Persulfate Oxidation and Diphenylcarbazide Photometric Determination of Chromium in Super Alloys

The quantitative analysis of Cr in super alloys with the presence of a wide variety of elements, Al, B, C, Co, Cu, Hf, Fe, Mn, Mo, Ni, Nb, P, Si, S, Ti, Ta, W, Zr; and trace amounts (a few ppm) of Pb, Se, Bi, Tl and Te has been studied. Persulfate oxidation and diphenylcarbazide photometric method were studied with the purpose of developing a relatively fast and reliable measurement for Cr by wet chemical analysis. The results indicate that the latter is supperior to the former in practical view. In the photometric method, solid sample (0.1g alloys) when treated with HClO₄ and H₂SO₄ took ca. 72 hrs. for complete dissolution. When treated with HCl followed by HNO₃, 0.1 g alloys were completely dissolved within 1&1/2; hours. The best experimental conditions for diphenylcarbazide photometric determination of Cr was thus established. Photometric determination of Cr complexes was made at 540 nm.     

Enthalpies of mixing in the iron-manganese system by direct reaction calorimetry

Integral enthalpies of mixing of solid iron—manganese alloys have been obtained at 1443K, 1073K and 873K using a modified Dench-type calorimeter. The modifications in calorimetric technique required to cope with the high volatility of manganese are described. Results are presented and discussed.Dedicated to Prof. Dr.Kurt L. Komarek on the occasion of his 60th birthday on 23rd June 1986.     

Thermal behavior of the Cu-10 mass%Al AND Cu-10 mass%Al-4 mass%Ag alloys

The thermal behavior of the Cu-10 mass%Al and Cu-10 mass%Al-4 mass%Ag alloys was studied using classical differential thermal analysis (DTA), optical microscopy (OM) and X-ray diffractometry (XRD). The DTA curves were obtained for annealed and quenched samples. The results indicated that the presence of silver introduces new thermal events, associated to the formation of a silver-rich phase, to the shift of the equilibrium concentration to higher Al contents and to the decomposition of the silver-rich phase in the same temperature range of the b₁ phase decomposition. This revised version was published online in August 2006 with corrections to the Cover Date.     

示波滴定法测定铝合金中铜的含量

研究了铝合金中铜含量的示波滴定法。在酸性溶液中抗坏血酸将铜（Ⅱ）还原为铜（Ⅰ），用过量四苯硼钠沉淀铜（Ⅰ），过量的四苯硼钠用氯化四乙基铵标准溶液返滴定，以四苯硼钠切口消失为终点，计算出铜含量。方法终点变化敏锐，不外加指示剂，与标准分析方法相比较，操作简便、快速，所用分析试剂无毒，测定结果的RSD小于0．19％，标准加入回收率为98．7％～102．0％。     

甲烷在稀土助剂修饰的Ni/α-Al2O3催化剂上的解离

采用脉冲－色谱法，考察了甲烷在La2O3、CeO2修饰的Ni/α-Al2O3催化剂上的解离，并用TPR、XRD等方法对催化剂进行了表征。结果表明，添加La2O3，能促进甲烷的解离，并可使解离产生的碳保持较高的活性；CeO2的添加对甲烷的解离积炭有一定的抑制作用；La2O3和CeO2均能抑制镍晶粒的聚集。甲烷在Ni基催化剂上的解离，具有一定的结构敏感性。     

乙烷氧化脱氢制乙烯反应中制备方法及助剂对镍基催化剂性能的影响

采用不同方法制备了镍基催化剂,并考察了乙烷氧化脱氢制乙烯(ODE)的反应活性,结果表明,在3种不同制备方法的催化剂上,ODE反应的活性及产物选择性存在明显差异,浸渍法制备的催化剂性能最佳.在相同的条件下,以共浸渍法引入CeO2助剂后,N iO/-γA l2O3催化剂上的低温选择氧化活性显著提高,而目的产物C2H4的选择性变化不大.XRD,还原TG和XPS对催化剂进行表征的结果显示:反应的活性物相可能是易于还原的高度分散于催化剂表面的微晶N iO和表面尖晶石N iA l2O4物相;高分散的微晶N iO,类似于纯N iO,有利于ODE反应低温选择氧化生成目的产物C2H4,而易还原的表面尖晶石N iA l2O4物相的存在则可能是在高温下获得高选择氧化活性和选择性的主要原因之一.     

Curie temperature in Fe(Ni)Nb based mechanically alloyed materials

Summary A conventional thermogravimeter has been adapted with a small magnet to detect the Curie temperature, T_C. The measurements were performed in several Fe(Ni)NbB alloys developed in a nanocrystalline form by mechanical alloying. The B addition favors a slight diminution (10-20°C), and the Ni addition the existence of three transitions related with bccFe, fcc(Fe-Ni) abd fccNi-rich environments. Furthermore, complementary analysis were performed by means of differential thermal analysis, scanning electron microscopy with energy dispersive X-ray microanalysis and by induced coupled plasma. Small contamination was found. A mass increase (about 1 mass%) was detected by thermogravimetry related to oxidation. Analysis allows us to state the inhomogeneity of the alloys obtained after 80 h of milling.     

钨—镍—铁系重合金中粘结相的定量测定

通过对９３Ｗ－Ｎｉ－Ｆｅ－Ｃｏ（Ｍｎ）合金中粘结相和钨颗粒化学及电化学性质的研究，提出了一种定量提取Ｗ－Ｎｉ－Ｆｅ系重合金中粘结相的电解液，建立了定量测定其粘结相和钨颗粒组成及含量的方法。     

Heat capacity measurement of ZrOx and (Zr1−yNby)Ox from 325 TO 905 K

Heat capacities of zirconium-oxygen alloys, ZrO_x (x=0.17, 0.20, 0.28 and 0.31), and those of niobium doped alloys, (Zr_1–yNb_y)O_x (x=0.17 and 0.28, y=0.005 and 0.01), were measured from 325 to 905 K by an adiabatic scanning calorimeter. Two kinds of heat capacity anomalies were observed for all samples. The anomaly at higher temperatures was assigned to be due to an order-disorder rearrangement of oxygen atoms. Another anomaly at lower temperatures was due to a non-equilibrium phenomenon. The entropy change due to the order-disorder transition for Zr-O solid solution at higher temperature obtained from this experiment was compared with the theoretical value. The transition temperature, transition enthalpy and entropy changes due to the order-disorder transition decreased with increasing niobium contents, indicating that arrangement of oxygen atoms in lower temperature phase may be partially disordered by the interaction between niobium and oxygen atoms.

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Zusammenfassung Mittels eines adiabatischen Scanning-Kalorimeters wurden im Temperaturbereich 325–905 K die Wärmekapazitäten von Zirkonium-Sauerstoff Legierungen ZrO, (mit x=0.17, 0.20, 0.28 und 0.31) und von mit Niob versetzten Legierungen (Zr_1–yNb_y)O_x gemessen. Für alle Proben konnten zwei Arten von Wärmekapazitätsanomalien beobachtet werden. Die Anomalie bei höherer Temperatur wird einer Ordnung-Unordnung-Umwandlung von Sauerstoffatomen zugeschrieben. Eine andere Anomalie bei niedrigerer Temperatur steht mit einer Nicht-Gleichgewichtserscheinung in Zusammenhang. Die Entropieänderung der Ordnung-Unordnung-Umwandlung für einen Zr-O Mischkristall aus diesem Experiment wurde mit dem theoretischen Wert verglichen. Umwandlungstemperatur, Umwandlungsenthalpie- und Entropieänderungen der Ordnung-Unordnung-Umwandlung nehmen mit steigendem Niobgehalt ab, was zeigt, daß die Anordnung der Sauerstoffatome in Phasen mit niedrigerer Temperatur partiell durch die Wechselwirkungen zwischen Niob- und Sauerstoffatomen gestört werden kann.

     

Investigation of Nickel-Based Alloys Exposed to Supercritical Water Environments

Experimental tube reactors made of the nickel based alloys C-22 and Inconel 625 were exposed to supercritical water (SCW) environments. During this experiments, various inclusions and precipitates from a submicron size range to bulk scale-like layers were formed. The corrosion products and layers, located at the sub- and supercritical parts of the tubular flow reactors, were imaged and analyzed by field-emission scanning electron microscopy, combined with an energy-dispersive X-ray spectrometer (FESEM/EDX). The microanalysis was performed on metallographically prepared specimen. To obtain additional information regarding surface morphology, scanning force microscopy (SFM) and microhardness testing were applied at selected specimen.