Phase Transformation of Calcium Phosphates by Electrodeposition and Heat Treatment

The effect of heat treatment on the calcium phosphate deposited on Ti-6Al-4V substrate using an electrolytic process is investigated. The calcium phosphate was deposited in a 0.04 M Ca(H₂PO₄)₂·H₂O (MCPM) solution on a Ti-6Al-4V substrate at 333 K (60 °C), 10 V, and 80 Torr for 1 hour, and calcined at various temperatures for 4 hours. The X-ray diffraction (XRD) results demonstrate that the phases are dicalcium phosphate (CaHPO₄, DCPD) and hydroxyapatile [Ca(PO₄)₆ (OH)₂, HAP] for the as-deposited samples. When the deposited sample was calcined at 873 K (600 °C) for 4 hours, the XRD results show that the transformation of DCPD to HAP occurs. Moreover, HAP converts to β-TCP, CPP, and CaO. For the sample calcined at 1073 K (800 °C) for 4 hours, the scanning electron microscopy (SEM) micrograph reveals that the crack of the calcined sample propagates with a width of about 3 μm. This result is due to HAP becoming decomposed and converting to β-TCP, CPP, CaO, and H₂O. The vaporization of H₂O within the calcined sample promotes the crack propagation and growth.     

Measurements of Vapor Pressures of Sc,La, and Ce by Multi-Knudsen Cell Mass Spectrometry

The vapor pressures of Sc, La, and Ce were determined by multi-Knudsen cell mass spectrometry with ionized cross sections as described in the literature. The vapor pressure of Sc at temperatures from 1373 K to 1573 K was measured using Cu as a reference material, and those of La and Ce from 1473 K to 1573 K were measured using Y as a reference material. From the measured vapor pressures, the Gibbs energy of formation of each gaseous element was derived.     

Thermodynamic Stabilities of Lanthanum Tungstates Using a Calcium Fluoride Solid Electrolyte Galvanic Cell

Abstract

A knowledge of the thermodynamic stabilities of the lanthanum tungstates measured as the Gibbs energies of formation from the free oxides is important as lanthanum is used as a powerful desulphurizing agent and tungsten as a special alloying element in the production of clean steels and special steels. These data will also be useful as the system La₂O₃ WO₃ can be a model since it exhibits many compounds between the end members. Excepting one EMF work, no information is available in the literature on the thermodynamics of this system. This system exhibits the compounds 5 La₂O₃·22 WO₃, La₂ O₃ · 3 WO₃, La₂O · 2 WO₃, 7 La₂O₃ · 8 WO₃,La₂O · WO₃, 3 La₂O₃ · 2 WO₃ and 5 La₂O₃ · 2 WO₃. The compounds were prepared from reagent grade free oxides by solid state sintering at high temperature followed by X-ray diffraction. The standard Gibbs energies of formation of the compounds from the free oxides were determined by operating the following galvanic cells with calcium fluoride as solid electrolyte.

O₂(g), Pt/ La₂O₃ · LaOF// CaF₂/ / 5 La₂O₃ · 22 WO₃, WO₃, LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂//5 La₂O₃ · 22 WO₃, La₂O₃ · 3 WO₃, LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂// La₂O₃ · 3 WO₃, La₂O₃ · 2 WO₃ LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂// La₂O₃ · 2 WO₃, 7 La₂O₃ · 8 WO₃, LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂//La₂O₃ · WO₃, 3La₂O₃ · 2 WO₃ LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂//3 La₂O₃ · 2 WO₃, 5La₂O₃ · 2 WO₃ LaOF/Pt, O₂(g)

O₂(g), Pt/ La₂O₃ LaOF// CaF₂/ / 3 La₂O₃2 WO₃, La₂O₃, 2 WO₃ LaOF/Pt, O₂(g)

Stable, reproducible EMFs were obtained in the temperature range 1123 to 1273 K. The net cell reactions are respectively as follows:

5 La₂O₃ + 22 WO₃ = 5 La₂O₃ · 22 WO₃

7 La₂O₃ + 3 (5 La₂O₃ · 22 WO₃) = 22 (La₂O₃ · 3 WO₃)

La₂O₃ + 2 (La₂O₃ · 3 WO₃) = 3 (La₂O₃ · 2 WO₃)

3 La₂O₃ + 4 (La₂O₃) = 7 La₂O₃ · 8 WO₃

La₂O₃ + 7 La₂O₃ · 8 WO₃ = 8 (La₂O₃ · WO₃)

La₂O₃ + 2 (La₂O₃ · WO₃) = 3 La₂O₃ · 2 WO₃

2 La₂O₃ + 3 La₂O₃ · 2 WO₃ = 5 La₂O₃ · 2 WO₃

The standard Gibbs energies of formation of the different lanthanum tungstates are then calculated by appropriately combining from the above cell reactions and their Gibbs energy changes obtained from the experimental EMF data. The present data are discussed in the light of EMF data reported in the literature for WO₃-rich compounds in the system.     

ICP-MS法测定钢铁中痕量镁和钙含量

建立了电感耦合等离子体质谱法测定钢铁中痕量镁和钙元素含量的分析方法。在优化的仪器工作条件下,采用内标法与加入校正法相结合,在补偿基体效应的同时．提高了测定结果的稳定性。该方法加标回收率为90．0％～110．0％,相对标准偏差小于10．0％．该方法准确、快速,满足冶金行业对钢铁中痕量镁和钙元素的测试需要。     

X射线荧光光谱法分析硅钙复合脱氧剂中的硅、钙含量

采用X射线荧光光谱仪分析硅钙复合脱氧剂的硅、钙,以高炉渣、硅石、石灰石标样混合制备的标准样品作为校准样品,进行工作曲线的绘制,曲线适应硅钙复合脱氧剂的硅、钙的含量范围。灼烧后的样品用四硼酸锂做熔剂,高温熔融制样,消除粒度效应。将该方法与化学法进行对照,硅、钙的分析结果准确度能够满足要求,且快速、简便。     

ICP-MS法测定八氧化三铀中钼的测量结果的不确定度评定

介绍了ICP—MS法测定八氧化三铀中钼质量分数的测量不确定度的影响因素。对各不确定度分量进行了分析和计算。八氧化三铀中钼质量分数为29．1μg／g时,测量结果的扩展不确定度为4．2μg／g。     

“钠钙双碱法”脱硫技术探析

石油焦在煅烧过程中有少量硫分燃烧生成二氧化硫,直接排空会对环境造成污染.经过对国内炭素行业脱硫现状的调查研究,结合回转窑生产工艺和设备情况,对3种脱硫技术进行了分析,对＂钠钙双碱法＂脱硫技术的优势及工艺进行了论述.     

Thermodynamic Measurement of Di-calcium Phosphate

The thermodynamic properties of the CaO-P₂O₅ system are important to develop an effective refining process in the iron and steel industry. In this study, the thermodynamic properties of (CaO)₂P₂O₅ were investigated because the properties are necessary to develop a new dephosphorization process. The vapor of gaseous phosphorus and phosphorus oxide in equilibrium with a mixture of (CaO)₂P₂O₅ and (CaO)₃P₂O₅ at 1373 K to 1498 K (1100 °C to 1225 °C) were detected directly as an ion current by double Knudsen cell mass spectrometry. Comparing the ion currents with those from a mixture of Al₂O₃P₂O₅ and Al₂O₃, which is used as a reference mixture in this study, the Gibbs energy change of the following reaction was calculated:

Thermodynamic investigation of the A2/B2 region of the Fe-Al system by Knudsen effusion mass spectrometry

The vaporization of Fe-Al alloys has been investigated in the temperature range of 1140 to 1600 K by Knudsen effusion mass spectrometry. Eleven different compositions were examined in the composition range between 30 and 51 at. pct Al, mostly in the B2 region of the phase diagram. The partial pressures and thermodynamic activities of both Fe and Al were evaluated: directly from the measured ion intensities for a component in both the alloy and the pure element, I _M ⁺ /I _M ⁺⁰ , and also from the ion-intensity ratios of the alloy components, I _Al ⁺ /I _Fe ⁺ , by means of a Gibbs-Duhem integration. Reliable partial and integral molar enthalpies and entropies of mixing have been obtained by mass spectrometry for this system for the first time. Nearly temperature-independent integral enthalpies and entropies of mixing over the wide temperature range investigated were found, with the mixing entropies being large and negative.     

钢液钙处理的热力学分析

通过热力学计算分析了铝镇静钢钙处理时Fe-Al-Ca-O-S系中的各种平衡曲线。分析了1873K时在各种平衡态下的Al—O、Ca-Al、S-Al、S-Ca平衡曲线,并分析了在不同平衡状态下温度对平衡曲线的影响。得出了为避免生成固态铝酸钙、CaS理论上应满足的条件。     

X射线荧光光谱法测定石灰石中CaO不确定度评定

采用X射线荧光光谱法测定石灰石中Ca O含量,应用统计学理论对其测量结果的不确定度来源进行分析,并对各不确定度分量进行评定,计算合成标准不确定度和扩展不确定度,完成不确定度报告,为提高检测工作的科学性和准确性提供了保证。     

电感耦合等离子质谱法测定钽粉中杂质

采用电感耦合等离子质谱法测定钽粉中的杂质,对仪器的工作条件、样品制备、样品分析模式、基体浓度、精密度、回收率等进行了较为系统的研究.结果表明,该检测方法准确可靠、精密度高,钽粉中各杂质元素的相对标准偏差为1.64％～15.99％,加标回收率为92％～128％,可满足钽粉的分析要求.     

Extraction of Actinides by Trialkyl Phosphates

Abstract

Tri-n-Butyl Phosphate has been found to be an extractant-par-excellence for nuclear fuel reprocessing. It has a unique combination of physical and chemical proerties and is commercially available at relatively low cost. However, the other homologues of TBP-with branched alkyl chains as well as linear alkyl chains-do possess advantages for specific applications that merit attention. Thus, a relative comparison of the extraction properties of the trialkyl phosphates is rewarding, both from a fundamental as well as technological point of view. The present review attempts to survey the data reported and the understanding generated on the extraction of actinides by trialkyl phosphates, with an emphasis on the elements U, Th and Pu, taking into account their importance derived from their primary role in the nuclear fuel cycles. While reviewing the data, emphasis is placed on data measured for extraction by 1.09 M solution of the extrac-tant, from nitric acid medium.     

电感耦合等离子体质谱法测定稀土研究进展

电感耦合等离子体质谱法(ICP-MS)具有检测限低,干扰少等优点,在痕量稀土的测定中应用越来越广。综合介绍了近年来各种环境水质、食品、动植物组织、土壤及地质样品、高纯稀土产品中痕量稀土的ICP-MS法测定最新研究进展。     

Compositions of Co – Cr – Mo Alloys Examined by Glow-Discharge Mass Spectrometry

A method has been developed for the quantitative elemental analysis of Co – Cr – Mo alloys which are used for making surgical implants, and which is done by glow-discharge mass spectrometry. There is a discussion of the effects of molecular ions and an estimate is made of the sensitivity limits in the detection of traces of toxic elements. A method has been devised for calculating the concentrations of molecular ions that increases the analysis reliability. It is shown that raising the argon pressure and discharge current substantially reduces the relative concentrations of molecular ions and allows one to raise the analysis sensitivity.     

原子吸收分光光度法测定铁矿中氧化钙、氧化镁

提出了一个用火焰原子吸收分光光度法测定铁矿中氧化钙、氧化镁的方法。研究讨论了酸度、干扰离子、工作条件等因素的影响。分析中。以HNO3—HF—HCLO4混合酸分解样品。以SrCL2作为钙、镁的释放剂,用工作曲线法测定。方法简便、快速、准确。应用于铁矿样品的测定,结果令人满意。     

原子吸收光谱法测定锡精矿中的氧化钙及氧化镁

建立了火焰原子吸收光谱法测定锡精矿中CaO及MgO量的方法。所建立的方法CaO及MgO的特征浓度分别为0．087μg／mL,0．0034μg／mL;检出限分别为0．022μg／mL,0．0028μg／mL;标准曲线的线性相关系数均大于0．999;测定范围分别为0．050％-7．50％,0．010％-2．00％;对11个代表样及2个标样进行考察,精密度分别为0．7％-11．1％,2．5％～10．5％;样品加标回收率分别为91．5％～102．7％,98．6％～102．7％。     

火焰原子吸收光谱法测定高纯稀土氧化物中钙

以盐酸溶解试样,建立了火焰原子吸收光谱法测定高纯稀土氧化物中钙的分析方法.在大量稀土基体中测定微量钙,干扰复杂.实验采用标准加入法消除基体效应,测定了酸度对钙的影响.结果表明,酸度对测定有影响.同时采用正交试验设计对仪器的工作条件进行了优选.在优化的工作条件下,该方法简便、快速,钙的回收率在98.0%～102.0%.     

共沉淀法制备锰锌软磁铁氧体前躯体共沉过程中钙、镁深度脱除的热力学分析

通过对Fe(Ⅱ)-Mn(Ⅱ)-Zn(Ⅱ)-Ca(Ⅱ)-Mg(Ⅱ)-NH3-NH4HCO3-H2O体系的热力学分析,得到各金属离子浓度与pH的关系,从而确定共沉法制备锰锌软磁铁氧体前躯体共沉过程中钙、镁深度脱除的共沉区域。热力学分析结果表明,溶液中钙、镁的含量随着体系pH的增大而降低,在相同条件下镁的溶解度大于钙的溶解度。为减少进入共沉粉中的钙、镁含量,需要保证在铁、锰、锌共沉完全的基础上降低体系的pH。当溶液中[C]T=0．1mol／L,[N]T=1．0mol／L时,pH控制在6．23～6．50之间可以大大降低进入共沉粉中的钙、镁含量。确定共沉过程钙,镁深度脱除的共沉区域,对于生产高纯锰锌软磁铁氧体前躯体具有重要的指导意义。