掺硼改性碳化硼陶瓷的研究

以碳化硼粉、无定形硼粉为主要原料,热压烧结制备了B4C陶瓷.研究了不同的硼加入量和烧成温度对样品致密度和力学性能的影响.结果表明,当硼的加入量为11.6wt%时,样品的硬度、断裂韧性、抗弯强度和弹性模量分别达到32.9GPa、3.53MPa·m1/2、544.8MPa和405.3GPa.利用XRD、SEM测试手段对样品的物相组成和显微结构进行了分析.     

B_4C废料酸洗除Fe_2O_3和Al粉加入量对烧结B_4C制品性能的影响

为了改善以碳化硼除尘废料为主原料的烧结制品的性能,利用硫酸溶液与Fe_2O_3反应生成可溶性硫酸盐的原理对碳化硼除尘废料进行了超声酸洗除Fe_2O_3,经烘干、混料、成型后于1 400℃保温90 min烧成,研究了Al粉加入量(加入质量分数分别为3%、6%、9%、12%和15%)对以除Fe_2O_3后的碳化硼粉末为原料的试样性能的影响以及除Fe_2O_3对碳化硼制品烧结及力学性能的影响。结果表明,酸洗除杂后,碳化硼废料中Fe_2O_3含量由3.43%(w)降低至0.17%(w);随着Al粉加入量的增加,烧后试样的显气孔率先减小后增大,力学性能先提高后降低,当Al粉的加入量为6%(w)时,试样的耐压强度、弹性模量、抗折强度比未经除Fe_2O_3制得的碳化硼制品分别提高了20.96%、11.86%、19.15%;烧结过程中,Al夺取Fe_2O_3中的O生成Al_2O_3,导致Al对B_4C不润湿,降低了碳化硼试样的力学性能。因此,碳化硼除尘废料除Fe_2O_3对其烧结制品性能有良好的促进作用。     

添加碳化硼对低碳铝碳耐火材料显微结构和性能的影响EI北大核心CSCD

以板状刚玉和活性氧化铝微粉为主要原料、纳米炭黑为碳源、碳化硼(质量分数0、0.5%、1%)和单质硅粉为添加剂,制备了低碳铝碳耐火材料。利用X射线衍射仪、场发射扫描电子显微镜分别检测和观察了材料的物相组成和显微结构。采用三点弯曲法研究了材料的常温和高温力学性能,采用水淬冷法研究了材料的热震稳定性。结果表明:与空白试样相比,在1 000℃处理的含碳化硼的试样中发现碳纳米管(MWCNTs);温度高于1 200℃,在材料表面出现了明显的含氧化硼反应层,形成了外层Si C晶须较多、内层Si C晶须较少的分层结构。由于原位碳纳米管的形成,1 000℃处理后含碳化硼试样的抗折强度由空白试样的3.4 MPa提高到11.6 MPa;而1 200和1 400℃处理后,试样也因碳纳米管和Si C晶须协同作用,材料的抗折强度进一步提高至15~17和26~28 MPa。此外,引入碳化硼的铝碳材料高温抗折强度和热震稳定性也都大幅提升。     

添加碳化硼对低碳铝碳耐火材料显微结构和性能的影响

以板状刚玉和活性氧化铝微粉为主要原料、纳米炭黑为碳源、碳化硼(质量分数0、0.5%、1%)和单质硅粉为添加剂,制备了低碳铝碳耐火材料。利用X射线衍射仪、场发射扫描电子显微镜分别检测和观察了材料的物相组成和显微结构。采用三点弯曲法研究了材料的常温和高温力学性能,采用水淬冷法研究了材料的热震稳定性。结果表明:与空白试样相比,在1 000℃处理的含碳化硼的试样中发现碳纳米管(MWCNTs);温度高于1 200℃,在材料表面出现了明显的含氧化硼反应层,形成了外层Si C晶须较多、内层Si C晶须较少的分层结构。由于原位碳纳米管的形成,1 000℃处理后含碳化硼试样的抗折强度由空白试样的3.4 MPa提高到11.6 MPa;而1 200和1 400℃处理后,试样也因碳纳米管和Si C晶须协同作用,材料的抗折强度进一步提高至15~17和26~28 MPa。此外,引入碳化硼的铝碳材料高温抗折强度和热震稳定性也都大幅提升。     

前驱体法制备B4C-TiB2复相陶瓷及其性能研究

以B4C粉、钛酸四丁酯为主要原料，通过烧结过程中的原位反应，在2100℃热压烧结制备了B4C—TiB2复相陶瓷。分别采用XRD和SEM分析了其物相组成和显微结构，并测试了其致密度和力学性能。结果表明，在B4C基体中生成了弥散分布的超细TiB2颗粒，TiB2的引入使样品的致密度提高。添加2vol％TiB2的样品的硬度、抗弯强度、弹性模量和断裂韧性分别达到了31GPa、586．6MPa、4087GPA和7.61MPa.m^1/2，比相同条件下制备的碳化硼单相陶瓷均有提高。     

3YPSZ-Al2O3-Co3O4陶瓷力学性能的研究

为了提高3YPSZ陶瓷的强度和韧性,先研究了Al2O3的加入量对3YPSZ陶瓷力学性能的影响,结果表明,当Al2O3含量为25wt%时,3YPSZ陶瓷综合力学性能最佳,抗弯强度为582.4MPa,维氏硬度15.4GPa,断裂韧性为6.6MPa.m1/2。再将Al2O3的含量控制在25wt%,通过改变Co(NO3)2.6H2O添加剂的含量来研究3YPSZ-25wt%Al2O3陶瓷材料力学性能的变化,研究发现,当Co3O4的引入量为0.25wt%时,3YPSZ-25wt%Al2O3陶瓷材料综合力学性能最佳,抗弯强度为623.5MPa,维氏硬度为16.9GPa,断裂韧性为7.2MPa.m1/2。并利用XRD和SEM等表征方法分析了Co(NO3)2.6H2O添加剂对材料力学性能和显微组织结构的影响。     

轻质碳化硼复合材料的制备工艺及性能研究

本研究以B4C、Si C、Ti C、C等为原料,经过喷雾干燥工艺造粒,采用无压烧结制备了轻质碳化硼复合材料。探讨了浆料中不同料水比对碳化硼造粒料的影响,测试了碳化硼烧结体的相关性能,并借助SEM对烧结体进行断口形貌观察。实验结果表明:当料水比为1:1.5时,料浆经过喷雾干燥工艺制粒,可制得颗粒表面形貌近似为圆形的碳化硼混合造粒料,所压素坯经过无压烧结,制得了结构致密,组织均匀,力学性能优良的轻质碳化硼复合材料。其体积密度为2.53 g/cm3、相对密度为97.76%、维氏硬度为25.5GPa、抗弯强度为437 MPa、断裂韧性为5.24 MPa·m-1/2。     

机床用Al_2O_3/TiB_2复相陶瓷刀具材料的研究

以α-Al2O3和TiB2为主要原料,采用真空热压烧结工艺制备机床用Al2O3/TiB2复相陶瓷刀具材料。测试和分析了烧结样品的相对密度、弯曲强度、断裂韧性、硬度值、相组成以及显微结构。结果表明,当α-Al2O3添加量为75 wt%,微米TiB2添加量为20 wt%时,所制备的Al2O3/TiB2复相陶瓷刀具材料性能最佳,其相对密度值为98.8%,弯曲强度为606.25 MPa,断裂韧性为4.85 MPa·m1/2,硬度值为26.55 GPa。最佳样品的主晶相为刚玉(Al2O3)和硼化钛(TiB2),次要晶相为氧化钇(Y2O3)。     

粉体合成工艺对TiB_2–TiC复相陶瓷微观组织及力学性能的影响

分别以直接法和间接法碳硼热还原工艺合成的TiB_2–TiC复合粉体为原料,采用热压烧结工艺制备了共晶成分的TiB_2–44%TiC(摩尔分数)复相陶瓷,研究了粉体合成工艺和烧结温度对TiB_2–TiC复相陶瓷显微组织和力学性能的影响。结果表明:以直接法合成粉末为原料烧结的TiB_2–TiC复相陶瓷中,TiB_2晶粒多呈棒状、组织细小均匀;而以间接法合成粉末为原料制备的复相陶瓷中TiB_2晶粒多呈等轴状。随着烧结温度的升高,复相陶瓷致密度提高,晶粒长大,但力学性能变化不明显。以直接法合成复合粉末为原料,在烧结温度为2 000℃、压力为30 MPa、保温时间为1 h工艺条件下制备的TiB_2–TiC复相陶瓷综合性能最佳,其致密度、弹性模量、Vickers硬度、抗弯强度和断裂韧性分别为99.9%、537 GPa、19.0 GPa、598 MPa、5.3 MPa·m~(1/2)(压痕法)和11.6 MPa·m1/2(单边切口梁法)。TiB_2–TiC复相陶瓷主要的增韧机制为裂纹偏转和分叉。     

碳热还原法制备碳化硼粉末的工艺研究

采用碳热还原法制备了碳化硼粉末样品,讨论了硼碳比、煅烧合成和粉碎过程等工艺参数对其粉末性能的影响。借助XRD分析手段测试了其成分,并用化学方法分析了粉末的总碳含量,用激光粒度分布仪测试了其粒度分布。实验结果表明:以工业用硼酸和炭黑为原料,在1700～1850℃、保温0.5～1h煅烧合成能制得纯度较高的碳化硼粉末。其总碳含量为20.7%,接近理论值。中位径为32.56μm,经球磨粉碎后,其中位径可以达到2.42μm。     

SEDIMENTATION OF BINARY MIXTURES OF PARTICLES OF UNEQUAL DENSITIES AND OF DIFFERENT SIZES

A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases.     

COMPARISON OF METHODS OF ANALYSIS OF GYPSUM1

The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO₃ and determination of CaO by KMnO₄ titration, the SO₃ by Andrews method of titration of BaCrO₄ has been found to give very reliable results with the least consumption of time.     

骑式摩托车油箱喷涂工艺的改进

面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。     

氢气纯度分析方法准确性的探讨

ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l／3为氧气,2／3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中：A一混…     

HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.

Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology.     

用两个形状指数表征粉煤灰颗粒形貌的研究

引用两个形状指数表征颗粒形状的概念,即先将颗粒形状近似为椭圆,再将椭圆图像分离:以圆为基准的颗粒宏观形状指数δ;以光滑椭圆为基准的颗粒轮廓凹凸度,即微观形状指数ζ。分析和发展了近似椭圆模型。并运用图像分析仪对粉煤灰、水泥样品进行实验。结果表明,粉煤灰颗粒的两个形状指数δ和ζ都大于水泥颗粒。证明粉煤灰颗粒的球形度、表面光滑度优于水泥,而且,随着粒径增大,δ和ζ呈下降趋势,表明磨制颗粒越粗。(?)粒形状越不规则。文中还运用近似椭圆模型再现了颗粒的模拟图像。     

典型煤碳燃烧特性研究和数值模拟

本文以三种典型煤的碳燃烧为研究对象，分别采用简单一维沉降燃烧方式和等温加热燃烧方式，实验研究了煤在快速加热条件下，其碳的初期和中，后期燃烧过程。以实验为基础，建立了煤的碳燃烧模型，变工况数值模拟了煤的碳燃烧过程，揭示了煤不同条件下的单颗粒碳燃烧特性。     

茶多酚提取方法进展

本文综述了国内外现有茶多酚提取方法的现状以及近期的研究进展，并对其优缺点进行了评价。这将有助于中低档茶的综合利用和茶多酚的进一步开发应用。     

卫生陶瓷烧成用窑炉发展之我见

归纳了当今卫生陶瓷工业的发展现状和水平 ,对窑炉产业提出了的新要求 ,分析了某一新型窑炉的特点 ,对发展我国陶瓷窑炉产业提出了建议     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log₁₀ viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log₁₀ viscosity as a function of soda content are smooth up to 50% Na₂O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO₂, 2Na₂O) due to Molecular Substitution of CaO, MgO and Al₂O₃ for Na₂O The effect is clearly brought out by plotting (from the results of English) the change of log₁₀η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T_a. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log₁₀η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1₂O₃) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al₂O₃) per 100°. At the aggregation temperature the change of log₁₀η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al₂O₃. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log₁₀η due to substitution of an oxide for Na₂O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na₂O-CaO-SiO₂. Change of Viscosity of Glass (4SiO₂, 2Na₂O) due to of Substitution of B₂O₃ for SiO₂ The change of log₁₀η (from the results of English) is plotted as a function of temperature, and also the change of log₁₀η per per cent B₂O₃. The curves are more complex than for the substitution for Na₂O.