Electrodeposition of Zn–Mn alloys in acidic and alkaline baths. Influence of additives on the morphological and structural properties

Electrodeposition of Zn–Mn alloys on steel was achieved using alkaline pyrophosphate-based baths or acidic chloride-based baths. Cyclic voltammetry was used to determine the potential ranges where the various redox processes were taking place. It appeared that the reduction of Mn(II) was generally hidden by the other reduction reactions, especially by the hydrogen evolution reaction. Zn–Mn alloys containing up to 25 at.% Mn in the alkaline bath and 12 at.% in the acidic bath could be obtained at the cost of very low current efficiencies. The characterisation of the deposits obtained either by galvanostatic polarisation or potentiostatic polarisation was performed by Scanning Electron Microscopy and X-Ray Diffraction. Various Zn–Mn phases were obtained, depending on the current densities, the composition of the deposit and that of the electrolytic bath. Two commercial additives usually used for zinc electrodeposition, one in alkaline baths, the other in acidic baths, were tested. Their effects upon the composition, the morphology and the microstructure of the deposit were investigated.     

碳含量及水韧处理温度对Mn13Mo1钢机械性能的影响

通过拉伸实验、冲击实验及断口观察试验,研究了碳含量、水韧处理温度对Mn13Mo1钢机械性能的影响。结果表明:Mn13Mo1钢经1080～1100℃水韧处理后,强度和塑性有最佳配合,并且随碳含量的增加,强度、塑性都明显提高。碳含量对冲击韧性影响小,但冲击韧性随水韧处理温度的提高而增大。总之,为获得较理想的机械性能,Mn13Mo1钢应选较高的含碳量,同时水韧处理温度应选在1080～1100℃范围内。     

催化分光光度法测定润滑油中的痕量锰

在pH值9.8的Clark-Lubs缓冲溶液中,Mn(Ⅱ)能催化过氧化氢氧化钙红(CR)而褪色,本文进一步考查了该法的测定条件,并详尽地研究了干扰离子的分离条件,在此基础上。用该法测定了使用前、后润滑油中的痕量锰。该法的表现摩尔吸收系数为12×10~7L·mol~(-1)·cm~(-1),最低检测限为2.6ng/25mL。     

Mn-P共掺杂氮化碳的制备及其光催化性能研究

采用四水氯化锰、磷酸氢二铵和三聚氰胺为原料制备了Mn-P共掺杂的石墨相氮化碳(g-C3 N4).使用X射线衍射光谱(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、光致荧光光谱(PL)、紫外-可见漫反射光谱(UV-Vis DRS)、电化学阻抗谱(EIS)、瞬态光电流响应等分析测试手段对制备的催化剂...     

电解锰压滤渣高温脱硫研究

采用直接煅烧法、还原法及添加脱硫剂煅烧法对电解锰压滤渣进行了高温脱硫,研究了不同方法得到的脱硫产物的物相、残硫量和活性,并比较了几种方法的工业适用性。结果表明:直接煅烧法的脱硫渣和坩埚粘连严重,实际操作困难;加入煤粉并没有改善脱硫渣和坩埚的粘连问题,且脱硫渣中残硫量高;石灰石虽能减弱脱硫渣和坩埚的粘连,但由于生成惰性物质石英,降低了脱硫渣的活性;采用铝矾土作为脱硫剂进行脱硫,脱硫渣的残硫量低,脱硫渣和坩埚不粘连,脱硫渣活性高。铝矾土添加量为42%(质量分数),脱硫温度为1 250 ℃,脱硫保温时间为5 min时,脱硫渣中硫含量为0.089 4%(质量分数),达到脱硫要求。     

Enhanced Mn2+ solidification and NH4+-N removal from electrolytic manganese metal residue via surfactants

Electrolytic manganese metal residue (EMMR) harmless treatment has always lacked a low-cost and quick processing technology. In this study, surfactants, namely tetradecyl trimethylammonium chloride (TTC), sodium dodecyl benzene sulfonate (SDBS), sodium lignin sulfonate (SLS), and octadecyl trimethylammonium chloride (OTC), were used in the solidification of Mn²⁺ and removal of NH₄⁺-N from EMMR. The Mn²⁺ and NH₄⁺-N concentrations under different reaction conditions, Mn²⁺ solidification and NH₄⁺-N removal mechanisms, and leaching behavior were studied. The results revealed that the surfactants could enhance the Mn²⁺ solidification and NH₄⁺-N removal from EMMR, and the order of enhancement was as follows: TTC > SDBS > OTC > SLS. The NH₄⁺-N and Mn²⁺ concentrations were 12.3 and 0.05 mg·L^-1 with the use of 60.0 mg·kg^-1 TTC under optimum conditions (solid–liquid ratio of 1.5:1, EMMR to BRM mass ratio of 100:8, temperature of 20 ℃, and reaction duration of 12 h), which met the integrated wastewater discharge standard (GB8978-1996). Mn²⁺ was mainly solidified as Mn(OH)₂, MnOOH and MnSiO₃, and NH₄⁺-N in EMMR was mostly removed in the form of ammonia. The results of this study could provide a new idea for cost-effective EMMR harmless treatment.     

锰渣与再生砖骨料制备免烧砖的性能及应用

锰渣与再生砖骨料均属于大宗固废,提升大宗固废利用率具有重要的环境效益和经济效益。本文利用锰渣、再生砖骨料等制备了免烧砖,探究了锰渣掺量对免烧砖各项性能的影响,且对其微观结构及有害物质浸出行为进行了分析。结果表明:制备的免烧砖外观质量优良,色泽均一,尺寸标准;结合强度要求和抗冻性要求,锰渣掺量不超过10%(质量分数)时,可制备出强度、耐水性和耐久性优异的MU20免烧砖,锰渣掺量不超过15%时,可制备出性能优异的MU15免烧砖;掺适量锰渣的免烧砖中形成了较多的钙矾石相,有利于强度发展。锰渣和再生砖骨料制备的免烧砖可以应用于人行道等市政工程,应用效果良好。研究结果可为锰渣低碳资源化利用以及生态砖制品的生产和应用提供技术支持。     

氨缓冲体系强化高纯重质碳酸锰的制备

以碳酸钠和高纯硫酸锰为原料,通过共沉淀法在氨缓冲溶液中制备高纯重质碳酸锰。当硫酸锰和碳酸钠溶液浓度都为1.5 mol·L^-1、碳酸钠过量系数为110%、溶液pH为8.5、温度为50℃、滴加速率为120 ml·h^-1时,得到的碳酸锰视密度达1.67 g·cm^-3,振实密度达2.15 g·cm^-3。氨缓冲体系增加了溶液的稳定性,抑制了溶液中氢氧化锰和偏氢氧化锰的生成,制备出的高密度碳酸锰形貌趋于球形,粒径分布均匀,D₅₀平均大小为30.32 μm。以本研究制备的碳酸锰为锰原料焙烧得到的四氧化三锰松装密度为1.09 g·cm^-3,振实密度为2.18 g·cm^-3,锰的含量可达71.85%。     

Magnetodielectric coupling in barium titanate–cobalt ferrite composites obtained via thermally-assisted high-energy ball milling

In this work, a magnetodielectric coupling observed in barium titanate–cobalt ferrite composites synthesized using high-energy ball milling assisted via a thermal treatment is discussed. Vibrating sample magnetometry and dielectric spectroscopy showed that multiferroic composites possess both ferromagnetic and dielectric behaviors inherited from the parent ferromagnetic cobalt ferrite and ferroelectric barium titanate phases. The magnetocapacitance (up to 35%) recorded for x = 0.3, (1-x)BaTiO₃–xCoFe₂O₄, can be attributed to the spin-dependent filtering mechanism. The composite with the aforementioned composition exhibited a homogeneous matrix–particle composite microstructure, which was achieved via high-energy ball milling during the mixing stage.     

A-site Ca/Sr co-doping to optimize room-temperature TCR of La0.7Ca0.3-xSrxMnO3 films

Based on the analysis of crystal structure, Mn³⁺/Mn⁴⁺ pairs, distortion of MnO₆ octahedron, and electrical transport properties of La_1-xCa_xMnO₃ and La_1-xSr_xMnO₃ materials, room-temperature coefficient of resistivity (TCR) of La_0.7Ca_0.3-xSr_xMnO₃ (LCSMO) films was optimized by Ca/Sr co-doping at the A-site. LCSMO films are successfully fabricated on LaAlO₃ (100) substrates via facile spin coating technology. The microstructure of LCSMO films is characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy and X-ray photoemission spectroscopy. Results reveal that A-site Ca/Sr co-doping significantly influenced crystal structure, formation of Mn³⁺/Mn⁴⁺ pairs, and distortion of MnO₆ octahedron. The correlation between microstructure and electrical transport properties was explained through the phenomenological percolation model, double-exchange mechanism and Jahn-Teller effect. Furthermore, the TCR reached 10.2% K^-1 at 296.1 K in La_0.7Ca_0.18Sr_0.12MnO₃ films.