The evaporation of lanthanum hexaboride

Summary A mass spectrometric investigation of the evaporation of lanthanum hexaboride showed that the vapor effusing from a Knudsen cell consists chiefly of atomic lanthanum. The ion current ratio at 2100°K is 1 0.007. The heat of sublimation of LaB₆ at a mean test temperature of 2200°C, determined on the basis of the second law of thermodynamics, is estimated to be 536 ± 8.8 kJ/mole. The emission power of the tungsten cathode is found to increase as lanthanum is vapor-deposited on the latter.     

High-temperature oxidation of sintered lanthanum hexaboride

Conclusions The intense interaction between sintered LaB₆ with atmospheric oxygen starts, at temperatures close to 700°C, The mechanism of the process and composition of the interaction products change depending on temperature. Oxidation resistance of LaB₆ up to 1200°C is satisfactory. At higher temperatures, catastrophic oxidation of the material caused by active evaporation of boron oxide takes place.Translated from Poroshkovaya Metallurgiya, No. 11(299), pp. 56–59, November, 1987.     

分子光谱法测定镧的研究进展

对1990-2014年间分子光谱法测定镧的国内外研究进行了综述。具体内容包括:普通光度法、动力学光度法、荧光光度法、化学发光法和计算光度法。其中普通光度法是目前应用最为广泛的方法,偶氮胂和偶氮氯膦是最常用的显色剂,同时新显色剂如二溴氟基偶氮甲胂(5-MasA-DBF)等的研究也在不断增加。而动力学光度法和荧光光度法因其灵敏度高,相应体系也在逐渐增多。化学发光法具有线性范围宽的优点,相应研究也会不断增加。对每种分析方法从测定体系、测定条件、灵敏度以及实际应用等方面进行归纳和分析。     

Spectroscopic studies of gel-grown lanthanum malonate crystals

Lanthanum malonate crystals were grown by single tube ionic diffusion through silica gel. The crystallinity of the grown crystals was analyzed by powder X-ray diffraction studies. Fourier transform infrared spectroscopy (FTIR) and fourier transform (FT) Raman studies confirmed the presence of functional groups in the title compound. The optical band gap energy of the material was extracted from diffuse reflectance spectrum.     

Control effect of lanthanum against plant disease

Effect of La on emergence, growth and development of Isatis indigotica Fort. and Festuca arundinacea seedlings was researched by pot experiments of inoculating Rhizoctonia solani and with the mixture ofRhizoctonia solani and Fusarium solani in disinfected soil after the seeds were soaked in the solution with different concentrations of La^3＋. The results indicated that infection rate decreased and there were significant disease controlling effects on seed rot, bud rot and root rot caused by pathogenic fungi when the seeds were soaked by La^3＋. Thus, the rates of emergence of Isatis indigotica Fort. and turfgrass Festuca arundinacea were increased, When La^3＋ concentration was in a proper range, the growth and development of plant seed/ings were promoted. Spraying La on rice plants showed a significant controling effect on Rhizoctonia solani. Furthermore, the EC50 of La^3＋performed 128.7 and 128.1 mg/L at 1 and 7 d after spraying La in rice plants, respectively. The EC50 of La^3＋ performed in vivo （in rice plant） was lower than that in vitro （171.9 mg/L）.     

High-temperature evaporation of lanthanum and praseodymium silicides

Mass spectrometry is used to study the evaporation of silicides LaSi, LaSi₂, PrSi_1.8 and PrSi_1.8 at 1800–2000 K. Their standard enthalpies of atomization and formation are determined.