Powder Blends Research Articles

Manufacturing of biomedical Ti alloys with controlled oxygen content by blended elemental powder metallurgy

Biomedical Ti-xNb-7Zr-0.7O (wt%) alloys were manufactured from elemental powders and controlled addition of TiO2 using field assisted sintering technique (FAST). First, sintering parameters were optimized on the benchmark Ti-29Nb-7Zr-0.7O alloy. Second, alloys with various content of Nb (20, 23, 26 and 29 wt%) were manufactured. FAST is capable to produce homogeneous material with controlled amount of oxygen. In addition, FAST is a valuable method for fast sampling of alloys with different compositions. Detailed XRD and SEM study proved that oxygen prevents formation of α” martensite phase. Presence of α phase, α” phase and especially ω phase causes an increase of elastic modulus and microhardness. Single phase β Ti-29Nb-7Zr-0.7O alloy can be manufactured by FAST from elemental powders and subsequent solution treatment. The alloy is proposed for biomedical use due to its low elastic modulus.

Effect of heparin drug loading on biodegradable polycaprolactone–iron pentacarbonyl powder blend stents fabricated by solvent cast 3D printing

PurposeThe purpose of this paper is to fabricate pre-existing geometries of the stents using solvent cast 3D printing (SC3P) and encapsulation of each stent with heparin drug by using aminolysis reaction.Design/methodology/approachThe iron pentacarbonyl powder and poly-ɛ-caprolactone blend (PCIP) were used to print stent designs of Art18z, Palmaz-Schatz and Abbott Bvs1.1. The properties of antithrombosis, anticoagulation and blood compatibility were introduced in the stents by conjugation of heparin drug via the aminolysis process. The aminolysis process was confirmed by energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy due to presence of amide group and nitrogen peak in the respective analysis. Biological studies were performed to depict the cell viability, hemocompatibility and antithrombotic properties. Besides, mechanical behaviors were analyzed to study the behavior of the stents under radial compression load and bending load.FindingsThe amount of heparin immobilized on the Art18z, Palmaz-Schatz and Abbott Bvs1.1 stents were 255 ± 27, 222 ± 30 and 212 ± 13 µg, respectively. The cell viability studies using L929 fibroblast cells confirmed the cytocompatibility of the stents. The heparinized SC3P printed stents displayed excellent thrombo-resistance, anticoagulation properties and hemocompatibility as confirmed by blood coagulation analysis, platelet adhesion test and hemolysis analysis. Besides, mechanical behavior was found in context of the real-life stents. All these assessments confirmed that the developed stents have the potential to be used in the real environment of coronary arteries.Originality/valueVarious customized shaped biodegradable stents were fabricated using 3D printing technique and encapsulated with heparin drug using aminolysis process.

Evaluating the Taste Masking Ability of Two Novel Dispersible Tablet Platforms Containing Zinc Sulfate and Paracetamol Reconstituted in a Breast Milk Substitute.

Milk is often used as a dispersion medium for medicines administration in young children but its taste-masking ability is unknown. A human taste panel was conducted to assess the potential of infant formula milk (Aptamil® 1) to mask the taste of two model WHO priority medicines, zinc sulfate and paracetamol, manufactured as dispersible tablets. Simultaneously, the palatability of powder blends of the tablet platforms was assessed. Twenty healthy adult volunteers performed a swirl-and-spit assessment of placebos and API-containing blends in either a lactose-based or a mannitol-based dispersible tablet platform, reconstituted in 10 mL of either water or Aptamil® 1. Eighteen samples were rated for aversion using a 100-mm Visual Analogue Scale, grittiness using a 5-point Likert scale, and “acceptability-as-a-medicine” evaluated as: “Would you find this sample acceptable to swallow as a medicine?” with binary answers of Yes/No. The API-containing formulations were more aversive than the placebos; the paracetamol-containing samples being more aversive than zinc sulfate samples. The platforms themselves were not aversive. Non-gritty samples had four-fold greater odds of being acceptable as a medicine. Aptamil® 1 masked the taste of zinc sulfate in the mannitol-based formulation but did not mask the taste of paracetamol in either platform, suggesting a limited taste-masking ability, which may be API and formulation dependent.

Residual properties of alkali-activated slag concrete exposed to elevated temperatures

PurposeThis paper attempted to study the alkali-activated (AA) binder consisting of 94% of ground granulated blast furnace slag (GGBFS) and 6% of blended powder of alkali metal hydroxide and metal sulfate, which acted as an activator.Design/methodology/approachSeveral concrete specimens (cubes, cylinders and prisms), which were casted using AA binders, were further tested for mechanical properties after exposure to elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C. Additionally, to understand the structural behavior in uniaxial compressive load, reinforced concrete short columns were cast, cured and tested at ambient temperature as well as after exposure to 300 °C, 600 °C and 900 °C, to know the residual strength after exposure to elevated temperature.FindingsThe findings for the residual strength of alkali-activated slag binder concrete (AASBC) indicated a substantial agreement with the results obtained for the residual strength of Portland slag cement (PSC) concrete, thereby showing the effectiveness of binder when used as a replacement of cement.Originality/valueThe study clearly indicates that the binder developed is an effective approach for the 100% replacement of cement in the concrete.

Direct cyclodextrin-based powder extrusion 3D printing for one-step production of the BCS class II model drug niclosamide

Niclosamide (NCS) is a drug that has been used as an anthelmintic and anti-parasitic drug for about 40 years. Recently, some studies have highlighted its potential in treating various tumors, allowing a repositioning of this drug. Despite its potential, NCS is a Biopharmaceutical Classification System (BCS) Class II drug and is consequently characterized by low aqueous solubility, poor dissolution rate and reduced bioavailability, which limits its applicability. In this work, we utilize a very novel technique, direct powder extrusion (DPE) 3D printing, which overcomes the limitations of previously used techniques (fused deposition modelling, FDM) to achieve direct extrusion of powder mixtures consisting of NCS, hydroxypropyl methylcellulose (HPMC, Affinisol 15 LV), hydroxypropyl-β-cyclodextrin (HP-β-CD) and polyethylene glycol (PEG) 6000. For the first time, direct printing of powder blends containing HP-β-CD was conducted. For all tablets, in vitro dissolution studies showed sustained drug release over 48 h, but for tablets containing HP-β-CD, the release was faster. Solid-state characterization studies showed that during extrusion, the drug lost its crystal structure and was evenly distributed within the polymer matrix. All printed tablets have exhibited good mechanical and physical features and a stability of the drug content for up to 3 months. This innovative printing technique has demonstrated the possibility to produce personalized pharmaceutical forms directly from powders, avoiding the use of filament used by FDM.Graphical abstract

Prediction of the effect of water on the glass transition temperature of low molecular weight and polysaccharide mixtures

The right storage conditions for food powders containing amorphous carbohydrates are crucial to avoid structural changes. By combining the sorption isotherm and the glass transition temperature (Tg) data for these food powders enables the determination of appropriate moisture and temperature conditions for their storage. In this study, the modified Flory-Huggins free volume theory was utilized to predict the stability diagrams purely from the composition of the powders. The validation of the approach using the literature data of blends of grapefruit, mango and acai powders with various blends of maltodextrin (MD) and gum Arabic. The blends of fructose, glucose individual and in combination with citric acids as well as blackcurrant juice concentrate with MD DE 9–13 were also investigated. The alignment of experimental and predicted data of fruit powders demonstrates that it was possible to predict the relation of the Tg well as a function of the water activity for carbohydrate mixtures.

Effect of stand-off-distance on the performance of TIG cladded TiC-Co coating deposited on Ti-6Al-4V alloy

TiC-Co layer was fabricated on Ti-6Al-4V alloy plate by TIG cladding route using TiC/Co powder blend of equal weight ratio. The distance between the electrode and the work, namely stand-off-distance (SOD), was varied between 4 and 6 mm during the TIG arc scanning, which altered the arc volume and subsequent heat intensity in the powder melt pool. A significant variation in the clad track width and depth was noticed due to the discrepancy in the arc-workpiece interaction area for increasing the SOD. Although almost uniform thickness in the clad layer was obtained, owing to discrepancies in the specific density and thermal conductivity between TiC, Co powder, and Ti-6Al-4V substrate, the constituents of the clad layer were found in-homogenously distributed. Consequently, a marginal diversity in the micro-hardness and wear resistance of the clad layer was recorded for the alteration of SOD conditions. Variation in the concentration of partially melted spherical shaped TiC particles, resolidified dendritic TiC, and other intermediate phases alter the microhardness value in different regions of the clad layer. The results indicated that the wear value or height reduction of the clad specimen was up to 15 times lower than the substrate material when tested against hardened steel. In contrast, the wear value was reduced almost three times when tested against the alumina abrasive disc under different load conditions.

Powder bed selective laser process (sintering/melting) applied to tailored calcium phosphate-based powders

This paper focuses on the tailoring of calcium phosphate powders for their use as powder bed selective laser process feedstock. Hydroxyapatite and chlorapatite were used as starting powders for the preparation of different blends through the addition of graphite as a laser absorptance additive. A methodical study was conducted to compare the processing windows of the blends containing different amounts of graphite through the laser patterning of circular samples. It was found that the addition of graphite increases the process window of the powder blends being the powder without additive non processable. Hydroxyapatite showed a clear phase transition (decreased when using higher volumetric energy density) into other calcium phosphate phases while chlorapatite was demonstrated to be thermally stable during the whole process (examined through X-ray diffraction and vibrational spectroscopies). In parallel, the study evaluating the powder blend composed of hydroxyapatite and graphite for the production of solid and complex parts was carried out although it required long printing times. The productivity of the process was improved by modification of printing parameters. Then, a series of solid samples were produced for the analysis of the microstructure and mechanical properties. High interconnected porosity was observed in the samples which could improve the bioactivity of the bioceramic scaffolds. A post-treatment of the parts increased their proportion in the hydroxyapatite phase and their mechanical properties. These results are expected to contribute to the application of powder bed selective laser processing of calcium phosphates powders toward bone tissue engineering. • Graphite as absorption additive improves the laser-material interaction enlarging the process window. • Laser parameters directly influence the hydroxyapatite phase transition into other calcium phosphate phases. • Chlorapatite did not undergo phase transition during the process due to its inherent higher thermal stability. • Solid parts containing a majority of HA phase in the structure were obtained although with low mechanical properties.

Characterization of the Salt and Free Base of Active Pharmaceutical Ingredients Based on NMR Relaxometry Measured by Time Domain NMR.

NMR relaxometry measurement by time domain NMR (TD-NMR) is a promising technique for characterizing the properties of active pharmaceutical ingredients (APIs). This study is dedicated to identifying the salt and free base of APIs by NMR relaxometry measured by the TD-NMR technique. Procaine (PC) and tetracaine (TC) were selected as model APIs to be tested. By using conventional methods including powder X-ray diffraction and differential scanning calorimetry, this study first confirmed that the salt and free base of the tested APIs differ from each other in their crystalline form. Subsequently, measurements of T1 and T2 relaxation were performed on the tested APIs using TD-NMR. The results demonstrated that these NMR relaxometry measurements have sufficient capacity to distinguish the difference between the free base and salt of the tested APIs. Furthermore, quantification of the composition of the binary powder blends consisting of salt and free bases was conducted by analyzing the acquired T1 and T2 relaxation curves. The analysis of the T1 relaxation curves provided a partly acceptable estimation: a good estimation of the composition was observed from PC powders, whereas for TC powders the estimation accuracy changed with the free base content in the binary blends. For the analysis on T2 relaxation curves, a precise estimation of the composition was observed from all the samples. From these findings, the NMR relaxometry measurement by TD-NMR, in particular the T2 relaxation measurement, is effective for evaluating the properties of APIs having different crystalline forms.

In Situ Ti6Al4V/TiB Composites Prepared by Hydrogen-Assisted Sintering of Blends Containing TiH2 and Ball-Milled Ti+TiB2 Powders.

In the present study, 98.6–99.5% dense in situ reinforced Ti6Al4V/TiB composites were manufactured with a newly developed approach based on hydrogen-assisted blended elemental powder metallurgy (BEPM). The approach includes the activation milling of titanium powder produced with hydrogenation-dehydrogenation (HDH-Ti powder) with finer TiB2 additives, following blending with TiH2 and master alloy (MA) powders, and final press-and-sinter operations. Scanning electron microscope (SEM) observations prove the formation of microstructures with improved density and homogeneous distribution of TiB reinforcements in a sintered Ti6Al4V matrix. Hardness and compressive tests validated the high mechanical characteristics of produced composites. The effect of preliminary milling time over 2–6 h and the ratio of hydrogenated and non-hydrogenated titanium powders used (TiH2 vs. HDH Ti) on microstructure and mechanical properties were studied to further optimize the processing parameters. Test results indicate the above approach can be regarded as a promising route for the cost-effective manufacturing of Ti6Al4V/TiB composite with reduced porosity, tailored microstructure uniformity, acceptable impurity level and, hence, mechanical characteristics sufficient for practice applications.

Discrete element method simulation of binary blend mixing of cohesive particles in a high‐intensity vibration system

AbstractThe effects of processing intensity, time, and particle surface energy on mixing of binary cohesive powder blends in high‐intensity vibration system were investigated via discrete element method simulations. The mixedness was quantified by the coefficient of variation, Cv; lower being better. The mixing rate, which is the speed at which homogeneity was achieved, was inversely proportional to the mixing Bond number, defined as the ratio of particle cohesion to the shear force resulting from the mixing intensity. Results show that both increasing processing intensity and reducing surface energy led to a faster mixing rate. However, the mixedness improved initially as mixing action (the product of mixing rate and mixing time) increased, but later deteriorated upon its further increase. Thus, both mixing rate and mixing intensity need to be tuned for optimum mixing performance depending on the cohesion level of particles; too high or too low mixing action should be avoided.

Technology of Processing Plant Extracts Using an Aluminometasilicate Porous Carrier into a Solid Dosage Form.

A method of preparing tablets called liquisolid technique is currently emerging. In these formulations, an important role is played by porous carriers, which are the basic building blocks of liquisolid systems (LSSs). The most common are microcrystalline cellulose (MCC), magnesium aluminometasilicates, silica aerogels, mesoporous silicates, clays, etc. In this study, magnesium aluminometasilicate is used to prepare modified LSS formulations with plant extracts as model drugs dissolved in water (W) or ethanol (E). The modification involves drying tablets in a microwave (MW) and hot air dryer (HA) for a specified period. Powder blends and tablets were evaluated for physical properties, and their antioxidant activity (AA) was measured in a modified dissolution by ferric reducing antioxidant power assay (FRAP). PLS and ANOVA were used to compare tablets properties depending on the composition and technology. The experiment is based on a previous one, in which the plant extracts were processed into tablets using a similar method. Therefore, extending the study to include more plants and the robust statistical evaluation and comparison of the products was a procedure to justify the suitability of the presented method for a wide range of liquid plant extracts. As a result, we obtained tablets with excellent physical properties, including a short disintegration and dissolution, which is problematic in tableted extracts.

Development of Ni-base metal matrix composites by powder metallurgy hot isostatic pressing for space applications

In this work, near-net-shape powder metallurgy hot isostatic pressing (NNS PM HIP) of Ni-base metal matrix composite (Ni-MMC) was developed to improve the hardness and wear properties of turbopumps mechanical seals. Silicon carbide (SiC) and titanium diboride (TiB2) fine powders were used as reinforcements with different ratios to improve the hardness and consequently the tribological properties of the developed Ni-MMC material. Powder characterisation was performed on the blended powders to check the homogeneity of the mixed powders. The hot isostatically pressed (HIPed) Ni-MMC microstructures were analysed using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. The HIPed material showed a fully dense microstructure with a continuous network of ceramic reinforcement particles at the prior particle boundaries (PPBs). Furthermore, microhardness tests were performed on IN625, IN625-SiC and IN625-TiB2 to understand the impact of the reinforcement on the microhardness. It was demonstrated that the volume percentage of ceramic reinforcement in the IN625 matrix plays a crucial role in achieving higher hardness by increasing the fraction of hard phases appearing in the microstructure of the developed Ni-MMC material. The final part of the work focuses on the canister design and manufacture of a near-net-shape (NNS) mechanical gas seal using IN625 based MMC to demonstrate the feasibility of manufacturing mechanical seals through the NNS PM HIP technique. Overall, IN625 based MMCs resulted in a drastic improvement in tribological properties if compared to the base material. Furthermore, the employment of the PM HIP consolidation technique resulted in a fully dense and homogeneous microstructure, highlighting the potentials of PM HIP in the generation of novel composite materials.

FORMULATION AND EVALUATION OF THYROID HORMONE (T4) IMMEDIATE RELEASE TABLETS

The aim of this research work is to formulate and evaluate Levothroxine sodium immediate release tablets prepared by direct compression method . Five formulations were evaluated for different pre and post compression parameter and in vitro drug release studies.The results of pre compression parameters of formluation 1 to 5 were compared with prescribed limits. It showed that formulation 1 to 5 powder blend exhibit good flow property and compressibility property. The disintegration time of all formulation was found to be in the range 2mins 09 secsto 4mins 03 secs.Thus, based on evaluation of different parameters it was concluded that formulation of immediate release tablet Levothyroxine sodium was successfully done and F-5 showed almost 93% drug release at 45 mins in Alkaline borate buffer( pH 10). Keywords: Thyroid hormone (T4), Immediate release tablets, Direct compression, Dissolution.

Microstructure and Tensile Properties of Fine-Grained Bulk Copper Fabricated by Thermomechanical Consolidation of Copper Nanopowder/Micron-Sized Powder Blend

Samples of fine structured Cu were fabricated by spark plasma sintering (SPS) of compacts of Cu nanopowder/micron-sized powder blend with a ratio of 3:7 by weight, and one of the SPSed samples was further processed by hot extrusion. The microstructures of the as-SPSed and the as-extruded samples and the tensile properties and fracture behavior of the as-extruded sample were studied. It was found that the microstructures of the samples consist of a concoction of ultrafine and coarse grains with high dislocation densities (~1015 m-2) as a result of microstructural evolution during material processing. Some nanograins were oxidized to form Cu2O particles residing around the coarse grains. Extrusion of the SPSed sample increases its microhardness from 70 HV to 90 HV. The electrical conductivity of the as-extruded sample reaches 87% international annealed copper standard (IACS), and its tensile properties are 200 MPa for yield strength, 218 MPa for ultimate tensile strength and 9% for elongation to fracture. The tensile test specimens from the as-extruded sample exhibit nearly ideal plastic deformation and undergo ductile fracture, suggesting that the fine-grained copper is a highly desirable material for high strength electrical conductors.

Efficacy of elemental mixing of in situ alloyed Al-33wt%Cu during laser powder bed fusion

Challenges in developing novel alloys, specifically for use in laser powder bed fusion, may be overcome by in situ alloying of elemental powders during laser melting. This process could expedite prototyping of various alloy compositions and alleviate the restrictions and cost barriers of creating custom made alloy powder. In this research, the efficacy of in situ alloying is studied with respect to particle size distributions of the powder blends and the laser process parameters. The microstructure of the Al-Cu eutectic system is used here as an indicator of mixing quality of the constituent elements during laser melting of the particles. Hypo- or hypereutectic regions are readily visible through the dendritic growth of the α or θ phases, indicating regions where the solute concentration deviates from the nominal eutectic composition. Samples were built from four powder blends at a range of scan speeds and powers to show how mixing is affected at different processing parameters. Image analysis and Vickers microhardness tests are both used to characterize the degree of mixing within the samples. Results of this study show that poor mixing can occur due to segregation of elemental powder within the powder blend. This produces local build compositions different than the mean powder composition when the mean particle volume is large enough that the melt pool encompasses too few particles to be a stochastic representation of the blend. Liquid phase intermixing limitations within the pool are thought to be less important than the melt pool volume itself.

Development of cucurbocitrin based nutraceutical formulation: A potential adjuvant herbal therapy in the management of hypertension

Nearly half of the hypertensive patients fail to manage their blood pressure despite pharmacological interventions, which reflects the dire need for adjuvant anti-hypertensive therapies. Nutraceutical formulations are attractive in this regard owing to their efficacy, ease of availability, and moderate pricing. The current investigation involves the formulation of cucurbocitrin nutraceutical tablets by direct compression method and evaluated for its anti-hypertensive effect in the management of hypertension. Cucurbocitrin is a natural compound prepared from Citrullus lanatus seeds belonging to the family Cucurbitaceae. The powder blend was examined for pre-compression studies such as angle of repose, bulk density, tapped density, Carr’s index, Hausner's ratio, etc. Based on acute-oral toxicity results, two tablet formulations were prepared using a different dose of cucurbocitrin and evaluated for post-compression parameters such as friability, hardness, weight variation, disintegration time, and in vitro drug release studies. In vivo studies were also performed for both formulations using a 10% Glucose solution-induced hypertension model in albino rats to observe its anti-hypertensive activity. The study indicated that nutraceutical formulation was found to be effective in reducing hypertension in an animal model.

Influence of flow aid additives on optical properties of polyamide for Laser-Based Powder Bed Fusion

Aim of this paper is to investigate the influence of flow aid additives on beam matter interaction of polyamide for laser-based powder bed fusion of polymers (PBF-LB/P). The optical energy input determines the laser beam powder interaction, quantified by absorption within the optical properties of a material. Additives like fumed silica for increasing powder flowability are important for using PBF-LB/P materials. The aid of those additives and restrictions in mechanical properties of built components using high portions of additives are already investigated, but not the change in relevant optical properties. Dry blends of polyamide powder with different weight percentage of additives, such as fumed silica, alumina and titania are investigated. A measurement system with a double-integrating-sphere setup and CO2 laser is used to characterize the beam matter interaction as the absorptance of optical energy in the powder layer. Based on this, the change in absorptance due to the influence of flow aid additives is investigated in order to be able to estimate possible effects on the processability.

Development of Bioglass/PEEK Composite Coating by Cold Gas Spray for Orthopedic Implants.

Cold gas spray (CGS) technology has allowed the development of biofunctional coatings composed of 45S5 and polyetheretherketone (PEEK). The combination of a bioactive glass material embedded in a polymeric matrix makes this composite an interesting material for orthopedic applications since this composite meets the biomechanical and biological requirements of an implant. In the present study, blends of bioactive glass 45S5 and PEEK powder with different granulometry and 45S5/PEEK ratio have been prepared. These mixtures of powders have been deposited onto PEEK substrates by CGS with the goal of incorporating a bioactive additive to the biocompatible polymer, which can improve the bone-implant interaction of PEEK. The deposition efficiency (DE) of the coatings has been evaluated, and from the results obtained, it was possible to conclude that DE is significantly affected by the granulometry and by the 45S5/PEEK ratio of the blends. By scanning electron microscopy (SEM) inspection, it was observed that the use of blends with high 45S5/PEEK ratio lead to the deposition of coatings with high content of 45S5. Finally, the friction behavior of the coatings was analyzed performing ball-on-disk tests and these experiments showed that the presence of glass particles has a beneficial role in the wear resistance.

High-temperature NO sensing performance of WO3 deposited by spray coating.

Nitric oxide (NO) selective sensors capable of sensing in a hot-gas environment are increasingly required for monitoring combustion and processes yielding high temperature gas containing NO. This work reports the fabrication of sensors by a facile deposition of water-based ink blended commercial WO3 powders via spray coating on sensor platforms fitted with Au-interdigitated electrodes (IDEs) and the characterization of their sensing performances under hot NO-containing air at temperatures exceeding 500 °C. After deposition and heat treatment of the sensing material on the substrate fitted with Au-IDE at 700 °C, the composition and morphology of the active material were analyzed and the presence of a single phase, fine particulates of WO3, has been confirmed by XRD and SEM, respectively. The investigation of the sensing properties revealed that, contrary to the previous reports, this WO3 sensor can detect NO with a good sensitivity (∼22% for 200 ppm NO) and selectivity at 700 °C under humidity. The effect of relative humidity on sensing performance was also investigated. Also, under humidity values as high as 10% RH and at gas temperatures as high as 700 °C, a reasonably good sensor performance has been observed. It is likely that the improved response towards NO at moderately elevated temperatures resulted from the humidity related water molecules which are adsorbed on the surfaces of WO3 particles, providing high affinity hydrogen bonds between NO and OH.