Preparation of Manganese Oxide and Its Adsorption Properties

The in-situ oxidation of manganese sulfate solution with H2O_(2),sodium hypochlorite,potassium permanganate and oxygen as oxidants was investigated by means of SEM,EDS,XRD,BET and infrared analysis,and the effects of different oxidants on the morphology,phase composition,surface properties and specific surface area of manganese oxides were investigated.The experimental results show that the diameter of manganese oxide particles prepared with H_(2)O_(2)is the smallest,about 50 nm,and the specific surface area is the largest,63.8764 m^(2)/g.It has the advantages of abundant surface hydroxyl groups,no introduction of other impurities and large adsorption potential.It is most suitable to be used as an oxidant for oxidizing manganese sulfate solution to prepare manganese oxide by in-situ oxidation.Nano manganese oxide prepard by H_(2)O_(2)in-situ oxidation method is used as adsorbent to adsorb cobalt and nickel impurities in manganese sulfate.When the reaction pH is 6,the reaction time is 30min and the amount of adsorbent is 1.0 g,the adsorption rates of cobalt and nickel impurities in 100ml manganese sulfate solution are 97.59%and 97.67%,respectively.The residual amounts of cobalt and nickel meet the industrial process standard of first-class products(Co,Ni w/%≤0.005)of high-purity manganese sulfate(Hg/t4823-2015)for batteries.The study plays a guiding role in the preparation and regulation of manganese oxide,and provides a new method with high efficiency,purity and adsorbent availability for the preparation of high-purity manganese sulfate solution.

Enhanced recovery of high-purity Fe powder from iron-rich electrolytic manganese residue by slurry electrolysis

Iron-rich electrolytic manganese residue(IREMR)is an industrial waste produced during the processing of electrolytic metal manganese,and it contains certain amounts of Fe and Mn resources and other heavy metals.In this study,the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR.The effects of IREMR and H2SO4 mass ratio,current density,reaction temper-ature,and electrolytic time on the leaching and current efficiencies of Fe were studied.According to the results,high-purity Fe powder can be recovered from the cathode plate,and the slurry electrolyte can be recycled.The leaching efficiency,current efficiency,and purity of Fe reached 92.58%,80.65%,and 98.72wt%,respectively,at a 1:2.5 mass ratio of H2SO4 and IREMR,reaction temperature of 60℃,electric current density of 30 mA/cm^(2),and reaction time of 8 h.In addition,vibrating sample magnetometer(VSM)analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m,which reached the advanced magnetic grade of electrical pure-iron powder(DT4A coercivity standard).The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.

Covalency competition induced selective bond breakage and surface reconstruction in manganese cobaltite towards enhanced electrochemical charge storage

Manganese cobaltite(MnCo_(2)_(4))is a promising electrode material because of its attractive redox chemistry and excellent charge storage capability.Our previous work demonstrated that the octahedrally-coordinated Mn are prone to react with the hydroxyl ions in alkaline electrolyte upon electrochemical cycling and separates on the surface of spinel to reconstruct into d-MnO_(2) nanosheets irreversibly,thus results in a change of the reaction mechanism with Kþion intercalation.However,the low capacity has greatly limited its practical application.Herein,we found that the tetrahedrally-coordinated Co_(2) þions were leached when MnCo_(2)_(4) was equilibrated in 1 mol L^(-1) HCl solution,leading to the formation of layered CoOOH on MnCo_(2)_(4) surface which is originated from the covalency competition induced selective breakage of the CoT–O bond in CoT–O–CoO and subsequent rearrangement of free Co_(6) octahedra.The as-formed CoOOH is stable upon cycling in alkaline electrolyte,exhibits conversion reaction mechanism with facile proton diffusion and is free of massive structural evolution,thus enables utilization of the bulk electrode material and realizes enhanced specific capacity as well as facilitated charge transfer and ion diffusion.In general,our work not only offers a feasible approach to deliberate modification of MnCo_(2)_(4)'s surface structure,but also provides an in-depth understanding of its charge storage mechanism,which enables rational design of the spinel oxides with promising charge storage properties.

Effect of manganese on the formation of hybrid zirconiumbased conversion coating on low carbon steel surface

This study revealed the effect of Mn on the formation of hybrid zirconium-based conversion coatings(HZCC)on low carbon steel.The XPS results indicated that the Mn compounds on the surface of low carbon steel were mainly MnO and Mn_(2)SiO_(4).Combined with the electrochemical measurements,the corrosion resistance of HZCC showed an increase followed by a decrease with increasing Mn concentration,which was related to the Mn_(2)SiO_(4) and SiO_(2) on the surface of low carbon steel.The excessive Mn concentration resulted in the loss of SiO_(2) and aggregation of Mn_(2)SiO_(4) on the low carbon steel surface,which caused the aggregation of Zr compounds on the surface and reduced the uniformity of the coating.Meanwhile,a moderate amount of Mn addition would be beneficial to increase the adhesion of organic coatings.

Mn掺杂Zigzag(8,0)型单壁碳纳米管吸附甲醛分子的密度泛函理论研究

甲醛是一种对人体健康造成巨大威胁的污染物。气态甲醛浓度的准确检测对大气空气治理评估和室内环境安全均有重要意义,而高效传感器的研发则是甲醛分子检测技术优化的关键。本研究通过基于第一性原理的DFT计算软件VASP,对甲醛分子在Mn掺杂Zigzag(8,0)型单臂碳纳米管上的吸附特性进行研究。结果表明:Mn掺杂Zigzag(8,0)型单臂碳纳米管是一种稳定的分子构型。区别于在原始CNT上的物理吸附过程,甲醛分子在Mn掺杂CNT上的吸附键长更短,吸附能更大,属于化学吸附过程。同时,甲醛分子在Mn掺杂CNT上的吸附过程还伴随着明显的电荷转移。吸附过程发生后,吸附样品的光吸收曲线在580~705 nm以及365~447 nm的范围内出现明显的蓝移,在307~360 nm的范围内出现了明显的红移。

Mn微合金化Al-Si-Cu-Mg合金显微组织及耐蚀性能研究

Al-Si-Cu-Mg系列合金具有优异的强韧性,但其中的含Cu强化相极大地影响了该系合金的耐蚀性能。因此,本文通过对不同Mn含量的Al-7Si-2Cu-0.6Mg合金进行显微组织观察和电化学分析,探究Mn元素的添加对T6热处理状态下合金微观结构和耐蚀性的影响。结果表明,Mn添加量的提高对合金显微硬度几乎没有影响,但在合金基体中可以观察到弥散相。随着Mn含量升高,合金的耐蚀性呈现先升高后降低的趋势。添加0.360%Mn(质量分数)合金具有最佳耐蚀性,腐蚀电流密度比基础合金减少了54%。腐蚀形貌观察结果表明,Mn的添加可以显著减弱合金的点蚀趋势。

Fe^(2+)/Mn^(2+)活化亚硫酸盐降解盐酸土霉素的机理研究

盐酸土霉素常被用于治疗畜禽疾病,但是它不能被畜禽完全代谢,残留的盐酸土霉素进入水体危害水环境的健康。铁锰作为常见的过渡金属,通常以二价态活化亚硫酸盐来降解有机污染物,反应条件温和、操作简单,但是单独的二价铁与二价锰氧化还原电势低,活化亚硫酸盐效果较差。本研究采用Fe^(2+)/Mn^(2+)共活化Na_(2)SO_(3)降解水中的盐酸土霉素,考察药剂用量、pH、溶解氧、氯离子、碳酸根及腐殖酸对Fe^(2+)/Mn^(2+)/Na_(2)SO_(3)体系降解盐酸土霉素的影响;通过焦磷酸盐实验、自由基淬灭实验和EPR实验分析Fe^(2+)/Mn^(2+)/Na_(2)SO_(3)体系中的活性物种;利用紫外可见光谱、傅里叶红外光谱、气相色谱-质谱联用仪识别盐酸土霉素的官能团及其降解中间产物的变化,推断盐酸土霉素的降解途径。结果表明:当Fe^(2+)/Mn^(2+)/Na_(2)SO_(3)浓度比为1∶4∶20(浓度分别为0.1、0.4和2 mmol/L)时,在反应45 min、pH为9.0条件下,盐酸土霉素的去除率和矿化率最高,分别达到94%和49%。随着溶解氧从9 mg/L下降至1.89 mg/L,盐酸土霉素去除率从94%下降至17%;氯离子、腐殖酸和碳酸根均对盐酸土霉素的降解产生抑制作用。Mn(Ⅲ)和SO_(4)·^(-)是降解盐酸土霉素的主要活性氧化剂,盐酸土霉素的降解经过电子转移、开环与酰基化等过程。

Mn/TiO_(2)低温SCR催化剂钾中毒机理研究

Mn/TiO_(2)具有良好的低温NH3选择性催化还原NOx(SCR)的活性。烟气中存在的碱金属会从物理和化学上毒害催化剂导致Mn/TiO_(2)催化剂中毒失活。论文以暴露{101}面TiO_(2)为载体制备Mn/TiO_(2)催化剂,采用浸渍法制备K中毒催化剂,研究了Mn/TiO_(2)低温SCR催化剂钾中毒机理。实验发现,Mn/TiO_(2)催化剂脱硝效率随K中毒浓度增加而减少;新鲜Mn/TiO_(2)催化剂表面NH3-SCR反应由E-R和L-H机理共同控制;K吸附会导致催化剂比表面积降低,催化剂表面Mn4+、化学吸附氧比例降低,表面酸性位点数量减少,导致脱硝活性降低;同时K更易吸附在Mn顶位以及桥接O位附近,导致NO的吸附活化受到严重遏制,同时削弱NH3的吸附,使得L-H机理受到阻断,只能以E-R机理控制为主。

小尺寸Mn^(4+) 掺杂氟化物制备方法的研究进展

Mn^(4+)掺杂氟化物荧光材料展现出众多优势,包括无毒、蓝光激发、超窄发射谱带、高发光效率、符合Rec.2020标准的发射波长、无重吸收以及优良的热稳定性。这些特点使其成为下一代Mini/Micro-LED显示技术的理想红光介质材料。然而,要应用于Mini/Micro-LED,需要小尺寸的氟化物。因此,本文从制备方法入手,深入探讨了国内外小尺寸Mn^(4+)掺杂氟化物的研究现状。在此基础上,总结并提出当前小尺寸Mn^(4+)掺杂氟化物面临的关键问题,旨在为研发高效优质的小尺寸Mn^(4+)掺杂氟化物提供参考。

Mn18Cr18N加压冶炼的氮含量精准控制工艺分析与实验

高氮不锈钢中氮含量的精准控制是生产关键控制要素。以Mn18Cr18N高氮钢为研究对象,利用冶金学原理、Factsage热力学软件及热态实验与检测分析等方法,对加压感应熔炼过程钢种成分、温度及氮气压力与氮含量控制的关系进行研究。结果表明,基于理论数据的“成分-温度-压力”关系方程可信度高,3炉实验的氮气压力理论值、预测值与实际控制值吻合度良好。热态实验验证发现,Mn和Cr含量不变时,依靠提高氮分压可以提高钢锭中N含量,但是w[N]达到约1%时,通过提高氮分压增加氮含量的效果降低。Mn或Cr含量低时,可以通过提高氮分压达到提高氮含量的目的。降低钢中C和Si含量有利于钢中高氮含量的合金化及稳定控制。当需要控制Mn18Cr19N钢中的w[N]≥0.8%时,宜控制加压炉熔炼温度在1500~1550℃,氮气压力在0.225~0.325 MPa。

Fe对Ni-Mn-Ga合金微丝形状记忆效应的影响

以Ni-Mn-Ga合金微丝为基础分析Fe元素掺杂前后对合金微丝的形状记忆效应的变化。用真空磁控钨极电弧熔炼炉制备Ni-Mn-Ga-Fe合金,并用高真空精密熔体抽拉设备将母合金制备成微丝。采用EDS能谱分析仪、DSC差示扫描量热分析仪、XRD、DMA动态机械分析仪,研究Fe元素掺杂Ni-Mn-Ga合金微丝后的物相、马氏体相变行为、微丝的形状记忆效应。结果表明,Ni-Mn-Ga-Fe合金微丝显示的是四方结构马氏体相和面心立方结构奥氏体相的混合相,对微丝采用步进式阶梯有序化热处理,有序化热处理能有效降低微丝内部缺陷,释放内应力,细化微丝内部晶粒,收缩晶格体积,马氏体孪晶界面更加平直,孪晶面更易移动,微丝的伸长率提高。在258 K下对制备态Ni-Mn-Ga-Fe合金微丝进行单程形状记忆的测试,拉伸到350 MPa后卸载到0 MPa,随后将微丝升温到奥氏体态后,应变恢复率为78.75%,而在289K对有序化热处理态Ni-Mn-Ga-Fe合金微丝进行单程形状记忆测试,应变恢复率达到100%。在126 MPa和240 MPa下分别对有序化热处理态三元Ni-Mn-Ga合金微丝和Ni-Mn-Ga-Fe合金微丝进行恒应力拉伸,两种微丝双程形状恢复能力均接近100%,但Ni-Mn-Ga-Fe合金微丝在发生形变时的弹性应变储能略高于Ni-Mn-Ga合金微丝。Fe的加入使得到的合金微丝的力学性能高于传统三元形状记忆合金微丝;制备态下和热处理态的Ni-Mn-Ga-Fe合金微丝的马氏体相变温度较Ni-Mn-Ga合金微丝分别提高6.0 K和11.5 K,热滞分别降低6.7 K和1.5 K。

Recent Advances on Challenges and Strategies of Manganese Dioxide Cathodes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries(AZIBs)are regarded as promising electrochemical energy storage devices owing to its low cost,intrinsic safety,abundant zinc reserves,and ideal specific capacity.Compared with other cathode materials,manganese dioxide with high voltage,environmental protection,and high theoretical specific capacity receives considerable attention.However,the problems of structural instability,manganese dissolution,and poor electrical conductivity make the exploration of high-performance manganese dioxide still a great challenge and impede its practical applications.Besides,zinc storage mechanisms involved are complex and somewhat controversial.To address these issues,tremendous efforts,such as surface engineering,heteroatoms doping,defect engineering,electrolyte modification,and some advanced characterization technologies,have been devoted to improving its electrochemical performance and illustrating zinc storage mechanism.In this review,we particularly focus on the classification of manganese dioxide based on crystal structures,zinc ions storage mechanisms,the existing challenges,and corresponding optimization strategies as well as structure-performance relationship.In the final section,the application perspectives of manganese oxide cathode materials in AZIBs are prospected.

Upcycling of spent LiCoO_(2) cathodes via nickel- and manganese-doping

Direct recycling has been regarded as one of the most promising approaches to dealing with the increasing amount of spent lithium‐ion batteries(LIBs).However,the current direct recycling method remains insufficient to regenerate outdated cathodes to meet current industry needs as it only aims at recovering the structure and composition of degraded cathodes.Herein,a nickel(Ni)and manganese(Mn)co‐doping strategy has been adopted to enhance LiCoO_(2)(LCO)cathode for next‐generation high‐performance LIBs through a conventional hydrothermal treatment combined with short annealing approach.Unlike direct recycling methods that make no changes to the chemical composition of cathodes,the unique upcycling process fabricates a series of cathodes doped with different contents of Ni and Mn.The regenerated LCO cathode with 5%doping delivers excellent electrochemical performance with a discharge capacity of 160.23 mAh g^(−1) at 1.0 C and capacity retention of 91.2%after 100 cycles,considerably surpassing those of the pristine one(124.05 mAh g^(−1) and 89.05%).All results indicate the feasibility of such Ni–Mn co‐doping‐enabled upcycling on regenerating LCO cathodes.

Fe-Mn/TiO_(2)的制备及其催化臭氧氧化双酚A的性能研究

采用浸渍法制备Fe-Mn/TiO_(2)双金属催化材料,以双酚A(BPA)为目标降解物,探究了Fe-Mn/TiO_(2)对其的降解效果及降解机制。结果表明,Fe-Mn/TiO_(2)催化臭氧氧化降解BPA的去除率相较于单独TiO_(2)处理提升了83.4%;Fe、Mn成功负载且催化剂孔洞较丰富;相较于TiO_(2),Fe-Mn/TiO_(2)中锐钛矿质量分数增加能产生更多的羟基自由基。同时,Fe、Mn在TiO_(2)表面能发生价态转化,可作为活性位点促进臭氧分解为·OH等活性物质,增强催化反应活性。

Treatment of mine water high in Fe and Mn by modified manganese sand

The iron and manganese absorption properties of several filter media were studied. Four plain filter media and six surface-modified media were examined. The surface modification was performed using potassium permanganate as a surface treatment. The surface-modified manganese sand was found to be most efficient at removing iron and manganese from water. The metal concentrations in filtered effluent were between 0.01 and 0.04 mg/L, which is far lower than the standard for recycle water. A concen-tration of 5% KMnO4 was found to be most effective as surface modifier. The surface of the manganese sand modified by 5% KMnO4 was examined and found to be covered with a dense membrane of some compound. The membrane had the advantages of uniform texture, large surface area and physical and chemical stability. It was effective at removing iron and manganese from mine water.

Mn/Fe比对Al-Mg-Si合金组织和性能的影响

以Al-Mg-Si合金为研究对象,采用金属型铸造研究Mn/Fe比对其组织和性能的影响。结果表明:Al-Mg-Si铸态合金组织中枝晶间存在α-Al基体和大量析出相,主要以Mg_(2)Si相为主,还存在少量的共晶Si相、AlFeSi相和Al(FeMn)Si相。随Mn/Fe比的增大,合金中的晶粒逐渐变得细小圆整,且由树枝晶向等轴晶发生转变。Mn可以促进铝合金中针状的β-AlFeSi相向骨骼状、颗粒状或块状的α-Al(FeMn)Si相的转变。当Mn/Fe比为0.5时,合金的热导率达到最大值181.08 W·m^(-1)·K^(-1)。当Mn/Fe比为1.0时,合金的晶粒尺寸最小且具有最佳的力学性能,抗拉强度、伸长率和硬度相较于Mn/Fe为0.2时分别提升17.45%、49.57%和27.48%,达到167.35 MPa、17.23%、HV 62.86。

孔隙和α-Al(Fe/Mn)Si相对高压压铸Al-7Si-0.2Mg合金塑性的影响

采用高压压铸工艺制备两批次不同尺寸的Al-7Si-0.2Mg(质量分数,%)合金,获得显微组织和孔隙非均匀分布的薄壁铸件,并对比研究孔隙和显微组织对铸态合金塑性的影响。结果表明:不同铸件和不同位置样品的伸长率有较大波动(9.7%~17.9%)。当合金存在大面积孔隙时,有效承载面积减小导致由孔隙产生的应力集中使合金伸长率显著降低。当合金只存在小面积孔隙时,塑性变形过程中合金中的α-Al(Fe/Mn)Si相先于共晶硅相发生脆性断裂,α-Al(Fe/Mn)Si相的数量密度对伸长率的波动起主导作用,具有高数量密度α-Al(Fe/Mn)Si相试样的伸长率显著降低。此外,局部较高的冷却速率导致铸件α-Al(Fe/Mn)Si相数量密度的增加。

Mechanism of Capacity Fading Caused by Mn(Ⅱ)Deposition on Anodes for Spinel Lithium Manganese Oxide Cell

The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn（Ⅱ） ions in the anode are reduced to the metallic manganese that helps for catalyzing electrolyte decomposition.This could poison and damage the solid electrolyte interface（SEI） film,leading to the the capacity fade in Li-ion batteries.We propose a new mechanism that Mn（Ⅱ） deposites at the anode hinders and/or blocks the intercalation/de-intercalation of lithium ions,which leads to the capacity fade in Li-ion batteries.Based on the new mechanism assumption,a kind of new structure with core-shell characteristic is designed to inhabit manganese ion dissolution,thus improving electrochemical cycle performance of the cell.By the way,this mechanism hypothesis is also supported by the results of these experiments.The LiMn2-xTixO4 shell layer enhances cathode resistance to corrosion attack and effectively suppresses dissolution of Mn,then improves battery cycle performance with LiMn_2O_4 cathode,even at high rate and elevated temperature.

Mn含量对Inconel718板材焊接接头组织性能的影响

采用w[Mn]<0.01%、0.24%、0.34%三种不同合金的固溶态Inconel718热轧板材进行直流脉冲电弧焊接,经双级热时效处理后进行室温拉伸实验,研究Mn含量的变化对焊接接头微观组织及时效态力学性能影响规律。结果表明,三种不同Mn含量焊接接头组织中只存在Laves相,没有δ相析出,随着w[Mn]由<0.01%提高至0.34%,焊接接头中Laves相析出体积分数略有增多。经过双级热时效处理后,γ’’开始析出,焊接接头组织中Laves相含量略有减少。与时效态母材拉伸性能相比,焊接接头拉伸强度和伸长率有所降低。且随着Mn含量的增加,时效态焊接接头拉伸性能略有降低,抗拉强度由1250 MPa小幅降低至1178 MPa和1213 MPa,三种不同Mn含量的焊接接头时效态拉伸样品断裂位置皆为焊缝区域,且均为韧性断裂。

Cobalt and manganese stress in the microalga Pavlova viridis (Prymnesiophyceae):Effects on lipid peroxidation and antioxidant enzymes

Pollution of marine environment has become an issue of major concern in recent years. Serious environmental pollution by heavy metals results from their increasing utilization in industrial processes and because most heavy metals are transported into the marine environment and accumulated without decomposition. The aim of the present study is to investigate the effects on growth, pigments, lipid peroxidation, and some antioxidant enzyme activities of marine microalga Pavlova viridis, in response to elevated concentrations of cobalt （Co） and manganese （Mn）, especially with regard to the involvement of antioxidative defences against heavy metal-induced oxidative stress. In response to Co^2＋, lipid peroxidation was enhanced compared to the control, as an indication of the oxidative damage caused by metal concentration assayed in the microalgal cells but not Mn^2＋. Exposure of Pavlova viridis to the two metals caused changes in enzyme activities in a different manner, depending on the metal assayed： after Co^2＋ treatments, total superoxide dismutase （SOD） activity was irregular, although it was not significantly affected by Mn^2＋ exposure. Co^2＋ and Mn^2＋ stimulated the activities of catalase （CAT） and glutathione （GSH）, whereas, glutathione peroxidase （GPX） showed a remarkable increase in activity in response to Co^2＋ treatments and decreased gradually with Mn^2＋ concentration, up to 50 μmol/L, and then rose very rapidly, reaching to about 38.98% at 200 μmol/L Mn^2＋. These results suggest that an activation of some antioxidant enzymes was enhanced, to counteract the oxidative stress induced by the two metals at higher concentration.