稀土元素Nd对ZM6镁合金力学性能的影响

笔者主要研究稀土元素Nd对ZM6镁合金力学性能的影响,通过浇筑不同Nd含量的ZM6试棒及显微组织腐蚀试样来研究其显微组织、成分分析,找出镁合金在室温下最高抗拉强度时的Nd含量。Nd可在一定程度上细化ZM6合金组织,且热处理后的细化效果与铸态相近,但热处理后出现了富锌相颗粒,随Nd含量的增加,富锌相颗粒尺寸增大。试验结果表明,局部基体Nd、Zr、Zn的含量极低,Mg的含量几乎是百分之百,加入的合金元素主要集中在晶界上,从成分分析以及Mg的相图来看,晶界上的析出物为Mg、Nd、Zn组成的Mg_(12)(Nd,Zn)相。热处理能改善ZM6合金晶界状态,使Nd元素在组织内弥敞分布,从而提高晶界强度,使合金性能提高。ZM6合金的硬度随着Nd含量的增加而增加。随着Nd含量的增加,合金的室温抗拉强度增加。当Nd含量超过3.0%时,ZM6镁合金的室温拉伸强度有下降趋势。     

聚乳酸/聚碳酸酯合金的机械性能和耐热性能研究

研究了聚碳酸酯(PC)含量变化对聚乳酸/聚碳酸酯(PLA/PC)合金机械性能和热变形温度的影响规律。研究结果显示,随PC含量的增加,PLA/PC合金的热变形温度提高,PC含量增加至50%时,热变形温度达到138℃。从相差显微镜的观察结果我们发现,PC含量较少时,PC作为分散相分散在PLA基体中,PC含量达到50%时,PLA由连续相变为分散相,而PC由分散相变为连续相;并且随着PC含量的增加,PLA/PC合金中两相的相容性越来越差。PLA/PC合金的力学性能测试结果显示:PC含量的变化对PLA/PC合金拉伸强度和弯曲强度的影响不大;而随PC含量的增加,PLA/PC合金的断裂伸长率和有/无缺口冲击强度先减小后增大。     

高强钛合金板材的室温成形

<正>科研人员对经820℃退火处理后的2 mm厚高强Ti-6Al-4V合金板材在室温下的成形及回弹行为进行了实验室研究。实验选用的Ti-6Al-4V合金板材的原始组织由93.86%的等轴α相和6.14%的β相组成,平均晶粒尺寸为1.3μm±0.7μm。室温拉伸测试结果显示,其各向异性较大,与轧制方向呈45°方向时,试样的屈服强度最低,延伸率较高,且当达到极     

Mn添加量对TiCrVMn合金储氢性能的影响

研究了Mn含量对(Ti_(0.28)Cr_(0.50)V_(0.22))_(1-x)Mn_x(x=0,0.06,0.1,0.14)合金储氢性能的影响,结果表明:合金中Mn含量低于6％(atom)时,合金为单一的体心立方固溶体,随Mn量增加,合金放氢压力平台升高,PCT曲线斜率减小,但储氢容量变化不明显;当合金中Mn含量超过6％(atom)时,合金由固溶体和TiMn两相组成,合金的放氢平台压力虽然随Mn量增加而升高,但储氢容量却明显降低。(Ti_(0.28)Cr_(0.50)V_(0.22))_(1-x)Mn_x合金储氢性能变化原因,与合金中添加Mn元素改变了固溶体相的晶格常数和晶胞体积有关。     

ABS树脂中胶含量对PC/ABS合金性能及微观结构的影响

采用胶含量(质量分数,下同)为60％的丙烯腈-丁二烯-苯乙烯接枝共聚物(ABS)接枝粉料与苯乙烯-丙烯腈共聚物(SAN)以不同比例进行共混,制备了胶含量范围为10％～55％的ABS树脂.将胶含量不同的ABS树脂与聚碳酸酯(PC)以30/70、50/50、70/30的质量比利用熔融共混技术,制备了组成不同的PC/ABS共混物,考察了ABS树脂胶含量对不同组成的PC/ABS合金性能的影响.研究结果表明:随着ABS树脂中胶含量的增加,ABS树脂的冲击强度不断提高,屈服强度、模量及熔体流动速率逐渐降低.随着PC/ABS合金中ABS胶含量的增加,合金的冲击强度显著提高,ABS树脂中胶含量大于30％以后,合金的冲击强度变化不大,且3种组成的PC/ABS合金的冲击强度相差不大.合金的屈服强度、模量及熔体流动速率却随着ABS中胶含量的增加不断降低,其中组成为30/70的PC/ABS合金最低.利用扫描电镜观察了PC/ABS组成为70/30合金的微观结构,研究表明,ABS树脂形成连续相,PC为分散相,随ABS树脂胶含量的增加,合金的相形态变得更精细.     

电镀Fe-Cr-Ni及Fe-Ni合金相组成研究

用x-射线衍射法测定了Fe-cr-Ni合金镀层及Fe-Ni合金镀层的相组成。这些合金镀层的相组成很复杂。一般含有Cr、Fe碳化物、富Cr、富Ni、富α-Fe及γ-NiFe相。在Fe-Cr-Ni合金镀层中,Fe含量80％左右时,合金含(Cr、Fe)_7C_3,相。当合金中Ni的含量增加时,富Ni相消失,而合金中Cr含量增加时有Fe-cr相形成。这种不形成均匀固溶体合金相的现象称为相分离。     

烧结压力对生物医用Ti-Nb-Zr-Mn合金显微组织与力学性能的影响

以单质金属粉末为原料,采用机械合金化(MA)和放电等离子烧结(SPS)法制备了力学性能优异的生物医用Ti24Nb4Zr3Mn合金,研究了烧结压力对Ti24Nb4Zr3Mn合金显微组织和力学性能的影响.结果表明,不同烧结压力下获得的Ti24Nb4Zr3Mn合金均为体心立方β相和斜方马氏体α"相双相合金.随着烧结压力的增加...     

Zr/Mn元素替代及退火处理对汽车电池用储氢合金电化学性能的影响

采用真空感应熔炼的方法制备了(La,Mg)_1-xZr_x Ni_3.3-2xMn_2x(x=0、0.1、0.2)储氢合金，研究了Zr/Mn元素替代和退火处理对储氢合金相结构、显微形貌和电化学性能的影响。结果表明：Zr/Mn元素替代后储氢合金中出现了新相La Mg Ni₄相，退火处理后储氢合金中La Ni₅相和La Mg Ni₄相含量减小，(La,Mg)₂Ni₇相和(La,Mg)₅Ni₁₉相含量增加；当储氢合金中x值从0增加至0.2时，储氢合金电极的活化次数N_a逐渐减小、最大放电容量C_max逐渐降低，且相同x值时退火态储氢合金电极的C_max要高于铸态储氢合金电极。Zr/Mn元素替代会提高储氢合金电极的24 h荷电保持率、降低循环100次后的容量保持率，且退火后二者都会相对提高；铸态储氢合金电...     

PVC/ABS合金性能研究

对软质聚氯乙烯(PVC)/丙烯腈-丁二烯-苯乙烯共聚物(ABS)合金的力学性能、加工性能进行了测试,并利用差示扫描量热仪和扫描电镜对试样断面结构以及两相的相容性进行了表征。结果表明:随着ABS含量的增加,PVC/ABS合金的相容性和加工性得到改善;当ABS含量在20~30份时,随着ABS含量的增加,合金的断裂伸长率、拉伸强度都有适当的提高。     

溴化聚苯乙烯对PBT/EPDM合金的阻燃改性

采用溴化聚苯乙烯阻燃剂对PBT/EPDM合金进行改性,研究了阻燃剂含量对PBT/EPDM合金力学、阻燃性能和热稳定性的影响.研究结果表明:随着阻燃剂含量的增加,PBT/EPDM合金的阻燃等级、极限氧指数均有显著提高.TGA曲线显示,随着阻燃剂的增加,起始失重温度和最大热失重速率温度均向高温移动,且最终的残留率均明显增多.同时,随着阻燃剂的增加,PBT/EPDM合金的拉伸强度呈先上升后下降趋势,合金的断裂伸长率和冲击强度呈下降趋势.     

铝合金表面脱氧化物/出光处理技术研究

以含有较多较难去除的含铜金属间化合物黑色颗粒的铝合金2024-T3为研究对象,通过金相观察,开发了一种用于碱蚀后铝合金表面脱氧化物/出光的浓–稀两阶段处理技术。室温下先用含有5.0g/LNaHF2和100g/LFe2(SO4)3的30%(质量分数)硝酸溶液处理7min,然后用含有0.5g/LNaHF2的1%(质量分数)硝酸溶液处理4min,可有效去除碱洗后铝合金表面的黑色氧化物,形成无污染的氧化铝薄层。该工艺简单、快速、成本低,为后续转化反应的顺利进行奠定了基础。     

Electrochemical behavior of Al-brass in polluted natural seawater

An electrochemical study on Al-brass alloy (76% Cu, 22% Zn, 2% Al) was conducted. The study focused on determining the corrosion susceptibility of the alloy in seawater in the absence and presence of manganese and chlorine in a stagnant condition. The results show that the addition of Mn from 0.5-5 ppm in seawater increases the corrosion current density of the Al-brass compared to samples tested only in seawater. In contrast, the addition of Cl₂ from 0.5-4 ppm slightly improves the corrosion resistance of the alloy in seawater.     

Ergodicity of fine-grained canonical relaxor ferroelectric (Bi0.5Na0.5)1-xBaxTiO3 films

The drastic reduction in dimensions in thin films, together with the low crystallization temperatures used, normally results in a large reduction in the grain size. It has been reported that relaxor ferroelectric states are stabilized at room temperature for fine-grained ceramics and films that behave as normal ferroelectrics for large grains. In this work, the effects of the grain size reduction on the relaxor characteristics are analyzed for a composition that is already a canonical relaxor with a nonergodic state at room temperature: (Bi_0.5Na_0.5)_1-xBa_xTiO₃ (BNBT). The comparison of the local polar ordering within BNBT grains studied with piezoresponse force microscopy on large-grained ceramics and fine-grained thin films shows that the development of stable long-range ferroelectric order with the application of an electric field is hampered due to the small grain size of the grains. The ergodic character of the high-temperature phase is thus stabilized at room temperature, following a similar mechanism as the one discussed for other noncanonical relaxors.     

Spin valve effect in sputtered FL-MoS2 and ferromagnetic shape memory alloy based magnetic tunnel junction

In the last decade, two-dimensional (2D) transition metal dichalcogenides have been introduced with great significance in the spintronic devices for their extraordinary electrical, optical, and spin-dependent properties. In this work, we have fabricated a few-layer molybdenum disulfide (FL-MoS₂) (~6 nm) as a non-magnetic spacer layer in Ni–Mn–In/FL-MoS₂/Ni–Mn–In magnetic tunnel junction (MTJ) using DC magnetron sputtering. FL-MoS₂ thin film sandwiched between two ferromagnetic shape memory alloy based electrodes exhibit semiconducting behavior, confirmed by current-voltage (I–V) characteristics and temperature dependent resistance measurement. The fabricated MTJ shows spin valve effect in the presence of an external magnetic field. The tunneling magnetoresistance (TMR) has been recorded in 10 K–300 K temperature range. The highest TMR ratio of 0.51% was obtained at a low temperature ~10 K, corresponding to the spin polarization of ~5%. This TMR ratio reduces to a value of 0.032% as the temperature of the device increases up to 300 K, displaying a finite TMR at room temperature. A detailed study of thickness and temperature-dependent magnetization versus magnetic field (M ? H) hysteresis loops of Ni–Mn–In thin films has been performed to understand the complex TMR behavior. The present study paves the way for the use of sputtered FL-MoS₂ and ferromagnetic shape memory alloy in ultrafast spintronics for advanced magnetic devices application.     

成型条件对CuO-Ce0.5Mn0.5O2成型载体性能的影响

以CuO-Ce0.5Mn0.5O2粉体为原料,采用挤条成型法制备了相应的成型载体,考察了成型过程中不同胶溶剂及其用量、焙烧时间及焙烧温度对该成型载体性能的影响,并对成型载体进行了抗压强度测试,且通过BET、SEM等手段对载体结构进行了表征,同时对相应的载钯催化剂进行了活性评价。结果表明,胶溶剂的添加可以不同程度地提高载体的抗压强度,改善载体的孔径分布,其中,柠檬酸作为胶溶剂时载体的抗压强度最大;使用硝酸作为胶溶剂时载体孔径分布向中孔方向集中;不同胶溶剂对载体的比表面积影响不大。固定硝酸质量分数3%,m(柠檬酸)∶m(胶粘剂)=4∶6,在600℃焙烧5 h可得到抗压强度98.65 N/cm2、比表面积为36.938 m2/g、孔容0.177 cm3/g的载体,对应载Pd(占载体质量的0.5%)催化剂的催化活性较高,在反应总压5 MPa,p(CO)∶p(O2)=94∶6、反应时间4 h、反应温度65℃的条件下,DPC收率9.91%。     

Preparation of Grain-Oriented Sr0.5Ba0.5Nb2O6 Ferroelectric Ceramics by Magnetic Alignment

The properties of polycrystalline ceramics are strongly influenced by their crystallographic texture. In this study, highly grain-oriented tungsten bronze structure ferroelectric ceramics, Sr_0.5Ba_0.5Nb₂O₆, were successfully fabricated by magnetic alignment and gelcasting techniques using only the conventional solid-state-synthesized starting powder. Spherical Sr_0.5Ba_0.5Nb₂O₆ particles were aligned according to their anisotropic magnetic property in 40 vol% slurry in a 10 T magnetic field, and then in situ locked by polymerization via a gelcasting technique for 30 min. A 〈00 l 〉-axis orientation perpendicular to the magnetic field direction ( B ) was obviously observed in the green compact and sintered sample. The sintered Sr_0.5Ba_0.5Nb₂O₆ sample contained equiaxial grains and reached 98% theoretical density. Compared with the sample with randomly oriented grains, the magnetically aligned sample showed an enhanced with dielectric constant in the ⊥ B direction (1100 versus 750 at room temperature and 4300 versus 2800 at Curie temperature). This new method is readily applicable to other ceramics with tungsten bronze structure, and is expected to facilitate mass preparation of large and dense grain-oriented ceramic materials.     

Study of Mn doped multiferroic DyFeO3 ceramics

Structural, Raman, room temperature and temperature dependent leakage current density, dielectric, magnetization and room temperature Mossbauer studies of Mn doped DyFeO₃ (i.e., DyFe_1−xMn_xO₃; x=0 to 0.5) polycrystalline materials prepared through sol-gel route are reported in this paper. From Rietveld refinement of x-ray diffraction (XRD) patterns it is found that all the samples are formed in single phase without any detectable impurity. The Raman modes with doping are consistent with literature of such doped orthoferrites. From the room temperature (RT) leakage current density (J-E) measurements, it is observed that leakage current density increases with Mn doping concentration, which is explained in terms of microstructure. The leakage current density is found to decrease with the decrease of temperature in each sample as observed from low temperature leakage current density (J-E) measurements. Further, activation energy is calculated from the temperature dependent J-E data. The dielectric loss data is observed to exhibit frequency dependence and the activation energy obtained indicate the contribution from space charges. From temperature dependent magnetization data, it is found that with the increase of Mn content, the spin reorientation (SR) transition temperature (T_SR) moves towards higher temperature. From M-H curves at 10 K and 300 K with different Mn doping concentrations, it is found that saturation Magnetization (M_S) decreases with increase of Mn doping. Room temperature Mossbauer data shows the presence of Fe³⁺ state and the gradual decrease of internal hyperfine filed with increase of Mn content.     

KNN based high dielectric constant X9R ceramics with fine grain structure and energy storage ability

In this study, SrZrO₃ doped K_0.5Na_0.5NbO₃ ceramics with Cu, Sn, and Mn as sintering aid are prepared to modulate the temperature stability by conventional solid-state sintering, and samples are denoted as KNNC-100xSZ, KNNS-100xSZ, and KNNM-100xSZ, respectively, where x is the doping amount. The average grain size of the KNNC-12.75SZ sample was ~150 nm. The dielectric constant of KNNC-13.00SZ was 2072 and its dielectric loss was 1.8% at room temperature, with a wide temperature stability range from −55°C to 220°C satisfying the X9R criteria. The discharge energy density of KNNC-12.75SZ reached 1.47 J/cm³ at room temperature; therefore, the modified KNN is a promising candidate for X9R dielectrics with a fine grain structure and potential anti-reduction capability due to the absence of variable valence elements. The modified KNN can also be applied to energy storage capacitors subjected to high working temperatures.     

A New Strategy for the Preparation of Terephthalic Acid by the Aerobic Oxidation of p‐Xylene using N‐Hydroxyphthalimide as a Catalyst

A new methodology for the production of terephthalic acid ( 3 ) by the aerobic oxidation of p‐xylene ( 1 ) using a combined catalytic system of N‐hydroxyphthalimide (NHPI)/Co(OAc) ₂/Mn(OAc) ₂was developed. The oxidation of 1 under a dioxygen atmosphere in the presence of a catalytic amount of NHPI/NHPI(OAc) ₂/Mn(OAc) ₂at 100 °C for 14 h afforded terephthalic acid in 82% yield. Removal of Mn(OAc) ₂ from the catalytic system resulted in considerable reduction in the yield of 3 . When the oxidation of 1 was carried out under a pressure of air (30 atm) at 150 °C, the reaction was completed within 3 h to give 3 in 84% yield. The oxidation of p‐toluic acid ( 2 ), which can be prepared by the oxidation of 1 using the NHPI/NHPI(OAc) ₂ system at room temperature, by the NHPI/NHPI(OAc) ₂/Mn(OAc) ₂system under pressure of air (30 atm) at 150 °C gave 3 in 95% yield. N‐Acetoxyphthalimide (NAPI) was found to require a lower catalyst loading than NHPI, but oxidation with NAPI was slower. Thus, the oxidation of 1 catalyzed by NAPI (5 mol %)/Co(OAc) ₂ (0.5 mol %)/Mn(OAc) ₂ (0.5 mol %) under a dioxygen atmosphere (1 atm) in acetic acid at 100 °C gave 3 in 80% yield.     

过滤-树脂吸附法处理焦化废水的研究

采用高温炉渣过滤 ,再用南开牌 H - 10 3大孔树脂室温下以 4BV/h流速吸附处理含酚 5 2 0 mg/L、COD 32 0 0 m g/L的焦化废水 ,调节废水 p H值为 6 ,处理体积为 6 0 BV ,处理出水酚含量≤ 0 .5 m g/L ,COD≤ 80mg/L ,达到国家排放标准。选用 0 .5 BV甲醇做脱附剂 ,室温下以 2 BV/h流速进行洗脱再生 ,脱附率达 99%以上。经 10 0次循环使用 ,树脂性能不变。脱附剂脱附达饱和后 ,再通过蒸馏回收甲醇和其中的酚 ,残渣进行焚烧处理