固溶处理对AM60B＋xRE及AZ9lD＋xRE镁合金性能的影响

研究了添加少量富铈混合稀土的AM60B xRE及AZ9lD xRE合金(x＝0．4、0．8、1．2、1．6和2．0％，质量分数)固溶处理后的显微组织与机械性能．结果表明，添加混合稀土能显著提高合金的抗拉强度σb和屈服强度σ0.2，固溶处理明显提高AZ9lD xRE合金的强度；AM60B xRE及AZ9lD xRE合金的铸态组织由α(Mg)固溶体、杆状Al11RE3相、颗粒状Al10Ce2Mn7相以及网状Mg17Al12相组成，经过固溶处理后，网状Mg17Al12相完全溶解，只剩下热稳定性较高的Al11RE3相和Al10Ce2Mn7相，随固溶时间的延长，其形态略有改变．AM60B xRE合金拉伸试样断口呈带局部韧窝的准解理断裂形式，而AZ9lD xRE合金则呈现沿晶断裂 解理断裂的混合断口形态．     

Si对AZ91D镁合金显微组织与力学性能的影响

利用光学金相显微镜OM和XRD分析了加入微量Si的AZ91D合金显微组织和相组成,测试了合金室温拉伸力学性能和硬度,利用SEM分析了合金拉伸断口形貌.结果表明,加入一定量Si后AZ91D合金组织中形成汉字状Mg2Si相,富集于固液界面前沿,阻碍α-Mg基体的自由长大,从而细化合金铸态组织;汉字状Mg2Si相的存在导致合金力学性能的降低;AZ91D合金室温拉伸断口是以解理断裂为主的脆性断裂,加入Si后,断裂常发生于α-Mg基体和汉字状Mg2Si相间的界面处.     

稀土元素铈对AZ61镁合金铸态显微组织及结构的影响

运用金相显微镜、电子探针和X ray等手段分析了AZ61合金添加稀土元素Ce后铸态显微结构的变化。结果表明 ,Ce的加入细化了 β相和晶粒 ,并减少了 β相的量。Ce在AZ61合金中以呈块状和杆状Al4 Ce化合物的形式存在 ,这两种化合物熔点极高 ,几乎不溶于基体 ,有极少部分偏聚在晶界上。固溶处理后 ,AZ61合金中的 β (Mg12Al17)相几乎全部溶入基体 ;而加入稀土Ce后 ,AZ61合金中的Al4 Ce化合物几乎很少溶入基体。Ce的加入能够提高AZ61合金基体相的显微硬度 ,但幅度不大 ;而将其固溶处理后 ,Ce显著提高了AZ61合金的显微硬度。     

稀土元素对AZ61镁合金铸态显微组织及结构的影响

运用金相显微镜、电子探针和X-ray等手段分析了AZ61合金添加稀土元素Ce后铸态显微结构的变化。结果表明，Ce的加入细化了β相和晶粒，并减少了β相的量。Ce在AZ61合金中以呈块状和杆状Al4Ce化合物的形式存在，这两种化合物熔点极高，几乎不溶于基体，有极少部分偏聚在晶界上。固溶处理后，AZ61合金中的β（Mg12Al17)相几乎全部溶入基体；而加入稀土Ce后，AZ61合金中的Al4Ce化合物几乎很少溶入基体。Ce的加入能够提高AZ61合金基体相的显微硬度，但幅度不大；而将其固溶处理后，Ce的显著提高了AZ61合金的显微硬度。     

添加稀土元素Ce对AZ91D镁合金组织的影响

用金相显微镜、能量色散谱仪(EDS)和X射线衍射仪(XRD)研究了稀土元素Ce对AZ91D镁合金铸态组织的影响.结果表明,Ce对AZ91D镁合金具有明显的变质效果,加入0.4%Ce后,α-Mg树枝晶变化不明显,晶界上的β-Mg17Al12相呈断续网状分布;加入0.8%Ce后,合金晶界上的离异共晶β相基本上断裂成骨骼状,转变为颗粒状且分布比较均匀;加入1.2%稀土Ce后,枝晶变细,共晶β相完全变为颗粒相,弥散分布于晶界处.微结构分析发现,组织中出现了分布于晶界处的杆状Al10Ce2Mn7化合物.     

挤压态Mg–9Al–Zn–0.5RE–Ca–Si合金微观组织和力学性能

目的 改善AZ91镁合金在温度超过120℃时的力学性能。方法 在AZ91合金中添加Ca、Si和La/Ce混合稀土元素。在360℃下等温挤压,平均挤压速度为1.2 mm/s,挤压比为30︰1,以探究Ca、Si和La/Ce混合稀土元素对AZ91合金力学性能、物相组成和显微组织等的影响。结果 在AZ91挤压态合金中,与添加Si元素相比,Ca元素对挤压态合金的力学性能影响更大。在室温时,Mg–9Al–Zn–0.5RE–Si挤压态合金的屈服强度、极限抗拉强度和伸长率分别是254 MPa、306MPa、7.0%,而Mg–9Al–Zn–0.5RE–0.5Ca挤压态合金的屈服强度、极限抗拉强度和伸长率分别是308 MPa、330 Ma、7.1%。Mg–9Al–Zn–0.5RE–0.5Ca–0.5Si挤压态合金室温力学性能最佳,其屈服强度、极限抗拉强度和伸长率分别是351 MPa、383 MPa、7.4%,说明Ca、Si这2种元素的协同作用可同时提高室温下AZ91合金的强度和塑性。在150℃和200℃下,Mg–9Al–Zn–0.5RE–0.5Ca–0.5Si合金仍然具有最佳的力学性能。在150℃下,其屈...     

Si-RE复合合金化对AZ31镁合金显微组织及力学性能的影响

采用Si-RE元素对AZ31镁合金进行复合微合金化,利用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)及拉伸实验仪等手段研究Si-RE元素对AZ31镁合金的微观组织和力学性能的影响规律。结果表明,Si-RE复合加入可以明显细化AZ31镁合金的铸态组织,β-Mg17Al12相也由网状分布变为颗粒状,同时生成了短棒状和针状的Mg2Si相及Al11RE3相;合金的综合力学性能显著改善,AZ31+0.4%Si+0.5%RE的强度和延伸率比原始AZ31镁合金分别提高了42MPa和3.9%,试样室温拉伸断口虽然是以解理为主的脆性断裂,但断口中出现了少量的韧窝,解理面也较小。     

电磁搅拌对富Ce混合稀土合金化AZ91D组织结构的影响

用光学显微镜、扫描电镜、电子耗散能谱和X射线衍射仪研究了电磁搅拌对富Ce混合稀土(MM)合金化AZ91D镁合金组织和结构的影响。结果表明,随富Ce混合稀土加入量的增加,初生相细化,β相(Mg17Al12)的相对量降低,尺寸减小,由连续网状向分离的球粒状转变。形成的Al11MM3化合物数量增多,由主要以短棒状在晶内和晶界分布向大的针状在晶界分布过渡,甚至在晶界成簇聚集。强电磁搅拌作用下,随等温搅拌温度降低,初生相尺寸变小,其形貌由球粒状加少量的玫瑰状向类球状和多边形演变;Al11MM3以类球状和细小的针状分布于晶粒和液相中。富Ce混合稀土可显著细化晶粒,改善β相的形貌和分布,降低体积分数;改变富Ce混合稀土含量可控制Al11MM3化合物的形貌和分布。电磁搅拌可同时使初生相和第二相Al11MM3细化和球粒化。     

稀土元素Gd，Nd在AM50镁合金中的固溶强化作用

通过AM50合金与稀土元素Gd、Nd的合金化,得到AM50—6Gd-2Nd（wt．％）镁合金。研究发现,固溶处理使得铸态组织中粗大的晶间共晶相溶解于基体中,充分实现了稀土元索固溶强化的作用。这种组织的优化导致了合金强度及塑性的明显提升,合金的断裂模式从准解理转变为微孔聚集型塑性断裂模式。     

Ce对Mg-Al-Zn系合金焊接接头显微组织及力学性能的影响

研究了Ce对Mg-Al-Zn系合金焊接接头显微组织及力学性能的影响,结果表明,稀土Ce对改善AZ31、AZ61合金接头强度及提高接头有效系数有明显作用,添加1.0%Ce将使AZ31合金的焊接接头有效系数由0.66提高到0.81。Ce能改善Mg-Al-Zn合金焊接性的原因是Ce与Al形成高熔点的Al4Ce相,减少了粗大的Mg17Al12相的数量并细化了焊缝区的晶粒。通过分析AZ31、AZ61Ce镁合金焊接熔池的特点和结晶过程,获得了焊缝边缘区域依托母材未熔晶粒形核与长大的联生生长机制。     

Measurement of solubility and density of water + lithium bromide + lithium chloride and water + lithium bromide + sodium formate systems

Solubility of aqueous solutions containing lithium bromide + lithium chloride and lithium bromide + sodium formate were measured (LiBr/NaHCO₂ = 2 and LiBr/LiCl = 2 by mass ratio) at different temperatures. Visual polythermal method was used in the temperature range of (283.15–340.15) K and mass fraction range of (0.4–0.8). Also density of mentioned systems was reported in the temperature range of (288.15–333.15) K. Each set of experimental measurements were correlated using least-square regression as a function of temperature. Our results indicate that solubility of LiBr + LiCl is higher than LiBr and its density is lower than density of aqueous solution of LiBr.     

Electrical characterization of Si+ and Si+/P+ implanted N+P+In0.53Ga0.47As junctions

In this communication, we present I–V and admittance spectroscopy measurements of shallow n⁺p junctions into p-InGaAs made by Si⁺ implantation, including a complete study of the conduction mechanisms as a function of temperature. The effect of P⁺ co-implantation is also analysed. The I–V characteristics of both junctions show that recombination in the space-charge zone is the dominant transport mechanism in forward bias, with ideality factors around 1.5 at 300 K that increase with decreasing temperature of measurement. Activation energies of the reverse saturation current are obtained at room temperature, being 0.5 eV and 0.4 eV for Si⁺ and Si⁺P⁺ implanted diodes, respectively, indicating that recombination currents occur through a near midgap center. Reverse current–voltage measurements show a higher conduction in the P⁺ co-implanted junction due to a higher concentration of traps. In both types of junctions, the reverse characteristics can be fitted to a thermally-activated trap-assisted tunneling mechanism at low bias, involving traps at 0.41 eV and 0.44 eV for Si⁺ and P⁺ co-implanted junctions, respectively, whereas different trap-assisted tunneling processes dominate at medium and high bias. The small signal analysis show a clear difference between the two types of junctions. The use of Kramers–Kronig transforms on the admittance spectroscopy data reveals the presence of a defect level at 0.35 eV in both types of junctions, probably assigned to Zn, the native acceptor present in the p-InGaAs. Another trap level at 0.30 eV is detected at the P⁺ co-implanted junctions, not appearing in the Si doped junctions, which could probably be due to damage produced by the co-implantation.     

La3+ and Ce3+ Doping of Hard-Magnetic Ferrites

Rare-earth-doped ferrites with the general formula M_{1 – x} R _x · nFe₂O₃ (M = Ba, Sr, Pb; R = La, Ce; x = 0–0.1; n = 4–6) are prepared by solid-state combustion synthesis. The effects of the doping procedure (before or after combustion synthesis), dopant content, and heat-treatment conditions on the magnetic and mechanical properties of the ferrites are examined. The results indicate that doped materials can be used to fabricate permanent magnets with enhanced density, remanence, and energy product. In addition, rare-earth doping improves the strength of the ferrite materials, eliminating their main drawback—inherent brittleness.     

Mechanochemical fabrication of C (matrix) + Cu + Si + W + Mo nanocomposites

Using magnesiothermic reduction of WO₃, MoO₃, SiO₂, and CuO through mechanochemical activation, we prepared high-purity (∼99.3%) nanopowders with a particle size from 9 to 350 nm for the fabrication of functional materials and nanocomposite systems for anode electrodes of lithium ion (polymeric) batteries.     

The thermal conductivity of n-hexadecane+ ethanol and n-decane+butanol mixtures

New absolute measurements, by the transient hot-wire technique, of the thermal conductivity of n-hexadecane and binary mixtures of n-hexadecane with ethanol and n-decane with butanol are presented. The temperature range examined was 295–345 K and the pressure atmospheric. The concentrations of the mixtures studied were 92% (by weight) of n-hexadecane and 30 and 70% (by weight) of n-decane. The overall uncertainty in the reported thermal conductivity data is estimated to be ±0.5%, an estimate confirmed by the measurement of the thermal conductivity of water. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to correlate and predict the thermal conductivity of these mixtures, as a function of both composition and temperature.     

白钙沸石的制备及其对Cs+、Sr2+离子的吸附性能

通过水热合成法,制备了白钙沸石,同时研究了合成矿物对于Cs+和Sr2+的离子吸附性能。研究表明,采用氧化钙、氧化硅、氧化铁、氧化镁和氧化铝作为原料,适当配比,在240℃、保温7天水热反应条件下,可制得白钙沸石以及掺杂白钙沸石。白钙沸石对Sr2+的吸附性能优于对Cs+的吸附性能。掺杂一定量的Mg2+、Al3+或Fe3+可以改善白钙沸石的吸附性能。