铁磷和硼硅酸盐熔体对耐火材料的腐蚀性能

耐火材料的选择对放射性核废料的玻璃化过程是至关重要的,本文采用动态耐火材料腐蚀速度技术比较了铁磷模拟放射性核废料熔体和硼硅酸盐熔体DWPF的腐蚀性质,测量在1000至1300℃之间进行。在铁磷熔体中,致密氧化铝和氧化铬耐火材料有最低的熔线腐蚀速度,二氧化硅、锆英石和AZS耐火材料的腐蚀速度比较高。同时,氧化铝和氧化铬耐火材料在铁磷熔体中的腐蚀速度小于它们在硼硅酸盐熔体DWPF中的腐蚀速度。对氧化铬耐火材料来说,其在三种含有模拟HLW废料的铁磷熔体中的熔线腐蚀速度小于0.1mm/day。按照DWPF熔化器的设计标准,Alumina和Zircon商品耐火材料可以用来熔化多种HLW废料。     

铁磷和硼硅酸盐熔体对耐火材料的腐蚀性能

耐火材料的选择对放射性核废料的玻璃化过程是至关重要的 ,本文采用动态耐火材料腐蚀速度技术比较了铁磷模拟放射性核废料熔体和硼硅酸盐熔体DWPF的腐蚀性质 ,测量在10 0 0至 130 0℃之间进行。在铁磷熔体中 ,致密氧化铝和氧化铬耐火材料有最低的熔线腐蚀速度 ,二氧化硅、锆英石和AZS耐火材料的腐蚀速度比较高。同时 ,氧化铝和氧化铬耐火材料在铁磷熔体中的腐蚀速度小于它们在硼硅酸盐熔体DWPF中的腐蚀速度。对氧化铬耐火材料来说 ,其在三种含有模拟HLW废料的铁磷熔体中的熔线腐蚀速度小于 0 1mm day。按照DWPF熔化器的设计标准 ,Alumina和Zircon商品耐火材料可以用来熔化多种HLW废料。     

氘束轰击石墨化学腐蚀的实验进展

在ＳＭＦ－８００石墨第一壁化学腐蚀温度特性的实验研究基础上，进一步测试了Ｇ３石墨、ＳＭＦ－８００高纯石墨和硼化石墨，以及ＳｉＣ镀层等在１．３μＡ／３ｋｅＶ氘束轰击下化学腐蚀的温度特性。从中优选出Ｃ２Ｂ１０Ｈ１２氦辉光放电法制取的ＳＭＦ－８００石墨硼化层，它具有最佳的抗化学腐蚀性能。其ＣＤ４产额较ＳＭＦ－８００高纯石墨降低一个量级以上，ＣＤ４产额峰值温度下移至６５０Ｋ附近。用小角度转动样品法，初步地观察了氘束轰击下石墨释放ＣＤ４的角分布特性，为托卡马克偏滤器实验中建立ＣＤ４辐射区的定位及其控制等可行性进行了探索。     

AZ31镁合金在Hank’s模拟体液中的腐蚀行为研究

研究了AZ31镁合金在Hank's模拟体液中的腐蚀行为,包括腐蚀形貌、腐蚀速度和腐蚀电化学特征参数.通过扫描电子显微镜(SEM)比较了不同腐蚀环境中镁合金样品的腐蚀形貌特征.利用失重法测量了镁合金的腐蚀速度,并依此分析了Hank's模拟体液中各成分对镁合金腐蚀速度的影响.测量并分析了不同pH值下的动电位动态极化曲线.结果表明,镁合金在Hank's模拟体液中的腐蚀主要为氯离子引起的点蚀;H_2PO_4~-和HPO_4~(2-)具有缓蚀作用;pH值的升高可以提高镁合金腐蚀反应的自腐蚀电位,降低腐蚀反应的热力学倾向,稳定腐蚀过程中形成的钝化膜,从而降低了腐蚀速度.     

Mo-B耐熔锌侵蚀合金涂层在锌及其合金水平连铸中的应用

水平连铸工艺制取锌及其合金线坯的过程中,对熔体温度测控精度有较高要求,但是浸入熔体中的测温热电偶金属保护管,容易被熔锌及其合金侵蚀,造成熔体温度测控失效。本文采用在热电偶金属保护管表面热喷涂一层Mo-B合金层,同时涂衬一层非有机密封材料,试验表明,在热电偶金属保护管热喷涂一层0.1-0.2mm、且硼含量在10％左右的Mo-B合金喷涂层,能起到最佳的耐侵蚀性能,寿命最长可达1000h。     

射频热等离子体制备球形氧化铝粉末的数值模拟及实验研究

研究粉末颗粒在热等离子体(ICTP)中的行为可以为射频等离子体制备球形粉末工艺过程的优化提供参考。首先, 利用FLUENT软件对具有不同粒径分布的氧化铝粉末颗粒在射频热等离子体中的运动轨迹及加热历程进行了数值模拟; 然后, 根据模拟结果所确定的实验参数范围进行了射频热等离子体粉末球化实验, 并将实验测量与数值模拟的结果相结合, 研究了输入功率、送粉速率等参数的改变对具有不同粒径分布的氧化铝粉末球化效果的影响。研究结果表明: 粒径较小的氧化铝粉末颗粒在飞行过程中可以从等离子体内吸收更多的热量, 因此能够被充分加热至完全熔化; 增加系统输入功率、降低送粉速率均能提高单位质量的颗粒从等离子体中获得的能量, 从而在一定程度上提升氧化铝粉末的球化率。     

分子动力学模拟在冶金熔渣中的应用进展

冶金熔渣是由多种氧化物组成的熔体,常见的有硅酸盐熔渣和铝酸盐熔渣.冶金熔渣具有绝热保温、防止二次氧化、吸收钢液中夹杂物、去除钢液中有害元素等重要作用,制备性能优良的熔渣是实现冶金流程节能减排和绿色发展的重要保证,为此有必要系统地研究冶金熔渣的熔体结构和性质.目前,采用模拟实验直接研究高温熔渣熔体结构和性质的限制因素较多,分子动力学模拟可以弥补实验研究方面的不足.由于冶金熔渣种类繁多、复杂多变,如何在冶金熔渣的微观结构与宏观性质之间建立广泛的关联是当今国内外学者的研究重点.分子动力学模拟可以获得熔渣中不同粒子对的键长、键角、配位数等完整的熔体结构数据.基于此,研究者利用熔体结构的聚合度建立了多组元熔渣黏度与熔体结构单元的定量关系.此外,熔渣的电导率与熔体结构中离子的扩散能力有关,可以通过Nernst-Einstein关系式建立电导率和熔体结构之间的关系.本文综述了分子动力学模拟在冶金熔渣中应用的相关研究.首先,对分子动力学模拟在冶金熔渣中的模拟过程进行了介绍.然后,分别详述了分子动力学模拟技术在硅酸盐熔渣和铝酸盐熔渣中的应用现状.最后,总结了现有的问题,并对分子动力学模拟在冶金熔渣中的应用进行了展望.     

一种新型的骨组织工程用支架材料的制备与性能表征

以硼硅酸盐玻璃粉为原料,采用有机泡沫浸渍工艺,制备了高孔隙率的网眼多孔支架.应用XRD、SEM及ICP-AES等对硼酸盐生物玻璃粉末在生理模拟液中的降解性能、生物活性等进行了测试分析.结果表明,硼硅酸盐生物玻璃的降解性和生物活性与材料的组成配比有关,因此,可以通过调整玻璃的组成有效控制材料的降解性和表面形成的羟基磷灰石晶体的形态.硼硅酸盐生物活性玻璃作为硬组织工程支架材料的研究具有重要的意义和广泛的应用前景.     

采用无容器凝固技术研究过冷熔体热物理性质

深过冷是获得特殊性能亚稳材料的一种非常重要的手段,采用无容器凝固技术可以在较低的冷却速度下实现并保持较长时间熔体的深过冷,使过冷熔体热物理性质参数的测量成为可能.介绍了电磁悬浮、助熔剂处理等几种常用的无容器凝固技术,阐述了它们在测量过冷熔体比热容等热物理性质方面的应用,同时综述了过冷状态下熔体比热容等热物理性质的研究现状,并展望了今后的发展趋势.     

工艺参数对不锈钢表面激光熔覆Ni基涂层组织及耐腐蚀性能的影响

利用6kW横流CO2激光器在1Cr18Ni9Ti不锈钢表面进行了不同工艺参数下单道Ni25WC35合金粉末熔覆。分析了熔覆层的物相组成,研究了不同工艺参数对熔覆层耐腐蚀性能的影响。结果表明:熔覆层主要由(Fe,Ni)固溶体和WC原位自生成的W2C组成,同时含有CrNiFeC,Cu3.8Ni化合物和FeW3C,Ni2Si,Fe3Ni3B等硬质相。光学显微观察显示熔覆层组织均匀、致密,与基体结合良好。在5.0%NaCl饱和溶液中电化学腐蚀测量分析结果得出,随着激光功率的增加,熔覆层的耐腐蚀性能降低;随着扫描速率增加,耐腐蚀性能先增加,后降低。最高自腐蚀电位为-554.70mV,最低腐蚀电流密度为0.55μA.cm-2。综合得出,Р=3.0kW,ν=500mm.min-1的试样熔覆层耐腐蚀性能最好。     

Oxides reactions with a High-chrome sesquioxide refractory

In slagging coal-gasifier systems, the combination of oxides present as impurities in coal and combustion temperatures that can exceed 1650°C restrict the use of liner materials in the coal combustion chambers to refractories. In this study, the slag-refractory interactions of a new high chrome sesquioxide refractory was characterized. High-temperature cup tests showed that the molten oxides infused into the refractory and that the sesquioxide refractory reacts with the oxides in a manner similar to spinel phase refractories. Studies of the coal slag's individual oxide components showed CaO reacts with the chrome refractory to form a low melting Ca(CrO₂)₂. FeO reacts with the sesquioxide to form a interface layer of (Cr,Fe)₃O₄ spinel phase. Results of this study now make it possible to design studies for improving corrosion resistance to increase refractory life.     

温度对含模拟α-高放核废液的磷酸镁水泥固化体性能的影响

利用磷酸镁水泥(Magnesium potassium phosphate cement,MPC)对模拟α-高放核废液(HLW)进行固化,研究温度对固化体力学性能、物相组成、微观形貌及核素Cs~+浸出率的影响。BET、XRD、SEM及AAS等测试结果表明,室温下MgO、KH2PO4与高放核废液反应形成致密结构;随着温度的升高,固化体脱水,400℃时孔道结构增多,平均孔径增大,抗压强度降低,Cs~+浸出率增加;温度继续升高,磷酸镁水泥烧结陶瓷化,平均孔径逐渐减小,抗压强度增大;900℃时固化体表现出良好的陶瓷结构特征,晶粒完全熔融,晶粒间没有明显界线,Cs~+的28d浸出率为7.21×10~(-6) g/(cm~2·d)。不同温度下高放核废液的磷酸镁水泥固化体核素Cs~+的浸出率均能达到玻璃固化体的性能要求,表明磷酸镁水泥用于固化高放核废液具有明显优势。     

Ferrous-ferric equilibrium in BaO-B2O3 melts

The ferrous-ferric equilibrium in different BaO-B₂O₃ melts containing iron oxides have been studied as functions of temperature and total iron concentration. On equilibrating the melts at 1200° C with air, 3 to 6% of the total iron was reduced to the ferrous state. The equilibrium ferric/ferrous ratio in the melt decreased with increasing temperature and with decreasing BaO content of the melt. Total iron content (in the concentration range of 0.6 to 11.5 wt% Fe) had no significant effect on the equilibrium ferric/ferrous ratio of the melts.     

Phase equilibrium,microstructure and properties of some magnesite-chromite refractories

The effect of phase equilibrium and microstructure of magnesite-chromite batches containing from 0 to 100% Egyptian chrome ore, with intervals of 10%, on their physical properties was studied. The phase equilibrium data were calculated using the phase relationships within the system M-M₂S-CMS-MR (M=MgO, S=SiO₂, C=CaO, R=R₂O₃). A computerized electron-probe microanalyser was applied to study the microstructure as well as microchemistry of the fired magnesite-chromite co-clinkers. Some physical and technological properties of the co-clinkered briquettes were also investigated by determining densification parameters, spalling resistance and load-bearing capacity.It is concluded that dense, spalling resistant and refractory magnesite, magnesite-chrome and chrome-magnesite refractories could be produced by co-clinkering of magnesite-chromite batches of 1000, 7030 and 3070 weight ratios, respectively, at 1600 °C. The prepared co-clinkers were subsequently graded, moulded and refired up to 1700 °C in order to obtain direct-bonded bricks. Meanwhile, dense chromite refractories with lower refractory quality could be processed by firing the Egyptian chrome ore up to 1600 °C.     

Effects of Sr-modification and melt cleanliness on melt hydrogen absorption of 319 aluminium alloy

The effect of Sr-modification on hydrogen content of commercial 319 aluminium alloy melts has been quantified, by using HYSCAN instrument at 685°C and 735°C. In addition, the effect of melt cleanliness on the hydrogen content of the melt has been studied. It has been found that the melt cleanliness has a significant effect on the reduction of hydrogen content of the melt. The hydrogen contents of Sr-modified cleaned melts were significantly lower (30-45%) than uncleaned melts (melts containing surface oxide layers) at both temperatures. Sr-modification had no marked effect on the hydrogen content of the melt at both temperatures, when measurements were carried out in a cleaned melt. Hydrogen content of strontium modified, uncleaned melts has been increased, particularly at 685°C. In order to study the melt hydrogen absorption susceptibility in Sr-modified alloys, the formation of different hydrogen containing compounds such as hydrides and hydroxide of modifiers and other alloying elements in Al-Si melts has been evaluated thermodynamically. It has been found that there is no hydrogen containing compound, which can form in aluminium melts, and if these compounds are introduced into the melt they will dissociated to release hydrogen.     

含Zn-Al磷酸盐防腐蚀涂层的制备与腐蚀机理研究

为制备出具有更高耐蚀性、尤其是耐海洋气候腐蚀的Zn-Al基金属陶瓷涂层,以磷酸二氢铝作为粘结剂,氧化镁、氧化锌作为固化剂,锌、铝粉作为填料,聚四氟乙烯作为助剂,制备了一种含Zn-Al磷酸盐防腐蚀涂料,通过空气喷涂后热固化的方式在300M高强钢表面制备出含Zn-Al磷酸盐防腐蚀涂层,并对涂层进行了中性盐雾试验以及电化学试验,采用扫描电镜和能谱分析形貌及成分。结果表明:涂层中性盐雾腐蚀寿命达到1 000 h;涂层的自腐蚀电位低于基体,能为基体提供阴极保护;含Zn-Al磷酸盐防腐蚀涂层的腐蚀过程分为4个阶段,涂层的主要防护机制为金属粉的牺牲阳极作用和腐蚀产物的屏蔽效应。     

Use of Ionic Liquids as Innovative Solvents in Primary Aluminum Production

Today, the primary aluminum production is based on two processes: (a) the Bayer process and (b) the Hall–Heroult process. Both processes deal with several economic and environmental drawbacks. The production of aluminum is an energy intensive process, consuming 53–61 GJ/t of aluminum, while huge amount of red mud and gaseous emissions are inevitably produced through the whole process. The utilization of a new family of solvents called ionic liquids (ILs) in the primary aluminum production is the subject of this paper, which examines the possibility of dissolving metallurgical alumina, hydrated alumina, and bauxites in 1-ethyl-3-methyl-imidazolium hydrogen sulfate ([Emim]HSO₄). The results show that hydrated alumina can be dissolved relatively easily at 210°C, forming a melt that contains 9% w/w of dissolved alumina, which is higher than the alumina content in Hall–Heroult melts. Bauxites can also be directly dissolved in this IL with iron presenting higher dissolution than aluminum, while silicon dissolution is negligible.     

Production of materials with alumina and ashes from incineration of chromium tanned leather shavings: environmental and technical aspects

The leather tannery industry produces a significant amount of solid and hazardous wastes. Chromium-containing wastes like tanned shavings used to be incinerated in order to recover energy. The incineration process generates ashes that must be disposed of. This paper is a report on the results of the evaluation of technological properties and environmental compatibility of products made of alumina and ashes from incinerated chrome tanned shavings. The raw materials, tannery ashes and alumina were mixed together in different proportions. The ceramic bodies were molded using a hydraulic press and fired with a heating rate of 100 K/h until 1400 degrees C for 4 h in a muffle furnace. The ceramic specimens were characterized regarding physical, mechanical and thermal properties. Leaching tests, according to Brazilian, German and Dutch regulations, were performed on ceramic bodies containing different additions of ash. Results show that the ceramic materials produced are acceptable for refractory applications.     

The immobilization of high level radioactive wastes using ceramics and glasses

An overview is given of the immobilization of high level radioactive waste (HLW) and surplus materials from a variety of commercial and defence sources employing glass and ceramic hosts. A number of specific host materials are reviewed, including borosilicate and phosphate glasses, glass-ceramics and crystalline ceramics. Topics covered include wasteform processing and manufacture, in addition to wasteform stability, durability and mechanical behaviour. Although, at the present time, borosilicate glass is the generally accepted first generation wasteform for the immobilization of HLW, the emergence of new sources of radioactive materials requiring immobilization has renewed interest in many of the alternative candidates. These include, in particular, titanate, zirconate and phosphate based ceramics, together with iron phosphate based glasses and basaltic glass-ceramics. The relative merits and limitations of each host material are compared and discussed, with particular reference to processing considerations and to current and likely future requirements. This revised version was published online in November 2006 with corrections to the Cover Date.     

Application of grey relational analysis based on Taguchi method for optimizing machining parameters in hard turning of high chrome cast iron

High chrome white cast iron is particularly preferred in the production of machine parts requiring high wear resistance. Although the amount of chrome in these materials provides high wear and corrosion resistances, it makes their machinability difficult. This study presents an application of the grey relational analysis based on the Taguchi method in order to optimize chrome ratio, cutting speed, feed rate, and cutting depth for the resultant cutting force (F_R) and surface roughness (R_a) when hard turning high chrome cast iron with a cubic boron nitride (CBN) insert. The effect levels of machining parameters on F_R and R_a were examined by an analysis of variance (ANOVA). A grey relational grade (GRG) was calculated to simultaneously minimize F_R and R_a. The ANOVA results based on GRG indicated that the feed rate, followed by the cutting depth, was the main parameter and contributed to responses. Optimal levels of parameters were found when the chrome ratio, cutting speed, feed rate, and cutting depth were 12%, 100 m/min, 0.05 mm/r, and 0.1 mm, respectively, based on the multiresponse optimization results obtained by considering the maximum signal to noise (S/N) ratio of GRG. Confirmation results were verified by calculating the confidence level within the interval width.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0231-z