Copper corrosion in buffered and non-buffered synthetic seawater: a comparative study

The electrochemical behaviour of copper in neutral buffered and non-buffered synthetic seawater and in pure chloride solutions has been studied by cyclic voltammetry, weight loss measurements, open circuit potential and scanning electron microscopy (SEM). Values of the repassivation potentials of Cu in non-buffered and buffered synthetic seawater, at 50 mV s^–1, were 0.12 and 0.46 V vs. SCE, respectively. The sharpness, heights and location of the different peaks as well as their charges were shown to be influenced by the composition of the solution, buffering conditions, deoxygenation, polarization potential and time. High chloride concentrations lead to higher oxidation charges. The anodic and the cathodic charges were shown to increase as the chloride concentration increases. The open circuit potential transients of copper in non-deoxygenated, non-buffered synthetic seawater indicate pitting from the beginning of the exposure, while in buffered solutions the pitting appeared only after a quite long exposure period, i.e. after 40 days. Corrosion rates of Cu samples after 3 months of immersion were higher in solutions of pure chloride (0.5 M) than in synthetic seawater. After six months the differences were even more noticeable. SEM images have showed a somewhat higher density of pits on copper samples immersed in the chloride solution (0.5 M), in comparison with those in synthetic seawater.     

硼砂珠实验的改进研究

硼砂珠实验是硼的元素及其化合物实验中的一个很重要的实验,但此实验用传统的镍丝载体不容易做成功,且不同教材对不同金属的硼砂珠颜色的描述不一致。对硼砂珠实验从载体的选择、用量、比例、温度、机理,常见金属盐的硼砂珠颜色的实验验证等多方面进行了详细的研究。     

Synthesis and Characterization of Borax-Polyimide for Flame Retardant Applications

Polyamide-borax composites were prepared from solution of polyimide and the borax using N-methyl-2-pyrrolidone as a solvent. The Polyimide-borax composites films (PI-BX) characterized by FTIR, SEM and x-ray. The borax content significantly influences thermal behavior of the polymeric films, such as glass transition and decomposition temperatures of polyimide-borax composites. The glass transition temperatures of the composites were higher than that of the original polyimide. The flammability properties of them were demonstrated by cone calorimeter and indicate that the borax composites have significantly decreased in heat release rate, and mass loss rate. The PI-BX composites appears very good the flame retardant properties.     

添加硼砂助熔剂煤灰熔融性的量子化学与实验研究

将硼砂按不同比例分别掺入四种高灰熔点煤灰中,对混合灰样熔融特性进行实验研究。 采用密度泛函理论对熔融过程中作为反应物的莫来石反应活性进行计算。莫来石属于正交晶系Pbam空间群。计算结果表明,莫来石很容易与电子接受体结合,不容易与电子给予体结合。当莫来石与电子给予体结合时,Si原子的活性高于Al。因此,向莫来石中加入助熔剂硼砂时,硼砂中的Na＋作为电子接受体,非常容易进入莫来石的晶格中,促使莫来石转变为霞石,降低了灰熔融温度。在还原性气氛下,煤灰熔融特性实验证实了理论计算结果。     

锌粉-硼砂-硼酸熔融-碘酸钾滴定法测定高硅锡精矿中的锡

针对高硅锡精矿中锡的测定时通常用锌粉-氢氧化钠熔融,精密度差,不能满足分析要求的问题,建立了锌粉-硼砂-硼酸熔融,盐酸浸取,铝粒将锡还原,碘酸钾滴定法测定高硅锡精矿中锡的分析方法。方法结果稳定,精密度好,相对标准偏差在0.19%~0.55%,加标回收率在96.9%~105%。分析结果能够满足高硅锡精矿中锡的测定要求。     

硼砂作稳定剂时胶体Sb2O5制备条件的优化

硼砂作稳定剂时胶体Sb2O5制备条件的优化     

Simple and New Method for the Synthesis of β-Acetamido Ketones on a Solid Surface

Diels–Alder reactions of 3-vinylindoles were carried out with methyl acrylate and N-phenylmaleimide as dienophiles under microwave conditions to furnish unreported tetrahydrocarbazoles regio- and stereoselectively in good yields. Further dehydrogenation resulted in new substituted carbazoles.     

黄原胶和瓜尔胶混合溶液及其硼砂交联体系的流变性能

本文研究了黄原胶(XG)和瓜尔胶(GG)的混合溶液及其硼砂(B)交联体系的流变性,考察了XG/GG间的“协同增效作用”以及溶液组成、pH和电解质(NaCl和CaCl 2)对其流变性的影响。结果表明,所有溶液体系均为假塑型流体,其流变曲线可用Herschel-Bulkley和Casson模型描述。XG和GG复配具有明显的“协同增粘效应”,在XG占两聚合物的质量分数w(XG)为20%和90%时协同增粘效应最强,其“协同增粘率”(R m)分别约为42%和34%。硼砂(B)可交联XG/GG混合溶液,其交联增粘效果随w(XG)的减小和硼砂质量浓度ρ(B)的增大而增大;在w(XG)=50%和ρ(B)=1.00 g/L时,“交联增粘率”可达85%。在所研究的pH值范围(6.2~10.0)内,XG/GG混合溶液的流变性基本无变化,而XG/GG/B交联体系(w(XG)=50%和ρ(B)=0.75~1.00 g/L)的表观粘度随pH值增大先升高后降低,pH=9.0时出现最大值,交联增粘率达107%。电解质可使XG/GG/B交联溶液(w(XG)=10%和ρ(B)=0.50 g/L)体系的粘度大幅下降,且CaCl 2的影响明显高于NaCl,表明交联结构的耐盐能力较差。这些结果加深了对XG/GG混合溶液流变性的认识,可为其实际应用(如在强化采油中的应用)提供依据。     

Breaking the Passivation: Sodium Borohydride Synthesis by Reacting Hydrated Borax with Aluminum

A significant obstacle in the large-scale applications of sodium borohydride (NaBH₄) for hydrogen storage is its high cost. Herein, we report a new method to synthesize NaBH₄ by ball milling hydrated sodium tetraborate (Na₂B₄O₇ ⋅ 10H₂O) with low-cost Al or Al₈₈Si₁₂, instead of Na, Mg or Ca. An effective strategy is developed to facilitate mass transfer during the reaction by introducing NaH to enable the formation of NaAlO₂ instead of dense Al₂O₃ on Al surface, and by using Si as a milling additive to prevent agglomeration and also break up passivation layers. Another advantage of this process is that hydrogen in Na₂B₄O₇ ⋅ 10H₂O serves as a hydrogen source for NaBH₄ generation. Considering the low cost of the starting materials and simplicity in operation, our studies demonstrate the potential of producing NaBH₄ in a more economical way than the commercial process.     

非抑制离子色谱法测定膨化食品中硼砂(硼酸)

建立了非抑制离子色谱法测定膨化食品中硼砂(硼酸)的分析方法,优化了色谱分离条件.样品在甲基磺酸溶液中超声提取后,经离心、过滤,依次过RP固相萃取柱、银柱、钠柱、滤膜后,进样分析.采用5 mmol/L氢氧化钠作为淋洗液,硼酸根经Dionex Ionpac AG16(50 mm ×4 mm)+ AS16(250 mm×4 ...