Variation of the porous structure and leakage currents of anodes of niobium condensers in electrolytic oxidation

Conclusions Shaping of the anodes results in a large reduction of the total volume and dimensions of the pores. The magnitude of this reduction is determined unambiguously by the dispersion of the initial powder and oxidation voltage. Shaping results in the formation of a certain number of closed pores.Formation of closed porosity is accompanied by a large reduction of the leakage currents. This is explained by a reduction of the number of impurity atoms concentrated mainly on the surface of sintered anodes. Therefore, the high-dispersion powders which contain, per unit mass, approximately the same amount of impurities as the standard powders can be used to produce anodes with permissible leakage currents at low sintering temperatures.Translated from Poroshkovaya Metallurgiya, No. 3(339), pp. 56–59, March, 1991.     

The effect of quality of anodes on the process of electrolytic of manganese dioxide

During the electrosynthesis of manganese dioxide, the anode material and anode current density (i _a) exert the largest influence on the characteristics of electrolysis and the quality of the obtained material. The activation of anodes, which consists of the deposition of the titanium-manganese alloy on the titanium base of the electrode by the thermal-diffusion method, prevents passivation at i _a = 100 and 200 A/m². The electrochemical characteristics of electrolysis for NTMA (a built-up titanium-manganese activated anode) and ATDP (an experimental activated anode with thermodiffusion coating) anodes at i _a = 100 and 200 A/m² have close values. The voltage across the bath does not exceed 2.2–3.0 V, the current efficiency is 95–98%, and electrical power consumption is 1.33–1.80 (kW h)/kg. The chemical composition and the crystalline modification of electrical manganese dioxide corresponds to the requirements of GOST (State Standard) 25823-83. The activated ATDP anodes behave similarly to the known HTMA anodes. After electrolysis, no variations in the surface layer are found on them.     

削减电解金属锰工艺废水的生产实践

结合生产实际,分析了电解金属锰废水产生量大的原因。介绍了采用电解金属锰工艺废水全过程控制技术对金旭冶化有限责任公司5 000 t/a电解金属锰生产线进行的改造。生产实践表明:通过改造,电解液和钝化液挟带量削减65%,废水水量削减80%,通过离子交换几乎全部回收废水中的Mn²⁺、Cr（Ⅵ）,将其回用到生产工艺中,有效解决目前电解金属锰废水处理中存在的铬渣二次污染问题。     

Relationship between the specific charge of nobium anodes and parameters of their porous structure

Conclusions The specific surface of the anodes after shaping is determined unambiguously by the total volume of the pores and their mean size.The experiments confirm the direct proportional relationship in the specific surface of the pores of the high-porosity niobium anodes and their specific charge. A model of the porous structure of the anodes was proposed. At the given porosity of the sintered anodes, the model can be used to calculate the dependence of the specific surface of the pores after shaping on their radius prior to shaping at different oxidation voltages, and estimate the optimum size of the pores prior t shaping and the maximum specific surface after shaping. The validity of the model was confirmed by means of experiments.Translated from Poroshkovaya Metallurgiya, No. 5(341), pp. 61–64, May, 1991.     

An investigation of the effect of the electrolyte composition on the consumption of fired anodes during electrolytic aluminum production

The effect of adding CaF₂, AlF₃, and KF into electrolyte on the consumption of fired anode during aluminum electrolysis is investigated. The CaF₂ content varied from 5 to 10 wt % in the electrolyte of the industrial composition. Correspondingly, the concentration of AlF₃ and KF varied from 4 to 10 and from 0 to 4.7 wt % in the modified electrolytes. Based on the procedure used, the total consumption of carbon and the amount of carbon transported into the gas phase (m _g) and foam (m _f) were determined. Electrolysis duration was 12 h, the distance between the poles was 40 mm, the temperature was 960°C, and the current density was 0.85 and 1.2 A/cm². It is established that adding CaF₂ and AlF₃ increases the consumption of anode, while adding KF decreases it. For CaF₂, ?m _f/?[CaF₂] is larger than ?m _g/?[CaF₂], 15.4 and 6.6 kg/(t_Al wt %) CaF₂, respectively. For AlF₃, ?m _f/?[AlF₃] is also larger than ?m _g/?[AlF₃] and equals 6.8 and 4.2 kg/(t_Al wt %) AlF₃. For KF, ?m _f/?[KF] is smaller than ?m _g/?[KF], being ?11.3 and ?8.1 kg/(t_Al wt %) KF.     

The radiographic and imaging characteristics of porous tantalum implants within the human cervical spine

STUDY DESIGN: Seven cadaveric cervical spines were implanted with a porous tantalum spacer and a titanium alloy spacer, and their radiographic and imaging characteristics were evaluated. OBJECTIVE: To determine the radiographic characteristics of porous tantalum and titanium implants used as spacers in the cervical spine. SUMMARY OF BACKGROUND DATA: Anterior decompressive surgery of the disc space or the vertebral body creates a defect that frequently is repaired with autologous bone grafts to promote spinal fusion. Donor site morbidity, insufficient donor material, and additional surgical time have spurred the development of biomaterials to replace or supplement existing spinal reconstruction techniques. Although the promotion of a solid bony fusion is critical, the implanted biomaterial should be compatible with modern imaging techniques, should allow visualization of the spinal canal and neural foramina, and should permit radiographic assessment of bony ingrowth. METHODS: Cadaveric spines containing the implants were imaged with plain radiography, computerized tomography, and magnetic resonance imaging. The image distortion produced by the implants was determined qualitatively and quantitatively. RESULTS: The tantalum and titanium spacers were opaque on plain radiographic films. On computed tomographic scans, more streak artifact was associated with the tantalum implants than with the titanium. On magnetic resonance imaging, the porous tantalum implant demonstrated less artifact than did the titanium spacer on T1- and T2-weighted spin echo and on T2*-weighted gradient-echo magnetic resonance images. Overall, the tantalum implant produced less artifact on magnetic resonance imaging than did the titanium spacer and therefore allowed for better visualization of the surrounding bony and neural structures. CONCLUSION: The material properties of titanium and porous tantalum cervical interbody implants contribute to their differential appearance in different imaging methods. The titanium implant appears to image best with computed tomography, whereas the porous tantalum implant produces less artifact than does the titanium implant on several magnetic resonance imaging sequences.