磨边机的磨削过程的数学模型的研究

在参考金属磨削过程动态模型以及对墙地砖磨边机磨削过程分析折基础上,建立了磨边机磨削数学动态模型。该模型反映了砖的形态等因素与磨削力的关系,并提出了改进磨边机磨削质量的途径。     

理想的的固体推进剂粘合剂的分子结构

对粘合剂的分子结构和固体推进剂的力学以及流变性能之间的关系进行了研究.由发动机中药住的操作条件对推进剂力学性能的要求以及已有的加工技术对药浆流变性能的限制出发.反推得出固体推进剂粘合剂理想的分子结构.结构和加工要求是由三种类型的火箭发动机的应用要求决定的:航天转运、运载火箭和弹道导弹以及空对空战术导弹.考虑了可满足这些应用要求的三种一般的配方.除假想的全粘合剂推进剂外,还包括传统的复合和硝酸酯增塑的推进剂配方.对这三类中的各种配方按分子量、交联密度、溶解度参数、链的刚硬性、单体的摩擦系数、填充物的体积分数和增塑剂的体积分数确定了各种聚合物的分子特性.10个聚合物粘合剂系统的特性数据说明了它们的分子结构如何影响制得的推进剂的性能.     

合成氨的生产工艺的现状及发展趋势的探讨

本文通过对合成氨的工艺流程和发展情况对合成氨的生产工艺的现状及发展趋势进行阐述。     

神彩的玻璃 神秘的宗教 神圣的殿堂

在国外学习艺术玻璃这几年,谈起彩色玻璃镶嵌,自然会联想到欧洲教堂里的彩色玻璃窗。它是中世纪教堂装饰的一种独特方法,主要盛行于罗马式、哥特式和拜占庭式建筑。前两种建筑的窗户多而大,几乎布满整个建筑立面,便于采光。     

物理化学的概念教学的启发式模式的构建

通过对目前物理化学教材内容和讲授模式的分析,针对在概念著述和课堂讲授中存在的误区,结合物理化学家吉布斯的启发式教学典故,本文构建一种"立足客观自然、环环相扣启发"的概念教学模式,以"焓"概念的讲授为例,化抽象为直观,收了良好的教学效果。启发式模式对当前物理化学的概念教学有重要的参考价值。     

丁二酸酐的生产工艺的研究

丁二酸酐的化学简式是C4H4O3丁二酸酐是医药、染料、涂料的主要原材料,同时还是重要的药物和化学试剂成分,另外丁二酸酐可以用于生胃酮、琥珀酸胺噻唑的生产,并且可以广泛的应用于树脂的合成和制备。目前工业上对丁二酸酐的制备主要有以下两种方法：第一种方法就是对顺丁烯二酸酐的直接催化加氢法。现在对顺丁烯二酸酐直接催化加氢的生产工艺流程研究的比较广泛,特别是对丁二酸酐生产工艺中的热力学以及探索新的催化研究体系等方面的研究更为广泛;第二种方法就是直接对丁二酸进行脱水。第二种方法的主要优点就在于它对环境污染较小且不使用苯类溶剂,所以国内外很多丁二酸酐生产厂家都普遍采用第二种方法。     

复古的，摩登的

这是—个典型的“墙边店”。倚墙的褐色矮柜上,是泛着漆光的有着胡桃木外壳的复古电唱机,墙上装裱好的镜框里,是店主张强收藏的经典唱片。张强打开最华贵的一台唱机,低沉悠扬的蓝调爵士立刻回荡在空旷无人的店堂里。     

优质的产品 完善的服务 理想的选择

<正>企业概述为了满足石油化工、有色冶炼、硫磷工业、环境保护、焦化行业技术的快速发展以及生产规模的不断扩大带来的市场需求,"扬州建业投资有限公司"和"扬州庆松化工设备有限公司"部分股东共同组建了"建业庆松集团有限公司"。新成立的"建业庆松集团有限公司"将传承老公司的优秀业绩、优良传统,发扬新公司的开拓理念、创新精神,     

Micronization of creatine monohydrate via Rapid Expansion of Supercritical Solution (RESS)

In the pharmaceutical industry, an even greater number of products are in the form of particulate solids. In the case of pharmaceutical substances the particle size is quite important since it can limit the bioavailability of poorly water soluble drugs. Since the mid-1980s, a new method of powder generation has appeared involving crystallization with supercritical fluids. In this study, RESS was used to micronize the creatine monohydrate particles. The RESS process consists in solvating the product in the fluid and rapidly depressurizing this solution through an adequate nozzle, causing an extremely rapid nucleation of the product into a highly dispersed material. In addition, the effect of six different RESS parameters including, extraction temperature (313-333 K), extraction pressure (140-220 bar), nozzle length (2-15 mm), effective nozzle diameter (450-1700 μm), spraying distance (1-7 cm) and pre-expansion temperature (353-393 K) were investigated on the size and morphology of the precipitated particles of creatine monohydrate. The characterization (size and morphology) of the precipitated particles of creatine monohydrate was determined by scanning electron microscopy (SEM). The results show great reduction in the size of the precipitated particles of creatine monohydrate (0.36-9.06 μm) compared with the original particles of creatine monohydrate. Moreover, a slight change into spherical form was observed for the precipitated particles of creatine monohydrate while the original particles were irregular in shape.     

Micronization of drug particles via RESS process

The rapid expansion of a supercritical solution (RESS) process is an attractive technology for the production of small, uniform and solvent-free particles of low vapour pressure solutes. The RESS containing a nonvolatile solute leads to the loss of solvent power by the fast expansion of the supercritical solution through an adequate nozzle, which can cause solute precipitation. The nozzle configuration plays an important role in RESS method and has a great effect on the size and morphology of the precipitated particles. In this study, ibuprofen was used as a simple test. In addition, besides the nozzle configuration, the effect of other parameters including extraction pressure (140-220 bar), extraction temperature (313-333 K), spraying distance (1-10 cm) and pre-expansion temperature (363-423 K) was investigated on the size and morphology of the precipitated particles of mefenamic acid. The SEM images also show that the precipitated particles of ibuprofen and mefenamic acid had a slight modification in morphology.     

Investigation of the rapid expansion of supercritical solution parameters effects on size and morphology of cephalexin particles

The particle size of organic and inorganic materials is vital parameter to determine its final use. Most of the newly developed pharmaceutical materials are poorly soluble or insoluble in the aqueous media such as biological fluids. Particle size reduction of such pharmaceuticals is one of the clues to improve the dissolution rate, adsorption and bioavailability. In this study, the effect of extraction and expansion parameters of the RESS process such as extraction temperature (313–333 K), extraction pressure (140–230 bar), effective nozzle diameter (450–1700 μm), nozzle length (2–15 mm) and spraying distance (1–7 cm) on the size and morphology of the precipitated particles of cephalexin were investigated. The morphology and particle size of the unprocessed and processed (precipitated) particles were examined by the SEM images. The mean particle size of the precipitated particles was between 0.86 and 7.22 μm depending upon the different experimental conditions used. The precipitated cephalexin particles were close to spherical form while the unprocessed particles were irregular or needle in shape.     

Formation of ultrafine aspirin particles through rapid expansion of supercritical solutions (RESS)

The performance of pharmaceuticals in biological systems can be enhanced by reducing the particle size of pharmaceuticals. Rapid expansion from supercritical solution (RESS) has provided a promising alternative to comminute contaminant-free particles of heat-sensitive materials such as drugs. In this work, aspirin has been successfully precipitated by the RESS technology. The performances of the RESS process under different operating conditions are evaluated through the analysis of the particle characteristics. Our results show that extraction pressure and extraction temperature can significantly affect the morphology and size of the precipitated particles whereas the nozzle diameter and pre-expansion temperature are not observed to apparently influence the RESS particles. The RESS process could produce ultrafine spherical particles (0.1-0.3 μm) of aspirin as reflected by SEM observations.     

Preparation of submicron-sized RDX particles by rapid expansion of solution using compressed liquid dimethyl ether

Cyclotrimethylenetrinitramine (RDX) was precipitated to submicron-sized particles with spherical morphology by the rapid expansion from supercritical solution (RESS). Compressed liquid dimethyl ether (DME) was used as a solvent for the RDX. This study examined the influence of extraction temperature (293-333 K), extraction pressure (8-20 MPa) and size of orifice nozzle (50, 100, 200, and 250 μm) on the size and morphology of the RDX particles in the RESS process. The precipitated RDX particles were characterized by using the following instruments: field emission scanning electron microscope (FE-SEM), image analyzer, powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). The precipitated RDX particles showed granular and spherical morphologies, submicron-sized particles, and narrow particle size distributions. The mean particle size of the precipitated RDX ranged from 2.48 to 0.36 μm, and the crystallinity of the precipitated RDX decreased. The enthalpy change for the exothermic decomposition of the precipitated RDX (ΔH = 714.4 J/g) was much higher than that of the original RDX (ΔH = 381.5 J/g).     

超临界溶液快速膨胀法制备二氯二茂钛微粒及催化乙烯聚合

为克服茂金属催化剂得到的聚合物形态难以控制、表观密度较低、易粘釜和不适于气相淤浆聚合等缺点,以超临界溶液快速膨胀过程为手段,以期制得颗粒分布均匀的细微催化剂颗粒,继而得到形态良好的聚合物.作为超临界流体技术的基础,首先测定了二氯二茂钛在超临界丙烷中的溶解度.在此基础上,用RESS方法制得了均匀的超细催化剂颗粒,且系统考察了溶液浓度、预膨胀温度、喷嘴结构和接收距离对沉析颗粒粒径的影响.最后,将RESS所制得的催化剂颗粒进行乙烯淤浆聚合,并分析聚合物形态结构.实验结果表明,在温度为383.15～408.15 K和压力为10～35 MPa范围内,溶解度随温度的增加而增加,随压力的升高而增加,说明在该操作范围内,不存在反向区.RESS操作的结果显示,二氯二茂钛颗粒粒径随溶液浓度的增大而减小,随预膨胀温度的升高而增大,而喷嘴直径的减小和喷嘴长度的增加将使得颗粒粒径增大,而收集距离的增加将使得颗粒粒径先增加后减缓,直至不再变化.通过对原始的催化剂颗粒和RESS制得的催化剂颗粒进行乙烯淤浆聚合表征发现,相比于原始催化剂,由于烯烃催化剂的复制原理,RESS制得的催化剂颗粒的聚合物具有良好的形态.     

超临界流体快速膨胀法制备超细氟比洛芬粒子

文章选用二氧化碳作为超临界溶剂,采用超临界溶液快速膨胀技术制备超细氟比洛芬药物粒子,在较宽的温度压力范围内测定了氟比洛芬在超临界二氧化碳中的溶解度,考察了各种操作参数对药物粒子粒径的影响,研究了药物粒子粒径随各种操作参数的变化规律。结果表明：在实验考察的范围内,氟比洛芬的溶解度较小,在10-5~10-7之间（摩尔分率）,溶解度随着温度和压力的升高而增大。同时实验结果表明：粒径随预膨胀压力的升高而减小;一定范围内随接收距离的增大而增大;在萃取温度较低的情况下,粒子粒径基本随着萃取温度的升高而减小;随着萃取温度的升高,在相对较高预膨胀温度下,粒径随着萃取温度升高而增大。     

Preparation of anthracene fine particles by rapid expansion of a supercritical solution process utilizing supercritical CO<Subscript>2</Subscript>

The rapid expansion of a supercritical solution (RESS) process is an attractive technology for the production of small, uniform and solvent-free particles of low vapor pressure solutes. The RESS containing a nonvolatile solute leads to loss of solvent power by the fast expansion of the supercritical solution through an adequate nozzle, which can cause solute precipitation. A dynamic flow apparatus was used to perform RESS studies for the preparation of fine anthracene particles in pure carbon dioxide over a pressure range of 150–250 bar, an extraction temperature range of 50–70 °C, and a pre-expansion temperature range of 70–300 °C. To obtain fine particles, 100, 200 and 300 μm nozzles were used to disperse the solution inside of the crystallizer. Both average particle size and particle size distribution (PSD) were dependent on the extraction pressure and the pre-expansion temperature, whereas extractor temperature did not exert any significant effect. Smaller particles were produced with increasing extraction pressure and preexpansion temperature. In addition, the smaller the nozzle diameter, the smaller the particles and the narrower the PSD obtained.     

Processing naproxen with supercritical CO2

Naproxen has been processed with supercritical fluids in order to improve the dissolution rate and bioavailability. Microparticles of naproxen have been obtained by a Rapid Expansion of Supercritical Solutions (RESS) process in which carbon dioxide has been used as a solvent and methanol as a cosolvent. The influence of extraction pressure (200–300 bar) and extraction temperature (60 °C and 100 °C) on the naproxen precipitation has also been investigated. In general, the morphology of the precipitated particles improved and particle size (PS) decreased in comparison to the raw material. Lower extraction pressure and higher extraction temperature led to a smaller particle size. On the other hand, a supercritical antisolvent (SAS) process has been applied due to the relative medium solubility values of naproxen in supercritical carbon dioxide, with precipitation obtained successfully in all cases. The initial concentration of the solution and the solvent effect has both been analysed. Morphologies and mean diameter ranges have been analysed by scanning electron microscopy (SEM) and the influence on crystallinity of both supercritical processes has been evaluated by X-ray diffraction (XRD) measurements.     

Effects of extraction temperature, extraction pressure and nozzle diameter on micronization of cholesterol by RESS process

Micronized cholesterol particles were produced via the Rapid Expansion of Supercritical CO₂ Solutions (RESS) process. Taguchi design was used for designing the experimental plan to investigate the effects of three parameters including extraction temperature (40-60 °C), extraction pressure (100-160 bar) and nozzle diameter (0.15-0.24 mm) on the size and morphology of the cholesterol particles produced by the RESS process. The characterization of the particles was carried out using scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements to evaluate the performance of RESS process. The average particle size of the original material was 55 μm ± (2.84) while the average particle size of cholesterol after size reduction via the RESS process was between the minimum of 0.62 μm ± (0.03) and the maximum of 4.83 μm ± (0.18) depending upon the experimental conditions used. It was observed that both increasing the temperature from 40 to 60 °C and increasing the nozzle diameter from 0.15 to 0.24 mm result a reducing effect on the average particle size, whereas extraction pressure (100-160 bar) change has slight effect on the average particle size.