基于模型复制法的金刚石微结构制备研究

CVD金刚石膜是一种具有众多卓越特性的功能材料,在微机电系统(MEMS)领域有着广泛的应用前景.金刚石膜的精密微细图形化加工技术是将金刚石材料应用于MEMS微器件的关键技术.本文开展了金刚石微结构的制备实验研究,利用在硅微模具中沉积金刚石膜的方法成功制作了微细梁、微圆柱、十字结构、文字图形等一系列金刚石微结构.Raman、SEM、ADE等多种理化分析结果表明采用这种模型复制工艺能够获得表面质量好、图形复杂、形状和尺寸精度很高的金刚石微结构,并能够实现批量制造,是制作金刚石微器件的理想方法.     

片状纳米氧化锌单晶的制备和表征

本文提供了一种应用二步法制备片状纳米氧化锌单晶的实验方法--首先,以尿素为沉淀剂宿主,以氯化锌、碱式碳酸锌为原料,应用均匀沉淀法获得纳米氧化锌的片状纳米级前驱物;然后通过控温热分解前驱物制备出片状纳米氧化锌单晶.用扫描电镜观测了制备的ZnO单晶的形貌,并通过红外光谱对其进行了表征;讨论了溶液中生成纳米氧化锌的前驱物的热力学趋势,并对氧化锌制备过程进行了结晶动力学分析.结果表明:实验制备的氧化锌均为无色透明的片状单晶,结晶形貌为正六边形、五边形、矩形以及其它不规则形状,单晶直径在3～30μm之间,厚30～60nm;影响纳米氧化锌单晶制备的主要因素是反应物料配比、沉淀剂宿主尿素的浓度(1∶6)以及反应温度(70～85℃).此外,乙醇的含量对片状纳米ZnO前驱物的形貌影响很大,过高(＞40;)或过低(＜10;)的乙醇含量都不利于形成片状纳米氧化锌单晶的前驱物.     

2A12铝块体超细晶材料的ECAP制备

本文采用自行制造的内角为90°、外角为30°模具对工业用2A12铝合金材料进行了ECAP实验,并采用HitachiS-800透射电镜(TEM)观察和分析了挤压前后材料的微观结构.结果表明:在室温下采用90°模具、加工路径Bc,以5mm/s速度,挤压八次后,成功制备了晶粒尺寸约为200nm、具有大角度晶界的2A12铝块体超细晶材料.     

模具法制备CVD金刚石热沉片的温度场与流场研究

本文通过有限元仿真研究了模具法制备CVD金刚石热沉片的温度场和流场,并对制备参数进行了优化.实验与仿真的结果均表明,进气量的大小对衬底附近流场的均匀性影响显著,热丝温度、热丝间距以及热丝到衬底的距离对衬底的平均温度影响显著,热丝间距和热丝温度对衬底温度的均匀性影响显著;模具法制备的CVD金刚石复制了模具型腔,保证了热沉片的结构完整性和尺寸精度,最终制备了精度较高的小型CVD金刚石热沉片.     

石膏晶须的制备方法与应用

石膏晶须是一种性价比高、力学性能良好以及对环境友好的材料,可应用于复合材料、造纸、催化、可生物降解材料等领域.石膏晶须的制备大多停留在工艺参数研究上,对石膏晶须特征和应用研究不足.本文讨论了石膏晶须的结构,从产物形成过程上对石膏晶须的制备方法进行了分类和评述;对不同制备方法和不同应用领域的石膏晶须的产物特征进行了总结,讨论了制备和应用之间的相关性;并讨论了石膏晶须未来的发展方向.     

热压工艺对Ti(C,N)基纳米复合金属陶瓷模具材料力学性能与微观结构的影响

采用真空热压烧结工艺制备了Ti(C,N)基纳米复合金属陶瓷模具材料,并研究了该模具材料的力学性能与微观结构.结果表明,当烧结温度为1450℃,保温时间为10 min时,模具材料的硬度、断裂韧性和抗弯强度分别为14.57 GPa、8.6 MPa·m1/2和1144 MPa;当烧结温度为1450℃,保温时间为30 min时,模具材料的硬度、断裂韧性和抗弯强度分别为16.29 GPa、7.53 MPa·m1/2和1035 MPa.在这两种烧结工艺下制备的模具材料均具有良好的综合力学性能,烧结工艺得到优化,可以满足不同硬度材料的成型需求.在对模具材料的微观结构分析时发现,模具材料的断裂方式是以沿晶断裂为主的穿晶与沿晶断裂的混合断裂模式.     

碳热还原氮化法制备β-Sialon粉体的研究

采用山西大同土为主要原料,利用碳热还原氮化法(CRN)制备了β-Sialon材料,并利用SEM、XRD等检测手段对其进行了检测分析.研究了温度、N2流量、保温时间以及配碳量等因素对制备β-Sialon的影响,采用正交设计的方法确定了反应的最佳工艺参数,并在此基础上讨论了α-Si3N4晶种对生成产物的影响.实验结果表明,烧结温度为1500℃,氮气流量为1 L/min,保温时间为2 h,配碳量为0.8化学计量时可以生成较多的β-Sialon相.SEM微观形貌表明具有一定长径比的β-Sialon柱状晶呈均匀分布.此外,加入3;的晶种α-3N4可促使晶粒大小均匀并获得高品质细密结构的粉体.     

片状纳米氧化锌单晶的制备和表征

本文提供了一种应用二步法制备片状纳米氧化锌单晶的实验方法--首先,以尿素为沉淀剂宿主,以氯化锌、碱式碳酸锌为原料,应用均匀沉淀法获得纳米氧化锌的片状纳米级前驱物;然后通过控温热分解前驱物制备出片状纳米氧化锌单晶.用扫描电镜观测了制备的ZnO单晶的形貌,并通过红外光谱对其进行了表征.结果表明:实验制备的氧化锌均为无色透明的片状单晶,结晶形貌为正六边形、五边形、矩形以及其它不规则形状,单晶直径在30～600μm之间,厚30～60nm;影响纳米氧化锌单晶制备的主要因素是反应物料配比、沉淀剂宿主尿素的浓度(1∶6)以及反应温度(70～85℃).此外,乙醇的含量对片状纳米前驱物的形貌影响很大,10;～40;的乙醇含量利于形成片状纳米氧化锌单晶.     

低成本无机陶瓷膜制备研究进展

无机陶瓷膜是MBR污水处理技术的关键,与有机膜相比,无机膜具有化学稳定性好,耐酸碱、耐有机溶剂,孔径分布窄,分离效率高且易控制,热稳定性强等优点.本文介绍了无机陶瓷膜制备过程的工艺流程且分析了成本构成要素,主要从陶瓷膜制备过程中原料成分、制备方法、影响降低成本的因素、烧结温度的控制过程等方面分析降低成本的方法,通过建立一套低成本的理论框架,实现陶瓷膜材料选择与工艺参数的共同优化,促进无机陶瓷膜技术的快速发展,并对后期研究无机陶瓷膜的发展方向进行了探讨与展望.     

金刚石微铣刀头图形化法的制备研究

微细铣削加工技术是具有较高相对精度的精密三维微小零件的制造技术,微零件尺寸和精度在很大程度上依赖于微切削刀具的切削性能.CVD金刚石膜作为一种具有众多卓越特性的功能材料,是制造新型超硬微铣刀的优越刀具材料.本文开展了硅微模具图形化法沉积金刚石膜微铣刀头的实验研究,成功制作了特征尺寸为25 μm、50 μm和100 μm双层金刚石微铣刀头.SEM,ADE等分析结果表明采用的工艺能够获得表面质量好、形状和尺寸精度很高的金刚石微铣刀头,该工艺能够实现批量制造,是制作金刚石微铣刀的理想方法.     

Three-dimensional circular spiral photonic crystal structures recorded by femtosecond pulses

Photonic crystal structures having three-dimensional (3D) circular spiral architecture have large theoretical photonic band-gap but cannot be implemented by most of the existing microfabrication techniques. We have successfully used a highly versatile 3D microstructuring technique called femtosecond laser microfabrication to prepare templates of the circular spiral photonic crystals in a commercially available photoresist SU-8. The structures fabricated have good structural quality, are highly periodic and exhibit spectral signatures of photonic bands dispersion in the short infrared wavelength region.     

Friction measurement in precision glass molding: An experimental study

Understanding the frictional behavior between glass and metals at elevated temperatures is necessary for accurate modeling and simulation of the state of the art applications such as the PGM process, pressing of micro lens arrays, hot embossing, and extrusion or drawing of glass fiber. In this research, the frictional behavior of N-BK7, an oxide glass, at elevated temperatures in contact with polished and coated tungsten carbide (WC) material and under conditions similar to the PGM process has been studied.The experimental results show that the friction coefficient between a polished and coated WC mold and N-BK7, which is a typical material for glass molding, and in conditions similar to those used in the PGM process ramps up to 0.7 and then levels off around 0.6 with a smooth transition, meaning that there is not a specific point to differentiate between static and dynamic friction. The friction coefficient of 0.6 is reported in literature for best fitting in micro lens molding simulation. Moreover, increasing the temperature in the transition regime in the mold/glass interface causes the friction force to increase which is in good agreement with the data published for the friction between soft polymeric material and metal in the transition regime.     

溶剂蒸汽退火辅助微距升华法制备C8-BTBT单晶

有机半导体单晶由于具有内部长程有序的分子排列结构、缺陷及晶界少等优点,表现出优异的光电性能,是实现有机半导体器件实用化的一种重要材料。目前,研究者们已经发展出多种可应用于有机单晶的生长方法,其中,微距升华法是一种可以在大气环境下采用蒸镀的方式制备有机微/纳单晶的方法。然而,当将这种方法应用于C8-BTBT时发现,由于分子的熔点较低,蒸镀得到的是分子直接从液态凝固为无定形/多晶的结构。在本工作中,通过使用溶剂蒸汽退火的方式对其进行后处理,成功地将这种无定形/多晶结构转化为分立的单晶。为了表征所得到的晶体形貌和结构,分别使用光学显微镜、X射线衍射和原子力显微镜等仪器对其进行了表征,发现所制备的晶体结构具备单晶的典型特征。     

Agglomeration control during the selective epitaxial growth of Si raised sources and drains on ultra-thin silicon-on-insulator substrates

We have studied the impact of several Si selective epitaxial growth (SEG) process on the agglomeration of ultra-thin, patterned silicon-on-insulator (SOI) layers. Through a careful analysis of the effects of the in situ H₂ bake temperature (that followed an ex situ “HF-last” wet cleaning) and of the silicon growth temperature on the SOI film quality, we have been able to develop a low-temperature SEG process that allows the growth of Si on patterned SOI layers as thin as 3.4 nm without any agglomeration or Si moat recess at the Si window/shallow trench isolation edges. This process consists of an in situ H₂ bake at 650 °C for 2 min, followed by a ramping-up of the temperature to 750 °C, then some SEG of Si at 750 °C using a chlorinated chemistry (i.e. SiH₂Cl₂+HCl).     

Investigations on glass-to-mold sticking in the hot forming process

The sticking behavior of various mold materials and coatings for hot glass melt forming processes, like, e.g. glass container manufacturing, was investigated using a new testing procedure. The mold material specimens under test were subjected to frequent contact with hot viscous glass gobs in a pressing process with presetting well defined non-isothermal pressing parameters to simulate industrial working conditions. Three different glass compositions were used in this investigation, soda-lime silicate glass, lead crystal glass, and borosilicate glass. The sticking characteristics of the tested mold materials and coatings were described by two quantities, a ‘lower’ and an ‘upper’ sticking temperature, which are specific for each mold material and type of glass in the non-isothermal pressing process. The ‘lower’ sticking temperatures of uncoated mold materials were found to depend monotonically on the thermal effusivity (heat penetration coefficient) of the bulk mold materials. All of the coating materials applied to various substrate mold materials were found to reduce the ‘lower’ sticking temperature as compared to the uncoated materials. Most of the coating materials were found to reduce also the ‘upper’ sticking temperature.     

人造金刚石微粉和氟化钙在等温成形模具中的应用研究

为了提高等温成形过程中零件的表面质量,延长等温成形模具的使用寿命,对人造金刚石微粉和氟化钙微粉进行适当的表面处理,采用化学复合镀的方法,在等温成形模具上得到Ni-P/C+CaF2复合镀层,改善了模具表面的摩擦系数、提高耐磨性能,为等温成形新技术推广,提供技术上的支持.     

Temperature field design,process analysis and control of SAPMAC method for the growth of large size sapphire crystals

In this paper, the relationship between quality of sapphire crystal and growing parameters of SAPMAC (Sapphire growth technique with micro‐pulling and shoulder‐expanding at cooled center) method was discussed. Optimized temperature distribution and technique control were proposed by theoretical analysis, numerical simulation computation and experimental validation to obtain large size sapphire crystals. For a‐axis crystallized direction, with 1.0‐5.0mm/h growth velocity and 10‐30K/h temperature decreasing speed, large sapphire single crystal (∅︁240mm×210mm, 27.5kg) having high optical quality was successfully grown. The absorption spectrum of standard samples was measured as well. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigation on heat transfer performance of fluoride-free and titanium-bearing mold fluxes

Fluorine erodes continuous casters and pollutes the environment. In order to reduce the damage caused by fluorine, it is necessary and urgent to carry out research on fluoride-free mold fluxes. There has been little research done on the heat transfer performance of fluoride-free mold fluxes either domestically or abroad. The present work adopted TiO₂ to take the place of fluorine in mold fluxes and studies its heat transfer performance. Heat flux simulation equipment was developed and the heat flux density of titanium-bearing mold fluxes containing TiO₂ was measured; in addition, a solid slag film was obtained. The crystallization behavior and the change of activation energy for crystallization of the slag film was analyzed. Our results show that when the TiO₂ content is increased, the heat flux density of fluoride-free mold fluxes decreases, the crystallization activation energy of mold fluxes is diminished and the crystallization ratio of mold fluxes increases, and the mineral phase of the slag film turns from akermanite into perovskite. When the basicity is increased, the heat flux of fluoride-free mold fluxes is reduced, the crystallization ratio of mold fluxes increases and the mineral phase of the slag film turns from unitary akermanite into the coexistence of two phases of akermanite and perovskite. Furthermore, the capability of fluoride-free and titanium-bearing mold fluxes to control heat transfer is better, so it can be expected to replace industrial slag containing fluorine completely.     

Growth and characterization of pure and lithium doped L‐alanine single crystals for NLO devices

Single crystals of pure and lithium substituted L‐alanine are successfully grown by slow evaporation method at constant temperature of 32°C. The effect of lithium dopant on crystal properties has been studied. Powder and single crystal XRD analysis confirms the structure and change in lattice parameter values for the doped crystals. The crystals were characterized by solubility studies, density, melting point measurements, FTIR and UV‐Vis‐NIR techniques. Thermal and mechanical stability of crystals were tested by TGA/DTA and micro hardness analysis. NLO activity of the crystals is found to be increased in the presence of lithium ions. The dielectric constant and dielectric loss of the crystals were studied as a function of frequency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fabrication of flexible organic thin-film transistors based on negative acting photosensitive novolak polymer as an organic gate insulator

A diazonaphthoquinone (DNQ)-based cross-linkable photo-sensitive cresol novolak resin through acid-catalyzed condensation with melamine molecules is presented as an organic gate insulator (OGI) for the fabrication of poly(3-hexylthiophene) thin-film transistors. This novolak OGI exhibits a remarkably smooth surface of Ra 1.0 nm and RMS 0.3 nm and shows excellent chemical resistance against common process solvents upon a post exposure bake ≥150°C. The corresponding metal-insulator-metal diode incorporated with a 200 nm thick OGI demonstrates remarkable low leakage current level of 10 pA/cm² @3 MV/cm. Bottom-contact poly(3-hexylthiophene) (P3HT) transistors with novolak OGI on both rigid glass and flexible polyethylene terephthalate (PET) plastic substrates are further demonstrated, suggesting that novolak polymer is a promising candidate for realizing a high performance OGI at low processing temperature.