Surface Modification Of Implants For Bone Surgery

Rare earth solution (RES) surface modification and air-oxidation methods were used to improve the interfacial adhesion of the carbon fiber reinforced polyimide (CF/PI) composite. The mechanical and tribological properties of the PI composites reinforced by the carbon fibers treated with different surface modification methods were comparatively investigated. Results showed that both the strength parameters (tensile and flexural) of the CF/PI composites improved remarkably due to RES treatment along with enhancement in friction and wear performance.

In this overview passivation mechanisms of high nitrogen steels (HNS) are decribed first and then the various corrosion properties related to general corrosion, pitting corrosion, crevice corrosion, intergranular corrosion (sensitization), stress corrosion cracking and hydrogen embrittlement are summarized based on the present knowledge. The effects of nitrogen on pitting corrosion of stainless steels have been studied most systematically and a number of different mechanisms have been proposed for the effect of nitrogen on pitting and crevice corrosion related to observed synergistic interactions with Mo in the alloy. There is a fairly consistent agreement that N additions improve the pitting corrosion resistance of austenitic and duplex stainless steels by increasing the pitting potential or temperature in aqueous chloride solutions or by decreasing the weight loss in standard FeCl 3 test. There is much less results on the effects of nitrogen alloying on active dissolution or general corrosion, and almost no systematic studies on the effects of N content on environment sensitive cracking of these steels.

The modern textile fibre treatments aim to obtain the required level of beneficial effect while attempting to confine the modification to the fibre surface. Recently, much attention has been focused on different physical methods of fibre surface modification, cold plasma treatment being considered as very useful. Moreover, there are efficient chemical methods available, such as peroxide, biopolymer and enzyme treatment. Some interesting combinations of these physical and chemical surface modification methods as means to modify fibre surface topography and thus controlling the surface-related properties of the fibre are presented in this paper. The properties obtained are discussed on the basis of the physico-chemical changes in the surface layer of the fibre, being assessed by wettability and contact angle measurements, as well as by FTIR-ATR and XPS analysis. The SEM and AFM technique are used to assess the changes in the fibre surface topography and to correlate these changes to the effectiveness, uniformity and severity of the textile fibre surface modification treatments.

Exploring the susceptibility of P110 pipeline steel to stress corrosion cracking in CO2-rich environments

One of the promising directions of hardening of high-speed steel tool is the creation on their surface of the layered structures with the gradient of physic-chemical properties between the wear-resistant coatings to the base material. Among the methods of such surface modification, a special process takes place based on the use of pulsed high-intensity charged particle beams. The high speed of heating and cooling allows structural-phase transformations in the surface layer, which cannot be realized in a stationary mode. The treatment was conducted in a RITM-SP unit, which constitutes a combination of a source of low-energy high-current electron beams “RITM” and two magnetron spraying systems on a single vacuum chamber. The unit enables deposition of films on the surface of the desired product and subsequent liquid-phase mixing of materials of the film and the substrate by an intense pulse electron beam. The article discusses features of the structure of the subsurface layer of high-speed steel M2, modified by surface alloying of a low-energy high-current electron beam, and its effect on the wear resistance of the tool when dry cutting hard to machine Nickel alloy. A significant decrease of intensity of wear of high-speed steel with combined treatment happens due to the displacement of the zone of wear and decrease the radius of rounding of the cutting edge because of changes in conditions of interaction with the material being treated.

Propagation of stress corrosion cracks of 26Cr-1Mo ferritic stainless steels in a hot chloride solution

Influence of Cu-, Fe-, Co-, and Mn-oxide nanoclusters on sensing behavior of SnO 2 films

Cellular adhesion on surface structures from PA 2200 made through Selective Laser Sintering (SLS) process can be improved by modifying the parts surface. In this paper, different methods for surface modification are presented. The PA 2200 samples were immersed in six different solvents. SEM images and surface roughness tests were performed in order to evaluate the surface modification both for the control group and for the tested groups. The obtained results clearly show that there is a significant difference between the roughness of the control (untreated) surface and each of the treated surfaces. Modifying by immersion, of the PA 2200 structures produced by Selective Laser Sintering process, brings original approaches concerning the use of those procedures in the increase of the surfaces quality.

The article is an overview of various materials used in power hydraulics for basic hydraulic actuators components such as cylinders, cylinder caps, pistons, piston rods, glands, and sealing systems. The aim of this review is to systematize the state of the art in the field of materials and surface modification methods used in the production of actuators. The paper discusses the requirements for the elements of actuators and analyzes the existing literature in terms of appearing failures and damages. The most frequently applied materials used in power hydraulics are described, and various surface modifications of the discussed elements, which are aimed at improving the operating parameters of actuators, are presented. The most frequently used materials for actuators elements are iron alloys. However, due to rising ecological requirements, there is a tendency to looking for modern replacements to obtain the same or even better mechanical or tribological parameters. Sealing systems are manufactured mainly from thermoplastic or elastomeric polymers, which are characterized by low friction and ensure the best possible interaction of seals with the cooperating element. In the field of surface modification, among others, the issue of chromium plating of piston rods has been discussed, which, due, to the toxicity of hexavalent chromium, should be replaced by other methods of improving surface properties.

Pitting, crevice and stress corrosion cracking are the most damaging corrosion forms of stainless steels in industrial applications. Generally, pitting and crevice susceptibility depends on a variety of factors related to the metal (chemical composition, differences in the metallurgical structure, inclusions), the environment (chloride content, pH, temperature, differential aeration) and the geometry of the system. Due to their unpredictable occurrence, localized corrosion events cannot be explained without using a proper statistical method. In this work a probabilistic approach based on Markov chains for the assessment of pitting and crevice corrosion initiation is proposed. A Markov chain is a stochastic process that undergoes transitions from one state to another through a finite number of possible states, until a so-called "absorbing state” from which the system has no tendency to evolve is attained. Formally, a Markov chain is characterized by a set of states and a transition probability matrix. The model calculates the probability to have pitting (and vice versa to maintain a stable passive condition) involving a large number of operating parameters related to both metal and environment. Experimental tests were carried out to validate the model which requires more accurate investigations.

Preparation of high level waste for vitrification involves in part the dissolution of salt cake from the carbon steel storage tanks. During dissolution, a point is reached in which the corrosion inhibitors, hydroxide and nitrite, are diluted below established guidelines, and nitrate stress corrosion cracking (SCC) is possible. Because the addition of inhibitors may be counterproductive to process efficiency and waste minimization, corrosion testing was initiated to revisit and possibly revise the guidelines for inhibitor limits. The bases for the work summarized in this status report are results from previously-completed phases of study. In the first two phases of study, several reduced-inhibitor levels were tested in HLW simulants with nitrate concentrations ranging from 4.5 M to 8.5 M. The first two phases of work determined, among other things, the reduced-inhibitor levels and solution chemistries in which heat-treated and non-heat-treated A537 carbon steel is susceptible to SCC, crevice corrosion, and pitting. The work covered in this current task both builds on and verifies the conclusions of the previous work. The current work involves testing of low levels of inhibitors in HLW simulants with 5.5 M to 8.5 M nitrate concentrations. Stressed U-bend specimens, both polarized and non-polarized, were tested. Non-polarized U-bend testing is ongoing, with the U-bends currently in test for 100 days. The purpose of the testing is to determine SCC susceptibility in the vapor space (VS) and liquid air interface (LAI) regions of the HLW tanks under conditions expected during salt dissolution, and also to verify previous accelerated testing. The simulated wastes being tested have nitrate concentrations of 5.5 M and 8.5 M and inhibitor levels of 0.01 M/0.01 M hydroxide/nitrite and 0.1 M/ 0.1 M hydroxide/nitrite. The open circuit potential measurements being monitored and the corrosion morphology of the U-bends are in agreement with results and observations of previous phases of work. No SCC has occurred in the first 100 days of testing. The LAI specimens experienced minor corrosion at the liquid line with corrosion products visible on the weld material and in the heat-affected zones on either side of the welds. The VS specimens are more evenly and slightly more corroded. Polarized U-bend testing is complete after approximately 80 days of testing. No SCC occurred, but the results are inconclusive due to a competing, unexpected galvanic corrosion mechanism that interfered in the last 50 days of testing. No cracking was indicated during the first month. The tests will be repeated in order to satisfy the original objective which was to determine the effect of grinding HLW tank welds and heat treating the tanks had on corrosion. Both the non-polarized and polarized U-bend tests will continue. Additionally, cyclic polarization (CP) testing will be performed to examine the effects of surface oxides on corrosion and the differences in corrosion susceptibility between welded and un-welded areas.

Although a wide variety of degradation modes can occur in aqueous environments for corrosion-resistant metallic materials, localized corrosion such as pitting corrosion, crevice corrosion, SCC, and hydrogen embrinlement (HE) is considered to be the primary mode. The evaluation of the susceptibility of candidate corrosion-resistant container materials to pitting and crevice corrosion is well underway using electrochemical polarization techniques described in the Activity Plan E-20-43144. The proposed activity (E-20-56) is aimed at evaluating the SCC behavior of these materials in susceptible environments using the linearelastic-fracture-mechanics (LEFM) concept. The mechanical driving force for crack growth, or the stress distribution at the crack tip is quantified by the stress intensity factor, K, for the specific crack and loading geometry. The critical stress intensity factor for SCC, KISCC for candidate materials will be evaluated in environments of interest, and their comparisons will be made to select the waste package inner container material having an optimum SCC resistance.

Stress corrosion cracking (SCC) of carbon and alloy steels in liquid ammonia has occurred spasmodically over the last twenty years. At the present time, U. S. Department of Transportation regulations provide effective safeguards to prevent this problem through the required use of postweld heat treatment and the use of 0.2% water as an inhibitor. In view of the increasing use of ammonia as a direct fertilizer and as a chemical intermediate necessitating the increasing use of steel for transport and storage tanks, a research program was undertaken to identify the environmental factors that control SCC of steels in ammonia and also to evaluate present and potential palliative procedures to inhibit SCC of steels in service. In this program, numerous accelerated SCC tests were conducted on ASTM A517 Grade F steel, and the results may be summarized as follows: (1) Oxygen contamination in ammonia is the primary cause of SCC. The simultaneous presence of nitrogen contamination markedly increases susceptibility to SCC; (2) as little as 0.01 ppm oxygen will cause SCC; (3) water additions as low as 0.08 Wt% are effective in inhibiting SCC in ammonia contaminated with up to 200 ppm oxygen in the liquid phase. Hydrazine additions at the 0.025% level were also found to be effective; and (4) the mechanism accounting for SCC of steel in ammonia is believed to be the rupture of the corrosion-product film at sites of slip-step emergence caused by stress.

Surface modification with polyethylene glycol–corn trypsin inhibitor conjugate to inhibit the contact factor pathway on blood-contacting surfaces

The aim of this study was to investigate and compare the surface characteristics and initial bioactivity of ceria-stabilized zirconia/alumina nanocomposite (NANOZR) with those of yttria-stabilized zirconia (3Y-TZP) and pure titanium (CpTi) following the use of three surface modification methods; polishing, sandblasting/acid-etching (SB-E) and electrochemical deoxidation (ECD). Physical properties including surface morphology, chemical composition, X-ray diffraction, surface wettability, surface roughness, and hardness were measured. Osteoblast-like MC3T3-E1 cells were used to examine cell morphology and attachment to the surfaces of the materials. ECD treated NANOZR (NANOZR-E) showed a well-arranged, self-organized microporous surface structure with significantly low contact angles when compared with the other specimens (p < 0.05). NANOZR-E also demonstrated a slight decrease in monoclinic phase content (-4.4 wt %). The morphology and attachment of MC3T3-E1 cells on NANOZR-E were similar to those on polished and SBE-treated CpTi surfaces. Higher cell affinity was observed on NANOZR-E when compared with ECD treated 3Y-TZP. The findings of this study indicate the effectiveness of the novel technique, ECD, in the formation of a microporous surface on NANOZR when compared with both CpTi and 3Y-TZP. Moreover, this method also appears to improve the biological activity of NANOZR during the initial stage. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2641-2652, 2017.