堆积法制造青瓷用胎体陶瓷粉料体制备及表征

针对堆积法制造龙泉青瓷,采用水基料浆与流态化喷雾造粒相结合制备青瓷胎体陶瓷粉料,研究了水基料浆的分散稳定机制及其喷雾造粒行为,分析了固相含量对料浆流变性能、造粒粉粒径分布及成型性能的影响机制。研究表明:水基料浆具有宾汉型流体特性,固相含量为40%的料浆具有较低粘度和剪切应力,而固相含量为50%的料浆的稳定性和分散性更好;喷雾造粒后,固相含量为50%料浆喷雾造粒颗粒呈规则球形,粒径分布较宽,具有较好的填充性能和成型性能。     

喷雾造粒SiC粉料在成型过程中的破碎行为

采用压力喷雾造粒的方式对ＳｉＣ粉体进行喷雾造粒处理，研究了喷雾造粒过程中工艺条件和浆料中粘合剂含量对成型过程中粉料颗粒破碎行为的影响。实验结果指出：喷雾造粒过程中粘合剂含量过多或进口热风温度过高，都会使喷雾造粒粉料颗粒的团聚强度增加，在成型过程中不易破碎，残留在素坯中的硬团聚将对烧结致密化产生不利影响。ＳｉＣ粉体在雾造粒时最佳粘合剂含量和进口热风温度分别为５０ｍｌ／ｋｇ和２４０℃。     

喷雾造粒ZrO2粉料坯体性能的研究

以喷雾造粒ＺｒＯ２粉料为研究对象,通过对粉料的压力－密度曲线及坯体的ＳＥＭ显微结构分析,发现喷雾造粒粉料的粒度分布对坯体密度的影响较小;颗粒强度的大小是获得均匀的坯体结构的关键,颗粒的强度与其大小及环境湿度有关,因此颗粒适当的增塑及去除大颗粒均有利于坯体显微结构的改善。     

粘结剂对喷雾造粒ZrO2(Y2O3)粉末特性的影响

采用喷雾造粒工艺对及ZrO2(Y2O3)粉体进行造粒，研究喷雾造粒过程中粘结剂含量对粉料流动性、填充性、造粒团聚体强度的影响，并对坯体成形过程中团聚体的破碎行为进行了分析。结果表明：喷雾造粒过程中粘结剂含量较高时，造粒团聚体粒子具有良好的填充性，但粒子强度高，在成形过程中不易破碎，将阻碍致密化烧结。     

水分和粘结剂含量对坯体冷等静压成型和性能的影响

以Si粉(粒度≤0.044mm)和聚乙烯醇水溶液(PVA,其中聚乙烯醇质量份数为5%)按一定比例混匀,过筛造粒,振动装料后进行冷等静压成型,研究了水分和PVA含量对硅粉坯体成型和性能的影响。研究表明:当水分含量大于1wt%时,粉料填充密度低,填充不均匀,导致压制时压缩比大,压缩不均匀,坯体外形不规整;当水分在0.5～1wt%时,硅粉填充密度较大,粉料的成型性较好,粉料中水分含量确定为0.5～1wt%。当加入的PVA的量从5wt%增加到15wt%时,坯体强度随PVA含量增加而增加;当加入的PVA的量从15%wt增加到25wt%时,坯体强度有降低的趋势,而且坯体中存在残余颗粒团聚体;当加入的聚乙烯醇溶液质量份数为15wt%时,坯体强度最大(约1.62MPa),并且不存在残余颗粒团聚体,确定粘结剂含量为15wt%。     

水基SiC料浆的分散稳定机制及喷雾造粒

以去离子水为液体介质,引入有机添加剂,配制水基SiC悬浮料浆,研究了水基料浆的分散稳定机制及其喷雾造粒行为,分析了有机添加剂和固相含量对料浆流变性能、造粒粉粒径分布及成型性能的影响机制.结果表明:当料浆pH≥10时,水基碳化硅料浆的分散性和稳定性较好,料浆具有剪切稀化的非Newton体特性:当加入0.2%(质量分数,下同)四甲基氢氧化铵、2.0%聚乙烯醇和1.0%聚乙二醇时,料浆黏度较小:固相含量为50%水基料浆喷雾造粒后,造粒粉的流动性、填充性能及成型性能明显提高,但球状造粒粉需要在一定成型压力下才能完全破碎.     

氧化锆料浆性能对其喷雾造粒粉料性质的影响

本文研究了料浆含固量和粘度对其喷雾造粒粉料性质影响。结果表明：氧化锆料浆含固量是喷雾造粒（ＳＤ．）粉料填充密度的主要控制因素，高含固量料浆能得到高填充密度喷雾造粒粉料，且其颗粒显微结构相对致密；随着ＺｒＯ２料浆含固量、粘度增加，喷雾造粒粉料平均粒径增大，粗颗粒含量增多，细颗粒含量减少。     

锆英石陶瓷生产工艺对力学性能的影响

对锆英石陶瓷的生产工艺对材料的显微结构、力学性能的影响进行了研究.结果表明:造粒粉颗粒的硬壳与空洞在坯体中形成了颗粒,如果在成型过程中末被完全破坏,遗留在烧结体中而引起材料内部气孔的存在,材料的力学强度和可靠性能明显下降.制定合理的锆英石材料生产工艺、控制气孔的产生,是提高材料强度和可靠性的有效措施.     

锆英石陶瓷生产工艺对力学性能的影响

对锆英石陶瓷的生产工艺对材料的显微结构、力学性能的影响进行了研究.结果表明:造粒粉颗粒的硬壳与空洞在坯体中形成大颗粒,如果在成型过程中末被完全破坏遗留在烧结体中而引起材料内部气孔的存在,使材料的力学性能明显下降.制定合理的锆英石材料生产工艺、控制气孔的产生,是提高材料强度和可靠性的有效措施.     

关于砖坯强度影响因素的答疑

<正>问:韩工,请问是否砖坯粉料越细强度越高?影响坯体强度的因素有哪些?答:你好,你问的问题很笼统,传统的建筑陶瓷坯体成型一般为喷雾粉料半干压成型,喷雾粉料半干压具有三个特点:一是粉料颗粒是假颗粒,含有固相(矿物颗粒)、液相(水分)和气相(空气)。这些含有水分(一般在3%~12%范围)和空气的假颗粒需要具备流动性、压缩性     

Influence of Granule Character on Strength and Weibull Modulus of Sintered Alumina

Alumina specimens were prepared by compacting well-characterized spray-dried alumina granules of excellent deformability, followed by sintering. The strength and Weibull modulus were measured and microstructure was evaluated for specimens prepared from granules with different density and morphology. Compacts of spheroidal granules with lower density and lower granule strength sintered to 98% relative density and had fewer microstructural defects than compacts prepared from spheroidal or hollow granules of higher density. Flexural strength of sintered material was found to depend on initial granule size but not density or morphology of the granules. Weibull moduli of 18–20 were independent of particular granule characteristics.     

省时、省工的农药新剂型——漂浮粒剂

论述了颗粒剂、漂浮泡腾粒剂和漂浮粒剂的进展、特点和加工。指出漂浮粒剂比漂浮泡腾粒剂更有优势:不使用固体酸和固体碱成分,节约了原料成本;抛撒使用后,对水稻安全性高;一劳永逸地解决了漂浮泡腾粒剂产品在贮存期间,容易发生鼓气和涨包的老大难问题。     

Modelling spatial distributions of moisture and quality during drying of granular baker's yeast

A distributed parameter model was developed to predict the drying behaviour of granular baker's yeast by setting up material and heat balances at the particle level. Temperature and moisture gradients were calculated for cylindrical and spherical granules. The performance of the model with two granule sizes was compared with experimental measurements. The model was initially used for non‐shrinking granules but later modified to take shrinkage into account. The reduction in granule size during the course of drying was estimated and good correspondence with experimental measurements was obtained. In addition to temperature and moisture gradients, the product quality was predicted during drying and compared to experimental results. The accuracy of the model was better than the lumped parameter model.     

Mechanische Eigenschaften zyklisch be‐ und entfeuchteter Zeolithgranulate

The production of zeolite granules varies in the amounts of binder content and different drying/activation temperatures. Here, the influence of moisture content and cyclic moisture loading and unloading on the mechanical properties like the strength of three different types of zeolite granules has been studied by uniaxial compression tests. The force‐displacement curves and scanning electron microscopy pictures of the granule and fracture surfaces show that with increasing number of moistening‐drying cycles, a continuous decrease in the strength of granules take place due to non‐regenerative damage of the structure.     

Compression mechanics of granule beds: A combined finite/discrete element study

Compression of three-dimensional beds comprising 1000 plastically deforming initially spherical granules is investigated by using the combined finite/discrete element (FE/DE) method. The material model is formulated within the framework of multiplicative plasticity, and utilizes a density-dependent elliptic yield surface that allows porous particles to both deform and to densify plastically, whereas only volume-preserving plastic deformation is possible for nonporous ones. Granules with different characteristics (yield stress and initial porosity) are studied, and the relationship between the single-granule properties and the global compression behaviour of the granule bed is investigated. It is demonstrated that the FE/DE method may shed light on the deformation and densification behaviour of individual granules, since the size and shape of each granule are continually determined as an integral part of the solution procedure, and that the method thus provides a comprehensive picture of the processes occurring during confined compression of granular materials.     

Effect of Moisture on the Structure and Fracture Strength of Ceramic Green Bodies

To study independently the effects of moisture on the structure and the mechanical strength of the binder in green bodies, specimens of the system alumina/PVA were formed with spray-dried granules of various moisture contents. The structure and fracture strength of these specimens then were examined after their moisture contents had been adjusted to specified values. As moisture content increased in the granules during compaction, the density and strength of the green body also increased. The accompanying change in the fracture mode, from intergranular to transgranular, showed that the strength of the green bodies was affected more significantly by bonding between granules than by bonding between powder particles.     

GRANULAR FERTILIZER DRYING AND AGGLOMERATION IN STORAGE

ABSTRACT

In the manufacture of granular NPK fertilizer the product is cooled before packaging and storage in moisture-proof bags. It has been shown that the temperature of the fertilizer prior to packing is significant in that at high temperatures, drying of the granules takes place in the bag which causes an increase in the humidity of the air surrounding the granules and thus an increase in moisture content at the granule - granule interface. This surface moisture was shown to increase the likelihood of agglomeration in the fertilizer by a capillary adhesion / unconfined yield stress model. An iterative model was set up to establish conditions that would prevent drying occurring, which takes into account fertilizer drying rate, fertilizer cooling rate cooling rate and the effect of coaling oils on the drying mechanism.     

Effect of Humidity on NPK Fertilizer Drying

The drying process within rotary coolers during the manufacture of granular NPK fertilizer plays an important role in the production of fertilizer granules possessing both a low moisture content and low caking propensity. A theory for fertilizer drying has been developed which takes into account the low critical relative humidity of complex fertilizer found at high temperature. The theory proposes that the gradient between the partial vapour pressure of moisture in the air and the vapour pressure moisture adjacent to the surface of the fertilizer granule, is the rate controlling stage in the drying of hot granular fertilizer rather than the internal diffusion of moisture within the particle.     

Morphology of alumina granules obtained by spray freeze drying with twin-fluid atomization

This study presents the results of the morphological dependence of alumina granules obtained by spray freeze drying (SFD) with twin-fluid atomization. It is shown that the introduction of 1-, 2- and 4-wt.% polyvinyl alcohol (PVA) as a binder in an alumina suspension leads to the formation of irregular granules. Depending on atomization conditions, spherical, “tadpole-like,” granule-satellite and granule aggregates may form during SFD. Increasing the flight time of droplets before the fixing of their shape when they come in contact with liquid nitrogen effectively contributes to the spheroidization of alumina granules. Compacting PVA-free SFD granules leads to the formation of diagonal flaws in a green-body structure. Adding PVA prevents the abovementioned defects by increasing the strength of alumina granules. Increasing the amount of PVA leads to an increase in “tadpole-like” granule content and, consequently, a decrease in a green-body density.     

Improvement of Industrial Drying of Natural Rubber Through Analysis of Heat and Mass Transfers

An analysis of convective drying of natural rubber in granule form. Exploitation of the mathematical model developed from analysis of internal transfers requires determination of the 'drying rate' and the 'energy exchange coefficient' between the material and the drying air. This was performed using a portable laboratory drier at the production site, avoiding the problem of changes in the material during transport. Analysis of the drying kinetics of material in thin layers led to modelling the drying rate at the temperatures, rates and relative humidity values encountered in industrial driers. The energy exchange coefficient was found by measurement of air and granule temperatures. Thick layer trials showed the suitability of the model for simulation of changes in moisture content and temperature of air and granules in a granular environment. The study as a whole led to the development of a computer program for simulating a zone drier. This software can be used to optimise the management of an industrial natural rubber drying installation.