共查询到20条相似文献，搜索用时 375 毫秒
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以Ca（NO3）2和（NH4）2HPO4为原料，采用沉淀法合成羟基磷灰石（HAP）粉体。采用正交实验设计讨论了反应物浓度、反应温度、分散削聚乙二醇的添加量对羟基磷灰石粉体粒径的影响，并在此基础上考察了热处理温度对粉体粒径的影响。采用激光粒度仪测定粉体的粒径，并用XRD、IR等手段对粉体进行表征。实验结果表明，合成羟基磷灰石的最佳工艺条件：温度为60℃、浓度为0．8mol／L、分散剂聚乙二醇的添加量为3％。随热处理温度的升高，羟基磷灰石粉体颗粒长大并发生团聚。经XRD和IR测试结果分析表明，采用该方案可制备出纯度较高的羟基磷灰石超细粉体。 相似文献
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以自制硅酸钙（CaSiO3）和羟基磷灰石（HAP）超细粉体为原料,按照不同的比例混合、成型、煅烧制得CaSiO3-HAP复合生物陶瓷。采用X-射线衍射仪（XRD）和扫描电镜（SEM）对粉体及陶瓷样品进行物相成分和显微结构分析,并对复合生物陶瓷的收缩率、抗弯强度、断裂韧性和硬度等性能进行测定。研究结果表明：在HAP中添加一定量的CaSiO3,可以减小HAP陶瓷的收缩,并能提高其力学性能,CaSiO3含量为30wt％的CaSiO3-HAP复合生物陶瓷综合性能最佳,其抗弯强度和断裂韧性分别达到156．7MPa和2．32MPa·m^1/2,维氏硬度值达到6．5GPa,比纯HAP陶瓷的性能均有了较大的提高。 相似文献
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用溶胶-凝胶法在多孔钛基体上制备羟基磷灰石涂层,用扫描电镜(SEM)对不同处理温度和不同pH值下生成的羟基磷灰石涂层样品进行测试分析.结果表明,相同烧结温度下,pH=0.5比pH=0能够更好地促进孔数量的产生、增大HA涂层与外界环境的接触面积;pH值相同的情况下,800℃时形成的孔比600℃时形成的孔要小;失重法研究HA涂层的抗腐蚀性能结果表明,pH越低,烧结温度越高,HA涂层在HCl中抗腐蚀性能越好. 相似文献
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以CaCO3 和CaHPO4 ·2H2 O为原料 ,研究羟基磷灰石合成过程中混合料在水介质及高速球磨条件下发生的机械化学作用 .混合料球磨 1h可合成结晶良好、含碳酸根及磷酸氢根的羟基磷灰石 ,其化学组成与由骨水泥水化而成的羟基磷灰石相同 ,颗粒呈球状或短棒状 ,粒径分布范围为 2 0— 10 0 nm . 相似文献
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超细碳酸钙的制备与表征 总被引：2，自引：0，他引：2
分别以硅酸钠和硫酸锌为晶型控制添加剂，通过石灰乳碳化工艺制备超细CaCO3粉体。研究了添加剂用量对CaCO3颗粒尺寸的影响，并用TEM，XRD和TG－DTA对CaCO3粉体进行了表征。结果表明，添加0．7％－1．5％硅酸钠和0．5％－1．2％硫酸锌可分别制得颗粒尺寸为40－50m和40－60nm的球形和立方形超细CaCO3粉体。 相似文献
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羟基磷灰石是人体硬组织中主要的无机成分,与人体组织具有良好的生物相容性,并能与骨组织形成骨性结合.对不同配方的原料预先进行压制成型,采用原位反应法在1 100℃烧结70 min制备多孔生物陶瓷,并对陶瓷的物相、微观相貌及吸水率进行了研究.实验结果表明:添加Y2O3,对合成HA的反应的催化效果最好,生成的生物陶瓷性能最佳. 相似文献
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多孔羟基磷灰石生物材料的制备 总被引：3，自引：0，他引：3
在特殊的条件下，将鸭蛋壳(主要成分碳酸钙)经过“热液交换反应”转化为多孔羟基磷灰石生物材料。X射线衍射、红外光谱分析证实，制得的产物纯度高，实验测得n（Ca)／n(P)约为1．668与人骨组成相似，表明其可能具有较好的生物活性。 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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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
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Anton Franks 《English in Education》1999,33(2):39-49
This paper looks at the way drama works to bring a model of an arts curriculum into reality. He also shows how drama is valuable when discussed as a separate, autonomous subject in the school curriculum as opposed to one subsumed within English. He argues for a view of the arts and gives an example of a sequence of work in an English GCSE class based around Arthur Miller's play View from the Bridge. From this he draws out several strands about the relationship of the drama curriculum to the individual students and teachers, the school, and to culture. He also emphasises the primacy of performance in drama education. 相似文献