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1.
采用了溶剂热法(水和乙醇做溶剂)合成出了物相和形貌可控的一维硼酸镁纳米棒.研究结果表明,在溶剂的超临界状态下,无需表面活性剂的参与,能直接合成出一维硼酸镁纳米棒.通过对不同反应阶段生成产物的XRD结构分析,表明Mg2B2O5结构的形成经历了从Mg(OH)2到MgBO2(OH)的转变;通过对相应阶段生成产物的SEM观察,表明Mg2B2O5纳米棒的形貌经历了从片状到短柱状再到棒状的演变.分析认为Mg2B2O5纳米棒的形成遵循着形核→溶解→各向异性生长→再结晶的过程.  相似文献   

2.
以浓海水、硼酸、氢氧化钠为原料,采用三元助熔剂工艺制备了硼酸镁纳米棒。应用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)以及高分辨透射电镜(HRTEM)对制备的产品进行了表征。XRD物相分析结果表明制备的产品为三斜结构硼酸镁(Mg2B2O5)。XPS表明制备的产品中Mg、B、O的摩尔比为1∶1.02∶2.51,且价态分别为+2,+3,-2,与Mg2B2O5化学计量比以及价态一致。SEM和HRTEM显微图像表明合成的产品为纳米棒,最后对生长过程进行了初步探讨。  相似文献   

3.
向聚苯乙烯材料中添加阻燃剂可提高其阻燃性能.本文提出了一步沉淀合成片状纳米硼酸锌阻燃剂的新方法.采用Na284O7·10H2O和Zn(N03)2·6H2O为原料,通过一步沉淀法合成了片状纳米4ZnO·B2O3·H2O,并通过X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、傅里叶红外光谱仪(FT—IR)和热重一差热分析(TG—DTA)对不同反应条件下合成产物的物相和形貌进行了表征.结果表明,反应时间是影响合成的重要因素;'-3Na2B4O7·10H2O和Zn(NO3)2·6H2O的摩尔比为1:2、反应温度为70℃、反应时间为8h时,合成的纳米4ZnO·B2O3·H2O呈片状,直径为50~100nm,性能最优.将片状纳米4ZnO·B2O3·H2O添加到聚苯乙烯中,考察其阻燃性能.实验结果表明:与以相同方式添加到聚苯乙烯的商业化纳米2ZnO·382O3·3.5H2O相比,片状纳米4ZnO·B2O3·H2O的加入显著提高了燃烧后碳残量,说明用本文方法合成的片状纳米硼酸锌具有良好的阻燃性能.  相似文献   

4.
以Bi(NO3)3·5H2O,Nd(NO3)3·6H2O和Ti(OC4H9)4为原料,NaOH为矿化剂,聚乙烯醇-124(PVA-124)为模板剂,采用水热法在2OO℃经48h合成了铋层状钙钛矿结构Bi3.15Nd0.85Ti3O12(BNdT)纳米棒。利用X射线衍射(XRD)、透射电子显微镜(TEM),选区电子衍射(SAED)和扫描电子显微镜(SEM)研究产物的物相和显微结构特征.结果表明合成的BNdT纳米棒为单晶,直径约10~200nm,长度达数微米。Raman光谱分析表明,Nd离子取代了类钙钛矿层中A位的Bi。  相似文献   

5.
刘奕  钱逸泰 《无机材料学报》2007,22(6):1139-1141
以醋酸为酸化剂,Mn(CH3COO)2·4H2O和NH4VO3为原料,在180℃反应18h,经水热制备了MnV2O6纳米片.利用X射线衍射(XRD)、场发射扫描电镜(FESEM),透射电子显微镜(TEM)和X射线光电子能谱(XPS)对产物进行了表征,该产物由宽约0.85μm,长度约1.7μm,厚度平均为100nm的纳米片构成.  相似文献   

6.
半化学法制备0.80Pb(Mg1/3Nb2/3)O3-0.20PbTiO3陶瓷的反应机理   总被引:4,自引:0,他引:4  
采用半化学法制备了纯钙钛矿相的0.80Pb(Mg1/3Nb2/3)O3-0.20PbTiO3(简称为0.80PMN-0.20PT)陶瓷。反应前驱体是以硝酸镁的饱和溶液代替传统氧化物混合法中的氧化镁,与PbO、Nb2O5和TiO2混合球磨得到的。该前驱体的TG-DTG-DSC和XRD分析表明,半化学法的反应机理不同于传统氧化物混合法和二次合成法的反应机理。在煅烧过程中,硝酸镁与氧化铅反应生成铅的活化中间体Pb6O5(NO3)2,由此活化的PbO或Pb3O4可与Nb2O5生成不稳定的、缺B位的焦绿石相Pb3Nb2O8,再与MgO反应生成钙钛矿相PMN-PT。  相似文献   

7.
采用液相沉淀法合成两种水合硼酸锶SrB_2O_4·4H_2O和SrB_6O_(10)·5H_2O,将其高温煅烧制备出纯四硼酸锶(SrB_4O_7)相,分析了高温煅烧过程、产物的物相和形貌,研究了煅烧温度和保温时间等因素的影响。结果表明,在加热过程中水合硼酸锶发生脱水→非晶化→晶化过程,且SrB_6O_(10)在800℃左右分解为SrB_4O_7和液态氧化硼;将SrB_2O_4·4H_2O和SrB_6O_(10)·5H_2O在900℃煅烧4 h可制得纯相四硼酸锶;延长煅烧时间可提高产物的晶化程度,但是其晶型没有明显的变化。用该法制备的SrB_4O_7:Eu荧光粉,其发光强度明显比以SrCO_3和H_3BO_3为原料制备的样品高.  相似文献   

8.
尹正帅  李勇  薛向欣 《材料导报》2013,27(14):38-41
以MgCl2·6H2O、H3BO3和H2C2O4·2H2O为原料,利用草酸盐法制备出长度为4.0~8.0μm,直径为0.6~1.5μm,长径比约为10,形貌良好的硼酸镁晶须。采用XRD、SEM及TG-DTA等分析手段,研究了烧结温度、烧结时间、n(B)/n(Mg)、n(H2C2O4)/n(Mg)对硼酸镁晶须的生长过程和质量的影响,探讨了其最佳制备条件。结果显示,硼酸镁晶须的最佳制备条件为:烧结温度为800℃,烧结时间为4.0h,n(B)/n(Mg)=1.2,n(H2C2O4)/n(Mg)=1.2。根据XRD和TG-DTA分析,MgC2O4前驱体对硼酸镁晶须的形成和生长有较大的促进作用,分解产物不引入其它杂质,使得制备的晶须纯度较高。晶须的生长机理为S-L-S机理。  相似文献   

9.
MnOOH纳米棒的低温水热合成   总被引:1,自引:0,他引:1  
以KMnO4和N4(CH2)6为主要原料,在130℃反应16h,水热法制备了MnOOH纳米棒,并利用X射线粉末衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段对产物进行了表征.探索了KMnO4和N4(CH2)6间的摩尔比以及反应温度对合成产物的影响.实验结果表明:产物为具有单斜结构的MnOOH纯相,形貌为棒状,呈现单晶特性.  相似文献   

10.
以AZ80A市售镁合金为参照,研究了镁基纳米复合材料镁,即:碳纳米管(Mg/CNT)复合材料及氧化镁(Mg/MgO)纳米复合材料在模拟体液中的腐蚀行为.浸泡过程中测量溶液的pH值变化,在浸泡1、4、8、10、20和30d后计算其腐蚀速率,并通过XRD分析腐蚀产物成分.结果显示:Mg/MgO纳米复合材料比Mg/CNT复合材料耐腐蚀,Mg/CNT复合材料在4d时已经腐蚀完,AZSOA型镁舍金最耐腐蚀。三者的腐蚀产物成分基本相同,均为Mg2CI(0H)3-4H2O及少量的MgCl2.  相似文献   

11.
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.  相似文献   

12.
13.
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.  相似文献   

14.
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.……  相似文献   

15.
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……  相似文献   

16.
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill.  相似文献   

17.
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.  相似文献   

18.
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...  相似文献   

19.
Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.  相似文献   

20.
Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.  相似文献   

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