Wax Matrix Research Articles

Hybrid of MoS₂ and Reduced Graphene Oxide: A Lightweight and Broadband Electromagnetic Wave Absorber.

Electromagnetic wave absorbing materials that can exhibit effective absorption in a broad bandwidth at a thin thickness are strongly desired due to their widespread applications in electronic devices. In this study, hybrids of MoS2 and reduced graphene oxide (RGO) were prepared and their microwave absorption performance was investigated for the first time. It was found that a thin sample consisting of 10 wt % MoS2/RGO hybrid in the wax matrix exhibited an effective microwave absorption bandwidth of 5.72 GHz at the thickness less than 2.0 mm. The highest reflection loss of -50.9 dB was observed at 11.68 GHz for a sample with a thickness of 2.3 mm. Results obtained in this study indicate that hybrids of MoS2 and RGO are promising microwave absorbing materials, which can exhibit broad effective absorption bandwidth at low filler loading and thin thickness.

Easy gas-flow-induced CVD synthesis and tunable electromagnetic characteristics of centipede-shaped iron/cementite/multiwalled carbon nanotube (Fe/Fe3C/MWCNT) heterostructures

Abstract Centipede-shaped iron/cementite/multiwalled carbon nanotube (Fe/Fe 3 C/MWCNT) heterostructures were synthesized via a novel and easy gas-flow-induced in situ two-step chemical vapour deposition (CVD) method for the first time. The formation mechanism was studied via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The cooperation between the carrier gas flow and the spontaneous magnetization caused the assembly of Fe nanocrystals from the pyrolysis of Fe(CO) 5 into Fe nanofibers, which subsequently functioned as substrates and catalyst precursors for Fe 3 C-catalyzed MWCNT growth. The aspect ratio and the MWCNT content of the products were easily controlled by changing the feeding ratio of Fe(CO) 5 volume to polyethylene glycol 20 000 (PEG 20 000) mass. The electromagnetic property study revealed that increasing the aspect ratio and length can improve the material's dielectric properties. Simulation studies show that 40 wt.% of Fe/Fe 3 C/MWCNT heterostructures in a wax matrix exhibits high values of reflection loss (

Tunable optical nonlinearity of silicon nanoparticles in solid state organic matrix

In this paper, a novel approach to fabricate a hybrid solid state system with both tunable nonlinearity and self-repairing property is studied. The optical nonlinear properties of a silicon nanoparticles system based on gel wax matrix were experimentally investigated. Tunable optical nonlinearities from optical limiting to saturable absorption were achieved by simply changing the concentration of nanoparticles inside the matrix. This approach opens a route for a low cost, one-step-synthesis nonlinear system being highly compatible with silicon optoelectronic circuits. This hybrid system also demonstrates the self-repairing property after excess exposure to laser irradiation.

Thermal Properties of Phase Change Composites Containing Ferric Oxide Nanoparticles.

We prepared a series of homogeneous nanocomposites by suspending Fe2O3 nanoparticles into paraffin wax (PW) matrix. Fe2O3/PW nanocomposites have reduced both solid-solid phase change latent heat capacity (Ls-s) and solid-liquid phase change latent heat capacity (Ls-l) with an increase in the mass fraction of Fe2O3 nanoparticles. There is almost equable solid-solid phase change temperature (Ts-s) between PW and Fe2O3/PW composites, as well as melting temperature (Ts-l). Fe2O3 nanoparticle addition leads to substantial enhancement in the thermal conductivity of Fe2O3/PW and the enhancement ratio increases with the nanoparticle loading. Thermal conductivity of Fe2O3/PW composite with 3.0 wt% nanoparticles is about 0.27 W/(m · K) at 15 °C, which close to that of γ-Al2O3/PW with 5.0 wt% nanoparticles but higher than that of ZnO/PW containing 5.0 wt% nanoparticles. At 60 °C, Fe2O3/PW has higher thermal conductivity than γ-A12O3/PW and ZnO/PW contained with same fraction of nanoparticles.

Controllable synthesis and electromagnetic interference shielding properties of magnetic CoNi alloy nanoparticles coated on biocarbon nanofibers

CoNi alloy nanoparticles with different molar ratios of Co:Ni were uniformly coated on the surface of biocarbon nanofibers (BCF) by electroless plating. Transmission electron microscopy, X-ray diffraction and vibration sample magnetometry were employed to characterize the morphologies, phase structures and magnetic properties of the coated BCF. The permittivity behavior of coated BCF-paraffin wax matrix composites was studied in the frequency range of 8.2–12.4 GHz by vector network analysis. Magnetic measurements showed that the saturation magnetizations increased linearly with increasing Co content in CoNi deposits and that the coercivity is insensitive towards the Co content. Of the four synthesized BCF with various Co:Ni molar ratios, the BCF with Co:Ni molar ratio of 1:2 displayed higher electromagnetic interference shielding efficiencies of 30.7 dB (99.91 % attenuation) due to its higher permittivity.

Development and evaluation of modified release wax matrix tablet dosage form for tramadol hydrochloride

Development and evaluation of modified release wax matrix tablet dosage form for tramadol hydrochloride

Single and dual drug release patterns from shellac wax-lutrol matrix tablets fabricated with fusion and molding techniques.

The objective of this investigation was to prepare the shellac wax matrix tablets by fusion and molding technique incorporated with Lutrol in different ratios to modify the hydrophobicity of matrix tablet. The matrix tablets with single drug were loaded either with propranolol hydrochloride or hydrochlorothiazide as hydrophilic and hydrophobic model drugs, and a dual drug formula was also prepared. The single and dual drug release patterns were studied in a dissolution apparatus using distilled water as medium. Propranolol hydrochloride released from matrix was easier than hydrochlorothiazide. Drug release from shellac wax matrix could be enhanced by incorporation of Lutrol. However retardation of drug release from some matrix tablets was evident for the systems that could form dispersion in the dissolution medium. The gel network from high content of Lutrol was hexagonal which was a dense and more compact structure than the other structures found when low amounts of Lutrol were present in the formula. Therefore, the formulae with high content of Lutrol could prolong drug release more efficiently than those containing low content of Lutrol. Hence shellac wax matrix could modulate the drug release with the addition of Lutrol. Sustainable dual drug release was also obtained from these developed matrix tablets. Thus shellac wax-Lutrol component could be used as a potential matrix tablet prepared with fusion and molding technique with excellent controlled drug release.

Preparation and Study of Electromagnetic Interference Shielding Materials Comprised of Ni‐Co Coated on Web‐Like Biocarbon Nanofibers via Electroless Deposition

Electromagnetic interference (EMI) shielding materials made of Ni‐Co coated on web‐like biocarbon nanofibers were successfully prepared by electroless plating. Biocarbon nanofibers (CF) with a novel web‐like structure comprised of entangled and interconnected carbon nanoribbons were obtained using bacterial cellulose pyrolyzed at 1200°C. Paraffin wax matrix composites filled with different loadings (10, 20, and 30 wt%, resp.) of CF and Ni‐Co coated CF (NCCF) were prepared. The electrical conductivities and electromagnetic parameters of the composites were investigated by the four‐probe method and vector network analysis. From these results, the EMI shielding efficiencies (SE) of NCCF composites were shown to be significantly higher than that of CF at the same mass fraction. The paraffin wax composites containing 30 wt% NCCF showed the highest EMI SE of 41.2 dB (99.99% attenuation), which are attributed to the higher electrical conductivity and permittivity of the NCCF composites than the CF composites. Additionally, EMI SE increased with an increase in CF and NCCF loading and the absorption was determined to be the primary factor governing EMI shielding. This study conclusively reveals that NCCF composites have potential applications as EMI shielding materials.

Disintegration mediated controlled release supersaturating solid dispersion formulation of an insoluble drug: design, development, optimization, and in vitro evaluation.

The objective of this study was to develop a solid dispersion based controlled release system for drug substances that are poorly soluble in water. A wax-based disintegration mediated controlled release system was designed based on the fact that an amorphous drug can crystallize out from hydrophilic matrices. For this study, cilostazol (CIL) was selected as the model drug, as it exhibits poor aqueous solubility. An amorphous solid dispersion was prepared to assist the drug to attain a supersaturated state. Povidone was used as carrier for solid dispersion (spray drying technique), hydrogenated vegetable oil (HVO) as wax matrix former, and sodium carboxymethyl cellulose (NaCMC) as a disintegrant. The extreme vertices mixture design (EVMD) was applied to optimize the designed and developed composition. The optimized formulation provided a dissolution pattern which was equivalent to the predicted curve, ascertaining that the optimal formulation could be accomplished with EVMD. The release profile of CIL was described by the Higuchi's model better than zero-order, first-order, and Hixson-Crowell's model, which indicated that the supersaturation state of CIL dominated to allow drug release by diffusion rather than disintegration regulated release as is generally observed by Hixson-Crowell's model. The optimized composition was evaluated for disintegration, dissolution, XRD, and stability studies. It was found that the amorphous state as well as the dissolution profile of CIL was maintained under the accelerated conditions of 40°C/75% RH for 6 months.

Graphene-wrapped ZnO hollow spheres with enhanced electromagnetic wave absorption properties

Graphene-wrapped ZnO hollow spheres were synthesized by a two-step process, which combined a hydrothermal reaction with surface modification. The experimental results show that reduced graphene oxide sheets adhere entirely to the surface of the ZnO hollow spheres consisting of nanoparticles. The unique structure effectively decreases the density of the composite without sacrificing the contact between graphene and the nanoparticles. Different mass ratios of graphene to ZnO hollow spheres mixed in a paraffin wax matrix (50 wt%) were prepared to investigate the electromagnetic wave absorption properties in the X-band region. When the mass ratio of graphene oxide to ZnO is 12 : 88, the composite exhibits a maximum absorption of −45.05 dB at 9.7 GHz with a sample thickness of only 2.2 mm. The fundamental mechanism based on electrical conductivity and the polarization between the graphene sheets and ZnO nanoparticles is discussed. The hierarchical structure of graphene-wrapped ZnO hollow spheres exhibits a promising designable approach to lightweight electromagnetic wave absorbing materials.

Microwave absorption properties of FeSiBNbCu glass-covered amorphous wires

Coaxially dielectric samples consisting of different packing ratios of glass-covered Fe73.5Si13.5B9Nb3Cu1 amorphous wires embedded in a paraffin wax matrix were fabricated, and the influence of short-wire packing ratio (3%–9% in mass fraction) and thickness (1–7 mm) on the microwave absorption properties was systematically investigated in microwave frequency range of 2–18 GHz. X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and scalar network analyzer (SNA) were used for characterizing microstructure and evaluating microwave absorption properties. Experimental results show the significant frequency (6–18 GHz) dependence of the complex relative permeability and permittivity. The reflection loss (RL) with different thickness and short-wire packing ratio reveals that the composite sample containing 7% exhibits better microwave absorption behavior with its minimum value of RL reaching −34 dB in thickness of 3 mm at 14 GHz. Therefore, it is significantly useful to develop microwire-dielectric materials with much wider absorption band for microwave absorption applications.

Improved thermal properties of paraffin wax by the addition of TiO2 nanoparticles

TiO2 nanoparticles about 20 nm in diameter in the form of anatase were prepared and characterized. The nanoparticles were successfully dispersed into a paraffin wax (PW) matrix without any surfactant. The differential scanning calorimetric instrument and the transient short hot-wire method were used to measure the thermal properties of the TiO2/PW composites. It is found that the phase-change temperature and latent heat capacity vary with TiO2 nanoparticles loading levels. When the loading is not over 1 wt%, the phase-change temperature drops, and the latent heat capacity increases. When the loading is over 2 wt%, the phase-change temperature increases, and the latent heat capacity drops. A significant increase in latent heat capacity is found around 0.7 wt% loading. The thermal conductivity of the composites increases monotonically with increasing TiO2 loading. But such a tendency tends to decrease when the loading is over 3 wt%.

PREPARATION AND EVALUATION OF SUSTAINED RELEASE TABLET OF EPERISONE HYDROCHLORIDE BY COMPRITOL ATO 888 AS A MATRIX FORMING AGENT.

Objective: The objective of this work was to prepare and evaluate oral sustained release matrix tablet of highly water soluble drug and to study the effect of proportion of wax and addition of release liner on in-vitro release of drug. Method: The matrix tablets were prepared by melt granulation method using drug:wax in 1:1, 1:2 & 1:3 proportions and evaluated for on in-vitro drug release. Then the proportion 1:1 was selected and wax matrix tablets were prepared by three techniques melt granulation, wet granulation and direct compression to check their in-vitro release profiles. Results: The study revealed that Compritol ATO 888 is potent sustained release polymer and released only 72.45% in 24 h even at 1:1 proportion. So, lactose was added as release liner in further study which helped in achieving complete release in 24 h. Conclusion: The present study has concluded that Compritol ATO 888 can be used as matrix-forming agent to control the release of a highly water soluble drug such as Eperisone HCl. It was also observed that melt granulation technique was found more effective. Release liner like lactose may help enhancing the release profile when it is marginally slow. Keywords: - Eperisone Hydrochloride, Compritol ATO 888, Sustained release, Melt granulation, Release liner

Fabrication, microstructure and microwave absorption of multi-walled carbon nanotube decorated with CdS nanocrystal

In this work, CdS–MWCNT heterostructure was achieved via a one-step approach. CdS–MWCNT composites with wax matrix were prepared. The composites show high permittivity and excellent microwave absorption. Compared to the MWCNT composites, microwave absorption of the CdS–MWCNT composites with the same mass ratio increases to about 1–1.6 times, and the increment of bandwidth is over 1GHz. The enhanced attenuation capacity arises from CdS nanocrystal and heterostructure interface. Cooperation of interface polarization and conductivity inside the composites increases the microwave attenuation of the composites. Furthermore, light weight is achieved due to the decreasing thickness of the CdS–MWCNT composites. The results suggest that the CdS–MWCNT composite is a highly promising candidate for microwave attenuation in many application fields.

Formulation of Novel Artesunate-Loaded Solid Lipid Microparticles (SLMs) Based on Dika Wax Matrices: In Vitro and in Vivo Evaluation

The aims of the work were to formulate artesunate-loaded solid lipid microparticles (SLMs) based on dika wax matrices and to study the in vitro and in vivo properties. Lipid matrices consisting of mixtures of Phospholipon 90G (P90G) and dika wax were formulated and characterized by differential scanning calorimetry (DSC), small angle X-ray diffraction (SAXD) and wide angle X-ray diffraction (WAXD). The SLMs were prepared by melt-homogenization. Time-dependent particle size analysis, pH studies, encapsulation efficiency (EE%), in vitro drug release and anti-malarial properties were studied. Results show that SAXD diffractograms showed strong reflection at 2θ = 2.48°, d = 3.56 A. Particle size of SLMs increased with time (from 1 to 90 days). The SLMs exhibited maximum EE% of 80.6 % and had good sustained release properties. In vivo studies showed that the SLMs had significant (p

Influence of Waste Rubber on the Properties and Microstructure of Injection Moulded M2 High Speed Steel

New feedstock formulation for metal injection moulding (MIM) of Molybdenum High Speed Steel (M2 HSS) has been developed. The binder is a multicomponent system consisting of major binder paraffin wax (PW), stearic acid (SA) and minor binder polyethelene waste rubber (PEWR). Injection moulding was conducted successfully using a powder loading of 0.65. Scanning electron micrograph of the green injection moulded part revealed homogenous distribution of the M2 HSS particles in the wax matrix. Paraffin wax and stearic acid were driven off by immersing the injection moulded part into n-heptane for five hours. Vacuum sintering of the brown parts at a temperature range of 1240°C-1280°C resulted in high quality M2 HSS parts. The properties of the sintered part such as physical, mechanical and microstructure were studied and discussed to evaluate the influence of waste rubber in MIM of M2 HSS.

Preparation of a prototype radioactive probe for treatment of lacrimal ducts stenosis and a study of its dose distribution.

Our aim was to prepare a radioactive lacrimal passages probe, study its dose distribution in a phantom and suggest security indexes and therapeutic effective doses for brachytherapy. We prepared the radioactive probes by laying 125I particles into plastic tubes. We conducted temperature tests, pressure tests, soak tests and shock tests, to obtain security indexes. The dose distributions in phantom and wax matrix were also detected, and the surface dose rates on different parts of the phantom and the dose absorbed by the operator were examined. The radioactive lacrimal passage probe demonstrated no form changes in temperature tests, pressure tests and soak tests when using a surface radioactive contamination dose lower than 185 Bq. The probe was waferinged in shock tests with a surface radioactive contamination dose lower than 185 Bq. The dose detection in the phantom and the wax matrix showed that for distances of 1 mm-12 mm off the tube, there were statistical differences of the absorbed dose (P<0.05). However, for the range of 12 mm-40 mm, there was no statistical difference (P>0.05). The dose rates administered by the radioactive probe used for radiotherapy to the lacrimal passages were within safe limits both for the phantom (Sichuan Keyi Corporation, China) and the operator. In conclusion, our study showed that this prototype lacrimal passages probe can be a useful and effective method for clinical brachytherapy of lacrimal ducts stenosis.

The Effect of Acid pH Modifiers on the Release Characteristics of Weakly Basic Drug from Hydrophlilic–Lipophilic Matrices

The solubility of weakly basic drugs within passage though GI tract leads to pH-dependent or even incomplete release of these drugs from extended release formulations and consequently to lower drug absorption and bioavailability. The aim of the study was to prepare and evaluate hydrophilic-lipophilic (hypromellose-montanglycol wax) matrix tablets ensuring the pH-independent delivery of the weakly basic drug verapamil-hydrochloride by an incorporation of three organic acidifiers (citric, fumaric, and itaconic acids) differing in their concentrations, pK a, and solubility. The dissolution studies were performed by the method of changing pH values, which better corresponded to the real conditions in the GI tract (2h at pH1.2 and then 10h at pH6.8). Within the same conditions, pH of matrix microenvironment was measured. To determine relationships between the above mentioned properties of acidifiers and the monitored effects (the amount of released drug and surface pH of gel layer in selected time intervals-360 and 480min), the full factorial design method and partial least squares PLS-2 regression were used. The incorporation of the tested pH modifiers significantly increased the drug release rate from matrices. PLS-components explained 75% and 73% variation in the X- and Y-data, respectively. The obtained results indicated that the main crucial points (p < 0.01) were the concentration and strength of acidifier incorporated into the matrix. Contrary, the acid solubility surprisingly did not influence the selected effects except for the surface pH of gel layer in time 480min.

Controlling solid lipid nanoparticle adhesion by polyelectrolyte multilayer surface modifications

This study addresses the tunability of polyelectrolyte multilayers (PEM) toward adsorption of solid lipid nanoparticles (SLN). In SLN production for pharmaceutical applications, repellence from production equipment is desired while targeted adsorption is necessary for the functionalization of surfaces. SLN containing triglyceride/phospholipid or wax matrices were exposed to different PEM (consisting of poly(allylamine hydrochloride) (PAH), poly(diallyldimethylammonium chloride), and poly(acrylic acid)). PEM varied regarding layer architecture and surface properties by means of deposition pH, top layer variation, PEGylation with poly(acrylic acid)-graft-poly(ethylene glycol) copolymer, and thermal crosslinking. FTIR-ATR and SEM revealed SLN adhesion depending on PEM composition. Particle adsorption was tunable toward attraction as well as repellence: PEGylated PEM displayed lowest adsorption while PEM capped with PAH provided the strongest attraction of particles. Examinations at elevated temperatures resembled production conditions of SLN where these are processed as emulsions. Crystalline triglyceride SLN displayed high anisometry and, consequently, a large specific surface area. These platelets were more adherend than spherical droplets from the same formulation as an emulsion. Wax-based nanoparticles showed spherical shape, both in crystalline and molten state. However, adsorption was fostered as the fluidity of the disperse phase increased upon melting. Additionally, coalescence of adsorbed droplets took place, further increasing adsorption.

Facile Preparation, Characterization, and Highly Effective Microwave Absorption Performance of CNTs/Fe3O4/PANI Nanocomposites

A facile method has been developed to synthesize light‐weight CNTs/Fe3O4/PANI nanocomposites. The formation route was proposed as the coprecipitation of Fe2+ and Fe3+ and an additional process of in situ polymerization of aniline monomer. The structure and morphology of CNTs/Fe3O4/PANI were characterized by transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. The TEM investigation shows that the CNTs/Fe3O4/PANI nanocomposites exhibit less intertwined structure and that many more Fe3O4 particles are attached homogeneously on the surface of CNTs, indicating that PANI can indeed help CNTs to disperse in isolated form. The wave‐absorbing properties were investigated in a frequency of 2–18 GHz. The results show that the CNTs/Fe3O4/PANI nanocomposites exhibit a super absorbing behavior and possess a maximum reflection loss of −48 dB at 12.9 GHz, and the bandwidth below −20 dB is more than 5 GHz. More importantly, the absorption peak frequency ranges of the CNTs/Fe3O4/PANI composites can be tuned easily by changing the wax weight ratio and thickness of CNTs/Fe3O4/PANI paraffin wax matrix.