一种镍基合金在900和1000℃的高温氧化行为

采用X射线衍射(XRD),扫描电镜(SEM)及能谱(EDAX)等方法,研究了Cr5.0 Co8.0 Mo0.9W5.5 Ta7.4 Al6.0 Re4.2合金在900和1 000℃的氧化行为。结果表明,氧化动力学曲线遵循氧化初期氧化增重速率较快,氧化期间氧化动力学曲线呈波浪式变化,且呈现氧化温度越高波浪式越明显的特征。在900℃氧化300 h后合金表面氧化物膜分为3层,外层为Ni O、Ni2Cr2O4、Ni2Co O4和Cr Ta O4;中间层为平直的Al2O3层,内氧化层为Al2O3,氧化期间,分布在外层的Cr Ta O4抑制基体中Al向外扩散,并抑制氧化膜的生长,使氧化速度降低。1 000℃时合金表面的氧化物膜分为2层,外层为Ni O、Ni2Cr2O4、Ni2Co O4和Cr Ta O4;内氧化层为Al2O3。在900和1 000℃氧化期间,合金均发生元素Al的内氧化和内氮化,与外氧化膜相邻的区域为元素Al的内氧化区,远离外氧化膜的基体内部形成元素Al的内氮化区,随氧化温度升高,内氧化区和内氮化区的深度增加,内氧化物和内氮化物的尺寸增大。     

晶粒细化对Cu-45Ni-30Cr合金抗高温氧化性能的影响

为了探讨晶粒细化对三元复相合金抗高温氧化行为的影响,采用机械合金化热压制备了纳米晶Cu-45Ni-30Cr 合金,并以热重法及SEM/EDX研究了其在700,800 ℃、0.1 MPa纯氧气中的氧化行为.结果表明: Cu-45Ni-30Cr合金为三相组织,每一相中Cr的含量均较高;合金的氧化动力学较复杂,其瞬时抛物线速率常数随时间延长而降低;晶粒细化降低了合金表面由混合内氧化膜向单一Cr2O3外氧化膜转变的临界浓度,促使Cu-45Ni-30Cr合金表面由混合内氧化膜向单一选择性Cr2O3外氧化膜转化.     

Fe-Cr合金预氧化后涂覆KCl盐膜的热腐蚀行为

为开发新型耐高温氯化腐蚀合金及防护涂层,对比研究了750 ℃下Fe-20%Cr(质量分数)合金直接涂KCl和预氧化后再涂KCl盐膜条件下的热腐蚀行为.采用XRD及EPMA对其现象进行分析,结果表明:预氧化生成的初始Cr2O3层对Fe-20%Cr合金在KCl盐膜下的热腐蚀有一定的保护作用,表现为降低腐蚀速率,减轻腐蚀对基体的破坏并维持氧化膜的完整性;Fe-20%Cr在750℃KCl盐膜下的腐蚀产物主要是Fe2O3,Cr2O3以及少量K2Fe2O4和K2Cr2O7等复杂氧化物,其中Fe2O3分布在氧化膜外层,而Cr2O3集中于靠近氧化膜/基体界面的氧化膜内侧.用热力学理论解释了这种氧化膜的形成原因.     

新型Cr19Ni28Ti合金空气中高温氧化的研究

利用增重法研究了新型Cr19Ni28Ti合金在700、800和900℃空气中的高温氧化行为,绘制了高温氧化动力学增重曲线,并利用XRD、SEM和EDS对氧化膜进行了表征。结果表明,700、800和900℃氧化增重分别为0.07、0.1和0.45mg/cm2,具有良好的抗氧化性;高温氧化动力学曲线符合抛物线规律。700℃氧化100h的氧化膜主要由Mn1.5Cr1.5O4、Fe(Ni)Cr2O4和Cr2O3组成;800℃氧化后增加了产物Fe2.95-Si0.05O4;900℃氧化Ti已经开始向金属表面扩散,并与氧发生反应,生成了TiO2。     

9Cr-1Mo钢在含水蒸汽气氛中的氧化行为

研究了9Cr-1Mo(ASME T91)钢在(Ar 10%H_2O)气氛中600℃、650℃和700℃下的高温氧化行为.在恒温氧化10 h过程中,在600℃氧化遵从抛物线规律;而在650℃和700℃氧化则遵从分阶段抛物线规律,且后一阶段的速度常数高于前一阶段的;随着温度的升高,氧化速度明显增大;氧化激活能为157.2 kJ/mol.T91钢氧化时表面形成了多层结构的氧化膜,从外到内依次为Fe_2O_3、Fe_3O_4和(Fe,Cr)_3O_4;钢基体也发生了内氧化,内氧化物为FeO和Cr_2O_3.只有在700℃氧化时没有外层Fe_2O_3形成和内氧化发生.9Cr-1Mo钢氧化后冷却至室温后,氧化膜发生开裂或局部剥落.最外层Fe_2O_3与次外层Fe_3O_4间出现很大的裂隙,Fe_2O_3层容易剥落.同时探讨了9Cr-1Mo钢在含水蒸汽气氛中的氧化机制.     

喷丸对TP304H钢高温水蒸气氧化行为的作用

研究了表面喷丸形变处理对TP304H钢在610～770℃水蒸气中的氧化行为的影响,采用SEM、EDX和EPMA分析了不同喷丸强度对合金水蒸气氧化65 h的氧化膜形貌、结构和表面合金元素的影响.结果表明:表面喷丸形变可有效减缓氧化动力学速度,在0.5 MPa喷丸强度和730℃条件下提高抗氧化性能的效果最好,表面氧化膜颗粒得到细化,膜中Cr相对浓度明显提高,氧化膜物相构成由纯Fe和Fe、Cr混合氧化物转变为Cr2O3.分析认为:表面喷丸形变处理增加了合金表层区域的位错、空位等缺陷浓度,提高了氧化初期的形核密度,为Cr提供了大量短路扩散通道,降低了Cr选择氧化的临界浓度;基体表层Cr的短路扩散保证了Cr2O3膜稳定生长的扩散通量,从而抑制了Fe氧化物的形成.     

铬、铝、硅对铁基高温合金抗氧化性能的影响

采用正交设计的实验方法探讨了铬、铝、硅元素含量对铁基高温合金抗氧化性的影响规律。为获得稳定的抗氧化能力,上述各元素的含量应分别高于17%Cr,4%Al,1.5%Si。结果表明:当三元素同原子比时对铁基高温合金抗氧化性的影响次序为Si最大,Al次之,Cr最小。结构平坦、组织致密、颗粒细小均匀的氧化膜抗氧化性较好,反之较差。当氧化膜由Cr2O3,Al2O3,SiO2,Fe(Ni)Cr2O4多种氧化物组成复合氧化膜时于1250℃表现为强抗氧化性,当缺少Al2O3或SiO2时表现为弱抗氧化性。     

Ni-Cr-Co-Mo-W-Ta-Al合金在900℃和1000℃的高温氧化行为

采用X射线衍射(XRD),扫描电镜(SEM)及能谱(EDAX)等方法,研究了Ni-4.66Cr-5.87Co-7.54Mo-2.90W-4.97Ta-6.32Al合金在900℃和1000℃的高温氧化行为。结果表明,合金氧化动力学曲线遵循氧化初期氧化增重速率较快,氧化期间氧化动力学曲线呈波浪式变化,且呈现氧化温度越高波浪式越明显的特征;氧化300h后合金表面氧化物膜分为2层,外层氧化物为NiO、Ni_2Cr_2O_4、Ni_2CoO_4和CoTa_2O_6,分布在外层的CoTa_2O_6抑制基体中元素Al向外扩散,形成内层氧化物Al_2O_3。在氧化期间,合金内部生成了内氮化物AlN,且在合金内部AlN与Al_2O_3成规律性分布,与外氧化膜相邻的为元素Al的内氧化物Al_2O_3区域,远离外氧化膜的基体内部为元素Al的内氮化物AlN区域,随氧化温度升高,内氧化区和内氮化区的深度增加,内氧化物和内氮化物的尺寸增大。     

涂覆Na_2SO_4-25%NaCl盐膜的Super304H的热腐蚀行为

应用增重分析法研究涂有Na_2SO_4-25%NaCl盐膜的Super304H在650,750℃空气中的腐蚀动力学曲线,采用XRD,SEM(EDS)和EPMA对腐蚀产物、腐蚀截面形貌和元素分布进行分析。结果表明:涂覆Na_2SO_4-25%NaCl盐膜的合金在650,750℃的腐蚀动力学曲线均呈"抛物线"趋势;合金表面形成了含CuFe_2O_4的富Fe氧化物(外层)与富Cr_2O_3(内层)组成的双层氧化膜以及含有孔隙的贫Cr、富Ni的腐蚀影响区;提高腐蚀温度或延长腐蚀时间均可以导致氧化膜与基体分离甚至剥落,腐蚀影响区孔隙密度增大,裂纹向基体延伸。分析认为:腐蚀初期合金发生选择性氧化,形成多层氧化膜;复合盐的熔融破坏氧化膜的完整性,加速氧化、氯化以及硫化的交互作用,导致内硫化和内氧化。     

水蒸气温度对700℃先进超超临界锅炉候选合金GH2984氧化行为的影响

采用X射线衍射仪、扫描电子显微镜对比研究GH2984合金在750℃和850℃纯水蒸气中的氧化行为。结果表明:GH2984合金的氧化动力学遵循抛物线规律;温度升高,Cr挥发加速,外氧化和内氧化的速率急剧增加,氧化膜的组成结构发生明显的变化。750℃时,合金表面形成单层致密的(Cr,Mn)_2O_3膜;温度升至850℃,氧化膜中空洞的数量大幅增加,氧化膜转变为由薄的外层Fe_2TiO_5和厚的次外层(Cr,Mn)_2O_3及薄的内层(Nb,Mo)_2O_5组成的三层结构。Ti,Al优先于晶界处发生内氧化,分别形成TiO_2和Al_2O_3;两种内氧化产物的尺寸和数量均随温度升高而增加。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.