金属阳离子对医用镁合金降解行为的影响规律

医用镁合金的降解特性直接影响其在心血管支架和骨替换材料等领域的应用。本研究在保持与生理体液氯离子浓度一致的基础上,选用镁合金AZ31B分别浸入NaCl溶液,KCl溶液,MgCl2溶液和CaCl2溶液中,对比研究金属阳离子对医用镁合金的降解行为影响。通过动电位极化曲线和电化学阻抗谱测试分析,发现镁合金浸泡在4种氯盐溶液时的腐蚀电位、阻抗与其在降解过程中溶液pH变化、样品失重变化趋势一致,即金属阳离子直接影响医用镁合金的降解特性:NaClKClCaCl2MgCl2,其中Na+和K+比Ca2+和Mg2+更能促进镁合金降解。     

盐沉积条件下CO2对LY12铝合金大气腐蚀的影响

目的研究在有/无CO_2存在的恒温恒湿条件下,表面有沉积盐的LY12铝合金的大气腐蚀行为与腐蚀机理,搞清CO_2对其大气腐蚀的影响。方法将LY12铝合金表面分别沉积不同浓度的NaCl和MgCl_2,分别进行通/不通CO_2的恒温恒湿实验,借助扫描电镜(SEM/EDS)、X射线衍射(XRD)和X光电子能谱(XPS)等表面技术以及腐蚀失重分析方法,研究盐沉积条件下CO_2对LY12铝合金大气腐蚀的影响。结果在试验条件下,MgCl_2造成的LY12铝合金腐蚀都以点蚀为主,失重高于NaCl造成的。以MgCl_2为介质时,主要腐蚀产物都为(Mg1–xAlx(OH)_2)x+(Cl~–,CO~(2–))x×mH_2O(简写为LDH);以NaCl为介质时,主要腐蚀产物都为Al_2O_3或Al(OH)_3。两种介质的腐蚀产物都出现了Cu元素的富集。结论无论是否存在CO_2,Mg元素都参与了腐蚀产物的形成。合金元素Cu的存在及其富集,是造成CO_2对纯铝和LY12铝合金腐蚀行为不同影响的主要因素。     

PROPERTIES OF MgB_2 FILMS FABRICATED ON COPPER CATHODES BY ELECTROCHEMICAL TECHNIQUE

An electrochemical technique has been introduced and applied to fabricate superconducting MgB2 films in molten salts. MgCl2, Mg（BO2）2, NaCl, and KCl were used as electrolyte, graphite was used as the anode, and copper was used as the cathode, respectively. X-ray diffraction （XRD） analysis was chosen to investigate the phase composition and crystallinity of the films at different electrolysis temperatures. Stan- dard four-probe technique and SQUID were applied to investigate the temperature dependence of resistance （R-T） properties and magnetic properties of the films, respectively. The results indicate that MgB2 films have been fabricated on the copper cathodes, and superconducting transition takes place close to 50 K.     

High temperature oxidation of metallic chromium exposed to eight different metal chlorides

The influence of eight different chlorides (BaCl₂, CaCl₂, KCl, LiCl, MgCl₂, NaCl, PbCl₂, and ZnCl₂) on the oxidation of metallic chromium powder was studied at four different temperatures (400 °C, 500 °C, 550 °C, and 600 °C) under dry conditions in synthetic air by using a DTA/TG-apparatus. BaCl₂, CaCl₂, and MgCl₂ did not react with chromium at any of the studied temperatures. ZnCl₂ evaporated already before the air was introduced. KCl, LiCl, NaCl, and PbCl₂ were all found to be reactive and to accelerate the oxidation of chromium. LiCl reacted only at 600 °C, whereas the other three chlorides mentioned above reacted from 500 °C upwards.     

氯化焙烧-水浸法从锂云母矿提锂(英文)

采用氯化焙烧-水浸法处理锂云母矿,并对氯化处理温度、时间、氯化剂的类型及用量进行研究。条件优化实验表明,在锂云母、氯化钠、氯化钠的质量比为 1:0.6:0.4,氯化处理温度为 880 °C,氯化处理时间为 30 min时,锂的提取率可达 92.86%,钾、铷、铯的提取率分别为 88.49%、93.60%和 93.01%,。采用 XRD 对锂云母原矿及焙烧后物料的物相进行分析。XRD 结果分析表明,当将锂云母和混合氯化剂一起焙烧(氯化钙及氯化钠)时,所得物相为 SiO2、CaF2、KCl、CaSiO3、CaAl2Si2O8、NaCl 和 NaAlSi3O8。     

Current efficiency in electro-winning of lanthanum and cerium metals from molten chloride electrolytes

The objective of this study is to prepare lanthanum and cerium metals by fused salt electrolysis of their anhydrous chloride in molten media such as LiCl-KCl, NaCl-KCl, KCl, NaCl, and LiCl and to characterize the metal deposit by X-ray diffraction, energy dispersive X-ray fluorescence, and inductive coupled plasma-atomic emission spectroscopy. Deposit metal of purity more than 99 % was obtained in each of the experiments. The entire process starting from preparation of anhydrous lanthanum/cerium chloride to electrolysis yielding of metal deposits has been described. The effect of process parameters such as temperature, electrolyte composition, and current density on the current efficiency was studied. All these parameters were varied to get the highest current efficiency and metal yield. The major non-rare earth impurities with the deposit are found to be Fe, Cr, and Ni along with ～1×10-3 of total gaseous impurities.     

Gypsum crystallization and potassium chloride regeneration by reaction of calcium chloride solution with potassium sulfate solution or solid

Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was added into the CaCl2 solution by slow titration or in multiple stages over 2-8 h followed by 2 h equilibration.In order to regenerate KCl solution as concentrated as possible,K2SO4 solid was added into the given CaCl2 solution instead of K2SO4 solution,obtaining gypsum crystals with almost the same quality by multistage addition with[SO4 2-]/[Ca 2+]molar ratio no larger than 0.8.However,impurity of K2SO4·CaSO4·H2O was detected by XRD and was further confirmed by SEM-EDS in the produced crystals when the[SO4 2-]/[Ca 2+] ratio increased to 1.1.It is proved that appearance of the double sulfate is attributed to the relatively high concentration of K2SO4.So,it is essential to properly control the[SO4 2-]/[Ca 2+]ratio and make sure[Ca 2+ ]in excess to suppress the solubility of CaSO4 even at the expense of low calcium removal rate.     

铁和钼在LiCl-KCl熔盐中的电化学行为

采用电化学方法研究了S2 -离子在Pt电极上的电极过程机理、铁和钼电极在Li2 S(sat) LiCl KCl和LiCl KCl两种熔融盐体系中的电化学行为 ,铁和钼电极的氧化起始电位差约为 0 .6V .探讨了FeS2 阴极的充电极限电位 ,控制FeS2 阴极的充电电位在钼的钝化区内 ,钼可以用作FeS2 阴极的集流体     

Direct synthesis of Nb–Al intermetallic nanoparticles by sodiothermic homogeneous reduction in molten salts

Nb–Al intermetallic nanoparticles were directly synthesized via sodiothermic reduction process in molten salts using NbCl₅ and AlCl₃ as the raw materials. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The NbCl₅ and AlCl₃ were dissolved in LiCl–KCl–CaCl₂ or LiCl–KCl–NaCl–CaCl₂ molten salts forming a homogeneous system. It was found that a series of intermetallic nanoparticles, such as Nb₃Al, Nb₂Al, NbAl₃ and Nb₂Al/NbAl₃, were successfully synthesized at low temperature of 350–500 °C using the homogeneous molten salt systems. The phase transformations of Nb₃Al, Nb₂Al and NbAl₃, were achieved via the controllable variation of molar ratio of Nb to Al. Furthermore, the influence of the reaction temperature on the particle size of the intermetallic nanoparticles was also investigated.     

Melting characteristics of magnesium—lithium alloys

Mg-Li-Al alloys containing 4–14 wt% Li and 1.5 wt% Al have been prepared by melting Mg/Mg-Al master alloy and Li separately under MgCl2 + KCl + MgO + CaF₂ and LiCl + LiF flux covers, respectively, and mixing the two together. The observed lithium loss and the pick-up of impurity elements in the melt have been correlated with various physico-chemical phenomena occurring during melting. The effect of holding time on melt composition was also examined. The results indicate that it is possible to control the alloy composition within specified limits by the selection of proper melting fluxes and crucible materials and by restricting the holding time to the minimum possible. These findings suggest that flux-cover melting is a viable route for the production of sound cast ingots of highly reactive magnesium—lithium alloys.     

Corrosion behavior of T24, T92, VM12, and AISI 304 steels exposed to KCl–NaCl–K2SO4–Na2SO4 salt mixtures

The corrosion mechanisms of T24, T92, VM12, and AISI 304 steels are studied under the influence of NaCl–KCl, NaCl–Na₂SO₄, and KCl–K₂SO₄ salt mixtures in a dry air atmosphere at 650°C for 15 days. NaCl–KCl was the most aggressive deposit and AISI 304 stainless steel exhibited the highest corrosion resistance. There was no relation between the Cr content of the ferritic steels and their corrosion resistance in NaCl–KCl. In contrast, the resistance of high-Cr steels was better when exposed to NaCl–Na₂SO₄ and KCl–K₂SO₄. The high-Cr and the low-Cr steels were more susceptible to NaCl–Na₂SO₄ and to KCl–K₂SO₄, respectively.     

Electrolytic Preparation of Mg-La Alloy in Chloride Molten Salt: Effect of Electrolyte Composition

在MgCl2-LaCl3-KCl熔盐体系中,系统研究了恒电位电解过程中,电解质组成对平均电解电流、电解效率和合金成分的影响。用XRD、SEM和EDS对Mg-La合金样品进行了表征。随着初始电解质中LaCl3浓度的增加,平均电解电流逐渐降低。这是由于与MgCl2相比,LaCl3较低的电导率引起的。当LaCl3在初始电解质中的浓度为15%~20%（质量分数）时,电流效率超过90%。合金组成可通过改变电解质组成来调节。     

高浓度氯离子溶液中Na2MoO4、NaNO2和BTA对铝合金缓蚀的AFM研究

应用原子力显微镜研究铝合金在含不同缓蚀剂的高浓度氯离子溶液中的腐蚀行为。结果表明：与不存在缓蚀剂的情况比较，加入0．20％的Na2MoO4可以对铝合金起到较好的缓蚀作用；在含有0．20％Na2MoO4的CaCl2溶液中加入0．20％BTA后，缓蚀效果下降，铝合金的点蚀现象有所加剧；虽然NaNO2单独使用能使铝合金表面形成致密的氧化膜，但其与BTA协同作用的效果并不理想，0．20％Na2MoO4和0．20％BTA的协同作用效果要优于0．15％NaNO2和0．20％BTA的协同作用效果。     

DETERMINATION OF PrCl_3-NaCl-LiCl PHASE DIAGRAM

PrCl_3-NaCl-LiCl phase diagram has been constructed from the phase diagrams of itssub-binary systems and of six quasi-binary systems measured by DTA technique.It is foundthat this ternary system is composed of five liquidus surfaces,seven second crystallizationlines,two peritectic points and one eutectie point.The temperatures and compositions ofinvariant points are as follows:P_1(416℃,30.3 mol% NaCl,44.2 mol% LiCl,25.5 mol%PrCl_3);P_2(409℃,25.0 mol% NaCl,50.0 mol% LiCl,25.0 mol% PrCl_3);E(404℃,20.0mol% NaCl,55.4 mol% LiCl,24.6 mol% PrCl_3).     

PHASE DIAGRAM OF SYSTEM NdCl_3-LiCl-KCl

The phase diagram of system NdCl_3-LiCl-KCl has been investigated by DTA.Six surfacescorresponding to the prhnary crystallization of NdCl_3,LiCl,KCl,γ-KCl·NdCl_3,β-3KCl·NdCl_3 and 2KCl·NdCl_3 respectively,eleven univariant lines related to the sec-ondary crystallization,two ternary eutectics E_1(70.5wt-% NdCl_3+8.0wt-% KCl,360℃)and E,(5.0wt-% NdCl_3+ 53.0wt-% KCl,355℃)and one ternary peritectic P(67.0wt-% NdCl_3+10.0wt-% KCl,375℃)were found.It is also chtrified that this studyon the system NdCl_3- KCl differs from previous work in the two transition temperatures:e_1(77.0 wt-% NdCl_3,484℃),e_2(40.0wt-% NdCl_3,620℃),p(70.0wt-%NdCl_3,610℃),3KCl·NdCl_3(690℃)and two reactions:α-3KGl·NdCl_3β-3KGl·NdCl_3 (355℃)β-SKGl·NdCl_3γ-3KCl·NdCl_3 (450℃)The eutectic point e_5(31.0wt-%LiCl,460C)is determined for the pseudobinary system3KCl·NdCl_3—LiCl.     

LIQUIDUS OF TERNARY SYSTEM LaCl_3-MgCl_2-LiCl

Two surfaces correponding to LaCl_3 and α-solid solution(MgCl_2.LiCl) respectively:and one secondary crystallization curve with a minimum M at 63.8 wt-％ LaCl_3,2.0 wt-％MgCl_2,34.2 wt-％ LiCl and 492℃ were fonud by means of DTA.In combination withliquidus determination.an approach was also made to the alteration in LnCl_3-MgCl_2-LiClsvstem,where Lu denotes La.Ce.Pr or Nd.     

Electrochemical behavior and electrolytic preparation of lead in eutectic NaCl−KCl melts

A novel molten salt extraction process consisting of chlorination roasting and molten salt electrolysis was proposed to develop a more efficient and environmental friendly technology for recovering lead from spent lead acid batteries (LABs). The feasibility of this process was firstly assessed based on thermodynamics fundamentals. The electrochemical behavior of Pb(II) on a tungsten electrode in the eutectic NaCl−KCl melts at 700 °C was then investigated in detail by transient electrochemical techniques. The results indicated that the reduction reaction of Pb(II) in NaCl−KCl melts was a one-step process exchanging two electrons, and it was determined to be a quasi-reversible diffusion-controlled process. Finally, potentiostatic electrolysis was carried out at −0.6 V (vs Ag/AgCl) in the NaCl−KCl−PbCl₂ melts, and the obtained cathodic product was identified as pure Pb by X-ray diffraction analysis. This investigation demonstrated that it is practically feasible to produce pure Pb metal by electrochemical reduction of PbCl₂ in eutectic NaCl−KCl melts, and has provided important fundamental for the further study on lead recovery from spent LABs via molten salt extraction process.     

Electrochemical reduction mechanism of Zn2+ in molten NaCl−KCl eutectic

A process comprising selective chlorination and molten salt electrolysis was proposed to develop an efficient and environmental-friendly technology for zinc recovery from metallurgical dusts. The theoretical feasibility of this technology was firstly estimated based on thermodynamic fundamentals. Subsequently, the electrochemical behavior of Zn²⁺ on tungsten electrode was investigated in molten NaCl?KCl eutectic at 973 K by many electrochemical transient methods. The results showed that the reduction of Zn²⁺ on tungsten electrode was found to be a one-step process exchanging two electrons with the initial reduction potential of ?0.74 V (vs Ag/AgCl), and the electrode process was considered as quasi-reversible and controlled by diffusion. The diffusion coefficient of Zn²⁺ ions in the melts was determined in the order of 10^?5 cm²/s. Finally, the electrolytic preparation of zinc was carried out by potentiostatic electrolysis in molten NaCl?KCl?ZnCl₂ eutectic at ?1.6 V (vs Ag/AgCl). Spheroidic granular metal with silver-white luster was attained after electrolysis for 9.5 h, and identified as pure Zn. The present study confirms that it is practically feasible to extract pure zinc metal by direct electrolysis of ZnCl₂ in molten NaCl?KCl eutectic, and provides a valuable theoretical reference for the efficient recovery of zinc from metallurgical dusts.     

Preparation of niobium nanoparticles by sodiothermic reduction of Nb2O5 in molten salts

Niobium nanoparticles with high purity were prepared by a sodiothermic reduction process using Nb2O5 as the raw material, LiCl, NaCl, KCl and CaCl2 as the diluents and sodium as the reducing reagent. The effects of the different molten salt systems, CaCl2 content, reaction time, excessive sodium and reaction temperature on the characteristics of the obtained niobium powder were discussed. The as-prepared niobium nanoparticles under the optimum experimental conditions were obtained by sodiothermic reduction ...     

Alkali Induced High Temperature Corrosion of Stainless Steel: The Influence of NaCl, KCl and CaCl2

The influence of KCl, NaCl and CaCl₂ on the oxidation of 304-type (Fe18Cr10Ni) stainless steel at 600?°C in 5?%O₂?+?40?%H₂O was investigated. Prior to exposure, a small amount of the preferred salt (cation equivalent: 1.35?μmol/cm²) was deposited on the samples. Exposure time was 1–168?h. The oxidized samples were analyzed by SEM/EDX, XRD, FIB and IC. The presence of KCl and NaCl strongly accelerates high temperature corrosion of 304L. Corrosion attack is initiated by the formation of alkali chromate through the reaction of alkali with the protective oxide. Chromate formation is a sink for chromium in the oxide and leads to a loss of its protective properties. Subsequently a rapidly growing scale forms, consisting of an outer hematite layer with chromate particles on top and an inner spinel oxide layer. In contrast to NaCl and KCl, CaCl₂ is not very corrosive. At temperature, CaCl₂ is rapidly converted to CaO. Small amounts of CaCrO₄ form where CaO is in direct contact with the scale. CaO also reacts with the scale to form Ca₂Fe₂O₅.