AACH热分解制备超细α-Al2O3粉末

以Al2(SO4)3与(NH4)2CO3为原料,采用液相沉淀法制备出前驱物碳酸铝铵(AACH),并煅烧得到超细Al2O3粉末。研究加料次序、pH值、加料方式以及表面活性剂等因素对反应产物的影响,同时分析前驱物AACH的高温相变过程。利用X射线衍射(XRD)、扫描电镜(SEM)、比表面积(BET)、热重/差示扫描法(DTA/TGA)等多种分析检测技术对粉体的性能进行表征。结果表明:只有将硫酸铝溶液雾化加入到碳酸铵溶液中,添加适量PEG1000作为分散剂,控制反应终点pH值为8以上,才能制备出粒度分布均匀、分散性能优异的前驱物AACH;而AACH的高温相变过程为:AACH→AlOOH→Al2O3(无定型)→-γAl2O3→-θAl2O3→α-Al2O3;合成的AACH于1 200℃煅烧2 h,能得到粒度分布均匀、形貌为球形且分散性良好的-αAl2O3粉体。     

超声沉淀法制备纳米A12O3粉体

将超声辐射应用于以硫酸铝铵(NH4Al(SO4)2*12H2O )和碳酸氢铵(NH4HCO3)为原料的沉淀法制备Al2O3纳米粉体的化学反应工艺过程, 制备了粒径为12 nm的α-Al2O3纳米粉体.通过SEM、TEM等分析手段研究了超声辐射对前驱体NH4Al(OH)2CO3沉淀物及最终粉体尺寸、形貌及其团聚行为的影响, 并探讨了其作用机理.结果表明 超声辐射由于其自身的空化作用不仅细化了前驱体颗粒、抑制了其间的团聚, 而且延缓了其向凝胶的转变过程, 从而有效地细化α-Al2O3颗粒, 但过高的频率却易导致颗粒间的进一步聚合.     

球形高纯氧化铝粉体的制备

以硫酸铝铵和碳酸氢铵为原料,采用碳酸铝铵热解和摩擦球化相结合的方法制各球形高纯氧化铝粉体.研究了前驱体碳酸铝铵(AACH)合成过程中反应初始时间、反应体系pH值等因素对AACH球形颗粒形貌的影响,以及AACH焙烧过程中Al2O3物相的变化情况.研究表明反应初始时间过短或过长、反应体系PH值远离AACH等电点均不利于得到球形度好的、粒径大小均一的AACH球形颗粒.研究结果显示在反应初始时间55 h、反应pH7.0±0.2时制备的前驱体为平均粒径9.42 μm、大小均一、松装密度0.49 g/cm3、安息角38.5°的流动性极好的AACH球形颗粒,经1200℃,30 min焙烧得到平均粒径8.74μm、大小均一、松装密度0.35 g/cm3、安息角52.3°的球形高纯α-Al2O3粉体.     

纳米结构Al2O3+13%TiO2热喷涂喂料的研究

纳米结构的Al2O3 13％TiO2混合粉经过球磨制浆和喷雾干燥，制得了25～50μm的球形大颗粒结构，分别采用高温电炉和高速火焰两种方式，对喷雾造粒的纳米结构Al2O3 13％TiO2颗粒进行了致密化处理，制备了适合热喷涂的纳米颗粒喂料。测试了喂料形貌、晶粒尺寸及物相成分。分析结果表明，应用高温电炉烧结造粒喂料时，在选定的温度范围内(110-1300℃)，喂料的相成分没有改变，晶粒没有显著长大；采用高速火焰烧结造粒喂料，喂料经高温快速激冷，Al2O3晶粒尺寸仍在100nm以下，但因火焰温度高(2500-3200℃)，相成分分析表明，喂料中发生α-Al2O3→γ-Al2O3及金红石TiO2→板钛矿TiO2的转变。     

碳酸铝铵热分解法制备超细氧化铝粉体

以分析纯的NH4Al(SO4)2和NH4HCO3为原料,选择合适的溶液浓度、分散剂及pH值,在合适的工艺条件下,得到NH4Al(OH)2CO3前驱体化合物.前驱体在1100℃下煅烧1h,得到粒径为80～100nm的超细α-Al2O3,Al2O3颗粒基本上呈球形,粒度均匀.研究了溶液浓度、分散剂及pH值对前驱体化合物颗粒细度的影响,用XRD法对前驱体化合物及其煅烧产物进行了表征,并研究了热处理过程中的相变化,对Al2O3多晶转变与热处理温度之间的关系进行了讨论.用SEM对Al2O3粉体的形貌、大小进行了表征.该方法工艺简单,原料易得便宜,综合成本较低,易实现工业化生产.     

添加Al_2O_3对Ti_3SiC_2复合材料性能的影响

采用反应热压烧结法制备Ti3SiC2-Al2O3复合材料,研究热压温度和Al2O3含量对Ti3SiC2-Al2O3复合材料相组成、力学性能及抗氧化性能的影响。结果表明:采用反应热压烧结,可以在1450℃烧结得到致密度高、性能良好的Ti3SiC2-Al2O3复合材料。添加Al2O3可以起到第二相增强的作用,从而提高材料的强度。随着添加量的增加,复合材料的力学性能先提高后降低,当Al2O3添加量为20%(质量分数)时断裂韧性达最大值(7.10 MPa-m1/2),当Al2O3添加量为30%时抗弯强度达最大值(512 MPa)。Al2O3在高温下与TiO2反应生成具有耐高温和高抗热震性能的Al2Ti O5,可以有效提高Ti3SiC2基复合材料高温抗氧化性能。     

Al对ZrO_2增韧Si_3N_4烧结体的相变及性能的影响

在高温 (140 0℃ )、超高压 (4.2GPa)条件下制备了Al ZrO2 (Y2 O3 ) Si3 N4 烧结体。采用XRD分析及力学强度测试等方法 ,研究了Al对ZrO2 相变能力及ZrO2 增韧烧结体作用的影响。结果表明 :在烧结体中加入 2 %Al,利用Al与N反应生成AlN可阻止Zr O N化合物生成 ,避免ZrO2 在Si3 N4 基体中被N稳定生成不可相变t′ ZrO2 ,提高ZrO2 的t→m相变能力 ,使ZrO2 起到增韧氮化硅烧结体的作用 ;当Y2 O3 含量为 2 %～ 2 .5 % (摩尔分数 )时 ,烧结体抗压强度及断裂韧性均较高 ,ZrO2 相变增韧作用最大。     

AlF3对γ→α-Al2O3相变及α-Al2O3显微结构的影响

以Al(OH)3为原料,采用烧结法,运用SEM、XRD、DSC等分析技术,研究了AlF3对γ→α-Al2O3 的相变过程及α-Al2O3显微结构的影响.结果表明:AlF3 可以显著促进亚稳相氧化铝到α-Al2O3的物相转变,在没有添加剂的情况下,γ→α-Al2O3 的相变温度为1 300 ℃,在AlF3的作用下,其相变温度只有1 150 ℃.在没有添加剂的作用下,生成的α-Al2O3是蠕虫状空间网状结晶,固相传质是主要的传质形式,在AlF3的作用下,α-Al2O3是典型的片状结晶,气相传质占主导地位.     

尿素均匀沉淀法制备超细α-Al2O3粉体

以Al2（SO4）3和CO（NH2）2为原料,通过均匀沉淀法制备出前驱物Al（OH）3,并煅烧得到超细α-Al2O3粉体。研究CO（NH2）2和Al2（SO4）3的摩尔比、Al2（SO4）3起始摩尔浓度、反应温度、反应时间等对前驱物制备的影响。利用X射线衍射仪、扫描电镜、热重/差示扫描法（DTA/TGA）等多种现代分析检测技术对粉体的性能进行了表征。结果表明：在CO（NH2）2和Al2（SO4）3的摩尔比为10：1、Al2（SO4）3起始浓度为0.05mol/L、反应温度为90℃、反应时间为60min的条件下,能得到分散性能良好、粒径为2μm左右且粒度分布均匀的球形超细α-Al2O3粉体。     

Alx-(Cr-Fe)100-x系激光烧结合金的组织及性能

对掺杂不同原子分数(80%、85%、90%、95%)的铝粉和高碳铬铁粉末混合压坯进行激光诱导自蔓延烧结,利用金相显微镜(OM)、X射线衍射仪(XRD)及硬度计、磨粒磨损机、电化学腐蚀仪等试验仪器,分析烧结合金的显微组织、物相结构及力学性能。结果表明：烧结合金物相主要为α-Al 、Al2Fe、AlFe、Fe2AlCr、Al2O3及富Al相,随着Al含量增多,富Al相Al13Fe4、Al13Cr2逐渐消失,产物相多转化为固溶体α-Al相;在Al含量为80%时,烧结合金孔隙率(1.7%)最小,烧结密度(3.35 g/cm3)最大,硬度(817.5 HV0.2)最高,烧结合金的磨损率(0.08 mg/mm2)最低;合金耐蚀性能在Al含量为90%时最好,钝化电流(110.3 μA/cm2)最小。     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

Formulas of Tension of Continuous Rolling Process

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.