氮化烧成铝–方镁石–刚玉复合材料的显微结构和反应机理

在刚玉(电熔刚玉、板状刚玉)–高纯镁砂中加入质量分数分别为0、4%、6%、10%的铝粉,在碳管炉1 600℃氮气气氛下制备Al–Mg O–Al_2O_3复合材料。结果表明:烧后试样的主晶相为刚玉和镁铝尖晶石固溶体,基质是由镁铝尖晶石固溶体、氮化铝、Al ON和Mg Al ON等增强相组成的复合结构。随铝粉含量增加,Al N、Al ON和Mg Al ON含量增加且存在未反应的铝粉。铝粉氮化机理为Al反应生成Al N,Al N与Al_2O_3固溶形成Al ON相,氧化镁或新形成的尖晶石与Al ON相固溶形成Mg Al ON相。建立了金属铝粉氮化反应模型,反应模型呈明显的环状结构:内层产物为未反应的铝和反应后形成的微孔;中间层产物为氮化铝和阿隆的复合结构;外层环带状产物为阿隆和镁阿隆的复合结构。电熔刚玉颗粒部分参与反应形成环带状镁铝尖晶石固溶体。     

熔铸耐火材料抗盖板玻璃熔体侵蚀行为研究

本文以熔铸耐火材料为研究对象进行抗盖板玻璃熔体侵蚀试验,采用化学分析、岩相分析和电子显微镜能谱分析等测试分析方法,对比研究钠钙玻璃熔体、高铝玻璃熔体和锂铝玻璃熔体对熔铸耐火材料的侵蚀行为。结果表明,玻璃熔体中的碱金属离子向耐火材料中的玻璃相扩散,导致玻璃相黏度降低,同时耐火材料中刚玉相溶解,斜锆石分散,主体结构遭到破坏,并形成界面层。界面层内存在富铝含锆的玻璃相,由于高铝玻璃和锂铝玻璃氧化铝含量高,表面张力大,界面层内的玻璃相聚集在试样周围且扩散慢,从而阻止了侵蚀的发展。玻璃熔体的侵蚀速率为钠钙玻璃熔体＞高铝玻璃熔体＞锂铝玻璃熔体。     

电感耦合等离子体原子发射光谱法测量铝-锂合金阳极氧化液中的Li含量

建立了采用电感耦合等离子体原子发射光谱法测量铝-锂合金铬酸阳极氧化液中Li含量的分析方法,探讨了在标准溶液中加入铬酸酐、钇离子和氯化铷对测量结果的影响。结果表明,铬酸酐和钇离子的加入,使测量方法的准确度提高,铷元素的加入,能够抑制铬元素含量的测量结果随重复测量的增加而降低的现象。该方法的检出限为0.00172μg/g;样品的回收率为99.428%~100.426%,相对标准偏差RSD(n=24)为0.236%。该方法准确、快速,具有良好的精密度和准确度,能够满足日常生产监控需要。     

化学组成对OLED基板玻璃熔体表面张力的影响

以 OLED基板玻璃为研究对象,基于座滴法进行玻璃熔体表面张力实验,研究化学组成对无碱铝硼硅玻璃表面张力的影响.研究结果表明:Al2 O3/SiO2 和 MgO/RO (RO 为碱土金属氧化物总和)的增加会导致玻璃熔体表面张力增大,增加 ZnO/(ZnO+SrO)有降低玻璃熔体表面张力的作用;增加 RO/(Al2 O3+B2 O3 ),玻璃表面张力会呈现先增大后减小的趋势,且在RO/(Al2 O3+B2 O3 )=1 处出现极大值.     

非化学计量比镁铝尖晶石粉体的制备及性能

将异丙醇镁铝双金属醇盐滴加到含有5%(质量分数)EDTA分散剂的水解液中,制得镁铝氢氧化物无色透明溶胶,后经干燥、高温焙烧得到非化学计量比的铝镁尖晶石粉体。研究了Mg/Al摩尔比、焙烧温度、干燥工艺流程以及助溶剂的添加对粉体材料性能影响。结果表明:Mg/Al摩尔比在1.0:(2.5～4.0)范围内,1 200℃焙烧后对应粉体为纯相镁铝尖晶石结构,随铝含量增加,衍射峰向大角度方向偏移,且粉体颗粒粒径逐渐增大,Mg O·1.25Al_2O_3粉体红外透过率较高,可潜在应用于红外隐身等材料。     

共沉淀法制备镁铝水滑石及其表征

采用共沉淀法以硝酸铝、销售镁、氢氧化钠及碳酸钠为原料,制备镁铝水滑石,通过XRD、TG-DTA对不同初始溶液Mg/Al摩尔比制备的水滑石进行表征,结果表明:不同初始溶液Mg/Al摩尔比的情况下均能制备出结晶度好,晶相比较单一,晶型结构较为完整的Mg/Al-CO3水滑石,随Mg/Al摩尔比增加,水滑石热稳定性相应升高,样品结晶度提高。     

LiCoO2合成过程对镁铝尖晶石陶瓷侵蚀的研究

研究了LiCoO2合成粉体过程对镁铝尖晶石陶瓷的侵蚀,并探讨了相关侵蚀机制.研究结果显示,经历10次的LiCoO2粉体合成过程后,镁铝尖晶石陶瓷的平均被侵蚀深度仅约100μm;其侵蚀机制为:含锂化合物先于含钴化合物对镁铝尖晶石陶瓷进行侵蚀并形成LixMyOz(M=Al/Mg)化合物,含钴化合物进一步侵蚀渗透形成LixMyOx(M'=Al/Mg/Co)化合物并从LixMyOz(M=Al/Mg)化合物中析出.研究认为,用镁铝尖晶石陶瓷制备合成钴酸锂粉体用匣钵具有良好的抗侵蚀性能.     

吸附法从盐湖卤水中提取锂的研究

研究了吸附法从盐湖卤水中提取锂的工艺过程,不单独制备吸附剂,并用氢氧化钙代替传统的氢氧化钠作沉淀剂。研究了铝锂摩尔比、氢氧化钙加入量、反应时间等因素对锂吸附效果的影响,并用X射线衍射(XRD)、原子吸收光谱法(AAS)对各样品进行了表征。实验结果表明:所得沉淀产物为Li Cl·2Al(OH)3·x H2O,铝锂摩尔比、氢氧化钙加入量、反应时间对锂吸附效果影响显著。在室温下,铝锂摩尔比为4,氢氧化钙加入量为9 g,反应时间为2 h时,锂吸附效果较佳,锂吸附率可达96.4%。吸附产物经脱附,镁锂分离情况较理想。     

PP/Al(OH)_3/Mg(OH)_2阻燃复合材料的流动性能

制备了PP/Al(OH)_3/Mg(OH)_2阻燃复合材料,利用熔体流动速率仪测定了复合材料的熔体体积流动速率(MVR),并计算出其密度。结果表明:MVR随着阻燃剂质量分数的增加而减小,随着阻燃剂粒径的增加先降后升;复合材料密度随阻燃剂用量的增加呈近似线性增加,随阻燃剂粒径的增加呈近似线性降低,随着载荷的增加而提高。     

界面反应对铝熔体定向渗透氮化过程的影响

将外形尺寸为φ15 mm×10 mm的一级工业纯铝锭(w(Al)=99%)6.5 g放入石墨坩埚内,在其四周及底部填充氧化铝粉阻生剂,采用粒度均为1～0.5 mm、固定量均为3 g的电熔镁砂(w(MgO)=95%)、镁铝尖晶石(31.9%MgO,58.1% Al2O3)和电熔刚玉(w(Al2O3>)=95%)3种颗粒作为填充剂,分别与占铝锭质量10%的金属Mg粉(w(Mg)=99%)混合后,松散堆积在铝锭表面上,在1 200℃氮气气氛中处理10 h.利用XRD、SEM、EPMA及OM分析了反应后得到复合材料的物相组成和显微结构,研究了定向金属氮化制备氮化铝基复合材料过程中金属铝熔体和填充剂间的界面反应对渗透氮化的影响.结果表明:1 200℃下,镁砂与铝熔体剧烈反应生成大量镁,促进了铝熔体的渗透和氮化过程;镁铝尖晶石与铝熔体反应明显减弱,但生成少量的镁,也在一定程度上有利于渗透和氮化过程;相比之下,刚玉与熔体界面反应消耗了反应体系的镁,影响了铝熔体的渗透,但渗入铝的氮化较为完全,且复合材料结构致密.     

Effect of Iron Coating on Thermal Properties of Aluminum‐Lithium Alloy Powder

Aluminum‐lithium alloys are widely studied to improve performance in energetic materials. However, their high reactivity causes severe surface oxidation over micro‐Al particles in storage, resulting in significant deterioration in the overall performance. This study deals with the effect of iron coating on thermal properties and aging stability of aluminum‐lithium alloy powder. Gas atomized Al‐3Li (3 wt. %) alloy powder was prepared and then successfully coated with nano‐sized iron film by modified chemical liquid deposition method. The morphology, thermal properties and combustion enthalpies were characterized by SEM/EDX, TG/DTA and oxygen bomb calorimeter. The results showed that Fe/Al‐3Li composite powder presented obvious core‐shell structure and the outer iron film was very uniform and compact. Significantly enhanced thermal reactivities of Al‐3Li alloy powder and Fe/Al‐3Li composite powder were achieved compared with pure Al. In addition, aging studies indicated that, after coating, the reactivity decay rates of alloy powder decreased significantly, and the mass combustion enthalpies remained basically stable, which demonstrated that iron coating indeed prevented pre‐oxidation of the alloy powder and improved its aging stability.     

Electrochemical study of the codeposition of Mg–Li–Al alloys from LiCl–KCl–MgCl<Subscript>2</Subscript>–AlCl<Subscript>3</Subscript> melts

This work presents a novel electrochemical study on the codeposition of Mg, Li and Al on a molybdenum electrode in LiCl–KCl–MgCl₂–AlCl₃ melts at 943 K to form Mg–Li–Al alloys. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of magnesium on pre-deposited aluminum leads to the formation of a liquid Mg–Al solution, and the succeeding underpotential deposition of lithium on pre-deposited Mg–Al leads to the formation of a liquid Mg–Li–Al solution. Chronopotentiometric measurements indicated that the codeposition of Mg, Li and Al occurs at current densities lower than −0.47 A cm⁻² in LiCl–KCl–MgCl₂ (0.525 mol kg⁻¹) melts containing 0.075 mol kg⁻¹ AlCl₃. Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li and Al is −2.100 V, and the codeposition of Mg, Li and Al is formed when the applied potentials are more negative than −2.100 V. The diffusion coefficient of aluminum ions in the melts was determined by different electrochemical techniques. X-ray diffraction and inductively coupled plasma analysis indicated that α, α + β and β Mg–Li–Al alloys with different lithium and aluminum contents were obtained via potentiostatic and galvanostatic electrolysis.     

Extraction of europium and electrodeposition of Al–Li–Eu alloy from Eu2O3 assisted by AlCl3 in LiCl–KCl melt

The work presents an electrochemical study on preparation of Al–Li–Eu alloys on a tungsten electrode in molten LiCl–KCl–AlCl₃–Eu₂O₃ system at 753 K and 953 K. Gibbs energy shows that AlCl₃ can chloridize Eu₂O₃, with a discharge in the form of Eu(III) ions on the cathode. The electrochemical behavior of Al(III), Li(I) and Eu(III) and alloy formation processes were investigated by cyclic voltammetry, square wave voltammetry, and chronopotentiometry. Cyclic voltammetry indicated that the underpotential deposition of europium on pre-deposited Al forms two Al–Eu intermetallic compounds at electrode potentials around ?2.00 V and ?2.34 V, respectively. And the underpotential deposition of lithium on Al surface at about ?2.24 V leads to a formation of Al–Li alloy. X-ray diffraction (XRD) indicated that Al–Li–Eu alloys with different phases were obtained via galvanostatic electrolysis. The microstructure and micro-zone chemical analysis of Al–Li–Eu alloy were characterized by scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), respectively. The analysis of EDS showed that element Eu mainly distributes on needle-like precipitate, and not homogeneously in the Al–Li–Eu alloy. Composition of the alloys was analyzed by inductive coupled plasma analysis, and current efficiency was also determined with respect to the alloy composition.     

纳滤膜对高镁锂比盐湖卤水镁锂分离性能研究

纳滤作为一种新兴的膜分离技术,在高镁锂比盐湖卤水镁、锂分离领域具有非常好的应用前景。研究了不同镁锂比、原料液循环流量对镁锂分离过程的影响,并对膜分离过程中的分离机理进行分析。结果表明原料液镁锂比对膜通量影响较小,镁、锂离子截留率及镁锂分离效果均随原料液镁锂比的增加而降低。当原料液循环流量为225 L/h时,镁离子截留率为95%,锂离子截留率为-66%,透过液镁锂比降低至1.2。膜分离传质机理研究表明,镁离子在分离过程中受到较强的介电排斥效应与尺寸筛分效应。纳滤技术能够有效降低高镁锂比盐湖卤水的镁锂比,为后续高纯锂盐的制备提供基础。     

Effect of adding magnesium to lithium on the performance of discharge and hydrogen evolution of the lithium anode

The present study evaluates the effect of magnesium as an inhibitor on the performance of discharge and hydrogen evolution of lithium anode in alkaline electrolyte with additives. The electrochemical behaviors of lithium and lithium–magnesium alloy are assessed by hydrogen evolution rate, discharge current density, anodic potential, and potentiodynamic polarization. For these conditions, the results show that addition of magnesium to lithium enhances the current efficiency. Addition of 0.07 wt% Mg to lithium has minor effect on discharge current and anodic potential of lithium anode. The chemical composition and the morphology of the anode surfaces were evaluated by X-ray diffraction and scanning electron microscopy. The results show that the slow dissolution of lithium–magnesium alloy generates the formation of LiOH, LiOH·H₂O, and Mg(OH)₂. After discharge in saturated alkaline electrolyte with additives, the lithium–magnesium surface is less porous than lithium surface. Hydrogen evolution decrease, prompted by adding magnesium to lithium, is related to surface integrity enhanced by Mg(OH)₂.     

An investigation of the effects of polymer binder compositional variables on the corrosion control of aluminum alloys using magnesium-rich primers

It has recently been shown that magnesium (Mg) particles possessing a thin oxide surface layer can be used to produce primers that provide corrosion protection to aluminum (Al) alloys through a galvanic coupling mechanism. In addition to the Mg particles, polymer binder properties also affect corrosion protection. As a result, the effects of compositional variables associated with a two-component epoxy binder system on the ability of Mg-rich primers to protect an aerospace Al alloy were determined. The variables investigated were epoxy resin molecular mass, curing agent functionality, epoxy/NH ratio, and Mg content. All of the variables investigated had a significant effect on coating system performance and an optimized coating composition was identified that showed very good corrosion protection for at least 3,000 h of ASTM B117 salt spray exposure.     

A New Approach to the Synthesis of Mg–Al Layered Hydroxides

Theoretical Foundations of Chemical Engineering - Mg–Al layered hydroxides with the composition Mg4Al2(OH)12CO3?3H2O are synthesized by mixing crystalline magnesium and aluminum...     

氟化物包覆对镁铝合金与水催化反应效率的影响

为了提高镁铝合金与水的反应效率,采用氟化物对镁铝合金粉进行表面包覆,利用扫描电镜、X射线衍射仪和粒度分析仪对合金粉与高温水反应产物进行表征,对比研究了高温下不同比例的氟化物对镁铝合金与水催化反应效率的影响。结果表明,包覆氟化物的镁铝合金与高温水反应产物的粒径减小,分散性明显改善;固相燃烧产物中主要包含Al_2MgO_4、MgO和Al,表明Al未完全反应;合金粉包覆氟化物后铝的反应效率明显提高,其中,包覆质量分数2%氟橡胶和2%有机氟化物的合金粉反应效率高达89.7%,与未包覆样品相比提高了14.6%。     

Co-deposition of Al-Zn on AZ91D magnesium alloy in AlCl3-1-ethyl-3-methylimidazolium chloride ionic liquid

The co-deposition of Al and Zn on AZ91D magnesium alloy from a Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl₃-EMIC, with a molar ratio of 60:40) ionic liquid containing 1 wt% ZnCl₂ at room temperature was studied. The effect of potential on the deposition rate, the microstructure and the chemical composition of the deposit was explored. The experimental results show that the simultaneous deposition of Al and Zn on Mg alloy can be achieved under properly controlled potential conditions. The deposition rate increased while the amount of Zn existing in the coating decreased with increasing negative deposition potential. In the ionic liquid studied, a uniform chemical composition of the coating was obtained when the deposition was performed at −0.2 V (vs. Al).     

Facile synthesis and exfoliation of micro-sized LDH to fabricate 2D membranes towards Mg/Li separation

Two-dimensional (2D) membranes have demonstrated potential for molecular separation; however, their applicability for Li/Mg ion separation has been restricted by their negatively-charged and easily-swellable properties in water. Moreover, their practical application has been hindered by the challenge of producing significant quantities of single-layer nanosheets. To overcome these challenges, we have developed a scalable method for synthesizing micro-sized nitrate ZnAl layered double hydroxide (LDH) and subsequent exfoliating to yield monolayer nanosheets for the construction of 2D membranes. The sub-nanometer channels of the LDH membrane is positively charged, which prevents the passage of magnesium ions. These channels also impede the flow of magnesium ions that are more difficult to dehydrate. As a result, the LDH membranes exhibit robust lithium–magnesium separation ability, with a separation ratio of 6 (Li/Mg). This work provides a method for producing high-quality LDH nanosheets and validates the enormous potential of LDH membranes in the field of lithium–magnesium separation.