Effect of carbon on the microstructure, mechanical properties and metal ion release of Ni-free Co-Cr-Mo alloys containing nitrogen.

This paper investigated the effect of carbon addition on the microstructure and tensile properties of Ni-free biomedical Co-29Cr-6Mo (mass%) alloys containing 0.2 mass% nitrogen. The release of metal ions by the alloys was preliminarily evaluated in an aqueous solution of 0.6% sodium chloride (NaCl) and 1% lactic acid, after which samples with different carbon contents were subjected to hot rolling. All specimens were found to primarily consist of a γ-phase matrix due to nitrogen doping, with only the volume fraction of M23C6 increasing with carbon concentration. Owing to the very fine size of these carbide particles (less than 1 µm), which results from fragmentation during hot rolling, the increased formation of M23C6 increased the 0.2% proof stress, but reduced the elongation-to-failure. Carbon addition also increased the amount of Co and Cr released during static immersion; Co and Cr concentrations at the surfaces, which increased with increasing the bulk carbon concentrations, possibly enhanced the metal ion release. However, only a very small change in the Mo concentration was noticed in the solution. Therefore, it is not necessarily considered a suitable means of improving the strength of biomedical Co-Cr-Mo alloys, even though it has only to date been used in this alloy system. The results of this study revealed the limitations of the carbon strengthening and can aid in the design of biomedical Co-Cr-Mo-based alloys that exhibit the high durability needed for their practical application.

Comparative measurement of gas temperature in a graphite atomizer by a two-line method of iron and nickel spectral lines in graphite furnace atomic absorption spectrometry.

The gas temperature of atomospheric gas in a graphite atomizer was measured during an atomization stage in graphite furnace atomic absorption spectrometry (GF-AAS), by using a two-line method under the assumption of Boltzmann distribution. Iron and nickel were chosen as the probe elements to compare the gas temperatures obtained with different pairs of spectral lines. The atomic absorptions of two iron atomic lines and those of two nickel atomic lines were simultaneously monitored to obtain their absorbances for the temperature determination. Their gas temperatures were lower than the wall temperature which was monitored by the conventional temperature control for GF-AAS. Furthermore, the temporal variations at the atomizing stage were different between the iron lines and the nickel lines: the maximum peak of the nickel gas temperature appeared to be more delayed and broadly than that of the iron gas temperature. This result could be attributed to the fact that nickel species began to be atomized a little behind iron species, probably because it was more difficult to reduce nickel oxide with graphite carbon than an iron oxide when these oxide species would be formed at the charring stage. A graphite furnace varies the temperature during the atomizing-duration time and also the distribution becomes inhomogeneous at different portions; therefore, the gas temperature would provide overall information along the optical path of incident radiation, when the probe elements diffuse in the furnace. The two-line method enables variations not only in the gas temperature but in the atomizing of probe elements to be directly determined, due to the ability of remote sensing and rapid response.

Role of a binary metallic modifier in the determination of cadmium in graphite furnace atomic absorption spectrometry.

In order to discuss the matrix modifier effect of palladium, iron, and a mixture of palladium and iron for the determination of cadmium in graphite-furnace atomic absorption spectrometry (GF-AAS), we measured the absorption profiles of a cadmium line at various compositions of these elements. Variations in the gas temperature were also estimated with the progress of atomization, by using a two-line method under the assumption of a Boltzmann distribution. The atomic absorption of cadmium appeared on the way of heating from the charring temperature to the atomizing temperature while the gas temperature was still low; it was thus considered that cadmium was atomized through direct conductive heating from the wall of the graphite furnace. Therefore, the effectiveness of modifiers for cadmium would be determined through any reactions on the furnace wall at the programmed charring and atomizing temperatures. The addition of iron, palladium, and an iron-palladium mixture all enhanced the absorption signal of cadmium compared to a pure cadmium sample; however, their effects were different from one another. Each addition of iron or palladium to the sample solution led to an enhancement of the cadmium absorbance, indicating that iron or palladium individually became an effective matrix modifier for the determination of cadmium. However, the addition of palladium was ineffective for the matrix modification in the coexistence of large amounts of iron. Although these phenomena are very complicated, and thus cannot be understood completely, any metallurgical reaction between the constituent elements during heating of the furnace wall, such as the formation of solid solutions and intermetallic compounds, would cause the effect of a matrix modifier in GF-AAS.

Temporal variation in gas temperature at the atomization stage in several types of graphite furnaces for atomic absorption spectrometry.

In order to compare and evaluate the atomization process occurring in several types of graphite furnaces for atomic absorption spectrometry, the authors estimated temporal variations in the gas temperature by using a two-line method under the assumption of a Bolzmann distribution. The atomization furnaces employed were a graphite tube, a graphite tube coated with pyrolitic carbon, a graphite tube with a platform and a graphite cup. Differences in the temporal variation in the gas temperature among these graphite furnaces were observed.

Temporal variations in gas temperature in an atomization stage of cadmium and tellurium evaluated by using the two-line method in graphite furnace atomic absorption spectrometry.

In order to discuss the atomization process of an analyte element occurring in a graphite furnace for atomic absorption spectrometry, we measured variations in the characteristic temperature with the progress of an atomization stage, by using a two-line method under the assumption of a Boltzmann distribution. For this purpose, iron was chosen as the analyte element. Also, the atomic absorption of two iron atomic lines, Fe I 372.0 nm and Fe I 373.7 nm, was simultaneously monitored as a probe for the temperature determination. This method enables variations in the gas temperature to be directly traced, yielding a temperature distribution closely related to the diffusion behavior of the probe element in the furnace. This temperature variation was very different from the furnace wall temperatures, which were monitored in conventional temperature control for atomic absorption spectrometry. Correlations between the gas temperature and the charring/atomizing temperatures in the heating program of the furnace were investigated. The atomization of cadmium and tellurium was also investigated by a comparison between the gas temperature with the wall temperature of the furnace. The atomic absorption of cadmium or tellurium appeared to be apart from the absorption of iron while the gas temperature was still low. Therefore, the analyte atoms could be atomized through direct contact with the wall of the graphite furnace, which has a much higher temperature compared to the gas atmosphere during atomization. Their atomization would be caused by conductive heating from the furnace wall rather than by radiant heating in the furnace.

Investigation for analytical procedure for determination of trace metallic ions in simulated body fluids by inductively coupled plasma atomic emission spectrometry (ICP-AES).

Influences of matrix elements and high viscosity in three kind of simulated body fluids (SBFs) on determination of trace metallic elements (Co, Cr, Ni, Al and V) by inductively coupled plasma atomic emission spectrometry (ICP-AES) were investigated. In addition, decreases of these effects were attempted by H(2)SO(4) fume treatment. Calibration lines of the elements were constructed by the standard solutions made of elemental solutions and HCl or the SBFs. Gradients of calibration lines constructed by the each standard solution were different. Therefore, for accurate determination, calibration curve must be constructed by the elemental standard solution and the analytical solution. Limit of detection (LOD) of each element in the solutions was measured by a blank test. Although LODs of microg [Symbol: see text] L(-1) (ppb) order were nominal instrumental data, because of influences of the matrix elements and the high viscosity, the measured LODs of the elements in the SBFs were higher than those. However, the LODs were lowered by employing the H(2)SO(4)-fume treatment and approached to the nominal instrumental data. Therefore, H(2)SO(4)-fume treatment is extremely effective treatment in order to reduce the influences.