基于BP神经网络模型的Ni-TiN镀层耐磨性预测研究

采用超声电沉积方法,在C470型压缩机阀片表面制备Ni-TiN镀层.利用扫描电镜、X射线衍射仪和摩擦磨损试验机研究Ni-TiN镀层表面形貌、组织结构及耐磨性,并采用BP神经网络模型预测Ni-TiN镀层的磨损量.结果表明,BP神经网络模型的最佳结构组成为3×9×l,其预测值与实验值的拟合度R=0.99938,相对误差最大值与最小值分别为1.67;和0.63;.当TiN粒子浓度为8 g/L、超声波功率180 W、电流密度4 A/dm2时,Ni-TiN镀层表面犁沟较浅,磨损量较小.Ni-TiN镀层中存在Ni和TiN相,镍的衍射峰分别位于44.82°、52.22°和76.78°,TiN的衍射峰分别位于38.48°、42.82°和66.54°.     

基于RBF神经网络的Ni-TiN镀层耐蚀性能预测研究

采用脉冲电沉积方法在40Cr钢表面制备Ni-TiN复合镀层,并以TiN粒子浓度、电流密度以及占空比为输入层,以Ni-TiN复合镀层腐蚀量为输出层,建立RBF神经网络模型,对镀层腐蚀量进行预测研究,最后利用扫描电镜观察不同工艺参数下镀层表面形貌.结果表明,RBF神经网络对镀层腐蚀量有较强的预测能力,其预测值与实验值相对误差最小仅为0.73;;SEM分析表明,当TiN粒子浓度10 g/L,电流密度5 A/dm2,占空比60;时,Ni-TiN复合镀层经腐蚀后表面较为平整,腐蚀坑较少,耐腐蚀性能较好.     

超声辅助脉冲电沉积Ni-TiN复合镀层制备工艺研究

采用超声辅助脉冲电沉积方法在45#钢表面制备NI-TiN复合镀层..利用X射线衍射仪(XRD)对复合镀层的物相组成进行检测分析,并利用原子力显微镜(AFM)、透射电镜(TEM)对Ni-TiN复合镀层的立体表面形貌及晶粒的分布进行观察分析.结果表明:当超声波功率为300 W时,所制备的Ni-TiN纳米复合镀层衍射峰强度最高,且含有Ni、TiN两相,Ni晶粒得到显著细化,TiN纳米颗粒分布较为均匀,无显著团聚现象发生.     

钻井泥浆泵活塞表面多场耦合电沉积Ni-TiN纳米镀层研究

采用多场耦合电沉积方法,在钻井泥浆泵活塞表面制备Ni-TiN纳米镀层.利用X射线衍射仪(XRD)、原子力显微镜(AFM)、摩擦磨损试验机对Ni-TiN纳米镀层微观组织结构和耐磨性能进行研究.XRD分析表明,在钻井泥浆泵活塞试样表面存在金属镍晶粒和TiN粒子.当复合镀液中TiN粒子为6g/L时,Ni-TiN纳米镀层中镍晶粒和TiN粒子的平均粒径分别为65.5 nm和38.6 nm.AFM分析表明,当TiN粒子浓度为6g/L时,镀层表面镍晶的平均粒径最小,其均方根表面粗糙度(RMS)为44.077 nm.摩擦磨损实验测试表明,当复合镀液中TiN粒子为6g/L时,Ni-TiN纳米镀层的磨损量和摩擦系数都最小,其最小磨损量和摩擦系数分别为34.7 mg和0.44.     

基于BP神经网络的Ni-TiN镀层腐蚀速率预测研究

采用磁场电沉积方法在40Cr钢表面制备了Ni-TiN镀层,并在正交实验的基础上建立了BP神经网络模型对镀层腐蚀速率进行预测,最后利用扫描电镜、X射线衍射仪以及显微电子天平对镀层的表面形貌、组分以及腐蚀速率进行分析和研究.结果表明,当工艺组合为A2B2C3D1,即TiN粒子浓度6 g/L,磁场强度0.4T,占空比50;,电流密度0.5 A/dm2时,Ni-TiN镀层经腐蚀后表面较为平整,凸起状物质较少.BP神经网络模型能够较好的模拟Ni-TiN镀层腐蚀速率,腐蚀速率最小值仅为2.134 mg/m·h,因此也证明了BP神经网络的可靠性.经XRD分析,Ni-TiN镀层存在Ni、TiN两相.     

脉冲占空比对Ni-TiN镀层组织及其耐磨性能的影响

采用磁场-电沉积方法在40Cr钢表面制得Ni-TiN复合镀层.利用扫描电镜(SEM)、显微硬度计、X射线衍射仪(XRD)及磨损试验机等对Ni-TiN镀层的表面形貌、显微硬度、织构和耐磨性能进行研究.结果表明,脉冲占空比为50;时,镀层表面镍晶粒平均粒径65.3 nm,且镀层中TiN粒子复合量较多.随着脉冲占空比的增加,Ni-TiN镀层的显微硬度先增加后降低.脉冲占空比为50;时,Ni-TiN镀层的显微硬度达到最大值934 Hv,其磨损量和平均摩擦系数分别为28.5 mg和0.43.     

基于AR模型的Ni-Al2O3复合镀层显微硬度预测

采用磁场电沉积方法在45钢表面制备了Ni-Al2O3复合镀层,用扫描电镜、显微硬度计等仪器对复合镀层表面及显微硬度进行检测.最后用AR模型对Ni-Al2O3复合镀层显微硬度进行预测.结果表明,当磁场强度0.3T,Al2O3粒子浓度8 g/L,电流密度1.5 A/dm2时,Ni-Al2O3复合镀层表面较为平整,镀层缺陷较少.AR模型能够较好的预测Ni-Al2O3复合镀层显微硬度,最大相对误差仅为1.9;.     

ZrO2含量对Ni-Co-ZrO2复合镀层显微硬度和耐磨性能的影响

以硫酸镍、硫酸钴和氧化锆为主要原料,采用脉冲沉积技术在Q235钢基体表面沉积了Ni-Co-ZrO2复合镀层,利用扫描电镜、能谱仪、X射线衍射仪分别观察和表征了复合镀层的显微形貌、成分组成和相结构,并对Ni-Co-ZrO2复合镀层的显微硬度和耐磨性进行了研究.结果表明:ZrO2颗粒弥散分布于Ni-Co合金中,基体与镀层界面处无孔隙、裂纹等缺陷,镀层厚度约为60μm;镀态下Ni-Co-ZrO2复合镀层基质合金为晶态结构,主要生长晶面为Ni(111)和Co (110),XRD衍射图谱呈现出低强度、大峰宽和多晶向的相结构特征.随着镀层内ZrO2颗粒含量的增加,Ni-Co-ZrO2复合镀层的显微硬度呈现先提高后降低、磨损量先减少后增加的趋势,当ZrO2含量为20 g/L时,复合镀层的硬度最高、磨损量最少,磨痕形貌呈现出轻微磨损.     

热处理温度对Ni-P-TiN纳米镀层的结构及其摩擦学性能影响

为改善机械零件的表面性能,采用超声波辅助化学沉积方法,在45钢基体表面制得Ni-P-TiN纳米镀层,利用透射电镜、X射线衍射仪、显微硬度计、扫描电镜、摩擦磨损试验机对其进行微观组织、机械性能及摩擦学性能研究.结果表明,镀态Ni-P-TiN纳米镀层主要由大量Ni和少量TiN组成,镍晶粒和TiN粒子的平均粒径分别为95nm和42 nm.当热处理温度达到300℃时,Ni-P-TiN纳米镀层中出现Ni3P相和NiO相,其显微硬度高达951.9Hv,其平均摩擦系数为0.43.     

超音速火焰喷涂HA/Ti复合涂层组织与性能研究

采用超音速火焰喷涂技术在304不锈钢基体上制备了纯HA涂层、30wt;HA/Ti及70wt;HA/Ti复合涂层,运用扫描电镜、X射线衍射和傅立叶变换红外光谱研究了涂层微观组织,物相和化学结构,并分析了涂层的结合强度和显微硬度及模拟体液下的生物性能.结果表明:HA/Ti复合涂层截面呈现典型的层状组织结构,表面存在大量球形/扁平化熔化颗粒及破碎粒子;大量Ti粒子在喷涂过程中被氧化且部分HA粒子产生分解,复合涂层主相为HA和TiO相,并含有少量TiO2、CaTiO3、CaO、Ti和α-TCP;Ti粒子添加有利于提高复合涂层力学性能,30wt; HA/Ti和70wt;HA/Ti涂层的结合强度分别为46.3 MPa和21.5 MPa,显微硬度分别为329 HV0.1和198 HV0.1;复合涂层经模拟体液浸泡7 d后,表面生成了磷灰石相,呈现出良好生物活性且随着HA含量增加而提高.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

电子显微分析在表征纳米晶体化学组分中的应用

纳米材料的化学组分及含量影响其光、电、声、热、磁等物理性能,电子显微分析是表征纳米晶体化学组分的重要方法之一.本文综述了X-射线能谱(EDS)、X-射线波谱(WDS)、电子能量损失谱(EELS)和选区电子衍射(SAED)等现代电子显微分析技术在表征纳米晶体化学组分、形貌、尺寸和结构等方面的应用及其研究进展,并比较了这些分析方法存在的差异,提出了其应用中存在的不足及今后的研发方向.     

原位氮化法制备TiN纳米粉体

用溶胶凝胶法合成的纳米TiO2粉体作为原料,将该粉体在氨气中进行原位氮化制备了TiN纳米粉体.用XRD,TEM,化学分析等手段对合成的TiN纳米粉体的物相组成、形貌、成分进行了分析.实验分析表明:在1000℃和1100℃下分别氮化5h,可以制备粒径大约为40nm和80nm的TiN粉体,其TiN的含量分别为95.40;和98.37;;而在1000℃条件下氮化时间减少到2h时,TiN的含量仅为58.36;.氮化温度和氮化时间是合成纳米TiN的重要因素,提高合成温度和延长氮化时间均可形成纯度较高的TiN纳米粉体,但延长氮化时间更有利于获得粒径小的氮化钛粉体.     

Mesomorphism Dependence on the Position of Substitution of a Pair of Esters

A novel homologous series of ethylene derivatives of thermotropic liquid crystals has been synthesized. The methoxy to octyloxy derivatives are nematogenic, the decyloxy to tetradecyloxy derivatives are smectogenic, in addition to nematogenic, and the hexadecyloxy homologue is smectogenic only. All the members of the series are enantiotropically mesogenic. Thermotropic behavior was determined by an optical polarizing microscope equipped with a heating stage and Differential Scanning Calorimetry (DSC) study. Analytical and spectral data confirm the molecular structures of homologues (infrared, nuclear magnetic resonance, mass spectra, X-ray, and DSC data). Textures of the nematic phase are threaded or Schlieren and that of smectic phase are focal conic fan-shaped of smectic A or C. Transition curves of the phase diagram behave in a normal manner except one or two deviations from the normal trend. The mesophase range (Sm+N) varies from 3°C to 44°C. The average thermal stability for smectic is 93°C and that for nematic 117.4°C. The LC behavior of the novel series is compared with a structurally similar known series.     

On the influence of structural features of DNA on the possibility of metabolic transfer of electrons

Abstract

A fragment of a DNA molecule is considered as one of the channels of metabolic electron transfer. The heterogeneity of the complementary chains is effectively taken into account. This made it possible to find the speed of the electron injected into the DNA conduction band and the current density that it creates. Estimates of electron mobility in nucleic acid chains are made. They were an order of magnitude smaller than that of typical semiconductors. For the specific conductivity of nucleic acid chains, estimates provide a conductivity of one to two orders of magnitude lower than in graphite.     

PEG聚合度对氧化铝造粒粉的性能影响

为制备适用于干压成型的氧化铝造粒粉,研究了PEG聚合度对氧化铝造粒粉微观形貌、流动性和松装密度的影响.结果表明PEG的聚合度对氧化铝浆料粘度影响显著,PEG2000-6000是较为理想的粘结剂选择,造粒粉的流动性与环境温度及湿度相关.采用正交实验设计,以造粒粉的流动性和松装密度为评价指标,对PEG聚合度、粘结剂添加量和固含量进行了优选,其影响顺序为PEG聚合度＞固含量＞粘结剂添加量.以优选参数PEG6000、添加量为4wt;、固含量为80wt;,制备了性能优良的氧化铝喷雾造粒粉.     

Ni-ZrO2纳米复合电铸层的制备及纳米颗粒分布均匀性研究

研究了在复合电铸过程中,当其它工艺参数一定时,复合电铸层的沉积速率及其厚度随时间的变化趋势, 以及复合电铸层表面微观形貌随电沉积时间的变化趋势.测定了复合电铸层的组织成分,并就纳米颗粒在复合电铸层表面和横截面上分布的均匀性进行了评价.结果表明,复合电铸层表面平整,组织均匀致密,其组成主要是镍和所复合的纳米颗粒,纳米颗粒较为均匀地分散在复合电铸层中.     

Effect of alumina on enthalpy of mixing of mixed alkali silicate glasses

The enthalpy of mixing of mixed alkali (Na₂O and K₂O) silicate glasses containing various concentrations of alumina was determined using an ion-exchange equilibrium method. For glasses with a constant alkali concentration, the enthalpy of mixing was found to become less negative with alumina addition. Consistent with our previous results on the enthalpy of mixing of alumina-free mixed alkali silicate glasses, the magnitude of enthalpy of mixing exhibited a good correlation with the molar volume mismatch of the corresponding two single alkali glasses as well as with the extent of conductivity mixed alkali effect, e.g. excess activation energy of conductivity, ΔE. The reduction of the magnitude of the enthalpy of mixing with alumina addition can be attributed to the reduction of non-bridging oxygen and ionic field strength. Combining the present results with results obtained earlier, the magnitude of the enthalpy of mixing for all mixed alkali (Na₂O and K₂O) silicate glasses with and without alumina was expressed by a simple function of a modified Tobolsky parameter, which takes into account the alkali concentration and the difference in cation-to-effective anion distances. The enthalpy of mixing data of the mixed alkali glasses was then compared with reported experimental data on the conductivity of mixed alkali aluminosilicate glasses. What appears to be conflicting experimental data can be understood in terms of the magnitude of the enthalpy of mixing and we can conclude that the mixed alkali effect is closely correlated with the negative enthalpy of mixing.     

近化学计量比铌酸锂晶体组分测定与缺陷观察

采用助熔剂提拉法生长得到近化学计量比LiNbO3晶体.用多种方法测定了晶体组分,结果表明生长得到的晶体中[Li2O]含量为49.80;摩尔分数;对晶体缺陷的研究表明晶体质量有待提高,并分析了晶体中出现包裹物的原因.     

Some peculiarities of spectral proprieties of leukocytes

This article presents the results of spectral investigations of white blood human cells including absorption, fluorescence and phosphorescence (using low-temperature measurements). For this research, the main optical centres were identified and local distribution of emitting and absorbing centres into white blood human cells was determined. In addition, the spectra of normal and pathological (B-cell chronic lymphocytic leukemia, B-CLL) cells were compared.