Littérature scientifique sur le sujet « Black chrome »

Modified peanut husk was used as an adsorbent to remove chrome blue-black from its aqueous solution. Results of kinetic experiments demonstrated that the adsorption was effective and rapid.Three different kinetic models (i.e.,intraparticular diffusion model, Lagergren-first-order and second-order equations) were used to describe the adsorption mechanisms. The adsorption of chrome blue-black on modified peanut husk was not controlled by intraparticular diffusion. The kinetic adsorption data can be well simulated by the second-order equation and the adsorption might be rate-limiting controlled. The suitability of the adsorbent was tested by fitting the equilibrium data with Langmuir and Freundlich isotherms, which gave good fits with both isotherms.

Abstract In the 16th century, the Spanish brought logwood from Mexico to Europe. Its extract was used for textile dyeing. The French introduced the logwood tree to Western Hispaniola, which became Haiti in 1804. Around 1880, Haiti exported most of its logwood to France. In 1847, Runge introduced the black chrome-logwood ink as an alternative for iron-gall ink, because the latter attacked the steel writing nibs. The most important constituents of logwood are hematoxylin and hematein. Due to the profitable import conditions from Haiti, chrome-logwood ink became the cheapest and most commonly used black writing ink in France. This could explain why Vincent van Gogh, during his French period, used it for writing and drawing and why most of the French postcards from the first half of the 20th century, studied in this publication, were written with chrome-logwood ink, while most of the Dutch postcards were written with an iron gall ink.

An attack that can leak authentication credentials on a Windows operating system by using the SMB file sharing protocol on a Windows operating system is an ever-present problem. It's been exploited in many ways, but the only solution found is limited to local area networks. Jonathan Brossard and Hormazd Billimoria recently presented one study involving internet attacks at the Black Hat security conference in 2015. However, no SMB-related attacks were published. In this paper, we will explain how an attack can cause Windows credential theft, which may affect the default configuration in Google Chrome browser.Key words— Kredensial Windows, Google Chrome, Vulnerability

We evaluated the adhesion, friction characteristics, durability against bodily acids, sterilization, cleaning, and anti-reflection performance of diamond-like carbon (DLC) coatings formed as a surface treatment of intracorporeal medical devices. The major coefficients of friction during intubation in a living body in all environments were lower with DLC coatings than with black chrome plating. DLC demonstrated an adhesion of approximately 24 N, which is eight times stronger than that of black chrome plating. DLC-coated samples also showed significant stability without being damaged during acid immersion and high-pressure steam sterilization, as suggested by the results of durability tests. In addition, the coatings remained unpeeled in a usage environment, and there was no change in the anti-reflection performance of the DLC coatings. In summary, DLC coatings are useful for improving intracorporeal device surfaces and extending the lives of medical devices.

For as long as I can remember, I have struggled with understanding who I am. What makes me is something I try to make sense of through art. When I started working on this my graduation show, the idea behind it was to make a portrait of the Mexico I know, but when the pandemic hit, I found myself locked down at home, completely alone in a new country for the first time. This led me to question my existence and the belief systems I espoused and prompted me to try to understand myself better in the context of a foreign culture. As a result, the concept behind the show evolved from being about the Mexico I know to exploring who I am and how my upbringing has shaped my art and trying to make sense of my existence.

Il mercato del solare termodinamico offre varie soluzioni tecnologiche e impiantistiche in funzione dei livelli di temperatura che si vogliono ottenere. Le esigenze energetiche nei vari settori industriale, residenziale e commerciale, però, spingono il mercato verso i collettori solari capaci di operare con rendimenti maggiori del 50% a temperature superiori a 100 °C, fino anche a 250 °C (nel range cosiddetto “a media temperatura”'). In questo ambito, la tecnologia che dimostra di essere più matura per la penetrazione del mercato risulta essere quella dei collettori parabolici lineari (PTC), e in particolar modo quelli di piccola taglia. L'assorbitore solare riveste un ruolo di estrema importanza per il buon funzionamento dell'intero PTC. In particolare la scelta del coating superficiale per il tubo rappresenta un punto focale per lo sviluppo e l'ottimizzazione del sistema in termini tecnici ed economici. Per il raggiungimento degli obiettivi è necessario orientarsi verso soluzioni tecnologiche che abbiano proprietà chimiche, fisiche e ottiche tali da garantire elevate prestazioni in termini di efficienza energetica e stabilità nel tempo alle temperature di esercizio desiderate. I coatings a base di cromo nero presentano ottime caratteristiche ottiche (α≈0.90-0.92; εT≈0.10-0.15) e risultano essere stabili anche fino a 300 °C. Il più grande problema legato alla realizzazione di rivestimenti cromati è legato all'inquinamento conseguente all'utilizzo nel bagno elettrolitico di ossidi di cromo esavalente. Agli inizi del nuovo secolo, con l'avvento di nuove soluzioni chimiche meno inquinanti per la produzione di oggetti cromati e con il crescente interesse verso i collettori solari piani, le tecniche galvaniche hanno trovato largo uso nella produzione di impianti solari termodinamici. L'assorbitore che è stato studiato è un assorbitore a base di cromo nero, e questo rientra nella categoria dei “tandem-absorber”: lo studio è cominciato quindi dal substrato. Lo studio del substrato ha portato alla comprensione delle caratteristiche che questo deve possedere e quali sono le condizioni operative per ottenerle. Il substrato per il cromo nero deve possedere appropriate caratteristiche ottiche, ovvero bassa emittanza, ma deve anche favorire la deposizione e l'adesione dell'assorbitore. I materiali candidati a questo scopo sono stati il nichel, ottenuto con due diversi processi di deposizione e il rame. Poiché questi tre materiali favoriscono egualmente deposizione ed adesione del cromo nero, è da preferire il materiale che garantisce la minore emittanza, ovvero il nichel ottenuto con il processo di deposizione di Watts (ε300 °C≈ 0.4). Si è mostrato inoltre, facendo chiarezza rispetto a quanto riportato in letteratura, come gli spessori dei substrati non influenzino le caratteristiche ottiche. Quindi al fine di contenere i costi di produzione è da preferire il minore spessore che garantisca una buona adesione del substrato e questo è stato individuato in uno spessore di 2 µm. Si sono poi trattate le caratteristiche ottiche dell'assorbitore, ponendo particolare attenzione al contesto in cui questo verrà utilizzato: infatti il parametro di selettività, comunemente utilizzato in letteratura per il confronto degli assorbitori solari selettivi, non fornisce indicazioni valide sul comportamento dell'assorbitore nell'impianto solare. Si è quindi introdotto il parametro di efficienza η che tiene conto delle condizioni in cui verrà impiegato l'assorbitore. Ipotizzando un plausibile caso di lavoro con temperatura di esercizio 300 °C e rapporto di concentrazione di 40, si è mostrato come sia necessario cercare di massimizzare l'assorbanza del materiale assorbitore al fine di ottimizzare l'efficienza, piuttosto che limitarne l'emittanza. L'analisi dei parametri di deposizione che ha portato a determinare l'insieme di condizioni da cui deriva la migliore efficienza ha mostrato la fondamentale importanza della composizione chimica del bagno galvanico: infatti, oltre alla presenza del costituente principale, ovvero il Cr+3, si è verificato il contributo determinante apportato dai ``catalizzatori''. Questi facilitano il trasporto dello ione principale in soluzione e la sua deposizione al catodo, limitando al contempo le reazioni collaterali. In questo modo si riesce ad ottenere il cromo nero con un miglioramento di η del 5-8 % ed a densità di corrente molto inferiori rispetto al caso in cui i catalizzatori non sono presenti. Densità di corrente e temperatura del bagno galvanico sono i parametri principali su cui operare. I migliori risultati sono stati ottenuti a 20 °C con una densità di corrente di 60 A dm-2. Il tempo della deposizione è molto importante: infatti, dagli studi condotti, il tempo ottimale di deposizione è 1 minuto, poiché sia per tempi minori che maggiori si ha un peggioramento dell'efficienza. Dall'analisi della superficie si è visto che il cromo nero è uno strato di materia soffice, non compatta, con aspetto estremamente frastagliato e composta da globuli di piccole dimensioni costituiti da un nucleo di cromo metallico circondato da uno strato di ossidi e idrossidi di cromo. L'aspetto della superficie influenza le caratteristiche ottiche del materiale: infatti esiste una correlazione tra la rugosità superficiale e α/εT secondo cui all'aumentare di Rz si ha una perdita di selettività. Numerose e importanti informazioni si sono ottenute dalla valutazione degli effetti provocati dai trattamenti termici: infatti per un assorbitore solare è di fondamentale importanza conoscere le caratteristiche ottiche alla temperatura di funzionamento. Il cromo nero analizzato è caratterizzato da un miglioramento della selettività dopo essere stato esposto alle alte temperature (300 °C e 400 °C) soprattutto nei casi in cui il substrato sia Ni Watts. Si è potuto valutare anche che il rame non è un buon substrato per applicazioni che possano trovarsi a temperature superiori ai 300 °C a causa della sua facile interdiffusione con altri metalli. L'esposizione dell'assorbitore alla temperatura di esercizio si comporta inoltre come una sorta di livellante nei confronti di η il cui valore medio si attesta a circa 0.8. Infatti il trattamento termico a 300 °C provoca un miglioramento delle efficienze degli assorbitori che inizialmente possedevano delle η abbastanza basse e un cambiamento esattamente opposto per gli assorbitori che appena deposti presentavano le migliori efficienze. La presenza dello ione fluoruro nella composizione del bagno galvanico comporta invece una minore resistenza dello strato assorbitore nei confronti della temperatura. Alla luce di queste considerazioni la composizione ottimale del bagno galvanico individuata è costituita da CrCl3·6H2O 266 g l-1, H2SiF6 10 g l-1, NaH2PO4 4 g l-1 e CoCl2 ·6H2O 15 g l-1 . Infine, nonostante in precedenza si sia individuato il miglior substrato in base alle sue caratteristiche ottiche, si è visto sperimentalmente come questo parametro non si rifletta in maniera determinante sull'efficienza finale. Infatti, come già detto, è importante massimizzare l'assorbimento piuttosto che limitare l'emissione dell'assorbitore. Per questo motivo e considerate le prove effettuate, si può affermare che i substrati considerati sono tra loro equivalenti. Alla luce di ciò il substrato più adatto è il nichel ottenuto con il metodo di Wood, poiché è quello che necessita di minor lavorazione e non presenta le limitazioni riguardo alle temperature di utilizzo viste per il rame. Il miglior campione ottenuto, che rispetta le condizioni appena elencate, presenta una efficienza di conversione energetica η=0.88: questo valore non è molto lontano, e talvolta migliore, delle efficienze dei ben più costosi CERMET (η=0.85-0.93), oltre ad essere migliore delle efficienze dei campioni ottenuti da cromo esavalente. ***************** The use of a low-intensity source like sunlight, for energy generation requires an efficient system to concentrate and capture radiation and to transfer the energy to the exchange fluid. Sunlight is abundant, renewable and free of charge. Therefore the development and diffusion of solar energy exploitation is a key issue for the future. However, at present solar energy technologies are generally affected by a not high enough efficiency and a high cost, making them not fully competitive yet over conventional fossil fuels. Thus, it is clear that both increasing the efficiency and reducing the cost is mandatory to promote solar energy exploitation. Systems operating at mid-temperatures (i.e. using fluids at about 200-300 °C) and in particular parabolic trough collectors (PTCs) offer several advantages in comparison with conventional flat plates thanks to their higher efficiency and reduced receiver surface. In these systems the incident solar radiation is converted into heat either by sunlight absorption by blackened or specially developed absorbing surfaces that collect the solar energy and transfer it to the fluid. Required characteristics for the absorber surface are chemical and physical stability at the operating temperatures, as well as good performances in terms of energy efficiency. Moreover a production process characterized by a low cost and a high repeatability should promote a large scale diffusion. Several direct industrial applications, like Direct Steam Generation (DSC) and Solar Heating and Cooling (SHC), could exploit mid-temperature solar energy as energy source. This interest drives the research of novel technologies focused on this market sector where the technologies developed for systems operating at higher temperatures (e.g. CSP plants) cannot be used. Electrodeposition techniques are a promising route to obtain surfaces with tailored optical characteristics. Black chrome coatings have excellent optical properties, as they are strongly absorbing in the sunlight spectral region, with a high absorbance α ≈ 0.90-0.92 and a low thermal emittance ε ≈ 0.10-0.15. Moreover they remain stable up to 300 °C. However, a relevant drawback correlated to chrome electrodeposition is represented by pollution derived from Cr6+ ions. Because of that, the technological development of these processes underwent a sharp slowdown since '90. Only with the advent of new studies about Cr3+ baths, since the beginning of 2000's, the electrodeposition processes have found new interest in mass production of components for thermal solar plants. To obtain a good coating by black chrome, a preliminary deposition of a nickel layer on the substrate is needed to ensure a better chrome adherence to the surface and an improved wear and corrosion resistance. Moreover this creates an ``absorber/reflector tandem'' having both the high solar absorbance of the black exterior deposit and the low thermal emittance of the metallic inner coating. The first step of this study was the investigation of structural features and optical properties of the nickel and copper surfaces, correlating them to coating thickness and deposition process, in the perspective to assess optimal conditions for solar absorber applications. The second step of this study was the investigation of structural features and optical properties of the black chrome absorber taking into account several bath's operational parameters. This black chrome was obtained by a solution of Cr+3. In order to compare the performance obtained by the materials in a working configuration has been paid attention to a parameter that can provide some information: this parameter is the efficiency η that take into account the working temperature and the concentration ratio. Moreover has been done several thermal aging cycle on the materials in order to predict the effect of the aging on the optical properties. The optimal set-up that has been found is: for a galvanic bath composition CrCl3·6H2O 266 g l-1, H2SiF6 10 g l-1, NaH2PO4 4 g l-1 and CoCl2 ·6H2O 15 g l-1; for the operational parameters 20 °C and current density of 60 A~dm-2. With this set-up the best result is a sample with η=0.88: this value is rather similar to the efficiency of the more expensive CERMET (η=0.85-0.93).

Samples from both hydrothermal and melt growth techniques were characterized for absorption, index of refraction, and photorefractive dynamics. Doped hydrothermal samples possessed similar photorefractive properties to nominally undoped melt growth samples. BSO operates over a wide range of wavelengths, and it would be desirable to maintain the sensitivity of BSO while controlling the absorption coefficient at wavelengths into the infrared laser-diode operating region. The doped hydrothermal crystal is very transparent, having a light green color. In addition, a variety of response times may be useful in implementing optical analog devices in analogue to electronic devices. For example, heavy doping with chrome produces a dark, almost black, sample with an extremely long response time.

Given the largely untapped solar energy resource, there has been an ongoing international effort to engineer improved solar-harvesting technologies. Towards this, the possibility of engineering a solar selective volumetric receiver (SSVR) has been explored in the present study. Common heat transfer liquids (HTLs) typically have high transmissivity in the visible-near infrared (NIR) region and high emission in the mid-infrared region, due to the presence of intra-molecular vibration bands. This precludes them from being solar absorbers. In fact, they have nearly the opposite properties from selective surfaces such as cermet, TiNOx, and black chrome. However, liquid receivers which approach the radiative properties of selective surfaces, can be realized through a combination of anisotropic geometries of metal nanoparticles and transparent heat mirrors. Solar selective volumetric receivers represent a paradigm shift in the manner in which solar thermal energy is harnessed and promise higher thermal efficiencies (and lower material requirements) than their surface-absorption based counterparts. In this paper, the ‘effective’ solar absorption to infrared emission ratio has been evaluated for a representative SSVR employing copper nanospheroids and Sn-In2O3 based heat mirrors. It has been found that a solar selectivity comparable to (or even higher than) cermet-based Schott receiver is achievable through control of the cut-off solar selective wavelength. Theoretical calculations show that the thermal efficiency of Sn-In2O3 based SSVR is 6 to 7% higher than the cermet-based Schott receiver. Furthermore, stagnation temperature experiments have been conducted on a lab-scale SSVR to validate the theoretical results. It has been found that higher stagnation temperatures (and hence higher thermal efficiencies) compared to conventional surface absorption-based collectors are achievable through proper control of nanoparticle concentration.

Abstract HVOF sprayed tungsten carbide (WC) thermal spray coatings are finding increasing acceptance for replacement of electroplated chromium on aircraft landing gear parts. In order to replace chrome plating by an HVOF WC coating, the latter should exhibit wear and fatigue characteristics at least as good as those of chrome plating. Sliding wear performance and fatigue life of tungsten carbide coated parts depend on morphology and phase composition of the coating which in turn depend on spray parameters such as powder characteristics, powder feed rate, gas flow rates, and spray distance. A Design of Experiments (DOE) approach for a Jet Kote™ HVOF spray system was used to identify optimal spray parameters for WC-Co and WC-Co-Cr coatings based on best sliding wear and best fatigue characteristics. Best sliding wear was defined as minimum block loss in the standard ASTM-G77 wear test in which a rotating WC coated ring is tested against a stationary Al-Ni-Bz block. Best fatigue characteristics were defined as compressive residual stresses in the coating in the range 250 to 450 MPa. Spray parameters found to strongly affect wear were powder feed rate, oxygen flow rate, powder size, and a powder type-powder size interaction. Spray parameters strongly affecting residual stresses include powder type, hydrogen flow rate, and powder feed rate. Some spray parameters were found to be orthogonal with respect to wear behavior and residual stress. This means some parameters can be adjusted to maximize one performance criterion (wear or residual stress) without adversely affecting the other.

H13 has been widely used in hot and cold work tooling applications and the thermal processing of H13 has important industrial significance particularly where longer tool life is important. This paper presents some results of the CO2 laser assisted processing of H13 tool steel. A block of preheated H13 tool steel was laser processed at six different parameters. Laser power (P) and Scan speed (V) were chosen as the primary variables. The processed region was characterized for geometry, micro hardness and microstructure. The block temperature was monitored using an alumel-chromel thermocouple. Optical observations indicated that the aspect ratios of the processed zone increased with power. Microhardness observations indicate that higher cooling rate parameters had higher hardness values. Finer dendrites were visible at higher power values. These observations were corroborated by magnitude of thermal change predictions made using the Rosenthal equation

To better constrain the origin of the chromitites associated with the Esker Intrusive Complex (EIC) of the Ring of Fire Intrusive Suite (RoFIS), a total of 50 chromite-bearing samples from the Black Thor, Big Daddy, Blackbird, and Black Label chromite deposits have been analysed for major and trace elements. The samples represent three textural groups, as defined by the relative abundance of cumulate silicate phases and chromite. To provide deposit-specific partition coefficients for modeling, we also report on the results of laboratory experiments to measure olivine- and chromite-melt partitioning of V and Ga, which are two elements readily detectable in the chromites analysed. Comparison of the Cr/Cr+Al and Fe/Fe+Mg of the EIC chromites and compositions from previous experimental studies indicates overlap in Cr/Cr+Al between the natural samples and experiments done at >1400oC, but significant offset of the natural samples to higher Fe/Fe+Mg. This is interpreted to be the result of subsolidus Fe-Mg exchange between chromite and the silicate matrix. However, little change in Cr/Cr+Al from magmatic values, owing to the lack of an exchangeable reservoir for these elements. A comparison of the composition of the EIC chromites and a subset of samples from other tectonic settings reveals a strong similarity to chromites from the similarly-aged Munro Township komatiites. Partition coefficients for V and Ga are consistent with past results in that both elements are compatible in chromite (DV = 2-4; DGa ~ 3), and incompatible in olivine (DV = 0.01-0.14; DGa ~ 0.02), with values for V increasing with decreasing fO2. Simple fractional crystallization models that use these partition coefficients are developed that monitor the change in element behaviour based on the relative proportions of olivine to chromite in the crystallizing assemblage; from 'normal' cotectic proportions involving predominantly olivine, to chromite-only crystallization. Comparison of models to the natural chromite V-Ga array suggests that the overall positive correlation between these two elements is consistent with chromite formed from a Munro Township-like komatiitic magma crystallizing olivine and chromite in 'normal' cotectic proportions, with no evidence of the strong depletion in these elements expected for chromite-only crystallization. The V-Ga array can be explained if the initial magma responsible for chromite formation is slightly reduced with respect to the FMQ oxygen buffer (~FMQ- 0.5), and has assimilated up to ~20% of wall-rock banded iron formation or granodiorite. Despite the evidence for contamination, results indicate that the EIC chromitites crystallized from 'normal' cotectic proportions of olivine to chromite, and therefore no specific causative link is made between contamination and chromitite formation. Instead, the development of near- monomineralic chromite layers likely involves the preferential removal of olivine relative to chromite by physical segregation during magma flow. As suggested for some other chromitite-forming systems, the specific fluid dynamic regime during magma emplacement may therefore be responsible for crystal sorting and chromite accumulation.