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1.
The inhomogeneity of bulk density distribution created during the die filling process might cause quality problems for powder compacts, such as distortion, lamination, and cracking. To avoid these problems, understanding the die filling process and ensuring a uniform pre-compaction powder deposition are necessary. The second-generation pressure deposition tester (PDT-II) was developed to investigate simultaneous deposition of powder into multiple dies. Its design requirements and new features were proposed through evaluating the main strength and limitations of the mass deposition tester (MDT). The operation of the PDT-II and analysis of its data showed that it generates real-time deposition profiles of the entire process for multiple locations. PDT-II data can be used to study the effects of various filling-related parameters (such as die shape, powder flowability, and feed shoe speed) on the deposition process and final pressure distribution. For cylindrical dies filled with a granulated powder with d50 = 600 μm (1) at low feed shoe speeds (20 and 100 mm/s), the half circle close to the leeward end had higher final pressure values than the forward half circle; (2) at high feed shoe speed (500 mm/s), the final pressure distribution was more uniform than at lower feed shoe speed; (3) the final within-die pressure distribution at the bottom of the dies was not always symmetrical about the center line of the feed shoe movement direction, even though sometimes it was quite symmetrical; (4) the overall trend was that pressure decreases with increasing radial distance for lower feed shoe speeds; and (5) higher feed shoe speed (500 mm/s) resulted in higher final pressure values (774.5 to 1424.5 Pa) than lower feed shoe speeds (20 and 100 mm/s) (235.2 to 1136.0 Pa) at most of the locations. The results proved that feed shoe speed does have an effect on pressure distribution and its uniformity. 相似文献
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Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7-648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation. 相似文献
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Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7–648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation. 相似文献
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The inhomogeneity of the pressure distribution after completion of the filling process might create tablet and compact quality issues. Generating a uniform precompaction powder deposition into a die would minimize one source of tablet quality issues. This article determines the characteristics of the deposition process into a rectangular die and a circular shallow die, using a feed shoe with a square cross-section tube. A series of experiments were performed that determined the cumulative influence of particle size, die geometry, and feed shoe speed on uniformity of pressure distribution at the end of filling process. For uniformity comparison, the profiles of pressure distribution at the end of filling process were displayed as contour plots. Symmetry analysis, variance metrics, and uniformity analysis were implemented to quantify the deposition characteristics. Feed shoe speeds of 20 and 100 mm/s were used to fill the die. Due to their differing particle characteristics and importance, a pharmaceutical powder filler (microcrystalline cellulose-Avicel PH102) and a battery powder mixture (BPM) were used as test materials. The results showed that (1) contour plot was the most reliable method for evaluating uniformity deposition characteristics in dies; (2) based on contour plot analysis, BPM deposition at 100 mm/s feed shoe speed for circular shallow dies resulted in the most uniform pressure distribution among all, that is, 64% uniformity at ±20 dm (decimeter) resolution and 14.7% coefficient of variation (COV); (3) Avicel deposition at 20 mm/s feed shoe speed for circular dies had the least uniformity (46%); (4) rectangular dies generally had lower symmetry index (61%) in comparison with circular dies, which was attributed to sharp edges of rectangular die, that is, particles trapped in corners generated higher stresses inside the rectangular die versus circular die. 相似文献
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The process of die filling is a significant unit operation in many industries. Inhomogeneity of distribution such as in mass, bulk density, and pressure might cause many tablet and compact quality issues, such as lamination, capping, and distortion. No systematic investigations have been done to evaluate pressure distribution characteristics in dies with small aspect ratios (ratio of fill height to characteristic cross section dimension <0.5). In order to evaluate pressure distribution during filling of shallow dies, a circular cross section feed shoe was used at two speeds. The deposition characteristics of two powders with differing particle characteristics were studied in this research. The second-generation pressure deposition tester (PDT-II) was used to measure the two powders' pressure distribution characteristics. A battery powder mixture (BPM) and microcrystalline cellulose (Avicel PH102) were used to fill a rectangular shallow die 32 × 30 mm in dimension and 6.5 mm deep. Feed shoe speeds of 20 and 100 mm/s were used to fill the die. Symmetry analysis, variance metrics, Gini coefficient, and uniformity analysis were used to quantify the deposition characteristics. The results showed that (1) the contour plot was the most reliable method for measuring powder deposition characteristics; (2) the leeward and forward pressure distrbution comparisons generated a larger symmetry index than the front and back pressure distribution; (3) based on contour plot analysis, BPM at 100 mm/s feed shoe speed resulted in the most uniform pressure distribution (64% uniformity at +/?20 dm (decimeter) resolution) among all; (4) feed shoe speed greatly influenced pressure distribution uniformity inside the die; and (5) the high stress zone was mostly observed in forward and back regions inside the die. 相似文献
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为了提高羰基铁粉的抗腐蚀能力及改善其电磁性能, 以TMA和H2O为前驱体, 利用原子层沉积(ALD)方法对羰基铁粉进行表面包覆改性, 在羰基铁粉表面包覆不同厚度的氧化铝。通过扫描电镜(SEM)、透射电镜(TEM)、综合热分析仪(TGA)、红外光谱(FTIR)和矢量网络分析仪等技术手段系统分析了改性前后羰基铁粉性能指标。结果表明, 通过ALD方法可在羰基铁粉表面生长纳米级别具有良好保型的氧化铝薄膜, 形成了极佳的羰基铁/氧化铝壳层结构复合材料。与原样品相比, 包覆改性后的羰基铁粉热稳定性与抗腐蚀性有极大的提高, 且随着包覆厚度的增加, 抗氧化能力增强, 最大抗氧化温度可超过550℃。同时羰基铁粉包覆氧化铝后, 其介电常数明显减小, 磁导率变化相对较小, 改善了原羰基铁粉的电磁参数与吸波性能。 相似文献
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Additive manufacturing (AM) is the process of fabricating 3D physical models by layered manufacturing without the need of molds or dies. The surface finish of AM physical models is not satisfactory for most general engineering purposes. The aim of this study is to develop an acetone-vapor polishing system to smooth acrylonitrile butadiene styrene (ABS) parts fabricated by fused deposition modeling (FDM). Acetone vapor dissolved the outer surface of ABS parts, and the surface roughness of ABS parts with complex geometries can be significantly reduced. The advantages of this system include the flexibility to maintain dimensional accuracy, high polishing efficiency, low equipment costs, and no waste chemicals compared with conventional approaches. 相似文献
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An apparatus for simultaneous deposition of large size double-sided YBCO thin films by sputtering from single inverted cyclindrical target was constructed. Double-sided YBCO thin films on LaAlO3 (100) substrate up to 30 mm in diameter were prepared to test the performance of the apparatus. The microwave surface resistance, R
s (77 K, 10 GHz, 0 T), of the YBCO thin films on both sides of the wafer ranged from 500 to 800 . Values of R
s (75 K, 145 GHz, 0 T) below 60 m were reached over the area of 20 mm × 15 mm on the wafer. The majority of the wafer area given in percent has R
s (75 K, 145 GHz, 0 T) values in the range of 21.5– 45.5 m. Lateral homogeneity of R
s values in the whole wafer was good enough to well meet the microwave application. 相似文献
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目的 研究柱形空气衬垫的振动传递特性,以获取振动传递率曲线。方法 在频率为3~100 Hz区间对柱形空气衬垫和确定载荷质量形成的振动系统进行正弦扫频振动试验,分析初始内压和厚度对其振动传递特性的影响规律。结果 初始内压对空气衬垫的隔振能力没有显著影响,3种初始内压下振动系统的共振频率均在35 Hz左右,传递率峰值集中在11左右。当厚度增大时,共振频率和传递率峰值同时减小,空气衬垫隔振能力增强。结论 在满足缓冲性能的前提下,选择合适的初始内压,以及采用多层空气衬垫可显著提高其隔振能力。研究结果可为柱形空气衬垫的缓冲隔振包装设计提供基本依据。 相似文献
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自熔合金粉末性能对粉末沉积率的影响 总被引:2,自引:0,他引:2
对具有不同的粉末粒度分布、熔点和颗粒形貌的火焰喷焊自熔合金粉末的沉积率进行了测试分析。结果表明,粒度组成呈正态分布义峰值在—61 74μm之间的粉末沉积率最高,随着粉末熔点的降低和回波相区间的扩大,沉积率明显提高,不规则状粉末比球形粉末沉积率高,粉末流动性在18~21s/50g之间的粉末更适合喷焊。 相似文献
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Zdenek Zatloukal 《Particulate Science and Technology》2013,31(4):316-328
In this work, the influence of the geometry of a cylindrical flat-bottomed hopper orifice on the mass discharge rate of six free-flowable powder excipients with the size fraction 0.050–0.063 cm was investigated. Sixteen combinations of the orifice diameter and the height were used. The influence of the orifice diameter was described by the flow equation. However, the discharge rate was also affected by the orifice height. The influence of the orifice geometry on the powder discharge rate was indirectly studied by the parameters of the Beverloo equation. The value of the coefficient of determination and the precision of the discharge rate prediction were the basic criteria. The mean relative differences between the actual discharge rate at the combination of the orifice diameter and its height and the average discharge rate allowed a direct study of the effect of the orifice geometry. The complex nature of the orifice height impact on the powder discharge rate through the hopper opening has been determined. Based on the results, the orifice diameter of 0.8 cm with the height less than 0.8 cm is recommended. The method of powder flow evaluation proposed here can be used in testing of other powder fractions in future. 相似文献
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H. BERTHIAUX K. MARIKH V. MIZONOV D. PONOMAREV E. BARANTZEVA 《Particulate Science and Technology》2013,31(4):379-389
This article demonstrates the efficiency of the application of the theory of Markov chains as a tool to model and simulate continuous powder mixing to aid in better design of such equipment. Markov chain models allow calculating practically all parameters of the process necessary for its characterization, and in particular those related to particle residence time distribution (RTD). Some numerical examples from the model, which are important for better understanding the process, are also included. It is shown that the main factor defining the efficiency of continuous mixing, through the variance reduction ratio (VRR), is the ratio of the mean residence time and the period of inflows fluctuation, rather than the variance of the RTD. Also, the influence of the dimensions of the mixer outlet on the mean residence time, and in turn on the VRR, is examined as another way of improving the design. 相似文献
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H. Berthiaux K. Marikh V. Mizonov D. Ponomarev E. Barantzeva 《Particulate Science and Technology》2004,22(4):379-389
This article demonstrates the efficiency of the application of the theory of Markov chains as a tool to model and simulate continuous powder mixing to aid in better design of such equipment. Markov chain models allow calculating practically all parameters of the process necessary for its characterization, and in particular those related to particle residence time distribution (RTD). Some numerical examples from the model, which are important for better understanding the process, are also included. It is shown that the main factor defining the efficiency of continuous mixing, through the variance reduction ratio (VRR), is the ratio of the mean residence time and the period of inflows fluctuation, rather than the variance of the RTD. Also, the influence of the dimensions of the mixer outlet on the mean residence time, and in turn on the VRR, is examined as another way of improving the design. 相似文献
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《Drug development and industrial pharmacy》2013,39(3):205-212
The aim of this study was to compare, using gamma scintigraphy, the lung deposition of a novel mucoactive agent, Nacystelyn (NAL), administered as a dry powder inhaler (DPI) in six healthy volunteers, six adult patients with cystic fibrosis (CF), and six children and adolescents patients with CF. The correlation between in vitro and in vivo results was also tested. It was first demonstrated that the method of labeling of NAL with 99mTc was reliable as tested by three in vitro methods (multistage liquid impinger, multistage cascade impactor, and 2-stage glass impinger). The deposition of unlabeled NAL, labeled NAL, and the radiolabel was similar in all stages of each device. Furthermore, the fine particle fraction (FPF) was the same on all apparatuses. The mean lung deposition obtained in volunteers was 27.5 ± 13.5%. The results are approximately three times higher than the results obtained previously in healthy volunteers with NAL metered-dose inhalers (MDIs). As expected, the lung deposition observed in patients with CF was lower, e.g., 23.5 ± 7.0% for adults and 16.5 ± 5.9% for children and adolescents. A significant correlation was found between lung deposition and both the patient weight (p < 0.02) and height (p < 0.04). Surprisingly, the peripheral:central (P:C) ratio was similar for the three populations, indicating that the presence of mucus in moderately ill patients with CF does not modify the lung distribution of NAL. The FPF measured in vitro was similar to that obtained in volunteers but higher than that found in both patient populations. The DPI formulation of NAL developed will probably improve patient compliance and comfort in future clinical trials and postmarketing use of the drug. 相似文献
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