Physicochemical Characteristics of Commercial Aluminum Hydroxycarbonate Gels

Abstract

Four commercial samples of AHC each from different manufacturer or distributor in the USA, Canada and Mexico, were studied to determine particle size distribution, viscosity, rate of settling, pH, point of zero charge (PZC), IR spectra and sodium content. These properties are of interest to the raw material manufacturer, the formulator and the consumer, since they impart desirable characteristics to the finished product. It was found in this work, that the average particle size varied between 3.90 and 2.01 μm with standard deviations of 4.10 μm and 3.99 μm, respectively; the viscosities of 4% (w/w) equivalent Al(OH)₃, suspensions, ranged from 49 to 10 mPa.s and the sediment fractions after 24 hours for these suspensions oscillated from 0.44 to 0.59. The pH was between 5.61 and 7.60 and the PZC varied from 6.45 to 7.33. The sodium content found in this work was between 0.0406 and 0.5620 g/L. The infrared spectra obtained for the obtained for the four samples indicated the presence of the absorption bands assigned to carbonates in the range of 1525 and 1518 cm^?1, 1440 cm^?1, 1104 and 1088 cm^?1 and 857 to 843 cm^?1. These results are discussed from the implications that they have to the manufacturer and to the formulator, including the aesthetics of the finished product.     

Particle Morphology of Amorphous Aluminum Hydroxycarbonate and Its Effect on Tablet Production

Abstract

The particle morphology of amorphous aluminum hydroxycarbonate was studied by disaggregation induced by phosphate adsorption and direct observation by high resolution transmission electron microscopy. The primary particles are sheet-like and have equivalent diameters of 55A or less. The primary particles are believed to correspond to planar polymers comprised of six-membered rings of aluminum ions joined by double hydroxide bridges. Secondary particles form by attractive interaction of primary particles. The size of the primary particles affects the porosity of the secondary particles. The granulating and tableting properties of two spray dried amorphous aluminum hydroxycarbonates were shown to be related to the size of the primary particles and the porosity of the secondary particles.     

Particle Morphology of Amorphous Aluminum Hydroxycarbonate and Its Effect on Tablet Production

The particle morphology of amorphous aluminum hydroxycarbonate was studied by disaggregation induced by phosphate adsorption and direct observation by high resolution transmission electron microscopy. The primary particles are sheet-like and have equivalent diameters of 55A or less. The primary particles are believed to correspond to planar polymers comprised of six-membered rings of aluminum ions joined by double hydroxide bridges. Secondary particles form by attractive interaction of primary particles. The size of the primary particles affects the porosity of the secondary particles. The granulating and tableting properties of two spray dried amorphous aluminum hydroxycarbonates were shown to be related to the size of the primary particles and the porosity of the secondary particles.     

Fluidization of Aluminum Hydroxide Gels Containing Xanthan Gum

Suspensions of aluminum hydroxide dried gel interacted with xanthan gum to form a thick coagulum. Addition of low concentrations of deflocculants (sodium tripolyphosphate, sodium citrate, potassium phosphate dibasic) prevented coagulum formation. Sorbitol, 5%, was also effective. Suspensions made from a fluid aluminum hydroxide concentration did not become coagulated in the presence of xanthan gum.     

Mucoadhesive and Physicochemical Characterization of Carbopol-Poloxamer Gels Containing Triamcinolone Acetonide

The viscosity and bioadhesive property of Carbopol-Poloxamer gels containing triamcinolone acetonide to mucosa were tested according to various concentrations of Carbopol gels of various pH. The increase in Carbopol concentration caused increased viscosity and bioadhesiveness. The neutralization of pH in various concentrations of Carbopol gels showed the increased viscosity, showing the highest viscosity and highest bioadhesiveness when neutralized to pH 6. A relationship between the viscosity and bioadhesive strength was shown from the neutralized Carbopol gels. The physicochemical interactions between triamcinolone acetonide and polymers were investigated by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectrophotometry. According to FTIR and XRD studies, the drug did not show any evidence of an interaction with the polymers used and was present in an unchanged state.     

Effect of Precipitation Temperature, pH and Agitation on the Acid Reactivity of Aluminum Hydroxycarbonate Gel

A completely randomized 2³-factorial design study of the precipitation of aluminum hydroxycarbonate gel by the reaction of aluminum chloride with sodium carbonate and sodium bicarbonate showed that the precipitation temperature and end-point pH were significant in terms of the rate of acid neutralization at the 0.01 level and that stirring speed was significant at the 0.05 level. No significant interactions occurred between the parameters. The most reactive gels were precipitated at 25°, pH 6.5 and either 15 or 500 rpm. After aging for 105 days at 25° these gels exhibited a twelvefold greater rate of acid neutralization than the least reactive gel which was precipitated at 4°, pH 5.8 and 15 rpm. The results are analyzed in terms of the effect of each parameter on the particle size and structure of aluminum hydroxycarbonate gel     

Physicochemical Characterization of Interaction of Ibuprofen by Solid-State Milling with Aluminum Hydroxide

This present study is a preliminary exploration of the affinity between a carboxylic model drug ibuprofen and aluminum hydroxide. Ibuprofen was comilled with aluminum hydroxide in different weight ratios in the solid state and was characterized by scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and in vitro dissolution studies. XRD and SEM studies indicated complete interaction of ibuprofen with aluminum hydroxide and complete amorphization of aluminum hydroxide–ibuprofen complexed salt as well, on comilling with aluminum hydroxide at 1:2 ratio. FTIR data showed the disappearance of acid carbonyl peak with the appearance and the corresponding increase in absorbance of new signal at 1,682 cm^?1 in the 1:1 and 1:2 ibuprofen–aluminum hydroxide-comilled powder. The accompanied increase in the absorbance of carboxylate peak in the ibuprofen–aluminum hydroxide physical mixture, and 1:0.1, 1:0.5, 1:1, and 1:2 (IBA_pm, and IB₁A_0.1, IB₁A_0.5, IB₁A₁, and IB₁A₂, respectively) comilled powder indicated an acid–base reaction between ibuprofen and aluminum hydroxide. On storage at 40°C and 75% relative humidity (RH) for 10 weeks, XRD study showed the absence of reversion to the crystalline state and FTIR data revealed continued increase of new signal at 1,682 cm^?1 relative to carboxylic acid peak and no reappearance of carboxylic acid peak. In vitro dissolution studies revealed that the percent release of ibuprofen from the aluminum hydroxide-comilled powder is in the following order: IB₁A₂ < IB₁A₁ < ibuprofen crystal < ibuprofen milled alone < IB₁A_0.1 < IB₁A_0.5. Aluminum metal cation might have interacted to form a complex through the carboxyl and carbonyl groups of ibuprofen. Improved dissolution of drug associated with IB₁A_0.1 and IB₁A_0.5 is because of the absence of a new signal at 1,682 cm^?1 and improved amorphization of the drug to some extent. Dissolution of drug affected in IB₁A₂ and IB₁A₁ may be because of the insoluble stable complex formation.     

铝纳米梁的电学特性测试

对铝纳米梁进行了力学和电学特性测试．力学测试结果表明,铝纳米梁处于弹性形变区,具有张应力、电学测试结果表明,纳米梁电阻随着扫描次数增加而增加．通过分析电学实验结果可知,扫描次数增加使纳米梁发生塑性形变,并使纳米梁上张应力减小．研究结果表明,纳米梁电阻随着纳米梁张应力增大而减小．     

泡沫铝的吸声特性及影响因素

介绍了泡沫铝的吸声特性,研究了泡沫铝的厚度、孔隙率、压缩率、空腔对其吸声性能的影响。     

硼酸铝晶须氮化特性研究

针对硼酸铝晶须增强铝基复合材料的界面反应问题,经热力学预测,首次提出对硼酸铝晶须进行氮化处理这一新工艺。采用Ｘ射线光电子能谱（ＸＰＳ）研究了硼酸铝晶须的氮化特性。实验结果表明：硼酸铝晶须中已渗入氮元素;同时,硼酸铝晶须中硼元素向ＢＮ转变。硼酸铝晶须的氮化反应受扩散控制,为一热激活过程,其反应活化能为３０６．３４ｋＪ／ｍｏｌ。     

中空挤压铝型材振动声辐射特性

随着高速列车车体结构轻量化的发展,中空挤压铝型材结构的车体在高速列车上得到广泛应用,而车体的振动声辐射是高速列车车内噪声的主要来源之一。基于FE-SEA混合法和统计能量分析（SEA）分别建立了高速列车车体铝型材振动声辐射的中频和高频预测模型,计算了在粉红噪声谱激励下和实测轮轨激励下铝型材辐射至半空间的声功率,探索了铝型材几何特征因素和不同速度实测轮轨激励对振动声辐射特性的影响。计算结果表明,在粉红噪声谱激励下,下板对铝型材振动声辐射影响最大,与参考铝型材相比相差大于1 dB。铝型材在实测轮轨激励下,辐射声功率的主要贡献频段为400 Hz～1 600 Hz,速度增大加剧了铝型材在400 Hz以上中高频频段的振动声辐射。相关计算结果将为高速列车车体铝型材的设计提供理论参考。     

The Physicochemical Characteristics of Freeze-Dried Scutellarin-Cyclodextrin Tetracomponent Complexes

ABSTRACT

In an effort to improve the solubility of the insoluble drug scutellarin, a novel complexation of scutellarin with β-cyclodextrin (β-CD) was studied. Tetracomponent freeze-dried complex was prepared with scutellarin, β-CD, Hydroxypropyl Methylcellulose (HPMC), and triethanolamine. To confirm complex formation, complex was characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction, and differential scanning calorimetry (DSC). Phase-solubility analysis suggested the soluble complexes having 1:1 stoichiometry. The β-CD solubilization of scutellarin could be improved significantly by combining water-soluble polymer and pH adjuster. Comparing the binary, ternary solid systems with tetrary systems, tetracomponent freeze-dried complex showed the best effect of solubilization. A maximal solubility of scutellarin (23.65 mg/ml) was achieved with tetracomponent freeze-dried complex, up to 148-fold increase over scutellarin solubility in water, and the solubility of scutellarin is 15.35 ug/ml (up to 6-fold) in simulated gastric fluid.     

The Response Surface Approach to Spot Welding Commercial Aluminum Sheets

The present paper reports experimental investigations on the spot welding of commercial aluminum sheets. Experiments were carried out to study the influence of spot welding parameters (welding current, welding time, electrode force and sheet thickness) on the strength of spot welded aluminum sheets with commercial purity.

Experiments were carried out on the basis of response surface methodology (RSM) technique. The mathematical models (failure load and nugget area) correlating process parameters and their interactions with response parameters have been established. These models have been used in selecting the optimum process parameters for obtaining the desired spot welding quality at the least possible consumed power.     

镍铝青铜的熔铸工艺特点

介绍了镍铝青铜的铸造工艺性能,对镍铝青铜在熔铸过程中的常见缺陷及成因进行了详细分析,重点探讨了镍铝青铜的熔铸工艺方法,提出了能够提高铸件质量的多种工艺措施和建议。     

Microstructural Characteristics of Underwater Shock Consolidated Aluminum Composites

Metal matrix composites (MMCs) offer extra strength and high temperature capabilities in comparison with unrein-forced metals. Aluminum composites possess higher stiffness, strength, fatigue properties and low weight advantages.Carbon fiber reinforced Al composites (Al-Cf) and silicon carbide particulate reinforced Al composites (Al-SiCp) were shock densified using axisymmetric assemblies for underwater explosions. Unidirectional planar shock waves were applied to obtain uniform consolidation of the composites. The energy generator was a high explosive of 6.9 km/s detonation velocity. Irregular morphological powders of Al were the base material. The reinforcement ratio was 15 Vol. pct for Al-Cf composites and 30 Vol. pct for Al-SiCp composites. The microstructural and the strength characteristics of the shock consolidated Al composites are reported.     

Application of Nonlinear Superposition to Creep and Relaxation of Commercial Die-Casting Aluminum Alloys

Die-cast aluminum alloys are heavily used in small engines, where they are subjected to long-term stresses at elevated temperatures. The resulting time-dependent material responses can result in inefficient engine operation and failure. A method to analytically determine the stress relaxation response directly from creep tests and to accurately interpolate between experimental time-history curves would be of great value. Constant strain, stress relaxation tests and constant load, creep tests were conducted on aluminum die-casting alloys: B-390, eutectic Al–Si and a 17% Si–Al alloy. A nonlinear superposition integral was used to (i) interpolate between empirical primary inelastic creep-strain and stress-relaxation time histories and (ii) to determine the stress relaxation response from corresponding creep data. Using isochronal stress-strain curves, prediction of the creep response at an intermediate stress level from empirical creep curves at higher and lower stresses resulted in a correlation (R) of 0.98. Similarly for relaxation, correlations of 0.98 were obtained for the prediction of an intermediate strain level curve from higher and lower empirical relaxation curves. The theoretical prediction of stress relaxation from empirical creep curves fell within 10% of experimental data.This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to Mechanics of Time-Dependent Materials     

地方特色的城市商业银行标志设计

以城市商业银行标志设计的地方特色问题为探讨对象,阐述了造型、图案、哲学思想理念等方面在商业银行标志设计中的应用,提出了只有更好地了解地方特色元素,遵循设计中的城市特色和文化底蕴、金融行业属性、现代感等原则,使地方特色元素与商业银行标志设计和谐运用,才能设计出真正被人们乃至世界所认同的具有地方特色的商业银行标志。     

Gelatine Gels and Polyoxyethylene-Polyoxypropylene Gels: Comparative Study of Their Properties

ABSTRACT

Gelatine gels and polyoxyethylene-polyoxypropylene (Pluroni^R) F-108 and F-127 gels were prepared at concentrations ranging between 5 and 25% (W/V), the former by dispersion at 37°C, the later by dispersion at 4°C. The viscosity, the gel-sol transition temperature and the “in vitro” release kinetics of these gels were compared as a first step for the elaboration of parented controlled release formulations. Phenolsulphonftaleine (PR) was used as a tracer.

In all cases the viscosity increased with the rise in the concentration of gelatin (20 to 264 cps for 5 to 20%) or pluronic (260 and 1,520 cps for 20 and 25% F-108). The gel-sol transition temperature for gelatine gels was directly related to the concentration. On the contrary, for pluronic gels an inverse relation was observed, being the gel-sol transition temperature higher in copolymers with a large percentage of polyoxyethylene groups (30±0.2 °C for 25 % F-108). In both types of gels, a rise in pH and ionic strength decreased the gel-sol transition temperature, whereas PR increase this temperature. The release of the tracer, from the gels to the aqueous medium, showed a zero-order kinetics and the release rates were inversely proportional to the concentration of gelling agent.     

Gelatine Gels and Polyoxyethylene-Polyoxypropylene Gels: Comparative Study of Their Properties

Abstract

Gelatine gels and polyoxyethylene-polyoxypropylene (Pluroni^R) F-108 and F-127 gels were prepared at concentrations ranging between 5 and 25% (W/V), the former by dispersion at 37°C, the later by dispersion at 4°C. The viscosity, the gel-sol transition temperature and the “in vitro” release kinetics of these gels were compared as a first step for the elaboration of parented controlled release formulations. Phenolsulphonftaleine (PR) was used as a tracer.

In all cases the viscosity increased with the rise in the concentration of gelatin (20 to 264 cps for 5 to 20%) or pluronic (260 and 1,520 cps for 20 and 25% F-108). The gel-sol transition temperature for gelatine gels was directly related to the concentration. On the contrary, for pluronic gels an inverse relation was observed, being the gel-sol transition temperature higher in copolymers with a large percentage of polyoxyethylene groups (30±0.2 °C for 25 % F-108). In both types of gels, a rise in pH and ionic strength decreased the gel-sol transition temperature, whereas PR increase this temperature. The release of the tracer, from the gels to the aqueous medium, showed a zero-order kinetics and the release rates were inversely proportional to the concentration of gelling agent.     

Formation of Amorphous Telmisartan Polymeric Microparticles for Improvement of Physicochemical Characteristics

In order to improve solubility and dissolution rate of poorly aqueous soluble telmisartan, its amorphous polymeric microparticles with PVP K30 were prepared with or without aid of adsorbent (Aerosil200/Sylysia350) using spray-drying technique. The pure drug and formulations were evaluated for their morphology, particle size, aqueous solubility, and in vitro drug release. Solid state characterization of pure drug and microparticles was carried out by Fourier transform infrared spectroscopy (FTIR), x-ray powder diffraction (XRPD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). FTIR indicated hydrogen bonding interaction with an absence of any other chemical interaction between drug and excipient. The results of DSC and XRPD revealed transformation of crystalline drug to amorphous form which was confirmed by SEM. Significant solubility and dissolution enhancement was observed for all polymeric microparticles over pure drug and spray-dried pure drug. This enhancement was attributed to the wetting effect of polymers, altered surface morphology with micronization and decreased crystallinity of drug particles.