几种粒度测定方法的比较

简要介绍了几种常用粒度测试方法的原理、特点和各自的适用范围,并针对特种陶瓷与耐火材料领域中常用粉体的特征,提出了其粒度测试中应注意的问题.  

铝酸钠(钾)溶液种分过程的分解率和粒度分布

采用等温间歇式反应器研究了纯铝酸钠和铝酸钾溶液在种分过程的分解率、粒度分布(PSD)的变化规律,同时对分解产品进行了XRD、SEM和TG/DTG分析.结果表明,在相同的分解条件下,铝酸钾溶液的分解率大于铝酸钠溶液;铝酸钠和铝酸钾溶液中颗粒的粒度分布随时间变化具有显著差异;产品的XRD显示,分解过程中铝酸钾比铝酸钠溶液中的晶体结晶度完整,但产品的TG/DTG曲线却没有明显的差别.对于不同ακ值的铝酸钠和铝酸钾溶液,这些差异是相似的.铝酸钾与铝酸钠溶液在种分过程中的成核速率不同可能是引起分解率和粒度分布产生差异的原因.  

Recent developments of high-performance NEOMAX magnets

For further improvement in achieving extremely high magnetic properties of Nd- Fe- B sintered magnets, extensive investigation has been done to densify the magnet up to the theoretical value, to increase the volume fraction of the Nd ₂Fe₁₄B matrix phase, and to achieve a high degree of alignment. By controlling chemical composition and the amount of constituent phases,improving particle size distribution, and adopting the isostatic pressing method to get better alignment of fine particles, we have succeeded in obtaining a high-performance magnet having residual flux density (B_r) of 1.495 T (14.95 kG), maximum energy product [(BH)_max] of 431 kj/m³ (54.2 MGOe), and intrinsic coercivity (iH_c) of 845 kA/m (10.62 kOe).  

热压烧结制备近全致密W-Cu梯度热沉材料

采用粒度配比和热压固相烧结方法制备高致密W-Cu梯度热沉材料，考察烧结温度、压力和保温时间对梯度材料密度和硬度的影响，并对材料的显微组织进行观察。结果表明：采用热压固相烧结和粒度配比法可以制备近全致密的W-Cu梯度热沉材料，各梯度层分界清晰，各层组织致密，成分保持为最初的梯度设计；在烧结温度1060℃、压力85MPa、保温时间3h的工艺条件下，所制备的W-Cu三层梯度热沉材料的封接层、中间层、散热层的相对密度分别达到98．6％、99．1％和99．5％，硬度HRB分别为91，6、95．6和74．4。  

颗粒度对贮氢合金MlNi_(3.65)Co_(0.75)Mn_(0.4)Al_(0.2)电化学性能的影响

研究了贮氢合金MlNi3.65Co0.75Mn0.4Al0.2的颗粒浓度及粒度分布均匀性对其电化学性能的影响。结果表明：在200mA/g（以贮氢合金的质量计算，下同）的充放电电流下，合金的粒度越小，首次放电容量越大，且活化速度越快，但其饱和容量（活化后稳定的放电容量）随粒度的增大而增加，且在某个最佳粒度时达到最大值，然后又逐渐降低；该合金的高倍率放电容量与其粒度之间也有相同的规律，只是在不同的放电电流下最佳粒度值不同，当放电电流小于600mA/g时，30μm-76μm合金粉的放电容量最大，当放电电流等于或大于600mA/g时，40μm-50μm合金粉的放电容量最大；放电电流越大，颗粒度对合金粉电化学性能的影响越显著；在放电电流为300mA/g时，除30μm以下的合金粉性能衰减较快外，其余各个粒度的合金粉的性能衰减速度几乎相等；均匀的粒度分布有利于合金粉电化学性能的提高。  

粉末粒度测试方法述评

综述了目前常用的粉末粒度与粒度分布测定方法的原理、特点及适用范围 ,并对粒度测试技术的发展作了展望  

Coarsening behavior of γ particles in a nickel-base superalloy

The coarsening behavior of γ' particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000,1080 and 1140°C for different times,the relation of average particle size to time obeys the cube law ( a /2)3= kt,where k is 15.49 × 103,77.5 × 103 and 230.04 × 103 nm3/min,respectively. The particle size distributions are better fit to the LSW theoretical distributions when aging at 1000°C within 1440 min....  

晶种活化强化铝酸钠溶液的种分分解

采用一种新方法活化氢氧化铝晶种，可以强化铝酸钠溶液的种分分解。晶种在沸腾的蒸馏水中蒸煮后得到活化，实验研究了活化晶种对铝酸钠溶液种分附聚过程以及全过程的强化分解作用及其对产品粒度分布的影响。在种分附聚实验中，对于苛碱浓度比较低的铝酸钠溶液，晶种活化0．5h就能有效地提高溶液的分解率，而活化时间超过0．5h对分解率的促进作用不明显；对于苛碱浓度比较高的铝酸钠溶液，晶种活化2.0h以上才能较明显地提高溶液的分解率。在种分全过程实验中，溶液分解率的提高在10h以后出现并逐渐增大。晶种被活化可能是因为晶种表面被有机杂质吸附封闭的活性点被活化后重新显露，活化晶种及原始晶种在溶液中种分1．0h后的形貌初步证实了这种设想。种分附聚产品的粒度分布结果显示，只要晶种活化时间合适，产品的粒度也能明显改善。  

An analytical model of the effect of particle size distribution on the surface profile evolution in abrasive jet micromachining

An analytical model to estimate the spatial distribution of erosive efficacy across the mask opening in the abrasive jet micromachining (AJM) of substrates is presented. A closed form analytical expression is derived which allows the erosive efficacy in the vicinity of the mask edge to be estimated as a function of the measured abrasive particle size distribution and the width of the mask opening. This analytical expression was used in a previously developed analytical surface evolution model to predict the time dependent eroding surface profiles of micro-holes and micro-channels of various sizes in glass and polymethylmethacrylate (PMMA), using aluminum oxide abrasive powders of different sizes. Use of the measured powder size distributions in the analytical models resulted in excellent agreement between the measured and model predicted channel profiles. The results of the study demonstrate that the particle size distribution and mask opening width can greatly affect the shape and depth of micro-channel profiles. A major improvement over previously developed models is ease-of-application since the erosive efficacy is given by an analytical expression rather than by the use of a computer simulation or a semi-empirical approach.  

Nucleation during gibbsites precipitation with seeds from sodium aluminate solution processed under ultrasound

1　INTRODUCTIONItisknown[14 ] thatnucleationcanbehastenedbyultrasoundduringthecrystallizationofsolutions .Forsodiumaluminatesolutionwithhighviscidityandsurfacetension ,primarynucleationisdifficulttotakeplacewithoutseedsunderindustrialconditions[58] .When gibbsitesareprecipitatedfromliquorwithseeds,therearemanysecondarynucleinearthede fectsandactivesitesofsurfacesofseedsandsec ondarynucleationdependsmuchonthe qualityofseeds.Accordingto particledistributiondata[911] ,thediametersofnewcritic…