,在300℃以下未出现明显的热降解现象,耐高温性能低于普通的甲基乙烯基硅橡胶。     

MQ硅树脂的制备及热性能研究

以六甲基二硅氧烷(MM)、四甲基二乙烯基二硅氧烷、硅酸乙酯为原料,异丙醇为溶剂,盐酸为催化剂,通过受控水解反应合成了不同乙烯基含量的MQ硅树脂。并表征了产物的性能。结果表明,所合成的MQ硅树脂具有良好的热稳定性,其质量损失率为5%时的热分解温度在276～389℃之间;随着乙烯基含量的增加,MQ硅树脂的热稳定性下降;甲基MQ硅树脂在DSC第一次升温过程中存在熔融峰70.6℃,表明具有一定程度的结晶性。     

氟硅共聚生胶的合成及结构分析

以1,3,5-三(3,3,3-三氟丙基)-1,3,5-三甲基环三硅氧烷(D3F)和六甲基环三硅氧烷为原料合成了高分子量的氟硅共聚生胶,研究了反应时间和反应温度对产物分子量的影响,以及单体投料比对共聚物链节含量的影响.通过红外光谱和核磁共振波谱对共聚生胶的结构进行了表征,并用乌氏黏度计测定了其分子量.结果表明,在D3F用...     

三氟丙基甲基二氯硅烷的水解及一步法裂解制备环体

采用正交实验法,将3,3,3-三氟丙基甲基二氯硅烷水解为3,3,3-三氟丙基甲基聚硅氧烷(DnF),然后以一步法裂解新工艺,在强碱催化下裂解、重整成环、精馏,得到3,3,3-三氟丙基甲基环三硅氧烷(D3F)。实验结果表明,无论是从DnF还是D3F收率来看,最佳水解条件为:30℃,水解介质为w(HC l)=20%的盐酸,V(盐酸)∶V(三氟丙基甲基二氯硅烷)=3∶1,滴加速度为20 mL/m in(以1 000 mL反应器为例),裂解催化剂氢氧化钠的用量为水解物质量的0.01%~10%,助剂十八醇的用量为水解物质量的1%~5%,裂解时间为7~10 h,裂解产物D3F的收率达到85%以上,精馏可得到w(D3F)≥99%的产品。     

Defect control and ionic conductivity of oxynitride perovskite Sr0.83Li0.17Ta0.83O1.88N0.74

Perovskite lattice was tailored by introducing site vacancies and mixed anion composition, to produce Sr_0.83Li_0.17Ta_0.83O_1.88N_0.74 (Li02N). Further, Li02N was converted to a defect oxide Sr_0.83Li_0.17Ta_0.83O₃ (Li02O) by applying an optimized treatment: heating in air at 1173 K for 2 h. According to the neutron Rietveld refinement, Li02N and Li02O are tetragonal and orthorhombic, respectively, where the lattice volume of Li02O is significantly smaller than that of Li02N. The ionic conductivity (σ_ion) of Li02N and Li02O was evaluated by the ac impedance spectroscopy and the equivalent circuit analysis. Both Li02N (σ_ion = 10^?5.5 S/cm at 671 K) and Li02O (σ_ion = 10^?6.2 S/cm at 667 K) exhibited an Arrhenius behavior of ionic conductivity with activation energies of 0.87 eV and 0.75 eV, respectively. It is interpreted that the nitride component enhances the ionic conduction of Li02N, while the vacancy of the anion lattice makes an opposite effect.     

核壳型苯丙乳液的冻融稳定性

采用半连续乳液聚合法合成了具有核壳结构的苯丙乳液,考察了玻璃化转变温度（ T_g）、核中丙烯酸的用量、亲水单体用量及种类对乳液冻融稳定性的影响。结果表明： T_g在 20.94 ℃左右、核中丙烯酸的用量为 2.5%时,苯丙乳液的冻融稳定性较好,不同亲水单体和用量对冻融稳定性的影响不大,也表明了在该体系下丙烯酸已为乳液提供了足够的冻融稳定性。     

Interface control for high-performance all-solid-state Li thin-film batteries

We fabricated and evaluated four types of Li batteries, in this case a LTO/liquid electrolyte/Li battery, a LTO/LiPON/Li all-solid-state battery, and LTO/LiPON + liquid electrolyte/Li batteries with and without a separator to investigate and clarify the effects of each interface. Through the present research, it was found that a conventional polymer-based separator increases the impedance in the middle frequency region, resulting in an increase in the total cell resistance. After replacing the polymer-based separator with a thin-film solid electrolyte, the cycleability and capacity of the cell were comparable to those of a conventional Li-ion battery with a polymer separator. The all-solid-state Li thin-film battery without a liquid electrolyte exhibits the lowest capacity due to the large interfacial resistance between the Li metal and the LiPON solid electrolyte. However, we found that the insertion of an Al₂O₃ interlayer between the Li and LiPON improves the capacity.     

Li3PO4助熔剂添加对Li1.3Al0.3Ti1.7(PO4)3性质的影响研究

采用溶胶-凝胶法合成Li1.3Al0.3Ti1.7(PO4)3粉末,向Li1.3Al0.3Ti1.7(PO4)3粉末中添加不同摩尔分数的Li3PO4助熔剂烧结制备锂离子固体电解质Li1.3Al0.3Ti1.7(PO4)3烧结片。通过X射线衍射仪、扫描电子显微镜研究合成产物的结构与形貌,采用循环伏安及交流阻抗技术研究合成产物的氧化-还原电位、离子电导率和活化能。结果表明,添加与未添加Li3PO4助熔剂的Li1.3Al0.3Ti1.7(PO4)3烧结片具有相似的X射线衍射结果。添加Li3PO4的Li1.3Al0.3Ti1.7(PO4)3烧结片空隙率较小,更为致密。添加Li3PO4对Li1.3Al0.3Ti1.7(PO4)3的氧化-还原电位影响不大。在所有添加Li3PO4助熔剂的Li1.3Al0.3Ti1.7(PO4)3烧结片中,添加摩尔分数1%Li3PO4的烧结片具有最高的离子电导率6.15×10-4S.cm-1和最低的活化能0.314 2 eV。     

Formation of SBS thermoplastic block copolymer using hexamethyleneimine alkenyl lithium (N‐Li) initiator

Styrene and butadiene block copolymers (SBS) end functionalized with amino group at the initiating chain ends were synthesized using hexamethyleneimine alkenyl lithium (N‐Li) as initiator, tetrahydrofuran (THF) as polar modifier, and cyclohexane as solvent. By attaching a few number of butadiene molecules to N‐lithium hexamethyleneimine, a new N‐Li initiator that can effectively initiate the polymerization of SBS was obtained. ¹H NMR spectrums of the N‐Li initiator terminated by ethanol, end functionalized polystyrene, and SBS block copolymer proved the structure of N‐Li and its ability to initiate the polymerization of styrene and SBS block copolymer. Kinetics studies suggested that the polymerization rate of styrene in the first block reached the maximum when the ratio of THF/Li was increased to 5, while further increase of the ratio of THF/Li could not improve the polymerization rate. The molecular weight distribution (MWD) of SBS initiated by N‐Li varied with the ratio of THF/Li. The vinyl content of polybutadiene block increased by improving the ratio of THF/Li, while the content of cis‐1,4 and trans‐1,4 structures decreased. The vinyl content of end functionalized SBS was somewhat higher than that of SBS initiated by classical n‐butyllithium when other condition was the same. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 81–88, 2006     

Lithium aluminum-layered double hydroxide chlorides (LDH): Formation enthalpies and energetics for lithium ion capture

Layered aluminum double hydroxide chloride sorbents, LiCl∙Al₂(OH)₆.nH₂O, Li-LDH, have shown promising application in selective Li extraction from geothermal brines. Maintaining LiCl uptake capacity and retaining a long cycle life are critical to widespread application of sorbent materials. To elucidate the energetics of Li capture, enthalpies of LDH with different Li content have been measured by acid solution calorimetry. The formation enthalpies generally become less exothermic as the Li content increases, which indicates that Li intercalation destabilizes the structure, and the enthalpies seem to approach a limit after the Li content x = 2Li/Al exceeds 1. To improve stability, metal doping of the aluminum LDH structure with iron was performed. Introduction of a metal with greater electron density but a similar ionic radius was postulated to improve the stability of the LDH crystal structure. The calorimetric results from Fe-doped LDH samples corroborate this as they are more exothermic than LDH-lacking Fe. This suggests that Fe doping is an effective way to stabilize the LDH phase.     

A theoretical study on storage states of Li ions in carbon anodes of Li ion batteries using molecular orbital calculations

Semi-empirical molecular orbital calculations were carried out to clarify storage states of Li ions in amorphous carbon anodes of Li ion batteries. Storage states of Li ions between two graphene sheets were investigated and a favorable structure for a carbon anode to produce large reversible and small irreversible capacities is discussed. A polycyclic hydrocarbon molecule, C₅₄H₁₈, was used as a model of a graphene sheet. Relations between the interlayer distance of two graphene sheets and the storage state of Li ions were investigated, and preferable interlayer distances for specific numbers of Li ions were estimated. In particular, storage states with all Li ions on the basal area were treated, because the amount of basal carbons should be larger than that of edge carbons. The charge distribution of Li ions was also investigated. Calculated results suggested that a storage state in which a double Li ion layer was formed was preferable to achieve a larger capacity than the theoretical maximum capacity of graphitic carbons (372 mAh/g) and to reduce hysteresis in the charge-discharge process. Moreover, suitable distance between edges of graphene sheets to prevent the intercalation of electrolyte species was discussed. A recommended structure of carbon anodes suitable for the double Li ion layer storage and prevention of the intercalation of electrolyte species is proposed.     

Application of room temperature ionic liquids to Li batteries

Novel electrolyte materials, room temperature ionic liquids (RTILs) were applied to the Li battery system and their characteristics in Li-metal batteries are discussed, partly reviewing authors work in the past. Quaternary ammonium (QA) cation-imide RTIL was focused on because of the excellent stability in cathodic environment of Li. Li/LiCoO₂ cell performance and Li cycling efficiency using the selected QA-imide RTIL was almost satisfactory. In addition, thermal stability of selected QA-imide RTIL with the charged positive electrode and Li was the advantage for Li battery. On the other hand, further improvement in the conducting properties is required with balanced approach for both electrochemical stability and thermal stability in order to use the RTIL electrolyte practically in batteries.     

Na and Li ion diffusion in modified ASTM C 1260 test by Magnetic Resonance Imaging (MRI)

In the current study, MRI was applied to investigate lithium and sodium ion diffusion in cement paste and mortars containing inert sand and borosilicate glass. Paste and mortars were treated by complying with ASTM C 1260. Lithium and sodium distribution profiles were collected at different ages after different treatments. Results revealed that sodium ions had a greater diffusion rate than lithium ions, suggesting that Na reaches the aggregate particle surface before Li. Results also showed that Na and Li ions had a competitive diffusion process in mortars; soaking in a solution with higher [Li] favored Li diffusion but hindered Na diffusion. In mortars containing glass, a substantial amount of Li was consumed by the formation of ASR products. When [Li] in soaking solution was reduced to 0.37 N, a distinctive Na distribution profile was observed, indicating the free-state Na ions were continuously transformed to solid reaction products by ASR. Hence, in the modified ASTM C 1260 test, [Li] in the storage solution should be controlled at 0.74 N, in order to completely prevent the consumption of Na ions and thus stop ASR.     

Density-functional theory calculations of the electron energy-loss near-edge structure of Li-intercalated graphite

We have studied the structural and electronic properties of lithium-intercalated graphite (LIG) for various Li content. Atomic relaxation shows that Li above the center of the carbon hexagon in a AAAA stacked graphite is the only stable Li configuration in stage 1 intercalated graphite. Lithium and Carbon 1s energy-loss near-edge structure (ELNES) calculations are performed on the Li-intercalated graphite using the core-excited density-functional theory formulation. Several features of the Li 1s ELNES are correlated with reported experimental features. The ELNES spectra of Li is found to be electron beam orientation sensitive and this property is used to assign the origin of the various Li 1s ELNES features. Information about core-hole screening by the valence electrons and charge transfer in the LIG systems is obtained from the C 1s ELNES and valence charge density difference calculations, respectively.