共查询到19条相似文献，搜索用时 125 毫秒
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以溶胶－凝胶－酯化法在２２０℃即可得到纯相的ＬｉｘＭｎ２ｏ４尖晶石粉体材料。它在８８０℃时发生立方相向四方相的转变：９００℃－１０００℃间,四方相渐变为正交相ＬｉＭｎＯ２,这程中有Ｌｉ２ＭｎＯ３生成。 相似文献
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用等温溶解平衡法研究了盐湖卤水体系Ｌｉ＋，Ｎａ＋，Ｋ＋，Ｍｇ２＋／ＳＯ＿４￣２－Ｈ２Ｏ２５℃溶解度，获得了该五元体系２５℃溶解度相图的十个无变量点和十个结晶区．十个结晶区分别对应于原始组份Ｋ２ＳＯ４、Ｌｉ２ＳＯ４·Ｈ２Ｏ、ＭｇＳＯ４·７Ｈ２Ｏ、Ｎａ２ＳＯ４·１０Ｈ２Ｏ、复盐３Ｋ２ＳＯ４·Ｎａ２ＳＯ４、Ｎａ２ＳＯ４·ＭｇＳＯ４·４Ｈ２Ｏ、Ｌｉ２ＳＯ４·３Ｎａ２ＳＯ４·１２Ｈ２Ｏ、２Ｌｉ２ＳＯ４·Ｎａ２ＳＯ４·Ｋ２ＳＯ４·Ｌｉ２ＳＯ４·Ｋ２ＳＯ４和Ｋ２ＳＯ４·ＭｇＳＯ４·６Ｈ２Ｏ，此外没有产生新的复盐或固溶体，用现代电解质溶液理论－Ｐｉｔｚｅｒ模型校验该体系的溶解度测定值，结果令人满意． 相似文献
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研究了ＣＨＩＮＡＲＥ－６和ＣＨＩＮＡＲＥ－９普里兹湾内营养盐的分布及变化,采用化学质量平衡方法估计了该海区新生产力的大小。结果表明在ＣＨＩＮＡＲＥ－６期间,ＮＯ３－Ｎ、ＰＯ４－Ｐ、ＳｉＯ３－Ｓｉ消耗分别为１０６４．８、６９．２、２１９６．９ｍｍｏｌ／ｍ２,ＮＰ、ＳｉＰ吸收比分别为１５．３、３１．７,平均新生产力为９９２．４ｍｇＣ／（ｍ２ｄ）。在ＣＨＩＮＡＲＥ－９期间,ＮＯ３－Ｎ、ＰＯ４－Ｐ消耗分别为５５１．９、４１．２ｍｍｏｌ／ｍ２,ＮＰ吸收比为１３．４,平均新生产力３９０．１ｍｇＣ／（ｍ２ｄ）,表现出很大的季节和／或年际变化。估算的新生产力值都大于１４Ｃ测定的初级生产力值,表明普里兹湾海区夏季有很大的新生产力。元素吸收比和外海测定值不同,表明营养盐的吸收和循环在南极海区有很大的区域差异性。 相似文献
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用锂离子选择电极和经典Ａｇ－ＡｇＣｌ电极测定了２９８．１５Ｋ下ＬｉＣｌ－Ｌｉ２Ｂ４Ｏ７－Ｈ２Ｏ体系中离子强度范围为０．０１～２．５０ｍｏｌ．ｋｇ＾－１,不同Ｌｉ２Ｂ４Ｏ７离子强度分数的ＬｉＣｌ的平均活度系数。由实验数据,用迭代法及多元线性回归法,求取了Ｌｉ２Ｂ４Ｏ７的化学计量离解平均常数Ｋｍ,热力学离解平衡常数Ｋ及Ｐｉ－ｔｚｅｒ离子作用参数,并与实验值比较标准偏差为０．０５００,同时该实验结果在０ 相似文献
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希夏邦马峰冰川粒雪中环境季节变化记录研究 总被引：9，自引：0，他引：9
在希夏邦马峰达索普冰川海技７０００ｍ冰雪平台钻取１４ｍ粒雪芯一支。通过对粒雪芯中δ＾１８Ｏ和主要离子浓度的季节变化分析,认识希夏邦马峰地区大气环境的季节变化特征。相关分析和经验正交函数（ＥＯＦ）分析结果表明,达索普粒雪芯内的δ＾１８Ｏ与Ｃａ＾２＋、Ｍｇ＾２＋、ＳＯ４＾２－、ＮＯ３＾－和ＮＨ４＾＋浓度之间正相关显著,而与Ｎａ＾＋、Ｃｌ＾－和Ｋ＾＋浓度之间的关系不明显。ＥＯＦ１代表了以尘埃来源为主的离 相似文献
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分析了威德尔海周边雪冰和大气中ＭＳＡ和ｎｓｓＳＯ２－４浓度资料。结果表明,威德尔海是造成这一地区大气中高含量生物硫化物的“源”,其周边岛屿及冰架表层雪冰记载和反映了大气中生物硫化物的空间分布和季节变化特点。源区产出硫化物的强度存在显著差异：靠近南极半岛一侧高于靠近Ｆｉｌｃｈｎｅｒ－Ｒｏｎｎｅ冰架一侧。尽管诸多因素对输运和沉降过程发生影响,表层积雪ＭＳＡ和ｎｓＳＯ２－４浓度仍呈现出很有规律性的空间分布：随沉降地点离海距离和海拔高度的增加,浓度值递减;但在一定海拔之下,“高程效应”不显著。冰芯中ＭＳＡ浓度垂向分布显示出季节分配“滞后”现象,在表层表现为受天气条件制约的输运过程造成的相位差,在深层则归因于有待验证的“迁移”机制作用的结果。大气和雪冰样品对比研究结果表明,在类似威德尔海这样的高纬地区,大气中的ＳＯ２－４和ＭＳＡ“信号”在雪冰样品中会遭到不同程度的减弱。但就空间变化趋势和季节分布而言,表层雪冰仍是大气中组分（在本文是ＳＯ２－４和ＭＳＡ）的良好载体。十分接近的大气和雪冰ＭＳＡ对ｎｓｓＳＯ２－４（或ＳＯ２－４）比率证实,这两种大气组分在由大气洗净和沉降到冰雪过程中只发生微弱的分离作用。这也就是大气和雪冰中 相似文献
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The crystal structure of metal borates has been extensively investigated by X-ray and neutron diffraction,but,the structure of aqueous polyborate solutions are still largely unknown.Over the last decade,our group has focused on studying the structure of complex aqueous polyborate solutions of Li,Na,K,Rb,Cs,and Mg using synchrotron radiation X-ray scattering(XRS),EXAFS,Raman,NMR,and DFT,as well as determining the density,conductivity and pH of such solutions.Polyborate species distributions were calculated using pH measurements,and the main species in the solution have been confirmed by NMR and Raman spectra.For alkali-metal metaborates,the dominant species is always B(OH)-4in a wide range of concentration,while the presence of others species is negligible.For alkali metal tetraborates,when concentration is in the extreme low range,only B(OH)3 and B(OH)-4 are present in these solutions.As the total boron concentration increases,B(OH)3 and B(OH)-4 polycondensated to form more complex oligomers.Of them,while B4O5(OH)2-4 in the tetraborate solutions is the main species,B(OH)3,B(OH)-4,and B3O3(OH)-4 are minor species,and B3O3(OH)2-5 and B5O6OH)-4 are present only in negligible amounts.As solution continues to concentrate,B4O5(OH)2-4 eventually becomes the dominant species,which is consistent with the congruent compound M2B4O7·nH2O(M=Li,Na,K,Rb,Cs) in the system M2O-B2O3-H2O(M=Li,Na,K,Rb,Cs).For alkali metal pentaborates,B(OH)3 and B(OH)-4 are the main species at low concentrations.The species distribution,Raman and NMR spectroscopy results verified that the dominant species in concentrated pentaborate solutions with Li and Na is pentaborate B5O6OH)-4,but it is surprising that the main species with K,Rb,and Cs is always the triborate monoanion B3O3(OH)-4.Although all M[B5O6OH)4]·nH2O(M=Li,Na,K,Rb,Cs) are all congruent compounds in the system M2O-B2O3-H2O(M=Li,Na,K,Rb,Cs) ,the main species in aqueous solutions are quite different because of various cation hydration distance(d),hydration number(CN),and configuration,especially charge(Z).For bivalent Mg2+,three borate minerals,namely,Inderite(2MgO·3B2O3·15H2O),Hungchaoite(MgO·2B2O3·9H2O),and Mcallisterite(MgO·3B2O3·7.5H2O),exist in the system MgO-B2O3-H2O at 298K.Inderite is a congruent compound,but Hungchaoite and Mcallisterite are incongruent compounds.The species distribution and Raman spectra demonstrat that the predominant species in all the solutions with magnesium borates is bivalent triborate B3O3(OH)2-5,while the subordinate species are B(OH)-4 at a low B2O3/MgO ratio and B(OH)3at a high B2O3/MgO ratio,and the other anions are negligible,as the high Z of the borate anion must match that of Mg2+.The disappearance of divalent B4O5(OH)2-4 is in agreement with its incongruent nature.The DFT and XRS results showed that tetrahedral Li(H2O)+4(d=0.20 nm,CN=4),octahedral Na(H2O)6+(d=0.236 nm,CN=6),and Mg(H2O)2+6(d=0.210 nm,CN=6) in the first hydration shell belong to Platonic polyhedra.However,K(H2O)+8(d=0.28 nm,CN=8,XRS and DFT),Rb(H2O)+8(d=0.293 nm,CN=7.7-8.2,EXAFS),and Cs(H2O)+8(d=0.320-0.326 nm,CN=7.6-7.9,EXAFS) are inclined Voronoi polyhedra.Therefore,the effects of cation Z and d on the structure of polyborates in aqueous solutions are deterministic,while the effect of hydrated-cation symmetry is secondary.Their hydrolysis order was:Mg＞Li＞Na＞K＞Rb＞Cs,in step with hydration power.Among them,Mg2+ and Li+have a strong tendency towards hydrolysis,but Na+ scarcely hydrolyzes,especially Rb+ and Cs+ have a little protonation.X-ray scattering of aqueous alkaline sodium borohydride solutions confirmed that dihydrogen bonds exist in an aqueous solution.The four distinct features of dihydrogen bonds in aqueous solution-unidirectionality,divaricativity,multicentricity,and multidentativity have been also described here in brief. 相似文献
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Boron resources are abundant in the Da Qaidam Salt Lake of the Qaidamu basin in China,which has generated significant attention due to the presence of polyborate species in brine from this lake. In this study,Raman spectroscopy was used to investigate the existing form of boron in brine during evaporation. MgO·2 B_2 O_3-H_2 O,MgO·2 B_2 O_3-MgCl_2-H_2 O,and MgO·2 B_2 O_3-MgSO_4~-H_2 O solutions were also studied to determine the influence of boron concentration,pH,and electrolytes on the borate speciation from brine. The mononborates B( OH)_3 and B( OH)_4~-were found to be the only forms present in natural salt lake brine. Brine evaporation promoted the formation of the polyborate anions B_3 O_3( OH)_4~-,B_5 O_6( OH)_4~-,and B_6 O_7( OH)_6~(2-)and also promoted the disappearance of the B( OH)_4~-ion from brine at boron concentrations of more than 11 g/L B_2 O_3. The pentaborate ion B_5 O_6( OH)_4~-was sensitive to the solution pH and appeared only at p H values less than 8. 0. Meanwhile,the hexaborate ion B_6 O_7( OH)_6~(2-)was observed to be more dependent on the electrolyte magnesium chloride due to its special properties,such as promoting boron accumulation,lowering solution pH,and also its strong affinity for water molecules,which were all beneficial for the polymerization of borate ions in brine. Interaction mechanisms between polyborate anions during evaporation are also proposed herein. ake; evaporation; polyborate species; interaction mechanism. 相似文献
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Li2SO4溶液中离子间的缔合相互作用:基于密度泛函理论和分子动力学模拟的研究 总被引：1，自引：1，他引：0
基于密度泛函理论,使用B3LYP/aVDZ方法对[Li_2SO_4(H_2O)_n]~0(n=0~10、18)水合团簇的结构和性质进行了系统地研究,并结合Car-Parrinello分子动力学(CPMD)模拟了不同浓度的Li_2SO_4溶液结构,目的在于理解在Li_2SO_4溶液中离子间缔合相互作用及可能存在的物种。研究发现,对于[Li_2SO_4(H_2O)_n]~0(n=0~10、18)水合团簇,双配位单齿螯合接触离子对结构比双配位双齿螯合接触离子对结构更稳定,溶剂共享离子对结构最不稳定。同时,CPMD模拟结果表明,在3.09和3.17 mol/kg的Li_2SO_4溶液中,双配位单齿螯合接触离子对结构仍然是主要物种。以上结果表明在饱和的Li_2SO_4溶液(3.16 mol/kg)中,Li~+和SO_4~(2-)离子间的相互缔合作用主要以双配位单齿螯合接触离子对结构的物种存在,而具有双配位双齿螯合离子对结构的物种占少数,溶剂共享离子对结构几乎不存在。 相似文献
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Li brines are the primary resources for Li salt industries. Evaporation is necessary to concentrate Li due to its low level of concentration in raw brines. The salt sequences during the evaporation of Li brines,especially the behavior of Li salts,represent key data for solar technologies. However,chemists cannot use any phase diagram to estimate Li salt sequences during evaporation at 25℃ . The thermodynamic model proposed by us in2003 represents the only tool for the prediction of equilibrium conditions during the evaporation of solutions containing Li~+,Na~+,K~+,Mg~(2+)/Cl~-,SO_4~(2-),and-H_2 O components at 25℃ . In this paper,the predicted salt sequences of 20 brines are reported. The results indicate that( 1) the first crystallized Li salt during evaporation of Li brine varies in brine composition;( 2) lithium sulfate is crystallized in many cases initially for brines of magnesium sulfate subtype,while Db4( Li_2 SO_4·K_2 SO_4) or Db3( 2 Li_2 SO_4·Na_2 SO_4·K_2 SO_4) appears first for sodium sulfate and magnesium sulfatesubtypes with lower Mg/Li composition,and the final eutectic point is H ~+ LiC ~+ Lc ~+ Ls ~+ Car;( 3) the final eutectic point is H ~+ LiC ~+ Lc ~+ Car for brines of chloride type; and( 4) Li content corresponding to the first crystallized Li salt is in the range of 0. 43%-1%. These findings enhance our knowledge of Li chemistry and provide insights into solar pond technology of the Li-brine process. 相似文献
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用柠檬酸作为螯合物的载体,采用溶胶-凝胶法合成了Al3+掺杂的锂离子电池正极材料LiAlxMn2-xO4,并用XRD、SEM等多种测试手段研究了不同掺杂铝量对粉体形貌、晶体结构的影响。结果表明,800℃烧结可获得单一尖晶石结构的物相。随着Al3+掺入量的增加,LiAlxMn2-xO4的晶格常数变小,晶格更趋于完整,有利于抑制因锂的反复脱嵌而造成结构的破坏。实验表明,当掺Al量为0.05时,首次放电容量为103.8 mAh/g,25次循环后容量还有100.6 mAh/g,容量衰减仅为3.08%。该正极材料具备高的容量和优异的循环性能。 相似文献
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新疆巩乃斯河水化学分析 总被引：4，自引：1，他引：3
通过对伊犁河支流巩乃斯河河水取样分析,结果表明:巩乃斯河河水阴离子中HCO3-占优势,阳离子中Ca2+占主要地位。主要离子含量表现为阴离子HCO3-C l-SO42-;阳离子Ca2+Na++K+Mg2+。巩乃斯河河水均属于HCO3-C l-Ca-Na型水。河水pH为7.56~8.01;矿化度为80~155 mg/L;总硬度为0.620~1.446 mmol/L;河水总碱度为0.778~1.676 mmol/L。另外,对离子浓度的空间变化及离子的来源分析研究表明,巩乃斯河流域的地形,地貌及气候的差异决定了河水主要离子浓度、pH和矿化度自河流上游至下游,基本呈现先逐步降低后显著升高的趋势;巩乃斯河河水主要离子来源于河水对基岩的溶滤作用,同时钠长石斑岩及人类活动所产生的物质也是主要离子的来源之一。 相似文献