共查询到20条相似文献，搜索用时 62 毫秒
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不同硅含量Cr3Si基合金的抗氧化性研究 总被引：1，自引：0，他引：1
用循环氧化法研究了Cr-25%Si（at%）、Cr-23.1%Si(at%)和Cr-20%Si(at%)三种以Cr3Si为基的合金在850℃、1150℃和1400℃静态空气中100h的高温氧化行为。结果表明三种合金在850℃和1150℃下表现良好的抗氧化性，同时发生CrO3的挥发现象；在1400℃只有Cr-25%Si(at%) 表现有好的抗氧化性，其它两种合金氧化比较厉害。在低温下氧化，三种合金生成以Cr2O3为主的氧化层；在高温下氧化生成SiO2和Cr2O3混合体为主的氧化层，其中Cr-25%Si(at%)合金的氧化层为SiO2为主的SiO2和Cr2O3混合体，另外两种合金的氧化层以Cr2O3为主。以Cr2O3为主的氧化层，在1150℃下具有较好的抗氧化性，而在1400℃只有形成以SiO2为主的氧化层才上有较好的抗氧化性。 相似文献
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激光重熔Al2O3+13%wt.TiO2-SiC纳米复合陶瓷涂层组织 总被引：2，自引：0，他引：2
采用激光重熔等离子喷涂陶瓷涂层技术，以纳米SiC材料为填料，在45钢表面，制备了Al2O3＋13％wt．TiO2-SiC纳米复合陶瓷涂层。用X射线衍射、扫描电镜研究了纳米SiC复合陶瓷涂层的微观组织结构。结果表明，重熔层由仪-Al2O3、TiO2、Si、SiC以及新相Al4C3组成。在激光的作用下，原等离子喷涂层的片层状组织结构得以消除；纳米SiC颗粒填充在大颗粒Al2O3或TiO2之间。 相似文献
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程奕天 《深圳职业技术学院学报》2021,(1)
采用Al+α-Al2O3复合材料及Al100-xCrx(x=10,20,30)合金作为靶材,用反应磁控溅射将α型籽晶引入氧化铝基薄膜中,研究了籽晶对氧化铝基薄膜的元素比例、相组成、结构特征、表面形貌及纳米硬度的影响.结果显示,在550℃时溅射Al+α-Al2O3复合靶所得的薄膜由单相的α-Al2O3组成,而在同一温度下采用Al70Cr30合金靶所制得的薄膜中检测到α-(Al0.7Cr0.3)2O3固溶体.纯α-Al2O3薄膜及α-(Al0.7Cr0.3)2O3固溶体薄膜的纳米硬度分别达到~23.5GPa和~28.5GPa. 相似文献
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采用包渗法在钼表面原位制备了（Mo,W）Si2-Si3N4复合涂层,考察了其在大气中于500℃和600℃等温循环的氧化性能,利用XRD和SEM等研究了其组织形貌.结果表明：（Mo,W） Si2-Si3N4涂层具有良好的低温抗氧化性,其在空气中500℃和600℃氧化480 h的氧化速率分别为0.0145 g/（m2·h）和0.0191g/ （m2·h）,归因于涂层氧化表面形成了致密的SiO2膜. 相似文献
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孙龙 《实验室研究与探索》2005,24(8):19-20
介绍了用于压力测量的新型bridgman装置，并结合X射线衍射分析技术（XRD）研究了常压、高压条件下Zr41．2Ti13．8Cu12．5Ni10Be22．5块体非晶合金的晶化。结果表明，在相同的退火条件下（400℃，退火3小时），增大压力有利于Zr41．2Ti13．8Cu12．5Ni10Be22．5块体非晶合金的晶化；压力越大获得晶化相的晶粒尺寸越大。 相似文献
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用热重分析(TGA)研究了Co-40Cr合金及其离子注钇样品在1 000℃空气中的恒温氧化动力学规律.用扫描电镜(SEM)对不同样品表面Cr2O3氧化膜的形貌进行了观测.用声发射(AE)方法对合金表面氧化膜在恒温生长阶段和空冷阶段的开裂与剥落进行了实时监测,根据相应的氧化膜开裂模型,对声发射信号在时域和数域上的分布情况进行了分析.结果表明离子注钇降低了Co-40Cr合金的恒温氧化速率,并提高了合金表面Cr2O3氧化膜的抗开裂和抗剥落性能.离子注钇提高合金抗氧化性能的主要原因在于钇细化了合金表面Cr2O3氧化膜的晶粒,提高了氧化膜的高温塑性和蠕变能力,并且显著降低了Cr2O3/Co-40Cr界面缺陷的数量和大小. 相似文献
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用高能球磨制备等原子比铁(Fe)钴(Co)镍(Ni)铁镍钴复合粉体,用激光熔覆方法制备复合粉铁镍钴体合金涂层。用OM、HV、XRD、SEM、EDS、SVET等对复合粉体及熔覆合金层进行了组织表征及性能测试。结果表明,复合粉体经3 h高能球磨后均匀细化,平均尺寸从35μm到15μm左右,镍晶格有一定畸变,有新相Co3Fe7产生;用优化后的激光熔覆工艺激光功率2000 W,激光扫描速度10 mm/s,保护Ar气流速度12 L/min制备中熵熔覆合金FeCoNi涂层;XRD、SEM、EDS表明熔覆层合金是单一的面心立方(FCC)相,Fe,Co,Ni成分均匀分布,没有金属间化合物产生;熔覆层的HV约是243,在0.5 mol/L氯化钠溶液中熔覆层的SVET表明耐腐蚀性能好。 相似文献
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钟平 《赣南师范学院学报》1991,(Z1)
本文研究了含有不同合金元素的Cr—Ni—Fe合金在600℃、Ps_2为48mmHg的硫蒸气下的腐蚀行为,这些合金在此条件下出现了以硫化为主的高温腐蚀。腐蚀产物以多层金属硫化物为主,也夹杂着少量金属氧化物。结果表明:当C含量在0.15％～0.45％时,合金的腐蚀速度在含C量为0.3％时有最小值,合金元素Cr含量的提高,使合金的抗硫腐蚀性能加强,合金元素Ni含量的提高,降低合金的抗硫腐蚀性能;而合金元素Al的加入,由于在合金表面形成了保护性较好的Al_2O_3及CrS的混合层,则显著提高了合金的抗硫腐蚀性。 相似文献
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考察了不同Ni担栽量的Ni/α-Al2O3催化剂对甲烷部分氧化的催化性能的影响和助剂Ce对Ni基催化剂性能的调变作用.采用沉淀法以NH3·H2O、Al(NO3)3·9H2O和Ni(NO3)3·6H2O为原料合成Ni/α-Al2O3凝胶,经过高温煅烧制备纳米级催化剂Ni/α-Al2O3粉末.通过固定床反应器进行催化剂的活性评价,并对其进行XRD和TPR分析.结果表明:8%Ni(质量分数)的Ni/α-Al2O3催化剂催化活性最佳,同时添加稀土Ce有助于提高催化剂的活性、选择性和稳定性. 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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陈美曦 《山东教育学院学报》2008,23(2):103-107
Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language. 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献