A new method of regeneration of anion exchangers used for recovering chromates from wastewater

A new economically attractive method of recovery of water and chromates from wastewater has been presented. In order to obtain a high enough concentrated regeneration effluent for refilling plating bath, high concentrated sodium hydroxide (45%) was used for regeneration of a weakly based anion exchanger bed (Wofatit AD 41). Further increase of the concentration of the regeneration effluent was obtained by recycling certain frontal and tail parts of regeneration effluent to raw wastewater. It permits to recycle only a high concentrated part of the regeneration effluent to refilling the plating bath.The influence of flow rates, doses of sodium hydroxide and recirculation ratio on the average concentration of the regeneration effluent and ion exchange capacity has been presented.     

RF deposition of soft hydrogenated amorphous carbon coatings for adhesive interfaces on highly elastic polymer materials

Developing soft and elastic coating materials is one of the future challenges in research on new coating materials for vacuum deposition processes. This development direction is in its infancy and fully contrary to the thin film research mainstream. Such coatings - tailor-made with gradients in hardness and elastic modulus - could work as adhesive and load-supporting layers on polymers bridging the properties from soft substrate to the stiff, wear-resistant hard top coating.In this work we used the approach of a chemical vapour deposition process with plasma assistance from an unbalanced RF (13.56 MHz) powered magnetron sputtering cathode in planar parallel plate arrangement. The characterization of the amorphous hydrogenated and polymer-like carbon films showed a high influence of the used precursor gas (acetylene, butane) on hardness and elasticity. The elastic moduli were found to be between 2 and 35 GPa for the fully amorphous films with a-C:H structure. Specific growth structures were found in HR-TEM imaging of the amorphous coatings. All coatings adhere strongly on a rubber-like polymer (thermoplastic polyurethane).     

Silver Salt of 4,6‐Diazido‐N‐nitro‐1,3,5‐triazine‐2‐amine – Characterization of this Primary Explosive

A new primary explosive, the silver salt of 4,6‐diazido‐N‐nitro‐1,3,5‐triazine‐2‐amine (AgDANT), was synthesized and characterized. AgDANT was prepared with a 97 % yield and characterized by IR spectroscopy, single‐crystal X‐ray diffraction, and DTA. The crystal density of AgDANT is 2.530 g cm⁻³ and the molecule consists of a centro‐symmetric dimer with a high degree of planarity. The intramolecular Ag Ag distance is relatively low (331 pm) and can be considered as a strong argentophilic interaction. AgDANT is non‐hygroscopic and its solubility in water (1.27 mg in 100 mL at 23 °C) is on a similar level of solubility to that of silver azide. The sensitivity of AgDANT to impact is slightly higher than that for MF, sensitivity to friction is the same as for LA, and sensitivity to electric discharge is between that for LS and MF. Initiation efficiency of AgDANT was tested in electric detonators and compared to dextrinated lead azide (initiation efficiency of AgDANT is 40 mg for PETN secondary charge). The thermal resistance of detonators with AgDANT is satisfactory; all detonators were fully functional after exposure at 65 °C (30 d) and 85 °C (2 d).     

Note: Light ageing with simultaneous colorimetry via fibre optics reflection spectrometry

In this article, the design and characteristics of a micro-fadeometer is presented. The technique allows for a non-(micro-) destructive evaluation of the light fastness of colorants on various materials and can be used to directly assess valuable materials, such as heritage objects, and develop safer display strategies to promote their preservation. The presented instrument has several benefits over standard light ageing methods--low operating cost, non-damaging, real time measurement of induced changes for kinetics studies, and automated high throughput screening of materials. A selection of data is presented to demonstrate the flexibility of the presented instrument and illustrate how it can be used to evaluate museum lighting and oxygen-free display of heritage objects.     

Machinable α-SiAlON/BN Composites

Dense machinable α-SiAlON/BN composites were fabricated by hot-pressing using turbostratic boron nitride (tBN) obtained from nitridation of melamine diborate. The tBN was added to the starting powders, or introduced as a coating that formed in situ on α-Si₃N₄ carrier powders during nitridation, and was subsequently converted to hexagonal boron nitride (hBN) during hot pressing by solution reprecipitation. These composites maintain high strength at 1000°C and their strength/hardness are much higher than similar composites prepared using commercial hBN powder, which yielded a coarser microstructure. Good machinability was achieved despite a flat R curve.     

Characterization of sepiolite as a support of silver catalyst in soot combustion

Turkish sepiolite–zirconium oxide mixtures were applied as a support for the silver catalyst in a soot combustion. Sepiolite–Zr–K–Ag–O catalyst was characterized by XRD, N₂ adsorption, SEM, TPR-H₂ and EGA-MS. The combustion of soot was studied with a thermobalance (TG-DTA). The modification resulted in a partial degradation of the sepiolite structure, however, the morphology was preserved. The adsorption of N₂ of the modified sepiolite is a characteristic for mesoporous materials with a wide distribution of pores. The specific surface area S_BET equals 83 m²/g and the pores volume is 0.23 cm³/g. The basic character of the surface centers of sepiolite is indicated by CO₂ desorption (TPD-MS) at 170 °C and at about 620 °C due to a surface carbonates decomposition. The thermodesorption of oxygen at 650–850 °C indicates the decomposition of AgO_x phases at the surface. The presence of AgO_x phases is also confirmed by TPR-H₂ spectrum (low temperature reduction peak at 130 and 180 °C). The high-temperature reduction at about 570 °C is probably related to Ag–O–M phases on the support.The soot combustion takes place at T₅₀ = 575 °C. Without silver (sepiolite–Zr–K–O) T₅₀ = 560 °C but sepiolite modified with silver (sepiolite–Zr–K–Ag–O) undergoes the same process at T₅₀ = 490 °C.     

Occurrence of dyslipidemia in spontaneous intracerebral hemorrhage

Background: Dyslipidemia, mainly hypocholesterolemia is considered to be a risk factor (RF) for spontaneous intracerebral hemorrhage (SICH). The aim of our study was to assess its role in our SICH patients. Methods: In a hospital‐based cross‐section study, laboratory assessments of total cholesterol (TC), triglycerides (TG), high‐density cholesterol (HDL‐C) and low‐density cholesterol (LDL‐C) plasma levels were performed in 80 SICH patients without vascular malformation and in a control group (CG) of 80 age‐ and sex‐matched patients with low back pain. All patients were treated at the Departments of Neurology and Neurosurgery, University Hospital, Olomouc, Czech Republic. Two‐sample t‐test and Mann‐Whitney test were applied when assessing statistical significance. Results: The following mean lipid plasma levels were found in SICH patients versus CG subjects (in mmol/L): TC, 5.89 vs. 5.48 (p = 0.007); TG, 1.31 vs. 2.10 (p <0.0001); HDL‐C, 1.58 vs. 1.33 (p = 0.0001); LDL‐C, 3.70 vs. 3.18 (p = 0.0004). Conclusions: TC and LDL‐C plasma levels were higher in SICH patients in the Olomouc region of the Czech Republic.     

How do polypropylene fibers improve the spalling behavior of in-situ concrete?

The results of a recently finished research project have shown a great influence of the amount of polypropylene (PP) fibers on the spalling behavior of concrete under fire loading. Starting from the identification of the permeability as the parameter with the greatest influence on spalling, results of permeability tests on normal-strength in-situ concrete without and with PP-fibers (1.5 kg/m³) are presented in this paper. The values for the permeability, which are obtained for concrete pre-heated to different temperature levels, are related to the pore structure, accessible by mercury-intrusion-porosimetry (MIP) tests. The considered concrete was prepared under on-site conditions, accounting for the workability and densification when casting at the construction site. In order to illustrate the effect of the permeability of concrete with and without PP-fibers on spalling, which was experienced during the aforementioned research project, a finite-element analysis, taking the coupling between heat and mass transport into account, is performed. The so-obtained results provide insight into the risk of spalling of concrete with varying amount of PP-fibers.     

Three-half and half-axis patch-by-patch NC machining of sculptured surfaces

Despite the inbuilt advantages offered by five-axis machining, the manufacturing industry has not widely adopted this technology due to the high cost of machines and insufficient support from CAD/CAM systems. Companies are used to three-axis machining and their shop floors are not yet ready for five-axis machining in terms of training and programming. The objective of this research is to develop and implement a machining technique that uses the simplicity of three-axis tool positioning and the flexibility of five-axis tool orientation, to machine sculptured surfaces. This technique, 3½½-axis, divides a sculptured surface into patches and then machines each patch using a fixed tool orientation. This paper presents the surface partitioning scheme and the method of selecting an optimum number of sub-divisions along with actual machining experiments. For the example surface utilized in this study, the proposed hybrid method led to shorter machining time compared to traditional three-axis machining and comparable to simultaneous five-axis machining.     

Influence of polymer surface chemistry on frictional properties under protein-lubrication conditions: implications for hip-implant design

Wear processes in hip joints are believed to occur chiefly under boundary lubrication conditions. We have shown that the efficiency of boundary lubrication of the ultrahigh-molecular-weight polyethylene (UHWMPE)–alumina tribopair in protein-containing solutions can be improved by modifying the surface hydrophilicity of the UHMWPE. Our experiments show that an oxygen-plasma treatment of polyethylene, producing significantly greater hydrophilicity due to modified surface chemistry, leads to faster and modified protein adsorption. A denser boundary layer of human serum albumin (HSA) proteins on the PE surface appears to enhance boundary lubrication, which leads to a 50% reduction of dynamic friction, as well as to a reduction of stiction, which is believed to be a key factor in wear mechanisms occurring in artificial hip joints. Following tribological testing in pure water, we observed the presence of a polyethylene transfer film on the alumina disc. This film was not formed after tribotesting either in protein or in Ringer's solution.