Comparative study on the hydrogen storage performance of as-milled MgRENi rapid quenched alloy catalyzed by metal sulfides

The composites of Mg_(20)Pr_(1)Sm_(3)Y_(1)Ni_(10)as-quenched alloy and 3 wt.%M(M=CoS,CoS_(2),MoS_(2))catalyst were prepared by high-speed vibration ball mill.The effects of metal sulfides on the hydrogenation and dehydrogenation dynamics of alloys were compared.The results show that the as-milled composites contain a large number of amorphous embedded by a small amount of nanocrystals,and there are many point defects.After ball milling,the crystal grain size in the composites containing CoS is relatively larger,followed by CoS_(2)and MoS_(2)again.After hydrogenation,the amorphous phase is crystallized to form Mg_(2)NiH_(4),YH_(3),Pr_(8)H_(18.96),Sm_(3)H_7,Mg,Co or Mo phases,however,Mg_(2)Ni,YH_(2),PrH_(2)and Ni_(3)Y phases appeared after dehydrogenation.The maximum hydrogenation capacity of the composites containing CoS,CoS_(2)and MoS_(2)are 3.939,4.265 and 4.507 wt.%,respectively.The hydrogenation saturation ratio of composite containing MoS_(2)is higher than that of the composites containing CoS and CoS_(2).The dehydrogenation activation energy of the composites containing CoS,CoS_(2)and MoS_(2)is 107.76,68.43 and 63.28 kJ.mol^(-1).H_(2).On the improvement of hydrogen storage performance of Mg_(20)Pr_(1)Sm_(3)Y_(1)Ni_(10)alloy,the catalytic effect of MoS_(2)sulfide is better than that of CoS_(2)sulfide,and which is better than CoS sulfide.

EVOLUTION OF SULFIDE SCALES ON Fe-Mo ALLOYS DURING SULFIDATION

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Effect of Microstructure and Sulfide on Corrosion of Cu-Ni Alloys in Seawater

The microstructure and the corrosion product films have been investigated on Cu-Ni alloys by TEM, SEM, AES and electrochemical technique as well as natural seawater exposure tests. Experimental results showed that the alloys had two kinds of microstructure, i.e. recrystallizatjon and incomplete recrystallization. In synthetic seawater containing 2x10^-6 S^2-, the stability of the alloy increased with the increase of deformation and annealing temperature, i.e., the degree of recrystallization. After exposure to natural seawater for different periods of time, the corrosion product films of the recrystallized alloy were rich in Ni and compact, and there were cracks in the outer layer which contained a small amount of S; the films of the alloy of incomplete recrystallization became thick, loose and porous, and obviously of layered structure, and the intergranular corrosion took place in the underlying substrate Besides, a great amount of seawater substance existed in the outer layer and some sulfur was found within the grain boundaries that prefer to corrode. The accelerating effect of sulfides in corrosion of Cu-Ni alloys in seawater is attributed to the coexistence and absorption of sulfides and carbides promoting the preference of corrosion where they absorb, and the formation of dissolvable Cu2S results in keeping the surface of the alloys in the active state.

GEOCHEMICAL CHARACTERISTICS OF PLATINUM GROUP ELEMENTS IN JINCHUAN SUPER-LARGE SULFIDE COPPER-NICKEL DEPOSIT, JINCHANG CITY, GANSU PROVINCE, CHINA

The platinum-group element geochemistry of rocks and ores from Jinchuan super-large copper-nickel sulfide deposit is systemically studied in this paper. The Cu/Pd mean ratio of Jinchuan intrusion is lower than that of original mantle magma, which indicates that these ultrabasic rocks were crystallized from magma that lost Pd in the form of melting segregation of sulfides. The PGE of the rocks show trend of partial melting, similar to that of mantle peridotite, which shows that magma formation occurs during rock-forming and ore-forming processes. The chondrite normalized PGE patterns of the rocks and ores are well related to each other, which signifies the signatures of multi-episode magmatic intrusion, melting and differentiation in the formation processes of rocks and ores. In addition, analyses about the relation between PGE and S, and study on Re-Os isotopes indicate that few contamination of the crustal substances occurred during the magmatic intrusion and the formation of deposit. However, contamination by crustal substances helps to supply part of the S for the enrichment of PGE. Meanwhile, the hydrothermal process is also advantageous for the enrichment of PGE, especially lbr Pt and Pd, due to deep melting segregation. The characteristic parameters （such as Pt/（Pt＋Pd）, （Pt＋Pd）/（Ru＋Ir＋Os）, Pd/Ir, Cu/（Ni＋Cu）, and so on.） for platinum-group elements for Jinchuan sulfide copper-nickel deposit show the same features as those for sulfide copper-nickel deposit related to basic magma, which also illustrates its original magma property representative of Mg-high tholeiite. Therefore, it is the marie （not ultramafic） magma that resulted in the formation of the superlarge sulfide copper-nickel deposit enriched in Cu and PGE. To sum up, the geochemical characteristics of platinum-group elements in rocks and ores from Jinchuan copper-nickel sulfide deposit are constrained by the continental rift tectonic environment, the parent magma features, the enriched mantel magma source, the complex metallogenesis and PGE geochemical signatures, and this would be rather significant for the study about the genetic mechanism of copper-nickel sulfide deposits.

Processing Map of C71500 Copper-nickel Alloy and Application in Production Practice

The isothermal compression tests of C71500 copper-nickel alloy at different temperatures (1 073-1 273 K) and strain rates (0.01-10 s^-1) were carried out on Gleeble-3500 thermo-mechanical simulator.The real stress-strain data were obtained.On the basis of dynamic material model,the power dissipation was established.The peak efficiency of the power dissipation is 57%.At the same time,Prasad’s,Murty’s and Babu’s instability criteria based on Ziegler’s expectant rheology theory,and Gegel’s and Malas’s instability criteria based on Lyaponov’s function theory,were used to predict the unstable regions in the processing map.The maximum entropy generation rate and large plastic deformation principle are more in line with the hot deformation process of C71500 alloy,so the accuracy of Prasad’s instability criterion is much better.According to the obtained macro-crack and micro-metallographic structure morphologies,the temperature range of 1 098-1 156 K and the strain rate range of 2.91-10 s^-1,and the temperature range of 1 171-1 273 K and the strain rate range of 0.01-0.33 s^-1 are more suitable for the processing area of C71500 alloy.The accuracy of the above conclusions were verified by the forging of materials and the analysis of hot piercing tubes.The significance of this paper is to provide theoretical basis and technological conditions for hot-press processing of C71500 alloy.

THE SULFIDATION/OXIDATION RESISTANCE OF TWO Ni-Cr-Al-Y ALLOYS AT 700℃

The high temperature corrosion resistance of Ni-25.9Cr-13.5Al-1.2Y-0.6Si and Ni-10.2Co-12.4Cr16.0Al-0.5Y-0.2Hf alloys was assessed in sulfidation/oxidation envi-ronments. In the environment with a sulfur partial pressure of 1Pa. and an oxygenpartial pressure of 10^(-19)Pa, both these alloys exhibited three distinct stages in theweight gain-time curve when tested at 700℃. In the initial stage, selective sulfidationof Cr suppressed the formation of the other metal sulfides, resulting in lower weightgains. In the transient stage, breakdown and cracking of Cr sulfides and insufficientconcentration of Cr at the outer zone led to the rapid formation of Ni sulfides anda rapid increase in weight. In the steady-state stage, corrosion was controlled by thediffusion of anions and/or cations, which led to a parabolic rate law.

SULFIDATION OF Co-15wt%Y ALLOY IN H_2-H_2S MIXTURES AT 600-800℃

The corrosion properties of a Co-15wt% Y alloy were studied in H_2-H_2S mixtures under a sulfur pressure of 10-3 Pa at 600-800℃ and of 10-2 Pa at 800℃ to examine the effect of Y on the resistance of pure cobalt to sulfur attack at high temperatures.The alloy is nearly single-phase.containing mostly the intermetallic compound Co17Y2 plus a little amount of the solid solution of Y in cobalt.At 600-700℃ and at 800℃ under 10-2 Pa of S2 the alloy forms multi-layered scales consisting of an outer region of pure cobalt sulfide,an intermediate region of a mixture of the sulfides of the two metals and finally an innermost layer of a mixture of yttrium sulfide with metal cobalt.At 800℃ under 10-3Pa of S2,below the dissociation pressure of cobalt sulfide, the alloy forms only a single layer composed of a mixture of metallic cobalt with yttrium sulfide.Pure Y produces only the oxysulfide Y2O2S, as a result of the good stability of this compound and of the presence of some impurities in the gas mixtures used The corrosion kinetics is generally rather complex and irregular except al 800℃under 10-3 Pa of S2.The addition of yttrium always reduces the sulfidation rate of cobalt, even though the formation of a continuous protective external layer of yttrium sulfide is never achieved.The internal sulfidation of Y in Co-15% Y is not associated with a depletion of Y in the alloy.This kind of diffusionless internal attack is typical of alloys with a very small solubility of the most reactive component Y in the base metal A.which restricts severely the Y flux from the alloy towards the alloy-scale interface.

High-Temperature Sulfidation of Mo-Nb Alloys

The sulfidation rates and sulfide scales of pure Mo, pure Nb, and Mo Nb alloys are studied. By comparing the rates, an alloy with best sulfidation resistance is found. In addition, the sulfidation kinetics of Mo-50 %Nb is studied in detail.

Factors Influencing the Sulfidation Rate of Fe-Mo Binary Alloys

The sulfidation rate constants of various Fe-Mo binary alloys in S2 vapor with different sulfidation parameters were collected to summarize the correlation between the sulfidation rate and alloy composition, sulfur pressure and sulfldation temperature. The octivation energies indicate that the sulfidation process of the alloys is exclusively controlled, at a given temperature, by one alloying component i.e. either Mo or Fe. The sulfidation rate declines exponentially with the increasing of Mo content in alloy. And the influence of sulfur pressure is relatively slight.

Liquid-solid interface control of BFe10-1-1 cupronickel alloy tubes during HCCM horizontal continuous casting and its effect on the microstructure and properties

Based on horizontal continuous casting with a heating-cooling combined mold （HCCM） technology, this article investigated the effects of processing parameters on the liquid-solid interface （LSI） position and the influence of LSI position on the surface quality, microstructure, texture, and mechanical properties of a BFe10-1-1 tube （φ50 mm × 5 mm）. HCCM efficiently improves the temperature gradient in front of the LSI. Through controlling the LSI position, the radial columnar-grained microstructure that is commonly generated by cooling mold casting can be eliminated, and the axial columnar-grained microstructure can be obtained. Under the condition of 1250℃ melting and holding temperature, 1200-1250℃ mold heating temperature, 50-80 mm/min mean drawing speed, and 500-700 L/h cooling water flow rate, the LSI position is located at the middle of the transition zone or near the entrance of the cooling section, and the as-cast tube not only has a strong axial columnar-grained microstructure （{hkl}〈621〉, {hkl}〈221〉） due to strong axial heating conduction during solidification but also has smooth internal and external surfaces without cracks, scratches, and other macroscopic defects due to short solidified shell length and short contact length between the tube and the mold at high temperature. The elongation and tensile strength of the tube are 46.0%-47.2% and 210-221 MPa, respectively, which can be directly used for the subsequent cold-large-strain processing.

Electrolytic production of Cu-Ni alloys in CaCl_2-Cu_2S-NiS molten salt

An alternative metal/alloy production method,known as direct electrochemical reduction(DER),was introduced for the fabrication of CuNi alloys from mixed sulfides(Cu2S,NiS)under both galvanostatic and potentiostatic conditions.The influences of the process parameters(e.g.,cell voltage and current)on the compositions of the reduced compounds were investigated to yield industrially desirable alloys,namely,CuNi10,CuNi20,and CuNi30.The electrochemical behaviors of Cu2S and NiS in CaCl2 melt were examined at a temperature of 1200°C via cyclic voltammetry(CV).Based on the CV results,the cathodic reduction of Cu2S occurred in one step and cathodic reductions of NiS occurred in two steps,i.e.,Cu2S?Cu for copper reduction and NiS?Ni3S2?Ni for nickel reduction.Galvanostatic studies revealed that it was possible to fabricate high-purity CuNi10 alloys containing a maximum sulfur content of 320×10-6 via electrolysis at 10 A for 15 min.Scanning electron microscopy along with energy-dispersive X-ray spectrometry and optical emission spectroscopy(OES)examinations showed that it was possible to fabricate CuNi alloys of preferred compositions and with low levels of impurities,i.e.,less than 60×10-6 sulfur,via DER at 2.5 V for 15 min.

Corrosion behavior of B10 copper-nickel alloy beneath a deposit caused by sulfate-reducing bacteria with carbon source starvation in marine environments

Copper-nickel alloys can suffer severe localized corrosion in marine environments containing sulfate-reducing bacteria(SRB),but the effect of SRB on the under-deposit corrosion of copper-nickel alloys is unknown.In this work,the corrosion behavior of B10 copper-nickel alloy beneath a deposit caused by SRB with carbon source starvation in artificial seawater was studied based on electrochemical measurements and surface analysis.Results demonstrate that SRB with an organic carbon starvation can survive in artificial water but most SRB cells have died.The survived SRB cells can attach to the bare and deposit-covered B10 copper-nickel alloy,leading to the corrosion acceleration.Due to the limitation of organic carbon source,the pitting corrosion of B10 copper-nickel alloy caused by SRB is not serious.However,serious pitting corrosion of the deposit-covered B10 copper-nickel alloy can be found both in abiotic and biotic conditions,and the pitting corrosion and uniform corrosion are further accelerated by SRB.There is a galvanic effect between the bare and deposit-covered specimens in the presence of SRB in the early stage but the galvanic effect after 5 d of testing can be neglected due to the low OCP difference values.

CORROSION OF A Co-15 Ce ALLOY UNDER 10-3PaS2 AT 700℃

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Control of equiaxed grains in a complicated Cu-Ni based alloy prepared by centrifugal casting

A complicated Cu-Ni based alloy was developed to fabricate wear-resisting bush for high temperature application.The concern focuses on the control of equiaxed grains in the developed alloy ingot prepared by centrifugal casting.The results show that the equiaxed grains are determined by the pouring temperature of the melt,the cooling rate and the rotation speed of the mold.With the decrease in pouring temperature,the fraction of the equiaxed grains in the transverse section of the ingot increases and the average length of columnar grain decreases.When the pouring temperature is confined below 1,250℃,complete equiaxed grains can be obtained.Based on the optimal centrifugal casting processing,the tensile strength of the developed alloy ingot with complete equiaxed grains reaches to 810 MPa and 435 MPa at room temperature and 500℃,respectively,which is 14% and 110% higher than that of common commercial QAl10-4-4 alloy.The wear rate of the developed alloy is 7.0 × 10-8 and 3.8 × 10-7 mm3?N-1?mm-1 at room temperature and 500℃,respectively,which is 5 times and 39 times lower than that of QAl10-4-4 alloy.

Corrosion performance and applicability evaluation of nickel-based alloys for oil and gas production tubing applications

The sulfide stress corrosion cracking（ SSC） performance of G3 and 028 nickel-based alloys w as studied using slow strain rate test（ SSRT） and the four-point bend（ FPB） test under simulated dow nhole conditions. The effect of high temperature,high H2 S / CO2 partial pressure,and the presence of sulfur on SSC susceptibility w as investigated. The G3 alloy w as found to have a higher SSC resistance than the 028 alloy. Presence of sulfur and temperature bear a strong influence on the SSC performance of the metals,particularly on the 028 alloy. The applicability of 028 and G3 alloys may be expanded and both could safely be used beyond the limits set by the ISO15156-3 standard.

含钴三元硫化物常压硫酸浸出钴的动力学研究

开展含钴三元硫化物常压硫酸浸出的实验研究。考察搅拌速度、浸出温度、硫酸浓度和粒度对钴浸出率的影响,并分析从含钴三元硫化物中浸出钴的动力学。结果表明,在最佳条件下,钴和铁被选择性浸出,且浸出率均大于99%,而钼和铜则富集于浸出渣。通过对实验数据的分析可知,钴的浸出符合由固体产物层产生的收缩核模型,且浸出过程受内扩散控制。浸出反应的活化能为49.86k J/mol,硫酸浓度和粒度的反应级数分别为0.57和-1.4。

The 982 Ma Re-Os age of copper-nickel sulfide ores in the Baotan area,Guangxi and its geological significance

Re-Os dating on copper-nickel sulfide ores from the Baotan area, Guangxi, yielded an ore-forming age of 982±21 Ma(2σ), which demonstrates that copper-nickel sulfide deposits and their related mafic-ultramafic rocks occurred in the same period of time with the ophiolites in northeastern Jiangxi. Both of them are the products of collision-convergence between the Cathaysian plate and Yangtze plate and the subsequent extensional environment. Calculation of the γOs of the 982 Ma copper-nickel sulfide ores and its correlation with Re/Os indicate that injection-type massive ores display lower γOs values(-15.6 to -8.2) and lower Re/Os ratios(0.32 to 0.43), while basal liquation-type ores have γOs= -27.9 to -7.3 and Re/Os=5.36 to 11.24. This suggests that these copper-nickel sulfide ores and their related mafic-ultramafic rocks were derived from a Re-depleted mantle source and that contamination with some crustal material occurred during their intrusion.

聚苯硫醚共混合金的研究进展

本文简述了特种工程塑料聚苯硫醚 (PPS)与其它多种高聚物的共混改性 ,分别介绍了PPS/PA、PPS/PEEK、PPS/PSF、PPS/TLCP、PPS/PF、PPS/PBT、PPS/PES、PPS/PC、PPS/PEK -C、PPS/PS以及其它PPS共混合金在国内外的研究进展及其生产应用 ,其中重点论述了PPS与聚四氟乙烯 (PTFE)树脂的共混改性及其该共混合金的性能与用途。并展望了PPS合金的发展。

铜合金在3.5%NaCl+S^(2-)溶液中的腐蚀磨损行为

测定了HAl77-2铝黄铜、BFe30-1-1白铜在3.5％NaCI和3.5％NaCI+S^(2-)溶液中的腐蚀速率、腐蚀磨损率和电化学行为;观察了腐蚀磨损后铜合金的微观形貌;研究了腐蚀后样品的表层性能。实验结果表明,S^(2-)的存在加速了铜合金的腐蚀、腐蚀磨损,使E_corr明显负移,i_corr增加;硫离子对铜合金腐蚀磨损的加速作用与腐蚀磨损过程中的硫致脆性有关。

CoCrFeNiTi_(0.5)高熵合金在熔融Na_2SO_4-25%NaCl中的腐蚀行为

研究Co Cr Fe Ni Ti0.5高熵合金在熔融Na2SO4-25%Na Cl(质量分数)中的腐蚀行为,应用TGA获得其在650和750℃空气中的腐蚀动力学曲线;采用XRD、SEM(EDS)和EPMA对腐蚀产物的截面形貌及元素分布进行分析。结果表明:喷涂Na2SO4-25%Na Cl的Co Cr Fe Ni Ti0.5高熵合金在650和750℃时的腐蚀动力学曲线相似,呈"指数"增长规律;腐蚀截面由含较多Ti O2、部分Cr2O3以及微量尖晶石结构氧化物构成的氧化层与含孔隙且贫Cr和Ti、富Fe、Ni和Co的腐蚀影响区两部分构成;延长腐蚀时间或提高腐蚀温度后,氧化层破裂,与基体的结合程度显著下降,发生严重剥离甚至脱落。分析认为:Co Cr Fe Ni Ti0.5高熵合金在Na2SO4-25%Na Cl中的高温腐蚀归因于氧化、硫化以及氯化的综合作用。