Ca含量对时效态Mg-6.5Al-xCa-1Sn-0.3Sr镁合金显微组织和性能的影响

通过XRD、SEM和性能测试研究了Ca含量的变化对时效态Mg-6.5Al-xCa-1Sn-0.3Sr(x=1,1.5,2,2.5)镁合金的显微组织和性能的影响。结果表明,时效态合金主要由α-Mg和Al_(2)Ca相组成,Al_(2)Ca相成网状分布。合金的抗拉强度和伸长率随着Ca加入量的增加而逐渐降低,当Ca含量为1%时合金的拉伸性能最佳,而合金的硬度随着Ca的加入而增加。在175℃、70 MPa下,Ca的添加使时效态合金的稳态蠕变速率降低。

Calcium-Magnesium Ca/Mg Ratios and Their Agronomic Implications for the Optimization of Phosphate Fertilization in Rainfed Rice Farming on Acidic Ferralsol in the Forest Zone of Ivory Coast

This study is a contribution to improving rice productivity on acidic plateau soils of the tropical rainforest zone. It is based on taking into account the cationic balances of the soil in order to optimize the phosphorus (P) nutrition of rice on these acidic soils, where this nutrient constitutes a limiting factor for agricultural production. Three (3) pot trials were conducted in Adiopodoumé in the forested south of Côte d’Ivoire. The interactive effects of calcium carbonate (0, 25, 50 and 75 kg Ca ha−1) and magnesium sulfate (0, 25, 50 and 75 kg Mg ha−1) were evaluated on the response of NERICA 5 rice at doses 0, 25, 50 and 75 kg P ha−1 of natural phosphate from Togo, applied only once at the start of the experiment. Additional fertilizers of nitrogen (N) (100 kg N ha−1) and potassium (K) (50 kg KCl ha−1) were added to each of the tests in a split-plot device. The test results revealed a paddy production potential of approximately 3 to 5 t⋅ha−1 for NERICA 5 on an acidic soil, under the effect of the interaction of P, Ca and Mg. The quadratic response of rice yield to the doses of these fertilizers would be more dependent on their balance, itself influenced by Ca nutrition. For the sustainability and maintenance of rice production in agro-ecology studied, it was recommended doses of 38 kg Ca ha−1, 34 kg Mg ha−1 in a Ca/Mg ratio (1/1) with intakes of 41 kg P ha−1, overall in a ratio 1/1/1 (P/Ca/Mg) more favorable to the availability of free iron considered a guiding element of mineral nutrition. Thus, these promising results should be confirmed in a real environment for better management of the fertilization of rice cultivated on acidic plateau soils in Côte d’Ivoire.

Influence of Ca/P ratio on the catalytic performance of hydroxyapatite for decarboxylation of itaconic acid to methacrylic acid

Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.

Morphotype dependence of Globigerinoides ruber(white)and Trilobatus sacculifer Mg/Ca ratios in the western tropical Pacific:implications for reconstructing the mixed-layer depth

Planktonic foraminifer Globigerinoides ruber(white)and Trilobatus sacculifer are the most frequently used mixedlayer dwelling species for reconstructing past oceanic environments.Specifically,the Mg/Ca ratios of these two foraminiferal species have been used for reconstructing tropical/subtropical changes in sea surface temperature(SST).However,these two species have different morphotypes,of which the spatial and temporal differences in Mg/Ca ratios and their influencing factors are still unclear.Our objective is to investigate the potential differences between the Mg/Ca ratios of these different morphotypes of G.ruber(white)and T.sacculifer in the western Philippine Sea(WPS)and determine their implications for the reconstruction of SST and upper-ocean structure.Mg/Ca measurements are made on two basic morphotypes of G.ruber(white)[sensu stricto(s.s.)and sensu lato(s.l.)]and T.sacculifer[with(w)and without(w/o)a sac-like final chamber]on samples of Site MD06-3047B from the WPS.Our results reveal that Mg/Ca ratios of different G.ruber morphotypes show consistent differences;and those of T.sacculifer morphotypes show staged variations since MIS 3.It is suggested to select a single morphotype for reconstructing SST changes using the Mg/Ca ratios of G.ruber and T.sacculifer in the WPS.Furthermore,the Mg/Ca ratios between G.ruber s.s.and G.ruber s.l.[Δ(Mg/Ca)_(G.ruber s.s.-s.l.)]downcore MD06-3047B covaries with indexes of summer monsoon.Combining with the core-top results,showing regional variation of differences in theΔ(Mg/Ca)_(G.ruber s.s.-s.l.)over the western tropical Pacific,we propose thatΔ(Mg/Ca)_(G.ruber s.s.-s.l.)may tend to reflect summer mixed layer depth.

Mg/Ca,Ba/Ca,and S/Ca ratios as environmental and growth proxies for bivalve shells from the Haima cold seep,South China Sea

Bivalve shell fossils,cemented by authigenic carbonates,are widely spread in the Haima cold seep,Qiongdongnan Basin of the South China Sea(SCS).In this study,we examined an element profile of Gigantidas platifrons in the Haima cold seeps at a water depth of 1381 m.Based on the scanning electron microscope(SEM)analyses,the prismatic layer and nacreous layer were identified,which are characterized by prismatic structure and stratified structure,respectively.In addition,the profile can be subdivided into two parts:altered and unaltered zones.Laser inductively coupled plasma mass spectrometry(LA-ICP-MS)mapping shows that the element concentrations of the altered zones were influenced by the authigenic carbonate rocks,whereas the element concentrations of unaltered zones remain stable.In-situ X-ray diffraction(XRD)analyses show that the mineral constituent of the prismatic layer is mainly composed of aragonite.Along with the growth profile,Mg/Ca ratios of unaltered zones have minor variations,ranging 0.72-0.97 mmol/mol(mean=0.87 mmol/mol),with estimated temperatures of 3.8-4.1℃,indicating that the temperature of the surrounding seawater remains constant and agree with the measured data of 3.9℃which was conducted by a conductivity-temperature-depth system(CTD).The minor variations of Ba/Ca ratios(0.01-0.06 mmol/mol;mean=0.04 mmol/mol)indicate a relatively stabilized salinity of the surrounding seawater.S/Ca ratios show large variations of 0.04-4.15 mmol/mol(mean=1.37 mmol/mol).S/Ca ratios have regular variations which generally correspond to the variations of the Mg/Ca ratios,highlighting that the S/Ca ratios of bivalve shells show the potential to reflect the growth rate of the Gigantides.However,further studies should be carried out on the understanding of the links between the S/Ca ratios and seepage intensity of cold-seep fluids.

挤压处理与Ca添加对Mg-7Sn合金显微组织与耐蚀性的影响

利用金相显微镜(OM)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、电化学试验与浸泡试验等研究了挤压处理与添加合金元素Ca对Mg-7Sn合金显微组织、耐蚀性及力学性能的影响。结果表明:添加Ca元素可以明显细化铸态Mg-7Sn合金的晶粒,并在晶粒内部与晶界形成了棒状的CaMgSn相,同时,腐蚀过程中,添加Ca会使合金表面形成含Ca的化合物,阻止或延缓腐蚀的进行,提高合金的耐蚀性。挤压处理使得合金的平均晶粒尺寸由55.2μm减小到3.3μm,粗大棒状的CaMgSn相被破碎成细小的块状。挤压处理后Mg-7Sn-1Ca合金的耐蚀性出现轻微下降,但保证了较高的显微硬度。挤压态Mg-7Sn-1Ca合金兼具力学性能和耐蚀性。

热处理对ATX525镁合金中CaMgSn相形貌演化的影响

采用XRD、SEM和EDS研究了热处理温度对ATX525镁合金相组成、显微组织和析出相成分的影响,考察了保温时间为24 h条件下,Ca Mg Sn相随温度变化的演化规律。结果表明,合金组织中析出相由热稳定性较高的Mg2(Al,Ca)、Al2Ca和Ca Mg Sn等相组成。其中,Ca Mg Sn相中Sn和Ca含量随处理温度变化而变化,从而使其热稳定性和形貌发生变化。当温度低于500℃时,主要发生Ca Mg Sn溶断和破碎过程,体积分数没有显著变化;当温度为550℃时,Ca Mg Sn相发生溶入基体过程,体积分数减少;然而当处理温度为570~600℃,Ca Mg Sn相出现长大现象。获得细化Ca Mg Sn相貌的热处理温度为500~550℃。合金经过550℃/24 h处理后,经200℃/96 h时效,Ca Mg Sn相以条状和细小的颗粒状析出,与颗粒形貌相比,条状Ca Mg Sn相具有铸态时的形貌特征。

Ca,Pd,Sn,La对MgH_2电子结构的影响

采用基于第一原理的离散变分方法(DVM),研究了Ca,Pd,Sn,La等原子替代镁氢化物MgH2原子团簇中心Mg原子对镁氢化物电子结构及其成键特性的影响。通过分析晶体轨道重叠集居数(COOP),键序(BO)和键差分电荷密度等计算结果表明:Ca,Pd,Sn,La等原子对关系到Mg(M)H2结构稳定性的Mg-H键具有明显影响;它们最近邻镁原子周围的电荷密度重新分布并具有明显的各向异性,当M是Ca,Pd,La时,其最近邻Mg和H之间键序变化不大,稍有增加,当M是Sn时,则大幅减弱,其逐增顺序为Sn < La < Pd < Ca;而且,对其它位置Mg与氢之间相互作用也有一定程度的影响。

冷轧变形Pb-Ca-Sn-Al合金在回复和再结晶过程中的晶界特征分布

采用电子背散射衍射(EBSD)技术研究了冷轧变形Pb-0．1％Ca-1．5％Sn-0．026％Al合金在回复和再结晶过程中的晶界特征分布(GBCD)．结果表明:在回复过程中,合金内形成了比例接近50％的平直∑3晶界,这类晶界不处在由一般大角度晶界构成的晶界网络上,不能使合金的GBCD得到优化;相反,在再结晶过程中,除了生成比例超过50％的∑3晶界外, 还出现了较多的∑9和∑27等低∑重位点阵晶界(CSL),并且这些晶界和相当多的弯曲的∑3晶界均处在由一般大角度晶界构成的晶界网络上,可以使合金的GBCD得到优化．进一步的分析指出:回复过程中所形成的平直的∑3晶界是共格孪晶界, 它们能量很低,很难迁移;在再结晶过程中,除了生成不可迁移的共格的∑3孪晶界外,还可形成大量可迁移的弯曲的非共格∑3 晶界,这类晶界的迁移和彼此会合可形成∑9和∑27等∑3n(n为正的整数)晶界,这是合金GBCD得到优化的根源．

Sol-gel法制备(Ba_(0.95)Ca_(0.05))(Sn_(0.05)Ti_(0.95))O_3薄膜及升温速度对形貌的影响

用溶胶 -凝胶法制备了光滑的 (Ba0 .95Ca0 .0 5) (Sn0 .0 5Ti0 .95)O3(以下称BCST)薄膜。研究了热处理的升温速率和处理温度对薄膜形貌的影响。SEM测试结果表明快速升温和低温 (刚高出成晶温度 )有利于获得好质量的BCST薄膜。

锡含量对Pb-Ca-Sn-Al合金性能的影响

采用恒电位阳极极化、线性扫描阴极极化、交流伏安、恒流阳极腐蚀和金相显微观察等方法,研究锡(Sn)在铅钙合金(Pb-Ca-x%Sn-Al)中的作用和锡含量对铅钙合金性能的影响。锡的加入可以细化铅钙合金晶粒。随着锡含量从0.1%增加到2.0%,铅钙合金在1.2 V下腐蚀电流下降55%,腐蚀膜的形成量减少49%,0.5 A/cm^2下恒流阳极腐蚀3 d,失重减少75%;腐蚀膜转化阻抗下降到4.1Ω/cm2;在相同的阴极或阳极极化电位下,析氢或析氧反应速度减小。

Mg−6Zn−1Mn−4Sn−0.5Ca合金在挤压和时效过程中的组织演变和析出强化

采用光学显微镜、扫描电子显微镜、透射电镜、硬度试验和拉伸试验对Mg−6Zn−1Mn−4Sn−0.5Ca(ZMT614−0.5Ca)合金在挤压态和时效态的组织变化及力学性能进行研究。结果表明:铸态ZMT614−0.5Ca合金主要包含α-Mg、Mg−Zn和CaMgSn相。热挤压过程有效地细化晶粒且形成完全动态再结晶组织。挤压态合金的平均晶粒尺寸约为4.85μm。固溶处理后,高熔点CaMgSn仍然存在,起着重要的钉扎作用和阻碍晶界移动。时效处理后,合金ZMT614−0.5Ca具有良好的综合力学性能,屈服强度、抗拉强度和伸长率分别为338 MPa、383 MPa和7.5%。和挤压态相比,合金屈服强度提升约36%,其主要原因是时效过程β相的析出强化。

锡含量对电积铜用Pb-Ca-Sn合金阳极电化学性能的影响

交叉轧制的合金材料各向异性明显减小,性能较好,目前将其用作电积铜阳极并对其耐蚀性能进行研究的报道较少。采用恒电流极化曲线、循环伏安曲线、交流阻抗曲线、X射线衍射、扫描电镜等测试手段研究了不同Sn含量交叉轧制8次的Pb-Ca-Sn合金的性能。结果表明:随着Sn含量的增加,合金的耐腐蚀性和导电性逐渐增加,析氧过电位逐渐降低,其中Pb-Ca-(1.20%)Sn合金的综合性能最好。

挤压态Mg-Sn-Ca合金的显微组织、力学及生物腐蚀性能（英文）

制备了用于骨科的挤压态Mg-Sn-Ca合金,并应用金相显微镜、扫描电子显微镜、X射线衍射仪、拉伸测试、浸泡测试和电化学测试等仪器和方法对其进行研究。结果表明:当锡添加量为1%,钙含量从0.2%增加到0.5%时,挤压态Mg-Sn-Ca合金的显微组织变得均匀,力学性能增加,耐腐蚀性提高。钙含量进一步增加到1.5%时,合金的强度增加,但伸长率和耐腐蚀性降低。在钙含量为0.5%的合金中,锡的含量从1%增加到3%时,合金的最大抗拉强度增加,耐腐蚀性降低。当锡含量为2%时,合金呈现最低的屈服强度和伸长率。挤压态Mg-Sn-Ca合金的这些行为受到Sn/Ca比率的控制。分析表明挤压态Mg-1Sn-0.5Ca合金有潜力作为可降解骨科植入体。

Sn元素对Mg-Zn-Ca合金非晶形成能力和耐蚀性的影响

采用熔体旋淬和铜模喷铸法制备了不同Sn含量的Mg-Zn-Ca-Sn合金带材和直径2 mm的棒材试样。运用XRD、SEM、DSC和电化学测试方法研究了Sn元素对Mg-Zn-Ca合金非晶形成能力和在模拟体液中腐蚀行为的影响。结果表明,带材组织均为非晶态,而棒材试样随着Sn含量的增加,由不含Sn元素的完全非晶态,逐渐转变为由Mg和Mg2Sn相组成的多晶态组织,说明Sn元素的添加恶化了Mg-Zn-Ca合金的非晶形成能力。电化学腐蚀测试结果表明随着Sn含量的增多,腐蚀电位负向移动,腐蚀电流密度增大,合金的耐蚀性逐渐下降。

蓄电池板栅Pb-Ca-Sn-Al合金组织与性能的研究

采用连铸连轧工艺成功制备了Pb-Ca-Sn-Al合金的蓄电池板栅,通过光学显微观察、力学性能实验、腐蚀实验和电导率实验对不同浇铸温度、轧制温度、冷却方式及轧制变形量的蓄电池板栅Pb-Ca-Sn-Al合金的金相组织及其性能进行研究。结果表明:采用480℃浇注温度、93℃轧制温度、水喷淋冷却方式生产的Pb-Ca-Sn-Al合金厚板带的力学与导电等综合性能最优,通过五道变形量为20%的轧制后,Pb-Ca-Sn-Al合金板带的抗拉强度σb与屈服强度σp0.2分别提高了40.3%和61.5%,抗腐蚀性能是轧制一道的1.69倍。

极化时间对Pb-Ca-1.2%Sn合金阳极的影响

采用阳极极化曲线、塔菲尔曲线、循环伏安曲线、交流阻抗曲线和腐蚀性能的测试研究了不同极化时间对交叉轧制八次的Pb-Ca-1.2%Sn合金阳极的性能影响。实验结果表明,随着极化时间的增加,合金阳极的耐腐蚀性和导电性逐渐增加,而析氧电位逐渐降低。其中,以极化时间为12天的Pb-Ca-1.2%Sn合金阳极的性能最佳。

Ca和Sr对铸态Mg-Sn-Si合金组织和性能的影响

用X射线衍射仪(XRD)、扫描电镜(SEM)、光学显微镜(OM)研究了铸态Mg-Sn-Si-Ca-Sr合金的相组成和显微组织,用力学性能试验机测定了合金的拉伸性能.结果表明,Mg-5Sn-xSi-0.5Ca-0.5Sr(x=1,2)合金由α-Mg、Mg2Sn、Mg2Si和CaMgSn相所组成,Mg2Si相含量随Si元素的增加而增加.对于Mg-5Sn-1Si-yCa-0.5Sr(y=0.5,2)合金,Ca的质量分数提高到2%后会促进Mg2Ca相和CaMgSn相形成,但同时抑制了Mg2Sn、Mg2Si相的析出,从而导致合金性能下降.对于Mg-5Sn-2Si-0.5Ca-ySr(y=0.5,2)合金,当Sr的质量分数由0.5%提高到2%时,Mg2Si和Mg2Sn相均得到显著细化,并促进了基体内MgSn(Sr,Ca)相形成,从而提高了合金的抗拉强度与屈服强度.

铋对铅酸蓄电池用Pb-Ca-Sn合金性能的影响

实验采用塔菲尔曲线、动电位线性扫描、交流伏安等电化学方法研究了不同铋含量的铅钙锡铝板栅合金的电化学性能,并用显微硬度计测试硬度。结果表明,添加适量的铋,可以提高合金的耐腐蚀性,抑制Pb(Ⅱ)的生长,减小阳极膜的阻抗,提高电池的深充/放电性能,提高合金板栅的显微硬度。但过多的铋反而恶化Pb-Ca合金的电化学性能和机械性能。

Ca和Sn对ZM61合金微观组织和性能的影响

采用光学显微镜(OM),扫描电镜(SEM),X射线衍射仪(XRD)等分析方法研究了添加Ca和Sn对Mg-6Zn-1Mn(ZM61)合金显微组织和力学性能的影响。结果表明:ZM61合金中主要的第二相为Mg7Zn3,添加0.5 mass%Ca后合金中出现Ca2Mg6Zn3相,Mg7Zn3相减少,动态再结晶不完全,织构增强,强度和塑性提高;在ZM61-0.5Ca合金中添加1 mass%Sn,合金中出现针状新相CaMgSn,该相抑制Ca2Mg6Zn3的形成。ZM61-0.5Ca-1Sn合金综合力学性能最佳,屈服强度、抗拉强度和伸长率分别为319 MPa,358 MPa和13.5%。